Hydrostatic pressure mediates epithelial-mesenchymal transition of cholangiocytes through RhoA/ROCK and TGF-β/smad pathways.

Biomechanical cue within the tissue microenvironment is known to play a critical role in regulating cell behaviors and maintaining tissue homeostasis. As hydrostatic pressure often increases in biliary system under pathological states, we investigated the effect of the moderate elevation of the hydrostatic pressure on biliary epithelial cells, especially on the epithelial-mesenchymal transition (EMT). Human intrahepatic biliary epithelial cells were loaded to hydrostatic pressure using a commercial device. We found that loading the cells to 50 mmHg hydrostatic pressure induced obvious morphological changes and significantly upregulated vimentin, ZEB1, and pSmad2/3, fibronectin, and collagen 1α. All changes induced by hydrostatic pressure loading were effectively mitigated by either ROCK inhibitor (Y-27632) or ALK5 inhibitor (SB-431542). Our in vitro experimental data suggests that hydrostatic pressure loading induces EMT of cholangiocytes through RhoA/ROCK and TGF-β/Smad pathways. Elevated hydrostatic pressure in biliary duct system under pathological states may promote the biliary epithelial cells shifting to profibrotic and mesenchymal characteristics.