OPN-immunoreactive cells were mostly bile duct cells in both Ptc+/− and wild-type mice. Hepatic stellate cells isolated from Ptc+/− mice expressed higher mRNA levels of Gli-2, OPN, collagen and α-smooth muscle actin (α-SMA) compared with the cells from wild-type
mice. Neutralizing OPN with RNA aptamers significantly reduced collagen and α-SMA expressions, but had little effect on Gli-2 expression in stellate cells from Ptc+/− mice. Furthermore, in patients with NASH, ballooned hepatocytes produced Hedgehog ligands and were surrounded by Gli-2 positive stromal cells expressing myofibroblastic markers. These findings suggested that OPN induced by Hedgehog pathway activation, promoted selleck chemicals llc fibrogenic responses in NASH. It was reported that NKT cells could promote liver fibrogenesis by producing profibrotic cytokines such as Hedgehog ligands, OPN, interleukin (IL)-4 and IL-13. Mice genetically deficient in NKT cells developed significantly
less hepatic fibrosis and liver injury, with significantly reduced hepatic and plasma OPN levels compared to wild-type mice after feeding with MCD diet. Activated NKT cells generated OPN and Hedgehog ligands, and neutralizing OPN with aptamers or inhibition of Hedgehog signal transduction attenuated the fibrogenic effect of NKT cells on hepatic stellate cells. These findings suggested see more that OPN can function as check details a paracrine factor, secreted by cholangiocytes or NKT cells, and also as an autocrine factor
to promote fibrogenesis in hepatic stellate cells (Fig. 2). It was suggested that Sex-determining region Y-box 9 (Sox9) was downstream of Gli-2 and responsible for OPN expression in hepatic stellate cells. Co-localized staining for OPN and Sox9 was found in spindle-shaped hepatic stellate cells in the area of fibrosis in mice fed an MCD diet. In adult human hepatic stellate cell lines, LX2 cells, a Hedgehog agonist, increased SOX9 and OPN proteins and siRNA abrogation of Sox9 attenuated the effect of the Hedgehog agonist on OPN expression. Similarly, overexpression of Sox9 rescued the inhibitory effect of a Hedgehog antagonist on OPN expression in the cells. HEPATIC OPN MRNA level was correlated with hepatic neutrophil infiltration and fibrosis in patients with alcoholic liver disease. Hepatic expressions of uncleaved and thrombin-cleaved forms of OPN protein, and OPN mRNA were significantly increased in rat alcoholic steatohepatitis models.[42, 43] It was also shown that the extent of hepatic neutrophil infiltration was significantly correlated with the level of cleaved form of OPN in the model. OPN protein was localized predominantly to the hepatocytes surrounding the inflammatory foci,[42, 43] and OPN mRNA expression was found within biliary epithelium, suggesting that OPN was secreted from biliary epithelium.