Journal of Neuroscience, Vol 1, 1155-1162, Copyright © 1981 by Society for Neuroscience
Action of a trophic factor(s) from rabbit corneal epithelial culture on dissociated trigeminal neurons
KY Chan and RH Haschke
Cultured corneal epithelial cells release a factor(s) that stimulates
trigeminal neurons to form neurites in vitro. To characterize this trophic
effect, conditioned media (serum free, supplemented) from cultures for
corneal epithelium, stromal fibroblasts, and endothelium were studied
further. Only epithelial conditioned medium (PCM) prolonged neuronal
survival and induced neurite outgrowth. This trophic influence peaked after
2 to 3 days and gradually declined thereafter during a week when the medium
was not renewed. Using a bioassay to score the percentage of initially
viable neurons that extended neurites, it was found that the trophic effect
of PCM was proportional to the conditioned medium concentration and to the
cell density of the epithelial culture used for the conditioning. Maximum
activity in PCM was correlated with confluency of the epithelial culture.
Experiments using antiserum to nerve growth factor (NGF) and purified
antibody to cold-insoluble globulin (CIG) indicated that the tropic effect
of PCM was not derived from NGF or CIG. The trophic activity of PCM was
abolished totally by heat or trypsin treatment but was not affected by
collagenase. Although a fraction of the trophic activity was associated
with the substratum after adsorption of PCM, this and other evidence did
not suggest that the primary action of PCM was to enhance neuronal
adhesion.