Role of Platelet derived growth factor receptor-a in Liver Patho-biology

描述（由申请人提供）：慢性肝病是美国常见的发病原因，约有550万美国人患有肝纤维化和肝硬化。慢性肝损伤可以是任何数量的单独或组合损伤的结果，包括酒精、病毒性肝炎、代谢缺陷或其他。肝硬化可以进一步复杂化肝脏 肝衰竭、门静脉高压和肝细胞癌（HCC）的发展，使慢性肝病成为美国第12大死亡原因和主要的社会经济负担。 NIH肝脏研究行动计划确定了一些领域，如了解正常肝细胞功能的细胞和分子过程;肝脏再生和发育;和肝纤维化;对肝脏健康产生全面影响。 目前的资助重点是了解一个鲜为人知的分子在肝细胞生物学中的作用，血小板衍生生长因子受体-α（PDGFR）基于过去几年的一些有趣的观察。PDGFR的高表达和磷酸化在小鼠肝脏发育的早期阶段被鉴定。具体而言，成肝细胞和未成熟肝细胞在早期肝脏发育阶段显示出高表达，这与正在进行的细胞增殖和细胞存活相一致。在胚胎肝培养中阻断PDGFR证实了这些作用，从而进行了深入的研究。 同样，我们已经确定了在小鼠三分之二或部分肝切除术（PH）后肝再生过程中PDGFR暂时急剧增加。 最后，在患者肝纤维化期间和小鼠胆管结扎（BDL）后，在肝细胞中观察到PDGFR上调。为了明确地阐述 PDGFR在肝脏生长和发育方面，我们已经产生了几种小鼠模型，这些模型将使我们能够解决以下总体假设：“PDGFR是肝细胞增殖和存活的关键介质，其调节中的异常导致肝脏稳态的显著破坏，从而导致肝脏生长障碍，包括异常发育、再生、纤维化和增生”。我们建议通过三个具体的目标，这是不同的，采用平衡的体内和体外方法来研究这一假设。 在目标1中，我们建议通过全面的个体发育分析来研究早期肝脏发育中的PDGFR信号传导，以解决其作用和调节。这些研究将通过产生在成肝细胞中缺乏PDGFR的条件无效小鼠来补充。在目标2中，我们将在部分肝切除模型中研究肝再生过程中的PDGFR <$信号传导，然后利用实验室中产生的新动物模型来解决肝细胞中PDGFR <$过表达和缺失对再生反应的影响。在目标3中，我们将在胆管结扎和四氯化碳给药的小鼠模型中研究肝纤维化和肝硬化中的PDGFR信号。这些研究将通过在我们实验室的新型转基因小鼠中检查肝细胞中PDGFR <$缺失或过表达的疾病过程的细胞和分子基础来补充，并通过利用物种特异性PDGFR <$阻断抗体来补充，以确定对这些模型中疾病进展的影响，以解决治疗效果。因此，这项非常重要的提案将明确和全面地解决PDGFR在肝脏健康和疾病中的作用和调节。

DESCRIPTION (provided by applicant): Chronic liver disease is a common cause of morbidity in the U.S.A. with around 5.5 million Americans suffering from hepatic fibrosis and cirrhosis. Chronic liver injury can be the result of any number of insults alone or in combination, including alcohol, viral hepatitis, metabolic defect or others. Cirrhosis can be further complicated by liver failure, portal hypertension and development of hepatocellular cancer (HCC), making chronic liver disease as the 12th leading cause of mortality in the U.S.A and a major socio-economic burden. The NIH action plan for liver research, identifies areas such as understanding cellular and molecular processes of normal liver cell functioning; liver regeneration and development; and hepatic fibrosis; to make an overall impact on liver health. The present grant is focused on understanding the role of a lesser known molecule in hepatocyte biology, platelet derived growth factor receptor-alpha (PDGFR¿) based on some intriguing observations made over last several years. High expression and phosphorylation of PDGFR¿ was identified during early stages of liver development in mice. Specifically, hepatoblasts and immature hepatocytes displayed high expression at early hepatic developmental stages that coincide with ongoing cell proliferation and cell survival. Blocking PDGFR¿ in embryonic liver culture verified these effects thus warranting an in depth investigation. Similarly, we have identified a dramatic increase in PDGFR¿ temporally during liver regeneration after two-third or partial hepatectomy (PH) in mice. Lastly, PDGFR¿ upregulation was observed in hepatocytes during hepatic fibrosis in patients, and after bile duct ligation (BDL) in mice. In order to unequivocally address the role of PDGFR¿ in liver growth & development, we have generated several mouse models that will enable us to address the overarching hypothesis that 'PDGFR¿ is a critical mediator of hepatocyte proliferation and survival and aberrations in its regulation lead to significant disruption of liver homeostasis leading to disorders of hepatic growth including aberrant development, regeneration, fibrosis & cirrhosis'. We propose to investigate this hypothesis through three specific aims, which are distinct and employ balanced in vivo and in vitro approaches. In aim 1, we propose to investigate PDGFR¿ signaling in early liver development via comprehensive ontogenic analysis to address its role and regulation. These studies will be complemented by generation of conditional null mice that lack PDGFR¿ in hepatoblasts. In aim 2, we will study PDGFR¿ signaling during liver regeneration in partial hepatectomy model and then address the impact of PDGFR¿ overexpression and deletion in hepatocytes on regenerative response utilizing novel animal models generated in the lab. In aim 3, we will study PDGFR¿ signaling in hepatic fibrosis and cirrhosis in murine models of bile duct ligation and carbon tetrachloride administration. These studies will be complemented by examining the cellular and molecular basis of the disease process in absence or overexpression of PDGFR¿ in hepatocytes in novel transgenic mice in our lab and complemented by utilization of species-specific PDGFR¿ blocking antibodies to determine impact on disease progression in these models to address therapeutic efficacy. Thus, this highly significant proposal will unequivocally and comprehensively address the role and regulation of PDGFR¿ in liver health and disease.