High concentrations of HGF inhibit skeletal muscle satellite cell proliferation in vitro by inducing expression of myostatin: a possible mechanism for reestablishing satellite cell quiescence in vivo

Abstract

Skeletal muscle regeneration and work-induced hypertrophy rely on molecular events responsible for activation and quiescence of resident myogenic stem cells, satellite cells. Recent studies demonstrated that hepatocyte growth factor (HGF) triggers activation and entry into the cell cycle in response to mechanical perturbation, and that subsequent expression of myostatin may signal a return to cell quiescence. However, mechanisms responsible for coordinating expression of myostatin after an appropriate time lag following activation and proliferation are not clear. Here we address the possible role of HGF in quiescence through its concentration-dependent negative-feedback mechanism following satellite cell activation and proliferation. When activated/proliferating satellite cell cultures were treated for 24 h beginning 48-h postplating with 10-500 ng/ml HGF, the percentage of bromodeoxyuridine-incorporating cells decreased down to a baseline level comparable to 24-h control cultures in a HGF dose-dependent manner. The high level HGF treatment did not impair the cell viability and differentiation levels, and cells could be reactivated by lowering HGF concentrations to 2.5 ng/ml, a concentration that has been shown to optimally stimulate activation of satellite cells in culture. Coaddition of antimyostatin neutralizing antibody could prevent deactivation and abolish upregulation of cyclin-dependent kinase (Cdk) inhibitor p21. Myostatin mRNA expression was upregulated with high concentrations of HGF, as demonstrated by RT-PCR, and enhanced myostatin protein expression and secretion were revealed by Western blots of the cell lysates and conditioned media. These results indicate that HGF could induce satellite cell quiescence by stimulating myostatin expression. The HGF concentration required (over 10-50 ng/ml), however, is much higher than that for activation, which is initiated by rapid release of HGF from its extracellular association. Considering that HGF is produced by satellite cells and spleen and liver cells in response to muscle damage, local concentrations of HGF bathing satellite cells may reach a threshold sufficient to induce myostatin expression. This time lag may delay action of the quiescence signaling program in proliferating satellite cells during initial phases of muscle regeneration followed by induction of quiescence in a subset of cells during later phases.

Numb-deficient satellite cells have regeneration and proliferation defects

“…Similarly, knockdown of Numb in MDCK cells destabilizes E-cadherin-based cell adhesion and potentiates sensitivity to hepatocyte growth factor (HGF) (74,75). Intriguingly, we recently reported that high concentrations of HGF inhibit satellite cell proliferation by inducing Mstn (76). This observation opens the possibility that HGFdependent signaling could link Numb to Mstn expression.…”

Are Human and Mouse Satellite Cells Really the Same?

“…Even the concentration of a particular growth factor and its interaction with other factors, e.g. HGF and myostatin, may be crucial for its effect on satellite cells (Yamada et al 2010). …”

Muscle stem cells and reversible quiescence: The role of sprouty

“…The temporal reimmergence of the satellite cell quiescent state occurring after extensive repair of the myofibers may be related to a niche-based signaling mechanism. Recently, HGF 45 and Ang1, 30 have been implicated as quiescence-inducing, ligand derived-growth factors. The Ang1/Tie-2 signaling cascade also regulates quiescence and self renewal of the HSCs, 46 suggesting certain conservation for quiescence regulation, at the level of RTK signaling and niche-based regulatory mechanisms.…”