Three-dimensional fibroblast aggregate and in vitro 3D skin dermis model comprising same

Abstract

Provided are a three-dimensional (3D) fibroblast cluster, a method of preparing the same, an in vitro 3D skin dermis model including a fibroblast cluster cultured from a fibroblast, and a method of screening a drug by using the in vitro 3D skin dermis model.

Claims

1. A method of producing a fibroblast cluster, the method comprising: culturing fibroblasts in a culture broth in a culture container having a surface coated with a protein having fibroblast-binding activity; obtaining a culture including a fibroblast cluster that is formed by detaching the cultured fibroblasts from the surface; and separating the fibroblast cluster from the culture, wherein binding between the protein having fibroblast-binding activity and fibroblasts is weaker than binding between fibroblasts.

2. The method of claim 1, wherein, in the culturing of fibroblast, the fibroblast is initially adhered to the surface of the culture container for proliferation, but as growing, the fibroblast is detached from the surface of the culture container.

3. The method of claim 1, wherein the protein having fibroblast-binding activity weakly binds to the fibroblast as compared with binding between fibroblast and a fibronectin in the culture broth.

4. The method of claim 1, wherein the protein having fibroblast-binding activity does not bind to integrin present in a cell membrane of the fibroblast.

5. The method of claim 1, wherein the protein having fibroblast-binding activity binds to heparan sulfate proteoglycan present in a cell membrane of the fibroblast.

6. The method of claim 1, wherein the protein having fibroblast-binding activity is a fibroblast growth factor (FGF).

7. The method of claim 1, wherein the protein is immobilized on the surface of the culture container by connecting the protein to one of the group consisting of a maltose-binding protein (MBP), hydrophobin, and a hydrophobic cell penetrating peptide (CPP), or a combination thereof.

8. The method of claim 1, wherein the surface of the culture container is a hydrophobic surface selected from the group consisting of a silanized surface, a hydrocarbon coated surface, a polymer surface, and a metallic surface.

9. The method of claim 1, wherein the culturing of the fibroblast is performed for 1 day to 1 week.

10. The method of claim 1, wherein the separating of the formed fibroblast cluster from the culture is carried out without treatment of enzyme.

11. A method of preparing an in vitro three-dimensional (3D) artificial skin model, the method comprising: culturing fibroblasts in a culture broth container having a surface coated with a protein having fibroblast-binding activity to thereby obtain a culture including a fibroblast cluster that is formed by detaching the cultured fibroblasts from the surface, wherein binding between the protein having fibroblast-binding activity and fibroblasts is weaker than binding between fibroblasts; and further culturing the fibroblast cluster from the obtained culture for at least 12 hours.

12. The method of claim 11, wherein the protein having fibroblast-binding activity does not bind to integrin present in a cell membrane of the fibroblasts.

13. The method of claim 11, wherein the fibroblast cluster that is further cultured for at least 12 hours decreases expression or activity of collagen, or increases activity or expression of matrix metalloproteinase (MMP).

14. The method of claim 11, the fibroblast cluster additionally decreases expression or activity of fibronectin, or increases expression or activity of elastin.

Description

DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram showing a preparation process of a three-dimensional (3D) fibroblast cluster according to an embodiment;

(2) FIG. 2 is a graph showing cell adhesion levels of fibroblasts according to an embodiment, the levels being quantified according to contents of proteins;

(3) FIG. 3 shows fluorescence staining images of cell morphology of fibroblasts according to an embodiment;

(4) FIG. 4 shows results of phosphorylation activity of FAK in fibroblasts according to an embodiment;

(5) FIG. 5 is a diagram showing formation of a 3D fibroblast cluster according to an embodiment;

(6) FIG. 6 is a diagram showing formation of a 3D fibroblast cluster according to an embodiment;

(7) FIG. 7 shows results of Haematoxylin and Eosin (H&E) staining on a 3D fibroblast cluster according to an embodiment;

(8) FIG. 8 shows results of immunofluorescence staining on collagen type I in a 3D fibroblast cluster according to an embodiment;

(9) FIG. 9 is a diagram showing secretion levels of VEGF in a 3D fibroblast cluster according to an embodiment;

(10) FIG. 10 is a diagram showing microscopic observation of a formation process of a 3D fibroblast cluster according to an embodiment;

(11) FIG. 11 is a graph showing relative expression levels of extracellular matrix-related genes in a 3D fibroblast cluster according to an embodiment;

(12) FIG. 12 is a graph showing hydroxyproline assay results of measuring a collagen amount in a 3D fibroblast cluster according to an embodiment;

(13) FIG. 13 is a graph showing immunostaining results of measuring an expression level of collagen type I in a 3D fibroblast cluster according to an embodiment;

(14) FIG. 14 is a diagram showing western blotting results of measuring an expression level of collagen type I in a 3D fibroblast cluster according to an embodiment;

(15) FIG. 15 is a graph showing expression levels and secretion levels of MMP 1 by a 3D fibroblast cluster according to an embodiment;

(16) FIG. 16 is a graph showing secretion levels of MMP1 in cells after the cells are treated with an MMP1 inhibitor in a 3D fibroblast cluster according to an embodiment;

(17) FIG. 17 is a graph showing secretion levels of MMP1 in cells, after fibroblasts that are cultured two-dimensionally and irradiated with ultraviolet rays to induce overexpression of MMP1 was treated with an MMP1 inhibitor, and

(18) FIG. 18 is a schematic diagram showing a drug-screening device including a 3D fibroblast cluster according to an embodiment, and a method of screening a drug by using the drug-screening device.

MODE OF THE INVENTION

(19) Hereinafter, the present invention is described in detail with reference to Examples. However, Examples shown and described herein are illustrative examples of the present invention and are not intended to otherwise limit the scope of the inventive concept in any way.

Example 1: Formation of 3D Fibroblast Cluster and Analysis of Characteristics of the 3D Fibroblast Cluster

(20) In present Example, fibroblasts were cultured in a culture container including a surface coated with a fibroblast-binding protein, thereby forming a 3D fibroblast cluster.

(21) FIG. 1 is a schematic diagram showing a preparation process of the 3D fibroblast cluster according to an embodiment.

(22) Referring to FIG. 1, fibroblasts were seeded onto a culture container coated with MBP-FGF2. Then, the fibroblasts were cultured in a 2D manner on a surface of the culture container, and separated from the surface. Such separated or delocalized 2D fibroblast cluster was then continuously cultured while floating in the culture container, and after one day, a 3D fibroblast cluster was formed. The 3D fibroblast cluster formed according to an embodiment was confirmed to have capability of secreting an extracellular matrix and a vascular endothelial growth factor (VEGF). Hereinafter, the formation process of the 3D fibroblast cluster shown in FIG. 1, and methods and results of analyzing characteristics of the 3D fibroblast cluster will be described.

(23) (1) Analysis of Cell Adhesion Characteristics of Fibroblasts and Morphological Changes of Fibroblasts after Adhesion

(24) To establish a culture method for inducing formation of a 3D fibroblast cluster, cell adhesion characteristics of fibroblasts, and cell adhesion signals and cell morphology upon adhesive features of fibroblasts were analyzed

(25) (1.1) Analysis of Cell Adhesion Characteristics of Fibroblasts

(26) A non-tissue culture treated 96-well plate (NTCP) (NTCP made of polystyrene and including a hydrophobic surface, Falcon Company) was coated with each of ECM fibronectin (20 g/ml), MBP (10 g/ml), MBP-VEGF (10 g/ml), MBP-HBD (100 g/ml), and MBP-FGF2 (10 g/ml) for 4 hours, and then, washed three times with PBS. Afterwards, the NTCP was blocked with 100 g/ml of BSA for 1 hour, and washed three times with PBS. 510.sup.4 cells/cm.sup.2 of fibroblasts per well were suspended in a serum-free DEME culture medium, and then, seeded onto the NTCP coated with each of the proteins above. The cells were subjected to lysis for 1 hour in an incubator at a temperature of 37 C., and the morphology of the cells was observed. The adhered cells were subjected to lysis by using a cell lysis buffer, and then, quantified by measuring each of the proteins according to bicinchoninic acid (BCA) assay.

(27) FIG. 2 is a graph showing cell adhesion levels of the fibroblasts according to an embodiment, the levels being quantified according to contents of proteins.

(28) As shown in FIG. 2, the NTCPs coated with BSA, MBP, and MBP-VEGF showed no cell adhesion. Meanwhile, 1 hour after the cell seeding, the NTCP coated with MBP-FGF2 showed a lower cell adhesion level than that of the NTCP coated with ECM-fibronectin, wherein ECM-fibronectin binds to integrins of a cell membrane.

(29) (1.2) Analysis of Cell Morphology of Fibroblasts by Adhesiveness

(30) To compare the cell morphology of the fibroblasts cultured in the NTCP according to Example 1(1.1) coated with each of fibronectin and MBP-FGF2, palloidin staining was performed on the fibroblasts that have been cultured for 30 minutes, 1 hour, and 4 hours after the adhesion.

(31) FIG. 3 shows fluorescence staining images of the cell morphology of the fibroblasts according to an embodiment.

(32) As shown in FIG. 3, it was confirmed that the fibroblasts adhered to MBP-FGF2 had a cytoskeleton that is not activated as much as that of the fibroblasts adhered to fibronectin. That is, as compared with the fibroblasts adhered to fibronectin, the fibroblasts adhered to MBP-FGF is meant to have limited activity in cell adhesion mediated by integrins, which are cell adhesion molecules present in a cell membrane.

(33) (1.3) Analysis of Cell Adhesion Signals of Fibroblasts by Adhesiveness

(34) To compare cell adhesion signals of the fibroblasts cultured in the NTCP according to Example 1(1.1) coated with each of fibronectin and MBP-FGF2, phosphorylation of focal adhesion kinase (FAK) in the fibroblasts was measured. To measure phosphorylation of FAK, the western blotting analysis using phospho-FAK antibody (Cell Signaling Company) was performed on the fibroblasts that have been cultured for 30 minutes, 1 hour, and 4 hours after the adhesion.

(35) FIG. 4 shows the phosphorylation activity of FAK in the fibroblasts according to an embodiment.

(36) As shown in FIG. 4, it was confirmed that the fibroblasts adhered to MBP-FGF2 showed less phosphorylation of FAK than the fibroblasts adhered to fibronectin. That is, as compared with the fibroblasts adhered to fibronectin, the fibroblasts adhered to MBP-FGF is meant to have limited activity in cell adhesion mediated by integrins.

(37) (2) Formation of 3D Fibroblast Cluster

(38) Based on the results of Examples 1(1.3) to 1(1.3), a culture method for forming a 3D fibroblast cluster was established.

(39) Fibroblasts were seeded onto each of 12, 24, 48, and 96-well NTCPs at a concentration of 0.510.sup.4 cells/cm.sup.2 to 1.510.sup.5 cells/cm.sup.2 per well, the NTCPs containing high-concentration glucose DMEM culture medium (FGM culture medium) and including a polystyrene surface coated with MBP-FGF2. The fibroblasts were then cultured in a stationary incubator at a temperature of 37 C. for 1, 2, and 3 days. The fibroblasts existing in the form of a sheet at the beginning of the culture were separated from the surface of the culture container over time, and accordingly the fibroblasts were present as a cell cluster from the first day of the culture and can be then easily collected by pipette without enzyme such as trypsin.

(40) FIG. 5 is a diagram showing the formation of a 3D fibroblast cluster according to an embodiment.

(41) As shown in FIG. 5, it was confirmed that, when cultured in the FGM culture medium, the formation of the 3D fibroblast cluster was effectively induced at a cell concentration of at least 1.2510.sup.5 cells/cm.sup.2. When cultured under conditions of the culture at a lower cell concentration than the above, an intracellular distance required for the cell-cell interactions was not close enough so that a cell cluster may not be easily formed. A cell cluster may be also formed in a culture medium other than the FGM culture medium, but such a cell cluster formed therefrom may require a higher cell concentration than that of cells constituting the cell cluster formed in the FGM culture medium.

(42) FIG. 6 is a diagram showing the formation of a 3D fibroblast cluster according to an embodiment.

(43) As shown in FIG. 6, it was confirmed that, depending on a well size, a 3D spherical cell cluster having a size detectable with the naked eye on the surface coated with MBP-FGF2, for example, a size in a range of about 400 m to about 1,000 m, was formed.

(44) (3) Analysis of Secretion Ability of 3D Fibroblast Cluster

(45) (3.1) Analysis of Ability of Extracellular Matrix (ECM) Secretion

(46) The 3D cell cluster formed by seeding cells at a concentration of 1.2510.sup.5 cells/cm.sup.2 onto the NTCPs (12-well, 24-well, 48-well, and 96-well) of Examples 1(2) coated with various types of MBP-FGF2 was washed several times with PBS, and then, immobilized by treatment using 4% paraformaldehyde at room temperature for 30 minutes. Afterwards, the resulting 3D cell cluster was dehydrated with ethanol at various concentrations (50-100%), and then, embedded in paraffin. A paraffin block formed therefrom was cut to a thickness of 4 m by using a microtome, fixed on a slide glass, and then, subjected to H&E staining and immunofluorescence staining with respect to fibronectin and collagen type I. The staining of collagen type I was carried out according to immunofluorescence staining. The prepared slide glass was first treated with BSA (4%) for 1 hour, and immersed in PBS containing primary antibodies overnight for a reaction. The slide glass was washed three times with PBS, and allowed again for a reaction with secondary antibodies for 1 hour in a dark room. Nuclear staining using DAPI was additional performed, and the results were analyzed by using a confocal microscope. Here, a control group was subjected to analysis performed under the same conditions, except that no primary antibody was used

(47) FIG. 7 shows the results of H&E staining on the 3D fibroblast cluster according to an embodiment.

(48) As shown in FIG. 7, it was confirmed that one day after the culture, fibroblasts treated at the same concentration in all wells formed a cell cluster.

(49) FIG. 8 shows the results of immunofluorescence staining on collagen type I in the 3D fibroblast cluster according to an embodiment.

(50) As shown in FIG. 8, it was confirmed that collagen was stained throughout the 3D fibroblast cluster so that collagen was secreted during the formation of a cell cluster.

(51) (3.2) Analysis of Levels of Vascular Endothelial Growth Factor (VEGF) Secretion

(52) The 3D cell cluster formed by seeding cells at a concentration of 1.2510.sup.5 cells/cm.sup.2 onto the of 96-well NTCP Example 1(2) coated with MBP-FGF2 were collected to measure levels of VEGF secretion.

(53) In detail, the formed 3D cell clusters were collected in tens, transferred to a 6-well NTCP, and then, washed once with PBS. Additionally, the cell clusters were washed once with FBS-free alpha MEM (Lonza Company), and alpha MEM (1.5 mL) was added thereto to be cultured in a stationary incubation for one day. Afterwards, a culture broth was obtained for each predetermined date, and an equivalent fresh culture broth was added. The VEFG present in the obtained culture broth was then quantified by using the ELISA kit (R&D Company). A method of using the kit was proceeded according to the supplier's protocol. FIG. 9 is a diagram showing the secretion levels of VEGF in the 3D fibroblast cluster according to an embodiment.

(54) FIG. 9 is a diagram showing the secretion levels of VEGF in the 3D fibroblast cluster according to an embodiment.

(55) As shown in FIG. 9, it was confirmed that the level of VEGF in the 3D fibroblast cluster increased more than twice as much as that of VEGF in the cells cultured in a 2D manner.

Example 2: Preparation of In Vitro 3D Artificial Dermis Model and Characterization of Dermis Model

(56) (1) Preparation of In Vitro 3D Artificial Dermis Model

(57) To prepare an in vitro 3D artificial dermis model, fibroblasts were first cultured. In detail, human dermal fibroblasts were cultured in high glucose Dulbecco's modified Eagle's medium (DMEM, Welgene, Daegu, South Korea) by using a tissue culture flask under conditions of 37 C., 5% CO.sub.2, and 95% O.sub.2 atmosphere. Human dermal fibroblasts of 5 passages were used for all experiments.

(58) Next, a culture container for culturing fibroblasts in a 3D manner was prepared as follows. An NTCP (NTCP made of polystyrene and including a hydrophobic surface, Falcon Company) was coated with maltose binding protein (MBP)-fibroblast growth factor (FGF) (20 g/ml) at room temperature for 4 hours. The NTCP was washed three times with PBS, and then, unbound MBP-FGF was removed therefrom. A detailed manufacturing method for the culture container is disclosed in KR 10-2010-0122778, which is incorporated herein by reference in its entirety.

(59) The fibroblasts were seeded onto the culture container, thereby preparing a 3D fibroblast cluster. In detail, fibroblasts were seeded onto the 96-well NTCP containing fibroblast growth medium (FGM, Lonza) at a concentration of 1.2510.sup.5 cells/cm.sup.2 per well, and cultured at a temperature of 37 C. The fibroblasts were cultured in a 2D manner on a surface of the culture container, and separated from the surface. Such separated or delocalized 2D fibroblast cluster was then continuously cultured while floating in the culture container, and within 24 hours, a 3D fibroblast cluster was formed spontaneously. The formed 3D fibroblast cluster was collected on the 1.sup.st day (Day 1), 3.sup.rd day (Day 3), and 5.sup.th day (Day 5) of the culture. The formation of the 3D fibroblast cluster consisting of adhesive fibroblasts was observed with a phase contrast microscope (Carl Zeiss, Germany), and the results are shown in FIG. 10. Hereinafter, the 3D fibroblast cluster was represented by 3DCM.

(60) In addition, as a comparative example, the fibroblasts were cultured in a 2D manner. In detail, 1.2510.sup.5 cells/cm.sup.2 of adipose stem cells were inoculated into each well of a 96-well tissue culture plate (TCP), and cultured in a fibroblast growth medium (FGM, Lonza Company). In the same manner as in the 3D cell cluster, cells were collected on the 1.sup.st day (Day 1), 3.sup.rd day (Day 3), and 5.sup.th day (Day 5) of the culture for analysis of characteristics of an artificial dermis model. Hereinafter, the cells cultured in a 2D manner are represented by 2D cells.

(61) FIG. 10 is a diagram showing the microscopic observation of the formation process of a 3D fibroblast cluster according to an embodiment.

(62) As shown in FIG. 10, it was confirmed that a 3D spherical cell cluster having a size detectable with the naked eye, for example, a size in a range of about 400 m to about 1,000 m, was formed.

(63) (2) Analysis of Characteristics of In Vitro 3D Artificial Dermis Model

(64) The following experiment was carried out to analyze the characteristics of the 3D fibroblast cluster prepared above.

(65) (2.1) Analysis of Expression of Extracellular Matrix (ECM) Gene in 3D Fibroblast Cluster

(66) To analyze expression amounts of ECM-related genes, such as genes of collagen, fibronectin, and elastin, qantitative real-time polymerase chain reaction (qRT-PCR) was used.

(67) In detail, total RNAs were extracted from the 3D cell cluster and the 2D cells at different times (on the 1.sup.st, 3.sup.rd, and 5.sup.th day of the culture) according to the manufacturer's instructions using a Qiagen miniprep kit (Qiagen Inc., USA). The extracted RNAs were dissolved in nuclease-free water, and then, the concentration of the resulting RNAs was quantified using a NanoDrop ND1000 spectrophotometer (Thermo Fisher Scientific). Here, synthesis of complementary DNA was performed by using Maxime RT PreMix (iNtRon, South Korea) according to the manufacturer's instructions. All target primers were purchased from Bioneer (South Korea). All polymerase chain reactions were performed using ABI Prism 7500 (Applied Biosystems), and gene expression levels were quantified using SYBR Premix Ex Taq (TaKaRa, Japan). Relative gene expression levels were calculated using the comparative (Ct) method, and the results are shown in FIG. 11.

(68) FIG. 11 is a graph showing relative expression levels of ECM-related genes in a 3D fibroblast cluster according to an embodiment.

(69) As shown in FIG. 11, it was confirmed that expression levels of genes of collagen type I and fibronectin were almost three times lower in the 3D cell clusters than those of genes of collagen type I and fibronectin in the 2Dcells, and that expression levels of genes of elastin increased in the 3D cell cluster as compared with those of genes of elastin in the 3D cell cluster. In particular, in the case of elastin, the expression levels of genes thereof were similar in the 2D cells and the 3D cell cluster on the first day of the culture. However, from the third day of the culture, the expression levels of genes of elastin significantly increased in the 3D cell cluster. Consequently, it was confirmed that, in the 3D fibroblast cluster according to an embodiment, the expression of collagen and fibronectin decreased, whereas the expression of elastin increased. Thus, the 3D fibroblast cluster was able to mimic the environment of skin dermis, and accordingly, was able to be utilized for the development of materials targeting the 3D fibroblast cluster.

(70) (2.2) Analysis of Collagen Expression by 3D Fibroblast Cluster

(71) To analyze collagen in the 3D fibroblast cluster, hydroxyproline assay, immunostaining, and western blotting were performed on the 3D fibroblast cluster.

(72) In detail, for the hydroxyproline assay, RIPA buffer (Sigma-Aldrich) was used to collect 2D cells and 3D cell clusters (including 310.sup.6 cells) at different times (on the 1.sup.st, 3.sup.rd, and 5.sup.th day of the culture), and the collected cells 2D cells and 3D cell clusters were hydrolyzed in a 12 N HCl solution at a temperature of 120 C. for 3 hours. The assay was performed according to the manufacturer's instructions using a hydroxyproline kit (Sigma-Aldrich). Here, the absorbance was measured using a Multisakn meter (Thermo) at 560 nm, and the results are shown in FIG. 12.

(73) For the immunostaining, the 3D cell clusters and 2D cells collected at different times were washed three times with PBS, and immobilized with 4% PFA for 30 minutes. Then, the resulting product was embedded in an optimal cutting temperature (OCT) compound (TISSUE-TEK.sup.C.sup.c 4583; Sakura Finetek USA, Inc.), frozen at a temperature of 28 C., and cut to a thickness of 6 m. To avoid nonspecific binding thereto, a section was incubated in BSA (4%) at room temperature for 1 hour. Afterwards, the section was incubated overnight at a temperature of 4 C. with primary antibodies (Rabit, Abicam) that were specific to collagen type I. Then, a sample on the section was washed with PBS, and incubated for 1 hour with corresponding fluorescent conjugated secondary antibodies (Donkey anti-rabbit)(Life Technologies) in 1% BSA. In addition, 4,5-diamino-2-phenylindole (DAPI) (Vector Laboratories) was used for nuclear staining. Here, a control group was subjected to experiments performed under the same conditions, except that no primary antibody was used, and was observed with a confocal microscope (Carl Zeiss). The results are shown in FIG. 13.

(74) For the western blotting, the same cultured cells as the above were soluble in RIPA buffer (Sigma-Aldrich) together with a protease inhibitor cocktail. Afterwards, the lysate was centrifuged at a speed of 15,000 g at a temperature of 4 C. for 30 minutes, diluted with a Laemmli sample containing 2% SDS and 5% (v/v) 2-mercaptoethanol, and then, heated at a temperature of 90 C. for 5 minutes. The proteins were separated by SCD-polyacrylamide gel electrophoresis (SDS-PAGE) with use of 10% resolving gel, and transferred to a nitrocellulose membrane (Bio-Rad, USA). The membrane was then incubated overnight at a temperature of 4 C. with primary antibodies that are specific to collagen type I (Colla1, Boster Bio CO. Ltd) and -actin (Santan Cruz Biotechnology). For detection, the membrane was incubated with peroxidase-conjugate antibodies (Santa Cruz Biotechnology) at room temperature for 1 hour. Scanning was then performed thereon by using an imaging analyzer (LSA3000, Fujifilm) to form a chemiluminescence image, and the results are shown in FIG. 14.

(75) FIG. 12 is a graph showing the hydroxyproline assay results measuring a collagen amount in a 3D fibroblast cluster according to an embodiment.

(76) FIG. 13 is a graph showing the immunostaining results of measuring an expression level of collagen type I in a 3D fibroblast cluster according to an embodiment.

(77) FIG. 14 is a diagram showing the western blotting results of measuring an expression level of collagen type I in a 3D fibroblast cluster according to an embodiment.

(78) As shown in FIG. 12, it was confirmed that the total amount of collagen secreted in the 3D cell cluster increased with increasing incubation time, but were reduced as compared with that of collagen secreted in the 2D cells. The results are consistent with the results of Example 2(2.1).

(79) In addition, as shown in FIG. 13, the staining of collagen type I decreased during the culture of the 3D cell cluster, whereas the staining did not decrease in the 2D cells. The results refer that collagen type I had been degraded during the culture in a 3D culture system.

(80) In addition, as shown in FIG. 14 and in the same manner as in the results shown in FIG. 12, collagen type I was fragmented during the culture of 3D cell cluster, whereas such fragmentation did not occur in the 2D cells.

(81) Based on the results above, it was confirmed that the expression of collagen was decreased in the 3D fibroblast cluster according to an embodiment so that the 3D fibroblast cluster can be utilized for screening a candidate material for increasing the collagen amount.

(82) (2.3) Analysis of MMP Expression by 3D Fibroblast Cluster

(83) To analyze expression of MMP by the 3D fibroblast cluster, RT-PCR was performed in the same manner as in Example 2(2.1), and the results are shown in FIG. 15A.

(84) In addition, to analyze total secretion amounts of MMP-1, ELISA was performed. In detail, a culture medium was prepared with normal 2D cells and 3D cell cluster (3DCM) at different times (1.sup.st day, 3.sup.rd day, and 5.sup.th day). The assay was performed thereon by using the Quantikine ELISA kit for human total MMP 1 (R&D System) according to the manufacturer's instructions. Here, the absorbance was measured by using a Multisakn (Thermo) at 560 nm, and the results are shown in FIG. 15B.

(85) FIG. 15 is a graph showing expression levels and secretion levels of MMP1 by the 3D fibroblast cluster according to an embodiment.

(86) As shown in FIG. 15, the expression level of MMP 1 gene was significantly increased in the 3D cell cluster, as compared with that in the 2D cells. In addition, as shown in the ELISA assay the secretion level of MMP 1 was significantly increased in the 3D cell cluster, as compared with that in 2D cells. Consequently, it was confirmed that the fibroblast cluster according to an embodiment showing significantly increased expression of MMP can be effectively utilized for the development of a substance targeting the MMP.

(87) (3) Evaluation of Inhibitory Effect of MMP Inhibitor by Using 3D Fibroblast Cluster

(88) To additionally determine whether the 3D fibroblast cluster according to an embodiment was usable for screening an MMP inhibitor, the 3D fibroblast cluster was treated with the existing MMP inhibitors already known in the art, and then, the secretion of MMP was confirmed.

(89) In detail, the 3D fibroblast cluster of the culture at Day 1 prepared according to Example 2(1) was inoculated with retinoic acid (10 mM), abietic acid (100 mM), transforming growth factor-b1 (TGF-b1) (5 ng/ml) that were diluted in a fibroblast growth factor (FGM, Lonza Company). The inoculated 3D fibroblast cluster was then cultured in a stationary incubator at a temperature of 37 C. for 2 and 4 days, separately. The culture broth was recovered therefrom, and was subjected to measurement of secretion of MMP1. Through the measurement, the culture broth was quantified by using the ELISA kit (R&D Company), wherein a method of using the kit was proceeded according to the supplier's protocol. The results thus obtained are shown in FIG. 16.

(90) As a control group for the 3D fibroblast cluster and for the comparison of the inhibitory effect of MMP inhibitors using the two-dimensionally cultured fibroblasts, fibroblasts irradiated with ultraviolet B (UVB) were used. In detail, fibroblasts that were suspended in high-concentration glucose DMEM were seeded onto each well of a tissue culture treated 6-well plate at a concentration of 2.510.sup.5 cells/cm.sup.2, and then, cultured in a stationary incubator at a temperature of 37 C. for 1 day. Next, a washing process was performed thereon three times by using PBS, a serum-free MEM medium was added thereto, and the fibroblasts were cultured in a stationary incubator at a temperature of 37 C. for 1 hour. After a washing process was performed thereon three times by using PBS, to induce overexpression of MMP1, UVB (20 mJ/cm.sup.2) was irradiated thereto. Following UV irradiation, the resulting fibroblasts were inoculated with various concentrations of retinoic acid (2, 10, 40 mM), abietic acid (20, 100, 400 mM), and TGF-b1 (1, 5, 20, ng/ml) that were diluted in a fibroblast growth medium (FGM, Lonza Company). The inoculated fibroblasts were then additionally cultured in a stationary incubator at a temperature of 37 C. for 2 days. The culture broth was recovered therefrom, and was subjected to measurement of secretion of MMP1. Through the measurement, the culture broth was quantified by using the ELISA kit (R&D Company), wherein a method of using the kit was proceeded according to the supplier's protocol. The results thus obtained are shown in FIG. 17.

(91) FIG. 16 is a graph showing secretion levels of MMP1 in cells after the cells were treated with an MMP1 inhibitor in a 3D fibroblast cluster according to an embodiment.

(92) FIG. 17 is a graph showing secretion levels of MMP1 in cells, after fibroblasts that are cultured two-dimensionally and irradiated with ultraviolet rays to induce overexpression of MMP1 was treated with an MMP1 inhibitor.

(93) As shown in FIG. 16, after an incubation period of 2 days and 4 days, the secretion levels of MMP1 in the fibroblast cluster that was not treated with the MMP1 inhibitor was increased to about 2.1 times and about 2.4 times, respectively. However, the secretion levels of MMP1 in the fibroblast cluster treated with retinoic acid and abietic acid were each about 80% and 81% of those of MMP1 in the control group. The secreted amount of MMP1 in the fibroblasts treated with TGF-b1 was about 60% of that of MMP1 in the control group.

(94) As shown in FIG. 17, the secreted amount of MMP1 in the fibroblasts that were cultured two-dimensionally and irradiated with UVB was increased to about 1.3 times the fibroblasts that were not irradiated with UV rays. However, the secreted amount of MMP1 in the fibroblasts that were treated with retinoic acid was reduced to about 30% of that of MMP1 in the control group. In comparison with the fibroblasts treated with TGF-b1, depending on the amount of the TGF-b1 used for the treatment, the secreted amount of MMP1 therein was reduced to about 25-35% of that of MMP1 in the control group. In particular, when the fibroblasts were treated with abietic acid, for example, treated at a concentration of 20 mM of abietic acid, the secreted amount of MMP1 was approximately reduced to half of that of MMP1 in the control group, However, when the fibroblasts were treated with abietic acid at a concentration of at least 100 mM, the secreted amount of MMP1 was about 2% of the that of MMP1 in the control group. In comparison with the results obtained by using the 3D cell cluster, the tendency of reduced secretion amount upon the treatment of the inhibitor is the same. However, in comparison with the 3D cell cluster, the decrease of the MMP inhibitor in the 2D cells was higher about 2.7 times (retinoic acid-treated fibroblasts), about 1.7 to 2.4 times (TGF-b1-treated fibroblasts), and about 1.7 to about 40 times (abietic acid-treated fibroblasts) the control group.

(95) Consequently, it was confirmed that, the 2D cells were not suitable for drug screening due to significantly high drug sensitivity, and that the 3D cell cluster was effectively usable for screening a drug including the MMP inhibitor.

(96) FIG. 18 is a schematic diagram showing a drug-screening device including a 3D fibroblast cluster according to an embodiment, and a method of screening a drug by using the drug-screening device. Referring to FIG. 18, there is provided the drug-screening device including a well plate having at least one well, wherein one or more 3D fibroblast clusters according to an embodiment are seeded per well. The 3D fibroblast cluster may include 3.010.sup.5 cells to about 1.010.sup.6 cells. In addition, the 3D fibroblast cluster may have a diameter in a range of about 300 m to about 2,000 m, and may be formed into spheres (including spheroids) or sheets. The drug, i.e., the candidate substance, is the same as described above. The present inventive concept also provides a method of screening a drug, the method including: injecting a solution containing a candidate substance per well of a cell plate included in the drug-screening device; culturing the well plate to which the candidate substance is injected; collecting a fibroblast cluster from the well plate or recovering a culture broth from the well plate; and performing assay on the collected fibroblast cluster or on the culture broth. Here, the candidate substance may be identical to or different from the candidate substance described above. Regarding the culturing of the well plate, culture time and temperature may be arbitrarily determined by one of ordinary skill in the art. The assay performed herein may be, for example, MMP secretion assay using ELISA on the culture broth, western blotting on the fibroblast cluster, or ECM secretion assay using immunohistochemistry.