The role of stem cells in atherosclerosis

Accumulating evidence indicates the involvement of stem cells and/or progenitors in the development of arteriosclerosis, including transplant arteriosclerosis, angioplasty-induced restenosis, vein graft atherosclerosis and spontaneous atherosclerosis. Recently, it was demonstrated that stem/progenitor cells existing in the circulation and adventitia contribute to endothelial repair and smooth muscle cell (SMC) accumulation. Atherosclerosis can be initiated by endothelial death in specific areas, e.g. bifurcation regions, and subsequent replacement by stem/progenitor cells. Meanwhile, progenitor cells from blood and the adventitia migrate into the intima where they proliferate and differentiate into neo-SMC. Stem/progenitor cells are responsible for the formation of atherosclerotic lesions, which appear as an inflammatory disease. Thus, these cells may be a source of endothelial cells and SMC, and might have implications for cellular, genetic, and tissue engineering approaches to vascular disease.     

Modification of environmental toxicity by nutrients

We hypothesize that nutrition can modulate the toxicity of environmental pollutants and thus modulate health and disease outcome associated with chemical insult. There is now increasing evidence that exposure to persistent organic pollutants, such as PCBs, can contribute to the development of inflammatory diseases such as atherosclerosis. Activation, chronic inflammation, and dysfunction of the vascular endothelium are critical events in the initiation and acceleration of atherosclerotic lesion formation. Our studies indicate that an increase in cellular oxidative stress and an imbalance in antioxidant status are critical events in PCB-mediated induction of inflammatory genes and endothelial cell dysfunction. Furthermore, we have found that specific dietary fats can further compromise endothelial dysfunction induced by selected PCBs and that antioxidant nutrients (such as vitamin E and dietary flavonoids) can protect against endothelial cell damage mediated by these persistent organic pollutants. Our recent data suggest that membrane lipid rafts such as caveolae may play a major role in the regulation of PCB-induced inflammatory signaling in endothelial cells. In addition, PCB- and lipid-induced inflammation can be down-regulated by ligands of anti-atherogenic peroxisome proliferator-activated receptors (PPARs). We hypothesize that PCBs contribute to an endothelial inflammatory response in part by down-regulating PPAR signaling. Our data so far support our hypothesis that antioxidant nutrients and related bioactive compounds common in fruits and vegetables protect against environmental toxic insult to the vascular endothelium by down-regulation of signaling pathways involved in inflammatory responses and atherosclerosis. Even though the concept that nutrition may modify or ameliorate the toxicity of environmental chemicals is provocative and warrants further study, the implications for human health could be significant. More research is needed to understand observed interactions of PCB toxicity with nutritional interventions.     

Inflammatory mediators in atherosclerotic vascular disease

An impressive body of work has established the current paradigm of atherosclerosis as an inflammatory process that promotes lesion development and progression. Early atheroma formation is characterized by leukocyte recruitment and expression of inflammatory mediators which is confounded in the context of hyperlipidemia. Evidence for an involvement of both innate and adaptive immunity in lesion formation has emerged, supporting a causal relation between the balance of pro- and anti–inflammatory cytokines and atherogenesis. The function of chemokines in distinct steps during mononuclear cell recruitment to vascular lesions has been studied in genetically deficient mice and other suitable models, and displays a high degree of specialization and cooperation. The contribution of platelet chemokines deposited on endothelium to monocyte arrest, differences in the presentation and involvement of chemokines between native and neointimal lesion formation, and related functions of macrophage migration inhibitory factor, a cytokine with striking structural homology to chemokines are of note. A novel role of chemokines in the recruitment of vascular progenitors during neointimal hyperplasia and in the recovery of endothelial denudation underscores their relevance for atherosclerotic vascular disease. The functional diversity of chemokines in vascular inflammation may potentially allow the selective therapeutic targeting of different atherosclerotic conditions.     

Thrombosis formation on atherosclerotic lesions and plaque rupture

Atherosclerosis is a silent chronic vascular pathology that is the cause of the majority of cardiovascular ischaemic events. The evolution of vascular disease involves a combination of endothelial dysfunction, extensive lipid deposition in the intima, exacerbated innate and adaptive immune responses, proliferation of vascular smooth muscle cells and remodelling of the extracellular matrix, resulting in the formation of an atherosclerotic plaque. High‐risk plaques have a large acellular lipid‐rich necrotic core with an overlying thin fibrous cap infiltrated by inflammatory cells and diffuse calcification. The formation of new fragile and leaky vessels that invade the expanding intima contributes to enlarge the necrotic core increasing the vulnerability of the plaque. In addition, biomechanical, haemodynamic and physical factors contribute to plaque destabilization. Upon erosion or rupture, these high‐risk lipid‐rich vulnerable plaques expose vascular structures or necrotic core components to the circulation, which causes the activation of tissue factor and the subsequent formation of a fibrin monolayer (coagulation cascade) and, concomitantly, the recruitment of circulating platelets and inflammatory cells. The interaction between exposed atherosclerotic plaque components, platelet receptors and coagulation factors eventually leads to platelet activation, aggregation and the subsequent formation of a superimposed thrombus (i.e. atherothrombosis) which may compromise the arterial lumen leading to the presentation of acute ischaemic syndromes. In this review, we will describe the progression of the atherosclerotic lesion along with the main morphological characteristics that predispose to plaque rupture, and discuss the multifaceted mechanisms that drive platelet activation and subsequent thrombus formation. Finally, we will consider the current scientific challenges and future research directions.     

Cardiac abnormalities in the toxic oil syndrome, with comparative observations on the eosinophilia-myalgia syndrome

Early in the course of studies of the Spanish toxic oil syndrome it was recognized that vascular lesions were a major problem, most logically attributable to endothelial damage by the toxic oil. However, most clinical attention has been directed to the pulmonary complications and the evolution into a scleroderma-like illness later. In this study of 11 victims of the toxic oil syndrome careful postmortem studies of the coronary arteries and conduction system and neural structures of the heart demonstrated major injury to all those components of the heart. Obliterative fibrosis of the sinus node in four cases resembled findings in fatal scleroderma heart disease, and in eight the cardiac lesions resembled those of lupus erythematosus. The more impressive pathologic features involved the coronary arteries and neural structures, which were abnormal in every heart. The arterial disease included widespread focal fibromuscular dysplasia, but there was also an unusual myointimal proliferative degeneration of both small and large coronary arteries in five patients, four of whom were young women. In two hearts, portions of the inner wall of the sinus node artery had actually detached and embolized downstream. Coronary arteritis was rarely found. Inflammatory and noninflammatory degeneration of cardiac nerves was widespread. Fatty infiltration, fibrosis and degeneration were present in the coronary chemoreceptor. In most respects these cardiac abnormalities resemble those described in the eosinophilia-myalgia syndrome caused by an altered form of L-tryptophan. In both diseases there is good reason to anticipate more clinical cardiac difficulties than have so far been reported, and even more basis for future concern, especially relative to coronary disease and cardiac electrical instability.     

茶多酚对兔颈总动脉血管成形术后再狭窄的影响

为探讨茶多酚对血管成形术后动脉中膜平滑肌增生及胶原增生的影响,以及与组织型纤溶酶原激活物和血管紧张素Ⅱ活性改变的关系,将雄性新西兰白兔30只随机分为对照组、低剂量茶多酚组和高剂量茶多酚组,用球囊导管剥脱右颈总动脉内皮,造成内皮及中膜损伤,分别在术前、术后3、7、11、14、22和28 d采动脉血应用酶联免疫法测血浆组织型纤溶酶原激活物活性及放射免疫法测血管紧张素Ⅱ血清水平,术后28 d处死动物并取右颈总动脉观察动脉中膜平滑肌和胶原增生程度.结果发现,高剂量茶多酚组组织型纤溶酶原激活物血浆活性为0.169±0.067 IU/L,低剂量茶多酚组为0.141±0.043 IU/L,对照组为0.126±0.043 IU/L,高剂量茶多酚组高于对照组和低剂量茶多酚组,差异具有显著性(P<0.05).高剂量茶多酚组血管紧张素Ⅱ血清水平为1 229±283 ng/L,低剂量茶多酚组为1 302±284 ng/L,对照组为1 309±263 ng/L,三组动物术后血管紧张素Ⅱ血清水平比较差异无显著性.高剂量茶多酚组动脉中膜胶原含量为50.1%+5.82%、低剂量茶多酚组为56.7%±2.3%,对照组为62.8%±2.1%,高剂量茶多酚组低于对照组及低剂量茶多酚组,差异具有显著性 (P<0.05);低剂量茶多酚组低于对照组,差异具有显著性(P<0.001).高剂量茶多酚组中膜平滑肌细胞计数为0.022±0.006/μm2,低剂量茶多酚组为0.034±0.008/μm2,对照组为0.033±0.007/μm2,高剂量茶多酚组低于对照组及低剂量茶多酚组,差异具有显著性(P<0.01).结果提示,高剂量茶多酚可提高血管成形术后血浆组织型纤溶酶原激活物活性,对血管紧张素Ⅱ血清水平无显著性影响,可抑制动脉中膜胶原及平滑肌细胞的增生,这可能有助于减轻或预防动脉血管成形术后再狭窄.     

外膜炎症诱发载脂蛋白E基因敲除鼠冠状动脉粥样硬化病灶

研究载脂蛋白E基因敲除(载脂蛋白E°)小鼠冠状动脉内粥样硬化病灶的分布、组成与动脉外膜炎症的关系.取载脂蛋白E°小鼠心脏作连续切片,Movat法染色,追踪冠状动脉主干及其心肌内的小分支;寻找病灶,观察病灶内组成,分析其分布规律.复制小鼠股动脉外膜无菌性炎症模型,用免疫组织化学方法检查内膜粘附分子的表达.结果发现,冠状动脉主干内有延伸病灶,在主干以下分支(包括心肌内小分支)内有在原位生成的病灶,在两类病灶相邻的外膜有炎性细胞浸润,外膜炎症面积大于动脉粥样硬化病灶累及的内膜面积,亦发现一些部位血管外有炎性细胞浸润,而尚无病灶形成.原位病灶均发生于心室壁,大的原位病灶多发生在左室壁心肌内、血管分支处和乳头肌附近的冠状动脉分支内.股动脉外膜炎症可诱发内膜表达细胞间粘附分子1和血管细胞粘附分子1,同时伴白细胞的附壁.以上提示血管外膜炎症是小鼠冠状动脉内病灶的一个始动环节.     

Atherosclerosis--an immune disease: The Anitschkov Lecture 2007

Atherosclerosis is an inflammatory disease. This article reviews the emergence of this concept from studies of patients and their lesions, experimental animal models, and epidemiological cohorts. Immunohistochemical studies identified immune cells and mediators and provided evidence for inflammatory activation in the atherosclerotic lesion. In parallel, cell culture studies demonstrated the capacity of vascular cells to interact with immune cells. Subsequent studies of clinical and epidemiological materials have identified inflammatory markers and immunoregulatory genes as contributors of risk for myocardial infarction and stroke. Finally, experiments using gene-targeted mice have provided mechanistic understanding of the disease process. It is now thought that the atherosclerotic process is initiated when low-density lipoproteins accumulate in the intima, activate the endothelium, and promote recruitment of monocytes and T cells. Monocytes differentiate into macrophages, internalize modified lipoproteins, and end up as foam cells. T cells in lesions recognize local antigens and mount T helper-1 responses that contribute to local inflammation and plaque growth. This atherogenic pathway is counterbalanced by anti-inflammatory signals provided by regulatory immunity. Intensified inflammatory activation may lead to local proteolysis, plaque rupture, thrombus formation, ischemia and infarction. Novel therapeutic opportunities may emerge from understanding the role of inflammation in atherosclerosis.     

Inflammation and atherosclerosis

Atherosclerosis is a vascular pathology in which inflammation plays a major role at every stage of the disease. The inflammatory process develops in response to abnormal cholesterol deposits in the intima of large arteries. The inflammatory reaction is initiated by a phase of endothelial activation induced by cytokines, oxidized low density lipoprotein (LDL) and/or changes in endothelial shear stress. This leads to the primary expression of endothelial adhesion molecules and chemokines followed by the recruitment and activation of circulating monocytes and lymphocytes. The clinical manifestations of atherosclerosis, including acute coronary syndromes, are the consequences of atherosclerotic plaque rupture/erosion that triggers thrombus formation leading to the occlusion of the vessel lumen. The local inflammatory process at the level of the atherosclerotic plaque might influence the stability of the plaque through its potential effects on the extracellular matrix, and on the plaque thrombogenicity. In humans, systemic inflammation has been recognized as a major risk factor of occurrence of acute coronary syndromes.     

Disappearance of intima over the stent and ulcer formation after intracoronary radiation for in-stent restenosis.

Little is known about the alterations of the vascular surface after radiation therapy for in-stent restenosis in humans, even though animal experiments suggest that delayed healing of the neointima is a cause of late thrombosis. Coronary angioscopy, together with coronary angiography, was performed at 3 months follow-up of 7 patients with in-stent restenosis who underwent beta-radiation therapy. Minimal lesion diameter (MLD) of the lesion increased from 1.00+/-0.30 mm (immediately before) to 2.44+/-0.39 mm (immediately after) and the MLD was well maintained 3 months later (2.34+/-0.62 mm) without any cases of restenosis. In 5 patients, the intima was so thin that some stent struts could be seen through it on angioscopy and in 2 of those, the intima over the stent had disappeared and 1 patient showed ulceration of the vascular wall beneath the stent. After intracoronary radiation therapy, the intima can become so thin that some stent struts are exposed to the lumen, which may be related to the occurrence of late thrombosis. Accordingly, patients who are treated with intracoronary radiation therapy may need long-term antiplatelet therapy.     

adipophilin及蛋白激酶C在动脉粥样硬化模型中的表达

目的探讨动脉粥样硬化病变区动脉壁增厚与adipophilin表达及蛋白激酶C(PKC)活性三者之间的关系。方法将24只新西兰白兔随机分为对照组(12只)和实验组(12只)。高TC饮食喂饲12周,动脉切片HE染色;采用PepTagAssay法检测PKC活性变化,Western blot印迹和免疫组织化学染色检测PKCα和adipophilin表达。并进一步在细胞学水平观察平滑肌细胞、巨噬细胞和内皮细胞PKC活性的分布及adipophilin的表达。结果主动脉病变区可见内膜增生、中层增厚,脂质条纹突起,增生内膜内蓄积大量的泡沫细胞。病变区PKC活性和adi-pophilin表达上调,与adipophilin阳性颗粒仅局限于增生内膜不同,PKCα在内膜、近内膜的中层区均呈强阳性表达。细胞学实验显示adipophilin表达于巨噬细胞,而PKC活性则以平滑肌细胞最强,内皮细胞最弱。结论动脉粥样硬化病变区内膜增生、中层增厚可能与PKC介导的细胞增殖凋亡紊乱及adipophilin介导的脂质蓄积有关。在巨噬细胞adipophilin的表达可能与细胞膜PKC活性的改变有着某种潜在联系。     

Neovascular expression of VE-cadherin in human atherosclerotic arteries and its relation to intimal inflammation

OBJECTIVE: The present work aimed to investigate how the Ca(2+)-dependent cell adhesion molecule vascular endothelial (VE)-cadherin might be involved in atherogenesis. METHODS: Specimens of human carotid artery and aorta were obtained at operation. An immunohistochemical approach using cell-type specific antibodies examined how VE-cadherin expression in areas of neovascularisation related to the accumulation of immunocompetent and inflammatory cells within atherosclerotic plaque. Electron microscopy was used to examine the structural characteristics of neovessels and the cell composition in the surrounding intimal matrix. RESULTS: In all the non-atherosclerotic aortic segments, VE-cadherin expression was observed only in the adventitia and the outer third of the media. Within the atherosclerotic arterial segments, VE-cadherin was expressed in all layers of the arterial wall including the intima where VE-cadherin was expressed by endothelial cells in areas of neovascularization. In some neovessels, loss of VE-cadherin expression was associated with increased focal accumulation of T-cells, macrophages and dendritic cells. Electron-microscopic examination demonstrated varying degrees of endothelial continuity in the intimal neovessels. Within those neovessels which were surrounded by a large number of immunocompetent and inflammatory cells, some inter-endothelial cell contacts were open allowing the penetration of blood cells through patent intercellular zones. CONCLUSIONS: VE-cadherin is expressed in atherosclerotic lesions by endothelial cells associated with neovascularisation. Downregulation of VE-cadherin expression within some intimal neovessels is accompanied by increased entry of immunocompetent cells into the intimal matrix surrounding areas of neovascularization which suggests that disorganizing endothelial cell-to-cell interactions within neovessels is significant in atherogenesis.     

Ultrasound imaging and atherogenesis

The in vivo detection of early atherosclerosis remains a problem. First, atherogenesis is a process with an insidious onset and course. Once clinical signs and symptoms have developed the lesion usually is in an advanced stage. Second, the detection of early atherosclerotic lesions creates the problem of distinguishing between almost natural, age-related intimai changes and intimai thickening as a precursor lesion of atherosclerosis. The hallmark of atherosclerosis is the abnormal deposition of lipids within the intima. This process is accompanied by a cellular response, composed of macrophages, lymphocytes and proliferating vascular smooth muscle cells. An increasing quantity of collagen and elastin fibers eventually will replace the cellular constituents. In other words, a changing histological picture with respect to component make up in time. Third, an adequate interpretation of intimai thickening may be complicated further by tissue characteristics of the arterial media. The elastin units of an elastic type artery produce an echo-dense image, whereas a muscular media is hypoechoic. All in all it seems fair to state that ultrasound imaging techniques, at least for the time being, will be inadequate to distinguish between early atherosclerotic lesions and intimai thickenings which will not necessarily progress to the full blown lesion.     

Oxidative stress,atherogenesis and cardiovascular risk factors

Cardiovascular diseases are the main cause of mortality in the western world. It is widely accepted that atherosclerosis, the first etiology, is influenced by free radicals and the oxidizing stress that they cause. In the oxidative theory of atherosclerosis, the atheromatous lesion is initiated by oxidation of two density lipoproteins (LDL), a process still known as lipid peroxidation. Oxidized LDL have many effects on the cells of the vessel wall which, provide an explanation to most of the cellular and tissular changes observed in the plaque. The vascular complications of hypercholesterolaemia, diabetes, hyperhomocysteinemia, hypertension and smoking may, in part, be secondary to oxidizing stress that impairs endothelial function and modify the lipids in the intima of the vessels. The aim of this paper is to review the modes of free radical production, to determine the role of oxidizing stress in the development of atherosclerosis and to show how the different risk factors may initiate atheroma through oxidizing stress.     

Glimepiride exhibits prophylactic effect on atherosclerosis in cholesterol-fed rabbits

AIMS/HYPOTHESIS: The purpose of this study was to examine the potential prophylactic effect of glimepiride on experimental atherosclerosis in rabbits and to elucidate the mechanism of action. METHODS: Rabbits were fed an atherogenic diet containing 1% cholesterol and glimepiride 0.1mg/kg/day for 10 weeks. Plasma lipid levels were determined every 2 weeks. The percentage of atherogenic lesions of thoracic aorta stained with oil red O was calculated and histological examination of the lesions was performed. Lipid and lipid peroxide contents in thoracic aorta and liver were also determined. In addition, the inhibitory effect of glimepiride on human coronary arterial endothelial cell-mediated LDL oxidation was evaluated. RESULTS: Accumulation of lipid-laden foam cells in the focal areas of arterial intima was observed in oil red O-positive atherosclerotic lesions. Glimepiride treatment produced significant reduction of atherosclerotic lesions (control, 57.5+/-7.1% versus glimepiride, 20.6+/-4.8%; P<0.01) with no significant change observed in levels of plasma lipids. There were marked decreases in lipid and lipid peroxide contents in the thoracic aorta in glimepiride-treated rabbits with no significant change in levels of liver lipids. In cultured human coronary arterial endothelial cells, glimepiride inhibited oxidative modification of LDL in a dose-dependent manner (IC(50)=8.8 x 10(-7)M) without cytotoxicity. CONCLUSIONS/INTERPRETATION: These findings suggest that glimepiride prevents the development of aortic atherosclerosis in fat-fed rabbits. The underlying mechanism may be inhibition of endothelial cell-mediated LDL oxidation.     

Pulmonary hypertension due to toxic oil syndrome. A clinicopathologic study

Clinical and pathologic findings in seven patients who died of severe pulmonary artery hypertension due to toxic oil syndrome are assessed. These cases correspond to a late stage of evolution of the disease characterized by progressive deterioration in clinical features--increasing dyspnea, chest pain, syncope, and death (in low-output heart failure). The main pathologic pulmonary vascular findings consisted of plexiform lesions, thromboses, and venous lesions. Endothelial damage induced by the toxic agents is suggested as an initial causative mechanism, perpetuated by intimal proliferation and in situ thrombosis. Plexiform lesions appear late and active histologically. This new cause of pulmonary artery hypertension, with pathologic findings similar to those found in primary pulmonary hypertension, may help in understanding the pathophysiology of this unknown disease.     

易损斑块与内皮祖细胞研究进展

研究证实易损斑块出现的同时伴随着内皮功能紊乱、内皮细胞脱失以及炎症反应的存在。内皮受损后可引起炎症反应激活、单核细胞浸润和血管平滑肌细胞增生,进而促发动脉粥样硬化和再狭窄形成,故修复受损血管内皮、促使血管重新内皮化已经成为防止动脉粥样硬化及再狭窄领域的重要课题。与此同时,内皮祖细胞参与受损血管的重新内皮化,吸引了越来越多的关注。现就内皮祖细胞与易损斑块的研究进展进行综述。     

循环内皮细胞在狼疮性肾炎血管病变诊断中的应用

目的：检测狼疮性肾炎（LN）患者循环血内皮细胞（CECs），探讨其在肾脏血管病变的诊断和判断病情中的作用。方法：60例经肾活检诊断为LN患者，其中30例伴血管病变患者，30例不伴血管病变患者。正常对照为30名健康志愿者。抽取外周血，采用免疫磁珠分离方法计数CECs的数量，同时进行血清肌酐、尿蛋白和尿红细胞等临床项目检查。结果：不伴血管病变组LN患者CECs数目与正常对照组相比差异无统计学意义，伴血管病变组患者CECs数目显著高于不伴血管病变组和正常对照组（P〈0．01）。伴血管病变组患者CECs与血清肌酐水平呈正相关（r=0．513，P〈0．01）。在伴血管病变LN患者中，合并血栓性微血管病变（TMA）患者CECs数量明显高于不伴有TMA患者（P〈0．01）。结论：CECs检测不仅能反映LN患者血管病变的存在，而且还能作为判断血管病变严重程度的指标。     

Impaired apoptosis of pulmonary endothelial cells is associated with intimal proliferation and irreversibility of pulmonary hypertension in congenital heart disease.

OBJECTIVES: This study sought to assess the cellular and histologic basis of irreversible pulmonary hypertension (PHT) in the clinical setting of congenital heart disease (CHD). BACKGROUND: Although many children with CHD develop pulmonary vascular disease, it is unclear why this complication is reversible after complete repair in some cases but irreversible in others. Because failure of endothelial cell apoptosis might lead to intimal proliferation and lack of reversibility of PHT, we investigated this and other key markers of vasoactivity and angiogenesis in subjects with PHT and CHD. METHODS: We assessed antiapoptotic and proapoptotic markers in vascular and perivascular cells in lung biopsy samples from 18 patients with CHD, 7 with reversible and 11 with irreversible PHT, and 6 control patients. Immunostaining for endothelial nitric oxide synthase, vascular endothelial growth factor, and CD34 (markers of vasoactivity and neoangiogenesis) was also performed. RESULTS: The antiapoptotic protein Bcl-2 was highly expressed by pulmonary endothelial cells in all cases of irreversible PHT but in no cases of reversible PHT, nor in control patients (p < 0.001). Intimal proliferation was present in 10 of 11 irreversible PHT cases, but never observed in reversible PHT (p < 0.001). Similarly, perivascular inflammatory T-cells expressed more antiapoptotic proteins in irreversible PHT (p < 0.01). Irreversible PHT cases were also more likely to show compensatory upregulation of vascular endothelial growth factor and new small vessel formation at the sites of native vessel stenosis or occlusion (p < 0.001). CONCLUSIONS: Irreversible PHT is strongly associated with impaired endothelial cell apoptosis and antiapoptotic signaling from perivascular inflammatory cells. These changes are associated with intimal proliferation and vessel narrowing, and thereby may contribute to clinical outcomes associated with pulmonary hypertension.