肝细胞的衰老机制及衰老逆转的研究

Population aging and health problems caused by the aging organs have become the major scientific issues of population in the field of health sciences. Understanding of both development and the mechanism for liver aging has the special significance, which could be used to delay or reverse liver senescence. Liver cells in vivo are special in that they are the highly differentiated cells with strong capacity of cell proliferation. Mature hepatocytes keep quiescent, but are immediately entering into cell cycle under the stimulation of injury. Until now, the limit of proliferation capacity for hapatocytes is still a long-term unsolved question. The proliferation characteristic of hepatocytes during liver regeneration has not been studied yet for without an in vivo model system capable of keeping hepatocytes in continuous proliferation. Taking advantaging of Fah-/- mouse model with hepatocyte serial transplantation, this application proposes to study the details of how proliferating hepatocytes avoid or inhibit their senescence during their process of continuous proliferation. The proposed researches will also include to study the role of chromosome ploidy conversion in the process of inhibiting hepatocyte senescence, and to find the special cell signaling pathways involved in the regulation of by-path or reversal of hepatocyte senescence. The molecular mechanism underlying inhibition on hepatocyte senescence will also be analyzed. These studies will supply important information to establish strategies for the by-path or reversal of hepatocyte senescence in future clinic, which have important biological and medical significances.

人口老龄化带来的器官衰老与人类的健康密切相关，其中肝脏衰老的机理是最亟待解决的问题之一。关于损伤后肝脏重建和肝细胞移植的研究表明，在成体动物中肝脏的连续再生实现了肝细胞的连续增殖，这种情况下的肝细胞打破了细胞衰老的规则，表现为无限增殖的能力。但由于缺乏理想的动物模型，既不能实现特定肝细胞在体内的长期连续增殖，也无法对体内连续增殖的肝细胞进行分离纯化或追踪分析，成为制约肝细胞衰老机制研究的瓶颈问题。本申请旨在利用FAH基因剔除小鼠能够连续移植肝细胞的特性，使得肝细胞的连续增殖及其分离、分选和追踪分析成为可能。运用细胞遗传学和分子生物学研究手段，分析连续增殖中肝细胞衰老的表型特征，探讨倍体转换在肝细胞衰老或衰老逆转中的作用，分析连续增殖中肝细胞衰老抑制或逆转的分子机制。由此获得肝脏衰老的发生发展规律，理解延缓或逆转肝脏衰老的机制，制定延缓或逆转肝脏衰老的参考方案，具有重要的生物学和医学意义。

人口老龄化带来的器官衰老与人类的健康密切相关，其中肝脏衰老的机理是最亟待解决的问题之一。关于损伤后肝脏重建和肝细胞移植的研究表明，在成体动物中肝脏的连续再生实现了肝细胞的连续增殖，这种情况下的肝细胞打破了细胞衰老的规则、表现为无限的增殖能力。但由于缺乏理想的动物模型，既不能实现特定肝细胞在体内的长期连续增殖，也无法对体内连续增殖的肝细胞进行分离或追踪分析，成为制约肝细胞衰老机制研究的瓶颈问题。本申请旨在利用FAH基因剔除小鼠能够连续移植肝细胞的特性，使得肝细胞的连续增殖及其分离、分选和追踪分析成为可能。. 通过研究开展，我们在肝细胞衰老及衰老逆转方面取得标志性成果。我们建立了肝细胞衰老的鉴定方案，发现肝细胞随年龄增长而逐渐衰老，衰老肝脏中多倍体肝细胞的增加与细胞衰老密切相关，DNA损伤及INK4α/ARF位点抑制丧失是肝细胞衰老的主要机制；发现连续移植的肝细胞具有衰老抑制的特性，衰老肝细胞移植后经倍体转换机制其衰老特性可以逆转，衰老的肝细胞可作为肝病细胞治疗潜在的细胞来源。该研究为年老肝细胞应用于肝细胞移植、拓展细胞来源建立了理论基础，也为下一步制定延缓或逆转肝细胞衰老的参考方案奠定了理论和技术基础。该研究发表在肝脏病学研究领域权威期刊Hepatology 上。在完成课题既定全部研究内容基础上，我们还发现肝细胞的衰老及其分泌的生长因子IGF-2可以促进移植肝细胞再殖肝脏。这一递进工作已形成论文准备第二次投稿Hepatology。. 受本基金资助取得的其他成绩还有：在谱系重编程上连续取得原创性重大进展，首次实现将小鼠成纤维细胞直接诱导为具有肝胆分化潜能的肝干细胞，标志“我国肝干细胞研究取得重大突破”（Cell Stem Cell 2013）；首次实现将人成纤维细胞直接诱导为功能性肝细胞（Cell Stem Cell 2014)；发现肝细胞经FoxM1基因修饰后能显著增强其肝脏再殖能力，为促进非供体来源肝细胞再殖受体肝脏、实现治疗性肝脏再殖提供了实验方案（Cell Death ＆ Disease 2014）。