Assessing identity, phenotype, and fate of endothelial progenitor cells

Deep partial thickness burn blister fluid promotes neovascularization in the early stage of burn wound healing

The effect of burn blister fluid in neovascularization during burn wound healing is unknown. Burn blister fluid, containing a large amount of chemokines, is thought to play a role in the early stage of neovascularization. This process includes angiogenesis and vasculogenesis. Because of different healing time of burn wounds, we hypothesized that neovascularization in superficial partial thickness burn (SPTB) and deep partial thickness burn (DPTB) wounds were different. The neovasculogenic effects of two different burn blister fluids were also different. We found Day 7 DPTB wounds had a significant increase in blood vessels compared with SPTB wounds by immunohistochemistry. DPTB blister fluid significantly promoted neovascularization via increasing endothelial cell proliferation, and migration and differentiation of circulating angiogenic cells relative to SPTB blister fluids. In the animal study, DPTB blister fluids markedly promoted new blood vessel formation compared with those from SPTB blister fluids using in vivo Matrigel plug assay. These results suggest that DPTB wounds require more new vessel formation than SPTB. Furthermore, the measurement of angiogenic activities in burn blister fluids serves as a possible tool for assessing burn wound status.

Immune privilege of endothelial cells differentiated from endothelial progenitor cells

AIMS

The application of autologous endothelial progenitor cells (EPC) is a promising approach in cardiovascular regeneration, but the availability of cells in appropriate numbers is the limiting factor. Allogeneic EPC would be an alternative, and we therefore analysed the immunogenicity of EPC-derived endothelial cells (EC) to evaluate their potential usefulness.

METHODS AND RESULTS

Circulating EPC from rat were differentiated into EC and characterized phenotypically and functionally. Major histocompatibility complex (MHC) expression in response to interferon-gamma was determined compared with rat aortic EC, and in vitro humoral and cellular allogeneic responses were analysed. To determine the in vivo effects, acellular aortic grafts were endothelialized in vitro with EPC-derived EC and transplanted in a complete allogeneic mismatch rat aortic interposition model. EPC-derived EC expressed endothelial-specific markers and low levels of MHC class I (MHC I), but no constitutive MHC class II (MHC II). When stimulated with interferon-gamma, they upregulated MHC I and moderately upregulated MHC II. They were protected against alloantibody/complement-mediated lysis and allospecific cytotoxic T lymphocyte activity. They were less potent in allogeneic stimulation of CD4 T cells than aortic EC. Seeding of EPC-derived EC into acellular grafts led to excellent endothelialization, and allogeneic aortic transplantation induced only mild inflammatory responses without signs of rejection.

CONCLUSION

EPC-derived EC are protected against allospecific cellular immune responses and humoral-mediated attacks in vitro. When transplanted in vivo as a component of vascular grafts, these cells are not rejected, which makes them useful in therapeutic applications, especially vascular reconstruction.

Allergen-induced, eotaxin-rich, proangiogenic bone marrow progenitors: a blood-borne cellular envoy for lung eosinophilia

BACKGROUND

Eosinophilic inflammation is closely related to angiogenesis in asthmatic airway remodeling. In ovalbumin (OVA)-sensitized mice bone marrow-derived, proangiogenic endothelial progenitor cells (EPCs) are rapidly recruited into the lungs after OVA aerosol challenge and promptly followed by mobilization and recruitment of eosinophils.

OBJECTIVE

We hypothesized that bone marrow-derived EPCs initiate the recruitment of eosinophils through expression of the eosinophil chemoattractant eotaxin-1.

METHODS

EPCs were isolated from an OVA murine model of allergic airway inflammation and from asthmatic patients. Endothelial and smooth muscle cells were isolated from mice. Eotaxin-1 expression was analyzed by means of immunofluorescence, real-time PCR, or ELISA. In vivo recruitment of eosinophils by EPCs was analyzed in mice.

RESULTS

Circulating EPCs of asthmatic patients had higher levels of eotaxin-1 compared with those seen in control subjects. In the murine model OVA allergen exposure augmented eotaxin-1 mRNA and protein levels in EPCs. The EPCs from OVA-sensitized and OVA-challenged mice released high levels of eotaxin-1 on contact with lung endothelial cells from sensitized and challenged mice but not from control animals and not on contact with cardiac or hepatic endothelial cells from sensitized and challenged mice. Intranasal administration of the eotaxin-rich media overlying cultures of EPCs caused recruitment into the lungs, confirming functional chemoattractant activity.

CONCLUSIONS

Bone marrow-derived EPCs are early responders to environmental allergen exposures and initiate a parallel switch to a proangiogenic and proeosinophilic environment in the lungs of asthmatic patients.

Elusive identities and overlapping phenotypes of proangiogenic myeloid cells in tumors

It is now established that bone marrow-derived myeloid cells regulate tumor angiogenesis. This was originally inferred from studies of human tumor biopsies in which a positive correlation was seen between the number of tumor-infiltrating myeloid cells, such as macrophages and neutrophils, and tumor microvessel density. However, unequivocal evidence was only provided once mouse models were used to examine the effects on tumor angiogenesis by genetically or pharmacologically targeting myeloid cells. Since then, identifying the exact myeloid cell types involved in this process has proved challenging because of myeloid cell heterogeneity and the expression of overlapping phenotypic markers in tumors. As a result, investigators often simply refer to them now as "bone marrow-derived myeloid cells." Here we review the findings of various attempts to phenotype the myeloid cells involved and discuss the therapeutic implications of correctly identifying-and thus being able to target-this proangiogenic force in tumors.

Requirement of alpha(4)beta(1) and alpha(5)beta(1) integrin expression in bone-marrow-derived progenitor cells in preventing endotoxin-induced lung vascular injury and edema in mice

The goal of this study was to determine the role of integrin-mediated adhesion of bone-marrow-derived progenitor cells (BMPCs) as a requirement for the endothelial barrier protection in a lung injury model. C57BL mice were used as the source for BMPCs, which were characterized as CD34(+) and fetal liver kinase-1 (Flk1)(+) and also an expression of a repertoire of integrins. We used a mouse model of bacterial lipopolysaccharide (LPS)-induced lung vascular injury and edema formation to test the effects of BMPC integrin expression in preventing endothelial barrier injury. Adhesion of BMPCs to purified extracellular matrix proteins induced focal adhesion kinase (Fak) phosphorylation and formation of branching point structures in a alpha(4) and alpha(5) integrin-dependent manner. BMPCs expressing red fluorescent protein (RFP) were administered via the retro-orbital venous route in mice treated intraperitonially with LPS (7.5 mg/kg body weight). We observed increased retention of RFP-labeled Flk1(+) and CD34(+) BMPCs for up to 8 weeks in mice injured with LPS. BMPC transplantation increased survival by 50% (at 72-96 hours after LPS) and reduced lung vascular injury and extravascular water content induced by LPS. However, blocking with anti-alpha(4) or anti-alpha(5) integrin antibody or shRNA-mediated silencing of alpha(4) or alpha(5) integrins in donor BMPCs failed to prevent the vascular injury or edema formation and mortality. Thus, alpha(4) and alpha(5) integrin-dependent adhesion of BMPCs in lung tissue plays a critical role in preventing lung vascular injury and increasing survival in a mouse model of LPS-induced acute lung injury.

Endothelial progenitor cells are mobilized after major laparotomic surgery in patients with cancer

The progression of cancer is largely dependent on neoangiogenesis. Circulating endothelial progenitor cells (EPC) have the ability to form complete vascular structures in vitro and play a crucial role in tumor vasculogenesis. Emerging evidence suggests that surgical injury may induce the mobilization of EPC in animal models, and this might have a negative effect on the prognosis of cancer patients. We studied 20 patients (10 men, 65+/-13 years) undergoing laparotomy for surgical treatment of various forms of abdominal cancer, and 20 age- and sex-matched healthy control subjects. The number of circulating EPC, defined as CD34+/KDR+ cells identified among mononuclear cells isolated from peripheral venous blood, was determined preoperatively and at days 1 and 2 after surgery. Surgery induced a significant increase in circulating EPC levels at day 1 (from 278/mL, interquartile range 171-334, to 558/mL, interquartile range 423-841, p<0.001) and day 2 (709/mL, interquartile range 355-834, p<0.001)compared with baseline values. EPC levels did not change in control subjects. Seven subjects who underwent laparotomic surgery for non-neoplastic disease also showed an increase in EPC levels after surgery (p=0.009 and p=0.028 at day 1 and day 2, respectively). We conclude that patients undergoing elective laparotomic surgery for cancer demonstrate an increase in EPC post-operatively. The potential adverse effects of surgical stress-induced EPC mobilization on tumor and metastasis growth in cancer patients need to be addressed in future studies.

Exercise acutely reverses dysfunction of circulating angiogenic cells in chronic heart failure

AIMS

Recruitment of endothelial progenitor cells (EPCs) and enhanced activity of circulating angiogenic cells (CACs) might explain the benefits of exercise training in reversing endothelial dysfunction in chronic heart failure (CHF) patients. We studied baseline EPC numbers and CAC function and the effect of a single exercise bout.

METHODS AND RESULTS

Forty-one CHF patients (mild, n = 22; severe, n = 19) and 13 healthy subjects were included. Migratory activity of CACs was evaluated in vitro and circulating CD34+ and CD34+/KDR+ (EPC) cells were quantified by flow cytometry before and after cardiopulmonary exercise testing (CPET). Circulating stromal cell-derived factor-1alpha (SDF-1alpha) and vascular endothelial growth factor (VEGF) concentrations were measured. Both CAC migration as well as CD34+ cell numbers were significantly reduced in CHF, whereas CD34+/KDR+ cells were not different from controls. Endothelial dysfunction was related to impaired CAC migration (r = 0.318, P = 0.023). Cardiopulmonary exercise testing improved CAC migration in severe (+52%, P < 0.005) and mild CHF (+31%, P < 0.005), restoring it to levels similar to controls. Following CPET, SDF-1alpha increased in healthy controls and mild CHF (P < 0.005). Vascular endothelial growth factor, CD34+, and CD34+/KDR+ cell numbers remained unchanged.

CONCLUSION

The present findings reveal a potent stimulus of acute exercise to reverse CAC dysfunction in CHF patients with endothelial dysfunction.

Endothelial colony-forming cell role in neoangiogenesis and tissue repair

PURPOSE OF REVIEW

Patients suffering from vascular disease often have impaired angiogenic ability contributing to impaired tissue repair. One potential therapy is to deliver cells that can aid in angiogenesis. This review will discuss the ability of endothelial progenitor cells (EPCs), which have been reported to contribute to neoangiogenesis in both physiological and pathological conditions, to contribute to neoangiogenesis in tissue repair.

RECENT FINDINGS

In recent years, various reports have described conflicting roles for EPC in vessel formation. Currently there are three different assays for outgrowth of EPC all resulting in the isolation of different cell populations. This confusion is partially due to limited functional characterization of putative EPC populations. One population, endothelial colony-forming cell (ECFC), has been shown to possess all the characteristics of a true endothelial progenitor.

SUMMARY

The review overviews the role of putative EPC populations in angiogenesis and tissue repair. Whereas all EPC populations have been shown to play a role in angiogenesis, only ECFC have demonstrated the ability to form de-novo blood vessels in vivo. Additionally ECFC have been shown to play a role in neovascularization in several preclinical rodent models suggesting that it may be an excellent cell source for treatment of patients with diminished vascular function.

Culture-modified bone marrow cells attenuate cardiac and renal injury in a chronic kidney disease rat model via a novel antifibrotic mechanism

BACKGROUND

Most forms of chronic kidney disease are characterized by progressive renal and cardiac fibrosis leading to dysfunction. Preliminary evidence suggests that various bone marrow-derived cell populations have antifibrotic effects. In exploring the therapeutic potential of bone marrow derived cells in chronic cardio-renal disease, we examined the anti-fibrotic effects of bone marrow-derived culture modified cells (CMCs) and stromal cells (SCs).

METHODOLOGY/PRINCIPAL FINDINGS

In vitro, CMC-conditioned medium, but not SC-conditioned medium, inhibited fibroblast collagen production and cell signalling in response to transforming growth factor-beta. The antifibrotic effects of CMCs and SCs were then evaluated in the 5/6 nephrectomy model of chronic cardio-renal disease. While intravascular infusion of 10(6) SCs had no effect, 10(6) CMCs reduced renal fibrosis compared to saline in the glomeruli (glomerulosclerosis index: 0.8+/-0.1 v 1.9+/-0.2 arbitrary units) and the tubulointersitium (% area type IV collagen: 1.2+/-0.3 v 8.4+/-2.0, p<0.05 for both). Similarly, 10(6) CMCs reduced cardiac fibrosis compared to saline (% area stained with picrosirius red: 3.2+/-0.3 v 5.1+/-0.4, p<0.05), whereas 10(6) SCs had no effect. Structural changes induced by CMC therapy were accompanied by improved function, as reflected by reductions in plasma creatinine (58+/-3 v 81+/-11 micromol/L), urinary protein excretion (9x/divided by 1 v 64x/divided by 1 mg/day), and diastolic cardiac stiffness (left ventricular end-diastolic pressure-volume relationship: 0.030+/-0.003 v 0.058+/-0.011 mm Hg/microL, p<0.05 for all). Despite substantial improvements in structure and function, only rare CMCs were present in the kidney and heart, whereas abundant CMCs were detected in the liver and spleen.

CONCLUSIONS/SIGNIFICANCE

Together, these findings provide the first evidence suggesting that CMCs, but not SCs, exert a protective action in cardio-renal disease and that these effects may be mediated by the secretion of diffusible anti-fibrotic factor(s).

Role of the multidrug resistance protein-1 (MRP1) for endothelial progenitor cell function and survival

The multidrug resistance related protein-1 (MRP1) is a member of the ATP binding cassette (ABC) of cell surface transport proteins expressed in multiple cell lines and tissues including endothelial cells and haematopoietic stem cells. MRP1 blockade has been shown to prevent endothelial cell apoptosis and improve endothelial function. Besides mature endothelial cells vascular homing of endothelial progenitor cells (EPC) contributes to endothelial regeneration after vascular damage. Thus, we hypothesized that MRP1 influences number and function of EPCs and mechanisms of vascular repair. To test this, we investigated the effects of MRP1 inhibition in vitro and in vivo. MRP1 is abundantly expressed in cultured human early outgrowth EPCs. Pharmacological inhibition of MRP1 by MK571 increased intracellular glutathione levels and reduced intracellular reactive oxygen species levels. This stabilization of the intracellular redox homeostasis via inhibition of MRP1 prevented angiotensin II-induced apoptosis and increased the number of early outgrowth EPCs and colony forming units in vitro. To extend the observed cytoprotective effect of MRP1 blockade in EPCs to an in vivo situation, MRP1(-/-) knockout mice were investigated. MRP1(-/-) knockout mice showed significantly increased numbers of EPCs circulating in the peripheral blood and residing in the bone marrow. Consistently, colony forming unit formation was enhanced and rate of apoptosis reduced in early outgrowth EPCs derived from MRP1(-/-) knockout mice. In addition, MRP1(-/-) knockout mice showed improved reendothelialization after carotid artery injury, and transfusion of MNCs derived from MRP1(-/-) knockout mice into wild-type mice accelerated reendothelialization compared to transfusion of wild-type cells. These findings indicate that the enhanced function and survival of EPCs in MRP1(-/-) knockout mice resulted in improved reendothelialization. In conclusion, MRP1 negatively influences EPC function and survival via perturbation of the intracellular redox homeostasis which finally leads to increased cellular apoptosis. These results reveal novel mechanistic insights and may identify MRP1 as therapeutic target to improve reendothelialization after vascular damage.

Effects of obesity and weight loss on the functional properties of early outgrowth endothelial progenitor cells

OBJECTIVES

The purpose of this study was to examine the impact of obesity and weight loss on the angiogenic and regenerative capacity of endothelial progenitor cells (EPCs).

BACKGROUND

EPCs participate in angiogenesis and tissue repair. Several cardiovascular risk factors are associated with EPC dysfunction.

METHODS

Early outgrowth EPCs were isolated from 49 obese (age 42 +/- 14 years; body mass index 42 +/- 7 kg/m(2)) normoglycemic participants in a professional weight reduction program and compared with those from 49 age-matched lean controls. EPC function was tested both in vitro and in vivo.

RESULTS

EPCs expanded from the obese possessed reduced adhesive, migratory, and angiogenic capacity, and mice treated with obese EPCs exhibited reduced EPC homing in ischemic hind limbs in vivo. EPCs from the obese subjects failed to respond to conditioned medium of lean controls or to potent angiogenic factors such as vascular endothelial growth factor. Although no differences existed between lean and obese EPCs regarding the surface expression of vascular endothelial growth factor or chemokine receptors, basal p38 mitogen-activated protein kinase (MAPK) phosphorylation was elevated in obese EPCs (3.7 +/- 2.1-fold increase; p = 0.006). These cells also showed reduced secretion of the angiogenic chemokines interleukin-8 (p = 0.047) and monocyte chemoattractant protein-1 (p = 0.012). By inhibiting p38 MAPK, we could restore chemokine levels to those of lean control EPCs and also improve the angiogenic properties of obese EPCs. Accordingly, 6-month follow-up of 26 obese persons who achieved significant weight reduction revealed normalization of p38 MAPK phosphorylation levels and improved EPC function.

CONCLUSIONS

Obesity is associated with a reversible functional impairment of EPCs. This involves reduced secretion of angiogenic chemokines and increased basal phosphorylation of signaling molecules, notably p38 MAPK.

Endothelial precursors in vascular repair

The endothelium is an essential component of the cardiovascular system, playing a vital role in blood vessel formation, vascular homeostasis, permeability and the regulation of inflammation. The integrity of the endothelial monolayer is also critical in the prevention of atherogenesis and as such, restoration of the monolayer is essential following damage or cell death. Over the past decade, data has suggested that progenitor cells from different origins within the body are released into the circulation and contribute to re-endothelialisation. These cells, termed endothelial progenitor cells (EPCs), also gave rise to the theory of new vessel formation within adults (vasculogenesis) without proliferation and migration of mature endothelial cells (angiogenesis). As such, intense research has been carried out identifying how these cells may be mobilised and contribute to vascular repair, either encouraging vasculogenesis into regions of ischemia or the re-endothelialisation of vessels with a dysfunctional endothelium. However, classification and isolation procedures have been a major problem in this area of research and beneficial use for therapeutic application has been controversial. In the present review we focus on the role of EPCs in vascular repair. We also provide an update on EPC classification and discuss autologous stem cell-derived endothelial cell (EC) as a functional source for therapy.

Endothelial progenitor cells: what use for the cardiologist?

Endothelial Progenitor Cells (EPC) were first described in 1997 and have since been the subject of numerous investigative studies exploring the potential of these cells in the process of cardiovascular damage and repair. Whilst their exact definition and mechanism of action remains unclear, they are directly influenced by different cardiovascular risk factors and have a definite role to play in defining cardiovascular risk. Furthermore, EPCs may have important therapeutic implications and further understanding of their pathophysiology has enabled us to explore new possibilities in the management of cardiovascular disease. This review article aims to provide an overview of the vast literature on EPCs in relation to clinical cardiology.

Circulating endothelial progenitor cells do not contribute to plaque endothelium in murine atherosclerosis

BACKGROUND

It has been reported that circulating endothelial progenitor cells (EPCs) home to and differentiate into endothelial cells after various kinds of arterial injury. By inference, EPCs are also proposed to be important in the most important arterial disease, atherosclerosis, but the evidence for this theory is not clear. In the present study, we assessed the contribution of circulating EPCs to plaque endothelium in apolipoprotein E-deficient (apoE(-/-)) mice.

METHODS AND RESULTS

To investigate whether EPCs in the circulating blood are a source of plaque endothelial cells during atherogenesis, we examined plaques in lethally irradiated apoE(-/-) mice reconstituted with bone marrow cells from enhanced green fluorescent protein (eGFP) transgenic apoE(-/-) mice and plaques induced in segments of common carotid artery transplanted from apoE(-/-) mice into eGFP(+)apoE(-/-) mice. Among 4232 endothelial cells identified by a cell-type-specific marker (von Willebrand factor) and analyzed by high-resolution microscopy, we found only 1 eGFP(+). Using the Y chromosome to track cells after sex-mismatched transplants yielded similar results. To investigate whether circulating EPCs are involved in plaque reendothelialization after plaque disruption and superimposed thrombosis, we produced mechanical plaque disruptions in carotid bifurcation plaques in old lethally irradiated apoE(-/-) mice reconstituted with eGFP(+)apoE(-/-) bone marrow cells and carotid bifurcation plaques transplanted from old apoE(-/-) mice into eGFP(+)apoE(-/-) mice. Only 1 eGFP(+) endothelial cell was found among 3170 analyzed.

CONCLUSIONS

Circulating EPCs rarely, if ever, contribute to plaque endothelium in apoE(-/-) mice. These findings bring into question the prevailing theory that circulating EPCs play an important role in atherogenesis.

Troubleshooting: Quantification of mobilization of progenitor cell subsets from bone marrow in vivo

INTRODUCTION

The molecular mechanisms that control the mobilization of specific stem cell subsets from the bone marrow are currently being intensely investigated. It is anticipated that boosting the mobilization of these stem cells via pharmacological intervention will not only produce more effective strategies for bone marrow transplant patients, but also provide novel therapeutic approaches for tissue regeneration.

METHODS

Measurement of stem cell mobilization by sampling peripheral blood is problematic because it is technically difficult to accurately determine absolute numbers of rare progenitor cells by blood sampling. Furthermore a rise in progenitors may be caused by release of stem cells from tissues other than the bone marrow (e.g. spleen and adipose), or indeed an inhibition of stem cell homing back to the bone marrow or other tissues. Finally it is not possible to distinguish whether the pharmacological agent is acting directly at the level of the bone marrow or mobilizing progenitors by a distinct indirect mechanism. To resolve these problems, we have developed a technique that allows perfusion of the vasculature of the hind limb bone marrow in situ in mice. In this system, the femoral artery and vein are cannulated in situ such that the femur and tibia bone marrow are perfused in isolation under anaesthesia. As such, pharmacological agents can be administered directly into the bone marrow vasculature. Mobilized cells are then collected via the femoral vein and colony assays performed in defined growth media to allow identification of haematopoietic, endothelial, and mesenchymal progenitor cells. We have used this system to determine the ability of a CXCR4 antagonist to mobilize these distinct types of progenitor cells from the bone marrow of mice pre-conditioned with either G-CSF or VEGF.

RESULTS AND CONCLUSION

This isolated hind limb perfusion system has allowed comparisons to be made between cytokines (G-CSF and VEGF) that act chronically, either alone or in combination with agents that act acutely on the bone marrow (CXCR4 antagonist) on their ability to directly mobilize specific populations of stem cells. Data obtained therefore gives a more accurate understanding of the efficacy of different mobilizing strategies compared to peripheral blood analysis.

Comparison between Culture Conditions Improving Growth and Differentiation of Blood and Bone Marrow Cells Committed to the Endothelial Cell Lineage

The aim of this study was to compare different cell sources and culture conditions to obtain endothelial progenitor cells (EPCs) with predictable antigen pattern, proliferation potential and in vitro vasculogenesis. Pig mononuclear cells were isolated from blood (PBMCs) and bone marrow (BMMCs). Mesenchymal stem cells (MSCs) were also derived from pig bone marrow. Cells were cultured on fibronectin in the presence of a high concentration of VEGF and low IGF-1 and FGF-2 levels, or on gelatin with a lower amount of VEGF and higher IGF-1 and FGF-2 concentrations. Endothelial commitment was relieved in almost all PBMCs and BMMCs irrespective of the protocol used, whilst MSCs did not express a reliable pattern of EPC markers under these conditions. BMMCs were more prone to expand on gelatin and showed a better viability than PBMCs. Moreover, about 90% of the BMMCs pre-cultured on gelatin could adhere to a hyaluronan-based scaffold and proliferate on it up to 3 days. Pre-treatment of BMMCs on fibronectin generated well-shaped tubular structures on Matrigel, whilst BMMCs exposed to the gelatin culture condition were less prone to form vessel-like structures. MSCs formed rough tubule-like structures, irrespective of the differentiating condition used. In a relative short time, pig BMMCs could be expanded on gelatin better than PBMCs, in the presence of a low amount of VEGF. BMMCs could better specialize for capillary formation in the presence of fibronectin and an elevated concentration of VEGF, whilst pig MSCs anyway showed a limited capability to differentiate into the endothelial cell lineage.

Optical characterization of colloidal CdSe quantum dots in endothelial progenitor cells

We have quantitatively analyzed the confocal spectra of colloidal quantum dots (QDs) in rat endothelial progenitor cells (EPCs) by using Leica TCS SP5 Confocal Microscopy System. Comparison of the confocal spectra of QDs located inside and outside EPCs revealed that the interaction between the QDs and EPCs effectively reduces the radius of the exciton confinement inside the QDs so that the excitonic energy increases and the QD fluorescence peak blueshifts. Furthermore, the EPC environment surrounding the QDs shields the QDs so that the excitation of the QDs inside the cells is relatively weak, whereas the QDs outside the cells can be highly excited. At high excitations, the occupation of the ground excitonic state in the QD outside the cells becomes saturated and high-energy states excited, resulting in a large relaxation energy and a broad fluorescence peak. This permits, in concept, to use QD biomarkers to monitor EPCs by characterizing QD fluorescence spectra.

Dual role of parathyroid hormone in endothelial progenitor cells and marrow stromal mesenchymal stem cells

Hematopoietic stem cells derive regulatory information also from parathyroid hormone (PTH). To explore the possibility that PTH may have a role in regulation of other stem cells residing in bone marrow, such as mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) we assessed the effect of this hormone on the in vitro behavior of MSCs and EPCs. We evidenced that MSCs were much more responsive to PTH than EPCs. PTH increased the proliferation rate of MSCs with a diminution of senescence and apoptosis. Taken together, our results may suggest a protective effect of PTH on MSCs that reduces stress phenomena and preserve genome integrity. At the opposite, PTH did not modify the fate of EPCs in culture.

Comparison of endothelial cell phenotypic markers of late-outgrowth endothelial progenitor cells isolated from patients with coronary artery disease and healthy volunteers

The lack of easily isolated autologous endothelial cell (EC) sources is one of the major challenges with vascular tissue engineering interventions. This article examines the isolation and expansion of late-outgrowth endothelial progenitor cells (EPCs) from 50-mL samples of peripheral blood drawn from patients with significant coronary artery disease (CAD) and healthy young adult volunteers. In cases in which late-outgrowth EPCs were successfully isolated, the cells were assayed in vitro for their expression of EC markers, proliferation potential and ability to endothelialize synthetic materials, form new blood vessels, and produce nitric oxide. Late-outgrowth EPCs from patients with CAD and healthy volunteers exhibited critical EC markers and morphological characteristics that were analogous to a control population of human aortic ECs. To our knowledge, this is the first study to examine the suitability of late-outgrowth EPCs from patients with CAD for autologous endothelialization applications.

CD133+ circulating haematopoietic progenitor cells predict for response to sorafenib plus erlotinib in non-small cell lung cancer patients

BACKGROUND

Blood-based biomarkers may be particularly useful for patient selection and prediction of treatment response for angiogenesis inhibitors. Circulating endothelial cells (CECs) and haematopoietic progenitor cells (HPCs) might have a role in tumour angiogenesis and in tumour growth. Measurement of CECs and HPCs in the blood of patients could be a simple, non-invasive way to monitor or predict responses to treatment.

METHODS

(VEGFR2(+)) CECs(,) (CD133(+)) HPCs, plasma vascular endothelial growth factor (VEGF) and erythropoietin were measured in blood from 25 non-small cell lung cancer (NSCLC) patients before and during treatment with sorafenib plus erlotinib (SO/ER). In order to assess the drug specificity of changes in CECs and HPCs, 18 patients treated with bevacizumab plus erlotinib (BV/ER) and 10 patients with erlotinib (ER) monotherapy were studied. Response was measured in all patient groups by Response Evaluation Criteria in Solid Tumors (RECIST).

RESULTS

At day 7, SO/ER-treated patients showed a three-fold increase in CECs (P<0.0001) comparable to BV/ER-treated patients (P<0.01), and the CECs did not change with erlotinib treatment (P=0.8). At day 7, CD133(+)/HPCs decreased with SO/ER treatment (P<0.0001). HPC numbers did not change with either BV/ER or erlotinib. In SO/ER-treated patients pre-treatment CD133(+)/HPCs were significantly lower in responders (P=0.01) and pre-treatment CD133(+)/HPC numbers lower than the median correlated with a longer time-to-progression (TTP) (P=0.037).

CONCLUSION

Pre-treatment CD133(+)/HPCs are a promising candidate biomarker to further explore for use in selecting NSCLC patients who might benefit from SO/ER treatment.

Endothelial-regenerating cells: an expanding universe

Atherosclerosis is the most common cause for cardiovascular diseases and is based on endothelial dysfunction. A growing body of evidence suggests the contribution of bone marrow-derived endothelial progenitor cells, monocytic cells, and mature endothelial cells to vessel formation and endothelial rejuvenation. To this day, various subsets of these endothelial-regenerating cells have been identified according to cellular origin, phenotype, and properties in vivo and in vitro. However, the definition and biology, especially of endothelial progenitor cells, is complex and under heavy debate. In this review, we focus on current definitions of endothelial progenitor cells, highlight the clinical relevance of endothelial-regenerating cells, and provide new insights into cell-cell interactions involved in endothelial cell rejuvenation.

Cord blood-derived early outgrowth endothelial progenitor cells

The presence of circulating endothelial repopulating cells in the adult human peripheral blood has been proposed since long time ago. In the late 1990s, the putative endothelial progenitor cells (EPCs) were first identified and reported by Asahara and co-workers. Since then, a number of studies have demonstrated that these cells are derived from bone marrow and induce microvascular vasculogenesis and re-endothelialization of injured vessels. Meantime, human umbilical cord blood also gained much attention for the reason of possible additional source to obtain EPCs since cord blood has been shown to contain more number of active hematopoietic stem cells as compared to adult peripheral blood. This review summarizes the aspect of human cord blood-derived EPCs with special focuses into their identity and future clinical application.

An optimized flow cytometry protocol for analysis of angiogenic monocytes and endothelial progenitor cells in peripheral blood

Circulating adult CD34(+)VEGFR2(+) endothelial progenitor cells (EPCs) have been shown to differentiate into endothelial cells, thus contributing to vascular homeostasis. Furthermore, a subset of circulating CD14(+) monocytes coexpresses CD16 together with the angiopoietin receptor Tie2 and has been functionally implicated in tumor angiogenesis. However, clinically applicable protocols for flow cytometric quantification of EPCs and Tie2(+) monocytes in peripheral blood and a consensus on reference values remain elusive. The number of Tie2(+)CD14(+)CD16(mid) angiogenic monocytes and CD34(+)VEGFR2(+)CD45(low/-) EPCs was assessed in the peripheral venous blood of patients with stable coronary artery disease by three-color flow cytometry using specific monoclonal antibodies conjugated to PerCP, PE, PE-Cy7, APC, and APC-Cy7. Scatter multigating with exclusion of dead cells was performed to dissect complex mononuclear cell populations. This analysis was further refined by matching bright fluorochromes (PE-Cy7, PE, APC) with dimly expressed markers (CD34, VEGFR2, Tie2), by automatic compensation for minimizing fluorescence spillover and by using fluorescence-minus-one (FMO) controls to determine positive/negative boundaries. Presuming a Gaussian distribution, we obtained average values (mean +/- SD) of 1.45 +/- 1.29% for Tie2(+)CD14(+)CD16(mid) monocytes (n = 11, range: 0.12-3.64%) and 0.019 +/- 0.013% for CD34(+)VEGFR2(+)CD45(low/-) EPCs (n = 17, range: 0.003-0.042%). The intra- and inter-assay variability was 1.6% and 4.5%, respectively. We have optimized a fast and sensitive assay for the flow cytometric quantification of circulating angiogenic monocytes and EPCs in cardiovascular medicine. This protocol may represent a basis for standardized analysis and monitoring of these cell subsets to define their normal range and prognostic/diagnostic value in clinical use.

Mechanisms and markers of vascular damage in ANCA-associated vasculitis

Much progress has been made in understanding the pathogenesis of anti-neutrophil cytoplasmic antibodies (ANCA)-associated small-vessel vasculitis and interaction between ANCA and micro-vascular endothelial cells are centre stage. The interactions of these key players culminate in respiratory burst of the neutrophil with release of radicals and proteases and subsequent endothelial cell and tissue damage. During the last decade, markers have become available to assess the extent and/or acuity of vascular damage in a clinical setting. First, circulating endothelial cells (CEC) have emerged as reliable surrogate markers of endothelial damage in vasculitis. More recently, endothelial microparticles have been used and appear to reflect damage and activation of the cells. Data on endothelial progenitor cells in vasculitis are sparse but intriguing while a genuine progenitor cell deficiency remains controversial. The severely damaged phenotype of CEC in vasculitis led to the hypothesis that such circulating apoptotic and/or necrotic debris may itself be a mediator of disease and first data from experimental studies have added proof to this assumption. Such effects may well contribute to a pro-inflammatory environment in ANCA-associated small-vessel vasculitis and in vascular disease in general. Here, we review mechanisms and markers of endothelial damage and repair in ANCA-associated vasculitis and put these findings into perspective.

Endothelial progenitor cells in vascular health: focus on lifestyle

Endothelial dysfunction, which is considered the functional equivalent of a disrupted balance between endothelial injury and repair, precedes overt atherosclerosis by many years. Although this phenomenon is part of the normal aging process, prevention of early and progressive endothelial dysfunction has become an important therapeutic target. Evidence has accumulated to show that endothelial progenitor cells (EPC), contribute substantially to preservation of a structurally and functionally intact endothelium. There has been considerable progress in our understanding of the various cell types that were in the past all covered by the term "EPC." EPC home to sites of endothelial injury and ischemia, where they proliferate, differentiate and integrate into the endothelial layer or exert a paracrine function by producing vascular growth factors. Although more emphasis has been put on the pharmacological approach of endothelial dysfunction, the effect of a healthy lifestyle, via mobilization and functional improvement of EPC, is increasingly recognized. This review will focus on successful lifestyle interventions that aim to maintain vascular health through beneficial actions on cell populations with vasculogenic potential ("EPC"). The role of physical activity and dietary recommendations, which are considered essential elements of a healthy lifestyle, will be particularly emphasized. A thorough understanding of the physiology of endothelial benefits, derived from such interventions, may help to implement these measures on top of classical drug therapy, but also provides a solid basis for primary prevention. The effects of additional elements of a comprehensive lifestyle advice, such as smoking cessation, weight and stress reduction, also comprise a modulation of EPC function and circulating numbers and are therefore included in this review as well.

Soluble CD40 ligand impairs the function of peripheral blood angiogenic outgrowth cells and increases neointimal formation after arterial injury

BACKGROUND

Recent work has revealed an essential involvement of soluble CD40 ligand (sCD40L) in inflammation and atherosclerosis. We investigated whether sCD40L functionally affects peripheral blood-derived angiogenic early outgrowth cells (EOCs) and neointimal remodeling after arterial injury.

METHODS AND RESULTS

Besides myeloid and endothelial markers, cultured human EOCs strongly expressed CD40 mRNA and protein. EOC adhesion to fibronectin, fibrinogen, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 under flow conditions, as well as their transmigration toward stromal cell-derived factor-1alpha, was dose-dependently reduced after preincubation with recombinant human sCD40L for 24 hours. Integrin expression was unaffected by sCD40L, implying that integrin adhesiveness was attenuated. Surface-immobilized CD40L supported much lower adhesion of EOCs than fibronectin. Treatment of EOCs with sCD40L increased superoxide anion production and decreased viability and proliferation. Notably, CD40(-/-) mice displayed reduced neointima and improved re-endothelialization after carotid wire injury compared with wild-type mice, and therapeutic infusion of control EOCs but not EOCs pretreated with sCD40L attenuated neointimal growth after wire injury in nude mice. Furthermore, neointimal growth was more markedly diminished by infusion of spleen-derived CD40(-/-) mouse EOCs than by that of wild-type EOCs. Preincubation of wild-type EOCs but not CD40(-/-) EOCs with sCD40L before their infusion markedly aggravated neointimal formation. Treatment with sCD40L attenuated luminal incorporation of EOCs and accelerated neointimal progression.

CONCLUSIONS

Endothelial dysfunction due to persistently elevated plasma levels of sCD40L may be attributable to an impairment of EOC function. Hence, in the context of arterial injury, therapeutic blockade of sCD40L may provide a novel strategy for accelerating endothelial regeneration and attenuating neointimal remodeling.

Bone regeneration: the stem/progenitor cells point of view

After bone injuries, several molecular mechanisms establish bone repair from stem/progenitor cells. Inflammation factors attract regenerative cells which expand and differentiate in order to build up a bone highly similar to that before injury. Bone marrow (BM) mesenchymal stem cells (MSCs) as skeletal stem cells and endothelial progenitors (EPCs) are at the origin of such reparation mechanisms. However, discrepancies exist about their identities. Although cultured MSCs are extensively described, their in vivo native forms are poorly known. In addition, recent experiments show that several types of EPC exist. We therefore review up-to-date data on the characterization of such stem/progenitor cells and propose a new point of view of their function in bone regeneration.

Cross-Linking Enhances Deposition of Human Endothelial Progenitor Cells in the Rat Heart after Intracoronary Transplantation

Transplantation of human endothelial progenitor cells (hEPCs) may improve vascularization and left ventricular function after myocardial infarction. The scope of this study was to explore, whether cross-linking of EPCs may enhance the deposition of cells in the rat heart after clinical-like, intracoronary transplantation. To this end, 111In-oxinate-labeled hEPCs were infused by a minimally invasive technique into the coronary arteries of immunosuppressed Wistar rats under control conditions and after ischemia/reperfusion. In a second set of experiments hEPCs were treated with phytohemagglutinin to create small cell clusters prior to transplantation. Continous three-dimensional HiSPECT images for 1 h and after 48 h revealed that cell deposition was significantly higher when hEPCs were cross-linked. Therefore, cross-linking of hEPCs may provide a promising approach to enhance the number of trapped cells also in a clinical setting.

Aging decreases expression and activity of glutathione peroxidase-1 in human endothelial progenitor cells

The mechanisms underlying effects of aging on functions of pro-angiogenic endothelial progenitor cells (EPCs) are poorly understood. Previous studies demonstrated that human EPCs express high levels of antioxidant enzymes as compared to mature endothelial cells. Here, we hypothesized that aging impairs antioxidant capacity of EPCs. So called "early EPCs" derived from cultured blood mononuclear cells were obtained from healthy young (average=24 years old) and old (average=72 years old) subjects. In EPCs of old subjects, the levels of glutathione peroxidase-1 (GPX1) protein and enzymatic activity were significantly reduced. The serum selenium levels in young and old subjects were not significantly different. Increasing selenium concentration in the cell culture also did not affect the protein levels of GPX1, suggesting the reduced GPX1 in old subject's EPCs is selenium independent. Expressions of catalase, Mn-superoxide dismutase (MnSOD), and CuZnSOD were not affected by aging. EPCs of old subjects were more sensitive to oxidative stress induced by H(2)O(2) as compared with EPCs of young subjects, suggesting that impairment of GPX1 during aging may contribute to low survival ability of EPCs in response to oxidative stress. The results indicate that GPX1 may represent a potential therapeutic target for enhancement of regenerative capacity of EPCs in old subjects.

Heterogeneity of atherosclerosis in mesenteric arteries and outgrowth remodeling

BACKGROUND

In patients with acute mesenteric ischemia by occlusive thrombo-embolism, the superior mesenteric artery (SMA) is more affected than the inferior mesenteric artery (IMA).

METHODS

This study investigated postmortem mesenteric arteries from aged subjects (n=21). Four atherosclerotic stages were defined by signs of degeneration and inflammation in sections stained with Elastica-van-Gieson and immunohistology, respectively.

RESULTS

In females and males, Stages 3 and 4 were found in 62% of the SMA and 24% of the IMA. Lumenal areas based on diameter measurements remained essentially unchanged between Stages 1 and 4. Compared to a Stage 1 reference, remodeling was associated with thinning of the media below the plaque base and with pronounced thickening below the shoulder in the IMA. In Stages 3 and 4, the adventitia of the IMA had more vasa vasorum and a higher number of CD45-positive leukocytes than the adventitia of the SMA. During atherosclerotic progression, a stable fraction of leukocytes represented mast cells (6%) and CD117-positive cells as potential progenitor cells (1%).

CONCLUSIONS

Outgrowth remodeling occurred in both the SMA and the IMA. Less severe atherosclerosis in the IMA than in the SMA was associated with stronger signs of inflammation.

Stem cell-related therapies for vascular diseases

The therapeutic potential of 'adult' or at least non-embryonic stem cells and their progeny has developed gradually over the past half century as a consequence of the wealth of knowledge derived from stem cell research. Translational research coupled with clinical trials and derived from basic research has led the way to the clinic. This commenced with the use of haematopoietic stem cell transplantation (HSCT), to treat haematological malignancies, to be followed by the most recent clinical trials to treat a variety of coronary and peripheral artery diseases. Stem cells and their progeny isolated from bone marrow or blood appear to exert an ameliorating effect in certain vascular disorders. Although promising, some of these treatments remain controversial and further research and, where indicated, appropriately powered trials are required to confirm the safety and determine the efficacy of these novel therapies.

Leptin enhances the potency of circulating angiogenic cells via src kinase and integrin (alpha)vbeta5: implications for angiogenesis in human obesity

OBJECTIVE

To investigate the capacity of the adipokine leptin to promote angiogenesis by modulating the function of circulating angiogenic cells (CACs).

METHODS AND RESULTS

In vitro, leptin specifically promoted CAC adhesion to tubular endothelial structures and migration along outgrowing sprouts of endothelial cells. In vivo, stimulation of CACs with leptin increased their capacity to promote new vessel formation in the chorioallantoic membrane of chicken embryos and to improve neovascularization of ischemic murine hind limbs. These effects required the phosphorylation of alphavbeta5 integrins, which depended on the interaction of leptin with its receptor ObR, and on Janus kinase (JAK) 2- and phospholipase C (PLC) gamma-mediated activation of Src kinase. Protein tyrosine phosphatase 1B, a negative regulator of leptin signaling, was overexpressed in CACs from obese, hyperleptinemic individuals, and this was associated with insensitivity of CACs to the angiogenic effects of leptin. Weight loss (by 30+/-15 kg) normalized protein tyrosine phosphatase 1B expression in CACs and restored their responsiveness to leptin. A similar dose-dependent response was found after incubation of CACs from obese subjects with a protein tyrosine phosphatase 1B inhibitor ex vivo.

CONCLUSIONS

Our results point to the ObR-Src kinase-alphavbeta5 cross talk as a distinct novel component of the network of specific interactions between integrins and cytokine receptors in angiogenesis.

Endothelial progenitor cells and cardiovascular cell-based therapies

Since their initial discovery more than a decade ago, bone marrow (BM)-derived circulating endothelial progenitor cells (EPC) have been reported to play a role in postnatal vasculogenesis through vessel regeneration and remodeling. These cells have been reported to mobilize into the blood stream in response to vascular injury, and differentiate into cells expressing a host of endothelial cell (EC) markers in vitro. Because of demonstrable regenerative capacity in animal models of human disease, EPC are thought to represent a novel treatment option for problematic cardiovascular conditions such as myocardial infarction (MI) and peripheral vascular disease (PVD). Various studies have been performed to test the clinical efficacy of EPC in patients with cardiovascular disease (CVD), including the mobilization of EPC with pharmacologic agents in patients with heart disease, and harvesting of cells from the circulation and BM for autologous reinfusion in affected patients. The outcomes of these trials have been mixed and not as robust as predicted from the animal models, partly because of the variation in the definition of human EPC and the resulting heterogeneity in cell populations used in the treatments. This review will decipher a number of published studies that have been conducted to examine cell therapies for treatment of CVD, will attempt to explain why efficacy of treatment with putative EPC has been inconsistent, and predict which aspects of these trials may need to be redesigned for future successful treatment of CVD.

Functional alterations of myeloid cell subsets in hyperlipidaemia: relevance for atherosclerosis

Atherosclerosis is a chronic inflammatory disease wherein the infiltration of myeloid cells of the vessel wall is a hallmark event. Lymphocytes, platelets and endothelial cells stand out as prominent suspects being involved in atherosclerosis. However, recent advances suggest a crucial role for myeloid leucocytes, specifically monocyte subsets, neutrophils, dendritic cells and endothelial progenitor cells. These cell types are not just rapidly recruited or already reside in the vascular wall, but also initiate and perpetuate core mechanisms in plaque formation and destabilization. Hyperlipidaemia is an independent risk factor for atherosclerosis. Herein, hyperlipidaemia skews myeloid cell haemostasis, phenotype and transcriptional regulation of pro-inflammatory factors ultimately promoting myeloid cell extravasation and atherosclerosis. We here review the role of myeloid cells in atherosclerosis as well as the effects of hyperlipidaemia on these cells.

Role of endothelial progenitor cells in diabetes mellitus

Endothelial progenitor cells (EPCs) are bone marrow-derived cells involved in endothelial healing and angiogenesis. EPCs are considered an integrated component of the cardiovascular system, which promotes vascular health. Derangement of EPC biology in diabetes has been hailed as a novel concept in the pathogenesis of micro- and macro-vascular complications. Additionally, EPCs are considered to be disease biomarkers, as they provide an index of cardiovascular risk. The mechanisms leading to EPC dysfunction in diabetes may include defective mobilization from bone marrow to peripheral blood and reduced half-life. Hyperglycemia is considered the major determinant of microvascular complications, while other mechanisms concur to increase the risk of cardiovascular disease in diabetic patients. EPCs may represent a novel pathophysiological connection to understand development and progression of diabetic complications.

Nitric oxide and superoxide dismutase modulate endothelial progenitor cell function in type 2 diabetes mellitus

BACKGROUND

The function of endothelial progenitor cells (EPCs), which are key cells in vascular repair, is impaired in diabetes mellitus. Nitric oxide (NO) and reactive oxygen species can regulate EPC functions. EPCs tolerate oxidative stress by upregulating superoxide dismutase (SOD), the enzyme that neutralizes superoxide anion (O2-). Therefore, we investigated the roles of NO and SOD in glucose-stressed EPCs.

METHODS

The functions of circulating EPCs from patients with type 2 diabetes were compared to those from healthy individuals. Healthy EPCs were glucose-stressed, and then treated with insulin and/or SOD. We assessed O2- generation, NO production, SOD activity, and their ability to form colonies.

RESULTS

EPCs from diabetic patients generated more O2-, had higher NAD(P)H oxidase and SOD activity, but lower NO bioavailability, and expressed higher mRNA and protein levels of p22-phox, and manganese SOD and copper/zinc SOD than those from the healthy individuals. Plasma glucose and HbA1c levels in the diabetic patients were correlated negatively with the NO production from their EPCs. SOD treatment of glucose-stressed EPCs attenuated O2- generation, restored NO production, and partially restored their ability to form colonies. Insulin treatment of glucose-stressed EPCs increased NO production, but did not change O2- generation and their ability to form colonies. However, their ability to produce NO and to form colonies was fully restored after combined SOD and insulin treatment.

CONCLUSION

Our data provide evidence that SOD may play an essential role in EPCs, and emphasize the important role of antioxidant therapy in type 2 diabetic patients.

Acute lung injury but not sepsis is associated with increased colony formation by peripheral blood mononuclear cells

Acute lung injury (ALI) and severe sepsis are common critical illnesses associated with the mobilization of bone marrow-derived cells into the circulation. By identifying and determining these cells' functional characteristics, unique prognostic biomarkers can be developed to help investigators understand the mechanisms underlying the pathophysiology of these disorders. We previously demonstrated an increased colony-forming unit (CFU) ability of circulating peripheral blood mononuclear cells (PBMCs) in patients with ALI, compared with healthy control subjects, that also correlated with improved survival. Here we hypothesized that the increased CFUs in ALI are associated with lung injury, and therefore ALI will result in an increased number of CFUs compared with patients exhibiting severe sepsis. To test this, blood was collected from 80 patients (63 with ALI, and 17 with severe sepsis) within 72 hours of diagnosis, and from 5 healthy control subjects. A CFU assay was performed on isolated PBMCs. Lung injury scores and the need for mechanical ventilation were greater in patients with ALI than in patients with severe sepsis (P < 0.0001 for each). CFU numbers were highest in patients with ALI compared with patients manifesting severe sepsis or control subjects (median CFU number [25-75% quartiles] of 61 [13-104] versus 17 [3-34] versus 5 [2-13], P < 0.0005). A trend toward improved survival was demonstrated in patients with high (> or = 48) CFUs (P = 0.06). No relationship between CFUs and mechanical ventilation was evident. Our findings suggest that increased colony-forming ability by PBMCs in ALI results from lung injury, independent of sepsis and mechanical ventilation. Factors contributing to colony formation by PBMCs in ALI, and the role PBMCs play in its pathogenesis remain to be fully established.

Circulating endothelial cells and circulating progenitor cells in breast cancer: relationship to endothelial damage/dysfunction/apoptosis, clinicopathologic factors, and the Nottingham Prognostic Index

BACKGROUND AND METHODS

Abnormal circulating endothelial cell (CEC) and circulating progenitor cell (CPC) numbers are present in cancer, but their relationship with angiogenesis, apoptosis, vascular biology, and prognosis is unclear. We prospectively studied 160 patients with breast cancer and 63 age-matched controls free of breast cancer, measuring CECs (CD45(-)/CD146(+)/CD34(+)) and CPCs (CD45(-)/CD133(+)/CD34(+)) by flow cytometry and plasma markers of endothelial damage/dysfunction (von Willebrand factor), apoptosis (Fas/Fas-L) and angiogenesis (vascular endothelial growth factor [VEGF], angiogenin) by ELISA. These were compared with clinicopathophysiologic features and the Nottingham Prognostic Index (NPI). An additional blood sample was taken 6 to 8 weeks after surgery from 15 women to test the effect of tumor removal.

RESULTS

CECs were significantly higher in the NPI poor prognostic group compared with moderate and good prognostic groups, and the cancer-free controls, whereas CPCs were lower in the poor prognosis group (both P < .05). Levels of von Willebrand factor, VEGF, angiogenin, and Fas-L (but not soluble Fas) were abnormal in breast cancer compared with controls (P < .05), with no relationship to prognosis groups. VEGF (P = .04) and angiogenin (P = .001) were markedly different after surgery. In multivariate analysis, vascular invasion (P < .05) and tumor size (P < .001) were independently associated with CECs. CPCs did not significantly associate with NPI in a linear regression model; age (P < .05) was a negative predictor, whereas Her-2 status (P < .05) positively predicted CPCs. After adjustment, no variable independently predicted CPC levels.

CONCLUSIONS

CECs and CPCs demonstrate a strong relationship with NPI groups, but only CECs positively predict higher NPI scores and correlate with tumor invasiveness and size, possibly reflecting total tumor vascular volume.

Future of cord blood for non-oncology uses

For the last 5 years cord blood (CB) has been under intense experimental investigation in in vitro differentiation models and in preclinical animal models ranging from bone to muscle regeneration, cardiovascular diseases including myocardial and peripheral arterial disease, stroke and Parkinson's disease. On the basis of its biological advantages, CB can be an ideal source for tissue regeneration. However, in the hype of the so-called 'plasticity', many cell types have been characterized either on cell surface Ag expression alone or by RNA expression only, and without detailed characterization of genetic pathways; frequently, cells are defined without analysis of cellular function in vitro and in vivo, and the definition of the lineage of origin and cells have not been defined in preclinical studies. Here, we explore not only the most consistent data with regard to differentiation of CB cells in vitro and in vivo, but also show technical limitations, such as why in contrast to cell populations isolated from fresh CB, cryopreserved CB is not the ideal source for tissue regeneration. By taking advantage of numerous CB units discarded due to lack of sufficient hematopoietic cells for clinical transplantation, new concepts to produce off-the-shelf products are presented as well.

[Perspectives of regenerative mechanisms in cardiovascular disease spotlighting endothelial progenitor cells]

Cardiovascular diseases are the most common cause of death in the Western world. In general, the underlying disease is atherosclerosis, which is hallmarked by deterioration of the endothelial monolayer. Restoration of an intact endothelial monolayer for prevention and therapy of cardiovascular diseases is one key concept of regenerative medicine. This article offers a review of state-of-the-art regenerative mechanisms in cardiovascular disease spotlighting endothelial progenitor cells, and further features the perspectives of regenerative medicine in vascular biology.

Platelet MPs obscure some EPC definitions

The cell surface phenotype used to define an EPC, in one commonly used in vitro assay, may arise from an uptake of contaminating platelet MPs by cultured mononuclear cells, resulting in a gross misinterpretation of the assay results.