Transplantation of retinal progenitor cells from GFP–transgenic pigs to the injured retina of allogeneic recipients

Abstract

Abstract: : Purpose: To evaluate the survival of GFP+ porcine retinal progenitor cells (gpRPCs) following transplantation to the subretinal space of allogeneic recipients, to assess GFP reporter gene expression in vivo, and to evaluate the extent of morphological integration and phenotypic differentiation exhibited by gpRPCs within the injured retina. Methods: Retinal progenitor cells, harvested from GFP–transgenic pigs on embryonic day 60, were transplanted to the subretinal space of 3 month old Danish Landrace pigs (N=9) as small spheres. No immunosuppression was used. Prior to transplantation, retinal injury was induced using laser or subretinal scraping. Eyes were collected and examined histologically at 2, 5, and 10 week survival times. Results: Survival of GFP+ gpRPCs was seen in all eyes at all time points (9/9), with good survival in most (7/9), and inflammation limited to one case at 5 weeks (1/9). There was no evidence for in vivo down–regulation of GFP transgene expression over the course of this 10 week study. A subset of eyes (4/9) showed intraretinal integration of gpRPCs. GFP expression allowed visualization of cytoarchitectural details such as the extension of fibers from donor cells into the host plexiform layers. Expression of rod and cone markers by grafted gpRPCs was also seen. Conclusions:Retinal progenitor cells from fetal GFP–transgenic pigs exhibit long–term survival following transplantation to the retina of allogeneic hosts, despite sustained expression of a foreign protein and the absence of immunosuppression. These cells are capable of morphological integration in the injured retina and appear to differentiate along both photoreceptor lineages. Reliable GFP reporter gene expression makes gpRPCs a valuable tool for retinal transplantation studies in the pig model.

Keywords: transplantation • retinal culture • regeneration