Development, Cell Differentiation, Angiogenesis—Microparticles and Their Roles in Angiogenesis

Peto's "Paradox" and Six Degrees of Cancer Prevalence

Peto's paradox and the epidemiologic observation of the average six degrees of tumor prevalence are studied and hypothetically solved. A simple consideration, Petho's paradox challenges our intuitive understanding of cancer risk and prevalence. Our simple consideration is that the more a cell divides, the higher the chance of acquiring cancerous mutations, and so the larger or longer-lived organisms have more cells and undergo more cell divisions over their lifetime, expecting to have a higher risk of developing cancer. Paradoxically, it is not supported by the observations. The allometric scaling of species could answer the Peto paradox. Another paradoxical human epidemiology observation in six average mutations is necessary for cancer prevalence, despite the random expectations of the tumor causes. To solve this challenge, game theory could be applied. The inherited and random DNA mutations in the replication process nonlinearly drive cancer development. The statistical variance concept does not reasonably describe tumor development. Instead, the Darwinian natural selection principle is applied. The mutations in the healthy organism's cellular population can serve the species' evolutionary adaptation by the selective pressure of the circumstances. Still, some cells collect multiple uncorrected mutations, adapt to the extreme stress in the stromal environment, and develop subclinical phases of cancer in the individual. This process needs extensive subsequent DNA replications to heritage and collect additional mutations, which are only marginal alone. Still, together, they are preparing for the first stage of the precancerous condition. In the second stage, when one of the caretaker genes is accidentally mutated, the caused genetic instability prepares the cell to fight for its survival and avoid apoptosis. This can be described as a competitive game. In the third stage, the precancerous cell develops uncontrolled proliferation with the damaged gatekeeper gene and forces the new game strategy with binary cooperation with stromal cells for alimentation. In the fourth stage, the starving conditions cause a game change again, starting a cooperative game, where the malignant cells cooperate and force the cooperation of the stromal host, too. In the fifth stage, the resetting of homeostasis finishes the subclinical stage, and in the fifth stage, the clinical phase starts. The prevention of the development of mutated cells is more complex than averting exposure to mutagens from the environment throughout the organism's lifetime. Mutagenic exposure can increase the otherwise random imperfect DNA reproduction, increasing the likelihood of cancer development, but mutations exist. Toxic exposure is more challenging; it may select the tolerant cells on this particular toxic stress, so these mutations have more facility to avoid apoptosis in otherwise collected random mutational states.

Persistent circulating platelet and endothelial derived microparticle signature may explain on-going pro-thrombogenicity after acute coronary syndrome

AIMS

Microparticles (MPs) are submicron vesicles, released from activated, and apoptotic cells. MPs are elevated in the circulation of patients with coronary artery disease (CAD) and have pro-thrombotic potential. However, limited data exists on MP signature over time following an acute coronary event.

METHODS & RESULTS

Circulating total annexin v + (Anv+) MPs of endothelial (EMP), platelet (PMP), monocyte (MMP), neutrophil (NMP) and smooth muscle cell (SMMP) origin were quantified by flow cytometry. 13 patients with acute coronary syndrome (ACS) were prospectively enrolled and 12 patients with stable angina (SA) were included as a comparator group. A panel of MP was measured at baseline, after percutaneous coronary intervention (PCI) and at days 1, 7, 30 and 6 months. Intra & inter group comparison was made between various time points. MP mediated thrombin generation was measured by recording lag phase, velocity index, peak thrombin and endogenous thrombin potential at these time points and compared with healthy controls. The total AnV+ MP levels were similar in ACS and SA groups at baseline, peaked immediately after PCI and were at their lowest on day 1. PMP & EMP levels remained significantly elevated in ACS patients at 6 months when compared to SA. No such difference was noted with NMP, MMP and SMMP. Patients with coronary artery disease showed abnormal thrombograms when compared to controls. Peak thrombin (nano moles) was significantly higher in CAD when compared to controls (254 IQR [226, 239] in ACS, 255 IQR [219, 328] in SA and 132 IQR [57, 252] in controls; p = 0.006). Differences in thrombin generation between ACS and SA were not significant (p = 1). Furthermore, thrombin parameters remained abnormal in ACS & SA patients at 6 months.

CONCLUSIONS

Total MP and individual MP phenotypes were significantly elevated after PCI reflecting endothelial injury. Elevated PMP and EMP levels at 6 months in ACS patients is suggestive of on-going inflammation, endothelial injury and may explain on-going pro-thrombogenicity seen up to 6 months after ACS despite dual antiplatelet therapy.

Microparticles in the pathogenesis of TB: Novel perspectives for diagnostic and therapy management of Mycobacterium tuberculosis infection

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis, usually chronic and has a progressive clinical course. Despite the availability of effective chemotherapy, TB is a leading killer of young adults worldwide and the global multi-drug resistant TB is reaching epidemic proportions. Interrupt transmission through early detection and treatment of the patients is a main element of the drug-resistant TB control strategy. However, many drugable targets in pathogens are already inhibited by current antibiotics and there is not a biomarker that indicate normal or pathogenic biological processes, or pharmacological responses to therapeutic intervention. Studies directed at evaluate key elements of host response to infection may identify biomarkers with measurable characteristics that indicate pathogenic biological processes. Cell-derived microparticles (MPs) are membrane-coated vesicles that represent subcellular elements and have been identified increasingly in a broad range of diseases and emerging as potential novel biomarker to pathological processes. In addition, MPs carry contents from their cells of origin as bioactive molecules as cytokines, enzymes, surface receptors, antigens and genetic information and may provide a means of communication between cells. Molecules-loaded MPs may interplay with the immune system and therefore can acts on inflammation, cell activation and migration. Therefore, MPs may be an important factor to immune process during Mtb infection, especially in pulmonary granulomas and influence the outcome of infection. Their characterization may facilitate an appropriate diagnosis, optimize pharmacological strategies and might be further explored as potential targets for future clinical interventions.

The Extraordinary Role of Extracellular RNA in Arteriogenesis, the Growth of Collateral Arteries

Arteriogenesis is an intricate process in which increased shear stress in pre-existing arteriolar collaterals induces blood vessel expansion, mediated via endothelial cell activation, leukocyte recruitment and subsequent endothelial and smooth muscle cell proliferation. Extracellular RNA (eRNA), released from stressed cells or damaged tissue under pathological conditions, has recently been discovered to be liberated from endothelial cells in response to increased shear stress and to promote collateral growth. Until now, eRNA has been shown to enhance coagulation and inflammation by inducing cytokine release, leukocyte recruitment, and endothelial permeability, the latter being mediated by vascular endothelial growth factor (VEGF) signaling. In the context of arteriogenesis, however, eRNA has emerged as a transmitter of shear stress into endothelial activation, mediating the sterile inflammatory process essential for collateral remodeling, whereby the stimulatory effects of eRNA on the VEGF signaling axis seem to be pivotal. In addition, eRNA might influence subsequent steps of the arteriogenesis cascade as well. This article provides a comprehensive overview of the beneficial effects of eRNA during arteriogenesis, laying the foundation for further exploration of the connection between the damaging and non-damaging effects of eRNA in the context of cardiovascular occlusive diseases and of sterile inflammation.

Procoagulant tumor microvesicles attach to endothelial cells on biochips under microfluidic flow

Tumor patients are at a high risk of venous thromboembolism (VTE), and the mechanism by which this occurs may involve tumor-derived microvesicles (MVs). Previously, it has been shown that tumor MVs become attached to endothelial cells in static conditions. To investigate whether this process occurs under physiologically relevant flow rates, tumor MVs were perfused across a microfluidic device coated with growing human umbilical vein endothelial cells (HUVECs). Cell lines were screened for their ability to form tumor spheroids, and two cell lines, ES-2 and U87, were selected; spheroids formed were transferred to a microfluidic chip, and a second endothelial cell biochip was coated with HUVECs and the two chips were linked. Media flowed through the spheroid chip to the endothelial chip, and procoagulant activity (PCA) of the tumor media was determined by a one-stage prothrombin time assay. Tumor MVs were also quantified by flow cytometry before and after interaction with HUVECs. Confocal images showed that HUVECs acquired fluorescence from MV attachment. Labeled MVs were proportionally lost from MV rich media with time when flowed over HUVECs and were not observed on a control chip. The loss of MV was accompanied by a proportional reduction in PCA. Flow cytometry, confocal microscopy, and live flow imagery captured under pulsatile flow confirmed an association between tumor MVs and HUVECs. Tumor MVs attached to endothelial cells under physiological flow rates, which may be relevant to the VTE pathways in cancer patients.

Microparticles and cardiovascular diseases

Microparticles are a distinctive group of small vesicles, without nucleus, which are involved as significant modulators in several physiological and pathophysiological mechanisms. Plasma microparticles from various cellular lines have been subject of research. Data suggest that they are key players in development and manifestation of cardiovascular diseases and their presence, in high levels, is associated with chronic inflammation, endothelial damage and thrombosis. The strong correlation of microparticle levels with several outcomes in cardiovascular diseases has led to their utilization as biomarkers. Despite the limited clinical application at present, their significance emerges, mainly because their detection and enumeration methods are improving. This review article summarizes the evidence derived from research, related with the genesis and the function of microparticles in the presence of various cardiovascular risk factors and conditions. The current data provide a substrate for several theories of how microparticles influence various cellular mechanisms by transferring biological information.

Micropassage-embedding composite hydrogel fibers enable quantitative evaluation of cancer cell invasion under 3D coculture conditions

Cell migration and invasion are of significant importance in physiological phenomena, including wound healing and cancer metastasis. Here we propose a new system for quantitatively evaluating cancer cell invasion in a three-dimensional (3D), in vivo tissue-like environment. This system uses composite hydrogel microfibers whose cross section has a relatively soft micropassage region and that were prepared using a multilayered microfluidic device; cancer cells are encapsulated in the core and fibroblasts are seeded in the shell regions surrounding the core. Cancer cell proliferation is guided through the micropassage because of the physical restriction imposed by the surrounding solid shell regions. Quantitative analysis of cancer cell invasion is possible simply by counting the cancer cell colonies that form outside the fiber. This platform enables the evaluation of anticancer drug efficacy (cisplatin, paclitaxel, and 5-fluorouracil) based on the degree of invasion and the gene expression of cancer cells (A549 cells) with or without the presence of fibroblasts (NIH-3T3 cells). The presented hydrogel fiber-based migration assays could be useful for studying cell behaviors under 3D coculture conditions and for drug screening and evaluation.

Circulating and platelet-derived microparticles in human blood enhance thrombosis on atherosclerotic plaques

Plaque rupture followed by thrombosis is the underlying cause of the majority of acute coronary syndromes. Circulating microparticles (cMPs), membrane blebs released into blood by activated cells, have been associated to vascular diseases. Specifically, high levels of platelet-derived microparticles (pMPs) have been found in patients with coronary disease. However, it is unknown whether microparticles have a contributing role to the development of damaged vessel wall-induced arterial thrombi. The aim of this proof of concept study was to investigate whether an increased number of cMPs and pMPs could functionally contribute to blood thrombogenicity on areas of arterial damage. Microparticles were isolated from blood of healthy volunteers and were characterised by flow cytometry. Effects of microparticles on platelet deposition were assessed under controlled flow conditions exposing damaged arterial wall in the Badimon perfusion chamber and collagen type-I in the flat perfusion chamber to human blood. Platelet deposition on damaged arteries was significantly increased in cMP- and pMP-enriched bloods (p<0.05). pMPs also induced increase in platelet (p<0.05) and fibrin (p<0.05) deposition on human atherosclerotic arteries and in platelet adhesion to purified collagen surfaces. pMP-enriched blood induced a dose-dependent shortening of epinephrine/collagen closure time evaluated by PFA-100 (p<0.001), increased lowdose ADP-induced platelet aggregation by LTA (p<0.05), and decreased clotting time by thromboelastography (p<0.01). In conclusion, an increased content of cMPs and pMPs, even in normal blood conditions, enhance platelet deposition and thrombus formation. This study shows for the first time that, beyond biomarkers of cell activation, blood microparticles have functional effects on cardiovascular atherothrombotic disease.

Cancer Patient-Derived Circulating Microparticles Enhance Lung Metastasis in a Rat Model: Dual-Source CT, Cellular, and Molecular Studies

PURPOSE

This study aimed to test the hypothesis that lung cancer patient-derived circulating microparticles (LCC-MPs) enhance metastatic lung tumors in a rat model.

PROCEDURES

The controls (n = 6) and LCC-MP-treated rats (n = 6) with N1S1-induced pulmonary metastatic hepatocellular carcinoma (HCC) underwent dual-source CT (DSCT) on days 10, 15, and 20. Cellular and molecular studies were performed subsequently.

RESULTS

DSCT revealed slow progression of metastatic lung tumors in the controls. Compared with the controls, the LCC-MP-treated rats exhibited significantly more and larger metastatic tumors on days 15 and 20 on DSCT, enhanced angiogenesis with higher microvessel count (CD34+), more CXCR4+ and VEGF+ cells in immunohistofluorescence studies, and higher protein expression levels of eNOS, angiopoietin, vascular endothelial growth factor, and CD31 on western blotting (Mann-Whitney test, all P < 0.05).

CONCLUSIONS

LCC-MPs can elicit oncogenic stimulation and accelerate metastatic HCC growth in rat lung as demonstrated on DSCT and enhanced tumoral angiogenesis as confirmed in cellular and molecular studies.

Influence of sex on the number of circulating endothelial microparticles and microRNA expression in middle-aged adults

NEW FINDINGS

What is the central question of this study? Are there sex-related differences in the number of circulating endothelial microparticles (EMPs) and microparticle microRNA expression in middle-aged adult humans? What is the main finding and its importance? Although the numbers of circulating endothelial microparticles do not differ between middle-aged men and women, there are sex-related differences in the expression of miR-125a in activation-derived EMPs and miR-34a in apoptosis-derived EMPs. Differences in circulating endothelial microparticle microRNA content may provide new insight into the sex-related disparity in the risk and prevalence of vascular disease in middle-aged adults. The aims of this study were to determine: (i) whether circulating concentrations of endothelial microparticles (EMPs) differ in middle-aged men compared with women; and (ii) whether there are sex-related differences in microRNA expression in EMPs. Peripheral blood was collected from 30 sedentary adults: 15 men (56 ± 6 years old) and 15 women (56 ± 5 years old). Endothelial microparticles were defined by markers of activation (CD62e⁺ ) or apoptosis (CD31⁺ /CD42b^- ) by flow cytometry. Expression of microRNA (miR-34a, 92a, 125a and 126) in activation- and apoptosis-derived EMPs was measured by RT-PCR. Circulating activation- (33 ± 31 versus 39 ± 35 microparticles μl^-1 ) and apoptosis-derived EMPs (49 ± 54 versus 42 ± 43 microparticles μl^-1 ) were not significantly different between men and women. Expression of miR-125a (2.23 ± 2.01 versus 6.95 ± 3.99 a.u.) was lower (∼215%; P < 0.05) in activation-derived EMPs, whereas expression of miR-34a (1.17 ± 1.43 versus 0.38 ± 0.35 a.u.) was higher (∼210%; P < 0.05) in apoptosis-derived EMPs from men compared with women. Expression of microRNA in circulating EMPs may provide new insight into sex-related differences in cardiovascular disease.

A direct-imaging cryo-EM study of shedding extracellular vesicles from leukemic monocytes

The human leukemia monocytic cell line (THP-1) is known to shed extracellular vesicles (EVs) under various stimulations. We studied the effects of two types of common stimulation types, lipopolysaccharide (LPS) and starvation conditions by high resolution cryogenic electron microscopy, namely, cryo-SEM and cryo-TEM. Cryo-SEM data of cells undergoing EV blebbing and shedding is presented here for the first time. The high-resolution images show good agreement with models describing the membrane processes of shedding. Cells that underwent a 48-h starvation treatment exhibited differing morphological features, including shrunken nucleus and elongated membrane protrusions. LPS treated cells, however, showed extensive blebbing originating from the cell membrane, in good agreement with the sizes of EVs imaged by cryo-TEM. EVs isolated from both types of stimulations were measured by nanoparticle tracking analysis (NanoSight), by which LPS-EVs samples exhibited higher concentration and smaller mean diameter, as compared to starvation-EVs. Our results suggest a difference in the effects of the two stimulation types on the shedding process and possibly on the type of EVs shed. Our unique methodologies provide an important and innovative outlook of the shedding process and on its products, paving the way to further discoveries in this developing field of research, in which much is still unknown.

Microvesicles in Autoimmune Diseases

During apoptosis or activation, cells can release a subcellular structure, called a membrane microvesicle (also known as microparticle) into the extracellular environment. Microvesicles bud-off as a portion of cell membrane with its associated proteins and lipids surrounding a cytosolic core that contains intracellular proteins, lipids, and nucleic acids (DNA, RNA, siRNA, microRNA, lncRNA). Biologically active molecules on the microvesicle surface and encapsulated within can act on recipient cells as a novel mode of intercellular communication. Apoptosis has long been known to be involved in the development of diseases of autoimmunity. Abnormally persistent microvesicles, particularly apoptotic microvesicles, can accelerate autoimmune responses locally in specific organs and tissues as well as systemically. In this review, we focus on studies implicating microvesicles in the pathogenesis of autoimmune diseases and their complications.

Inflammation-induced endothelial cell-derived extracellular vesicles modulate the cellular status of pericytes

Emerging lines of evidence have shown that extracellular vesicles (EVs) mediate cell-to-cell communication by exporting encapsulated materials, such as microRNAs (miRNAs), to target cells. Endothelial cell-derived EVs (E-EVs) are upregulated in circulating blood in different pathological conditions; however, the characteristics and the role of these E-EVs are not yet well understood. In vitro studies were conducted to determine the role of inflammation-induced E-EVs in the cell-to-cell communication between vascular endothelial cells and pericytes/vSMCs. Stimulation with inflammatory cytokines and endotoxin immediately induced release of shedding type E-EVs from the vascular endothelial cells, and flow cytometry showed that the induction was dose dependent. MiRNA array analyses revealed that group of miRNAs were specifically increased in the inflammation-induced E-EVs. E-EVs added to the culture media of cerebrovascular pericytes were incorporated into the cells. The E-EV-supplemented cells showed highly induced mRNA and protein expression of VEGF-B, which was assumed to be a downstream target of the miRNA that was increased within the E-EVs after inflammatory stimulation. The results suggest that E-EVs mediate inflammation-induced endothelial cell-pericyte/vSMC communication, and the miRNAs encapsulated within the E-EVs may play a role in regulating target cell function. E-EVs may be new therapeutic targets for the treatment of inflammatory diseases.

Assays to examine endothelial cell migration, tube formation, and gene expression profiles

Common methods for studying angiogenesis in vitro include the tube formation assay, the migration assay, and the study of the endothelial genome. The formation of capillary-like tubes in vitro on basement membrane matrix mimics many steps of the angiogenesis process in vivo and is used widely as a screening test for angiogenic or antiangiogenic factors. Other assays related to the study of angiogenesis include the cell migration assay, the study of gene expression changes during the process of angiogenesis, and the study of endothelial-derived microparticles. Protocols for these procedures will be described here.

Microparticles and microRNAs: new players in the complex field of coagulation

Atherosclerosis is a complex process that begins with endothelial dysfunction, and continues with several inflammatory processes leading, eventually, to plaque rupture and formation of arterial thrombus. Increased platelet reactivity and classical coagulation pathways are not the only players of the whole thrombotic process: microparticles (MPs), irregularly shaped small vesicles released from the plasma membrane after cell activation, apoptosis, or exposure to shear stress have been demonstrated to be involved in such a process. MicroRNAs (MiRs), small-non-coding single-strand RNAs acting as post-transcriptional modulator of target gene expression are expressed in the large majority of eukaryotes. MiRs are implicated in several phenomena: control of metabolism, control of cell-differentiation, control of cell-proliferation and control of cell-apoptosis, therefore contributing to physiologic and pathogenic processes in hematologic, genetic, infective and cardiac diseases. Microparticles operate as a delivery system of MiRs, playing an active and important role in processes such as coagulation and thrombosis. These novel findings also suggest MPs and, in particular MIRs, as possible and promising therapeutic targets.

Microvesicles as potential ovarian cancer biomarkers

Although the incidence of ovarian cancer is low (i.e., less than 5% in European countries), it is the most lethal gynecologic malignancy and typically has a poor prognosis. To ensure optimal survival, it is important to diagnose this condition when the pathology is confined to the ovary. However, this is difficult to achieve because the first specific symptoms appear only during advanced disease stages. To date, the biomarker mainly used for the diagnosis and prognosis of ovarian cancer is CA125; however, this marker has a low sensitivity and specificity and is associated with several other physiological and pathological conditions. No other serum ovarian cancer markers appear to be able to replace or complement CA125, and the current challenge is therefore to identify novel markers for the early diagnosis of this disease. For this purpose, studies have focused on the microvesicles (MVs) released from tumor cells. MVs may represent an ideal biomarker because they can be easily isolated from blood, and they have particular features (mainly regarding microRNA profiles) that strongly correlate with ovarian cancer stage and may be effective for early diagnosis.

Platelet-associated angiogenesis regulating factors: a pharmacological perspective

Platelets, in addition to maintaining hemostasis, also stimulate angiogenesis by generating and releasing, upon activation, factors that promote the growth of new blood vessels. To date, at least 20 angiogenesis-regulating factors have been identified in platelets, including both promoters and inhibitors. Platelet-derived angiogenesis regulators promote angiogenesis during wound healing, tumor growth, and in response to ischemia. Within platelets, angiogenesis regulators are primarily stored in α-granules, but are also found in the cytosol or derived from membrane lipids. Their release can be inhibited pharmacologically by anti-platelet agents, which consequently suppress platelet-stimulated angiogenesis. Several years ago, our research group discovered that platelets generate the angiogenesis inhibitor angiostatin independent of the activation state of platelets, and that platelet-derived angiostatin serves to limit the angiogenesis-stimulating effects of platelets. In this review, we summarize the current knowledge of platelet-associated angiogenesis regulators, how they impact angiogenesis, and how they are controlled pharmacologically.

Aspects on the integrative actions of the brain from neural networks to "brain-body medicine"

"Integration" is a key term in describing how nervous system can perform high level functions. A first condition to have "integration" is obviously the presence of efficient "communication processes" among the parts that have to be combined into the harmonious whole. In this respect, two types of communication processes, called wiring transmission (WT) and volume transmission (VT), respectively, were found to play a major role in the nervous system, allowing the exchange of signals not only between neurons, but rather among all cell types present in the central nervous system (CNS). A second fundamental aspect of a communication process is obviously the recognition/decoding process at target level. As far as this point is concerned, increasing evidence emphasizes the importance of supramolecular complexes of receptors (the so called receptor mosaics) generated by direct receptor-receptor interactions. Their assemblage would allow a first integration of the incoming information already at the plasma membrane level. Recently, evidence of two new subtypes of WT and VT has been obtained, namely the tunnelling nanotubes mediated WT and the microvesicle (in particular exosomes) mediated VT allowing the horizontal transfer of bioactive molecules, including receptors, RNAs and micro-RNAs. The physiological and pathological implications of these types of communication have opened up a new field that is largely still unexplored. In fact, likely unsuspected integrative actions of the nervous system could occur. In this context, a holistic approach to the brain-body complex as an indissoluble system has been proposed. Thus, the hypothesis has been introduced on the existence of a brain-body integrative structure formed by the "area postrema/nucleus tractus solitarius" (AP/NTS) and the "anteroventral third ventricle region/basal hypothalamus with the median eminence" (AV3V-BH). These highly interconnected regions operate as specialized interfaces between the brain and the body integrating brain-borne and body-borne neural and humoral signals.

Imbalance between endothelial progenitors cells and microparticles in HIV-infected patients naive for antiretroviral therapy

BACKGROUND

Cardiovascular events have been reported among HIV-infected patients following antiretroviral therapy. However, the role of HIV itself in determining vascular damage is less described. Chronic inflammatory state might impair some regulatory endothelium properties leading to its activation, apoptosis or erosion.

OBJECTIVES

To evaluate the balance between endothelial progenitor cells and microparticles in HIV-infected antiretroviral drug-naive patients.

DESIGN

A case-control study comparing HIV-infected patients (n = 35) with sex-matched and age-matched healthy controls (n = 33).

METHODS

Endothelial progenitor cells populations expressing CD34, CD133 and KDR were quantified by flow cytometry. Endothelial-derived microparticles, expressing CD51, and platelet-derived microparticles, expressing CD31/CD42, were also measured. Endothelial function was estimated by flow-mediated dilation.

RESULTS

Lower percentages of endothelial progenitor cells (CD34/KDR) were observed in HIV-infected individuals compared with controls (0.02 vs. 0.09%, P = 0.045). In addition, endothelial microparticles concentration was higher in HIV-infected individuals (1963 vs. 436 microparticles/μl platelet-poor plasma, P = 0.003), with similar number of platelet-derived microparticles among groups. Furthermore, flow-mediated dilation was lower among HIV-infected individuals compared with controls [mean (SEM): 10 (1) and 16% (2), respectively; P = 0.03].

CONCLUSION

Our findings suggest an imbalance between endothelial progenitor cells mobilization and endothelial apoptosis. The alteration in the turnover of endothelial cells may contribute to cardiovascular events in HIV-infected patients.