Compositions and methods for neuralgenesis
11654161 · 2023-05-23
Assignee
Inventors
- Thomas Hartung (Baltimore, MD, US)
- David Pamies (Baltimore, MD, US)
- Helena T. Hogberg (Nottingham, MD, US)
Cpc classification
C12N2506/45
CHEMISTRY; METALLURGY
C12N5/0622
CHEMISTRY; METALLURGY
C12N2501/22
CHEMISTRY; METALLURGY
C12N2501/13
CHEMISTRY; METALLURGY
A61K35/30
HUMAN NECESSITIES
C12N2501/999
CHEMISTRY; METALLURGY
C12N5/0062
CHEMISTRY; METALLURGY
G01N33/50
PHYSICS
C12N5/0696
CHEMISTRY; METALLURGY
C12N2501/115
CHEMISTRY; METALLURGY
C12N5/0697
CHEMISTRY; METALLURGY
International classification
A61K35/30
HUMAN NECESSITIES
C12N5/00
CHEMISTRY; METALLURGY
G01N33/50
PHYSICS
Abstract
The present invention relates to novel compositions and methods to produce 3D organ equivalents of the brain (i.e. “mini-brains”). The invention also relates to methods of using human induced pluripotent stem cells, a combination of growth and other soluble factors and gyratory shaking. Cells from healthy or diseased donors or animals can be used to allow testing different genetic backgrounds. The model can be further enhanced by using genetically modified cells, adding micro-glia or their precursors or indicator cells (e.g. with reporter genes or tracers) as well as adding endothelial cells to form a blood-brain-barrier.
Claims
1. An in vitro brain microphysiological system (BMPS), comprising A. an induced pluripotent stem cell (iPSC) wherein the iPSC is configured to differentiate into at least one neural cell type aggregated into a spheroid mass; and a population of microglia-like cells, wherein B. the in vitro BMPS is electrophysiologically active in a spontaneous manner.
2. The BMPS of claim 1, wherein the micro-glia like cells comprise microglia, microglia precursor cells, or a combination thereof.
3. The BMPS of claim 1, wherein the micro-glia like cells comprise monocytes, human monocytes, pro-monocyte cell lines, hematopoietic stem cells, isolated microglia, immortalized microglia, or combinations thereof.
4. The BMPS of claim 3, where the monocytes comprise adult cell-derived monocytes, embryonic cell-derived monocytes, or a combination thereof.
5. The BMPS of claim 4, wherein the monocytes comprise embryonic stem cell (ESC)-derived monocytes, induced pluripotent stem cell (iPSC)-derived monocytes, or a combination thereof.
6. The BMPS of claim 3, wherein the isolated microglia comprise adult microglia, fetal microglia, or a combination thereof.
7. The BMPS of claim 3, wherein the microglia-like cells are derived from somatic cells, neuronal cells, myeloid progenitor cells, or a combination thereof.
8. The BMPS of claim 1, wherein the microglia-like cells express one or more of the following biomarkers: HLA-DR, Iba1, CD14, CX3CR1, F4/80, CD80, CD86, CD36, iNOS, COX2, ARG1, PPARγ, SOCS-3, TMEM119, Mertk, Ax1, CD11b, CD11c, P2RY12, CD45, CD68, CD40, B7, ICAM-1, or any combination thereof.
9. The BMPS of claim 1, wherein the BMPS expresses receptors associated with microglia function.
10. The BMPS of claim 9, wherein the receptors associated with microglia function comprise CCL2, CX3CL, RAGE, NLRP3, SR-AI, TREM2, FPRL1/FPR2, CD36, CD33, C5a, CR1, CR3/Mac-1, FcRs, FPRs, TLRs, or a combination thereof.
11. The BMPS of claim 1, wherein the BMPS is configured to elicit a pro-inflammatory response, an anti-inflammatory response, or a combination thereof in response to a stimulus.
12. The BMPS of claim 10, the BMPS being configured to elicit a pro-inflammatory response, and the stimulus comprises viral infection, LPS exposure, or a combination thereof.
13. The BMPS of claim 10, the BMPS being configured to elicit an anti-inflammatory response, and the stimulus comprises IL-3, IL-4, IL-10, IL-13, IL-1β, IL-6, TNF-α, TGF-β, or a combination thereof.
14. The BMPS of claim 10, wherein the microglia-like cells comprise about 20% or less of the BMPS.
15. The BMPS of claim 10, wherein the at least one neural cell type comprises a mature neuron, a glial cell, or a combination thereof.
16. The BMPS of claim 15, wherein the at least one neural cell type further comprises astrocytes, polydendrocytes, oligodendrocytes, or combinations thereof.
17. The BMPS of claim 10, wherein the in vitro BMPS has neural characteristics selected from the group consisting of synaptogenesis, neuron-neuron interactions, neuronal-glial interactions, axon myelination, cell migration, neurological development, disease phenotypes, and combinations thereof.
18. The BMPS of claim 17, wherein disease process phenotypes comprise autophagy, integrated stress response, non-sense mediated decay, lesions, amyloid deposition, plaque formation, protein aggregation, or combinations thereof.
19. The BMPS of claim 10, wherein the at least one neural cell type express one or more biomarker selected from the group consisting of MBP, PLP, NG2, Olig1, Olig2, Olig 3, OSP, MOG, SOX10, neurofilament 200 (NF200), GRIN1, GAD1, GABA, TH, LMX1A, FOXO1, FOXA2, FOXO4, CNP, TH, TUBIII, NEUN, SLC1A6, and any combination thereof.
20. The in vitro BMPS of claim 10, wherein the spheroid mass comprises a diameter that is about 1000 μm or less.
21. The in vitro BMPS of claim 20, wherein the spheroid mass comprises a diameter that is about 500 μm or less.
22. The BMPS of claim 10, further comprising one or more endothelial cells, pericytes, or a combination thereof capable of forming a blood-brain-barrier.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The patent or applicatin file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawings will be provided by the Office upon request and payent of the necessary fee.
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DETAILED DESCRIPTION OF THE INVENTION
(16) The present invention is based, at least in part, upon the discovery that brain microphysiological systems (BMPS) can be produced from induced pluripotent stem cells (iPSCs). Furthermore, the invention provides for reproducible BMPS that differentiate into mature neurons and glial cells (astrocytes and oligodendrocytes) in the central nervous system. This model is spontaneously electrophysiological active and may be reproduced with patient or genetically modified cells. The derivation of 3D BMPS from iPSCs has applications in the study and treatment of neurological and neurodevelopmental diseases. In some embodiments, the present disclosure provides for compositions and methods to study and/or treat neurodevelopmental and neurodegenerative disorders. In some cases, the neurodevelopmental and neurodegenerative disorders treated and/or studied by the present disclosure include, but are not limited to, autism, encephalitis, trauma, brain cancer, stroke, Amyotrophic lateral sclerosis, Huntington's Disease, muscular dystrophy, neurodegenerative disorder, neurodevelopmental disorder, Multiple Sclerosis, infection, Parkinson's Disease and Alzheimer's Disease.
(17) As described herein, the present disclosure provides for the derivation of a multitude of identical brain microphysiological systems (BMPS) from stem cells, preferably of human origin, but including stem cells from animal origin. The preferred starting material are human induced pluripotent stem cells or embryonic stem cells, although other pluripotent stem cells such as, for example, neuronal precursor cells and mesenchymal stem cells may also be employed. Human in-vitro models of brain neurophysiology are needed to investigate molecular and cellular mechanisms associated with neurological disorders and neurotoxicity. The techniques herein provide a reproducible iPSC-derived human 3D BMPS that includes differentiated mature neurons and glial cells (astrocytes and oligodendrocytes) that reproduce neuronal-glial interactions and connectivity. BMPS mature over about eight weeks and show the critical elements of neuronal function including, but not limited to, synaptogenesis and neuron-to-neuron (e.g. spontaneous electric field potentials) and neuronal-glial interactions (e.g. myelination). Advantageously, the BMPS described herein include mature neurons (e.g., glutamatergic, dopaminergic and GABAergic neurons) and glial cells (e.g., astrocytes and oligodendrocytes). Quantification of the different cell types exhibited high reproducibility between experiments. Moreover, the BMPS disclosed herein present neuron and glial functions such as spontaneous electrical activity and axon myelination. The BMPS described herein are able to mimic the microenvironment of the central nervous system, which is a significant advance in the field of neurobiology as this ability has not been achieved at this level of functionality, reproducibility, and consistency in prior art in vitro systems.
(18) In particular, the high amount of myelination of axons (up to 40%) in the disclosed BMPS represents a significant improvement over the prior art. Myelin pathology is a rather frequent condition in demyelinating and inflammatory disorders such as multiple sclerosis and post-infection diseases as well as other neurological diseases such as acute and post-traumatic brain injury, stroke and neurodegenerative disorders (see e.g., Fumagalli et al., 2016; Tse and Herrup, 2016). Moreover, the myelination process can be perturbed by exposure to chemicals and drugs (see e.g., Garcia et al., 2005; Brubaker et al., 2009; Creeley et al., 2013) during brain development and adulthood. For example, the BMPS disclosed herein show 40% overall myelination after 8 weeks of differentiation. Myelin was observed by immunohistochemistry and confirmed by confocal microscopy 3D reconstruction and electron microscopy. These findings are of particular relevance since myelin is crucial for proper neuronal function and development. The ability to assess oligodendroglia function and mechanisms associated with myelination in this BMPS model provide an excellent tool for future studies of neurological disorders such as multiple sclerosis and other demyelinating diseases. Thus, the BMPS provides a suitable and reliable model to investigate neuron-neuroglia function in neurotoxicology or other pathogenic mechanisms that has heretofore not been available in the prior art.
(19) The method disclosed combines gyratory shaking or regular stirring and the addition of growth factors to obtain the basic model. Suitable conditions as to how to achieve reproducible brain composition are disclosed herein. In contrast to earlier models, identical units of BMPS are produced, which allow comparative testing for the purpose of product development or safety assessments.
(20) According to the techniques herein, a number of additional measures complement the basic BMPS to increase their completeness in modeling the human brain and improve its usefulness for such testing, for example:
(21) 1. The addition of microglia: All stem-cell-derived brain models described so far lack micro-glia. The techniques herein provide that the addition of micro-glia precursor cells and suitable growth factors may allow microglia to be added to the model. Suitable cells may be monocytes (e.g., human monocytes), hematopoetic stem cells, respective (pro-)monocyte cell lines, and isolated microglia.
(22) 2. The addition of a blood-brain-barrier: The human brain is protected by a tight blood-brain-barrier that excludes many substances from the brain. For the first time, the techniques herein provide a method to form a blood-brain-barrier to the BMPS via cells such as, for example, human endothelial cells.
(23) 3. Addition of reporter and reporter cells: During the generation of the BMPS, cells carrying reporter for testing purposes may be used or added. These include, but are not limited to, fluorescent or luminescent markers to indicate a certain cell lineage or cell response. Genetic transient or permanent transfections are the primary, but not only, method of choice.
(24) 4. The BMPS may also be produced, entirely or in its components, from cells from a specific genetic background, e.g. from patients with a specific disease or after selective genetic manipulation of the cells.
(25) 5. The versatility of the BMPS may be improved by combining it with electrodes including, but not limited to, micro-electrode arrays (MEA).
(26) 6. The versatility of the BMPS may be improved by combining it with other MPS (organ models) platforms such as, for example, microfluidic human-on-chip systems, perfusion chambers and others.
(27) 7. Transportability of BMPS: Methods to cryopreserve BMPS were developed, which allow transport to other laboratories and testing or integration into multi-MPS platforms.
(28) Simplified neural in vitro systems do not reflect physiology, interactions between different cell types, or human genetics. Induced pluripotent stem cells (iPSC)-derived human-relevant microphysiological systems (MPS) better mimic the organ level, but are too complex for chemical and drug screening. As described herein, a reproducible 3D brain MPS (BMPS) that differentiates into mature neurons and glial cells (astrocytes and oligodendrocytes), which reproduces the topology of neuronal-glial interactions and connectivity in the central nervous system was developed. BMPS from healthy donors or patients evolve from a period of differentiation to maturity over about 8 weeks, including synaptogenesis, neuron-neuron interactions (e.g. spontaneous electric field potentials) and neuronal-glial interactions (e.g. myelination of axons), which mimic the microenvironment of the central nervous system. Effects of substances on neurodevelopment may be studied during this phase of BMPS development. In an exemplary embodiment, the techniques herein were used to study Parkinson's disease (PD) by evaluating neurotoxicants with a link to PD pathogenesis. Exposure to 5 μM rotenone or 100 μM 1-methyl-4-phenylpyridinium (MPP+) (or 1 mM 1-methyl-4-phenylpyridinium (MPP+) for gene expression studies) disrupted dopaminergic neurons, as observed by immunohistochemistry and altered expression of PD-related genes (TH, TBR1, SNCA, KEAP1, NDUFB1, ATP5C1, ATP50 and CASP1), thus recapitulating hallmarks of PD pathogenesis linked to toxicant compounds in the respective animal models. The BMPS, as described herein, provide a suitable and reliable model to investigate neuron-neuroglia function in neurotoxicity or other pathogenic mechanisms.
(29) There is growing concern about the continuing increase in neurodevelopmental and -degenerative disorders such as autism [1, 2], Parkinson's [3] and Alzheimer disease [4]. Although genetic factors play an important role, environmental factors such as pesticides, air pollution, cigarette smoke, and dietary toxicants appear to contribute [5, 6, 7]. Due to a lack of mechanistic understanding, it is difficult to study their contributions and interactions with respect to neurotoxicity and neurological disorders. The complexity of the CNS makes it challenging to find appropriate in vitro human-relevant models, ideally from different genetic backgrounds, that are able to recapitulate the relevant pathophysiology. The poor predictive ability of animal-based models for human health, which may fail to mimic human pathology as outlined in the costly and time-consuming current developmental neurotoxicity (DNT) guidelines, contributes to the lack of reliable information on DNT mechanisms [8]. At the same time, more than 90% of all drugs fail clinical trials after extensive animal testing [9] due, in part, to the fact that animal studies often do not reflect human physiology and inter-individual differences. Simple in vitro systems do not represent physiology and organ function [10], which creates a critical demand for better models in drug development, study of disease mechanisms and progression, bioengineering and toxicological testing.
(30) Attempts to generate more complex organotypic cultures or microphysiological systems (MPS) [11, 12, 13, 14] have resulted in more physiological multicellular 3D co-culture models able to simulate a functional part of the brain [15, 16]. 3D MPS have shown increased cell survival, differentiation, cell-cell interactions and can reproduce the complexity of the organ more closely [18]. Recent US research programs by NIH, FDA, DARPA, and DTRA have initiated the systematic development of MPS, including the model presented here, and their combinations to human-on-a-chip technologies to assess the safety and efficacy of countermeasures to biological and chemical terrorism and warfare [19].
(31) The discovery of induced pluripotent stem cells (iPSC) and new protocols to differentiate them into various cell types have boosted the development of human in vitro models [20, 21]. iPSC from healthy or patient donors with a specific disease [22, 23, 24, 12] used in MPS promise more human-representative models, e.g. the brain organoids by Lancaster et al. and Kadoshima et al., have been able to recapitulate features of human cortical development [15, 16]. These complex systems present novel tools to study biological mechanisms in the CNS, however, they have certain limitations: 1) an elaborate and complex protocol, 2) size differences between organoids, 3) necrosis in the center of the organoid, 4) low reproducibility in cell differentiation. The human BMPS described herein overcomes these limitations. The reproducible in vitro iPSC-derived human 3D brain microphysiological system (BMPS) is comprised of differentiated and mature neurons and glial cells (astrocytes and oligodendrocytes).
(32) The techniques herein provide a reproducible BMPS that contains several different cell types of the human brain, such as glutamatergic, dopaminergic and GABAergic neurons, astrocytes and oligodendrocytes. Moreover, the system has shown neural functionality as observed by spontaneous electrical activity and myelination of axons. Furthermore, the BMPS is reproducible from batch to batch and displays differences between healthy and patient donors. In addition, the obtained results demonstrate the application of such BMPS to the study of neurological disorders such as, for example, Parkinson's Disease (PD).
(33) The brain MPS described herein is a versatile tool for more complex testing platforms and strategies as well as research into neurotoxicity (e.g., developmental), CNS physiology and pathology. Some stem cell-derived brain microphysiological systems have been developed in the latest years showing the capability to recapitulate some of the in vivo biological process [36, 37, 38]. These models have an enormous advantage over the classical in vitro models to study various differentiation mechanisms, developmental processes and diseases [15]. However, they are mostly based on human embryonic stem cells raising ethical concerns and not allowing the use of patient cells. Moreover, they require complicated protocols that may reduce the reproducibility of the system and make it difficult to use in other fields such as chemical and drug screening. Some of these complex organoids have a large diameter, which can lead to extensive cell death, visible in the core of these tissues [15]. This may be due to insufficient diffusion of nutrients and oxygen in these non-vascularized systems, which may generate artifacts in toxicological and disease measurements and make it difficult to study different endpoints in a medium- to high-throughput manner. In addition, it will be challenging to adapt endpoints, established for relative simple 2D cultures, to such complex models. In the study described herein, the ability to generate a high number of viable (about 800 per batch), BMPS that are homogeneous in size (e.g., about 300 μm) and shape using iPSC by applying a constant or regular gyratory shaking or stirring technique as described earlier for rat re-aggregating brain cell cultures [40] is shown. Control of the size using specific shaker speed allowed the aggregates to be maintained below 350 μM in diameter (
(34) The 3D differentiation protocol described herein covered stages from neuronal precursors to different cell types of the mature CNS. After 2 weeks, BMPS consisted of an immature population of cells, showing minimal neuronal networks, low percentage of mature astrocytes and oligodendrocytes, with no myelin basic protein expression (
(35) Most of the brain MPS published so far are entirely focused on neurons and not glia populations [45, 46]; the brain MPS described herein is the first 3D model with fully characterized mature human oligodendrocytes, astrocytes and neurons, derived from iPSC. Astrocytes and oligodendrocytes play an important role during neuronal development, plasticity and neuronal injury. Astrocytes have a role in protecting neurons, increasing neuronal viability and mitochondrial biogenesis from both exogenous (e.g. chemicals) or endogenous (such as glutamate-induced excitotoxicity or the Alzheimer related Aβ1-42) toxicity [47, 48, 49, 50]. Astrocytes have an especially important role in neuroprotection from oxidative stress. Oxidative stress is known to be involved in a number of neuropathological conditions (such as neurodegenerative diseases) [51, 52, 53]. Thus, the presence of astrocytes in a biological system to study disease is crucial due to their role in detoxification and neuronal protection. Immunochemistry results from the iPSC-derived BMPS showed low numbers of astrocytes (GFAP-positive cells) at 2 weeks of differentiation, which increased continuously throughout differentiation (
(36) The presence of astroglia and oligodendroglia in the model described herein brings the system closer to the in vivo brain physiology, which is a crucial component to study neurodegeneration and neurotoxicity. In addition, the system has shown functionality as seen by imaging of cell-cell junctions, myelination, a rich astroglial network and electrical activity (
(37) An assessment of the myelination process by quantification of MBP immunostaining along axons showed an increase over time reaching 42% of myelinated axons at 8 weeks (
(38) In one embodiment, the model described herein is useful for studying Parkinson's disease (PD). Traditionally, PD has been described as a pre-synaptic degenerative process that affects dopaminergic neurons and induces a fundamental motor disorder [66], however, non-motor symptoms can also be present [67]. Research in Parkinson's disease is experiencing an upswing at the moment, owing to a lack of curative drugs for the large number of patients. Drug testing is nearly exclusively performed in vivo in the so-called MPTP (the parent compound to the metabolite MPP+ used here), rotenone, methamphetamine and 6-hydroxydopamine models requiring tens of thousands of animals [68, 69, 70]. These model toxins are mainly used in mice and primates (and less in cell cultures) to model a disease state resembling PD. Human neurons, which would be most relevant, are not usually available and existing cell lines are only very poor substitutes. The model described herein shows that treatment with MPP+ or rotenone induced specific degeneration of dopaminergic neurons in agreement with Parkinson patients and current animal models of the disease (
(39) This disclosure provides for a description of a brain microphysiological system aiming to study various aspects of brain development, pathophysiology and disturbance by genetic and environmental factors. The possibilities to study developmental and neurodegenerative disorders, infections, toxicity and trauma are emerging with such a system. Furthermore, the potential to use iPSC from different donors adds a personalized component to these studies. The high reproducibility and relatively easy protocol, enables future higher throughput testing of chemicals, and drugs and their potential to induce or treat diseases.
(40) Autism
(41) Autism is a highly variable neurodevelopmental disorder that first appears during infancy or childhood, and generally follows a steady course without remission. Patients with autism may be severely impaired in some respects but normal, or even superior, in others. Overt symptoms gradually begin after the age of six months, become established by age two or three years, and tend to continue through adulthood, although often in more muted form. It is distinguished not by a single symptom, but by a characteristic triad of symptoms: impairments in social interaction; impairments in communication; and restricted interests and repetitive behavior. Other aspects, such as atypical eating, are also common but are not essential for diagnosis. Autism's individual symptoms occur in the general population and appear not to associate highly, without a sharp line separating pathologically severe from common traits.
(42) While autism is highly heritable, researchers suspect both environmental and genetic factors as causes. In rare cases, autism is strongly associated with agents that cause birth defects. Controversies surround other proposed environmental causes; for example, the vaccine hypotheses have been disproven. Autism affects information processing in the brain by altering how nerve cells and their synapses connect and organize; how this occurs is not well understood. It is one of three recognized disorders in the autism spectrum (ASDs), the other two being Asperger syndrome, which lacks delays in cognitive development and language, and pervasive developmental disorder, not otherwise specified (commonly abbreviated as PDD-NOS), which is diagnosed when the full set of criteria for autism or Asperger syndrome are not met.
(43) Globally, autism is estimated to affect 21.7 million people as of 2013. As of 2010, the number of people affected is estimated at about 1-2 per 1,000 worldwide. It occurs four to five times more often in boys than girls. About 1.5% of children in the United States (one in 68) are diagnosed with ASD as of 2014, a 30% increase from one in 88 in 2012. The rate of autism among adults aged 18 years and over in the United Kingdom is 1.1%. The number of people diagnosed has been increasing dramatically since the 1980s, partly due to changes in diagnostic practice and government-subsidized financial incentives for named diagnoses; the question of whether actual rates have increased is unresolved.
(44) Autism has a strong genetic basis, although the genetics of autism are complex and it is unclear whether ASD is explained more by rare mutations with major effects, or by rare multigene interactions of common genetic variants. Complexity arises due to interactions among multiple genes, the environment, and epigenetic factors which do not change DNA but are heritable and influence gene expression. Studies of twins suggest that heritability is 0.7 for autism and as high as 0.9 for ASD, and siblings of those with autism are about 25 times more likely to be autistic than the general population. However, most of the mutations that increase autism risk have not been identified. Typically, autism cannot be traced to a Mendelian (single-gene) mutation or to a single chromosome abnormality, and none of the genetic syndromes associated with ASDs have been shown to selectively cause ASD. Numerous candidate genes have been located, with only small effects attributable to any particular gene. The large number of autistic individuals with unaffected family members may result from copy number variations-spontaneous deletions or duplications in genetic material during meiosis. Hence, a substantial fraction of autism cases may be traceable to genetic causes that are highly heritable but not inherited: that is, the mutation that causes the autism is not present in the parental genome.
(45) Several lines of evidence point to synaptic dysfunction as a cause of autism. Some rare mutations may lead to autism by disrupting some synaptic pathways, such as those involved with cell adhesion. Gene replacement studies in mice suggest that autistic symptoms are closely related to later developmental steps that depend on activity in synapses and on activity-dependent changes. All known teratogens (agents that cause birth defects) related to the risk of autism appear to act during the first eight weeks from conception, and though this does not exclude the possibility that autism can be initiated or affected later, there is strong evidence that autism arises very early in development.
(46) Exposure to air pollution during pregnancy, especially heavy metals and particulates, may increase the risk of autism. Environmental factors that have been claimed to contribute to or exacerbate autism, or may be important in future research, include certain foods, infectious diseases, solvents, diesel exhaust, PCBs, phthalates and phenols used in plastic products, pesticides, brominated flame retardants, alcohol, smoking, illicit drugs, vaccines, and prenatal stress, although no links have been found, and some have been completely disproven.
(47) Autism does not have a clear unifying mechanism at either the molecular, cellular, or systems level; it is not known whether autism is a few disorders caused by mutations converging on a few common molecular pathways, or is (like intellectual disability) a large set of disorders with diverse mechanisms. Autism appears to result from developmental factors that affect many or all functional brain systems, and to disturb the timing of brain development more than the final product. Neuroanatomical studies and the associations with teratogens strongly suggest that autism's mechanism includes alteration of brain development soon after conception. This anomaly appears to start a cascade of pathological events in the brain that are significantly influenced by environmental factors. Just after birth, the brains of children with autism tend to grow faster than usual, followed by normal or relatively slower growth in childhood. It is not known whether early overgrowth occurs in all children with autism. It seems to be most prominent in brain areas underlying the development of higher cognitive specialization. Hypotheses for the cellular and molecular bases of pathological early overgrowth include the following: an excess of neurons that causes local over connectivity in key brain regions, disturbed neuronal migration during early gestation, unbalanced excitatory-inhibitory networks, and abnormal formation of synapses and dendritic spines, for example, by modulation of the neurexin-neuroligin cell-adhesion system, or by poorly regulated synthesis of synaptic proteins.
(48) The immune system is thought to play an important role in autism. Children with autism have been found by researchers to have inflammation of both the peripheral and central immune systems as indicated by increased levels of pro-inflammatory cytokines and significant activation of microglia. Biomarkers of abnormal immune function have also been associated with increased impairments in behaviors that are characteristic of the core features of autism such as deficits in social interactions and communication. Interactions between the immune system and the nervous system begin early during the embryonic stage of life, and successful neurodevelopment depends on a balanced immune response. It is thought that activation of a pregnant mother's immune system such as from environmental toxicants or infection can contribute to causing autism through causing a disruption of brain development. This is supported by recent studies that have found that infection during pregnancy is associated with an increased risk of autism.
(49) The relationship of neurochemicals to autism is not well understood; several have been investigated, with the most evidence for the role of serotonin and of genetic differences in its transport. The role of group I metabotropic glutamate receptors (mGluR) in the pathogenesis of fragile X syndrome, the most common identified genetic cause of autism, has led to interest in the possible implications for future autism research into this pathway. Some data suggests neuronal overgrowth potentially related to an increase in several growth hormones or to impaired regulation of growth factor receptors. Also, some inborn errors of metabolism are associated with autism, but probably account for less than 5% of cases.
(50) The mirror neuron system (MNS) theory of autism hypothesizes that distortion in the development of the MNS interferes with imitation and leads to autism's core features of social impairment and communication difficulties. The MNS operates when an animal performs an action or observes another animal perform the same action. The MNS may contribute to an individual's understanding of other people by enabling the modeling of their behavior via embodied simulation of their actions, intentions, and emotions. Several studies have tested this hypothesis by demonstrating structural abnormalities in MNS regions of individuals with ASD, delay in the activation in the core circuit for imitation in individuals with Asperger syndrome, and a correlation between reduced MNS activity and severity of the syndrome in children with ASD. However, individuals with autism also have abnormal brain activation in many circuits outside the MNS and the MNS theory does not explain the normal performance of children with autism on imitation tasks that involve a goal or object.
(51) The under connectivity theory of autism hypothesizes that autism is marked by under functioning high-level neural connections and synchronization, along with an excess of low-level processes. Evidence for this theory has been found in functional neuroimaging studies on autistic individuals and by a brainwave study that suggested that adults with ASD have local over connectivity in the cortex and weak functional connections between the frontal lobe and the rest of the cortex. Other evidence suggests the under connectivity is mainly within each hemisphere of the cortex and that autism is a disorder of the association cortex.
(52) From studies based on event-related potentials, transient changes to the brain's electrical activity in response to stimuli, there is considerable evidence for differences in autistic individuals with respect to attention, orientation to auditory and visual stimuli, novelty detection, language and face processing, and information storage; several studies have found a preference for nonsocial stimuli. For example, magnetoencephalography studies have found evidence in children with autism of delayed responses in the brain's processing of auditory signals.
(53) Relations have been found between autism and schizophrenia based on duplications and deletions of chromosomes; research showed that schizophrenia and autism are significantly more common in combination with 1q21.1 deletion syndrome. Research on autism/schizophrenia relations for chromosome 15 (15q13.3), chromosome 16 (16p13.1) and chromosome 17 (17p12) are inconclusive.
(54) Diagnosis is based on behavior, not cause or mechanism. Under the DSM-5, autism is characterized by persistent deficits in social communication and interaction across multiple contexts, as well as restricted, repetitive patterns of behavior, interests, or activities. These deficits are present in early childhood, typically before age three, and lead to clinically significant functional impairment. Sample symptoms include lack of social or emotional reciprocity, stereotyped and repetitive use of language or idiosyncratic language, and persistent preoccupation with unusual objects. The disturbance must not be better accounted for by Rett syndrome, intellectual disability or global developmental delay. ICD-10 uses essentially the same definition. A pediatrician commonly performs a preliminary investigation by taking developmental history and physically examining the child. If warranted, diagnosis and evaluations are conducted with help from ASD specialists, observing and assessing cognitive, communication, family, and other factors using standardized tools, and taking into account any associated medical conditions. A pediatric neuropsychologist is often asked to assess behavior and cognitive skills, both to aid diagnosis and to help recommend educational interventions.
(55) Clinical genetics evaluations are often done once ASD is diagnosed, particularly when other symptoms already suggest a genetic cause. Although genetic technology allows clinical geneticists to link an estimated 40% of cases to genetic causes, consensus guidelines in the US and UK are limited to high-resolution chromosome and fragile X testing. Metabolic and neuroimaging tests are sometimes helpful, but are not routine.
(56) Many medications are used to treat ASD symptoms that interfere with integrating a child into home or school when behavioral treatment fails. More than half of US children diagnosed with ASD are prescribed psychoactive drugs or anticonvulsants, with the most common drug classes being antidepressants, stimulants, and antipsychotics. Antipsychotics, such as risperidone and aripiprazole, have been found to be useful for treating some conditions associated with autism, including irritability, repetitive behavior, and sleeplessness. A person with ASD may respond atypically to medications, the medications can have adverse effects, and no known medication relieves autism's core symptoms of social and communication impairments. Experiments in mice have reversed or reduced some symptoms related to autism by replacing or modulating gene function, suggesting the possibility of targeting therapies to specific rare mutations known to cause autism. Although many alternative therapies and interventions are available, few are supported by scientific studies. Some alternative treatments may place the child at risk. A 2008 study found that compared to their peers, autistic boys have significantly thinner bones if on casein-free diets; in 2005, botched chelation therapy killed a five-year-old child with autism. There has been early research looking at hyperbaric treatments in children with autism.
(57) Parkinson's Disease
(58) Parkinson's disease (PD, also known as idiopathic or primary parkinsonism, hypokinetic rigid syndrome (HRS), or paralysis agitans) is a degenerative disorder of the central nervous system mainly affecting the motor system. The motor symptoms of Parkinson's disease result from the death of dopamine-generating cells in the substantia nigra, a region of the midbrain. The causes of this cell death are poorly understood. Early in the course of the disease, the most obvious symptoms are movement-related; these include shaking, rigidity, slowness of movement and difficulty with walking and gait. Later, thinking and behavioral problems may arise, with dementia commonly occurring in the advanced stages of the disease, and depression is the most common psychiatric symptom. Other symptoms include sensory, sleep and emotional problems. Parkinson's disease is more common in older people, with most cases occurring after the age of 50; when it is seen in young adults, it is called young onset PD (YOPD).
(59) The main motor symptoms are collectively called “parkinsonism,” or a “parkinsonian syndrome.” The disease can be either primary or secondary. Primary Parkinson's disease is referred to as idiopathic (having no known cause), although some atypical cases have a genetic origin, while secondary parkinsonism is due to known causes like toxins. The pathology of the disease is characterized by the accumulation of a protein into Lewy bodies in neurons, and insufficient formation and activity of dopamine in certain parts of the midbrain. Where the Lewy bodies are located is often related to the expression and degree of the symptoms of an individual. Diagnosis of typical cases is mainly based on symptoms, with tests such as neuroimaging being used for confirmation.
(60) Diagnosis of Parkinson's disease involves a physician taking a medical history and performing a neurological examination. There is no lab test that will clearly identify the disease, but brain scans are sometimes used to rule out disorders that could give rise to similar symptoms. People may be given levodopa and resulting relief of motor impairment tends to confirm diagnosis. The finding of Lewy bodies in the midbrain on autopsy is usually considered proof that the person had Parkinson's disease. The progress of the illness over time may reveal it is not Parkinson's disease, and some authorities recommend that the diagnosis be periodically reviewed. Other causes that can secondarily produce a parkinsonian syndrome are Alzheimer's disease, multiple cerebral infarction and drug-induced parkinsonism. Parkinson plus syndromes such as progressive supranuclear palsy and multiple system atrophy must be ruled out. Anti-Parkinson's medications are typically less effective at controlling symptoms in Parkinson plus syndromes. Faster progression rates, early cognitive dysfunction or postural instability, minimal tremor or symmetry at onset may indicate a Parkinson plus disease rather than PD itself. Genetic forms are usually classified as PD, although the terms familial Parkinson's disease and familial parkinsonism are used for disease entities with an autosomal dominant or recessive pattern of inheritance.
(61) The PD Society Brain Bank criteria require slowness of movement (bradykinesia) plus either rigidity, resting tremor, or postural instability. Other possible causes for these symptoms need to be ruled out prior to diagnosis with PD. Finally, three or more of the following features are required during onset or evolution: unilateral onset, tremor at rest, progression in time, asymmetry of motor symptoms, response to levodopa for at least five years, clinical course of at least ten years and appearance of dyskinesias induced by the intake of excessive levodopa. Accuracy of diagnostic criteria evaluated at autopsy is 75-90%, with specialists such as neurologists having the highest rates. Computed tomography (CT) and conventional magnetic resonance imaging (MRI) brain scans of people with PD usually appear normal. These techniques are nevertheless useful to rule out other diseases that can be secondary causes of parkinsonism, such as basal ganglia tumors, vascular pathology and hydrocephalus. A specific technique of MRI, diffusion MRI, has been reported to be useful at discriminating between typical and atypical parkinsonism, although its exact diagnostic value is still under investigation. Dopaminergic function in the basal ganglia can be measured with different PET and SPECT radiotracers. Examples are ioflupane (123I) (trade name DaTSCAN) and iometopane (Dopascan) for SPECT or fluorodeoxyglucose (18F) and DTBZ for PET. A pattern of reduced dopaminergic activity in the basal ganglia can aid in diagnosing PD.
(62) Treatments, typically the medications L-DOPA and dopamine agonists, improve the early symptoms of the disease. As the disease progresses and dopaminergic neurons continue to be lost, these drugs eventually become ineffective at treating the symptoms and at the same time produce a complication marked by involuntary writhing movements. Surgery and deep brain stimulation have been used to reduce motor symptoms as a last resort in severe cases where drugs are ineffective. Although dopamine replacement alleviates the symptomatic motor dysfunction, its effectiveness is reduced as the disease progresses, leading to unacceptable side effects such as severe motor fluctuations and dyskinesias. Furthermore, there is no therapy that will halt the progress of the disease. Moreover, this palliative therapeutic approach does not address the underlying mechanisms of the disease.
(63) The term parkinsonism is used for a motor syndrome whose main symptoms are tremor at rest, stiffness, slowing of movement and postural instability. Parkinsonian syndromes can be divided into four subtypes according to their origin: primary or idiopathic, secondary or acquired, hereditary parkinsonism, and Parkinson plus syndromes or multiple system degeneration. Usually classified as a movement disorder, PD also gives rise to several non-motor types of symptoms such as sensory deficits, cognitive difficulties or sleep problems. Parkinson plus diseases are primary parkinsonisms which present additional features. They include multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration and dementia with Lewy bodies.
(64) In terms of pathophysiology, PD is considered a synucleiopathy due to an abnormal accumulation of alpha-synuclein protein in the brain in the form of Lewy bodies, as opposed to other diseases such as Alzheimer's disease where the brain accumulates tau protein in the form of neurofibrillary tangles. Nevertheless, there is clinical and pathological overlap between tauopathies and synucleinopathies. The most typical symptom of Alzheimer's disease, dementia, occurs in advanced stages of PD, while it is common to find neurofibrillary tangles in brains affected by PD. Dementia with Lewy bodies (DLB) is another synucleinopathy that has similarities with PD, and especially with the subset of PD cases with dementia. However, the relationship between PD and DLB is complex and still has to be clarified. They may represent parts of a continuum or they may be separate diseases.
(65) Mutations in specific genes have been conclusively shown to cause PD. These genes encode alpha-synuclein (SNCA), parkin (PRKN), leucine-rich repeat kinase 2 (LRRK2 or dardarin), PTEN-induced putative kinase 1 (PINK1), DJ-1 and ATP13A2. In most cases, people with these mutations will develop PD. With the exception of LRRK2, however, they account for only a small minority of cases of PD. The most extensively studied PD-related genes are SNCA and LRRK2. Mutations in genes including SNCA, LRRK2 and glucocerebrosidase (GBA) have been found to be risk factors for sporadic PD. Mutations in GBA are known to cause Gaucher's disease. Genome-wide association studies, which search for mutated alleles with low penetrance in sporadic cases, have now yielded many positive results.
(66) The role of the SNCA gene is important in PD because the alpha-synuclein protein is the main component of Lewy bodies. The histopathology (microscopic anatomy) of the substantia nigra and several other brain regions shows neuronal loss and Lewy bodies in many of the remaining nerve cells. Neuronal loss is accompanied by death of astrocytes (star-shaped glial cells) and activation of the microglia (another type of glial cell). Lewy bodies are a key pathological feature of PD.
(67) Alzheimer's Disease
(68) Alzheimer's disease (AD) accounts for 60% to 70% of cases of dementia. It is a chronic neurodegenerative disease that often starts slowly, but progressively worsens over time. The most common early symptom is short-term memory loss. As the disease advances, symptoms include problems with language, mood swings, loss of motivation, disorientation, behavioral issues, and poorly managed self-care. Gradually, bodily functions are lost, ultimately leading to death. Although the speed of progression can vary, the average life expectancy following diagnosis is three to nine years. The cause of Alzheimer's disease is poorly understood. About 70% of the risk is believed to be genetic with many genes involved. Other risk factors include a history of head injuries, hypertension, or depression. The disease process is associated with plaques and tangles in the brain.
(69) Alzheimer's disease is characterized by loss of neurons and synapses in the cerebral cortex and certain subcortical regions. This loss results in gross atrophy of the affected regions, including degeneration in the temporal lobe and parietal lobe, and parts of the frontal cortex and cingulate gyrus. Alzheimer's disease has been hypothesized to be a protein misfolding disease (proteopathy), caused by accumulation of abnormally folded A-beta and tau proteins in the brain. Plaques are made up of small peptides, 39-43 amino acids in length, called beta-amyloid (also written as A-beta or Aβ). Beta-amyloid is a fragment from a larger protein called amyloid precursor protein (APP), a transmembrane protein that penetrates through the neuron's membrane. APP is critical to neuron growth, survival and post-injury repair. In Alzheimer's disease, an unknown process causes APP to be divided into smaller fragments by enzymes through proteolysis. One of these fragments gives rise to fibrils of beta-amyloid, which form clumps that deposit outside neurons in dense formations known as senile plaques.
(70) A probable diagnosis is based on the history of the illness and cognitive testing with medical imaging and blood tests to rule out other possible causes. Initial symptoms are often mistaken for normal ageing. Examination of brain tissue is needed for a definite diagnosis. Alzheimer's disease is diagnosed through a complete medical assessment. There is no one clinical test that can determine whether a person has Alzheimer's. Usually several tests are performed to rule out any other cause of dementia. The only definitive method of diagnosis is examination of brain tissue obtained from a biopsy or autopsy. Tests (such as blood tests and brain imaging) are used to rule out other causes of dementia-like symptoms. Laboratory tests and screening include: complete blood cell count; electrolyte panel; screening metabolic panel; thyroid gland function tests; vitamin B-12 folate levels; tests for syphilis and, depending on history, for human immunodeficiency antibodies; urinalysis; electrocardiogram (ECG); chest X-ray; computerized tomography (CT) head scan; and an electroencephalogram (EEG). A lumbar puncture may also be informative in the overall diagnosis.
(71) There are no known medications or supplements that decrease risk of Alzheimer's. Additionally, no known treatments stop or reverse Alzheimer's progression, although some may temporarily improve symptoms.
(72) This invention is further illustrated by the following examples, which should not be construed as limiting. The contents of all references, patents, and published patent applications cited throughout this application, as well as the figures, are incorporated herein by reference.
EXAMPLES
Example 1: Characterization of BMPS by Expression of Neural Specific Genes During Differentiation
(73) According to the techniques herein, the BMPS model established herein follows a stepwise differentiation protocol (
(74) In order to characterize different stages of the differentiation and maturation process, BMPS were collected every week up to 8 weeks of differentiation (FIGS. 1C1-C5). Analysis of different neuronal and glial cell-specific genes by real-time reverse transcription polymerase chain reaction (RT-PCR) was performed to characterize the presence of neurons, astrocytes, oligodendrocytes and neural precursor cells (NPC). NPC are self-renewing and proliferating multi-potent cells able to generate different cell types of the central nervous system. The differentiation of NPC in 3D was initiated by changing the medium to differentiation medium. Gene expression of the cell proliferation marker Ki67 decreased 95% after 2 weeks of differentiation (FIG. 1C1, proliferation and stem cell markers). The remaining Ki67 expression appears to be due to the presence of a small population of NPC and other proliferating cell types such as oligodendrocytes and astrocytes (FIG. 1C2, astroglia and oligodendroglia). Astrocyte-specific genes (S100B and GFAP) showed a constant increase after two weeks, while, differentiation of oligodendrocytes was induced later, after six weeks of differentiation as shown by OLIG2 gene expression (FIG. 1C2).
(75) Gene expression of specific neurotransmitters or their receptors was used to characterize the identity of different neuronal populations and the differentiation patterns of the human iPSC derived BMPS (FIG. 1C4, neuronal markers; right y-axis relative quantification of GRIN1 and GABRA1; MBP, FOXA2, and SLC1A3). GRIN1 encodes the essential Glutamate [NMDA] receptor subunit zeta-1 [25] was increased at very early stages of differentiation (one week after induction of differentiation) and continued to increase up to 5 weeks when it reached a plateau (FIG. 1C4). Similarly, GAD1, a GABAergic neuronal gene marker which encodes the Glutamate decarboxylase 1, and catalyzes decarboxylation of glutamate to GABA, showed an increase in expression during the first 4 weeks of differentiation, reaching a plateau thereafter (FIG. 1C4). The expression of tyrosine hydroxylase (TH) a gene, which identifies dopaminergic neurons, was observed first after three weeks, showing delayed differentiation compared to glutamatergic neurons. The expression of TH increased constantly thereafter reaching an 86-fold increase at seven weeks compared to NPC (week 0; FIG. 1C4). GABRA1, which encodes the gamma-aminobutyric acid (GABA) receptor, showed a steady increase of expression after 2 weeks and reached its maximum increase of a 150-fold change at 8 weeks compared to week 0 (FIG. 1C4). Moreover other markers for specific part of the brain, such as ventral midbrain neuron marker LMX1A, FOXO1 and FOXA2 (Hedlund et al., 2016; Stott et al., 2013), cerebral cortex marker FOXO4, or markers for myelination CNP and MBP (Li and Richardson, 2008; Agrawal et al., 1994) and L-glutamate transport SLC1A6 (Sery et al., 2015) has been studied (
(76) To prove that BMPS can be generated from different IPCs, another healthy line (IPS IMR90) and Down syndrome line (DYP0730) were used (FIG. 1C5). Both lines were able to generate BMPS and differentiated to neurons (MAP2 marker), astrocytes (GFAP marker) and oligodendrocytes (OLIG1 marker).
Example 2: Characterization of BMPS by Flow Cytometry Analysis Shows Neuronal Maturation of the Human Induced Pluripotent Stem Cells Over Time
(77) In order to quantify cell populations in the iPSC-derived BMPS and verify the reproducibility between experiments and batches of the cell line (C1, CRL-2097), flow cytometry was performed using CNS-specific antibodies for identification of neural markers (Table 1). Flow cytometry allowed quantifying 60% of cells with proliferation marker (Ki67) at the NPCs stage (week 0), which was reduced during differentiation down to 9% at 2 weeks, 7% at 4 weeks and 1% at 8 weeks (
(78) Quantification of the cell population in at least three independent experiments showed low variability between cultures, demonstrating the reproducibility of the system. The variation (standard deviation, SD) between experiments decreased with the cell differentiation process and was very small at the latest maturation stage (eight weeks); DCX SD 0.9%, Ki67 SD 0.2%, SOX1 SD 0.7%, SOX2 SD 1.2%, NES SD 0.7% and Tuj1 SD 9.8% (
(79) TABLE-US-00071 TABLE 1 Gene and miRNAs Taqman Assays. List of the primers used for the experiments. Catalog Assay ID Assay Type Availability Number Assay Name Gene Expression Taqman Primers Hs01060665 TaqMan ® Gene Inventoried 4331182 BACT Expression Assay Hs99999901 TaqMan ® Gene Inventoried 4331182 18S Expression Assay Hs04187831 TaqMan ® Gene Inventoried 4331182 NES Expression Assay Hs01032443 TaqMan ® Gene Inventoried 4331182 Ki67 Expression Assay Hs01088112 TaqMan ® Gene Inventoried 4331182 PAX6 Expression Assay Hs00909233 TaqMan ® Gene Inventoried 4331182 GFAP Expression Assay Hs00300164 TaqMan ® Gene Inventoried 4331182 OLIG2 Expression Assay Hs00902901 TaqMan ® Gene Inventoried 4331182 S100B Expression Assay Hs00609557 TaqMan ® Gene Inventoried 4331182 GRIN1 Expression Assay Hs00165941 TaqMan ® Gene Inventoried 4331182 TH Expression Assay Hs00971228 TaqMan ® Gene Inventoried 4331182 GABRA1 Expression Assay Hs01065893 TaqMan ® Gene Inventoried 4331182 GAD1 Expression Assay Hs00199577 TaqMan ® Gene Inventoried 4331182 SYN1 Expression Assay Hs00232429 TaqMan ® Gene Inventoried 4331182 TBR1 Expression Assay Hs01003383 TaqMan ® Gene Inventoried 4331182 SNCA Expression Assay Hs01003430 TaqMan ® Gene Inventoried 4331182 KEAP1 Expression Assay Hs00929425 TaqMan ® Gene Inventoried 4331182 NDUFB1 Expression Assay Hs01101219 TaqMan ® Gene Inventoried 4331182 ATP5C1 Expression Assay Hs00919163 TaqMan ® Gene Inventoried 4331182 ATP50 Expression Assay Hs00354836 TaqMan ® Gene Inventoried 4331182 CASP1 Expression Assay Hs00263981 TaqMan ® Gene Inventoried 4331182 CNP Expression Assay Hs01054576 TaqMan ® Gene Inventoried 4331182 FOXO1 Expression Assay Hs00188193 TaqMan ® Gene Inventoried 4331182 SLC1A3 Expression Assay Hs00936217 TaqMan ® Gene Inventoried 4331182 FOXO4 Expression Assay Hs00892663 TaqMan ® Gene Inventoried 4331182 LMX1A Expression Assay Hs00232764 TaqMan ® Gene Inventoried 4331182 FOXA2 Expression Assay miRNA Taqman Assays 1182 TaqMan ® Inventoried 4427975 mmu-miR- microRNA Assay 124a 2216 TaqMan ® Inventoried 4427975 hsa-miR- microRNA Assay 128a 457 TaqMan ® Inventoried 4427975 hsa-miR- microRNA Assay 132 2247 TaqMan ® Inventoried 4427975 hsa-miR- microRNA Assay 133b 1129 TaqMan ® Inventoried 4427975 mmu-miR- microRNA Assay 137 1094 Control miRNA Inventoried 4427975 RNU44 Assay
Example 3: MicroRNAs as Neuronal Differentiation Markers in Human iPSC-Derived BMPS
(80) MicroRNAs (miRNA), known as posttranscriptional regulators of developmental timing, have recently been established as markers to study the differentiation process [26]. Expression of neural-specific miRNAs showed strong induction of miRNAs involved in neurogenesis (FIG. 1C3, miRNA). mir-124, the most abundant brain miRNA, was strongly induced in the earlier stages of differentiation, then slightly down-regulated at eight weeks of differentiation. This finding correlates with previous studies, where mir-124 was shown to promote neuronal lineage commitment at earlier stages of neural stem cells specification by targeting anti-neuronal factors [26]. mir-128, a modulator of late neural differentiation, was strongly up-regulated after 5 weeks of differentiation. mir-137, the most induced miRNA over time in the system described herein, is known as a regulator of neural differentiation of embryonic stem cells (ESCs) [27]. mir-132 and mir-133b which are involved in regulation of dopaminergic neuron maturation and function, were induced in week three of differentiation, a finding which correlates with the expression pattern of TH. Moreover, mir-132 is involved in dendritic spine formation [28]. These results support the view of a coordinated mechanism of neuronal differentiation as reflected by the patterns of neuronal gene and miRNA expression and neuronal and neurotransmitter identity.
Example 4: Characterization of Human BMPS by Immunohistochemistry and Electron Microscopy Shows Evidence of Differentiation into Mature Brain Cell Types
(81) In order to assess the cellular composition and the process of maturation of the cells within the human BMPS, the expression of markers for different CNS cell populations including neurons and glial cells at 2, 4 and 8 weeks of differentiation were evaluated using immunohistochemistry and electron microscopy techniques. A reproducible pattern of expression consistent with maturation of the BMPS towards mature neural phenotypes was found. After 4 weeks of differentiation, the BMPS showed positive staining for mature neuronal markers such as microtubule-associated protein 2 (MAP2), neurofilament-heavy chain (NF, SMI32) and synaptophysin (
(82) A subset of neuronal cells exhibited immunoreactivity for markers such as NOGOA, O1, O2, and CNPase (
(83) GFAP-positive cells formed numerous cell processes organized in a network typical for human astrocyte glial processes in vivo, which established contacts with other glial cells and neurons (
(84) The morphology of cell nuclei observed by immunocytochemistry and electron microscopy showed some variation in nuclear morphology attributed to (i) cell proliferation as seen by positive staining for Ki67 and Nestin markers, and (ii) nuclear fragmentation likely associated with apoptosis as indicated by caspase 3 staining (
(85) Further analysis of neuronal cell populations and morphology presented a pattern of evolution that suggests BMPS maturation as seen by Nestin-positive cells decreasing over time of differentiation while MBP expressing cells increased (
Example 5: Microelectrode Array Recording of Spontaneous Electrical Activity of BMPS
(86) To test the neurophysiological properties of the cells within the BMPS model, spontaneous electrical activity in BMPS was analyzed by micro-electrode array (MEA)(see
Example 6: A Human 3D Model to Study Parkinson's Disease
(87) Due to the presence of TH-positive dopaminergic neurons in the iPSC-derived BMPS (
Example 7: Addition of Microglia
(88) Peripheral blood mononuclear cells (PBMCs) are isolated from fresh or commercially available cryo-preserved whole blood of pooled healthy donors by Ficoll or Percoll gradient centrifugation. Monocyte populations are obtained by negative magnet-antibody selection after Ficoll or Percoll gradient and then re-suspend in RPMI 1640. Monocytes are cultured in macrophage serum-free medium, stimulated with a cocktail of cytokines, GM-CSF and IL-34. Monocytes may also be obtained by differentiation of iPSCs, hematopoetic or other stem cells. The microglia-like cells are combined with neuronal precursor cells in shaker cultures to preferably arrive at a final concentration of 5-8% microglia.
(89) Primary monocytes or iPSC-derived monocytes may be incorporated into the system, both at early and later stages of BMPS differentiation. For the early stages, a number of 2×10.sup.6 NPCs mixed with 2×10.sup.4 monocytes are plated per 1 well (6 well-plate). Gyratory shaking is used at 88 rpms to generate spheres. After 2 days media are replaced with ½ CNS differentiation medial (Neurobasal® electro Medium (Gibco) supplemented with 5% B-27® Electrophysiology (Gibco), 1% glutamax (Gibco), 10 μg human recombinant GDNF (Gemini), 10 μg human recombinant BDNF (Gemini)) and ½ macrophage differentiation media (Dulbecco's modified Eagle's medium (Invitrogen) supplemented with 10% FCS, 0.055 mM β-mercaptoethanol, M-CSF (50 ng/ml), and IL-3 (25 ng/ml) (R&D Systems). The medium is replaced every 3 days.
(90) Monocytes can also be incorporated after BMPS differentiation. For that, BMPS are differentiated up to 8 weeks. BMPS spheres are separated in 500 μl Eppendorf tubes. 2×10.sup.4 monocytes are added to the Eppendorf with the BMPS. Tubes are shaking manually every hour, up to 8 hours. After that, BMPS-monocytes are collected and plated in 6 well plates. Cells are kept on constant shaking until use.
(91) The characterization of the immune-competent human organoids can be carried out by immunocytochemically assessing the presence of markers such as HLA-DR, and the ionized calcium-binding adapter molecule 1 (Iba1), specific microglial markers. Measures of cytokines and chemokines release and expression of receptors associated with microglia function (e.g., CCL2 and CX3CL) demonstrates successful engrafting of the microglia cells. This modified model is more suitable to investigate the neuroimmunological component associated with many substance exposures and diseases.
Example 8: Addition of a Blood Brain Barrier
(92) The blood brain barrier (BBB) has a crucial role in neurotoxicity, being the last barrier for substances before reaching the brain. Moreover, the BBB is the bottleneck in brain drug development and is the single most important factor limiting the future growth of neurotherapeutics [81]. Most of the in vitro models do not incorporate BBB.
(93) Human brain microvascular endothelial cells (hBMECs) from human iPSCs are incorporated into the BMPS by two techniques. In the first approach, mature BBB endothelial cells and neuronal precursors cells (NPCs) are combined in a single cells suspension in a ratio of 1:5, gyratory shaking or stirring are used to generated spheroids and aggregates are cultured up to 8 weeks. In the second technique, mature BMPS (8 weeks of differentiation) are covered by BBB endothelial cells using gravity systems (aggrewell, gravity well or hanging drops). Cells may be covered as well with other cell types, such as fluorescent LUHMES cells (
Example 9: Addition of Reporters
(94) The BMPS gives the opportunity to develop cell-based assays allowing for high-content imaging (HCI) that can be adapted to high-throughput platforms, to evaluate the effects of toxicants on key cellular processes of neural development and physiology in the culture system.
(95) Example of establishing fluorescent iPSC cell line: Creation of reporter cells lines greatly assists imaging efforts by allowing us to avoid complications associated with staining 3D cultures, to image subsets of cells, and to perform functional assays. Differentiated 3D aggregates from iPSC cultures spiked with 1-2% of iPSCs ubiquitously expressing fluorescent protein allow visualizing individual cells within the aggregates aiding quantification of phenotypic parameters, including neurite outgrowth and migration. Lines expressing markers allow measurement of synapse formation (PSD95, Synapsin 1), proliferation (Ki67), glial maturation (GFAP), and calcium signaling (GCaMP). Clustered Regularly Interspaced Short Palindromic Repeats/Cas (CRISPR) were used to create the various lines. Similar in function to the well-established zinc-finger (ZFNs) and TALEN nucleases, the Cas9-CRISPR system is a new entrant into the rapidly emerging field of genome engineering and has been quickly adopted and validated across a wide array of human stem cells. Gene-editing in hiPSCs has traditionally been a technically difficult task but with these advances it is now possible to generate reporter and mutant cell lines with genetically matched controls [83, 84, 85, 86]; essential tools not only for this project but also for the future success of using human iPSC-derived cells in quantitative live-cell phenotypic assays of toxicant testing.
(96) Using the CRISPR-Cas9 system, fluorescent protein (FxP) reporter cell lines were generated by generating gRNAs targeting the gene of interested. In this system as described herein, an RNA guided Cas9 endonuclease is used in conjunction with customizable small guide RNAs (gRNAs) to target and cleave any DNA template with a GN21GG sequence; the first G is for the U6 polymerase promoter while the N21GG is for the protospacer adjacent motif (PAM) sequence requirement of Cas9 [86, 87, 89].
(97) For reporter cell generation, homology-directed repair (HDR) guides the insertion of the appropriate DNA donor fragment into a target site at regions of homology between the donor fragment and the genomic DNA target. An ES line that ubiquitously expresses GFP was created by introducing CAG promoter-driven GFP into the AAVS1 safe harbor locus, and can use these constructs to transfect iPSC cells. For other reporters, constructs may be created that will direct the integration of a self-cleaving P2A peptide sequence [90] targeted fluorescent protein cassette in frame at the stop codon of the gene of interest. The P2A sequence engineered between the C-terminus of the endogenous protein and the fluorescent protein may minimize possible fusion protein functional defects. Plasmids encoding the Cas9 nuclease, the targeting gRNA, and appropriate donor DNA will be introduced by electroporation, recombinant hiPSC clones will be manually selected and screened for the desired insertion by PCR, and the genotype may be verified by sequencing. Reporter hiPSCs will be subjected to a differentiation protocol and expression of the reporter validated by examining expression patterns and through immunohistochemistry experiments where it may be determined whether the FxP expressing cells co-label with known markers.
Example 10: Using Cells with Specific Genetic Backgrounds
(98) The use of iPSCs, as described herein, has created new opportunities to study human diseases and gene/environment interaction [20, 21]. Fibroblasts or other somatic cells from healthy and diseased individuals can be reprogrammed into iPSCs, and subsequently be differentiated into all neural cell types. Similarly, iPSC can be genetically modified before creating the BMPS. As a proof-of-principle, iPSCs were obtained from patients with Down's syndrome (FIGS. 1C5 and 5A-D), Rett Syndrome and from individuals with mutations in disrupted in schizophrenia 1 (DISC1). DISC1 may have some functional overlap with TSC-iPSCs as both are involved in the mTOR cell signaling pathway.
(99) The Down's syndrome model is further characterized (see
Example 11: Combining the BMPS with Other Organoids
(100) In some embodiments, BMPS may be combined with other organs and/or organ model systems. Several groups have been developing organ-on-a-chip platforms for different organs by using microfluidic techniques. Those platforms are designed to mimic in-vivo fluidic flows in the organs by separating cell culture chambers and perfusion channels, and successfully demonstrate recapitulation of iPSC-based organ functions. Together with other organ models on these platforms, the BMPS can be integrated, which allow us to untwine the complex toxicology from organ interactions. Such platforms allow (1) in-situ and high-throughput production of mini-brains on chip, (2) in-vivo like fluidic flow around mini-brains with enough supply of nutrient and small molecule through diffusion, (3) a large number of parallel test of toxic materials, and (4) a real-time monitoring of electrophysiological activities from BMPS with integrated electrodes. Companies such as TissUse GmbH have designed microfluidics platform that allow culture of floating spheres like the BMPS as described herein.
Example 12: Cryopreservation and Other Modes of Transportability
(101) In order to e.g. incorporate the BMPS into platforms or enable any use in other laboratories, transportability of the system was optimized. Preliminary studies have shown possible recovery of the neuronal 3D aggregates after cryopreservation (
(102) Human iPSC derived mini-brains are kept in culture at 37° C. In order to transport the live mini-brains, temperature must be controlled. Different methods can be used to control temperature during transport. Heating pads combined with an insulated box have been used to transport live biological material. Disposable chemical pads employ a one-time exothermic chemical reaction such as catalyzed rusting of iron, or dissolving calcium chloride. The most common reusable heat pads are based on a chemical reaction that transforms a liquid into a solid thus releasing energy. Some new heating pads (such as Deltaphase Isothermal Pad 3SET, from Braintree Scientific, Inc.) have been able to maintain 37° C. for more than 6 hours. 3D mini-brains cultured up to 8 weeks are sent in an insulated material box with heating pads. After transport, viability may be measured.
Example 13: Overview
(103) The techniques herein provide a human BMPS model that is a versatile tool for more complex testing platforms, as well as for research into CNS physiology, mechanisms associated with (developmental) neurotoxicity, and pathogenesis of neurological disorders. Prior art stem cell-derived brain model systems developed in the past few years have shown the capability to recapitulate some of the in vivo biological processes (Juraver-Geslin and Durand, 2015; Nakano et al., 2012; Krug et al., 2014) and have an advantage over other classical in vitro models as they facilitate the study of various differentiation mechanisms, developmental processes and diseases (Lancaster et al., 2013). Unfortunately, these prior art systems require complicated protocols that reduce the reproducibility of the system and make it difficult to use in other fields such as chemical toxicity and drug screening. Additionally, these prior art models are also limited by large diameters, which lead to extensive cell death in the interior regions due to insufficient diffusion of oxygen and nutrients (Lancaster et al., 2013) and other artifacts.
(104) The techniques herein overcome the limitations of the prior art by developing a human in vitro model by the gyratory shaking technique that enables reliably generation of a high number (about 500 per six-well plate) of viable BMPS that are homogeneous in size and shape. Control of size makes it possible to keep cell aggregates below 350 μM in diameter (
(105) As described herein, the 3D differentiation protocol for the BMPS covers stages from neuronal precursors to different cell types of the mature CNS. As discussed in detail above, at two weeks, BMPS consisted of an immature population of cells, showing minimal neuronal networks, a low percentage of mature astrocytes and oligodendrocytes, and minimal but early stages of myelin basic protein (MBP) expression. iPSC differentiation into mature BMPS was indicated by decreasing NES expression over time and a progressive expression of mature neuronal and glial markers such as MAP2, GFAP, 01 and MBP. Gene expression studies, flow cytometry, image analysis, immunostaining and miRNA studies have shown increase of cell maturation markers, which follow the BMPS differentiation. The presence of GABAergic neurons, dopaminergic neurons and glutamatergic neurons was documented by immunohistochemistry and real-time PCR data. Moreover, the BMPS showed spontaneous electrical activity, indicating neuronal functionality of the system.
(106) Since astrocytes and oligodendrocytes play important roles during neuronal development, plasticity and injury, the presence of glial cell populations in the presently disclosed BMPS model provides an excellent opportunity for the evaluation of neuronal-glial interactions and the role of glia in pathogenesis and toxicity processes. Astrocytes have an important role in protecting neurons, increasing neuronal viability and mitochondrial biogenesis from both exogenous (e.g. chemicals) and endogenous toxicity (Shinozaki et al., 2014; Aguirre-Rueda et al., 2015), especially against oxidative stress (Shao et al., 1997; Schwab and McGeer, 2008). Thus, their presence in a biological system to study disease and neurotoxicity is crucial. Immunohistochemistry and RT-PCR results showed increasing numbers of astrocytes (GFAP-positive cells) in the BMPS model reaching 19% astrocytes of the total cell population at eight weeks, which is earlier than in previously described cortical spheroids, where similar proportions of GFAP-positive cells were observed first at day 181, at day 86 the number of GFAP+ cells was below 10% (Pasca et al., 2015).
(107) The most novel element of this BMPS is the presence of mature human oligodendrocytes with myelination properties, which has not been achieved in the prior art. Immunocytochemical and ultrastructural studies confirmed the morphological identity of these cells (
(108) In conclusion, the techniques herein provide a BMPS that replicates crucial aspects of brain physiology and functionality. The potential for studying developmental and neurodegenerative disorders, brain infections, toxicity and trauma with such a system is growing. Furthermore, the potential to use iPSCs from different donors adds a personalized component to these studies. The high reproducibility and relatively simple protocol, enables future medium-throughput (96-well format) testing of chemicals, drugs and their potential to induce or treat diseases.
(109) Methods and Materials
(110) Chemicals
(111) Rotenone and MPP+ were supplied from Sigma-Aldrich (St. Louis, Mo.). A 10 mM rotenone stock was prepared in DMSO Hybri-Max (Sigma) while MPP+ was diluted in water to a concentration of 30 mM.
(112) iPSC Generation
(113) CCD1079Sk (ATCC® CRL2097™), IPS IMR90 (WiCELL) and ATCCDYP0730 Human (IPS) Cells (ATCC® ACS1003™) fibroblasts were originally purchased from ATCC. All studies followed institutional IRB protocols approved by the Johns Hopkins University School of Medicine. Human fibroblasts and mouse embryonic fibroblasts (MEFs) were cultured in Dulbecco's modified Eagle's medium (DMEM, Mediatech Inc.) supplemented with 10% fetal bovine serum (FBS, HyClone) and 2 mM L-glutamine (Invitrogen). MEFs were derived from E13.5 CF-1 mouse embryos. Human iPCS cells were generated with the EBV-based vectors as previously described [75]. iPSC from other sources were used as well. Colonies of iPSCs were manually picked after 3-6 weeks for further expansion and characterization. iPSCs (passage ≤20) were cultured on irradiated MEFs in human embryonic stem cell (hESC) medium comprising D-MEM/F12 (Invitrogen), 20% Knockout Serum Replacement (KSR, Invitrogen), 2 mM L-glutamine (Invitrogen), 100 μM MEM NEAA (Invitrogen), 100 μM β-mercaptoethanol (Invitrogen), and 10 ng/mL human basic FGF (bFGF, PeproTech). Media were changed daily and iPSC lines were passaged using collagenase (Invitrogen, 1 mg/ml in D-MEM/F12 for 1 hr at 37° C.). These iPSC lines have been previously fully characterized [75].
(114) Neuronal Progenitor Cells (NPC) Production
(115) NPC generated followed the previous published protocol [75]. Briefly, iPSCs colonies were detached from the feeder layer with collagenase (1 mg/ml) treatment for 1 hr and suspended in EB medium, comprising of FGF-2-free hESC medium supplemented with Dorsomorphin (2 μM) and A-83 (2 μM), in non-treated polystyrene plates for 4 days with a daily medium change. After 4 days, EB medium was replaced by neural induction medium (hNPC medium) comprising of DMEM/F12, N2 supplement, NEAA, heparin (2 μg/ml) for 15 more days. The floating neurospheres were then dissociated to single cells in Accutase and plated in 175 mm flasks and were allowed to expand for 7 days. NPCs were expanded in poly-1-ornithine and laminin-coated 175 mm flask on StemPro® NSC SFM (Life Technologies). Half of the media was changed every day. Cultures were maintained at 37° C. in an atmosphere of 5% CO.sub.2. After NPC generation, iPSCs colonies were detached and NPCs were expanded in poly-1-ornithine and laminin-coated 175 mm flask in StemPro® NSC SFM (Life Technologies). Half of the media was changed every day. Cultures were maintained at 37° C. in an atmosphere of 5% CO2.
(116) BMPS Differentiation
(117) At 100% confluence NPCs were detached mechanically and counted. 2×10.sup.6 cells per well were plated in 2 ml of medium in non-treated 6 well-plates. Cells were grown in NPC media for two days under constant gyratory shaking. Subsequently, medium was changed to differentiation medium (Neurobasal® electro Medium (Gibco) supplemented with 5% B-27® Electrophysiology (Gibco), 1% glutamax (Gibco), 0.02 μg/ml human recombinant GDNF (Gemini), 0.02 μg/ml human recombinant BDNF (Gemini)). Cultures were maintained at 37° C., 5% CO.sub.2 under constant gyratory shaking for up to 8 weeks. Differentiation medium was routinely changed every 2 days.
(118) Size Measurement
(119) Aggregates (n=20) from 3 independent experiments were randomly selected per time point for obtaining pictures and measuring size using SPOT software 5.0. Results were expressed as mean±SD. Cells were kept two days in NPC medium, indicated as NPC med. 2d in
(120) RNA and miRNA Extraction
(121) Total RNA was extracted from aggregates every week up to 8 weeks of differentiation using Tripure (Roche, Switzerland) according to Chomczynski and Sacchi (1987) [76]. The same RNA extraction method was used to isolate RNA after toxicant treatment. RNA quantity and purity was determined using NanoDrop 2000c (Thermo Scientific). One microgram of RNA was reverse-transcribed using the M-MI V Promega Reverse Transcriptase (Promega) according to the manufacturer's recommendations. For miRNA reverse-transcription 60 ng of RNA were reverse transcribed using TaqMan microRNA Reverse transcription kit in combination with miRNA specific stem-loop primers, which are a part of TaqMAn microRNA expression assay. Upto eight stem-loop primers were multiplexed in one reaction.
(122) Quantitative RT-PCR
(123) The expression of genes was evaluated using specific Taqman® gene expression assays (Life Technologies). miRNA expression was analyzed using TaqMAn microRNA expression assay in combination with TaqMan miRNA Reverse Transcription kit using protocol described in [77]. Table 1 shows a summary of the genes assayed. Real time RT-PCRs were performed using a 7500 Fast Real Time system machine (Applied Biosystems). Fold changes were calculated using the 2(−ΔΔCt) method [78]. β-actin and 18s were used as a housekeeping genes for mRNA and RNU44 for miRNA. There were no statistically significant differences in expression for β-actin, 18s, and RNU44. Data were presented as mean±SD, normalized to housekeeping genes and week 0.
(124) Immunocytochemistry of the BMPS
(125) BMPS aggregates were collected at 2, 4 and 8 weeks. BMPS were fixed in 4% paraformaldehyde for 1 hour, washed 3 times in PBS, then incubated for 1 hour in blocking solution consisting of 5% normal goat serum (NGS) in PBS with 0.4% TritonX (Sigma). BMPS were then incubated at 4° C. for 48 hours with a combination of primary antibodies (Table 2) diluted in PBS containing 3% NGS and 0.1% TritonX. BMPS were washed in PBS 3 times after which they were incubated with the appropriate fluorophore-tagged secondary antibody for 1 hour in PBS with 3% NGS at room temperature. Double immunostaining was visualized using the proper combination of secondary antibodies (e.g., goat anti-rabbit secondary antibody conjugated with Alexa 594 and goat anti-mouse secondary antibody conjugated with Alexa 488 (Molecular Probes). Nuclei were counterstained with DRAQ5 dye (Cell Signaling; 1:5000 in 1×PBS) or NucRed Live (Molecular Probes) for 15 minutes before mounted on slides with coverslips and Prolong Gold antifade reagent (Molecular Probes); BMPS used as negative controls for immunostaining were processed omitting the primary antibody. Images were taken using a Zeiss UV-LSM 510 confocal microscope. The experiments were performed in duplicates; at least three different fields of view were analyzed for each combination of antibodies. 3D reconstruction was done using Imaris 7.6.4 software for scientific imaging.
(126) TABLE-US-00072 TABLE 2 Primary Antibodies. Antibody Host Type Source Dilution NF-H Rabbit Polyclonal Enzo 1:1000 GFAP Rabbit Polyclonal Dako 1:500 Olig1 Mouse Monoclonal Millipore 1:500 CNPase Mouse Monoclonal Millipore 1:500 Calbindin Mouse Monoclonal SIGMA 1:500 NOGO-A Rabbit Polyclonal Santa Cruz 1:500 Map2 Mouse Monoclonal Chemicon 1:1000 MBP/SMI99 Mouse Monoclonal COVANCE 1:1000 SMI-32 Mouse Monoclonal Stenberger 1:2000 Monoclonals Synaptophysin Mouse Monoclonal SIGMA 1:500 VGLUT1 Rabbit Polyclonal Alpha Diagnostic 1:500 TH Mouse Monoclonal Millipore 1:250 Nestin Rabbit Polyclonal Millipore 1:200 Ki67 Rabbit Polyclonal abcam 1:100 Caspase3 Rabbit Polyclonal R&D 0.2 μg/ml OLIG1 Mouse Monoclonal Millipore 1:200 TUJ1 Mouse Monoclonal Stemcell 1:200 technologies S100B Rabbit Polyclonal Santa Cruz 1:200
Automated Quantitation of Cell Types
(127) BMPS was differentiated for 8 weeks. Randomly selected pictures from three experiments were acquired by confocal imaging and then analyzed with a custom algorithm created with the Cellomics TargetActivation (Thermo Fisher Scientific, Pittsburgh, Pa.) image-analysis software package. With this algorithm, cells were identified based on DRAQ5 stained nucleus and quantified oligodendrocytes and astrocytes based on staining of CNPase, NOGO1 and GFAP.
(128) Myelination Assessment and Quantification
(129) To calculate the percentage of axonal myelination, a semi-automated computer platform was used, termed computer-assisted evaluation of myelin formation (CEM) [82], which uses NIH Image J built-in tools as well as a Math lab processing functions. The results were generated as pixel counts and percent values. The percent of myelinated axons was calculated by dividing the pixel count for myelin by the pixel count for axons after cell body removal and multiplying by 100. For each time point at least 18 fields from at least two independent experiments were analyzed.
(130) Electron Microscopy
(131) BMPS aggregates were collected at 2, 4 and 8 weeks and were fixed in 2% glutaraldehyde and 4% formaldehyde in 0.1M Sodium Cacodylate buffer (EMS, electron microscopy sciences) pH 7.4 with 3% sucrose and 3 mM CaCl.sub.2. Post-fixation was done with 2% osmium for 2 hours. The BMPS aggregates were then stained en bloc with 2% uranyl acetate in distilled water for 30 min and subsequently dehydrated in graded ethanol. Embed 812 (EMS) was used as the embedding media. Thin sections (70-80 nm) were cut on a Reichert Jung Ultracut E microtome and placed on formvar coated 100 mesh copper grids. The grids were stained with uranyl acetate and followed by lead citrate. All imaging was performed on a Zeiss Libra 120 electron microscope with a Veleta (Olympus) camera.
(132) Treatment and Cytotoxicity Assay
(133) BMPS was exposed to different concentrations of rotenone and MPP+ for 24 and 48 hours after 4 weeks of differentiation. Rotenone working solutions were prepared in differentiation medium from 10 nM or 100 μM stocks to reach final concentrations of 0.1, 1, 10, 25 and 50 μM. DMSO was used as vehicle control. MPP+ working solutions were prepared in differentiation medium from 30 mM stocks to reach final concentrations of 10, 50, 100, 500, 1,000, 5,000 and 10,000 μM. Four independent experiments in 3 replicates were performed for each experimental condition (control and toxicant exposure for the different time points). Resazurin reduction assay was performed in order to determine cell viability after rotenone and MPP+ treatment. Resazurin (7-Hydroxy-3H-phenoxazin-3-one 10-oxide) is a blue dye that is reduced into red fluorescent resorufin by redox reactions in viable cells. 100 μl Resazurin (2 mg/ml stock) were added directly to the 6 well plates (2 ml/well). Plates were incubated for 3 h at 37° C., 5% CO.sub.2. Subsequently, 50 μl of medium were transferred from each well in triplicates to a 96-well plate and fluorescence was measured at 530 nm/590 nm (excitation/emission) using a multi-well fluorometric reader CytoFluor series 4000 (PerSeptive Biosystems, Inc). Data were presented as mean±SD. Statistical analysis was performed using Dunnett's test.
(134) Reactive Oxygen Species Measurement
(135) Reactive oxygen species (ROS) were measured in cell media collected 24 hours after treatment with 5 μM rotenone or 1,000 μM MPP+ using the OxiSelect™ In Vitro ROS/RNS Assay Kit (Cell Biolabs, San Diego, Calif.). This is a fluorescence-based assay measuring the presence of total free radicals within a sample and was used according to the manufacturer's protocol. The quenched fluorogenic dye dichlorodihydrofluorescin-DiOxyQ (DCFH-DiOxyQ) which is similar to the popular 2′,7′-dichlorodihydrofluorescein diacetate (DCFH-DA) is first primed with a quench removal reagent. The resulted highly reactive non-fluorescent DCFH can react with present ROS species in the cell supernatant and is then oxidized to the highly fluorescent DCF (2′,7′-dichlorodihydroxyfluorescein). At every time point, 50 μl of the cell supernatant was added to a 96-well plate in triplicates and was mixed and incubated with the DCFH-DiOxyQ for 45 minutes. The fluorescence intensity was measured with a fluorescence microplate reader at 480 nm/530 nm (excitation/emission) and was proportional to the total ROS/RNS levels within the sample.
(136) Flow Cytometry
(137) In order to quantify percentage of NPCs, and neurons within the aggregates, flow cytometry with NPC and neuronal markers was performed. Flow cytometry was performed according to previously published protocol [77] with some optimization steps for 3D cultures. Aggregates were washed once with PBS/1 mM EDTA and trypsinized directly in the well using TrypLE Express containing 4 units/ml DNAse for 30 min at 37° C. on the shaker. Pipetting the aggregates up and down with a 1 ml syringe and a 26G3/8 needle ensured generation of single cell suspension. Cells were counted, washed once with PBS/1 mM EDTA, fixed with 2% PFA for 20 min at 4° C., washed twice with PBS/1% BSA (wash solution I, WS I) and blocked for 30 min in blocking solution (PBS/1% BSA/0.15% saponin/10% NGS). 1×10.sup.6 cells were stained for one hour at 4° C. with fluorochrome-conjugated antibodies dissolved in blocking solution (Table 3). Unstained cells as well as cells incubated with isotype controls were used as negative controls to set the gates for measurements. Cells were washed twice with PBS/1% BSA/0.15% saponin, once with PBS/1% BSA. Flow cytometry was performed using a Becton Dickinson FACSCalibur system by measuring 10.sup.4 gating events per measurement. Data was analyzed using FlowJo v10 software.
(138) TABLE-US-00073 TABLE 3 Antibodies for flow cytometry analysis Antibodies Host type Source Dilution Alexa Fluor ® Mouse Monoclonal, BD Pharmingen 1:05 647 Nestin clone 25 Alexa Fluor ® Mouse Monoclonal, BD Pharmingen 1:05 488 β-III- clone TUJ1 Tubulin PerCP-Cy ™ Mouse Monoclonal, BD Pharmingen 1:20 5.5 Sox2 clone 030-678 PerCP-Cy ™ Mouse Monoclonal, BD Pharmingen 1:20 5.5 Sox1 clone N23-844 PE Doublecortin Mouse Monoclonal, BD Pharmingen 1:20 clone 30 Alexa Fluor ® Mouse Monoclonal, BD Pharmingen 1:20 647 Ki67 clone B56
Microelectrode Array (MEA) Recordings
(139) After 8 weeks of differentiation, BMPS were plated on 48-well MEA plates previously coated with Matrigel. During two weeks spontaneous electrical activity was recorded using the ‘Maestro’ MEA platform and Axion's Integraded Studio (AXIS) software [Axion Biosystems inc.; Atlanta, US]. Each well of the 48-well MEA plate contains 16 individual microelectrodes (˜40-50 μm diameter, center-to-center spacing 350 μm) with integrated ground electrodes, resulting in a total of 768 electrodes/plate. The ‘Maestro’ MEA platform has an integrated heating system, which can be controlled by AXIS software. All recordings were performed at a constant temperature of 37° C. Prior to a twenty minutes recording, the MEA plates were placed in the Maestro MEA platform and equilibrated for five min. AXIS software was used to control heating system and monitor the recordings, which includes simultaneously sampling of the channels at 12.5 kHz/channel with a gain of 1200× and a band pass filter of 200-5000 Hz. The recordings were converted into RAW files. After a recording the RAW-files were re-recorded with AXIS to convert the data into a spike file, which includes spike timing and profile information. A variable threshold spike detector was used for the spike-file, it was set at 6 times standard deviations of the rms-noise on each channel. The spike file was later used for data analysis with NeuroExplorer® [Nex Technologies, Madison (AL), US] to convert data into Microsoft Excel files. Using the function rate histogram, a summary of the spikes of all electrodes of one plate was put into one Excel sheet. Only electrodes that recorded activity higher than 0.05 spikes/sec at least once over the time measured were included for data analysis.
(140) Statistical Analysis
(141) Statistical analysis was performed using GraphPad InStat 3. The Dunnett's test was applied to all the experiments shown here that compare to a control group. Statistically significant values (p<0.01) are marked with an asterisk (*). For myelination quantification at the different time points, a Kruskal-Wallis test was employed, statistical significance was considered for p values <0.05.
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EQUIVALENTS
(143) Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.