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复合bFGF的PCL/PLGA肝素化支架在心肌血运重建中应用的实验研究
【作者】 赵健；
【作者基本信息】 中国协和医科大学 ， 心血管外科学， 2008， 博士
【摘要】 目的:冠心病严重威胁着人类的健康,冠状动脉搭桥术和经皮冠脉介入治疗挽救了大量冠心病患者的生命。但是,约12%的患者因弥漫性冠脉血管病变、搭桥远端靶血管直径偏小以及二次手术缺乏桥血管等原因不适合上述治疗;而基于心肌窦状隙理论衍生的激光打孔方式,经动物实验及临床尸检证实,2周后孔道血栓化完全闭塞。本文在缺血部位室壁产生直径3.0mm的透壁孔道,同时植入具有良好力学弹性并复合碱性成纤维细胞生长因子(basic fibroblast growthfactor,bFGF)的肝素缓释抗凝支架,以尝试支撑孔道开放,抑制凝血途径激活,诱导血管再生,改善周围心肌血流灌注及心脏功能。方法:(1)通过静电纺丝法、溶剂挥发铸膜法、熔融挤塑法,优化工艺,制作复合bFGF的肝素化PCL/PLGA双层支架。(2)进行机械打孔、支架植入的可行性及损伤性评价。(3)在小型猪心梗模型基础上,设立对照组、单纯孔道组、孔道-空白支架组和孔道-肝素化支架组,在肝素缓释抗凝的前提下,进行孔道的长期开放性研究。(4)在机械打孔联合肝素化支架孔道开放的前提下,设立空白支架组、肝素化支架组和复合bFGF的肝素化支架组,通过在肝素化支架内同步复合bFGF,研究二者能否发挥协同作用,进一步促进缺血区域血流灌注及心功能的改善。结果:(1)力学测试PCL/PLGA支架具有良好的抗压强度,扫描电镜观察无明显变形,支架肝素含量25mg,bFGF含量15μg。(2)机械打孔及支架植入操作简便,无恶性心律失常、出血、栓塞等情况发生;在CVP、MAP、HR稳定的前提下,通过对左室短轴缩短率的分析,打孔及支架植入前后心功能无显著差异(P＞0.05)。(3)单纯孔道及空白支架植入6周后均发生闭塞,而肝素化支架孔道保持开放,扫描电镜观察管腔内皮化,并且周围新生血管密度显著增加,心肌灌注核素扫描质量缺损百分率、左室短轴缩短率均较其它组显著改善(P＜0.05)。(4)复合bFGF的肝素化支架组细胞因子VEGF、vWF、TGF-β3、IL-1β表达增强,并且新生血管密度、灌注质量缺损百分率与空白及肝素化支架组存在显著差别(P＜0.05);复合bFGF的肝素化支架组及肝素化支架组左室短轴缩短率均较空白支架组显著改善(P＜0.001),但前两组间比较,无显著统计学差异,但提示心功能有进一步改善的趋势(P=0.058)。结论:(1)复合bFGF的肝素化PCL/PLGA支架具有良好的抗压强度,能够耐受心肌的反复挤压。(2)肝素化处理后的支架通过缓释抗凝保持孔道长期开放,并且诱导部分管壁内皮化,增加血流灌注,改善心脏功能。(3)复合的肝素和bFGF能够协同发挥生物学作用,促进周围血管新生,增加心肌血流灌注,显示心功能有进一步改善的趋势。
【Abstract】 Objective.Coronary artery disease remains the leading cause of morbidity and mortality in the world.Approximately 12%of patients with coronary artery disease,because of unfavorable characteristics such as diffuse coronary atherosclerosis,small distal vessels or lack of suitable bridge vessels,are not amenable to coronary artery bypass grafting(CABG) or percutaneous coronary intervention(PCI).In this setting,transmyocardial laser revascularization(TMLR) derived from the idea of myocardial sinusoids has been explored, however,histologic observations in experimental specimens and clinical postmortem studies have demonstrated initial thrombus and eventually entire obliteration of the channels.The objective of this study,by producing transmural channels of 3.0mm in diameter and then implanting heparinized bFGF-incorporating PCL/PLGA stentts,is to investigate the potentiality of channel patency and new vessels density,and further study the concomitant efficacy in improving myocardial perfusion and function.Methods.(1) By electrospinning technology,solvent casting and surface spraying,a kind of novel heparinized bFGF-incorporating PCL/PLGA bilayer stent was fabricated.(2) Evaluate the feasibility of transmyocardial drilling revascularization(TMDR) and stent implantation,and the potential injury to the heart.(3) After myocardial infarction model,the miniswines were grouped:Control Group, TMDR Group,TMDR with Blank Stentt Group(TMDR-BS group) and TMDR with Heparinized Stent Group(TMDR-HS Group),and investigated the channel patency and myocardial perfusion improvement.(4) Based on the long-term patency of the heparinized channel,the miniswines were grouped:TMDR with Blank Stent Group(TMDR-BS Group),TMDR with Heparinized Stentt Group(TMDR-HS Group),and TMDR with Heparinized bFGF-incorporating Stentt Group(TMDR-HBS Group),and evaluated whether heparinized bFGF-incorporating stent could further enhance myocardial perfusion and function by the biologically synergetic role of bFGF and heparin.Results.(1) Each PCL/PLGA stent,with 25mg heparin and 15μg bFGF,could keep original shape and maintain control-release of heparin and bFGF for 4 weeks.(2) Both TMDR and stent implantation were accomplished readily,without any side effects,such as embolism,bleeding,and hemodynamic abnormality.(3) In TMDR and TMDR-BS group,the channels were occluded 6 weeks later. However,heparinized stent could keep the channel patent and induce luminal endothelialization.In TMDR-HS group,the neovascular density significantly increased, mass defect percentage(MDP%) of myocardial perfusion and fractional shortening(FS%) in TMDR-HBS group also revealed significant improvements compared with other groups (P＜0.05).(4) In TMDR-HBS group,pro-angiogenic factors ofVEGF、vWF、TGF-β3、IL-1βmarkedly expressed.Vascular density and MDP%significantly increased compared with TMDR-BS and TMDR-HS group(P＜0.05).FS%in both TMDR-HBS and TMDR-HS group significantly improved compared with TMDR-BS group(P＜0.001),however,there existed a trend towards improvement between TMDR-HBS and TMDR-HS group (P=0.058),although no statistical difference was revealed.Conclusions.PCL/PLGA bilayer stent could withstand recurrent crushing in vivo and maintain original contour.The stent with heparinized procedure could keep the channel open and promote luminal endothelialization by continuous anticoagulation.The control-released heparin and bFGF promoted neovascular formation and collateral development,and further improved cardiac function by increasing blood flow perfusion of ischemic "hibernated" myocardium.