Schwann Cells Secrete a PDGF-like Factor: Evidence for an Autocrine Growth Mechanism involving PDGF

We have investigated the influence of platelet-derived growth factor (PDGF) in peripheral nervous system gliogenesis using two types of Schwann cell cultures. Short-term Schwann cell cultures grow very slowly, but when maintained in culture for several months the division rate of some cells increases, and cell lines can be established. We show that Schwann cells in both short- and long-term culture possess PDGF receptors and synthesize DNA in response to PDGF. Competitive binding experiments show that Schwann cells express mainly PDGF beta-receptors and respond better to PDGF-BB than to PDGF-AA. Conditioned media from short- and long-term Schwann cell cultures contain PDGF-like mitogenic activity, and anti-PDGF immunoglobin partially inhibits DNA synthesis in long-term Schwann cell cultures. Antibody neutralization experiments and Northern blot analyses both indicate that the predominant PDGF isoform in these cultures is PDGF-BB. PDGF-like activity is also detected in extracts of rat sciatic nerve. Taken together, these results suggest that PDGF-BB may stimulate Schwann cell proliferation in an autocrine manner during normal development.