Liu Y, Liang J, Zeng W, Wang Y
Southern Medical University Biomedical Research Center, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou 510515, China.
Nan Fang Yi Ke Da Xue Xue Bao. 2022 Sep 20;42(9):1324-1334. doi: 10.12122/j.issn.1673-4254.2022.09.08.
To explore the changes in Yes-associated protein (YAP) activity at the early stage of nonalcoholic steatohepatitis (NASH) and the spatiotemporal relationship between YAP and ductular reaction (DR).
Male C57BL/6J mouse models of NASH were established by feeding with a methionine- and choline-deficient (MCD) diet or a thioacetamide (TAA) diet for 12 weeks. At different time points during the feeding, liver histology of the mice was observed with HE and Masson trichrome staining. The mRNA expressions of YAP and its target genes (, , ) were determined by qPCR, and the total protein expression level of YAP was measured with immunoblotting. The expression and distribution of YAP and the markers of DR (K19 and Sox9) were observed with immunohistochemical staining.
At the early stage of NASH induced by MCD diet (1 to 4 weeks), the mRNA expression of YAP and its target genes and the total protein expression of YAP increased significantly ( < 0.01). The number of YAP-positive hepatocytes reached the peak level of 90.8 (cells per ×400 field of view) at week 2 and then decreased to 30.8 at week 4 ( < 0.001); YAP-positive ductular cells appeared near the portal area, where DR began to occur. From 8 to 12 weeks, numerous K19/Sox9-positive DR cells were observed in the hepatic lobules around the central vein ( < 0.01), while only a few YAP-positive hepatocytes were present in the liver tissue ( > 0.05), and the number of YAP-positive ductular cells gradually increased with time ( < 0.001). At the early stage of NASH induced by TAA diet (3 days to 2 weeks), the mRNA expression of YAP and its target genes and the total protein expression of YAP increased significantly ( < 0.05), and the number of YAP-positive hepatocytes reached the peak of 69.2 at week 2 and then decreased to 55.2 at week 4 ( < 0.001); YAP-positive ductular cells first appeared at the initial location of DR near the central vein. From 6 to 12 weeks, numerous K19/Sox9-positive DR cells occurred in the hepatic lobules around the central vein ( < 0.01). While the number of YAP-positive hepatocytes decreased ( < 0.001), the number of YAP-positive ductular cells continued to increase ( < 0.001).
During the development of NASH, YAP activation occurs earlier than DR but they are spatiotemporally correlated. YAP activation in hepatocytes may participate in DR by promoting hepatocyte dedifferentiation.
探讨非酒精性脂肪性肝炎（NASH）早期Yes相关蛋白（YAP）活性的变化以及YAP与小胆管反应（DR）之间的时空关系。
通过给予蛋氨酸和胆碱缺乏（MCD）饮食或硫代乙酰胺（TAA）饮食12周建立雄性C57BL/6J小鼠NASH模型。在喂养期间的不同时间点，用苏木精-伊红（HE）和Masson三色染色观察小鼠肝脏组织学。通过qPCR测定YAP及其靶基因（ 、 、 ）的mRNA表达，并用免疫印迹法测量YAP的总蛋白表达水平。用免疫组织化学染色观察YAP以及DR标志物（K19和Sox9）的表达和分布。
在MCD饮食诱导的NASH早期（1至4周），YAP及其靶基因的mRNA表达以及YAP的总蛋白表达显著增加（ < 0.01）。YAP阳性肝细胞数量在第2周达到峰值水平90.8（每×400视野细胞数），然后在第4周降至30.8（ < 0.001）；YAP阳性小胆管细胞出现在门静脉区域附近，DR开始发生的部位。从8至12周，在中央静脉周围的肝小叶中观察到大量K19/Sox9阳性DR细胞（ < 0.01），而肝组织中仅存在少数YAP阳性肝细胞（ > 0.05），且YAP阳性小胆管细胞数量随时间逐渐增加（ < 0.001）。在TAA饮食诱导的NASH早期（3天至2周），YAP及其靶基因的mRNA表达以及YAP的总蛋白表达显著增加（ < 0.05），YAP阳性肝细胞数量在第2周达到峰值69.2，然后在第4周降至55.2（ < 0.001）；YAP阳性小胆管细胞首先出现在中央静脉附近DR的起始部位。从6至12周，在中央静脉周围的肝小叶中出现大量K19/Sox9阳性DR细胞（ < 0.01）。虽然YAP阳性肝细胞数量减少（ < 0.001），但YAP阳性小胆管细胞数量持续增加（ < 0.001）。
在NASH发展过程中，YAP激活比DR更早发生，但它们在时空上相关。肝细胞中的YAP激活可能通过促进肝细胞去分化参与DR。
