METHOD FOR REDUCING PARAVALVULAR LEAKS WITH DECELLULARIZED TISSUE

Abstract

A method for preparing tissue, in particular pericardial tissue, in particular for use as a sealing means for a heart valve prosthesis for paravalvular leaks, characterised in that the tissue, in particular pericardial tissue, is decellularized (4), subjected to a cross-linking (6) with a glutaraldehyde-containing solution, and subjected to a shape- and a structure-stabilising step (7, 8, 9). The invention also relates to a heart valve prosthesis.

Claims

1. A method for preparing tissue, in particular pericardial tissue, in particular for use as a sealing means for a heart valve prosthesis for paravalvular leaks, the method comprising: decellularizing the tissue (4); subjecting the decellularized tissue to a cross-linking solution (6) comprising glutaraldehyde; subjecting the tissue to a shape- and structure-stabilizing step (7, 8, 9), in which the tissue is exposed to a first solution (7) containing glycerol and is exposed to a second solution (8) containing polyethylene glycol; and drying the tissue after the shape- and structure-stabilizing step.

2. The method according to claim 1, further comprising fastening (13) the dried tissue to a heart valve prosthesis as sealing means or part of a sealing means for paravalvular leaks, wherein the tissue is optionally fastened to an expandable or self-expanding main body of an implant, which can be implanted by catheter.

3. The method according to claim 1, further comprising arranging the dried tissue on an outer side of the heart valve prosthesis (13) so that, in an implanted state, the dried tissue lies against tissue surrounding the heart valve prosthesis so that as the tissue is rehydrated, the rehydrated tissue seals a gap between the tissue and the heart valve prosthesis on account of an increase in thickness of the rehydrated tissue.

4. The method according to claim 1, further comprising exposing the tissue is exposed to a third solution (9) containing polyethylene glycol having a mean molecular weight different from the second solution, prior to the step of drying (10) the tissue.

5. The method according to claim 4, characterised in that the third solution contains polyethylene glycol having a mean molecular weight between 200 g/mol and 6,000 g/mol.

6. The method according to claim 4, characterised in that the tissue is exposed to the first, second and/or the third solution for 5 minutes to 2 hours.

7. The method according to claim 4, characterised in that polyethylene glycol is present in the second and/or the third solution in a concentration of from 5% w/v to 60% w/v.

8. The method according to claim 1, characterised in that the glycerol is present in the first solution in a concentration of from 5% w/v to 50% w/v.

9. The method according to claim 1, characterised in that the second solution contains polyethylene glycol having a mean molecular weight between 100 g/mol and 1,000 g/mol, in particular 200 g/mol.

10. The method according to claim 1, characterised in that the tissue is decellularised (4) in an aqueous decellularization solution containing a decellularization agent, wherein the decellularization solution optionally comprises 0.1% w/v to 15% w/v of the decellularization agent, optionally 0.5% w/v to 15% w/v of the decellularization agent, optionally in 0.9% w/v NaCl or a comparable isotonic aqueous solution.

11. The method according to claim 10, characterised in that the step of decellularizing the tissue comprises exposing the tissue to a decellularization solution over a period from 12 hours to 48 hours (4), optionally at a temperature in the range of from 15 C. to 40 C.

12. The method according to claim 1, characterised in that the tissue is of xenogenic or allogenic origin, optionally sought from a member selected from the group consisting of pericardial tissue, mucosa, kidney tissue, and tissue from the lung, stomach or intestine.

13. The method according to claim 1, characterised in that the dried tissue, prior to being fastened to the heart valve prosthesis, is cut to size (11) and hot-pressed (12), optionally at a temperature in a range of 40 C. to 70 C.

14. A decellularized and dried tissue, characterised in that the tissue, by means of rehydration, has an increase in thickness by at least 110% compared to a native untreated tissue.

15. A heart valve prosthesis, comprising a tissue which has been subjected to a method according to claim 1, optionally wherein the heart valve prosthesis comprises a sealing means which comprises the tissue or which is formed thereby, wherein the tissue is is fastened to an expandable or self-expanding main body of the heart valve prosthesis, which can be implanted by catheter, optionally fastened to an outer side of the heart valve prosthesis, such that, in an implanted state, it lies against a tissue surrounding the heart valve prosthesis and, as the tissue is rehydrated, seals off a gap between the tissue and the heart valve prosthesis on account of an increase in thickness of the rehydrated tissue.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention will be explained in greater detail hereinafter on the basis of exemplary embodiments (see FIG. 1) and a comparison, presented in FIG. 2, between an untreated pericardial tissue and a pericardial tissue treated in accordance with the invention. In the drawings:

[0039] FIG. 1 shows a flow diagram of an embodiment of a method according to the invention; and

[0040] FIG. 2 from left to right: shows the thickness of porcine pericardium in the native state, after subsequent decellularization in 2% w/v, 5% w/v, 10% w/v SDS in 0.9% w/v NaCl, after subsequent cross-linking in 0.65% v/v glutaraldehyde in DPBS without Ca/Mg under slight pretension, after subsequent stabilisation in glycerol 30% w/v, 30 minutes/PEG200 40% w/v, 30 minutes/PEG400, 40% w/v, 30 minutes (GPP, glycerol, PEG200, PEG400) and drying in a climate chamber, after subsequent hot-pressing at 60 C., 10 kg/cm2, 30 minutes, and after subsequent rehydration in 0.9% w/v NaCl, 37 C., 10 minutes.

DETAILED DESCRIPTION

EXAMPLE 1

[0041] Example 1 discloses an embodiment of the method according to the invention for preparing porcine pericardial tissue with subsequent drying, illustrated schematically in FIG. 1.

[0042] A pericardium is firstly removed fresh from a pig (for example at the slaughterhouse) and is stored for 2 hours at a temperature of 4 C. in a 0.9% w/v NaCl containing penicillin and/or streptomycin (1) [step 1].

[0043] In the next step (2), fat and connective tissue are separated in moist state (in 0.9% w/v NaCl) from the pericardial tissue, and the pericardial tissue is cut to size.

[0044] The tissue is the rinsed, with slight movement, in 100 ml 0.9% w/v NaCl solution (3).

[0045] The pericardial tissue thus obtained is then subjected to a decellularization and subsequent cross-linking.

[0046] Here, the pericardial tissue was decellularized with 100 ml 0.5% w/v to 10% w/v SDS (sodium dodecyl sulphate) in 0.9% w/v NaCl for 24 hours at 37 C. with slight movement (4) and then rinsed repeatedly in an aqueous isotonic solution, preferably 0.9% w/v NaCl, with io slight movement (5) (see also FIG. 2).

[0047] The pericardial tissue was then subjected to a cross-linking (6) with glutaraldehyde, more specifically for 48 hours in 0.04% v/v to 2% v/v glutaraldehyde solution (glutaraldehyde in buffered saline solution at 4 C. (for example DPBS solution, Lonza; DPBS w/o Ca+/Mg+; is product number 17-512)), wherein this solution then worked for 12 days at room temperature (typically 20 C. to 25 C.) and was replaced every 48 hours with a similar, fresh solution).

[0048] The resultant decellularised and cross-linked pericardial tissue was stabilised in this embodiment of the invention in three steps, wherein the cross-linked pericardial tissue from step (6) was treated for 30 min with slight movement at 37 C. with 20% w/v to 40% w/v glycerol in water (7), then for 30 minutes with slight movement 37 C. with 20% w/v to 50% w/v PEG200 (polyethylene glycol 200) in water (8), and then for 30 minutes with slight movement at 37 C. with 20% w/v to 50% w/v PEG400 (polyethylene glycol 400) in water (9).

[0049] The pericardial tissue was then dried, for example in a climate chamber (for example 40 C. and 10% rel. humidity) (10). If the drying is carried out under these conditions for 48 hours, the moisture of the tissue can be reduced from 95% to 10%.

[0050] The dry pericardial tissue is cut to size, for example so as to form a sealing means described herein (11).

[0051] The dried and cut-to-size shaped pieces are then hot-pressed, for example at 60 C. (12). The hot pressing is typically carried out at a pressure of 2-15 MPa, preferably 5-12 MPa for 5-50 min, preferably for 30 min. Steps (11) and (12) can also be carried out in the reverse order.

[0052] The hot-pressed and cut-to-size pericardial tissue is lastly fixed as sealing means to the heart valve prosthesis as described herein (13), wherein the sealing means is designed to seal off paravalvular leaks.

[0053] Lastly, the heart valve prosthesis can be loaded onto a catheter and can be sterilised (14).

[0054] If the pericardial tissue is now rehydrated at the site of use, its thickness increases significantly and said sealing effect takes hold.

[0055] FIG. 2 shows the absolute thicknesses in mm of porcine pericardial tissue at different stages for an exemplary production process. The native tissue with a thickness of less than 0.2 mm increases significantly in thickness by a factor of approximately four as a result of decellularization in the SDS solutions (2% w/v, 5% w/v, 10% w/v). The cross-linking under slight pretension leads to a slight reduction of the thickness with a planar surface. The subsequent stabilization in solutions formed from glycerol/PEG200/PEG400 with subsequent drying in a climate chamber (10% rel. humidity) does not change the thickness significantly. By hot pressing, the thickness of the porcine pericardium pre-treated in this way can be reduced purposefully by a factor of at least two to three. The tissue thickness, after the hot pressing, is again in the range of the native tissue, in particular for the lower SDS concentrations. By means of final rehydration in 0.9% w/v saline solution, the pressed porcine pericardium swells considerably, and the thickness increases by approximately 100%.

[0056] In the exemplary embodiment, porcine pericardial tissue, which is used in TAVI valves, is preferably used as starting material. However, in order to seal off paravalvular leaks, the mechanical requirements on the tissue are lower than for valve cusps. As already discussed, the use of other biological tissues without pronounced internal fibre structure can also be implemented, said tissues possibly having an intrinsic sponge-like or branched structure, for example porcine or bovine kidney, stomach or intestinal tissue.

[0057] It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teaching. The disclosed examples and embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention.