骨髓间充质干细胞旁分泌BDNF调控TRPC6通道抗心肌缺血作用及其机制

The therapeutical role of bone marrow mesenchymal stem cells (BMSCs) by its paracrine effect for ischemic heart disease (IHD) has been paid more and more attention nowadays. However, the underlying regulatory mechanisms remain deeply discussed. Our previous studies found that the protein expression of TRPC6 channel in cardiomyocytes was dysregulated in myocardial ischemia (MI), which implied that TPRC6 channel may participate in the pathophysiological process of MI. Furthermore, studies also indicated that TRPC6 channel was closely related to BMSCs and the paracrined brain derived neurotrophic factor(BDNF) in ischemic neurons. Thus, the present project hypothesized that: BMSCs paracrines BDNF which combines with TrkB receptor, then activates PLC-DAG signaling pathway and regulates TRPC6 channel in the membrane of cardiomyocytes. TRPC6 channel further activates downstream signaling pathways. The protein expression of ERK, CAMKⅡand CREB is upregulated to suppress the apoptosis of cardiomyocytes to repair the injured myocardium. Molecular biological, electrophysiological and gene transfection methods were employed in our project to explore the potential mechanisms of TRPC6 channel in cardiac repair of BMSCs for ischemic myocardium, which providing the rational for novel anti-myocardial ischemic drug targets and stem cell transplantation therapy in clinics.

骨髓间充质干细胞（BMSCs）通过旁分泌作用治疗缺血性心肌病成为近年来研究热点，但其确切调节机制有待进一步深入探讨。我们前期研究发现心肌细胞中TRPC6通道蛋白在心肌缺血时表达发生异常，提示其可能参与心肌缺血病理生理过程，并且有研究表明脑缺血时神经细胞中TRPC6通道与BMSCs及其旁分泌的脑源性神经营养因子（BDNF）密切相关。因此本项目提出如下科学假设：BMSCs通过旁分泌BDNF与TrkB受体结合，激活PLC-DAG通路调控心肌细胞膜上TRPC6通道，TRPC6通道激活后上调ERK、CAMKⅡ、CREB表达，抑制心肌细胞凋亡，修复缺血受损心肌。本项目拟从动物、细胞及分子水平应用分子生物学、电生理学及基因转染等技术深入探讨BMSCs旁分泌BDNF调控TRPC6通道修复缺血心肌的作用机制，为寻找新的抗心肌缺血药物靶点提供理论基础，同时为临床干细胞移植治疗缺血性心肌病提供新依据。

骨髓间充质干细胞（BMSCs）通过旁分泌作用治疗缺血性心脏病成为近年来研究热点，但其确切调节机制尚不清楚。本项目主要围绕脑源性神经营养因子（BDNF）调控心肌细胞TRPC3/6通道抗心肌缺血损伤的作用及机制展开研究。通过检测急性心梗患者血样，发现心梗患者血浆中BDNF水平明显增加。通过结扎大鼠冠状动脉左前降支建立心肌缺血动物模型，发现心肌缺血大鼠血浆及心肌组织中BDNF表达水平均明显增加。并且，缺血时心肌组织中BDNF及其特异性受体TrkB蛋白表达上调。小鼠心脏点注射BDNF可明显减少心肌梗死面积和乳酸脱氢酶LDH活性，改善心脏功能。体外水平分离培养乳鼠原代心室肌细胞并进行缺氧培养，发现BDNF抑制缺氧诱导的心肌细胞凋亡。BDNF的心肌保护作用是由于激活了TrkB及TRPC3/6通道，调节细胞内钙及下游信号，进而上调抗凋亡分子bcl-2表达，抑制促凋亡分子caspase-3表达及活性，抗心肌细胞凋亡。综上，本研究首次证实BDNF调控TRPC3/6通道抑制缺血/缺氧诱导的心肌细胞凋亡的心肌保护作用及机制。本项目揭示了BDNF抗心肌缺血损伤的保护作用及分子机制，发现BDNF是调控心肌缺血的新靶点并有望成为心肌梗死的临床预警检测分子，同时为临床干细胞治疗缺血心肌提供参考。