过刊浏览

模拟失重致大鼠弹力型大动脉血管区域特异性重塑及其重力性对抗措施

高放^*, 程九华, 薛军辉, 白云刚, 陈名声, 黄威权, 黄静, 武胜昔, 韩海潮, 张立藩

第四军医大学 航空航天生理学教研室， 航空航天临床医学教研室， 解剖学教研室， 西京医院检验科，西安 710032； 美国德克萨斯大学圣安东尼分校机械工程系，圣安东尼，德克萨斯 78249

摘要

为阐明失重致大动脉区域特异性重塑的特点和重力性对抗措施的机理，我们进行了整体与血管培养实验研究。整体实验：以大鼠尾部悬吊法模拟失重4周(SUS组)，以1 h/d 恢复站立体位模拟间断性人工重力(S + D组)，并设同步对照组(CON)。观察模拟失重对大鼠大动脉血管(颈总动脉和腹主动脉)的重塑影响及对抗措施的效果；用免疫组织化学、蛋白免疫印迹分析、原位杂交及实时PCR等方法检测血管组织血管紧张素原(angiotensinogen, Ao)和血管紧张素II 1型受体(angiotensin II type 1 receptor, AT1R)的蛋白与基因表达变化，以揭示血管局部肾素-血管紧张素系统(local renin-angiotensin system, L-RAS)是否参与调节。结果显示：与CON组相比，SUS组颈总动脉与腹主动脉近管腔的平滑肌层分别发生肥厚与萎缩变化；Ao与AT1R表达分别上调和下调。但在S + D组，上述适应性变化可被完全防止。血管培养实验：本文建立了可以控制流量、压力的血管培养系统，并得到下述结果。在高压(150 mmHg)下培养颈总动脉3 d，可引起平滑肌层c-纤维粘连蛋白表达增强，且以靠近管腔的肌层最为显著；培养液Ang II的生成量也增多；但如在3 d灌流期间，每天有4或1 h使灌流压降至0或80 mmHg，则上述改变即可被完全防止。以上结果支持我们的假说：跨壁压分布变化是失重引起动脉区域性重塑的始动原因；但每日只要短时间使其恢复常态，血管重塑及L-RAS的变化即可被完全防止。

关键词： 微重力; 航天飞行后心血管失调; 间断性人工重力; 血管重塑; 局部肾素-血管紧张素系统; 血管灌流培养

分类号：R318.01

[In-vivo and ex-vivo studies on region-specific remodeling of large elastic arteries due to simulated weightlessness and its prevention by gravity-based countermeasure.] [Article in Chinese]

Gao Fang^*, CHENG Jiu-Hua, XUE Jun-Hui, BAI Yun-Gang, CHEN Ming-Sheng, HUANG Wei-Quan, HUANG Jing, WU Sheng-Xi, HAN Hai-Chao, ZHANG Li-Fan

Departments of 1Aerospace Physiology, 2Aerospace Clinical Medicine, 3Anatomy, and 4Clinical Laboratory, Xijing Hospital, the Fourth Military Medical University, Xi’an 710032, China； 5 Department of Mechanical Engineering, University of Texas at San Antonio, San Antonio, TX 78249, USA

Abstract

The present study was designed to test the hypothesis that a medium-term simulated microgravity can induce region-specific remodeling in large elastic arteries with their innermost smooth muscle (SM) layers being most profoundly affected. The second purpose was to examine whether these changes can be prevented by a simulated intermittent artificial gravity (IAG). The third purpose was to elucidate whether vascular local renin-angiotensin system (L-RAS) plays an important role in the regional vascular remodeling and its prevention by the gravity-based countermeasure. This study consisted of two interconnected series of in-vivo and ex-vivo experiments. In the in-vivo experiments, the tail-suspended, hindlimb unloaded rat model was used to simulate microgravity-induced cardiovascular deconditioning for 28 days (SUS group); and during the simulation period, another group was subjected to daily 1-hour dorso-ventral (−Gx) gravitation provided by restoring to normal standing posture (S + D group). The activity of vascular L-RAS was evaluated by examining the gene and protein expression of angiotensinogen (Ao) and angiotensin II receptor type 1 (AT1R) in the arterial wall tissue. The results showed that SUS induced an increase in the media thickness of the common carotid artery due to hypertrophy of the four SM layers and a decrease in the total cross-sectional area of the nine SM layers of the abdominal aorta without significant change in its media thickness. And for both arteries, the most prominent changes were in the innermost SM layers. Immunohistochemistry and in situ hybridization revealed that SUS induced an up- and down-regulation of Ao and AT1R expression in the vessel wall of common carotid artery and abdominal aorta, respectively, which was further confirmed by Western blot analysis and real time PCR analysis. Daily 1-hour restoring to normal standing posture over 28 days fully prevented these remodeling and L-RAS changes in the large elastic arteries that might occur due to SUS alone. In the ex-vivo experiments, to elucidate the important role of transmural pressure in vascular regional remodeling and differential regulation of L-RAS activity, we established an organ culture system in which rat common carotid artery, held at in- vivo length, can be perfused and pressurized at varied flow and pressure for 7 days. In arteries perfused at a flow rate of 7.9 mL/min and pressurized at 150 mmHg, but not at 0 or 80 mmHg, for 3 days led to an augmentation of c-fibronectin (c-FN) expression, which was also more markedly expressed in the innermost SM layers, and an increase in Ang II production detected in the perfusion fluid. However, the enhanced c-FN expression and increased Ang II production that might occur due to a sustained high perfusion pressure alone were fully prevented by daily restoration to 0 or 80 mmHg for a short duration. These findings from in-vivo and ex-vivo experiments have provided evidence supporting our hypothesis that redistribution of transmural pressures might be the primary factor that initiates region-specific remodeling of arteries during microgravity and the mechanism of IAG is associated with an intermittent restoration of the transmural pressures to their normal distribution. And they also provide support to the hypothesis that L-RAS plays an important role in vascular adaptation to microgravity and its prevention by the IAG countermeasure.

Key words: Microgravity; postflight cardiovascular dysfunction; intermittent artificial gravity; vascular remodeling; local renin-angiotensin system; artery organoid culture

收稿日期：2011-07-01　　录用日期：2011-08-08

通讯作者：高放　　E-mail: zhanglf@fmmu.edu.cn

引用本文：

高放, 程九华, 薛军辉, 白云刚, 陈名声, 黄威权, 黄静, 武胜昔, 韩海潮, 张立藩. 模拟失重致大鼠弹力型大动脉血管区域特异性重塑及其重力性对抗措施[J]. 生理学报 2012; 64 (1): 14-26.

Gao Fang, CHENG Jiu-Hua, XUE Jun-Hui, BAI Yun-Gang, CHEN Ming-Sheng, HUANG Wei-Quan, HUANG Jing, WU Sheng-Xi, HAN Hai-Chao, ZHANG Li-Fan. [In-vivo and ex-vivo studies on region-specific remodeling of large elastic arteries due to simulated weightlessness and its prevention by gravity-based countermeasure.] [Article in Chinese]. Acta Physiol Sin 2012; 64 (1): 14-26 (in Chinese with English abstract).