Survival, Integration and Differentiation of Retinal Progenitor Cells from GFP Transgenic Mice Transplanted Subretinally to Adult, Normal Pigs

Abstract

Abstract: : Purpose: To investigate the survival, integration and differentiation of retinal progenitor cells from GFP transgenic mice after subretinal transplantation to adult normal pigs. Methods: Retinal progenitor cells derived from postnatal day 1 GFP-transgenic mice were transplanted subretinally either as single cell suspension, as spheres or as a biodegradable polymer/progenitor composite to 20 normal non-immunosuppressed adult pigs. Prior to transplantation, small areas of the retina of 10 pigs were damaged with either laser treatment or by mechanical scraping of the neuroretina. The pigs were sacrificed at different intervals ranging from 30 minutes to five weeks post-transplantation. The eyes were immunohistochemically examined for various progenitor-, retina-, RPE or glial specific antibodies. Results: The GFP expressing mice cells survived well up to 14 days post-transplantation. After 5 weeks, only a few GFP cells were found in 3 out of 6 pigs. The cells integrated mainly into the RPE in the non-damaged pig retinas transplanted with cell suspension. In the animals grafted with spheres or polymer membranes, no integrating cells were found, although cells survived in the subretinal space either as spheres or within the membrane. In the pigs receiving laser treatment prior to grafting of cell suspension, GFP cells were found integrating into all layers of the retina. Cells co-expressing PCNA or Ki67 and GFP were only found in the pig sacrificed after 30 minutes. Although the grafted cells ceased proliferation and in some cases differentiated into cells morphologically similar to mature retinal neurons, only nestin and GFAP co-localized with GFP among all the various progenitor-, retina-, RPE or glial specific antibodies used. Conclusions: Our results show that retinal progenitor cells from GFP transgenic mice can survive, integrate and differentiate in the xenogeneic pig retina. However, the cells do not survive for extended periods, and do not differentiate into mature RPE or retinal cells. The cells integrate into the RPE and retina only when delivered as a cell suspension. The retinal integration is markedly enhanced by laser treatment prior grafting. Allogeneic progenitor cells will likely be better tolerated, and therefore more useful for studying cell replacement strategies in large animal models.

Keywords: transplantation • immunohistochemistry • plasticity