Reduced endothelial progenitor cells in children with hemodialysis but not predialysis chronic kidney disease

Increased circulating endothelial progenitor cells (EPCs) in prepubertal children born prematurely: a possible link between prematurity and cardiovascular risk

BACKGROUND

Endothelial progenitor cells (EPCs) ensure vascular integrity and neovascularization. No studies have investigated EPCs in preterm-born children beyond infancy.

METHODS

One hundred and thirty-six prepubertal children were enrolled: 63 preterm and 73 born at term (controls). Circulating CD34(+)/VEGFR-2(+)/CD45(-) and CD34(+)/VEGFR-2(+)/CD45dim EPCs were measured in preterm-born children compared to controls. Body mass index (BMI), waist-to-hip ratio (WHR), neck circumference, systolic and diastolic blood pressure (SBP and DBP, respectively), fasting glucose, insulin, lipid profile, common carotid and abdominal aortic intima-media thickness (cIMT and aIMT, respectively), endothelium-dependent brachial artery flow-mediated dilation (FMD), and echocardiographic parameters were also assessed.

RESULTS

Circulating CD34(+)/VEGFR-2(+)/CD45(-) and CD34(+)/VEGFR-2(+)/CD45dim EPCs were significantly higher in preterm-born children compared to controls (p < 0.001 and p < 0.001, respectively). In total study population and in the preterm-born group, EPCs were significantly lower in children born to mothers with gestational diabetes compared to non-diabetic mothers. Prematurity was associated with higher WHR, neck circumference, SBP, DBP, cIMT, aIMT, mean pressure, and velocity of pulmonary artery; the peak velocity of the brachial artery was significantly lower in children born prematurely. In multiple regression analysis, preterm birth and maternal gestational diabetes were recognized as independent predictors of EPCs.

CONCLUSIONS

Circulating EPCs were increased in prepubertal preterm-born children in comparison with peers born full-term. Maternal gestational diabetes was associated with a decrease in EPCs.

IMPACT

Mounting evidence supports the adverse effect of prematurity on cardiovascular health. However, the underlying mechanisms that could lead to endothelial dysfunction in preterm-born individuals are not fully understood. Endothelial progenitor cells (EPCs) ensure vascular integrity, normal endothelial function and neovascularization. No studies have investigated the EPCs counts in peripheral blood beyond infancy in children born prematurely. Circulating EPCs were significantly higher in preterm-born prepubertal children compared to controls, thus indicating that prematurity is possibly associated with endothelial damage. In total study population and in the preterm-born group, maternal gestational diabetes was associated with decreased EPCs concentrations.

Prospective assessment of subclinical cardiovascular damage and associated factors in liver transplant recipients

Cardiovascular (CV) disease plays a major role after liver transplantation (LT). This prospective study assessed subclinical CV damage after LT by measuring pulse wave velocity (PWV), intima-media thickness (IMT) and left-ventricular mass index (LVMI) and characterized associated risk factors. We included 112 patients with a median of 1.8 years after LT (q1-q3 0.9-9.2). Fifty-three percent (n = 59) of patients had ≥2 annual assessments (median follow-up 1.6 years, q1-q3 1.1-2.0), with a total of 195 assessments. We found increased PWV (indicating arteriosclerosis) in 16% (n = 17), elevated IMT in 5% (n = 5; indicating atherosclerosis) and increased LVMI in 25% (n = 24; indicating left-ventricular hypertrophy). A linear mixed model analysis using all 195 assessments revealed that higher age and systolic blood pressure (BP) were associated with higher PWV (β = 0.069, P < 0.001 and β = 0.022, P = 0.005) and higher IMT (β = 0.005, P < 0.001 and β = 0.001, P = 0.029), while higher body mass index was associated with higher IMT (β = 0.004, P = 0.023). Higher systolic BP (β = 0.200, P = 0.034), male sex (β = 8.847, P = 0.031) and lower glomerular filtration rate (β = -0.288, P < 0.001) were associated with higher LVMI. Our data highlight not only the rate of subclinical CV damage in LT patients, but also the impact of classical CV risk factors (such as BP and body mass index) which outweighed LT-related factors. These modifiable risk factors are suitable targets for interventions to reduce CV morbidity in LT patients.

Vascular toxicity of urea, a new "old player" in the pathogenesis of chronic renal failure induced cardiovascular diseases

Chronic kidney disease in children is an irreversible process that may lead to end-stage renal disease. The mortality rate in children with end-stage renal disease who receive dialysis increased dramatically in the last decade, and it is significantly higher compared with the general pediatric population. Furthermore, dialysis and transplant patients, who have developed end-stage renal disease during childhood, live respectively far less as compared with age/race-matched populations. Different reports show that cardiovascular disease is the leading cause of death in children with end-stage renal disease and in adults with childhood-onset chronic kidney disease, and that children with chronic kidney disease are in the highest risk group for the development of cardiovascular disease. Urea, which is generated in the liver during catabolism of amino acids and other nitrogenous metabolites, is normally excreted into the urine by the kidneys as rapidly as it is produced. When renal function is impaired, increasing concentrations of blood urea will steadily accumulate. For a long time, urea has been considered to have negligible toxicity. However, the finding that plasma urea is the only significant predictor of aortic plaque area fraction in an animal model of chronic renal failure -accelerated atherosclerosis, suggests that the high levels of urea found in chronic dialysis patients might play an important role in accelerated atherosclerosis in this group of patients. The aim of this review was to provide novel insights into the role played by urea in the pathogenesis of accelerated cardiovascular disease in renal failure.

Methods to evaluate arterial structure and function in children - State-of-the art knowledge

BACKGROUND

With increasing rates of hypertension, obesity, and diabetes in the pediatric population, wide available, and reproducible methods are necessary to evaluate arterial structure and function in children and adolescents.

METHODS

MEDLINE/Pubmed was searched for articles published in years 2012-2017 on methodology of, current knowledge on, and limitations of the most commonly used methods to evaluate central, proximal and coronary arteries, as well as endothelial function in pediatric patients.

RESULTS

Among 1528 records screened (including 1475 records from years 2012 to 2017) 139 papers were found suitable for the review. Following methods were discussed in this review article: ultrasound measurements of the intima-media thickness, coronary calcium scoring using computed tomography, arterial stiffness measurements (pulse wave velocity and pulse wave analysis, carotid artery distensibility, pulse pressure, and ambulatory arterial stiffness index), ankle-brachial index, and methods to evaluate vascular endothelial function (flow-mediated vasodilation, peripheral arterial tonometry, Doppler laser flowmetry, and cellular and soluble markers of endothelial dysfunction).

CONCLUSIONS

Ultrasonographic measurement of carotid intima-media thickness and measurement of pulse wave velocity (by oscillometry or applanation tonometry) are highly reproducible methods applicable for both research and clinical practice with proved applicability for children aged ≥6 years or with height ≥120cm. Evaluation of ambulatory arterial stiffness index by ambulatory blood pressure monitoring is another promising option in pediatric high-risk patients. Clearly, further studies are necessary to evaluate usefulness of these and other methods for the detection of subclinical arterial damage in children.

Pivotal Cytoprotective Mediators and Promising Therapeutic Strategies for Endothelial Progenitor Cell-Based Cardiovascular Regeneration

Cardiovascular diseases (CVDs), including atherosclerosis, stroke, and myocardial infarction, is a major cause of death worldwide. In aspects of cell therapy against CVD, it is generally accepted that endothelial progenitor cells (EPCs) are potent neovascular modulators in ischemic tissues. In response to ischemic injury signals, EPCs located in a bone marrow niche migrate to injury sites and form new vessels by secreting various vasculogenic factors including VEGF, SDF-1, and FGF, as well as by directly differentiating into endothelial cells. Nonetheless, in ischemic tissues, most of engrafted EPCs do not survive under harsh ischemic conditions and nutrient depletion. Therefore, an understanding of diverse EPC-related cytoprotective mediators underlying EPC homeostasis in ischemic tissues may help to overcome current obstacles for EPC-mediated cell therapy for CVDs. Additionally, to enhance EPC's functional capacity at ischemic sites, multiple strategies for cell survival should be considered, that is, preconditioning of EPCs with function-targeting drugs including natural compounds and hormones, virus mediated genetic modification, combined therapy with other stem/progenitor cells, and conglomeration with biomaterials. In this review, we discuss multiple cytoprotective mediators of EPC-based cardiovascular repair and propose promising therapeutic strategies for the treatment of CVDs.

Circulating Progenitor Cells and Childhood Cardiovascular Disease

Circulating progenitor cells have been extensively studied in the context of heart disease in adults. In these patients, they have been demonstrated to be markers of myocardial injury and recovery as well as potential therapeutic agents. However, studies in children are much more limited. Here we review current knowledge pertaining to circulating progenitor cells in the context of childhood cardiovascular disease. Priorities for further research are also highlighted.

Challenges and opportunities for stem cell therapy in patients with chronic kidney disease

Chronic kidney disease (CKD) is a global health care burden affecting billions of individuals worldwide. The kidney has limited regenerative capacity from chronic insults, and for the most common causes of CKD, no effective treatment exists to prevent progression to end-stage kidney failure. Therefore, novel interventions, such as regenerative cell-based therapies, need to be developed for CKD. Given the risk of allosensitization, autologous transplantation of cells to boost regenerative potential is preferred. Therefore, verification of cell function and vitality in CKD patients is imperative. Two cell types have been most commonly applied in regenerative medicine. Endothelial progenitor cells contribute to neovasculogenesis primarily through paracrine angiogenic activity and partly by differentiation into mature endothelial cells in situ. Mesenchymal stem cells also exert paracrine effects, including proangiogenic, anti-inflammatory, and antifibrotic activity. However, in CKD, multiple factors may contribute to reduced cell function, including older age, coexisting cardiovascular disease, diabetes, chronic inflammatory states, and uremia, which may limit the effectiveness of an autologous cell-based therapy approach. This Review highlights current knowledge on stem and progenitor cell function and vitality, aspects of the uremic milieu that may serve as a barrier to therapy, and novel methods to improve stem cell function for potential transplantation.

Effects of acute exercise on markers of inflammation in pediatric chronic kidney disease: a pilot study

BACKGROUND

Children and adolescents with chronic kidney disease (CKD) are chronically exposed to high levels of inflammation, placing them at an increased risk of secondary health complications. Regular exercise may represent an effective therapy to reduce inflammation. The aims of this pilot study were to determine the effects of acute exercise on inflammation and immune cell counts in CKD.

METHODS

Nine children and adolescents (4 males) with CKD stages III-V performed a graded exercise test to determine peak oxygen uptake (VO2peak). Following a 10-min break, participants cycled for 20 min at 50 % of VO2peak. Blood samples were collected before and after the exercise period for the determination of complete blood counts, natural killer cells (NK(bright), NK(dim)) and circulating progenitor cell (CPC) counts, as well as interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) concentrations.

RESULTS

Complete blood counts and NK(dim) cell and CPC counts were unchanged with exercise. Following exercise, NK(bright) cell counts increased (7.4 ± 4.3 vs. 12.2 ± 8.3 × 10(6) cells/L; p = 0.02), while trends were observed for an increase in IL-6 (2.1 ± 2.2 vs. 2.7 ± 2.6 pg/mL; p = 0.08), decrease in TNF-α (4.5 ± 1.2 vs. 4.2 ± 1.0 pg/mL; p = 0.08) and an increase in the IL-6:TNF-α ratio (0.6 ± 0.7 vs. 0.8 ± 0.8; p = 0.07).

CONCLUSIONS

Our findings suggest that acute exercise may create an anti-inflammatory environment in children and adolescents with CKD stages III-V.

The ontogeny of endothelial progenitor cells through flow cytometry

PURPOSE OF REVIEW

Since the discovery of endothelial progenitor cells (EPCs), there have been conflicting reports as to the precise phenotypic identity, and thus an accurate description of the function of these cells in disease pathology is lacking. This review will detail the protocols that have been published within 2010 to help decipher the true identity of the various cells that have been reported as EPCs in numerous clinical trials.

RECENT FINDINGS

Throughout 2010, three protocols have been published alleging to identify EPCs, yet only one provides a true nonhematopoietic origin for a cell that is classified as an EPC. In addition to the protocols published to try to establish a consensus definition, 10 studies involving EPCs across disease pathologies were published with various degrees of correlation to disease phenotype and cellular level.

SUMMARY

A true phenotypic definition of a circulating EPC capable of becoming an endothelial colony forming cell with proliferative potential has been given. It is now time the EPC field drops this ambiguous term (i.e. EPCs), as many studies purporting to measure EPCs are in fact still quantifying cells of a hematopoietic origin. It is necessary for cross study comparisons that a uniform phenotypic definition be adhered to when using the term EPC.