Hepatocyte growth factor promotes the growth of cytotrophoblasts by the paracrine mechanism.

Both placental and decidual tissues contained extractable HGF, the former HGF level (31.4 +/- 23.4 ng/mg total protein) being approximately 30 times the latter HGF level. When the localization of HGF protein and HGF mRNA in placental tissues was examined by immunohistological staining and in situ hybridization, HGF protein and HGF mRNA were detected in the mesenchymal cells of the placenta, but were absent in the cytotrophoblast and syncytiotrophoblast. Although c-met protein was expressed in the cytotrophoblast, this receptor was not detectable in the syncytiotrophoblast by immunohistochemical methods. c-met mRNA was detected in placental cell line (tPA30-1) and 4 choriocarcinoma cell lines (BeWo, Jar, Jeg-3, and NUC-1), but HGF mRNA was absent in these cells. When cytotrophoblast cells were cultured in a serum-free medium in the presence of HGF, their DNA synthesis was enhanced depending on the HGF concentration, although human placental lactogen secretion itself was not affected by HGF. These results demonstrated that HGF promotes the growth of the cytotrophoblast by the paracrine mechanism, although it does not serve as a placental differentiation factor.