DEVELOPMENTALLY-REGULATED RELEASE OF INTRARETINAL NEUROTROPHIC FACTORS IN-VITRO

The effects of conditioned media either from aggregates or from explan ts of embryonic chick retinae and of recombinant neurotrophins were te sted upon the survival in vitro of ganglion cells in dissociated cell cultures from the retina of newborn rats. Ganglion cells were identifi ed by the detection of retrogradely transported horseradish peroxidase injected bilaterally into the superior colliculus. Conditioned media increased significantly the survival of ganglion cells after 2 days in culture, at a wide range of plating densities, and had no effect upon adhesion of rat retinal cells. Media conditioned by cell ensembles fr om chick retinae from embryonic day 8 (E8) to E16 had neurotrophic eff ects. Release of neurotrophic activity peaked at E10-E12, irrespective of the numbers of cells or total concentration of protein in the cond itioned media. The active molecules were non-dialyzable. and were rele ased either in the presence or in the absence of fetal calf serum. The neurotrophic activity was abolished by trypsinization, and recovered by salting-out with 25-75% ammonium sulfate. NT-4, BDNF and, to a less er extent, NT-3, increased the survival of ganglion cells in our assay , while NGF had no effect. The data show-that chick retinal cells rele ase soluble trophic proteins according to a developmentally regulated pattern. These neurotrophic factors may be involved in local competiti ve interactions that help control naturally occurring neuron death amo ng ganglion cells of the vertebrate retina. (C) 1997 ISDN.