Myelin Treated Macrophages Release Mitogen for Schwann Cells

Schwann cell (SC) proliferation is a prominent feature of Wallerian degeneration, however the signal for this response is not yet known. Interruption of cellular contact between SCs (1) or SC and axolemma (2) have been proposed as possible stimuli for SC mitosis. A possible involvement of the myelin sheath has been suggested by Salzer and Bunge (3). Finally, the role of macrophages (macs) has been implicated by Beuche and Friede (4) who correlate SC division with mac phagocytosis of myelin debris. We have previously shown that cultured SCs prepared from sciatic nerves of two day old rat pups proliferate in response to an exogenously added rat CNS myelin-(MEF) and axolemma-enriched fraction (AEF) (5). We are studying the role of macs in mediating the mitogenic response of cultured SCs to MEF using cultured rat peritoneal macs. We have shown that conditioned medium (CM) from rat peritoneal macs which have phagocytosed rat CNS MEF is mitogenic to SCs.