内皮祖细胞分泌SDF-1及其抗内皮祖细胞凋亡作用

目的探讨内皮祖细胞（EPC）能否分泌基质细胞衍生因子-1（SDF-1）,及SDF-1能否抑制紫杉醇、AMD3100（特异性阻断SDF-1与其受体CXCR4结合）等诱导的EPC凋亡。方法取不同时间段的EPC培养液上清,采用ELISA检测上清中SDF-1a浓度。用不同浓度的紫杉醇、AMD3100及无血清培养诱导EPC凋亡;或在上述基础上加不同浓度的SDF-1a处理;48 h后采用TUNEL法和流式细胞仪检测各组EPC凋亡率。结果EPC培养液上清中SDF-1a浓度显著高于对照组（P<0.01）。紫杉醇、AMD3100和无血清培养一样,均可显著增高EPC凋亡率（P<0.01）;加入外源性SDF-1a可显著降低紫杉醇组、无血清培养组EPC凋亡率（P<0.01）,却不能降低AMD3100组EPC凋亡率。结论体外培养的EPC可分泌SDF-1a,采用AMD3100阻断其作用可诱导EPC凋亡;SDF-1a可对抗紫杉醇和无血清培养诱导的EPC凋亡,但对AMD3100诱导的凋亡无效。     

Degradation of BM SDF-1 by MMP-9: the role in G-CSF-induced hematopoietic stem/progenitor cell mobilization

The major involvement of chemokines and proteolytic enzymes has recently been discovered in the mobilization process. Here, we report that the degradation of BM stromal cell-derived factor (SDF-1) by matrix metalloproteinase (MMP)-9 is important in G-CSF-mediated hematopoietic stem/progenitor cells (HSPCs) mobilization. In this study, the SDF-1 concentration in healthy donors BM plasma decreased significantly after 5 days of G-CSF administration, with no obvious change of SDF-1 in the peripheral blood. We also observed a similar result by immunohistochemical staining on the BM biopsy slides. In vitro, mobilized BM plasma exhibited decreased chemotactic effect on CD34(+) cells, compared with steady-state BM plasma. MMP-9 protein and mRNA increased dramatically in the BM plasma in accordance with SDF-1 decrease. MMP-9 enriched supernatant from HT1080 cell-conditioned medium upregulated CXCR4 expression and the migration of BM CD34(+) cells toward SDF-1. SDF-1 was a substrate for MMP-9, furthermore, SDF-1 also stimulated MMP-9 proteolytic enzyme activity of BM CD34(+) cells, which facilitate HSPCs migration. In BALB/c mice, HSPCs mobilization was significantly inhibited by anti-SDF-1 antibodies or MMP inhibitor, o-phenanthroline. In conclusion, the degradation of BM SDF-1 by MMP-9 is a vital step in mobilization.     

Estrogen-mediated endothelial progenitor cell biology and kinetics for physiological postnatal vasculogenesis

Estrogen has been demonstrated to promote therapeutic reendothelialization after vascular injury by bone marrow (BM)-derived endothelial progenitor cell (EPC) mobilization and phenotypic modulation. We investigated the primary hypothesis that estrogen regulates physiological postnatal vasculogenesis by modulating bioactivity of BM-derived EPCs through the estrogen receptor (ER), in cyclic hormonally regulated endometrial neovascularization. Cultured human EPCs from peripheral blood mononuclear cells (PB-MNCs) disclosed consistent gene expression of ER alpha as well as downregulated gene expressions of ER beta. Under the physiological concentrations of estrogen (17beta-estradiol, E2), proliferation and migration were stimulated, whereas apoptosis was inhibited on day 7 cultured EPCs. These estrogen-induced activities were blocked by the receptor antagonist, ICI182,780 (ICI). In BM transplanted (BMT) mice with ovariectomy (OVX) from transgenic mice overexpressing beta-galactosidase (lacZ) regulated by an endothelial specific Tie-2 promoter (Tie-2/lacZ/BM), the uterus demonstrated a significant increase in BM-derived EPCs (lacZ expressing cells) incorporated into neovasculatures detected by CD31 immunohistochemistry after E2 administration. The BM-derived EPCs that were incorporated into the uterus dominantly expressed ER alpha, rather than ER beta in BMT mice from BM of transgenic mice overexpressing EGFP regulated by Tie-2 promoter with OVX (Tie-2/EGFP/BMT/OVX) by ERs fluorescence immunohistochemistry. An in vitro assay for colony forming activity as well as flow cytometry for CD133, CD34, KDR, and VE-cadherin, using human PB-MNCs at 5 stages of the female menstrual-cycle (early-proliferative, pre-ovulatory, post-ovulatory, mid-luteal, late-luteal), revealed cycle-specific regulation of EPC kinetics. These findings demonstrate that physiological postnatal vasculogenesis involves cyclic, E2-regulated bioactivity of BM-derived EPCs, predominantly through the ER alpha.     

Relaxin increases human endothelial progenitor cell NO and migration and vasculogenesis in mice

The ovarian peptide hormone, relaxin, circulates during pregnancy, contributing to profound maternal vasodilation through endothelial and nitric oxide (NO)-dependent mechanisms. Circulating numbers of bone marrow-derived endothelial cells (BMDECs), which facilitate angiogenesis and contribute to repair of vascular endothelium, increase during pregnancy. Thus, we hypothesized that relaxin enhances BMDEC NO production, circulating numbers, and function. Recombinant human relaxin-2 (rhRLX) stimulated PI3K/Akt B-dependent NO production in human BMDECs within minutes, and activated BMDEC migration that was inhibited by L-N(G)-nitroarginine methyl ester. In BMDECs isolated from relaxin/insulin-like family peptide receptor 2 gene (Rxfp2) knockout and wild-type mice, but not Rxfp1 knockout mice, rhRLX rapidly increased NO production. Similarly, rhRLX increased circulating BMDEC number in Rxfp2 knockout and wild-type mice, but not Rxfp1 knockout mice as assessed by colony formation and flow cytometry. Taken together, these results indicate that relaxin effects BMDEC function through the RXFP1 receptor. Finally, both vascularization and incorporation of GFP-labeled BMDECs were stimulated in rhRLX-impregnated Matrigel pellets implanted in mice. To conclude, relaxin is a novel regulator of BMDECs number and function, which has implications for angiogenesis and vascular remodeling in pregnancy, as well as therapeutic potential in vascular disease.     

环氧化酶在大鼠缺血心肌血管生成及内皮祖细胞动员中的作用

目的探讨环氧化酶（COX）1、2在缺血心肌血管生成和内皮祖细胞动员中的作用及机制。方法实验大鼠随机分为心肌缺血加选择性COX2抑制剂罗非昔布组、心肌缺血加选择性COX1抑制剂valeryl salicylate（VS）组和单纯心肌缺血组。心肌缺血组于术后1周取血浆测血管内皮生长因子（VEGF）,外周血分离单个核细胞培养计数内皮祖细胞和缺血心肌组织检测缺氧诱导因子-1α mRNA,28天后取缺血区心肌免疫组化法测毛细血管密度。结果心肌缺血加罗非昔布组与单纯心肌缺血组、心肌缺血加VS组比较,血浆VEGF水平、循环血内皮祖细胞计数、缺血心肌毛细血管密度和缺氧诱导因子-1α mRNA表达均显著减少（P〈0．05）,其余指标两组差异无统计学意义。结论COX2在心肌缺血时内皮祖细胞动员和缺血心肌血管生成中起重要作用,其可能机制与增加缺氧诱导因子-1α和VEGF的表达有关,而COX1没有作用。     

Modeling SDF-1-induced mobilization in leukemia cell lines

The stromal cell-derived factor 1 (SDF-1) is essential for circulation, homing, and retention of hematopoietic stem cells in the bone marrow. Present evidence indicates that this factor might play an important role in leukemia cells as well. The aim of this study is to present a model of SDF-1-induced mobilization using leukemia cell lines. CXCR4 expression was compared in Kasumi-1, Jurkat, HL-60, KG-1a, and K562 cells by flow cytometry and Western blot. Migration was analyzed with Transwell assays, and adhesive cell-cell interaction was quantified with a standardized adhesion assay and flow cytometry. CXCR4 was expressed by all leukemic cell lines analyzed, although surface expression of this receptor was found in Kasumi-1 and Jurkat cells only. Correspondingly, SDF-1α effects on migration and cell-cell adhesion were observed in Kasumi-1 and Jurkat cells only, and this could be blocked by AMD3100 in a reversible manner. We have provided evidence that SDF-1α acts as a chemotactic and chemokinetic agent. In addition, surface expression of integrin-β2, activated leukocyte cell adhesion molecule and N-cadherin decreased after stimulation with SDF-1α. SDF-1α affects cell-cell adhesion and migration only in leukemia cells on which the CXCR4 receptor is present on the surface. An SDF-1 gradient is not necessarily required to induce migration, as chemokinesis can also occur. Upon stimulation with SDF-1, CXCR4 promotes modifications on the surface pattern of adhesion molecules, which have an influence on adhesion and migration.     

Endothelin-1 levels predict endothelial progenitor cell mobilization after acute myocardial infarction

IntroductionEndothelin-1 (ET-1), circulating endothelial cells (CEC) and endothelial progenitor cells (EPC) are well-known modulators of endothelial function with important cardiac effects after an acute myocardial infarction. However, the relationship between them has never been assessed.The objective of the present study was to establish the relationship between ET-1, CEC, and EPC concentrations after ST-elevation myocardial infarction (STEMI).MethodsEndothelin-1, CEC, and EPC levels were measured in 61 patients presenting with a first STEMI. Samples were withdrawn acutely 6–24 h and 1 week after admission. Assessments included reperfusion outcomes (angiography), left ventricular ejection fraction (echocardiography), and 30-day mortality.ResultsMean age was 60.6 ± 12.6 years and 45 (74%) were males. Higher ET-1 plasma levels were associated with lower EPC count after 1 week (7.45 ± 2.53 pg/ml if EPCs in the first quartile vs 5.72 ± 1.49 pg/ml if EPCs in the fourth quartile; P = 0.04).In contrast with CEC and EPC count, higher ET-1 concentrations on admission were associated with Killip ≥ 2 (9.92 ± 2.01 pg/ml vs 7.32 ± 2.13 pg/ml; P < 0.001), post-reperfusion thrombolysis in myocardial infarction (TIMI) < 3 (8.65 ± 2.86 pg/ml vs 5.87 ± 1.93 pg/ml; P = 0.002), myocardial blush grade (MBG) < 3 (7.46 ± 2.48 pg/ml vs 5.99 ± 2.01 pg/ml; P = 0.004) and higher 30-day mortality (10.29 ± 2.02 pg/ml vs 6.57 ± 2.20 pg/ml; P = 0.005).ConclusionsIn STEMI patients, high ET-1 levels on admission predict a lower EPC mobilization after 1 week. Endothelin-1 provides better clinical, angiographic and echocardiographic information for prognosis than do CEC and EPC concentrations.     

Erythropoietin is a potent physiologic stimulus for endothelial progenitor cell mobilization

Increasing evidence suggests that postnatal neovascularization involves the recruitment of circulating endothelial progenitor cells (EPCs). Hematopoietic and endothelial cell lineages share common progenitors. Cytokines formerly thought to be specific for the hematopoietic system have only recently been shown to affect several functions in endothelial cells. Accordingly, we investigated the stimulatory potential of erythropoietin (Epo) on EPC mobilization and neovascularization. The bone marrow of Epo-treated mice showed a significant increase in number and proliferation of stem and progenitor cells as well as in colony-forming units. The number of isolated EPCs and CD34+/flk-1+ precursor cells was significantly increased in spleen and peripheral blood of Epo-treated mice compared with phosphate-buffered saline-treated mice. In in vivo models of postnatal neovascularization, Epo significantly increased inflammation- and ischemia-induced neovascularization. The physiologic relevance of these findings was investigated in patients with coronary heart disease. In a multivariate regression model, serum levels of Epo and vascular endothelial growth factor were significantly associated with the number of stem and progenitor cells in the bone marrow as well as with the number and function of circulating EPCs. In conclusion, the present study suggests that Epo stimulates postnatal neovascularization at least in part by enhancing EPC mobilization from the bone marrow. Epo appears to physiologically regulate EPC mobilization in patients with ischemic heart disease. Thus, Epo serum levels may help in identifying patients with impaired EPC recruitment capacity.     

S1P promotes murine progenitor cell egress and mobilization via S1P1-mediated ROS signaling and SDF-1 release

The mechanisms of hematopoietic progenitor cell egress and clinical mobilization are not fully understood. Herein, we report that in vivo desensitization of Sphingosine-1-phosphate (S1P) receptors by FTY720 as well as disruption of S1P gradient toward the blood, reduced steady state egress of immature progenitors and primitive Sca-1(+)/c-Kit(+)/Lin(-) (SKL) cells via inhibition of SDF-1 release. Administration of AMD3100 or G-CSF to mice with deficiencies in either S1P production or its receptor S1P(1), or pretreated with FTY720, also resulted in reduced stem and progenitor cell mobilization. Mice injected with AMD3100 or G-CSF demonstrated transient increased S1P levels in the blood mediated via mTOR signaling, as well as an elevated rate of immature c-Kit(+)/Lin(-) cells expressing surface S1P(1) in the bone marrow (BM). Importantly, we found that S1P induced SDF-1 secretion from BM stromal cells including Nestin(+) mesenchymal stem cells via reactive oxygen species (ROS) signaling. Moreover, elevated ROS production by hematopoietic progenitor cells is also regulated by S1P. Our findings reveal that the S1P/S1P(1) axis regulates progenitor cell egress and mobilization via activation of ROS signaling on both hematopoietic progenitors and BM stromal cells, and SDF-1 release. The dynamic cross-talk between S1P and SDF-1 integrates BM stromal cells and hematopoeitic progenitor cell motility.     

Insulin modulates ischemia-induced endothelial progenitor cell mobilization and neovascularization in diabetic mice

Decreased levels of circulating endothelial progenitor cells (EPCs) predict increased risk of cardiovascular events in diabetic patients. Insulin treatment exerts important cardiovascular protection. Whether and how insulin participates in the EPC regulation of postnatal neovascularization are currently unclear. We employed a mouse hindlimb ischemia model to study EPC mobilization in non-diabetic and streptozotocin-induced diabetic mice. Insulin was administered to diabetic animals postoperatively. To determine the role of EPCs contributing to postnatal vasculogenesis, we used bone marrow-transplanted mice whose bone marrow cells selectively expressed enhanced green fluorescent protein (EGFP). Insulin treatment improved EPC mobilization into peripheral blood, accelerated transcutaneous oxygen pressure restoration and increased capillary density in the ischemic limb associated with partial incorporation of EGFP-positive cells into the capillaries. Insulin treatment restored ischemia-induced release of stromal-derived growth factor 1α and vascular endothelial growth factor (VEGF), and consequently enhanced the activity of Akt and endothelial nitric oxide synthase (eNOS) as well as matrix metalloproteinase-9 in bone marrow. Insulin also augmented tissue-level activation of VEGF/Akt/eNOS pathway. However, all such effects of insulin were completely blocked by combined treatment with a NOS inhibitor. Our data suggested that insulin treatment improved ischemia-induced EPC mobilization and contributed to compensatory neovascularization in diabetic mice through a VEGF/eNOS-related pathway.     

SDF-1 involvement in endothelial phenotype and ischemia-induced recruitment of bone marrow progenitor cells

Chemokine stromal derived factor 1 (SDF-1) is involved in trafficking of hematopoietic stem cells (HSCs) from the bone marrow (BM) to peripheral blood (PB) and has been found to enhance postischemia angiogenesis. This study was aimed at investigating whether SDF-1 plays a role in differentiation of BM-derived c-kit(+) stem cells into endothelial progenitor cells (EPCs) and in ischemia-induced trafficking of stem cells from PB to ischemic tissues. We found that SDF-1 enhanced EPC number by promoting alpha(2), alpha(4), and alpha(5) integrin-mediated adhesion to fibronectin and collagen I. EPC differentiation was reduced in mitogen-stimulated c-kit(+) cells, while cytokine withdrawal or the overexpression of the cyclin-dependent kinase (CDK) inhibitor p16(INK4) restored such differentiation, suggesting a link between control of cell cycle and EPC differentiation. We also analyzed the time course of SDF-1 expression in a mouse model of hind-limb ischemia. Shortly after femoral artery dissection, plasma SDF-1 levels were up-regulated, while SDF-1 expression in the bone marrow was down-regulated in a timely fashion with the increase in the percentage of PB progenitor cells. An increase in ischemic tissue expression of SDF-1 at RNA and protein level was also observed. Finally, using an in vivo assay such as injection of matrigel plugs, we found that SDF-1 improves formation of tubulelike structures by coinjected c-kit(+) cells. Our findings unravel a function for SDF-1 in increase of EPC number and formation of vascular structures by bone marrow progenitor cells.     

Impaired endothelial progenitor cell mobilization and colony-forming capacity in chronic obstructive pulmonary disease

Background and objective: Recent studies suggest that there is endothelial impairment in both the systemic and pulmonary circulations of patients with COPD. Endothelial progenitor cells (EPC) are mobilized into the circulation by physiological stressors such as surgery, and are thought to play a role in the repair of damaged endothelium. There has been a steady increase in the frequency of surgery among COPD patients, due to the incidence of complications and lung cancer; however, the mobilization of EPC during lung resection has not been examined. We evaluated whether the mobilization and proliferation of EPC are impaired in COPD patients. Methods: The numbers of circulating EPC (CD34/KDR/AC133‐positive mononuclear cells) were measured by flow cytometry, in COPD patients (n = 30) and non‐COPD patients (n = 30) who were undergoing thoracic surgery. EPC colony‐forming units (EPC‐CFU) were also examined. Results: In non‐COPD patients, both circulating EPC and EPC‐CFU were significantly increased 2 h after the operation started, whereas in COPD patients there were no changes in circulating EPC or EPC‐CFU, irrespective of the severity of COPD. Multiple linear regression analysis demonstrated that the presence of COPD was the only significant independent predictor of reduced mobilization of EPC during thoracic surgery. Conclusions: The number of circulating EPC and EPC‐CFU was not increased during thoracic surgery in COPD patients. These results indicate that both the mobilization and proliferative capacity of EPC are severely impaired in COPD patients.     

Irradiation induces homing of donor endothelial progenitor cells in allogeneic hematopoietic stem cell transplantation

Functional abnormalities of the endothelial system may be caused by allogeneic hematopoietic stem cell transplantation (HSCT). The aim of this study is to explore the possibility that endothelial progenitor cells (EPCs) can be used in endothelial repair post-HSCT. EPCs were isolated from mouse bone marrow by density centrifugation and differential adherence. Numbers of endothelial cells (ECs) (CD31⁺CD133⁻CD45⁻), EPCs (CD31⁺CD133⁺–CD45^low/−) and carboxyfluorescein succinimidyl ester (CFSE)-positive cells in peripheral blood, spleen and bone marrow were determined at various time points by flow cytometry. The distribution of labeled EPCs was observed by fluorescence microscopy; morphological alterations of tissues were assessed by light microscopy and transmission electron microscopy. In the irradiated group, the numbers of circulating ECs and EPCs were elevated after pre-conditioning, reaching peaks at days 3 and 5; the counts remained high for about 5 days. In addition, CFSE-labeled cells were visualized in tissue and bone marrow. In conclusion, these results suggest the following: (a) the EPCs derived from mouse bone marrow mononuclear cells express phenotypes characteristic of normal EPCs, (b) irradiation during preconditioning damaged the endothelium, which initiated mobilization of EPCs, and (c) injury to the endothelium also caused extrinsic EPCs home to the damaged tissue.