Human endothelial progenitor cells

Endothelial progenitor cells as a biological marker of peripheral artery disease

The role of endothelial progenitor cells (EPCs) in peripheral artery disease (PAD) remains unclear. We hypothesized that EPC mobilization and function play a central role in the development of endothelial dysfunction and directly influence the degree of atherosclerotic burden in peripheral artery vessels. The number of circulating EPCs, defined as CD34(+)/KDR(+) cells, were assessed by flow cytometry in 91 subjects classified according to a predefined sample size of 31 non-diabetic PAD patients, 30 diabetic PAD patients, and 30 healthy volunteers. Both PAD groups had undergone endovascular treatment in the past. As a functional parameter, EPC colony-forming units were determined ex vivo. Apart from a broad laboratory analysis, a series of clinical measures using the ankle-brachial index (ABI), flow-mediated dilatation (FMD) and carotid intima-media thickness (cIMT) were investigated. A significant reduction of EPC counts and proliferation indices in both PAD groups compared to healthy subjects were observed. Low EPC number and pathological findings in the clinical assessment were strongly correlated to the group allocation. Multivariate statistical analysis revealed these findings to be independent predictors of disease appearance. Linear regression analysis showed the ABI to be a predictor of circulating EPC number (p=0.02). Moreover, the functionality of EPCs was correlated by linear regression (p=0.017) to cIMT. The influence of diabetes mellitus on EPCs in our study has to be considered marginal in already disease-affected patients. This study demonstrated that EPCs could predict the prevalence and severity of symptomatic PAD, with ABI as the determinant of the state of EPC populations in disease-affected groups.

Poly(ethylene glycol) Hydrogel Scaffolds Containing Cell-Adhesive and Protease-Sensitive Peptides Support Microvessel Formation by Endothelial Progenitor Cells

The development of stable, functional microvessels remains an important obstacle to overcome for tissue engineered organs and treatment of ischemia. Endothelial progenitor cells (EPCs) are a promising cell source for vascular tissue engineering as they are readily obtainable and carry the potential to differentiate towards all endothelial phenotypes. The aim of this study was to investigate the ability of human umbilical cord blood-derived EPCs to form vessel-like structures within a tissue engineering scaffold material, a cell-adhesive and proteolytically degradable poly(ethylene glycol) (PEG) hydrogel. EPCs in co-culture with angiogenic mural cells were encapsulated in hydrogel scaffolds by mixing with polymeric precursors and using a mild photocrosslinking process to form hydrogels with homogeneously dispersed cells. EPCs formed 3D microvessels networks that were stable for at least 30 days in culture, without the need for supplemental angiogenic growth factors. These 3D EPC microvessels displayed aspects of physiological microvasculature with lumen formation, expression of endothelial cell proteins (connexin 32, VE-cadherin, eNOS), basement membrane formation with collagen IV and laminin, perivascular investment of PDGFR-β and α-SMA positive cells, and EPC quiescence (<1% proliferating cells) by 2 weeks of co-culture. Our findings demonstrate the development of a novel, reductionist system that is well-defined and reproducible for studying progenitor cell-driven microvessel formation.

Dysregulation of VEGF-induced proangiogenic Ca2+ oscillations in primary myelofibrosis-derived endothelial colony-forming cells

Endothelial progenitor cells could be implicated in the aberrant neoangiogenesis that occurs in bone marrow and spleen in patients with primary myelofibrosis (PMF). However, antivascular endothelial growth factor (VEGF) monotherapy had only a modest and transient effect in these individuals. Recently it was found that VEGF-induced proangiogenic intracellular Ca(2+) oscillations could be impaired in endothelial progenitor cells of subjects with malignancies. Therefore, we employed Ca(2+) imaging, wavelet analysis, and functional assays to assess whether and how VEGF-induced Ca(2+) oscillations are altered in PMF-derived endothelial progenitor cells. We focused on endothelial colony-forming cells (ECFCs), which are the only endothelial progenitor cell subtype capable of forming neovessels both in vivo and in vitro. VEGF triggers repetitive Ca(2+) spikes in both normal ECFCs (N-ECFCs) and ECFCs obtained from PMF patients (PMF-ECFCs). However, the spiking response to VEGF is significantly weaker in PMF-ECFCs. VEGF-elicited Ca(2+) oscillations are patterned by the interaction between inositol-1,4,5-trisphosphate-dependent Ca(2+) mobilization and store-operated Ca(2+) entry. However, in most PMF-ECFCs, Ca(2+) oscillations are triggered by a store-independent Ca(2+) entry pathway. We found that diacylglycerol gates transient receptor potential canonical 1 channel to trigger VEGF-dependent Ca(2+) spikes by recruiting the phospholipase C/inositol-1,4,5-trisphosphate signaling pathway, reflected as a decrease in endoplasmic reticulum Ca(2+) content. Finally, we found that, apart from being less robust and dysregulated as compared with N-ECFCs, VEGF-induced Ca(2+) oscillations modestly stimulate PMF-ECFC growth and in vitro angiogenesis. These results may explain the modest effect of anti-VEGF therapies in PMF.

Impaired function of endothelial progenitor cells in children with primary systemic vasculitis

INTRODUCTION

Previously, we demonstrated that children with active systemic vasculitis (SV) have higher circulating CD34 + CD133 + KDR+ endothelial progenitor cells (EPC); the function of these EPCs, and their relationship with disease activity in vasculitis remains largely unexplored. We hypothesized that although EPC numbers are higher, EPC function is impaired in active SV of the young. The aims of this study were therefore to: 1. investigate the relationship between disease activity and EPC function in children with SV; and 2. study the influence of systemic inflammation on EPC function by investigating the effects of hyperthermia and TNF-α on EPC function.

METHODS

We performed a cross-sectional study of unselected children with SV with different levels of disease activity attending a single center (Great Ormond Street Hospital, London) between October 2008 and December 2014. EPCs were isolated from peripheral blood of children with SV, and healthy child controls. EPC function was assessed by their potential to form colonies (EPC-CFU), and ability to form clusters and incorporate into human umbilical vein endothelial cell (HUVEC) vascular structures in matrigel. The effects of hyperthermia and TNF-α on EPC function were also studied.

RESULTS

Twenty children, median age 12-years (5-16.5; nine males) were studied. EPC-CFU and the number of EPC clusters formed on matrigel were significantly reduced in children with active vasculitis compared with healthy controls (p = 0.02 for EPC-CFU; p = 0.01 for EPC cluster formation). Those with active vasculitis had lower EPC-CFU and EPC cluster formation than those with inactive disease, although non-significantly so. In addition, EPC incorporation into matrigel HUVEC networks was lower in children with SV compared with healthy children, irrespective of disease activity. Ex-vivo pre-treatment of EPC with hyperthermia impaired EPC function; TNF-α down-regulated EPC expression of CD18/CD11b and resulted in decreased incorporation into HUVEC networks.

CONCLUSIONS

Whilst our previous work showed that circulating CD34 + EPC numbers are well preserved, this study revealed that EPC function is significantly impaired in children with vasculitis. It is possible that the chronic inflammatory milieu associated with vasculitis may impair EPC function, and thus contribute to an unfavourable balance between endothelial injury and repair. The mechanism of this remains to be established, however.

Tailoring biomaterial surface properties to modulate host-implant interactions: implication in cardiovascular and bone therapy

Host body response to a foreign medical device plays a critical role in defining its fate post implantation. It is thus important to control host-material interactions by designing innovative implant surfaces. In the recent years, biochemical and topographical features have been explored as main target to produce this new type of bioinert or bioresponsive implants. The review discusses specific biofunctional materials and strategies to achieve a precise control over implant surface properties and presents possible solutions to develop next generation of implants, particularly in the fields of bone and cardiovascular therapy.

Cellular connections, microenvironment and brain angiogenesis in diabetes: Lost communication signals in the post-stroke period

Diabetes not only increases the risk but also worsens the motor and cognitive recovery after stroke, which is the leading cause of disability worldwide. Repair after stroke requires coordinated communication among various cell types in the central nervous system as well as circulating cells. Vascular restoration is critical for the enhancement of neurogenesis and neuroplasticity. Given that vascular disease is a major component of all complications associated with diabetes including stroke, this review will focus on cellular communications that are important for vascular restoration in the context of diabetes. This article is part of a Special Issue entitled SI: Cell Interactions In Stroke.

Stem cell therapies in the treatment of diabetic retinopathy and keratopathy

Nonproliferative diabetic retinopathy (DR) is characterized by multiple degenerative changes that could be potentially corrected by stem cell therapies. Most studies so far have attempted to alleviate typical abnormalities of early retinopathy, including vascular hyperpermeability, capillary closure and pericyte dropout. Success was reported with adult stem cells (vascular progenitors or adipose stem cells), as well as induced pluripotent stem cells from cord blood. The cells were able to associate with damaged vessels in both pericyte and endothelial lining positions in models of DR and ischemia-reperfusion. In some diabetic models, functional amelioration of vasculature and electroretinograms was noted. Another approach for endogenous progenitor cell therapy is to normalize dysfunctional diabetic bone marrow and residing endothelial progenitors using NO donors, PPAR-δ and -γ agonists, or inhibition of TGF-β. A potentially important strategy would be to reduce neuropathy by stem cell inoculations, either naïve (e.g., paracrine-acting adipose stem cells) or secreting specific neuroprotectants, such as ciliary neurotrophic factor or brain-derived neurotrophic factor that showed benefit in amyotrophic lateral sclerosis and Parkinson's disease. Recent advances in stem cell therapies for diabetic retinal microangiopathy may form the basis of first clinical trials in the near future. Additionally, stem cell therapies may prove beneficial for diabetic corneal disease (diabetic keratopathy) with pronounced epithelial stem cell dysfunction.

The role of adult tissue-derived stem cells in chronic leg ulcers: a systematic review focused on tissue regeneration medicine

Wound healing is an articulated process that can be impaired in different steps in chronic wounds. Chronic leg ulcers are a special type of non-healing wounds that represent an important cause of morbidity and public cost in western countries. Because of their common recurrence after conventional managements and increasing prevalence due to an ageing population, newer approaches are needed. Over the last decade, the research has been focused on innovative treatment strategies, including stem-cell-based therapies. After the initial interest in embryonic pluripotent cells, several different types of adult stem cells have been studied because of ethical issues. Specific types of adult stem cells have shown a high potentiality in tissue healing, in both in vitro and in vivo studies. Aim of this review is to clearly report the newest insights on tissue regeneration medicine, with particular regard for chronic leg ulcers.

Heart valve tissue engineering: how far is the bedside from the bench?

Heart disease, including valve pathologies, is the leading cause of death worldwide. Despite the progress made thanks to improving transplantation techniques, a perfect valve substitute has not yet been developed: once a diseased valve is replaced with current technologies, the newly implanted valve still needs to be changed some time in the future. This situation is particularly dramatic in the case of children and young adults, because of the necessity of valve growth during the patient's life. Our review focuses on the current status of heart valve (HV) therapy and the challenges that must be solved in the development of new approaches based on tissue engineering. Scientists and physicians have proposed tissue-engineered heart valves (TEHVs) as the most promising solution for HV replacement, especially given that they can help to avoid thrombosis, structural deterioration and xenoinfections. Lastly, TEHVs might also serve as a model for studying human valve development and pathologies.

Determination of Early and Late Endothelial Progenitor Cells in Peripheral Circulation and Their Clinical Association with Coronary Artery Disease

The clinical implications of early and late endothelial progenitor cells (EPCs) in coronary artery disease (CAD) remain unclear. We investigated endothelial dysfunction in CAD by simultaneously examining early and late EPC colony formation and gene expression of specific surface markers in EPCs. EPCs were extracted from a total of 83 subjects with (n = 47) and without (n = 36) CAD. Early and late EPC colonies were formed from mononuclear cells extracted from peripheral blood. We found that fewer early EPC colonies were produced in the CAD group (7.2 ± 3.l/well) than those in the control group (12.4 ± 1.4/well, p < 0.05), and more late EPC colonies were produced in the CAD group (0.8 ± 0.2/well) than those in the control group (0.25 ± 0.02/well, p < 0.05). In the CAD group, the relative expression of CD31 and KDR of early and late EPCs was lower than in the control group. These results demonstrate that CAD patients could have increased late EPC density and that early and late EPCs in CAD patients exhibited immature endothelial characteristics. We suggest that changes in EPC colony count and gene expression of endothelial markers may have relation with development of CAD.

The development of depressive symptoms during medical internship stress predicts worsening vascular function

OBJECTIVE

We sought to prospectively determine whether the onset of internship stress and any subsequent depression alters physiological markers of early vascular disease

METHODS

We explored potential mechanisms linking stress and depression to vascular disease in a prospective cohort of 37 participants exposed to medical internship stress, an established precipitant of depressive symptomatology.

RESULTS

Change in depressive symptom score from baseline over one year of internship stress was inversely correlated with change in the reactive hyperemia index (RHI), a measure of peripheral endothelial function (r=0.41, p=0.01). The change in depressive symptoms in the first six months of internship was similarly related to change in RHI over one year (r=0.38, p=0.02). While the development of depressive symptoms did not significantly impact changes in endothelial progenitor cells (EPCs), EPCs did significantly decrease with the year of internship stress (11.9 to 3.4cells/ml blood; p=0.01).

CONCLUSION

Endothelial function may be a critical link between stress, depression, and cardiovascular disease and a feasible surrogate outcome for prospective studies.

A Pilot Study of Circulating Endothelial and Hematopoietic Progenitor Cells in Children With Sarcomas

Utilizing a multiparametric flow cytometry protocol, we assessed various cell types implicated in tumor angiogenesis that were found circulating in the peripheral blood of children with sarcomas (cases) based on their cell surface antigen expression. Circulating endothelial cells (CECs), endothelial colony-forming cells (ECFCs), and the ratio of 2 distinct populations of circulating hematopoietic stem and progenitor cells (CHSPCs), the proangiogenic CHSPCs (pCHSPCs) and nonangiogenic CHSPCs (nCHSPCs) were enumerated. Multiparametric flow cytometry was analyzed in cases at baseline and at 4 additional timepoints until the end of treatment and levels compared with each other and with healthy controls. At all timepoints, cases had significantly lower levels of CECs, but elevated ECFCs and a pCHSPC:nCHSPC ratio compared with controls (all P-values <0.05). There was no significant difference in any of the cell types analyzed based on tumor histology, stage (localized vs. metastatic), or tumor size. After treatment, only the CECs among the complete responders were significantly lower at end of therapy (P<0.01) compared with nonresponders, whereas the ECFCs among all cases significantly increased (P<0.05) compared with baseline. No decline in the pCHSPC:nCHSPC ratio was observed despite tumor response. On the basis of these results, a validation of CECs as prognostic biomarker is now warranted.

Endothelial NO-Synthase Gene-Enhanced Progenitor Cell Therapy for Pulmonary Arterial Hypertension: The PHACeT Trial

RATIONALE

Pulmonary arterial hypertension (PAH) remains a progressive and eventually lethal disease characterized by increased pulmonary vascular resistance because of loss of functional lung microvasculature, primarily at the distal (intracinar) arteriolar level. Cell-based therapies offer the potential to repair and regenerate the lung microcirculation and have shown promise in preclinical evaluation in experimental models of PAH.

OBJECTIVE

The Pulmonary Hypertension and Angiogenic Cell Therapy (PHACeT) trial was a phase 1, dose-escalating clinical study of the tolerability of culture-derived endothelial progenitor cells, transiently transfected with endothelial nitric oxide synthase, in patients with PAH refractory to PAH-specific therapies.

METHODS AND RESULTS

Seven to 50 million endothelial nitric oxide synthase-transfected endothelial progenitor cells, divided into 3 doses on consecutive days, were delivered into the right atrium via a multiport pulmonary artery catheter during continuous hemodynamic monitoring in an intensive care unit setting. Seven patients (5 women) received treatment from December 2006 to March 2010. Cell infusion was well tolerated, with no evidence of short-term hemodynamic deterioration; rather, there was a trend toward improvement in total pulmonary resistance during the 3-day delivery period. However, there was 1 serious adverse event (death) which occurred immediately after discharge in a patient with severe, end stage disease. Although there were no sustained hemodynamic improvements at 3 months, 6-minute walk distance was significantly increased at 1, 3, and 6 months.

CONCLUSION

Delivery of endothelial progenitor cells overexpressing endothelial nitric oxide synthase was tolerated hemodynamically in patients with PAH. Furthermore, there was evidence of short-term hemodynamic improvement, associated with long-term benefits in functional and quality of life assessments. However, future studies are needed to further establish the efficacy of this therapy.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00469027.

Dysfunctional endothelial progenitor cells in cardiovascular diseases: role of NADPH oxidase

Endothelial progenitor cells (EPCs) play a critical role in maintenance of the endothelial integrity and vascular homeostasis, as well as in neovascularization. Dysfunctional EPCs are believed to contribute to the endothelial dysfunction and are closely related to the development of various cardiovascular diseases, such as hypertension, hyperlipidemia, and stroke. However, the underlying mechanisms of EPC dysfunction are complicated and remain largely elusive. Recent studies have demonstrated that reactive oxygen species (ROS) are key factors that involve in modulation of stem and progenitor cell function under various physiologic and pathologic conditions. It has been shown that NADPH oxidase (NOX)-derived ROS are the major sources of ROS in cardiovascular system. Accumulating evidence suggests that NOX-mediated oxidative stress can modulate EPC bioactivities, such as mobilization, migration, and neovascularization, and that inhibition of NOX has been shown to improve EPC functions. This review summarized recent progress in the studies on the correlation between NOX-mediated EPC dysfunction and cardiovascular diseases.

Histone Demethylases KDM4A and KDM4C Regulate Differentiation of Embryonic Stem Cells to Endothelial Cells

Understanding epigenetic mechanisms regulating embryonic stem cell (ESC) differentiation to endothelial cells may lead to increased efficiency of generation of vessel wall endothelial cells needed for vascular engineering. Here we demonstrated that the histone demethylases KDM4A and KDM4C played an indispensable but independent role in mediating the expression of fetal liver kinase (Flk)1 and VE-cadherin, respectively, and thereby the transition of mouse ESCs (mESCs) to endothelial cells. KDM4A was shown to bind to histones associated with the Flk1 promoter and KDM4C to bind to histones associated with the VE-cadherin promoter. KDM4A and KDM4C were also both required for capillary tube formation and vasculogenesis in mice. We observed in zebrafish that KDM4A depletion induced more severe vasculogenesis defects than KDM4C depletion, reflecting the early involvement of KDM4A in specifying endothelial cell fate. These findings together demonstrate the essential role of KDM4A and KDM4C in orchestrating mESC differentiation to endothelial cells through the activation of Flk1 and VE-cadherin promoters, respectively.

Healing arterial ulcers: Endothelial lining regeneration upon vascular denudation injury

Thrombosis and restenosis are the most prevalent late complications of coronary artery stenting. Current standards of clinical care focus on prevention of smooth muscle cell proliferation by the use of drug-eluting stents able to release anti-proliferative drugs. Unfortunately, these drugs also block endothelial cell proliferation and, in this manner, prevent recovery of endothelial cell coverage. Continued lack of endothelial repair leaves the root cause of thrombosis and restenosis unchanged, creating a vicious cycle where drug-mediated prevention of restenosis simultaneously implies promotion of thrombosis. In this issue of Vascular Pharmacology, Hussner and colleagues provide in vitro evidence and a mechanistic basis for the use of atorvastatin in stents as a way to bypass this roadblock. Here we review the pathological mechanisms and therapeutic approaches to restore flow in occluded arteries. We argue that rational design of drug eluting stents should focus on specific inhibition of smooth muscle cell proliferation with concurrent stimulation of endothelial regeneration. We comment on the current poor understanding of the cellular and molecular regulation of endothelial cell proliferation in the context of a functional artery, and on the pitfalls of extrapolating from the well-studied process of neovascularization by sprouting vessel formation.

Scarring, stem cells, scaffolds and skin repair

The treatment of full thickness skin loss, which can be extensive in the case of large burns, continues to represent a challenging clinical entity. This is due to an on-going inability to produce a suitable tissue engineered substrate that can satisfactorily replicate the epidermal and dermal in vivo niches to fulfil both aesthetic and functional demands. The current gold standard treatment of autologous skin grafting is inadequate because of poor textural durability, scarring and associated contracture, and because of a paucity of donor sites in larger burns. Tissue engineering has seen exponential growth in recent years with a number of 'off-the-shelf' dermal and epidermal substitutes now available. Each has its own limitations. In this review, we examine normal wound repair in relation to stem/progenitor cells that are intimately involved in this process within the dermal niche. Endothelial precursors, in particular, are examined closely and their phenotype, morphology and enrichment from multiple sources are described in an attempt to provide some clarity regarding the controversy surrounding their classification and role in vasculogenesis. We also review the role of the next generation of cellularized scaffolds and smart biomaterials that attempt to improve the revascularisation of artificial grafts, the rate of wound healing and the final cosmetic and functional outcome.

Resistin Promotes Angiogenesis in Endothelial Progenitor Cells Through Inhibition of MicroRNA206: Potential Implications for Rheumatoid Arthritis

Endothelial progenitor cells (EPCs) promote angiogenesis and are therefore key contributors to a wide variety of angiogenesis-related autoimmune diseases such as rheumatoid arthritis (RA). However, the signaling mechanisms through which these progenitor cells influence RA pathogenesis remain unknown. The aim of this study was to examine whether resistin plays a role in the pathogenesis of and angiogenesis associated with RA by circulating EPCs. We found that levels of resistin in synovial fluid and tissue from patients with RA and from mice with collagen-induced arthritis were overexpressed and promoted the homing of EPCs into the synovium, thereby inducing angiogenesis. EPCs isolated from healthy donors were used to investigate the signal transduction pathway underlying EPC migration and tube formation after treatment with resistin. We found that resistin directly induced a significant increase in expression of vascular endothelial growth factor (VEGF) in EPCs. We also found that the expression of microRNA-206 (miR-206) was negatively correlated with the expression of resistin during EPC-mediated angiogenesis. Notably, the increased expression of VEGF was associated with decreased binding of miR-206 to the VEGF-A 3' untranslated region through protein kinase C delta-dependent AMP-activated protein kinase signaling pathway. Moreover, blockade of resistin reduced EPC homing into synovial fluid and angiogenesis in vivo. Taken together, our study is the first to demonstrate that resistin promotes EPCs homing into the synovium during RA angiogenesis via a signal transduction pathway that involves VEGF expression in primary EPCs. These findings provide support for resistin as a therapeutic target for the patients with RA. Stem Cells 2015;33:2243-2255.

Growth differentiation factor 11 supports migration and sprouting of endothelial progenitor cells

BACKGROUND

Neovascularization plays an important role in tissue engineering applications. In animal models, it was demonstrated that implantation of endothelial progenitor cells (EPCs) from cord blood led to the formation of a complex functional neovasculature, whereas EPCs isolated from peripheral blood (pbEPCs) showed a limited vasculogenic potential, which may be attributed to age-related dysfunction. Growth differentiation factor 11 (GDF11) was recently identified as a rejuvenation factor, which was able to reverse age-related dysfunction of stem cells. Therefore, we hypothesized that GDF11 may improve the vasculogenesis-related phenotype of pbEPCs.

MATERIALS AND METHODS

pbEPCs were isolated from adult peripheral blood. Transforming growth factor (TGF)-β type-I receptor expression was analyzed by immunostaining. pbEPCs were treated with recombinant GDF11 for various time periods. Thereafter, phosphorylation of Smad2/Smad3, adhesion, proliferation, cell survival, migration, and in vitro sprout formation was investigated.

RESULTS

pbEPCs express the TGF-β type-I receptors ALK4 and ALK5, but not ALK7. Treatment of pbEPCs with recombinant GDF11 resulted in activation of the Smad2/Smad3 pathway and in increased migration, which was inhibited by the TGF-β1 superfamily type-I activin receptor-like kinase inhibitor SB431542, demonstrating that the TGF-β receptor-Smad2/Smad3 pathway is involved in GDF11 induced migration. Moreover, in vitro sprout formation was increased as well by GDF11 treatment. However, other parameters such as adherence, proliferation, and apoptosis were not affected by GDF11.

CONCLUSIONS

This study provides evidence that GDF11 improves vasculogenesis-related growth parameters in pbEPCs and may represent a therapeutic option to ameliorate the angiogenic and vasculogenic properties of pbEPCs.

Interleukin-3 greatly expands non-adherent endothelial forming cells with pro-angiogenic properties

Circulating endothelial progenitor cells (EPCs) provide revascularisation for cardiovascular disease and the expansion of these cells opens up the possibility of their use as a cell therapy. Herein we show that interleukin-3 (IL3) strongly expands a population of human non-adherent endothelial forming cells (EXnaEFCs) with low immunogenicity as well as pro-angiogenic capabilities in vivo, making their therapeutic utilisation a realistic option. Non-adherent CD133(+) EFCs isolated from human umbilical cord blood and cultured under different conditions were maximally expanded by day 12 in the presence of IL3 at which time a 350-fold increase in cell number was obtained. Cell surface marker phenotyping confirmed expression of the hematopoietic progenitor cell markers CD133, CD117 and CD34, vascular cell markers VEGFR2 and CD31, dim expression of CD45 and absence of myeloid markers CD14 and CD11b. Functional experiments revealed that EXnaEFCs exhibited classical properties of endothelial cells (ECs), namely binding of Ulex europaeus lectin, up-take of acetylated-low density lipoprotein and contribution to EC tube formation in vitro. These EXnaEFCs demonstrated a pro-angiogenic phenotype within two independent in vivo rodent models. Firstly, a Matrigel plug assay showed increased vascularisation in mice. Secondly, a rat model of acute myocardial infarction demonstrated reduced heart damage as determined by lower levels of serum creatinine and a modest increase in heart functionality. Taken together, these studies show IL3 as a potent growth factor for human CD133(+) cell expansion with clear pro-angiogenic properties (in vitro and in vivo) and thus may provide clinical utility for humans in the future.

Mobilization of circulating progenitor cells following brain injury in premature neonates could be indicative of an endogenous repair process. A pilot study

BACKGROUND

Preclinical data and adult studies have showed an endogenous regeneration process following brain damage that involves mobilization of progenitor cells. This process is not well described in preterm neonates. The present study aims to investigate the mobilization of Circulating Progenitor Cells (CPCs) and their relation to biomarkers of brain injury in preterm neonates.

METHODS

This is a prospective cohort study of preterm infants with gestational age (GA) <34 weeks. Serial cranial ultrasounds scans were performed in all neonates. Brain injury was defined by the presence of intraventricular hemorrhage grade III/IV, cystic periventricular leukomalacia or infarct. Peripheral blood samples were collected from all neonates on days(d) 1, 3, 9, 18 and 45 of life for the measurement of levels of CPCs [early and late Endothelial Progenitor Cells (EPCs), Haematopoietic Stem Cells (HSCs) and Very Small Embryonic-Like Stem Cells (VSELs)], Neuron-Specific Enolase (NSE), S100b, Erythropoietin (EPO) and Stromal Cell-Derived Factor-1 (SDF-1) .

RESULTS

Ten out of the 23 preterm infants included in the study developed brain injury; the remaining thirteen infants served as controls. In the brain injury group a significant increase of HSCs (d9, d45), early EPCs (d3, d9, d18) and late EPCs (d1, d3, d9, d18, d45) was observed compared to controls. VSELs on d45 were significantly higher in controls. S100b on d1, EPO on d1, SDF-1 on d3 and NSE on d18 were significantly increased in the brain injury group. Moreover, CPCs were significantly related to S100b, NSE, EPO and SDF-1 levels at multiple time points.

CONCLUSIONS

The observed pattern of CPCs mobilization and its association with biomarkers following brain injury in preterm neonates indicate the existence of an endogenous brain regeneration process. Enhancement of this process with exogenous progenitor cell transplantation might be a powerful therapeutic strategy to restore brain damage and improve the neurodevelopmental outcome in premature infants. Hippokratia 2015; 19 (2):141-147.

Research on potential biomarkers in hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is a genetically heterogeneous disorder, involving mutations in two predominant genes known as Endoglin (ENG; HHT1) and activin receptor-like kinase 1 (ACVRL1/ALK1; HHT2), as well as in some less frequent genes, such as MADH4/SMAD4 (JP-HHT) or BMP9/GDF2 (HHT5). The diagnosis of HHT patients currently remains at the clinical level, according to the “Curaçao criteria,” whereas the molecular diagnosis is used to confirm or rule out suspected HHT cases, especially when a well characterized index case is present in the family or in an isolated population. Unfortunately, many suspected patients do not present a clear HHT diagnosis or do not show pathogenic mutations in HHT genes, prompting the need to investigate additional biomarkers of the disease. Here, several HHT biomarkers and novel methodological approaches developed during the last years will be reviewed. On one hand, products detected in plasma or serum samples: soluble proteins (vascular endothelial growth factor, transforming growth factor β1, soluble endoglin, angiopoietin-2) and microRNA variants (miR-27a, miR-205, miR-210). On the other hand, differential HHT gene expression fingerprinting, next generation sequencing of a panel of genes involved in HHT, and infrared spectroscopy combined with artificial neural network patterns will also be reviewed. All these biomarkers might help to improve and refine HHT diagnosis by distinguishing from the non-HHT population.

Impaired Endothelial Regeneration Through Human Parvovirus B19-Infected Circulating Angiogenic Cells in Patients With Cardiomyopathy

Human parvovirus B19 (B19V) is a common pathogen in microvascular disease and cardiomyopathy, owing to infection of endothelial cells. B19V replication, however, is almost restricted to erythroid progenitor cells (ErPCs). Endothelial regeneration attributable to bone marrow-derived circulating angiogenic cells (CACs) is a prerequisite for organ function. Because of many similarities of ErPCs and CACs, we hypothesized that B19V is a perpetrator of impaired endogenous endothelial regeneration. B19V DNA and messenger RNA from endomyocardial biopsy specimens, bone marrow specimens, and circulating progenitor cells were quantified by polymerase chain reaction analysis. The highest B19V DNA concentrations were found in CD34(+)KDR(+) cells from 17 patients with chronic B19V-associated cardiomyopathy. B19V replication intermediates could be detected in nearly half of the patients. Furthermore, chronic B19V infection was associated with impaired endothelial regenerative capacity. B19V infection of CACs in vitro resulted in expression of transcripts encoding B19V proteins. The capsid protein VP1 was identified as a novel inducer of apoptosis, as were nonstructural proteins. Inhibition studies identified so-called death receptor signaling with activation of caspase-8 and caspase-10 to be responsible for apoptosis induction. B19V causally impaired endothelial regeneration with spreading of B19V in CACs in an animal model in vivo. We thus conclude that B19V infection and damage to CACs result in dysfunctional endogenous vascular repair, supporting the emergence of primary bone marrow disease with secondary end-organ damage.

In vitro evaluation of endothelial progenitor cells from adipose tissue as potential angiogenic cell sources for bladder angiogenesis

Autologous endothelial progenitor cells (EPCs) might be alternative angiogenic cell sources for vascularization of tissue-engineered bladder, while isolation and culture of EPCs from peripheral blood in adult are usually time-consuming and highly inefficient. Recent evidence has shown that EPCs also exist in the adipose tissue. As adipose tissue is plentiful in the human body and can be easily harvested through a minimally invasive method, the aim of this study was to culture and characterize EPCs from adipose tissue (ADEPCs) and investigate their potential for the neovascularization of tissue-engineered bladder. Adipose stromal vascular fraction (SVF) was isolated and used for the culture of ADEPCs and adipose derived stem cells (ADSCs). After SVF was cultured for one week, ADEPCs with typical cobblestone morphology emerged and could be isolated from ADSCs according to their different responses to trypsinization. Rat bladder smooth muscle cells (RBSMCs) were isolated and cultured from rat bladder. RBSMCs exhibited typical spindle-shaped morphology. ADEPCs had higher proliferative potential than ADSCs and RBSMCs. ADEPCs stained positive for CD34, Stro-1, VEGFR-2, eNOS and CD31 but negative for α-SMA, CD14 and CD45. ADSCs stained positive for CD34, Stro-1 and α-SMA but negative for VEGFR-2, eNOS, CD31, CD14 and CD45. RBSMCs stained only positive for α-SMA. ADEPCs could be expanded from a single cell at an early passage to a cell cluster containing more than 10,000 cells. ADEPCs were able to uptake DiI-Ac-LDL, bind UEA-1 and form capillary-like structures in three-dimensional scaffolds (Matrigel and bladder acellular matrix). ADEPCs were also able to enhance the human umbilical vein endothelial cells’ capability of capillary-like tube formation on Matrigel. Additionally, significantly higher levels of mRNA and protein of vascular endothelial growth factor were found in ADEPCs than in RBSMCs. These results suggest the potential use of ADEPCs as angiogenic cell sources for engineering bladder tissue.

Contrasting biofunctionalization strategies for the enhanced endothelialization of biodegradable vascular grafts

Surface modification of biodegradable vascular grafts is an important strategy to improve the in situ endothelialization of tissue engineered vascular grafts (TEVGs) and prevent major complications associated with current synthetic grafts. Important strategies for improving endothelialization include increasing endothelial cell mobilization and increased endothelial cell capture through biofunctionalization of TEVGs. The objective of this study was to assess two biofunctionalization strategies for improving endothelialization of biodegradable polyester vascular grafts. These techniques consisted of cross-linking heparin to graft surfaces to immobilize vascular endothelial growth factor (VEGF) or antibodies against CD34 (anti-CD34Ab). To this end, heparin, VEGF, and anti-CD34Ab attachment and quantification assays confirmed the efficacy of the modification strategy. Cell attachment and proliferation on these groups were compared to unmodified grafts in vitro and in vivo. To assess in vivo graft functionality, the grafts were implanted as inferior vena cava interpositional conduits in mice. Modified vascular grafts displayed increased endothelial cell attachment and activity in vivo, according to microscopy techniques, histological results, and eNOS expression. Inner lumen diameter of the modified grafts was also better maintained than controls. Overall, while both functionalized grafts outperformed the unmodified control, grafts modified with anti-CD34Ab appeared to yield the most improved results compared to VEGF-loaded grafts.

A functional transient receptor potential vanilloid 4 (TRPV4) channel is expressed in human endothelial progenitor cells

Endothelial progenitor cells (EPCs) are mobilized into circulation to replace damaged endothelial cells and recapitulate the vascular network of injured tissues. Intracellular Ca(2+) signals are key to EPC activation, but it is yet to be elucidated whether they are endowed with the same blend of Ca(2+) -permeable channels expressed by mature endothelial cells. For instance, endothelial colony forming cells (ECFCs), the only EPC subset truly committed to acquire a mature endothelial phenotype, lack canonical transient receptor potential channels 3, 5 and 6 (TRPC3, 5 and 6), which are widely distributed in vascular endothelium; on the other hand, they express a functional store-operated Ca(2+) entry (SOCE). The present study was undertaken to assess whether human circulating EPCs possess TRP vanilloid channel 4 (TRPV4), which plays a master signalling role in mature endothelium, by controlling both vascular remodelling and arterial pressure. We found that EPCs express both TRPV4 mRNA and protein. Moreover, both GSK1016790A (GSK) and phorbol myristate acetate and, two widely employed TRPV4 agonists, induced intracellular Ca(2+) signals uniquely in presence of extracellular Ca(2+). GSK- and PMA-induced Ca(2+) elevations were inhibited by RN-1734 and ruthenium red, which selectively target TRPV4 in mature endothelium. However, TRPV4 stimulation with GSK did not cause EPC proliferation, while the pharmacological blockade of TRPV4 only modestly affected EPC growth in the presence of a growth factor-enriched culture medium. Conversely, SOCE inhibition with BTP-2, La(3+) and Gd(3+) dramatically decreased cell proliferation. These data indicate that human circulating EPCs possess a functional TRPV4 protein before their engraftment into nascent vessels.

Fundamentals and application of magnetic particles in cell isolation and enrichment: a review

Magnetic sorting using magnetic beads has become a routine methodology for the separation of key cell populations from biological suspensions. Due to the inherent ability of magnets to provide forces at a distance, magnetic cell manipulation is now a standardized process step in numerous processes in tissue engineering, medicine, and in fundamental biological research. Herein we review the current status of magnetic particles to enable isolation and separation of cells, with a strong focus on the fundamental governing physical phenomena, properties and syntheses of magnetic particles and on current applications of magnet-based cell separation in laboratory and clinical settings. We highlight the contribution of cell separation to biomedical research and medicine and detail modern cell-separation methods (both magnetic and non-magnetic). In addition to a review of the current state-of-the-art in magnet-based cell sorting, we discuss current challenges and available opportunities for further research, development and commercialization of magnetic particle-based cell-separation systems.

Clinical trials of adult stem cell therapy for peripheral artery disease

Peripheral artery disease (PAD) refers to noncoronary vascular disease affecting the peripheral arteries. Most commonly the term is applied to occlusive arterial disease affecting the limb arteries, typically due to atherosclerosis. Preclinical studies indicate that a variety of stem cell therapies provide growth factors and cytokines for therapeutic angiogenesis. Small clinical trials with bone marrow mononuclear cells, as well as other cell types, have shown promise. However, mechanisms of therapeutic effect, if any, are not understood. Definitive clinical trials are needed to determine if there are any beneficial effects on functional capacity or morbidity.

Increase of circulating endothelial cells in patients with Hereditary Hemorrhagic Telangiectasia

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant disorder characterized by vascular malformations. The genes known to be associated with HHT include ENG (HHT1), ACVRL1 (HHT2) and SMAD4 (JPHT). It has been reported that circulating CD34(+) cell subsets repair damaged vessels. To investigate whether mobilization of these cells is present in the peripheral blood (PB) of HTT patients, we analyzed CD34(+) cells, CD34(+)VEGFR-2(+) progenitor or mature endothelial cells, and CD34(+)CD133(+)VEGFR-2(-) hematopoietic progenitor cells (HPCs). Cytofluorimetric analysis was performed in 150 HTT patients and 43 healthy subjects (CTRLs). In HTT patients, PB CD34(+) cells were significantly increased; the frequency of endothelial cells was higher (P = 0.002), while the frequency of CD34(+)CD133(+)VEGFR-2(-) HPCs was lower (P = 0.00007) than in CTRLs. Results were comparable in patients with ENG or ACVRL1 gene mutation; in patients with ENG mutation, the frequency of the cell subsets inversely correlated with the age of the patients at time of sampling (CD34(+)), disease duration (CD34(+)VEGFR-2(+)), and age at disease onset (CD34(+)CD133(+) VEGFR-2(-)). In conclusion, HHT patients show an increase of circulating endothelial cells and a decrease of HPCs. In patients with ENG mutation, the frequency of CD34(+) endothelial cells correlates with specific clinical characteristics suggesting that their active turnover characterizes the initial phase of the disease.

Targeted delivery of genes to endothelial cells and cell- and gene-based therapy in pulmonary vascular diseases

Pulmonary arterial hypertension (PAH) is a devastating disease that, despite significant advances in medical therapies over the last several decades, continues to have an extremely poor prognosis. Gene therapy is a method to deliver therapeutic genes to replace defective or mutant genes or supplement existing cellular processes to modify disease. Over the last few decades, several viral and nonviral methods of gene therapy have been developed for preclinical PAH studies with varying degrees of efficacy. However, these gene delivery methods face challenges of immunogenicity, low transduction rates, and nonspecific targeting which have limited their translation to clinical studies. More recently, the emergence of regenerative approaches using stem and progenitor cells such as endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) have offered a new approach to gene therapy. Cell-based gene therapy is an approach that augments the therapeutic potential of EPCs and MSCs and may deliver on the promise of reversal of established PAH. These new regenerative approaches have shown tremendous potential in preclinical studies; however, large, rigorously designed clinical studies will be necessary to evaluate clinical efficacy and safety.

May the remodeling of the Ca²⁺ toolkit in endothelial progenitor cells derived from cancer patients suggest alternative targets for anti-angiogenic treatment?

Endothelial progenitor cells (EPCs) may be recruited from bone marrow to sustain the metastatic switch in a number of solid cancers, including breast cancer (BC) and renal cellular carcinoma (RCC). Preventing EPC mobilization causes tumor shrinkage. Novel anti-angiogenic treatments have been introduced in therapy to inhibit VEGFR-2 signaling; unfortunately, these drugs blocked tumor angiogenesis in pre-clinical murine models, but resulted far less effective in human patients. Understanding the molecular mechanisms driving EPC proliferation and tubulogenesis in cancer patients could outline novel targets for alternative anti-angiogenic treatments. Store-operated Ca²⁺ entry (SOCE) regulates the growth of human EPCs, and it is mediated by the interaction between the endoplasmic reticulum Ca²⁺-sensor, Stim1, and the plasmalemmal Ca²⁺ channels, Orai1 and TRPC1. EPCs do not belong to the neoplastic clone: thus, unlike tumor endothelium and neoplastic cells, they should not remodel their Ca²⁺ toolkit in response to tumor microenvironment. However, our recent work demonstrated that EPCs isolated from naïve RCC patients (RCC-EPCs) undergo a dramatic remodeling of their Ca²⁺ toolkit by displaying a remarkable drop in the endoplasmic reticulum Ca²⁺ content, by down-regulating the expression of inositol-1,4,5-receptors (InsP3Rs), and by up-regulating Stim1, Orai1 and TRPC1. Moreover, EPCs are dramatically less sensitive to VEGF stimulation both in terms of Ca²⁺ signaling and of gene expression when isolated from tumor patients. Conversely, the pharmacological abolition of SOCE suppresses proliferation in these cells. These results question the suitability of VEGFR-2 as a therapeutically relevant target for anti-angiogenic treatments and hint at Orai1 and TRPC1 as more promising alternatives. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

Concurrent hypermulticolor monitoring of CD31, CD34, CD45 and CD146 endothelial progenitor cell markers for acute myocardial infarction

The circulating endothelial progenitor cells (EPCs) in blood of acute myocardial infarction (AMI) patient have been monitored in many previous studies. The number of circulating EPC increases in the blood of patients at onset of the AMI. EPC is originated from bone marrow. It performs vessel regeneration. There are many markers used for detecting EPC. Four of these markers, CD31, CD34, CD45, and CD146, were concurrently detected at the single cell level for the identification of EPC in the present preliminary study. The CD45 negative cell sorting was performed to peripheral blood mononuclear cells (PBMCs) acquired from four AMI patients with a magnetic bead sorter, since, EPCs expressed CD45 negative or dim. The resultant PBMC eluents were treated with quantum-antibody conjugates for the probing four different markers of EPCs and then applied to a high-content single cell imaging cytometer using acousto-optical tunable filter (AOTF). The use of quantum dot, with narrow emission wavelength range and AOTF enabling cellular image at a particular single wavelength, is very advantageous for accurate high-content AMI diagnosis based on simultaneous monitoring of many markers. The number of EPC increased as compared with control in three of four AMI patients. In this approach, two EPC subtypes were found, CD31(+), CD34(+), CD45(-/dim), CD146(-) as early outgrowth EPCs and CD31(+), CD34(+), CD45(-/dim), CD146(+) as late outgrowth EPCs. Patient 1 had CD31(+), CD34(+), CD45(-/dim), CD146(+) cells whose percentage was 4.21% of cells. Patient 2 had 2.38% of CD31(+), CD34(+), CD45(-/dim), CD146(-) cells and patient 3 had 4.28% of CD31(+), CD34(+), CD45(-/dim), CD146(+) cells.

Grain and bean lysates improve function of endothelial progenitor cells from human peripheral blood: involvement of the endogenous antioxidant defenses

Increased oxidative stress contributes to the functional impairment of endothelial progenitor cells (EPCs), the pivotal players in the servicing of the endothelial cell lining. Several evidences suggest that decreasing oxidative stress by natural compounds with antioxidant properties may improve EPCs bioactivity. Here, we investigated the effects of Lisosan G (LG), a Triticum Sativum grain powder, and Lady Joy (LJ), a bean lysate, on function of EPCs exposed to oxidative stress. Peripheral blood mononuclear cells were isolated and plated on fibronectin-coated culture dishes; adherent cells, identified as early EPCs, were pre-treated with different concentrations of LG and LJ and incubated with hydrogen peroxide (H2O2). Viability, senescence, adhesion, ROS production and antioxidant enzymes gene expression were evaluated. Lysate-mediated Nrf-2 (nuclear factor (erythroid-derived 2)-like 2)/ARE (antioxidant response element) activation, a modulator of oxidative stress, was assessed by immunocytochemistry. Lady Joy 0.35-0.7 mg/ml increases EPCs viability; pre-treatment with either LG 0.7 mg/ml and LJ 0.35-0.7 mg/ml protect EPCs viability against H2O2-induced injury. LG 0.7 and LJ 0.35-0.7 mg/ml improve EPCs adhesion; pre-treatment with either LG 0.35 and 0.7 mg/ml or LJ 0.35, 0.7 and 1.4 mg/ml preserve adhesiveness of EPCs exposed to H2O2. Senescence is attenuated in EPCs incubated with lysates 0.35 mg/ml. After exposure to H2O2, LG pre-treated cells show a lower senescence than untreated EPCs. Lysates significantly decrease H2O2-induced ROS generation. Both lysates increase glutathione peroxidase-1 and superoxide dismutase-2 (SOD-2) expression; upon H2O2 exposure, pre-treatment with LJ allows higher SOD-2 expression. Heme oxigenase-1 increases in EPCs pre-treated with LG even upon H2O2 exposure. Finally, incubation with LG 0.7 mg/ml results in Nrf-2 translocation into the nucleus both at baseline and after the oxidative challenge. Our data suggest a protective effect of lysates on EPCs exposed to oxidative stress through the involvement of antioxidant systems. Lisosan G seems to activate the Nrf-2/ARE pathways.

Microfluidic capture of endothelial colony-forming cells from human adult peripheral blood: phenotypic and functional validation in vivo

INTRODUCTION

Endothelial colony-forming cells (ECFCs) are endothelial progenitors that circulate in peripheral blood and are currently the subject of intensive investigation due to their therapeutic potential. However, in adults, ECFCs comprise a very small subset among circulating cells, which makes their isolation a challenge.

MATERIALS AND METHODS

Currently, the standard method for ECFC isolation relies on the separation of mononuclear cells and erythrocyte lysis, steps that are time consuming and known to increase cell loss. Alternatively, we previously developed a novel disposable microfluidic platform containing antibody-functionalized degradable hydrogel coatings that is ideally suited for capturing low-abundance circulating cells from unprocessed blood. In this study, we reasoned that this microfluidic approach could effectively isolate rare ECFCs by virtue of their CD34 expression.

RESULTS

We conducted preclinical experiments with peripheral blood from four adult volunteers and demonstrated that the actual microfluidic capture of circulating CD34(+) cells from unprocessed blood was compatible with the subsequent differentiation of these cells into ECFCs. Moreover, the ECFC yield obtained with the microfluidic system was comparable to that of the standard method. Importantly, we unequivocally validated the phenotypical and functional properties of the captured ECFCs, including the ability to form microvascular networks following transplantation into immunodeficient mice.

DISCUSSION

We showed that the simplicity and versatility of our microfluidic system could be very instrumental for ECFC isolation while preserving their therapeutic potential. We anticipate our results will facilitate additional development of clinically suitable microfluidic devices by the vascular therapeutic and diagnostic industry.

Cell-based therapies for the preterm infant

The severely preterm infant receives a multitude of life-saving interventions, many of which carry risks of serious side effects. Cell therapy is an important and promising arm of regenerative medicine that may address a number of these problems. Most forms of cellular therapy use stem/progenitor cells or stem-like cells, which have the capacity to migrate, engraft and exert anti-inflammatory effects. Although some of these cell-based therapies have made their way to clinical trials in adults, little headway has been made in the neonatal patient group. This review discusses the efficacy of cell therapy in preclinical studies to date and their potential applications to diseases that afflict many prematurely born infants. Specifically, we identify the major hurdles that must be overcome before cell therapies can be safely used in the neonatal intensive care unit.

RNA-Seq for the identification of novel Mediator transcripts in endothelial progenitor cells

Mediator (MED) complex is a multiprotein playing a key role in the eukaryotic transcription. Alteration of MED function may have enormous pathophysiological consequences and several MED genes have been implicated in human diseases. Here, we have combined computational and experimental approaches to identify and characterize, new transcripts generated by alternative splicing (AS) for all MED genes, through the analysis of our recently published RNA-Sequencing datasets of endothelial progenitor cells (EPCs). This combined strategy allowed us to identify novel transcripts for MED4, MED9, MED11, MED14, MED27 and CDK8 most of them generated by AS. All the newly identified transcripts, except MED11, are predicted to encode novel protein isoforms. The identification of novel MED variants could lead to the finding of other MED complexes with different functions depending on their subunit composition. Finally, the expression profile of all MED genes, together with an extensive gene expression analysis, may be useful to better classify the diverse subsets of cell populations that contribute to neovascularization.

Bone marrow-derived cells are implicated as a source of lymphatic endothelial progenitors in human breast cancer

Bone marrow-derived endothelial progenitor cells (EPCs) infiltrate into sites of neovascularization in adult tissues and mature into functional blood endothelial cells (BECs) during a process called vasculogenesis. Human marrow-derived EPCs have recently been reported to display a mixed myeloid and lymphatic endothelial cell (LEC) phenotype during inflammation-induced angiogenesis; however, their role in cancer remains poorly understood. We report the in vitro differentiation of human cord blood CD133⁺CD34⁺ progenitors into podoplanin⁺ cells expressing both myeloid markers (CD11b, CD14) and the canonical LEC markers vascular endothelium growth factor receptor 3 (VEGFR-3), lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1), and prospero homeobox 1 (PROX-1). These podoplanin⁺ cells displayed sprouting behavior comparable to that of LECs in vitro and a dual hemangiogenic and lymphangiogenic activity in vivo in an endothelial cell sprouting assay and corneal vascularization assay, respectively. Furthermore, these cells expressed vascular endothelium growth factor (VEGF) family members A, -C, and -D. Thus, bone-marrow derived EPCs stimulate hemangiogenesis and lymphangiogenesis through their ability to differentiate into LECs and to produce angiogenic factors. Importantly, plasma from patients with breast cancer induced differentiation of CD34⁺ cord blood progenitors into hemangiogenic and lymphangiogenic CD11b⁺ myeloid cells, whereas plasma from healthy women did not have this effect. Consistent with these findings, circulating CD11b⁺ cells from breast cancer patients, but not from healthy women, displayed a similar dual angiogenic activity. Taken together, our results show that marrow-derived EPCs become hemangiogenic and lymphangiogenic upon exposure to cancer plasma. These newly identified functions of bone-marrow derived EPCs are expected to influence the diagnosis and treatment of breast cancer.

The impact of endothelial progenitor cells on restenosis after percutaneous angioplasty of hemodialysis vascular access

Objective

We prospectively investigate the relation between baseline circulating endothelial progenitor cells and the subsequent development of restenosis after angioplasty of hemodialysis vascular access.

Background

Effect of angioplasty for hemodialysis vascular access is greatly attenuated by early and frequent restenosis. Circulating endothelial progenitor cells (EPCs) play a key role in vascular repair but are deficient in hemodialysis patients.

Method

After excluding 14 patients due to arterial stenosis, central vein stenosis, and failed angioplasty, 130 patients undergoing angioplasty for dysfunctional vascular access were prospectively enrolled. Flow cytometry with quantification of EPC markers (defined as CD34⁺, CD34⁺KDR⁺, CD34⁺KDR⁺CD133⁺) in peripheral blood immediately before angioplasty procedures was used to assess circulating EPC numbers. Patients were followed clinically for up to one year after angioplasty.

Results

During the one-year follow-up, 95 patients (73%) received interventions for recurrent access dysfunction. Patients in the lower tertile of CD34⁺KDR⁺ cell count had the highest restenosis rates (46%) at three month (early restenosis), compared with patients in the medium and upper tertiles of CD34⁺KDR⁺ cell count (27% and 12% respectively, p = 0.002). Patients in the lower tertile of CD34⁺KDR⁺ cell count received more re-interventions during one year. Patients with early restenosis had impaired EPC adhesive function and increased senescence and apoptosis. In multivariate analysis, the CD34⁺KDR⁺ and CD34⁺KDR⁺CD133⁺ cell counts were independent predictors of target-lesion early restenosis.

Conclusion

Our results suggest that the deficiency of circulating EPCs is associated with early and frequent restenosis after angioplasty of hemodialysis vascular access.

Combined intermittent hypobaric hypoxia and muscle electro-stimulation: a method to increase circulating progenitor cell concentration?

BACKGROUND

Our goal was to test whether short-term intermittent hypobaric hypoxia (IHH) at a level well tolerated by healthy humans could, in combination with muscle electro-stimulation (ME), mobilize circulating progenitor cells (CPC) and increase their concentration in peripheral circulation.

METHODS

Nine healthy male subjects were subjected, as the active group (HME), to a protocol involving IHH plus ME. IHH exposure consisted of four, three-hour sessions at a barometric pressure of 540 hPa (equivalent to an altitude of 5000 m). These sessions took place on four consecutive days. ME was applied in two separate 20-minute periods during each IHH session. Blood samples were obtained from an antecubital vein on three consecutive days immediately before the experiment, and then 24 h, 48 h, 4 days, 7 days and 14 days after the last day of hypoxic exposure. Four months later a control study was carried out involving seven of the original subjects (CG), who underwent the same protocol of blood samples but without receiving any special stimulus.

RESULTS

In comparison with the CG the HME group showed only a non-significant increase in the number of CPC CD34+ cells on the fourth day after the combined IHH and ME treatment.

CONCLUSION

CPC levels oscillated across the study period and provide no firm evidence to support an increased CPC count after IHH plus ME, although it is not possible to know if this slight increase observed is physiologically relevant. Further studies are required to understand CPC dynamics and the physiology and physiopathology of the hypoxic stimulus.

Reduced levels of circulating endothelial progenitor cells in acute myocardial infarction patients with diabetes or pre-diabetes: accompanying the glycemic continuum

Background

Diabetic patients have a significantly worse prognosis after an acute myocardial infarction (AMI) than their counterparts. Previous studies have shown that the number of circulating endothelial progenitor cells (EPCs) significantly increase early after an AMI in normoglycemic patients. However, it is well known that type 2 diabetes mellitus (DM) is associated with impaired function and reduced circulating EPCs levels. Nonetheless, few studies have analyzed EPCs response of diabetics to an AMI and the EPC response of pre-diabetic patients has not been reported yet. Therefore, we hypothesized that in the acute phase of an AMI, diabetic and pre-diabetics have lower circulating EPCs levels than patients with normal glucose metabolism. We also evaluated the possible capacity of chronic antidiabetic treatment in the recovery of EPCs response to an AMI in diabetics.

Methods

One-hundred AMI patients were prospectively enrolled in the study. Using the high-performance flow cytometer FACSCanto II, circulating EPCs (CD45dimCD34+KDR+ and CD45dimCD133+KDR+ cells) were quantified, within the first 24 hours of admission. In addition, as an indirect functional parameter, we also analyzed the fraction of EPCs coexpressing the homing marker CXCR4.

Results

We found that in the acute phase of an AMI, diabetic patients presented significantly lower levels of circulating CD45dimCD34+KDR+ and CD45dimCD133+KDR+ EPCs by comparison with nondiabetics, with a parallel decrease in the subpopulations CXCR4+ (p < 0.001). Indeed, this study suggests that the impaired response of EPCs to an AMI is an early event in the natural history of DM, being present even in pre-diabetes. Our results, also demonstrated that numbers of all EPCs populations were inversely correlated with HbA1c (r = -0.432, p < 0.001 for CD45dimCD34+KDR+ cells). Finally, this study suggests that previous chronic insulin therapy (but not oral antidiabetic drugs) attenuate the deficient response of diabetic EPCs to an AMI.

Conclusion

This study indicates that there is a progressive decrease in EPCs levels, from pre-diabetes to DM, in AMI patients. Moreover, glycemic control seems to be determinant for circulating EPCs levels presented in the acute phase of an AMI and chronic insulin therapy may probably attenuate the deficit in EPCs pool seen in diabetics.

Stem cells, cell therapies, and bioengineering in lung biology and diseases. Comprehensive review of the recent literature 2010-2012

A conference, "Stem Cells and Cell Therapies in Lung Biology and Lung Diseases," was held July 25 to 28, 2011 at the University of Vermont to review the current understanding of the role of stem and progenitor cells in lung repair after injury and to review the current status of cell therapy and ex vivo bioengineering approaches for lung diseases. These are rapidly expanding areas of study that provide further insight into and challenge traditional views of mechanisms of lung repair after injury and pathogenesis of several lung diseases. The goals of the conference were to summarize the current state of the field, to discuss and debate current controversies, and to identify future research directions and opportunities for basic and translational research in cell-based therapies for lung diseases. The goal of this article, which accompanies the formal conference report, is to provide a comprehensive review of the published literature in lung regenerative medicine from the last conference report through December 2012.

Endothelial progenitor cell mobilization by preoperative exercise: a bone marrow response associated with postoperative outcome

BACKGROUND

Preoperative anaemia is associated with increased morbidity in patients undergoing major surgery. Whether erythrocytes are the only bone-marrow-derived cell lineage that associates with increased surgical complications is unknown. This prospective observational trial studied the mobilization of endothelial progenitor cells (EPCs) in response to exercise in association with postoperative complications.

METHODS

After IRB approval, 60 subjects undergoing major thoracic surgery were exercised to exhaustion (peak V̇(O₂)). Peripheral blood collected before and after peak exercise was quantified for EPC lineages by fluorescence-activated cell sorter analysis. Complication analysis was based on the Clavien-Dindo classification.

RESULTS

Exhaustive exercise increased EPC [CD45-133+34+ cells=150 (0.00-5230) to 220 (0.00-1270) cells μl(-1); median change (range)=20 (-4,180-860) cells μl(-1); P=0.03] but not mature endothelial cell (EC) subpopulations. Pre-exercise levels [odds ratio (OR)=0.86, 95% confidence interval (CI): 0.37-2.00, P=0.72), change after exercise as a continuous variable (OR=0.95, 95% CI: 0.41-2.22, P=0.91) and a positive response after exercise (change >0 cells μl(-1); OR=0.41, 95% CI: 0.13-1.28, P=0.12) were not statistically significantly associated with the incidence of postoperative complications. Post-hoc receiver operating characteristic curve analyses revealed that subjects with a CD45-133+34+ increase ≥60 cells μl(-1) in response to exercise suffered fewer postoperative complications [86% sensitivity, 48% specificity and AUC=0.67 (95% CI: 0.52-0.81)].

CONCLUSIONS

Preoperative exercise induces EPC into the peripheral circulation. Subjects with a poor EPC response had a pre-existing propensity for postoperative complications. This warrants further research into the role of bone marrow function as a critical component to endothelial repair mechanisms.

CLINICAL TRIAL REGISTRATION

IRB 2003-0434 (University of Texas M.D. Anderson Cancer Center, Houston, TX, USA).

Recruitment of bone marrow derived cells during anti-angiogenic therapy in GBM: the potential of combination strategies

Glioblastoma (GBM) is a highly vascular tumor characterized by rapid and invasive tumor growth, followed by oxygen depletion, hypoxia and neovascularization, which generate a network of disorganized, tortuous and permeable vessels. Recruitment of bone marrow derived cells (BMDC) is crucial for vasculogenesis. These cells may act as vascular progenitors by integrating into the newly formed blood vessels or as vascular modulators by releasing pro-angiogenic factors. In patients with recurrent GBM, anti-vascular endothelial growth factor (VEGF) therapy has been evaluated in combination with chemotherapy, yielding improvements in progression-free survival (PFS). However, benefits are temporary as vascular tumors acquire angiogenic pathways independently of VEGF. Specifically, acute hypoxia following prolonged VEGF depletion induces the recruitment of certain myeloid cell subpopulations, which highly contribute to treatment refractoriness. Here we review the molecular mechanisms of neovascularization in relation to bevacizumab therapy with special emphasis on the recruitment of BMDCs and possible combination therapies for GBM patients.