Department of Cardiology, Peking University China-Japan Friendship School of Clinical Medicine, Beijing 100029, China.
Graduate School of Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing 100730, China; Department of Cardiology, China-Japan Friendship Hospital, Beijing 100029, China.
Microvasc Res. 2022 Jul;142:104349. doi: 10.1016/j.mvr.2022.104349. Epub 2022 Mar 1.
Ischemia preconditioning (IPC) ameliorates coronary no-reflow induced by ischemia/reperfusion (I/R) injury, and pericytes play an important role in microvascular function. However, it is unclear whether IPC exerts a protective effect on coronary microcirculation and regulates the pericytes.
The purpose of this study was to assess whether IPC improves coronary microvascular perfusion and reduces pericyte constriction after myocardial I/R injury.
Rats were randomly divided into three groups: the sham group, the I/R group, and the IPC + I/R group. The left anterior descending artery (LAD) of rats in the I/R group were ligated for 45 min, and the rats in the IPC + I/R group received 4 episodes of 6min occlusion followed by 6min reperfusion before the LAD was ligated. After 24 h of reperfusion, the area of no-reflow, and area at risk were evaluated with thioflavin-S and Evens blue staining, and infarct size with triphenyl tetrazolium chloride staining, respectively. Besides, fluorescent microspheres were perfused to enable visualization of the non-obstructed coronary vessels. Cardiac pericytes and microvascular were observed by immunofluorescence, and the diameter of microvascular at the site of the pericyte somata was analyzed.
The infarct size, and area of no-reflow in the IPC + I/R group were significantly reduced compared with the I/R group (infarct size, 33.5% ± 11.9% vs. 49.2% ± 9.4%, p = 0.021；no-reflow, 12.7% ± 5.2% vs. 26.6% ± 5.0%, p < 0.001). IPC improved microvascular perfusion and reduced the percentage of the blocked coronary capillary. Moreover, we found that cardiac pericytes were widely distributed around the microvascular in various regions of the heart, and expressed the contractile protein α-smooth muscle actin. The microvascular lumen diameter at pericyte somata was reduced after I/R (4.3 ± 1.0 μm vs. 6.5 ± 1.2 μm, p < 0.001), which was relieved in IPC + I/R group compared with the I/R group (5.2 ± 1.0 μm vs. 4.3 ± 1.0 μm, p < 0.001). Besides, IPC could reduce the proportion of apoptotic pericytes compared to the I/R group (22.1% ± 8.4% vs. 38.5% ± 7.5%, p < 0.001).
IPC reduced no-reflow and inhibited the contraction of microvascular pericytes induced by cardiac I/R injury, suggesting that IPC might play a protective role by regulating the pericyte function.
缺血预处理（IPC）可改善缺血/再灌注（I/R）损伤引起的无复流现象，周细胞在微血管功能中起重要作用。然而，IPC 是否对冠状动脉微循环有保护作用，以及是否调节周细胞，目前尚不清楚。
本研究旨在评估 IPC 是否改善心肌 I/R 损伤后的冠状动脉微血管灌注并减少周细胞收缩。
大鼠随机分为三组：假手术组、I/R 组和 IPC+I/R 组。I/R 组结扎左前降支（LAD）45min，IPC+I/R 组在结扎 LAD 前接受 4 个 6min 闭塞和 6min 再灌注。再灌注 24h 后，采用噻唑蓝（Evens 蓝）染色评估无复流区和危险区面积，氯化三苯基四氮唑（TTC）染色评估梗死面积。此外，通过荧光微球灌注使非阻塞性冠状动脉血管可视化。免疫荧光观察心肌周细胞和微血管，分析周细胞体部位微血管直径。
IPC+I/R 组的梗死面积和无复流面积明显小于 I/R 组（梗死面积，33.5%±11.9%比 49.2%±9.4%，p=0.021；无复流面积，12.7%±5.2%比 26.6%±5.0%，p<0.001）。IPC 改善了微血管灌注，减少了阻塞性毛细血管的比例。此外，我们发现心脏周细胞广泛分布在心脏各个区域的微血管周围，并表达收缩蛋白α-平滑肌肌动蛋白。I/R 后周细胞体部位的微血管管腔直径减小（4.3±1.0μm比 6.5±1.2μm，p<0.001），IPC+I/R 组与 I/R 组相比，该直径减小得到缓解（5.2±1.0μm比 4.3±1.0μm，p<0.001）。此外，IPC 可减少与 I/R 组相比的凋亡周细胞比例（22.1%±8.4%比 38.5%±7.5%，p<0.001）。
IPC 减少了无复流，并抑制了心肌 I/R 损伤引起的微血管周细胞收缩，提示 IPC 通过调节周细胞功能发挥保护作用。
