Erythropoietin regulates endothelial progenitor cells

Thrombopoietin improves the functions of bone marrow endothelial progenitor cells via METTL16/Akt signalling of haematological patients with chemotherapy-induced thrombocytopenia

Bone marrow endothelial progenitor cells (BM EPCs) are crucial in supporting haematopoietic regeneration, while the BM EPCs of haematological patients with chemotherapy-induced thrombocytopenia (CIT) are unavoidably damaged. Therefore, the present study aimed to examine the effect of thrombopoietin (TPO) on the recovery of BM EPCs of CIT patients and to identify the underlying mechanisms. The cell functions were determined by 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (Dil)-acetylated low-density lipoprotein (Dil-Ac-LDL) uptake and fluorescein isothiocyanate (FITC)-labeled Ulex europaeus agglutinin-I (FITC-UEA-I) binding assay, as well as proliferation, migration and tube formation experiments. Endothelial cells were transfected with METTL16 lentivirus, followed by methylated RNA immunoprecipitation sequencing. Zebrafish with vascular defect was used as the in vivo model. TPO significantly improved the quantity and functions of BM EPCs from CIT patients in vitro and restored the subintestinal vein area of zebrafish with vascular defect in vivo. Mechanically, TPO enhanced the BM EPC functions through Akt signal mediated by METTL16, which was downregulated in BM EPCs of CIT patients and involved in the regulation of endothelial functions. The present study demonstrates that TPO improves the recovery of BM EPCs from CIT patients with haematological malignancies via METTL16/Akt signalling, which provides new insights into the role of TPO in treating CIT in addition to direct megakaryopoiesis.

Advancing Anemia Management in Chronic Kidney Disease: Assessing the Superiority of Darbepoetin Alfa Over Erythropoietin Alpha

Anemia is a prevalent and debilitating complication in patients with chronic kidney disease (CKD). It presents multifaceted challenges that impact patients' quality of life and overall well-being. The advent of darbepoetin alfa (DPO) as a therapeutic alternative to recombinant human erythropoietin alpha (EPO) has revolutionized the management of CKD-associated anemia. This review article presents a comprehensive comparative analysis highlighting the advantages of DPO over EPO in the effective management of anemia, in both predialysis and dialysis-dependent (DD) CKD patients. DPO's distinct pharmacokinetic advantages play a pivotal role in its efficacy and safety. With a significantly longer half-life and several-fold increased biological activity compared to EPO, DPO enables extended dosing intervals. Through an in-depth examination of diverse clinical trials, it becomes evident that DPO consistently demonstrates remarkable efficacy and safety in improving and maintaining hemoglobin (Hb) levels. Furthermore, its simplified dosage regimen, coupled with the convenience of less frequent administration, not only improves patient adherence but also translates to reduced healthcare costs and resource utilization. In conclusion, this review provides compelling evidence of the advantages of DPO over conventional recombinant human EPO for managing anemia in CKD patients, both in the predialysis and dialysis-dependent CKD patients. DPO's pharmacokinetic advantages, patient-centered advantages, enhanced compliance, and cost-effectiveness converge to establish DPO as a transformative therapeutic option. In both predialysis and dialysis settings, DPO's superior efficacy and patient-centric attributes collectively redefine the landscape of anemia management in CKD.

Recent progress in bone-repair strategies in diabetic conditions

Bone regeneration following trauma, tumor resection, infection, or congenital disease is challenging. Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia. It can result in complications affecting multiple systems including the musculoskeletal system. The increased number of diabetes-related fractures poses a great challenge to clinical specialties, particularly orthopedics and dentistry. Various pathological factors underlying DM may directly impair the process of bone regeneration, leading to delayed or even non-union of fractures. This review summarizes the mechanisms by which DM hampers bone regeneration, including immune abnormalities, inflammation, reactive oxygen species (ROS) accumulation, vascular system damage, insulin/insulin-like growth factor (IGF) deficiency, hyperglycemia, and the production of advanced glycation end products (AGEs). Based on published data, it also summarizes bone repair strategies in diabetic conditions, which include immune regulation, inhibition of inflammation, reduction of oxidative stress, promotion of angiogenesis, restoration of stem cell mobilization, and promotion of osteogenic differentiation, in addition to the challenges and future prospects of such approaches.

Microvessel density (Cluster of Differentiation-34 & Vascular Endothelial growth factor) in Nasopharyngeal Angiofibroma: Clinical correlation

BACKGROUND

The literature on microvessel density (MVD) signifying neoangiogenesis/tumour-activity in juvenile nasopharyngeal angiofibroma (JNA) is limited. Accordingly, this study evaluates and correlates MVD characteristics with clinical parameters/aggressiveness/recurrence.

MATERIAL AND METHODS

Sixty-two paraffin blocks of JNA were studied histopathologically and MVD was assessed following immunohistochemistry using VEGF and CD34 as vascular markers. A clinical correlation of MVD was undertaken in 43 cases.

RESULTS

MVD scores of VEGF and CD34 showed strong inter-correlation. The 'age', 'duration of disease' and 'haemoglobin%' were the only clinical parameters that revealed significance with MVD. Significantly higher MVD scores were appreciated in recurrent cases as well as some other clinical differences from upfront cases.

CONCLUSION

This is the first study of MVD with CD34 and VEGF simultaneously depicting clinical correlation. The strong correlation, supports a prognostic role of MVD scores in JNA and this can be better established in a larger multicentre study involving comprehensive examination of tumour dimensions.

Beyond brain injury biomarkers: chemoattractants and circulating progenitor cells as biomarkers of endogenous rehabilitation effort in preterm neonates with encephalopathy

Introduction

Preclinical work and studies in adults have shown that endogenous regeneration efforts that involve mobilization of progenitor cells take place after brain injury. However, kinetics of endogenous circulating progenitor cells (CPCs) in preterm neonates is not well described, particularly their possible role regarding brain injury and regeneration. We aimed to assess the kinetics of CPCs in neonates with encephalopathy of prematurity in relation to brain injury biomarkers, chemoattractants and relevant antenatal and postanal clinical factors, in an effort to outline the related pathophysiology.

Materials and methods

47 preterm neonates (of 28-33 weeks GA) were enrolled: 31 newborns with no or minimal brain injury (grade I IVH) and 16 prematures with encephalopathy (grade III or IV IVH, PVL or infarct). Peripheral blood samples obtained on days 1, 3, 9, 18 and 45 after birth were analyzed using flow cytometry, focusing on EPCs (early and late Endothelial Progenitor Cells), HSCs (Hematopoietic Stem Cells) and VSELs (Very Small Embryonic-Like Stem Cells). At the same time-points serum levels of S100B, Neuron-specific Enolase (NSE), Erythropoietin (EPO), Insulin-like growth factor-1 (IGF-1) and SDF-1 were also measured. Neonates were assessed postnatally with brain MRI, and with Bayley III developmental test at 2 years of corrected age.

Results

Preterms with brain injury proved to have significant increase of S100B and NSE, followed by increase of EPO and enhanced mobilization mainly of HSCs, eEPCs and lEPCs. IGF-1 was rather decreased in this group of neonates. IGF-1 and most CPCs were intense decreased in cases of antenatal or postnatal inflammation. S100B and NSE correlated with neuroimaging and language scale in Bayley III test, providing good prognostic ability.

Conclusion

The observed pattern of CPCs' mobilization and its association with neurotrophic factors following preterm brain injury indicate the existence of an endogenous brain regeneration process. Kinetics of different biomarkers and associations with clinical factors contribute to the understanding of the related pathophysiology and might help to early discriminate neonates with adverse outcome. Timely appropriate enhancement of the endogenous regeneration effort, when it is suppressed and insufficient, using neurotrophic factors and exogenous progenitor cells might be a powerful therapeutic strategy in the future to restore brain damage and improve the neurodevelopmental outcome in premature infants with brain injury.

Endothelial progenitor cells in the host defense response

Extensive injury of endothelial cells in blood vasculature, especially in the microcirculatory system, frequently occurs in hosts suffering from sepsis and the accompanied systemic inflammation. Pathological factors, including toxic components derived from invading microbes, oxidative stress associated with tissue ischemia/reperfusion, and vessel active mediators generated during the inflammatory response, are known to play important roles in mediating endothelial injury. Collapse of microcirculation and tissue edema developed from the failure of endothelial barrier function in vital organ systems, including the lung, brain, and kidney, are detrimental, which often predict fatal outcomes. The host body possesses a substantial capacity for maintaining vascular homeostasis and repairing endothelial damage. Bone marrow and vascular wall niches house endothelial progenitor cells (EPCs). In response to septic challenges, EPCs in their niche environment are rapidly activated for proliferation and angiogenic differentiation. In the meantime, release of EPCs from their niches into the blood stream and homing of these vascular precursors to tissue sites of injury are markedly increased. The recruited EPCs actively participate in host defense against endothelial injury and repair of damage in blood vasculature via direct differentiation into endothelial cells for re-endothelialization as well as production of vessel active mediators to exert paracrine and autocrine effects on angiogenesis/vasculogenesis. In recent years, investigations on significance of EPCs in host defense and molecular signaling mechanisms underlying regulation of the EPC response have achieved substantial progress, which promotes exploration of vascular precursor cell-based approaches for effective prevention and treatment of sepsis-induced vascular injury as well as vital organ system failure.

Endogenous Glycosaminoglycans in Various Pathologic Plasma Samples as Measured by a Fluorescent Quenching Method

Endogenous glycosaminoglycans (GAGs) with a similar structure to heparin are widely distributed in various tissues. A fluorescence probe, namely Heparin Red, can detect polyanionic GAGs in plasma samples. The purpose of this study is to measure endogenous GAGs in various plasma samples obtained from different pathologic states in comparison to healthy controls utilizing this method. Plasma samples were obtained from patient groups including atrial fibrillation (AF), end-stage-renal-disease (ESRD), diabetes mellitus (DM), sepsis, cancer, liver disease (LD), and pulmonary embolism (PE). Normal human plasma (NHP) was used as healthy controls. The Heparin Red kit from Red Probes (Münster, Germany) was used for the quantification of endogenous GAGs in each sample before and after heparinase I degradation. All results were compiled as group means  ±  SD for comparison. NHP was found to have relatively low levels of endogenous GAGs with a mean concentration of 0.06 μg/mL. The AF, ESRD, DM, and sepsis patient samples had a mean endogenous GAG concentration of 0.55, 0.72, 0.92, and 0.94 μg/mL, respectively. The levels of endogenous GAGs were highest in cancer, LD, and PE patient plasma samples with a mean concentration of 1.95, 2.78, and 2.83 μg/mL, respectively. Heparinase I degradation resulted in a decline in GAG levels in plasma samples. These results clearly show that detectable Heparin Red sensitive endogenous GAGs are present in circulating plasma at varying levels in various patient groups. Additional studies are necessary to understand this complex pathophysiology.

A Promising Candidate in Tendon Healing Events—PDGF-BB

Tendon injuries are one of the most common musculoskeletal disorders for which patients seek medical aid, reducing not only the quality of life of the patient but also imposing a significant economic burden on society. The administration of growth factors at the wound site is a feasible solution for enhancing tendon healing. Platelet-derived growth factor-BB (PDGF-BB) has a well-defined safety profile compared to other growth factors and has been approved by the Food and Drug Administration (FDA). The purpose of this review is to summarize the role of PDGF-BB in tendon healing through a comprehensive review of the published literature. Experimental studies suggest that PDGF-BB has a positive effect on tendon healing by enhancing inflammatory responses, speeding up angiogenesis, stimulating tendon cell proliferation, increasing collagen synthesis and increasing the biomechanics of the repaired tendon. PDGF-BB is regarded as a promising candidate in tendon healing. However, in order to realize its full potential, we still need to carefully consider and study key issues such as dose and application time in the future, so as to explore further applications of PDGF-BB in the tendon healing process.

Diagnostic Imaging Studies on Local and Systemic Erythropoietin Application for Promoting Bone Regeneration in Rat Calvarial Defects

The purpose of this study was to compare the effects of local and systemic application of recombinant human erythropoietin (rhEPO) on the healing of rat calvarial defects. Twenty-four male skeletally-mature Wistar rats were used. Two bone 5 mm critical size defects were created in calvarial bones of each rat. In rats from experimental group I (n = 12), EPO was applied locally on a collagen cone in left defects, whereas a collagen cone soaked with physiological saline was placed in right defects. The rats from experimental group II were injected once intraperitoneally with 4900 IU/kg EPO; a collagen cone was only placed in left defects, whereas the right defects were left empty. The systemic effect of EPO treatment was monitored by haematological analyses on days 0, 30 and 90. Bone healing was monitored via radiography and computed tomography on the same time intervals. The results demonstrated that local EPO application had no significant effect on haemopoiesis, unlike the systemic application. At the same time, it resulted in new bone formation and therefore, could be successfully used as a means of promoting bone regeneration.

Ramipril Improves Endothelial Function and Increases the Number of Endothelial Progenitor Cells in Patients With Systemic Lupus Erythematosus

BACKGROUND/OBJECTIVES

Endothelial dysfunction and reduced number of endothelial progenitor cells (EPCs) in peripheral blood are contributing factors to cardiovascular disease in systemic lupus erythematosus (SLE) patients. Endothelial progenitor cell proliferation is regulated by vascular endothelial growth factor (VEGF). Angiotensin-converting enzyme inhibitors reduce cardiovascular mortality in patients with coronary heart disease.

METHODS

This was a randomized trial including 37 female SLE patients without cardiovascular risk factors allocated into 2 groups: 19 patients received ramipril 10 mg/d for 12 weeks (IG) and 18 patients maintained without ramipril (CG). Endothelial function was assessed by brachial artery ultrasound measuring flow-mediated dilation, and EPCs were quantified by flow cytometry and cell culture, at baseline and after 12 weeks. Serum VEGF levels were measured by enzyme-linked immunosorbent assay. Statistical analysis was intention to treat. p < 0.05 was considered significant.

RESULTS

After 12 weeks, higher flow-mediated dilation (6.17% vs. 11.14%, p < 0.001) was observed in IG, without change in CG (5.37% vs. 5.02%, p = 0.630). Higher number of EPC colony-forming units was also observed in IG (21.3 ± 10.4 vs. 31.6 ± 8.5, p < 0.001), without difference in CG ( p = 0.714). No difference was found in EPCs evaluated by flow cytometry. Vascular endothelial growth factor level increased after 12 weeks in IG ( p = 0.048), with no difference in CG ( p = 0.661).

CONCLUSION

Ramipril improved endothelial function and increased the numbers of EPCs evaluated by cell culture and VEGF levels in SLE patients without cardiovascular risk factors. These data suggest that angiotensin-converting enzyme inhibitor bring an extra benefit beyond the hypotensive action and should be considered as a preferred antihypertensive drug in SLE patients.

Endothelial Progenitor Cells as Biomarkers of Cardiovascular Pathologies: A Narrative Review

Endothelial progenitor cells (EPC) may influence the integrity and stability of the vascular endothelium. The association of an altered total EPC number and function with cardiovascular diseases (CVD) and risk factors (CVF) was discussed; however, their role and applicability as biomarkers for clinical purposes have not yet been defined. Endothelial dysfunction is one of the key mechanisms in CVD. The assessment of endothelial dysfunction in vivo remains a major challenge, especially for a clinical evaluation of the need for therapeutic interventions or for primary prevention of CVD. One of the main challenges is the heterogeneity of this particular cell population. Endothelial cells (EC) can become senescent, and the majority of circulating endothelial cells (CEC) show evidence of apoptosis or necrosis. There are a few viable CECs that have properties similar to those of an endothelial progenitor cell. To use EPC levels as a biomarker for vascular function and cumulative cardiovascular risk, a correct definition of their phenotype, as well as an update on the clinical application and practicability of current isolation methods, are an urgent priority.

Post-COVID-19 patients show an increased endothelial progenitor cell production

SARS-CoV-2, the cause of COVID-19, has generated a global emergency. The endothelium is a target of SARS-CoV-2, generating endothelial dysfunction, an essential step for the development of cardiovascular complications. The number of endothelial progenitor cells acts as an indicator of vascular damage. However, its role in SARS-CoV-2 is unknown. The aim of this study was to quantify the number of endothelial colony forming cells (ECFCs) and assess for the first time if there is a significant increase after SARS-CoV-2 infection. This study also evaluates whether the number of ECFC is related to the presence of pulmonary embolism (PE), and if this increase correlates with any of the clinical parameters studied. A total of 63 subjects were recruited including 32 subjects 3-months after overcoming COVID-19 and 31 healthy controls. The results confirm the presence of vascular sequelae in post-COVID-19 patients, with an abnormal increase in the number of ECFCs in blood circulation compared to controls (2.81 ± 2.33 vs 1.23 ± 1.86, P = 0.001). There was no difference in ECFC production in COVID-19 who presented acute PE compared to those that did not (3.21 ± 2.49 vs 2.50 ± 2.23, P > 0.05). The appearance of ECFC colonies in COVID-19 patients was significantly related to male gender (P = 0.003), the presence of systemic hypertension (P = 0.01) and elevated hemoglobin levels (P = 0.02) at the time of ECFC isolation and lower PaO₂ levels (P = 0.01) at admission. Whether these results indicate a prompt response of the patient to repair the damaged endothelium or reflect a postinfection injury that will persist in time is not known.

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.

EPO and EPO-Receptor System as Potential Actionable Mechanism for the Protection of Brain and Heart in Refractory Epilepsy and SUDEP

The most important activity of erythropoietin (EPO) is the regulation of erythrocyte production by activation of the erythropoietin receptor (EPO-R), which triggers the activation of anti-apoptotic and proliferative responses of erythroid progenitor cells. Additionally, to erythropoietic EPO activity, an antiapoptotic effect has been described in a wide spectrum of tissues. EPO low levels are found in the central nervous system (CNS), while EPO-R is expressed in most CNS cell types. In spite of EPO-R high levels expressed during the hypoxicischemic brain, insufficient production of endogenous cerebral EPO could be the cause of determined circuit alterations that lead to the loss of specific neuronal populations. In the heart, high EPO-R expression in cardiac progenitor cells appears to contribute to myocardial regeneration under EPO stimulation. Several lines of evidence have linked EPO to an antiapoptotic role in CNS and in heart tissue. In this review, an antiapoptotic role of EPO/EPO-R system in both brain and heart under hypoxic conditions, such as epilepsy and sudden death (SUDEP) has been resumed. Additionally, their protective effects could be a new field of research and a novel therapeutic strategy for the early treatment of these conditions and avoid SUDEP.

Functional recovery with histomorphometric analysis of nerves and muscles after combination treatment with erythropoietin and dexamethasone in acute peripheral nerve injury

Introduction

Peripheral nerve injury (PNI) often leads to significant functional loss in patients and poses a challenge to physicians since treatment options for improving functional outcomes are limited. Recent studies suggest that erythropoietin and glucocoticoids have beneficial effects as mediators of neuro-regenerative processes. We hypothesized that combination treatment with erythropoietin and glucocoticoids would have a synergistic effect on functional outcome after PNI.

Materials and methods

Sciatic nerve crush injury was simulated in ten-week-old male C57BL/6 mice. The mice were divided into four groups according to the type of drugs administered (control, erythropoietin, dexamethasone, and erythropoietin with dexamethasone). Motor functional recovery was monitored by walking track analysis at serial time points up to 28 days after injury. Morphological analysis of the nerve was performed by immunofluorescent staining for neurofilament (NF) heavy chain and myelin protein zero (P0) in cross-sectional and whole-mount nerve preparations. Additionally, morphological analysis of the muscle was performed by Hematoxylin and eosin staining.

Results

Combination treatment with erythropoietin and dexamethasone significantly improved the sciatic functional index at 3, 7, 14, and 28 days after injury. Fluorescence microscopy of cross sectional nerve revealed that the combination treatment increased the ratio of P0/NF-expressing axons. Furthermore, confocal microscopy of the whole-mount nerve revealed that the combination treatment increased the fluorescence intensity of P0 expression. The cross-sectional area and minimum Feret’s diameter of the muscle fibers were significantly larger in the mice which received combination treatment than those in the controls.

Conclusion

Our results demonstrated that combination treatment with erythropoietin and dexamethasone accelerates functional recovery and reduces neurogenic muscle atrophy caused by PNI in mice, which may be attributed to the preservation of myelin and Schwann cell re-myelination. These findings may provide practical therapeutic options for patients with acute PNI.

Erythropoietin Preconditioning Mobilizes Endothelial Progenitor Cells to Attenuate Nephron-Sparing Surgery-Induced Ischemia-Reperfusion Injury

The purpose of this study was to examine the role of endothelial progenitor cells (EPCs) in protection against ischemic-reperfusion injury (IRI) in a nephron-sparing surgery (NSS) rat model using erythropoietin (EPO) preconditioning. Fifty-four male Sprague-Dawley rats were randomly divided into 3 groups for right kidney nephrectomy treatment: sham group (exposure without clamp treatment), NSS group (3 days of peritoneal phosphate buffered saline [PBS] injection before renal blood vessels were clamped for 40 mins and NSS was performed), and EPO group (3 days of EPO abdomen injections prior to renal blood vessel clamping for 40 min before NSS was performed). After 12, 24, and 72 hours, inferior vena cava blood and renal tissues were harvested. The extent of renal injury was assessed, along with EPC number, cell proliferation, angiogenesis, and vascular growth factor expression. EPO preconditioning significantly improved renal function and histologic morphology, indicated by reduced blood urea nitrogen (BUN) ([33.12 ± 1.88] vs [16.03 ± 0.91], P < .05) and serum creatinine (Scr) ([190.2 ± 20.23] vs [77.23 ± 5.82], P < .05) levels and histologic injury scores ([3.20 ± 0.78] vs [1.70 ± 0.67], P < .05). Angiogenesis in peritubular capillaries markedly increased in the EPO group. EPC numbers increased in the kidneys at 24 hours following reperfusion in the EPO group, compared to the NSS group. Furthermore, EPO preconditioning also increased SDF-1α and CXCR7 expression at 24 hours following reperfusion relative to the NSS group. These findings suggest that EPO pretreatment can reduce renal injury in rats caused by IRI. Mechanistically, this may be related to EPC mobilization and recruitment to injured renal tissues by SDF-1α and CXCR7.

Effects and Mechanisms of Five Psoralea Prenylflavonoids on Aging-Related Diseases

During the aging process, senescent cells gradually accumulate in the organs; they secrete proinflammatory cytokines and other factors, collectively known as the senescence-associated secretory phenotype (SASP). SASP secretions contribute to “inflammaging,” which is a state of chronic, systemic, sterility, low-grade inflammatory microenvironment and a key risk factor in the development of aging-related diseases. Fructus psoraleae is a traditional Chinese medical herb best known for delaying aging and treating osteoporosis. Prenylflavonoids from fructus psoraleae are the main bioactive compounds responsible for its pharmacological applications, such as beaching, bavachinin, bavachalcone, isobavachalcone, and neobavaisoflavone. In previous decades, there have been some promising studies on the pharmacology of fructus psoraleae. Here, we focus on the anti-inflammatory and antiaging diseases of five psoralea prenylflavonoids, such as cardiovascular protection, diabetes and obesity intervention, neuroprotection, and osteoporosis, and discuss the mechanism of these active ingredients for better understanding the material basis and drug application of fructus psoraleae in Chinese medicine.

Endothelium as a Therapeutic Target in Diabetes Mellitus: From Basic Mechanisms to Clinical Practice

Endothelium plays an essential role in human homeostasis by regulating arterial blood pressure, distributing nutrients and hormones as well as providing a smooth surface that modulates coagulation, fibrinolysis and inflammation. Endothelial dysfunction is present in Diabetes Mellitus (DM) and contributes to the development and progression of macrovascular disease, while it is also associated with most of the microvascular complications such as diabetic retinopathy, nephropathy and neuropathy. Hyperglycemia, insulin resistance, hyperinsulinemia and dyslipidemia are the main factors involved in the pathogenesis of endothelial dysfunction. Regarding antidiabetic medication, metformin, gliclazide, pioglitazone, exenatide and dapagliflozin exert a beneficial effect on Endothelial Function (EF); glimepiride and glibenclamide, dipeptidyl peptidase-4 inhibitors and liraglutide have a neutral effect, while studies examining the effect of insulin analogues, empagliflozin and canagliflozin on EF are limited. In terms of lipid-lowering medication, statins improve EF in subjects with DM, while data from short-term trials suggest that fenofibrate improves EF; ezetimibe also improves EF but further studies are required in people with DM. The effect of acetylsalicylic acid on EF is dose-dependent and lower doses improve EF while higher ones do not. Clopidogrel improves EF, but more studies in subjects with DM are required. Furthermore, angiotensin- converting-enzyme inhibitors /angiotensin II receptor blockers improve EF. Phosphodiesterase type 5 inhibitors improve EF locally in the corpus cavernosum. Finally, cilostazol exerts favorable effect on EF, nevertheless, more data in people with DM are required.

Erythropoietin and its derivatives: from tissue protection to immune regulation

Erythropoietin (EPO) is an evolutionarily conserved hormone well documented for its erythropoietic role via binding the homodimeric EPO receptor (EPOR)₂. In past decades, evidence has proved that EPO acts far beyond erythropoiesis. By binding the tissue-protective receptor (TPR), EPO suppresses proinflammatory cytokines, protects cells from apoptosis and promotes wound healing. Very recently, new data revealed that TPR is widely expressed on a variety of immune cells, and EPO could directly modulate their activation, differentiation and function. Notably, nonerythropoietic EPO derivatives, which mimic the structure of helix B within EPO, specifically bind TPR and show great potency in tissue protection and immune regulation. These small peptides prevent the cardiovascular side effects of EPO and are promising as clinical drugs. This review briefly introduces the receptors and tissue-protective effects of EPO and its derivatives and highlights their immunomodulatory functions and application prospects.

Chronic Hypoxia-Induced Microvessel Proliferation and Basal Membrane Degradation in the Bone Marrow of Rats Regulated through the IL-6/JAK2/STAT3/MMP-9 Pathway

Chronic hypoxia (CH) is characterized by long-term hypoxia that is associated with microvessel proliferation and basal membrane (BM) degradation in tissues. The IL-6/JAK2/STAT3/MMP-9 pathway has been described in a variety of human cancers and plays an essential role in microvessel proliferation and BM degradation. Therefore, this study investigated the role of the IL-6/JAK2/STAT3/MMP-9 pathway in hypoxia-mediated microvessel proliferation and BM degradation in the rat bone marrow. Eighty pathogen-free Sprague Dawley male rats were randomly divided into four groups (20 per group)—control group, CH group (exposed to hypoxia in a hypobaric chamber at a simulated altitude of 5000 m for 28 d), CH + STAT3 inhibitor group (7.5 mg/kg/d), and CH + DMSO group. Microvessel density (MVD) and BM degradation in the bone marrow were determined by immunofluorescence staining and transmission electron microscopy. Serum IL-6 levels were assessed by enzyme-linked immunosorbent assay (ELISA), and the levels of P-JAK2, P-STAT3, and MMP-9 were assessed by western blot analysis and real-time reverse transcription PCR (RT-PCR). Hypoxia increased serum IL-6 levels, which in turn increased JAK2 and STAT3 phosphorylation, which subsequently upregulated MMP-9. Overexpression of MMP-9 significantly promoted the elevation of MVD and BM degradation. Inhibition of STAT3 using an inhibitor, SH-4-54, significantly downregulated MMP-9 expression and decreased MVD and BM degradation. Surprisingly, STAT3 inhibition also decreased serum IL-6 levels and JAK2 phosphorylation. Our results suggest that the IL-6/JAK2/STAT3/MMP-9 pathway might be related to CH-induced microvessel proliferation and BM degradation in the bone marrow.

Cardioprotective effects of erythropoietin in diabetic rats determined by CD34 and vascular endothelial growth factor levels

Introduction

In this study, the effects of diabetes mellitus on the cardiovascular system were investigated by assessing the stem cell levels in serum and heart and compared with the normal population. Additionally, efficacy of erythropoietin, which is known to increase stem cells, was studied in diabetic rats.

Material and methods

Twenty-five male Sprague Dawley rats were divided into three groups as a control group (group 1), diabetic group (group 2) and erythropoietin induced diabetic group (group 3). A diabetes model was created with streptozocin. In group 3 rats received 3000 U/kg of erythropoietin. At the end of 1 month blood reticulocyte levels, degree of tissue fibrosis and immunohistochemical assessment of reliable stem cell markers, CD34 and vascular endothelial growth factor (VEGF), were analyzed.

Results

The increase in the blood glucose levels resulted in a significant decrease in reticulocyte levels in group 2. The increase in blood glucose levels resulted in a statistically significant increase in tissue level of fibrosis, CD34 and VEGF. When the rats in groups 1 and 2 were compared, the fibrosis, CD34 and VEGF levels were found to increase significantly. When group 2 and group 3 were compared, the amount of fibrosis was lower and the levels of CD34 and VEGF were significantly higher in group 3 than group 2.

Conclusions

The results of our study indicated that the amount of CD34 and VEGF which function in cellular protection and tissue regeneration may be enhanced with safely applicable erythropoietin leading to increase in reticulocyte levels in serum, and CD34 and VEGF levels in right atrium, right ventricle, left atrium, and left ventricle as a protective mechanism in diabetic rats.

Serum erythropoietin concentration and its correlation with stage of diabetic retinopathy

BACKGROUND

Erythropoietin (EPO) is one of the systemic angiogenic factors, and its role in ocular angiogenesis and in diabetic retinopathy (DR) is not yet fully understood. The latest research data reveal a possible correlation of higher erythropoietin concentrations in the blood and in the eye with the development of more advanced stages of DR. The main aim of this work was to examine the possible influence of serum concentrations of erythropoietin on the development of diabetic retinopathy in patients with diabetes mellitus type 2.

METHODS

The research involved 90 patients examined at the University Eye Clinic of the Clinical Center of Vojvodina, Novi Sad, Serbia. The first group comprised 60 patients with diabetes mellitus lasting for 10 years or more, with diabetic retinopathy. The second, control group consisted of 30 healthy individuals. In the first group of 60 patients with diabetes, 30 of them had non-proliferative diabetic retinopathy (NPDR), and 30 had proliferative diabetic retinopathy (PDR). Laboratory EPO serum levels were determined, and they were correlated to the stage of DR. Concentration of EPO was assessed by ELISA method.

RESULTS

The highest average concentration of EPO in serum (9.95 mIU/ml) was determined in the group of people with diabetes with PDR. The lowest average concentration of EPO in the serum (6.90 mIU/ml) was found in the control group. The average concentration of EPO in serum in the group of patients with diabetes with NPDR was 7.00 mIU/ml. The EPO concentration in serum was elevated in the group of PDR, and it was directly proportional to the level of the clinical stadium of PDR, being significantly higher in the moderate and severe subgroup of PDR comparing to the control healthy subjects, NPDR and mild PDR (p = 0.007).

CONCLUSIONS

Significantly elevated serum concentration of EPO in the advanced stages of DR, and positive correlation between EPO serum concentration and clinical stages of PDR, suggest that erythropoietin represents an important growth factor from blood, which plays a significant role in retinal ischemia and angiogenesis in diabetic retinopathy, especially in the proliferative stage of this disease.

Mobilization of Transplanted Bone Marrow Mesenchymal Stem Cells by Erythropoietin Facilitates the Reconstruction of Segmental Bone Defect

Reconstruction of segmental bone defects poses a tremendous challenge for both orthopedic clinicians and scientists, since bone rehabilitation is requisite substantially and may be beyond the capacity of self-healing. Bone marrow mesenchymal stem cells (BMSCs) have been identified as an optimal progenitor cell source to facilitate bone repair since they have a higher ability for proliferation and are more easily accessible than mature osteoblastic cells. In spite of the potential of BMSCs in regeneration medicine, particularly for bone reconstruction, noteworthy limitations still remain in previous application of BMSCs, including the amount of cells that could be recruited, the compromised bone migration of grafted cells, reduced proliferation and osteoblastic differentiation ability, and likely tumorigenesis. Our current work demonstrates that BMSCs transplanted through the caudal vein can be mobilized by erythropoietin (EPO) to the bone defect area and participate in regeneration of new bone. Based on the histological analysis and micro-CT findings of this study, EPO can dramatically promote the effects on the osteogenesis and angiogenesis efficiency of BMSCs in vivo. Animals that underwent EPO+BMSC administration demonstrated a remarkable increase in new bone formation, tissue structure organization, new vessel density, callus formation, and bone mineral density (BMD) compared with the BMSCs alone and control groups. At the biomechanical level, we demonstrated that combing transplantation of EPO and BMSCs enhances bone defect reconstruction by increasing the strength of the diaphysis, making it less fragile. Therefore, combination therapy using EPO infusion and BMSC transplantation may be a new therapeutic strategy for the reconstruction of segmental bone defect.

Regenerative therapies in young hearts with structural or congenital heart disease

Pediatric heart failure (HF) is rare. The prognosis is generally poor. HF is most frequently related to cardiomyopathy or congenital heart disease (CHD). Associated phenotypes are HF with preserved (HFpEF) or reduced ejection fraction (HFrEF); both in children with biventricular or univentricular circulation. Cardiac growth, differentiation, proliferation and consecutively regenerative and repair mechanisms are inversely related to the patient's age; edaphic and circulating cardiac progenitor cells as well; in sum, there are enormous endogenous potentials repairing a diseased heart in particular in young children. Efforts supporting pediatric cardiac regeneration are clearly justified; cell-based therapies have been addressed in small series of children with end-stage HF of either the left or right ventricle, more recently in randomized clinical trials. Different cell populations like autologous bone marrow mononuclear cells, progenitor cells or cardiac derived cells have been injected into coronaries or directly into the myocardium. Beneficial at least transient improvement of cardiac function was observed in patients with dilative cardiomyopathy and CHD, mainly hypoplastic left heart syndrome (HLHS). Cellular repopulation and possibly more crucial, paracrine effects contributed in slowing down progression of pediatric end-stage HF. Our review summarizes the current knowledge in different scenarios of HF by cell-based cardiac therapies in critically ill children. Based on the actual clinical experience future work to distinguish responders from non-responders among other refinements will lead to individualized precision treatment of HF in children, what means a lot to a child on a long list waiting for heart transplantation (HTX).

Pleiotropic effects of Erythropoietin. Influence of Erythropoietin on processes of mesenchymal stem cells differentiation

Structure and synthesis of Erythropoietin: Erythropoietin (EPO) is a glycoprotein hormone.

Recombinant Erythropoietin (Epoetin): Human recombinant erythropoietin is characterised as a factor which stimulates differentiation and proliferation of erythroid precursor cells, and as a tissue protective factor.

Anti-ischemic effects of recombinant Erythropoietin: Erythropoietin is one of the most perspective humoral agents which are involved in the preconditioning phenomenon.

Erythropoietin receptors and signal transduction pathways: Erythropoietin effects on cells through their interconnection with erythropoietin receptors, which triggers complex intracellular signal cascades, such as JAK2/STAT signaling pathway, phosphatidylinositol 3-kinase (PI3K), protein kinase C, mitogen-activated protein kinase (MAPK), and nuclear factor (NF)-κB signaling pathways.

Mechanisms of the effect of Erythropoietin on hematopoietic and non-hematopoietic cells and tissues: In addition to regulation of haemopoiesis, erythropoietin mediates bone formation as it has an effect on hematopoietic stem cells and osteoblastic niche, and this illustrates connection between the processes of haematopoiesis and osteopoiesis which take place in the red bone marrow.

The effect of Erythropoietin on mesenchymal stem cells and process of bone tissue formation: Erythropoietin promotes mesenchymal stem cells proliferation, migration and differentiation in osteogenic direction. The evidence of which is expression of bone phenotype by cells under the influence of EPO, including activation of bone specific transcription factors Runx2, osteocalcin and bone sialoprotein.

Conclusion: Erythropoietin has a pleiotropic effect on various types of cells and tissues. But the mechanisms which are involved in the process of bone tissue restoration via erythropoietin are still poorly understood.

The vasoreparative potential of endothelial colony-forming cells in the ischemic retina is enhanced by cibinetide, a non-hematopoietic erythropoietin mimetic

PURPOSE

Retinal ischemia remains a common sight threatening end-point in blinding diseases such as diabetic retinopathy and retinopathy of prematurity. Endothelial colony forming cells (ECFCs) represent a subpopulation of endothelial progenitors with therapeutic utility for promoting reparative angiogenesis in the ischaemic retina. The current study has investigated the potential of enhancing this cell therapy approach by the dampening of the pro-inflammatory milieu typical of ischemic retina. Based on recent findings that ARA290 (cibinetide), a peptide based on the Helix-B domain of erythropoietin (EPO), is anti-inflammatory and tissue-protective, the effect of this peptide on ECFC-mediated vascular regeneration was studied in the ischemic retina.

METHODS

The effects of ARA290 on pro-survival signaling and function were assessed in ECFC cultures in vitro. Efficacy of ECFC transplantation therapy to promote retinal vascular repair in the presence and absence of ARA290 was studied in the oxygen induced retinopathy (OIR) model of retinal ischemia. The inflammatory cytokine profile and microglial activation were studied as readouts of inflammation.

RESULTS

ARA290 activated pro-survival signaling and enhanced cell viability in response to H₂O₂-mediated oxidative stress in ECFCs in vitro. Preconditioning of ECFCs with EPO or ARA290 prior to delivery to the ischemic retina did not enhance vasoreparative function. ARA290 delivered systemically to OIR mice reduced pro-inflammatory expression of IL-1β and TNF-α in the mouse retina. Following intravitreal transplantation, ECFCs incorporated into the damaged retinal vasculature and significantly reduced avascular area. The vasoreparative function of ECFCs was enhanced in the presence of ARA290 but not EPO.

DISCUSSION

Regulation of the pro-inflammatory milieu of the ischemic retina can be enhanced by ARA290 and may be a useful adjunct to ECFC-based cell therapy for ischemic retinopathies.

Evaluation of the effects of erythropoietin and interleukin-6 in rats submitted to acute spinal cord injury

OBJECTIVE

To evaluate the effects of interleukin-6 (IL-6) and erythropoietin (EPO) in experimental acute spinal cord injury (SCI) in rats.

METHODS

Using standardized equipment, namely, a New York University (NYU) Impactor, a SCI was produced in 50 Wistar rats using a 10-g weight drop from a 12.5-mm height. The rats were divided into the following 5 groups of 10 animals each: "Group EPO", treated with erythropoietin only; "Group EPO + IL-6", treated with both substances; "Group IL-6", receiving IL-6 administration only; "Group Placebo", receiving a placebo solution; and "Group Sham", submitted to an incomplete procedure (only laminectomy, without SCI). All drugs and the placebo solution were administered intraperitoneally for three weeks. The animals were followed up for 42 days. Functional motor recovery was monitored by the Basso, Beattie, and Bresnahan (BBB) scale on days 2, 7, 14, 21, 28, 35 and 42. Motor-evoked potential tests were performed on the 42nd day. Histological analysis was performed after euthanasia.

RESULTS

The group receiving EPO exhibited superior functional motor results on the BBB scale. IL-6 administration alone was not superior to the placebo treatment, and the IL-6 combination with EPO yielded worse results than did EPO alone.

CONCLUSIONS

Using EPO after acute SCI in rats yielded benefits in functional recovery. The combination of EPO and IL-6 showed benefits, but with inferior results compared to those of isolated EPO; moreover, isolated use of IL-6 resulted in no benefit.

Effects of SGLT2 Inhibitors on Circulating Stem and Progenitor Cells in Patients With Type 2 Diabetes

CONTEXT

Reduction in the levels of circulating stem cells (CSCs) and endothelial progenitor cells (EPCs) predicts development or progression of microangiopathy and macroangiopathy in patients with type 2 diabetes (T2D).

OBJECTIVE

We tested whether treatment with sodium glucose cotransporter-2 (SGLT2) inhibitors affected the levels of CSCs and EPCs.

DESIGN

A randomized trial of dapagliflozin vs placebo with open-label extension, and an open-label observational study of empagliflozin treatment.

SETTING

Tertiary referral diabetes outpatient clinic.

PATIENTS

Patients with T2D aged 18 to 75 years.

INTERVENTION

Dapagliflozin at 10 mg vs placebo (n = 31); empagliflozin at 10 mg (n = 15).

MAIN OUTCOME MEASURES

We measured CSCs (CD34+) and EPCs (CD34+KDR+) by flow cytometry at baseline, at 12 weeks, and after the extension period.

RESULTS

After 12 weeks, CSCs declined nonsignificantly in the dapagliflozin group, remained stable in the placebo group, and the change from baseline was not significantly different between the two groups. EPCs declined nonsignificantly in the dapagliflozin group, increased nonsignificantly in the placebo group, and the change from baseline was significantly different between the two groups. After an open-label extension period of about 1.5 years, CSCs remained stable over time, whereas EPCs significantly increased in patients who received dapagliflozin. In all patients, irrespectively of treatment, EPCs increased significantly from baseline to the end of observation, concomitantly with improvement in HbA1c. In a cohort of 15 patients who received open-label empagliflozin for 12 weeks, CSCs declined nonsignificantly, whereas EPCs remained stable.

CONCLUSION

SGLT2 inhibitors do not significantly increase CSCs or EPCs. Thus, cardiovascular protection by SGLT2 inhibitors may not directly involve stem/progenitor cells.

Nrf2 protects against diabetic dysfunction of endothelial progenitor cells via regulating cell senescence

Diabetes is associated with an increased risk of cardio-vascular disease. A decrease in the number and functionality of endothelial progenitor cells (EPCs) leads to reduced endothelial repair and the development of cardiovascular disease. The aim of the present study was to explore the effect and underlying mechanisms of nuclear factor erythroid 2-related factor 2 (Nrf2) on EPC dysfunction caused by diabetic mellitus. The biological functions of EPCs in streptozotocin-induced diabetic mice were evaluated, including migration, proliferation, angiogenesis and the secretion of vascular endothelial growth factor (VEGF), stromal-derived growth factor (SDF) and nitric oxide (NO). Oxidative stress levels in diabetic EPCs were also assessed by detecting intracellular reactive oxygen species (ROS), superoxide dismutase (SOD) and malondialdehyde (MDA). EPC senescence was evaluated by measuring p16 and b-gal expression and observing the senescence-associated secretory phenotype. In addition, the function of EPCs and level of oxidative stress were assessed following Nrf2 silencing or activation. Nrf2 silencing resulted in a decrease of EPC biological functions, accelerated cell senescence and increased oxidative stress, as indicated by ROS and MDA upregulation accompanied with decreased SOD activity. Furthermore, Nrf2 silencing inhibited migration, proliferation and secretion in EPCs, while it increased oxidative stress and cell senescence. Nrf2 activation protected diabetic EPCs against the effects of oxidative stress and cell senescence, ameliorating the biological dysfunction of EPCs derived from mice with diabetes. In conclusion, Nrf2 overexpression protected against oxidative stress-induced functional damage in EPCs derived from diabetic mice by regulating cell senescence.

Decreased Count and Dysfunction of Circulating EPCs in Postmenopausal Hypercholesterolemic Females via Reducing NO Production

Endothelial progenitor cells (EPCs) contribute to the endogenous endothelial repair program during hypercholesterolemia. EPC count and migratory and proliferative capacities remain unchanged in the premenopausal female with hypercholesterolemia. However, the changes of count and activity of circulating EPCs in the hypercholesterolemic postmenopausal females are unknown. Here, we find that the migratory and proliferative capacities of circulating EPCs were decreased in patients with hypercholesterolemia versus normocholesterolemia. No significant differences were found between postmenopausal females and age-matched males. NO production showed positive correlation with the activity and count of circulating EPCs in patients with hypercholesterolemia. Flow-mediated dilatation (FMD) is directly interrelated with EPC counts and function. Our findings reveal that decreased EPC count and endothelial dysfunction lead to less NO production in hypercholesterolemic postmenopausal females. Maintaining the EPC numbers and activity might be emerging as a potential therapeutic strategy to reduce the risk of cardiovascular injury in elder women.

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.

Microparticles of healthy origins improve endothelial progenitor cell dysfunction via microRNA transfer in an atherosclerotic hamster model

AIM

In this study, we aimed: (i) to obtain and functionally characterize the cultures of late endothelial progenitor cells (EPCs) from the animal blood; (ii) to investigate the potential beneficial effects of circulating microparticles (MPs) of healthy origins on EPC dysfunctionality in atherosclerosis as well as involved mechanisms.

METHODS

Late EPCs were obtained and expanded in culture from peripheral blood isolated from two animal groups: hypertensive-hyperlipidaemic (HH) and control (C) hamsters. In parallel experiments, late EPC cultures from HH were incubated with MPs from C group.

RESULTS

The results showed that late EPCs display endothelial cell phenotype: (i) have ability to uptake 1,1-dioctadecyl-3,3,3,3 tetramethylindocarbocyanine-labelled acetylated low-density lipoprotein and Ulex europaeus agglutinin lectin-1; (ii) express CD34, CD133, KDR, CD144, vWF, Tie-2. Late EPCs from HH exhibited different morphological and functional characteristics compared to control: (i) are smaller and irregular in shape; (ii) present decreased endothelial surface marker expression; (iii) display reduced proliferation, migration and adhesion; (iv) lose ability to organize themselves into tubular structures and integrate into vascular network; (v) have diminished function of inward rectifier potassium channels. The incubation of late EPCs with MPs improved EPC functionality by miR-10a, miR-21, miR-126, miR-146a, miR-223 transfer and IGF-1 expression activation; the kinetic study of MP incorporation into EPCs demonstrated MP uptake by EPCs followed by the miRNA transfer.

CONCLUSION

The data reveal that late EPCs from atherosclerotic model exhibit distinctive features and are dysfunctional, and their function recovery can be supported by MP ability to transfer miRNAs. These findings bring a new light on the vascular repair in atherosclerosis.

AMPK-KLF2 signaling pathway mediates the proangiogenic effect of erythropoietin in endothelial colony-forming cells

Endothelial colony-forming cells (ECFCs) were proved to take part in postnatal vasculogenesis and injury repair. The angiogenic properties of ECFCs could be influenced by various cytokines, chemokines, and growth factors. Erythropoietin (EPO) is a promising cytokine participating in angiogenesis. However, the mechanisms for EPO's proangiogenic effect still remain largely elusive. Here, we investigated the role of the AMP-activated protein kinase (AMPK)-Krüppel-like factor 2 (KLF2) signaling pathway in the proangiogenic effect of EPO in ECFCs. Human ECFCs were isolated from cord blood and cultured. EPO significantly enhanced the migration and tube formation capacities of ECFCs and markedly increased the expression of endothelial markers and vascular endothelial growth factor (VEGF). Further, EPO caused the phosphorylation of AMPK and endothelial nitric oxide synthase, a process in which KLF2 was also upregulated on both mRNA and protein levels. The upregulation of KLF2 was blocked by inhibiting AMPK with Compound C or Ad-AMPK-DN, a recombinant adenovirus that encoded a dominant-negative mutant of AMPK. Furthermore, knockdown of KLF2 showed no effect on AMPK but abolished the EPO-enhanced migration and tube formation capacities of ECFCs. Of note, knockdown of KLF2 also diminished the EPO-induced expression of endothelial markers and VEGF; overexpression of KLF2 promoted the expression of endothelial markers and VEGF and enhanced the migration and tube formation capacities of ECFCs. These data suggest that upregulation of KLF2 by AMPK plays an essential role in EPO-induced angiogenesis.

Natural compound bavachalcone promotes the differentiation of endothelial progenitor cells and neovascularization through the RORα-erythropoietin-AMPK axis

In cardiovascular diseases, endothelial function is impaired and the level of circulating endothelial progenitor cells (EPCs) is low. This study investigated whether the natural bioactive component bavachalcone (BavaC) induces the differentiation of EPCs and neovascularization in vivo; the underlying mechanisms were also examined. We observed that the treatment of rat bone marrow–derived cells with a very low dose of BavaC significantly promoted EPC differentiation. In our hindlimb ischemia models, low–dose BavaC administered orally for 14 days stimulated the recovery of ischemic hindlimb blood flow, increased circulating EPCs, and promoted capillary angiogenesis. The BavaC treatment of rat bone marrow cells for 24 h initiated the AMP–activated protein kinase (AMPK) activity required for the differentiation of EPCs. Further testing revealed that BavaC and CGP52608, a retinoic acid receptor–related orphan receptor α (RORα) activator, enhanced the activity of RORα1 and EPO luciferase reporter gene. BavaC treatment also elevated EPO mRNA and protein expression in vitro and in vivo and the circulating EPO levels in rats. By contrast, the RORα antagonist VPR66 inhibited BavaC–induced EPO reporter activity, and differentiation of bone marrow cells into endothelial progenitor cells. Overall, this study revealed that BavaC promotes EPC differentiation and neovascularization through a RORα–EPO–AMPK axis. BavaC can be used as a promising angiogenesis agent for enhancing angiogenesis and tissue repair.

Anemia as a risk factor for all-cause mortality: obscure synergic effect of chronic kidney disease

BACKGROUND

Anemia is common in chronic kidney disease (CKD) and may be associated with mortality in CKD patients. However, few studies have examined this relationship in Asian populations.

METHODS

A total of 62,931 Japanese people (age 64.0 ± 8.0 years; men 38.5%) were followed up from 2008 to 2012. Participants were divided into six groups in accordance with their estimated glomerular filtration rate (eGFR) (<45, 45-59, ≥60 mL/min/1.73 m²) and by hemoglobin levels (13.0 g/dL for men; 12.0 g/dL for women). Hazard ratio and confidence interval (CI) for mortality with a combination of eGFR and anemia were calculated. After matching using propensity score (PS) for anemia, survival analysis between anemic and non-anemic people, independent from some variables, including eGFR, was performed.

RESULTS

A total of 828 (1.3%) participants died (non-anemic vs. anemic, 1.2 vs. 2.3%, p < 0.01). Multivariable Cox analysis showed that, independent of eGFR levels, anemic people had significantly higher mortality. Anemic people were found to have significantly poorer survival than non-anemic people as per a log-rank test (p < 0.01) for the PS-matching cohort. Further stratified logistic analysis using PS in the overall cohort odds ratio (95% CI) showed 2.25 (1.89-2.67) with p < 0.01.

CONCLUSION

The results of the present study showed that anemia was an independent risk factor of all-cause mortality.

Physiological Plasticity of Neural-Crest-Derived Stem Cells in the Adult Mammalian Carotid Body

Adult stem cell plasticity, or the ability of somatic stem cells to cross boundaries and differentiate into unrelated cell types, has been a matter of debate in the last decade. Neural-crest-derived stem cells (NCSCs) display a remarkable plasticity during development. Whether adult populations of NCSCs retain this plasticity is largely unknown. Herein, we describe that neural-crest-derived adult carotid body stem cells (CBSCs) are able to undergo endothelial differentiation in addition to their reported role in neurogenesis, contributing to both neurogenic and angiogenic processes taking place in the organ during acclimatization to hypoxia. Moreover, CBSC conversion into vascular cell types is hypoxia inducible factor (HIF) dependent and sensitive to hypoxia-released vascular cytokines such as erythropoietin. Our data highlight a remarkable physiological plasticity in an adult population of tissue-specific stem cells and could have impact on the use of these cells for cell therapy.

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Adult carotid body stem cells display multipotency during organ adaptation to hypoxia

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Neural-crest-derived stem cells contribute to angiogenesis in the adult carotid body

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Endothelial differentiation from carotid body stem cells is HIF2α and EPO dependent

Rehabilitation Treatment and Progress of Traumatic Brain Injury Dysfunction

Traumatic brain injury (TBI) is a major cause of chronic disability. Worldwide, it is the leading cause of disability in the under 40s. Behavioral problems, mood, cognition, particularly memory, attention, and executive function are commonly impaired by TBI. Spending to assist, TBI survivors with disabilities are estimated to be costly per year. Such impaired functional outcomes following TBI can be improved via various rehabilitative approaches. The objective of the present paper is to review the current rehabilitation treatment of traumatic brain injury in adults.

Absence of macrophage migration inhibitory factor reduces proliferative retinopathy in a mouse model

AIMS

Ischemia-induced neovascularization is the key feature of proliferative diabetic retinopathy. Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory and proangiogenic cytokine, and its levels are elevated in the vitreous of patients with proliferative diabetic retinopathy. In this study, we aimed at investigating the relative potential of MIF in the ischemia-induced retinal neovascularization.

METHODS

Both WT and MIF-knockout mice were subjected to the retinopathy of prematurity (ROP) model. Intraretinal vessel regrowth was assessed by whole-mount immunofluorescence, and preretinal neovascularization was analyzed in retinal vertical sections after periodic acid-Schiff staining in the hypoxic stage of the ROP model. Gene expression of selected proangiogenic and proinflammatory factors at postnatal day 13 (p13) was measured by real-time PCR. Vascular endothelial growth factor (VEGF) expression, recruitment of endothelial progenitor cells (EPCs) and microglial activation were analyzed with immunofluorescence.

RESULTS

MIF deficiency increased areas of vascular obliteration by 49%, reduced sprouting tips by 27% and inhibited preretinal angiogenesis by 35%. VEGF expression was reduced in Müller cells of MIF-knockout mice. MIF absence reduced gene expression of erythropoietin, tumor necrosis factor alpha and intercellular adhesion molecule-1 by 30, 70 and 50%, respectively, decreased the number of retinal EPCs by 37.5% and inhibited microglial activation in the hypoxic condition.

CONCLUSIONS

In conclusion, we found that MIF has proangiogenic and proinflammatory properties in retinal neovascularization. The proangiogenic role of MIF in ischemia-induced retinal neovascularization is associated with the expression of VEGF and erythropoietin, EPC recruitment and inflammation. Therefore, MIF has a potential role in the pathological angiogenesis of proliferative retinopathy.

Endothelial progenitor cells: Exploring the pleiotropic effects of statins

Statins have become a cornerstone of risk modification for ischaemic heart disease patients. A number of studies have shown that they are effective and safe. However studies have observed an early benefit in terms of a reduction in recurrent infarct and or death after a myocardial infarction, prior to any significant change in lipid profile. Therefore, pleiotropic mechanisms, other than lowering lipid profile alone, must account for this effect. One such proposed pleiotropic mechanism is the ability of statins to augment both number and function of endothelial progenitor cells. The ability to augment repair and maintenance of a functioning endothelium may have profound beneficial effect on vascular repair and potentially a positive impact on clinical outcomes in patients with cardiovascular disease. The following literature review will discuss issues surrounding endothelial progenitor cell (EPC) identification, role in vascular repair, factors affecting EPC numbers, the role of statins in current medical practice and their effects on EPC number.

Bone Niches, Hematopoietic Stem Cells, and Vessel Formation

Bone marrow (BM) is a source of hematopoietic stem cells (HSCs). HSCs are localized in both the endosteum, in the so-called endosteal niche, and close to thin-walled and fenestrated sinusoidal vessel in the center of BM, in the so-called vascular niche. HSCs give rise to all types of mature blood cells through a process finely controlled by numerous signals emerging from the bone marrow niches where HSCs reside. This review will focus on the description of the role of BM niches in the control of the fate of HSCs and will also highlight the role of the BM niches in the regulation of vasculogenesis and angiogenesis. Moreover, alterations of the signals in niche microenvironment are involved in many aspects of tumor progression and vascularization and further knowledge could provide the basis for the development of new therapeutic strategies.

Prevention of contrast-induced nephropathy with single bolus erythropoietin in patients with diabetic kidney disease: A randomized controlled trial

AIM

Contrast-induced-nephropathy (CIN) is associated with poor outcomes, thus prevention of CIN may be of clinical value. Erythropoietin (EPO) has been shown to elicit tissue-protective effects in experimental models and in clinical studies of acute kidney injury. We therefore evaluated its effectiveness for prevention of CIN after coronary angiography (CA) ± percutaneous coronary intervention (PCI) in diabetic patients with chronic kidney disease.

METHODS

A prospective, randomized, controlled trial was carried out in 138 diabetic patients with eGFR <60 mL/min who underwent non-urgent CA ± PCI. Patients received normal saline and n-acetyl cysteine before CA, with or without 50,000 U of EPO administered 30 min prior to CA. CIN was defined as an increase in serum creatinine of at least 0.5 mg/dL during the first 2 days after exposure to contrast media. Primary outcome was the incidence of CIN. Secondary outcomes were the sensitivity and positive predictive value (PPV) of Cystatin C (CC) and Neutrophil-gelatinase-associated-lipocalin (NGAL) for diagnosis of CIN.

RESULTS

The observed incidence of CIN was 8.7%, significantly lower than the expected for such high-risk population. The administration of EPO prior to CA did not reduce the incidence of CIN (9.7% vs. 7.6%, P = 0.65). CC and NGAL demonstrated a low sensitivity (16.6%) and low PPV (6.7 and 33.3%, respectively) for detecting CIN.

CONCLUSION

The administration of EPO prior to CA did not reduce the incidence of CIN. Additional prospective research with a larger sample size and in other patient categories is essential to further define the potential protective effect of EPO on prevention of CIN.

Spotlight on endothelial progenitor cell inhibitors: short review

Endothelial progenitor cells (EPCs) are bone-marrow-derived cells that enter the systemic circulation to replace defective or injured mature endothelial cells. EPCs also contribute to neovascularization and limit the progression of atherosclero sis. Patients with reduced EPC levels or dysfunctional EPCs are at increased risk for coronary artery disease. Drug-mediated improvement of the mobilization, differenti ation, function and homing of EPCs to sites of ischemia or injured endothelium may therefore be a promising novel therapeutic approach for various cardiovascular dis eases. On the other hand, endogenous inhibitors of EPCs could also be valuable drug targets. The identification of EPC inhibitors and the development of novel drugs that can efficiently regulate production or elimination of these molecules may also be a promising approach for the future treatment of atherosclerosis. In the present review we summarize potential endogenous and exogenous inhibitors of EPCs, such as oxidized low-density lipoproteins, angiotensin II, glucose, cigarette smoke and others. Whenever possible, we also describe the underlying molecular events. Drug- induced mobilization and improvement of EPC function, as well as reduction of EPC inhibitors, is likely to enhance endothelial function and reduce atherosclerotic processes.

Erythropoietin and a nonerythropoietic peptide analog promote aortic endothelial cell repair under hypoxic conditions: role of nitric oxide

The cytoprotective effects of erythropoietin (EPO) and an EPO-related nonerythropoietic analog, pyroglutamate helix B surface peptide (pHBSP), were investigated in an in vitro model of bovine aortic endothelial cell injury under normoxic (21% O₂) and hypoxic (1% O₂) conditions. The potential molecular mechanisms of these effects were also explored. Using a model of endothelial injury (the scratch assay), we found that, under hypoxic conditions, EPO and pHBSP enhanced scratch closure by promoting cell migration and proliferation, but did not show any effect under normoxic conditions. Furthermore, EPO protected bovine aortic endothelial cells from staurosporine-induced apoptosis under hypoxic conditions. The priming effect of hypoxia was associated with stabilization of hypoxia inducible factor-1α, EPO receptor upregulation, and decreased Ser-1177 phosphorylation of endothelial nitric oxide synthase (NOS); the effect of hypoxia on the latter was rescued by EPO. Hypoxia was associated with a reduction in nitric oxide (NO) production as assessed by its oxidation products, nitrite and nitrate, consistent with the oxygen requirement for endogenous production of NO by endothelial NOS. However, while EPO did not affect NO formation in normoxia, it markedly increased NO production, in a manner sensitive to NOS inhibition, under hypoxic conditions. These data are consistent with the notion that the tissue-protective actions of EPO-related cytokines in pathophysiological settings associated with poor oxygenation are mediated by NO. These findings may be particularly relevant to atherogenesis and postangioplasty restenosis.

Erythropoietin Induces Excessive Neointima Formation: A Study in a Rat Carotid Artery Model of Vascular Injury

A therapeutic strategy that would mitigate the events leading to hyperplasia and facilitate re-endothelialization of an injured artery after balloon angioplasty could be effective for a long-term patency of the artery. It is hypothesized that erythropoietin (EPO), which has both anti-inflammatory and antiapoptotic properties, will prevent hyperplasia, and its ability to proliferate and mobilize endothelial progenitor cells will re-endothelialize the injured artery. To test this hypothesis, EPO (5000 IU/kg) in solution was injected intraperitoneally 6 hours before vascular injury and then on every alternate day for a week or as a single dose (5000 IU/kg) in a sustained release gel formulation 1 week before the vascular injury. Morphometric analysis revealed nearly continuous re-endothelialization of the injured artery in EPO solution-treated animals (90% vs less than 20% in saline control); however, the treatment also caused excessive neointima formation (intima/media ratio, 2.10 ± 0.09 vs 1.60 ± 0.02 saline control, n = 5, P < .001). The EPO gel also induced similar excessive neointima formation. Immunohistochemical analysis of the injured arteries from the animals treated with EPO solution demonstrated a significant angiogenic response in adventitia and media, thus explaining the formation of excessive neointima. Although the results are in contrast to expectation, they explain a greater degree of stenosis seen in hemodialysis access fistulas in patients who are on EPO therapy for anemic condition. The results also caution the use of EPO, particularly in patients who are at a risk of vascular injury or are suffering from an atherosclerotic condition.

Erythropoietin Stimulates Endothelial Progenitor Cells to Induce Endothelialization in an Aneurysm Neck After Coil Embolization by Modulating Vascular Endothelial Growth Factor

: This study explored a new approach to enhance aneurysm (AN) neck endothelialization via erythropoietin (EPO)-induced endothelial progenitor cell (EPC) stimulation. Results suggest that EPO enhanced the endothelialization of a coiled embolization AN neck by stimulating EPCs via vascular endothelial growth factor modulation. Thus, the promotion of endothelialization with EPO provides an additional therapeutic option for preventing the recurrence of ANs. Endovascular coil embolization is an attractive therapy for cerebral ANs, but recurrence is a main problem affecting long-term outcomes. In this study, we explored a new approach to enhance AN neck endothelialization via EPO-induced EPC stimulation. Ninety adult male Sprague-Dawley rats were selected for an in vivo assay, and 60 of them underwent microsurgery to create a coiled embolization AN model. The animals were treated with EPO, and endothelial repair was assessed via flow cytometry, immunofluorescence, electronic microscopy, cytokine detection, and routine blood work. EPO improved the viability, migration, cytokine modulation, and gene expression of bone marrow-derived EPCs and the results showed that EPO increased the number of circulating EPCs and improved endothelialization compared with untreated rats (p < .05). EPO had no significant effect on the routine blood work parameters. In addition, the immunofluorescence analysis showed that the number of KDR(+) cells in the AN neck was elevated in the EPO-treated group (p < .05). Further study demonstrated that EPO promoted EPC viability and migration in vitro. The effects of EPO may be attributed to the modulation of vascular endothelial growth factor (VEGF). In particular, EPO enhanced the endothelialization of a coiled embolization AN neck by stimulating EPCs via VEGF modulation. Thus, the promotion of endothelialization with EPO provides an additional therapeutic option for preventing the recurrence of ANs.

SIGNIFICANCE

Erythropoietin (EPO) is involved in erythropoiesis and related conditions and is reported to enhance stem-cell mobilization from bone marrow while elevating stem-cell viability and function. In this study, EPO was also found to stimulate endothelial progenitor cells to induce the endothelialization of a coiled embolic aneurysm neck via vascular endothelial growth factor modulation. Endothelialization induction provides an additional therapeutic opportunity during vascular inner layer repair and remodeling. The results provide important information on the unique role EPO plays during vascular repair and remodeling.

Endothelial Progenitor Cells in Diabetic Microvascular Complications: Friends or Foes?

Despite being featured as metabolic disorder, diabetic patients are largely affected by hyperglycemia-induced vascular abnormality. Accumulated evidence has confirmed the beneficial effect of endothelial progenitor cells (EPCs) in coronary heart disease. However, antivascular endothelial growth factor (anti-VEGF) treatment is the main therapy for diabetic retinopathy and nephropathy, indicating the uncertain role of EPCs in the pathogenesis of diabetic microvascular disease. In this review, we first illustrate how hyperglycemia induces metabolic and epigenetic changes in EPCs, which exerts deleterious impact on their number and function. We then discuss how abnormal angiogenesis develops in eyes and kidneys under diabetes condition, focusing on “VEGF uncoupling with nitric oxide” and “competitive angiopoietin 1/angiopoietin 2” mechanisms that are shared in both organs. Next, we dissect the nature of EPCs in diabetic microvascular complications. After we overview the current EPCs-related strategies, we point out new EPCs-associated options for future exploration. Ultimately, we hope that this review would uncover the mysterious nature of EPCs in diabetic microvascular disease for therapeutics.

Preservation and enumeration of endothelial progenitor and endothelial cells from peripheral blood for clinical trials

AIMS

Endothelial progenitor cells (EPCs) are markers of vascular repair. Increased numbers of circulating endothelial cells (ECs) are associated with endothelial damage.

MATERIALS & METHODS

We enumerated EPC-EC by using Enrichment kit with addition of anti-human CD146-PE/Cy7 from peripheral blood mononuclear cell (PBMC) isolated either by red blood cell (RBC) lysing solution or by Ficoll centrifugation, and from fresh and preserved samples. PBMCs were quantified by flow cytometry.

RESULTS

RBC lysis yielded higher percentage of PBMC (p = 0.0242) and higher numbers of PBMC/ml (p = 0.0039) than Ficoll. Absolute numbers of CD34(+)CD133(+)VEGFR2(+) and CD146(+)CD34(+)VEGFR2(+) were higher (p = 0.0117 for both), when isolated by RBC lysis than by Ficoll, when no difference in other subsets was found. Cryopreservation at -160°C and -80°C and short-term preservation at room temperature decreased EPC-EC.

CONCLUSIONS

Our data support use of fresh samples and isolation of PBMC from human blood by RBC lysis for enumeration of EPC and EC.

Sequential Functions of CPEB1 and CPEB4 Regulate Pathologic Expression of Vascular Endothelial Growth Factor and Angiogenesis in Chronic Liver Disease

BACKGROUND & AIMS

Vascular endothelial growth factor (VEGF) regulates angiogenesis, yet therapeutic strategies to disrupt VEGF signaling can interfere with physiologic angiogenesis. In a search for ways to inhibit pathologic production or activities of VEGF without affecting its normal production or functions, we investigated the post-transcriptional regulation of VEGF by the cytoplasmic polyadenylation element-binding proteins CPEB1 and CPEB4 during development of portal hypertension and liver disease.

METHODS

We obtained transjugular liver biopsies from patients with hepatitis C virus-associated cirrhosis or liver tissues removed during transplantation; healthy human liver tissue was obtained from a commercial source (control). We also performed experiments with male Sprague-Dawley rats and CPEB-deficient mice (C57BL6 or mixed C57BL6/129 background) and their wild-type littermates. Secondary biliary cirrhosis was induced in rats by bile duct ligation, and portal hypertension was induced by partial portal vein ligation. Liver and mesenteric tissues were collected and analyzed in angiogenesis, reverse transcription polymerase chain reaction, polyA tail, 3' rapid amplification of complementary DNA ends, Southern blot, immunoblot, histologic, immunohistochemical, immunofluorescence, and confocal microscopy assays. CPEB was knocked down with small interfering RNAs in H5V endothelial cells, and translation of luciferase reporters constructs was assessed.

RESULTS

Activation of CPEB1 promoted alternative nuclear processing within noncoding 3'-untranslated regions of VEGF and CPEB4 messenger RNAs in H5V cells, resulting in deletion of translation repressor elements. The subsequent overexpression of CPEB4 promoted cytoplasmic polyadenylation of VEGF messenger RNA, increasing its translation; the high levels of VEGF produced by these cells led to their formation of tubular structures in Matrigel assays. We observed increased levels of CPEB1 and CPEB4 in cirrhotic liver tissues from patients, compared with control tissue, as well as in livers and mesenteries of rats and mice with cirrhosis or/and portal hypertension. Mice with knockdown of CPEB1 or CPEB4 did not overexpress VEGF or have signs of mesenteric neovascularization, and developed less-severe forms of portal hypertension after portal vein ligation.

CONCLUSIONS

We identified a mechanism of VEGF overexpression in liver and mesentery that promotes pathologic, but not physiologic, angiogenesis, via sequential and nonredundant functions of CPEB1 and CPEB4. Regulation of CPEB4 by CPEB1 and the CPEB4 autoamplification loop induces pathologic angiogenesis. Strategies to block the activities of CPEBs might be developed to treat chronic liver and other angiogenesis-dependent diseases.