血小板调控肝前体细胞活化增殖的研究

Liver injury related chronic diseases seriously threaten people's health in our country. It has been demonstrated that chronic liver injury results in significant changes of liver microenvironment, which are closely associated with the prognosis of liver damage. Recently, many researches have shown that platelets play an important role in liver regeneration after injury. However, the mechanism is still unclear. In our previous works, we found that massive platelets accumulated around the newborn bile ducts in chronic liver injury animal model. Furthermore, double immunofluorescent staining revealed co-localization of platelets and hepatic progenitor cells. Therefore, we suppose that platelets play a vital role in the activation, expansion and subsequent functional performance of hepatic progenitor cells. In this study, mouse CDE (choline-deficient, ethionine-supplemented diet) model and 2-AAF/hepatotectomy model are used to induce different liver chronic diseases. Combined with platelet-deficiency mouse model, high-throughput sequencing, protein chip, molecular biology, in-vitro co-culture system and platelets transfusion technologies are applied to detect the changes of numbers, location and secreted protein of platelets, and their influence on hepatic progenitor cells in the setting of liver injury. These results will help us to elucidate the role and mechanism of platelets in regulating the activation and expansion of hepatic progenitor cells, and to reveal the significance of platelets in reconstruction and regeneration of liver damage. The results will further provide new strategies for treatment of liver injury related chronic diseases.

肝损伤相关的慢性疾病严重危害我国人民的健康。研究表明，慢性肝损伤会导致肝内微环境的显著改变，并与疾病的预后密切相关。近年来，有文献报道血小板在肝脏的损伤修复中发挥着重要的作用，但机制尚不明确。我们前期研究发现，在CDE诱导的慢性肝损伤动物模型中，新生胆管周围聚集大量的血小板，且免疫荧光共染发现血小板与肝前体细胞存在共定位。由此，我们推测血小板在肝前体细胞的活化、增殖及相关功能的发挥中扮演着重要角色。本研究将在前期工作基础上采用小鼠CDE和2-AAF联合肝部分切除模型，结合血小板缺陷动物模型，通过高通量测序、蛋白芯片、分子生物、体外细胞共培养、血小板输注等实验技术，探究肝损伤肝脏微环境中血小板的数量、定位和分泌蛋白等的改变，以及对肝前体细胞的影响，阐明血小板在调控肝前体细胞活化、增殖中的作用及其作用机制，揭示血小板对肝损伤修复的意义，最终为肝损伤相关疾病的治疗提供新策略。

在我国，肝脏相关慢性疾病严重危害人们的健康。肝脏是一种再生能力很强的器官，当肝脏受到持续严重的损伤时，肝细胞的增殖会受到抑制，而诱导增殖一种被称作“卵圆细胞”的肝干细胞/肝前体细胞，依赖卵圆细胞完成对肝脏的修复和肝再生过程。阐明调节肝前体细胞的活化、增殖以及它们在肝脏损伤修复中的作用，具有重大意义。.血小板不仅是止血和凝血反应的关键物质，而且能在组织受损时分泌多种生长因子和其它修复因子帮助受损组织重建。肝脏血液供应丰富，血小板作为微环境中的一种活性物质，在肝脏的损伤修复中发挥着重要的作用。许多研究表明血液中的血小板能促进肝切后肝脏的再生，血小板数量低提示不良的预后。体内研究发现：在多种肝损伤动物模型中伴血小板聚集，降低血小板能显著抑制胆管反应，主要表现为CK19+细胞比率明显下调，而当对低血小板血症伴肝损伤的动物模型回输血小板时，其胆管反应得到部分恢复。体外实验中：血小板能显著促进肝前体细胞的增殖，呈密度依赖性，这种促增殖作用并不需要二者的直接接触，进一步的转录组测序结果证实，血小板可以促进肝前体细胞细胞周期、增殖等通路，更有趣的是，血小板在促进肝前体细胞增殖的同时，还能促进肝前体释放一些活性因子，如IGF1、PDGF。本课题首次发现血小板肝内聚集是肝干细胞活化、增殖的重要启动因素，血小板在促进肝干细胞活化、增殖的同时，还能促进肝干细胞释放活性因子进而对肝脏微环境进行调控，为肝损伤相关研究以及发展肝脏疾病治疗新策略提供了理论依据。