Cultivated corneal endothelial transplantation in a primate: Possible future clinical application in corneal endothelial regenerative medicine

Purpose: To review our attempt to devise a method of cultivated corneal endothelial transplantation using primates in which corneal endothelium, like that of humans, has low proliferative ability. Methods: Monkey corneal endothelial cells (MCECs) were cultivated, with Subcultures grown on collagen type I carriers. The corneal endothelia of 6 eyes of 6 monkeys were scraped intensively, after which cultivated MCEC sheets were inserted into the anterior chamber of 4 eyes. As controls, a collagen sheet without MCECs was transplanted in 1 eye of a monkey, and a suspension of cultivated MCECs was injected into the anterior chamber of 1 eye of another monkey. Results: MCECs produced a confluent monolayer of closely attached hexagonal cells. which expressed both ZO-1 and Na+-K adenosine triphosphatase. Early postoperative period MCEC sheets were attached to Descemet membrane, and corneal clarity was recovered. Six months after transplantation, MCEC-transplanted corneas remained clear, and closely attached hexagonal cells were observed. In 1 animal with longer observation, polygonal cells were observed by in vivo specular microscopy at a density of >2000 cells/mm(2) and remained > 1600 cells/mm(2) for <= 2 years. Control eyes showed irreversible bullous keratopathy throughout the observation period. Conclusions: Cultivated MCECs become attached to the transplanted eye and maintain a clear cornea <= 2 years postoperatively, suggesting that corneal endothelial cells of primates might have proliferative ability in vivo once they have been cultured and proliferated in vitro. Our monkey model constitutes all important step forward for regenerative medicine with possible future application ill patients with corneal endothelial dysfunction.