Macrophages enhance muscle satellite cell proliferation and delay their differentiation

This study investigated the effect of macrophages on in vitro satellite cel l myogenesis in the turkey and mouse. Macrophages are considered to act as scavengers of tissue debris during the muscle degeneration-regeneration pro cess. The number of dividing cells and of myoblasts expressing the myogenic regulatory factor MyoD indicated that macrophages enhanced satellite cell proliferation in both species. This was confirmed by observations with cult ures treated for bromodeoxyuridine (BrdU) incorporation. In mouse and turke y macrophage-satellite cell cocultures, the number of differentiated myobla sts, the frequency of myogenin-positive cells, and the expression of develo pmental myosin isoforms were reduced as compared with control cultures, ind icating that macrophages delayed satellite cell differentiation. The possib ility that macrophages facilitate muscle fiber reconstitution by enhancing satellite cell proliferation should be taken into consideration in designin g future strategies of satellite cell transplantation as a treatment for mu scular dystrophies. (C) 1999 John Wiley & Sons, Inc.