The multidrug 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 in the 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 noncoding 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 days old) but not in age‐matched male Mdr2–/– mice. During the early stages of cholestasis, H19 expression was minimal. We further determined that hepatic H19 was mainly expressed in cholangiocytes, not hepatocytes. Both taurocholate and estrogen significantly activated the extracellular signal–regulated kinase 1/2 signaling pathway and induced H19 expression in cholangiocytes. Knocking down H19 not only significantly reduced taurocholate/estrogen‐induced expression of fibrotic genes and sphingosine 1‐phosphate receptor 2 in cholangiocytes but also markedly reduced cholestatic injury in female Mdr2–/– mice. Furthermore, expression of small heterodimer partner was substantially inhibited at advanced stages of liver fibrosis, which was reversed by H19 short hairpin RNA in female Mdr2–/– mice. Similar findings were obtained in human primary sclerosing cholangitis 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. (Hepatology 2017;66:869–884).

中文翻译：

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长链非编码RNA H19在多药耐药2基因敲除小鼠胆汁淤积性肝损伤性别差异中的作用

多药耐药 2 基因敲除 (Mdr2–/–) 小鼠是一种成熟的胆汁淤积性胆管病模型。雌性 Mdr2-/- 小鼠比雄性 Mdr2-/- 小鼠发生更严重的肝胆损伤，这与胆汁中牛磺胆酸盐的比例更高有关。尽管雌激素已被确定为肝内胆汁淤积的重要参与者，但胆汁淤积损伤的性别差异的潜在分子机制仍不清楚。长链非编码 RNA H19 是一种印记的、母体表达的、雌激素靶向基因，在人纤维化/肝硬化和胆管结扎的小鼠肝脏中被显着诱导。然而，H19 的异常表达是否解释了 Mdr2–/– 小鼠胆汁淤积损伤的性别差异仍然未知。目前的研究表明，H19 在胆汁淤积晚期（100 天大）的雌性 Mdr2-/- 小鼠的肝脏中被显着诱导（~200 倍），但在年龄匹配的雄性 Mdr2-/- 小鼠中没有。在胆汁淤积的早期阶段，H19 表达极少。我们进一步确定肝 H19 主要在胆管细胞中表达，而不是在肝细胞中表达。牛磺胆酸盐和雌激素均显着激活细胞外信号调节激酶 1/2 信号通路并诱导胆管细胞中 H19 的表达。敲低 H19 不仅显着降低了牛磺胆酸/雌激素诱导的胆管细胞中纤维化基因和鞘氨醇 1-磷酸受体 2 的表达，而且还显着减少了雌性 Mdr2–/– 小鼠的胆汁淤积性损伤。此外，在肝纤维化的晚期阶段，小异二聚体伴侣的表达被显着抑制，这在雌性 Mdr2–/– 小鼠中被 H19 短发夹 RNA 逆转。在人类原发性硬化性胆管炎肝脏样本中也获得了类似的发现。结论：H19在胆汁淤积的疾病进展中起关键作用，是导致Mdr2-/-小鼠胆汁淤积性肝损伤性别差异的关键因素。（肝病学 2017；66：869-884）。