Apoptotic cell death and regeneration in the newborn retina after irradiation prior to bone marrow transplantation

Purpose: We studied the contribution made by circulating bone marrow (BM)-derived cells to the newborn and mature retinas of BM-transplanted mice. Methods: Newborn and adult C57BL/6J mice were administered a lethal dose of total-body irradiation, after which pathologic changes to the retinas were periodically assessed. In addition, mice received BM cells from 8-week-old green fluorescent protein (GFP) transgenic mice, and the subsequent differentiation of GFP+ cells was studied. Results: Within 5 hr after irradiation of newborn mice, retinal cells began to die due to apoptosis. By contrast, irradiation of adult mice elicited no histologic changes in the retina. BM cells generally did not differentiate in adult mice, but numerous GFP+ BM cells were integrated into the retinal tissue of newborn mice, where they expressed various cell type-specific markers. Finally, examination of whole retina mounts showed that GFP+ cells also contributed to retinal vascularization. Conclusions: Our findings underscore the importance of careful evaluation of the biological effects of irradiation in models making use of BM transplantation.