Mechanisms of Early RPE Allograft Cell Loss

Abstract

Abstract: : Purpose: We have recently described the rapid loss of grafted cells in the Royal College of Surgeons (RCS) rat (ARVO 2002 No. 705). In this project we aim to identify some of the key factors responsible for that cell loss in the allogeneic system. We will test the hypothesis that the early loss (1-7 days post graft) of grafted allogeneic RPE is due to macrophage invasion and/or programmed RPE cell death (apoptosis). Methods: Eighteen eyes of 21 day old RCS rats received grafts of an immortalised allogeneic RPE cell line (LD7.4) to the subretinal space. Eyes were harvested at 1, 3 and 7 days following transplantation. Grafts were assessed for apoptosis using NeuroTACS apoptosis detection kit and cellular infiltration (ED-1 and ED-2 labeling) at these time points. Results: At day one there was marked apoptosis of the grafted cells which continued at day three and at a reduced level by day seven. Subretinal grafts were associated with a rapid influx of ED-1 positive cells at one day post transplant. This level of ED-1 cells persisted at day 3 and reduced by day seven. Conclusions: Subretinal RPE grafts of immortalized allogeneic undergo rapid cell loss (up to 95% of the original graft number) in the first week. The early loss is due to apoptosis and followed by an influx of ED positive cells which may result in further destruction of the graft. This early cell loss needs to be prevented, with efforts made to prolong survival with improved integration: then we may be better placed to assess delayed graft loss and its mechanism.

Keywords: retinal pigment epithelium • immune tolerance/privilege • inflammation