Hepatocyte growth factor induces MDCK cell morphogenesis without causing loss of tight junction functional integrity

Abstract

Hepatocyte growth factor (HGF) induces mitogenesis, motogenesis, and tubulogenesis of cultured Madin-Darby canine kidney (MDCK) epithelial cells. We report that in addition to these effects HGF stimulates morphogenesis of tight, polarized MDCK cell monolayers into pseudostratified layers without loss of tight junction (TJ) functional integrity. We tested TJ functional integrity during formation of pseudostratified layers. In response to HGF, the TJ marker ZO-1 remained in morphologically complete rings and functional barriers to paracellular diffusion of ruthenium red were maintained in pseudostratified layers. Transepithelial resistance (TER) increased transiently two-to threefold during the morphogenetic transition from monolayers to pseudostratified layers and then declined to baseline levels once pseudostratified layers were formed. In MDCK cells expressing the trk/met chimera, both HGF and NGF at concentrations of 2.5 ng/ml induced scattering. However, 2.5 ng/ml HGF did not affect TER. The peak effect of HGF on TER was at a concentration of 100 ng/ml. In contrast, NGF at concentrations as high as 25 g/ml had no effect on TER or pseudostratified layer morphogenesis of trk/met-expressing cultures. These results suggest that altered presentation of the stimulus, such as through HGF interaction with low-affinity sites, may change the downstream signaling response. In addition, our results demonstrate that HGF stimulates pseudostratified layer morphogenesis while inducing an increase in TER and maintaining the overall tightness of the epithelial layer. Stimulation of epithelial cell movements by HGF without loss of functional TJs may be important for maintaining epithelial integrity during morphogenetic events such as formation of pseudostratified epithelia, organ regeneration, and tissue repair. c-met protooncogene; transepithelial resistance; Madin-Darby canine kidney cell MORPHOGENETIC CELL REARRANGEMENTS are stimulated by hepatocyte growth factor (HGF), a fibroblast-derived growth factor (77) that has paracrine actions on a variety of cell types. In vivo, HGF is important for the development of the placenta, liver, limbs, and kidney (6,28,67,71,72,82,87) and induces morphogenesis of blood vessels (9,22,47,70). In addition, both HGF and the c-met protooncogene (c-met) (31, 86), a tyrosine kinase receptor (11,19,51,54) to which HGF binds with high affinity (25,32), are regulated in response to organ injury and stimulate epithelial morphogenesis that contributes to tissue repair and regeneration in liver, kidney, lung, gastric mucosa, and muscle (12,38,40,66,81,88). In vitro, many of the pleiotropic effects of HGF can be modeled and show a dependence on both the target cell type and environmental context: paracrine actions of HGF increase hepatocyte mitogenesis (20,41,49,50,90), inhibit growth of tumor cells (69, 78), activate motogenesis and invasiveness of epithelial and endothelial cells (9,18,63,64,70,75,84,85), stimulate wound repair (53), and induce morphogenesis of either epithelial tubes or pseudostrati...

Molecular mechanisms regulating the establishment of hepatocyte polarity during human hepatic progenitor cell differentiation into a functional hepatocyte-like phenotype

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