ED2+ Macrophages Increase Selectively Myoblast Proliferation in Muscle Cultures (original) (raw)

1997, Biochemical and Biophysical Research Communications

some macrophages, are present at the site of muscle We have previously shown by coculturing myoblasts damage a few hours after injury. Two days after the and macrophages that myotube formation is strongly infiltrating cell population is almost exclusively comincreased in vitro by the presence of an acid stable, posed of recruited monocytes/macrophages, which are heat-labile, soluble growth factor(s) secreted by macinvolved in removing the necrotic muscle (7-10). Afterrophages. In this paper we obtained macrophages wards, myoblasts accumulate and fuse to regenerate from peritoneal washing which also contained limited the lost myofibers. amounts of other cells such as lymphocytes and meso-A great number of growth factors such as FGF (11thelial cells. We here demonstrate that an ED2-positive 16), IGF (17,18), TGFbeta (19,20), PDGF (21,22), LIF (ED2/) macrophage subpopulation is responsible for (23,24), IL-6 (25-27) and CSF-1 (28) are involved in the myoblast enhanced proliferation. ED2/ macrophages proliferation and differentiation of satellite cell progwere separated by a magnetic-activated cell sorter eny as demonstrated by in vitro studies (see for review (MACS) using a monoclonal antibody against ED2, a ref. 29) and many of these growth factors are secreted membrane antigen peculiar to macrophages. Both by macrophages (30). Therefore it has been hypothe-ED2/ macrophages and their conditioned medium insized that these cells might play a pivotal role in the creased myotube formation when added to primary muscle cultures. Furthermore we demonstrate that regulation of cell mitosis during muscle regeneration. muscle growth induced by macrophages is mainly the To this respect we have recently demonstrated that consequence of an increased myoblast proliferation by rat macrophages obtained from peritoneal exudate coshowing the presence of an increased number of cultured with either embryonic myoblasts or satellite MyoD-positive (MyoD/) myonuclei.