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1.
The focus of this study was identification of the contribution of the plasminogen activator-plasmin system to smooth muscle cell proliferation and migration in human saphenous vein. Segments of human saphenous vein were grown in organ culture for up to 14 days. Smooth muscle cell proliferation and migration were measured by incubating vein segments in bromodeoxyuridine, and smooth muscle cell death was detected by in situ end-labelling. Tissue-type (tPA) and urokinase-type (uPA) plasminogen activator enzymic activities were detectable in cultured saphenous vein segments, and were concentrated in focal zones. Inhibition of plasmin activity with alpha-N-acetyl-L-lysine methyl ester (NALME) or of uPA activity with a neutralising antibody caused significant decreases in smooth muscle cell proliferation in the media and the intima, but no significant changes in smooth muscle cell migration. Intimal thickness was also significantly decreased. Incubation with plasminogen or plasmin caused fibroblast growth factor-2 (FGF2) to be released into the medium. Addition of FGF2 to segments cultured with NALME reversed the inhibition of smooth muscle cell proliferation, and blocking the activity of FGF2 with a neutralising antibody caused a significant decrease in medial smooth muscle cell proliferation. These data suggest that plasmin mobilises FGF2 bound to the extracellular matrix of human saphenous vein, so that it can support smooth muscle cell proliferation and intimal thickening.  相似文献   

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OBJECTIVES: Increases in urokinase plasminogen activator (uPA) have been reported in tissues undergoing remodelling, but its effects on the vessel intima formation are not known. We investigated its effects on carotid artery intima, media and lumen size, as well as smooth muscle cell (SMC) proliferation and migration in vivo. DESIGN AND METHODS: Carotid arteries of rats were distended with an inflated balloon catheter and uPA, or uPA-neutralizing antibodies were applied perivascularly in pluronic gel; control rats received vehicle. Carotid artery structure, cell migration and proliferation were assessed after 4 days by quantitative morphometry and immunohistochemistry. RESULTS: Four days after increasing vessel uPA, the intima/media ratio was double compared to that in control rats (both P < 0.05). The size of the lumen reduced by 75%, compared to the vehicle-treated vessels (P < 0.05). The elevation in uPA also increased SMC numbers in the intima and media, compared to the vehicle-treated vessels (both P < 0.05). Antibody neutralizing endogenous uPA attenuated the growth responses in the distended arteries, reduced neointimal SMC numbers by approximately 50% and prevented much of the reduction in lumen size. CONCLUSIONS: Thus, local increases in uPA in distended, injured arteries augment SMC migratory and proliferative responses, leading to increases in the thickness of the carotid artery intima and media and a reduction in lumen size; effects at least partially attributable to its proteolytic properties.  相似文献   

4.
To evaluate the initial mechanism involving atherosclerotic changes of the saphenous vein graft implanted for coronary artery revascularization in the early stage, immunocytochemical analysis was performed to determine the cell components and kinetics of saphenous vein grafts. Specimens of saphenous vein grafts were obtained from 7 necropsy patients who died at 4 days to 6 months after surgery. Monoclonal antibodies specific for smooth muscle cells (HHF35) and macrophages (HAM56) were used for analysis of the cell components. Migration of macrophages into the intima and the media was observed on the fourth postoperative day. Intimal thickening was characterized by the proliferation of smooth muscle cells, and scattered macrophages were present in the subendothelial layer 1 month after surgery. At 2 months, intimal thickening became prominent and macrophages were recognized circumferentially throughout the layer. At 5 to 6 months, some of the saphenous vein grafts were almost occluded by severe intimal thickening due to proliferation of the smooth muscle cells. Macrophages were also observed both inside and outside of the internal elastic lamina; these are rarely found in the artery. These results suggest that compared with the arterial graft, cytokinesia of the saphenous vein graft contributes to the development of early graft failure because of its rapidity in progression and severity.  相似文献   

5.
OBJECTIVES: Saphenous vein graft failures, resulting from thrombosis and the abnormal proliferation, migration and apoptosis of vascular smooth muscle cells (VSMC) are major limitations of coronary artery bypass surgery. We investigated whether surgical trauma of human saphenous vein induces the early response gene c-fos and causes alterations in rates of proliferation and apoptosis. METHODS: Surgically prepared human vein consisted of distended (at 350 mmHg for 2 min) or non-distended segments of vein maintained in serum free RPMI at 37 degrees C and 5% CO2 for various time intervals. c-fos expression was detected by Northern analysis. Cell proliferation and apoptosis were determined by [3H]thymidine incorporation combined with proliferation cell nuclear antigen (PCNA) immunostaining and TUNEL, respectively. Labelling indices for proliferation and apoptosis were correlated with vessel was thicknesses. RESULTS: Control, freshly isolated vein expressed no c-fos. Surgically prepared vein synthesized c-fos 1 h following harvesting. There was a significant increase in c-fos in distended compared to non-distended vein. c-Fos protein increased in surgically prepared vein 24 h after harvesting. There was a significant increase in vascular cell proliferation in the non-distended compared to the distended vein: mean (S.E.M.) 1279 (218) vs. 863 (155) dpm/microgram DNA, P < 0.05, n = 6. In addition, the apoptotic index was significantly lower in the media of non-distended vs. distended vein 0.82 (0.2) vs. 5.5 (1.5), P < 0.05, n = 5. CONCLUSIONS: These findings demonstrate that surgical preparation of human saphenous vein increases expression of c-fos mRNA and apoptosis and reduces proliferation when compared with non-distended vein. These changes may influence the failure of saphenous vein grafts.  相似文献   

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Atherogenesis refers to the development of atheromatous plaques in the inner lining of the arteries. These atherosclerotic lesions are characterized by accumulation of monocyte-derived macrophage-foam cells loaded with cholesterol, which eventually undergo apoptotic death, leading finally to formation of the necrotic core of the plaque. Atheroma formation also involves the recruitment of smooth muscle cells (SMC) from the media into the intima, where they proliferate and form the neointima in a process called "remodeling". Cells in the advanced atherosclerotic plaques express high levels of the serine protease urokinase-type plasminogen activator (uPA) and its receptor (uPAR). uPA is a multi-functional multi-domain protein that is not only a regulator of fibrinolysis, but it is also associated with several acute and chronic pathologic conditions. uPA mediate the extracellular matrix (ECM) degradation, and plays a pivotal role in cell adhesion, migration and proliferation, during tissue remodeling. On cell surface uPA binds to the high affinity urokinase receptor, providing a strictly localized proteolysis of ECM proteins. The uPA/uPAR complex also activates intracellular signaling, thus regulating cellular function. An imbalance in the uPA/uPAR system leads to dis-orders in tissue structure and function. This review summarizes recent progress in understanding the role and mechanisms of the uPA/uPAR system in atherogenesis.  相似文献   

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This report describes morphologic changes in saphenous veins used as aortocoronary bypass conduits, and discusses the relative contribution of various factors to these changes. The three primary changes are: (1) medial fibrous replacement, (2) adventitial fibrous proliferation, and (3) intimal fibrous proliferation. Medial fibrous replacement is caused by vein wall ischemia with loss of smooth muscle cells; adventitial fibrous proliferation is the result of organization of fibrin deposits and repair of ischemic injury; and intimal fibrous proliferation results from some stimulus, probably fibrin deposition on injured intima, which causes stimulation of smooth muscle cells to become fibroblasts or "myointimal cells". Although all grafts show some changes, the degree and severity of these three changes is variable along the length of the grafts and among separate grafts in the same patient.  相似文献   

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为探讨氟伐他汀对内膜增厚的影响其与细胞增殖,细胞凋亡的关系,将雄性新西兰白兔56只随机平分为用药组和非用药组,用高胆固醇饮食和球囊导管剥脱内皮造成动脉粥样内皮损伤,分别在内皮损伤后1,2,4和8w处死动物并取髂动脉,用常规HE染色,免疫组织化学染色,原位细胞凋亡检测和计算机图像分析方法,观察氟伐他汀对动脉新生内膜厚度和内膜/中膜厚度比,平滑肌细胞凋亡的影响,结果发现,用药组的新生内膜厚度和内膜/中膜厚度比明显薄于非用药组(P<0.01),PCNA阳性细胞率及Actin含量均明显少于非用药组(P<0.05),细胞凋亡率随用药时间延长而逐渐增高,且各时间点均高于非用药组(P<0.05),以上提示,氟伐他汀能有效抑制血管内膜过度增生,可能与其抑制平滑肌细胞增殖并可促进细胞凋亡有关。  相似文献   

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Myo-intimal proteoglycan metabolism is thought to be important in blood vessel homeostasis, blood clotting, atherogenesis, and atherosclerosis. Human platelet-derived transforming growth factor type beta (TGF-beta) specifically stimulated synthesis of at least two types of chondroitin sulfate proteoglycans in nonproliferating human adult arterial smooth muscle cells in culture. Stimulation of smooth muscle cell proteoglycan synthesis by smooth muscle cell growth promoters (epidermal growth factor, platelet-derived growth factor, and heparin-binding growth factors) was less than 20% of that elicited by TGF-beta. TGF-beta neither significantly stimulated proliferation of quiescent smooth muscle cells nor inhibited proliferating cells. The extent of TGF-beta stimulation of smooth muscle cell proteoglycan synthesis was similar in both nonproliferating and growth-stimulated cells. TGF-beta, which is a reversible inhibitor of endothelial cell proliferation, had no comparable effect on endothelial cell proteoglycan synthesis. These results are consistent with the hypothesis that TGF-beta is a cell-type-specific regulator of proteoglycan synthesis in human blood vessels and may contribute to the myo-intimal accumulation of proteoglycan in atherosclerotic lesions.  相似文献   

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Occlusion of saphenous vein coronary artery bypass grafts remains a significant clinical problem. Early occlusion can be minimized by optimizing surgical techniques and by antithrombotic treatments. Unfortunately, no modification of surgical technique or drug therapy has been shown to reduce late vein graft occlusion. This results from excessive proliferation of vascular smooth muscle cells and the superimposition of atheroma on the resulting thickened intima. Understanding the basic mechanisms underlying this response may be helpful in developing strategies to reduce vein graft occlusion.  相似文献   

12.
Arteriosclerosis and the development of restenosis still remain a significant clinical problem. Migration of vascular smooth muscle cells from the media to the intima and cell proliferation are the hallmarks of the underlying pathomechanisms. Cell migration requires chemotaxis, phenotypic changes of cells, cell adhesive and de-adhesive events and the coordinated remodeling of the extracellular matrix. One of the phenotypic changes induced in migrating cells is the increased expression of urokinase plasminogen activator (uPA) and of its specific receptor uPAR. They are polarized to the leading edge of migrating cells. Both uPA and uPAR are key mediators of extracellular proteolysis. They participate in extracellular matrix remodeling, activate cells and enable them to migrate and invade into different tissue layers. UPA/uPAR are multifunctional proteins influencing a great variety of signal transduction pathways ultimately culminating in the regulation of cell migration and proliferation. In addition to time- and space-confined proteolysis this powerful system can mediate chemotaxis, cell adhesion and gene expression, partly by interacting in concert with integrins, G proteins, or with yet unidentified coreceptors or adapter molecules. Interaction with the uPA/uPAR system or components of its specific signal transduction pathways may serve as a guide for the development of effective therapeutic strategies to prevent arteriosclerosis and restenosis after percutaneous arterial angioplastic interventions.  相似文献   

13.
Pathologic changes in aortocoronary saphenous vein grafts   总被引:8,自引:0,他引:8  
Aortocoronary saphenous vein grafts from 40 patients (total 62 grafts) were studied at autopsy. The earliest change seen was the insudation of blood constituents into the vein intima. Occluding thrombi were seen in six grafts from short-term survivors, and one organized thrombus was seen in a graft from a long-term survivor (28 months). Various degrees of intimai thickening were seen in grafts from all patients surviving for more than a month; this had progressed to diffuse occlusion in three cases. Gross and microscopic findings correlated well with postmortem angiographic findings in the long-term survivors. Electron microscopic examination showed smooth muscle cells, collagen fibers and ground substance in the thickened intima. Fibroblasts were not a feature of this thickening. Increased permeability of the graft endothelium, due to injury or hemodynamic factors, may result in exposure of medial smooth muscle cells to certain plasma factors and thus promote smooth muscle cell hyperplasia as has been produced in certain experimental models.  相似文献   

14.
BACKGROUND: The remarkable patency of internal mammary artery (MA) grafts compared to saphenous vein (SV) grafts has been related to different biological properties of the two blood vessels. We examined whether proliferation and apoptosis of vascular smooth muscle cells (VSMC) from human coronary artery bypass vessels differ according to patency rates. METHODS AND RESULTS: Proliferation rates to serum or platelet-derived growth factor (PDGF)-BB were lower in VSMC from MA than SV. Surface expression of PDGF beta-receptor was slightly lower, while that of alpha-receptor was slightly higher in MA than SV. Cell cycle distribution, expression of cyclin E, cdk2, p21, p27, p57, and cdk2 kinase activity were identical in PDGF-BB-stimulated cells from MA and SV. However, apoptosis rates were higher in MA than SV determined by lactate dehydrogenase release, DNA fragmentation, and Hoechst 33258 staining. Moreover, caspase inhibitors (Z-VAD-fmk, Boc-D-fmk) abrogated the different proliferation rates of VSMC from MA versus SV. Western blotting and GSK3-beta kinase assay revealed lower Akt activity in VSMC from MA versus SV, while total Akt expression was identical. Adenoviral transduction of a constitutively active Akt mutant abrogated the different proliferation rates of VSMC from MA versus SV. CONCLUSIONS: Higher apoptosis rates due to lower Akt activity rather than different cell cycle regulation account for the lower proliferation of VSMC from MA as compared to SV. VSMC apoptosis may protect MA from bypass graft disease.  相似文献   

15.
Dendritic cells in venous pathologies.   总被引:1,自引:0,他引:1  
Dendritic cells are potent antigen-presenting cells responsible for the activation of T-lymphocytes in various immune responses. Their role in the initiation of immune reactions in allergies, autoimmune diseases, tumors, transplantation, and, more recently, in atherosclerosis has been well established, but their involvement in venous pathologies has not been previously investigated. The aim of this study was to determine whether dendritic cells are present in veins affected by varicosity and thrombophlebitis. Three groups of veins obtained at operation were studied: (1) varicose veins of the great saphenous vein from patients who were undergoing vein stripping for primary varicosity; (2) segments of the great saphenous vein from patients with varicosity complicated by thrombophlebitis; and (3) great saphenous veins without varicosity or thrombophlebitis from patients who were undergoing femoropopliteal bypass grafting. The specimens were fixed in 10% neutral buffered formalin and embedded in paraffin, and the sections were stained with antibodies to S-100 (to identify dendritic cells), CD3 (T-lymphocytes), CD68 (macrophages), von Willebrand factor (endothelial cells), alpha-smooth muscle actin (smooth muscle cells), and CD15 (mast cells) by use of avidin-biotin complex (ABC) immunoperoxidase technique. Immunohistochemical examination showed that no S-100-positive dendritic cells were present in normal saphenous veins. In contrast, S-100-positive cells with dendritic cell morphology were detected in the intima and media of veins with varicosity and thrombophlebitis, where they represented a minor cell population. S-100-positive dendritic cells were located between smooth muscle cells as well as around areas of neovascularization where they colocalized with T-lymphocytes. The present work suggests that dendritic cells might be involved in pathological processes in veins affected by varicosity and thrombophlebitis. The authors speculate that dendritic cells may be involved in the inflammatory mechanisms in these veins through their interaction with T-lymphocytes.  相似文献   

16.
目的研究纤维蛋白胶血管外周支持对静脉移植物平滑肌细胞增殖、凋亡的影响。方法建立大鼠颈总动脉自体颈静脉移植模型,按照有无纤维蛋白胶血管外周支持,分为外周支持组、无外周支持组,每组24只。术后1周、2周、4周分别切除移植静脉,用免疫组织化学方法检测静脉移植物平滑肌细胞增殖细胞核抗原(PCNA)表达,用原位DNA断裂位点3’-羟基末端标记(TUNEL)法检测静脉移植物平滑肌细胞凋亡的变化,以及检测内膜厚度。结果静脉移植术后1-4周,无外周支持组静脉移植物血管平滑肌细胞的凋亡和增殖均明显升高,内膜明显增厚;纤维蛋白胶血管外周支持组静脉移植物血管平滑肌细胞的凋亡和增殖同处于低水平,内膜增厚不明显。两组静脉移植物血管平滑肌细胞的凋亡和增殖具有显著相关性。结论纤维蛋白胶外周支持可以抑制血管平滑肌的增殖和凋亡,使两者同时处于低水平,一方面减少细胞凋不足所造成的对血管重塑造成的影响,另一方面使凋亡程度与巨噬细胞及正常血管平滑肌吞噬作用达到平衡,抑制了静脉移植物的内膜增生。  相似文献   

17.
Angiotensin II (Ang II) has been implicated in the regulation of smooth muscle cell proliferation after vascular injury, but the molecular mechanisms of this effect remain obscure. The aims of the present study were 1) to determine if Ang II was mitogenic (in a defined serum-free medium) for aortic smooth muscle cells derived from spontaneously hypertensive rats, either alone or in combination with epidermal growth factor, basic fibroblast growth factor, or platelet-derived growth factor-BB; and 2) to determine if the Ang II effects were mediated by autocrine production of transforming growth factor-beta (TGF-beta). Results demonstrated that Ang II increased the proliferative response of smooth muscle cells to epidermal growth factor or platelet-derived growth factor-BB. Ang II alone and in combination with basic fibroblast growth factor induced a small delayed increase (48-72 hours after treatment) in DNA synthesis and [3H]thymidine labeling indexes without an increase in cell number. Ang II effects were at least partially mediated by autocrine production of active TGF-beta in that 1) treatment with Ang II increased TGF-beta activity in conditioned media and 2) TGF-beta neutralizing antibody inhibited Ang II-induced increases in DNA synthesis. However, treatment with exogenous TGF-beta at concentrations induced by Ang II failed to elicit a mitogenic response, thus implicating other autocrine factors in mediation of Ang II effects. Results suggest a potential mechanism whereby Ang II might regulate smooth muscle cell mitogenesis after vascular injury.  相似文献   

18.
Although the level of plasminogen activator (PA) expression has been correlated with cellular proliferation and migration in vitro, this relation has not been established in tissue undergoing repair. In a rat model of arterial injury, we have measured the expression of PAs by vascular smooth muscle cells (SMCs) during entry into the growth cycle (0-24 hours) and subsequent migration from the media to the intima (starting at approximately 4 days). In normal rat carotid, low levels of urokinase-type PA (uPA) and tissue-type PA (tPA) are present; after removal of the endothelium, only uPA is detected in the media. uPA activity in extracts of carotid arteries increases and reaches a maximum between 16 and 24 hours after injury; uPA mRNA increases steadily and is maximal at 7 days. tPA activity appears at 3 days and is maximal at 7 days; tPA mRNA is present in normal vessels and reaches a maximum by 7 days. Most of the tPA in the media is associated with SMC and not with regenerating endothelium. Furthermore, tPA is present in the media before the SMCs migrate into the intima. These results demonstrate that PA expression by vascular SMCs is differentially regulated, with uPA present during mitogenesis and tPA during migration.  相似文献   

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OBJECTIVE: Vascular endothelial growth factor (VEGF) induces the release of nitric oxide (NO) from endothelial cells. There is also limited data suggesting that NO may enhance VEGF generation. METHODS: To further investigate this interaction, we examined the effect of exogenous and endogenous NO on the synthesis of VEGF by rat and human vascular smooth muscle cells (VSMC) by exposing cells to exogenous NO donors, or to genetic augmentation of eNOS or iNOS. RESULTS: NO-donors potentiated by 2-fold the generation of VEGF protein by rat or human VSMC. Similarly, rat or human VSMC transiently transfected with plasmid DNA encoding eNOS or iNOS, synthesized up to 3-fold more VEGF than those transfected with control plasmid DNA, an effect which was reversed after treatment with the NOS antagonist L-NAME. Rat VSMC stably transfected with pKeNOS plasmid, constitutively produced NO and released high concentrations of VEGF. In these cells, L-NAME significantly reduced NO synthesis and decreased VEGF generation. The VEGF protein produced by NOS-transfected VSMC was biologically active, as conditioned media harvested from these cells increased endothelial cell proliferation. CONCLUSION: These studies reveal that NO derived from NO-donors or generated by NOS within the cells, upregulates the synthesis of VEGF in vascular smooth muscle cells. Administration of NO donors, or augmentation of endogenous NO synthesis, may be an alternative approach in therapeutic angiogenesis.  相似文献   

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