Figure 6.

Schematic representation of the role of SDC4 during myoblast proliferation. The level of SDC4 is gradually decreasing during in vivo skeletal muscle regeneration, and in vitro myoblast differentiation. SDC4 has a complex effect on myoblast proliferation. It can increase myoblast proliferation by enhancing the effect of the proliferative factors (e.g. FGF2, HGF), and by simultaneously decreasing the anti‐proliferative myostatin signalling. The lack of SDC4 increases the level of mature myostatin that can act through its type II Activin receptor (ActRII) to decrease myoblast proliferation. SDC4 may function as a reservoir for the precursor promyostatin; thereby regulating the local bioavailability of mature myostatin by diminishing the formation of the active form (SDC4, syndecan‐4; FGF2, fibroblast growth factor 2; HGF, hepatocyte growth factor).