Short-term study of allogeneic retinal pigment epithelium transplants ontodebrided Bruch's membrane

Purpose. To investigate the survival and behavior of retinal pigment epithe lium (RPE) microaggregates transplanted onto hydraulically debrided Bruch's membrane and to compare results of using three different vehicles for cell delivery. Methods. RPE microaggregates obtained from male cats were transplanted onto the tapetal area of female cats after native RPE was debrided. For the con trol, one of three vehicles was introduced into the debridements. Each tran splant Or control specimen was analyzed histologically and immunohistochemi cally. Transplanted male RPE cells were identified by in situ labeling of t he cat Y chromosome. Results. Histologically, significant numbers of condensed. darkly stained R PE nuclei were observed in all transplants compared with few TUNEL-positive RPE cells. Cellular retinal-dehyde-binding protein was present Lip to day 7 in all RPE cells in transplants. In both transplant and control specimens , the antibody against the Ki-67 nuclear antigen labeled some RPE cells at day 3. TUNEL-positive outer nuclear layer nuclei were most frequently obser ved at day 1. but were much less frequent at 7 days in both transplant and control specimens. Conclusions. Transplanted RPE appeared to retain at least some markers of d ifferentiation up to 7 days after surgery. Some proliferation of transplant ed RPE cells was also seen. Apoptotic cell death of transplanted RPE, as ju dged by TUNEL staining was observed rarely. RPE transplants imposed no adve rse effect on the overlying retina. RPE survival appeared to be similar wit h each of the three vehicles for cell delivery.