A KLF2-BMPER-Smad1/5 checkpoint regulates high fluid shear stress-mediated artery remodeling

Vascular remodeling to match arterial diameter to tissue metabolic requirements commonly fails in ischemic disease. Endothelial cells (EC) sense fluid shear stress (FSS) from blood flow to maintain FSS within a narrow range in healthy vessels. Higher FSS induces vessel outward remodeling to return FSS to physiological levels, but mechanisms are poorly understood. We previously reported that Smad1/5 is maximally activated at physiological FSS and suppressed at higher flow. The Smad1/5 pathway opposes activation of Akt, suggesting that inhibiting Smad1/5 may be required for outward remodeling. Here, we report that suppression of Smad1/5 at high FSS is mediated by elevated KLF2, which induces the BMP pathway inhibitor BMPER, which suppresses Smad1/5 and de-inhibits Akt. In a mouse arteriovenous fistula (AVF) model, high FSS induces arterial outward remodeling coincident with elevated BMPER expression and Smad1/5 inactivation. Endothelial BMPER deletion impaired blood flow recovery and vascular remodeling in the AVF and a hindlimb ischemia (HLI) model, with the latter reversed by BMP9/10 blocking antibodies (bAbs). In both STZ-induced type 1 and HFD-induced type 2 diabetic mice that show poor recovery from HLI, BMP9/10 bAbs improved outcomes. Thus, suppression of Smad1/5 is required for high FSS-mediated outward remodeling and is a potential therapeutic approach for ischemic disease. Human umbilical vein endothelial cells (HUVECs) were transfected with Ctrl (siCtrl) or KLF2 (siKLF2) siRNA for 4 days, total RNA was extracted and subjected to RNAseq, n=4 samples for each group.

在缺血性疾病中，匹配动脉直径与组织代谢需求的血管重构通常会失效。内皮细胞（Endothelial cells, EC）可感知血流产生的流体切应力（Fluid Shear Stress, FSS），在健康血管中将FSS维持在狭窄的生理区间内。当FSS升高时，血管会发生外向性重构以将FSS恢复至生理水平，但其具体分子机制尚不清楚。我们此前的研究表明，Smad1/5在生理性FSS下被最大程度激活，而在高流量状态下则被抑制。Smad1/5通路可拮抗Akt的激活，这提示外向性重构可能需要抑制Smad1/5的活性。本研究发现，高FSS下Smad1/5的抑制作用由表达上调的KLF2介导：KLF2可诱导骨形态发生蛋白（Bone Morphogenetic Protein, BMP）通路抑制剂BMPER的表达，而BMPER可抑制Smad1/5，从而解除其对Akt的抑制作用。在小鼠动静脉瘘（Arteriovenous Fistula, AVF）模型中，高FSS可诱导动脉外向性重构，同时伴随BMPER表达上调与Smad1/5失活。在内皮细胞中敲除BMPER会损害AVF模型与后肢缺血（Hindlimb Ischemia, HLI）模型中的血流恢复与血管重构，而后肢缺血模型的表型可通过BMP9/10封闭抗体（Blocking Antibodies, bAbs）得到逆转。在链脲佐菌素（Streptozocin, STZ）诱导的1型糖尿病小鼠与高脂饮食（High Fat Diet, HFD）诱导的2型糖尿病小鼠中，HLI后的血流恢复均较差，而BMP9/10封闭抗体可改善其预后。综上，高FSS介导的外向性重构需要Smad1/5的抑制作用，这为缺血性疾病提供了一种潜在的治疗策略。将人脐静脉内皮细胞（Human Umbilical Vein Endothelial Cells, HUVECs）分别转染阴性对照小干扰RNA（siCtrl）与KLF2靶向小干扰RNA（siKLF2），培养4天后提取总RNA并进行RNA测序，每组设置4个生物学重复样本。