Intravitreal and subretinal syngeneic bone marrow mononuclear stem cell transplantation improves photoreceptor survival but does not ameliorate retinal function in two rat models of retinal degeneration

Purpose To study and compare effects of syngeneic bone marrow mononuclear stem cells (BM-MNCs) transplants on inherited retinal degeneration in two animal models with different etiologies: the RCS and the P23H-1 rats. To compare the safety and efficacy of two methods of intraocular delivery: subretinal and/or intravitreal. Methods A suspension of BM-MNCs was injected subretinally or intravitreally in the left eyes of P23H-1 and RCS rats at post-natal day (P) 21. At different survival intervals after the injection: 7, 15, 30 or 60 days, the retinas were cross-sectioned, and photoreceptor survival and glial cell responses were investigated using immunodetection of cones (anti-cone arrestin), synaptic connections (anti-bassoon), microglia (anti-Iba-1), astrocytes and Muller cells (anti-GFAP). Electroretinographic function was also assessed longitudinally. Results Intravitreal injections (IVIs) or subretinal injections (SRIs) of BM-MNCs did not produce adverse effects. The transplanted cells survived for up to 15 days but did not penetrate the retina. Both IVIs and SRIs increased photoreceptor survival, decreased synaptic degeneration and glial fibrillary acidic protein (GFAP) expression in Muller cells but did not modify microglial cell activation and migration or the electroretinographic responses. Conclusions Intravitreal and subretinal syngeneic BM-MNCs transplantation decreases photoreceptor degeneration and shows anti-gliotic effects on Muller cells but does not ameliorate retinal function. Moreover, syngeneic BM-MNCs transplants are more effective than the xenotransplants of these cells. BM-MNC transplantation has potential therapeutic effects that merit further investigation.