Early Early Endothelial Progenitor Cells Research Articles

Update on the pathogenesis of Scleroderma: focus on circulating progenitor cells

In systemic sclerosis (SSc), the development of fibrosis seems to be a consequence of the initial ischemic process related to an endothelial injury. The initial trigger event in SSc is still unknown, but circulating progenitor cells (CPCs) might play a key role. Such cells have the ability to traffic into injury sites, exhibiting inflammatory features of macrophages, tissue remodeling properties of fibroblasts, and vasculogenesis functions of endothelial cells. The different subsets of CPCs described thus far in SSc arise from a pool of circulating monocyte precursors (CD14 + cells) and probably correspond to a different degree of differentiation of a single cell of origin. Several subsets of CPCs have been described in patients with SSc, all have a monocytic origin but may or may not express CD14, and all of these cells have the ability to give origin to endothelial cells, or collagen (Col)-producing cells, or both. We were able to identify six subsets of CPCs: pluripotent stem cells (CD14 +, CD45 +, and CD34 +), monocyte-derived multipotential cells (MOMCs) or monocyte-derived mesenchymal progenitors (CD14 +, CD45 +, CD34 +, Col I +, CD11b +, CD68 +, CD105 +, and VEGFR1 +), early endothelial progenitor cells (EPCs) or monocytic pro-angiogenic hematopoietic cells or circulating hematopoietic cells (CD14 +, CD45 +, CD34 low/−, VEGFR2 +/−, CXCR4 +, c-kit +, and DC117 +), late EPCs (CD14 −, CD133 +, VEGFR2 +, CD144 + [VE-cadherin +], and CD146 +), fibroblast-like cells (FLCs)/circulating Col-producing monocytes (CD14 +, CD45 +, CD34 +/−, and Col I +), and fibrocytes (CD14 −, CD45 +, CD34 +, Col I +, and CXCR4 +). It has been demonstrated that circulating CD14 + monocytes with an activated phenotype are increased in patients with SSc when compared with normal subjects. CD14 +, CD34 +, and Col I + spindle-shaped cells have been found in increased numbers in lungs of SSc patients with interstitial lung disease. Elevated blood amounts of early EPCs have been found in patients with SSc by different groups of researchers and such levels correlate directly with the interstitial lung involvement. The prevalence of hematopoietic markers expressed by CPCs that migrate from blood into injury sites in SSc differs and changes according to the degree of differentiation. CXCR4 is the most commonly expressed marker, followed by CD34 and CD45 at an end stage of differentiation. Such difference also indicates a continuous process of cell differentiation that might relate to the SSc clinical phenotype (degree of fibrosis and vascular involvement). A deeper understanding of the role of each subtype of CPCs in the development of the disease will help us to better classify patients in order to offer them targeted approaches in the future.

CILOSTAZOL IMPROVES PROANGIOGENESIS FUNCTIONS IN HUMAN EARLY ENDOTHELIAL PROGENITOR CELLS AND HYBRID THERAPY PROVIDES A SYNERGISTIC EFFECT IN HINDLIMB ISCHAEMIA THROUGH STROMAL CELL-DERIVED FACTOR SYSTEM

The effect of cilostazol on human early endothelial progenitor cells (EPCs) is not well understood. This study aimed at the investigation of the effect of cilostazol on pro-angiogenesis functions in human early EPCs in vitro as well as therapeutic implication of hybrid therapy with cilostazol and

Indoxyl Sulfate Impairs Endothelial Progenitor Cells and Might Contribute to Vascular Dysfunction in Patients with Chronic Kidney Disease

Background/Aims: Indoxyl sulfate (IS) is a protein-bound uremic toxin that accumulates in patients with chronic kidney disease (CKD). We explored the effect of IS on human early endothelial progenitor cells (EPCs) and analyzed the correlation between serum IS levels and parameters of vascular function, including endothelial function in a CKD-based cohort. Methods: A cross-sectional study with 128 stable CKD patients was conducted. Flow-mediated dilation (FMD), pulse wave velocity (PWV), ankle brachial index, serum IS and other biochemical parameters were measured and analyzed. In parallel, the activity of early EPCs was also evaluated after exposure to IS. Results: In human EPCs, a concentration-dependent inhibitory effect of IS on chemotactic motility and colony formation was observed. Additionally, serum IS levels were significantly correlated with CKD stages. The total IS (T-IS) and free IS (F-IS) were strongly associated with age, hypertension, cardiovascular disease, blood pressure, PWV, blood urea nitrogen, creatine and phosphate but negatively correlated with FMD, the estimated glomerular filtration rate (eGFR), hemoglobin, hematocrit, and calcium. A multivariate linear regression analysis also showed that FMD was significantly associated with IS after adjusting for other confounding factors. Conclusions: In humans, IS impairs early EPCs and was strongly correlated with vascular dysfunction. Thus, we speculate that this adverse effect of IS may partly result from the inhibition of early EPCs.

Cilostazol Improves Proangiogenesis Functions in Human Early Endothelial Progenitor Cells through the Stromal Cell-Derived Factor System and Hybrid Therapy Provides a Synergistic Effect In Vivo.

This study investigated the effect of cilostazol on proangiogenesis functions in human early endothelial progenitor cells (EPCs) in vitro and the therapeutic implication of hybrid therapy with cilostazol and human early EPCs in vivo. Cilostazol significantly increased colony-forming units and enhanced differentiation of EPCs toward endothelial lineage. Treatments resulted in antiapoptotic effects and stimulated proliferation and migration and in vitro vascular tube formation through activation of stromal cell-derived factor-1 (SDF-1)/C-X-C chemokine receptor type 4 (CXCR4)/phosphatidylinositol-3 kinase (PI3K)/Akt signaling pathway. Blood flow recovery and capillary density in murine ischemic hindlimbs were significantly improved in cilostazol-treated, human early EPCs-treated, and cotreatment groups. The effects were attenuated with SDF-1α inhibition. Plasma SDF-1α levels were significantly higher in 3 active treatment groups after surgery, with greatest effects observed in hybrid therapy. The angiogenic effects of transplanted EPCs pretreated with cilostazol ex vivo were superior to untreated EPCs using in vivo Matrigel assay. Implanted EPCs were incorporated into the capillary, with pretreatment or cotreatment with cilostazol resulting in enhanced effects. Taken together, cilostazol promotes a large number of proangiogenic functions in human early EPCs through activation of SDF-1/CXCR4/PI3K/Akt signaling, and hybrid therapy provides a synergistic effect in vivo. Cotreatment may be beneficial in ischemic disease.

Pathogenesis of human hemangiosarcomas and hemangiomas

Hemangiosarcomas are uncommon aggressive vascular tumors that have recently become the focus of attention because several chemicals and pharmaceuticals increase their incidence in mice. The relevance of these mouse vascular tumors to humans is unclear. In the present study, we semiquantitatively evaluated the expression profiles of hematopoietic stem cell markers (CD117 [c-kit], CD133, CD34, and CD45), endothelial cell markers (vascular endothelial growth factor receptor 2, CD31, and factor VIII-related antigen), and a myeloid lineage cell marker (CD14) in human hemangiosarcoma (n = 12) and hemangioma (n = 10) specimens using immunohistochemistry. CD133 was completely negative in almost all cases of hemangiosarcomas and hemangiomas. Most hemangiosarcomas, but not hemangiomas, stained for CD117 and CD45. Both groups diffusely expressed CD34, vascular endothelial growth factor receptor 2, and factor VIII-related antigen; however, hemangiomas had more intense and diffuse CD34 and factor VIII-related antigen expression compared with hemangiosarcomas, whereas CD31 was positive in all hemangiosarcomas but only half of the hemangiomas. CD14 staining was negative in most hemangiosarcoma and hemangioma cases. Our results indicate that multipotential bone marrow-derived hematopoietic stem cells or early endothelial progenitor cells (EPCs) expressing CD117, CD34, and CD45 are involved in hemangiosarcoma formation, whereas hemangiomas originate from late EPCs or differentiated endothelial cells, which have lost the expression of most hematopoietic stem cell markers. This contrasts with our previous results that demonstrated that both hemangiosarcomas and hemangiomas in mice may be derived from early EPCs that are not completely differentiated.

Apelin and vascular endothelial growth factor are associated with mobilization of endothelial progenitor cells after acute myocardial infarction

This study was designed to determine the levels of early endothelial progenitor cells (EPCs), apelin, vascular endothelial growth factor (VEGF) and stromal cell-derived growth factor-1 (SDF-1) after acute myocardial infarction (AMI), and to investigate the relationships between these cytokines and early EPCs. Early EPCs, defined as CD133+, KDR+, and CD34+ cells, were quantified by flow cytometry. The levels of early EPCs and those cytokines in AMI patients were significantly different from those with coronary artery disease or controls (P < 0.05). Plasma apelin levels were inversely correlated with Gensini score and early EPCs (both P < 0.01). Early EPCs, VEGF and SDF-1 showed different patterns of changes in AMI patients during the first 24 h. The trend in the change of early EPCs was proportionally correlated with that of VEGF (P < 0.05). AMI patients exhibited increased early EPCs with remarkably decreased apelin levels and enhanced VEGF levels.

Therapeutic Angiogenesis of Human Early Endothelial Progenitor Cells Is Enhanced by Thrombomodulin

We examined the effect of thrombomodulin (TM) domains 2 and 3 (TMD23) on human early endothelial progenitor cells (EPCs). TM was expressed and released by human EPCs cultured from peripheral blood mononuclear cells (PBMCs). Addition of TMD23 (100 ng/mL) to the cultured PBMCs increased the colony-forming units, chemotactic motility, matrix metalloproteinase activity, and interleukin-8 secretion but decreased tumor necrosis factor-α (TNF-α) release. Analysis of the signal pathway showed that TMD23 activated Akt. Inhibition of phosphatidylinositol-3 kinase-Akt blocked the effects of TMD23 on chemotactic motility, matrix metalloproteinase-9, interleukin-8, and TNF-α. In hindlimb ischemia mice, laser Doppler perfusion imaging of the ischemic limb during the 21 days after arterial ligation showed that the perfusion recovered best with intraperitoneal infusion of TMD23 plus local injection of early EPCs, followed by either infusion of TMD23 or injection of the cells. Animals without either treatment had the worst results. Animals treated with TMD23 also had lower circulating and tissue levels of TNF-α. TM is expressed and released by human circulating EPCs. Exogenous TMD23 enhances the angiogenic potential of early EPCs in vitro through activation of phosphatidylinositol-3 kinase-Akt pathway. Coadministration of TMD23 plus early EPCs augments therapeutic angiogenesis of the EPCs in ischemic tissues.

Exercise training improves in vivo endothelial repair capacity of early endothelial progenitor cells in subjects with metabolic syndrome

Endothelial dysfunction and injury are considered to contribute considerably to the development and progression of atherosclerosis. It has been suggested that intense exercise training can increase the number and angiogenic properties of early endothelial progenitor cells (EPCs). However, whether exercise training stimulates the capacity of early EPCs to promote repair of endothelial damage and potential underlying mechanisms remain to be determined. The present study was designed to evaluate the effects of moderate exercise training on in vivo endothelial repair capacity of early EPCs, and their nitric oxide and superoxide production as characterized by electron spin resonance spectroscopy analysis in subjects with metabolic syndrome. Twenty-four subjects with metabolic syndrome were randomized to an 8 weeks exercise training or a control group. Superoxide production and nitric oxide (NO) availability of early EPCs were characterized by using electron spin resonance (ESR) spectroscopy analysis. In vivo endothelial repair capacity of EPCs was examined by transplantation into nude mice with defined carotid endothelial injury. Endothelium-dependent, flow-mediated vasodilation was analysed using high-resolution ultrasound. Importantly, exercise training resulted in a substantially improved in vivo endothelial repair capacity of early EPCs (24.0 vs 12.7%; p < 0.05) and improved endothelium-dependent vasodilation. Nitric oxide production of EPCs was substantially increased after exercise training, but not in the control group. Moreover, exercise training reduced superoxide production of EPCs, which was not observed in the control group. The present study suggests for the first time that moderate exercise training increases nitric oxide production of early endothelial progenitor cells and reduces their superoxide production. Importantly, this is associated with a marked beneficial effect on the in vivo endothelial repair capacity of early EPCs in subjects with metabolic syndrome.

Impaired Endothelial Repair Capacity of Early Endothelial Progenitor Cells in Prehypertension

Prehypertension is a highly frequent condition associated with an increased cardiovascular risk. Endothelial dysfunction is thought to promote the development of hypertension and vascular disease; however, underlying mechanisms remain to be further determined. The present study characterizes for the first time the in vivo endothelial repair capacity of early endothelial progenitor cells (EPCs) in patients with prehypertension/hypertension and examines its relation with endothelial function. Early EPCs were isolated from healthy subjects and newly diagnosed prehypertensive and hypertensive patients (n=52). In vivo endothelial repair capacity of EPCs was examined by transplantation into a nude mouse carotid injury model. EPC senescence was determined (RT-PCR of telomere length). NO and superoxide production of EPCs were measured using electron spin resonance spectroscopy analysis. CD34(+)/KDR(+) mononuclear cells and circulating endothelial microparticles were examined by fluorescence-activated cell sorter analysis. Endothelium-dependent and -independent vasodilations were determined by high-resolution ultrasound. In vivo endothelial repair capacity of EPCs was substantially impaired in prehypertensive/hypertensive patients as compared with healthy subjects (re-endothelialized area: 15+/-3%/13+/-2% versus 28+/-3%; P<0.05 versus healthy subjects). Senescence of EPCs in prehypertension/hypertension was substantially increased, and NO production was markedly reduced. Moreover, reduced endothelial repair capacity of early EPCs was significantly related to an accelerated senescence of early EPCs and impaired endothelial function. The present study demonstrates for the first time that in vivo endothelial repair capacity of early EPCs is reduced in patients with prehypertension and hypertension, is related to EPC senescence and impaired endothelial function, and likely represents an early event in the development of hypertension.

Rationale and design of Enhanced Angiogenic Cell Therapy in Acute Myocardial Infarction (ENACT-AMI): The first randomized placebo-controlled trial of enhanced progenitor cell therapy for acute myocardial infarction

Despite the widespread use of pharmacological and/or interventional reperfusion therapies, recovery of cardiac function in myocardial infarction (MI) patients is often modest or even absent. Unlike classical pharmacological treatments, the use of progenitor cells could potentially restore functional tissue in regions that otherwise would form only scar. However, a major limitation of autologous cell therapy is the deleterious influence of age and cardiac risk factors on progenitor cell activity. The ENACT-AMI trial is a phase IIb, double-blind, randomized placebo-controlled trial, using transplantation of autologous early endothelial progenitor cells (EPCs) for patients who have suffered large MI. Circulating mononuclear cells (MNCs) are obtained by apheresis and subjected to differential culture for 3 days to select a population of highly regenerative, endothelial-like, culture modified MNCs (E-CMMs), often referred to as "early EPCs." A total of 99 patients will be randomized to placebo (Plasma-Lyte A), autologous E-CMMs, or E-CMMs transfected with human endothelial nitric oxide synthase delivered by coronary injection into the infarct-related artery. The primary efficacy end point is change from baseline to 6 months in global left ventricular ejection fraction by cardiac MRI; secondary endpoints include regional wall motion, wall thickening, infarct volume, time to clinical worsening, and quality of life. This will be the first clinical trial to include a strategy designed to enhance the function of autologous progenitor cells by overexpressing endothelial nitric oxide synthase, and the first to use combination gene and cell therapy for the treatment of cardiac disease.

Pleiotrophin induces nitric oxide dependent migration of endothelial progenitor cells

Pleiotrophin (PTN) is produced under ischemic conditions and has been shown to induce angiogenesis in vivo. We studied whether or not PTN exerts chemotaxis of pro-angiogenic early endothelial progenitor cells (EPCs), a population of circulating cells that have been reported to participate in and stimulate angiogenesis. Chemotaxis of EPCs, isolated from blood of healthy humans (n = 5), was measured in transwell assays. PTN at 10-500 ng/ml elicited dose-dependent chemotaxis of both EPCs and human umbilical vein endothelial cells (HUVECs), but not of human coronary artery smooth muscle cells (CASMCs) and T98G glioblastoma cells that lack PTN receptors. The degree of chemotaxis was comparable to that induced by the angiogenic factors VEGF and SDF-1alpha. Chemotaxis to PTN was blocked by the NOS inhibitors L-NNA and L-NMMA, the NO scavenger PTIO, the phosphoinositide-3 kinase inhibitor wortmannin, and the guanylyl cyclase inhibitor ODQ, suggesting dependence of EPC chemotaxis on these pathways. PTN induced NOS-dependent production of NO to a similar degree as did VEGF, as indicated by the NO indicator DAF-2. PTN increased proliferation in EPCs and HUVECs to a similar extent as VEGF, but did not induce proliferation of CASMCs. While L-NNA abolished PTN-induced migration in EPCs and HUVECs, it did not inhibit PTN- and VEGF-enhanced proliferation and also caused proliferation by itself. These data suggest that PTN may mediate its pro-angiogenic effects by increasing the local number of not only endothelial cells but also early EPCs at angiogenic sites.

Identification of a Novel Role of T Cells in Postnatal Vasculogenesis

The colony number of early endothelial progenitor cells (EPCs) has been used as a quantitative indicator of the number of EPCs in the blood or as a biological marker of cardiovascular diseases. In the present study, we found a subset of T cells that were localized at the center of the EPC colony and played a pivotal role in colony formation and differentiation of early EPCs. We found that CD3+ CD31+ CXCR4+ T cells (referred to as angiogenic T cells in the present study) constituted the center of EPC colonies during cultures of human peripheral blood mononuclear cells. These angiogenic T cells were required for colony formation and differentiation of early EPCs. They secreted high levels of angiogenic cytokines such as vascular endothelial growth factor, interleukin-8, and matrix metalloproteinases. Angiogenic T cells showed superior angiogenic potential to the other subset of T cells in the experiments with regard to Matrigel tube formation, adhesion, transendothelial migration, and collagen invasion assay, mainly through the stromal cell-derived factor 1/CXCR-4 axis. Furthermore, angiogenic T cells enhanced endothelial cell proliferation and function. In vivo study showed that angiogenic T cells play an important role in the process of vessel formation. Clinical study showed that the level of angiogenic T cells in the peripheral blood was well correlated with EPC colony numbers and had inverse relationships with age and the number of risk factors for coronary artery disease. These findings suggest that angiogenic T cells could be a potential therapeutic target for ischemic cardiovascular diseases.

Synergistic Neovascularization by Mixed Transplantation of Early Endothelial Progenitor Cells and Late Outgrowth Endothelial Cells

Two types of cells are cultured from the human peripheral blood, early endothelial progenitor cells (EPCs) and outgrowth endothelial cells (OECs), as previously reported. Here, we further characterize these cells, especially with respect to their different origins and functions both in vitro and in vivo. We also investigated whether the combination of these different cell types shows synergism during neovascularization. Early EPCs were heterogeneously made up of both CD14+ monocyte-derived cells, which secrete cytokines, and CD14(-)-derived cells, which contain high levels of (CD34+)KDR+ cells. OECs were cultured almost exclusively from CD14- cells, not CD14+ cells, and were distinct from mature endothelial cells in terms of proliferation potential, KDR+ expression level, and telomerase activity. A portion of cells from CD14- cells and early EPCs produced rapidly proliferating, capillary-forming cells in both the Matrigel plug and the ischemic hind limb similar to OECs. Early EPCs and OECs expressed receptors for vascular endothelial growth factor and interleukin-8, cytokines secreted by early EPCs. There was a differential increase in matrix metalloproteinases (MMPs): MMP-9 in early EPCs and MMP-2 in OECs. In vitro, the angiogenic capability of the 2 cell types was augmented by mutual interaction through cytokines and MMPs. Injection of a mixture of the 2 cells resulted in superior neovascularization in vivo to any single-cell-type transplantation. Distinct origins of the different types of EPCs exist that have different functions in neovascularization. Mixed transplantation of these cells results in synergistic neovascularization through cytokines and MMPs.