Interleukin‐6‐induced satellite cell proliferation is regulated by induction of theJAK2/STAT3 signalling pathway through cyclin D1 targeting

Abstract

To determine whether interleukin-6 (IL-6) stimulates rat muscle satellite cell proliferation in culture, and if so, to clarify the signalling mechanisms. Primary satellite cells were isolated from thirty male F344 rats, 11weeks of age. IL-6 at concentrations of 0.01, 0.1, 1, 10 or 100ng/ml was added to culture media. IL-6 at 0.01-1ng/ml induced dose-dependent increase in cell proliferation. After treatment with 1ng/ml IL-6, cell proliferation increased by 31%, and p-STAT3(+) /MyoD(+) cells increased in number compared to those in control media (P<0.05). Inhibitors of JAK2 (AG 490) and STAT3 (STAT3 peptide) blocked the increase in BrdUrd(+) cell numbers at 6h post stimulation with 1ng/ml IL-6 (P<0.05). Furthermore, cyclin D1 mRNA expression and cyclin D1(+) /MyoD(+) cell numbers significantly increased in cultures treated with 1ng/ml IL-6 compared to those in control media (P<0.05). In contrast, treatment with 10 and 100ng/ml IL-6 did not stimulate cell proliferation. Treatment with 10ng/ml IL-6 induced greater SOCS3 mRNA expression than with 1ng/ml IL-6 and control media. Moreover, co-localization of SOCS3 and myogenin was observed after treatment with 10ng/ml IL-6. IL-6 induced dose-dependent increase in satellite cell proliferation by activating the JAK2/STAT3/cyclin D1 pathway.