Hepatocyte growth factor and c-MET are expressed in rat prepuberal testis

The hepatocyte growth factor (HGF) receptor (c-MET) is present in different mammalian tissues and transduces multiple biological effects. The HGF is known to regulate many fundamental cellular functions, such as cell growth, movement and differentiation, and is involved in embryonal morphogenesis. We have studied HGF and c-MET expression in prepuberal rat testis. c-MET gene expression was found in total testis and in homogeneous cell populations, as demonstrated by Northern blotting. In the seminiferous tubules, c-MET gene was only expressed in the myoid cells. In these cells, c-MET was detectable and constantly expressed for at least six days of culture. The interstitial tissue was also c-MET positive. The protein encoded by the MET proto-oncogene was detected in myoid cells, and HGF administration to these cells induced morphological changes in the cells. HGF expression was not detected by Northern blotting using RNA extracted from total testis. By contrast, when homogenous cell populations were used, HGF expression was detectable and exclusively localized in myoid cells. Myoid cell-conditioned medium was able to induce scattering of canine kidney epithelial (MDCK) cells, and the scatter effect of a 3-days conditioned medium was evident even after 7-fold dilution of the medium. Our findings demonstrate that HGF and its receptor are present in rat prepuberal testis. The coexpression of factor and receptor in the myoid cells suggests a new role for HGF as autocrine regulator of myoid cell function and, possibly, as regulator of mammalian testicular function.