Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University, Beijing, PR China; Key Laboratory of Molecular Cardiovascular Science, Ministry of Education, Beijing, PR China.
State Key Laboratory of Cardiovascular Disease, Fuwai Hospital, National Center for Cardiovascular Diseases, Chinese Academy of Medical Sciences and Peking Union Medical College, PR China.
J Mol Cell Cardiol. 2018 Aug;121:69-80. doi: 10.1016/j.yjmcc.2018.07.002. Epub 2018 Jul 4.
Cartilage oligomeric matrix protein (COMP), a protective component of vascular extracellular matrix (ECM), maintains the homeostasis of mature vascular smooth muscle cells (VSMCs). However, whether COMP modulates the differentiation of stem cells towards the smooth muscle lineage is still elusive. Firstly, purified mouse COMP directly induced mouse embryonic stem cell (ESC) differentiation into VSMCs both in vitro and in vivo, while the silencing of endogenous COMP markedly inhibited ESC-VSMC differentiation. RNA-Sequencing revealed that Notch signaling was significantly activated by COMP during ESC-VSMC differentiation, whereas the inhibition of Notch signaling attenuated COMP-directed ESC-VSMC differentiation. Furthermore, COMP deficiency inhibited Notch activation and VSMC differentiation in mice. Through silencing distinct Notch receptors, we identified that Notch1 mainly mediated COMP-initiated ESC-VSMC differentiation. Mechanistically, COMP N-terminus directly interacted with the EGF11-12 domain of Notch1 and activated Notch1 signaling, as evidenced by co-immunoprecipitation and mammalian two-hybrid assay. In conclusion, COMP served as a potential ligand of Notch1, thereby driving ESC-VSMC differentiation.
软骨寡聚基质蛋白（COMP）是血管细胞外基质（ECM）的保护性成分，维持成熟血管平滑肌细胞（VSMC）的内稳态。然而，COMP 是否调节干细胞向平滑肌谱系的分化仍不清楚。首先，纯化的小鼠 COMP 直接诱导小鼠胚胎干细胞（ESC）在体外和体内分化为 VSMC，而内源性 COMP 的沉默则显著抑制 ESC-VSMC 分化。RNA 测序显示，在 ESC-VSMC 分化过程中 Notch 信号显著被 COMP 激活，而 Notch 信号的抑制减弱了 COMP 指导的 ESC-VSMC 分化。此外，COMP 缺乏抑制了小鼠的 Notch 激活和 VSMC 分化。通过沉默不同的 Notch 受体，我们发现 Notch1 主要介导了 COMP 启动的 ESC-VSMC 分化。在机制上，COMP N 端直接与 Notch1 的 EGF11-12 结构域相互作用并激活 Notch1 信号，这一点通过共免疫沉淀和哺乳动物双杂交实验得到了证实。总之，COMP 作为 Notch1 的潜在配体，从而驱动 ESC-VSMC 的分化。
