Hydrostatic pressure mediates epithelial-mesenchymal transition of cholangiocytes through RhoA/ROCK and TGF-ß/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-ß/Smad pathways. Elevated hydrostatic pressure in biliary duct system under pathological states may promote the biliary epithelial cells shifting to profibrotic and mesenchymal characteristics.

Morphological changes in intraepithelial and stromal telocytes in Cyprinus carpio in response to salinity stress.

Telocytes establish connections and communicate with various types of cells and structures. Few experimental studies have been performed on telocytes. In this study, we investigated the effect of salinity stress on telocytes in relation to osmoregulatory, immune, and stem cells. After exposing the common carp to 0.2 (control), 6, 10, or 14 ppt salinity, we extracted and fixed gill samples in glutaraldehyde, processed and embedded the samples in resin, and prepared semi-thin and ultrathin sections. Two types of telocytes were identified: intraepithelial and stromal telocytes. Intraepithelial telocytes were found to form part of the cellular lining of the lymphatic space and shed secretory vesicles into this space. Stromal telocytes were observed to shed their secretory vesicles into the secondary circulatory vessels. Both intraepithelial and stromal telocytes were enlarged and exhibited increased secretory activities as salinity increased. They exerted their effects via direct contact and paracrine signaling. The following changes were observed in samples from fish exposed to high salinity levels: chloride cells underwent hypertrophy, and their mitochondria became cigar-shaped; pavement cells were enlarged, and their micro-ridges became thin and elongated; stromal telocytes established contact with stem cells and skeletal myoblasts; skeletal muscle cells underwent hypertrophy; and macrophages and rodlet cells increased in number. In conclusion, our findings indicate that intraepithelial and stromal telocytes respond to salinity stress by activating cellular signaling and that they play major roles in osmoregulation, immunity, and regeneration.

Negative pressure induces dedifferentiation of hepatocytes via RhoA/ROCK pathway.

Biomechanical forces are known to regulate the biological behaviors of cells. Although negative pressure has been used for wound healing, it is still unknown about its role in regulating cell plasticity. We investigated whether negative pressure could induce the dedifferentiation of hepatocytes. Using a commercial device, we found that the exposure of primary human hepatocytes to -50 mmHg quickly induced the formation of stress fibers and obviously changed cell morphology in 72 h. Moreover, the exposure of hepatocytes to -50 mmHg significantly upregulated RhoA, ROCK1, and ROCK2 in 1-6 h, and dramatically enhanced the expression of marker molecules on "stemness", such as OCT4, SOX2, KLF4, MYC, NANOG, and CD133 in 6-72 h. However, all these changes in hepatocytes induced by -50 mmHg stimulation were almost abrogated by ROCK inhibitor Y27623. Our data suggest that an appropriate force of negative pressure stimulation can effectively induce the dedifferentiation of hepatocytes via RhoA/ROCK pathway activation.

Hydrostatic pressure induces profibrotic properties in hepatic stellate cells via the RhoA/ROCK signaling pathway.

Elevated interstitial fluid hydrostatic pressure is commonly observed in diseased livers. We herein examined the hypothesis that hydrostatic pressure induces hepatic stellate cells to acquire profibrotic properties under pathological conditions. Human hepatic stellate cells were exposed to 50 mmHg pressure for 24 h. Although we observed few changes of cell growth and morphology, PCR array data on the expression of fibrosis-associated genes suggested the acquisition of profibrotic properties. The exposure of hepatic stellate cells to 50 mmHg pressure for 24 h also significantly enhanced the expression of RhoA, ROCK1, α-SMA, TGF-ß1 , p-MLC, and p-Smad2, and this was effectively attenuated by the ROCK inhibitor Y-27632. Our ex vivo experimental data suggest that elevated interstitial fluid hydrostatic pressure under pathological conditions may promote liver fibrosis by inducing acquisition of profibrotic properties of hepatic stellate cells through the RhoA/ROCK signaling pathway.

Angiotensin receptor blocker alleviates liver fibrosis by altering the mechanotransduction properties of hepatic stellate cells.

Angiotensin receptor blockers have been reported to be beneficial to liver fibrosis, but the relevant molecular and cellular mechanisms remain unclear. We herein investigated whether low-dose angiotensin receptor blocker alleviated liver fibrosis through mechanotransduction regulation. Hydrostatic pressure-induced liver fibrosis model was established in mice by ligating partially the inferior vena cava, and then randomly received a very low dose of losartan (0.5 mg/kg) or placebo treatment for 8 weeks. We found that losartan administration interfered the expression of several mechanotransductive molecules, and effectively alleviated liver fibrosis. Using a commercial device, we further confirmed that ex vivo loading of hepatic stellate cells to 50 mmHg hydrostatic pressure for 24 h significantly upregulated RhoA, ROCK, AT1R, and p-MLC2, which was effectively attenuated by adding 10 nM losartan in medium. Our in vivo and ex vivo experimental data suggest that low-dose angiotensin receptor blockers may alleviate hydrostatic pressure-induced liver fibrosis by altering the mechanotransduction properties of hepatic stellate cells.NEW & NOTEWORTHY Our ex vivo and in vivo experiments clearly indicated that low-dose losartan alleviated liver fibrosis, likely by modulating the mechanotransduction properties of HSCs. Uncovering the biomechanical signaling pathway of ARB treatment on liver fibrosis will be helpful to develop novel molecular targeting therapy for liver diseases.

Developmental morphological analyses on the preglottal salivary gland in Japanese quails (Coturnix japonica).

To understand the development of the mucous preglottal salivary gland in Coturnix japonica (Japanese quail), morphological and histochemical studies were performed on 20 healthy Japanese quail embryos (aging from 10th to 17th incubation days) and 25 healthy quail chicks (aging from 0th to 60th days). The primordia of preglottal salivary gland were observed as an epithelial bud at the early embryonic stage, which then elongated and differentiated into secretory units by the end of this stage. In Japanese quails, the preglottal salivary gland was a mucous polystomatic tubuloalveolar unpaired gland composed of two lateral portions and a middle one embedded into the submucosa of the lingual root. The gland openings accompanied taste pore (8.17 µm) of taste buds associated salivary glands type; some skeletal muscle fibers embedded among secretory lobules extended from muscle cricohyoideus at 14th day-old quail chick. Also, both herbts corpuscles and secretory motor plexus could be detected among secretory lobules. Based on our investigations, the development of the preglottal salivary gland could clearly be distinguished in the embryonic stage into pre bud and bud stages at 10th day old, cord and branching stages ended by cavitation at 11th day old, canalization stage at 13th day old, lobulation and secretory stages by the 17th day old. The secretory materials showed different histochemical reactions ended with highly alcinophilic mucous indicated highly sialomucin (acidic) content. Myoepithelial cells could be demonstrated at a 17-day old quail embryo and thereafter surrounded the secretory endpieces of the preglottal salivary gland.