Department of Biomedical Engineering, University of Virginia, Charlottesville, VA.
Department of Biomedical Engineering, University of Virginia, Charlottesville, VA
J Am Heart Assoc. 2017 Nov 30;6(12):e007673. doi: 10.1161/JAHA.117.007673.
Arteriogenesis is initiated by increased shear stress and is thought to continue until shear stress is returned to its original "set point." However, the molecular mechanism(s) through which shear stress set point is established by endothelial cells (ECs) are largely unstudied. Here, we tested the hypothesis that DNA methyltransferase 1 (DNMT1)-dependent EC DNA methylation affects arteriogenic capacity via adjustments to shear stress set point.
In femoral artery ligation-operated C57BL/6 mice, collateral artery segments exposed to increased shear stress without a change in flow direction (ie, nonreversed flow) exhibited global DNA hypermethylation (increased 5-methylcytosine staining intensity) and constrained arteriogenesis (30% less diameter growth) when compared with segments exposed to both an increase in shear stress and reversed-flow direction. In vitro, ECs exposed to a flow waveform biomimetic of nonreversed collateral segments in vivo exhibited a 40% increase in DNMT1 expression, genome-wide hypermethylation of gene promoters, and a DNMT1-dependent 60% reduction in proarteriogenic monocyte adhesion compared with ECs exposed to a biomimetic reversed-flow waveform. These results led us to test whether DNMT1 regulates arteriogenic capacity in vivo. In femoral artery ligation-operated mice, DNMT1 inhibition rescued arteriogenic capacity and returned shear stress back to its original set point in nonreversed collateral segments.
Increased shear stress without a change in flow direction initiates arteriogenic growth; however, it also elicits DNMT1-dependent EC DNA hypermethylation. In turn, this diminishes mechanosensing, augments shear stress set point, and constrains the ultimate arteriogenic capacity of the vessel. This epigenetic effect could impact both endogenous collateralization and treatment of arterial occlusive diseases.
血管生成是由剪切力增加引发的，据认为它会持续下去，直到剪切力恢复到原来的“设定点”。然而，内皮细胞（ECs）建立剪切力设定点的分子机制在很大程度上仍未得到研究。在这里，我们测试了这样一个假设，即 DNA 甲基转移酶 1（DNMT1）依赖性 EC 中的 DNA 甲基化通过调整剪切力设定点来影响血管生成能力。
在股动脉结扎手术的 C57BL/6 小鼠中，与暴露于增加的剪切力但没有血流方向改变的侧支动脉段（即非反向血流）相比，暴露于增加的剪切力和反向血流方向的侧支动脉段表现出全基因组 DNA 超甲基化（增加 5-甲基胞嘧啶染色强度）和限制血管生成（直径生长减少 30%）。在体外，与暴露于仿生反向血流波形的 EC 相比，暴露于体内非反向侧支段仿生血流波形的 EC 中，DNMT1 表达增加了 40%，基因启动子的全基因组超甲基化，以及 DNMT1 依赖性单核细胞黏附的 60%减少。这些结果促使我们在体内测试 DNMT1 是否调节血管生成能力。在股动脉结扎手术的小鼠中，DNMT1 抑制恢复了血管生成能力，并使非反向侧支段的剪切力恢复到原来的设定点。
没有血流方向改变的增加的剪切力引发了血管生成性生长；然而，它也引发了 DNMT1 依赖性 EC DNA 超甲基化。反过来，这降低了机械感觉，增加了剪切力设定点，并限制了血管的最终血管生成能力。这种表观遗传效应可能会影响内源性侧支形成和治疗动脉闭塞性疾病。
