Molecular biological study for mechanism of intraplaque hemorrhage in carotid stenosis

近年来有研究报道血管内皮生长因子（VEGF）及其受体Flt-1可能对动脉粥样硬化斑块的形成起改变作用，抗fit -1抗体可抑制动脉粥样硬化。由于VEGF是血管生成/渗透因子，它可以促进血管生成，并可能导致斑块内出血。此外，VEGF可通过缺氧诱导因子（HIF）上调，而von Hippel-Lindau （VHL）蛋白下调。本研究的目的是阐明这些因素在颈动脉狭窄病变中的作用。我们检查了有症状的颈动脉狭窄患者在颈动脉内膜切除术中获得的颈动脉斑块标本。采用平滑肌细胞抗VEGF、Flt-1、HIF-1α、VHL、α-actin抗体和巨噬细胞抗CD68抗体进行免疫组化研究。血管内皮生长因子在颈动脉粥样硬化斑块深层纤维帽和斑块肩的泡沫细胞中明显表达。泡沫细胞大部分来源于巨噬细胞，部分来源于平滑肌细胞。VEGF阳性细胞中大部分为Flt-1阳性细胞。在大多数vegf阳性细胞中鉴定出HIF-1α阳性细胞，而在少数vegf阳性细胞中鉴定出vhl阳性细胞，特别是在颈动脉斑块中新形成的血管中。综上所述，VEGF在颈动脉斑块中的表达主要来源于颈动脉斑块深层巨噬细胞的泡沫细胞。提示HIF-1α上调VEGF表达，VHL部分下调VEGF表达。由于有报道称VEGF的表达受氧化LDL的调控，VEGF相关通路可能在颈动脉粥样硬化斑块的进展和斑块内出血的发生中起关键作用。

Recently it is reported that vascular endothelial growth factor (VEGF) and its receptor (Flt-1) may exert effects to alter the role of atherosclerotic plaque development and that atherosclerosis is inhibited by anti-Fit-1 antibody. Since VEGF is angiogenesis/permeable factor, it can promote angiogenesis and may lead to intraplaque hemorrhage. In addition, VEGF is up-regulated by hypoxia-inducible factor (HIF) which is down-regulated by von Hippel-Lindau (VHL) protein. The object of the study is elucidate the roles of these factors in cervical carotid stenotic lesion. We examined specimens of carotid plaques obtained at carotid endarterectomy for patients with symtptomatic carotid stenosis. Immunohistochemical study was performed with antibodies against VEGF, Flt-1,HIF-1α,VHL,α-actin for smooth muscle cell, and CD68 for macrophage. VEGF was expressed distinctly at foamy cells in fibrous cap and plaque shoulder in the deep layer of atherosclerotic carotid plaques. Most of foamy cells were derived from macrophages, but a part of them from smooth muscle cells. Flt-1 positive cells were identified at most of VEGF positive cells. HIF-1α -positive cells were identified at a majority of VEGF-positive cells while VHL-positive cells at a minority of VEGF-positive cells, particularly at newly formed vessels in carotid plaques. In conclusion, VEGF expression in carotid plaque is identified at foamy cells mostly derived from macrophages in the deep layer of carotid plaque. It is suggested that VEGF expression is up-regulated by HIF-1α which is partially down-regulated by VHL. Since it is reported that VEGF expression is regulated by oxidated LDL, VEGF-related pathway might play critical role in the advancement of atherosclerotic carotid plaque and the development of intraplaque hemorrhage.