内皮祖细胞内皮修复的影响因素

内皮祖细胞（EPC）来源于骨髓,能够定向分化为成熟有功能的血管内皮细胞,是血管内皮细胞的前体细胞,又称血管母细胞。内皮祖细胞在组织缺血和血管损伤时动员入血,促进微血管的生成和血管内皮的修复,不仅参与胚胎血管生成,也参与出生后的血管发生过程,具有保护血管内皮、减少心血管疾病的发生率和死亡率的作用。许多试验证实冠状动脉粥样硬化性心脏病（冠心病）和心力衰竭患者EPC数量减少,外周循环内皮细胞功能受损。研究发现,EPC的生物学特性受到诸多冠心病危险因素的影响,致使其功能异常。     

Circulating endothelial cells: a novel marker of endothelial damage

Circulating endothelial cells (CECs) were first described over 30 years ago in smears of peripheral blood. Since then, more sophisticated techniques for CEC isolation have become available. In particular, immunomagnetic isolation and fluorescence-activated cell sorting (FACS) have been employed with success. We provide a short historical perspective and a comprehensive review on the subject. We review isolation and enumeration of CECs with an emphasis on CD146-driven immunomagnetic isolation and FACS. We describe, in great detail, advantages and pitfalls of both approaches and compare their specificity. Moreover, we provide a comprehensive list of clinical studies in this field and describe the possible clinical use of CECs. We also describe the phenotype of these cells and list typical surface markers. In addition, we review the phenotype of CECs and discuss mechanisms of detachment. We speculate about potential interactions between CECs and other cell subsets. We also describe other serum markers of endothelial damage and compare CECs with these markers. Finally, we highlight differences between circulating endothelial cells and endothelial progenitor cells. In summary, CECs must now be regarded as a sensitive and specific marker of endothelial damage. We emphasize that use of CECs in a clinical setting is on the horizon and pathogenetic clues may also be obtained.     

Origins of circulating endothelial cells and endothelial outgrowth from blood

Normal adults have a small number of circulating endothelial cells (CEC) in peripheral blood, and endothelial outgrowth has been observed from cultures of blood. In this study we seek insight into the origins of CEC and endothelial outgrowth from cultures of blood. Fluorescence in situ hybridization analysis of blood samples from bone marrow transplant recipients who had received gender-mismatched transplants 5-20 months earlier showed that most CEC in fresh blood had recipient genotype. Endothelial outgrowth from the same blood samples after 9 days in culture (5-fold expansion) was still predominantly of the recipient genotype. In contrast, endothelial outgrowth after approximately 1 month (102-fold expansion) was mostly of donor genotype. Thus, recipient-genotype endothelial cells expanded only approximately 20-fold over this period, whereas donor-genotype endothelial cells expanded approximately 1000-fold. These data suggest that most CEC in fresh blood originate from vessel walls and have limited growth capability. Conversely, the data indicate that outgrowth of endothelial cells from cultures of blood is mostly derived from transplantable marrow-derived cells. Because these cells have more delayed outgrowth but a greater proliferative rate, our data suggest that they are derived from circulating angioblasts.     

Parathyroid hormone stimulates the endothelial expression of vascular endothelial growth factor

Background We showed previously that parathyroid hormone (PTH) may stimulate the endothelial expression of pro‐atherosclerotic and pro‐inflammatory markers. Considering the impact of PTH on vasculature, we decided to evaluate its effect on mRNA and intra‐cellular protein expressions of endothelial vascular endothelial growth factor (VEGF) taking into account that VEGF may play a role in the pathogenesis of endothelial dysfunctions. Materials and methods Human umbilical vein cords endothelial cells (HUVEC) were stimulated for 24 h with 10^?12–10^?10 mol L^?1 PTH. The VEGF‐165 mRNA expression (critical in stimulating endothelial cell proliferation) was evaluated by RT/PCR and the intra‐cellular VEGF protein expression by flow cytometry. The pathways by which PTH may have an effect on VEGF expression were also evaluated. Results PTH (10^?10 mol L^?1) significantly increased VEGF‐165 mRNA expression (P < 0·05). The addition of 50 nmol L^?1 protein kinase C (PKC) and 10 µmol L^?1 protein kinase A (PKA) inhibitors significantly reduced the VEGF‐165 mRNA expression (P = 0·01). We also examined whether nitric oxide (NO) may be involved in the PTH‐induced stimulation of VEGF‐165 expression. Pre‐treatment of the cells with 200 µmol L‐nitro arginine methyl ester (L‐NAME, NO synthase inhibitor) was found to inhibit VEGF‐165 mRNA expression (P = 0·006). VEGF protein could not be detected in the medium of HUVEC but it was present in the cell cytoplasm. PTH had no significant effect on cytoplasmatic VEGF protein expression. Conclusion The stimulatory effect of PTH on endothelial VEGF‐165 mRNA expression is partly through PKC and PKA pathways and is also NO dependent.     

Detection of circulating endothelial cells and endothelial progenitor cells by flow cytometry

The finding of angiogenic and vasculogenic cells in the peripheral circulation may have profound effects on the course of a variety of diseases ranging from cancer to cardiovascular disease. These cells are ascribed to be endothelial in nature and are generally referred to as circulating endothelial cells if mature or as endothelial progenitor cells if immature. Different approaches have been used to detect these cells, including in vitro culture, magnetic bead isolation, and flow cytometry. We review flow cytometric methods for the detection and enumeration of these cells and provide technical suggestions to promote the accurate enumeration of circulating endothelial cells and endothelial progenitor cells.     

缺氧时内皮细胞中血管内皮生长因子受体的表达

目的 探讨脐带静脉内皮细胞在缺氧条件培养下血管内皮生长因子特异受体的表达，为进一步研究血管内皮生长因子及其受体在新血管生成中的作用提供理论依据。方法 体外培养脐带静脉内皮细胞，不同缺氧时间处理及血管活性因子刺激，提取组织总RNA，应用Northern杂交和逆转录聚合酶连扩增反应（RT－PCR）等方法，观察基因表达的变化。结果 内皮细胞无缺氧和缺氧3h均未见flt-1表达，缺氧6h可见flt-1摸板核糖核酸（mRNA)的表达。内皮细胞缺氧6h，内皮素（ET）、一氧化氮（NO）、LNNA对flt-1表达有影响。ET促进flt-1 mRNA的表达，NO抑制其表达，而LNNA部分恢复其表达。在无缺氧和缺氧3，6h KDR基因均有表达。内皮细胞缺氧6h，ET、NO、LNNA对KDR无影响。LNNA阻断了内源性NO后，明显促进KDR mNRA的表达，其他无作用。结论 在缺氧条件下血管内皮细胞生长因子的受体flt-1表达明显增加并受血管活性因子调节，KDR有表达且部分受血管活性因子调节。     

真核表达载体血管内皮生长因子转染血管内皮细胞及对新生血管形成的影响

背景:血管内皮生长因子(vascular endothelial growth factor,VEGF)能与存在内皮细胞表面的特异性受体结合,刺激体内新生血管形成,但在体内半衰期极短,在移植局部难以维持足够的浓度,限制了其临床应用.目的:观察VEGF与增强绿色荧光蛋白(enhanced green fluorescent,EGFP)共表达载体转染对大鼠血管内皮细胞形成新生血管的影响.设计、时间及地点:随机分组设计、对照动物实验,于2004-09/2005-01在中国医科大学附属第一医院器官移植实验室完成.材料:30只雄性Wistar大鼠按随机数字表法分为3组,每组10只.质粒pIRES2-EGFP/VEGF165由第四军医大学提供.方法:采用层析法大量提取pIRES2-EGFPNEGF165质粒,采用阳性脂质体法进行转染,计数1×106血管内皮细胞植入雄性Wiser大鼠肾被膜下.实验组:植入转染质粒pIRES2-EGFP/VEGF165的内皮细胞:空白转染组:植入转染质粒pIRES2-EGFP的内皮细胞:对照组:植入正常大鼠血管内皮细胞.主要观察指标:①转染72 h后观察EGFP及VEGF表达情况.②流式细胞仪检测转染效率.③植入后14 d苏木精-伊红染色观察植入血管内皮细胞处组织形态学变化.结果:30只大鼠均进入结果分析.①荧光显微镜下实验组内皮细胞有特异性的EGFP表达.②流式细胞仪分析转染效率为13.06%.③实验组血管内皮细胞胞核和胞浆中均有VEGF表达.反转录-聚合酶链反应显示实验组大鼠血管内皮细胞中有人源化VEGF165基因在mRNA水平表达.④移植后14 d.实验组大鼠肾被膜下可见成团的新生毛细血管网形成,而对照组及空白转染组虽血管内皮细胞仍存活,但未形成明显血窦.结论:转染VEGF基因是促进内皮细胞早期(14d内)形成新生血管的有效途径.     

冠状动脉内皮功能与肱动脉内皮功能的相关性研究

目的利用经胸超声心动图冠状动脉血流显像技术检测冠状动脉（冠脉）内皮功能，利用高分辨力超声检测肱动脉内皮功能，同时对冠脉内皮功能与肱动脉内皮功能进行相关性分析。方法应用彩色多普勒超声仪对43例冠心病患者及37例健康人进行冷加压试验检测冠脉内皮功能，肱动脉袖带加压检测肱动脉内皮功能。结果所有受试者冠脉冷加压前、肱动脉加压前血流速度以及冠脉冷加压后、肱动脉加压后血流速度比较差异均有统计学意义（P〈0．0001）；但冠脉反应性充血后血流速度变化率与肱动脉反应性充血后血流速度变化率差异性很小（P〉0．05），两者呈线性正相关，相关系数均接近1。结论冠脉内皮功能与肱动脉内皮功能呈高度相关。     

Direct evidence of endothelial injury during cardiopulmonary bypass by demonstration of circulating endothelial cells

Endothelial activation is considered a key process in the development of a whole body inflammatory response secondary to cardiopulmonary bypass (CPB). Increased levels of a multitude of soluble mediators have been described as being released during and after cardiac surgery. Circulating endothelial cells have recently been established as a novel marker of endothelial damage in a variety of vascular disorders. Blood samples from 20 patients undergoing elective coronary artery bypass surgery were obtained preoperatively and 1, 6, 12, 24, and 48 h after termination of CPB. Control samples were obtained from ten healthy volunteers. Circulating endothelial cells (CEC) were isolated with immunomagnetic anti-CD146-coated Dynabeads, and counted in a Nageotte chamber. Low numbers of CEC were observed in healthy control volunteers (12 +/- 6 cells/mL; median: 9 cells/mL). CEC numbers were already significantly elevated in all patients before CPB, and there was a further significant increase after weaning from CPB (maximum increase at 6 h after CPB: 73 +/- 30 cells/mL; range: 30-153 cells/mL, p < 0.001). The number of CEC provides further and direct evidence that CPB is associated with a pronounced endothelial injury and/or damage. CEC appear to be most useful markers for vascular endothelial activation because they are specific, stable, and circulating components of injured vessel wall.     

Markers of endothelial dysfunction.

The endothelium is a functional barrier between vessel wall and blood stream. Assuming the total human vascular and capillary system occupies a surface area of more than 1,000 m2 which is covered by 1,013 endothelial cells, the complex role of the endothelium for hemostasis and immunological and metabolic processes becomes obvious. Dysfunction of the endothelium is a critical factor in the pathogenesis of vascular diseases and thrombus formation. This paper provides a brief review of physiological endothelial functions and summarizes measurable changes in products released from endothelial cells under pathological conditions which were associated with endothelial dysfunction.     

Antithrombogenicity of human endothelial cells

In the preceeding decades, our understanding of the complexity in our haemostaseologic system has been evolutionized from a purely ex vivo standpoint to an increasingly in vivo oriented approach, by more and more respecting the immense metabolic interactions of our vascular endothelium, mainly thrombin, the central serine protease in our coagulatory system. So far, investigations concerning human endothelium only relied on experiments with embryonic human endothelial cells, derived from umbilical cord veins. The underlying investigation confronts the justified question about the transferability of such embryonic results to the adult vascular system. Material, methods: Micro- and macrovascular endothelial cells were isolated, purified and propagated in pure cultures. Integrated into an established filtration model, their potential to mediate antithrombogenicity was investigated. Results, conclusion: Surprisingly, immense differences in thrombin-induced antithrombogenicity were demonstrated. This justifies doubts concerning the transferability of HUVEC-based results to the whole human vascular system.     

Angiotensin II impairs endothelial function via tyrosine phosphorylation of the endothelial nitric oxide synthase

Proline-rich tyrosine kinase 2 (PYK2) can be activated by angiotensin II (Ang II) and reactive oxygen species. We report that in endothelial cells, Ang II enhances the tyrosine phosphorylation of endothelial NO synthase (eNOS) in an AT₁-, H₂O₂-, and PYK2-dependent manner. Low concentrations (1–100 µmol/liter) of H₂O₂ stimulated the phosphorylation of eNOS Tyr657 without affecting that of Ser1177, and attenuated basal and agonist-induced NO production. In isolated mouse aortae, 30 µmol/liter H₂O₂ induced phosphorylation of eNOS on Tyr657 and impaired acetylcholine-induced relaxation. Endothelial overexpression of a dominant-negative PYK2 mutant protected against H₂O₂-induced endothelial dysfunction. Correspondingly, carotid arteries from eNOS^−/− mice overexpressing the nonphosphorylatable eNOS Y657F mutant were also protected against H₂O₂. In vivo, 3 wk of treatment with Ang II considerably increased levels of Tyr657-phosphorylated eNOS in the aortae of wild-type but not Nox2^y/− mice, and this was again associated with a clear impairment in endothelium-dependent vasodilatation in the wild-type but not in the Nox2^y/− mice. Collectively, endothelial PYK2 activation by Ang II and H₂O₂ causes the phosphorylation of eNOS on Tyr657, attenuating NO production and endothelium-dependent vasodilatation. This mechanism may contribute to the endothelial dysfunction observed in cardiovascular diseases associated with increased activity of the renin–angiotensin system and elevated redox stress.Endothelial dysfunction is recognized as an independent risk factor for the development of cardiovascular diseases, and is characterized by a reduced bioavailability of the antithrombotic and antiatherosclerotic autacoid NO (Davignon and Ganz, 2004). The decrease in NO is directly related to increased vascular oxidative stress, as O₂⁻ readily reacts with NO to form peroxynitrite. Perhaps more importantly, the oxidative depletion of tetrahydrobiopterin causes the so-called uncoupling of endothelial NO synthase (eNOS), leading to the production of O₂⁻ instead of NO by the enzyme (Schulz et al., 2008). Despite the undisputed role of oxidative stress in the etiology of endothelial dysfunction, large clinical trials with antioxidant therapies have failed to show a beneficial effect on cardiovascular outcome (Thomson et al., 2007). This discrepancy is probably explained at least in part by the formation of other reactive oxygen species from O₂⁻ that have more complex roles in intracellular signaling beyond NO scavenging. Several superoxide dismutases convert O₂⁻ to the more stable H₂O₂ that has widespread and more prolonged effects on endothelial cell function (for review see Cai, 2005). H₂O₂ is in turn eliminated through the actions of catalase and peroxidases. However, it is important to note that the exogenous application of catalase can ameliorate endothelial dysfunction in some models of hypertension (Ulker et al., 2003), whereas catalase aggravates the situation in models characterized by the uncoupling of eNOS (Landmesser et al., 2003). To date, several studies have reported that promoting the conversion of O₂⁻ to H₂O₂ to relieve NO scavenging does not prevent the formation of atherosclerotic lesions and that superoxide dismutase activity actually correlates with lesion size (Tribble et al., 1997; Zanetti et al., 2001). These observations suggest that the impairment of eNOS activity by oxidative stress is more complex than hitherto assumed.We recently reported that Tyr657 in the reductase domain of eNOS is a critical determinant of enzymatic activity. For example, the phosphorylation of Tyr657 by proline-rich tyrosine kinase 2 (PYK2) decreases eNOS activity, and the mutation of Tyr657 to a phosphomimetic glutamate or aspartate residue completely abolished NO production (Fisslthaler et al., 2008). PYK2 is generally considered to be a redox-sensitive kinase that is activated after stimulation with angiotensin II (Ang II) as well as in other situations associated with elevated oxidative stress (Tai et al., 2002; Yin et al., 2003). As elevated Ang II levels and increased oxidative stress are hallmarks of most cardiovascular diseases and associated with impaired endothelial function, we hypothesized that direct inactivation of eNOS via its tyrosine phosphorylation by PYK2 contributes to the phenomenon of endothelial dysfunction.     

Internalization of microparticles by endothelial cells promotes platelet/endothelial cell interaction under flow

Summary. Background: Microparticles (MPs) released by activated or apoptotic cells increase in number in the blood of subjects with vascular or metabolic diseases and may contribute to thrombotic complications. Objectives: In this study, we investigated whether MPs promoted platelet recruitment to endothelial cells in flow conditions, and by which mechanism. Methods: Human umbilical vein endothelial cells (HUVECs) grown in microslide perfusion chambers were exposed to MPs prepared in vitro from HUVECs, monocytes or platelets. Results: Videomicroscopy of DIOC‐labelled blood perfused at arterial rate on human umbilical vein ECs demonstrated that, irrespective of their cell origin, MPs promoted the formation of platelet strings at the surface of HUVECs. This platelet/endothelial cell interaction was dependent on von Willebrand factor (VWF) expression at the HUVEC surface and involved Glycoprotein Ib and P‐selectin. Interestingly, HUVECs internalized MPs within a few hours through a process involving anionic phospholipids, lactadherin and αvβ3 integrin. This uptake generated the production of reactive oxygen species via the xanthine/xanthine oxidase system (inhibited by allopurinol and the ROCK inhibitor Y‐27632) and the NADPH oxidase (inhibited by SOD). Reactive oxygen species appeared essential for VWF expression at the endothelial cell surface and subsequent platelet/endothelial cell interaction under flow. The pathophysiological relevance of this process is underlined by the fact that circulating MPs from Type I diabetic patients induced platelet/endothelial cell interaction under flow, with an intensity correlated with the severity of the vasculopathy.     

血管内皮生长因子与促血管生成素1对大鼠血管内皮细胞的作用

背景：血管内皮生长因子、促血管生成素1是血管形成过程中始动并且使之持续的重要因子,研究其对血管内皮细胞的作用具有重要的意义。目的：观察血管内皮生长因子与促血管生成素1对培养血管内皮细胞迁移与增殖能力的影响,并探讨其在血管生成方面的作用机制。方法：在大鼠脐静脉内皮细胞内单独或联合加入血管内皮生长因子、促血管生成素1后,划痕实验和MTT检测对细胞迁移与增殖的影响,观察内皮细胞形态、活性、迁移能力。结果与结论：划痕实验显示单独血管内皮生长因子作用时,与空白对照组细胞迁移无明显差异,单独促血管生成素1作用时,不仅不能增加细胞的迁移作用,反较空白对照组有所减弱,当血管内皮生长因子与促血管生成素1联合作用时,细胞迁移较空白对照组明显增强;MTT实验结果表明：单纯加入血管内皮生长因子或促血管生成素1,均不能起到有效促进内皮细胞增殖的作用;联合应用血管内皮生长因子及促血管生成素1可有效促进增殖。结果可见当血管内皮生长因子与促血管生成素1联合应用时,才能有效促内皮细胞迁移与增殖,发挥促血管生成作用。