Atherosclerotic plaque-like lesions in synthetic arteriovenous grafts: implications for atherogenesis.

Atherosclerotic plaque-like lesions are prevalent in synthetic arteriovenous shunts created to provide vascular access for hemodialysis. Similarities to atherosclerotic plaques in native arteries include eccentric location, immunoreactivity for smooth muscle actin, dystrophic calcifications, superimposed thrombi, and foam cells. Fatty streaks were not grossly identified on Sudan IV staining. Because of the similarities to atherosclerosis in native vessels, these findings may have several implications for atherogenesis. The development of raised, fibrous lesions does not require decades. The presence of smooth muscle in atherosclerotic plaque-like lesions does not require a source from tunica media. A precursor fatty streak may not be required for the development of raised, fibrous lesions. Finally, development of atherosclerotic plaque-like lesions does not require putative inflammatory effects from cholesterol or LDL accumulation, or even a native vessel that can respond to injury. The atherosclerotic plaque-like lesions in this study probably developed from organization of mural thrombi.     

Relative distribution of fibronectin and type I, III, IV, V collagens in normal and atherosclerotic intima of human arteries

Spatial distribution of fibronectin and type I, III, IV and V collagen has been investigated in normal arterial intima, fatty streaks, and atherosclerotic plaques by indirect immunofluorescence on transverse sections. Two distinct types of extracellular matrix were revealed in atherosclerotic lesions. The fibrous plaques consisted mostly of interstitial collagen types I and III, contained moderate amounts of type V and none of type IV collagen or fibronectin. In the extracellular matrix of the fatty streaks and in some areas of the fibrous plaques containing large amounts of subendothelial cells, some interstitial collagen was revealed, an increased amount of type IV, some type V collagen and a lot of fibronectin. Similarities of the extracellular matrix in atherosclerotic lesions and granulation tissues are discussed.     

Immunocytochemical analysis of the atherosclerotic lesion.

We have performed immunocytochemical investigations on the distribution of various cell types and proliferating cells in human atherosclerotic lesions. Studies include fibrocellular tissue response following percutaneous transluminal coronary angioplasty (PTCA) or aortocoronary (A-C) bypass operation using monoclonal antibodies specific to smooth muscle cells, macrophages, endothelial cells, lymphocytes and proliferating cell nuclear antigen (PCNA). All studies were performed on methanol-Carnoy's-fixed, paraffin-embedded tissues. The cellular composition of the following three types of raised lesions were analyzed: 1) fibro-fatty lesions composed almost exclusively of macrophages; 2) fibrous lesions predominantly composed of smooth muscle cells; 3) advanced plaques characterized by complex layers of smooth muscle cells and macrophages with considerable variation from region to region. Also noted were foci of medial and even intimal vascularization subjacent to the more advanced plaques. Cells encountered within the fibrous intimal thickening in the vein graft or fibrocellular tissue response following PTCA were predominantly smooth muscle cells in origin. Some cells were PCNA-positive. These studies demonstrate the application of monoclonal antibody technology to the study of the cellular composition and cell kinetics of human atherosclerotic lesions.     

Immunohistochemical localization of C5b-9, S-protein, C3d and apolipoprotein B in human arterial tissues with atherosclerosis

The terminal C5b-9 neoantigens of the complement complex, S-protein (Vitronectin), C3c, C3d and apolipoprotein B were localized on 16 aortic fibrous plaques, 8 aortic intimal thickenings, 4 fatty streaks intimae, 12 coronary fibrous plaques, 3 coronary intimal thickenings, 6 femoral and 5 basilar fibrous plaques, using an indirect and double-staining immunoperoxidase method. The granular specific deposits were localized in the fibrous cap and deeper parts of the plaque or in the deeper intima and inner-third media of intimal thickenings and fatty streaks intimae, in relation to the degree of atherosclerotic involvement. The different localization of C5b-9 and S-protein demonstrated by the double-staining technique is more suggestive for the assembly of the complex into the arterial wall and not for its preformed passage from circulation. The relation of these immune deposits to the degree of fibrosis and necrosis and their presence from the initial stages through to the advanced lesions could ascribe a role to the complement system in atherosclerosis.     

Differences in the pattern of atherosclerotic involvement between non-branched regions and adjacent branching points of human coronary arteries

A light-microscopic study carried out on 816 coronary arterial trees revealed that the variety of atherosclerotic lesions detected in non-branched segments was 3-5 times greater than that recorded in branching points. The fibromuscular and fibronecrotic plaques, small fatty streaks, small intimal necrotic areas, incorporated microthrombi and intramural organized thrombi were recorded in both non-branched regions and branching points. The mucoid, foam cell-rich and necrotic plaques, large fatty streaks with abundant extracellular lipid and large intimal necrotic areas with lipid and fibrin deposition were recorded only in non-branched regions, whereas the fibrohyaline plaques were recorded only in the branching points. The complexity of atherosclerotic involvement of the branch areas increased with the branch mouth diameter: at a diameter of 1 mm only fibromuscular and fibrohyaline plaques were recorded; at a diameter between 1 and 2 mm the fibronecrotic plaques and at a diameter of more than 2 mm the small fatty streaks and small intimal necrotic areas were also detected. The results showed that along a distance of only 2-5 mm there are in the coronary arterial tree local hemodynamic and structural patterns which in non-branched regions favour and in adjacent branching sites restrict the onset and progression of atherosclerotic lesions; there are also local factors which in non-branched regions enlarge and in adjacent branching sites limit the types of atherosclerotic lesions which will develop. Any view on the etiopathogenesis of human coronary atherosclerosis needs to be considered in conjunction with the hemodynamic and structural patterns existing in the different parts of the coronary arterial tree, both closely related to the coronary branching anatomical pattern.     

Study of fibrous plaques occurring in the coronary arteries of children.

The pathology of the coronary arteries of children, in relation to atherosclerotic involvement, appeared as a pathology of the main emergence areas and branching points of the left coronary artery and particularly of the anterior descending artery. The first atherosclerotic lesions occurred as non-raised fibrous plaques in 2% of children 6--10 years old and in 4% of children and juveniles 11--15 years old. In the latter age group fatty streaks and gelatinous plaques were also seen in 6% of the subjects; in their appearance they lag behind fibrous plaques by 5--8 years. Indirect evidence was obtained that some branch pads or cushions might be converted into fibrous plaques. The transitional aspects included edema, histolysis (elastolysis, collagenolysis, ground-substance depletion and degenerative cell changes), followed by reorganization and homogeneization of the pre-existing heterogeneous microarchitecture; in a final stage the prevalent processes seemed to be the nodular proliferation of smooth muscle cells and the abundant neoformation of collagen fibers. In essence the results show that in atherosclerosis the coronary arteries are involved in a different sequence and histogenetic pattern than the aorta.     

Expression of CD40 in vascular smooth muscle cells and macrophages is associated with early development of human atherosclerotic lesions

CD40-CD154-mediated signaling has recently been described as playing a role in cellular functions involved in atherosclerotic processes. CD40 is expressed in macrophages, lymphocytes, endothelial cells, and vascular smooth muscle cells. However, cross-sectional studies investigating the expression of CD40 in atherosclerotic lesions are lacking. In the present study the expression of CD40 was studied in atherosclerotic lesions from 43 patients classified according to the World Health Organization criteria. Serial immunohistologic stainings of human iliac arteries from 43 patients were performed using monoclonal antibodies. Lesions were classified according to World Health Organization criteria, and CD40 expression was analyzed with regard to cell morphology and cellular markers by 2 independent observers. Human atherosclerotic lesions revealed a significant increase in intimal thickness, number of inflammatory infiltrates, and CD40-positive macrophages and vascular smooth muscle cells with progression of the lesions. This increase was most prominent from stage 0 to stage I. A significant correlation between intimal thickness and CD40-positive macrophages (r = 0.75, p <0.0005) and CD40-positive vascular smooth muscle cells (r = 0.81, p <0.0005) was observed. Ligation of the cellular CD40 receptor contributes to inflammatory cellular events in human vascular smooth muscle cells. These data suggest a direct association of CD40 expression in atherosclerotic lesions with early plaque development.     

Circulating smooth muscle progenitors and atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the arterial wall; during the transition from primitive fatty streaks to more complex lesions, smooth muscle cells play a pivotal role. According to the canonical view, smooth muscle cells migrate from tunica media and contribute to the development of neointima and the fibrous cap. New evidences suggest that bone marrow-derived smooth muscle progenitors might contribute to both neointima formation and fibrous cap development. In this review, we discuss the controversial identity and origin of circulating smooth muscle progenitors by focusing on the methodological clues for their isolation. Furthermore, we examine the potential contribution of smooth muscle progenitors in the development/progression of atherosclerotic lesions.     

Quantitation of apo b in human aortic fatty streaks A comparison with grossly normal intima and fibrous plaques

The content of apolipoprotein B (apo B)-containing lipoproteins was measured in aortic fatty streak lesions of 18 male individuals between the ages of 21 and 67 years, and compared to the values found in adjacent grossly normal intima. Extraction of apo B was accomplished by sequential treatment of aortic tissue homogenates with a standard buffer and one containing the detergent Triton X-100. Mean apo B values (μg per mg tissue dry weight) in fatty streaks were: BUFFER-EXTRACTED = 4.67 ± 0.51, Triton-extracted = 1.88 ± 0.39; while in adjacent grossly normal intima: BUFFER-EXTRACTED = 6.51 ± 0.92, Tritonextracted = 0.37 ± 0.15. Using a paired t-test, buffer-extracted apo B was marginally significantly greater in the adjacent normal intima than fatty streaks (P < 0.05), whereas Triton-extracted apo B was highly significantly greater in fatty streaks than adjacent normal intima (P < 0.0005). When the mean apo B values of these 18 fatty streaks and 23 fibrous plaques from separate cases were compared in a non-paired t-test, buffer-extracted apo B was slightly higher in fatty streaks than fibrous plaques (P < 0.025), whereas Triton-extracted apo B was much higher in fibrous plaques than in fatty streaks (P < 0.0005). The intermediate position of fatty streaks between grossly normal and fibrous plaques with respect to buffer- and Triton-extracted apo B content, gives additional support to the contention that this lesion is an intermediate step in the progression of the grossly normal intima to a fibrous plaque. Assuming this sequence of progression to occur, our results demonstrate a marginally significant decrease in buffer-extracted apo B but a highly statistically significant increase in Triton-extracted apo B with lesion development.     

Adult human aortic cells in primary culture: heterogeneity in shape

Summary Adult human aortic cells have different shapes in situ. To determine whether populations of cultured aortic cells are also polymorphic, a technique for separation of cells from the intimal and medial layers of the human aorta by enzymatic dispersion of the vascular tissue was employed. It was established that aortic cells are polymorphic in primary culture, at least within the first 7 days after seeding. Four main morphological cell types were identified—elongated, asymmetric, polygonal, and stellate. Polygonal and stellate cells are found only in cultures of grossly normal intima. Elongated and asymmetric cells are present in practically all cultures. The ratio of elongated to asymmetric cells in cultures obtained from healthy aortas and atherosclerotic plaques is more or less the same and is approximately 3 : 1. In cultures of fatty streaks, the portion of asymmetric cells exceeds 50%. With immunofluorescent staining and ultra-structural analysis, cells of all four types were identified as smooth muscle. Possible reasons for the cells polymorphism in primary culture and the prospects of utilizing this culture method in the investigation of cellular aspects of atherogenesis are discussed.     

Atherosclerosis of the aorta and coronary arteries and cardiovascular risk factors in persons aged 6 to 30 years and studied at necropsy (The Bogalusa Heart Study).

Race and sex differences in aorta and coronary atherosclerotic lesions were studied in 150 persons aged 6 to 30 years. The intimal surface involvement with aorta fatty streaks was extensive, 0 to 71%, and greater in blacks than in whites (32 vs 20%, p less than 0.001). Coronary artery fatty streaks were more extensive in male than in female subjects (range 0 to 22%). Fibrous plaque lesions were present but not extensive in either the aorta (0 to 12%) or the coronary artery (0 to 24%) specimens. Lesions were more prevalent in male than in female persons, particularly white male subjects. The relation of fatty streaks to fibrous plaques was greater in the coronary vessels than in the aorta. In male subjects, aorta fatty streaks were strongly related to antemortem levels of total cholesterol, low-density lipoprotein cholesterol and ponderal index in white male subjects. Coronary artery fatty streaks in white male persons were significantly associated with serum triglycerides, very low density lipoprotein cholesterol, systolic and diastolic blood pressure and ponderal index. These results link antemortem risk factors to the development of atherosclerotic lesions and emphasize the need for preventive cardiology in early life.     

Thrombosis and the development of atherosclerosis: Rokitansky revisited

In this article we have reviewed the evidence that implicates the organization and incorporation of mural thrombi as a significant component of atherosclerotic plaque growth in man. It has been emphasized that there is little or no evidence for a pathogenic role for thrombosis in plaque initiation or for the development of fatty streaks. We have suggested that the rapidly progressive category of atherosclerosis in man, as described by DeBakey, may well reflect a heightened propensity for mural or occlusive thrombosis in these patients. A broad spectrum of experimental studies examining the role of thrombosis in atherogenesis has been critically reviewed. These studies have established that experimental thrombi can become transformed into arterial fibrofatty plaques having many of the morphologic features of atherosclerosis. We have provided evidence, however, that the evolution of thrombi to fibrofatty lesions is dependent on the initial composition of the thrombi and that thrombi with a paucity of platelets and consisting predominantly of fibrin result only in fibrous intimal thickenings. The presence of hypercholesterolemia has been shown to influence the transformation of experimental thrombi. In particular, it slows the rate of thrombolysis, enhances the lipid content of the fibrofatty plaques, increases the numbers of macrophage-derived foam cells, and the frequency and extent of lesion calcification. Detailed lipid compositional studies of organizing thrombi in normolipidemic animals have shown that their lipid composition does not evolve toward the profile characteristic of atherosclerotic lesions and that the macrophage uptake of interstitial lipoproteins is probably a necessary component for the full biochemical development of the lesions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Progression of coronary atherosclerosis from adolescents to mature adults

Ten selected topographic sites of the coronary arteries were placed in sequence according to age, sex, branching anatomical pattern and smoking habit, in order to obtain an indirect sequencing of the pattern and rate of progression of early atherosclerotic lesions from adolescents to mature adults. The material came from 356 subjects aged 16-45 years who had died in violent accidents and included the light-microscopic examination of 3560 coronary artery samples. The dynamic reconstruction of thousands of static views revealed the existence of an age-related rate of progression of fibromuscular plaques, intimal necrotic areas, incorporated microthrombi and fatty streaks. All these early atherosclerotic lesions increased linearly and in parallel from one 5-year age group to the next and exhibited non-significant differences in their rate of progression over a period of 25 years. During this period the number of atherosclerotic plaques increased 4.7 times, of intimal necrotic areas 4.6 times, of incorporated microthrombi 4.3 times and of fatty streaks 3.9 times. Consequently, in the 10 selected topographic sites of the coronary arteries placed in sequence according to age, the pathological aspects became prevalent, microscopically, over the normal ones, starting from the fourth decade of life. This study also revealed that some endogenous and exogenous risk factors for coronary heart disease accelerated the age-related rate of progression of early atherosclerotic lesions. In addition, particular cycles of evolution towards advanced lesions appeared, leading to the onset of fibronecrotic and fibrohyaline plaques. Their obstructive character was related to both successive incorporation of microthrombi and the onset of large lipid deposits. Among the four types of early atherosclerotic lesions investigated, only the fatty streaks did not show this direct conversion to a lesion of possible clinical significance.     

Characterization of atherosclerosis in LDL receptor knockout mice: macrophage accumulation correlates with rapid and sustained expression of aortic MCP-1/JE

Atherosclerosis and the expression of monocyte chemoattractant protein-1 (MCP-1) were quantified in low density lipoprotein receptor knockout (LDLR KO) mice fed 1.25% cholesterol (study #1) or 0.2% cholesterol (study #2). In study #1 plasma total cholesterols leveled-off at 1800 mg/dl whereas plasma triglycerides remained low. In en face specimens of the aortic root and arch, intimal foam cells plus extracellular lipid particles accumulated and by 8 weeks the fatty streak surface area had rapidly expanded at both sites. In study #2, total cholesterols averaged 400 mg/dl and fatty streaks were 2-3-fold smaller compared to those in study #1. In study #3, LDLR KO mice were fed chow or 1.25% cholesterol, and immunostaining demonstrated a few Mac-2-positive intimal macrophages in mice fed chow, and during the first 10 weeks of hypercholesterolemia the number of intimal macrophages increased continuously. In chow-fed mice (0 weeks) there was little MCP-1 in the aorta. After 2 days of hypercholesterolemia intimal macrophages stained for MCP-1, and during the next 10 weeks recently recruited arterial macrophages also expressed MCP-1. Macrophage accumulation was highly correlated with MCP-1 expression. In study #4, feeding LDLR KO mice 1.25% cholesterol for 6 months produced atherosclerotic plaques at both sites and they contained a fibrous cap of smooth muscle cells, macrophage-foam cells, connective tissue and cholesterol crystals. In summary, LDLR KO mice fed cholesterol develop fatty streaks that transform into fibrous plaques. Hypercholesterolemia rapidly triggers MCP-1 expression in resident intimal macrophages, which is followed by the accumulation of more macrophages that also express MCP-1, suggesting that this chemokine may both initiate and amplify monocyte recruitment to the artery wall during early atherogenesis.     

Changes in aspects such as the collagenous fiber density and foam cell size of atherosclerotic lesions composed of foam cells,smooth muscle cells and fibrous components in rabbits caused by all-cis-5, 8, 11, 14, 17-icosapentaenoic acid

Atherosclerotic plaques composed of foamed macrophages, smooth muscle cells and fibrous components in the twice-injured carotid artery from 1% cholesterol diet (HCD)-fed rabbits were prepared and the effects of all-cis-5, 8, 11, 14, 17-icosapentaenoic acid (EPA) on the histopathological properties of atherosclerotic lesions were examined. During the test period, there was no significant difference between the control and the EPA-treated groups in serum lipid levels. In the control group, atherosclerotic lesions were composed of foamed macrophages, smooth muscle cells and fibrous components. Some of the lesions had a large core of foamed macrophages covered with a thin cap of smooth muscle cells and fibrous components, and were morphologically similar to human vulnerable plaques. The classification of plaques, composing atherosclerotic lesions based on collagenous fiber density and foam cell size indicated that over 70% of plaques in the control group were poor in collagenous fiber, while about 20% of plaques contained only large foam cells. In contrast to the control group, over 70% of plaques in the EPA-treated group were rich in collagenous fiber and only 3% consisted of large foam cells. These results suggest that EPA changes certain aspects of pre-existing atherosclerotic lesions.     

Chlamydia pneumoniae in atherosclerotic tissue

The majority of almost 30 publications from 1992 to 1999 describe Chlamydia pneumoniae organisms in atherosclerotic lesions of various major arteries. In the first study in the United Kingdom, C. pneumoniae was found in the aorta and femoral and iliac arteries. In a subsequent study, the organism was detected in arteries of subjects as young as 15 years. In a collaborative investigation, 71% of atheromatous arteries taken at autopsy from white South African subjects were C. pneumoniae positive compared with 9% of nonatheromatous arteries. Of interest, the organisms were detected in 67% of vessels that showed only early atherosclerotic lesions (fatty streaks). C. pneumoniae was also found in the ruptured coronary artery plaque of a black South African who died of myocardial infarction, a rare event. The presence of C. pneumoniae organisms within foam and smooth muscle cells of atherosclerotic plaques is beyond doubt, but their role in atherosclerosis remains enigmatic.     

不同程度动脉粥样硬化病变中弹力纤维的形态及含量改变

为探讨不同动脉粥样硬化程度病变中弹力纤维的形态及含量改变，对２１例中青年猝死者腹主动脉的正常内膜，脂斑脂纹和纤维斑块进行电镜观察，发现正常内膜弹力纤维呈条索状，而脂斑脂纹和纤维斑块中的弹力纤维呈斑片状，弹力纤维含量在脂斑脂纺中最多，正常内膜次之，纤维斑块中最少，三组之间相比较差异具显著性（Ｐ〈０．０１），提示随动脉继榇硬化的发展，病变中弹力纤维不仅有形态学改变，其含量也有明显改变。     

Immunoglobulins and complement components in human aortic atherosclerotic intima

Concentration and preferential retention of immunoglobulins and complement components were studied in comparison with other plasma proteins in 42 human aortae with atherosclerosis. Saline and acid extracted IgG, IgA, IgM, C1q, C3c, C4, C9, C3A, C-reactive protein, alpha 1-antitrypsin, alpha 2-macroglobulin, albumin, transferrin and fibrinogen were quantitatively determined using the radial immunodiffusion. The fibrous plaques and their adjacent areas contained higher levels of each protein than intima with only fatty streaks. No significant differences were found between the fibrous plaques and their adjacent areas presenting intimal thickenings. Saline eluted IgG and IgA were significantly higher in the fibrous plaque intima than in intimal samples with fatty streaks and were the only proteins detected in the acid eluates. The complement components were present in all saline eluates, while C-reactive protein was found in 23 samples. Crossed immunoelectrophoretic studies showed the activation of saline C3 and C4. In 8 cases serum levels of the studied proteins were compared with their concentration in saline eluates obtained from intima and media. The immunoglobulins and complement components presented higher intima/serum and lower media/intima retention ratios than the other studied proteins suggesting their preferential retention in the intima. The presence of immune related proteins in the atherosclerotic intima and their preferential retention might be explained not only by an altered permeability but also in relation to their function.     

The neglected coronary atherosclerosis

A study of the natural history of coronary heart disease by means of gross inspection and light microscopy, carried out on 640 subjects aged 1-50 years who had died of violent accidents, revealed a grossly neglected coronary atherosclerosis. It included fibromuscular plaques, intimal necrotic areas and incorporated microthrombi present in the longitudinally opened main coronary arteries but not visible to the naked eye, and some atherosclerotic lesions visible to the naked eye but present in branch vessels unopened or not removed during routine autopsy. There were approximately 500 grossly neglected intimal necrotic areas and approximately 120 grossly neglected incorporated microthrombi; from a total of 809 atherosclerotic plaques 261 (32%) were grossly neglected. The topographic distribution and the number of neglected and non-neglected atherosclerotic plaques, in successive age groups, were analyzed. A small subsample, including 32 patients 52-79 years old, dead of coronary heart disease, was used to demonstrate the importance of the detection of obstructive atherosclerotic lesions in some usually unopened or not removed branch vessels for a realistic anatomo-clinic-cardioangiographic and ECG correlation.