Blocking hepatocyte senescence as a novel therapeutic strategy for chronic liver diseases

摘要： 越来越多的证据表明，细胞衰老与慢性肝脏的进展有关。 疾病(CLD)。然而，支持细胞衰老介导的CLD进展的机制 目前仍不清楚。我们最近报道了激活素A/p15INK4b轴在诱导 肝细胞(HC)衰老。进一步提示激活素A/p15INK4b轴在诱导HC中的作用 慢性肝病的衰老，因为我们在肝硬变大鼠模型中的初步数据显示 活化素A和p15INK4b在肝硬变组织中的表达及其与肝功能升高的关系 SA-β-GAL活性。我们还发现，CCl4和CCl4处理的小鼠肝脏中p15INK4b的表达增加。 观察到激活素A抑制可明显减轻CCl4所致的肝损伤。提高激活素水平 在几种人类慢性肝病中也有报道，我们的初步数据表明激活素A增加了 在肝硬变患者肝脏中的表达。根据这一证据，我们假设激活素A 通过驱动p15INK4b介导的HC衰老，参与CLDs的发病机制。 衰老HCS促进产生的衰老相关分泌表型(SASP)因子 炎症和纤维化，导致慢性阻塞性肺疾病的进展。我们将使用我们的 建立大鼠肝细胞移植模型和CLD啮齿动物模型 明确的目标。在目标1中，我们将使用我们的HC移植模型来精确划分衰老和 相邻细胞，然后使用激光捕获显微切割(LCM)分离两个细胞群。 对这些病灶及其周围区域的对比分析将揭示出 衰老的HCs及其对邻近HCs的表型影响。目标2将研究激活素的作用 A/p15INK4b在CLD大鼠和小鼠模型中均可诱导HC衰老。在小鼠模型中的研究将 还包括对肝脏免疫细胞浸润物的全面表型和功能分析 确定HC衰老对免疫细胞的影响。我们还将评估肝组织表达的 共聚焦显微镜检测肝硬变患者活化素A和p15INK4b的临床相关性 激活素A/p15INK4b轴。最后，在目标3中，我们将研究靶向衰老的治疗益处。 CLDs。该应用程序利用了我们在肝移植模型(Oertel、MPI)、 肝脏疾病的动物模型(Oertel/Raeman，MPIs)、免疫学(Raeman)和衰老(Oertel)， 以及在肝脏病理学和RNA序列分析(Locker，Co-I)和 慢病毒/AAV表达系统(Bell，Co-I)，研究HC衰老的机制 衰老的HCS及其对邻近细胞的有害影响在HSC的发病机制中的作用 CLD.我们的调查结果将导致确定预防或阻止的治疗策略 以肝衰老为靶点的慢性肝病进展。

Summary: There is growing evidence implicating that cellular senescence is involved in the progression of chronic liver diseases (CLD). However, the mechanisms underpinning cellular senescence-mediated progression of CLD remain unclear. We have recently reported an important role of the activin A/p15INK4b axis in inducing hepatocyte (HC) senescence. Further suggesting a role of the activin A/p15INK4b axis in inducing HC senescence in CLD, because our preliminary data from rat models of liver cirrhosis revealed increased activin A and p15INK4b expression in cirrhotic liver tissue regions, which correlated with increased hepatic SA-β-gal activity. We also found that elevated p15INK4b expression in the livers of mice treated with CCl4 and observed that activin A inhibition markedly reduced CCl4-induced hepatic injury. Increased levels of activin A are also reported in several human CLDs, and our preliminary data demonstrate increased activin A expression in the livers of cirrhosis patients. Based on this evidence, we hypothesized that activin A contributes to the pathogenesis of CLDs by driving p15INK4b-mediated induction of HC senescence. Senescence-associated secretory phenotype (SASP) factors produced by senescent HCs promote inflammation and fibrosis, resulting in CLD progression. We will test our hypothesis using our established rat HC transplantation model and rodent models of CLD according to the following integrated Specific Aims. In Aim 1, we will use our HC-transplantation model to precisely demarcate senescent and neighboring cells, followed by isolation of both cell populations using laser-capture microdissection (LCM). Comparative analyses of these foci and their surrounding regions will reveal paracrine signals from senescent HCs and their phenotypic effects on neighboring HCs. Aim 2 will investigate the effect of activin A/p15INK4b-induced HC senescence in both rat and mouse models of CLD. Studies in the mouse model will also include a comprehensive phenotypic and functional analysis of hepatic immune cell infiltrates to determine the impact of HC senescence on immune cells. We will also evaluate hepatic expression of activin A and p15INK4b in cirrhotic patients by confocal microscopy to determine the clinical relevance of the activin A/p15INK4b axis. Lastly, in Aim 3, we will investigate the therapeutic benefit of targeting senescence in CLDs. This application leverages our combined expertise in liver transplantation models (Oertel, MPI), animal models of liver diseases (Oertel/Raeman, MPIs), immunology (Raeman), and senescence (Oertel), as well as extensive experience in hepato-pathology and RNA-seq analyses (Locker, Co-I) and lentiviral/AAV expression systems (Bell, Co-I), to investigate the mechanisms underpinning HC senescence and the role of senescent HCs and their detrimental effects on neighboring cells in the pathogenesis of CLD. The results of our investigations will lead to identification of therapeutic strategies to prevent or halt progression of CLD by targeting hepatic senescence.