Effects of haemodialysis on circulating endothelial progenitor cell count

Selenoprotein-P1 (SEPP1) Expression in Human Proximal Tubule Cells after Ischemia-Reperfusion Injury: An In Vitro Model

Background and Objectives: Selenium deficiency represents a risk factor for the occurrence of severe diseases, such as acute kidney injury (AKI). Recently, selenoprotein-p1 (SEPP1), a selenium transporter, mainly released by the liver, has emerged as a promising plasmatic biomarker of AKI as a consequence of cardio-surgery operations. The aim of the present study was to investigate, on an in vitro model of hypoxia induced in renal tubular cells, HK-2, the effects of sodium selenite (Na2SeO3) and to evaluate the expression of SEPP1 as a marker of injury. Materials and Methods: HK-2 cells were pre-incubated with 100 nM Na2SeO3 for 24 h, and then, treated for 24 h with CoCl2 (500 µM), a chemical hypoxia inducer. The results were derived from an ROS assay, MTT, and Western blot analysis. Results: The pre-treatment determined an increase in cells' viability and a reduction in reactive oxygen species (ROS), as shown by MTT and the ROS assay. Moreover, by Western blot an increase in SEPP1 expression was observed after hypoxic injury as after adding sodium selenite. Conclusions: Our preliminary results shed light on the possible role of selenium supplementation as a means to prevent oxidative damage and to increase SEPP1 after acute kidney injury. In our in vitro model, SEPP1 emerges as a promising biomarker of kidney injury, although further studies in vivo are necessary to validate our findings.

Evaluation of arteriovenous fistula for hemodialysis with a new generation digital stethoscope: a pilot study

BACKGROUND AND AIMS

The management of complications of arteriovenous fistula (AVF) for hemodialysis, principally stenosis, remains a major challenge for clinicians with a substantial impact on health resources. Stenosis not infrequently preludes to thrombotic events with the loss of AVF functionality. A functioning AVF, when listened by a stethoscope, has a continuous systolic-diastolic low-frequency murmur, while with stenosis, the frequency of the murmur increases and the duration of diastolic component decreases, disappearing in severe stenosis. These evidences are strictly subjective and dependent from operator skill and experience. New generation digital stethoscopes are able to record sound and subsequently dedicated software allows to extract quantitative variables that characterize the sound in an absolutely objective and repeatable way. The aim of our study was to analyze with an appropriate software sounds from AVFs taken by a commercial digital stethoscope and to investigate the potentiality to develop an objective way to detect stenosis.

METHODS

Between September 2022 and January 2023, 64 chronic hemodialysis (HD) patients were screened by two blinded experienced examiners for recognized criteria for stenosis by Doppler ultrasound (DUS) and, consequently, the sound coming from the AVFs using a 3 M™ Littmann® CORE Digital Stethoscope 8570 in standardized sites was recorded. The sound waves were transformed into quantitative variables (amplitude and frequency) using a sound analysis software. The practical usefulness of the core digital stethoscope for a quick identification of an AVF stenosis was further evaluated through a pragmatic trial. Eight young nephrologist trainees underwent a simple auscultatory training consisting of two sessions of sound auscultation focusing two times on a "normal" AVF sound by placing the digital stethoscope on a convenience site of a functional AVF.

RESULTS

In 48 patients eligible, all sound components displayed, alone, a remarkable diagnostic capacity. More in detail, the AUC of the average power was 0.872 [95% CI 0.729-0.951], while that of the mean normalized frequency was 0.822 [95% 0.656-0.930]. From a total of 32 auscultations (eight different block sequences, each one comprising four auscultations), the young clinicians were able to identify the correct sound (stenosis/normal AVF) in 25 cases, corresponding to an overall accuracy of 78.12% (95% CI 60.03-90.72%).

CONCLUSIONS

The analysis of sound waves by a digital stethoscope permitted us to distinguish between stenotic and no stenotic AVFs. The standardization of this technique and the introducing of data in a deep learning algorithm could allow an objective and fast method for a frequent monitoring of AVF.

New Insights on the Role of Marinobufagenin from Bench to Bedside in Cardiovascular and Kidney Diseases

Marinobufagenin (MBG) is a member of the bufadienolide family of compounds, which are natural cardiac glycosides found in a variety of animal species, including man, which have different physiological and biochemical functions but have a common action on the inhibition of the adenosine triphosphatase sodium-potassium pump (Na+/K+-ATPase). MBG acts as an endogenous cardiotonic steroid, and in the last decade, its role as a pathogenic factor in various human diseases has emerged. In this paper, we have collated major evidence regarding the biological characteristics and functions of MBG and its implications in human pathology. This review focused on MBG involvement in chronic kidney disease, including end-stage renal disease, cardiovascular diseases, sex and gender medicine, and its actions on the nervous and immune systems. The role of MBG in pathogenesis and the development of a wide range of pathological conditions indicate that this endogenous peptide could be used in the future as a diagnostic biomarker and/or therapeutic target, opening important avenues of scientific research.

Pleiotropic effect of erythropoiesis-stimulating agents on circulating endothelial progenitor cells in dialysis patients

BACKGROUND

Recent studies have suggested that erythropoiesis-stimulating agents (ESAs) may accelerate not only angiogenesis but also vasculogenesis, beyond erythropoiesis.

METHODS

We conducted a 12-week prospective study in 51 dialysis patients; 13 were treated with recombinant human erythropoietin (EPO, 5290.4 ± 586.9 IU/week), 16 with darbepoetin (DA, 42.9 ± 4.3 µg/week), 12 with epoetin β pegol (CERA, 40.5 ± 4.1 µg/week) and 10 with no ESAs. Vascular mediators comprising endothelial progenitor cells (EPCs), vascular endothelial growth factor (VEGF), matrix metalloproteinase-2 (MMP-2), and high-sensitivity C-reactive protein (hs-CRP) were measured at 0 and 12 weeks. EPCs were measured by flow cytometry as CD45^lowCD34⁺CD133⁺ cells.

RESULTS

The EPC count increased significantly to a greater extent in the EPO group than in the other three group, and increased significantly from 0 to 12 weeks in a EPO dose-dependent manner. In both the DA and CERA groups, the EPC count did not change at 12 weeks. Serum levels of VEGF, MMP-2 and hs-CRP were not affected by ESA treatment in all groups. In the CERA group, serum ferritin decreased significantly compared to the no-ESA group and correlated with CERA dose, although use of iron was permitted if required during the prospective study period of 12 weeks.

CONCLUSIONS

When patients on dialysis were treated with clinical doses of various ESAs, only EPO induced a significant increase of circulating EPCs from bone marrow, whereas, DA and CERA had no effect.

Circulating Endothelial Progenitor Cell Levels Predict Cardiovascular Events in End-Stage Renal Disease Patients on Maintenance Hemodialysis

BACKGROUND

The number of circulating endothelial progenitor cells (EPCs) has been identified as a surrogate biologic marker for vascular function and cumulative cardiovascular (CV) risk in the general population. Patients with end-stage renal disease (ESRD) on hemodialysis (HD) have markedly decreased EPC counts and function. We hypothesized that the number of circulating EPCs predicts death from all causes and CV events in patients with ESRD on HD.

METHODS

We quantified the EPCs in blood samples from 70 patients with ESRD on HD. Circulating EPCs were counted by flow cytometry as the number of CD45(low)CD34(+)VEGFR2(+) cells. Death from all causes and CV events served as outcome variables over a median follow-up period of 20 months.

RESULTS

It has been postulated that the number of circulating EPCs at baseline ranged from 1 to 350 cells/200 μl, with a mean of ± standard deviation (SD) of 26.0 ± 48.2 cells/200 μl. The median, lowest and highest tertiles of EPC counts were 11.0, 9.0, and 17.0 cells/200 μl, respectively. Patients with the lowest tertile EPC counts had significantly higher rates of CV events, but mortality was similar between the two groups. After adjusting for these risk factors, HbA1c and the lowest tertile EPC count remained as independent predictors of CV events. A cutoff value of 9.5 cells/200 μl maximized the power of the EPC count to predict future CV events as determined by ROC curve analysis.

CONCLUSIONS

Reduced circulating EPC counts independently predicted CV events in 70 patients with ESRD on maintenance HD. Circulating EPCs may play a role in vascular repair, thereby affecting the clinical course of CV events.

Impact of serum source and inflammatory cytokines on the isolation of endothelial colony-forming cells from peripheral blood

Endothelial colony-forming cells (ECFCs) isolated from peripheral blood are a highly promising cell source for a wide range of applications, including tissue engineering, in vivo vasculogenesis and anti-cancer therapeutics. Because of the potential for clinical translation, it is increasingly important to isolate and study ECFCs from patient cohorts that may benefit from such technologies. The primary objective of this investigation was to determine whether ECFCs could be obtained from patients with chronic kidney disease and diabetes (CKD-DM), using techniques that can be readily applied in the clinical setting. We also investigated the impact of autologous vs commercially available (i.e. allogeneic) human serum on ECFCs isolation. Surprisingly, the efficacy of ECFCs isolation from the CKD-DM group was comparable to a healthy control group when autologous serum was used. In contrast, substitution of allogeneic serum reduced ECFCs isolation in CKD-DM and control groups. In characterization studies, ECFCs were positive for several endothelial cell markers. ECFCs from the CKD-DM group were sensitive to inflammatory activation but their cellular proliferation was compromised. The concentrations of IL-4 and IL-8 were significantly increased in allogeneic serum, which induced a pro-inflammatory environment, including the release of IL-4, IL-6, IL-8 and MCP-1 into the conditioned media of cell cultures. Taken together, these data support further investigation into the use of autologous serum and cells for ECFC-based therapeutics and underscore the importance of the cytokine content in serum used for ECFCs isolation.

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.

Endothelial progenitor cells: a novel tool for the therapy of ischemic diseases

Circulating endothelial progenitor cells (EPCs) are believed to home to sites of neovascularization, contributing to vascular regeneration either directly via incorporation into newly forming vascular structures or indirectly via the secretion of pro-angiogenic growth factors, thereby enhancing the overall vascular and hemodynamic recovery of ischemic tissues. The therapeutic application of EPCs has been shown to be effective in animal models of ischemia, and we as well as other groups involved in clinical trials have demonstrated that the use of EPCs was safe and feasible for the treatment of critical limb ischemia and cardiovascular diseases. However, many issues in the field of EPC biology, especially in regard to the proper and unambiguous molecular characterization of these cells, still remain unresolved, hampering not only basic research but also the effective therapeutic use and widespread application of these cells. Further, recent evidence suggests that several diseases and pathological conditions are correlated with a reduction in the number and biological activity of EPCs, making the development of novel strategies to overcome the current limitations and shortcomings of this promising but still limited therapeutic tool by refinement and improvement of EPC purification, expansion, and administration techniques, a rather pressing issue.

Endothelial progenitor cells in patients on extracorporeal maintenance dialysis therapy

BACKGROUND

Chronic renal failure patients have a high cardiovascular disease burden, low numbers and impaired function of endothelial progenitor cells (EPCs). We hypothesized that enhanced uraemic toxin removal restores EPCs in haemodialysis patients.

METHODS

In a prospective, randomized, cross-over trial, 18 patients were subjected to 4 weeks of each low-flux haemodialysis, high-flux haemodialysis and haemodiafiltration differing in uraemic toxin removal. EPCs were determined at baseline and at the end of each 4-week period. A cohort of 16 healthy volunteers served as control. EPCs were studied after culture on fibronectin (CFU-Hill) and collagen-1 (ECFC).

RESULTS

Dialysis patients had a lower number of ECFCs than in healthy controls (P < 0.001) and a reduced fraction of vital ECFCs (P < 0.05), whereas the formation of endothelial cell colonies (ECCs) was increased (P < 0.05). Different middle molecular uraemic toxin removal had no effects on EPC numbers. The number of prototypical EPCs (CD34( +)/VEGFR2-KDR( +)/CD45( -) ECFCs) was similar between patients and controls. Correlations of plasma C-reactive protein with ECC count, CFU-Hill colony count and CD34( +)/VEGFR2-KDR( +)/CD45( -) subpopulation of both ECFC and CFU-Hill cells were observed.

CONCLUSIONS

Different middle molecule removal has no effect on EPCs. Reduced vitality and enhanced ECC formation suggest growth induction of impaired EPCs in chronic renal failure and are associated with inflammation.

Endothelial progenitor cell dysfunction in patients with progressive chronic kidney disease

Endothelial progenitor cells (EPC) contribute to repair and maintenance of the vascular system, but in patients with chronic kidney disease (CKD), the number and function of EPC may be affected by kidney dysfunction. We assessed numbers and the angiogenic function of EPC from patients with CKD in relation to disease progression. In a cross-sectional, prospective study, 50 patients with varying degrees of CKD, including 20 patients undergoing dialysis and 10 healthy controls, were included. Mononuclear cells were isolated, and circulating EPC were quantified by flow cytometry based on expression of CD14 and CD34. EPC were cultured on fibronectin-coated supramolecular films of oligocaprolactone under angiogenic conditions to determine their angiogenic capacity and future use in regenerative medicine. CKD patients had normal numbers of circulating CD14+ EPC but reduced numbers of circulating CD34+ EPC. Furthermore, EPC from patients with CKD displayed functional impairments, i.e., hampered adherence, reduced endothelial outgrowth potential, and reduced antithrombogenic function. These impairments were already observed at stage 1 CKD and became more apparent when CKD progressed. Dialysis treatment only partially ameliorated EPC impairments in patients with CKD. In conclusion, EPC number and function decrease with advancing CKD, which may hamper physiological vascular repair and can add to the increased risk for cardiovascular diseases observed in CKD patients.

Long-term clinical outcome after intramuscular implantation of bone marrow mononuclear cells (Therapeutic Angiogenesis by Cell Transplantation [TACT] trial) in patients with chronic limb ischemia

BACKGROUND

Angiogenic cell therapy by intramuscular injection of autologous bone marrow mononuclear cells was first attempted in patients with peripheral artery disease (PAD) with critical limb ischemia, and the feasibility was shown by a randomized controlled Therapeutic Angiogenesis by Cell Transplantation (TACT) study.

METHODS AND RESULTS

The present study was designed to assess the 3-year safety and clinical outcomes of this angiogenic cell therapy by investigating the mortality and leg amputation-free interval as primary end points. The median follow-up time for surviving patients was 25.3 months (range, 0.8-69.0 months), and 3-year overall survival rates were 80% (95% CI 68-91) in patients with atherosclerotic peripheral arterial disease (11 died in 74 patients) and 100% (no death) in 41 patients with thromboangiitis obliterans (TAO; Buerger's disease). Three-year amputation-free rate was 60% (95% CI 46-74) in PAD and 91% (95% CI 82-100) in patients with TAO. The multivariate analysis revealed that the severity of rest pain and repeated experience of bypass surgery were the prognostic factors negatively affecting amputation-free interval. The significant improvement in the leg pain scale, ulcer size, and pain-free walking distance was maintained during at least 2 years after the therapy, although the ankle brachial index and transcutaneous oxygen pressure value did not significantly change.

CONCLUSIONS

The angiogenic cell therapy using bone marrow mononuclear cells can induce a long-term improvement in limb ischemia, leading to extension of amputation-free interval. The safety and efficacy are not inferior to the conventional revascularization therapies.

Perioperative iloprost and endothelial progenitor cells in uremic patients with severe limb ischemia undergoing peripheral revascularization

The incidence of severe limb ischemia (SLI) is high among haemodialysis (HD) patients. Limb rescue rate after surgical revascularization is relatively poor compared with patients with normal renal function. Prostanoids are an interesting category as adjuvants to revascularization. New vessel growth develops not exclusively by proliferation of endothelial cells in vascular extremities but also by cells mobilized from the bone marrow (HSC), transformed into endothelial progenitor cells (EPC) contributing to both re-endothelialization and neovascularization. Basal number of HSC and EPC is significantly reduced in HD patients and correlated with a subsequent defective neovascularization. The aim of this study was to evaluate the effects of perioperative treatment with iloprost in uremic patients with acute ischemia of lower limbs, undergoing surgical revascularization, on endothelial progenitor cells, hypothesizing a possible biological mechanism induced by the prostanoids. A search was also made for vascular remodeling processes through the analysis of the concentrations of soluble adhesion molecules (i-CAM, v-CAM, e-selectin), biochemical markers of endothelial activation. Thirty HD patients with SLI undergoing peripheral revascularization were enrolled (15 were treated with iloprost and 15 with a placebo). Iloprost was administered as an intra-arterial bolus of 3000 ng over 1 to 3 min immediately after revascularization and in the same affected artery. Serum samples were taken before revascularization (T0), at 6 (T6) and 24 h (T24) after infusion to measure sICAM-1, sE-selectin, and sVCAM-1, and for quantification of HSC and EPC. Progenitors were identified by specific surface markers CD34+, CD133+ and VEGFR2+. Count was conducted using PROCOUNT performed in a TRUCOUNT tube and with a FACSort flow cytometer. Before revascularization, all patients showed a decreased number of HSC and EPC. After 6 h, HSC augmented significantly compared with T0 in both groups. The iloprost group attained a significant increase compared with the placebo group. HSC levels reduced drastically at T24. EPC augmented significantly compared with basal level after 24 h. In the iloprost group, the increase was considerable compared with the placebo group. A close negative correlation, assessed by Pearson coefficient (r), was found between HSC and EPC at T24 in the iloprost group (R = 0.82 P < 0.01). Adhesion molecules had increased levels at T6 and T24 in both groups. Moreover, a close positive correlation, assessed by Pearson coefficient, was found between EPC and adhesion molecules in both groups but the iloprost group maintained a better statistical association. Revascularization stimulated HSC and EPC release from bone marrow but at a different time: HSC increased suddenly at 6 h and diminished to a minimal amount at T24, conversely, EPC increased significantly only at T24. Iloprost treatment was able to amplify this mechanism validating recent findings (North TE et al., [31]). Adhesion molecules as markers of endothelial activation and vascular development confirmed this tendency.

Endothelial progenitor cells in neovascularization of infarcted myocardium

Historically, revascularization of ischemic tissue was believed to occur through the migration and proliferation of endothelial cells in nearby tissues; however, evidence accumulated in recent years indicates that a subpopulation of adult, peripheral-blood cells, collectively referred to as endothelial progenitor cells (EPCs), can differentiate into mature endothelial cells. After ischemic insult, EPCs are believed to home to sites of neovascularization, where they contribute to vascular regeneration by forming a structural component of capillaries and by secreting angiogenic factors; new evidence indicates that EPCs can also differentiate into cardiomyocytes and smooth-muscle cells. These insights into the molecular and cellular processes of tissue formation suggest that cardiac function may be preserved after myocardial infarction by transplanting EPCs into ischemic heart tissue, thereby enhancing vascular and myocardial recovery. This therapeutic strategy has been effective in animal models of ischemic disorders, and results from randomized clinical trials suggest that cell-based strategies may be safe and feasible for treatment of myocardial infarction in humans and have provided early evidence of efficacy. However, the scarcity of EPCs in the peripheral blood and evidence that several disease states reduce EPC number and/or function have prompted the development of several strategies to overcome these limitations, such as the administration of genetically modified EPCs that overexpress angiogenic growth factors. To optimize therapeutic outcomes, researchers must continue to refine methods of EPC purification, expansion, and administration, and to develop techniques that overcome the intrinsic scarcity and phenotypic deficiencies of EPCs.