Milk fat globule-EGF factor 8 and hepatocyte apoptosis-induced liver wound healing response

肝损伤相关疾病仍然是美国和VA医疗保健系统的主要公共卫生问题。 有证据表明，如果病原体未被清除或愈合中断，肝损伤可能持续存在。 严重急性肝损伤的缓解受损可导致危重疾病、肝衰竭和死亡。患者 持续性肝损伤的患者表现为慢性肝病，可进展为肝硬化和肝癌。因此，在本发明中， 因此，提高我们对如何保护肝脏免受损伤及其机制的认识至关重要。 伤口愈合以及肝脏疾病的发病机制和病因。先前的研究表明， 肝细胞凋亡是各种肝脏相关临床病症，例如肝脏 缺血/再灌注、药物诱导的肝损伤和慢性肝病如非酒精性脂肪肝 疾病到目前为止，很大程度上不知道肝脏是如何从糖尿病相关的肝损伤中愈合的， 分子可以促进肝脏从糖尿病相关的肝损伤中再生。在初步研究中，我们 开发了一种新的三重转基因（3xTg）小鼠模型，即3xTg-iHAP（诱导型肝细胞特异性 凋亡表型）小鼠。我们发现3xTg-iHAP小鼠携带一组转基因，用于诱导 肝细胞特异性凋亡。使用3xTg-iHAP小鼠，我们发现瞬时肝细胞 细胞凋亡随后导致肝脏炎性损伤，随后是肝脏再生和通过细胞凋亡而愈合。 促有丝分裂过程此外，我们发现肝细胞凋亡诱导的炎症损伤与 在受损肝细胞附近的肝实质细胞中，乳脂球-EGF因子8（MFG-E8）增加。 MFG-E8是一种营养型糖蛋白。我们和其他人已经证明MFG-E8可以保持组织的稳态， 防止组织损伤，减轻肠道和胰腺的炎症。近日有报道称 肝脏MFG-E8在脂肪肝和纤维化的减轻中起保护作用。然而， MFG-E8是否以及如何参与肝硬化诱导的炎性损伤的修复， 脂肪变性和非脂肪变性病症以及MFG-E8表达如何在病理学改变后在肝脏中调节 例如肝细胞增生相关的炎性损伤和脂肪肝。因此，我们将解决 这两个基本问题在这个MERIT奖的申请，重点放在三个具体目标：（1） 研究MFG-E8在肝细胞凋亡诱导的肝损伤愈合反应中的调节作用;（2） 阐明肝脏病理生理条件如何影响Mfge 8基因在肝脏中的表达;和（3） 检查MFG-E8对促进肝细胞凋亡导致的严重脂肪肝愈合的治疗效果- 诱导损伤。通过实现这些目标，我们将进一步了解MFG-E8如何促进肝脏 炎症性损伤后的再生以及病理条件如肝硬化相关的肝损伤 和脂肪变性调节Mfge 8基因表达。我们的研究将阐明新的治疗策略的见解 促进各种病理条件下的肝创伤愈合。

Liver injury-associated diseases remain a major public health problem in the U.S. and VA healthcare system. Evidence shows that liver injury can persist if either etiologic agents are not removed or healing is disrupted. Impaired resolving severe acute liver injury can lead to critical illness conditions, liver failure and death. Patients with persistent liver injury display chronic liver disease which can progress to cirrhosis and liver carcinoma. Thus, it is critical to advance our knowledge about how to protect liver from injury and mechanisms underlying liver wound healing in addition to the pathogenesis and etiology of liver disease. Previous studies show that hepatocyte apoptosis is a profound pathological feature of various liver-related clinical conditions such as liver ischemia/reperfusion, drug-induced liver injury, and chronic liver diseases such as nonalcoholic fatty liver disease. Up to date, it is largely unknown how liver is healed from apoptosis-associated liver injury and what molecules can promote liver to regenerate from apoptosis-associated liver injury. In preliminary studies, we developed a novel triple-transgenic (3xTg) mouse model, namely, 3xTg-iHAP (inducible hepatocyte specific apoptosis phenotype) mice. We showed that 3xTg-iHAP mice harbor a set of transgenes for induction of apoptosis in hepatocyte specific manner. Using 3xTg-iHAP mice, we have found that transient hepatocyte apoptosis subsequently leads to liver inflammatory injury followed by liver regeneration and healing through a mitogenic process. Furthermore, we found that hepatocyte apoptosis-induced inflammatory injury is associated with increase in milk fat globule-EGF factor 8 (MFG-E8) in liver parenchymal cells nearby damaged hepatocytes. MFG-E8 is a trophic glycoprotein. We and others have shown that MFG-E8 preserves tissue homeostasis, protects against tissue injury, attenuates inflammation in intestines and pancreas. Recently, it has been reported that hepatic MFG-E8 plays a protective role in attenuation of fatty liver and fibrosis. However, it remains unknown that whether and how MFG-E8 is involved in repairing liver from apoptosis-induced inflammatory injury in steatosis and non-steatosis conditions and how MFG-E8 expression is regulated in the liver upon pathological conditions such as hepatocyte apoptosis-associated inflammatory injury and fatty liver. Thus, we will address these two fundamental questions in this MERIT award application by focusing on three Specific Aims: (1) To study the role of MFG-E8 in regulation of hepatocyte apoptosis-induced liver wound-healing response; (2) To elucidate how liver pathophysiological conditions influence Mfge8 gene expression in the liver; and (3) To examine the therapeutic effect of MFG-E8 on promoting healing of severe fatty liver from hepatocyte apoptosis- induced injury. By accomplishing these aims, we will advance our understanding of how MFG-E8 promotes liver regeneration upon inflammatory injury and how pathological conditions such as apoptosis-associated liver injury and steatosis regulate Mfge8 gene expression. Our study will elucidate insights into novel therapeutic strategies to promote liver wound healing in various pathological conditions.