Estrogen increases bone marrow-derived endothelial progenitor cell production and diminishes neointima formation

Distinct roles of estrone and estradiol in endothelial colony-forming cells

Our current understanding of the relationship between estrogen and human endothelial colony-forming cell (hECFC) function is based almost exclusively on studies investigating estradiol action at nuclear estrogen receptors. In the current study the hypothesis was tested that the less potent estrogen receptor agonist, estrone, affects hECFC proliferation, migration, secretion, and tube formation in a way that is unique from that of estradiol. The relationship between the estrogens, estradiol and estrone, is clinically important, particularly in postmenopausal women where estradiol levels wane and estrone becomes the predominant estrogen. Cultured hECFCs from peripheral blood mononuclear cell fractions were treated with concentrations of estradiol and estrone ranging from 1 nM to 1 μM separately and in combination. Following treatment, proliferation, migration, ability to attract other hECFCs (autocrine secretion), and ability to enhance endothelial cell tube formation (tubulogenesis) were tested. Functional assays revealed unique, concentration-dependent physiological effects of estrone and estradiol. Estradiol exposure resulted in increased hECFC proliferation, migration, secretion of chemoattractant, and enhancement of tube formation as expected. As with estradiol, hECFC secretion of chemoattractant increased significantly with each increase in estrone exposure. Estrone treatment produced a biphasic, concentration-dependent relationship with proliferation and tube formation and relatively no effect on hECFC migration at any concentration. The quantitative relationship between the effects of estrone and estradiol and each hECFC function was analyzed. The extent to which estrone was similar in effect to that of estradiol was dependent on both the concentrations of estradiol and estrone and the hECFC function measured. Interestingly, when the two estrogens were present, differing ratios resulted in unique functional responses. hECFCs that were treated with combinations of estrone and estradiol with high estrone to estradiol ratios showed decreased proliferative capacity. Conversely, hECFCs that were treated with combinations that were relatively high in estradiol, showed increased proliferative capacity. Cells that were treated with estrone and estradiol in equal concentrations showed an attenuated proliferative response that was decreased compared to the proliferation that either estrone or estradiol produced when they were present alone. This co-inhibitory relationship, which has not been previously reported, challenges the prevailing understanding of estrone as solely a weak agonist at estrogen receptors. This study provides evidence that estrone signaling is distinct from that of estradiol and that further investigation of estrone's mechanism of action and the biological effect may provide important insight into understanding the dysfunction and decreased number of hECFCs, and the resulting cardiovascular disease risk observed clinically in menopausal women and women undergoing hormone replacement therapy.

Reduced Endothelial Progenitor Cells: A Possible Biomarker for Idiopathic Fetal Growth Restriction in Human Pregnancies

BACKGROUND

Circulating endothelial progenitor cells (EPCs) may be necessary throughout pregnancy by ensuring proper placentation and embryonic growth. The lack of standardized EPC quantification techniques has prevented conclusive proof of an increase in EPC during pregnancy.

OBJECTIVES

The purpose of this study was to determine whether EPC levels change for healthy and idiopathic fetal growth restriction (FGR) pregnancies.

MATERIALS AND METHODS

The study population consisted of 48 healthy pregnant females with no previous history of IUGR (10 in the first trimester, 15 in the second, and 23 in the third), 48 women with pregnancy complicated by idiopathic FGR, and 15 non-pregnant women. By using flow cytometry, EPCs in maternal blood were recognized as CD45dim/CD34/KDR cells. ELISA was used to measure plasmatic cytokines.

RESULTS

We ascertained a progressive rise in EPCs in healthy pregnancies that was apparent in the first but more pronounced in the third trimester. At comparable gestational ages, FGR-complicated pregnancies had impaired EPC growth. Placental growth factor and stromal-derived factor-1 levels in the blood were significantly lower in FGR than in healthy pregnancies, which may have contributed to the degradation of the EPCs.

CONCLUSION

The count in EPCs might hold considerable promise toward developing a peculiar authentication marker for observing pregnancies, and could be the focus of cutting-edge tactics for the prognosis and treatment of FGR pregnancies.

Sex hormones and immune system: Menopausal hormone therapy in the context of COVID-19 pandemic

The fatal outcomes of COVID-19 are related to the high reactivity of the innate wing of immunity. Estrogens could exert anti-inflammatory effects during SARS-CoV-2 infection at different stages: from increasing the antiviral resistance of individual cells to counteracting the pro-inflammatory cytokine production. A complex relationship between sex hormones and immune system implies that menopausal hormone therapy (MHT) has pleiotropic effects on immunity in peri- and postmenopausal patients. The definite immunological benefits of perimenopausal MHT confirm the important role of estrogens in regulation of immune functionalities. In this review, we attempt to explore how sex hormones and MHT affect immunological parameters of the organism at different level (in vitro, in vivo) and what mechanisms are involved in their protective response to the new coronavirus infection. The correlation of sex steroid levels with severity and lethality of the disease indicates the potential of using hormone therapy to modulate the immune response and increase the resilience to adverse outcomes. The overall success of MHT is based on decades of experience in clinical trials. According to the current standards, MHT should not be discontinued in COVID-19 with the exception of critical cases.

Impact of diabetes and ischemic stroke on the cerebrovasculature: A female perspective

There is a very complex interaction between the brain and the cerebral vasculature to meet the metabolic demands of the brain for proper function. Preservation of vascular networks and cerebrovascular function ultimately plays a key role in this intricate communication within the brain in health and disease. Experimental evidence showed that diabetes not only affects the architecture of cerebral blood arteries causing adverse remodeling, pathological neovascularization, and vasoregression, but also alters cerebrovascular function resulting in compromised myogenic reactivity and endothelial dysfunction. Coupled with the disruption of blood brain barrier (BBB) integrity, changes in blood flow and microbleeds into the brain can rapidly occur. When an ischemic insult is superimposed on this pathology, not only is the neurovascular injury greater, but repair mechanisms fail, resulting in greater physical and cognitive deficits. While clinically it is known that women suffer disproportionately from diabetes as well as ischemic stroke and post-stroke cognitive impairment, the cerebrovascular architecture, patho/physiology, as well as cerebrovascular contributions to stroke recovery in female and diabetic animal models are inadequately studied and highlighted in this review.

N‑acetyl cysteine prevents ambient fine particulate matter‑potentiated atherosclerosis via inhibition of reactive oxygen species‑induced oxidized low density lipoprotein elevation and decreased circulating endothelial progenitor cell

Ambient fine particulate matter (PM) serves an important role in the development of cardiovascular disease, including atherosclerosis. Antioxidant N‑acetyl cysteine (NAC) has protective effects in the cardiovascular system. However, it is unknown if NAC prevents PM‑potentiated atherosclerosis in hyperlipidemia. Low‑density lipoprotein (LDL) receptor knockout mice were pretreated with 1 mg/ml NAC in drinking water for 1 week and continued to receive NAC, high‑fat diet and intranasal instillation of PM for 1 week or 6 months. Blood plasma was collected for lipid profile, oxidized (ox‑)LDL, blood reactive oxygen species (ROS) and inflammatory cytokine (TNF‑α, IL‑1β and IL‑6) measurement. Blood cells were harvested for endothelial progenitor cell (EPC) population and intracellular ROS analysis. Murine aorta was isolated for atherosclerotic plaque ratio calculation. NAC treatment maintained circulating EPC level and significantly decreased blood ox‑LDL and ROS, inflammatory cytokines, mononuclear and EPC intracellular ROS levels as well as aortic plaque ratio. NAC prevented PM‑potentiated atherosclerosis by inhibiting plasma ROS‑induced ox‑LDL elevation, mononuclear cell and EPC intracellular ROS‑induced circulating EPC reduction and inflammatory cytokine production.

Endothelial Progenitor Cells as Biomarkers of Cardiovascular Pathologies: A Narrative Review

Endothelial progenitor cells (EPC) may influence the integrity and stability of the vascular endothelium. The association of an altered total EPC number and function with cardiovascular diseases (CVD) and risk factors (CVF) was discussed; however, their role and applicability as biomarkers for clinical purposes have not yet been defined. Endothelial dysfunction is one of the key mechanisms in CVD. The assessment of endothelial dysfunction in vivo remains a major challenge, especially for a clinical evaluation of the need for therapeutic interventions or for primary prevention of CVD. One of the main challenges is the heterogeneity of this particular cell population. Endothelial cells (EC) can become senescent, and the majority of circulating endothelial cells (CEC) show evidence of apoptosis or necrosis. There are a few viable CECs that have properties similar to those of an endothelial progenitor cell. To use EPC levels as a biomarker for vascular function and cumulative cardiovascular risk, a correct definition of their phenotype, as well as an update on the clinical application and practicability of current isolation methods, are an urgent priority.

Hormesis and Endothelial Progenitor Cells

Hormetic-biphasic dose response relationships are reported herein for human endothelial progenitor cells involving estradiol, nicotine, the anti-diabetic agent pioglitazone, resveratrol, and progesterone. In general, these studies demonstrate the capacity of these agents to enhance EPC proliferation and angiogenesis functional applications, having a focus on repairing endothelial tissue damage due to acute injury (e.g., stroke), as well as damage from chronic conditions (e.g., atherosclerosis) and normal aging processes.

Visit-to-visit fasting blood glucose variability and lifetime risk of cardiovascular disease: a prospective study

Aims

Previous studies suggested an adverse association between higher fasting blood glucose (FBG) variability and cardiovascular disease (CVD). Lifetime risk provides an absolute risk assessment during the remainder of an individual’s life. However, the association between FBG variability and the lifetime risk of CVD is uncertain.

Objective

We aimed to investigate the effect of the visit-to-visit FBG variability on the lifetime risk of CVD.

Methods

This study included participants from the Kailuan Study who did not have CVD at index ages 35, 45, and 55 years. The FBG variability was defined as the coefficient of variation (CV) of three FBG values that were measured during the examination periods of 2006–2007, 2008–2009, and 2010–2011. We used a modified Kaplan-Merrier method to estimate lifetime risk of CVD according to tertiles of FBG variability.

Results

At index age 35 years, the study sample comprised 46,018 participants. During a median follow-up of 7.0 years, 1889 participants developed CVD events. For index age 35 years, participants with high FBG variability had higher lifetime risk of CVD (32.5%; 95% confidence interval [CI]: 28.9–36.1%), compared with intermediate (28.3%; 95% CI: 25.5 –31.1%) and low (26.3%; 95% CI: 23.0–29.5%) FBG variability. We found that higher FBG variability was associated with increased lifetime risk of CVD in men but not women. Similar patterns were observed at index ages 45 and 55 years.

Conclusions

Higher FBG variability was associated with increased lifetime risk of CVD at each index age. Focusing on the FBG variability may provide an insight to the clinical utility for reducing the lifetime risk of CVD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-021-01397-1.

A Meta-Analysis of the Effects of Aerobic Exercise on the Basal Level of Endothelial Progenitor Cells in Middle-Aged and Older Adults

Circulatory endothelial progenitor cells (EPCs) play an important role in repairing damaged vascular endothelium and preventing cardiovascular diseases. The decrease in level of circulating EPCs in middle-aged and older adults can lead to an increase in cardiovascular events. Researchers have carried out several studies on the effects of aerobic exercise on circulating EPCs in middle-aged and older adults, but the results vary from one study to another. The aim of this study therefore is to systematically evaluate the effect of aerobic exercise on the basal level of circulating EPCs in middle-aged and older adults by meta-analysis. Randomized controlled trial studies on the effects of aerobic exercise on EPCs were searched for from CNKI, PubMed, EBSCO, Cochrane Library, Web of Science, and Embase databases. The literature was screened according to inclusion and exclusion criteria, research data were extracted, and the literature quality was evaluated by Cochrane scale. Software Review Manager (version 5.3) and Stata (version 15.0) were used for data analysis. A total of nine articles were included in this analysis, including 165 participants (40 healthy adults and 125 patients) who received exercise interventions and 162 participants (40 healthy adults and 122 patients) who served as the control, with an age range from 58 to 70 years. The meta-analysis found that long-term (≥12 weeks) aerobic exercise could improve the level of EPCs in the peripheral circulation (standardized mean differences [SMD] = 0.53, 95% confidence interval [0.30, 0.76], p < .01). The subgroup analysis found that aerobic exercise improved EPCs in healthy people better than in people with cardiovascular disease and that the intervention time needs to be over 12 weeks to have a significant impact. In conclusion, the authors suggest that middle-aged and older adults can improve their EPCs quantity by engaging in moderate-intensity aerobic exercise four to five times per week for no less than 12 weeks to reduce the risk of cardiovascular disease.

Role of β-Adrenergic Receptors and Estrogen in Cardiac Repair after Myocardial Infarction: An Overview

Acute myocardial infarction (MI) is associated with an intense inflammatory response that is critical for cardiac repair but is also involved in the pathogenesis of adverse cardiac remodeling, i.e., the set of size, geometry, and structure changes that represent the structural substrate for the development of post-MI heart failure. Deciphering the pathophysiological mechanisms underlying cardiac repair after MI is, therefore, critical to favorably regulate cardiac wound repair and to prevent development of heart failure. Catecholamines and estrogen play an active role in regulating the inflammatory response in the infarcted area. For example, stress-induced catecholamines alter recruitment and trafficking of leukocytes to the heart. Additionally, estrogen affects rate of cardiac rupture during the acute phase of MI, as well as infarct size and survival in animal models of MI. In this review, we will summarize the role of β-adrenergic receptors and estrogen in cardiac repair after infarction in preclinical studies.

To be or not to be: endothelial cell plasticity in development, repair, and disease

Endothelial cells display an extraordinary plasticity both during development and throughout adult life. During early development, endothelial cells assume arterial, venous, or lymphatic identity, while selected endothelial cells undergo additional fate changes to become hematopoietic progenitor, cardiac valve, and other cell types. Adult endothelial cells are some of the longest-lived cells in the body and their participation as stable components of the vascular wall is critical for the proper function of both the circulatory and lymphatic systems, yet these cells also display a remarkable capacity to undergo changes in their differentiated identity during injury, disease, and even normal physiological changes in the vasculature. Here, we discuss how endothelial cells become specified during development as arterial, venous, or lymphatic endothelial cells or convert into hematopoietic stem and progenitor cells or cardiac valve cells. We compare findings from in vitro and in vivo studies with a focus on the zebrafish as a valuable model for exploring the signaling pathways and environmental cues that drive these transitions. We also discuss how endothelial plasticity can aid in revascularization and repair of tissue after damage- but may have detrimental consequences under disease conditions. By better understanding endothelial plasticity and the mechanisms underlying endothelial fate transitions, we can begin to explore new therapeutic avenues.

Physical Exercise: A Novel Tool to Protect Mitochondrial Health

Mitochondrial dysfunction is a crucial contributor to heart diseases. Alterations in energetic metabolism affect crucial homeostatic processes, such asATP production, the generation of reactive oxygen species, and the release of pro-apoptotic factors, associated with metabolic abnormalities. In response to energetic deficiency, the cardiomyocytes activate the Mitochondrial Quality Control (MQC), a critical process in maintaining mitochondrial health. This process is compromised in cardiovascular diseases depending on the pathology's severity and represents, therefore, a potential therapeutic target. Several potential targeting molecules within this process have been identified in the last years, and therapeutic strategies have been proposed to ameliorate mitochondria monitoring and function. In this context, physical exercise is considered a non-pharmacological strategy to protect mitochondrial health. Physical exercise regulates MQC allowing the repair/elimination of damaged mitochondria and synthesizing new ones, thus recovering the metabolic state. In this review, we will deal with the effect of physical exercise on cardiac mitochondrial function tracing its ability to modulate specific steps in MQC both in physiologic and pathologic conditions.

Estrogen activates endothelial exocytosis

Estrogen therapy is used to treat patients with post-menopausal symptoms, such as hot flashes and dyspareunia. Estrogen therapy also decreases the risk of fractures from osteoporosis in post-menopausal women. However, estrogen increases the risk of venous thromboembolic events, such as pulmonary embolism, but the pathways through which estrogen increase the risk of thromboembolism is unknown. Here, we show that estrogen elicits endothelial exocytosis, the key step in vascular thrombosis and inflammation. Exogenous 17β-estradiol (E2) stimulated endothelial exocytosis of Weibel-Palade bodies (WPBs), releasing von Willebrand factor (vWF) and interleukin-8 (IL-8). Conversely, the estrogen antagonist ICI-182,780 interfered with E2-induced endothelial exocytosis. The ERα agonist propyl pyrazole triol (PPT) but not the ERβ agonist diarylpropionitrile (DPN) induced vWF release, while ERα silencing counteracted vWF release by E2, suggesting that ERα mediates this effect. Exocytosis triggered by E2 occurred rapidly within 15 min and was not inhibited by either actinomycin D or cycloheximide. On the contrary, it was inhibited by the pre-treatment of U0126 or SB203580, an ERK or a p38 inhibitor, respectively, suggesting that E2-induced endothelial exocytosis is non-genomically mediated by the MAP kinase pathway. Finally, E2 treatment enhanced platelet adhesion to endothelial cells ex vivo, which was interfered with the pre-treatment of ICI-182,780 or U0126. Taken together, our data show that estrogen activates endothelial exocytosis non-genomically through the ERα-MAP kinase pathway. Our data suggest that adverse cardiovascular effects such as vascular inflammation and thrombosis should be considered in patients before menopausal hormone treatment.

Protein kinase CK2 participates in estrogen-mediated endothelial progenitor cell homing to endometriotic lesions through stromal cells in a stromal cell-derived factor-1- CXCR4-dependent manner

OBJECTIVE

To explore the possible mechanism of protein kinase CK2, which participates in estrogen recruitment of endothelial progenitor cells (EPCs), and its role in the angiogenesis of endometriosis lesions.

DESIGN

Laboratory study.

SETTING

University.

ANIMAL(S)

BALB/c mice.

INTERVENTION(S)

Exposure of human endometrial stromal cells (HESCs) to estrogen and CK2 inhibitor CX-4945 and endometrial stromal cells transfected with the protein kinase CK2 vector (HESC-CK2). Endometriosis models were induced by allogeneic mice transplantation of the endometrium into dorsal skinfold chambers. The mice received an IP injection of 50 mg/kg emodin per day or were treated with 100 μg/kg estrogen by SC injection once a week.

MAIN OUTCOME MEASURE(S)

The concentration of cytokines in cells was measured with ELISA. The migration of EPCs was examined using the scratch assay method and Transwell, a capillary tube-formation assay to determine EPC tube-forming capacity, and protein and mRNA expression with Western blot and polymerase chain reaction analyses, respectively.

RESULT(S)

Protein kinase CK2 participates in estrogen-mediated EPC homing to endometriotic lesions through stromal cells in a stromal cell-derived factor-1 (SDF-1)-CXCR4-dependent manner. Conditioned medium from endometrial stromal cells that were stably transfected with the protein kinase CK2 vector (HESC-CK2) or pretreated with estrogen significantly enhanced the migration and recruitment of EPCs. In contrast, conditioned medium from HESCs that were treated with CX-4945, a selective inhibitor of CK2, inhibited the mobility and viability of EPCs. Furthermore, CK2 overexpression significantly upregulated SDF-1 expression and secretion in endometrial stromal cells by activating the AKT/mTOR pathway. Moreover, treatment with the SDF-1 receptor CXCR4-specific inhibitor AMD3100 completely reversed the CK2-enhanced migration of EPCs.

CONCLUSION(S)

This study demonstrates that CK2 participates in estrogen-mediated EPC homing to endometriotic lesions through stromal cells in an SDF-1-CXCR4-dependent manner and may be a therapeutic target.

Final five-year results of the REMEDEE Registry: Real-world experience with the dual-therapy COMBO stent

Objectives

This final report from the REMEDEE Registry assessed the long‐term safety and efficacy of the dual‐therapy COMBO stent in a large unselected patient population.

Background

The bio‐engineered COMBO stent (OrbusNeich Medical BV, The Netherlands) is a dual‐therapy pro‐healing stent. Data of long‐term safety and efficacy of the this stent is lacking.

Methods

The prospective, multicenter, investigator‐initiated REMEDEE Registry evaluated clinical outcomes after COMBO stent implantation in daily clinical practice. One thousand patients were enrolled between June 2013 and March 2014.

Results

Five‐year follow‐up data were obtained in 97.2% of patients. At 5‐years, target lesion failure (TLF) (composite of cardiac death, target‐vessel myocardial infarction, or target lesion revascularization) was present in 145 patients (14.8%). Definite or probable stent thrombosis (ST) occurred in 0.9%, with no additional case beyond 3‐years of follow‐up. In males, 5‐year TLF‐rate was 15.6 versus 12.6% in females (p = .22). Patients without diabetes mellitus (DM) had TLF‐rate of 11.4%, noninsulin‐treated DM 22.7% (p = .001) and insulin‐treated DM 41.2% (p < .001). Patients presenting with non‐ST segment elevation acute coronary syndrome (NSTE‐ACS) had higher incidence of TLF compared to non‐ACS (20.4 vs. 13.3%; p = .008), while incidence with STE‐ACS was comparable to non‐ACS (10.7 vs. 13.3%; p = .43).

Conclusion

Percutaneous coronary intervention with the dual‐therapy COMBO stent in unselected patient population shows low rates of TLF and ST to 5 years. Remarkably, no case of ST was noted beyond 3 years.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

Mechanisms of Sex Disparities in Cardiovascular Function and Remodeling

Epidemiological studies demonstrate disparities between men and women in cardiovascular disease prevalence, clinical symptoms, treatments, and outcomes. Enrollment of women in clinical trials is lower than men, and experimental studies investigating molecular mechanisms and efficacy of certain therapeutics in cardiovascular disease have been primarily conducted in male animals. These practices bias data interpretation and limit the implication of research findings in female clinical populations. This review will focus on the biological origins of sex differences in cardiovascular physiology, health, and disease, with an emphasis on the sex hormones, estrogen and testosterone. First, we will briefly discuss epidemiological evidence of sex disparities in cardiovascular disease prevalence and clinical manifestation. Second, we will describe studies suggesting sexual dimorphism in normal cardiovascular function from fetal life to older age. Third, we will summarize and critically discuss the current literature regarding the molecular mechanisms underlying the effects of estrogens and androgens on cardiac and vascular physiology and the contribution of these hormones to sex differences in cardiovascular disease. Fourth, we will present cardiovascular disease risk factors that are positively associated with the female sex, and thus, contributing to increased cardiovascular risk in women. We conclude that inclusion of both men and women in the investigation of the role of estrogens and androgens in cardiovascular physiology will advance our understanding of the mechanisms underlying sex differences in cardiovascular disease. In addition, investigating the role of sex-specific factors in the development of cardiovascular disease will reduce sex and gender disparities in the treatment and diagnosis of cardiovascular disease. © 2019 American Physiological Society. Compr Physiol 9:375-411, 2019.

Decreased Count and Dysfunction of Circulating EPCs in Postmenopausal Hypercholesterolemic Females via Reducing NO Production

Endothelial progenitor cells (EPCs) contribute to the endogenous endothelial repair program during hypercholesterolemia. EPC count and migratory and proliferative capacities remain unchanged in the premenopausal female with hypercholesterolemia. However, the changes of count and activity of circulating EPCs in the hypercholesterolemic postmenopausal females are unknown. Here, we find that the migratory and proliferative capacities of circulating EPCs were decreased in patients with hypercholesterolemia versus normocholesterolemia. No significant differences were found between postmenopausal females and age-matched males. NO production showed positive correlation with the activity and count of circulating EPCs in patients with hypercholesterolemia. Flow-mediated dilatation (FMD) is directly interrelated with EPC counts and function. Our findings reveal that decreased EPC count and endothelial dysfunction lead to less NO production in hypercholesterolemic postmenopausal females. Maintaining the EPC numbers and activity might be emerging as a potential therapeutic strategy to reduce the risk of cardiovascular injury in elder women.

Prevention of in-stent restenosis with endothelial progenitor cell (EPC) capture stent placement combined with regional EPC transplantation: An atherosclerotic rabbit model

BACKGROUND

Even with drug-eluting stents, the risk of in-stent restenosis (ISR) remains high. The goal of this study was to investigate the use of an endothelial progenitor cell (EPC) capture stent plus regional EPC transplantation to reduce the ISR rate.

METHODS

Endothelial progenitor cell capture stents were fabricated using fibrin gel and anti-CD34 plus anti-VEGFR-2 dual antibodies. Twenty male New Zealand white rabbits established as an atherosclerotic model were randomly divided into two groups: group 1 (n = 10), in which EPC capture stents were deployed into the right iliac artery; and group 2 (n = 10), in which sirolimus-eluting stents were placed. In both groups, EPCs were transplanted into target vessels beyond the stents, with outflow blocked. Radiologic-pathologic correlation outcomes were reviewed after 2 months.

RESULTS

The technical success rate of EPC capture stent placement plus EPC transplantation was 100%. The ISR rate in group 1 was lower than in group 2 (1/10 vs. 4/10; p > 0.05). Minimal luminal diameters were larger in group 1 than in group 2 (computed tomographic angiography, 1.85 ± 0.15 mm vs. 1.50 ± 0.20 mm; duplex ultrasound, 1.90 ± 0.10 mm vs. 1.70 ± 0.30 mm; p > 0.05). Transplanted EPCs were tracked positively only in group 1. Pathologic analysis demonstrated neointimal hyperplasia thickness of 0.21 ± 0.09 mm in group 1 vs. 0.11 ± 0.07 mm in group 2 (p < 0.05).

CONCLUSION

Endothelial progenitor cell capture stent placement plus local EPC transplant decreases the ISR rate through thrombosis reduction rather than through neointimal hyperplasia inhibition.

Estrogen, Angiogenesis, Immunity and Cell Metabolism: Solving the Puzzle

Estrogen plays an important role in the regulation of cardiovascular physiology and the immune system by inducing direct effects on multiple cell types including immune and vascular cells. Sex steroid hormones are implicated in cardiovascular protection, including endothelial healing in case of arterial injury and collateral vessel formation in ischemic tissue. Estrogen can exert potent modulation effects at all levels of the innate and adaptive immune systems. Their action is mediated by interaction with classical estrogen receptors (ERs), ERα and ERβ, as well as the more recently identified G-protein coupled receptor 30/G-protein estrogen receptor 1 (GPER1), via both genomic and non-genomic mechanisms. Emerging data from the literature suggest that estrogen deficiency in menopause is associated with an increased potential for an unresolved inflammatory status. In this review, we provide an overview through the puzzle pieces of how 17β-estradiol can influence the cardiovascular and immune systems.

Shear stress: An essential driver of endothelial progenitor cells

The blood flow through vessels produces a tangential, or shear, stress sensed by their innermost layer (i.e., endothelium) and representing a major hemodynamic force. In humans, endothelial repair and blood vessel formation are mainly performed by circulating endothelial progenitor cells (EPCs) characterized by a considerable expression of vascular endothelial growth factor receptor 2 (VEGFR2), CD34, and CD133, pronounced tube formation activity in vitro, and strong reendothelialization or neovascularization capacity in vivo. EPCs have been proposed as a promising agent to induce reendothelialization of injured arteries, neovascularization of ischemic tissues, and endothelialization or vascularization of bioartificial constructs. A number of preconditioning approaches have been suggested to improve the regenerative potential of EPCs, including the use of biophysical stimuli such as shear stress. However, in spite of well-defined influence of shear stress on mature endothelial cells (ECs), articles summarizing how it affects EPCs are lacking. Here we discuss the impact of shear stress on homing, paracrine effects, and differentiation of EPCs. Unidirectional laminar shear stress significantly promotes homing of circulating EPCs to endothelial injury sites, induces anti-thrombotic and anti-atherosclerotic phenotype of EPCs, increases their capability to form capillary-like tubes in vitro, and enhances differentiation of EPCs into mature ECs in a dose-dependent manner. These effects are mediated by VEGFR2, Tie2, Notch, and β1/3 integrin signaling and can be abrogated by means of complementary siRNA/shRNA or selective pharmacological inhibitors of the respective proteins. Although the testing of sheared EPCs for vascular tissue engineering or regenerative medicine applications is still an unaccomplished task, favorable effects of unidirectional laminar shear stress on EPCs suggest its usefulness for their preconditioning.

Mesenchymal stem cells and vascular regeneration

In recent years, MSCs have emerged as a promising therapeutic cell type in regenerative medicine. They hold great promise for treating cardiovascular diseases, such as myocardial infarction and limb ischemia. MSCs may be utilized in both cell-based therapy and vascular graft engineering to restore vascular function, thereby providing therapeutic benefits to patients. The efficacy of MSCs lies in their multipotent differentiation ability toward vascular smooth muscle cells, endothelial cells and other cell types, as well as their capacity to secrete various trophic factors, which are potent in promoting angiogenesis, inhibiting apoptosis and modulating immunoreaction. Increasing our understanding of the mechanisms of MSC involvement in vascular regeneration will be beneficial in boosting present therapeutic approaches and developing novel ones to treat cardiovascular diseases. In this review, we aim to summarize current progress in characterizing the in vivo identity of MSCs, to discuss mechanisms involved in cell-based therapy utilizing MSCs, and to explore current and future strategies for vascular regeneration.

Basic mechanisms of vascularization in endometriosis and their clinical implications

BACKGROUND

Vascularization is a major hallmark in the pathogenesis of endometriosis. An increasing number of studies suggests that multiple mechanisms contribute to the vascularization of endometriotic lesions, including angiogenesis, vasculogenesis and inosculation.

OBJECTIVE AND RATIONALE

In this review, we provide an overview of the basic mechanisms of vascularization in endometriosis and give special emphasis on their future clinical implications in the diagnosis and therapy of the disease.

SEARCH METHODS

Literature searches were performed in PubMed for English articles with the key words 'endometriosis', 'endometriotic lesions', 'angiogenesis', 'vascularization', 'vasculogenesis', 'endothelial progenitor cells' and 'inosculation'. The searches included both animal and human studies. No restriction was set for the publication date.

OUTCOMES

The engraftment of endometriotic lesions is typically associated with angiogenesis, i.e. the formation of new blood vessels from pre-existing ones. This angiogenic process underlies the complex regulation by angiogenic growth factors and hormones, which activate intracellular pathways and associated signaling molecules. In addition, circulating endothelial progenitor cells (EPCs) are mobilized from the bone marrow and recruited into endometriotic lesions, where they are incorporated into the endothelium of newly developing microvessels, referred to as vasculogenesis. Finally, preformed microvessels in shed endometrial fragments inosculate with the surrounding host microvasculature, resulting in a rapid blood supply to the ectopic tissue. These vascularization modes offer different possibilities for the establishment of novel diagnostic and therapeutic approaches. Angiogenic growth factors and EPCs may serve as biomarkers for the diagnosis and classification of endometriosis. Blood vessel formation and mature microvessels in endometriotic lesions may be targeted by means of anti-angiogenic compounds and vascular-disrupting agents.

WIDER IMPLICATIONS

The establishment of vascularization-based approaches in the management of endometriosis still represents a major challenge. For diagnostic purposes, reliable angiogenic and vasculogenic biomarker panels exhibiting a high sensitivity and specificity must be identified. For therapeutic purposes, novel compounds selectively targeting the vascularization of endometriotic lesions without inducing severe side effects are required. Recent progress in the field of endometriosis research indicates that these goals may be achieved in the near future.

Endothelial nitric oxide synthase overexpressing human early outgrowth cells inhibit coronary artery smooth muscle cell migration through paracrine functions

Cells mobilized from the bone marrow can contribute to endothelial regeneration and repair. Nevertheless, cardiovascular diseases are associated with diminished numbers and function of these cells, attenuating their healing potential. Gene transfer of endothelial nitric oxide synthase (eNOS) can restore the activity of circulating cells. Furthermore, estrogen accelerates the reendothelialization capacity of early outgrowth cells (EOCs). We hypothesized that overexpressing eNOS alone or in combination with estrogen stimulation in EOCs would potentiate the beneficial effects of these cells in regulating smooth muscle cell (SMC) function. Native human EOCs did not have any effect on human coronary artery SMC (hCASMC) proliferation or migration. Transfecting EOCs with a human eNOS plasmid and/or stimulating with 17β-estradiol (E₂) increased NO production 3-fold and enhanced EOC survival. Moreover, in co-culture studies, eNOS overexpressing or E2-stimulated EOCs reduced hCASMC migration (by 23% and 56% respectively), vs. control EOCs. These effects do not implicate ERK1/2 or focal adhesion kinases. Nevertheless, NOS-EOCs had no effect on hCASMC proliferation. These results suggest that overexpressing or activating eNOS in EOCs increases their survival and enhances their capacity to regulate SMC migration through paracrine effects. These data elucidate how eNOS overexpression or activation in EOCs can prevent vascular remodeling.

Circulating endothelial progenitor cells in pregnant women with premature rupture of membranes: potential association with placental disorders

The frequency of preterm labour has risen over the last few years. Plasma oestrogen concentrations differ between patients who deliver before term and those who deliver at term. Oestrogen can influence the kinetics of circulating endothelial progenitor cells (cEPCs). Here, we attempted to identify the potential association of cEPCs with the incidence of complications typical of prematurity. The study groups consisted of 60 pregnant women with premature rupture of membranes (PROM; less than 37 weeks) and 50 term pregnant women (more than 38 weeks). cEPCs were isolated from term pregnant women and pregnant women with PROM and then migratory, proliferative, tubulogenic and functional properties of these cells along with serum secretion of important EPC chemotactic cytokines were analysed. In addition, the effect of 17β-oestradiol on biological features of cEPCs harvested from pregnant women was investigated. Our results showed that an increased concentration of oestrogen in women with PROM was associated with increased numbers of cEPCs, with these cells having increased oestrogen receptor α expression together with augmented proliferative, migratory and colony-formation properties. 17β-oestradiol induced proliferation, migration and angiogenic secretory activity of cEPCs from pregnant women. Overall, circulation mobilisation of EPCs in pregnant women may be associated with placental disorders.

Irisin Increased the Number and Improved the Function of Endothelial Progenitor Cells in Diabetes Mellitus Mice

The dysfunction of endothelial progenitor cells (EPCs) was found to be associated with vascular complications in diabetes mellitus (DM) patients. Previous studies found that regular exercise could improve the function of EPCs in DM patients, but the underling mechanism was unclear. Irisin, a newly identified myokine, was induced by exercise and has been demonstrated to mediate some of the positive effects of exercise. In this study, we hypothesize that irisin may have direct effects on EPC function in DM mice. These data showed for the first time that irisin increased the number of EPCs in peripheral blood of DM mice and improved the function of EPCs derived from DM mice bone marrow. The mechanism for the effect of irisin is related to the PI3K/Akt/eNOS pathway. Furthermore, irisin was demonstrated to improve endothelial repair in DM mice that received EPC transplants after carotid artery injury. The results of this study indicate a novel effect of irisin in regulating the number and function of EPCs via the PI3K/Akt/eNOS pathway, suggesting a potential for the administration of exogenous irisin as a succedaneum to improve EPC function in diabetic patients who fail to achieve such improvements through regular exercise.

Sex Differences in Circulating Progenitor Cells

BACKGROUND

Lower levels of circulating progenitor cells (PCs) reflect impaired endogenous regenerative capacity and are associated with aging, vascular disease, and poor outcomes. Whether biologic sex and sex hormones influence PC numbers remains a subject of controversy. We sought to determine sex differences in circulating PCs in both healthy persons and patients with coronary artery disease, and to determine their association with sex hormone levels.

METHODS AND RESULTS

In 642 participants (mean age 48 years, 69% women, 23% black) free from cardiovascular disease, we measured circulating PC counts as CD45med+ mononuclear cells coexpressing CD34 and its subsets expressing CD133, chemokine (C-X-C motif) receptor 4, and vascular endothelial growth factor receptor 2 epitopes using flow cytometry. Testosterone and estradiol levels were measured. After adjustment for age, cardiovascular risk factors, and body mass, CD34+ (β=-23%, P<0.001), CD34+/CD133+ (β=-20%, P=0.001), CD34+/chemokine (C-X-C motif) receptor 4-positive (β=-24%, P<0.001), and CD34+/chemokine (C-X-C motif) receptor 4-positive/CD133+ (β=-21%, P=0.001) PC counts, but not vascular endothelial growth factor receptor 2-positive PC counts were lower in women compared with men. Estradiol levels positively correlated with hematopoietic, but not vascular endothelial growth factor receptor 2- positive PC counts in women (P<0.05). Testosterone levels and PC counts were not correlated in men. These findings were replicated in an independent cohort with prevalent coronary artery disease.

CONCLUSIONS

Women have lower circulating hematopoietic PC levels compared with men. Estrogen levels are modestly associated with PC levels in women. Since PCs are reflective of endogenous regenerative capacity, these findings may at least partly explain the rise in adverse cardiovascular events in women with aging and menopause.

The Role of Endothelial Progenitor Cells in Ischemic Cerebral and Heart Diseases

Ischemic heart and cerebral diseases are complex clinical syndromes. Endothelial dysfunction caused by dysfunctional endothelial progenitor cells (EPCs) is thought to play a major role in pathophysiology of both types of disease. Healthy EPCs may be able to replace the dysfunctional endothelium through endogenous repair mechanisms. EPC levels are changed in patients with ischemic cerebrovascular and cardiovascular disease and EPCs may play a role in the pathophysiology of these diseases. EPCs are also a marker for preventive and therapeutic interventions. Homing of EPCs to ischemic sites is a mechanism of ischemic tissue repair, and molecules such as stromal-derived factor-1 and integrin may play a role in EPC homing in ischemic disease. Potentiation of the function and numbers of EPCs as well as combining EPCs with other pharmaceutical agents may improve the condition of ischemia patients. However, the precise role of EPCs in ischemic heart and cerebral disease and their therapeutic potential still remain to be explored. Here, we discuss the identification, mobilization, and clinical implications of EPCs in ischemic diseases.

Urea-induced ROS accelerate senescence in endothelial progenitor cells

BACKGROUND AND AIMS

The pathogenic events responsible for the reduction of endothelial progenitor cell (EPC) number and function seen in patients with chronic renal failure (CRF) are poorly understood. Here we investigate the hypothesis that increased concentrations of urea associated with CRF increase ROS production directly in EPCs, causing abnormalities associated with coronary artery disease risk.

METHODS

Human EPCs were isolated from peripheral blood mononuclear cells of healthy donors and cultured in the presence or absence of 20 mmol/L urea.

RESULTS

Urea at concentrations seen in CRF induced ROS production in cultured EPCs. Urea-induced ROS reduced the number of endothelial cell colony forming units, uptake and binding of Dil-Ac-LDL and lectin-1, and the ability to differentiate into CD31- and vascular endothelial growth factor receptor 2-positive cells. Moreover, urea-induced ROS generation accelerated the onset of EPC senescence, leading to a senescence-associated secretory phenotype (SASP). Normalization of mitochondrial ROS production prevented each of these effects of urea.

CONCLUSIONS

These data suggest that urea itself causes both reduced EPC number and increased EPC dysfunction, thereby contributing to the pathogenesis of cardiovascular disease in CRF patients.

Progenitor Cells for Arterial Repair: Incremental Advancements towards Therapeutic Reality

Coronary revascularization remains the standard treatment for obstructive coronary artery disease and can be accomplished by either percutaneous coronary intervention (PCI) or coronary artery bypass graft surgery. Considerable advances have rendered PCI the most common form of revascularization and improved clinical outcomes. However, numerous challenges to modern PCI remain, namely, in-stent restenosis and stent thrombosis, underscoring the importance of understanding the vessel wall response to injury to identify targets for intervention. Among recent promising discoveries, endothelial progenitor cells (EPCs) have garnered considerable interest given an increasing appreciation of their role in vascular homeostasis and their ability to promote vascular repair after stent placement. Circulating EPC numbers have been inversely correlated with cardiovascular risk, while administration of EPCs in humans has demonstrated improved clinical outcomes. Despite these encouraging results, however, advancing EPCs as a therapeutic modality has been hampered by a fundamental roadblock: what constitutes an EPC? We review current definitions and sources of EPCs as well as the proposed mechanisms of EPC-mediated vascular repair. Additionally, we discuss the current state of EPCs as therapeutic agents, focusing on endogenous augmentation and transplantation.

Low concentration of ethanol favors progenitor cell differentiation and neovascularization in high-fat diet-fed mice model

Endothelial progenitor cells (EPCs) and monocytic cells from bone marrow (BM) can be recruited to the injured endothelium and contribute to its regeneration. During metabolic diseases such as obesity and diabetes, progenitor cell function is impaired. Several studies have shown that moderate alcohol consumption prevents the development and progression of atherosclerosis in a variety of animal/mouse models and increases mobilization of progenitor cells. Along with these studies, we identify ethanol at low concentration as therapeutic tool to in vitro expand progenitor cells in order to obtain an adequate number of cells for their use in the treatment of cardiovascular diseases. We evaluated the effects of ethanol on the phenotype of BM-derived cells from mice fed with high-fat diet (HFD). HFD did not induce changes in weight of mice but induced metabolic alterations. HFD feeding increased the differentiation of monocytic progenitors but not EPCs. Whereas ethanol at 0.6% is able to increase monocytic progenitor differentiation, 1% ethanol diminished it. Furthermore, ethanol at 0.6% increased the ability of progenitor cells to promote in vivo angiogenesis as well as secretome of BM-derived cells from mice fed with HFD, but not in mice fed normal diet. In conclusion, ethanol at low concentration is able to increase angiogenic abilities of progenitor cells from animals with early metabolic alterations.

Estrogen Stimulates Homing of Endothelial Progenitor Cells to Endometriotic Lesions

The incorporation of endothelial progenitor cells (EPCs) into microvessels contributes to the vascularization of endometriotic lesions. Herein, we analyzed whether this vasculogenic process is regulated by estrogen. Estrogen- and vehicle-treated human EPCs were analyzed for migration and tube formation. Endometriotic lesions were induced in irradiated FVB/N mice, which were reconstituted with bone marrow from FVB/N-TgN (Tie2/green fluorescent protein) 287 Sato mice. The animals were treated with 100 μg/kg β-estradiol 17-valerate or vehicle (control) over 7 and 28 days. Lesion growth, cyst formation, homing of green fluorescent protein(+)/Tie2(+) EPCs, vascularization, cell proliferation, and apoptosis were analyzed by high-resolution ultrasonography, caliper measurements, histology, and immunohistochemistry. Numbers of blood circulating EPCs were assessed by flow cytometry. In vitro, estrogen-treated EPCs exhibited a higher migratory and tube-forming capacity when compared with controls. In vivo, numbers of circulating EPCs were not affected by estrogen. However, estrogen significantly increased the number of EPCs incorporated into the lesions' microvasculature, resulting in an improved early vascularization. Estrogen further stimulated the growth of lesions, which exhibited massively dilated glands with a flattened layer of stroma. This was mainly because of an increased glandular secretory activity, whereas cell proliferation and apoptosis were not markedly affected. These findings indicate that vasculogenesis in endometriotic lesions is dependent on estrogen, which adds a novel hormonally regulated mechanism to the complex pathophysiology of endometriosis.

Low-dose estradiol and endothelial and inflammatory biomarkers in menopausal overweight/obese women

OBJECTIVE

We aimed to investigate the effects of low-dose transdermal estrogen on endothelial and inflammatory biomarkers in menopausal overweight/obese women.

METHODS

We recruited 44 menopausal women (47-55 years; body mass index 27.5-34.9 kg/m(2)) and divided them into estradiol (1 mg/day; n = 22) or placebo groups (n = 22). They were double-blinded, followed and treated for 3 months. At baseline and post-intervention, inflammatory biomarkers (hs-CRP, IL-1β, IL-6, MCP-1 and TNF-α) and of vascular injury (activated circulating endothelial cells, CEC-a) and repair (endothelial progenitor cells, EPC) were quantified. Resting CECs (CEC-r) were also assessed. Microvascular reactivity and vasomotion were analyzed by laser-Doppler flowmetry.

RESULTS

Volunteers (51.8 ± 2.3 years; mean body mass index 31.5 ± 2.5 kg/m(2)) had been menopausal for 3 (range 2-5) years. After treatment, no changes were observed in the placebo group, while levels of CEC-r and EPC increased in the estradiol group. In this group, no changes in inflammatory biomarkers were observed but it required a lower cumulative dose of acetylcholine to achieve peak velocity during endothelial-dependent vasodilatation and there was increased endothelial-independent vasodilatation.

CONCLUSIONS

The short-term use of low-dose transdermal estradiol therapy in overweight/obese menopausal women increased markers of vascular repair and improved microvascular reactivity without changing the inflammatory biomarkers.

CLINICAL TRIAL REGISTRATION

NCT01295892 at www.clinicaltrials.gov .

Sexual dimorphism in cancer

The incidence of many types of cancer arising in organs with non-reproductive functions is significantly higher in male populations than in female populations, with associated differences in survival. Occupational and/or behavioural factors are well-known underlying determinants. However, cellular and molecular differences between the two sexes are also likely to be important. In this Opinion article, we focus on the complex interplay that sex hormones and sex chromosomes can have in intrinsic control of cancer-initiating cell populations, the tumour microenvironment and systemic determinants of cancer development, such as the immune system and metabolism. A better appreciation of these differences between the two sexes could be of substantial value for cancer prevention as well as treatment.

Ambient particulate matter exposure and cardiovascular diseases: a focus on progenitor and stem cells

Air pollution is a major challenge to public health. Ambient fine particulate matter (PM) is the key component for air pollution, and associated with significant mortality. The majority of the mortality following PM exposure is related to cardiovascular diseases. However, the mechanisms for the adverse effects of PM exposure on cardiovascular system remain largely unknown and under active investigation. Endothelial dysfunction or injury is considered one of the major factors that contribute to the development of cardiovascular diseases such as atherosclerosis and coronary heart disease. Endothelial progenitor cells (EPCs) play a critical role in maintaining the structural and functional integrity of vasculature. Particulate matter exposure significantly suppressed the number and function of EPCs in animals and humans. However, the mechanisms for the detrimental effects of PM on EPCs remain to be fully defined. One of the important mechanisms might be related to increased level of reactive oxygen species (ROS) and inflammation. Bone marrow (BM) is a major source of EPCs. Thus, the number and function of EPCs could be intimately associated with the population and functional status of stem cells (SCs) in the BM. Bone marrow stem cells and other SCs have the potential for cardiovascular regeneration and repair. The present review is focused on summarizing the detrimental effects of PM exposure on EPCs and SCs, and potential mechanisms including ROS formation as well as clinical implications.

Sleep-disordered breathing is associated with depletion of circulating endothelial progenitor cells and elevation in pulmonary arterial pressure in patients with decompensated systolic heart failure

Background

Sleep-disordered breathing (SDB) is known to occur frequently in and may predict worsening progression of patients with congestive heart failure (CHF). SDB is also known to play an important role in the development of idiopathic pulmonary arterial hypertension (PAH) via inducing endothelial dysfunction and vascular remodeling, a pathological process that can be significantly influenced by factors such as osteoprotegerin (OPG) and endothelial progenitor cells (EPCs). The objective of this study is to determine if CHF with SDB is associated with changes in OPG, EPCs, and PAH.

Methods

EPCs were isolated, cultured, and quantified from CHF patients with SDB (n = 52), or without SDB (n = 68). OPG and N-terminal pro-brain natriuretic peptide (NT-proBNP) from each group was analyzed and correlated with EPCs and the mean pulmonary artery pressure (mPAP) measured by right heart catheterization.

Results

A significant decrease in circulating EPCs (29.30 ± 9.01 vs. 45.17 ± 10.51 EPCs/× 200 field; P < 0.05) was found in CHF patients with SDB compared to those without SDB. Both OPG (789.83 ± 89.38 vs. 551.29 ± 42.12 pg/mL; P < 0.05) and NT-proBNP (5946.50 ± 1434.50 vs. 3028.60 ± 811.90 ng/mL; P < 0.05) were also significantly elevated in SDB CHF patients who also had significantly elevated mPAP (50.2 ± 9.5 vs. 36.4 ± 4.1 mm Hg; P < 0.05). EPC numbers correlated inversely with the episodes of apnea and hypopnea per hour (RDI, r = –0.45, P = 0.037) and blood level of OPG (r = –0.53, P = 0.011). Although NT-proBNP was also increased significantly in patients with SDB, it had no correlation with either EPCs or RDI.

Conclusions

SDB due to hypoxemia from decompensated CHF is associated with (1) OPG elevation, (2) EPC depletion, and (3) mPAP elevation. The inverse relationship of circulating OPG with EPCs suggests a likely mechanism for hypoxemia and OPG in the development of pulmonary vascular dysfunction via depleting EPCs, thus worsening prognosis of CHF.

Progress and prospects of endothelial progenitor cell therapy in coronary stent implantation

Drug-eluting stents (DES) have been widely used to treat coronary artery disease (CAD) since their clinical use has significantly reduced the occurrence of in-stent restenosis (ISR) as compared with the initially applied bare-metal stents (BMS). However, analyses of long-term clinical outcome have raised concerns about the serious safety problem of DES, such as ISR caused by late or very late thrombosis. Various studies showed that those complications were associated with vascular endothelial injury/dysfunction or endothelialization delaying. Recently, through biological characterization of endothelial progenitor cells (EPCs), mechanistic understanding of rapid re-endothelialization of the vascular injury sites after coronary stenting has become possible and is a new research hotspot in the prevention of ISR and late/very late stent thrombosis. It has been well recognized that the formation of a functional endothelial layer from EPCs requires a coordinated sequence of multistep and signaling events, which includes cell mobilization, adhesion, migration and finally the differentiation to vascular endothelial cells (VECs). In this review, we summarize and discuss the currently relevant information about EPCs, the mechanism of DES interfering with the natural vascular healing process in preventing or delaying the formation of a functional endothelial layer, and EPCs-mediated acceleration of re-endothelialization at vascular injury sites. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1237-1247, 2016.

NF-κB increased expression of 17β-hydroxysteroid dehydrogenase 4 promotes HepG2 proliferation via inactivating estradiol

Hepatocellular carcinoma (HCC) arises in a setting of chronic inflammation induced by inflammatory cytokines, such as nuclear factor-kappaB (NF-κB). HCC is a male-predominant cancer that can be attenuated by estradiol (E2) in vitro and in vivo. Although 17β-hydroxysteroid dehydrogenase 4 (HSD17B4) has been implicated as an estradiol-inactivating enzyme, and its promoter sequence contains two putative NF-κB elements: it is currently unknown whether HSD17B4 is the link between inflammation, estradiol and proliferation in hepatoma cells. In this study, HepG2 cells were used to investigate the role of HSD17B4 in the proliferation of liver cancer cells treated with the NF-κB activator, tumor necrosis factor-alpha (TNF-α), with the inhibitor of NF-κB activation, pyrrolidinedithiocarbamate (PDTC), or with a related specific siRNA. We demonstrated that the human HSD17B4 gene is a target for NF-κB activation in inflammation-stimulated HepG2 cells. HSD17B4 is up-regulated via the binding of activated NF-κB to the distal NF-κB-responsive element via TNF-α stimulation, which then promotes cell proliferation by decreasing the levels of E2 and enhancing the expression of interleukin 6 (IL-6), cyclin D1 and proliferating cell nuclear antigen (PCAN). These results from HepG2 cells are consistent with the observation that HSD17B4 is highly expressed and activated NF-κB is highly co-localized with the NF-κB-responsive element of HSD17B4 in liver tumor tissues from HCC patients. Our findings indicate for the first time that HSD17B4 plays an important role in aggravated HCC progression and provides a novel therapeutic target for HCC.

Ambient Fine Particulate Matter Suppresses In Vivo Proliferation of Bone Marrow Stem Cells through Reactive Oxygen Species Formation

AIMS

Some environmental insults, such as fine particulate matter (PM) exposure, significantly impair the function of stem cells. However, it is unknown if PM exposure could affect the population of bone marrow stem cells (BMSCs). The present study was to investigate the effects of PM on BMSCs population and related mechanism(s).

MAIN METHEODS

PM was intranasally distilled into male C57BL/6 mice for one month. Flow cytometry with antibodies for BMSCs, Annexin V and BrdU ware used to determine the number of BMSCs and the levels of their apoptosis and proliferation in vivo. Phosphorylated Akt (P-Akt) level was determined in the BM cells with western blotting. Intracellular reactive oxygen species (ROS) formation was quantified using flow cytometry analysis. To determine the role of PM-induced ROS in BMSCs population, proliferation, and apotosis, experiments were repeated using N-acetylcysteine (NAC)-treated wild type mice or a triple transgenic mouse line with overexpression of antioxidant network (AON) composed of superoxide dismutase (SOD)1, SOD3, and glutathione peroxidase-1 with decreased in vivo ROS production.

KEY FINDINGS

PM treatment significantly reduced BMSCs population in association with increased ROS formation, decreased P-Akt level, and inhibition of proliferation of BMSCs without induction of apoptosis. NAC treatment or AON overexpression with reduced ROS formation effectively prevented PM-induced reduction of BMSCs population and proliferation with partial recovery of P-Akt level.

SIGNIFICANCE

PM exposure significantly decreased the population of BMSCs due to diminished proliferation via ROS-mediated mechanism (could be partially via inhibition of Akt signaling).

Diabetes, Endothelial Dysfunction, and Vascular Repair: What Should a Diabetologist Keep His Eye on?

Cardiovascular complications are the most common complications of diabetes mellitus. A prominent attribute of diabetic cardiovascular complications is accelerated atherosclerosis, considered as a still incurable disease, at least at more advanced stages. The discovery of endothelial progenitor cells (EPCs), able to replace old and injured mature endothelial cells and capable of differentiating into healthy and functional endothelial cells, has offered the prospect of merging the traditional theories on the pathogenesis of atherosclerosis with evolving concepts of vascular biology. The literature supports the notion that EPC alterations are involved in the pathogenesis of vascular diseases in diabetics, but at present many questions remain unanswered. In this review the aspects linking endothelial progenitor cells to the altered vascular biology in diabetes mellitus are discussed.

Cardiovascular risk factors have larger impact on endothelial function in self-reported healthy women than men in the HUNT3 Fitness study

Background

Several studies suggest that cardiovascular risk factors comprising the metabolic syndrome have larger effects on the development of cardiovascular disease in women than in men. A recent study in self-reported healthy subjects demonstrated a marked gender difference in endothelial dysfunction that may be an important precursor of manifest cardiovascular disease. The aim of the present study was to determine whether the association between endothelial function and cardiovascular risk factors is different in self-reported healthy women compared to self-reported healthy men.

Methods and Results

Associations between endothelial function (flow mediated dilation, FMD, of the brachial artery measured by ultrasound), anthropometric variables, peak oxygen uptake (VO_2peak), blood pressure, serum lipids, blood glucose and a questionnaire on general health and lifestyle including smoking status were studied by logistic and linear regression in 2 528 women and 2 211 men aged 20–89 years, free from self-reported cardiovascular disease. In women with hyperglycemia, endothelial dysfunction (FMD ≤0%) occurred twice as frequently as in male counterparts. The presence of the metabolic syndrome, high blood pressure and low VO_2peak increased the prevalence of endothelial dysfunction more in women than in men.

Conclusion

Endothelial dysfunction is more strongly associated with cardiovascular risk factors in self-reported healthy women than in self-reported healthy men. This finding could explain why the metabolic syndrome, and especially hyperglycemia, is associated with higher cardiovascular risk and a worse prognosis in women.