Regenerative and proliferative capacity of adult human retinal cells in vitro

The present work was undertaken (a) to determine whether adult human retinal neurons possess the ability to survive and regrow neurites in organ cultures and (b) to investigate the maintenance and proliferative activity of retinal glial cells in vitro. Using material from retinae obtained from human eyes postenucleation we established in vitro organ cultures of retinal pieces in a chemically defined, serum-free medium, previously developed for culturing adult rat and chick retinae. The time course of glial cell migration and of neurite extension was compared with that of adult rat and chick retinae which have been extensively investigated in our laboratory. It appeared from four explanted retinae that the human retinal cells survive for up to 4 weeks in culture and exhibit their typical morphologies. Immunohistochemical investigation of the migrating cells revealed that both astrocytes and Müller-like cells exhibit their typical morphologies in vitro. In explants obtained from a retina 30 years after very traumatic violence to the eye cup, the glial cells but not the neurons extended lengthy fibers. In the explants obtained from a retina about 2 months after traumatic optic nerve injury and subsequent ocular complications, several lengthy fibres were extended from the transplant's edge. They could be labeled with neurofilament antibodies but not with glial fibrillary acidic protein antibodies, indicating their neuronal origin. The results suggest that some injured human retinal neurons respond to exposure to growth-permissive substrates by regeneration of their neurites. Although some morphological features of the fibers suggest that they originate from ganglion cells in the retinal explants, definitive proof of this is not yet available.