Regulation of HNF4 in Hepatic Failure in Cirrhosis

描述（由申请人提供）：肝硬化中肝衰竭的原因尚不清楚，因为尽管损失了一半以上的肝细胞，但肝脏仍能够再生并正常发挥功能。因此，肝硬化中的肝功能衰竭是由剩余肝细胞的额外功能障碍引起的。我们的初步研究表明，来自失代偿性肝硬化肝的原代肝细胞在基因表达和增殖能力方面表现出许多改变。然而，尽管端粒严重缩短和端粒酶活性丧失，这些肝细胞在转移到正常肝脏后最终可以恢复其再生和功能的能力。我们的转录组分析表明，肝细胞衰竭的进展与转录因子HNF 4的下调及其调控网络的抑制有关。由于HNF 4？缺乏可以解释下游效应子、成熟肝细胞特异性基因和一般肝功能的抑制，我们研究了培养的终末期肝细胞，发现HNF 4？表达通过AAV转导恢复，显著并立即纠正了表型。接下来，将AAV-HNF 4 â静脉注射给患有失代偿性肝硬化的啮齿动物。他们的肝细胞功能在2周内改善到几乎正常的水平，生存期从2周延长到100天以上！因此，HNF 4？转录激活的破坏似乎是晚期肝硬化肝衰竭的机制。因此，我们假设HNF 4的恢复将通过纠正代谢缺陷和逆转肝细胞复制性衰老来有效治疗终末期肝功能衰竭的肝硬化患者。在这些研究中，我们将使用编码由诱导型启动子驱动的HNF 4 <$的重组AAV载体来确定HNF 4 <$的短期治疗是否可以导致肝功能和生存的持续正常化。此外，我们将评估HNF 4-AAV治疗在CCL 4持续损伤期间的效用，以确定这种治疗的潜在临床疗效。为了确定失代偿期肝硬化中HNF 4下调的机制，我们将对分离的肝细胞和整个肝脏进行全基因组ChIP-Seq分析。最后，我们将确定人类终末期肝病肝脏与我们的啮齿动物研究中鉴定的特征相同的程度，并将确定HNF 4？表达的恢复可以使来自这些终末期肝脏的人类肝细胞正常化的程度。

DESCRIPTION (provided by applicant): The cause of liver failure in cirrhosis is not well understood, as the liver is capable of regeneration and functions normally despite loss of more than half of its hepatocytes. Hepatic failure in cirrhosis therefore results from additional dysfunction of the remaining hepatocytes. Our Preliminary Studies showed that primary hepatocytes derived from cirrhotic livers with decompensated function exhibit numerous alterations in gene expression and proliferative capacity. Yet, despite critical shortening of telomeres and loss of telomerase activity, these hepatocytes can eventually recover their capacity for regeneration and function after transfer into a normal liver. Our transcriptome analysis demonstrated that progression to hepatocyte failure was associated with down regulation of transcription factor HNF4¿ and suppression of its regulatory network. Since HNF4¿ deficiency could explain the depression of downstream effectors, mature hepatocyte-specific genes, and general hepatic function, we studied end-stage cirrhotic hepatocytes in culture and found that HNF4¿ expression, restored via AAV transduction, dramatically and immediately corrected the phenotype. Next, AAV-HNF4¿ was given IV to rodents with decompensated cirrhosis. Their hepatocyte function improved to almost normal levels within 2 weeks and survival was prolonged from ~2 weeks to more than 100 days! Thus, disruption of HNF4¿ transcriptional activation appears to be the mechanism responsible for hepatic failure in advanced cirrhosis. We therefore hypothesize that restoration of HNF4¿ will effectively treat cirrhotic patients with end-stage liver failure by correcting the metabolic defects and reversing the hepatocyte replicative senescence. In these studies we will use a recombinant AAV vector that encodes HNF4¿ driven from an inducible promoter to determine whether short term treatment with HNF4¿ can lead to sustained normalization of hepatic function and survival. In addition, we will assess the utility of HNF4¿-AAV treatment during continuing injury with CCL4 to determine the potential clinical efficacy of such therapy. To determine the mechanism of HNF4¿ downregulation in decompensated cirrhosis, we will perform a genome-wide ChIP-Seq analysis of isolated hepatocytes and whole liver. Finally, we will determine the extent to which human end-stage cirrhotic livers share the same characteristics as those identified in our rodent studies, and will determine the extent that restoration of HNF4¿ expression can normalize human hepatocytes derived from these end-stage livers.