| Research Abstract |
Using primary serum-free culture of the epithelia from rat stomachs at various developmental stages, attachment, proliferation and motility differentiation of the epithelia on various substrata was investigated. At the same time the motility of the cells was also analyzed with ECIS. The results of the analyses indicate that morphology and function of the cells are regulated by substrata in a stage-specific manner. Next, the effect of mesenchyme-derived growth factors, HGF, KGF and EGF, on the proliferation and motility of fetal rat embryonic stomach epithelial cells were investigated in the same system.Substrata modulate the phosphorylation of the receptors of the growth factors and thereby regulate epithelial proliferation or motility induced by these growth factors. Then, the expression of various matrix metalloproteinases during the morph genesis of stomach epithelia was investigated. The enhanced expression of MMP2, but no no other MMP, and activation of the enzyme was observed dur
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ing the morphogenesis of the stomach. In vitro analyses using primary epithelial culture and embryonic stomach organ culture revealed that HGF, KGF and EGF stimulated the production of MMP2 in embryonic stomach epithelia and mesenchymes. The observed effect was remarkable especially when the epithelia are on type I collagen or on collagen gel, but not on type IV collagen or laminin.These results indicate that MMP2, of whch production is regulated by both substrata and soluble growth factors, is deeply involved in the morphogenesis of embryonic stomach.Finally, the expression and intracellular localization of a family of small GTP-binding protein (G-protein), was analyzed in the embryonic stomach epithelia during development and also in the epithelia cultured in vitro on various substrata, and no significant difference was observed. After introducing various oncogenes into stomach epithelia, it was recombined with the mesenchyme and the proliferation, motility and morphogenesis was analyzed. MEK (mitogen-activated protein kinasekinase) induced enhancement in the motility, and infiltration into mesenchymes. However, the expression level of Map-kinase (erk- 1, 2), their localization and activity with and without growth factor stimulation did not show any significant difference irrespective of kinds of substrata. Less
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