STAGE-SPECIFIC ELEVATED EXPRESSION OF THE GENES FOR HEPATOCYTE GROWTH-FACTOR, KERATINOCYTE GROWTH-FACTOR, AND THEIR RECEPTORS DURING THE MORPHOGENESIS AND DIFFERENTIATION OF RAT STOMACH MUCOSA

Hepatocyte growth factor (HGF) and keratinocyte growth factor (KGF) ar e two factors considered to be involved in the morphogenesis of severa l organs. To understand the role of HGF and KGF in the stomach develop ment, we analyzed changes in the levels of expression of the genes for the two growth factors and their receptors in the fetal rat stomach b y competitive RT-PCR. Resembling our previous results for HGF, the exp ression of the genes for KGF and its receptor was observed in the mese nchyme and epithelium of 16.5 day fetal stomach, respectively, indicat ing the possibility that KGF mediates the epithelial-mesenchymal inter action in the early stage of stomach development. The developmental pr ofile of the expression of the genes for the two growth factors and th eir receptors were different, indicating a difference in their roles; the genes for HGF and c-met, the receptor for HGF, are expressed mainl y during the morphogenetic period, while the genes for KGF and its rec eptor mainly after the morphogenetic period. Thus, it is probable that HGF controls the proliferation of epithelial cells during the morphog enetic process. The expression of the genes for KGF and its receptor i s not correlated with epithelial proliferation during morphogenesis, b ut it does appear to be linked with epithelial differentiation. These results, together with the absence of significant mitogenic effect of KGF on the epithelial cells of the fetal rat glandular stomach in vitr o, suggest a role for KGF as a differentiation factor. In addition, th e expression profile of the genes for KGF and its receptor towards the end of fetal period appears to be closely correlated with that of mes enchymal cell proliferation, suggesting another role for the growth fa ctor that is not regulated by the epithelial-mesenchymal interaction. (C) 1996 Academic Press, Inc.