Surgical retinal explants as a source of retinal progenitor cells.

PURPOSE To describe the novel observation of spontaneously migrating retinal cells from living donor surgical retinal explants which express progenitor cell markers in the absence of exogenous growth factors. METHODS Surgical retinal explants were harvested from 5 consecutive patients undergoing 23G pars plana vitrectomy for the management of rhegmatogenous detachment. During surgery, equatorial flap tears were trimmed with the vitreous cutter and aspirated. Excised tissue was then regurgitated into a syringe containing balanced salt solution and immediately transferred to tissue culture. Migrating cells subsequently underwent immunohistochemical staining and their characteristics were compared to those of a spontaneously immortalized Muller stem cell line. RESULTS Spontaneously migrating cells were observed from samples taken from all five patients from day 2 to 10 following transfer to culture. These cells were found to express embryonic cell markers, including paired box 6 (Pax-6), sex-determining region Y-box 2 (Sox-2), nestin, cone-rod homeobox (CRX) and cyclin-dependent kinase inhibitor 1B (p27Kip1) as well as proteins consistent with early or retained differentiation down the Muller cell lineage, including glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS). CONCLUSION Following injury, the human equatorial retina is capable of spontaneously producing cells which demonstrate migration and which express progenitor cell markers. Additionally, these cells express proteins consistent with Muller cell lineage. These initial observations support the assertion that the human retina may possess the potential for regeneration and that surgical retinal explants could also act as a ready source of retinal progenitor cells.