颈动脉分叉处血管粥样硬化斑块的体内应力分析

目的探究颈动脉分叉处血管斑块的体内应力分布,为颈动脉分叉处血管斑块破裂行为的研究和诊断治疗方案的设计提供力学机理参考。方法基于人体颈动脉分叉血管的平均几何参数,建立三维颈动脉分叉血管及其斑块的几何模型,通过"热-结构"耦合重建颈动脉分叉血管及其斑块的残余应力,并计算血压和血流分别作用下颈动脉分叉处血管斑块的体内应力。结果斑块的肩部同时存在着最大主应力和弹性剪切应力的应力集中。斑块肩部的弹性剪切应力随着狭窄率增大或血压升高均增加。斑块上游区域的流体壁面切应力明显高于斑块下游区域,斑块下游区域的振荡剪切指数则显著大于上游区域。且斑块的弹性剪切应力和流体壁面切应力大小随着狭窄率的变化呈现出不同的变化规律。结论斑块从内部中心位置到壁面肩部承受着非均匀的应力分布,血管严重狭窄时"内压外拉"的受力状态更容易导致斑块破裂。随着血压的变化,斑块结构应力的周期性变化可能使斑块产生结构疲劳,增加破裂风险。斑块上下游区域流体动力学参数的差异可能是斑块上下游组分、易损程度等性质不同的原因之一。     

Biomechanics of Atherosclerotic Coronary Plaque: Site,Stability and In Vivo Elasticity Modeling

Coronary atheroma develop in local sites that are widely variable among patients and are considerably variable in their vulnerability for rupture. This article summarizes studies conducted by our collaborative laboratories on predictive biomechanical modeling of coronary plaques. It aims to give insights into the role of biomechanics in the development and localization of atherosclerosis, the morphologic features that determine vulnerable plaque stability, and emerging in vivo imaging techniques that may detect and characterize vulnerable plaque. Composite biomechanical and hemodynamic factors that influence the actual site of development of plaques have been studied. Plaque vulnerability, in vivo, is more challenging to assess. Important steps have been made in defining the biomechanical factors that are predictive of plaque rupture and the likelihood of this occurring if characteristic features are known. A critical key in defining plaque vulnerability is the accurate quantification of both the morphology and the mechanical properties of the diseased arteries. Recently, an early IVUS based palpography technique developed to assess local strain, elasticity and mechanical instabilities has been successfully revisited and improved to account for complex plaque geometries. This is based on an initial best estimation of the plaque components’ contours, allowing subsequent iteration for elastic modulus assessment as a basis for plaque stability determination. The improved method has also been preliminarily evaluated in patients with successful histologic correlation. Further clinical evaluation and refinement are on the horizon.     

Accumulation of Cholesteryl Ester in Atherosclerotic Lesions

This article reviews aspects of the molecular pathology of cholesteryl ester accumulation in atherosclerotic lesions. 1. Transcytosis of lipoproteins through a cultured endothelial monolayer. 2. Effects of platelets and PGI, on intercellular transport of endothelial cells. 3. Transformation of macrophages to foam cells. 4. Cholesteryl ester deposition in the extracellular space of atherosclerotic lesions. The development and use of novel monoclonal antlbodies recognizing atherosclerotic lesions and peroxidized lipoproteins prepared from then are also discussed. Acta Pathol Jpn 42: 625–631, 1992.     

Differential Effects of Pioglitazone on Advanced Atherosclerotic Lesions

This Correspondence relates to Atherosclerosis in LDLR-knockout Mice in Inhibited, but not Reversed, by the PPARy Ligand Pioglitazone (Am J Pathol 2009 174:2007–2014).     

Differential Interference Contrast Microscopy of Human Atherosclerotic Lesions

Differential interference contrast microscopy was employed to study sections of human cerebral arteries and aorta. When this procedure was used to observe 0.5-μ-thick sections of plastic-embedded arteries, images were obtained with greater definition of detail than corresponding micrographs of the area using conventional bright-field microscopy. Since structures with different refractive indices are shown in geometric relief from one another, an apparent three-dimensional image is seen, which, together with the theoretically higher resolution and contrast achieved by this technic, gives an image with definition between conventional light and low magnification electron microscopy. The morphology of fatty streak lesions with aggregates of round and elongated lipid-filled cells was demonstrated, and clear images of different forms and sizes of intracellular lipid droplets were illustrated at magnifications around 1000. In atheromatous plaques, intra- and extracellular lipid droplets were observed, some with partially extracted cores or surfaces, as were amorphous lipid droplets coalescing with crystals whose centers had been extracted. We conclude that this optical accessory to a research photomicroscope is a valuable supplemental tool in studies on the morphology of atherosclerotic lesions.     

Viral and Bacterial DNA in Carotid Atherosclerotic Lesions

Atherosclerosis is a major health problem in industrialised countries. Several studies have suggested an association exists between certain microorganisms and the development of atherosclerosis. The aim of the study presented here was to assess the presence of viral or bacterial DNA in carotid atherosclerotic lesions. Nucleic acids were extracted from 18 carotid atherosclerotic lesions that had been collected surgically. Polymerase chain reaction was used to screen for specific genomic DNA from Chlamydia pneumoniae, cytomegalovirus and herpes simplex virus types 1 and 2. An original approach, based on the amplification by PCR of conserved bacterial 16S rDNA nucleotide sequences was also used to detect any bacterial species. The amplification product was identified by sequencing. Chlamydia pneumoniae, cytomegalovirus and herpes simplex 2 DNA were not detected in any of the samples. Herpes simplex 1 DNA was detected in 3 of the 18 samples. Genes encoding bacterial 16S rRNA were amplified and sequenced in eight atherosclerotic lesions. DNA sequences were identified by comparison with sequences registered in the GenBank database. These eight carotid atherosclerotic lesions were shown to contain several bacterial species belonging to human flora or the environment. The exact role of these microorganisms in the genesis or development of the atherosclerotic lesions remains unclear, but they may increase the inflammatory process or be an epiphenomenon. Electronic Publication     

Augmented Expression of Cyclooxygenase-2 in Human Atherosclerotic Lesions

Cyclooxygenase-1 (Cox-1) and Cox-2 convert arachidonic acid to prostaglandin H(2), the precursor of other prostaglandins and thromboxanes, eicosanoids important in vascular pathophysiology. However, knowledge of the expression of cyclooxygenases within atherosclerotic lesions is scant. This study tested the hypothesis that human atheroma and nonatherosclerotic arteries express the two Cox isoforms differentially. Cox-1 mRNA and protein localized on endothelial and medial smooth muscle cells of normal arteries (n = 5), whereas Cox-2 expression was not detectable. In contrast, atheromatous (n = 7) lesions contained both Cox-1 and Cox-2, colocalizing mainly with macrophages of the shoulder region and lipid core periphery, whereas smooth muscle cells showed lower levels, as demonstrated by immunohistochemical and in situ hybridization analysis. Furthermore, microvascular endothelium in plaques showed notable staining for both isoforms. In accord with immunohistochemical studies, Western blot analysis of protein extracts from normal arteries revealed constitutive Cox-1, but not Cox-2, expression. Extracts of atheromatous lesions, however, contained both Cox-1 and Cox-2 protein, detected as two immunoreactive proteins of approximately 70 and 50 kd. Macrophages expressed the short form of Cox-1/-2 constitutively after several days of in vitro culture, rather than the 70-kd protein. These results shed new light on the inflammatory pathways that operate in human atheroma. In particular, the expression of Cox-2 in atheromatous, but not in unaffected, arteries has therapeutic implications, given the advent of selective Cox-2 inhibitors.     

Calcification Locates to Transglutaminases in Advanced Human Atherosclerotic Lesions

Transglutaminases play an important role in vascular smooth muscle cell-induced calcification in vitro. In this study, we determined whether these enzymes are also involved in human atherosclerotic calcification using nine carotid artery specimens obtained at endarterectomy. Sections of the carotid artery specimens were registered to micro-computed tomography images and stained for tissue-type transglutaminase, plasma transglutaminase factor XIIIA (FXIIIA), the N^ε(γ-glutamyl)lysine cross-link, and the macrophage marker CD68. Ex vivo micro-computed tomography revealed extensive calcification, which significantly correlated with the cross-link. FXIIIA was found to be the dominant transglutaminase, rather than tissue-type transglutaminase, although staining of both transglutaminases correlated with the cross-link. Staining for FXIIIA colocalized with CD68 at both the cellular and tissue level. In conclusion, areas of calcification locate to the presence and activity of transglutaminases in human atherosclerotic arteries. FXIIIA seems to be the dominant transglutaminase and may be derived from local macrophages. These results are consistent with the hypothesis that transglutaminases participate in the calcification process of human atherosclerotic arteries.Vascular calcification is considered a tightly regulated process of matrix deposition by osteoblast-like cells.¹ These cells may be derived from stem cells or differentiate from smooth muscle cells or pericytes. Recent work from Johnson et al² suggests a role for transglutaminases in the process of arterial calcification. On the basis of in vitro experiments on cultured healthy arterial segments and smooth muscle cells, these authors proposed a novel mechanism of arterial calcification, for which tissue-type transglutaminase (TG2) is central in the chondro-osseous differentiation and calcification of smooth muscle cells. Transglutaminases form a class of enzymes with pleiotropic function³ that consists of nine known members. Among these, TG2 is expressed in endothelial cells, smooth muscle cells, and monocytes/macrophages. The plasma transglutaminase, factor XIIIA (FXIIIA) is expressed in monocytes/macrophages.⁴ TG2 has been implicated in an animal model for atherosclerotic lesion formation,⁵ whereas both TG2 and FXIIIA are involved in vascular remodeling.^6,7 TG2 and FXIIIA are also involved in normal bone formation, where they act in concert to promote chondrocyte maturation.⁸ Although these data suggest an important role of transglutaminases in the development of atherosclerotic calcification, evidence of their role in human atherosclerotic lesion development is lacking. Therefore, we investigated the presence of transglutaminases, ie, TG2 and FXIIIA, the transglutaminase-induced cross-link and macrophages in human atherosclerotic carotid arteries. These markers were correlated to calcified areas that were detected ex vivo with micro-computed tomography (μCT) imaging.     

Stimulation of Innate Immunity by In Vivo Cyclic di-GMP Synthesis Using Adenovirus

The bacterial second messenger cyclic di-GMP (c-di-GMP) stimulates inflammation by initiating innate immune cell recruitment and triggering the release of proinflammatory cytokines and chemokines. These properties make c-di-GMP a promising candidate for use as a vaccine adjuvant, and numerous studies have demonstrated that administration of purified c-di-GMP with different antigens increases protection against infection in animal models. Here, we have developed a novel approach to produce c-di-GMP inside host cells as an adjuvant to exploit a host-pathogen interaction and initiate an innate immune response. We have demonstrated that c-di-GMP can be synthesized in vivo by transducing a diguanylate cyclase (DGC) gene into mammalian cells using an adenovirus serotype 5 (Ad5) vector. Expression of DGC led to the production of c-di-GMP in vitro and in vivo, and this was able to alter proinflammatory gene expression in murine tissues and increase the secretion of numerous cytokines and chemokines when administered to animals. Furthermore, coexpression of DGC modestly increased T-cell responses to a Clostridium difficile antigen expressed from an adenovirus vaccine, although no significant differences in antibody titers were observed. This adenovirus c-di-GMP delivery system offers a novel method to administer c-di-GMP as an adjuvant to stimulate innate immunity during vaccination.     

In Vivo Measurement of Real-Time Aortic Segmental Volume Using the Conductance Catheter

The goal of this investigation was to determine if the conductance catheter technique for chamber volume measurement could be applied in vivo to determine real-time phasic aortic segmental volume. A four-electrode conductance catheter was used to measure time-varying resistance of the descending thoracic aorta in open-chest, anesthetized dogs. Resistance was converted to segmental volume and the slope correction factor () and parallel conductance volume (V _P ) were determined. The results showed excellent linear correlation between conductance and sonomicrometric segmental volume. The correction factors and V _P were found to be empirically related to average vessel diameter. The relatively high values for the slope correction factor (=4.59±0.17 SEM) were found to be primarily related to low-resistivity shunt paths probably originating in the periadventitial aortic wall and to a lesser extent to changes in flow-induced increases in blood resistivity, hematocrit, catheter position, and other adjacent tissue resistivity. The results demonstrate that correction factors empirically derived from measurements of mean aortic diameter could be used to determine absolute real-time phasic segmental volume, cross-sectional area, or diameter. The conductance technique may possess the same potential for determining aortic mechanical properties which has already been demonstrated for determining ventricular mechanical properties.     

Evaluation of Chemokine- and Phlogistin-mediated Leukocyte Chemotaxis Using an In Vivo Sponge Model

We have directly compared the in vivo activity of a number of chemokines and phlogistins using a modified murine in vivo sponge model in which gelatin sponges are soaked with chemoattractant and implanted in the peritoneal cavity. Sponges soaked with murine JE/MCP-1 (monocyte chemoattractant protein-1) or zymosan promoted the chemotaxis of specific leukocyte populations in a time-dependent manner, as judged by multiparameter flow cytometry, with granulocytes predominating in zymosan-soaked sponges and granulocytes and macrophages present in JE/MCP-1-soaked sponges. Smaller numbers of B, T and dendritic cells were identified as well. Eotaxin selectively chemoattracted eosinophils in this model, while MIG induced significant T cell migration relative to other chemokines. Cell migration was inhibited by administration of methotrexate, piroxicam or dexamethasone, and JE/MCP-1-mediated trafficking was impaired by treatment with anti-JE antibody or with IL-10, suggesting a role for pro-inflammatory factors in amplifying the JE/MCP-1-induced response. This amplification phase involves the production of the chemokine KC, since anti-KC antibody significantly attenuated JE/MCP-1-induced chemotaxis. These results indicate that intraperitoneally implanted chemoattractant-soaked gelatin sponges are capable of inducing a pronounced inflammatory response characterized by the selective migration of leukocyte populations, and suggest that this model may be useful for delineating the activity of novel inhibitors of leukocyte chemotaxis.     

Characterization of Two Unique Cholesterol-Rich Lipid Particles Isolated from Human Atherosclerotic Lesions

The authors' laboratory, using histochemical methods, previously identified two types of cholesterol-containing lipid particles in the extracellular spaces of human atherosclerotic lesions, one particle enriched in esterified cholesterol and the other particle enriched in unesterified cholesterol. The authors isolated and characterized these lipid particles. The esterified cholesterol-rich lipid particle was a small lipid droplet and differed from intracellular lipid droplets found in foam cells with respect to size and chemical composition. It had an esterified cholesterol core surrounded by a phospholipid-unesterified cholesterol monolayer. Some aqueous spaces were seen within the particle core. Unesterified cholesterol-rich lipid particles were multilamellated, solid structures and vesicles comprised of single or multiple lamellas. The esterified cholesterol-rich particle had a density less than 1.01 g/ml, whereas the unesterified cholesterol-rich particle had a density between 1.03 and 1.05 g/ml. Both particles were similar in size (90% of both particles ranged in size between 40 to 200 nm in diameter) and had an unesterified cholesterol-to-phospholipid molar ratio of 2.5:1. The predominant phospholipid in both particles was sphingomyelin. The fatty acyl compositions of cholesteryl ester and phospholipid also were similar in both particles. Palmitate, oleate, and linoleate were the major fatty acids in the cholesteryl ester fraction, whereas palmitate, stearate, oleate, and linoleate were predominant in the phospholipid fraction. The origins and the role of these two unusual lipid particles in vessel wall cholesterol metabolism remain to be determined.     

IL-8在兔动脉粥样硬化模型中斑块处的蛋白和基因表达

白细胞介素- 8(Interleukin- 8,IL- 8)是趋化因子CXC亚家族的一员,对中性粒细胞有趋化作用,可以诱导平滑肌细胞的增殖和迁移,是一个促血管生成因子,在动脉粥样硬化慢性炎症过程中起着重要作用。本文通过建立兔高脂血症动脉粥样硬化斑块模型,动态监测了在动脉粥样硬化发展过程中IL- 8的蛋白和基因表达,以了解IL- 8在动脉粥样硬化中的作用。采用免疫组化的方法定位IL- 8在高脂血症兔动脉粥样硬化斑块模型主动脉升弓部血管壁的蛋白表达,8、12周模型组内膜显著增厚并有明显阳性染色,半定量分析AS模型组阳性染色的面积分别是对照组的4 .4 8、8.76倍,平均积分光密度(IOD)值分别是对照组的4 .16、4 .36倍。采用双抗夹心EL ISA法测定兔血管组织匀浆液中的IL- 8蛋白表达量,8、12周AS模型组IL- 8蛋白含量与总蛋白比值和对照组比较均有显著性差异,分别是对照组的1.84、2 .0 6倍。用原位杂交的方法定位IL- 8m RNA的表达,8周模型组血管内膜有强的阳性染色,IL- 8m RNA的表达增加。本研究通过建立动脉粥样硬化模型,动态监测了整个动脉粥样硬化过程中IL-8的蛋白和基因表达。IL- 8的蛋白和基因上调主要是在高脂血症兔动脉粥样硬化模型的脂纹期     

Insight in Human Skin Microcirculation Using In Vivo Reflectance-Mode Confocal Laser Scanning Microscopy

Reflectance-mode confocal laser scanning microscopy allows in vivo imaging of the human skin. We hypothesized that this high-resolution technique enables observation of dynamic changes of the cutaneous microcirculation. Twenty-two volunteers were randomly divided in two groups. Group 1 was exposed to local heating and group 2 to local cold stress. Confocal microscopy was performed prior t ₀ (control), directly t ₁ and 5 min t ₂ after local temperature changes to evaluate quantitative blood cell flow, capillary loop diameter, and density of dermal capillaries. In group 1, blood flow increased at t ₁ (75.82 ± 2.86/min) and further at t ₂ (84.09 ± 3.39/min) compared to the control (61.09 ± 3.21/min). The control capillary size was 9.59 ± 0.25 μm, increased to 11.16 ± 0.21 μm (t ₁) and 11.57 ± 0.24 μm (t ₂). The dermal capillary density increased in t ₁ (7.26 ± 0.76/mm²) and t ₂ (8.16 ± 0.52/mm²), compared to the control (7.04 ± 0.62/mm²). In group 2, blood flow decreased at t ₁ (41.73 ± 2.61/min) and increased at t ₂ (83.27 ± 3.29/min) compared to the control (60.73 ± 2.90/min). The control capillary size was 9.55 ± 0.25 μm, decreased at t ₁ (7.78 ± 0.26 μm) and increased at t ₂ (11.38 ± 0.26 μm). Capillary density decreased at t ₁ (5.01 ± 0.49/mm²) and increased at t ₂ (7.28 ± 0.53/mm²) compared to the control (7.01 ± 0.52/mm²). Confocal microscopy is a sensitive and noninvasive imaging tool for characterizing and quantifying dynamic changes of cutaneous microcirculation on a histomorphological level.     

Subset of Vascular Dendritic Cells Transforming into Foam Cells in Human Atherosclerotic Lesions

It has been previously demonstrated that S-100 positive vascular dendritic cells are involved in human atherosclerosis and they usually show a low level of accumulation of lipids in their cytoplasm, even though they located among foam cells and cellular debris in atherosclerotic lesions. During ongoing immunohistochemical investigations, however, we have found that a few S-100 positive cells exhibited a foam cell appearance. Therefore, we undertook an electronmicroscopic examination to see if any foam cells exhibit the distinctive features of vascular dendritic cells such as the presence of dense granules and a tubulovesicular system uniquely found in well differentiated dendritic cells. Foam cells exhibiting the typical characteristics of vascular dendritic cells were indeed found. Their cytoplasm contained a large number of lipid vacuoles and cisterns of the tubulovesicular system as well as dense granules which, in contrast to lysosomes present in macrophages, did not transform into phagolysosomes. The formation of a central lamina inside cisterns of the tubulovesicular system was also detected. These pentalaminal structures, comprised of two parallel limiting membranes and a central lamina, are similar to the Birbeck granules present in human epidermal Langerhans cells. From our present observations we speculate that the defense mechanisms against extensive lipid accumulation may be broken in some vascular dendritic cells, causing them to transform into foam cells.