Evidence that hepatocyte growth factor abrogates contact inhibition of mitosis in Madin-Darby canine kidney cell monolayers

It is becoming increasingly apparent that hepatocyte growth factor (HGF)(1) plays an important role in kidney development, regeneration, and transform ation to carcinoma. Previous in vitro studies have shown that HGF stimulate s cell scattering, but not proliferation, in the renal epithelial cell line Madin-Darby canine kidney (MDCK) when grown on plastic at low density. Thi s communication demonstrates that HGF treatment of confluent monolayers of MDCK also stimulates DNA synthesis and cell division. HGF stimulated thymid ine incorporation in confluent MDCK cell monolayers grown on plastic in a d ose dependent fashion, but did not stimulate thymidine incorporation in MDC K cells at 10-20% confluency on plastic. Additionally, basolaterally, but n ot apically, applied HGF stimulated thymidine incorporation in confluent MD CK cell monolayers grown on filters. Immunofluorescent labeling of nuclei i n control and HGF treated MDCK cell monolayers grown on filters demonstrate d an increase in mitotic figures. Confocal X-Z section views and direct cel l counts of MDCK cell monolayers grown on filters demonstrated an increase in cell number after HGF treatment compared to controls. This is the first report of HGF stimulating cell proliferation in previously quiescent renal epithelial cell monolayers. This model will be useful for studying the mech anisms controlling cell proliferation rates in epithelial tissue.