Activation of hepatic stellate cells (HSCs) represents the primary driving force to promote the progression of chronic cholestatic liver diseases. We previously reported that cholangiocyte-derived exosomal long noncoding RNA-H19 (lncRNA-H19) plays a critical role in promoting cholestatic liver injury. However, it remains unclear whether cholangiocyte-derived lncRNA-H19 regulates HSC activation, which is the major focus of this study. Both bile duct ligation (BDL) and Mdr2 knockout (Mdr2 -/-) mouse models were used. Wild-type and H19 maternalΔExon1/+ (H19KO) mice were subjected to BDL. Mdr2 -/-H19 maternalΔExon1/+ (DKO) mice were generated. Exosomes isolated from cultured mouse and human cholangiocytes or mouse serum were used for in vivo transplantation and in vitro studies. Fluorescence-labeled exosomes and flow cytometry were used to monitor exosome uptake by hepatic cells. Collagen gel contraction and bromodeoxyuridine assays were used to determine the effect of exosomal-H19 on HSC activation and proliferation. Mouse and human primary sclerosing cholangitis (PSC)/primary biliary cholangitis (PBC) liver samples were analyzed by real-time PCR, western blot analysis, histology, and immunohistochemistry. The results demonstrated that hepatic H19 level was closely correlated with the severity of liver fibrosis in both mouse models and human patients with PSC and PBC. H19 deficiency significantly protected mice from liver fibrosis in BDL and Mdr2 -/mice. Transplanted cholangiocyte-derived H19-enriched exosomes were rapidly and preferentially taken up by HSCs and HSC-derived fibroblasts, and promoted liver fibrosis in BDL-H19KO mice and DKO mice. H19-enriched exosomes enhanced transdifferentiation of cultured mouse primary HSCs and promoted proliferation and matrix formation in HSC-derived fibroblasts. Conclusion: Cholangiocyte-derived exosomal H19 plays a critical role in the progression of cholestatic liver fibrosis by promoting HSC differentiation and activation and represents a potential diagnostic biomarker and therapeutic target for cholangiopathies. (Hepatology 2019;70:1317-1335).

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Bile duct obstruction is a potent stimulus for cholangiocyte proliferation, especially for large cholangiocytes. Our previous studies reported that conjugated bile acids (CBAs) activate the AKT and ERK1/2 signaling pathways via the sphingosine 1-phosphate receptor 2 (S1PR2) in hepatocytes and cholangiocarcinoma cells. It also has been reported that taurocholate (TCA) promotes large cholangiocyte proliferation and protects cholangiocytes from bile duct ligation (BDL)-induced apoptosis. However, the role of S1PR2 in bile acid-mediated cholangiocyte proliferation and cholestatic liver injury has not been elucidated. Here we report that S1PR2 is the predominant S1PR expressed in cholangiocytes. Both TCA- and S1P-induced activation of ERK1/2 and AKT were inhibited by JTE-013, a specific antagonist of S1PR2, in cholangiocytes. In addition, TCA- and S1P-induced cell proliferation and migration were inhibited by JTE-013 and a specific shRNA of S1PR2 as well as chemical inhibitors of ERK1/2 and AKT in mouse cholangiocytes. In BDL mice, the expression of S1PR2 was upregulated in whole liver and cholangiocytes. S1PR2 deficiency significantly reduced BDL-induced cholangiocyte proliferation and cholestatic injury as indicated by significant reduction of inflammation and liver fibrosis in S1PR2−/− mice. Treatment of BDL mice with JTE-013 significantly reduced total bile acid levels in the serum and cholestatic liver injury. This study suggests that the CBA-induced activation of S1PR2-mediated signaling pathways plays a critical role in obstructive cholestasis and may represent a novel therapeutic target for cholestatic liver diseases.

Cholangiocyte-derived exosomal-H19 plays a critical role in cholestatic liver injury. Serum exosomal H19 represents a noninvasive biomarker and potential therapeutic target for cholestatic diseases. (Hepatology 2018).

The multi-drug resistance 2 knockout (Mdr2−/−) mouse is a well-established model of cholestatic cholangiopathies. Female Mdr2−/− mice develop more severe hepatobiliary damage than male Mdr2−/− mice, which is correlated with a higher proportion of taurocholate (TCA) in bile. Although estrogen has been identified as an important player in intrahepatic cholestasis, the underlying molecular mechanisms of gender-based disparity of cholestatic injury remain unclear. The long non-coding RNA H19 is an imprinted, maternally expressed and estrogen-targeted gene, which is significantly induced in human fibrotic/cirrhotic liver and bile duct ligated mouse liver. However, whether aberrant expression of H19 accounts for gender-based disparity of cholestatic injury in Mdr2−/− mice remains unknown. The current study demonstrated that H19 was markedly induced (~200-fold) in the livers of female Mdr2−/− mice at advanced stages of cholestasis (100-day-old), but not in aged-matched male Mdr2−/− mice. During the early stages of cholestasis, H19 expression was minimal. We further determined that the hepatic H19 was mainly expressed in cholangiocytes, not hepatocytes. Both TCA and estrogen significantly activated the ERK1/2 signaling pathway and induced H19 expression in cholangiocytes. Knocking down H19 not only significantly reduced TCA/estrogen-induced expression of fibrotic genes and sphingosine 1-phosphate receptor 2 (S1PR2) in cholangiocytes, but also markedly reduced cholestatic injury in female Mdr2−/− mice. Furthermore, the expression of small heterodimer partner was substantially inhibited at advanced stages of liver fibrosis, which was reversed by H19 shRNA in female Mdr2−/− mice. Similar findings were obtained in human PSC liver samples. Conclusion H19 plays a critical role in the disease progression of cholestasis and represents a key factor that causes the gender disparity of cholestatic liver injury in Mdr2−/− mice.