Characteristics of retinal stem cells from rat optic cup at embryonic day 12.5 (tailbud stage)

Photoreceptor loss causes irreversible blindness in many retinal diseases. Repair of such damage by cell transplantation is one of the most feasible types of central nervous system treatment. Retinal stem cells (RSC) are a substrate for cell-replacement therapy, and previous studies have shown that RSCs from different developmental stages have distinct properties in proliferative capacity and differentiation potential. The tailbud stage is of special interest in retinogenesis, because RSCs commence differentiation after this period. However, no information about the characteristics of RSCs from the tailbud stage is available. In this study, the characteristics of cell cultures from the rat optic cup (referred to as optic-cup-derived RSCs; OC-RSCs) at embryonic day 12.5 (tailbud stage) were analyzed. OC-RSCs grew either as monolayers or as neurospheres in the presence of basic fibroblast growth factor and could be dissociated into a single cell suspension. Using the MTT assay, immunochemistry, cytogenetic analysis, and flow cytometry, we found that OC-RSCs were easily enriched to 92% by three passages, had a normal diploid karyotype, and exhibited no obvious differences in proliferative rate during eight passages (doubling time: 36 h). OC-RSCs produced retinal specific cells after the addition of serum to the medium, but the differentiation potential was affected by serum concentration. Preliminary results showed that transplanted OC-RSCs were incorporated into the degenerated retina of RCS rats and differentiated into rhodopsin-positive cells. Thus, OC-RSCs, after suitable enrichment, provide a population of stem cells with distinct growth and differentiation properties that make them suitable for research into RSC differentiation and transplantation.