Neuronal differentiation and morphological integration of hippocampal progenitor cells transplanted to the retina of immature mature dystrophic rats

Attempts to repopulate the retina with grafted neurons have been unsuccessful, in large part because donor cells prefer not to integrate with those of the host. Here we describe the first use of neural progenitor cells in the diseased adult retina. Adult rat hippocampal progenitor cells were injected into the eyes of rats with a genetic retinal degeneration. After survival times up to 16 weeks, the retinae of 1-, 4-, and 10-week-old recipients exhibited widespread incorporation of green fluorescent protein-expressing (GFP+) donor cells into the host retina. The 18-week-old recipients showed a similar pattern, but with fewer cells. Grafted cells expressed the mature neuronal markers NF-200, MAP-5, and calbindin. GFP+ cells extended numerous neurites into the host plexiform layers and these processes were intimately associated with synaptophysin+ profiles. GFP+ neurites also extended into the host optic nerve head. These results demonstrate the differentiation of substantial numbers of new neurons within the mature dystrophic retina.