Trophic Factors Produced by Retinal Cells Increase the Survival of Retinal Ganglion Cells In Vitro

The naturally occurring neuron death of normal development has been shown to depend on trophic factors produced and released by target cells. It has also been shown that the afferent supply and local interactions play a role in the control of this degenerative phenomenon. We studied the effect of trophic factors produced by intrinsic retinal cells on the survival of retinal ganglion cells in vitro. Retinae of newborn hooded rats were retrogradely labelled with horseradish peroxidase injected into the superior colliculus to permit the identification of retinal ganglion cells in culture. We tested the effect of conditioned media either from aggregates or from explants of retinal cells from neonatal rats on the survival of ganglion cells in vitro. Our results showed that both conditioned media increased the survival of these cells. The trophic activity was dose‐dependent, was maintained after dialysis against a 12 kDa membrane, was abolished by heating at 56°C for 30 min, and was not found in conditioned medium from cerebral cortical explants. Conditioned medium obtained without fetal calf serum presented the same trophic effect. These results suggest that the local control of developmental neuron death by intrinsic retinal cells may be mediated by neurotrophic factors.