Concise Review: Circulating Endothelial Progenitor Cells for Vascular Medicine

Biomaterials for Bioprinting Microvasculature

Microvasculature functions at the tissue and cell level, regulating local mass exchange of oxygen and nutrient-rich blood. While there has been considerable success in the biofabrication of large- and small-vessel replacements, functional microvasculature has been particularly challenging to engineer due to its size and complexity. Recently, three-dimensional bioprinting has expanded the possibilities of fabricating sophisticated microvascular systems by enabling precise spatiotemporal placement of cells and biomaterials based on computer-aided design. However, there are still significant challenges facing the development of printable biomaterials that promote robust formation and controlled 3D organization of microvascular networks. This review provides a thorough examination and critical evaluation of contemporary biomaterials and their specific roles in bioprinting microvasculature. We first provide an overview of bioprinting methods and techniques that enable the fabrication of microvessels. We then offer an in-depth critical analysis on the use of hydrogel bioinks for printing microvascularized constructs within the framework of current bioprinting modalities. We end with a review of recent applications of bioprinted microvasculature for disease modeling, drug testing, and tissue engineering, and conclude with an outlook on the challenges facing the evolution of biomaterials design for bioprinting microvasculature with physiological complexity.

Low Ethanol Concentrations Promote Endothelial Progenitor Cell Capacity and Reparative Function

Background

Endothelial progenitor cells (EPCs) are recruited to injured endothelium and contribute to its regeneration. There is evidence that moderate ethanol consumption prevents the development and progression of atherosclerosis in a variety of in vitro and in vivo models and increases the mobilization of progenitor cells. Furthermore, there are studies that identified ethanol at low concentration as a therapeutic tool to mobilize progenitor cells in peripheral blood. At the same time, the cell number of EPCs represents a close link to cardiovascular system constitution and function and contributes to cardiovascular risk. The aim of this study was to evaluate the effect of low dose ethanol on typical features of endothelial colony-forming cells (ECFCs), a proliferative subtype of EPCs.

Methods and Results

We tested whether ethanol impacts the functional abilities of ECFC (e.g., migration, tube formation, and proliferation) using in vitro assays, the intercommunication of ECFC by exploring cell surface molecules by flow cytometry, and the expression of (anti-)angiogenic molecules by ELISA. Low concentrations of ethanol concentration promoted migration, proliferation, and tubule formation of ECFC. The expression of the cell surface marker VE-cadherin, a protein which plays an important role in cell-cell interaction, was enhanced by ethanol, while (anti-)angiogenic molecule expression was not impacted.

Conclusion

Ethanol at moderate concentrations increases the angiogenic abilities of endothelial progenitor cells thus possibly contributing to vasoprotection.

Clarification of the Role of miR-9 in the Angiogenesis, Migration, and Autophagy of Endothelial Progenitor Cells Through RNA Sequence Analysis

We have previously reported that miR-9 promotes the homing, proliferation, and angiogenesis of endothelial progenitor cells (EPCs) by targeting transient receptor potential melastatin 7 via the AKT autophagy pathway. In this way, miR-9 promotes thrombolysis and recanalization following deep vein thrombosis (DVT). However, the influence of miR-9 on messenger RNA (mRNA) expression profiles of EPCs remains unclear. The current study comprises a comprehensive exploration of the mechanisms underlying the miR-9-regulated angiogenesis of EPCs and highlights potential treatment strategies for DVT. We performed RNA sequence analysis, which revealed that 4068 mRNAs were differentially expressed between EPCs overexpressing miR-9 and the negative control group, of which 1894 were upregulated and 2174 were downregulated. Gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses indicated that these mRNAs were mainly involved in regulating cell proliferation/migration processes/pathways and the autophagy pathway, both of which represent potential EPC-based treatment strategies for DVT. Reverse transcriptase quantitative polymerase chain reaction confirmed the changes in mRNA expression related to EPC angiogenesis, migration, and autophagy. We also demonstrate that miR-9 promotes EPC migration and angiogenesis by regulating FGF5 directly or indirectly. In summary, miR-9 enhances the expression of VEGFA, FGF5, FGF12, MMP2, MMP7, MMP10, MMP11, MMP24, and ATG7, which influences EPC migration, angiogenesis, and autophagy. We provide a comprehensive evaluation of the miR-9-regulated mRNA expression in EPCs and highlight potential targets for the development of new therapeutic interventions for DVT.

[Problems and prospects of cell therapy for critical ischaemia of lower limbs]

BACKGROUND

Cell therapy was proposed as a procedure of indirect revascularization for patients with critical ischaemia of lower extremities for whom endovascular and surgical revascularization is impossible. We present herein a review of the state of the art of studies in the field of cell therapy of this cohort of patients.

BASIC PROVISIONS

Cell therapy has proved safe, however, the results of studies of efficacy are relatively ambiguous and unconvincing. The number of patients in separately taken clinical trials is minimal. The reviewed studies differed not only by heterogeneity of the cell types used but by the routes of administration of cells (cells were delivered either intramuscularly (predominantly) or intraarterially) and the duration of follow up (time of assessment and duration of follow up varied from 1 month to 2 years). One of the problems became the lack of the routine study of the angiogenic potential of stem cells prior to their clinical application. It is known that the angiogenic activity of multipotent cells of apparently healthy patients may differ from that of patients suffering from atherosclerosis, chronic renal failure, diabetes.

CONCLUSIONS

It is supposed that treatment with stem cells or precursor cells is more efficient as compared to protein or gene therapy not only owing to direct vasculogenic properties but a paracrine action through excretion of proangiogenic biologically active substances. More studies with larger cohorts are necessary to provide stronger safety and efficacy data on cell therapy. Besides, a promising trend in the field of cellular approaches is modulation of regenerative capability of stem cells, which may help overcome difficulties in understanding the place of cell therapy in therapeutic angiogenesis.

Endothelial progenitor cells as the target for cardiovascular disease prediction, personalized prevention, and treatments: progressing beyond the state-of-the-art

Stimulated by the leading mortalities of cardiovascular diseases (CVDs), various types of cardiovascular biomaterials have been widely investigated in the past few decades. Although great therapeutic effects can be achieved by bare metal stents (BMS) and drug-eluting stents (DES) within months or years, the long-term complications such as late thrombosis and restenosis have limited their further applications. It is well accepted that rapid endothelialization is a promising approach to eliminate these complications. Convincing evidence has shown that endothelial progenitor cells (EPCs) could be mobilized into the damaged vascular sites systemically and achieve endothelial repair in situ, which significantly contributes to the re-endothelialization process. Therefore, how to effectively capture EPCs via specific molecules immobilized on biomaterials is an important point to achieve rapid endothelialization. Further, in the context of predictive, preventive, personalized medicine (PPPM), the abnormal number alteration of EPCs in circulating blood and certain inflammation responses can also serve as important indicators for predicting and preventing early cardiovascular disease. In this contribution, we mainly focused on the following sections: the definition and classification of EPCs, the mechanisms of EPCs in treating CVDs, the potential diagnostic role of EPCs in predicting CVDs, as well as the main strategies for cardiovascular biomaterials to capture EPCs.

MRI tracing of ultrasmall superparamagnetic iron oxide nanoparticle‑labeled endothelial progenitor cells for repairing atherosclerotic vessels in rabbits

Endothelial progenitor cells (EPCs) have been discovered to be relevant to the prognosis of cardiovascular diseases. Previous research has demonstrated that EPCs serve vital roles in the occurrence and development of atherosclerosis. Significant improvements have been made in MRI technology and in the experimental use of EPCs for therapeutic angiogenesis and vascular repair. Nevertheless, the migratory, adhesive, proliferative and angiogenic properties of EPCs remain unknown. The aims of the present study were to investigate the potential of using non-invasive monitoring with ultrasmall superparamagnetic iron oxide nanoparticle (USPION)-labeled endothelial progenitor cells (EPCs) after transplantation, and to assess the treatment outcomes in an atherosclerotic rabbit model. EPCs derived from rabbit peripheral blood samples were labeled with USPION-poly-l-lysine (USPION-PLL). The morphology, proliferation, adhesive ability and labeling efficiency of the EPCs were determined by optical and electron microscopy. Moreover, biological activity was assessed by flow cytometry. In addition, T2-weighted image fast spin-echo MRI was used to detect cell labeling. USPION content in the labeled EPCs was determined by Prussian blue staining and scanning electron microscopy. Rabbit atherosclerosis model was established using a high-fat diet. USPION-labeled EPCs were transplanted into rabbits, and in vivo MRI was performed 1 and 7 days after transplantation. It was found that EPCs cultured on Matrigel formed capillary-like structures, and expressed the surface markers CD133, CD31, CD34 and vascular endothelial growth factor receptor 2 (VEGFR2). The optimal USPION concentration was 32 µg/ml, as determined by adhesion and proliferation assays. It was identified that USPION-PLL nanoparticles were 10–20 nm in diameter. Histopathological analysis results indicated that 1 day after transplantation of the labeled EPCs, blue-stained granules were observed in the intima of vascular lesions in rabbit models after Prussian blue staining. Therefore, the present results suggest that USPION-labeled EPCs may play a role in repairing endothelial injury and preventing atherosclerosis in vivo.

Circulating CD34+VEGFR-2+ endothelial progenitor cells correlate with revascularization-mediated long-term improvement of cardiac function in patients with coronary chronic total occlusions

BACKGROUND

Endothelial progenitor cells (EPCs) participate in angiogenesis and neocollateralization. This study assessed if circulating EPCs can predict long-term improvement of global left ventricular systolic function in patients with coronary chronic total occlusions (CTOs) underwent successful percutaneous coronary intervention (PCI).

METHODS

In this single-center, prospective, observational study, 115 consecutive patients with CTOs were evaluated by standard transthoracic echocardiography (ECHO) before and 9-12 months after PCI. Numbers of circulating putative EPCs were determined by flow cytometry analysis of mononuclear cells isolated from peripheral blood samples drawn before and 72 h after PCI.

RESULTS

At mean 11.3 ± 2.5 months post vs. before PCI (all P < .05): by SAQ-7 summary scores, angina frequency, physical limitation and quality of life scores were greater; by ECHO, LVEDd decreased and LVEF increased, which were more significant in patients with Rentrop grades 2/3 vs. 0/1. At 72 h post vs. before PCI, CD34⁺VEGFR-2⁺CD133^- (0.82 ± 0.32 × 10⁶/L vs. 1.00 ± 0.39 × 10⁶/L, P = .003), CD34⁺VEGFR-2⁺CD133⁺ (0.24 ± 0.12 × 10⁶/L vs. 0.27 ± 0.14 × 10⁶/L, P = .028), and CD14⁺Tie2⁺VEGFR-2⁺ (6.60 ± 3.32 × 10⁶/L vs. 7.82 ± 3.91 × 10⁶/L, P = .006) cell numbers were lower. The baseline levels of CD34⁺VEGFR-2⁺cells (P = .001) and CD14⁺Tie2⁺VEGFR-2⁺cells (P < .001) were association with the grade of collateralization. In addition, the baseline and peri-procedural decrease of circulating CD34⁺VEGFR-2⁺ cells correlated with the increase of LVEF (P < .001, P < .001, respectively) and the decrease of LVEDd (P = .022, P = .029, respectively) at follow-up.

CONCLUSIONS

In this small study, the baseline levels of circulating CD34⁺VEGFR-2+ EPCs and its reduction after successful revascularization of CTOs correlated with long-term improvement in global LV systolic function.

The State of Art of Regenerative Therapy in Cardiovascular Ischemic Disease: Biology, Signaling Pathways, and Epigenetics of Endothelial Progenitor Cells

Ischemic heart disease is currently a major cause of mortality and morbidity worldwide. Nevertheless, the actual therapeutic scenario does not target myocardial cell regeneration and consequently, the progression toward the late stage of chronic heart failure is common. Endothelial progenitor cells (EPCs) are bone marrow-derived stem cells that contribute to the homeostasis of the endothelial wall in acute and chronic ischemic disease. Calcium modulation and other molecular pathways (NOTCH, VEGFR, and CXCR4) contribute to EPC proliferation and differentiation. The present review provides a summary of EPC biology with a particular focus on the regulatory pathways of EPCs and describes promising applications for cardiovascular cell therapy.

Activity of the human immortalized endothelial progenitor cell line HEPC-CB.1 supporting in vitro angiogenesis

The human HEPC-CB.1 cell line with many characteristics of endothelial progenitor cells (EPC) was tested for its proangiogenic properties as a potentially therapeutic compound. HEPC-CB.1 cells’ potential to differentiate into endothelial cells was revealed after treating the cells with a mixture of ATRA, cAMP and VEGF, as shown by the reduced expression levels of CD133, CD271 and CD90 antigens, augmentation of CD146 and CD31, and a decrease in cell clonogenicity. The cooperation of HEPC-CB.1 with the endothelial cell line HSkMEC.2 resulted in the formation of a common network. Tube formation was significantly more effective when resulting from HEPC-CB.1 and HSkMEC.2 cell co-culture as compared to a monoculture of each cell line. The exocrine mechanism of HEPC-CB.1 and HSkMEC.2 cross talk by secreted factors was evidenced using the HEPC-CB.1 supernatant to increase the efficacy of HSkMEC.2 tube formation. The proangiogenic factors produced by HEPC-CB.1 were identified using cytokine antibody array. Out of 120 examined factors, the HEPC-CB.1 cell line produced 63, some with known angiogenic activity. As in vivo the angiogenic process occurs at low oxygen tension, it was observed that in hypoxia, the production of defined factors was augmented. The presented results demonstrate that HEPC-CB.1 cells are able to both cooperate and integrate in a newly formed network and produce factors that help the network formation. The results suggest that HEPC-CB.1 cells are indeed endothelial progenitors and may prove to be an effective tool in regenerative medicine.

Gelatin Based Polymer Cell Coating Improves Bone Marrow-Derived Cell Retention in the Heart after Myocardial Infarction

BACKGROUND

Acute myocardial infarction (AMI) and the ensuing ischemic heart disease are approaching an epidemic state. Limited stem cell retention following intracoronary administration has reduced the clinical efficacy of this novel therapy. Polymer based cell coating is biocompatible and has been shown to be safe. Here, we assessed the therapeutic utility of gelatin-based biodegradable cell coatings on bone marrow derived cell retention in ischemic heart.

METHODS

Gelatin based cell coatings were formed from the surface-mediated photopolymerization of 3% gelatin methacrylamide and 1% PEG diacrylate. Cell coating was confirmed using a multimodality approach including flow cytometry, imaging flow cytometry (ImageStream System) and immunohistochemistry. Biocompatibility of cell coating, metabolic activity of coated cells, and the effect of cell coating on the susceptibility of cells for engulfment were assessed using in vitro models. Following myocardial infarction and GFP+ BM-derived mesenchymal stem cell transplantation, flow cytometric and immunohistochemical assessment of retained cells was performed.

RESULTS

Coated cells are viable and metabolically active with coating degrading within 72 h in vitro. Importantly, cell coating does not predispose bone marrow cells to aggregation or increase their susceptibility to phagocytosis. In vitro and in vivo studies demonstrated no evidence of heightened immune response or increased phagocytosis of coated cells. Cell transplantation studies following myocardial infarction proved the improved retention of coated bone marrow cells compared to uncoated cells.

CONCLUSION

Gelation based polymer cell coating is biologically safe and biodegradable. Therapies employing these strategies may represent an attractive target for improving outcomes of cardiac regenerative therapies in human studies.

Cellular Based Strategies for Microvascular Engineering

Vascularization is a major hurdle in complex tissue and organ engineering. Tissues greater than 200 μm in diameter cannot rely on simple diffusion to obtain nutrients and remove waste. Therefore, an integrated vascular network is required for clinical translation of engineered tissues. Microvessels have been described as <150 μm in diameter, but clinically they are defined as <1 mm. With new advances in super microsurgery, vessels less than 1 mm can be anastomosed to the recipient circulation. However, this technical advancement still relies on the creation of a stable engineered microcirculation that is amenable to surgical manipulation and is readily perfusable. Microvascular engineering lays on the crossroads of microfabrication, microfluidics, and tissue engineering strategies that utilize various cellular constituents. Early research focused on vascularization by co-culture and cellular interactions, with the addition of angiogenic growth factors to promote vascular growth. Since then, multiple strategies have been utilized taking advantage of innovations in additive manufacturing, biomaterials, and cell biology. However, the anatomy and dynamics of native blood vessels has not been consistently replicated. Inconsistent results can be partially attributed to cell sourcing which remains an enigma for microvascular engineering. Variations of endothelial cells, endothelial progenitor cells, and stem cells have all been used for microvascular network fabrication along with various mural cells. As each source offers advantages and disadvantages, there continues to be a lack of consensus. Furthermore, discord may be attributed to incomplete understanding about cell isolation and characterization without considering the microvascular architecture of the desired tissue/organ.

Nailfold Capillary Hemorrhages: Microvascular Risk Factors for Primary Open-Angle Glaucoma

Background

Primary open-angle glaucoma (POAG) is associated with systemic microvascular dysfunction including hemorrhages and other abnormalities of the nailfold capillary bed. This study aimed to verify the specificity of nailfold capillary hemorrhages and other abnormalities as risk factors for POAG.

Methods

Nailfold video capillaroscopy was performed using a JH-1004 capillaroscope on the fourth and fifth digits of the nondominant hand in control (n = 277), POAG (n = 206), OHT (n = 57), and SG (n = 29) subjects. The number of hemorrhages, dilated capillaries >50 µm, and avascular zones ≥200 µm were counted and adjusted to counts per 100 capillaries. Descriptive analyses as well as univariate- and multivariable-adjusted logistic regression were performed comparing all groups with controls and POAG with OHT and SG. Subanalyses were conducted in POAG patients examining the association between nailfold capillary outcomes and previous glaucoma surgery, successful IOP control, or disease severity.

Results

All nailfold capillary outcomes were significantly increased in POAG, no outcomes were increased in SG, and only hemorrhages were mildly increased in OHT. Hemorrhages were significantly more frequent in POAG compared with both OHT (P < 0.0001) and SG (P=0.001). There were significant trends between higher numbers of hemorrhages and POAG compared with controls, OHT, and SG, with odds ratios of 18.3 (8.5-39.4), 9.1 (1.9-13.4), and 11.8 (1.7-7.3), respectively, for the presence of two or more hemorrhages per 100 capillaries. Hemorrhages were not significantly associated with previous glaucoma surgery, successful postoperative IOP control, or disease severity in POAG.

Conclusions

These findings suggest that systemic microvascular dysfunction is frequent in POAG and occurs early in the disease process. The high specificity of nailfold hemorrhages makes them viable clinical risk factors for POAG.

Radiation Damage to Tumor Vasculature Initiates a Program That Promotes Tumor Recurrences

This review, mostly of preclinical data, summarizes the evidence that radiation at doses relevant to radiation therapy initiates a pathway that promotes the reconstitution of the tumor vasculature leading to tumor recurrence. The pathway is not specific to tumors; it promotes repair of damaged and ischemic normal tissues by attracting proangiogenic cells from the bone marrow. For irradiated tumors the pathway comprises: (1) loss of endothelial cells and reduced tumor blood perfusion leading to increased tumor hypoxia and increased levels of hypoxia inducible factor-1 (HIF-1). Alternatively, increased HIF-1 levels may arise by reactive oxygen species (ROS) production caused by tumor reoxygenation. (2) Increased HIF-1 levels lead to increased levels in the tumor of the chemokine stromal cell-derived factor-1 (SDF-1, CXCL12), which captures monocytes/macrophages expressing the CXCR4 receptor of CXCL12. (3) The increased levels of tumor-associated macrophages (TAMs) become highly proangiogenic (M2 polarized) and restore the tumor vasculature, thereby promoting tumor recurrence. The relevance of this pathway for radiation therapy is that it can be blocked in a number of different ways including by inhibitors of monocytes/macrophages, of HIF-1, of CXCL12, of CXCR4, and of CSF-1R, the latter of which is responsible for the M2 polarization of the TAMs. All of these inhibitors produce a robust enhancement of the radiation response of a wide variety of preclinical tumor models. Further, the same inhibitors actually provide protection against radiation damage of several normal tissues. Some of these pathway inhibitors are available clinically, and a first-in-human trial of the CXCR4 inhibitor, plerixafor, with radiation therapy of glioblastoma has yielded promising results, including an impressive increase in local tumor control. Further clinical trials are warranted.

Contribution of a GATA4-Expressing Hematopoietic Progenitor Lineage to the Adult Mouse Endothelium

Different sources have been claimed for the embryonic origin of the coronary endothelium. Recently, the potential of circulating cells as progenitors of the cardiac endothelium has also been suggested. In a previous study we have shown that circulating progenitors are recruited by the embryonic endocardium and incorporated into the coronary vessels. These progenitors derive from a mesodermal lineage characterized by the expression of Gata4 under control of the enhancer G2. Herein, we aim to trace this specific lineage throughout postnatal stages. We have found that more than 50% of the adult cardiac endothelium derives from the G2-GATA4 lineage. This percentage increases from embryos to adults probably due to differential proliferation and postnatal recruitment of circulating endothelial progenitors. In fact, injection of fetal liver or placental cells in the blood stream of neonates leads to incorporation of G2-GATA4 lineage cells to the coronary endothelium. On the other hand, labeling of the hematopoietic lineage by the stage E7.5 also resulted in positive coronary endothelial cells from both, embryos and adults. Our results suggest that early hematopoietic progenitors recruited by the embryonic ventricular endocardium can become the predominant source of definitive endothelium during the vascularization of the heart.

Novel Cell-Based and Tissue Engineering Approaches for Induction of Angiogenesis as an Alternative Therapy for Diabetic Retinopathy

Diabetic retinopathy (DR) is the most frequent microvascular complication of long-term diabetes and the most common cause of blindness, increasing morbidity in the working-age population. The most effective therapies for these complications include laser photocoagulation and anti-vascular endothelial growth factor (VEGF) intravitreal injections. However, laser and anti-VEGF drugs are untenable as a final solution as they fail to address the underlying neurovascular degeneration and ischemia. Regenerative medicine may be a more promising approach, aimed at the repair of blood vessels and reversal of retinal ischemia. Stem cell therapy has introduced a novel way to reverse the underlying ischemia present in microvascular complications in diseases such as diabetes. The present review discusses current treatments, their side effects, and novel cell-based and tissue engineering approaches as a potential alternative therapeutic approach.

Leukocyte Apheresis Using a Fiber Filter Suppresses Colonic Injury Through Calcitonin Gene-Related Peptide Induction

BACKGROUND

The aim of this study was to address whether the therapeutic effect of leukocytapheresis (LCAP) depends on calcitonin gene- related peptide (CGRP) induction.

METHODS

An HLA-B27 transgenic rat model was treated with an LCAP column. The effects of LCAP on clinical, endoscopic, and histologic disease activity, the colony-forming ability of colony-forming unit (CFU)-granulocyte macrophages (GMs), colonic blood flow, and tissue expression of tumor necrosis factor (TNF)-α and CGRP were examined. Changes in the effects of LCAP after pretreatment with the CGRP antagonist CGRP8-37 were also observed. A dextran sulfate sodium-induced colitis rat model included treatment with CGRP, and the effect was assessed based on clinical, endoscopic, and histologic disease activity, colonic blood flow, the colony-forming ability of CFU-GMs, and tissue expression of inflammatory cytokines and CGRP receptor families.

RESULTS

LCAP improved disease activity, enhanced colonic blood flow, and induced the bone marrow colony-forming ability of CFU-GMs with an increase in CGRP mRNA levels. These effects were abolished by pretreatment with CGRP8-37. The administration of CGRP suppressed colitis, promoting colonic blood flow, inducing bone marrow-derived cells, downregulating inflammatory cytokines, and upregulating receptor activity-modifying protein-1. The mRNA and protein levels of inflammatory cytokines in lipopolysaccharide-stimulated mononuclear cells were also decreased after CGRP treatment.

CONCLUSIONS

The therapeutic effects of LCAP depend on CGRP induction. CGRP can effectively suppress colitis through the downregulation of inflammatory events and upregulation of protective events.

Platelet-derived microvesicles promote endothelial progenitor cell proliferation in intimal injury by delivering TGF-β1

Intimal injury is an early stage of several cardiovascular diseases. Endothelial progenitor cells (EPCs) play a significant role in endothelial repair following vascular injury. Once the intima is damaged, EPCs are mobilized from the bone marrow to the injury site. Meanwhile, the injury to the intimal surface triggers platelet degranulation, aggregation, and adhesion to the damaged endothelium, and exposed collagen stimulates platelet to secrete platelet-derived microvesicles (PMVs). However, the role of PMVs in EPC function during this process remains unknown. In an in vivo study, EPCs and platelets were found to adhere to the injury site in Sprague-Dawley (SD) rat vascular injury model. In vitro, collagen stimulation induced the release of PMVs, and collagen-activated PMVs (ac.PMVs) significantly promoted EPC proliferation. Transforming growth factor-β1 (TGF-β1) content was increased in ac.PMVs. Activated PMVs significantly upregulated Smad3 phosphorylation in EPCs and increased Smad3 nuclear translocation from the cytoplasm. TGF-β1 knockdown ac.PMVs downregulated EPC proliferation. Recombinant TGF-β1 enhanced EPC proliferation. The TGF-β1 inhibitor SB431542 significantly repressed the intracellular signal triggered by ac.PMVs. Furthermore, the Smad3-specific phosphorylation inhibitor SIS3 effectively reversed the cell proliferation induced by ac.PMVs. Smad3 translocated to the nucleus and enhanced EPC proliferation via its downstream genes tenascin C (TNC), CDKN1A, and CDKN2A. r-TGF-β1 promoted reendothelialization and EPC proliferation in vivo. Our data demonstrate that activated PMVs deliver TGF-β1 from collagen-activated platelets to EPCs, which in turn activates Smad3 phosphorylation and regulates TNC, CDKN1A, and CDKN2A expression to promote EPC proliferation, suggesting that PMVs act as a key transporter and a potential therapeutic target for vascular injury.

Author Correction: Insufficient production of IL-10 from M2 macrophages impairs in vitro endothelial progenitor cell differentiation in patients with Moyamoya disease

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Macrophage exclusion after radiation therapy (MERT): A new and effective way to increase the therapeutic ratio of radiotherapy

Here we review a variety of preclinical studies and a first-in-human clinical trial of newly diagnosed glioblastoma (GBM) patients that have investigated the significance of the influx of tumor associated macrophages (TAMs) into tumors after irradiation. We summarize the effects on the response of the tumors and normal tissues to radiation of various agents that either reduce the influx of TAMs into tumors after radiation or change their M1/M2 polarization. The studies show that following irradiation there is an accumulation of bone marrow derived TAMs in the irradiated tumors. These TAMs stimulate the resumption of blood flow in the irradiated tumors thereby promoting recurrence of the tumors. A key mechanism for this accumulation of TAMs is driven by the SDF-1/CXCR4 chemokine pathway though other pathways could also be involved for some tumors. Blocking this pathway to prevent the TAM accumulation in the tumors both enhances tumor response to radiation and protects irradiated tissues. A clinical trial in which the CXCR4 antagonist plerixafor was added to standard therapy of glioblastoma validated the preclinical findings by demonstrating i) reduced blood flow in the irradiated site, and ii) significantly improved tumor local control compared to GBM patients not treated with plerixafor. We conclude that macrophage exclusion after radiation therapy (MERT) is an effective way both to enhance the tumor response to radiation and to protect the irradiated normal tissues. Further clinical trials are warranted.

Cell Therapy-a Basic Science Primer for the Sports Medicine Clinician

PURPOSE OF REVIEW

The emergence of cell-based therapies has brought much excitement to the field of orthopedic sports medicine. However, the significant inconsistency of reporting has led to the poor understanding, misinformation, and false expectations for patients and clinicians alike. In this paper, we aim to clarify the available cell-therapy treatments and summarize some of the latest research.

RECENT FINDINGS

Although this technology is in early development, our understanding of cell biology has grown significantly over the last decade. Furthermore, it is becoming evident that tissue specificity may play a significant role in determining the effectiveness and overall clinical benefit attributed to cell therapy. Cell therapy is an emerging field with tremendous potential for clinically significant benefit. However, in its current state, clinical application of these treatments is limited by federal regulations, variability in formulation, and limited understanding of the biologic activity of various cell formulations.

Stem Cells in Cardiovascular Medicine: Historical Overview and Future Prospects

Cardiovascular diseases remain the leading cause of death in the developed world, accounting for more than 30% of all deaths. In a large proportion of these patients, acute myocardial infarction is usually the first manifestation, which might further progress to heart failure. In addition, the human heart displays a low regenerative capacity, leading to a loss of cardiomyocytes and persistent tissue scaring, which entails a morbid pathologic sequela. Novel therapeutic approaches are urgently needed. Stem cells, such as induced pluripotent stem cells or embryonic stem cells, exhibit great potential for cell-replacement therapy and an excellent tool for disease modeling, as well as pharmaceutical screening of novel drugs and their cardiac side effects. This review article covers not only the origin of stem cells but tries to summarize their translational potential, as well as potential risks and clinical translation.

Low Pre-Treatment Count of Circulating Endothelial Progenitors as a Prognostic Biomarker of the High Risk of Breast Cancer Recurrence

Neoangiogenesis is mediated by circulating bone marrow-derived endothelial progenitors (circulating EPCs). The aim of the study was the quantification of circulating EPCs from the peripheral blood mononuclear cells of invasive breast cancer (IBrC) patients by flow cytometry, before and after cancer adjuvant treatment. A total of 88 stage IA-IIB primary IBrC patients were enrolled prospectively. Circulating EPCs with the immune-phenotype CD45−CD34+CD133+CD31+ were assessed. Treatment significantly reduced the number of EPCs/µL in the general IBrC cohort. However, there was a relevant elevation in the number of circulating EPCs after nine months of adjuvant treatment in the group of patients aged ≥ 55 years, of T2 clinical type, with nodal involvement (N1) and Ki67 expression > 15%. Follow-up revealed a significantly higher incidence of disease relapse in breast cancer patients with low pre-treatment circulating EPCs levels compared with those with a high baseline circulating EPCs count. The receiver-operating characteristic curve identified a tumour diameter of 2.1 cm as the best cut-off value to discriminate between disease-relapse subjects and non-relapse disease cases. Our study strongly indicates that, next to tumour diameter and Ki67 expression, circulating bone marrow-derived EPCs may serve as useful markers for predicting therapeutic outcomes as well as a future prognosis.

Mechanisms Underlying Cell Therapy in Liver Fibrosis: An Overview

Fibrosis is a common feature in most pathogenetic processes in the liver, and usually results from a chronic insult that depletes the regenerative capacity of hepatocytes and activates multiple inflammatory pathways, recruiting resident and circulating immune cells, endothelial cells, non-parenchymal hepatic stellate cells, and fibroblasts, which become activated and lead to excessive extracellular matrix accumulation. The ongoing development of liver fibrosis results in a clinically silent and progressive loss of hepatocyte function, demanding the constant need for liver transplantation in clinical practice, and motivating the search for other treatments as the chances of obtaining compatible viable livers become scarcer. Although initially cell therapy has emerged as a plausible alternative to organ transplantation, many factors still challenge the establishment of this technique as a main or even additional therapeutic tool. Herein, the authors discuss the most recent advances and point out the corners and some controversies over several protocols and models that have shown promising results as potential candidates for cell therapy for liver fibrosis, presenting the respective mechanisms proposed for liver regeneration in each case.

Endothelial progenitor cell therapy for chronic wound tissue regeneration

Despite advancements in wound care, healing of chronic diabetic wounds remains a great challenge for the clinical fraternity because of the intricacies of the healing process. Due to the limitations of existing treatment strategies for chronic wounds, stem/progenitor cell transplantation therapies have been explored as an alternative for tissue regeneration at the wound site. The non-healing phenotype of chronic wounds is directly associated with lack of vascularization. Therefore, endothelial progenitor cell (EPC) transplantation is proving to be a promising approach for the treatment of hypo-vascular chronic wounds. With the existing knowledge in EPC biology, significant efforts have been made to enrich EPCs at the chronic wound site, generating EPCs from somatic cells, induced pluripotent stem cells (iPSCs) using transcription factors, or from adult stem cells using chemicals/drugs for use in transplantation, as well as modulating the endogenous dysfunctional/compromised EPCs under diabetic conditions. This review mainly focuses on the pre-clinical and clinical approaches undertaken to date with EPC-based translational therapy for chronic diabetic as well as non-diabetic wounds to evaluate their vascularity-mediated regeneration potential.

The Potential Role of Circulating Endothelial Cells and Endothelial Progenitor Cells in the Prediction of Left Ventricular Hypertrophy in Hypertensive Patients

Background

The main aim of present study is to evaluate the potential role of circulating endothelial cells (CECs) and endothelial progenitor cells (CEPCs) – representing specific markers of endothelial damage, in the prediction of left ventricular hypertrophy (LVH) in hypertensive patients categorized into two groups; mild (MH) and resistant hypertension (RH).

Materials and Methods

Thirty patients with MH and 28 subjects with RH were involved in the study. In both groups, patients were divided into an LVH and non-LVH group. The control group included 33 age and sex-matched normotensive volunteers. Physical examination, laboratory tests and echocardiography were conducted.

Results

In both the MH and RH group, patients with as well as without LVH demonstrated a higher number of CECs and a lower ratio of CEPCs/CECs as compared to the healthy control. Multiple linear regression analysis showed a positive association of CEPCs with left ventricular mass (LVM) and left ventricular mass index (LVMI), independently of other confounders.

Conclusion

Our results suggest that endothelial injury observed as an elevated CECs number and its impaired regeneration, reflected by a lowered CEPCs/CECs ratio, precede LVH occurrence and may play a significant role in LVH development regardless of the clinical severity of hypertension. Moreover, independent correlation of CEPCs with echocardiographic (ECG) incidences of LVH suggests their potential use as a screening biomarker to stratify the risk of LVH development.

Angiogenic Factor AGGF1-Primed Endothelial Progenitor Cells Repair Vascular Defect in Diabetic Mice

Hyperglycemia-triggered vascular abnormalities are the most serious complications of diabetes mellitus (DM). The major cause of vascular dysfunction in DM is endothelial injury and dysfunction associated with the reduced number and dysfunction of endothelial progenitor cells (EPCs). A major challenge is to identify key regulators of EPCs to restore DM-associated vascular dysfunction. We show that EPCs from heterozygous knockout Aggf1^+/- mice presented with impairment of proliferation, migration, angiogenesis, and transendothelial migration as in hyperglycemic mice fed a high-fat diet (HFD) or db/db mice. The number of EPCs from Aggf1^+/- mice was significantly reduced. Ex vivo, AGGF1 protein can fully reverse all damaging effects of hyperglycemia on EPCs. In vivo, transplantation of AGGF1-primed EPCs successfully restores blood flow and blocks tissue necrosis and ambulatory impairment in HFD-induced hyperglycemic mice or db/db mice with diabetic hindlimb ischemia. Mechanistically, AGGF1 activates AKT, reduces nuclear localization of Fyn, which increases the nuclear level of Nrf2 and expression of antioxidative genes, and inhibits reactive oxygen species generation. These results suggest that Aggf1 is required for essential function of EPCs, AGGF1 fully reverses the damaging effects of hyperglycemia on EPCs, and AGGF1 priming of EPCs is a novel treatment modality for vascular complications in DM.

The Effect of Uncoated SPIONs on hiPSC-Differentiated Endothelial Cells

Background: Endothelial progenitor cells (EPCs) were indicated in vascular repair, angiogenesis of ischemic organs, and inhibition of formation of initial hyperplasia. Differentiation of endothelial cells (ECs) from human induced pluripotent stem cells (hiPSC)-derived endothelial cells (hiPSC-ECs) provides an unlimited supply for clinical application. Furthermore, magnetic cell labelling offers an effective way of targeting and visualization of hiPSC-ECs and is the next step towards in vivo studies. Methods: ECs were differentiated from hiPSCs and labelled with uncoated superparamagnetic iron-oxide nanoparticles (uSPIONs). uSPION uptake was compared between hiPSC-ECs and mature ECs isolated from patients by software analysis of microscopy pictures after Prussian blue cell staining. The acute and long-term cytotoxic effects of uSPIONs were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay) and Annexin assay. Results: We showed, for the first time, uptake of uncoated SPIONs (uSPIONs) by hiPSC-ECs. In comparison with mature ECs of identical genetic background hiPSC-ECs showed lower uSPION uptake. However, all the studied endothelial cells were effectively labelled and showed magnetic properties even with low labelling concentration of uSPIONs. uSPIONs prepared by microwave plasma synthesis did not show any cytotoxicity nor impair endothelial properties. Conclusion: We show that hiPSC-ECs labelling with low concentration of uSPIONs is feasible and does not show any toxic effects in vitro, which is an important step towards animal studies.

Identification of Circulating Endothelial Colony-Forming Cells from Murine Embryonic Peripheral Blood

Human umbilical cord blood contains highly proliferative circulating endothelial colony-forming cells (ECFC). These cells have promising therapeutic potential for various cardiovascular diseases by possessing robust in vitro clonal expansion potential and the ability to form functional blood vessels in vivo upon transplantation into recipient immunodeficient mice. However whether similar cells also exist in murine blood remains unresolved, which impedes the study of circulating ECFC biology using murine models. Here we describe a method to identify and culture murine embryonic peripheral blood-derived circulating ECFC through co-culture with OP9 stromal cells. Using this method, embryonic circulating ECFC can be identified by the formation of sheet-like or network-like endothelial colonies upon OP9 stromal cell monolayers.

Keloid patients have higher peripheral blood endothelial progenitor cell counts and CD34+ cells with normal vasculogenic and angiogenic function that overexpress vascular endothelial growth factor and interleukin-8

BACKGROUND

One suggested reason for aberrant wound healing in keloid scars is chronic inflammation of the dermis. We hypothesized that excessive blood vessel formation and high capillary density in keloid tissue is caused by dysfunction of endothelial progenitor cells.

METHODS

We compared the number of circulating endothelial progenitor cells and vasculogenic and angiogenic capacity, as well as secretory function, of circulating CD34⁺ cells in keloid patients and healthy individuals.

RESULTS

Compared to mononuclear cell cultures from healthy donors, cultures of peripheral blood mononuclear cells obtained from keloid patients showed a more than twofold increase in the number of peripheral blood EPCs (fibronectin-adhering cells that phagocytized acetylated low-density lipoprotein and bound Ulex europaeus agglutinin-I lectin). However, there was no difference in colony-forming ability and participation in in vitro angiogenesis between circulating CD34⁺ cells isolated from keloid patients and healthy individuals. This means that circulating CD34⁺ /endothelial progenitor cells in keloid patients have normal vasculogenic and angiogenic function. However, CD34⁺ cells derived from keloid patients demonstrated a more than sevenfold expression of the interleukin-8 gene and a more than fivefold expression of the vascular endothelial growth factor gene than CD34⁺ cells derived from healthy individuals.

CONCLUSIONS

These results support the role of vascular endothelial growth factor and interleukin-8 in increased recruitment of endothelial progenitor cells in keloid patients.

Strategies for derivation of endothelial lineages from human stem cells

Accumulating evidence demonstrates that pre-vascularization of tissue-engineered constructs can significantly enhance their survival and engraftment upon transplantation. Endothelial cells (ECs), the basic component of vasculatures, are indispensable to the entire process of pre-vascularization. However, the source of ECs still poses an issue. Recent studies confirmed that diverse approaches are available in the derivation of ECs for tissue engineering, such as direct isolation of autologous ECs, reprogramming of somatic cells, and induced differentiation of stem cells in typology. Herein, we discussed a variety of human stem cells (i.e., totipotent, pluripotent, multipotent, oligopotent, and unipotent stem cells), which can be induced to differentiate into ECs and reviewed the multifarious approaches for EC generation, such as 3D EB formation for embryonic stem cells (ESCs), stem cell-somatic cell co-culture, and directed endothelial differentiation with growth factors in conventional 2D culture.

Sphingosine-1-Phosphate Improves the Biological Features of Mouse Bone Marrow-Derived EPCs Partially through PI3K/AKT/eNOS/NO Pathway

Sphingosine-1-phosphate (S1P), a bioactive sphingolipid, is recognized as a critical regulator in physiological and pathophysiological processes of atherosclerosis (AS). However, the underlying mechanism remains unclear. As the precursor cells of endothelial cells (ECs), endothelial progenitor cells (EPCs) can prevent AS development through repairing endothelial monolayer impaired by proatherogenic factors. The present study investigated the effects of S1P on the biological features of mouse bone marrow-derived EPCs and the underlying mechanism. The results showed that S1P improved cell viability, adhesion, and nitric oxide (NO) release of EPCs in a bell-shaped manner, and migration and tube formation dose-dependently. The aforementioned beneficial effects of S1P on EPCs could be inhibited by the phosphatidylinositol 3-kinase (PI3K) inhibitor of LY294002 and nitric oxide synthase (NOS) inhibitor of N’-nitro-L-arginine-methyl ester hydrochloride (L-NAME). The inhibitor of LY294002 inhibited S1P-stimulated activation of phosphorylated protein kinase B (AKT) (p-AKT) and endothelial nitric oxide synthase (eNOS) (p-eNOS), and down-regulated the level of eNOS significantly. The results suggest that S1P improves the biological features of EPCs partially through PI3K/AKT/eNOS/NO signaling pathway.

MicroRNA-210-3p Targets RGMA to Enhance the Angiogenic Functions of Endothelial Progenitor Cells Under Hypoxic Conditions

Endothelial progenitor cells (EPCs) are multipotential stem cells considered to have immense clinical value for revascularization. However, the clinical application of EPCs has been hampered by their clinical potency in ischemic anoxic environments. This study aimed to explore the effect of microRNA-210 (miR-210) on EPCs under oxygen-glucose deprivation (OGD) conditions. We generated a model of EPCs cultured under OGD conditions to simulate ischemia and explore the expression of miR-210 in vitro. With longer exposure to hypoxia, we found that miR-210-3p expression was highly upregulated in OGD groups compared to that in controls from 4 to 24 h, but not miR-210-5p. We then transfected a miR-210-3p mimic and inhibitor into EPCs, and after 24 h, we exposed them to OGD conditions for 4 h to simulate ischemia. We detected miR-210 by real-time polymerase chain reaction (RT-PCR) and tested the proliferation, migration, and tube formation of normal EPCs and OGD-treated EPCs by CCK-8, transwell chamber, and Matrigel assays, respectively. The direct targets of miR-210-3p were predicted using miRWalk. Compared to that in normal EPCs, higher miR-210-3p expression was found in OGD-treated EPCs (p < 0.05). Moreover, upregulation of miR-210-3p was found to promote proliferation, migration, and tube formation in EPCs under normal and OGD conditions (p < 0.05), whereas down-regulation inhibited these abilities in OGD-treated EPCs (p < 0.05). Repulsive guidance molecule A (RGMA), a negative regulator of angiogenesis, was predicted to be a target of miR-210-3p. Accordingly, upregulation of miR-210-3p was found to inhibit its expression at the protein level in OGD-treated EPCs, whereas downregulation of miR-210-3p inhibited its expression (p < 0.05). A dual-luciferase reporter system confirmed that RGMA is a direct target of miR-210-3p. MicroRNA-210-3p overexpression enhances the angiogenic properties of OGD-treated EPCs by inhibiting RGMA.

Cell therapy of critical limb ischemia-problems and prospects

Cell therapy is proposed for indirect revascularization for the patient's incurable by endovascular or surgical revascularization. The therapy with stem cells (SCs) or progenitor cells is assumed to be more efficient as compared with protein or gene therapy not only because of their direct vasculogenic properties, but also thanks to their paracrine effect via secretion of manifold biologically active substances. This review gives an overview of the potential of SC-based therapy for critical limb ischemia (CLI), putative mechanism underlying cell therapy, and comparison of cell therapy to angiogenesis gene therapy in CLI treatment. Human trial data and meta-analysis, as well as some problems of clinical trials and considerations for future SC-based therapy in CLI are also discussed.

Diabetic cardiomyopathy - A comprehensive updated review

Diabetes causes cardiomyopathy and increases the risk of heart failure independent of hypertension and coronary heart disease. This condition called "Diabetic Cardiomyopathy" (DCM) is becoming a well- known clinical entity. Recently, there has been substantial research exploring its molecular mechanisms, structural and functional changes, and possible development of therapeutic approaches for the prevention and treatment of DCM. This review summarizes the recent advancements to better understand fundamental molecular abnormalities that promote this cardiomyopathy and novel therapies for future research. Additionally, different diagnostic modalities, up to date screening tests to guide clinicians with early diagnosis and available current treatment options has been outlined.

A Method to Isolate CD34+ Mononuclear Cells from Canine Peripheral Blood

Embryonic stem cells are pluripotent whereas adult stem cells are multipotent in nature. In recent years, evidence suggests that adult stem cells not only differentiate into specific cell lineages but also transdifferentiate into multiple cell lineages. Progenitor cells are found in adult bone marrow, blood, and other organs and differentiate into numerous cell lineages regardless of origin. Identifying a subset that can differentiate into mature endothelial cells is essential. This article describes peripheral blood collection in adult beagle dogs, isolation of peripheral blood mononuclear cells (PBMNCs) from the cell fraction, separation of a subset of CD34+ cells using immunomagnetic principles, characterization of PBMNCs and CD34+ cells using flow cytometry, and evaluation of gene expression of CD34, KDR, and CD133 in CD34+ fractions. Efficient methods of isolation of endothelial progenitor cells (EPCs) will promote the ex vivo expansion and transplantation of EPCs in ischemic injury to enable neovascularization. © 2019 by John Wiley & Sons, Inc.

Putative endothelial progenitor cells do not promote vascular repair but attenuate pericyte-myofibroblast transition in UUO-induced renal fibrosis

Background

Putative endothelial progenitor cells (pEPCs) have been confirmed to participate in alleviation of renal fibrosis in several ischaemic diseases. However, their mechanistic effect on renal fibrosis, which is characterized by vascular regression and further rarefaction-related pathology, remains unknown.

Methods

To explore the effect and molecular mechanisms by which pEPCs act on unilateral ureteral obstruction (UUO)-induced renal fibrosis, we isolated pEPCs from murine bone marrow. In vivo, pEPCs (2 × 10⁵ cells/day) and pEPC-MVs (microvesicles) were injected into UUO mice via the tail vein. In vitro, pEPCs were co-cultured with renal-derived pericytes. Pericyte-myofibroblast transition was evaluated using the myofibroblast marker α-smooth muscle actin (α-SMA) and pericyte marker platelet-derived growth factor receptor β (PDGFR-β).

Results

Exogenous supply of bone marrow-derived pEPCs attenuated renal fibrosis by decreasing pericyte-myofibroblast transition without significant vascular repair in the UUO model. Our results indicated that pEPCs regulated pericytes and their transition into myofibroblasts via pEPC-MVs. Co-culture of pericytes with pEPCs in vitro suggested that pEPCs inhibit transforming growth factor-β (TGF-β)-induced pericyte–myofibroblast transition via a paracrine pathway.

Conclusion

pEPCs effectively attenuated UUO-induced renal fibrosis by inhibiting pericyte–myofibroblast transition via a paracrine pathway, without promoting vascular repair.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1201-5) contains supplementary material, which is available to authorized users.

Label-Free Multi Parameter Optical Interrogation of Endothelial Activation in Single Cells using a Lab on a Disc Platform

Cellular activation and inflammation leading to endothelial dysfunction is associated with cardiovascular disease (CVD). We investigated whether a single cell label-free multi parameter optical interrogation system can detect endothelial cell and endothelial progenitor cell (EPC) activation in vitro and ex vivo, respectively. Cultured human endothelial cells were exposed to increasing concentrations of tumour necrosis factor alpha (TNF-α) or lipopolysaccharide (LPS) before endothelial activation was validated using fluorescence-activated cell sorting (FACS) analysis of inflammatory marker expression (PECAM-1, E-selectin and ICAM-1). A centrifugal microfluidic system and V-cup array was used to capture individual cells before optical measurement of light scattering, immunocytofluorescence, auto-fluorescence (AF) and cell morphology was determined. In vitro, TNF-α promoted specific changes to the refractive index and cell morphology of individual cells concomitant with enhanced photon activity of fluorescently labelled inflammatory markers and increased auto-fluorescence (AF) intensity at three different wavelengths, an effect blocked by inhibition of downstream signalling with Iκβ. Ex vivo, there was a significant increase in EPC number and AF intensity of individual EPCs from CVD patients concomitant with enhanced PECAM-1 expression when compared to normal controls. This novel label-free 'lab on a disc' (LoaD) platform can successfully detect endothelial activation in response to inflammatory stimuli in vitro and ex vivo.

Runx3 inhibits endothelial progenitor cell differentiation and function via suppression of HIF-1α activity

Endothelial progenitor cells (EPCs) are bone marrow (BM)‑derived progenitor cells that can differentiate into mature endothelial cells, contributing to vasculogenesis in the blood vessel formation process. Runt‑related transcription factor 3 (RUNX3) belongs to the Runt domain family and is required for the differentiation of specific immune cells and neurons. The tumor suppressive role of RUNX3, via the induction of apoptosis and cell cycle arrest in a variety of cancers, and its deletion or frequent silencing by epigenetic mechanisms have been studied extensively; however, its role in the differentiation of EPCs is yet to be investigated. Therefore, in the present study, adult BM‑derived hematopoietic stem cells (HSCs) were isolated from Runx3 heterozygous (Rx3+/‑) or wild‑type (WT) mice. The differentiation of EPCs from the BM‑derived HSCs of Rx3+/‑ mice was found to be significantly increased compared with those of the WT mice, as determined by the number of small or large colony‑forming units. The migration and tube formation abilities of Rx3+/‑ EPCs were also observed to be significantly increased compared with those of WT EPCs. Furthermore, the number of circulating EPCs, defined as CD34+/vascular endothelial growth factor receptor 2 (VEGFR2)+ cells, was also significantly increased in Rx3+/‑ mice. Hypoxia‑inducible factor (HIF)‑1α was upregulated in Rx3+/‑ EPCs compared with WT EPCs, even under normoxic conditions. Furthermore, in a hindlimb ischemic mouse models, the recovery of blood flow was observed to be highly stimulated in Rx3+/‑ mice compared with WT mice. Also, in a Lewis lung carcinoma cell allograft model, the tumor size in Rx3+/‑ mice was significantly larger than that in WT mice, and the EPC cell population (CD34+/VEGFR2+ cells) recruited to the tumor was greater in the Rx3+/‑ mice compared with the WT mice. In conclusion, the present study revealed that Runx3 inhibits vasculogenesis via the inhibition of EPC differentiation and functions via the suppression of HIF‑1α activity.

Systemic microcirculation dysfunction after low thoracic spinal cord injury in mice

BACKGROUND

Spinal cord injury (SCI) disturbs the autonomic nervous system and induces dysfunction or failure of multiple organs. The systemic microcirculation disturbance that contributes to the complications associated with SCI remains to be clarified.

METHODS

We used male mice (29-32 g) and modified weight-drop injury at T10 to evaluate the systemic microcirculation dysfunction during the first 2 weeks after SCI. We determined permeability and microvascular blood flow in several organs and evaluated their vasomotor function. We also measured circulating endothelial cells (CECs), circulating endothelial progenitor cells (CEPCs), circulating pericyte progenitor cells (CPPCs), and serum proinflammatory cytokines.

RESULTS

The endothelial permeability of almost all organs increased after SCI. Microvascular blood flow decreased in the bladder and kidney and increased in the spleen and was accompanied by endothelial vasomotor dysfunction. SCI also induced an increase in CECs, CEPCs, and CPPCs in peripheral blood. Finally, we confirmed changes in a systemic cytokine profile (interleukin [IL]-3, IL-6, IL-10, IL-13, granulocyte colony-stimulating factor, and regulated on activation normal T cell expressed and secreted) after SCI.

CONCLUSIONS

These data indicate that a systemic microcirculation disturbance occurs after SCI. This information may play a key role in the development of effective therapeutic strategies for SCI.

Cellular Therapy for Ischemic Heart Disease: An Update

Ischemic heart disease (IHD), which includes heart failure (HF) induced by heart attack (myocardial infarction, MI), is a significant cause of morbidity and mortality worldwide (Benjamin, et al. Circulation 139:e56-e66, 2019). MI occurs at an alarmingly high rate in the United States (approx. One case every 40 seconds), and the failure to repair damaged myocardium is the leading cause of recurrent heart attacks, heart failure (HF), and death within 5 years of MI (Benjamin, et al. Circulation 139:e56-e66, 2019). At present, HF represents an unmet need with no approved clinical therapies to replace the damaged myocardium. As the population ages, the number of heart failure patients is projected to increase, doubling the annual cost by 2030 (Benjamin, et al. Circulation 139:e56-e66, 2019). In the past decades, stem cell therapy has become a promising strategy for cardiac regeneration. However, stem cell-based therapy yielded modest success in human clinical trials. This chapter examines the types of cells examined in cardiac therapy in the setting of IHD, with a brief introduction to ongoing research aiming at enhancing the therapeutic potential of transplanted cells.

CD276 (B7-H3) Maintains Proliferation and Regulates Differentiation in Angiogenic Function in Late Endothelial Progenitor Cells

Endothelial progenitor cells (EPCs) provide an important source of recovery from blood vessel dysfunction. Late EPCs (LEPCs) are circulating blood cells that are capable of promoting vascular repair. Using transcriptome analysis, we identified distinctive LEPC profiles and found that CD276 (B7-H3) mRNA is strongly expressed in LEPCs. CD276 protein is present abundantly on the cell surface of LEPC when analyzed by fluorescence-activated cell sorter and immunocytochemistry. CD276, a B7 family member, is a type I transmembrane glycoprotein. The role of CD276 in LEPCs remains unknown. CD276 knockdown by lentivirus transduction in LEPCs significantly decreased proliferation and increased apoptosis of LEPCs in vitro. After CD276 silencing, the cell cycle of LEPCs was prone to remain at the G0/G1 phase, and the cell migration rates as well as transwell and wound-healing migration were decreased. CD276 knockdown in LEPCs increased the G1 phase regulators cyclin D2/D3/E1-cyclin-dependent kinases (CDK2/4/6), but decreased the S-G2-M phase regulators cyclin A/B-CDK1. However, LEPCs with CD276 knockdown resulted in increased tube formation in vitro and angiogenesis in a Matrigel plug assay in vivo. FoxC1/C2, an upstream signal of Notch in arterial cell proliferation, and Hey1/2, which is known to promote arterial differentiation in the vasculature, were upregulated in CD276 knockdown LEPCs. In LEPCS, CD276 has a positive effect on proliferation and migration of endothelial cells, but negative effects on angiogenesis, particularly endothelial cell differentiation. Our data indicate, for therapeutic purpose, that CD276 can be used to acquire and maintain cell populations of LEPCs and blocking CD276 will promote angiogenetic differentiation. We found that CD276 (B7-H3) is enriched on the cell membrane of LEPCs. CD276 knockdown reduced proliferation and migration of LEPCs by increasing cell cycle inhibitors such as p21^cip1 and pRb and decreasing pErk1/2 and pAkt but promoted angiogenesis and endothelial cell differentiation by elevating vascular endothelial growth factor-vascular endothelial growth factor receptor 1 and p-p38. Stem Cells 2019;37:382-394.

Endothelial colony-forming cell therapy for heart morphological changes after neonatal high oxygen exposure in rats, a model of complications of prematurity

Very preterm birth is associated with increased cardiovascular diseases and changes in myocardial structure. The current study aimed to investigate the impact of endothelial colony-forming cell (ECFC) treatment on heart morphological changes in the experimental model of neonatal high oxygen (O2 )-induced cardiomyopathy, mimicking prematurity-related conditions. Sprague-Dawley rat pups exposed to 95% O2 or room air (RA) from day 4 (P4) to day 14 (P14) were randomized to receive (jugular vein) exogenous human cord blood ECFC or vehicle at P14 (n = 5 RA-vehicle, n = 8 RA-ECFC, n = 8 O2 -vehicle and n = 7 O2 -ECFC) and the hearts collected at P28. Body and heart weights and heart to body weight ratio did not differ between groups. ECFC treatment prevented the increase in cardiomyocyte surface area in both the left (LV) and right (RV) ventricles of the O2 group (O2 -ECFC vs. O2 -vehicle LV: 121 ± 13 vs. 179 ± 21 μm2 , RV: 118 ± 12 vs. 169 ± 21 μm2 ). In O2 rats, ECFC treatment was also associated with a significant reduction in interstitial fibrosis in both ventricles (O2 -ECFC vs. O2 -vehicle LV: 1.07 ± 0.47 vs. 1.68 ± 0.41% of surface area, RV: 1.01 ± 0.74 vs. 1.77 ± 0.67%) and in perivascular fibrosis in the LV (2.29 ± 0.47 vs. 3.85 ± 1.23%) but in not the RV (1.95 ± 0.95 vs. 2.74 ± 1.14), and with increased expression of angiogenesis marker CD31. ECFC treatment had no effect on cardiomyocyte surface area or on tissue fibrosis of RA rats. Human cord blood ECFC treatment prevented cardiomyocyte hypertrophy and myocardial and perivascular fibrosis observed after neonatal high O2 exposure. ECFC could constitute a new regenerative therapy against cardiac sequelae caused by deleterious conditions of prematurity.

Recent Advances in Endothelial Colony Forming Cells Toward Their Use in Clinical Translation

The term “Endothelial progenitor cell” (EPC) has been used to describe multiple cell populations that express endothelial surface makers and promote vascularisation. However, the only population that has all the characteristics of a real “EPC” is the Endothelial Colony Forming Cells (ECFC). ECFC possess clonal proliferative potential, display endothelial and not myeloid cell surface markers, and exhibit pronounced postnatal vascularisation ability in vivo. ECFC have been used to investigate endothelial molecular dysfunction in several diseases, as they give access to endothelial cells from patients in a non-invasive way. ECFC also represent a promising tool for revascularization of damaged tissue. Here we review the translational applications of ECFC research. We discuss studies which have used ECFC to investigate molecular endothelial abnormalities in several diseases and review the evidence supporting the use of ECFC for autologous cell therapy, gene therapy and tissue regeneration. Finally, we discuss ways to improve the therapeutic efficacy of ECFC in clinical applications, as well as the challenges that must be overcome to use ECFC in clinical trials for regenerative approaches.

Stem/Progenitor Cells and Their Therapeutic Application in Cardiovascular Disease

Cardiovascular disease is the leading cause of death in the world. The stem/progenitor cell-based therapy has emerged as a promising approach for the treatment of a variety of cardiovascular diseases including myocardial infarction, stroke, peripheral arterial disease, and diabetes. An increasing number of evidence has shown that stem/progenitor cell transplantation could replenish damaged cells, improve cardiac and vascular functions, and repair injured tissues in many pre-clinical studies and clinical trials. In this review, we have outlined the major types of stem/progenitor cells, and summarized the studies in applying these cells, especially endothelial stem/progenitor cells and their derivatives, in the treatment of cardiovascular disease. Here the strategies used to improve the stem/progenitor cell-based therapies in cardiovascular disease and the challenges with these therapies in clinical applications are also reviewed.

Sonic Hedgehog Signaling Pathway in Endothelial Progenitor Cell Biology for Vascular Medicine

The Hedgehog (HH) signaling pathway plays an important role in embryonic and postnatal vascular development and in maintaining the homeostasis of organs. Under physiological conditions, Sonic Hedgehog (SHH), a secreted protein belonging to the HH family, regulates endothelial cell growth, promotes cell migration and stimulates the formation of new blood vessels. The present review highlights recent advances made in the field of SHH signaling in endothelial progenitor cells (EPCs). The canonical and non-canonical SHH signaling pathways in EPCs and endothelial cells (ECs) related to homeostasis, SHH signal transmission by extracellular vesicles (EVs) or exosomes containing single-strand non-coding miRNAs and impaired SHH signaling in cardiovascular diseases are discussed. As a promising therapeutic tool, the possibility of using the SHH signaling pathway for the activation of EPCs in patients suffering from cardiovascular diseases is further explored.

Effectiveness of endothelial progenitor cell culture under microgravity for improved angiogenic potential

Endothelial progenitor cell (EPC) transplantation is beneficial for ischemic diseases such as critical limb ischemia and ischemic heart disease. The scarcity of functional EPCs in adults is a limiting factor for EPC transplantation therapy. The quality and quantity culture (QQc) system is an effective ex vivo method for enhancing the number and angiogenic potential of EPCs. Further, microgravity environments have been shown to enhance the functional potential of stem cells. We therefore hypothesized that cells cultured with QQc under microgravity may have enhanced functionality. We cultured human peripheral blood mononuclear cells using QQc under normal (E), microgravity (MG), or microgravity followed by normal (ME) conditions and found that ME resulted in the most significant increase in CD34+ and double positive Dil-Ac-LDL-FITC-Ulex-Lectin cells, both EPC markers. Furthermore, angiogenic potential was determined by an EPC-colony forming assay. While numbers of primitive EPC-colony forming units (pEPC-CFU) did not change, numbers of definitive EPC-CFU colonies increased most under ME conditions. Gene-expression profiling also identified increases in angiogenic factors, including vascular endothelial growth factor, under MG and ME conditions. Thus, QQc along with ME conditions could be an efficient system for significantly enhancing the number and angiogenic potential of EPCs.