Retinal incorporation and differentiation of mesenchymal stem cells intravitreally injected in the injured retina of rats.

PURPOSE To evaluate the pattern of retinal integration and differentiation of mesenchymal stem cells (MSCs) injected into the vitreous cavity of rat eyes with retinal injury. METHODS Adult rat retinas were submitted to laser damage followed by transplantation of DAPI-labeled BM-MSCs grafts. To assess the integration and differentiation of BM-MSCs in laser-injured retina, host retinas were evaluated 2.4 and 8 weeks after injury/transplantation. RESULTS Our results demonstrated that the grafted cells survived in the retina for at least 8 weeks and almost all BM-MSCs migrated and incorporated into the neural retina, specifically in the outer nuclear layer (ONL), inner nuclear layer (INL) and ganglion cell layer (GCL) while a subset of grafted cells were found in the subretinal space posttransplantation. At 8 weeks immunohistochemical analysis with several retinal specific markers revealed that the majority of the grafted cells expressed rhodopsin, a rod photoreceptor marker, followed by parvalbumin, a marker for bipolar and amacrine cells. A few subsets of cells were able to express a glial marker, glial fibrillary acidic protein. However, grafted cells failed to express pan-cytokeratin, a retinal pigment epithelium marker. CONCLUSIONS These results suggest the potential of BM-MSCs to differentiate into retinal neurons. Taken together, these findings might be clinically relevant for future mesenchymal stem cell therapy studies concerning retinal degeneration repair.