Advances in bone marrow-derived cell therapy: CD31-expressing cells as next generation cardiovascular cell therapy

Imidazole functionalized photo-crosslinked aliphatic polycarbonate drug-eluting coatings on zinc alloys for osteogenesis, angiogenesis, and bacteriostasis in bone regeneration

Zinc (Zn) alloys have demonstrated significant potential in healing critical-sized bone defects. However, the clinical application of Zn alloys implants is still hindered by challenges including excessive release of zinc ions (Zn2+), particularly in the early stage of implantation, and absence of bio-functions related to complex bone repair processes. Herein, a biodegradable aliphatic polycarbonate drug-eluting coating was fabricated on zinc-lithium (Zn-Li) alloys to inhibit Zn2+ release and enhance the osteogenesis, angiogenesis, and bacteriostasis of Zn alloys. Specifically, the photo-curable aliphatic polycarbonates were co-assembled with simvastatin and deposited onto Zn alloys to produce a drug-loaded coating, which was crosslinked by subsequent UV light irradiation. During the 60 days long-term immersion test, the coating showed distinguished stable drug release and Zn2+ release inhibition properties. Benefiting from the regulated release of Zn2+ and simvastatin, the coating facilitated the adhesion, proliferation, and differentiation of MC3T3-E1 cells, as well as the migration and tube formation of EA.hy926 cells. Astonishingly, the coating also showed remarkable antibacterial properties against both S. aureus and E. coli. The in vivo rabbit critical-size femur bone defects model demonstrated that the drug-eluting coating could efficiently promote new bone formation and the expression of platelet endothelial cell adhesion molecule-1 (CD31) and osteocalcin (OCN). The enhancement of osteogenesis, angiogenesis, and bacteriostasis is achieved by precisely controlling of the released Zn2+ at an appropriate level, as well as the stable release profile of simvastatin. This tailored aliphatic polycarbonate drug-eluting coating provides significant potential for clinical applications of Zn alloys implants.

Bifunctional Hydrogel-Integrated 3D Printed Scaffold for Repairing Infected Bone Defects

The clinical treatment of infectious bone defects is difficult and time-consuming due to the coexistence of infection and bone defects, and the simultaneous control of infection and repair of bone defects is considered a promising therapy. In this study, a dual-drug delivery scaffold system was fabricated by the combination of a three-dimensional (3D) printed scaffold with hydrogel for infected bone defects repair. The 3D printed polycaprolactone scaffold was incorporated with biodegradable mesoporous silica nanoparticles containing the small molecular drug fingolimod (FTY720) to provide structural support and promote angiogenesis and osteogenesis. The vancomycin (Van)-loaded hydrogel was prepared from aldehyde hyaluronic acid (AHA) and carboxymethyl chitosan (NOCC) by the Schiff base reaction, which can fill the pores of the 3D-printed scaffold to produce a bifunctional composite scaffold. The in vitro results demonstrated that the composite scaffold had Van concentration-dependent antimicrobial properties. Furthermore, the FTY720-loaded composite scaffold demonstrated excellent biocompatibility, vascularization, and osteogenic ability in vitro. In the rat femoral defect model with bacterial infection, the dual-drug composite scaffold showed a better outcome in both infection control and bone regeneration compared to other groups. Therefore, the prepared bifunctional composite scaffold has potential application in the treatment of infected bone defects.

The decisive early phase of bone regeneration

Bone has a remarkable endogenous regenerative capacity that enables scarless healing and restoration of its prior mechanical function, even under challenging conditions such as advanced age and metabolic or immunological degenerative diseases. However - despite much progress - a high number of bone injuries still heal with unsatisfactory outcomes. The mechanisms leading to impaired healing are heterogeneous, and involve exuberant and non-resolving immune reactions or overstrained mechanical conditions that affect the delicate regulation of the early initiation of scar-free healing. Every healing process begins phylogenetically with an inflammatory reaction, but its spatial and temporal intensity must be tightly controlled. Dysregulation of this inflammatory cascade directly affects the subsequent healing phases and hinders the healing progression. This Review discusses the complex processes underlying bone regeneration, focusing on the early healing phase and its highly dynamic environment, where vibrant changes in cellular and tissue composition alter the mechanical environment and thus affect the signalling pathways that orchestrate the healing process. Essential to scar-free healing is the interplay of various dynamic cascades that control timely resolution of local inflammation and tissue self-organization, while also providing sufficient local stability to initiate endogenous restoration. Various immunotherapy and mechanobiology-based therapy options are under investigation for promoting bone regeneration.

Effects of Exercise Training on the Paracrine Function of Circulating Angiogenic Cells

Exercise training has various benefits on cardiovascular health, and circulating angiogenic cells have been proposed as executing these changes. Work from the late 1990s supported an important role of these circulating post-natal cells in contributing to the maintenance and repair of the endothelium and vasculature. It was later found that circulating angiogenic cells were a heterogenous population of cells and primarily functioned in a paracrine manner by adhering to damaged endothelium and releasing growth factors. Many studies have discovered novel circulating angiogenic cell secreted proteins, microRNA and extracellular vesicles that mediate their angiogenic potential, and some studies have shown that both acute and chronic aerobic exercise training have distinct benefits. This review highlights work establishing an essential role of secreted factors from circulating angiogenic cells and summarizes studies regarding the effects of exercise training on these factors. Finally, we highlight the various gaps in the literature in hopes of guiding future work.

Immune cell extracellular vesicles and their mitochondrial content decline with ageing

Background

Although the mechanisms of action are not fully understood, extracellular vesicles (EVs) have emerged as key indicators and effectors of immune function. Characterizing circulating EVs associated with stem and immune cells across the lifespan of healthy individuals could aid an understanding of immunosenescence, a process of age-related decline of cells in both adaptive and innate immune systems.

Results

Using high resolution multicolor flow cytometry, we identified three major subsets of EVs of varying sizes in healthy control (HC) plasma. Multiple plasma EVs associated with immune cells declined with ageing in HCs. In addition, we observed age-associated declines of respiring mitochondria cargo in EVs of several types of immune cells, suggesting that these parent cells may experience a decline in mitophagy or a mitochondrial dysfunction-induced immunosenescence. By contrast, the number of CD34⁺ hematopoietic stem cell-associated EVs were high and carried respiring mitochondria, which did not decline with age.

Conclusion

As demonstrated here, multicolor flow cytometry simultaneously measures plasma EV size, surface markers and cargo that reflect biological processes of specific cell types. The distinct surface markers and cytokine cargo of plasma EVs suggest that they may carry different bio-messages and originate by different biogenesis pathways.

Exercise and Cardiovascular Progenitor Cells

Autologous stem/progenitor cell-based methods to restore blood flow and function to ischemic tissues are clinically appealing for the substantial proportion of the population with cardiovascular diseases. Early preclinical and case studies established the therapeutic potential of autologous cell therapies for neovascularization in ischemic tissues. However, trials over the past ∼15 years reveal the benefits of such therapies to be much smaller than originally estimated and a definitive clinical benefit is yet to be established. Recently, there has been an emphasis on improving the number and function of cells [herein generally referred to as circulating angiogenic cells (CACs)] used for autologous cell therapies. CACs include of several subsets of circulating cells, including endothelial progenitor cells, with proangiogenic potential that is largely exerted through paracrine functions. As exercise is known to improve CV outcomes such as angiogenesis and endothelial function, much attention is being given to exercise to improve the number and function of CACs. Accordingly, there is a growing body of evidence that acute, short-term, and chronic exercise have beneficial effects on the number and function of different subsets of CACs. In particular, recent studies show that aerobic exercise training can increase the number of CACs in circulation and enhance the function of isolated CACs as assessed in ex vivo assays. This review summarizes the roles of different subsets of CACs and the effects of acute and chronic exercise on CAC number and function, with a focus on the number and paracrine function of circulating CD34+ cells, CD31+ cells, and CD62E+ cells. © 2019 American Physiological Society. Compr Physiol 9:767-797, 2019.

CD34- human placenta-derived mesenchymal stem cells protect against heat stroke mortality in rats

CD34 is a transmembrane phosphoglycoprotein used to selectively enrich bone marrow in hematopoietic stem cells for transplantation. Treating rats with CD34⁺ cells derived from human umbilical cord blood before or after heat stroke has been shown to promote survival. We investigated whether CD34^– human placenta-derived stem cells (PDMSCs) could improve survival following heat stroke in rats. Rats were subjected to heat stress (42°C for 98 min) to induce heat stroke. Intravenous administration of PDMSCs 1 day before or immediately after the onset of heat stroke improved survival by 60% and 20%, respectively. Pre-treatment with CD34⁻ PDMSCs protected against heat stroke injury more effectively than that treatment after injury. PDMSCs treatment attenuated cerebrovascular dysfunction, the inflammatory response, and lipid peroxidation. These data suggest human PDMSCs protect against heat stroke injury in rats. Moreover, these effects do not require the presence of CD34⁺ cells.

Endothelial cell markers from clinician's perspective

Endothelial cell markers are membrane-bound or cytoplasmic molecules expressed by endothelial cells, which help their easier identification and discrimination from other cell types. During vasculogenesis, endothelial cells differentiate from hemangioblasts to form new blood vessels. With the discovery of endothelial progenitor cells (EPC) and their ability to form new blood vessels, the term vasculogenesis is not only reserved for the embryonic development. Possibility of de novo blood vessel formation from EPC is now widely explored in different ischemic conditions, especially in cardiovascular medicine. Numerous clinical trials have tested enhancing tissue vascularization by delivering hematopoietic cells that expressed endothelial markers. This therapeutic approach proved to be challenging and promising, particularly for patients who have exhausted all conventional therapeutic modalities. Angiogenesis, which refers to the formation of new blood vessels from existing vasculature, is indispensable process during tumor progression and metastasis. Blockage of tumor angiogenesis by targeting and inhibiting endothelial cell has emerged as novel safe and efficacious method to control many advanced malignant diseases. Numerous clinical studies are currently testing new antiangiogenic drugs which target and inhibit endothelial cell markers, receptors or molecules which transmit receptor-mediated signals, therefore inhibiting endothelial cell proliferation, migration and vascular tube formation. Many of these drugs are now widely used in clinical settings as first- or second-line chemotherapy in advanced malignant conditions. So far, these therapeutic approaches gave modest, yet encouraging clinical improvements, prolonging survival and improving functional capacity and quality of life for many terminally ill patients. Here we present the most commonly used endothelial cell markers along with their applicability in contemporary clinical practice.

Mitochondria-specific antioxidant supplementation does not influence endurance exercise training-induced adaptations in circulating angiogenic cells, skeletal muscle oxidative capacity or maximal oxygen uptake

KEY POINTS

Reducing excessive oxidative stress, through chronic exercise or antioxidants, can decrease the negative effects induced by excessive amounts of oxidative stress. Transient increases in oxidative stress produced during acute exercise facilitate beneficial vascular training adaptations, but the effects of non-specific antioxidants on exercise training-induced vascular adaptations remain elusive. Circulating angiogenic cells (CACs) are an exercise-inducible subset of white blood cells that maintain vascular integrity. We investigated whether mitochondria-specific antioxidant (MitoQ) supplementation would affect the response to 3 weeks of endurance exercise training in CACs, muscle mitochondrial capacity and maximal oxygen uptake in young healthy men. We show that endurance exercise training increases multiple CAC types, an adaptation that is not altered by MitoQ supplementation. Additionally, MitoQ does not affect skeletal muscle or whole-body aerobic adaptations to exercise training. These results indicate that MitoQ supplementation neither enhances nor attenuates endurance training adaptations in young healthy men.

ABSTRACT

Antioxidants have been shown to improve endothelial function and cardiovascular outcomes. However, the effects of antioxidants on exercise training-induced vascular adaptations remain elusive. General acting antioxidants combined with exercise have not impacted circulating angiogenic cells (CACs). We investigated whether mitochondria-specific antioxidant (MitoQ) supplementation would affect the response to 3 weeks of endurance exercise training on CD3+ , CD3+ /CD31+ , CD14+ /CD31+ , CD31+ , CD34+ /VEGFR2+ and CD62E+ peripheral blood mononuclear cells (PBMCs), muscle mitochondrial capacity, and maximal oxygen uptake (VO2 max ) in healthy men aged 22.1 ± 0.7 years, with a body mass index of 26.9 ± 0.9 kg m-2 , and 24.8 ± 1.3% body fat. Analysis of main effects revealed that training induced 33, 105 and 285% increases in CD14+ /CD31+ , CD62E+ and CD34+ /VEGFR2+ CACs, respectively, and reduced CD3+ /CD31- PBMCs by 14%. There was no effect of MitoQ on CAC levels. Also independent of MitoQ supplementation, exercise training significantly increased quadriceps muscle mitochondrial capacity by 24% and VO2 max by roughly 7%. In conclusion, endurance exercise training induced increases in multiple CAC types, and this adaptation is not modified by MitoQ supplementation. Furthermore, we demonstrate that a mitochondrial-targeted antioxidant does not influence skeletal muscle or whole-body aerobic adaptations to exercise training.

Investigating the extremes of the continuum of paracrine functions in CD34-/CD31+ CACs across diverse populations

Paracrine function of circulating angiogenic cells (CACs) is thought to contribute to vascular maintenance. We previously identified S100A8 and S100A9 secreted from physically inactive individuals' CD34^-/CD31⁺ CACs as negative regulators of capillary-like network formation. The purpose of this study was to investigate further the extremes of the continuum of CAC paracrine actions using two distinctly different groups representing "healthy" and "impaired" CAC function. We aimed to determine how capillary-like network formation in human umbilical vein endothelial cells (HUVECs) is affected by S100A8 and S100A9 in concentrations secreted by CACs from different ends of the health spectrum. CD34^-/CD31⁺ CACs were isolated and cultured from 10 impaired function individuals defined as older (50-89 yr), non-ST-elevation myocardial infarction patients and 10 healthy individuals defined as younger (18-35 yr), healthy individuals, and conditioned media (CM) was generated. CM from the impaired function group's CACs significantly diminished network formation compared with CM from the healthy group (P < 0.05). We identified elevations in S100A8, S100A9, and S100A8/A9 in the CM from the impaired function group (P < 0.05). Pretreatment of HUVECs with inhibitors to a known S100A8 and S100A9 receptor, Toll-like receptor 4 (TLR4), but not receptor for advanced glycation end products, improved HUVEC network formation (P < 0.05) compared with CM alone in the impaired function conditions. Exposure of HUVECs to the TLR4 signaling inhibitor also blocked recombinant S100A8- and S100A9-mediated reductions in network formation. Collectively, the results suggest that the mechanisms behind impaired CAC CD34^-/CD31⁺ CM-mediated reductions in capillary-like network formation involve secretion of S100A8 and S100A9 and binding of these proteins to TLR4 receptors on HUVECs.

NEW & NOTEWORTHY

S100A8 and S100A9 proteins in concentrations secreted by CD34^-/CD31⁺ circulating angiogenic cells (CACs) with impaired function reduce endothelial cell capillary-like network formation. These effects appear to be mediated by Toll-like receptor 4 and are absent with S100A8 and S100A9 in concentrations secreted by healthy CD34^-/CD31⁺ CACs.

Chronic endurance exercise affects paracrine action of CD31+ and CD34+ cells on endothelial tube formation

We aimed to determine if chronic endurance-exercise habits affected redox status and paracrine function of CD34(+) and CD34(-)/CD31(+) circulating angiogenic cells (CACs). Subjects were healthy, nonsmoking men and women aged 18-35 yr and categorized by chronic physical activity habits. Blood was drawn from each subject for isolation and culture of CD34(+) and CD34(-)/CD31(+) CACs. No differences in redox status were found in any group across either cell type. Conditioned media (CM) was generated from the cultured CACs and used in an in vitro human umbilical vein endothelial cell-based tube assay. CM from CD34(+) cells from inactive individuals resulted in tube structures that were 29% shorter in length (P < 0.05) and 45% less complex (P < 0.05) than the endurance-trained group. CD34(-)/CD31(+) CM from inactive subjects resulted in tube structures that were 26% shorter in length (P < 0.05) and 42% less complex (P < 0.05) than endurance-trained individuals. Proteomics analyses identified S100A8 and S100A9 in the CM. S100A9 levels were 103% higher (P < 0.05) and S100A8 was 97% higher in the CD34(-)/CD31(+) CM of inactive subjects compared with their endurance-trained counterparts with no significant differences in either protein in the CM of CD34(+) CACs as a function of training status. Recombinant S100A8/A9 treatment at concentrations detected in inactive subjects' CD34(-)/CD31(+) CAC CM also reduced tube formation (P < 0.05). These findings are the first, to our knowledge, to demonstrate a differential paracrine role in CD34(+) and CD34(-)/CD31(+) CACs on tube formation as a function of chronic physical activity habits and identifies a differential secretion of S100A9 by CD34(-)/CD31(+) CACs due to habitual exercise.

Isolation of Foreign Material-Free Endothelial Progenitor Cells Using CD31 Aptamer and Therapeutic Application for Ischemic Injury

Endothelial progenitor cells (EPCs) can be isolated from human bone marrow or peripheral blood and reportedly contribute to neovascularization. Aptamers are 40-120-mer nucleotides that bind to a specific target molecule, as antibodies do. To utilize apatmers for isolation of EPCs, in the present study, we successfully generated aptamers that recognize human CD31, an endothelial cell marker. CD31 aptamers bound to human umbilical cord blood-derived EPCs and showed specific interaction with human CD31, but not with mouse CD31. However, CD31 aptamers showed non-specific interaction with CD31-negative 293FT cells and addition of polyanionic competitor dextran sulfate eliminated non-specific interaction without affecting cell viability. From the mixture of EPCs and 293FT cells, CD31 aptamers successfully isolated EPCs with 97.6% purity and 94.2% yield, comparable to those from antibody isolation. In addition, isolated EPCs were decoupled from CD31 aptamers with a brief treatment of high concentration dextran sulfate. EPCs isolated with CD31 aptamers and subsequently decoupled from CD31 aptamers were functional and enhanced the restoration of blood flow when transplanted into a murine hindlimb ischemia model. In this study, we demonstrated isolation of foreign material-free EPCs, which can be utilized as a universal protocol in preparation of cells for therapeutic transplantation.

Effect of calycosin on left ventricular ejection fraction and angiogenesis in rat models with myocardial infarction

OBJECTIVE

To evaluated the effect of calycosin on left ventricular ejection fraction and angiogenesis.

METHODS

Adult male Sprague-Dawley rats were randomly assigned into calycosin-treated groups (0.5, 1, 2, and 4 mg/kg qd), a dimethyl sulfoxide (DMSO), or a sham-operated control group. The myocardial ischaemia (MI) model was intraperitoneally administered calycosin for 28 days. The survival rates and left ventricular ejection fractions (LVEF) were compared between groups. The expression levels of vascular endothelial growth factor (VEGF) and cluster of differentiation 31 (CD31) in ischaemic myocardium were also measured and compared.

RESULTS

The construction of MI model resulted in a LVEF reduction of 50% compared with the sham-control. After 28 days, the LVEF value was 10% higher when calycosin (4 mg/kg) was administered compared with the DMSO group. The expression of VEGF and CD31 showed a dose-dependent manner when calycosin was administrated. The calycosin-treated (4 mg/kg) group displayed a two-fold increase in VEGF expression at both the mRNA and protein levels compared with the DMSO group. In addition, CD31 expression in the microvascular increased 1.5-fold in the 4 mg/kg calycosin-treated group.

CONCLUSION

Calycosin improved left ventricular ejection fraction in the MI rat models, induced VEGF expression in the ischaemic myocardium, increased CD31 expression and promoted angiogenesis.

Improved revascularization of islet grafts using an angiogenic monocyte subpopulation derived from spheroid culture of bone marrow mononuclear cells

The spheroid culture method is an effective strategy for ex vivo expansion of an autologous therapeutic cell population. We investigated if cotransplantation of bone marrow-derived spheroids (BM-spheroid) formed using 3D culture of BM-derived mononuclear cells (BM-MNCs) could improve the posttransplant outcome of islet grafts using a mouse syngeneic marginal mass renal subcapsular islet transplantation model. Using green fluorescent protein transgenic (GFP-Tg) mice, the role of the BM-spheroids and the contribution of vessels derived from donors and recipients in grafted areas were assessed by immunohistochemistry. Compared to fresh BM-MNCs and nonspheroid remnant cells (BM-nonspheroid), the BM-spheroids, mainly composed of CXCR4(+) CD14(+) myeloid cells, showed higher angiogenic capacity, such as in vitro self-formed vessel structures; increased expression of angiogenic and chemoattractive factors; and incorporation into new vessel formation in basement membrane matrix plugs. BM-spheroid cotransplantation with islets improved the posttransplant outcomes in terms of glucose tolerance, serum insulin level, and diabetes reversal rate when compared with cotransplantation of BM-nonspheroids. Immunohistochemistry revealed that cotransplantation of the BM-spheroids increased vessel density, area of grafted endocrine and non-endocrine tissue, and β cell proliferation. In conclusion, cotransplantation of islets and BM-spheroids improved islet function through facilitation of revascularization and an increase in cell proliferation and islet cell mass.

The role of eNOS in the migration and proliferation of bone-marrow derived endothelial progenitor cells and in vitro angiogenesis

The role of endothelial nitric oxide synthase (eNOS) in the activities of endothelial progenitor cells (EPCs) including migration, proliferation, and tube formation in vitro was investigated. EPCs were obtained from rat bone mononuclear cells by culturing for 7-10 days in EGM-2MV and identified by their capacity for FITC-UEA-1 binding and acetylated low-density lipoprotein (Dil-ac-LDL) intake using fluorescence microscopy. Migration, proliferation and tube formation activities were assessed in the presence or absence of N(ω)-nitro-L-argininemethylester (L-NAME), an eNOS inhibitor. mRNA and protein expression of CXCR4, CXCR7, VEGFR2, and eNOS were detected by real-time PCR and western blotting in the presence or absence of L-NAME. Nitric oxide production was detected by nitrate reductase in the presence or absence of L-NAME. Typical spindle-shaped cells appeared on the 7(th)-10(th) day and confluence reached about 80%. The percentage of FITC-UEA-1 and Dil-ac-LDL double-stained cells was about 85%. Cell migration, proliferation, and tube formation were significantly weakened after eNOS was inhibited (P < 0.05), and the expressions of CXCR4 and eNOS were significantly reduced (P < 0.05, respectively), but there was little change in CXCR7 and VEGFR2. NO production was dramatically decreased after eNOS was inhibited (P < 0.05). In summary, L-NAME significantly reduced the expression of eNOS and NO production by EPCs and inhibited migration, proliferation and tube formation by these cells, suggesting that eNOS affects EPC activities; CXCR4 may be implicated in the action of eNOS.

Prognostic significance of circulating and endothelial progenitor cell markers in type 2 diabetic foot

Objective. We studied circulating precursor cells (CPC) in type 2 diabetes mellitus (T2DM) with neuropathic foot lesions with or without critical limb ischemia and relationships between endothelial precursor cells (EPC) and peripheral neuropathy. Methods and Subjects. We measured peripheral blood CD34, CD133, and CD45 markers for CPC and KDR, CD31 markers for EPC by citofluorimetry and systemic neural nociceptor CGRP (calcitonin gene related protein) by ELISA in 8 healthy controls (C) and 62 T2DM patients: 14 with neuropathy (N), 20 with neuropathic foot lesions (N1), and 28 with neuroischemic recent revascularized (N2) foot lesions. Timing of lesions was: acute (until 6 weeks), healed, and not healed. Results. CD34+ and CD133+ were reduced in N, N1, and N2 versus C, and CD34+ were lower in N2 versus N1 (P = 0.03). In N2 CD34+KDR+ remain elevated in healed versus chronic lesions and, in N1 CD133+31+ were elevated in acute lesions. CGRP was reduced in N2 and N1 versus C (P < 0.04 versus C 26 ± 2 pg/mL). CD34+KDR+ correlated in N2 with oximetry and negatively in N1 with CGRP. Conclusions. CD34+ CPC are reduced in diabetes with advanced complications and diabetic foot. CD34+KDR+ and CD31+133+ EPC differentiation could have a prognostic and therapeutic significance in the healing process of neuropathic and neuroischemic lesions.

Circulating CD31+ leukocyte frequency is associated with cardiovascular risk factors

OBJECTIVES

CD31 identifies a heterogeneous population of cells in the blood, consisting of mature leukocytes and platelets, as well as smaller numbers of endothelial and progenitor cells. Because unfractionated CD31+ blood cells have demonstrated angiogenic properties in vivo, we hypothesized that circulating CD31+ cells would be related to the presence of cardiovascular risk factors in humans.

METHODS AND RESULTS

We studied 1487 participants, free of cardiovascular disease, from the Framingham Offspring Study. Using anti-human CD31 and CD45 antibodies, distinct CD31+/CD45+ leukocyte populations were enumerated in blood samples by FACS analysis. We used linear regression analyses to investigate the relation of each cell phenotype with cardiovascular risk factors. We identified 3 distinct leukocyte populations: CD31-, CD31 dim, and CD31 bright cells. Using forward/side scatter analyses, CD31- and CD31 dim cells mapped to lymphoid gates while CD31 bright cells were monocytoid. In multivariable analyses, higher frequency of CD31 bright cells was associated with older age, male sex, HDL cholesterol, and CRP (all P < 0.01). In contrast, CD31 dim was inversely associated with age, male sex, CRP, and smoking (all P < 0.01). Framingham Risk Score was positively associated with CD31 bright frequency (P = 0.002), and negatively associated with CD31 dim frequency (P = 0.020).

CONCLUSIONS

CD31+ staining identifies 2 major leukocyte populations, CD31 bright and CD31 dim, which demonstrated significant and opposite associations with cardiovascular risk in humans. Further research is needed to define the biological and potential therapeutic roles of CD31+ subpopulations in vascular disease.

Overexpression of angiopoietin-1 increases CD133+/c-kit+ cells and reduces myocardial apoptosis in db/db mouse infarcted hearts

Hematopoietic progenitor CD133(+)/c-kit(+) cells have been shown to be involved in myocardial healing following myocardial infarction (MI). Previously we demonstrated that angiopoietin-1(Ang-1) is beneficial in the repair of diabetic infarcted hearts. We now investigate whether Ang-1 affects CD133(+)/c-kit(+) cell recruitment to the infarcted myocardium thereby mediating cardiac repair in type II (db/db) diabetic mice. db/db mice were administered either adenovirus Ang-1 (Ad-Ang-1) or Ad-β-gal systemically immediately after ligation of the left anterior descending coronary artery (LAD). Overexpression of Ang-1 resulted in a significant increase in CXCR-4/SDF-1α expression and promoted CD133(+)/c-kit(+), CD133(+)/CXCR-4(+) and CD133(+)/SDF-1α(+) cell recruitment into ischemic hearts. Overexpression of Ang-1 led to significant increases in number of CD31(+) and smooth muscle-like cells and VEGF expression in bone marrow (BM). This was accompanied by significant decreases in cardiac apoptosis and fibrosis and an increase in myocardial capillary density. Ang-1 also upregulated Jagged-1, Notch3 and apelin expression followed by increases in arteriole formation in the infarcted myocardium. Furthermore, overexpression of Ang-1 resulted in a significant improvement of cardiac functional recovery after 14 days of ischemia. Our data strongly suggest that Ang-1 attenuates cardiac apoptosis and promotes cardiac repair by a mechanism involving in promoting CD133(+)/c-kit(+) cells and angiogenesis in diabetic db/db mouse infarcted hearts.