Further Evidence of Regenerative Capacity of Human Corneal Endothelial Cells in the Corneal Periphery

Abstract

Abstract: : Purpose: In a previous study we had shown, that human corneal endothelial cells isolated from the periphery of donor corneas exhibited proliferation in vitro whereas the cells from the center did not. In this study we demonstrate, that this difference between peripheral and central human corneal endothelial cells exists also when the cells are still attached to Descemets membrane. Methods: We investigated endothelial cell proliferation using either scleral rims about 5 hours after the corneas had been used for keratoplasty or whole donor corneas that were not suitable for keratoplasty. Descemet membrane of the whole corneas were separated in three zones by means of 6.5 and 9.0 mm trephines. After 5 hours of incubation in medium Descemet membranes with the attached endothelial cells were peeled off by means of fine forceps and directly used for determination of the proliferation associated protein Ki67. To measure alternatively DNA synthesis membranes were incubated in the presence of BrdU for 18 hours. Incorporation of BrdU and expression of the protein Ki67 were analysed by means of monoclonal antibodies. Results: Endothelium from five scleral rims was analysed for expression of Ki67, another four for BrdU incorporation. Stained cells were found in all nine preparations. Furthermore up to now 12 whole corneas were analysed. No positive cells were found within the inner circle of 6.5 mm. In 4 corneas positive cells were present in the zone between 6.5 and 9.0 mm and in 8 corneas positive cells were also found in the zone outside the 9.0 mm ring. Two corneas exhibited positive cells in both of these zones whereas two other corneas did not show any positive cell. Additionally three corneas were used to elucidate the induction of proliferation. In these cases the 5 hour period of incubation after trephination was omitted. No positiv cells were found in the endothelium. From one of these corneas the fellow cornea was available and was analysed including the 5 hour incubation period. Positive cells were seen in the periphery. Conclusions: Proliferative capacity of endothelial cells is not equaly distributed throughout the endothelium of human donor corneas. The presented results support our previous hypothesis, predicting a regenerative zone within the peripheral part of human corneal endothelium and the possibility to induce proliferation. Further studies are under investigation to elucidate the mechanism of this induction. For example we try to resolve the question whether this induction can be induced during eye banking or after cornea transplantation. Supported by the Ernst and Berta Grimmke foundation, Germany.

Keywords: cornea: endothelium • regeneration • cornea: basic science