Department of Integrated Biological Science, College of Natural Science, Pusan National University, Pusan, 46241, Korea.
Department of Biological Sciences, College of Natural Science, Pusan National University, Pusan, 46241, Korea.
Cell Death Dis. 2018 Jun 18;9(7):721. doi: 10.1038/s41419-018-0762-z.
Healthy livers have a remarkable regenerative capacity for reconstructing functional hepatic parenchyma after 70% partial hepatectomy (PH). Hepatocytes, usually quiescent in normal healthy livers, proliferate to compensate for hepatic loss after PH. However, the mechanism of hepatocyte involvement in liver regeneration remains unclear. Hedgehog (Hh) pathway plays an important role in tissue reconstitution by regulating epithelial-to-mesenchymal transition (EMT) in liver disease. MicroRNA (miRNA) is involved in cell proliferation and differentiation during embryonic development and carcinogenesis. It was recently reported that miR-378 inhibits transdifferentiation of hepatic stellate cells into myofibroblasts by suppressing Gli-Krüppel family member 3 (Gli3), the Hh-target gene. We hypothesized that miR-378 influences EMT in hepatocytes by interfering with Hh signaling during liver regeneration. As hepatocytes were highly proliferative after PH in mice, miR-378 and epithelial marker, Ppar-g or E-cadherin were downregulated, whereas both Hh activators, Smoothened (Smo) and Gli3, and the EMT-inducing genes, Tgfb, Snail and Vimentin, were upregulated in the regenerating livers and in hepatocytes isolated from them. Compared to cells with or without scramble miRNA, primary hepatocytes transfected with miR-378 inhibitor contained higher levels of Gli3 with increased expression of the EMT-promoting genes, Tgfb, Snail, Col1a1, and Vimentin, suggesting that miR-378 influenced EMT in hepatocytes. Smo-depleted hepatocytes isolated from PH livers of Smo-flox mice showed downregulation of EMT-promoting genes and Gli3, with upregulation of miR-378 and E-cadherin compared to Smo-expressing hepatocytes from PH liver. In addition, delivery hepatocyte-specific AAV8 viral vector bearing Cre recombinase into Smo-flox mice impeded EMT in Smo-suppressed hepatocytes of PH liver, indicating that Smo is critical for regulating hepatocyte EMT. Furthermore, the application of miR-378 mimic into mice with PH delayed liver regeneration by interrupting hepatocyte EMT. In conclusion, our results demonstrate that miR-378 is involved in hepatocyte EMT by regulating Hh signaling during liver regeneration.
健康的肝脏在接受 70%肝部分切除术后（PH）具有显著的重建功能性肝实质的再生能力。在 PH 后，通常处于静止状态的肝细胞增殖以补偿肝损失。然而，肝细胞参与肝再生的机制尚不清楚。Hedgehog (Hh) 途径通过调节肝脏疾病中的上皮间质转化（EMT）在组织重建中发挥重要作用。MicroRNA (miRNA) 参与胚胎发育和癌发生过程中的细胞增殖和分化。最近有报道称，miR-378 通过抑制 Hh 靶基因 Gli-Krüppel 家族成员 3 (Gli3) 抑制肝星状细胞向肌成纤维细胞的转分化。我们假设 miR-378 通过干扰肝再生过程中的 Hh 信号影响肝细胞 EMT。由于 PH 后小鼠的肝细胞高度增殖，miR-378 和上皮标志物 Ppar-g 或 E-cadherin 下调，而 Hh 激活剂 Smoothened (Smo) 和 Gli3 以及 EMT 诱导基因 Tgfb、Snail 和 Vimentin 在再生肝脏和分离的肝细胞中上调。与转染 scramble miRNA 的细胞相比，转染 miR-378 抑制剂的原代肝细胞含有更高水平的 Gli3，并增加 EMT 促进基因 Tgfb、Snail、Col1a1 和 Vimentin 的表达，表明 miR-378 影响肝细胞 EMT。从 PH 肝脏的 Smo-flox 小鼠中分离的 Smo 耗尽的肝细胞显示 EMT 促进基因和 Gli3 的下调，与 PH 肝脏中的 Smo 表达肝细胞相比，miR-378 和 E-cadherin 的表达上调。此外，将携带 Cre 重组酶的肝细胞特异性 AAV8 病毒载体递送至 Smo-flox 小鼠中，可阻止 PH 肝脏中 Smo 抑制的肝细胞的 EMT，表明 Smo 对于调节肝细胞 EMT 至关重要。此外，miR-378 模拟物在 PH 小鼠中的应用通过中断肝细胞 EMT 延迟了肝再生。总之，我们的研究结果表明，miR-378 通过调节肝再生过程中的 Hh 信号参与肝细胞 EMT。
