DNA甲基化调控脂肪祖细胞衰老和米色化的表观遗传机制

The aging of adipose progenitor cells serves as a key factor in the pathogenesis of adipose tissue aging and metabolic diseases. There is compelling evidence that DNA methylation is implicated in the aging processes in terms of invidiual cell and the entire body. However, the impact of DNA methylation on the aging of adipose progenitor cell and its capacity in beige cell induction has yet to be studied. Our pilot studies revealed that DNA methylation also regulates the aging processes of adipose progenitor cells, and particularly, loss of MBD2, a methylated CpG DNA binding protein specifically induced during the course of aging, attenuated the aging of adipose progenitor cell. Based thse discoveries we thus hypopthesize: during the course of adipose progenitor cell aging its genome undergoes a DNA methylation turnover as manifested by the changes of methylation levels and/or patterns, while MBD2 regulates adipose progenitor cell aging processes by intepreting the epigenetic information encoded through this DNA methylation turnover. To address this hypothesis, we will first establish the DNA methylomes, transcriptomes and alternative splicing isforms in young and aged adipose progenitor cells originated from humans and mice. We will then confirm that MBD2 specifically binds to the regulatory regions of methylated DNA in key genes relevant to adipose progenitor aging. Progenitor cell specific MBD2 knockout mice and other animal models will be next employed to domonstrate that MBD2 regulates the aging of adipose progenitor cell and its capacity for beige fat induction, and the underlying mechanisms will be also investigated. Finally, we will explore the feasibility of MBD2-siRNA nanoparticles to prevent or attenuate adipose progenitor cell aging. These studies will not only provide novel insight into the understanding of epigenetic mechanisms underlying adipose progenitor cell aging, but also have great potential for developing epigenetic based therapeutic strategies against metabolic diseases in clinical settings.

脂肪祖细胞衰老及米色化障碍是脂肪组织衰老及代谢性疾病的关键诱因。研究揭示DNA甲基化调控细胞和机体的衰老，但其对脂肪祖细胞衰老及米色化的调控研究尚未开展。我们前期研究揭示DNA甲基化亦调控脂肪祖细胞衰老，且其结合蛋白MBD2缺失抑制脂肪祖细胞衰老，故假设：脂肪祖细胞衰老伴随DNA甲基化水平及模式的改变，MBD2通过解读其表观遗传信息调控脂肪祖细胞衰老及米色化能力。本课题拟在建立人和小鼠脂肪祖细胞DNA甲基化图谱，RNA转录组图谱及mRNA可变剪切体基础上，应用祖细胞特异性MBD2敲除及其它工具小鼠确证MBD2解读DNA甲基化的表观遗传信息调控脂肪祖细胞衰老及其米色化功能，并阐明相关分子机制；继而探索以MBD2为表观遗传调控靶标抑制脂肪祖细胞衰老及米色化功能降低的可行性。上述研究不仅为解析脂肪细胞衰老的表观调控机制提供新的认识，而且还为开发以表观遗传为基础的代谢性疾病治疗策略提供实验依据。

脂肪祖细胞衰老及米色化障碍是脂肪组织衰老及代谢性疾病的关键诱因之一。本研究中，我们探究了脂肪祖细胞（APC）衰老进程中，MBD2通过调控DNA甲基化影响脂肪祖细胞米色化能力及相关机制。为阐明上述机制，负责人首先对不同年龄的人源及鼠源APC行RNA深度测序及DNA甲基化测序，并将上述筛选得到的靶标基因行交叉分析，筛选得OASL1等17个受DNA甲基化调控表达的差异基因。基于上述测序结果，负责人构建了MBD2 KO及SMA-Mbd2ko（APC特敲）小鼠，进一步确证MBD2对APC米色化能力的调控作用。经CHIP解析MBD2结合的DNA甲基化位点，筛选OASL1作为MBD2调控的靶基因。确证MBD2通过解读OASL1基因的甲基化信息，调控OASL1的表达，影响下游通路Oasl1/Chn1/Prkce/Adam12，最终调控APC的米色化进程。此外，负责人还以外泌体为媒介，探究不同状态（年轻或衰老）APC对小鼠代谢能力的调控作用。研究表明相较于年轻APC外泌体，衰老APC外泌体抑制巨噬细胞M1极化能力减弱。测序结果表明，衰老APC外泌体内miR-145a-5p显著下调。后续功能实验证实，miR-145a-5p可通过下调巨噬细胞L-选择素（Sell）的表达，抑制其M1极化，进而缓解衰老诱发的胰岛素抵抗。上述研究阐明了DNA甲基化参与APC衰老调控进而影响机体胰岛素敏感性的新机制，为治疗衰老诱发的代谢性疾病提供了新的靶点。