Erythropoietin regulates endothelial progenitor cells

Endothelial progenitor cells are suppressed in anemic patients with acute coronary syndrome

OBJECTIVE

Anemia is an independent predictor of poor prognosis in acute coronary syndrome. Endothelial progenitor cells are bone marrow-derived cells that are mobilized into the circulation in response to ischemia. The number of circulating endothelial progenitor cells increases within days of acute coronary syndrome. There is no confirmation regarding the correlation between the occurrence of anemia and the deficiency in endothelial progenitor cells in patients with acute coronary syndrome. The correlation between chronic anemia and endothelial progenitor cells in patients with acute coronary syndrome was investigated.

METHODS

Endothelial progenitor cells were examined in 26 patients with acute coronary syndrome. Fifteen patients had chronic nonprogressive anemia, and 11 patients had a normal blood count. Blood samples were drawn on the first day of admission and 4 to 7 days later. Mononuclear cells were separated and cultured on fibronectin-coated plates with EndoCult medium (StemCell Technologies, Vancouver, BC, Canada) for 5 days. Colony forming unit count and a migration assay were performed at each time point.

RESULTS

Baseline colony forming unit in the non-anemic group was higher than in the anemic group (P<.0001). There was a highly significant correlation between admission hemoglobin and colony forming unit count (R=0.83, P<.0001). Colony forming units increased in both groups on the second measurement but to a lower extent in the anemic group (P = .0004). The migration assay in the non-anemic group was higher than in the anemic group at baseline (P = .017) and 4 to 7 days later (P = .0054).

CONCLUSION

Patients with acute coronary syndrome with anemia demonstrate a reduced number of peripheral endothelial progenitor cells with impaired function, possibly representing a lower capacity for vascular healing. These phenomena may partly explain the poor prognosis observed in patients with acute coronary syndrome and anemia.

Erythropoietin-induced changes in brain gene expression reveal induction of synaptic plasticity genes in experimental stroke

Erythropoietin (EPO) is a neuroprotective cytokine in models of ischemic and nervous system injury, where it reduces neuronal apoptosis and inflammatory cytokines and increases neurogenesis and angiogenesis. EPO also improves cognition in healthy volunteers and schizophrenic patients. We studied the effect of EPO administration on the gene-expression profile in the ischemic cortex of rats after cerebral ischemia at early time points (2 and 6 h). EPO treatment up-regulated genes already increased by ischemia. Hierarchical clustering and analysis of overrepresented functional categories identified genes implicated in synaptic plasticity-Arc, BDNF, Egr1, and Egr2, of which Egr2 was the most significantly regulated. Up-regulation of Arc, BDNF, Dusp5, Egr1, Egr2, Egr4, and Nr4a3 was confirmed by quantitative PCR. We investigated the up-regulation of Egr2/Krox20 further because of its role in neuronal plasticity. Its elevation by EPO was confirmed in an independent in vivo experiment of cerebral ischemia in rats. Using the rat neuroblastoma B104, we found that wild-type cells that do not express EPO receptor (EPOR) do not respond to EPO by inducing Egr2. However, EPOR-expressing B104 cells induce Egr2 early upon incubation with EPO, indicating that Egr2 induction is a direct effect of EPO and that EPOR mediates this effect. Because these changes occur in vivo before decreased inflammatory cytokines or neuronal apoptosis is evident, these findings provide a molecular mechanism for the neuroreparative effects of cytokines and suggest a mechanism of neuroprotection by which promotion of a plastic phenotype results in decreased inflammation and neuronal death.

Bone marrow-CNS connections: implications in the pathogenesis of diabetic retinopathy

Diabetic retinopathy is the fourth most common cause of blindness in adults. Current therapies, including anti-VEGF therapy, have partial efficacy in arresting the progression of proliferative diabetic retinopathy and diabetic macular edema. This review provides an overview of a novel, innovative approach to viewing diabetic retinopathy as the result of an inflammatory cycle that affects the bone marrow (BM) and the central and sympathetic nervous systems. Diabetes associated inflammation may be the result of BM neuropathy which skews haematopoiesis towards generation of increased inflammatory cells but also reduces production of endothelial progenitor cells responsible for maintaining healthy endothelial function and renewal. The resulting systemic inflammation further impacts the hypothalamus, promoting insulin resistance and diabetes, and initiates an inflammatory cascade that adversely impacts both macrovascular and microvascular complications, including diabetic retinopathy (DR). This review examines the idea of using anti-inflammatory agents that cross not only the blood-retinal barrier to enter the retina but also have the capability to target the central nervous system and cross the blood-brain barrier to reduce neuroinflammation. This neuroinflammation in key sympathetic centers serves to not only perpetuate BM pathology but promote insulin resistance which is characteristic of type 2 diabetic patients (T2D) but is also seen in T1D. A case series of morbidly obese T2D patients with retinopathy and neuropathy treated with minocycline, a well-tolerated antibiotic that crosses both the blood-retina and blood-brain barrier is presented. Our results indicates that minocycine shows promise for improving visual acuity, reducing pain from peripheral neuropathy, promoting weight loss and improving blood pressure control and we postulate that these observed beneficial effects are due to a reduction of chronic inflammation.

Endothelial progenitor cells in diabetes mellitus

Diabetes mellitus is associated with an increased risk of cardiovascular disease due to its negative impact on the vascular endothelium. The damaged endothelium is repaired by resident cells also through the contribution of a population of circulating cells derived from bone marrow. These cells, termed endothelial progenitor cells (EPCs) are involved in maintaining endothelial homeostasis and contributes to the formation of new blood vessels with a process called postnatal vasculogenesis. The mechanisms whereby these cells allow for protection of the cardiovascular system are still unclear; nevertheless, consistent evidences have shown that impairment and reduction of EPCs are hallmark features of type 1 and type 2 diabetes. Therefore, EPC alterations might have a pathogenic role in diabetic complications, thus becoming a potential therapeutic target. In this review, EPC alterations will be examined in the context of macrovascular and microvascular complications of diabetes, highlighting their roles and functions in the progression of the disease.

The nonhematopoietic effects of erythropoietin in skin regeneration and repair: from basic research to clinical use

Erythropoietin (EPO) is the main regulator of red blood cell production but there exists also a variety of nonhematopoietic properties. More recent data show that EPO is also associated with the protection of tissues suffering from ischemia and reperfusion injury as well as with improved regeneration in various organ systems, in particular the skin. This review highlights the mechanisms of EPO in the different stages of wound healing and the reparative processes in the skin emphasizing pathophysiological mechanisms and potential clinical applications. There is clear evidence that EPO effectively influences all wound-healing phases in a dose-dependent manner. This includes inflammation, tissue, and blood vessel formation as well as the remodeling of the wound. The molecular mechanism is predominantly based on an increased expression of the endothelial and inducible nitric oxide (NO) synthase with a consecutive rapid supply of NO as well as an increased content of vascular endothelial growth factor (VEGF) in the wound. The improved understanding of the functions and regulatory mechanisms of EPO in the context of wound-healing problems and ischemia/reperfusion injury, especially during flap surgery, may lead to new considerations of this growth hormone for its regular clinical application in patients.

Stem cells for cardiac repair in acute myocardial infarction

Despite recent advances in medical therapy, reperfusion strategies, implantable cardioverter-defibrillators and cardiac assist devices, ischemic heart disease is a frequent cause of morbidity and mortality worldwide. Cell therapy has been introduced as a new treatment modality to regenerate lost cardiomyocytes. At present, several cell types seem to improve left ventricular function in animal models as well as in humans, but evidence for true generation of new myocardium is confined to the experimental models. In the clinical perspective, myocardial regeneration has been replaced by myocardial repair, as other mechanisms seem to be involved. Clinical studies on adult stem cells suggest, at best, moderate beneficial effects on surrogate end points, but some applications may qualify for evaluation in larger trials. Complete regeneration of the myocardium by cell therapy after a large myocardial infarction is still visionary, but pluripotent stem cells and tissue engineering are important tools to solve the puzzle.

Autologous peripheral blood-derived mononuclear cells induced by erythropoietin improve critical ischemic limbs

PURPOSE

Efficient and secure collection of CD34+ cells are crucial for the angiogenic therapies. We have developed autologous peripheral blood-mononuclear cell (MNC) transplantation induced by erythropoietin (rhEPO) for critical ischemic limbs.

METHODS

Seven patients, including five with arteriosclerosis obliterans, one with Buerger's disease and one with progressive systemic sclerosis, underwent ten cell therapies. The first administration of rhEPO was performed two weeks before apheresis, and the second administration and blood donation were performed one week before apheresis to activate bone marrow. MNCs including CD34+ cells, isolated from peripheral blood by apheresis, were immediately injected intramuscularly into ischemic limbs.

RESULTS

The number of peripheral blood-CD34 + cells had significantly increased from 1.32 ± 0.83/microL, before the rhEPO induction, to 1.86 ± 0.94/microL, before the apheresis. The number of transplanted MNCs ranged between 0.5 × 10(9) and 16.5 × 10(9), and that of CD34+ cells, between 0.1 × 10(6) and 12.7 × 10(6), accounting for 0.02%-0.1% of MNCs. There were no serious complications. Finger ulcers with Buerger's disease were significantly improved one month after the transplantations, but the same or other ulcer(s) appeared 2-6 months later. Three patients had an improvement in rest pain, and one patient extended maximum pain-free walking distance.

CONCLUSIONS

Erythropoietin-induced autologous peripheral blood-MNC transplantation is a useful and safe alternative for ischemic limbs.

Decrease in incidence of bronchopulmonary dysplasia with erythropoietin administration in preterm infants: a retrospective study

BACKGROUND

Despite advances in clinical care, the incidence of bronchopulmonary dysplasia (BPD) remains high in premature infants. Erythropoietin (EPO) is used for the treatment of anemia of prematurity (AOP) to decrease blood transfusion needs. EPO has been shown to mobilize circulating endothelial progenitor cells and to enhance lung repair in animal models.

OBJECTIVE

To determine whether EPO treatment for AOP was associated with a reduced incidence of BPD in premature infants.

METHODS

This retrospective study was performed on all live-born neonates with birth weights from 500 to 1,500 g and gestational age (GA) from 22 to 32 weeks admitted from 1994 to 2002. Infants who received EPO and those who did not receive EPO were compared for incidence of BPD and other morbidities.

RESULTS

Of 478 patients, 297 received EPO before 36 weeks' postmenstrual age (group 1) and 181 did not receive EPO (group 2). Group 1 was of similar birth weight but lower GA than group 2. The incidence of BPD was lower in group 1 than group 2 (26 vs. 36%, p = 0.03); after adjusting for significant risk factors, the adjusted odds ratio for BPD was 0.50 (95% CI 0.32, 0.79), p = 0.0028. The BPD rate was much lower when EPO was initiated before 4 weeks of age (16%) as compared to later initiation (44%).

CONCLUSIONS

This study shows an association between EPO treatment and reduced incidence of BPD in preterm infants, particularly when EPO treatment was initiated within the first 4 weeks of life.

Fast reduction of peripheral blood endothelial progenitor cells in healthy humans exposed to acute systemic hypoxia

There are hints that hypoxia exposure may affect the number of circulating endothelial progenitor cells (EPCs) in humans. To test this hypothesis, the concentration of EPCs was determined by flow cytometry in the peripheral blood of 10 young healthy adults before (0 h), at different times (0.5 h, 1 h, 2 h and 4 h) during a 4 h normobaric hypoxic breathing simulating 4100 m altitude, and in the following recovery breathing room air. Results were interpreted mainly on the basis of the changes in surface expression of CXC chemokine receptor-4 (CXCR-4, a chemokine receptor essential for EPC migration and homing) and the percentage of apoptotic cells, the plasmatic levels of markers of oxidative stress induced by hypoxic breathing. Compared to 0 h, the concentration of EPCs, identified as either CD45(dim)/CD34(+)/KDR(+) or CD45(dim)/CD34(+)/KDR(+)/CD133(+) cells, decreased from 337 ± 83 ml(-1) (mean ± SEM) to 223 ± 52 ml(-1) (0.5 h; P < 0.005) and 100 ± 37 ml(-1) (4 h; P < 0.005), and from 216 ± 91 to 161 ± 50 ml(-1) (0.5 h; P < 0.05) and 45 ± 23 ml(-1) (4 h; P < 0.005), respectively. Upon return to normoxia, their concentration increased slowly, and after 4 h was still lower than at 0 h (P < 0.05). During hypoxia, CXCR-4 expression and plasmatic stromal derived cell factor-1 (SDF-1) increased abruptly (0.5 h: +126% and +13%, respectively; P < 0.05), suggesting cell marginalization as a possible cause of the rapid hypoxia-induced EPC reduction. Moreover, hypoxia exposure induced an increase in EPC apoptosis and markers of oxidative stress, which was significantly evident only starting from 2 h and 4 h after hypoxia offset, respectively, suggesting that EPC apoptosis may contribute to the later phase of hypoxia-induced EPC reduction. Overall, these observations may provide new insights into the understanding of the mechanisms operated by EPCs to maintain endothelial homeostasis.

Incremental increase in VEGFR1⁺ hematopoietic progenitor cells and VEGFR2⁺ endothelial progenitor cells predicts relapse and lack of tumor response in breast cancer patients

Animal models have demonstrated the critical role of bone marrow-derived VEGFR1(+) hematopoietic progenitor cells (HPCs) and VEGFR2(+) endothelial progenitor cells (EPCs) in metastatic progression. We explored whether these cells could predict relapse and response in breast cancer (BC) patients. One hundred and thirty-two patients with stages 1-4 BC were enrolled on 2 studies. Circulating CD45(+)/CD34(+)/VEGFR1(+) HPCs and CD45(dim)/CD133(+)/VEGFR2(+) EPCs were assessed from peripheral blood mononuclear cells using flow cytometry. Changes in HPCs and EPCs were analyzed in (1) patients without overt disease that relapsed and (2) metastatic patients according to response by RECIST. At study entry, 102 patients were without evidence of disease and 30 patients had metastatic BC. Seven patients without evidence of BC by exam, labs, and imaging developed recurrence while on study. Median HPC/ml (range) increased from 645.8 (23.5-1,914) to 2,899 (1,176-37,336), P = 0.016, followed by an increase in median EPC/ml from 21.3 (4.7-42.5) to 94.7 (28.2-201.3), P = 0.016, prior to clinical relapse. In metastatic patients with progressive disease, median HPC/ml increased from 1,696 (10-16,470) to 5,124 (374-77,605), P = 0.0009, and median EPC/ml increased from 26 (0-560) to 71 (0-615) prior to progression, P = 0.10. In patients with responding disease, median HPC/ml decreased from 6,147 (912-85,070) to 633 (47-18,065), P = 0.05, and EPC/ml decreased from 46 (0-197) to 23 (0-105), P = 0.41, at response. There were no significant changes in these cells over time in patients with stable disease. Circulating bone marrow-derived HPCs and EPCs predict relapse and disease progression in BC patients.

PDGF-BB modulates hematopoiesis and tumor angiogenesis by inducing erythropoietin production in stromal cells

The platelet-derived growth factor (PDGF) signaling system contributes to tumor angiogenesis and vascular remodeling. Here we show in mouse tumor models that PDGF-BB induces erythropoietin (EPO) mRNA and protein expression by targeting stromal and perivascular cells that express PDGF receptor-β (PDGFR-β). Tumor-derived PDGF-BB promoted tumor growth, angiogenesis and extramedullary hematopoiesis at least in part through modulation of EPO expression. Moreover, adenoviral delivery of PDGF-BB to tumor-free mice increased both EPO production and erythropoiesis, as well as protecting from irradiation-induced anemia. At the molecular level, we show that the PDGF-BB-PDGFR-bβ signaling system activates the EPO promoter, acting in part through transcriptional regulation by the transcription factor Atf3, possibly through its association with two additional transcription factors, c-Jun and Sp1. Our findings suggest that PDGF-BB-induced EPO promotes tumor growth through two mechanisms: first, paracrine stimulation of tumor angiogenesis by direct induction of endothelial cell proliferation, migration, sprouting and tube formation, and second, endocrine stimulation of extramedullary hematopoiesis leading to increased oxygen perfusion and protection against tumor-associated anemia.

Vascular incompetence in dialysis patients--protein-bound uremic toxins and endothelial dysfunction

Patients with chronic kidney disease (CKD) have a much higher risk of cardiovascular diseases than the general population. Endothelial dysfunction, which participates in accelerated atherosclerosis, is a hallmark of CKD. Patients with CKD display impaired endothelium-dependent vasodilatation, elevated soluble biomarkers of endothelial dysfunction, and increased oxidative stress. They also present an imbalance between circulating endothelial populations reflecting endothelial injury (endothelial microparticles and circulating endothelial cells) and repair (endothelial progenitor cells). Endothelial damage induced by a uremic environment suggests an involvement of uremia-specific factors. Several uremic toxins, mostly protein-bound, have been shown to have specific endothelial toxicity: ADMA, homocysteine, AGEs, and more recently, p-cresyl sulfate and indoxyl sulfate. These toxins, all poorly removed by hemodialysis therapies, share mechanisms of endothelial toxicity: they promote pro-oxidant and pro-inflammatory response and inhibit endothelial repair. This article (i) reviews the evidence for endothelial dysfunction in CKD, (ii) specifies the involvement of protein-bound uremic toxins in this dysfunction, and (iii) discusses therapeutic strategies for lowering uremic toxin concentrations or for countering the effects of uremic toxins on the endothelium.

Endogenous serum erythropoietin and no-reflow in patients with ST-elevation myocardial infarction

BACKGROUND

In models of acute ischaemia, erythropoietin (EPO) administration has been found to attenuate vascular injury largely through reduced apoptosis, suppressed inflammation and increased nitric oxide availability. We studied the association between circulating endogenous EPO and no-reflow in patients with first ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention (PPCI).

METHODS

Blood sampling was performed before PPCI. Consecutive patients with (n = 24) or without (n = 24) evidence of angiographic no-reflow after PPCI were enrolled. Angiographic no-reflow was defined as Thrombolysis in Myocardial Infarction (TIMI) flow ≤ 2 or as TIMI flow = 3 but with myocardial blush grade < 2. We also assessed electrocardiographic (ECG) no-reflow as ≤ 50% resolution of maximal ST elevation 60 min after PPCI.

RESULTS

Baseline characteristics did not correlate significantly with EPO concentrations. In contrast, both angiographic and ECG no-reflow correlated with lower EPO levels at univariate analysis [median (interquartile): 4·2 (0·6-9·5) vs. 12·2 (5·2-20·3) mIU mL(-1), P = 0·001, and 4·0 (0·6-7·1) vs. 9·3 (1·0-12·6) mIU mL(-1), P = 0·01, respectively]. At multivariable analysis, decreasing EPO tertiles and left anterior descending as the infarct-related artery were the only factors that predicted both angiographic and ECG no-reflow (P = 0·017 and P = 0·02 for EPO; P < 0·005 and P > 0·05 for left anterior descending artery, respectively).

CONCLUSIONS

We found an independent, graded, inverse relation between endogenous EPO levels and angiographic and ECG no-reflow following PPCI. In animal models of ischaemia, EPO has been found to be protective. In humans, endogenous EPO may contribute to offset the mechanisms responsible for no-reflow.

Proteinuria is a predictor of posttransplant anemia

INTRODUCTION

Posttransplant anemia (PTA) involves many factors. Although the link between the hemoglobin (Hb) levels and renal function is known, the relationship between proteinuria and PTA hemoglobin has not been widely explored. The aim of this study was to evaluate whether proteinuria was a predictor of anemia and whether erythropoietin-stimulating agent therapy was a protective factor for kidney damage among transplantation patients.

METHODS

We retrospectively examined 144 kidney transplant recipients of mean age 44.4 ± 12.3 years and a mean follow-up period of 40.5 ± 4.6 months. Exclusion criteria were age under 18 years, multiorgan transplantation, proteinuria at 6 months over 1.5 g/d, and transplant failure within the first year. Using regression models, we evaluated the potential predictive power of proteinuria at 6 months after renal transplantation for anemia as expressed by Hb levels at 1 year.

RESULTS

The frequency of patients with PTA was 38.89% at 1 year, 35.21% at 2 years, and 31.43% at 3 years. Variables with significant correlations with anemia upon univariate analysis were: proteinuria, donor age, acute rejection, estimated glomerular filtration rate, s-creatinine, and salbumin. Upon multivariate regression analysis 24-hour proteinuria and s-albumin remained independent predictors of 1-year PTA. Univariate analysis among the entire cohort showed a significant correlation between 1-year Hb and proteinuria/24 hours at 6 months (P=.007), an observation that was confirmed in the adjusted model along with recipient sex. Patients were then divided into two groups regarding treatment with erythropoiesis stimulating agents (ESA). Multivariate analysis showed that proteinuria (P=.005) was a predictor of Hb only among the group of patients who did no receive erythropoietin, whereas this relationship disappeared among the group treated with ESA.

CONCLUSIONS

These results showed that proteinuria at 6 months was a predictor of Hb levels at 1 year. Treatment of transplant patients with ESA may be a protective factor for renal endothelial damage expressed as proteinuria.

Effect of darbepoetin alfa on endothelial progenitor cells and vascular reactivity in chronic kidney disease

Endothelial progenitor cells (EPCs) are thought to be important for maintaining normal vascular function. We conducted a prospective study evaluating the effect of the erythropoiesis-stimulating agent darbepoetin alfa on EPCs and vascular function in patients with chronic kidney disease (CKD), with or without diabetes. Thirty subjects with CKD (20 subjects with type II diabetes mellitus and 10 without diabetes mellitus) received weekly subcutaneous administration of darbepoetin alfa for 4 weeks. EPCs were measured at baseline and 2 and 4 weeks after drug administration. Vascular function was measured with brachial ultrasound and cell activity was measured with a cell proliferation assay. Cells expressing CD133, CD34, CD146 and CD146/31 were significantly elevated (all p < 0.05), flow-mediated vasodilatation increased 2.1%, 95% CI: (0.4%, 3.8%) and colony-forming units increased twofold, 95% CI: (1.7, 2.3) after 4 weeks of treatment with darbepoetin alfa. Subjects with diabetes exhibited an increase in a subset of EPCs (CD133( +) and 34(+), p < 0.01 and p = 0.06, respectively), vasodilatation and proliferation. In conclusion, the administration of darbepoetin alfa for 4 weeks increased a subset of EPCs, improved endothelial function and increased cell proliferation, including those with diabetes, which is consistent with a favorable improvement in vascular health.

Echocardiographic markers of elevated pulmonary pressure and left ventricular diastolic dysfunction are associated with exercise intolerance in adults and adolescents with homozygous sickle cell anemia in the United States and United Kingdom

BACKGROUND

Noninvasively assessed pulmonary pressure elevations and left ventricular (LV) diastolic dysfunction are associated with increased mortality in adults with sickle cell disease, but their relationship to exercise intolerance has not been evaluated prospectively.

METHODS AND RESULTS

Echocardiography, 6-minute walk distance, hemolytic rate, and serum concentrations of ferritin and erythropoietin were evaluated in a cohort of 483 subjects with homozygous hemoglobin S in the U.S. and U.K. Walk-Treatment of Pulmonary Hypertension and Sickle Cell Disease with Sildenafil Therapy (Walk-PHaSST) study. Tricuspid regurgitation velocity, which reflects systolic pulmonary artery pressure, was 2.7 to <3.0 m/s (mean±SD, 2.8±0.1) in 26% of the subjects and ≥3.0 m/s (mean±SD, 3.4±0.4) in 11%. The LV lateral E/e' ratio, which has been shown to reflect LV filling pressure in other conditions but has not been studied in sickle cell disease, was significantly higher in the groups with tricuspid regurgitation velocity ≥2.7 m/s. Increased hemolysis (P<0.0001), LV lateral E/e' ratio (P=0.0001), blood urea nitrogen (P=0.0002), and erythropoietin (P=0.002) were independently associated with an increased tricuspid regurgitation velocity. Furthermore, female sex (P<0.0001), older age (P<0.0001), LV lateral E/e' ratio (P=0.014), and tricuspid regurgitation velocity (P=0.019) were independent predictors of a shorter 6-minute walk distance.

CONCLUSIONS

Echocardiography-estimated elevated pulmonary artery systolic pressure and LV lateral E/e' ratio were independently associated with poor exercise capacity in a large cohort of patients with sickle cell anemia. Controlled trials investigating whether strategies to prevent or delay pulmonary hypertension and/or LV diastolic dysfunction will improve exercise capacity and long-term outcomes in sickle cell anemia should be considered. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00492531.

A pilot study of chronic, low-dose epoetin-{beta} following percutaneous coronary intervention suggests safety, feasibility, and efficacy in patients with symptomatic ischaemic heart failure

AIMS

Low-dose epoetin-β improved neo-angiogenesis and cardiac regeneration in experimental models of ischaemic cardiomyopathy without raising haemoglobin. No clinical study has tested this approach to date.

METHODS AND RESULTS

We performed a randomized, placebo-controlled, double-blind, single-centre study of 35 IU/kg body weight epoetin-β given subcutaneously once weekly for 6 months started within 3 weeks after successful percutaneous coronary intervention (PCI). Patients were included if they presented with a lesion within the proximal segment of the left anterior descending artery, the right coronary artery, or circumflex and had symptomatic heart failure. Patients with ST-segment elevation due to an acute myocardial infarct were excluded. The outcome variables were measured at baseline and at 6 months. Primary outcome measure was individual change in ejection fraction; secondary outcome was safety, change in N-terminal pro-brain natriuretic peptide, and peak VO(2). Twenty-four patients completed the 6-month treatment course. No adverse event related to the treatment occurred. Low-dose epoetin-β following PCI significantly improved global ejection fraction as measured by echocardiography (EPO: ΔEF 5.2 ± 2.0%, P= 0.013; placebo: ΔEF 0.3 ± 1.6%, P= 0.851; P= 0.019 for the inter-group difference) and cardiac magnetic resonance (EPO: ΔEF 3.1 ± 1.6%, P= 0.124; placebo: -1.9 ± 1.2%, P= 0.167; P= 0.042 for the inter-group difference). N-terminal pro-brain natriuretic peptide levels decreased in both groups without significant inter-group differences. Peak VO(2) levels increased significantly by 3.9 ± 1.1% (P< 0.05) in the EPO group, whereas in the placebo group the increase did not reach statistical significance (Δpeak VO(2) 3.0 ± 1.6, P = ns). No significant difference regarding peak VO(2) was observed between the EPO and placebo groups.

CONCLUSIONS

Low-dose epoetin-β treatment following PCI is safe and feasible, and has possible beneficial effects on global ejection fraction and measures of exercise capacity. Extended low-dose epoetin-β treatment warrants further mechanistic studies as well as larger clinical trials.

CLINICAL TRIAL REGISTRATION INFORMATION

NCT00568542.

Isolation and characterization of human anterior cruciate ligament-derived vascular stem cells

The anterior cruciate ligament (ACL) usually fails to heal after rupture mainly due to the inability of the cells within the ACL tissue to establish an adequate healing process, making graft reconstruction surgery a necessity. However, some reports have shown that there is a healing potential of ACL with primary suture repair. Although some reports showed the existence of mesenchymal stem cell-like cells in human ACL tissues, their origin still remains unclear. Recently, blood vessels have been reported to represent a rich supply of stem/progenitor cells with a characteristic expression of CD34 and CD146. In this study, we attempted to validate the hypothesis that CD34- and CD146-expressing vascular cells exist in hACL tissues, have a potential for multi-lineage differentiation, and are recruited to the rupture site to participate in the intrinsic healing of injured ACL. Immunohistochemistry and flow cytometry analysis of hACL tissues demonstrated that it contains significantly more CD34 and CD146-positive cells in the ACL ruptured site compared with the noninjured midsubstance. CD34+CD45- cells isolated from ACL ruptured site showed higher expansionary potentials than CD146+CD45- and CD34-CD146-CD45- cells, and displayed higher differentiation potentials into osteogenic, adipogenic, and angiogenic lineages than the other cell populations. Immunohistochemistry of fetal and adult hACL tissues demonstrated a higher number of CD34 and CD146-positive cells in the ACL septum region compared with the midsubstance. In conclusion, our findings suggest that the ACL septum region contains a population of vascular-derived stem cells that may contribute to ligament regeneration and repair at the site of rupture.

Circulating CD133(+)VEGFR2 (+) and CD34 (+)VEGFR2 (+) cells and arterial function in patients with beta-thalassaemia major

Arterial dysfunction has been documented in patients with beta-thalassaemia major. This study aimed to determine the quantity and proliferative capacity of circulating CD133(+)VEGFR2(+) and CD34(+)VEGFR2(+) cells in patients with beta-thalassaemia major and those after haematopoietic stem cell transplantation (HSCT), and their relationships with arterial function. Brachial arterial flow-mediated dilation (FMD), carotid arterial stiffness, the quantity of these circulating cells and their number of colony-forming units (CFUs) were determined in 17 transfusion-dependent thalassaemia patients, 14 patients after HSCT and 11 controls. Compared with controls, both patient groups had significantly lower FMD and greater arterial stiffness. Despite having increased CD133(+)VEGFR2(+) and CD34(+)VEGFR2(+) cells, transfusion-dependent patients had significantly reduced CFUs compared with controls (p = 0.002). There was a trend of increasing CFUs across the three groups with decreasing iron load (p = 0.011). The CFUs correlated with brachial FMD (p = 0.029) and arterial stiffness (p = 0.02), but not with serum ferritin level. Multiple linear regression showed that CFU was a significant determinant of FMD (p = 0.043) and arterial stiffness (p = 0.02) after adjustment of age, sex, body mass index, blood pressure and serum ferritin level. In conclusion, arterial dysfunction found in patients with beta-thalassaemia major before and after HSCT may be related to impaired proliferation of CD133(+)VEGFR2(+) and CD34(+)VEGFR2(+) cells.

Cell-based therapies for diabetic retinopathy

Autologous endothelial progenitor cell (EPC) populations represent a novel treatment for therapeutic revascularization and vascular repair for diabetic patients with complications including diabetic retinopathy. Current therapies are applicable to late-stage disease and carry significant side effects, whereas cell-based therapy may provide an alternative by repairing areas of vasodegeneration and reversing ischemia. However, EPCs from diabetic patients with vascular complications are dysfunctional. Moreover, the diabetic environment poses its own challenges and complicates the use of autologous EPCs. Before EPCs become the ideal "cell therapy," the optimal EPC must be determined, any functional dysfunction must be corrected prior to use, and the diabetic milieu will require modification to accept the EPCs. This review describes the rationale for harnessing the vascular reparative properties of EPCs with emphasis on the molecular and phenotypic nature of healthy EPCs, how diabetes alters them, and novel strategies to improve dysfunctional EPCs.

Effect of moderate-to-severe chronic kidney disease on flow-mediated dilation and progenitor cells

A reduction in progenitor cell populations that help preserve vascular continuity and induce vascularization may accentuate endothelial cell apoptosis and dysfunction, ultimately contributing to organ failure and increased cardiovascular disease in chronic kidney disease (CKD). We hypothesized that CD45+ myeloid and CD34+ hematopoietic circulating progenitor cell (CPC) subpopulations would be reduced, peripheral blood mononuclear cell (PBMNC) colony-forming units (CFU) would be impaired, and flow-mediated dilation (FMD) would be impaired in patients with moderate-to-severe CKD as compared with healthy controls. Eleven moderate-to-severe CKD patients (mean estimated glomerular filtration rate [eGFR]: 36 ± 5) and 14 healthy controls were studied; blood was drawn and FMD was assessed by brachial artery FMD. CPCs were quantified via flow cytometry, and isolated PBMNCs were cultured for the colony-forming assay. CKD patients had significantly impaired FMD; lower CD34+, CD34+/KDR+, CD34+/CD45- and CD34+/KDR+/CD45- hematopoietic CPCs; lower CD45+, CD45+/KDR+, CD34+/CD45+ and CD34+/KDR+/CD45+ myeloid CPCs; and impaired CFUs as compared with healthy controls. Regression analysis revealed that CD34+, CD34+/KDR+ and CD34+/CD45- hematopoietic CPCs were associated positively with eGFR and negatively with blood urea nitrogen and serum creatinine. The CD45+/KDR+ myeloid CPCs also were associated positively with eGFR and negatively with serum creatinine. CD34+ hematopoietic CPCs and CD45+/KDR+ as well as CD34+/CD45+ myeloid CPCs were associated positively with FMD. In conclusion, myeloid and hematopoietic CPCs are reduced and associated with renal function as well as FMD in CKD. Therefore, reductions in CPCs may be a potential mechanism by which vascular integrity is compromised, increasing cardiovascular disease risk and contributing to renal disease progression in CKD.

VDR expression on circulating endothelial progenitor cells in dialysis patients is modulated by 25(OH)D serum levels and calcitriol therapy

BACKGROUND/AIMS

Vitamin D deficiency is associated with endothelial dysfunction in uremic patients, possibly by the impairment in the number and function of endothelial progenitor cells (EPCs). In 89 hemodialysis patients, we investigated the factors associated with the number of circulating EPCs (CD34+/CD133+/KDR+ and CD34+/CD133-/KDR+ cells), the presence of VDR and the determinants of VDR expression on EPCs, in particular in calcitriol therapy.

METHODS

EPC counts, percentages of VDR-positive EPCs and VDR expression were assessed by flow cytometry. Cells isolated from a subgroup of patients were cultured to analyze colony-forming units, specific markers expression and a capillary-like structure formation.

RESULTS/CONCLUSIONS

Our study demonstrates the presence of VDR on EPCs. In our dialysis patients, the parameters studied on both CD34+/CD133+/KDR+ and CD34+/CD133-/KDR+ cells, in particular VDR expression, seem to be influenced by uremia-related factors, including anemia, inflammation, diabetes, 25(OH)D serum levels and calcitriol therapy.

Mechanism by which chronic kidney disease causes cardiovascular disease and the measures to manage this phenomenon

In Japan, the number of chronic kidney disease (CKD) patients is thought to be 13,300,000, next in size after those with hypertension and diabetes. Although the number of patients with CKD seems large, it does not mean that all these patients require special treatment. Among them, nephrologists should pay special attention to patients with glomerular filtration rate below 50 mL/min/1.73 m(2) and progressive deterioration of renal function. Treatment of these CKD patients by a limited number of specialists is simply impossible; hence, it is essential to request treatment from physicians who are involved in general internal medicine and primary care. It is well known that not only does CKD cause end-stage renal failure, it also causes the onset of cardiovascular diseases (CVD) such as cardiac infarction and cerebral stroke; however, the question is how much significance does CKD have as a risk factor for CVD. It is understandable that hypertension and CVD are often complications of CKD; however, in addition to what is conventionally mentioned, there are three or four mechanisms that we would like to emphasize, and discuss herein. Among them, we would like to stress the role of klotho genes with special reference to the generation of CVD in CKD patients. When patients develop CKD, it is therefore necessary to remove as far as possible any factors that could represent a risk for CVD. Moreover, by taking appropriate measures against clinical conditions that often complicate CKD, such as hypertension, renal anemia, hyperuricemia, and hyperlipidaemia, the development of CVD can be prevented.

Intravenous erythropoietin in patients with ST-segment elevation myocardial infarction: REVEAL: a randomized controlled trial

CONTEXT

Acute ST-segment elevation myocardial infarction (STEMI) is a leading cause of morbidity and mortality. In experimental models of MI, erythropoietin reduces infarct size and improves left ventricular (LV) function.

OBJECTIVE

To evaluate the safety and efficacy of a single intravenous bolus of epoetin alfa in patients with STEMI.

DESIGN, SETTING, AND PATIENTS

A prospective, randomized, double-blind, placebo-controlled trial with a dose-escalation safety phase and a single dose (60,000 U of epoetin alfa) efficacy phase; the Reduction of Infarct Expansion and Ventricular Remodeling With Erythropoietin After Large Myocardial Infarction (REVEAL) trial was conducted at 28 US sites between October 2006 and February 2010, and included 222 patients with STEMI who underwent successful percutaneous coronary intervention (PCI) as a primary or rescue reperfusion strategy.

INTERVENTION

Participants were randomly assigned to treatment with intravenous epoetin alfa or matching saline placebo administered within 4 hours of reperfusion.

MAIN OUTCOME MEASURE

Infarct size, expressed as percentage of LV mass, assessed by cardiac magnetic resonance (CMR) imaging performed 2 to 6 days after study medication administration (first CMR) and again 12 ± 2 weeks later (second CMR).

RESULTS

In the efficacy cohort, the infarct size did not differ between groups on either the first CMR scan (n = 136; 15.8% LV mass [95% confidence interval {CI}, 13.3-18.2% LV mass] for the epoetin alfa group vs 15.0% LV mass [95% CI, 12.6-17.3% LV mass] for the placebo group; P = .67) or on the second CMR scan (n = 124; 10.6% LV mass [95% CI, 8.4-12.8% LV mass] vs 10.4% LV mass [95% CI, 8.5-12.3% LV mass], respectively; P = .89). In a prespecified analysis of patients aged 70 years or older (n = 21), the mean infarct size within the first week (first CMR) was larger in the epoetin alfa group (19.9% LV mass; 95% CI, 14.0-25.7% LV mass) than in the placebo group (11.7% LV mass; 95% CI, 7.2-16.1% LV mass) (P = .03). In the safety cohort, of the 125 patients who received epoetin alfa, the composite outcome of death, MI, stroke, or stent thrombosis occurred in 5 (4.0%; 95% CI, 1.31%-9.09%) but in none of the 97 who received placebo (P = .04).

CONCLUSIONS

In patients with STEMI who had successful reperfusion with primary or rescue PCI, a single intravenous bolus of epoetin alfa within 4 hours of PCI did not reduce infarct size and was associated with higher rates of adverse cardiovascular events. Subgroup analyses raised concerns about an increase in infarct size among older patients.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00378352.

Erythropoietin: a hormone with multiple functions

Erythropoietin (EPO), the main hemopoietic hormone synthesized by the kidney as well as by the liver in fetal life, is implicated in mammalian erythropoiesis. Production and secretion of EPO and the expression of its receptor (EPO-R) are regulated by tissue oxygenation. EPO and EPO-R, expressed in several tissues, exert pleiotropic activities and have different effects on nonhemopoietic cells. EPO is a cytokine with antiapoptotic activity and plays a potential neuroprotective and cardioprotective role against ischemia. EPO is also involved in angiogenesis, neurogenesis, and the immune response. EPO can prevent metabolic alterations, neuronal and vascular degeneration, and inflammatory cell activation. Consequently, EPO may be of therapeutic use for a variety of disorders. Many tumors express EPO and/or EPO-R, but the action of EPO on tumor cells remains controversial. It has been suggested that EPO promotes the proliferation and survival of cancer cells expressing EPO-R. On the other hand, other reports have concluded that EPO-R plays no role in tumor progression. This review provides a detailed insight into the nonhemopoietic role of EPO and its mechanism(s) of action which may lead to a better understanding of its potential therapeutic value in diverse clinical settings.

Erythropoietin increases circulating endothelial progenitor cells and reduces the formation and progression of cerebral aneurysm in rats

Endothelial dysfunction triggers early pathological changes in vessel walls, potentially leading to the formation of cerebral aneurysm (CA). Endothelial progenitor cells (EPCs) are critical in repairing damaged endothelium and could prevent or slow CA formation. We hypothesize that erythropoietin (EPO) stimulates EPCs mobilization, could alter the rate of CA formation and progression. The hypothesis was tested in a rat model of CA. CAs were induced in male Sprague-Dawley rats and treated with s.c. administration of EPO. Circulating EPCs and serum vascular endothelial grow factor (VEGF) were measured be flow cytometry and ELISA, respectively. mRNAs for inducible nitric oxide synthase (iNOS), endothelial nitric oxide synthase (eNOS), matrix metalloproteinase-2 (MMP-2), and MMP-9 in aneurysm tissue were quantified by Real-time PCR. The size, internal elastic lamina (IEL), and media thickness of CAs were evaluated 1 and 3 months after aneurysm induction. Circulating EPCs were significantly lower in CA rats as compared to non-surgical controls. EPO increased levels of circulating EPCs and VEGF. It also decreased iNOS, MMP-2, and MMP-9 mRNA levels, while increased eNOS mRNA in aneurysm tissue. The changes in EPCs and biochemical markers are associated with suppression of new CA formation and prevention of preexisting CA progression. We have shown a close association among circulating EPCs, biochemical markers related to vascular remodeling, and the rate of CA formation and progression. Changes in patterns of cerebral blood flow and hypertension induced by surgical ligations of selected arteries exert significant hemodynamic stress to weaken vessel walls, primarily at sites of basilar bifurcation. The surgical stress also reduced circulating EPCs and slowed vascular repairs. EPO mobilizes EPCs from the bone marrow and promotes their homing. These results suggest that EPCs may serve as a marker for CA progression and EPO a promising candidate for the clinical management of CA.

Endothelial progenitor cells: novel biomarker and promising cell therapy for cardiovascular disease

Bone-marrow-derived EPCs (endothelial progenitor cells) play an integral role in the regulation and protection of the endothelium, as well as new vessel formation. Peripheral circulating EPC number and function are robust biomarkers of vascular risk for a multitude of diseases, particularly CVD (cardiovascular disease). Importantly, using EPCs as a biomarker is independent of both traditional and non-traditional risk factors (e.g. hypertension, hypercholesterolaemia and C-reactive protein), with infused ex vivo-expanded EPCs showing potential for improved endothelial function and either reducing the risk of events or enhancing recovery from ischaemia. However, as the number of existing cardiovascular risk factors is variable between patients, simple EPC counts do not adequately describe vascular disease risk in all clinical conditions and, as such, the risk of CVD remains. It is likely that this limitation is attributable to variation in the definition of EPCs, as well as a difference in the interaction between EPCs and other cells involved in vascular control such as pericytes, smooth muscle cells and macrophages. For EPCs to be used regularly in clinical practice, agreement on definitions of EPC subtypes is needed, and recognition that function of EPCs (rather than number) may be a better marker of vascular risk in certain CVD risk states. The present review focuses on the identification of measures to improve individual risk stratification and, further, to potentially individualize patient care to address specific EPC functional abnormalities. Herein, we describe that future therapeutic use of EPCs will probably rely on a combination of strategies, including optimization of the function of adjunct cell types to prime tissues for the effect of EPCs.

Vascular stem cells and ischaemic retinopathies

Retinal ischaemic disorders such as diabetic retinopathy and retinal vein occlusion are common. The hypoxia-related stimuli from oxygen-deprived neural and glial networks can drive expression of growth factors and cytokines which induce leakage from the surviving vasculature and/or pre-retinal and papillary neovascularisation. If left untreated, retinal vascular stasis, hypoxia or ischaemia can lead to macular oedema or fibro-vascular scar formation which are associated with severe visual impairment, and even blindness. Current therapies for ischaemic retinopathies include laser photocoagulation, injection of corticosteroids or VEGF-antibodies and vitreoretinal surgery, however they carry significant side effects. As an alternative approach, we propose that if reparative intra-retinal angiogenesis can be harnessed at the appropriate stage, ischaemia could be contained or reversed. This review provides evidence that reperfusion of ischaemic retina and suppression of sight-threatening sequelae is possible in both experimental and clinical settings. In particular, there is emphasis on the clinical potential for endothelial progenitor cells (EPCs) to promote vascular repair and reversal of ischaemic injury in various tissues including retina. Gathering evidence from an extensive published literature, we outline the molecular and phenotypic nature of EPCs, how they are altered in disease and provide a rationale for harnessing the vascular reparative properties of various cell sub-types. When some of the remaining questions surrounding the clinical use of EPCs are addressed, they may provide an exciting new therapeutic option for treating ischaemic retinopathies.

Exercise training improves in vivo endothelial repair capacity of early endothelial progenitor cells in subjects with metabolic syndrome

BACKGROUND

Endothelial dysfunction and injury are considered to contribute considerably to the development and progression of atherosclerosis. It has been suggested that intense exercise training can increase the number and angiogenic properties of early endothelial progenitor cells (EPCs). However, whether exercise training stimulates the capacity of early EPCs to promote repair of endothelial damage and potential underlying mechanisms remain to be determined. The present study was designed to evaluate the effects of moderate exercise training on in vivo endothelial repair capacity of early EPCs, and their nitric oxide and superoxide production as characterized by electron spin resonance spectroscopy analysis in subjects with metabolic syndrome.

METHODS AND RESULTS

Twenty-four subjects with metabolic syndrome were randomized to an 8 weeks exercise training or a control group. Superoxide production and nitric oxide (NO) availability of early EPCs were characterized by using electron spin resonance (ESR) spectroscopy analysis. In vivo endothelial repair capacity of EPCs was examined by transplantation into nude mice with defined carotid endothelial injury. Endothelium-dependent, flow-mediated vasodilation was analysed using high-resolution ultrasound. Importantly, exercise training resulted in a substantially improved in vivo endothelial repair capacity of early EPCs (24.0 vs 12.7%; p < 0.05) and improved endothelium-dependent vasodilation. Nitric oxide production of EPCs was substantially increased after exercise training, but not in the control group. Moreover, exercise training reduced superoxide production of EPCs, which was not observed in the control group.

CONCLUSIONS

The present study suggests for the first time that moderate exercise training increases nitric oxide production of early endothelial progenitor cells and reduces their superoxide production. Importantly, this is associated with a marked beneficial effect on the in vivo endothelial repair capacity of early EPCs in subjects with metabolic syndrome.

Erythropoietin and the heart: facts and perspectives

EPO (erythropoietin) has long been identified as a primary regulator of erythropoiesis. Subsequently, EPO has been recognized as playing a role in a broad variety of processes in cardiovascular pathophysiology. In particular, the tight interactions of EPO with the nitric oxide pathway, apoptosis, ischaemia, cell proliferation and platelet activation appear of great interest. Although enhanced EPO synthesis is viewed as an appropriate compensatory mechanism in the cardio-renal syndrome, which features CHF (congestive heart failure) and CRF (chronic renal failure), maladaptative excessive EPO synthesis in the advanced stages of these diseases appears to be predictive of higher mortality. Clinical trials based on the use of EPO in both heart and renal failure have so far produced contradictory results, whereas treatment targeted to restore low Hb levels appears rational and is supported by regulatory authorities. New areas for therapeutic use of EPO, such as acute coronary syndromes, are under investigation, and they are discussed in the present review together with other clinical applications in cardiovascular diseases. The revisited concept of a potential use of endogenous EPO levels as a predictor of CHF severity, as well as in the monitoring of responses to treatment, deserves appropriate investigation, as this may identify EPO as a useful biomarker in the clinical management of cardiovascular diseases.

Erythropoietin for stroke treatment: dead or alive?

Endothelial progenitor cell (EPC) mobilization from the bone marrow was considered to improve outcome after ischemic stroke. Erythropoietin (EPO) might be a potential candidate stroke drug that increases the number of circulating EPCs. In the previous issue of Critical Care, Yip and colleagues investigated the effect of EPO in stroke patients on both clinical outcome and EPC stimulation. Although beneficial effects of EPO were observed, several issues regarding EPO's suitability as a stroke drug remain.

Activation of vascular BK channels by docosahexaenoic acid is dependent on cytochrome P450 epoxygenase activity

AIMS

n-3 Polyunsaturated fatty acids (PUFAs) are known to protect the cardiovascular system and improve blood pressure control. These important dietary constituents are converted into bioactive metabolites, but their role in regulation of the cardiovascular system is unclear. In particular, the functions of the cytochrome P450 (CYP) metabolites of n-3 PUFAs remain virtually unexplored. In this study, we examined the effects of docosahexaenoic acid (DHA) on the regulation of large-conductance calcium-activated potassium (BK) channel activities in coronary arterial smooth muscle cells.

METHODS AND RESULTS

Using whole-cell patch-clamp techniques, we found that DHA is a potent activator of BK currents in rat coronary arterial smooth muscle cells with an EC(50) of 0.23 ± 0.03 µM. This effect was abolished by pre-incubation with the CYP epoxygenase inhibitor, SKF525A (10 µM). The effects of DHA on the BK channels were reproduced by 16,17-epoxydocosapentaenoic acid (16,17-EpDPE) with an EC(50) of 19.7 ± 2.8 nM. The physiological role of the CYP metabolites of DHA was confirmed by measuring DHA-mediated vasodilatation in isolated rat coronary arteries. DHA dilated pressurized isolated coronary arteries in a dose-dependent manner, and the DHA effects were abolished after pre-treatment with SKF525A (10 µM) or with iberiotoxin (100 nM). In addition, 16,17-EpDPE directly produced coronary vasodilatation that was iberiotoxin sensitive.

CONCLUSION

These results suggest that DHA-mediated vasodilatation is mediated through CYP epoxygenase metabolites by activation of vascular BK channels.

Short- and long-term effects of erythropoietin treatment on endothelial progenitor cell levels in patients with cardiorenal syndrome

Objective

Patients with cardiorenal syndrome (CRS) have high cardiovascular morbidity. Endothelial progenitor cells (EPC) constitute an endogenous vascular repairsystem, protecting against atherosclerosis development. Erythropoietin (EPO) treatment may have beneficial effects by mobilizing EPC from the bonemarrow. Our objective is to determine EPC levels and effects of EPO therapy on EPC levels in CRS patients.

Design

Open-label randomized trial.

Setting

Part of the EPOCARES-trial, conducted in Utrecht (Netherlands).

Patients

Patients with CRS and anaemia and healthy controls were included.

Interventions

Patients were randomized to receive EPO therapy (50 IU/kg/wk) for 52 weeks or no EPO therapy.

Main outcome measures

CD34⁺KDR⁺-EPC, cultured EPC outgrowth and function at baseline, after 18 days and after 52 weeks.

Results

Patients showed lower CD34⁺KDR⁺-cell numbers compared to controls (6(12) vs. 19(19) cells/10⁵ granulocytes; p=0.010), despite increased levels of stromal cell-derived factor-1α; (3.1(0.8) vs 2.6(0.3) ng/ml; p=0.001). EPC outgrowth and function were not different between patients and controls. EPC levels did not change after 18 days with or without EPO treatment. CD34⁺KDR⁺-cells significantly declined after 52 weeks in the non-treated group (p=0.028). Long-term EPO therapy did not significantly affect this reduction in CD34⁺KDR⁺-EPC levels.

Conclusions

CRS patients showed reduced CD34⁺KDR⁺-EPC levels compared to controls, consistent with a reduced vascular regenerative potential and despite upregulated SDF-1α levels. Over a one-year follow-up period a marked 68% further reduction in EPC levels was observed in the patient group without EPO treatment. In spite of promising experimental studies, our longitudinal, randomized study did not show significant influence of either short- or long-term EPO therapy on reduced EPC levels in CRS patients.

Endothelial progenitor cells as therapeutic agents in the microcirculation: an update

This review evaluates novel beneficial effects of circulating endothelial progenitor cells (EPCs) as shown by several preclinical studies and clinical trials carried out to test the safety and feasibility of using EPCs. There are 31 registered clinical trials (and many others still ongoing) and 19 published studies. EPCs originate in the bone marrow and migrate into the bloodstream where they undergo a differentiation program leading to major changes in their antigenic characteristics. EPCs lose typical progenitor markers and acquire endothelial markers, and two important receptors, (VEGFR and CXCR-4), which recruit circulating EPCs to damaged or ischemic microcirculatory (homing to damaged tissues) beds. Overall, therapeutic angiogenesis will likely change the face of regenerative medicine in the next decade with many patients worldwide predicted to benefit from these treatments.

Design and rationale of the Reduction of Infarct Expansion and Ventricular Remodeling with Erythropoietin after Large Myocardial Infarction (REVEAL) trial

BACKGROUND

Acute myocardial infarction (MI) remains a leading cause of death despite advances in pharmacologic and percutaneous therapies. Animal models of ischemia/reperfusion have demonstrated that single-dose erythropoietin may reduce infarct size, decrease apoptosis, and increase neovascularization, possibly through mobilization of endothelial progenitor cells.

STUDY DESIGN

REVEAL is a randomized, double-blind, placebo-controlled, multicenter trial evaluating the effects of epoetin α on infarct size and left ventricular remodeling in patients with large MIs. The trial comprises a dose-escalation safety phase and a single-dose efficacy phase using the highest acceptable epoetin α dose up to 60,000 IU. Up to 250 ST-segment elevation myocardial infarction patients undergoing primary or rescue percutaneous coronary intervention will be randomized to intravenous epoetin α or placebo within 4 hours of successful reperfusion. The primary study end point is infarct size expressed as a percentage of left ventricular mass, as measured by cardiac magnetic resonance imaging 2 to 6 days post study medication administration. Secondary end points will assess changes in endothelial progenitor cell numbers and changes in indices of ventricular remodeling.

CONCLUSION

The REVEAL trial will evaluate the safety and efficacy of the highest tolerated single dose of epoetin α in patients who have undergone successful rescue or primary percutaneous coronary intervention for acute ST-segment elevation myocardial infarction.

Targeting stem cell niches and trafficking for cardiovascular therapy

Regenerative cardiovascular medicine is the frontline of 21st-century health care. Cell therapy trials using bone marrow progenitor cells documented that the approach is feasible, safe and potentially beneficial in patients with ischemic disease. However, cardiovascular prevention and rehabilitation strategies should aim to conserve the pristine healing capacity of a healthy organism as well as reactivate it under disease conditions. This requires an increased understanding of stem cell microenvironment and trafficking mechanisms. Engagement and disengagement of stem cells of the osteoblastic niche is a dynamic process, finely tuned to allow low amounts of cells move out of the bone marrow and into the circulation on a regular basis. The balance is altered under stress situations, like tissue injury or ischemia, leading to remarkably increased cell egression. Individual populations of circulating progenitor cells could give rise to mature tissue cells (e.g. endothelial cells or cardiomyocytes), while the majority may differentiate to leukocytes, affecting the environment of homing sites in a paracrine way, e.g. promoting endothelial survival, proliferation and function, as well as attenuating or enhancing inflammation. This review focuses on the dynamics of the stem cell niche in healthy and disease conditions and on therapeutic means to direct stem cell/progenitor cell mobilization and recruitment into improved tissue repair.

Mesenchymal stem cell therapy for chronic renal failure

IMPORTANCE OF THE FIELD

Chronic kidney disease (CKD) has become a worldwide public health problem. Renal transplantation is the treatment of choice for end-stage renal disease, but is limited by a small number of organ donors and the immune barrier. To overcome these problems, new therapeutic strategies for tissue repair have recently emerged.

AREAS COVERED IN THIS REVIEW

We discuss the therapeutic potential of mesenchymal stem cells (MSCs) in kidney injury and examine the latest reports providing evidence supporting MSC efficacy in the treatment of chronic renal failure (CRF).

WHAT THE READER WILL GAIN

MSCs improve histological and functional outcomes in various CRF model systems. Paracrine effects rather than transdifferentiation might result in the prevention of progressive renal failure. In addition, MSCs can reprogram kidney cell differentiation, and modulate neo-kidney transplantation in CRF.

TAKE HOME MESSAGE

Although many practical problems remain to be addressed, treatment with MSCs will enter the mainstream of CRF treatment.