Characterization of neuritic outgrowth-promoting activity of conditioned medium on spinal cord explants

Conditioned medium (CM) from muscle or fibroblast cultures dramatically increases the outgrowth of neurites from fetal rat spinal cord slices in vitro. The factor(s) in CM responsible for this enhanced outgrowth is chymotrypsin-sensitive, but neuraminidase-insensitive. At neutral pH, the factor(s) binds to a concanavalin A-agarose affinity column, a zinc metal chelate affinity column, a DE-52 anion exchange column, but not to a carboxymethyl-52 cation exchange column. These results suggest that the active CM factor(s) is a glycoprotein that is negatively charged at neutral pH. Following gel chromatography the major peak of outgrowth-promoting activity elutes at a molecular weight of approximately 50,000 daltons.