由于缺乏基因动物模型,充分重建肝硬化的关键临床特征,肝硬化的分子发病机制尚未明确,治疗仍然有限。因此,我们的目的是使用一种新型小鼠模型更好地阐明肝硬化的病理机制。
我们报道了第一个模拟由肝细胞特异性消除微珠蛋白1(MCRS1)诱导的人类肝硬化的小鼠遗传模型,非特异性致死(NSL)和INO80染色质修饰复合物的成员。使用这种遗传工具和其他小鼠模型,细胞培养和人体样本,结合定量蛋白质组学,细胞核/细胞RNA测序和染色质免疫沉淀测定,我们研究了肝硬化的机制。
小鼠肝细胞中的MCRS1缺失调节胆汁酸(BA)转运体的表达-Na-牛磺胆酸共转运多肽(NTCP)的显着下调-浓缩窦中的BA,从而通过法尼醇X受体(FXR)激活肝星状细胞(HSC),其主要在人和小鼠HSC中表达。始终如一,NTCP在小鼠中的再表达减少肝硬化,HSC中FXR的遗传消融抑制小鼠和体外细胞培养中的纤维化标记。机械上,从MCRS1中删除假定的SANT结构域会从组蛋白H3锚定位点驱逐组蛋白脱乙酰酶1,增加BA转运蛋白基因的组蛋白乙酰化,调节它们的表达并扰乱BA流。因此,人肝硬化显示核MCRS1和NTCP表达降低。
我们的数据揭示了MCRS1作为关键组蛋白乙酰化调节因子的先前未被识别的功能,维持基因表达和肝脏稳态。MCRS1缺失诱导BA转运蛋白基因乙酰化,BA流的扰动,因此,HSC中的FXR活化。该轴代表肝硬化中的中心和普遍信号事件,这对肝硬化治疗有重要意义。
通过MCRS1在小鼠肝细胞中的遗传消融,我们产生了第一个能概括人类特征的肝硬化遗传小鼠模型。在这里,我们证明肝成纤维细胞中胆汁酸/FXR轴的激活是肝硬化发展的关键。
Owing to the lack of genetic animal models that adequately recreate key clinical characteristics of cirrhosis, the molecular pathogenesis of cirrhosis has been poorly characterized, and treatments remain limited. Hence, we aimed to better elucidate the pathological mechanisms of cirrhosis using a novel murine model.
We report on the first murine genetic model mimicking human cirrhosis induced by hepatocyte-specific elimination of microspherule protein 1 (MCRS1), a member of non-specific lethal (NSL) and INO80 chromatin-modifier complexes. Using this genetic tool with other mouse models, cell culture and human samples, combined with quantitative proteomics, single nuclei/cell RNA sequencing and chromatin immunoprecipitation assays, we investigated mechanisms of cirrhosis.
MCRS1 loss in mouse hepatocytes modulates the expression of bile acid (BA) transporters - with a pronounced downregulation of Na+-taurocholate cotransporting polypeptide (NTCP) - concentrating BAs in sinusoids and thereby activating hepatic stellate cells (HSCs) via the farnesoid X receptor (FXR), which is predominantly expressed in human and mouse HSCs. Consistently, re-expression of NTCP in mice reduces cirrhosis, and genetic ablation of FXR in HSCs suppresses fibrotic marks in mice and in vitro cell culture. Mechanistically, deletion of a putative SANT domain from MCRS1 evicts histone deacetylase 1 from its histone H3 anchoring sites, increasing histone acetylation of BA transporter genes, modulating their expression and perturbing BA flow. Accordingly, human cirrhosis displays decreased nuclear MCRS1 and NTCP expression.
Our data reveal a previously unrecognized function of MCRS1 as a critical histone acetylation regulator, maintaining gene expression and liver homeostasis. MCRS1 loss induces acetylation of BA transporter genes, perturbation of BA flow, and consequently, FXR activation in HSCs. This axis represents a central and universal signaling event in cirrhosis, which has significant implications for cirrhosis treatment.
By genetic ablation of MCRS1 in mouse hepatocytes, we generate the first genetic mouse model of cirrhosis that recapitulates human features. Herein, we demonstrate that the activation of the bile acid/FXR axis in liver fibroblasts is key in cirrhosis development.