在高血压动脉重建中microRNA-21对血管平滑肌细胞细胞外基质表达的调控作用

目的 探讨在高血压动脉重建中microRNA-21（miR-21) 对血管平滑肌细胞（vascular smooth muscle cells, VSMCs）细胞外基质（extracellular matrix, ECM）的调控作用及其机制。方法 建立腹主动脉缩窄型大鼠高血压模型，大鼠分为假手术对照组、高血压2周组和高血压4周组；对体外培养的大鼠主动脉 VSMCs 施加频率为1.25 Hz周期性张应变，加载幅度分别为0%（静态对照组）、5%（正常张应变组）、15%（模拟高血压状态的高张应变组），加载持续时间均为12 h。采用Western blotting和Real time RT-PCR 技术，分别检测动脉和细胞样品ECM以及miR-21的表达。用miR-21特异干扰片段抑制培养的VSMCs miR-21表达，然后检测VSMCs的ECM、miR-21和Smad 7表达变化。结果 与假手术对照组相比，高血压2周组胸主动脉ECM和miR-21的表达显著上升；高血压4周组胸主动脉的I型胶原、III型胶原和miR-21表达显著上升。与静态对照组和5%张应变组相比，15%张应变组VSMCs的I型胶原表达无显著变化，而III型胶原表达显著升高，Smad 7表达显著下降，周期性张应变增强VSMCs的miR-21表达。干扰miR-21降低周期性张应变状态下VSMCs的miR-21表达以及III型胶原蛋白水平表达，上调VSMCs的Smad 7表达。结论 高血压血管重建导致大鼠胸主动脉ECM和miR-21高表达。周期性高张应变可诱导VSMCs的miR-21高表达，再通过其调节Smad 7蛋白，进而调控VSMCs的ECM，尤其是III型胶原的表达，参与高血压血管重建。
Objective To investigate the regulating effect and mechanism of microRNA-21 (miR-21) on extracellular matrix (ECM) of vascular smooth muscle cells (VSMCs) by vascular remodeling of hypertension. Methods By narrowing the abdominal aorta in rats, the hypertension models were established and divided into 2-week hypertension group and 4-week hypertension group, and sham-operated group was also established as control. VSMCs from the rat aorta were subjected to 0% (static), 5% (normal) and 15%（hypertensive）elongation strain at a constant frequency of 1.25 Hz and duration of 12 hours, respectively. The expressions of Smad 7 and ECM were detected by Western blotting, and the expression of miR-21 was examined by Real-time RT-PCR. Finally, miR-21 siRNA was used to study the role of miR-21 in the mechanical strain-induced expression of ECM, miR-21 and Smad 7. Results Compared with the sham-operated group, ECM and miR-21 in thoracic aorta of 2-week hypertension group were significantly elevated. Collagen I, collagen III and miR-21 in thoracic aorta of 4-week hypertension group were significantly elevated. Compared with the static and 5% strain groups, the protein expression of collagen I in VSMCs did not show significant change, but the protein expression of collagen III was significantly elevated and Smad 7 expression was significantly decreased in 15% strain group. The cyclic strain also enhanced miR-21 expression in VSMCs. miR-21 inhibitor effectively decreased the expression of miR-21 in VSMCs and protein level of collagen III, while enhanced Smad 7 expression under the static and 15% strain. Conclusions The vascular remodeling of hypertension causes the high expressions of ECM and miR-21. The cyclic strain induces the high expression of miR-21, which via Smad 7 results in enhancing the expression of ECM, collagen III