Retinal neurospheres prepared as tissue for transplantation.

The present work was conducted to study the cellular composition and developmental capacity of retinal neurospheres. Furthermore, the ability of grafted neurospheres to integrate into adult retinal tissue was studied in an in vitro model. Retinal progenitor cells isolated from rat embryos were expanded into neurospheres in vitro in the presence of basic fibroblast growth factor (bFGF), epidermal growth factor (EGF) and leukemia inhibitory factor (LIF). Neurospheres labeled with a lipophilic dye were placed onto explants, and tissue interactions were analyzed after 2-6 days of culture. Immunocytochemical analysis of neurospheres revealed the presence of neuronal and glial cells. Proliferating neuronal and glial cells were observed after 2 weeks, whereas the neuronal cell proliferation declined considerably after 4 weeks. Few apoptotic cells were observed in the neurospheres. Neurospheres cultured on explanted adult retina engrafted with the surrounding tissue, but progenitor cell migration into the explants was low. However, the grafted neurospheres appeared to limit the experimentally induced photoreceptor apoptosis in the surrounding explant tissue.