通心络和他汀类药物对人内皮祖细胞数量与功能的影响

目的：观察中药通心络和他汀类药物对外周血内皮祖细胞（EPCs）数量和功能的影响。方法：采用密度梯度离心法分离培养人外周血EPCs,经FITC—UEA—I和Dil-acLDL双染色鉴定后,并进一步通过流式细胞仪检测其表面标志CD34、CD133．将贴壁细胞随机分为：对照组、阿托伐他汀组（终浓度10μmol／L）、通心络组（终浓度0、50、100、200、500、750和1000μg／m1）,作用不同时间（0、12、24、48、60和72h）后,检测细胞形态及计数,再采用四甲基偶氮唑盐微量酶反应比色法（MTT法）、Transwell小室、黏附功能检测评价其增殖、迁移和黏附能力。结果：不同浓度通心络组、阿托伐他汀组均能较对照组明显提高EPCs数量,显著改善其增殖、迁移、黏附能力,通心络在500μg／ml时对细胞数量及功能改善最为显著。采用500μg／ml的通心络进行时效作用的研究,各组呈时间依赖性增强,EPCs的数量和功能在72h达到高峰。结论：通心络和阿托伐他汀均能在体外提高内皮祖细胞的数量及功能。     

冠心病患者外周血内皮祖细胞数量及生物学功能与肝细胞生长因子的关系

目的观察冠心病患者外周血内皮祖细胞（EPCs）数量及生物学功能的变化,进一步探讨肝细胞生长因子（HGF）对其影响,为临床应用HGF提供理论依据。方法收集50例非冠心病患者（对照组）、50例冠心病患者（冠心病组;每例分为HGF干预组和非HGF干预组）外周血,应用流式细胞仪和ELISA法分别检测各组CD133＋／CD34＋细胞的数量和HGF水平;采用密度梯度离心法分离培养各组外周血中EPCs,通过MTT法、Transwell迁移试验、黏附能力测定试验及PI—AnnexinV双重染色法来分别检测EPCs的增殖、迁移、黏附能力和凋亡水平。结果与对照组比较,冠心病组外周血中CD133＋／CD34＋细胞数量减少[（2．15±0．69）％1）S（5．26±1．16）％,P〈0．011,血浆中HGF浓度升高[（6．80±1．22）w（2．62±0．83）gg／L,P〈0．01],EPCs增殖、迁移、黏附等生物学功能减弱（P〈0．05）;HGF干预组EPCs增殖、迁移、黏附等生物学功能显著改善（P〈0．05）。各组细胞凋亡水平差异无统计学意义（P〉0．05）。结论外周血中CD133＋／CD34＋细胞数量和血浆中HGF水平的变化可能成为冠心病患者新的危险评估因素。     

兔外周血与骨髓源性内皮祖细胞培养鉴定及生物学特性的研究

目的:探索并建立兔内皮祖细胞(EPCs)的体外培养、鉴定方法。方法:采用密度梯度分离法分别从兔外周血和骨髓中分离出单个核细胞,接种于预包被明胶的培养瓶,并应用培养基(EBM-2)诱导培养,诱导分化为EPCs;在倒置显微镜下观察两种源性细胞生长过程;台盼蓝法测定细胞传代成活率;通过绘制生长曲线法、MTT法、DNA周期检测比较两种源性获得的EPCs增殖情况;采用免疫荧光染色观察EPCs相关抗原CD34、CD31、CD133及vWF因子的表达。结果:两种源性EPCs均于培养3～4d完全贴壁,呈克隆样生长,7～9d形成类似成熟血管内皮细胞形态,细胞数量逐渐增多,细胞成活率均为95%。两种源性获得的第2代细胞生长曲线近似"s"形、MTT法显示3～5d细胞增殖较明显,外周血源性EPCs G0-G1期和S+G2+M期所占比例分别为96.48%和3.52%,骨髓源性EPCs G0-G1期和S+G2+M期所占比例分别为97.11%和1.84%。第2代EPCs进行免疫荧光鉴定结果显示:两种源性内皮祖细胞均阳性表达CD34、CD133、vWF因子,CD31弱阳性表达。结论:两种源性的EPCs均可高效获得且在体外稳定培养。与传统的骨髓源性EPCs相比较,从外周血源获得的EPCs是一种可靠、简便的培养方法,为组织工程学提供理想的细胞来源。     

成人骨髓源内皮祖细胞的体外分离培养及鉴定

目的探讨成人骨髓源内皮祖细胞（EPCs）体外分离培养的可行性。方法抽取成年男性骨髓,体外全骨髓培养,传代后采用免疫微珠分选方法收集CD南细胞,EGM—MV2条件培养基诱导培养EPCs,观察细胞形态、生长情况;采用流式细胞技术检测分选细胞纯度,免疫荧光法检测EPCs特殊分子标志物CD34,CD133和VE-cadherin表达,透射电子显微镜观察分选细胞超微结构,UEA-1和Dil-ac-LDL双染色法检测分选细胞的吞噬功能。结果分选后细胞培养第3天出现集落样生长,集落边缘细胞形态伸展呈梭形或多边形,传代后呈现串珠样排列;培养至5～6d,细胞连接成大片条索状结构;CD34^＋、CD133^＋细胞百分率分别为24．13％、93．29％,其表面特异性表达CD133、CD34、VE-cadherin,具有EPCs形态特征,能吞噬Dil-ac-LDL并结合UEA-1。结论成人骨髓来源的EPCs经体外培养后形态、增殖率、生存能力、表面标志表达、功能等均较为稳定,可作为心血管组织工程种子细胞或用于干细胞治疗。     

罗格列酮钠对中年男性糖尿病患者外周血内皮祖细胞的影响

目的观察罗格列酮钠对中年男性糖尿病患者血管内皮祖细胞（EPCs）数量和功能的影响。方法本实验纳入血糖控制良好（HbA1c〈7%）的30例中年男性糖尿病患者。体内实验：将上述患者随机分成罗格列酮钠组和常规治疗组。所有患者在用药前后均采集空腹静脉血,分离并培养EPCs,采用流式技术、免疫荧光双染法、MTT比色法、30 min贴壁方法、改良型Boyden小室法对EPCs进行计数、鉴定、增殖、黏附和迁移等功能检测。体外实验：随机抽取上述患者20例,提取其空腹静脉血单个核细胞,培养6 d后收集贴壁细胞,将收集到的每份贴壁细胞各分成药物干预组和对照组,用上述方法观察体外药物干预对EPCs数量和功能的影响。结果罗格列酮钠组用药后较用药前,CD3＋4/CD1＋33、vWF＋细胞数量增加,细胞增殖、黏附、迁移功能增强（P〈0.05或〈0.01）;较常规治疗组用药后,CD3＋4/CD1＋33、CD1＋33/KDR＋、vWF＋细胞数量增加,增殖、黏附、迁移功能增强（P〈0.01）。药物干预组EPCs增殖、黏附、迁移功能较对照组增强（P〈0.01）。结论罗格列酮能增加糖尿病患者EPCs数量,并能改善其增殖、黏附和迁移功能,且此作用独立于降糖、降压作用之外。     

急性心肌梗死患者循环内皮祖细胞不同集落成分数目及功能的变化

目的探讨急性心肌梗死（AMI）患者循环内皮祖细胞（EPCs）不同集落成分数目及功能的变化。方法入选28例AMI患者、22例稳定型心绞痛（SA）患者和19例健康志愿者。所有受试者取肘静脉血，密度梯度离心法获得单个核细胞（MNCs），用含生长因子的内皮培养基接种于纤连蛋白包被的培养板中。第7天和21天分别计数早期和晚期集落数目，流式细胞技术检测细胞表面抗原表达，直接荧光染色法测定细胞结合荆豆凝集素及摄取乙酰化低密度脂蛋白，ELISA法测定上清液中血管内皮生长因子（VEGF）浓度。结果早期集落属于单核细胞系列并能分泌VEGF，晚期集落可向内皮细胞分化。AMI患者早期集落数目（7．3±3．4）显著高于SA患者（4．2±2．8，P〈0．05）和健康对照者（3．6±1．9，P〈0．01），但其分泌VEGF水平与后两组相比显著降低（P〈0．05和P〈0．01）。EPCs晚期集落数目在AMI组（1．6±2．1）显著低于SA组（2．9±1．5，P〈0．05）和健康对照组（3．2±2．3，P〈0．05）。结论心肌梗死急性期循环内皮祖细胞早期集落数目增加，但其分泌功能严重受损并导致晚期集落数目减少。     

血管内皮生长因子调节内皮祖细胞生物学功能

目的研究血管内皮生长因子（VEGF）对体外培养骨髓源性内皮祖细胞（EPCs）数量及增殖、迁移、黏附功能的影响及机制初探。方法密度梯度离心法获取骨髓单个核细胞,FITC-荆豆凝集素I、DiI-乙酰化低密度脂蛋白荧光双染鉴定。单个核细胞培养7d后分为对照组和VEGF干预组。VEGF干预组加入不同浓度VEGF（25,50,75,100μg／L）培养48h,分别采用四氮唑溴盐比色法、改良的Boyden小室和黏附能力测定观察EPCs的增殖、迁移和黏附能力。RT—PCR法半定量检测VEGF对EPCs内皮型一氧化氮合酶（eNOS）mRNA表达的影响。硝酸还原酶法比色测定VEGF对EPCs分泌一氧化氮的影响。结果VEGF可浓度依赖性地增加EPCs数量并明显促进EPCs的黏附、迁移和增殖能力,与对照组比较差异显著。VEGF可上调EPCseNOSmRNA的表达,促进EPCs分泌一氧化氮。结论VEGF可能通过上调EPCseNOSmRNA的表达影响EPCs部分生物学功能。     

脐血、外周血内皮祖细胞分化成内皮细胞的实验研究

目的探讨人的脐血、外周血内皮祖细胞（endothelialprogenitorcells,EPCs）体外分离、纯化、诱导扩增和分化为内皮细胞的可行性,并检测其表型和功能。方法新鲜脐血和健康成年人的外周血,使用Ficoll密度梯度离心法得单个核细胞,在M199培养基中体外培养,3d后去除悬浮细胞,继续培养,诱导EPCs增殖和分化。流式细胞仪检测EPCs标志CD34和内皮细胞特异性标志CD31表型,RTPCR检测ecNOS,flk1/KDR基因水平表达,免疫组化验证蛋白水平表达,并进一步通过NO活性的变化检测内皮细胞的功能。结果流式细胞仪检测,外周血单个核细胞（peripheralbloodmononuclearcells,PBMC）刚分离时,CD34阳性表达率为（1.1±0.8）%,培养3d后为（16.9±6.2）%。细胞形态观察发现,刚分离的单个核细胞呈圆形,形态小,3d后有明显集落形成,7d后梭形细胞线样排列,随培养时间增加,细胞形态逐渐变大,呈现出典型铺路石样改变。脐血单个核细胞（umbilicalcordbloodmononuclearcells,CBMC）和PBMC培养10d后,CD31阳性表达率分别为（76±17）%和（82±9）%。RTPCR检测有内皮细胞特异性成分ecNOS,flk1/KDR的表达。免疫组化染色,细胞膜和细胞浆中有弥漫性棕色出现,呈阳性反应,证实了蛋白水平的表达。培养10d的贴壁细胞随着VEGF浓度增加,NO生成增加,具有内皮细胞的功能。结论脐血,外周血EPCs体外分离,纯化,诱导培养后的贴壁细胞表型检测,大部分细胞具有内皮系标志物,并具有产生NO功能。     

通心络体外促进人外周血内皮祖细胞的增殖、迁移、黏附的研究

目的：研究中药通心络对体外培养的人外周血内皮祖细胞（EPCs）增殖、迁移、黏附的影响。方法：采用密度梯度离心法分离培养人外周血单个核细胞,经FITC—UEA—I和Dil—acLDL双染色鉴定为正在分化的EPCs。进一步采用流式细胞仪检测其表面标志CD34、CD133,采用MTT比色法、transwell小室、细胞计数法分别观察50、100、200、500、750和1000μg／ml通心络超微粉溶液和500μg／ml通心络超微粉溶液作用0、6、12、24和36h后,对EPCs增殖、迁移、黏附的影响。结果：不同水平的通心络均改善了EPCs的增殖、迁移、黏附的功能,且在500μg／ml时作用最为显著。采用500μg／ml的通心络进行时效作用的研究显示,通心络呈时间依赖性地增强EPCs增殖、迁移、黏附能力,在36h达到高峰（P〈0．01）。结论：通心络能显著改善外周血内皮祖细胞增殖、迁移、黏附能力,这可能是通心络防治心脑血管疾病的新机制。     

姜黄素对内皮祖细胞功能及内皮型—氧化氮合酶的影响

目的观察姜黄素对体外培养的人外周血内皮祖细胞（EPCs）数量及功能的影响。方法采用贴壁选择法培养人外周EPCs，培养6d后，收集贴壁细胞并加入姜黄素（0、5、10、15μmol／L）培养一定时间（6、12、24和48h）。荧光显微镜鉴定EPCs，分别观察EPCs的体外增殖、黏附、迁移、体外血管生成能力。Griess法检测NO分泌量，并RT-PCR半定量测定eNOS基因表达。结果姜黄素增加外周血EPCs的数量，改善EPCs的体外增殖、黏附、迁移、体外血管生成能力（P〈0．01）。并上调eNOS基因表达，促进EPCs来源的NO的释放（P〈0．01）。结论姜黄素增加体外EPCs数量及改善其功能，上调eNOS基因表达并增加EPCs来源的NO分泌。     

Human CD34+AC133+VEGFR-2+ cells are not endothelial progenitor cells but distinct, primitive hematopoietic progenitors

OBJECTIVE: Endothelial progenitor cells (EPCs) are used for angiogenic therapies or as biomarkers to assess cardiovascular disease risk. However, there is no uniform definition of an EPC, which confounds EPC studies. EPCs are widely described as cells that coexpress the cell-surface antigens CD34, AC133, and vascular endothelial growth factor receptor-2 (VEGFR-2). These antigens are also expressed on primitive hematopoietic progenitor cells (HPCs). Remarkably, despite their original identification, CD34+AC133+VEGFR-2+ cells have never been isolated and simultaneously plated in hematopoietic and endothelial cell (EC) clonogenic assays to assess the identity of their clonal progeny, which are presumably the cellular participants in vascular regeneration. METHODS: CD34+AC133+VEGFR-2+ cells were isolated from human umbilical cord blood (CB) or granulocyte colony-stimulating factor-mobilized peripheral blood and assayed for either EPCs or HPCs. RESULTS: CD34+AC133+VEGFR-2+ cells did not form EPCs and were devoid of vessel forming activity. However, CD34+AC133+VEGFR-2+ cells formed HPCs and expressed the hematopoietic lineage-specific antigen, CD45. We next tested whether EPCs could be separated from HPCs by immunoselection for CD34 and CD45. CD34+CD45+ cells formed HPCs but not EPCs, while CD34+CD45- cells formed EPCs but not HPCs. CONCLUSIONS: Therefore, CD34+AC133+VEGFR-2+ cells are HPCs that do not yield EC progeny, and the biological mechanism for their correlation with cardiovascular disease needs to be reexamined.     

Endothelial progenitor cells: isolation and characterization

Bone marrow of adults contains a subtype of progenitor cells that have the capacity to differentiate into mature endothelial cells and have therefore been termed endothelial progenitor cells (EPCs). Of the three cell markers (CD133, CD34, and the vascular endothelial growth factor receptor 2) that characterize the early functional EPCs, located predominantly in the bone marrow, EPCs obviously lose CD133/CD34 and start to express CD31, vascular endothelial cadherin, and von Willebrand factor when migrating to the circulation. Various isolation procedures of EPCs from different sources by using adherence culture or magnetic microbeads have been described, but published findings with regard to the number of EPCs in the peripheral circulation of healthy adults are scanty and no data regarding the lifetime of EPCs in vivo exist. Clinical studies employing EPCs for neovascularization of ischemic organs have just been started; however, the mechanisms stimulating or inhibiting the differentiation of bone marrow-derived EPCs in vivo and the signals causing their adhesion, migration, and homing to sites of injured tissue are largely unknown at present.     

Endothelial progenitor cells: mobilization,differentiation, and homing

Postnatal bone marrow contains a subtype of progenitor cells that have the capacity to migrate to the peripheral circulation and to differentiate into mature endothelial cells. Therefore, these cells have been termed endothelial progenitor cells (EPCs). The isolation of EPCs by adherence culture or magnetic microbeads has been described. In general, EPCs are characterized by the expression of 3 markers, CD133, CD34, and the vascular endothelial growth factor receptor-2. During differentiation, EPCs obviously lose CD133 and start to express CD31, vascular endothelial cadherin, and von Willebrand factor. EPCs seem to participate in endothelial repair and neovascularization of ischemic organs. Clinical studies using EPCs for neovascularization have just been started; however, the mechanisms stimulating or inhibiting the differentiation of EPC in vivo and the signals causing their migration and homing to sites of injured endothelium or extravascular tissue are largely unknown at present. Thus, future studies will help to explore areas of potential basic research and clinical application of EPCs.     

Bone marrow endothelial progenitors are defective in systemic sclerosis

OBJECTIVE: Vascular abnormalities represent the main component of the pathobiology of systemic sclerosis (SSc), progressing from structural derangements of the microcirculation with abortive neoangiogenesis to final vessel loss. Since circulating endothelial progenitor cells (EPCs) are important in the vascular repair process, we undertook this study to examine their numbers in the peripheral blood (PB) of SSc patients and to evaluate whether their status is related to impaired quantitative and/or qualitative aspects of the bone marrow (BM) microenvironment. METHODS: Circulating EPCs from 62 SSc patients were evaluated by flow cytometry and characterized as CD45 negative and CD133 positive. BM EPCs, identified as CD133 positive, were isolated from 14 SSc patients and grown to induce endothelial differentiation. In addition, progenitor numbers and functional properties of hematopoietic and stromal compartments were analyzed by various assays. RESULTS: We found that EPCs were detectable in the PB of patients with SSc, and their number was significantly increased in patients with early-stage disease but not in those with late-stage disease. All of the examined BM samples contained reduced numbers of EPCs and stromal cells, both of which were functionally impaired. Both endothelial and stromal progenitors expressed vascular endothelial growth factor receptor, indicating that BM is strongly induced to differentiate into the endothelial lineage; furthermore, only BM EPCs from patients with early disease led to endothelial differentiation in vitro. CONCLUSION: This study provides the first demonstration that in SSc, there is a complex impairment in the BM microenvironment involving both the endothelial and mesenchymal stem cell compartments and that this impairment might play a role in defective vasculogenesis in scleroderma.     

Endothelial progenitor cells in infantile hemangioma

Infantile hemangioma is an endothelial tumor that grows rapidly after birth but slowly regresses during early childhood. Initial proliferation of hemangioma is characterized by clonal expansion of endothelial cells (ECs) and neovascularization. Here, we demonstrated mRNA encoding CD133-2, an important marker for endothelial progenitor cells (EPCs), predominantly in proliferating but not involuting or involuted hemangioma. Progenitor cells coexpressing CD133 and CD34 were detected by flow cytometry in 11 of 12 proliferating hemangioma specimens from children 3 to 24 months of age. Furthermore, in 4 proliferating hemangiomas, we showed that 0.14% to 1.6% of CD45(-) nucleated cells were EPCs that coexpressed CD133 and the EC marker KDR. This finding is consistent with the presence of KDR(+) immature ECs in proliferating hemangioma. Our results suggest that EPCs contribute to the early growth of hemangioma. To our knowledge, this is the first study to show direct evidence of EPCs in a human vascular tumor.     

Circulating progenitor cells can be reliably identified on the basis of aldehyde dehydrogenase activity.

OBJECTIVES: Our objective was to develop and assess a novel endogenous progenitor cell (EPC) assay based on aldehyde dehydrogenase (ALDH) activity, and to define the relationship of ALDH-bright (ALDH(br)) cells with previously defined EPCs, patient age, and extent of coronary artery disease. BACKGROUND: Accurate assessment of circulating EPCs is of significant interest, yet current assays have limitations. Progenitor cells display high levels of ALDH activity. An assay based on ALDH activity may offer a simple means for enumerating EPCs. METHODS: We simultaneously determined the numbers of EPCs based on ALDH activity and cell surface expression of CD133, CD34, and vascular endothelial growth factor receptor-2 in 110 patients undergoing cardiac catheterization. We assessed the reproducibility of these estimates, correlation among EPC assays, and the association of ALDH(br) numbers with age and disease severity. RESULTS: Aldehyde dehydrogenase-bright cells were easily identified in nonmobilized peripheral blood with median and mean frequencies of 0.041% and 0.074%, respectively. Aldehyde dehydrogenase-bright cells expressed CD34 or CD133 cell surface markers (57.0% and 27.1%, respectively), correlated closely with CD133+CD34+ cells (r = 0.72; p < 0.001), and differentiated into endothelial cells with greater efficiency than CD133+CD34+ cells. Aldehyde dehydrogenase-bright cell numbers were inversely associated with patient age and coronary disease severity. CONCLUSIONS: Aldehyde dehydrogenase activity represents a novel simplified method for quantifying EPCs. The correlation of ALDH(br) cells with clinical factors and outcomes warrants further study.     

Impaired progenitor cell activity in age-related endothelial dysfunction

OBJECTIVES: We investigated whether human age-related endothelial dysfunction is accompanied by quantitative and qualitative alterations of the endothelial progenitor cell (EPC) pool. BACKGROUND: Circulating progenitor cells with an endothelial phenotype contribute to the regeneration and repair of the vessel wall. An association between the loss of endothelial integrity and EPC modification may provide a background to study the mechanistic nature of such age-related vascular changes. METHODS: In 20 old and young healthy individuals (61 +/- 2 years and 25 +/- 1 year, respectively) without major cardiovascular risk factors, endothelial function, defined by flow-mediated dilation of the brachial artery via ultrasound, as well as the number and function of EPCs isolated from peripheral blood, were determined. RESULTS: Older subjects had significantly impaired endothelium-dependent dilation of brachial artery (flow-mediated dilation [FMD] 5.2 +/- 0.5% vs. 7.1 +/- 0.6%; p < 0.05). Endothelium-independent dilation after glycerol trinitrate (GTN) was not different, but the FMD/GTN ratio was significantly lower in old subjects (49 +/- 4% vs. 37 +/- 3%; p < 0.05), suggesting endothelial dysfunction. There were no differences in the numbers of circulating EPCs, defined as CD34/KDR or CD133/KDR double-positive cells in peripheral blood. In contrast, lower survival (39 +/- 6 cells/mm(2) vs. 65 +/- 11 cells/mm(2); p < 0.05), migration (80 +/- 12 vs. 157 +/- 16 cells/mm(2); p < 0.01), and proliferation (0.20 +/- 0.04 cpm vs. 0.44 +/- 0.07 cpm; p < 0.05) implicate functional impairment of EPCs from old subjects. The FMD correlated univariately with EPC migration (r = 0.52, p < 0.05) and EPC proliferation (r = 0.49, p < 0.05). Multivariate analysis showed that both functional features represent independent predictors of endothelial function. CONCLUSIONS: Maintenance of vascular homeostasis by EPCs may be attenuated with age based on functional deficits rather than depletion of CD34/KDR or CD133/KDR cells.     

Synergistic effect of combined intramyocardial CD34+ cells and VEGF2 gene therapy after MI

Previous studies have shown that local angiogenic gene therapy acts, in part, by recruiting endothelial progenitor cells (EPCs) to ischemic tissue. Recent data indicate that patients with the most severe vascular disease may have insufficient or deficient EPCs and the poorest response to angiogenic therapy. Accordingly, we hypothesized that combining human CD34(+) cell implantation with local vascular endothelial growth factor 2 (phVEGF2) gene therapy might overcome these deficiencies. The addition of VEGF2 to EPC cultures resulted in significant and dose-dependent decreases in EPC apoptosis. Phosphorylated Akt (p-Akt) was increased in VEGF2-treated EPCs. In vivo, myocardial infarction (MI) was induced by ligation of the left anterior descending coronary artery in 34 immunodeficient rats. The animals were then randomized to one of four treatment groups: cell therapy alone with human CD34(+) cells; VEGF2 gene therapy alone; combination therapy with CD34(+) cells plus phVEGF2; or CD34(-) cells and 50 microg empty plasmid. Four weeks after MI, animals treated with combination therapy showed improved fractional shortening, increased capillary density, and reduced infarct size compared with the other three groups. Combination therapy was also associated with an increased number of circulating EPCs 1 week after MI. Combined subtherapeutic doses of cell and gene therapy result in a significant therapeutic effect compared to monotherapy. This approach may overcome therapeutic failures (e.g. inability of certain patients to mobilize sufficient EPCs) and may also offer safety advantages by allowing lower dosing strategies.     

Vascular endothelial damage and repair in antineutrophil cytoplasmic antibody-associated vasculitis

OBJECTIVE: Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is characterized by necrotizing vessel wall inflammation, paralleled by the detachment of endothelial cells. The repair of such endothelial defects is crucial for the maintenance of regular structure and function of the injured vessels. Bone marrow-derived endothelial progenitor cells (EPCs) are thought to play a pivotal role in the regeneration of damaged endothelium. The aim of this study was to investigate whether EPCs are involved in vascular repair in AAV. METHODS: We assessed disease activity, CD34+ hematopoietic progenitor cells (HPCs) using flow cytometry, EPCs using an in vitro assay, and circulating endothelial cells (CECs) by immunomagnetic isolation from the peripheral blood of 31 patients with active AAV at 1, 3, and 6 months after the initiation of immunosuppressive therapy. RESULTS: In patients with untreated active disease, HPC and EPC numbers were comparable with those in healthy control subjects (n = 64). With the induction of remission, the number of HPCs and EPCs increased significantly, from a median of 1.5 cells/microl (range 0.0-7.0) to a median of 3.2 cells/microl (range 0.76-9.2) (P < 0.001) and from a median of 261 cells/high-power field (range 171-643) to a median of 470 cells/high-power field (range 168-996) (P < 0.021), respectively. In contrast, the initially elevated number of CECs decreased significantly (P < 0.001). We observed no correlation between the number of HPCs or EPCs and the leukocyte count, the thrombocyte count, or kidney function. CONCLUSION: In patients with AAV, the numbers of circulating CD34+ HPCs and EPCs increased significantly after the institution of immunosuppressive therapy and disease remission. This finding points to a role of circulating CD34+ HPCs and EPCs in endothelial repair in vasculitis. Targeted stimulation of these cells might represent a new possibility of improving vascular healing in AAV.