组蛋白变异体H3.3在主动脉夹层中的作用及其机制研究

Phenotypic switching of vascular smooth muscle cells (VSMC) has been proved as a critical factor for the development of aortic dissection (AD). Although several studies revealed that chromatin regulation plays a pivotal role in phenotypic switching, the molecular mechanism remains undetermined. Our preliminary single-cell sequencing showed that histone variant H3.3 is highly expressed in the VSMC cluster of the young patients. In addition, H3.3 overexpressed in VSMC down-regulates the expression of VSMC marker genes, but increase the level of several inflammatory genes. Therefore, we hypothesize that H3.3 gives rise to the development of AD by promoting the phenotypic switching of VSMC and activating inflammatory pathways. To test our hypothesis, we first uncover the role of H3.3 in VSMC phenotypic switching and the effects of it on vascular microenvironment; then, explore the molecular mechanism by genomic approaches; finally, discuss the possibility of alleviating AD by regulating the level of H3.3 in mouse BAPN AD model. Findings of this study can help us understand how H3.3 affects AD through regulating VSMC phenotypic switching, reveal the molecular mechanism of vascular homeostasis and remodeling, provide new strategy for the prevention and treatment of AD.

血管平滑肌细胞(VSMC)表型转化与主动脉夹层(AD)的发生发展密切相关。研究表明染色质调控在VSMC表型转化中起重要作用，但其分子机制远未阐明。课题组对收集的非遗传病AD病人标本进行单细胞测序发现：年轻患者的VSMC亚群中特异高表达组蛋白变异体H3.3。体外实验证实在VSMC中过表达H3.3会促使VSMC收缩型marker表达下调，同时多个炎症相关因子表达上升。因此我们推测H3.3通过促使VSMC表型转化，同时激活多条炎症通路导致夹层发生。为证明此假说，拟首先确定H3.3在VSMC表型转化中的作用，同时通过共培养实验明确高表达H3.3对血管微环境的影响；接着通过基因组学的方法探索其调控机制；最后在小鼠BAPN夹层模型中探讨调控H3.3的表达以减少夹层发生的风险。本研究通过揭示H3.3如何影响VSMC从而促进AD的发生，深化对血管稳态与重构分子调控机制的理解，并为AD预防和治疗提供新思路。

血管平滑肌细胞的表型转化与主动脉夹层的发生发展高度相关。以往研究揭示了多种层面上平滑肌细胞表型转化的机制以及主动脉夹层发生发展的原因，但在表观遗传学水平如何通过调控平滑肌细胞的表型状态来控制主动脉夹层的发展却尚未阐明。我们发现组蛋白变异体H3.3在主动脉夹层患者的标本以及小鼠主动脉夹层模型的血管中均高表达，体外过表达H3f3b基因可促进血管平滑肌细胞中细胞外基质及炎症相关基因的大量表达。进一步的研究发现H3.3通过结合在夹层相关的基因的染色体上直接对其进行调控。最后通过转基因小鼠在体干预H3f3b基因的表达，发现高表达H3.3会加重主动脉夹层的发病程度，而敲低H3.3则会大幅度降低夹层的风险。本研究帮助我们理解表观遗传学水平组蛋白变异体如何调控血管平滑肌细胞表型，进而抑制主动脉夹层的发展提供了新的思路。