EXTRACELLULAR-MATRIX, GROWTH-FACTORS, GENETICS - THEIR INFLUENCE ON CELL-PROLIFERATION AND MYOTUBE FORMATION IN PRIMARY CULTURES OF ADULT-MOUSE SKELETAL-MUSCLE

Cell proliferation and myotube formation in response to growth factors on various extracellular matrices (ECM) were investigated in primary skeletal muscle cultures from adult SJL/J and BALB/c mice. There was n o difference between the rates of proliferation from primary cultures of SJL/J and Balb/c mice measured at 48 h in response to a range of co ncentrations of PDGF-AA, -AB, -BB, TGF beta(1), or LIF (added at 24 h) . SJL/J primary cultures were more responsive to bFGF (which was the m ost potent mitogen) than were BALB/c cultures. Comparison of dose resp onse curves to bFGF and TGF beta(1) grown on gelatin or Matrigel showe d that the nature of the ECM did not have a significant affect. More m yotubes formed at 4 days in SJL/J than in parallel BALB/c cultures on gelatin or Matrigel (P < 0.05). On gelatin more myotubes with 4 or mor e nuclei were formed in cultures from SJL/J than BALB/c muscle (P < 0. 05); however, on Matrigel these myotubes occurred with similar frequen cy. Myotube formation examined in BALB/c muscle cultures grown on coll agen IV, entactin-free laminin, and fibronectin showed that none of th ese ECM components alone supported large myotube formation (4 or more nuclei) as well as did Matrigel, although fibronectin was as effective as Matrigel with respect to the total number of myotubes formed. Para llel experiments carried out using the myogenic H-2K(b)(27) cell line showed similar effects with the exception of laminin which enhanced la rge myotube formation and desmin expression in the H-2K(b)(27) but not in the primary muscle cultures, The greater sensitivity in mitogenic response to bFGF and the more extensive myotube formation seen in SJL/ J compared with BALB/c cultures in vitro reflects the superior capacit y for muscle regeneration of SJL/J mice in vivo. (C) 1995 Academic Pre ss, Inc.