LRP6基因R611C突变致心肌肥厚机制研究

Hypertrophy is the common precursor of heart failure which has high prevalence (42.7%) rate in community-based hypertensive patients in our country. The mechanism of hypertrophy remains unclear. The patients carrying LRP-R611C mutation presented with hypertrophy and heart failure during follow-up.In our previous study, we found cardiac hypertrophy in LRP6-R611C mutant mice. Further study indicated overexpressing of β-Catenin and p-RhoA and lower expression of GSK3βin cardiac tissue of LRP6-R611C mice. Based on the results above, we hypothesized that LRP6 mutation may promote hypertrophy through Wnt signaling pathway. To test our hypothesis, at first, we will investigate the mutation gene transfection effect on autocrine function, calcium transition, transmembrane electron flow of cardiac myocyte, functional regulations of the gene related to the mutation, and expression of Wnt pathway with experimental model in vitro.Furthermore, the changes of autocrine function, calcium transition, transmembrane electron flow, and functional regulations of cardiac myocyte after increasing the Wnt3a level in vitro will be studied. Next, LRP6-R611C mice will be used to study the expression of Wnt pathway factors and the changes of cardiac hypertrophy after increasing the Wnt3a level in vivo. We hope to verify the function of LRP6 and Wnt pathway as molecular risk factors for cardiac hypertrophy，dissect the underlying mechanism, and provide a novel target on prevention and therapy of hypertrophy and heart failure,through this project.

心肌肥厚是心力衰竭的前期表现，其在我国农村社区高血压患者中的患病率高达42.7%。LRP6基因R611C突变携带者在随访中出现心肌肥厚及心力衰竭，据此线索我们前期在已经构建的LRP6突变小鼠中发现了心肌肥厚。进一步研究显示Wnt信号通路上的重要因子在LRP6突变小鼠心肌组织中表达上调，推测Wnt 信号通路在LRP6突变致心肌肥厚中起关键作用。为明确LRP基因R611C突变导致心肌肥厚的机制，我们拟首先体外细胞学实验研究转染LRP6突变对心肌细胞自分泌、功能基因转录表达、钙瞬变、跨膜电子流的影响及Wnt信号系统表达情况，并观察上调Wnt信号系统后对心肌细胞功能的影响；在体研究以我们已经建立的LRP6基因R611C突变小鼠为模型，系统研究Wnt信号系统的表达情况，及上调Wnt后LRP6突变小鼠心肌肥厚及心功能改变，以期明确LRP6基因突变致心肌肥厚的作用机制，为心肌肥厚的治疗寻找新的靶点。

为探讨LRP6基因突变致心肌肥厚的机制，我们首先利用体外细胞学实验研究转染LRP6突变对心肌细胞自分泌、功能基因转录表达、钙瞬变、跨膜电子流的影响及Wnt信号系统的表达情况，并观察上调Wnt信号系统后对心肌细胞功能的影响；进一步以已经构建的LRP6突变小鼠为模型，系统研究Wnt信号系统中的三条主要通路β-Catenin介导的canonical信号通路、平面细胞极性通路（planar cell polarity pathway）和Wnt/钙通路肥厚心肌组织中的表达情况，我们的研究结果发现，LRP6基因突变通过上调平面细胞极性通路影响心肌细胞的内分泌、易感性及离子通道表达等致心肌肥厚的初步机制，并在整体动物水平高表达Wnt 信号系统后突变心肌肥厚进一步加重，心功能下降，证实了Wnt信号系统在心肌肥厚发生发展过程中起重要作用。