Recombinant platelet-derived growth factor-BB stimulates growth and inhibits differentiation of rat L6 myoblasts
P Jin1, T Sejersen, N R Ringertz
1Department of Medical Cell Genetics, Medical Nobel Institute, Karolinska Institutet, Stockholm, Sweden.
Abstract:
We previously found that L6 myoblasts and skeletal muscle isolated from developing rats express the platelet-derived growth factor (PDGF) beta-receptor gene (Jin, P., Rahm, M., Claesson-Welsh, L., Heldin, C.-H., and Sejersen, T. (1990) J. Cell Biol. 110, 1665-1672). We now report that recombinant human PDGF-BB is a mitogen for L6 myoblasts and also a potent inhibitor of myogenic differentiation. Treatment of L6J1 myoblasts with PDGF-BB increased the rate of DNA synthesis and stimulated cell proliferation. In differentiation medium (Dulbecco's modified Eagle's medium/0.5% fetal calf serum or Dulbecco's modified Eagle's medium/insulin), PDGF-BB prevented fusion of confluent myoblasts and suppressed biochemical differentiation in L6J1 cells. Inhibition of myoblast differentiation was, however, reversible. Withdrawal of PDGF-BB from the medium allowed myoblast fusion to occur. Northern blot hybridization showed that the PDGF beta-receptor mRNA was down-regulated to an undetectable level when confluent cultures of L6J1 myoblasts in growth medium (Dulbecco's modified Eagle's medium/5% fetal calf serum) were shifted to differentiation medium. Receptor binding assays further indicated that binding of PDGF-BB to its receptors on L6J1 myoblasts declined rapidly before creatine kinase activity rose. Our results provide the first demonstration that PDGF-BB is a potent regulator of myogenesis of L6 rat myoblasts and suggest that it may regulate muscle differentiation in vivo.
Insights
Platelet-derived growth factor-BB (PDGF-BB) stimulates proliferation but inhibits muscle cell differentiation in L6 myoblasts. This inhibition is reversible, suggesting PDGF-BB regulates myogenesis.
Area of Science:
- Cell Biology
- Molecular Biology
- Developmental Biology
Background:
- L6 myoblasts and developing rat skeletal muscle express the platelet-derived growth factor (PDGF) beta-receptor gene.
- Previous research established the presence of the PDGF beta-receptor in muscle cells.
Purpose of the Study:
- To investigate the role of PDGF-BB as a mitogen and regulator of myogenic differentiation in L6 myoblasts.
- To determine the effects of PDGF-BB on DNA synthesis, proliferation, and differentiation of L6 myoblasts.
Main Methods:
- Treatment of L6J1 myoblasts with recombinant human PDGF-BB in growth and differentiation media.
- Assays for DNA synthesis, cell proliferation, and biochemical differentiation markers (e.g., creatine kinase activity).
- Northern blot hybridization to analyze PDGF beta-receptor mRNA levels.
- Receptor binding assays to quantify PDGF-BB binding.
Main Results:
- PDGF-BB significantly increased DNA synthesis and proliferation in L6 myoblasts.
- PDGF-BB potently inhibited myoblast fusion and suppressed biochemical differentiation, an effect that was reversible upon withdrawal of PDGF-BB.
- PDGF beta-receptor mRNA levels decreased significantly during differentiation, and PDGF-BB binding declined before the rise in creatine kinase activity.
Conclusions:
- PDGF-BB acts as a potent regulator of myogenesis in L6 rat myoblasts, promoting proliferation while inhibiting differentiation.
- The findings suggest a potential in vivo role for PDGF-BB in regulating muscle differentiation.
