Circulating endothelial progenitor cell levels are not reduced in HIV-infected men

Circulating endothelial and angiogenic cells predict hippocampal volume as a function of HIV status

Circulating endothelial cells (CECs) and myeloid angiogenic cells (MACs) have the capacity to stabilize human blood vessels in vivo. Evidence suggests that these cells are depleted in dementia and in persons living with HIV (PWH), who have a higher prevalence of dementia and other cognitive deficits associated with aging. However, the associations of CECs and MACs with MRI-based measures of aging brain health, such as hippocampal gray matter volume, have not been previously demonstrated. The present study examined differences in these associations in 51 postmenopausal women with and without HIV infection. Gray matter volume was quantified using MRI. CECs and MACs were enumerated using fluorescence-activated cell sorting. Analyses examined the association of these cell counts with left and right hippocampal gray matter volume while controlling for age and hypertension status. The main finding was an interaction suggesting that compared to controls, postmenopausal PWH with greater levels of CECs and MACs had significantly greater hippocampus GMV. Further research is necessary to examine potential underlying pathophysiological mechanisms in HIV infection linking morpho-functional circulatory reparative processes with more diminished hippocampal volume in postmenopausal women.

Evaluation of endothelial function and subclinical atherosclerosis in patients with HIV infection

The aim of this study was to analyse the association between human immunodeficiency virus (HIV) related clinical and analytical parameters and the presence of subclinical atherosclerosis as well as endothelial dysfunction. This was a prospective cohort study of HIV-positive patients who underwent intima media thickness (IMT) determination and coronary artery calcium scoring to determine subclinical atherosclerosis. To detect endothelial dysfunction, the breath holding index, flow-mediated dilation and the concentration of endothelial progenitor cells (EPCs) were measured. Patients with an IMT ≥ 0.9 mm had an average of 559.3 ± 283.34 CD4/μl, and those with an IMT < 0.9 mm had an average of 715.4 ± 389.92 CD4/μl (p = 0.04). Patients with a low calcium score had a significantly higher average CD4 cell value and lower zenith viral load (VL) than those with a higher score (707.7 ± 377.5 CD4/μl vs 477.23 ± 235.7 CD4/μl (p = 0.01) and 7 × 10⁴ ± 5 × 10⁴ copies/ml vs 23.4 × 104 ± 19 × 104 copies/ml (p = 0.02)). The number of early EPCs in patients with a CD4 nadir < 350/µl was lower than that in those with a CD4 nadir ≥ 350 (p = 0.03). In HIV-positive patients, low CD4 cell levels and high VL were associated with risk of developing subclinical atherosclerosis. HIV patients with CD4 cell nadir < 350/µl may have fewer early EPCs.

The Role of Inflammation and Immune Activation on Circulating Endothelial Progenitor Cells in Chronic HIV Infection

Endothelial inflammation and damage are the main drivers of cardiovascular risk/disease. Endothelial repair is mediated in part by recruitment of bone marrow endothelial progenitor/endothelial colony forming cells (EPC/ECFC). People with HIV (PWH) have increased cardiovascular risk and the impact of infection in endothelial repair is not well defined. The low frequencies and challenges to in vitro isolation and differentiation of EPC/ECFC from PBMCs had made it difficult to study their role in this context. We hypothesized that HIV driven inflammation induces phenotypic changes that reflects the impact of infection. To test this hypothesis, we evaluated expression of markers of trafficking, endothelial differentiation, and angiogenesis, and study their association with biomarkers of inflammation in a cohort of PWH. In addition, we investigated the relationship of circulating endothelial progenitors and angiogenic T cells, a T cell subset with angiogenic function. Using a flow cytometry approach, we identified two subsets of circulating progenitors LIN4^-CD45^-CD34⁺ and LIN4^-CD45^dimCD34⁺ in PWH. We found that the phenotype but not frequencies were associated with biomarkers of inflammation. In addition, the percentage of LIN4^-CD45^dimCD34⁺ was associated with serum levels of lipids. This data may provide a new tool to better address the impact of HIV infection in endothelial inflammation and repair.

Deciphering Endothelial Dysfunction in the HIV-Infected Population

Cardiovascular disease (CVD), as a possible consequence of endothelial dysfunction, is prevalent among HIV-infected patients despite successful administration of antiretroviral drugs. This warrants the routine clinical assessment of endothelial function in HIV-positive patients to circumvent potential CVD events. Several different non-invasive strategies have been employed to assess endothelial function in clinical research studies yielding inconsistencies among these reports. This review summarises the different techniques used for assessing endothelial function, with a focus on proposed blood-based biomarkers, such as endothelial leukocyte adhesion molecule-1 (E-selectin), soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), von Willebrand factor (vWF), TNF-α, interleukin 6 (IL6) and soluble thrombomodulin (sTM). The identification of suitable blood-based biomarkers, especially those that can be measured using a point-of-care device, would be more applicable in under-resourced countries where the prevalence of HIV is high.

Variable endothelial cell function restoration after initiation of two antiretroviral regimens in HIV-infected individuals

Background

The effect of ART on endothelial cell function is incompletely characterized.

Methods

We performed a 24 week prospective, case-control and comparative pilot study of ART-naive HIV-infected patients who started a darunavir- or rilpivirine-based regimen, matched with non-HIV-infected volunteers, to compare changes at week 24 from baseline in levels of circulating endothelial cells (CECs), endothelial progenitor cells (EPCs) and circulating angiogenic cells, as well as changes in immune-activation markers.

Results

The study population comprised 24 HIV-infected patients and 24 non-infected volunteers. Both HIV groups completely suppressed viraemia. HIV-infected patients had higher levels of activation markers than the control group in CD8 T cells at baseline; these decreased after 24 weeks of treatment, but without reaching the levels of the control group. No statistical differences in immune activation were seen between the darunavir and rilpivirine groups. Levels of CECs were higher and levels of EPCs and circulating angiogenic cells were lower in HIV-infected patients than in the control group, although these parameters were similar between the darunavir group and the control group, but not the rilpivirine group, at week 24. An unfavourable association was observed between rilpivirine, age and increased number of CECs.

Conclusions

Restoration of circulating levels of EPCs and CECs in darunavir-treated patients was greater than in those treated with rilpivirine, suggesting ongoing endothelial repair mechanisms.

Low Levels of Endothelial Progenitor Cells and Their Association with Systemic Inflammation and Monocyte Activation in Older HIV-Infected Men

Endothelial progenitor cells (EPCs) repair damaged vascular endothelium, and low circulating EPC levels have been associated with cardiovascular disease (CVD). CD34⁺/KDR⁺ EPCs are commonly reported in the literature and CD34⁺/CD133⁺/KDR⁺ EPCs are rare in circulation but highly specific for endothelial lineage. HIV-infected (HIV+) adults have chronic inflammation and increased CVD risk, but the relationship between CVD, vascular inflammation, and EPCs in HIV remains unclear. In a pilot study, EPCs were measured in 57 HIV+ men [≥50 years old, HIV-1 RNA <50 copies/ml on antiretroviral therapy (ART)] by real-time flow cytometry using cellular immaturity (CD34 and/or CD133) and endothelial commitment (KDR) markers. Fasting inflammatory biomarker levels were measured by ELISA. Median age was 57 years; CD4⁺ T lymphocyte count was 570 cells/mm³. Prevalent CVD risk factors included 16% diabetes, 28% hypertension, 53% dyslipidemia, and 33% smoking. Median (interquartile range) EPC values were CD34⁺/KDR⁺ 0.1 (0.0-0.9) cells/10⁵ peripheral blood mononuclear cells (PBMCs) and CD34⁺/CD133⁺/KDR⁺ 0.1 (0.0-0.9) cells/10⁵ PBMCs. We observed a high prevalence of undetectable CD34⁺/KDR⁺ (40%) and CD34⁺/CD133⁺/KDR⁺ EPCs (44%). Men with undetectable EPCs were more likely to have ≥2 CVD risk factors, lower interleukin-6 (IL-6), and higher sCD163 levels. In these older HIV+ men on suppressive ART, CD34⁺/KDR⁺ and CD34⁺/CD133⁺/KDR⁺ EPC levels were low and often undetectable. Undetectable EPC levels were associated with greater CVD risk factor burden, lower IL-6 (consistent with decreased EPC production stimulus), and higher sCD163 (consistent with monocyte activation and prior CVD associations) levels, suggesting a potential relationship between EPCs and atherosclerotic burden in this population.

The evolution of coronary stents: a brief review

Percutaneous coronary intervention is the most prevalent method for coronary artery revascularization. Initial interventions using balloon angioplasty had limited efficacy because coronary dissections, arterial recoil, and neointimal formation led to high rates of abrupt vessel closure and clinical restenosis. With the introduction of coronary stents, vascular dissections were stabilized and arterial recoil was eliminated, but neointimal accumulation remained problematic, resulting in the development of in-stent restenosis (ISR) in 20%-30% of cases. Drug-eluting stents (DESs) were developed to release antiproliferative agents at the site of arterial injury to attenuate neointimal formation. Although DESs have incrementally improved outcomes after percutaneous coronary intervention, delayed re-endothelialization and stent thrombosis remain important challenges. Herein we review the pathophysiology of ISR, stent thrombosis, and briefly summarize the clinical evidence behind first- and second-generation DESs. Moreover, we discuss advancements in our understanding of the pathogenesis of ISR and potential novel therapeutic strategies to improve clinical outcomes.

Association of HIV-Infection and antiretroviral therapy with levels of endothelial progenitor cells and subclinical atherosclerosis

BACKGROUND

Although in the general population circulating vascular progenitor cell levels have been implicated in the homeostasis of the vascular wall through differentiation into endothelium and/or smooth muscle cells, it has not yet been assessed in HIV-infected patients. We herein investigated the number of progenitor cell subpopulations in HIV-infected patients and its relationship to carotid intima-media thickness (c-IMT).

METHODS

Blood samples were collected from 200 HIV-infected patients and CD34/KDR, CD34/VE-cadherin, and CD14/Endoglin progenitor cells were identified by flow cytometry. c-IMT was determined by ultrasonography. A group of 27 healthy subjects was used as control group.

RESULTS

In our population (20 ART-naive patients and 180 treated patients), traditional cardiovascular risk factors were not found predictive of vascular progenitor cell levels. However, antiretroviral therapy (ART)-treatment was identified as the main predictive value for low CD34/KDR cells and high CD14/Endoglin cells after adjustment by cardiovascular risk factors (age, sex, hypertension, diabetes, and hyperlipidaemia) and HIV-related characteristics (HIV duration and ART treatment). Low levels of circulating CD34/KDR or CD34/VE-cadherin endothelial progenitor cells tended to be associated with increased c-IMT. However, a positive association was found between CD14/Endoglin cells and c-IMT. Low number of CD34/KDR cells was also associated with the longest exposure to nucleoside reverse transcriptase inhibitors and/or protease inhibitors.

CONCLUSIONS

ART exposure is the main predictor of circulating vascular progenitor cell levels. However, their levels are only partially associated with high c-IMT in HIV-infected patients. ART has already been found to have proatherogenic effect, but our data first describe its relationship with vascular progenitor cells and c-IMT.

Short communication: proangiogenic hematopoietic cells in acute HIV infection

Chronic HIV infection induces significant changes in the trafficking of circulating endothelial progenitor cells (EPCs). Specifically, it causes marked depletion of proangiogenic hematopoietic cells, the so-called colony-forming unit-endothelial cells (CFU-ECs). In this study we evaluated CFU-ECs in two subjects with acute HIV infection. We found that both patients already had a low CFU-EC level at the time of diagnosis. Nevertheless, after 6 months of antiretroviral therapy, the CFU-EC concentration reverted to normal values in both cases. HIV significantly depletes the CFU-EC compartment even in the early phase of infection, while 6-month therapy appears to be able to restore it.