SUMMARY:Hepatocyte growth factor/scatter factor (HGF/SF) can stimulate growth of gastrointestinal epithelial cells in vitro;however, the physiological role of HGF/SF in the digestive tract is poorly understood. To elucidate this in vivo function, mice were analyzed in which an HGF/SF transgene was overexpressed throughout the digestive tract. Nearly a third of all HGF/SF transgenic mice in this study (28 of 87) died by 6 months of age as a result of sporadic intestinal obstruction of unknown etiology. Enteric ganglia were not overtly affected, indicating that the pathogenesis of this intestinal lesion was different from that operating in Hirschsprung's disease. Transgenic mice also exhibited a rectal inflammatory bowel disease (IBD) with a high incidence of anorectal prolapse. Expression of interleukin-2 was decreased in the transgenic colon, indicating that HGF/SF may influence regulation of the local intestinal immune system within the colon. These results suggest that HGF/SF plays an important role in the development of gastrointestinal paresis and chronic intestinal inflammation. HGF/SF transgenic mice may represent a useful model for the study of molecular mechanisms associated with a subset of IBD and intestinal pseudo-obstruction. Moreover, our data identify previously unappreciated side effects that may be encountered when using HGF/SF as a therapeutic agent. (Lab Invest 2001, 81:297-305).H epatocyte growth factor/scatter factor (HGF/ SF) was first identified as a highly potent hepatocyte mitogen (Gohda et al, 1988;Nakamura et al, 1989) but is now known as a multifunctional cytokine based on its ability to stimulate proliferation, movement, and/or morphogenesis of a broad spectrum of cultured epithelial cells expressing the tyrosine kinase receptor encoded by the c-met proto-oncogene (Gherardi and Stoker, 1991;Montesano et al, 1991;Rosen et al, 1994;Rubin et al, 1991;Vande Woude, 1992;Zarnegar and Michalopoulos, 1995). HGF/SF is produced in cells of mesenchymal origin, whereas c-met is expressed in adult and embryonic epithelium, implicating HGF/SF-Met signal transduction pathways as important in the epithelial-mesenchymal interaction that occurs during embryogenesis, tissue organization, and organogenesis. Gene targeting studies have shown that HGF/SF-Met signaling is required for the normal development of liver, skeletal muscle, and placenta Schmidt et al, 1995;Uehara et al, 1995).In the fetal digestive tract, c-met transcripts were found in the epithelia of the intestinal anlagen and the villi, whereas the distribution of HGF/SF RNA showed dynamic changes during mouse development by in situ hybridization (Sonnenberg et al, 1993). Immunohistochemical analysis of temporal expression revealed that both HGF/SF and c-Met could be detected between 7 and 8 weeks of gestation in human fetal digestive tissues (Kermorgant et al, 1997). These results suggest that HGF/SF-Met signaling participates in digestive system morphogenesis. Moreover, previous studies demonstrated that HGF/SF can stimulate both esophageal ...