INTRAOCULAR TRANSPLANTATION OF E1A-IMMORTALIZED RETINAL PRECURSOR CELLS

The purpose of this study was to examine the effect of the ocular envi ronment on the survival, tumorigenicity, and phenotypic marker express ion of immortalized retinal precursor cells transplanted into immunoco mpetent adult and neonatal Sprague-Dawley rats. E1A-NR3, a rat immorta lized retinal precursor cell culture, was used as an inexhaustible sou rce of experimental graft material, These cells were prelabeled with t he fluorescent marker diI -dioctadecyl-3,3,3',3'-tetramethylindocarboc yanine perchlorate) and transplanted intravitreally (50,000 cells per mu L) into 11 adult and 31 neonatal Sprague-Dawley rat eyes. At I mo p osttransplant, animals were sacrificed and retinal tissue sections exa mined histologically for the presence of grafted cells, signs of tumor formation, and retinal phenotypic marker expression. No obvious signs of tumor formation or rejection were seen in a total of 42 eyes in th e immunocompetent hosts. Our results indicate that EIA-NR,3 cells surv ive at least 1 month in vivo, and can migrate from the vitreous into n euroretinal cell layers. Subpopulations of surviving grafted cells wer e seen to express photoreceptor markers rhodopsin and recoverin compar ably between in vitro and in vivo conditions. However, the number of c ells immunoreactive for vimentin and E1A decreased significantly under in vivo conditions. This report represents the first experimental int ravitreal transplantation of E1A-immortalized retinal precursor cells into adult and neonatal rats. The intraocular location and environment appears to affect phenotypic expression of surviving grafted cells, e specially with respect to vimentin and EIA expression. The fact that E 1A-NR.3 cells survived intraocularly at least 1 mo without tumor forma tion suggests that the cells may continue to be useful for further in vivo studies of experimental retinal transplantation, and effects of h istological location on retinal cell phenotype and histogenesis in imm unocompetent hosts. (C) 1998 Elsevier Science Inc.