【作者】 田晓东；

【导师】 高长青；

【作者基本信息】 中国人民解放军军医进修学院 ， 外科学， 2005， 博士

【摘要】 目的:大隐静脉目前仍然是最常用的冠状动脉旁路移植材料之一,然而新内膜的生成及逐渐增厚导致晚期移植静脉再狭窄甚至闭塞,影响了手术的远期疗效。外支架能抑制移植静脉内膜增生和管壁增厚,是一种很有前景的防治移植静脉再狭窄的方法。本研究的目的在于探讨非限制性外支架防治移植静脉内膜增生和细胞增殖的效果及其可能的作用机制,同时探讨非限制性外支架对血小板源性生长因子(PDGF)表达的影响。 材料与方法:新西兰白兔36只随机分成两组,每只均实施颈外静脉-颈总动脉移植术,支架组(S组)在移植静脉外套以直径6mm的非限制性涤纶外支架,对照组(NS组)移植静脉外无外支架,分别于术后1周(1W)、2周(2W)、4周(4W)取材进行观察。术后应用彩色多普勒超声观察移植静脉的通畅情况。组织切片进行HE和弹力VG染色,光镜下观察病理和结构变化。采用计算机图像分析系统测量移植静脉内膜、中膜的厚度和面积,管腔面积,并计算内膜增值率(即内膜面积/内弹力板包围面积)。切片进行α-平滑肌肌动蛋白(α-SMA)和增殖细胞核抗原(PCNA)免疫组织化学染色,以鉴别血管内的平滑肌细胞并判断其增殖情况。PCNA增殖指数以每高倍视野(×400)PCNA阳性细胞数/总细胞数计算,分别计算移植静脉内膜、中膜、外膜的PCNA增殖指数。应用免疫组织化学和逆转录聚合酶链反应(RT-PCR)技术检测PDGF-B的表达,分别计算移植静脉内膜、中膜和外膜的PDGF-B阳性表达率,提取移植静脉管壁总RNA后,进行反转录扩增。 结果:(1) S组术后死亡1只,闭塞性血栓形成1只,在支架与移植静脉之间有“果冻样”物质(新外膜)形成;NS组术后偏瘫并死亡1只,血栓形成1只。超声检查移植静脉通畅情况与取材时结果完全一致。(2) HE染色显示:术后1W～4W,S组和NS组移植静脉内膜和中膜逐渐增生,S组新外膜为肉芽肿样增生,内有较多炎症细胞浸润。(3) 计算机图像分析结果:术后1～4W,S组和NS组内膜、中膜的厚度和面积均逐渐增加。术后1W时,S组的内膜厚度、面积和内膜增生率与NS组的差别无统计学意义,P>0.05;术后2W、4W时,S组的内膜厚度、面积和内膜增生率均小于NS组,P<0.05;术后更多还原

【Abstract】 Objective: Autologous saphenous vein continues to be one of the most commonly used conduits for coronary artery bypass graft surgery, however the long-term clinical success of the procedure is limited by the late graft failure due to neointima formation and progressive thickening. External-stenting of vein grafts is a promising approach to prevent neointima hyperplasia and wall thickness of the vein grafts. In the present study, we investigated the effect and the potential mechanisms of non-restrictive external stent to prevent neointima hyperplasia and cell proliferation of vein grafts and the influence of non restrictive external stent on expression of platelet-derived growth factor (PDGF) which is a potent mediator of vascular smooth muscle cell(VSMC).Material and methods: Thirty-six "New Zealand white rabbit" were randomly divided into two groups, stenting group (group S) and control group (non-stenting group, group NS). Each rabbit underwent a reversed autologous external jugular vein into common carotid artery bypass grafting. In group S, the vein graft were surrounded by a non restrictive stent which was 6mm in diameter (a kind of Dacron vascular prosthesis); and in group NS, there was no stent to support the vein grafts. The grafts were harvested at lweek(1W), 2weeks(2W), 4weeks(4W) after surgery, respectively. Color Doppler ultrasonography was applied to test the patency of the grafts. The sections were stained with hematoxylin and eosin stain and elastic van Gieson’s stain, and examined under a light microscope. The dimensions(including the thickness and area of the intima and media, luminal area) were measured by computer-aided image analysis system, and the intimal encroachment was defined as the percentage of the area enclosed by the internal elastic lamina occupied by the intima. Sections were also stained with a-smooth muscle actin(a-SMA) and proliferating cell nuclear antigen (PCNA) immunocytochemistry stain to identify the VSMC and judge the cell proliferation of the vein grafts. PCNA index was calculated as the percentage of positive cells among the total number cells in a microscopic field with x400 magnified in intima, media and adventitia, respectively. Imrnunohistochemistryand reverse transcription-polymerase chain reaction (RT-PCR) technique were employed to investigate the expression of PDGF in vein grafts. The percentage of PDGF immunocytochemistry stain positive cells were also calculated in intima, media and adventitia, respectively; and total RNA of whole wall of the vein grafts were extracted and performed RT-PCR.Results: (l)One rabbit died before harvest and one rabbit developed occlusive thrombus in group S, and the material like the"jelly" (neoadventitia) occupied the space between the grafts and the stents. Hemiplegia occurred in one rabbit and the rabbit died before harvest, and non-occlusive thrombus formed in one graft in group NS. The results of Color Doppler ultrasonography were in accordance with the findings of harvest. (2)HE stain: intima and media of vein grafts proliferated in both group S and NS gradually from 1W to 4W, and the neoadventitia in group S was formed with granulation, and many inflammatory cells aggregated in it. (3)Computer-aided image analysis system study: from 1W to 4W, the thickness and area of the intiam and media were increased gradually. At 1W, the difference of the thickness and area of the intiam and the intimal encroachment between group S and NS were no significance, P>0.05; at 2W, 4W, the thickness and area of the intiam in group S were smaller than those in group NS, P < 0.05; from 1W to 4W, the thickness and area of the media in group S were smaller than those in group NS, P<0.05. (4)PCNA index: the index of intima in both two groups were peaked at 2 W, and the index of intima in group S was less than in group NS at 2 W and 4W, P<0.05; the index of media in both two groups were peaked at 1W, and the index of media in group S was less than in group NS fron 1W to 4W, P<0.05; the index of adventitia in both two groups were peaked at 2W, and the index of adventitia in group S was greater than in group NS at 2W and 4W, P<0.05. (5)Immunocytochemistry stain of PDGF-B: the percentage of positive cells of intima in both two groups were peaked at 2W, and a significantly smaller percentage were detected in group S compared with in group NS at 2W and 4W, P <0.05; and the percentage of PDGF-B positive cells of media in both two groups were also peaked at 2 W, and the percentage of media in group S was smaller than in group NS fron 1W to 4W, P<0.05; and the percentage of PDGF-B positive cells of adventitia in group S was peaked at 4W, whereas the percentage of更多还原