Involvement of c-Src/STAT3 signal in EGF-induced proliferation of rat spermatogonial stem cells

Epidermal growth factor (EGF) plays a role in male germ cell development, but the precise function is yet to be defined. This study shows that EGF stimulates rat spermatogonial proliferation in a dose-dependent manner and significantly increased the protein levels of phosphated c-Src (p-c-Src) and phosphated signal transducer and activator of transcription 3 (p-STAT3). Moreover, overexpression of c-Src tagged with enhanced green fluorescence protein (EGFP) in rat spermatogonial stem cells enhances the cell viability. In contrast, knockdown or inhibition of c-Src inhibits rat spermatogonial stem cell proliferation; EGF could not abrogate the inhibitory effect. Evidently, the content of p-STAT3 protein was increased in c-Src-expressing cells and decreased in c-Src-suppressing cells. Furthermore, knockdown or inhibition of STAT3 also suppressed cell viability; neither EGF nor increased c-Src could reverse the inhibitory effect. These results are the first evidence that EGF induces proliferation of rat spermatogonial stem cells through c-Src/STAT3 signal.