CD31+ T cells represent a functionally distinct vascular T cell phenotype

Prognostic value of angiogenic T cells in hepatitis B-induced liver cirrhosis

This study was performed to investigate the frequency of angiogenic T cells (CD4+ Tang cells) among CD4+ T cells in patients with hepatitis B-induced liver cirrhosis (HBV-LC) and to evaluate the predictive role of these cells in the clinical outcome. In total, 185 patients with HBV-LC were recruited to measure the frequency of CD4+ Tang cells and chemokine levels using flow cytometry. RESULTS: There was 11.4% of death after 3-momth follow-up. The AUC for the ability of the frequency of CD4+ Tang cell to predict death was 0.724 (higher than those for the MELD score, FIB-4 score, and Child-Pugh classification). Cox regression analysis revealed an association between the frequency of CD4+ Tang cells and a 3-month survival chance. CONCLUSIONS: The lower frequency of CD4+ T ang cells was correlated with the severity of HBV-LC and may serve as a prognostic predictor.

Exercise-induced skeletal muscle angiogenesis: impact of age, sex, angiocrines and cellular mediators

Exercise-induced skeletal muscle angiogenesis is a well-known physiological adaptation that occurs in humans in response to exercise training and can lead to endurance performance benefits, as well as improvements in cardiovascular and skeletal tissue health. An increase in capillary density in skeletal muscle improves diffusive oxygen exchange and waste extraction, and thus greater fatigue resistance, which has application to athletes but also to the general population. Exercise-induced angiogenesis can significantly contribute to improvements in cardiovascular and metabolic health, such as the increase in muscle glucose uptake, important for the prevention of diabetes. Recently, our understanding of the mechanisms by which angiogenesis occurs with exercise has grown substantially. This review will detail the biochemical, cellular and biomechanical signals for exercise-induced skeletal muscle angiogenesis, including recent work on extracellular vesicles and circulating angiogenic cells. In addition, the influence of age, sex, exercise intensity/duration, as well as recent observations with the use of blood flow restricted exercise, will also be discussed in detail. This review will provide academics and practitioners with mechanistic and applied evidence for optimising training interventions to promote physical performance through manipulating capillarisation in skeletal muscle.

Angiogenic T Cells: Potential Biomarkers for the Early Diagnosis of Interstitial Lung Disease in Autoimmune Diseases?

(1) Background: We explored, for the first time, the contribution of angiogenic T cells (TAng) in interstitial lung disease associated to autoimmune disease (AD-ILD+) as potential biomarkers of the disease, evaluating their role in the underlying vasculopathy and lung fibrosis. Additionally, the relationship of TAng with clinical manifestations and cellular and molecular endothelial dysfunction-related biomarkers was assessed. (2) Methods: We included 57 AD-ILD+ patients (21 with rheumatoid arthritis (RA)-ILD+, 21 with systemic sclerosis (SSc)-ILD+ and 15 with other AD-ILD+) and three comparative groups: 45 AD-ILD− patients (25 RA-ILD− and 20 SSc-ILD−); 21 idiopathic pulmonary fibrosis (IPF) patients; 21 healthy controls (HC). TAng were considered as CD3+CD184+CD31+ by flow cytometry. (3) Results: A similar TAng frequency was found between AD-ILD+ and IPF, being in both cases lower than that observed in AD-ILD− and HC. A lower TAng frequency was associated with negative Scl-70 status and lower FEV1/FVC ratio in SSc-ILD+, as well as with men in RA-ILD+ and non-specific interstitial pneumonia radiological pattern in other AD-ILD+. No relationship between TAng and endothelial progenitor cells, endothelial cells and vascular endothelial growth factor gene expression and protein levels was disclosed. (4) Conclusions: Our findings suggest TAng as potential biomarkers for the early diagnosis of ILD in AD.

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.

Pulmonary involvement in systemic sclerosis: exploring cellular, genetic and epigenetic mechanisms

Systemic sclerosis (SSc) is a chronic progressive autoimmune disease characterized by immune inflammation, vasculopathy, and fibrosis. There are still numerous uncertainties in the understanding of disease initiation and progression. Pulmonary involvement in SSc, and particularly pulmonary fibrosis, is critical for all organ systems affections in this disease. This review is aimed to describe and analyze new findings in the pathophysiology of SSc-associated pulmonary involvement and to explore perspective diagnostic and therapeutic strategies. A myriad of cellular interactions is explored in the dynamics of progressive interstitial lung disease (ILD) and pulmonary hypertension (PH) in SSc. The role of exosomes, microvesicles, and apoptotic bodies is examined and the impact of micro and long non-coding RNAs, DNA methylation, and histone modification in SSc is discussed.

The risk of circulating angiogenic T cells and subsets in patients with systemic sclerosis

To ascertain the number and percentage of angiogenic T (Tang) cell subsets by flow cytometry in systemic sclerosis (SSc), and their relation with specific clinical features. Thirty SSc patients and 15 healthy controls (HCs) were included. Luminex was performed to analyze the levels of interleukin (IL)-17A, vascular endothelial growth factor (VEGF), tumor necrosis factor-α, and vascular cell adhesion molecule (VCAM). The ratio of circulating CD3 + CD31 + CXCR4 + T (CD3 + Tang) cells and CD8+ CD31 + CXCR4 + T (CD8+ Tang) cells in SSc patients was enlarger than in HCs, while CD4 + CD31 + CXCR4 + T cells (CD4 + Tang) exhibited no difference between SSc patients and HCs. The number and percentage of Tang cells were higher in SSc patients with pulmonary artery hypertension (PAH) than in non-PAH SSc patients and HCs. The ratios of Tang cell subsets in nucleolar pattern-positive SSc patients were markedly raised as compared with their negative ones and HCs. Additionally, the percentage of circulating CD3 + Tang cells was positively associated with VEGF serum levels in SSc patients. Meanwhile, the rate of CD8+ tang cells might have been emphatically corresponded to VEGF and VCAM serum levels in SSc patients. These results imply that the increase in Tang cells in peripheral blood are associated with immunoregulatory disturbances in SSc patients.

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.

Circulating angiogenic cell response to sprint interval and continuous exercise

INTRODUCTION

Although commonly understood as immune cells, certain T lymphocyte and monocyte subsets have angiogenic potential, contributing to blood vessel growth and repair. These cells are highly exercise responsive and may contribute to the cardiovascular benefits seen with exercise.

PURPOSE

To compare the effects of a single bout of continuous (CONTEX) and sprint interval exercise (SPRINT) on circulating angiogenic cells (CAC) in healthy recreationally active adults.

METHODS

Twelve participants (aged 29 ± 2 years, BMI 25.5 ± 0.9 kg m^- 2, [Formula: see text]peak 44.3 ± 1.8 ml kg^- 1 min^- 1; mean ± SEM) participated in the study. Participants completed a 45-min bout of CONTEX at 70% peak oxygen uptake and 6 × 20 s sprints on a cycle ergometer, in a counterbalanced design. Blood was sampled pre-, post-, 2 h and 24 h post-exercise for quantification of CAC subsets by whole blood flow cytometric analysis. Angiogenic T lymphocytes (T_ANG) and angiogenic Tie2-expressing monocytes (TEM) were identified by the expression of CD31 and Tie2, respectively.

RESULTS

Circulating (cells µL^- 1) CD3⁺CD31⁺ T_ANG increased immediately post-exercise in both trials (p < 0.05), with a significantly greater increase (p < 0.05) following SPRINT (+ 57%) compared to CONTEX (+ 14%). Exercise increased (p < 0.05) the expression of the chemokine receptor CXCR4 on T_ANG at 24 h. Tie2-expressing classical (CD14⁺⁺CD16^-), intermediate (CD14⁺⁺CD16⁺) and non-classical (CD14⁺CD16⁺⁺) monocytes and circulating CD34⁺CD45^dim progenitor cells were higher post-exercise in SPRINT, but unchanged in CONTEX. All post-exercise increases in SPRINT were back to pre-exercise levels at 2 h and 24 h.

CONCLUSION

Acute exercise transiently increases circulating T_ANG, TEM and progenitor cells with greater increases evident following very high intensity sprint exercise than following prolonged continuous paced endurance exercise.

Endothelial Regenerative Capacity and Aging: Influence of Diet, Exercise and Obesity

Background:

The endothelium plays an important role in cardiovascular regulation, from blood flow to platelet aggregation, immune cell infiltration and demargination. A dysfunctional endo-thelium leads to the onset and progression of Cardiovascular Disease (CVD). The aging endothelium displays significant alterations in function, such as reduced vasomotor functions and reduced angio-genic capabilities. This could be partly due to elevated levels of oxidative stress and reduced endothe-lial cell turnover. Circulating angiogenic cells, such as Endothelial Progenitor Cells (EPCs) play a significant role in maintaining endothelial health and function, by supporting endothelial cell prolifera-tion, or via incorporation into the vasculature and differentiation into mature endothelial cells. Howev-er, these cells are reduced in number and function with age, which may contribute to the elevated CVD risk in this population. However, lifestyle factors, such as exercise, physical activity obesity, and dietary intake of omega-3 polyunsaturated fatty acids, nitrates, and antioxidants, significantly af-fect the number and function of these circulating angiogenic cells.

Conclusion:

This review will discuss the effects of advancing age on endothelial health and vascular regenerative capacity, as well as the influence of diet, exercise, and obesity on these cells, the mecha-nistic links and the subsequent impact on cardiovascular health

Older men display elevated levels of senescence-associated exercise-responsive CD28null angiogenic T cells compared with younger men

Aging is associated with elevated cardiovascular disease risk. As a result of aging, endothelial dysfunction develops, partly due to a reduction in vascular regenerative ability. CD31+ T cells (angiogenic T cells; TANG ) possess highly angiogenic capabilities; however, these cells are significantly reduced in older populations. In addition, older populations possess significantly higher senescent and highly differentiated T-cell levels in circulation, and these are reported to be highly exercise responsive. We investigated whether older adults display greater levels of circulating senescent (CD28null ) TANG cells and whether these cells were more exercise responsive than CD28+ TANG cells. Young (18-25 years; n = 9) and older (60-75 years; n = 10) healthy men undertook a 30-min cycling bout at 70% V˙O2 peak, with circulating TANG cells (CD3+  CD31+  CD28+/null ; including CD4+ and CD8+ subsets) measured preexercise, postexercise, and 1 h post exercise by flow cytometry. Older adults displayed reduced basal levels of TANG cells (mean ± SEM: 410 ± 81 vs. 784 ± 118 cells·μL, P = 0.017), despite a greater proportion of these cells being CD28null (26.26 ± 5.08 vs. 13.36 ± 2.62%, P = 0.044). Exercise significantly increased the circulating number of TANG cells in both young and older men. However, in older men alone, exercise preferentially mobilized CD28null CD8+ TANG cells compared with CD28+ TANG cells (time × phenotype interaction: P = 0.022; Δ74 ± 29 vs. Δ27 ± 15 cells·μL, P = 0.059), with no such difference observed between these phenotypes in the young population. In conclusion, this is the first study to demonstrate that despite observing lower circulating numbers of TANG cells, older adults display greater levels of senescent TANG cells in comparison with younger individuals, and these cells are more exercise responsive than CD28+ TANG cells. Lower number of circulating TANG and greater levels of senescent-associated CD28null TANG may contribute to greater CVD risk with advancing age.

Lower resting and exercise-induced circulating angiogenic progenitors and angiogenic T cells in older men

Aging is associated with a dysfunctional endothelial phenotype as well as reduced angiogenic capabilities. Exercise exerts beneficial effects on the cardiovascular system, possibly by increasing/maintaining the number and/or function of circulating angiogenic cells (CACs), which are known to decline with age. However, the relationship between cardiorespiratory fitness (CRF) and age-related changes in the frequency of CACs, as well as the exercise-induced responsiveness of CACs in older individuals, has not yet been determined. One-hundred seven healthy male volunteers, aged 18-75 yr, participated in study 1. CRF was estimated using a submaximal cycling ergometer test. Circulating endothelial progenitor cells (EPCs), angiogenic T cells (T_ANG), and their chemokine (C-X-C motif) receptor 4 (CXCR4) cell surface receptor expression were enumerated by flow cytometry using peripheral blood samples obtained under resting conditions before the exercise test. In study 2, 17 healthy men (8 young men, 18-25 yr; 9 older men, 60-75 yr) were recruited, and these participants undertook a 30-min cycling exercise bout at 70% maximal O₂ consumption, with CACs enumerated before and immediately after exercise. Age was inversely associated with both CD34⁺ progenitor cells ( r² = -0.140, P = 0.000) and T_ANG ( r² = -0.176, P = 0.000) cells as well as CXCR4-expressing CACs (CD34⁺: r² = -0.167, P = 0.000; EPCs: r² = -0.098, P = 0.001; T_ANG: r² = -0.053, P = 0.015). However, after correcting for age, CRF had no relationship with either CAC subset. In addition, older individuals displayed attenuated exercise-induced increases in CD34⁺ progenitor cells, T_ANG, CD4⁺, T_ANG, and CD8⁺CXCR4⁺ T_ANG cells. Older men display lower CAC levels, which may contribute to increased risk of cardiovascular disease, and older adults display an impaired exercise-induced responsiveness of these cells. NEW & NOTEWORTHY Older adults display lower circulating progenitor cell and angiogenic T cell counts compared with younger individuals independently of cardiometabolic risk factors and cardiorespiratory fitness. Older adults also display impaired exercise-induced mobilization of these vasculogenic cells.

Biophysical induction of cell release for minimally manipulative cell enrichment strategies

The use of autologous cells harvested and subsequently transplanted in an intraoperative environment constitutes a new approach to promote regeneration. Usually cells are isolated by selection methods such as fluorescence- or magnetic- activated cell sorting with residual binding of the antibodies or beads. Thus, cell-based therapies would benefit from the development of new devices for cell isolation that minimally manipulate the target cell population. In the clinic, 5 to 10 percent of fractures do not heal properly and CD31+ cells have been identified as promising candidates to support bone regeneration. The aim of this project was to develop and prototype a simple system to facilitate the enrichment of CD31+ cells from whole blood. After validating the specificity of a commercially available aptamer for CD31, we combined this aptamer with traditional magnetic bead strategies, which led to enrichment of CD31+ cells with a purity of 91±10%. Subsequently, the aptamer was attached to agarose beads (Ø = 100–165 um) that were incorporated into a column-based system to enable capture and subsequent release of the CD31+ enriched cells. Different parameters were investigated to allow a biophysical-based cell release from beads, and a simple mixing was found sufficient to release initially bound cells from the optimized column without the need for any chemicals that promote disassociation. The system led to a significant enrichment of CD31+ cells (initial population: 63±9%, released: 87±3%) with excellent cell viability (released: 97±1%). The composition of the released CD31+ fraction indicated an enrichment of the monocyte population. The angiogenic and osteogenic potential of the released cell population were confirmed in vitro. These results and the simplicity of this system highlight the potential of such approach to enable cell enrichment strategies in intraoperative settings.

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.

Short-term exercise training improves flow-mediated dilation and circulating angiogenic cell number in older sedentary adults

Cardiovascular disease risk increases with age due, in part, to impaired endothelial function and decreased circulating angiogenic cell (CAC) number and function. We sought to determine if 10 days of aerobic exercise training improves endothelial function, CAC number, and intracellular redox balance in older sedentary adults. Eleven healthy subjects (4 men, 7 women), 61 ± 2 years of age participated in 60 min of aerobic exercise at 70% maximal oxygen consumption for 10 consecutive days while maintaining body weight. Before and after training, endothelial function was measured as flow-mediated dilation of the brachial artery and fasting blood was drawn to enumerate 3 CAC subtypes. Intracellular reactive oxygen species (ROS) and nitric oxide (NO) in CD34+ CACs were measured using fluorescent probes and reinforced via real-time quantitative polymerase chain reaction. Flow-mediated dilation improved significantly following training (10% ± 1.3% before vs. 16% ± 1.4% after training; P < 0.05). Likewise, CD34+/KDR+ number increased 104% and KDR+ number increased 151% (P < 0.05 for both), although CD34+ number was not significantly altered (P > 0.05). Intracellular NO and ROS levels in CD34+ CACs were not different after training (P > 0.05 for both). Messenger RNA expression of SOD1, endothelial nitric oxide synthase, and NADPH oxidase 2 and neutrophil cytosolic factor 1 in CD34+ CACs was not significantly altered with training (P > 0.05). In conclusion, 10 consecutive days of aerobic exercise increased flow-mediated dilation and CAC number in older, previously sedentary adults, but did not affect intracellular redox balance in CD34+ CACs. Overall, these data indicate that even short-term aerobic exercise training can have a significant impact on cardiovascular disease risk factors.

Uterine natural killer cell partnerships in early mouse decidua basalis

The decidua basalis of developing mouse implantation sites is highly enriched in CD45⁺ leukocytes. In intact, syngeneically mated C57BL/6 decidua basalis examined at gestation day 8.5 by whole-mount in situ immunohistochemistry, leukocyte, but not trophoblast, conjugations were reported. Nothing is known regarding time course, frequency, composition, or importance of physiologic decidual CD45⁺ cell pairing. In this study, we confirmed the presence of anti-CD54⁺/anti-CD11a⁺ immune synapses in CD45⁺ decidual cell conjugates and characterized their cellular heterogeneity. Conjugated cell pairs were virtually absent before implantation (virgin and gestation days 3.5 and 4.5), were infrequent at gestation day 5.5, but involved 19% of all CD45⁺ cells by gestation day 8.5, then declined. By gestation day 8.5, almost all CD45⁺ cells coexpressed CD31, and 2 CD45⁺CD31⁺ cells composed most conjugates. Conjugation partners were defined for 2 nonoverlapping uterine natural killer cell subsets (Ly49C/I ⁺/Dolichos biflorus agglutinin lectin^- and Ly49C/I^-/Dolichos biflorus agglutinin lectin⁺). Ly49C/I⁺ uterine natural killer cells were the major subset from before mating up to gestation day 6.5. At gestation day 5.5/6.5, uterine natural killer cell conjugates involving Ly49C/I ⁺ cells were more abundant. By gestation day 8.5/9.5, Dolichos biflorus agglutinin lectin⁺ uterine natural killer cells were the dominant subset with Dolichos biflorus agglutinin lectin⁺/Dolichos biflorus agglutinin lectin⁺ homologous conjugates and Dolichos biflorus agglutinin lectin⁺/Dolichos biflorus agglutinin lectin^- heterologous conjugates dominating uterine natural killer cell pairings. At gestation day 6.5, both Ly49C/I⁺/CD45⁺ and Dolichos biflorus agglutinin lectin⁺/CD45⁺ heterologous conjugate pairs strongly engaged antigen-presenting cells (CD11c⁺, CD68⁺, or major histocompatibility complex class II⁺). By gestation day 8.5, dominant partners of Ly49C/I⁺/CD45⁺ and Dolichos biflorus agglutinin lectin⁺/CD45⁺ heterologous conjugates are T cells (CD8⁺ >CD4⁺). Heterologous conjugates that did not involve uterine natural killer cells occurred but did not suggest antigen presentation to T cells. These data identify gestation day 6.5-8.5 in the pregnant mouse as a critical window for leukocyte interactions that may establish immune regulation within implantation sites.

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.

Receptors for non-MHC ligands contribute to uterine natural killer cell activation during pregnancy in mice

INTRODUCTION

Activated uterine natural killer (uNK) cells are abundant in early human and mouse decidual basalis. In mice, distinct uNK cell subsets support early endothelial tip cell induction, the pruning of new vessels and initiation of spiral arterial modification. While genetic studies indicate that NK/uNK cell activation via receptors recognizing Class I MHC-derived peptides promotes human pregnancy, roles for other activation receptors expressed by NK cells, such as the aryl hydrocarbon receptor (AHR) and natural cytotoxicity receptors (NCR) are undefined in human or mouse pregnancies.

METHODS

Expression of AHR and NCR1 (ortholog of human NKp46) by gestation day (gd)10.5 mouse uNK cell subsets was measured by quantitative real-time RT-PCR. Early implantation sites from mice lacking expression of either receptor were examined histologically.

RESULTS

Gd10.5 uNK cell subsets, separated by reactivity to Dolichos biflorus agglutinin lectin, differed in relative transcript abundance for Ahr and Ncr1. Quantitative histology revealed that, in comparison to C57BL/6 controls, implant sites from gd10.5 Ahr(-/-) and gd6.5-12.5 UkCa:B6.Ncr1(Gfp/Gfp) mice had normal uNK cell abundance but the uNK cells were smaller than normal and unable to trigger spiral arterial remodeling. Whole mount immunohistochemistry comparisons of viable, gd6.5-8.5 Ncr1(Gfp/Gfp) and C57BL/6 implant sites revealed deficits in implant site angiogenesis and conceptus growth in Ncr1(Gfp/Gfp).

DISCUSSION

In mice, activation of AHR and of NCR1 by endogenous, as yet undefined ligands, contributes to uNK cell activation/maturation and angiogenic functions during early to mid-gestation pregnancy. MHC-independent activation of uNK cells also likely makes critical contributions to human pregnancy success.

Imaging of vascular development in early mouse decidua and its association with leukocytes and trophoblasts

In species with endometrial decidualization and hemochorial placentation (humans, mice, and others), leukocytes localize to early implant sites and contribute to decidual angiogenesis, spiral arterial remodeling, and trophoblast invasion. Relationships between leukocytes, trophoblasts, and the decidual vasculature are not fully defined. Early C57BL/6J implant sites were analyzed by flow cytometry to define leukocyte subsets and by whole-mount immunohistochemistry to visualize relationships between leukocytes, decidual vessels, and trophoblasts. Ptprc(+) (CD45(+)) cells increased in decidua between Gestational Day (GD) 5.5 and GD 9.5. Uterine natural killer (uNK) cells that showed dynamic expression of Cd (CD) 69, an activating receptor, and Klrg1 (KLRG1), an inhibitory receptor, localized mesometrially and were the dominant CD45(+) cells between GD 5.5 and GD 7.5. At GD 8.5, immature monocytes that occurred throughout decidua exceeded uNK cells numerically and many leukocytes acquired irregular shapes, and leukocyte-leukocyte conjugates became frequent. Vessels were morphologically heterogeneous and regionally unique. Migrating trophoblasts were first observed at GD 6.5 and, at GD 9.5, breached endothelium, entered vascular lumens, and appeared to occlude some vessels, as described for human spiral arteries. No leukocyte-trophoblast conjugates were detected. Whole-mount staining gave unparalleled decidual vascular detail and cell-specific positional information. Its application across murine models of pregnancy disturbances should significantly advance our understanding of the maternal-fetal interface.

Exercise-induced Signals for Vascular Endothelial Adaptations: Implications for Cardiovascular Disease

This article reviews recent advances in our understanding of hemodynamic signals, external/compressive forces, and circulating factors that mediate exercise training-induced vascular adaptations, with particular attention to the roles of these signals in prevention and treatment of endothelial dysfunction and cardiovascular (CV) diseases.

CD31+ T cells, endothelial function and cardiovascular risk

Deficits in endothelial cell repair mechanisms are thought to contribute to the aetiology of endothelial dysfunction and, subsequently, cardiovascular disease (CVD). CD31(+) T cells or so-called "angiogenic T cells" are a newly defined T cell subset that exhibit favourable vascular qualities and show a strong negative relation with atherosclerotic disease severity. Despite growing evidence that CD31(+) T cells are important for vascular homeostasis, it is currently unknown if CD31(+) T cell number and function are related to endothelial function and CVD risk in healthy adults. To address this question, we studied 24 healthy adult men (ages: 21-70). Endothelial function was assessed by the forearm blood flow (FBF) response to intra-arterial infusion of acetylcholine (ACh) and CVD risk was estimated by Framingham Risk Score (FRS). CD31(+) T cell number was determined by fluorescence-activated cell sorting. Magnetic-activated cell sorting was used to isolate CD31(+) T cells for Boyden chamber migration. No relation was observed between CD31(+) T cell number and FBF response to ACh or FRS. However, CD31(+) T cell migration to stromal cell-derived factor (SDF)-1α and vascular endothelial growth factor (VEGF) was positively correlated with FBF response to ACh (r = 0.43 for SDF-1α; r = 0.38 for VEGF; both P<0.05) and inversely related to FRS (r = -0.53 for SDF-1α; r = -0.48 for VEGF; both P<0.05). These findings demonstrate that CD31(+) T cell function, but not number, is associated with in vivo endothelial function and CVD risk in healthy adult men.

Effects of acute and chronic endurance exercise on intracellular nitric oxide and superoxide in circulating CD34⁺ and CD34⁻ cells

We investigated the influence of acute and chronic endurance exercise on levels of intracellular nitric oxide (NO), superoxide (O₂·⁻), and expression of genes regulating the balance between these free radicals in CD34⁺ and CD34⁻ peripheral blood mononuclear cells (PBMCs; isolated by immunomagnetic cell separation). Blood samples were obtained from age- and body mass index (BMI)-matched endurance-trained (n = 10) and sedentary (n = 10) men before and after 30 min of exercise at 75% maximal oxygen uptake (·VO(₂max)). Baseline levels of intracellular NO (measured by DAF-FM diacetate) and O₂·⁻ (measured by dihydroethidium) were 26% (P < 0.05) and 10% (P < 0.05) higher, respectively, in CD34⁺ PBMCs from the sedentary group compared with the endurance-trained group. CD34⁺ PBMCs from the sedentary group at baseline had twofold greater inducible nitric oxide synthase (iNOS) mRNA and 50% lower endothelial NOS (eNOS) mRNA levels compared with the trained group (P < 0.05). The baseline group difference in O₂·⁻ was eliminated by acute exercise. Experiments with apocynin indicated that the training-related difference in O₂·⁻ levels was explained by increased NADPH oxidase activity in the sedentary state. mRNA levels of additional angiogenic and antioxidant genes were consistent with a more angiogenic profile in CD34⁺ cells of trained subjects. CD34⁻ PBMCs, examined for exploratory purposes, also displayed a more angiogenic mRNA profile in trained subjects, with vascular endothelial growth factor (VEGF) and eNOS being more highly expressed in trained subjects. Overall, our data suggest an association between the sedentary state and increased nitro-oxidative stress in CD34⁺ cells.

Human aging and CD31+ T-cell number, migration, apoptotic susceptibility, and telomere length

CD31(+) T cells, or so-called "angiogenic T cells," have been shown to demonstrate vasculoprotective and neovasculogenic qualities. The influence of age on CD31(+) T-cell number and function is unclear. We tested the hypothesis that circulating CD31(+) T-cell number and migratory capacity are reduced, apoptotic susceptibility is heightened, and telomere length is shortened with advancing age in adult humans. Thirty-six healthy, sedentary men were studied: 12 young (25 ± 1 yr), 12 middle aged (46 ± 1 yr), and 12 older (64 ± 2 yr). CD31(+) T cells were isolated from peripheral blood samples by magnetic-activated cell sorting. The number of circulating CD31(+) T cells (fluorescence-activated cell sorting analysis) was lower (P < 0.01) in older (24% of CD3(+) cells) compared with middle-aged (38% of CD3(+) cells) and young (40% of CD3(+) cells) men. Migration (Boyden chamber) to both VEGF and stromal cell-derived factor-1α was markedly blunted (P < 0.05) in cells harvested from middle-aged [306.1 ± 45 and 305.6 ± 46 arbitrary units (AU), respectively] and older (231 ± 65 and 235 ± 62 AU, respectively) compared with young (525 ± 60 and 570 ± 62 AU, respectively) men. CD31(+) T cells from middle-aged and older men demonstrated greater apoptotic susceptibility, as staurosporine-stimulated intracellular caspase-3 activation was ∼ 40% higher (P < 0.05) than young. There was a progressive age-related decline in CD31(+) T-cell telomere length (young: 10,706 ± 220 bp; middle-aged: 10,179 ± 251 bp; and older: 9,324 ± 192 bp). Numerical and functional impairments in this unique T-cell subpopulation may contribute to diminished angiogenic potential and greater cardiovascular risk with advancing age.

Effects of acute and chronic endurance exercise on intracellular nitric oxide in putative endothelial progenitor cells: role of NAPDH oxidase

We sought to delineate the effects of acute and chronic exercise on the regulation of intracellular nitric oxide (NO(i)) production in putative endothelial progenitor cells (EPCs). Putative EPC colony-forming units (CFU-EC) were cultured from blood drawn before and after 30 min of treadmill exercise at 75% of maximal oxygen uptake in active (n = 8) and inactive (n = 8) men. CFU-EC were similar between groups at baseline, but increased after exercise in active men only (P = 0.04). CFU-EC expressed lower NADPH oxidase subunit gp91(phox) mRNA and elevated endothelial nitric oxide synthase mRNA in active relative to inactive men at baseline (P < 0.05). Acute exercise reduced gp91(phox) mRNA in CFU-EC of both groups (P < 0.05), whereas p47(phox) mRNA levels were reduced in the inactive group only (P = 0.02). There were no differences between groups or with acute exercise in xanthine oxidase, superoxide dismutase isoforms, or gluthathione peroxidase-1 mRNA levels. NO(i) was significantly greater in CFU-EC of active men at baseline (P = 0.004). NO(i) increased in CFU-EC of inactive men with acute exercise, and in vitro experiments with apocynin indicated the increased NO(i) production was caused by suppression of NADPH oxidase. However, the increases in NO(i) with the different treatments in the inactive group did not reach the baseline levels in the active group (P < 0.05). We conclude that acute exercise increases NO(i) in cells generated by the CFU-EC assay through an NADPH oxidase-inhibition mechanism in sedentary men. However, differences due to chronic exercise must involve additional factors. Our findings support exercise as a means to improve putative EPC function and suggest a novel mechanism that may explain this effect.