Fetal mesenchyme-derived factors are likely to play an important role in pancreatic islet development and growth. We have used primary cultures of human fetal pancreatic tissue to identify growth factors that have morphogenic, mitogenic, and insulinotropic activity. The formation of islet-like cell clusters (ICCs) during a 6-day culture was stimulated two- to threefold by hepatocyte growth factor/scatter factor (HGF/SF) basic fibroblast growth factor (FGF)-2, and to a lesser extent by keratinocyte growth factor (FGF-7) and insulin-like growth factor-II (IGF-II). In contrast, transforming growth factor-β (TGF-β) had a strong inhibitory effect. The ICCs formed during HGF/SF stimulation consisted mainly of epithelial cells, whereas FGF-2-induced ICCs were predominantly nonepithelial. Furthermore, although both FGF-2 and HGF/SF increased the total insulin content of the cultures, only HGF/SF increased the insulin content per DNA. Quantitatively, HGF/SF stimulated a 2.3-fold increase in the proportion of insulin-positive cells and a 3-fold higher number of replicating β-cells. Blocking of the IGF-I receptor inhibited ICC formation but did not affect their insulin content. Immunoneutralizing TGF-β resulted in increased cell growth and insulin content, indicating the presence of an endogenous inhibitory TGF-β activity in the model system. Our results suggest that HGF/SF may be an important component of the fetal mesenchyme-derived factors responsible for pancreatic islet development. HGF/SF also may prove valuable for supporting the in vitro growth of islet cells.

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