Circulating endothelial progenitor cells after kidney transplantation

Impairment of endothelial progenitor cells in women after kidney transplantation

OBJECTIVE

The long-term survival of kidney transplant patients has substantially improved. However, there is a higher risk for cardiovascular events after transplantation, partly due to immunosuppression. A diminished number of endothelial progenitor cells (EPCs), which play an important role in angiogenesis and the repair of endothelial damage, are associated with an increased cardiovascular risk. The aim of this study was to evaluate whether kidney transplantation affects EPCs in women.

METHODS

Twenty-four healthy women and 22 female kidney transplant recipients were recruited. The ratio of angiogenic and non-angiogenic circulating progenitor cells (CPCs) was determined by multicolor flow cytometry and related to clinical parameters. Cord blood-derived endothelial colony-forming cells (ECFCs), a proliferative subgroup of endothelial progenitor cells, were treated with pooled sera from transplant patients or healthy controls and tested for their functional integrity using in vitro models.

RESULTS

Kidney transplant recipients displayed a reduced ratio of angiogenic and non-angiogenic CPCs compared to healthy controls. Differences were especially pronounced in premenopausal women. Exposure to sera of transplanted women led to a significant impairment of ECFC proliferation, migration, and angiogenesis ability.

CONCLUSIONS

Alterations of EPC populations may contribute to the higher cardiovascular risks after organ transplantation and should be considered in therapeutic strategies.

Endothelial Progenitor Cells and Kidney Diseases

Endothelial progenitor cells (EPC) are bone marrow derived or tissue-resident cells that play major roles in the maintenance of vascular integrity and repair of endothelial damage. Although EPCs may be capable of directly engrafting and regenerating the endothelium, the most important effects of EPCs seem to be depended on paracrine effects. In recent studies, specific microvesicles and mRNAs have been found to mediate the pro-angiogenic and regenerative effects of EPCs on endothelium. EPC counts have important prognostic implications in cardiovascular diseases (CVD). Uremia and inflammation are associated with lower EPC counts which probably contribute to increased CVD risks in patients with chronic kidney disease. Beneficial effects of the EPC therapies have been shown in studies performed on different models of CVD and kidney diseases such as acute and chronic kidney diseases and glomerulonephritis. However, lack of a clear definition and specific marker of EPCs is the most important problem causing difficulties in interpretation of the results of the studies investigating EPCs.

Asymmetric dimethylarginine and endothelial progenitor cells after renal transplantation: the effect of exercise training

Level of asymmetric dimethylarginine (ADMA) is elevated and endothelial progenitor cells (EPC) and stem cells (SC) are decreased in patients undergoing renal transplantation (Tx) and may contribute to cardiovascular complications. We tested the hypothesis that ADMA, EPC and SC can be influenced with regular physical exercise early after Tx. Blood samples of ADMA, EPC, SC, adipocytokines and metabolic parameters were randomly obtained from 50 transplant patients before and 6 months after exercise program (Group I). Fifty age, sex, HLA typing, duration of dialysis and immunosupression regimen-matched non exercising transplant were examined as controls (Group II). After 6 months, in Group I ADMA decreased (3.50+/-0.45 vs 2.11+/-0.35 micromol/l, P<0.01) and was lower comparing to Group II (P<0.01), SC and EPC also decreased (2816+/-600 vs 2071+/-480 cells/ml resp. 194+/-87 to 125+/-67 cells/ml, P<0.02). Next changes in Group I: adiponectin (P<0.01), leptin (P<0.01), resistin (P<0.02). Visfatin, blood lipids, HbA1c, insulin and blood pressure were also influenced by training program (P<0.05).

Association of circulating endothelial progenitor cells (CD14+-EPC) with renal function in patients with coronary artery disease

BACKGROUND

The relationships between the endothelial progenitor cells (EPCs)-CD34(+) and CD14(+) and coronary artery disease (CAD) were reported and the association of CD34(+) cells with renal function was studied previously. Another kind EPC-CD14(+) cell and its association with renal function in patients with CAD have not been reported yet. Our aim was to assess CD14(+) cell counts versus renal function in CAD.

METHODS AND RESULTS

We studied 242 patients with severe angiographic CAD and 30 healthy control participants. The CD14(+) cells were enumerated by flow cytometry. With lowering glomerular filtration rate (GFR), CD14(+) cell numbers (percentage of lymphocytes, median and interquartile range) decreased: 0.04 (0.03-0.06), 0.03 (0.02-0.05), 0.02 (0.01-0.03) for estimated glomerular filtration rate (eGFR) ≥90, 60 to 89, and 30 to 89 mL/min per 1.73 m(2), respectively (P < .001 for trend). The CD14(+) cell counts correlated with eGFR (r = .27, P = .03). By multivariate liner regression analysis, the difference remains significant (P = .02).

CONCLUSIONS

The CD14(+) cell depletion is associated with renal dysfunction in CAD.

Relationship among endothelial response to hyperemia, bone marrow-derived progenitor cells, and parathyroid hormone in renal transplantation

BACKGROUND

Endothelial dysfunction may contribute to modulate cardiovascular complications in renal transplant recipients (RTRs), and a relationship between endothelial dysfunction and parathyroid hormone (PTH) levels in RTRs has been demonstrated. We evaluated the relationship between endothelial response to hyperemia and circulating progenitor cells (CPCs) and endothelial progenitor cells (EPCs) PTH, and genetic parameters in RTRs.

METHODS

In 120 RTRs and in healthy subjects without (n=107, group A) and with cardiovascular risk factors (n=109, group B), we evaluated endothelial response to hyperemia through digital tonometry (peripheral arterial tonometry) detected by reactive hyperemia index (RHI) and EPCs and CPCs by flow cytometry.

RESULTS

In RTRs, RHI median value was lower than in group A (P=0.05). EPC number was significantly lower in RTRs than in groups A and B (P<0.0001), whereas PTH median value was significantly higher (P<0.0001). In RTRs, RHI values were significantly lower according to the presence of three or more risk factors (P=0.04) and positively correlated with EPCs (P=0.04) but not with PTH (P=0.2). In patients who underwent dialysis for more than 5 years, lower RHI values (P=0.08), EPC number (P=0.5), and higher PTH concentrations (P=0.09) than in patients with less than 1 year dialysis time were observed. No relationship between eNOS gene -786T>C, 894G>T, and 4a/4b polymorphisms and RHI, EPC, and CPC number was found.

CONCLUSIONS

This study shows an altered endothelial response, associated with reduced EPCs, and increased PTH in RTRs; the evaluation of endothelial status in RTRs may contribute to better assess the risk profile of these patients.

Circulating endothelial progenitor cells inversely associate with organ dysfunction in sepsis

PURPOSE

Endothelial dysfunction is a primary contributor to sepsis-related organ dysfunction and death. In sepsis animal models, endothelial progenitor cells (EPC) have contributed to vascular repair. The role of endothelial progenitor cells as a biomarker for organ dysfunction is still unknown. We hypothesized that circulating numbers of endothelial progenitor cells would be associated with improved outcomes in sepsis.

METHODS

Prospective, observational single-center cohort study in adult intensive care units at Grady Memorial Hospital, an affiliate of Emory University, from July 2007 through April 2009. Peripheral blood was obtained from 95 patients with sepsis, 37 intensive care unit controls, and 51 healthy controls, of whom only 86 patients with sepsis were used in the analysis because we were not able to obtain enough blood in 9 sepsis patients. Clinical data were obtained, and organ dysfunction was measured by Sepsis-Related Organ Failure Assessment (SOFA) score. Endothelial progenitor cells were assessed by a colony-forming unit (CFU) assay in which peripheral blood mononuclear cells were isolated using Ficoll density-gradient centrifugation and cultured in growth media.

RESULTS

The patients with sepsis had significantly lower mean endothelial progenitor cell colony counts compared with intensive care unit controls (p = 0.035) and healthy controls (p = 0.0005). There was no difference in colony counts between ICU controls and healthy controls (p = 0.81). In the sepsis patients, EPC CFU numbers inversely associated with SOFA score, adjusting for mortality (r (2) = 0.05, p = 0.04).

CONCLUSION

Increased circulating endothelial progenitor cells inversely correlate with organ dysfunction in sepsis patients.

Late outgrowth endothelial progenitor cells engineered for improved survival and maintenance of function in transplant-related injury

Chronic allograft vasculopathy (CAV) is a major cause of organ transplant failure that responds poorly to treatment. Endothelial activation, dysfunction and apoptosis contribute to CAV, whereas strategies for protecting endothelium and maximizing endothelial repair may diminish it. Late outgrowth endothelial progenitor cells (LO-EPC) can home to areas of injury and integrate into damaged vessels, implying a role in vascular repair; however, in an allograft, LO-EPC would be exposed to the hazardous microenvironment associated with transplant-related ischaemia reperfusion (I/R) injury and persistent inflammation. We evaluated the in vitro effect of I/R injury and the proinflammatory cytokine tumour necrosis factor (TNF)-α on LO-EPC phenotype and function. We show that LO-EPC are intrinsically more tolerant than mature EC to I/R injury induced apoptosis, maintaining their proliferative, migratory and network formation capacity. Under inflammatory conditions, LO-EPC were activated and released higher levels of inflammatory cytokines, upregulated adhesion molecule expression, and were more susceptible to apoptosis. Lentiviral vector-mediated overexpression of the protective gene A20 in LO-EPC maintained their angiogenic phenotype and function, and protected them against TNF-α-mediated apoptosis, reducing ICAM-1 expression and inflammatory cytokine secretion. Administration of ex vivo modified LO-EPC overexpressing A20 might effect vascular repair of damaged allografts and protect from CAV.

Circulating endothelial progenitor cells in kidney transplant patients

BACKGROUND

Kidney transplantation (RTx) leads to amelioration of endothelial function in patients with advanced renal failure. Endothelial progenitor cells (EPCs) may play a key role in this repair process. The aim of this study was to determine the impact of RTx and immunosuppressive therapy on the number of circulating EPCs.

METHODS

We analyzed 52 RTx patients (58±13 years; 33 males, mean ± SD) and 16 age- and gender-matched subjects with normal kidney function (57±17; 10 males). RTx patients received a calcineurin inhibitor (CNI)-based (65%) or a CNI-free therapy (35%) and steroids. EPC number was determined by double positive staining for CD133/VEGFR2 and CD34/VEGFR2 by flow cytometry. Stromal cell-derived factor 1 alpha (SDF-1) levels were assessed by ELISA. Experimentally, to dissociate the impact of RTx from the impact of immunosuppressants, we used the 5/6 nephrectomy model. The animals were treated with a CNI-based or a CNI-free therapy, and EPCs (Sca+cKit+) and CD26+ cells were determined by flow cytometry.

RESULTS

Compared to controls, circulating number of CD34+/VEGFR2+ and CD133+/VEGFR2+ EPCs increased in RTx patients. There were no correlations between EPC levels and statin, erythropoietin or use of renin angiotensin system blockers in our study. Indeed, multivariate analysis showed that SDF-1--a cytokine responsible for EPC mobilization--is independently associated with the EPC number. 5/6 rats presented decreased EPC counts in comparison to control animals. Immunosuppressive therapy was able to restore normal EPC values in 5/6 rats. These effects on EPC number were associated with reduced number of CD26+ cells, which might be related to consequent accumulation of SDF-1.

CONCLUSIONS

We conclude that kidney transplantation and its associated use of immunosuppressive drugs increases the number of circulating EPCs via the manipulation of the CD26/SDF-1 axis. Increased EPC count may be associated to endothelial repair and function in these patients.

Improved function of circulating angiogenic cells is evident in type 1 diabetic islet-transplanted patients

Circulating angiogenic cells (CACs) are vascular-committed bone marrow-derived cells that are dysfunctional in type 1 diabetes (T1D). Here we studied whether restoration of normoglycemia following islet transplantation is associated with better CAC function. We carried out a cross-sectional study of 18 T1D patients, 14 insulin-independent islet-transplanted patients (ITA) and 14 healthy controls (C) evaluating in vivo and in vitro CACs viability and function. We found that the percentage of CACs in vivo did not differ among the three groups while the number of CAC colonies obtained from T1D, but not from ITA, was reduced compared to C (C = 7.3 ± 1.9, T1D = 0.9 ± 0.4 and ITA = 4.7 ± 1.9; p < 0.05 T1D vs. all). In vitro CAC migration/differentiation were similar, while in vivo an improved angiogenic ability of ITA compared to T1D was shown (capillary density: C = 93.5 ± 22.1, T1D = 19.2 ± 2.8 and ITA = 44.0 ± 10.5, p < 0.05 T1D vs. all). Increased apoptosis and lesser IL-8 secretion were evident in CACs obtained from T1D compared to C and ITA. in vitro addition of anti-hIL-8 reduced the number of colonies obtained from C. Finally, T1D, but not ITA, had a lower endothelial-dependent dilatation (EDD) compared with C. These data suggest that CAC function is altered in T1D and may be improved after islet transplantation.

Host-derived smooth muscle cells accumulate in cardiac allografts: role of inflammation and monocyte chemoattractant protein 1

Transplant arteriosclerosis is characterized by inflammation and intimal thickening caused by accumulation of smooth muscle cells (SMCs) both from donor and recipient. We assessed the relationship between clinical factors and the presence of host-derived SMCs in 124 myocardial biopsies from 26 consecutive patients who received hearts from opposite-sex donors. Clinical and demographic information was obtained from the patients' medical records. Host-derived SMCs accounted for 3.35±2.3% of cells in arterioles (range, 0.08–12.51%). As shown by linear regression analysis, an increased number of SMCs was associated with rejection grade (mean, 1.41±1.03, p = 0.034) and the number of leukocytes (19.1±12.7 per 20 high-power fields, p = 0.01). The accumulation of host-derived SMCs was associated with an increased number of leukocytes in the allografts. In vitro, monocyte chemoattractant protein 1 (MCP-1) released from leukocytes was crucial for SMC migration. After heart allotransplantion, mice treated with MCP-1-specific antibodies had significantly fewer host-derived SMCs in the grafts than mice treated with isotypic antibody controls. We conclude that the number of host-derived SMCs in human cardiac allografts is associated with the rejection grade and that MCP-1 may play pivotal role in recruiting host-derived SMCs into cardiac allografts.

Endothelial progenitor cells are reduced in refractory hypertension

Circulating endothelial progenitor cells (EPCs) play a key role in the maintenance of endothelial homoeostasis and promote vascular repair. They may also be of predictive value for cardiovascular events. Reduced EPC number and functional activity have been associated with several cardiovascular risk factors, but their relationship with hypertension remains unclear. The objective of this study was to investigate if number and function of circulating EPCs are reduced in patients with refractory hypertension (RHT). Circulating EPCs (CD34+ CD133+/CD45+) were isolated from peripheral blood by flow cytometry in 39 RHT and 30 normotensive controls. EPC number was also determined in vitro after 7 days in culture. After age adjustment, EPC concentration was significantly reduced in RHT as compared with controls (mean (95% CI), 33.8 (18.1-49.6) vs 69.1 (50.7-87.5) EPCs per 10(5) peripheral mononuclear cells (MNCs), respectively; P=0.014). After in vitro culture, EPCs were also reduced in patients as compared with controls (mean (95% CI), 142.3 (49.5-235.0) vs 611.0 (480.2-741.8) EPCs per field, respectively, P<0.001). In multiple linear regression analysis, circulating EPCs were significantly reduced by 56.3% in RHT as compared with control (P=0.006), independently of all other known risk factors. Moreover, RHT had a high independent predictive value for lower EPC proliferation. The number of EPCs per field was reduced by 76.7% in RHT with respect to controls (P<0.001). In summary, the number of circulating EPCs after culture is reduced in patients with RHT, which may be related to the increased rate of endothelial dysfunction, atherosclerotic disease and cardiovascular events observed in this population.

The unique character of cardiovascular disease in chronic kidney disease and its implications for treatment with lipid-lowering drugs

Although the risk for cardiovascular disease (CVD) is high in individuals with chronic kidney disease (CKD), there are very limited data to guide the use of lipid-lowering drugs (LLDs) in this population because the major trials of LLDs in the general population have included very few individuals with CKD. The pathophysiologic and epidemiologic differences of CVD in the CKD population suggest that the study findings derived in the general population may not be directly applicable to those with CKD, and the few trials that have been directed at patients with kidney disease have not shown clear clinical benefits of LLDs. The National Kidney Foundation Kidney Disease Outcomes Quality Initiative (K/DOQI) Work Group has provided consensus-based guidelines for managing dyslipidemias in individuals with CKD and after renal transplantation. Since the publication of these statements, further data have emerged and multiple studies are ongoing to define better the role of LLDs in patients with CKD. In this article, the data that are pertinent to the CKD population are reviewed, and updated recommendations for use of LLD in the CKD population are provided.

Cell Therapy in Kidney Disease: Cautious Optimism … But Optimism Nonetheless

The recently discovered therapeutic potential of stem or progenitor cells has initiated development of novel treatments in a number of diseases—treatments that could not only improve patients’ quality of life, but also halt or even prevent disease progression. Hypertension; fluctuations in glycemia, electrolytes, nutrient levels, and circulating volume; and frequent infections and the associated inflammation all greatly impair the endothelium in patients undergoing peritoneal dialysis. As our understanding of the regulatory function of the endothelium advances, focus is increasingly being placed on endothelial repair in acute and chronic renal failure and after renal transplantation. The potential of progenitor cells to repair damaged endothelium and to reduce inflammation in patients with renal failure remains unexamined; however, a successful cell therapy could reduce morbidity and mortality in kidney disease.

Important contributions have been made in identifying progenitor cell populations in the kidney, and further investigations into the relationships of these cells with the pathophysiology of the disease are underway. As the kidney disease field prepares for the first human trials of progenitor cell therapies, we deemed it important to review representative original research, and to share our perspectives and lessons learned from clinical trials of progenitor cell–based therapies that have commenced in patients with cardiovascular disease.

Kidney transplantation substantially improves endothelial progenitor cell dysfunction in patients with end-stage renal disease

Endothelial progenitor cells (EPC) are involved in endothelial repair and maintenance. Dysfunction of EPC may contribute to accelerated arteriosclerosis in chronic kidney disease. Kidney transplantation (KTx) improves both survival and endothelial function of dialysis patients. In a prospective study, we tested to which extent KTx changes EPC biology. We studied number and function (migratory activity, adhesion to extracellular matrix proteins and to mature endothelial cells [EC]) of EPC in 20 patients during dialysis and 3, 6, 9 and 12 months after KTx. Twenty-two healthy volunteers served as matched controls. Circulating precursor populations were measured by flow cytometric analysis. Cytokines relevant for EPC mobilization were monitored. Compared to the dialysis state, KTx increased the migration of EPC to approximately 2-fold. Adhesion to fibronectin and to collagen type IV was significantly increased after KTx. An improved adhesion rate of EPC to mature EC was observed. The number of EPC decreased. The amount of precursor populations showed no difference compared to the pretransplant state. Our study shows an improved function of EPC after KTx. This finding indicates an improved potential for endothelial repair which in turn may contribute to enhanced endothelial function and reduced cardiovascular morbidity after KTx.

Cardiovascular Biomarkers in CKD: Pathophysiology and Implications for Clinical Management of Cardiac Disease

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in patients with all forms of chronic kidney disease (CKD). The underlying pathological state is caused by a complex interplay of traditional and nontraditional risk factors that results in atherosclerosis, arteriosclerosis, and altered cardiac morphological characteristics. This multifactorial disease introduces new challenges in predicting and treating patients with CVD sufficiently early in the course of CKD to positively alter patient outcome. Asymptomatic individuals with progressive CVD are a group of patients that deserve focused attention because early detection and intervention may provide the best opportunity for improved outcome. However, identifying CVD in asymptomatic patients with CKD or end-stage renal disease remains a significant hurdle in the management of these patients. Recently, a number of cardiovascular biomarkers were identified as predictors of patient outcome in individuals with CVD and, with additional research, may be used to guide the early diagnosis of and therapy for CVD in patients with CKD. This review examines the pathophysiological characteristics and potential clinical role of these novel cardiovascular biomarkers in risk stratification, risk monitoring, and selection of preventive therapies for patients with CKD.