WO2010099414A2

WO2010099414A2 - Protection of human corneal endothelial against cell death under storage conditions by anti-apoptotic genes

Info

Publication number: WO2010099414A2
Application number: PCT/US2010/025542
Authority: WO
Inventors: Thomas Fuchsluger; Andrius Kazlauskas; Reza Dana
Original assignee: Universitat Duisburg-Essen; Schepens Eye Research Institute
Priority date: 2009-02-27
Filing date: 2010-02-26
Publication date: 2010-09-02
Also published as: WO2010099414A3

Abstract

The invention relates to methods of modifying endothelial cells of corneal tissue to express an anti-apoptotic gene, to prevent endothelial cell loss during cornea storage and to improve the quality of cornea tissue prior to transplantation. The invention also relates to a kit for cornea storage comprising a media, an anti- apoptotic gene and a vector.

Description

Protection of human corneal endothelial against cell death under storage conditions by anti-apoptotic genes

Field of the Invention:

This invention relates generally to the field of cornea tissue storage and cornea transplantation.

Background of the Invention:

There are numerous diseases and disorders that can affect corneal and other ocular tissue and which can adversely affect or eliminate vision. For example, allergies, conjunctivitis, corneal infections, Fuchs' dystrophy, keratoconus, and a number of other conditions, as well as congenital ocular abnormalities, can be responsible for corneal damage or irregularity that may affect vision. In an endeavor to restore sight or improve vision in people suffering from corneal abnormalities, it has become particularly common to perform corneal transplant operation where the abnormal cornea is removed and replaced with normal corneal tissue obtained from a donor.

Corneal transplantation is the most common transplantation, with about 300,000 surgeries performed annually worldwide. Cornea transplantation is performed for several reasons like bullous keratopathy, keratoconus, repeated grafting, keratitis/postkeratitis (e.g. after contact lens wear) and corneal stromal dystrophies. Eye banks process about 600,000 donor corneas every year, still not fulfilling the overall need for corneal grafts since many donor corneas have to be discarded as a result of cell loss.

The primary function of the cornea to assure vision mainly relies on the quality of its endothelium, a monolayer with minimal proliferative capacity and irreversible impact once it is lost. Up to 30 % of donor corneas stored in eye banks have to be discarded due to corneal endothelium cell loss.

Once transplanted, the risk of graft rejection is 10 % in uncomplicated "low- risk" settings and 50 to 90 % when placed in "high-risk" inflamed and/or vascularized graft beds. Even in "low-risk" patients, the grafts lose about 50 % of their endothelium just within the first year after transplantation, and up to 63 % several years after the surgery. Hence, every third corneal transplantation has to be repeated as the number of vital endothelial cells falls below the threshold for retaining corneal clarity.

As such, there has been a long-felt need for a storage method that protects cornea endothelial cells from apoptosis.

Summary of the Invention:

The present invention refers - according to a first or second or third aspect, respectively - to a method as defined in independent Claim 1 or Claim 2 or Claim 3, respectively; further, advantageous embodiments are the subject- matter of the respective dependent claims.

Furthermore, according to another aspect, the present invention relates to a corneal tissue as defined in independent Claims 10, 11 and 18, respectively; further, advantageous embodiments are the subject-matter of the respective dependent claims.

Also, according to yet another aspect, the present invention relates to a kit for in-vitro-treatment of corneal tissue as defined in independent Claim 19; further, advantageous embodiments are the subject-matter of the respective dependent claims.

Further, the present invention refers - according to yet other aspects - to a use as defined in independent Claims 23, 24 or 25, respectively; further, advantageous embodiments are the subject-matter of the respective dependent claims.

In the following, it has to be noted that explanations, details, examples etc. given with respect to one aspect of the present invention only shall, of course, also refer to all the other aspects of the present invention, even without explicit mentioning of this fact. Thus, it may well be in the following that specific aspects, explanations, details etc. are only delineated with respect to one specific embodiment only in order to avoid unnecessary repetitions, but they also apply with respect to all other aspects of the present invention.

The invention provides a method for preventing death of cornea endothelial cells, including the steps of: (a) harvesting the cornea from a donor; (b) treating the cornea placed in a cornea storage media with an anti-apoptotic gene; and (c) storing the cornea until use in transplantation.

The invention also provides corneal tissue comprising cells modified to express an anti-apoptotic protein which is not expressed by normal corneal tissue or which is expressed at elevated levels relative to normal corneal tissue.

The invention provides a method for the treatment of human corneal endothelium in donor corneas or artificially manufactured corneas and endothelial sheets.

The invention provides a method to increase the availability of corneas for surgery and cornea transplantation. Presently, up to 30 % of donor corneas stored in eye banks have to be discarded due to corneal endothelium cell loss.

The invention further provides a method to improve the storage of corneas at temperatures ranging from about 0 °C to about 40 °C, especially from about 2 ⁰C to about 39 ⁰C, particularly from about 0 ⁰C to about 4 ⁰C or at about 37 °C, responding to the need of eye banks worldwide.

In this context, the inventive method can be applied to improve the storage of corneas, especially the hypothermic storage of corneas, at temperatures ranging from about 0 °C to about 6 °C, especially from about 2 °C to about 5 °C, preferably from about 3 °C to about 4.5 °C, more preferably at about 4 ⁰C.

The inventive method can be also applied to improve the storage of corneas, especially the storage in the form of a organ culture of corneas, at temperatures ranging from about 30 °C to about 40 °C, especially from about - A -

35 ⁰C to about 39 ⁰C, preferably from about 36 ⁰C to about 38.5 ⁰C, more preferably at about 37 °C.

The invention further provides a method to store the cornea for longer periods of time before use in cornea transplantation. Optisol-GS, a 4-degree corneal preservation media which is preferably used for storage at 4 °C, permits up to 14 days preservation. The present invention is expected to rise the storage time by at least 100 %.

The invention further provides a kit for treating cornea tissue in vitro, comprising (a) a cornea storage media; (b) an anti-apoptotic gene; and (c) a viral or non- viral vector to introduce the gene into the tissue.

In a preferred embodiment, the cornea storage media is chosen from Optisol GS (Bausch and Lomb, Irvine, CA), or Dexsol (Bausch and Lomb, Irvine, CA), or Biochrom liquid (Biochrom AG, Berlin, Germany Morton, HJ. In vitro 1970, 6, 89; Morton, JJ. et al. In vitro 1972 8, 106).

The invention, according to another aspect, further refers to the use of at least one anti-apoptotic gene for preventing death of endothelial cells in harvested or artificially manufactured corneas.

The invention, according to yet another aspect, further refers to the use of at least one anti-apoptotic gene for extending the storage life of harvested or artificially manufactured corneas.

The invention, according to yet another aspect, further refers to the use of at least one anti-apoptotic gene for facilitating the storage of harvested or artificially manufactured corneas, especially the storage at temperatures ranging from about 0 °C to about 40 °C, especially from about 2 °C to about 39 ⁰C, particularly from about 0 ⁰C to about 4 ⁰C or at about 37 ⁰C.

In a preferred embodiment of the inventive use, the harvested or artificially manufactured cornea are treated with the at least one anti-apoptotic gene. Using the methods and other aspects or embodiments of the invention, anti- apoptotic genes are introduced into the endothelial cells of cornea to promote cell survival. Anti-apoptotic genes can be introduced into the cells by viral vectors or by non-viral gene transfer.

Exemplary anti-apoptotic genes include Bcl-2, Bcl-xL, p35, Survivin. Bcl-w, MCLl, Al, Ced-9.

In a preferred embodiment of the invention, the anti-apoptotic gene used to protect corneal endothelial cell death is Bcl-xL, p35, Bcl-2.

The expression vector according to the present invention may constitute any of a wide variety of already known or even as yet unidentified types of expression vector, such as viral, bacterial or plasmid expressing vector systems. Examples of suitable viral vectors include HSV, lentivirus, retroviral vectors and adeno-associated viral vectors. Examples of suitable non-viral vectors are nanoparticles or transfer using nucleofection by liposomes.

The exposure of corneal tissue to expression vectors according to the invention will be in a manner that will allow infection by the expression vector of the corneal tissue cells. The exposure of the corneal tissue to the expression vector can simply be by including the expression vector into the corneal tissue culture media. Other means of exposure such as via direct injection of the expression vectors into the corneal tissue or via high velocity bombardment may also be adopted, although care should be taken to avoid damage to the corneal tissue.

In preferred embodiments of the invention the corneal tissue is harvested from a mammal, particularly preferably from a human. Preferably the recipient of transplanted corneal tissue is a mammal, particularly preferably a human. In a particularly preferred embodiment of the invention corneal tissue is harvested from a human and transplanted to another human recipient. The corneal tissues are preferably obtained from the donor within a relatively short period post mortem, preferably within four hours. The conditions under which the corneal tissue should be removed from the donor are well understood by persons skilled in the art. The present invention is not intended to be used after the cornea is transplanted to the patient, but rather after harvesting of the cornea and during the storage of the cornea in eye banks.

The present invention also provides a method to block the ATP induced activation of caspase-1 via purinergic receptors (ATP receptor antagonists) to protect corneal endothelial cells from cell death. ATP receptor antagonists can be given into a culture / storage medium without a need to enter the corneal endothelial cells. Additionally, ATP receptor gene expression can be blocked intracellularly.

Exemplary purinergic receptors are P2X₄ and/or P2X₇ and/or P2Y₂.

Brief description of the drawings:

The figures illustrate the present invention, however, without limiting the invention.

Fig. 1: Protection of primary human corneal endothelial cells infected with different concentrations of Lentivirus carrying an empty vector

(pHAGE-CMV-MCS-IZsGW) versus carrying the anti-apoptotic gene Bcl-xL (pHAGE-CMV-MCS-IZsGW-BclxL) before inducing apoptosis with Actinomycin for 72 hours {external apoptotic pathway (i.e. extrinsic apoptotic pathway));

Fig. 2: Protection of primary human corneal endothelial cells infected with different concentrations of Lentivirus carrying an empty vector (pHAGE-CMV-MCS-IZsGW) versus carrying the anti-apoptotic gene Bcl-xL (pHAGE-CMV-MCS-IZsGW-BclxL) before inducing apoptosis with Etoposide for 72 hours {internal apoptotic pathway

(i.e. intrinsic apoptotic pathway);

Fig. 3: Infection of immortalized human corneal endothelial cells (HCEC) with pHAGE-CMV MCS IZsGreen:

After 24 hours of infection time infection of the HCEC with the lentivirus could be visualized by epiflourescence microscopy; Fig. 4: Expression Rate for Lenti-IZsGreen in immortalized (iHCEC) versus primary human corneal endothelial cells (pHCEC):

The sensitivity of pHCEC and iHCEC against pHAGE- CMV MCS IZsGreen was measured by flow cytometry comparing different concentrations of the virus and the percentage of HCEC expressing IZsGreen. It could be demonstrated that pHCEC are much more sensitive to pHAGE-CMV MCS IZsGreen than iHCEC;

Fig. 5: Green Flourescent Protein (GFP) Expression of adeno-associated virus (AAV, Serotyp 2) in primary human corneal endothelial cells:

The percentage of GFP expressing primary HCEC was measured by flow cytometry over 23 days comparing different concentrations of rAAV2-GFP. After 15 days, the expression of GFP reaches a plateau at about 60% of expressing pHCEC;

Fig. 6: Early apoptosis (AnnexinV + Propidium Iodide-) in primary HCEC versus immortalized HCEC (comparing external (i.e. extrinsic)

[Actinomycin] versus the internal (i.e. intrinsic) [Etoposide] apoptotic pathway):

The percentage of CEC showing early apoptosis (AnnexinV + Propidium Iodide-) was measured between 2 and 48 hours of induction of apoptosis with the agents actinomycin/ etoposide by flow cytometry. Whereas iHCEC show a zig-zag pattern, pHCEC show a continuous increase in early apoptosis; Fig. 7: Flow cytometry analysis of apoptosis in human corneal endothelial cells (HCEC):

Flow cytometry was used to detect apoptosis in HCEC using AnnexinV and Propidium Iodide or 7-AAD. Flow cytometry allows a quantification of dead cells (Rl), late apoptotic / necrotic cells

(R2), vital cells (R3) and early apoptotic cells (R4); Fig. 8: Protection of human corneal endothelial cells of human donor corneas against apoptosis by gene therapy protection of human corneal endothelial cells with the mentioned genes against Etoposide (concentrations 1-fold and 2-fold for 3 hours and 6 hours):

Healthy corneal cells have a blue nucleus and green cell borders. Once the cell start dying, the nuclei turn red, indicating cell death. Apart, the cell membrane will lyse; Fig. 9: Protection of human corneal endothelial cells with the mentioned genes against Actinomycin (concentrations 1-fold and 2-fold for 3 hours and 6 hours):

Healthy corneal cells have a blue nucleus and green cell borders. Once the cell start dying, the nuclei turn red, indicating cell death.

Apart, the cell membrane will lyse;

Fig. 10: Kinetics of IZsGreenW expression and apoptosis in human corneal endothelium:

IZsGreenW expression following corneal transduction with 3 x 10⁵ IU/ml of pHAGE-CMV-MCS-IZsGreenW in Biochrome Cornea Medium I in the presence of 8 μg/ml polybrene. IZsGreenW expression was detected by laser scanning microscopy 24 hours after the respective transduction time. DNA fragmentation was subsequently detected with laser scanning microscopy using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). Columns display percentage of corneal endothelial cells (mean±SD) expressing IZsGreenW. At each time point, three corneas each cut into seven pieces were examined. Points (connected by black line) represent the percentage of corneal endothelial cells (mean±SD) showing TUNEL-positivity;

Fig. 11 : Expression of anti-apoptotic proteins by EC leads to a reduction of apoptosis during long-term storage:

DNA fragmentation, a late sign of apoptosis, was detected by TUNEL (red) and laser scanning microscopy. Corneas were stored at 4 ⁰C for 12 days (a: Optisol GS : PBS = 1 : 10) and at 37 ⁰C for 9 days (b: Biochrome Culture Medium I : PBS = 1 : 10). Nuclei were stained blue with TO-PRO3, a dicyanine dye which binds to DNA. The cell borders were visualized using an antibody against the tight junction protein 1 (ZO-I, green). Insert images show TUNEL positivity in EC expressing a parental vector (b) or Bcl-xL (c).

Columns display percentage of corneal endothelial cells (mean±SD) showing TUNEL-positivity;

Fig. 12: Assessment of corneal endothelial cell density and morphology during hypothermic storage at 4 ⁰C:

Untreated EC were compared to those expressing a parental vector (3 x 10⁵ IU/ml), Bcl-xL (3 x 10⁵ IU/ml or 1.2 x 10⁸ IU/ml) or p35 (3 x 10⁵ IU/ml). To exclude donor-related variation, donor corneas were cut into five single pieces and distributed across the varied experimental conditions and treated accordingly. EC densities and morphology of untreated endothelial cells and those expressing p35, Bcl-xL or a parental vector after storage for 11 weeks (a: Optisol GS : PBS = 1 : 1) or for 12 days (b: Optisol GS : PBS = 1 : 10) are demonstrated. Immunocyto chemistry imaging in (a) and (b): TO-

PRO3 (blue, nuclei), TUNEL (red, DNA fragmentation), IZsGreenW (a: green, co-expressed with the gene of interest) or ZO- 1 (b: green, zonula occludens antibody). Endothelial cell count was enumerated in EC stored in diluted Optisol GS as indicated above. The point of interception of x-axis and y-axis in (c) and (d) corresponds to 2,000 EC/mm², the minimum EC count used by eye banks to release donor corneas for transplantation. Corneal endothelial cell morphology was evaluated by enumeration of hexagonal EC (e: Optisol GS : PBS = 1 : 1; f: Optisol GS : PBS = 1 : 10; the higher this ratio the faster occurred decrease of physiological hexagonality and EC numbers). The dotted black line in (c) and (e) indicates a period of 14 days during which the use of Optisol GS, the most widespread culture medium for hypothermic corneal storage, is currently licensed. Points represent percent EC count (c, d) and percent hexagonal EC (e, f) (mean±SD). P-values are relative to untreated controls (* = p < 0.01); Fig. 13: Assessment of corneal endothelial cell density and morphology during organ storage at 37 ⁰C:

Untreated EC were compared to those expressing a parental vector, Bcl-xL or p35. To exclude donor-related variations, donor corneas were cut into five single pieces and distributed to each experimental condition. Dilutions of the storage medium were used to provoke cell loss. Endothelial cell counts were enumerated in EC stored in diluted organ culture medium (a: Biochrome Culture Medium I : PBS = 1 : 1; b: Biochrome Culture Medium I : PBS = 1 : 10). The point of interception of x-axis and y-axis in (a) and (b) corresponds to 2,000 EC/mm², the threshold for EC count used by eye banks to release donor tissue for transplantation. Corneal endothelial cell morphology was evaluated by enumeration of hexagonal EC (c: Biochrome Culture Medium I : PBS = 1 : 1; d: Biochrome Culture

Medium I : PBS = 1 : 4). Points represent percent EC count (a, b) and percent hexagonal EC (c, d) (mean±SD). P-values are relative to untreated controls; Fig. 14: Expression of anti-apoptotic proteins leads to extended EC survival comparing paired corneas from the same donors cultured under conditions that model an eye bank:

Organ storage in Biochrome Culture Medium (1 : 1 or 1 : 10 dilution with PBS) was performed in donor pairs. One cornea of a pair was transduced with lenti-IZsGreenW, the other cornea with the lenti-

IZsGreenW-Bcl-xL or lenti-IZsGreenW-p35. Enumeration of corneal endothelial cells is demonstrated in (a) and (b). The point of interception of x-axis and y-axis in (a) and (b) corresponds to 2,000 EC/mm , the minimum EC count used by eye banks to release donor corneas for transplantation. Representative images of EC layers expressing IZsGreenW or p35 are shown in the respective inserts

(TUNEL, TO-PRO3, ZO-I (green staining). Corneal endothelial cell morphology was evaluated by enumeration of hexagonal EC (c: Biochrome Culture Medium I : PBS = 1 : 1; d: Biochrome Culture

Medium I : PBS = 1 : 10). Points represent percent EC count (a, b) and percent hexagonal EC (c, d) (mean±SD). P-values are relative to untreated controls (* = p < 0.01);

Fig. 15: Evaluation of cell viability during long-term storage:

Defined phases of cell death (vital, chromatin condensation, single cell loss, massive cell loss) were evaluated by brightfield microscopy according to reference images (a) in corneas stored at 4 ⁰C (b, d) and 37 ⁰C (c, e). Controls (untreated cells and EC expressing IZsGreenW (b, c) were compared to EC expressing BcI- xL or p35 (d, e). EC expressing p35 or Bcl-xL show phases of cell death at later points in time compared to untreated EC or those expressing IZsGreenW only.

Detailed description of the Invention:

According to a first aspect of the present invention, the present invention refers to a method for preventing death of endothelial cells in harvested or artificially manufactured corneas. The method of the invention comprises treating the harvested or artificially manufactured cornea with at least one anti-apoptotic gene.

Furthermore, according to a second aspect of the present invention, the present invention also refers to a method for extending the storage life of harvested or artificially manufactured corneas, the method comprising treating the harvested or artificially manufactured cornea with at least one anti- apoptotic gene.

Further, according to a third aspect of the present invention, the present invention also refers to a method for facilitating the storage of harvested or artificially manufactured corneas, especially the storage at temperatures ranging from about 0 °C to about 40 °C, especially from about 2 °C to about

39 ⁰C, particularly from about 0 ⁰C to about 4 ⁰C or at about 37 ⁰C, the method comprising treating the harvested or artificially manufactured cornea with at least one anti-apoptotic gene. In this context, with respect to the aforementioned methods, the treatment may be performed in a cornea storage medium.

According to a preferred embodiment of the present invention, the corneas may be human or human-like or human-based corneas or corneas of human origin.

Furthermore, it is advantageous if the anti-apoptotic gene is selected among genes of the BCL-2 family, especially BCL-xL, BCL-2, BCL-w and MCLl; and P35.

In this context, the anti-apoptotic gene may be selected among animal- derived, preferably human genes, preferably selected from genes of the BCL-2 family, especially BCL-xL, BCL-2, BCL-w and MCLl .

The anti-apoptotic gene may also be selected among virus-derived genes, preferably P35.

Furthermore, the anti-apoptotic gene may be selected from the group consisting of BCL-xL, P35, BCL-2, Survivin, BCL-w, MCLl, Al, and CED-9, especially P35, BCL-xL, BCL-2 and BCL-w, preferably P35 and BCL-xL, more preferably P35.

According to another aspect of the present invention, the present invention also refers to a corneal tissue, especially a human, human-based or human-like corneal tissue, the corneal tissue being obtainable according to one or more of the inventive methods as defined above.

According to yet another aspect of the present invention, the present invention also refers to corneal tissue, especially a human, human-based or human-like corneal tissue, especially as defined above, the corneal tissue comprising cells modified to express at least one anti-apoptotic protein. In this context, according to an advantageous embodiment of the present invention, the anti-apoptotic protein might be an anti-apoptotic protein not normally expressed by normal corneal tissue or an anti-apoptotic protein expressed at elevated levels relative to normal corneal tissue.

According to the present invention, the cells may be modified by implementation of an anti-apoptotic gene, especially as defined above, especially wherein the implementation has been effected by incorporation of the anti-apoptotic gene, preferably via transformation, transduction, conjugation or transfection.

With respect to the inventive and above-defined corneal tissues, the anti- apoptotic protein may be Bcl-xL, p35, Bcl-2, Survivin, Bcl-w, McI-I, Al, or Ced-9, especially p35, Bcl-xL, Bcl-2 and Bcl-w, preferably p35 and Bcl-xL, more preferably p35.

Further, the anti-apoptotic protein might be selected among animal-derived, preferably human proteins, preferably selected from proteins of the Bcl-2 family, especially Bcl-xL, Bcl-2, Bcl-w and McI-I .

Moreover, with respect to the inventive and above-defined corneal tissues, the anti-apoptotic protein may be selected among virus-derived proteins, preferably p35.

The anti-apoptotic protein may be selected from the group consisting of Bcl-xL, p35, Bcl-2, Survivin, Bcl-w, McI-I, Al, and Ced-9, especially p35, Bcl-xL, Bcl-2 and Bcl-w, preferably p35 and Bcl-xL, more preferably p35.

Furthermore, according to yet another aspect of the present invention, the present invention refers to a corneal tissue, especially a human, human-based or human-like corneal tissue, especially as defined above, the corneal tissue comprising cells modified to express at least one anti-apoptotic protein, the cells comprising at least one implemented anti-apoptotic gene, especially as defined above. The present invention - according to a further aspect of the present invention - refers to a kit for treating cornea tissue in vitro, the kit comprising:

(a) a corneal storage medium; and

(b) a vector comprising at least one anti-apoptotic gene.

In this context, the anti-apoptotic gene may be as defined above.

With regard to the inventive kit, the corneal tissue may be a human, human- based or human-like corneal tissue.

The vector may be a viral, bacterial or plasmid-based vector, especially viral, bacterial or plasmid-based expression vector system.

The present invention - according to still another aspect of the present invention - refers to the use of at least one anti-apoptotic gene for preventing death of endothelial cells in harvested or artificially manufactured corneas.

Furthermore, according to another aspect of the present invention, the present invention also refers to the use of at least one anti-apoptotic gene for extending the storage life of harvested or artificially manufactured corneas.

Moreover, according to a further aspect of the present invention, the present invention also refers to the use of at least one anti-apoptotic gene for facilitating the storage of harvested or artificially manufactured corneas, especially the storage at temperatures ranging from about 0 °C to about 40 °C, especially from about 2 °C to about 39 °C, particularly from about 0 °C to about 4 ⁰C or at about 37 ⁰C.

According to the aforenamed inventive uses, the harvested or artificially manufactured cornea might be treated with the at least one anti-apoptotic gene.

In this context, the treatment may be performed in a cornea storage medium. According to the inventive uses as defined above, the corneas may be human or human-like or human-based corneas or corneas of human origin.

Furthermore, according to the inventive uses, the anti-apoptotic gene may be selected among genes of the BCL-2 family, especially BCL-xL, BCL-2, BCL-w and MCLl ; and P35.

According to the inventive uses as defined above, the anti-apoptotic gene may also be selected among virus-derived genes.

In this context, the anti-apoptotic gene might be P35.

Finally, the anti-apoptotic gene may be selected from the group consisting of BCL-xL, P35, BCL-2, Survivin, BCL-w, MCLl, Al, and CED-9, especially P35, BCL-xL, BCL-2 and BCL-w, preferably P35 and BCL-xL, more preferably P35.

Cornea

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, and as a result helps the eye to focus, accounting for approximately two-thirds of the eye's total optical power.

The human cornea, like that of other primates, has five layers. From the anterior to posterior they are the corneal epithelium, Bowman's layer, the corneal stroma, Descemet's membrane, and the corneal endothelium. The corneal epithelium is a thin epithelial multicellular tissue layer, stratified squamous epithelium, of continuously regenerating cells, kept moist with tears. Irregularity or edema of the corneal epithelium disrupts the smoothness of the air-tear film interface, the most significant component of the total refractive power of the eye, thereby reducing visual acuity. Bowman's layer, also known as the anterior limiting membrane, is a condensed layer of irregularly-arranged collagen, about 8 to 14 microns thick, that protects the corneal stroma. The corneal stroma, also known as the substantia propria, is a thick and transparent middle layer, consisting of regularly-arranged collagen fibers along with sparsely populated keratocytes.

The corneal stroma consists of approximately 200 layers of type I collagen fibrils. Ninety percent of the corneal thickness is composed of the stroma. Descemet's membrane, also known as the posterior limiting membrane, is a thin and acellular layer that serves as the modified basement membrane of the corneal endothelium. The corneal endothelium is a simple squamous or low cuboidal monolayer of mitochondria-rich cells responsible for regulating fluid and solute transport between the aqueous and corneal stromal compartments. The corneal endothelium is bathed by aqueous humour, not by blood or lymph, and has a very different origin, function, and appearance from vascular endothelia. Unlike the corneal epithelium, the cells of the endothelium do not regenerate. Instead, corneal endothelial cells expand or spread to compensate for dead cells which reduce the overall cell density of the endothelium and impacts fluid regulation.

Cornea Transplantation

Corneal transplantation, also known as corneal grafting or penetrating keratoplasty, is a surgical procedure where a damaged or diseased cornea is replaced by donated corneal tissue which has been removed from a recently deceased individual having no known diseases which might affect the viability of the donated tissue.

Indications for corneal transplantation include optical, reconstructive, therapeutic or cosmetic indications. In optical indications, the transplantation aims at improving the visual acuity by replacing the opaque or distorted host tissue by clear healthy donor tissue. The most common indication in this category is pseudophakic bullous keratopathy, followed by keratoconus, corneal degeneration, keratoglobus and dystrophy, as well as scarring due to keratitis and trauma. In tectonic/reconstructive indications, the transplantation aims at preserving the corneal anatomy and integrity in patients with stromal thinning and descemetoceles, or to reconstruct the anatomy of the eye, e.g. after corneal perforation. In therapeutic indications, the transplantation aims at removing the inflamed corneal tissue unresponsive to treatment by antibiotics or anti- virals. In cosmetic indications, the transplantation aims at improving the appearance of patients with corneal scars that have given a whitish or opaque hue to the cornea.

Cornea transplants normally enjoy a high percentage of survival, mainly because the eye is an immune-privileged site. When allograft failure occurs, it is most commonly due to rejection, an immune-mediated reaction that targets the corneal endothelium. It has been hypothesized that suppressing apoptosis in the graft endothelium will promote transplant survival. Moreover, it has been shown that Bcl-xL protects cultured corneal endothelial cells from the mouse from apoptosis and that lentiviral delivery of Bcl-xL to the corneal endothelium of donor corneas significantly improved the survival of transplanted murine allografts (Barcia et al. Am. J. Transplant. 2007, 7(9), 2082-2089).

Cornea Storage Media

Optisol GS and Dexsol are two chondroitin-sulfate-based, commercial available storage media. The main characteristics of these two media are summarized in the Table below.

Constituent Optisol Dexsol

Base medium Hybrid of TC- 199 and MEM

MEM

Chondroitin sulphate 2.5% 1.35%

Dextran 1% 1%

HEPES buffer Yes Yes

Gentamycin sulphate Yes Yes

Streptomycin Yes Yes

Nonessential amino acids 0.1 mmol/1 0.1 mmol/1

Sodium pyruvate 1 mmol/1 1 mmol/1

Additional antioxidants Yes Yes

Sodium bicarbonate Yes Yes MEM: minimum essential medium; TC- 199 = tissue culture medium 199; HEPES = N-2-hydroxyethylpiperazine-N'-2-ethane sulphonic acid

Biochrom Culture Medium I: # F9016 Biochrom AG seromed (Berlin)

MEM- Earle's (1Ox) 100.00 ml

(Biochrom, #F0333)

Penicillin/ Streptomycin 10.00 ml

(Biochrom, #A2213) L-Glutamin (200 mM) 10.00 ml

(Biochrom, #K0282)

Amphotericin B(250 μg/ml) 10.00 ml

(Biochrom, #A2610)

HEPES-buffer (1 M, 50x) 12.50 ml (Biochrom, #L1613)

NaHCO₃ 29.30 ml

(Biochrom, #L1713)

Aqua dest., sterile ad 1000.00 ml

(Biochrom, #L0015) pH: 7.2- 7.3

Biochrom Culture Medium II: # F9017 Biochrom AG seromed (Berlin)

Viral Vectors

Viral vectors are a tool commonly used by molecular biologists to deliver genetic material into cells. Viral vectors were originally developed as an alternative to transfection of naked DNA for molecular genetics experiments. Compared to traditional methods such as calcium phosphate precipitation, transduction can ensure that nearly 100% of cells are infected without severely affecting cell viability. Furthermore, some viruses integrate into the cell genome facilitating stable expression. Lentiviruses have been adapted as gene delivery vehicles (vectors) thanks to their ability to integrate into the genome of non-dividing cells, which is the unique feature of Lentiviruses. The viral genome in the form of RNA is reverse-transcribed when the virus enters the cell to produce DNA, which is then inserted into the genome at a random position by the viral integrase enzyme. Whereas lentiviruses are HIV-based, adeno-associated viruses (AAV) are entirely apothogenic for humans. B-cell lymphoma 2 "Bcl-2" and Basal cell lymphoma-extra large "Bcl-xl"

The extended BCL-2 family of proteins plays a central role in the mitochondrial pathway to programmed cell death. In mammalian cells, five pro-survival proteins - BCL-2, BCL-XL, BCL-w, MCLl and Al - antagonize the pro-apoptotic function of BAK and BAX4. The killing activity of BAX and BAK is localized on the mitochondrial outer membrane, which becomes permeabilized in response to death signals. As a result, cytochrome c is released into the cytosol, leading to the activation of the caspase cascade and the induction of apoptotic cell death. The five pro-survival proteins and BAK/BAX all share four domains of sequence homology known as BCL-2 homology 1 (BHl, BH2, BH3 and BH4). They also have a C-terminal membrane-anchoring sequence and a similar three-dimensional structure. The amino-acid sequence signature for life and death that distinguishes these two functional subfamilies remains elusive. Other key players that orchestrate apoptosis are the pro-apoptotic BH3-only proteins - so-called because they lack the BHl, BH2 and BH4 domains. Eight BH3-only proteins are known in mammals - BIM, BID, PUMA, NOXA, BAD, BMF, HRK and BIK - and they are upregulated by transcription or post-translational processing in response to various stress signals. (G. Lessene et al, Nature Drug Discovery, 2008, 7, 989).

Bcl-xL Bcl-xL as particularly used according to the present invention is especially referred to and/or identified, respectively, in the annexed sequence listing according to SEQ ID 003 (Bcl-xL; DNA sequence) and/or according to SEQ ID 004 (Bcl-xL; protein sequence; NCBI accession number CAA80661).

In general, the DNA sequence and/or the nucleotide sequence denote the gene, whereas the protein sequence and/or amino acid sequence denote the correlated gene product (i.e. the protein encoded by the correlated gene: For instance, the protein BCL-xL is encoded by the correlated gene Bcl-xL, or the protein BCL-xL is the correlated gene product encoded by the gene Bcl-xL, respectively, etc.). This also applies to the further sequences and species indicated below. Bcl-2

Bcl-2 as particularly used according to the present invention is especially referred to and/or identified, respectively, in the annexed sequence listing according to SEQ ID 001 (Bcl-2; DNA sequence; B-cell lymphoma protein 2 alpha isoform [homo sapiens]) and/or according to SEQ ID 002 (Bcl-2; protein sequence; B-cell lymphoma protein 2 alpha isoform [homo sapiens]; NCBI accession number NP 000624).

P35

P35 as particularly used according to the present invention is especially referred to and/or identified, respectively, in the annexed sequence listing according to SEQ ID 005 (P35; DNA sequence) and/or according to SEQ ID 006 (P35; protein sequence).

p35 is a broad-spectrum caspase inhibitor identified from the baculo virus, Autographa californica multiple Nucleopolyhedrovirus (AcMNPV). Caspases are key effector proteins activated during apoptosis and targeted by viruses for inhibition.

In general, the term "anti-apoptotic gene" used according to the present invention particularly refers to a gene encoding for a protein having an anti- apoptotic activity especially when being expressed in the endothelial cells of the cornea. The anti-apoptotic protein encoded by the anti-apoptotic gene thus inhibits or at least decreases apoptosis of the respective endothelial cells of the cornea.

Furthermore, the term "gene", especially "anti-apoptotic gene", used according to the present invention likewise includes the corresponding nucleic acid molecule or the corresponding DNA sequence. The term "nucleic acid molecule" is synonymous with the term "polynucleic acid" or "polynucleic acid molecule". Especially, the above-named genes may also refer to the respective mutations and/or isoforms encoding to a similar protein having an anti-apoptotic activity when being expressed in the endothelial cells of the cornea. Furthermore, the term "gene" may also include a nucleic acid molecule, the respective complementary strand of which hybridizes to the nucleic acid molecule of the gene as such and which also encodes for a protein having an anti-apoptotic effectiveness when expressed in the endothelial cells of the cornea. The term "gene" may also encompass a nucleic acid molecule, the sequence of which differs from the sequence of the gene as such due to the degeneration of the genetic code and which also encodes for a protein having an anti-apoptotic effectiveness especially when expressed in the endothelial cells of the cornea. Moreover, the term "gene" likewise refers to the RNA- sequence associated with the gene. This, however, is clear to the skilled practitioner.

Furthermore, with respect to the aforementioned proteins, it is pointed out that also functional analogons, derivatives, isoforms, mutations of the respective protein in the form of proteins and/or (poly-)peptides may be comprised, especially having a comparable action profile and/or having a similar amino acid sequence. This is also clear to the skilled practitioner.

The role of purinergic receptors in apoptosis Purinergic receptors

Purinergic receptors are a family of newly characterized plasma membrane molecules involved in several and as yet only partially known cellular functions such as vascular reactivity, apoptosis and cytokine secretion. In vitro studies indicate that the second signal involved in caspase-1 activation and IL- lbeta release can be derived from the activation of surface-expressed purinergic receptors of the P2X₇ and/or P2Y₂ subtype.

Caspase 1 Caspase 1 is an enzyme that proteolytically cleaves other proteins, such as the precursor forms of the inflammatory cytokines interleukin 1-β and interleukin 18, into active mature peptides. It belongs to a family of cysteine proteases known as caspases that always cleave proteins following an aspartic acid residue. Caspase 1 is produced as a zymogen that is cleaved into 20 kDa (p20) and 10 kDa (plO) subunits that become part of the active enzyme. Active caspase 1 contains two heterodimers of p20 and plO. It interacts with another CARD domain containing protein called PYCARD (or ASC) and is involved in inflammasome formation and activation of inflammatory processes. Caspase 1 has been shown to induce cell apoptosis and may function in various developmental stages. Studies of a similar protein in mouse suggest a role in the pathogenesis of Huntington's disease. Alternative splicing of the gene results in five transcript variants encoding distinct isoforms.

On the whole, the inventors have surprisingly found out a new approach for preventing the death of endothelial cells in corneas serving as grafts and transplants, respectively, especially during their storage. In this context and as delineated above in detail, the central idea of the present invention lies in the concept according to which - in a purposeful manner - apoptosis of the endothelial cells is inhibited or at least significantly reduced. This is realized according to the present invention by the specific concept according to which the respective cells are modified in so far as the modified cells exhibit an increased expression of specific anti-apoptotic proteins, especially on the basis of the purposeful introduction of corresponding anti-apoptotic genes into the endothelial cells.

As a surprising result, the respective corneas treated on the basis of the inventive concept exhibit a significant elongation of storage time and furthermore have outstanding properties as such since - due to the reduction of endothelial cell loss - they exhibit an endothelial cell layer comprising a very high cell density even after long storage times.

Thus, the inventive corneas form the basis for improved medical grafts and transplants, thereby also improving the overall procedure of transplantation and diminishing the costs related therewith due to both the elongated storage time and the improved durability and quality of the grafted transplant as such.

Thus, the use of a gene therapy with respect to harvested or artificially manufactured corneas protects the donor cornea's endothelial cells in storage.

Especially, it is completely surprising that endothelial cells expressing anti- apoptotic genes retain their physiological cell morphology. As delineated above, the inventive concept can be applied with respect to all common storage methods and conditions, respectively. Especially, the inventive concept is effective for the most common storage conditions under 4 ⁰C and 37 ⁰C.

To sum up, the present invention is able to enhance the number of high- quality grafts in eye banking and does, furthermore, also enlarge the storage time which enables the supply of donor tissue for longer periods. Also the graft failure following corneal transplantation is reduced.

Furthermore, the present invention can be effectively applied to precut corneas and to DSAEK- and/or DMEK-methods.

Further embodiments, modifications and variations of the present invention are obvious to the skilled practitioner by reading the present specification and/or can be implemented by him without leaving the scope of the present invention.

In the following, the present invention is illustrated on the basis of the following detailed explanations and exemplary embodiments as well as experimental data, which, however, do not limit the present invention in any way. The same applies accordingly to the detailed explanations and exemplary embodiments as well as experimental data given in the above description of the Figures.

EXAMPLES:

Example 1:

Characteristics of Primary Human Corneal Endothelial Cells (pHCEC) and immortalized HCEC (iHCEC) studying Early Apoptosis and Gene Transfer

This study evaluates characteristics of primary versus immortalized HCEC in early apoptosis and the response of these cells to gene transfer with empty vector (IZsGW, GFP) and the anti-apoptotic gene Bcl-xL.

Apoptosis was induced in immortalized and primary (passage 8) HCEC with an external apoptotic inducer (Actinomycin) - i.e. with an extrinsic apoptotic inducer - and with an internal apoptotic inducer (Etoposide) - i.e. with an intrinsic apoptotic inducer - (0.1 to 100 micrograms/ml for 2 to 12O h). Sensitivity towards Lentivirus and Adenovirus was examined using pHAGE- CMV-MCS-IZSGW (1.5 x 10^s IU/ml) and AAV2-GFP (3.2 x 10¹² IU/ml, 3.2 x 10³- 3.2 x 10^s; 24 hours of incubation, days 1 to 23). Flow cytometry was used to detect apoptosis with Annexin V-FITC and Propidium Iodide as well as expression rates of IZsGW and GFP. Apoptosis in Lenti-IZsGW-Bcl-xL versus Lenti-IZsGW (as empty vector, EV) was detected with Annexin V-PE, 7-AAD and flow cytometry.

Early apoptosis rates peaked in iHCEC 6 h and 30 h after induction of apoptosis (up to 50 % Ann+PI-), in pHCEC after 60 h (up to 60 % Ann+PI-). There was no significant dose dependency. In addition, pHCEC are much more sensitive to pHAGE-CMV-MCS-IZsGW than iHCEC, showing an IZsGreen expression rate of almost 100 % already with 0.9 x 10⁵ IU per 48well (iHCEC: max. 50 % expression rate with 2.25x10⁵ IU). The expression rates of AAV2-GFP reached a plateau of 80 % in pHCEC 17 days after infection, in iHCEC after 23 days showing only 30 % expression of GFP. Studying protection of HCEC with Lenti-IZsGr-BclxL resulted in early apoptosis in pHCEC of 63 % (EV) being significantly reduced to 24 % (see Fig. 1 and 2). In iHCEC there was no effect of EV versus Bcl-xL resulting in 15 to 20 % early apoptosis in each. iHCEC deliver notably diverse data in apoptosis and gene transfer with lentivirus and adenovirus compared to pHCEC. Our data suggest that pHCEC provide more reliable data in studying apoptosis and gene transfer than iHCEC.

Example 2: Protection of human corneal endothelia cells against cell death with anti- apoptotic genes.

The human corneal endothelium was stained with the following antibodies: ZO-I-FITC (green) for cell borders, TO-PRO 3 for vital nuclei (blue), TUNEL for DNA-fragmentation of the nuclei indicating cell death (apoptosis, red). Healthy corneal cells have a blue nucleus and green cell borders. Once the cell start dying, the nuclei turn red, indicating cell death. Apart, the cell membrane will lyse (see Fig. 8 and 9). This is the Proof of Principle experiment showing that corneal endothelial cells of human donor corneas can be protected against apoptosis by infection with anti-apoptotic genes.

Apoptosis was induced by Actinomycin (external apoptotic pathway (i.e. extrinsic apoptotic pathway)) and Etoposide (internal apoptotic pathway (i.e. intrinsic apoptotic pathway)) [concentration 1-fold and 2-fold for 3 hours and 6 hours].

The controls are treated with the apoptotic inducers without prior infection with Lentivirus containing apoptotic genes. In the 'experimental' group, corneas were infected with the anti-apoptotic genes Bcl-xL (1.2 x 10 IU/ml), p35 (3 x 10⁵ IU/ml) and diluted Bcl-xL (Bcl-xL diluted to 3 x 10⁵ IU/ml, the titer of p35). The virus serving as vector was the lentivirus used in the experiments above. IZsGreen allowed to detect infected HCEC due to its green fluorescence. It could be demonstrated that Bcl-xL, p35 and diluted Bcl- xL can effectively protect human corneal endothelial cells of donor corneas from cell death.

Claims

Claims:

1. A method for preventing death of endothelial cells in harvested or artificially manufactured corneas, the method comprising treating the harvested or artificially manufactured cornea with at least one anti- apoptotic gene.

2. A method for extending the storage life of harvested or artificially manufactured corneas, the method comprising treating the harvested or artificially manufactured cornea with at least one anti-apoptotic gene.

3. A method for facilitating the storage of harvested or artificially manufactured corneas, especially the storage at temperatures ranging from about 0 °C to about 40 °C, especially from about 2 °C to about 39 ⁰C, particularly from about 0 ⁰C to about 4 ⁰C or at about 37 ⁰C, the method comprising treating the harvested or artificially manufactured cornea with at least one anti-apoptotic gene.

4. The method of any of Claims 1 to 3, wherein the treatment is performed in a cornea storage medium.

5. The method of any of Claims 1 to 4, wherein the corneas are human or human-like or human-based corneas or corneas of human origin.

6. The method of any of Claims 1 to 5, wherein the anti-apoptotic gene is selected among genes of the BCL-2 family, especially BCL-xL, BCL-2, BCL-w and MCLl ; and P35.

7. The method of any of Claims 1 to 6, wherein the anti-apoptotic gene is selected among animal-derived, preferably human genes, preferably selected from genes of the BCL-2 family, especially BCL-xL, BCL-2, BCL-w and MCLl .

8. The method of any of Claims 1 to 7, wherein the anti-apoptotic gene is selected among virus-derived genes, preferably P35.

9. The method of any of Claims 1 to 8, wherein the anti-apoptotic gene is selected from the group consisting of BCL-xL, P35, BCL-2, Survivin, BCL-w, MCLl, Al, and CED-9, especially P35, BCL-xL, BCL-2 and BCL-w, preferably P35 and BCL-xL, more preferably P35.

10. A corneal tissue, especially a human, human-based or human-like corneal tissue, the corneal tissue being obtainable according to one or more of the methods of Claims 1 to 9.

11. A corneal tissue, especially a human, human-based or human-like corneal tissue, especially according to Claim 10, the corneal tissue comprising cells modified to express at least one anti-apoptotic protein.

12. The corneal tissue of Claim 10 or 11, wherein the anti-apoptotic protein is an anti-apoptotic protein not normally expressed by normal corneal tissue or an anti-apoptotic protein expressed at elevated levels relative to normal corneal tissue.

13. The corneal tissue of any of Claim 10 to 12, wherein the cells are modified by implementation of an anti-apoptotic gene, especially as defined in any of Claims 6 to 9, especially wherein the implementation has been effected by incorporation of the anti-apoptotic gene, preferably via transformation, transduction, conjugation or transfection.

14. The corneal tissue of any of Claim 10 to 13, wherein the anti-apoptotic protein is Bcl-xL, p35, Bcl-2, Survivin, Bcl-w, McI-I, Al, or Ced-9, especially p35, Bcl-xL, Bcl-2 and Bcl-w, preferably p35 and Bcl-xL, more preferably p35.

15. The corneal tissue of any of Claims 10 to 14, wherein the anti-apoptotic protein is selected among animal-derived, preferably human proteins, preferably selected from proteins of the Bcl-2 family, especially Bcl-xL, Bcl-2, Bcl-w and McI-I.

16. The corneal tissue of any of Claims 10 to 15, wherein the anti-apoptotic protein is selected among virus-derived proteins, preferably p35.

17. The corneal tissue of any of Claims 10 to 16, wherein the anti-apoptotic protein is selected from the group consisting of Bcl-xL, p35, Bcl-2,

Survivin, Bcl-w, McI-I, Al, and Ced-9, especially p35, Bcl-xL, Bcl-2 and Bcl-w, preferably p35 and Bcl-xL, more preferably p35.

18. A corneal tissue, especially a human, human-based or human-like corneal tissue, especially according to any Claims 10 to 17, the corneal tissue comprising cells modified to express at least one anti-apoptotic protein, the cells comprising at least one implemented anti-apoptotic gene, especially as defined in any of Claims 6 to 9.

19. A kit for treating cornea tissue in vitro, the kit comprising:

(a) corneal storage medium; and

(b) a vector comprising at least one anti-apoptotic gene.

20. The kit of Claim 19, wherein the anti-apoptotic gene is as defined in any of Claims 6 to 9.

21. The kit of Claims 19 or 20, wherein the corneal tissue is a human, human-based or human-like corneal tissue.

22. The kit of any of Claims 19 to 21, wherein the vector is a viral, bacterial or plasmid-based vector, especially viral, bacterial or plasmid-based expression vector system.

23. Use of at least one anti-apoptotic gene for preventing death of endothelial cells in harvested or artificially manufactured corneas.

24. Use of at least one anti-apoptotic gene for extending the storage life of harvested or artificially manufactured corneas.

25. Use of at least one anti-apoptotic gene for facilitating the storage of harvested or artificially manufactured corneas, especially the storage at temperatures ranging from about 0 °C to about 40 °C, especially from about 2 ⁰C to about 39 ⁰C, particularly from about 0 ⁰C to about 4 ⁰C or at about 37 ⁰C.

26. The use of any of Claims 23 to 25, wherein the harvested or artificially manufactured cornea are treated with the at least one anti-apoptotic gene.

27. The use of any of Claims 23 to 26, wherein the treatment is performed in a cornea storage medium.

28. The use of any of Claims 23 to 27, wherein the corneas are human or human-like or human-based corneas or corneas of human origin.

29. The use of any of Claims 23 to 28, wherein the anti-apoptotic gene is selected among genes of the BCL-2 family, especially BCL-xL, BCL-2, BCL-w and MCLl ; and P35.

30. The use of any of Claims 23 to 29, wherein the anti-apoptotic gene is selected among animal-derived, preferably human genes, preferably selected from genes of the BCL-2 family, especially BCL-xL, BCL-2, BCL-w and MCLl .

31. The use of any of Claims 23 to 30, wherein the anti-apoptotic gene is selected among virus-derived genes.

32. The use of any of Claims 23 to 31, wherein the anti-apoptotic gene is P35.

33. The use of any of Claims 23 to 32, wherein the anti-apoptotic gene is selected from the group consisting of BCL-xL, P35, BCL-2, Survivin, BCL-w, MCLl, Al, and CED-9, especially P35, BCL-xL, BCL-2 and BCL-w, preferably P35 and BCL-xL, more preferably P35.