Delineating the molecular mechanisms of hepatocyte-to-cholangiocyte reprogramming

摘要 排列在肝胆管树上的胆管上皮细胞(BECs；也称为胆管细胞)控制胆汁。 构图和流程。BECs的损伤会导致胆汁淤积，进而发展为纤维化、肝硬变和肝脏。 失败了。胆汁淤积性肝病与高发病率和高死亡率有关；然而，很少有效 治疗方法是可用的。事实上，肝移植是治疗终末期胆汁淤积症的唯一延长生命的方法。 肝脏疾病，但供体肝脏的短缺使这种疗法极其有限。在受伤的肝脏中 在胆道损伤中，肝细胞(HCs)可以促进BECs从BECs的丢失中恢复过来。最近的研究 小鼠已经证明，HC来源的BECs有助于肝内胆管，从而恢复适当的 胆汁流动。胆道梗阻或胆管疾病的患者也表现出胆道标志物在肥大细胞中的表达， 建议他们重新编程为BEC。因此，在胆汁淤积症中增加先天的HC-to-BEC重编程 肝脏疾病是改善胆汁淤积和随后的肝硬变的一种有吸引力的治疗选择。至 开发这样的治疗方法，关键是要更好地了解HC-to-BEC的分子机制 重新编程。此外，识别能够增强重新编程的小分子应该提供 对胆汁淤积性肝病患者有希望的治疗药物。我们的长期目标是完全 描述了HC-to-BEC重新编程的分子机制。作为追求这一目标的第一步， 这项建议的目的是确定HC-to-BEC的细胞和分子特征。 在我们的两个创新斑马鱼模型中，重新编程驱动的胆管再生，并阐明组蛋白如何 脱乙酰酶1(HDAC1)调节HC到BEC的重新编程。根据我们从以下地点获得的初步数据 药理学和遗传学研究，我们假设HDAC1抑制促进了HC到BEC的重新编程 Notch受体基因Notch2和信号转导与转录激活因子3基因失活 (统计数据3)。我们将检验这一假设，并通过(1)阐明整个 在两个斑马鱼模型中，HC-to-BEC重编程驱动的胆管再生过程，在这两个模型中， 实现了不存在BEC，并随后将HCS转换为BEC。(目标1)、(2)确定 HDAC1对斑马鱼和小鼠HC-to-BEC重编程的抑制(目标2)，以及(3)阐明 HDAC1抑制促进重编程的分子机制(目标3)。成功者 拟议研究的完成不仅将提供支持HC-to-TH的新的分子机制 BEC重新编程，但也建议HDAC1/2抑制剂作为有希望的治疗药物来促进 胆汁淤积性肝病患者的重新编程。

ABSTRACT Biliary epithelial cells (BECs; also called as cholangiocytes) that line the hepatic biliary tree control bile composition and flow. Injury to the BECs leads to cholestasis, which can progress to fibrosis, cirrhosis and liver failure. Cholestatic liver diseases are associated with high morbidity and mortality; however, few effective therapies are available. In fact, liver transplantation is the only life-extending treatment for end-stage cholestatic liver diseases, but the shortage of donor livers makes this therapy extremely limited. In the injured liver with biliary damage, hepatocytes (HCs) can contribute to BECs to recover from the loss of BECs. Recent studies in mice have shown that HC-derived BECs contribute to the intrahepatic bile ducts, thereby restoring appropriate bile flow. Patients with biliary obstruction or cholangiopathies also exhibit biliary marker expression in HCs, suggesting their reprogramming into BECs. Thus, augmenting innate HC-to-BEC reprogramming in cholestatic liver diseases is an attractive therapeutic alternative to ameliorate cholestasis and subsequent cirrhosis. To develop such a therapy, it is crucial to better understand the molecular mechanisms underlying HC-to-BEC reprogramming. Furthermore, identifying small molecules that can augment the reprogramming should provide promising therapeutic drugs for patients with cholestatic liver diseases. Our long-term goal is to completely delineate the molecular mechanisms underlying HC-to-BEC reprogramming. As a first step in pursuit of that goal, the objective of this proposal is to determine the cellular and molecular characteristics of HC-to-BEC reprogramming-driven biliary regeneration in our two innovative zebrafish models and to elucidate how histone deacetylase 1 (hdac1) regulates HC-to-BEC reprogramming. Based on our preliminary data obtained from pharmacological and genetic studies, we hypothesize that Hdac1 inhibition promotes HC-to-BEC reprogramming by derepressing the Notch receptor gene notch2 and the signal transducer and activator of transcription 3 gene (stat3). We will test this hypothesis and accomplish the objective of this application by (1) elucidating the entire process of HC-to-BEC reprogramming-driven biliary regeneration in the two zebrafish models, in which complete absence of BECs is achieved and subsequently HCs convert to BECs. (Aim 1), (2) determining the effects of Hdac1 inhibition on HC-to-BEC reprogramming in both zebrafish and mice (Aim 2), and (3) elucidating the molecular mechanisms by which Hdac1 inhibition promotes the reprogramming (Aim 3). The successful accomplishment of the proposed research will not only provide novel molecular mechanisms underlying HC-to- BEC reprogramming but also suggest HDAC1/2 inhibitors as promising therapeutic drugs to promote the reprogramming in patients with cholestatic liver diseases.