Abstract
Purpose: :
Loss of photoreceptors due to retinitis pigmentosa, age-related macular degeneration and other age, trauma and genetic-related retinal degenerative disorders currently leads to incurable blindness. Since the regenerative capacity of human neural retina is highly limited, one viable treatment option is cellular replacement. Retinal progenitor cells (RPC), isolated from the fetal retina, have been shown to form new functioning photoreceptors and restore retinal function following transplantation into retinal degenerative hosts. Compared to mouse RPC, not much is known about the hRPC phenotype.The aim of this study was to comprehensively describe the phenotype of GMP-manufactured hRPCs as a drug product for retinal degenerative disorders.
Methods: :
hRPC were isolated from human neural retina at 18 week of gestational age and expanded under low-oxygen (3%) conditions up to passage 9. Karyotype analysis, immunocytochemistry and flow cytometry analysis for stemness, eye field, neuronal, proliferation and retinal cell markers were performed. Also, functional properties were investigated using calcium imaging and differentiation assay.
Results: :
hRPC were found to have no chromosome abnormalities, respond to L-glutamate and NMDA-Glycine. Immunostaining has shown presence of Sox2, Klf4, Recoverin, Otx2, Pax6, Ki67, PCNA, CyclinD1, b3 tubulin, NF200, Nestin, Vimentin, SSEA4, CD24, Crx, Nrl, CD73, PSA-NCAM, PTK7. We were unable to detect significant expression of mature photoreceptor markers such as Rhodopsin, Opsin Red/Green, Nr2e3, Rod Outer Membrane. Also, we found hRPC to be negative for markers, specific for neural stem cells (CD133, CD15), retinal pigment epithelia (RPE65), and glial progenitors (A2B5, CD38). However, upon differentiation in vitro we observed more than 50% of cells to express mature photoreceptor markers (Rhodopsin, Opsin Blue, Opsin Red/Green).
Conclusions: :
The phenotype of hRPC may be used to compare different cell products to be prepared for transplantation. Presence of CD24 and CD73, previously found on mouse photoreceptor precursors, suggest the potential of hRPC population to form rods and cones and PSA-NCAM expression is characteristic of cells able to integrate into host retina.