Impaired endothelial progenitor cell function predicts age-dependent carotid intimal thickening

Vascular Aging: Assessment and Intervention

Vascular aging represents a collection of structural and functional changes in a blood vessel with advancing age, including increased stiffness, vascular wall remodeling, loss of angiogenic ability, and endothelium-dependent vasodilation dysfunction. These age-related alterations may occur earlier in those who are at risk for or have cardiovascular diseases, therefore, are defined as early or premature vascular aging. Vascular aging contributes independently to cardio-cerebral vascular diseases (CCVDs). Thus, early diagnosis and interventions targeting vascular aging are of paramount importance in the delay or prevention of CCVDs. Here, we review the direct assessment of vascular aging by examining parameters that reflect changes in structure, function, or their compliance with age including arterial wall thickness and lumen diameter, endothelium-dependent vasodilation, arterial stiffness as well as indirect assessment through pathological studies of biomarkers including endothelial progenitor cell, lymphocytic telomeres, advanced glycation end-products, and C-reactive protein. Further, we evaluate how different types of interventions including lifestyle mediation, such as caloric restriction and salt intake, and treatments for hypertension, diabetes, and hyperlipidemia affect age-related vascular changes. As a single parameter or intervention targets only a certain vascular physiological change, it is recommended to use multiple parameters to evaluate and design intervention approaches accordingly to prevent systemic vascular aging in clinical practices or population-based studies.

MiR-17-5p Mediates the Effects of ACE2-Enriched Endothelial Progenitor Cell-Derived Exosomes on Ameliorating Cerebral Ischemic Injury in Aged Mice

Aging is one of the key mechanisms of vascular dysfunction and contributes to the initiation and progression of ischemic stroke (IS). Our previous study demonstrated that ACE2 priming enhanced the protective effects of exosomes derived from endothelial progenitor cells (EPC-EXs) on hypoxia-induced injury in aging endothelial cells (ECs). Here, we aimed to investigate whether ACE2-enriched EPC-EXs (ACE2-EPC-EXs) could attenuate brain ischemic injury by inhibiting cerebral EC damage through their carried miR-17-5p and the underlying molecular mechanisms. The enriched miRs in ACE2-EPC-EXs were screened using the miR sequencing method. EPC-EXs, ACE2-EPC-EXs, and ACE2-EPC-EXs with miR-17-5p deficiency (ACE2-EPC-EXs^{antagomiR-17-5p}) were administered to transient middle cerebral artery occlusion (tMCAO)-operated aged mice or coincubated with hypoxia/reoxygenation (H/R)-treated aging ECs. The results showed that (1) the level of brain EPC-EXs and their carried ACE2 were significantly decreased in aged mice compared to in young mice, and (2) after tMCAO, aged mice displayed increases in brain cell senescence, infarct volume, and neurological deficit score (NDS) and a decrease in cerebral blood flow (CBF). (3) Compared with EPC-EXs, ACE2-EPC-EXs were enriched with miR-17-5p and more effective in increasing ACE2 and miR-17-5p expression in cerebral microvessels, accompanied by obvious increases in cerebral microvascular density (cMVD) and cerebral blood flow (CBF) and decreases in brain cell senescence, infarct volume, neurological deficit score (NDS), cerebral EC ROS production, and apoptosis in tMCAO-operated aged mice. Moreover, silencing of miR-17-5p partially abolished the beneficial effects of ACE2-EPC-EXs. (4) In H/R-treated aging ECs, ACE2-EPC-EXs were more effective than EPC-EXs in decreasing cell senescence, ROS production, and apoptosis and increasing cell viability and tube formation. In a mechanistic study, ACE2-EPC-EXs more effectively inhibited PTEN protein expression and increased the phosphorylation of PI3K and Akt, which were partially abolished by miR-17-5p knockdown. Altogether, our data suggest that ACE-EPC-EXs have better protective effects on ameliorating aged IS mouse brain neurovascular injury by inhibiting cell senescence, EC oxidative stress, apoptosis, and dysfunction by activating the miR-17-5p/PTEN/PI3K/Akt signaling pathway.

New insight into dyslipidemia‐induced cellular senescence in atherosclerosis

Atherosclerosis, characterized by lipid‐rich plaques in the arterial wall, is an age‐related disorder and a leading cause of mortality worldwide. However, the specific mechanisms remain complex. Recently, emerging evidence has demonstrated that senescence of various types of cells, such as endothelial cells (ECs), vascular smooth muscle cells (VSMCs), macrophages, endothelial progenitor cells (EPCs), and adipose‐derived mesenchymal stem cells (AMSCs) contributes to atherosclerosis. Cellular senescence and atherosclerosis share various causative stimuli, in which dyslipidemia has attracted much attention. Dyslipidemia, mainly referred to elevated plasma levels of atherogenic lipids or lipoproteins, or functional impairment of anti‐atherogenic lipids or lipoproteins, plays a pivotal role both in cellular senescence and atherosclerosis. In this review, we summarize the current evidence for dyslipidemia‐induced cellular senescence during atherosclerosis, with a focus on low‐density lipoprotein (LDL) and its modifications, hydrolysate of triglyceride‐rich lipoproteins (TRLs), and high‐density lipoprotein (HDL), respectively. Furthermore, we describe the underlying mechanisms linking dyslipidemia‐induced cellular senescence and atherosclerosis. Finally, we discuss the senescence‐related therapeutic strategies for atherosclerosis, with special attention given to the anti‐atherosclerotic effects of promising geroprotectors as well as anti‐senescence effects of current lipid‐lowering drugs.

Transforming growth factor-β1/Thrombospondin-1/CD47 axis mediates dysfunction in CD34+ cells derived from diabetic older adults

Aging with diabetes is associated with impaired vasoprotective functions and decreased nitric oxide (NO) generation in CD34+ cells. Transforming growth factor- β1 (TGF-β1) is known to regulate hematopoietic functions. This study tested the hypothesis that transforming growth factor- β1 (TGF-β1) is upregulated in diabetic CD34+ cells and impairs NO generation via thrombospondin-1 (TSP-1)/CD47/NO pathway. CD34+ cells from nondiabetic (ND) (n=58) or diabetic older adults (DB) (both type 1 and type 2) (n=62) were isolated from peripheral blood. TGF-β1 was silenced by using an antisense delivered as phosphorodiamidate morpholino oligomer (PMO-TGF-β1). Migration and proliferation in response to stromal-derived factor-1α (SDF-1α) were evaluated. NO generation and eNOS phosphorylation were determined by flow cytometry. CD34+ cells from older, but not younger, diabetics have higher expression of TGF-β1 compared to that observed in cells derived from healthy individuals (P<0.05, n=14). TSP-1 expression was higher (n=11) in DB compared to ND cells. TGFβ1-PMO decreased the secretion of TGF-β1, which was accompanied with decreased TSP-1 expression. Impaired proliferation, migration and NO generation in response to SDF-1α in DB cells were reversed by TGF-β1-PMO (n=6). TSP-1 inhibited migration and proliferation of nondiabetic CD34+ cells that was reversed by CD47-siRNA, which also restored these responses in diabetic CD34+ cells. TSP-1 opposed SDF-1α-induced eNOS phosphorylation at Ser1177 that was reversed by CD47-siRNA. These results infer that increased TGF-β1 expression in CD34+ cells induces dysfunction in CD34+ cells from diabetic older adults via TSP-1/CD47-dependent inhibition of NO generation.

Endothelial Progenitor Cells: An Appraisal of Relevant Data from Bench to Bedside

The mobilization of endothelial progenitor cells (EPCs) into circulation from bone marrow is well known to be present in several clinical settings, including acute coronary syndrome, heart failure, diabetes and peripheral vascular disease. The aim of this review was to explore the current literature focusing on the great opportunity that EPCs can have in terms of regenerative medicine.

Early onset of aging phenotype in vascular repair by Mas receptor deficiency

Aging is associated with impaired vascular repair following ischemic insult, largely due to reparative dysfunctions of progenitor cells. Activation of Mas receptor (MasR) was shown to reverse aging-associated vasoreparative dysfunction. This study tested the impact of MasR-deficiency on mobilization and vasoreparative functions with aging. Wild type (WT) or MasR-deficient mice (MasR^-/- or MasR^+/-) at 12-14 weeks (young) or middle age (11-12 months) (MA) were used in the study. Mobilization of lineage-negative, Sca-1-positive cKit-positive (LSK) cells in response to G-CSF or plerixafor was determined. Hindlimb ischemia (HLI) was induced by femoral artery ligation. Mobilization and blood flow recovery were monitored post-HLI. Radiation chimeras were made by lethal irradiation of WT or MasR^-/- mice followed by administration of bone marrow cells from MasR^-/- or WT mice, respectively. Nitric oxide (NO) generation by stromal-derived factor-1α (SDF) and mitochondrial reactive oxygen species (mitoROS) levels were determined by flow cytometry. Effect of A779 treatment on mobilization, blood flow recovery, and NO and ROS levels were determined in young WT and MasR^+/- mice. Circulating LSK cells in basal or in response to plerixafor or G-CSF or in response to ischemic injury were lower in MasR^-/- mice compared to the WT. Responses in MasR^+/- mice were similar to the WT at young age but at the middle age, impairments were observed. Impaired mobilization to ischemia or G-CSF was rescued in WT → MasR^-/- chimeras. NO levels were lower and mitoROS were higher in MasR^-/- LSK cells compared to WT cells. A779 precipitated dysfunctions in young-MasR^+/- mice similar to that observed in MA-MasR^+/-, and this accompanied decreased NO generation by SDF and enhanced mitoROS levels. This study shows that mice at MA do not exhibit vasoreparative dysfunction. Either partial or total loss of MasR precipitates advanced-aging phenotype likely due to lack of NO and oxidative stress.

Vascular Aging in Rodent Models: Contrasting Mechanisms Driving the Female and Male Vascular Senescence

Increasing scientific interest has been directed to sex as a biological and decisive factor on several diseases. Several different mechanisms orchestrate vascular function, as well as vascular dysfunction in cardiovascular and metabolic diseases in males and females. Certain vascular sex differences are present throughout life, while others are more evident before the menopause, suggesting two important and correlated drivers: genetic and hormonal factors. With the increasing life expectancy and aging population, studies on aging-related diseases and aging-related physiological changes have steeply grown and, with them, the use of aging animal models. Mouse and rat models of aging, the most studied laboratory animals in aging research, exhibit sex differences in many systems and physiological functions, as well as sex differences in the aging process and aging-associated cardiovascular changes. In the present review, we introduce the most common aging and senescence-accelerated animal models and emphasize that sex is a biological variable that should be considered in aging studies. Sex differences in the cardiovascular system, with a focus on sex differences in aging-associated vascular alterations (endothelial dysfunction, remodeling and oxidative and inflammatory processes) in these animal models are reviewed and discussed.

Endothelial Progenitor Cells Dysfunctions and Cardiometabolic Disorders: From Mechanisms to Therapeutic Approaches

Metabolic syndrome (MetS) is a cluster of several disorders, such as hypertension, central obesity, dyslipidemia, hyperglycemia, insulin resistance and non-alcoholic fatty liver disease. Despite health policies based on the promotion of physical exercise, the reduction of calorie intake and the consumption of healthy food, there is still a global rise in the incidence and prevalence of MetS in the world. This phenomenon can partly be explained by the fact that adverse events in the perinatal period can increase the susceptibility to develop cardiometabolic diseases in adulthood. Individuals born after intrauterine growth restriction (IUGR) are particularly at risk of developing cardiovascular diseases (CVD) and metabolic disorders later in life. It has been shown that alterations in the structural and functional integrity of the endothelium can lead to the development of cardiometabolic diseases. The endothelial progenitor cells (EPCs) are circulating components of the endothelium playing a major role in vascular homeostasis. An association has been found between the maintenance of endothelial structure and function by EPCs and their ability to differentiate and repair damaged endothelial tissue. In this narrative review, we explore the alterations of EPCs observed in individuals with cardiometabolic disorders, describe some mechanisms related to such dysfunction and propose some therapeutical approaches to reverse the EPCs dysfunction.

Exosomes and Exosomal MicroRNAs in Age-Associated Stroke

Aging has been considered to be the most important non-modifiable risk factor for stroke and death. Changes in circulation factors in the systemic environment, cellular senescence and artery hypertension during human ageing have been investigated. Exosomes are nanosize membrane vesicles that can regulate target cell functions via delivering their carried bioactive molecules (e.g. protein, mRNA, and microRNAs). In the central nervous system, exosomes and exosomal microRNAs play a critical role in regulating neurovascular function, and are implicated in the initiation and progression of stroke. MicroRNAs are small non-coding RNAs that have been reported to play critical roles in various biological processes. Recently, evidence has shown that microRNAs are packaged into exosomes and can be secreted into the systemic and tissue environment. Circulating microRNAs participate in cellular senescence and contribute to age-associated stroke. Here, we provide an overview of current knowledge on exosomes and their carried microRNAs in the regulation of cellular and organismal ageing processes, demonstrating the potential role of exosomes and their carried microRNAs in age-associated stroke.

ACE2 gene transfer ameliorates vasoreparative dysfunction in CD34+ cells derived from diabetic older adults

Diabetes increases the risk for ischemic vascular diseases, which is further elevated in older adults. Bone marrow-derived hematopoietic CD34+ stem/progenitor cells have the potential of revascularization; however, diabetes attenuates vasoreparative functions. Angiotensin-converting enzyme 2 (ACE2) is the vasoprotective enzyme of renin-angiotensin system in contrast with the canonical angiotensin-converting enzyme (ACE). The present study tested the hypothesis that diabetic dysfunction is associated with ACE2/ACE imbalance in hematopoietic stem/progenitor cells (HSPCs) and that increasing ACE2 expression would restore reparative functions. Blood samples from male and female diabetic (n=71) or nondiabetic (n=62) individuals were obtained and CD34+ cells were enumerated by flow cytometry. ACE and ACE2 enzyme activities were determined in cell lysates. Lentiviral (LV) approach was used to increase the expression of soluble ACE2 protein. Cells from diabetic older adults (DB) or nondiabetic individuals (Control) were evaluated for their ability to stimulate revascularization in a mouse model of hindlimb ischemia (HLI). DB cells attenuated the recovery of blood flow to ischemic areas in nondiabetic mice compared with that observed with Control cells. Administration of DB cells modified with LV-ACE2 resulted in complete restoration of blood flow. HLI in diabetic mice resulted in poor recovery with amputations, which was not reversed by either Control or DB cells. LV-ACE2 modification of Control or DB cells resulted in blood flow recovery in diabetic mice. In vitro treatment with Ang-(1-7) modified paracrine profile in diabetic CD34+ cells. The present study suggests that vasoreparative dysfunction in CD34+ cells from diabetic older adults is associated with ACE2/ACE imbalance and that increased ACE2 expression enhances the revascularization potential.

ACE2/ACE imbalance and impaired vasoreparative functions of stem/progenitor cells in aging

Aging increases risk for ischemic vascular diseases. Bone marrow–derived hematopoietic stem/progenitor cells (HSPCs) are known to stimulate vascular regeneration. Activation of either the Mas receptor (MasR) by angiotensin-(1-7) (Ang-(1-7)) or angiotensin-converting enzyme-2 (ACE2) stimulates vasoreparative functions in HSPCs. This study tested if aging is associated with decreased ACE2 expression in HSPCs and if Ang-(1-7) restores vasoreparative functions. Flow cytometric enumeration of Lin⁻CD45^lowCD34⁺ cells was carried out in peripheral blood of male or female individuals (22–83 years of age). Activity of ACE2 or the classical angiotensin-converting enzyme (ACE) was determined in lysates of HSPCs. Lin⁻Sca-1⁺cKit⁺ (LSK) cells were isolated from young (3–5 months) or old (20–22 months) mice, and migration and proliferation were evaluated. Old mice were treated with Ang-(1-7), and mobilization of HSPCs was determined following ischemia induced by femoral ligation. A laser Doppler blood flow meter was used to determine blood flow. Aging was associated with decreased number (Spearman r = − 0.598, P < 0.0001, n = 56), decreased ACE2 (r = − 0.677, P < 0.0004), and increased ACE activity (r = 0.872, P < 0.0001) (n = 23) in HSPCs. Migration or proliferation of LSK cells in basal or in response to stromal-derived factor-1α in old cells is attenuated compared to young, and these dysfunctions were reversed by Ang-(1-7). Ischemia increased the number of circulating LSK cells in young mice, and blood flow to ischemic areas was recovered. These responses were impaired in old mice but were restored by treatment with Ang-(1-7). These results suggest that activation of ACE2 or MasR would be a promising approach for enhancing ischemic vascular repair in aging.

Roles of exosomal miRNA in vascular aging

Aging is a major risk factor for human diseases. As global average life expectancy has lengthened, delaying or reducing aging and age-related diseases has become an urgent issue for improving the quality of life. The vascular aging process represents an important link between aging and age-related diseases. Exosomes are small extracellular vesicles (EV) that can be secreted by almost all eukaryotic cells, and they deliver characteristic biological information about donor cells to regulate the cellular microenvironment, mediate signal transmission between neighboring or distant cells, and affect the expression of target genes in recipient cells. Many recent studies have shown that exosomal microribonucleic acids (miRNA) are involved in the regulation of vascular aging by participating in the physiological functions of vascular cells and the destruction and remodeling of the extracellular matrix (ECM). This review summarizes the regulatory functions of exosomal miRNA in vascular aging because they interact with the ECM, and participate in vascular cell senescence, and the regulation of senescence-related functions such as proliferation, migration, apoptosis, inflammation, and differentiation.

Influencing factors of vascular endothelial function in patients with non-obstructive coronary atherosclerosis: a 1-year observational study

BACKGROUND

Endothelial dysfunction may play a key role in non-obstructive coronary artery atherosclerosis. Our study aimed to evaluate the vascular endothelial function and its influencing factors in patients with non-obstructive coronary artery atherosclerosis.

METHODS

A total of 131 consecutive patients with non-obstructive coronary artery atherosclerosis were enrolled. Flow-mediated dilatation (FMD) was measured at baseline and 1-year follow-up. Endothelial progenitor cells (EPCs) were counted by staining the fasting venous blood with antibodies against CD34 and vascular endothelial growth factor receptor 2.

RESULTS

Systolic blood pressure, pulse pressure and the levels of HbA1c in participants with baseline FMD < 6% (n = 65) were significantly higher than those with baseline FMD ≥ 6% (n = 66). Baseline FMD was negatively associated with EPC counts (r = - 0.199, P < 0.05) and systolic blood pressure (r = - 0.315, P < 0.01). The 1-year FMD was significantly increased compared to the baseline FMD [(9.31 ± 5.62) % vs (7.31 ± 5.26) %, P < 0.001]. Independent predictors of FMD improvement included elevated EPC counts (OR = 1.104, 95% CI: 1.047-1.165, P < 0.001) and decreased levels of serum creatinine (OR = 0.915, 95% CI: 0.843-0.993, P = 0.034).

CONCLUSIONS

Family history of premature cardiovascular diseases, hypertension, elevated systolic pressure, and HbA1c > 6.5% are independent risk factors for endothelial dysfunction in non-obstructive atherosclerotic patients. Elevated peripheral blood EPC counts and decreased levels of serum creatinine are independent predictors of endothelial function improvement.

Biomarkers for vascular ageing in aorta tissues and blood samples

OBJECTIVES

Functional and quantitative alterations and senescence of circulating and expanded endothelial progenitor cells (EPC), as well as systemic and tissue modifications of angiogenetic and inflammatory molecules, were evaluated for predicting age-related vessel wall remodeling, correlating them to intima media thickness (IMT) in the common carotid artery (CCA), a biomarker of early cardiovascular disease and aortic root dilation.

POPULATIONS AND METHODS

A homogenous Caucasian population was included in the study, constituted by 160 healthy subjects (80 old subjects, mean age 72 ± 6.4, range 66-83 years; and 80 younger blood donors, mean age 26.2 ± 3.4, range 21-33 years), and 60 old subjects (mean age 73 ± 1.4 (range 66-83) years) with aortic root dilatation and hypertension, and 60 old people (70 ± 2.8 (age range 66-83)) with sporadic ascending aorta aneurysm (AAA). In addition, 20 control individuals (10 men and 10 women, mean age: 65 ± 8), were also included in the study for evaluating the gene expression's levels, in aorta tissues. Appropriate techniques, practises, protocols, gating strategies and statistical analyses were performed in our evaluations.

RESULTS

Interestingly, old people had a significantly reduced functionality and a high grade of senescence (high SA-β-Gal activity and high levels of TP53, p21 and p16 genes) of EPC expanded than younger subjects. The values of related parameters progressively augmented from the old subjects, in good healthy shape, to subjects with hypertension and aorta dilation, and AAA. Moreover, they significantly impacted the endothelium than the alterations in EPC number. No changes, but rather increased systemic levels of VEGF and SDF-1 were also assessed in old people vs. younger donors. Old people also showed significantly increased systemic levels of inflammatory cytokines, and a reciprocal significant reduction of systemic s-Notch 1 than younger subjects. These parameters, also including the number EPC alterations, resulted to be significantly sustained in old people bearers of an inflammatory combined genotype. Consistent with these data, a reduced expression of Notch-1 gene, accompanied by a sustained expression of inflammatory genes (i.e. TLR4, IL-1β, IL-6 and IL-17) were detected in aortic tissues from old control people and AAA cases. Finally, we detected the biological effects induced by all the detected alterations on vessel wall age-related remodeling, by evaluating the IMT in the population studied and correlating it to these alterations. The analysis demonstrated that the unique independent risk predictors for vascular ageing are age, the EPC reduced migratory activity and senescence, high grade of expression of genes inducing EPC senescence and chronic tissue and systemic inflammation.

CONCLUSIONS

Thus, we propose these parameters, of easy determination in biological samples (i.e. blood and tissue samples) from alive human population, as optimal biomarkers for vascular ageing.

Mechanisms of Vascular Aging

Aging of the vasculature plays a central role in morbidity and mortality of older people. To develop novel treatments for amelioration of unsuccessful vascular aging and prevention of age-related vascular pathologies, it is essential to understand the cellular and functional changes that occur in the vasculature during aging. In this review, the pathophysiological roles of fundamental cellular and molecular mechanisms of aging, including oxidative stress, mitochondrial dysfunction, impaired resistance to molecular stressors, chronic low-grade inflammation, genomic instability, cellular senescence, epigenetic alterations, loss of protein homeostasis, deregulated nutrient sensing, and stem cell dysfunction in the vascular system are considered in terms of their contribution to the pathogenesis of both microvascular and macrovascular diseases associated with old age. The importance of progeronic and antigeronic circulating factors in relation to development of vascular aging phenotypes are discussed. Finally, future directions and opportunities to develop novel interventions to prevent/delay age-related vascular pathologies by targeting fundamental cellular and molecular aging processes are presented.

Endothelial dysfunction and angiogenesis impairment in the ageing vasculature

Ageing is the main risk factor for the development of cardiovascular diseases. A central mechanism by which ageing promotes vascular pathologies is compromising endothelial health. The age-related attenuation of endothelium-dependent dilator responses (endothelial dysfunction) associated with impairment of angiogenic processes and the subsequent pathological remodelling of the microcirculation contribute to compromised tissue perfusion and exacerbate functional decline in older individuals. This Review focuses on cellular, molecular, and functional changes that occur in the endothelium during ageing. We explore the links between oxidative and nitrative stress and the conserved molecular pathways affecting endothelial dysfunction and impaired angiogenesis during ageing. We also speculate on how these pathological processes could be therapeutically targeted. An improved understanding of endothelial biology in older patients is crucial for all cardiologists because maintenance of a competently functioning endothelium is critical for adequate tissue perfusion and long-term cardiac health.

CD34+ circulating cells display signs of immune activation in patients with acute coronary syndrome

Bone marrow-derived endothelial progenitor cells (EPC) are released into the peripheral blood in situations of vascular repair/angiogenesis. Regulation of vascular repair and angiogenesis by EPC depends not only on the number of circulating EPC but also on their functionality. As endothelial cells can act as antigen-presenting cells in coronary artery disease (CAD), we postulated that EPC can be immune activated here as well. CD34⁺-EPC were isolated from peripheral blood of patients with ST-elevation myocardial infarction (STEMI, n = 12), non-STEMI/unstable angina (UA, n = 15), and stable CAD (SA, n = 18). Expression of HLA-DR, adhesion and costimulatory molecules by isolated CD34⁺-EPC were compared with levels in healthy controls (n = 18). There were no significant differences in VCAM-1 and CD80 expression by peripheral circulating CD34⁺-EPC between the four groups, yet expression of CD86 was highest in UA (p < 0.05). ICAM-1 expression was lowest in SA (p < 0.01). CD34⁺-EPC constitutively expressed HLA-DR across all groups. Of note, patients pretreated with HMG-CoA reductase inhibitors exhibited lower expression of VCAM-1 by CD34⁺-EPC throughout all patient groups; furthermore, statins significantly limited ex vivo-induced upregulation of ICAM-1 by TNF-alpha. To the best of our knowledge, this is the first study to examine the expression of immune markers in peripheral circulating CD34⁺-EPC ex vivo. We demonstrate that CD34⁺-EPC display different patterns of adhesion and costimulatory molecules in various states of CAD. Expression levels were affected by pretreatment with statins. Hence, immune activity of peripheral circulating CD34⁺ cells might play a pathophysiologic role in evolution of CAD.

Angiogenesis, Cancer, and Vascular Aging

Several lines of evidence have revealed that the angiogenic response to ischemic injury declines with age, which might account for the increased morbidity and mortality of cardiovascular disease (CVD) among the elderly. While impairment of angiogenesis with aging leads to delayed wound healing or exacerbation of atherosclerotic ischemic diseases, it also inhibits the progression of cancer. Age-related changes of angiogenesis have been considered to at least partly result from vascular aging or endothelial cell senescence. There is considerable evidence supporting the hypothesis that vascular cell senescence contributes to the pathogenesis of age-related CVD, suggesting that vascular aging could be an important therapeutic target. Since therapeutic angiogenesis is now regarded as a promising concept for patients with ischemic CVD, it has become even more important to understand the detailed molecular mechanisms underlying impairment of angiogenesis in older patients. To improve the usefulness of therapeutic angiogenesis, approaches are needed that can compensate for impaired angiogenic capacity in the elderly while not promoting the development or progression of malignancy. In this review, we briefly outline the mechanisms of angiogenesis and vascular aging, followed by a description of how vascular aging leads to impairment of angiogenesis. We also examine potential therapeutic approaches that could enhance angiogenesis and/or vascular function in the elderly, as well as discussing the possibility of anti-senescence therapy or reversal of endothelial cell senescence.

Endothelial progenitor cells and plaque burden in stented coronary artery segments: an optical coherence tomography study six months after elective PCI

Background

Endothelial progenitor cells (EPC) are involved in neovascularization and endothelial integrity. They might be protective in atherosclerosis. Optical coherence tomography (OCT) is a precise intracoronary imaging modality that allows assessment of subintimal plaque development. We evaluated the influence of EPC on coronary plaque burden in stable disease and implemented a novel computational plaque analysis algorithm using OCT.

Methods

Forty-three patients (69.8% males, 69.6 ± 7.7 years) were investigated by OCT during re-angiography 6 months after elective stent implantation. Different subpopulations of EPCs were identified by flow cytometry according to their co-expression of antigens (CD34+, CD133+, kinase domain receptor, KDR+). An algorithm was applied to calculate the underlying total plaque burden of the stented segments from OCT images. Plaque morphology was assessed according to international consensus in OCT imaging.

Results

A cumulative sub-strut plaque volume of 10.87 ± 12.7 mm³ and a sub-stent plaque area of 16.23 ± 17.0 mm² were found within the stented vessel segments with no significant differences between different stent types. All EPC subpopulations (mean of EPC levels: CD34+/CD133+: 2.66 ± 2.0%; CD34+/KDR+: 7.50 ± 5.0%; CD34+/CD133+/KDR+: 1.12 ± 1.0%) inversely correlated with the identified underlying total plaque volume and plaque area (p ≤ 0.012).

Conclusions

This novel analysis algorithm allows for the first time comprehensive quantification of coronary plaque burden by OCT and illustration as spread out vessel charts. Increased EPC levels are associated with less sub-stent coronary plaque burden which adds to previous findings of their protective role in atherosclerosis.

Beneficial Effects of Reconstituted High-Density Lipoprotein (rHDL) on Circulating CD34+ Cells in Patients after an Acute Coronary Syndrome

Background

High-density lipoproteins (HDL) favorably affect endothelial progenitor cells (EPC). Circulating progenitor cell level and function are impaired in patients with acute coronary syndrome (ACS). This study investigates the short-term effects of reconstituted HDL (rHDL) on circulating progenitor cells in patients with ACS.

Methods and Findings

The study population consisted of 33 patients with recent ACS: 20 patients from the ERASE trial (randomized to receive 4 weekly intravenous infusions of CSL-111 40 mg/kg or placebo) and 13 additional patients recruited as controls using the same enrolment criteria. Blood was collected from 16 rHDL (CSL-111)-treated patients and 17 controls at baseline and at 6–7 weeks (i.e. 2–3 weeks after the fourth infusion of CSL-111 in ERASE). CD34⁺ and CD34⁺/kinase insert domain receptor (KDR⁺) progenitor cell counts were analyzed by flow cytometry. We found preserved CD34⁺ cell counts in CSL-111-treated subjects at follow-up (change of 1.6%), while the number of CD34⁺ cells was reduced (-32.9%) in controls (p = 0.017 between groups). The level of circulating SDF-1 (stromal cell-derived factor-1), a chemokine involved in progenitor cell recruitment, increased significantly (change of 21.5%) in controls, while it remained unchanged in CSL-111-treated patients (p = 0.031 between groups). In vitro exposure to CSL-111 of early EPC isolated from healthy volunteers significantly increased CD34⁺ cells, reduced early EPC apoptosis and enhanced their migration capacity towards SDF-1.

Conclusions

The relative increase in circulating CD34⁺ cells and the low SDF-1 levels observed following rHDL infusions in ACS patients point towards a role of rHDL in cardiovascular repair mechanisms.

Circulating angiogenic cell function is inhibited by cortisol in vitro and associated with psychological stress and cortisol in vivo

Psychological stress and glucocorticoids are associated with heightened cardiovascular disease risk. We investigated whether stress or cortisol would be associated with reduced circulating angiogenic cell (CAC) function, an index of impaired vascular repair. We hypothesized that minority-race individuals who experience threat in interracial interactions would exhibit reduced CAC function, and that this link might be explained by cortisol. To test this experimentally, we recruited 106 African American participants for a laboratory interracial interaction task, in which they received socially evaluative feedback from Caucasian confederates. On a separate day, a subset of 32 participants (mean age=26years, 47% female) enrolled in a separate biological substudy and provided blood samples for CAC isolation and salivary samples to quantify the morning peak in cortisol (the cortisol awakening response, CAR). CAC function was quantified using cell culture assays of migration to vascular endothelial growth factor (VEGF) and secretion of VEGF into the culture medium. Heightened threat in response to an interracial interaction and trait anxiety in vivo were both associated with poorer CAC migratory function in vitro. Further, threat and poorer sustained attention during the interracial interaction were associated with a higher CAR, which in turn, was related to lower CAC sensitivity to glucocorticoids. In vitro, higher doses of cortisol impaired CAC migratory function and VEGF protein secretion. The glucocorticoid receptor antagonist RU486 reversed this functional impairment. These data identify a novel, neuroendocrine pathway by which psychological stress may reduce CAC function, with potential implications for cardiovascular health.

Endothelial progenitor cells as a biological marker of peripheral artery disease

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

Effect of aging on the vascular system plus monitoring and support

Cardiovascular diseases have become a major cause of morbidity and mortality and are likely to only increase as the geriatric population continues to grow. Much is already known about the basic risk factors associated with vascular aging, but there is a new direction of investigation into the health and viability of the endothelium at a biochemical level. As we continue to shift much of our health care focus into prevention tactics and techniques, slowing or reversing the aging process of the vascular system could have a profound impact on our aging population.

Microphysiological modeling of the reproductive tract: a fertile endeavor

Preclinical toxicity testing in animal models is a cornerstone of the drug development process, yet it is often unable to predict adverse effects and tolerability issues in human subjects. Species-specific responses to investigational drugs have led researchers to utilize human tissues and cells to better estimate human toxicity. Unfortunately, human cell-derived models are imperfect because toxicity is assessed in isolation, removed from the normal physiologic microenvironment. Microphysiological modeling often referred to as 'organ-on-a-chip' or 'human-on-a-chip' places human tissue into a microfluidic system that mimics the complexity of human in vivo physiology, thereby allowing for toxicity testing on several cell types, tissues, and organs within a more biologically relevant environment. Here we describe important concepts when developing a repro-on-a-chip model. The development of female and male reproductive microfluidic systems is critical to sex-based in vitro toxicity and drug testing. This review addresses the biological and physiological aspects of the male and female reproductive systems in vivo and what should be considered when designing a microphysiological human-on-a-chip model. Additionally, interactions between the reproductive tract and other systems are explored, focusing on the impact of factors and hormones produced by the reproductive tract and disease pathophysiology.

Enhancing the efficacy of mesenchymal stem cell therapy

Mesenchymal stem cell (MSC) therapy is entering a challenging phase after completion of many preclinical and clinical trials. Among the major hurdles encountered in MSC therapy are inconsistent stem cell potency, poor cell engraftment and survival, and age/disease-related host tissue impairment. The recognition that MSCs primarily mediate therapeutic benefits through paracrine mechanisms independent of cell differentiation provides a promising framework for enhancing stem cell potency and therapeutic benefits. Several MSC priming approaches are highlighted, which will likely allow us to harness the full potential of adult stem cells for their future routine clinical use.

Diesel exhaust particles impair endothelial progenitor cells, compromise endothelial integrity, reduce neoangiogenesis, and increase atherogenesis in mice

The mechanisms of the harmful cardiovascular effects of small particulate matter are incompletely understood. Endothelial progenitor cells (EPCs) predict outcome of patients with vascular disease. The aim of our study was to examine the effects of diesel exhaust particles (DEP) on EPC and on the associated vascular damage in mice. C57Bl/6 mice were exposed to DEP. 2 μg DEP/day was applicated intranasally for 3 weeks. Exposure to DEP reduced DiLDL/lectin positive EPC to 58.4 ± 5.6% (p < 0.005). Migratory capacity was reduced to 65.8 ± 3.9% (p < 0.0001). In ApoE(-/-) mice, DEP application reduced the number of EPC to 75.6 ± 6.4% (p < 0.005) and EPC migration to 58.5 ± 6.8% (p < 0.005). Neoangiogenesis was reduced to 39.5 ± 14.6% (p < 0.005). Atherogenesis was profoundly increased by DEP treatment (157.7 ± 18.1% vs. controls, p < 0.05). In cultured human EPC, DEP (0.1-100 μg/mL) reduced migratory capacity to 25 ± 2.6% (p < 0.001). The number of colony-forming units was reduced to 8.8 ± 0.9% (p < 0.001) and production of reactive oxygen species was elevated by DEP treatment (p < 0.001). Furthermore, DEP treatment increased apoptosis of EPC (to 266 ± 62% of control, p < 0.05). In a blood-brain barrier model, DEP treatment impaired endothelial cell integrity during oxygen-glucose deprivation (p < 0.001). Diesel exhaust particles impair endothelial progenitor cell number and function in vivo and in vitro. The reduction in EPC was associated with impaired neoangiogenesis and a marked increase in atherosclerotic lesion formation.

Obesity impairs vasodilatation and blood flow increase mediated by endothelial nitric oxide: an overview

Obesity dramatically increases the risk of development of cardiovascular and metabolic diseases. Endothelial dysfunction induced by obesity is an important risk factor that impairs blood flow controls in various organs. Impaired endothelial function occurs early in life in obese children. Obesity-induced endothelial dysfunction is associated with decreased nitric oxide (NO) production due to impaired endothelial NO synthase activity and expression and increased production of superoxide anion and the endogenous NOS inhibitor ADMA, together with increased vasoconstrictor factors, such as endothelin-1 and sympathetic nerve activation. Decreased endothelial progenitor cells are also involved in endothelial cell senescence in obese individuals. Insulin resistance and diabetes mellitus augment obesity-induced endothelial dysfunction. Adipokines liberated from adipose tissues play roles in modulating endothelial function; adiponectin and ghrelin have beneficial effects on endothelial cells. Effects of leptin on endothelial function are controversial. Decreased body weight by physical exercise, dietary interventions, and bariatric surgery are effective measures that reverse endothelial dysfunction; however, the weight control is not only the reason for improving of endothelia function. Pharmacological therapies with β-adrenoceptor antagonists, resveratolol, anti-obesity agents, nifedipine, and NADPH oxidase inhibitors may also be effective; however, these treatments have to be utilized under the basis of exercise and dietary controls.

The Relationship between Testosterone Deficiency and Men's Health

Testosterone is important in the physiology of various organs and tissues. The serum testosterone concentration gradually declines as one of the processes of aging. Thus, the concept of late-onset hypogonadism has gained increasing attention in the last few years. Reported symptoms of late-onset hypogonadism are easily recognized and include diminished sexual desire and erectile quality, particularly in nocturnal erections, changes in mood with concomitant decreases in intellectual activity and spatial orientation, fatigue, depression and anger, a decrease in lean body mass with associated decreases in muscle volume and strength, a decrease in body hair and skin alterations, and decreased bone mineral density resulting in osteoporosis. Among these various symptoms, sexual dysfunction has been the most common and necessary to treat in the field of urology. It is well known that a low serum testosterone level is associated with erectile dysfunction and hypoactive sexual libido and that testosterone replacement treatment can improve these symptoms in patients with hypogonadism. Recently, in addition to sexual dysfunction, a close relationship between metabolic syndrome, characterized by central obesity, insulin resistance, dyslipidemia, and hypertension, and late-onset hypogonadism has been highlighted by several epidemiologic studies. Several randomized control trials have shown that testosterone replacement treatment significantly decreases insulin resistance in addition to its advantage for obesity. Furthermore, metabolic syndrome is one of the major risk factors for cardiovascular disease, and a low serum testosterone level is closely related to the development of atherosclerosis. Presently, it is speculated that a low serum testosterone level may increase the risk for cardiovascular disease. Thus, testosterone is a key molecule in men's health, especially that of elderly men.

Endothelial aging associated with oxidative stress can be modulated by a healthy mediterranean diet

Aging is a condition which favors the development of atherosclerosis, which has been associated with a breakdown in repair processes that occurs in response to cell damage. The dysregulation of the biological systems associated with aging are produced partly through damage which accumulates over time. One major source of this injury is oxidative stress, which can impair biological structures and the mechanisms by which they are repaired. These mechanisms are based on the pathogenesis of endothelial dysfunction, which in turn is associated with cardiovascular disease, carcinogenesis and aging. The dependent dysfunction of aging has been correlated with a reduction in the number and/or functional activity of endothelial progenitor cells, which could hinder the repair and regeneration of the endothelium. In addition, aging, inflammation and oxidative stress are endogenous factors that cause telomere shortening, which is dependent on oxidative cell damage. Moreover, telomere length correlates with lifestyle and the consumption of a healthy diet. Thus, diseases associated with aging and age may be caused by the long-term effects of oxidative damage, which are modified by genetic and environmental factors. Considering that diet is a very important source of antioxidants, in this review we will analyze the relationship between oxidative stress, aging, and the mechanisms which may be involved in a higher survival rate and a lower incidence of the diseases associated with aging in populations which follow a healthy diet.

The potential of flavanol and procyanidin intake to influence age-related vascular disease

Advancing age is an independent major risk factor for cardiovascular disease (CVD). Age-associated impairments in the control of inflammation, excessive oxidative stress, and reduced cellular repair can all contribute to the development and progression of CVD. Current recommendations for both the primary and secondary prevention of CVD promote lifestyle modifications that include the adoption of healthy dietary patterns, such as the consumption of diets rich in plant foods, as these have been associated with a lower lifetime risk for the development of CVD. The potential for a diet rich in plant foods to be cardiovascular protective is also supported by prospective studies that suggest the intake of foods providing high amounts of certain phytochemicals, in particular flavanols and procyanidins, reduce the risk for CVD. These observations are further supported by a number of dietary intervention trials that show improvements in vascular function and reduced platelet reactivity following the consumption of high flavanol foods. In the current article we review a selection of these studies, and comment on some of the potential mechanisms that have been postulated to underlie the health effects of flavanol and procyanidin-rich foods.

Pathologic endothelial response and impaired function of circulating angiogenic cells in patients with Fabry disease

Fabry disease is an X-chromosomal recessive deficiency of the lysosomal hydrolase alpha-galactosidase A (alpha-Gal). This results in an accumulation of globotriaosylceramide (GL-3) in a variety of cells often with subsequent functional impairment. Here, the impact of Fabry disease on the biology of circulating angiogenic cells (CACs) and the endothelial response to transient ischemia was investigated. Untreated patients with Fabry disease (n = 26), patients after initiation of alpha-Gal enzyme replacement therapy (ERT) (n = 16) and healthy controls (n = 26) were investigated. Endothelial function was assessed by the EndoPAT2000 device. CAC numbers were assessed by flow-cytometry, CAC function by a modified Boyden chamber assay. Fabry patients showed a pathologic endothelial response, which normalized after ERT. CACs were increased in number, but functionally impaired. Immunofluorescence and electron microscopy identified an accumulation of GL-3 in Fabry CACs. ERT attenuated CAC dysfunction and improved markers of oxidative stress response in Fabry patients via a reduction in GL-3 accumulation in vitro and in vivo. Silencing of alpha-Gal in healthy CACs impaired their migratory capacity underlining a key role of this enzyme for CAC function. CAC supernatant as well as CACs from Fabry patients impaired angiogenesis and migratory capacity of HUVECs providing a mechanistic link between CAC and endothelial dysfunction. CAC adhesion to TNF-α pre-stimulated HUVECs and tube formation was impaired by alpha-Gal knockdown. Fabry patients show a dysfunction of CAC and a pathologic endothelial response. ERT improves CAC and endothelial function and thus may attenuate development of cardiovascular disease in the long term in this patient population.

The cardiovascular effects of premature ovarian failure

BACKGROUND

Previous studies have shown that cardiovascular risk is increased in premature ovarian failure (POF). To determine the effects of POF on different parameters of cardiovascular health, we investigated the relationship between POF and circulating endothelial progenitor cells (EPC), endothelial function, carotid intima media thickness (CIMT) and left ventricular diastolic function.

METHODS

We compared 23 female POF patients (mean age; 37.8 ± 10.8 years) with 20 gender and age-matched healthy controls. Circulating CD133(+)/34(+) and CD34(+)/KDR(+) EPCs were determined by using flow-cytometry. Ultrasound assessment of endothelial function by brachial artery flow-mediated dilatation (FMD) and CIMT was made. Left ventricular systolic and diastolic function was assessed by standard 2D and M-mode echocardiography and tissue Doppler velocities.

RESULTS

Brachial artery FMD was significantly impaired in patients with POF compared with CG (6.3 ± 1.9% vs 10.4 ± 3.7%, p<0.05). Furthermore, circulating EPCs were lower among patients with POF compared to controls for CD133(+)/34(+) and CD34(+)/KDR(+) cells (p<0.05). There was a significant correlation between serum estradiol levels and EPC number (CD 133+/34+) (r=0.329, p<0.05). POF patients had increased CIMT compared to controls (0.67 ± 0.17 vs 0.43 ± 0.10, p<0.05). When diastolic functions were assessed, patients with POF had lower Epeak, Apeak and mitral CP and higher DT and IVRT (p<0.05, respectively).

CONCLUSION

Our findings indicate that endothelial function as well as circulating EPCs, CIMT and diastolic function are significantly affected in young women with POF which may have an adverse long-term effect on cardiovascular prognosis.

Mechanisms involved in the aging-induced vascular dysfunction

Vascular aging is a key process determining health status of aged population. Aging is an independent cardiovascular risk factor associated to an impairment of endothelial function, which is a very early and important event leading to cardiovascular disease. Vascular aging, formerly being considered an immutable and inexorable risk factor, is now viewed as a target process for intervention in order to achieve a healthier old age. A further knowledge of the mechanisms underlying the age-related vascular dysfunction is required to design an adequate therapeutic strategy to prevent or restore this impairment of vascular functionality. Among the proposed mechanisms that contribute to age-dependent endothelial dysfunction, this review is focused on the following aspects occurring into the vascular wall: (1) the reduction of nitric oxide (NO) bioavailability, caused by diminished NO synthesis and/or by augmented NO scavenging due to oxidative stress, leading to peroxynitrite formation (ONOO(-)); (2) the possible sources involved in the enhancement of oxidative stress; (3) the increased activity of vasoconstrictor factors; and (4) the development of a low-grade pro-inflammatory environment. Synergisms and interactions between all these pathways are also analyzed. Finally, a brief summary of some cellular mechanisms related to endothelial cell senescence (including telomere and telomerase, stress-induced senescence, as well as sirtuins) are implemented, as they are likely involved in the age-dependent endothelial dysfunction, as well as in the lower vascular repairing capacity observed in the elderly. Prevention or reversion of those mechanisms leading to endothelial dysfunction through life style modifications or pharmacological interventions could markedly improve cardiovascular health in older people.

Connecting the Lines between Hypogonadism and Atherosclerosis

Epidemiological studies show that atherosclerotic cardiovascular disease is a leading cause of morbidity and mortality worldwide and point to gender differences with ageing males being at highest risk. Atherosclerosis is a complex process that has several risk factors and mediators. Hypogonadism is a commonly undiagnosed disease that has been associated with many of the events, and risk factors leading to atherosclerosis. The mechanistic relations between testosterone levels, atherosclerotic events, and risk factors are poorly understood in many instances, but the links are clear. In this paper, we summarize the research journey that explains the link between hypogonadism, each of the atherosclerotic events, and risk factors. We look into the different areas from which lessons could be learned, including epidemiological studies, animal and laboratory experiments, studies on androgen deprivation therapy patients, and studies on testosterone-treated patients. We finish by providing recommendations for the clinician and needs for future research.

Dysfunctional endothelial progenitor cells in metabolic syndrome

The metabolic syndrome (MetS) is highly prevalent and confers an increased risk of diabetes and cardiovascular disease. A key early event in atherosclerosis is endothelial dysfunction. Numerous groups have reported endothelial dysfunction in MetS. However, the measurement of endothelial function is far from optimum. There has been much interest recently in a subtype of progenitor cells, termed endothelial progenitor cells (EPCs), that can circulate, proliferate, and dfferentiate into mature endothelial cells. EPCs can be characterized by the assessment of surface markers, CD34 and vascular endothelial growth factor receptor-2, VEGFR-2 (KDR). The CD34(+)KDR(+) phenotype has been demonstrated to be an independent predictor of cardiovascular outcomes. MetS patients without diabetes or cardiovascular diseases have decreased EPC number and functionality as evidenced by decreased numbers of colony forming units, decreased adhesion and migration, and decreased tubule formation. Strategies that have been shown to upregulate and enhance EPC number and functionality include statins, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and peroxisome-proliferator-activating-receptor gamma agonists. Mechanisms by which they affect EPC number and functionality need to be studied. Thus, EPC number and/or functionality could emerge as novel cellular biomarkers of endothelial dysfunction and cardiovascular disease risk in MetS.

Effects of ACE inhibition on circulating endothelial progenitor cells, vascular damage, and oxidative stress in hypertensive patients

PURPOSE

The pathogenic role of angiotensin-converting enzyme (ACE) inhibition in hypertensive patients regarding endothelial progenitor-cell (EPC) function is still poorly understood. The aim of the study was to evaluate EPC number, function, and relationship to carotid intima media thickness (IMT) progression.

METHODS

We studied 36 newly diagnosed mildly hypertensive patients free of cardiovascular disease and related risk factors without prior or concurrent therapy with ACE inhibitors. Patients were randomized to receive enalapril 20 mg/day (n = 18) or zofenopril 30 mg/day (n = 18). EPC number and migrating capacity, plasma nitrite and nitrate (NOx), and isoprostane concentrations were evaluated. Carotid IMT was determined by ultrasonography at baseline and after 1 and 5 years of follow-up.

RESULTS

EPC number increased during the follow-up, with no statistical differences between treatment groups. There was an inverse correlation between circulating EPCs and IMT increase over time. Plasma NOx decreased during the study without evident differences between treatment groups. Isoprostanes decreased more markedly in zofenopril-treated patients. Multiple linear regression model demonstrated that carotid IMT was significantly inversely correlated with EPC but not with migratory cells after adjusting for confounders.

CONCLUSIONS

The study demonstrated that EPC levels increased during the follow-up in both groups of newly diagnosed hypertensive patients treated with ACE inhibitors. These drugs prevented progression of vascular damage, with an inverse correlation between circulating EPC levels and IMT values.

Endothelial progenitor cells: novel biomarker and promising cell therapy for cardiovascular disease

Bone-marrow-derived EPCs (endothelial progenitor cells) play an integral role in the regulation and protection of the endothelium, as well as new vessel formation. Peripheral circulating EPC number and function are robust biomarkers of vascular risk for a multitude of diseases, particularly CVD (cardiovascular disease). Importantly, using EPCs as a biomarker is independent of both traditional and non-traditional risk factors (e.g. hypertension, hypercholesterolaemia and C-reactive protein), with infused ex vivo-expanded EPCs showing potential for improved endothelial function and either reducing the risk of events or enhancing recovery from ischaemia. However, as the number of existing cardiovascular risk factors is variable between patients, simple EPC counts do not adequately describe vascular disease risk in all clinical conditions and, as such, the risk of CVD remains. It is likely that this limitation is attributable to variation in the definition of EPCs, as well as a difference in the interaction between EPCs and other cells involved in vascular control such as pericytes, smooth muscle cells and macrophages. For EPCs to be used regularly in clinical practice, agreement on definitions of EPC subtypes is needed, and recognition that function of EPCs (rather than number) may be a better marker of vascular risk in certain CVD risk states. The present review focuses on the identification of measures to improve individual risk stratification and, further, to potentially individualize patient care to address specific EPC functional abnormalities. Herein, we describe that future therapeutic use of EPCs will probably rely on a combination of strategies, including optimization of the function of adjunct cell types to prime tissues for the effect of EPCs.

Glucose challenge increases circulating progenitor cells in Asian Indian male subjects with normal glucose tolerance which is compromised in subjects with pre-diabetes: A pilot study

BACKGROUND

Haematopoietic stem cells undergo mobilization from bone marrow to blood in response to physiological stimuli such as ischemia and tissue injury. The aim of study was to determine the kinetics of circulating CD34+ and CD133+CD34+ progenitor cells in response to 75 g glucose load in subjects with normal and impaired glucose metabolism.

METHODS

Asian Indian male subjects (n = 50) with no prior history of glucose imbalance were subjected to 2 hour oral glucose tolerance test (OGTT). 24 subjects had normal glucose tolerance (NGT), 17 subjects had impaired glucose tolerance (IGT) and 9 had impaired fasting glucose (IFG). The IGT and IFG subjects were grouped together as pre-diabetes group (n = 26). Progenitor cell counts in peripheral circulation at fasting and 2 hour post glucose challenge were measured using direct two-color flow cytometry.

RESULTS

The pre-diabetes group was more insulin resistant (p < 0.0001) as measured by homeostasis assessment model (HOMA-IR) compared to NGT group. A 2.5-fold increase in CD34+ cells (p = 0.003) and CD133+CD34+ (p = 0.019) cells was seen 2 hours post glucose challenge in the NGT group. This increase for both the cell types was attenuated in subjects with IGT. CD34+ cell counts in response to glucose challenge inversely correlated with neutrophil counts (ρ = -0.330, p = 0.019), while post load counts of CD133+CD34+ cells inversely correlated with serum creatinine (ρ = -0.312, p = 0.023).

CONCLUSION

There is a 2.5-fold increase in the circulating levels of haematopoietic stem cells in response to glucose challenge in healthy Asian Indian male subjects which is attenuated in subjects with pre-diabetes.

Differential chemokine receptor expression regulates functional specialization of endothelial progenitor cell subpopulations

Postnatal vasculogenesis is mediated by endothelial progenitor cells (EPCs) which consist of subpopulations with different functional capacities. Our goal was to profile chemokine receptor expression on relevant subsets of EPCs and to characterize their role for effector functions. CD34(+)/CD133(+)/VEGFR2(+) EPCs were characterized by high expression of chemokine receptors CXCR4, CX3CR1, BLT1, and low level expression of CXCR2 and CCR2, while primordial CD34(-)/CD133(+)/VEGFR2(+) EPCs express these chemokine receptors at comparably low levels. Migration assays revealed that SDF-1, fractalkine, and LTB4 significantly increase migration of CD34(-)/CD133(+)/VEGFR2(+) EPCs, while SDF-1 was the only potent agonist of migration of CD34(+)/CD133(+)/VEGFR2(+) EPCs. SDF-1, fractalkine, and LTB4 trigger significant increase adhesion of CD34(+)/CD133(+)/VEGFR2(+) EPCs, while in CD34(-)/CD133(+)/VEGFR2(+) EPCs SDF-1 and fractalkine are equipotent agonists and LTB4 triggers a smaller though still significant increase in adhesion. Differential expression of specific chemokine receptors is an important regulator in terms of migration and adhesion of biologically relevant EPC-subpopulations, which may have implications for cell therapeutic strategies for treatment of ischemic vascular disease.

Bone marrow mononuclear cell transplantation improves survival and induces hepatocyte proliferation in rats after CCl(4) acute liver damage

AIM

The aim of this research was to evaluate the effects of bone marrow mononuclear cell (BMC) transplantation in rats with toxic acute liver damage induced by carbon tetrachloride (CCl(4)).

METHODS

Cells from male Wistar rats were obtained using Ficoll density gradient and 0.2 ml (1 × 10(6) cells) were injected into the portal vein of female rats (n = 15) 24 h after damage. Sham group (n = 15) was performed injecting only vehicle in CCl(4)-treated animals. Survival, liver histology, number of mitosis and apoptosis, and identification of stained donor cells were observed 72 h after damage. ALT levels were measured at 0 h, 24 h, 48 h, and 72 h after injury.

RESULTS

Donor cells could be detected in recipient rats' livers by fluorescence staining and Sry PCR. The treated group revealed a significant improvement in survival rate after 72 h (p = 0.003). There was also a significant increase in the number of mitotic events in treated livers (p = 0.029). This result was confirmed using an in vitro cell proliferation assay in isolated hepatocytes treated with conditioned medium from BMC. ALT was reduced in the treated group after 72 h (p = 0.034).

CONCLUSIONS

Results indicate that BMC transplantation has potential as a new therapeutic option for acute liver disease and suggest that these cells may contribute to hepatic recovery through release of mitotic cytokines.

Impairment of endothelial progenitor cell function and vascularization capacity by aldosterone in mice and humans

Aims

Hyperaldosteronism is associated with vascular injury and increased cardiovascular events. Bone marrow-derived endothelial progenitor cells (EPCs) play an important role in endothelial repair and vascular homeostasis. We hypothesized that hyperaldosteronism impairs EPC function and vascularization capacity in mice and humans.

Methods and results

We characterized the effects of aldosterone and mineralocorticoid receptor (MR) blockade on EPC number and function as well as vascularization capacity and endothelial function. Treatment of human EPC with aldosterone induced translocation of the MR and impaired multiple cellular functions of EPC, such as differentiation, migration, and proliferation in vitro. Impaired EPC function was rescued by pharmacological blockade or genetic ablation of the MR. Aldosterone protein kinase A (PKA) dependently increased reactive oxygen species formation in EPC. Aldosterone infusion in mice impaired EPC function, EPC homing to vascular structures and vascularization capacity in a MR-dependent but blood pressure-independent manner. Endothelial progenitor cells from patients with primary hyperaldosteronism compared with controls of similar age displayed reduced migratory potential. Impaired EPC function was associated with endothelial dysfunction. MR blockade in patients with hyperaldosteronism improved EPC function and arterial stiffness.

Conclusion

Endothelial progenitor cells express a MR that mediates functional impairment by PKA-dependent increase of reactive oxygen species. Normalization of EPC function may represent a novel mechanism contributing to the beneficial effects of MR blockade in cardiovascular disease prevention and treatment.

The renin inhibitor aliskiren upregulates pro-angiogenic cells and reduces atherogenesis in mice

Sca-1 and VEGFR-2 positive pro-angiogenic cells (PAC) predict outcome of patients with vascular disease. Activation of the renin-angiotensin-aldosterone system impairs PAC function. The effects of the direct renin inhibitor aliskiren on PAC numbers and function are not known. Treatment of C57Bl/6 mice and Apo E(-/-) mice on high-cholesterol diet with aliskiren, 25 mg/kg/day s.c. for 3-6 weeks, reduced systolic and diastolic blood pressure by -11.5 and -13.7% compared to vehicle. Aliskiren increased Sca-1/VEGFR-2 positive PAC in the blood (159 ± 14%) and spleen-derived DiLDL/lectin positive PAC (180 ± 21%). Migratory capacity of PAC was increased to 165 ± 16%. In cultured human PAC, aliskiren dose-dependently increased the number of colony forming units to 152 ± 9% (1 μmol/l) and 187 ± 7% (10 μmol/l), which was prevented by the eNOS inhibitor LNMA. H₂O₂-induced apoptosis of cultured human PAC was reduced to 77 ± 23%. In Apo E(-/-) mice, aliskiren reduced atherosclerotic plaque area in the aortic sinus by 58 ± 4%. Circulating Sca-1/VEGFR-2 positive PAC were upregulated to 180 ± 25% and migratory capacity of PAC was increased to 127 ± 7%. Aliskiren reduced vascular NADPH oxidase activity to 41.6 ± 6.7%. Despite similar blood pressure lowering, treatment with hydralazine (25 mg/kg/day) did not significantly influence atherogenesis or PAC. Treatment of C57Bl/6 mice with a lower dose of aliskiren (15 mg/kg/day) did not affect blood pressure but increased cultured DiLDL/lectin positive PAC to 229 ± 30% and their migratory capacity to 214 ± 24%. Aliskiren increased number and function of PAC in mice and prevented atherosclerotic lesion formation. The effects were observed independent of blood pressure lowering.

Nitric oxide synthase expression and functional response to nitric oxide are both important modulators of circulating angiogenic cell response to angiogenic stimuli

OBJECTIVE

Circulating angiogenic cells (CACs), also termed endothelial progenitor cells, play an integral role in vascular repair and are functionally impaired in coronary artery disease (CAD). The role of nitric oxide (NO) in CAC function is poorly understood. We hypothesized that CAC migration toward angiogenic signals is modulated by both NO synthase (NOS) expression and functional response to NO.

METHODS AND RESULTS

Similar to endothelial cells, CAC chemotaxis to vascular endothelial growth factor (VEGF) was blocked by inhibition of NOS, phosphatidylinositol 3-kinase, or guanylyl cyclase or by treatment with an NO scavenger. Addition of an NO donor (S-nitroso-N-acetylpenicillamine) and the NOS substrate l-arginine increased random cell migration (chemokinesis) and enhanced VEGF-dependent chemotaxis. Healthy CACs expressed endothelial NOS, but endothelial NOS was not detected in CAD patient CACs. Both chemokinesis and chemotaxis to VEGF of patient CACs were decreased compared with healthy CACs but were restored to healthy values by S-nitroso-N-acetylpenicillamine. In parallel, CAD patients exhibited lower flow-mediated vasodilation and plasma NO source nitrite than young, healthy subjects, indicating endothelial dysfunction with reduced NO bioavailability.

CONCLUSIONS

NOS activity is required for CAC chemotaxis. In CAD patients, impairment of NOS expression and NO bioavailability, rather than response to NO, may contribute to dysfunction of CACs and limit their regenerative capacity.