Abstract
Purpose: :
A small number of cells that reside in the pigmented ciliary epithelium of the mammalian eye maintain stem cell properties and proliferate in vitro to form characteristic cell aggregates called neurospheres. These ciliary epithelium derived retinal stem cells (CE-RSCs) have the potential to differentiate into multiple retinal cell types and hold promise for treatment of retinal degenerative diseases by cell replacement therapies. Studies in rodents have shown that after allo/xenotransplantation these cells can integrate morphologically into recipient retina and acquire retinal cell phenotypes. To further evaluate the potential for proposed therapeutic strategies, we have carried out CE-RSC transplantations in the domestic pig, as its eye more closely resembles the human in terms of anatomy, size and photoreceptor distribution.
Methods: :
CE-RSCs were isolated from 1-2 week old piglets and expanded as neurospheres. The standard serum free culture medium was additionally supplemented with purine derivative compounds to improve cell proliferation. Primary neurospheres were dissociated and cells labelled with fluorescent vital dyes. Following posterior vitrectomy, about 1x106 cells were injected subretinally into the left eye of 8 week old allorecipients. Eyes were examined 8, 14 and 28 days after the transplantation.
Results: :
Supplementation of the culture media with purine derivatives improved CE-RSC proliferation without affecting their differentiation potential in vitro. Following transplantation at each time point examined, surviving pre-labelled grafted cells were found to have migrated from the site of injection. Grafted pre-labelled cells were often identified to populate the different retinal layers. They extended processes and, in some cases, expressed retinal cell markers including rhodopsin, PKC or calbindin.
Conclusions: :
In addition to complementing findings in rodents our use of the porcine eye as a model provides stronger support to the feasibility of the potential clinical application of CE-RSCs.
Keywords: retina • transplantation • ciliary body