Several studies have shown that human endothelial cells do not replicate in vivo even if they retain a proliferative potential, as seen in ex vivo wound healing experiment or in vitro. A recent study demonstrated that a few proliferating cells were found exclusively in extreme periphery of endothelium on human corneas with a short postmortem time and that a very slow and continuous centripetal cell migration might exist to partially compensate the physiological cell loss in vivo. Nevertheless, this CY7 cost mechanism cannot immediately compensate neither acute nor chronic important CEC losses which are replaced by enlargement and migration of neighboring cells resulting in shape modification and increase of cell size. In physiologic conditions the insufficient proliferative capacity leads to a gradual ECD decrease of 0.3�C0.6% per year. This decrease can be accelerated as a result of accidental trauma, certain systemic diseases like diabetes, treatment for glaucoma or endothelial dystrophies. When ECD falls below a critical threshold, the barrier and pump functions of the endothelium are compromised and this results in the formation of a corneal oedema and loss of visual acuity. The conventional treatment for such severe disorder is corneal transplantation, including penetrating keratoplasty and endothelial lamellar graft. Human corneas harvesting, evaluation, preservation and distribution are under the responsibility of eye banks, which stores corneal tissue either for short term at 2�C6uC or for long term at 30�C32uC in culture medium. Unfortunately, there is a worldwide IQ-1 shortage of donor corneas available for transplantation. Several approaches have been evaluated to overcome this lack of tissues. Improvement of surgical procedures allows optimizing the use of corneal graft, especially by lamellar technique, according to the principle of split cornea transplantation for two recipients. In order to extend the EC viability of organ-culture cornea, an anti-apoptotic gene therapy was also assessed. Experiments demonstrated that expression of anti-apoptotic proteins Bcl-xL or p35 allowed limiting the cell loss and increasing the number of available donors corneas.. During the last decades, in vitro culture technics of human corneal endothelial cells have greatly improved. These cells can be isolated and expanded in culture either as a monolayer or as sphere-forming colonies and a number of studies showed the possibility to transplant them as a cellular sheet with or without a carrier or by injecting them directly into the anterior chamber in animal models. Medical treatments are also considered in order to cure corneal endothelial diseases directly in vivo.
