Synergistic effects of telmisartan and simvastatin on endothelial progenitor cells

Orthogonal Gelations to Synthesize Core-Shell Hydrogels Loaded with Nanoemulsion-Templated Drug Nanoparticles for Versatile Oral Drug Delivery

Hydrophobic active pharmaceutical ingredients (APIs) are ubiquitous in the drug development pipeline, but their poor bioavailability often prevents their translation into drug products. Industrial processes to formulate hydrophobic APIs are expensive, difficult to optimize, and not flexible enough to incorporate customizable drug release profiles into drug products. Here, a novel, dual-responsive gelation process that exploits orthogonal thermo-responsive and ion-responsive gelations is introduced. This one-step "dual gelation" synthesizes core-shell (methylcellulose-alginate) hydrogel particles and encapsulates drug-laden nanoemulsions in the hydrogel matrices. In situ crystallization templates drug nanocrystals inside the polymeric core, while a kinetically stable amorphous solid dispersion is templated in the shell. Drug release is explored as a function of particle geometry, and programmable release is demonstrated for various therapeutic applications including delayed pulsatile release and sequential release of a model fixed-dose combination drug product of ibuprofen and fenofibrate. Independent control over drug loading between the shell and the core is demonstrated. This formulation approach is shown to be a flexible process to develop drug products with biocompatible materials, facile synthesis, and precise drug release performance. This work suggests and applies a novel method to leverage orthogonal gel chemistries to generate functional core-shell hydrogel particles.

Endothelial Progenitor Cells Dysfunctions and Cardiometabolic Disorders: From Mechanisms to Therapeutic Approaches

Metabolic syndrome (MetS) is a cluster of several disorders, such as hypertension, central obesity, dyslipidemia, hyperglycemia, insulin resistance and non-alcoholic fatty liver disease. Despite health policies based on the promotion of physical exercise, the reduction of calorie intake and the consumption of healthy food, there is still a global rise in the incidence and prevalence of MetS in the world. This phenomenon can partly be explained by the fact that adverse events in the perinatal period can increase the susceptibility to develop cardiometabolic diseases in adulthood. Individuals born after intrauterine growth restriction (IUGR) are particularly at risk of developing cardiovascular diseases (CVD) and metabolic disorders later in life. It has been shown that alterations in the structural and functional integrity of the endothelium can lead to the development of cardiometabolic diseases. The endothelial progenitor cells (EPCs) are circulating components of the endothelium playing a major role in vascular homeostasis. An association has been found between the maintenance of endothelial structure and function by EPCs and their ability to differentiate and repair damaged endothelial tissue. In this narrative review, we explore the alterations of EPCs observed in individuals with cardiometabolic disorders, describe some mechanisms related to such dysfunction and propose some therapeutical approaches to reverse the EPCs dysfunction.

Cigarette smoke extract affects methylation status and attenuates Sca-1 expression of mouse endothelial progenitor cell in vitro

INTRODUCTION

Endothelial dysfunction appears in many smoking-related diseases, it is also an important pathophysiological feature. Endothelial progenitor cells (EPCs) are precursors of endothelial cells and have a crucial effect on the repair and maintenance of endothelial integrity. Sca-1 is not only common in bone marrow-derived hematopoietic stem cells (HSCs), but it is also expressed in nonhematopoietic organs by tissue-resident stem and progenitor cells. The aim of this study is to investigate the impact of cigarette smoke extract (CSE) on the function of bone marrow-derived EPCs and the expression level of Sca-1 in EPCs, and also whether the methylation of Sca-1 is involved in EPC dysfunction.

METHODS

We measured EPC capacities including adhesion, secretion and proliferation, the concentration of endothelial nitric oxide synthase (eNOS) and apoptosis-inducing factor (AIF) in cell culture supernatant, and also Sca-1 expression and promoter methylation in EPCs induced by CSE. Decitabine (Dec) was applied to test whether it could alter the impact caused by CSE.

RESULTS

The adhesion, proliferation and secretion ability of EPCs can be induced to be decreased by CSE in vitro, accompanied by decreased concentrations of AIF and eNOS in cell culture supernatant and decreased Sca-1 expression in EPCs. In addition, Dec could partly attenuate the impact described above. There were no significant differences in the quantitative analysis of Sca-1 promoter methylation among different groups.

CONCLUSIONS

The decreased Sca-1 expression was related to EPC dysfunction induced by CSE. EPC dysfunction resulting from CSE may be related to methylation mechanism, but not the methylation of Sca-1 promoter.

Murine sca1/flk1-positive cells are not endothelial progenitor cells, but B2 lymphocytes

Circulating sca1⁺/flk1⁺ cells are hypothesized to be endothelial progenitor cells (EPCs) in mice that contribute to atheroprotection by replacing dysfunctional endothelial cells. Decreased numbers of circulating sca1⁺/flk1⁺ cells correlate with increased atherosclerotic lesions and impaired reendothelialization upon electric injury of the common carotid artery. However, legitimate doubts remain about the identity of the putative EPCs and their contribution to endothelial restoration. Hence, our study aimed to establish a phenotype for sca1⁺/flk1⁺ cells to gain a better understanding of their role in atherosclerotic disease. In wild-type mice, sca1⁺/flk1⁺ cells were mobilized into the peripheral circulation by granulocyte-colony stimulating factor (G-CSF) treatment and this movement correlated with improved endothelial regeneration upon carotid artery injury. Multicolor flow cytometry analysis revealed that sca1⁺/flk1⁺ cells predominantly co-expressed surface markers of conventional B cells (B2 cells). In RAG2-deficient mice and upon B2 cell depletion, sca1⁺/flk1⁺ cells were fully depleted. In the absence of monocytes, sca1⁺/flk1⁺ cell levels were unchanged. A PCR array focused on cell surface markers and next-generation sequencing (NGS) of purified sca1⁺/flk1⁺ cells confirmed their phenotype to be predominantly that of B cells. Finally, the depletion of B2 cells, including sca1⁺/flk1⁺ cells, in G-CSF-treated wild-type mice partly abolished the endothelial regenerating effect of G-CSF, indicating an atheroprotective role for sca1⁺/flk1⁺ B2 cells. In summary, we characterized sca1⁺/flk1⁺ cells as a subset of predominantly B2 cells, which are apparently involved in endothelial regeneration.

MiR-92a regulates endothelial progenitor cells (EPCs) by targeting GDF11 via activate SMAD2/3/FAK/Akt/eNOS pathway

Background

The effects of miR-92a on EPCs are still poorly elucidated. This study aimed to investigate the effects of miR-92a on EPCs (Endothelial progenitor cells) in a model of hypoxia (HO) or high glucose (HG)-induced EPCs injury by targeting GDF11 (Differentiation growth factor 11).

Methods

The effects of miR-92a on EPCs subjected to HO or HG were investigated firstly. Subsequently, the action mechanism of miR-92a on EPCs by targeting GDF11 was elucidated. Proliferation, apoptosis, migration, angiogenesis was measured with MTT, flow cytometry, transwell, tube formation respectively. After 24 h, levels of reactive oxygen species (ROS) were measured by fluorescence intensity. LDH and NO (nitric oxide) levels were determined by ELISA. The expression of FLK-1 (fetal liver kinase 1) and vWF (von Willebrand factor) was detected by immunofluorescence. mRNA and protein expression levels were examined using PCR and western blotting respectively. The interaction between miR-92a and GDF11 was evaluated by dual-luciferase reporter assay.

Results

Our results showed that HO or HG increased apoptosis, production of LDH and generation of ROS, but decreased the ability of migration and tube formation and generation of NO in EPCs; inhibiting of miR-92a decreased HO or HG-induced injury of EPCs, whereas miR-92a over-expression had the opposite effect; the protective effects induced by inhibiting of miR-92a on EPCs could be reversed by GDF11 siRNA and the harmful effects induced by over-expression of miR-92a could be rescued by over-expression of GDF11, which showed that the harmful effects of miR-92a be related to its inhibition of GDF11 and subsequent inactivation of the SMAD2/3/FAK/Akt/eNOS signaling pathway.

Conclusions

Inhibiting miR-92a can protect EPCs from HO or HG-induced injury. The effect of miR-92a on EPCs are mediated by regulating of GDF11 and downstream SMAD2/3/FAK/Akt/eNOS signaling pathway.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Endothelial progenitor cells in ischemic stroke: an exploration from hypothesis to therapy

As the population ages and lifestyles change in concordance, the number of patients suffering from ischemic stroke and its associated disabilities is increasing. Studies on determining the relationship between endothelial progenitor cells (EPCs) and ischemic stroke have become a new hot spot and have reported that EPCs may protect the brain against ischemic injury, promote neurovascular repair, and improve long-term neurobehavioral outcomes. More importantly, they introduce a new perspective for prognosis assessment and therapy of ischemic stroke. However, EPCs’ origin, function, influence factors, injury repair mechanisms, and cell-based therapy strategies remain controversial. Particularly, research conducted to date has less clinical studies than pre-clinical experiments on animals. In this review, we summarized and analyzed the current understanding of basic characteristics, influence factors, functions, therapeutic strategies, and disadvantages of EPCs as well as the regulation of inflammatory factors involved in the function and survival of EPCs after ischemic stroke. Identifying potential therapeutic effects of EPCs in ischemic stroke will be a challenging but an incredibly important breakthrough in neurology, which may bring promise for patients with ischemic stroke.

Mobilization of sca1/flk-1 positive endothelial progenitor cells declines in apolipoprotein E-deficient mice with a high-fat diet

BACKGROUND

Atherosclerosis features a deterioration of the endothelial layer in all stages. Restoration of the endothelium is associated with circulating stem cell antigen 1 (sca1) and vascular endothelial growth factor receptor type 2 (flk-1) positive endothelial progenitor cells (EPCs). We investigated whether EPC production and/or a mobilization from bone marrow are reduced in severe atherosclerosis.

METHODS AND RESULTS

EPCs in peripheral blood were diminished in ApoE-/- mice with high-fat diet (HFD) whereas bone marrow levels of these cells were not significantly altered compared to controls. In situ perfusion of the hind limbs demonstrated that EPC mobilization was reduced compared to ApoE-/- mice with normal chow, although increased plasma stromal cell-derived factor (SDF) 1α and responsivity suggested a mobilizing stimulus. The proliferation of sca1/flk-1 positive cells showed no functional impairment. EPCs could not only be significantly mobilized from the bone marrow through the application of granulocyte colony stimulating factor (GCSF), but also led by trend to a depletion of the bone marrow pool. GCSF levels in plasma were equal in ApoE-/- mice with normal chow or HFD, which excluded a decline in GCSF production.

CONCLUSION

The capability of the bone marrow pool to adapt the proliferation and mobilization of sca1/flk-1 positive EPCs seems overstrained in ApoE-/- mice with a HFD.

A vascular patch prepared from Thai silk fibroin and gelatin hydrogel incorporating simvastatin-micelles to recruit endothelial progenitor cells

Delayed re-endothelialization is one of the major disadvantages in synthetic vascular grafts, especially in small-diameter grafts (inner diameter <6 mm), leading to thrombosis and stenosis of the grafts. Simvastatin, a serum cholesterol-lowering drug, has promotional effects on endothelial progenitor cell (EPC) mobilization from bone marrow and recruitment to sites of vascular injury exhibiting acceleration of re-endothelialization. In this study, we prepared double-layer vascular patches from Thai silk fibroin/gelatin with gelatin hydrogel incorporating simvastatin-micelles (SM) for sustained release of simvastatin to recruit circulation EPCs. To enhance simvastatin solubility, simvastatin was entrapped in micelles of l-lactic acid oligomer-grafted gelatin. The drug loading efficiency was at 4.1 ± 0.5 μg/mg micelles. SM had a chemoattractive effect on EPCs comparable to nonmodified simvastatin. Gelatin hydrogel incorporating SM at 100 μM of simvastatin (GSM100) could enhance in vitro EPC activities of adhesion and proliferation. In vitro results showed the initial cell adhesion of 86%, specific growth rate of 15.33×10(-3) h(-1), and population doubling time of 46.21 h. In vivo implantation of the patches incorporating SM significantly increased the recruitment of circulating EPCs. From the results of immunofluorescence staining, they demonstrated the complete re-endothelialization on the implanted patches containing SM at 2 weeks after implantation in rat carotid arteries. The gelatin hydrogel incorporating SM could be an effective inner layer of multifunctional vascular grafts to accelerate re-endothelialization in vascular tissue engineering.

Vascular injury and repair: a potential target for cell therapies

ABSTRACT 

Whether due to atherosclerotic disease or mechanical intervention, vascular injury is a frequently encountered pathology in cardiovascular medicine. The past decade has seen growing interest in the role of circulating endothelial progenitor cells in vessel recovery postinjury. Despite this, the definition, origin and potential role of endothelial progenitor cells in vascular regeneration remains highly controversial. While animal work has shown early promise, evidence of a therapeutic role for endothelial progenitor cells in humans remains elusive. To date, clinical trials involving direct cell administration, growth factor therapy and endothelial cell capture stents have largely been disappointing, although this may in part reflect limitations in study design. This article will outline the pathophysiological mechanisms of vascular injury with an emphasis on endothelial progenitor cell biology and the potential therapeutic role of this exciting new field.

Specific role of impaired glucose metabolism and diabetes mellitus in endothelial progenitor cell characteristics and function

The disease burden of diabetes mellitus (DM) and its associated cardiovascular complications represent a growing and major global health problem. Recent studies suggest that circulating exogenous endothelial progenitor cells (EPCs) play an important role in endothelial repair and neovascularization at sites of injury or ischemia. Both experimental and clinical studies have demonstrated that hyperglycemia related to DM can induce alterations to EPCs. The reduction and dysfunction of EPCs related to DM correlate with the occurrence and severity of microvascular and macrovascular complications, suggesting a close mechanistic link between EPC dysfunction and impaired vascular function/repair in DM. These alterations to EPCs, likely mediated by multiple pathophysiological mechanisms, including inflammation, oxidative stress, and alterations in Akt and the nitric oxide pathway, affect EPCs at multiple stages: differentiation and mobilization in the bone marrow, trafficking and survival in the circulation, and homing and neovascularization. Several different therapeutic approaches have consequently been proposed to reverse the reduction and dysfunction of EPCs in DM and may represent a novel therapeutic approach to prevent and treat DM-related cardiovascular complications.

Diesel exhaust particles impair endothelial progenitor cells, compromise endothelial integrity, reduce neoangiogenesis, and increase atherogenesis in mice

The mechanisms of the harmful cardiovascular effects of small particulate matter are incompletely understood. Endothelial progenitor cells (EPCs) predict outcome of patients with vascular disease. The aim of our study was to examine the effects of diesel exhaust particles (DEP) on EPC and on the associated vascular damage in mice. C57Bl/6 mice were exposed to DEP. 2 μg DEP/day was applicated intranasally for 3 weeks. Exposure to DEP reduced DiLDL/lectin positive EPC to 58.4 ± 5.6% (p < 0.005). Migratory capacity was reduced to 65.8 ± 3.9% (p < 0.0001). In ApoE(-/-) mice, DEP application reduced the number of EPC to 75.6 ± 6.4% (p < 0.005) and EPC migration to 58.5 ± 6.8% (p < 0.005). Neoangiogenesis was reduced to 39.5 ± 14.6% (p < 0.005). Atherogenesis was profoundly increased by DEP treatment (157.7 ± 18.1% vs. controls, p < 0.05). In cultured human EPC, DEP (0.1-100 μg/mL) reduced migratory capacity to 25 ± 2.6% (p < 0.001). The number of colony-forming units was reduced to 8.8 ± 0.9% (p < 0.001) and production of reactive oxygen species was elevated by DEP treatment (p < 0.001). Furthermore, DEP treatment increased apoptosis of EPC (to 266 ± 62% of control, p < 0.05). In a blood-brain barrier model, DEP treatment impaired endothelial cell integrity during oxygen-glucose deprivation (p < 0.001). Diesel exhaust particles impair endothelial progenitor cell number and function in vivo and in vitro. The reduction in EPC was associated with impaired neoangiogenesis and a marked increase in atherosclerotic lesion formation.

Rosuvastatin-attenuated heart failure in aged spontaneously hypertensive rats via PKCα/β2 signal pathway

There are controversies concerning the capacity of Rosuvastatin to attenuate heart failure in end-stage hypertension. The aim of the study was to show whether the Rosuvastatin might be effective or not for the heart failure treatment. Twenty-one spontaneously hypertensive rats (SHRs) aged 52 weeks with heart failure were randomly divided into three groups: two receiving Rosuvastatin at 20 and 40 mg/kg/day, respectively, and the third, placebo for comparison with seven Wistar-Kyoto rats (WKYs) as controls. After an 8-week treatment, the systolic blood pressure (SBP) and echocardiographic features were evaluated; mRNA level of B-type natriuretic peptide (BNP) and plasma NT-proBNP concentration were measured; the heart tissues were observed under electron microscope (EM); myocardial sarcoplasmic reticulum Ca²⁺ pump (SERCA-2) activity and mitochondria cytochrome C oxidase (CCO) activity were measured; the expressions of SERCA-2a, phospholamban (PLB), ryanodine receptor2 (RyR2), sodium–calcium exchanger 1 (NCX1), Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and protein phosphatase inhibitor-1 (PPI-1) were detected by Western blot and RT-qPCR; and the total and phosphorylation of protein kinase Cα/β (PKCα/β) were measured. Aged SHRs with heart failure was characterized by significantly decreased left ventricular ejection fraction and left ventricular fraction shortening, enhanced left ventricular end-diastolic diameter and LV Volume, accompanied by increased plasma NT-proBNP and elevated BNP gene expression. Damaged myofibrils, vacuolated mitochondria and swollen sarcoplasmic reticulum were observed by EM. Myocardium mitochondria CCO and SERCA-2 activity decreased. The expressions of PLB and NCX1 increased significantly with up-regulation of PPI-1 and down-regulation of CaMKII, whereas that of RyR2 decreased. Rosuvastatin was found to ameliorate the heart failure in aged SHRs and to improve changes in SERCA-2a, PLB, RyR2, NCX1, CaMKII and PPI-1; PKCα/β2 signal pathway to be suppressed; the protective effect of Rosuvastatin to be dose dependent. In conclusion, the heart failure of aged SHRs that was developed during the end stage of hypertension could be ameliorated by Rosuvastatin.

Does drug therapy reverse endothelial progenitor cell dysfunction in diabetes?

Endothelial progenitor cells (EPCs) are vital for the maintenance and repair of the endothelium. Decreased EPC number and function have been associated with increased cardiovascular (CVD) risk. Patients with diabetes have decreased number of circulating EPCs and decreased EPC function. This may account for some of the increased CVD risk seen in patients with diabetes that is not explained by traditional risk factors such as glycemic control, dyslipidemia and hypertension. Recent studies seem to indicate that drugs commonly used in diabetes patients such as metformin, thiazolidinediones, GLP-1 agonists, DPP-4 inhibitors, insulin, statins and ACE inhibitors may increase EPC number and improve EPC function. The mechanisms by which these drugs modulate EPC function may involve reduction in inflammation, oxidative stress and insulin resistance as well as an increase in nitric oxide (NO) bioavailability. This review will discuss the evidence in the literature regarding the above mentioned topics.

Characterisation of a monoclonal antibody detecting Atlantic salmon endothelial and red blood cells, and its association with the infectious salmon anaemia virus cell receptor

Endothelial cells (ECs) line the luminal surfaces of the cardiovascular system and play an important role in cardiovascular functions such as regulation of haemostasis and vasomotor tone. A number of fish and mammalian viruses target these cells in the course of their infection. Infectious salmon anaemia virus (ISAV) attacks ECs and red blood cells (RBCs) of farmed Atlantic salmon (Salmo salar L.), producing the severe disease of infectious salmon anaemia (ISA). The investigation of ISA has up to now been hampered by the lack of a functional marker for ECs in Atlantic salmon in situ. In this study, we report the characterisation and use of a novel monoclonal antibody (MAb) detecting Atlantic salmon ECs (e.g. vessel endothelium, endocardial cells and scavenger ECs) and RBCs. The antibody can be used with immunohistochemistry, IFAT and on Western blots. It appears that the epitope recognised by the antibody is associated with the ISAV cellular receptor. Besides being a tool to identify ECs in situ, it could be useful in further studies of the pathogenicity of ISA. Finally, the detection of an epitope shared by ECs and RBCs agrees with recent findings that these cells share a common origin, thus the MAb can potentially be used to study the ontogeny of these cells in Atlantic salmon.

A systematic comparison of the properties of clinically used angiotensin II type 1 receptor antagonists

Angiotensin II type 1 receptor antagonists (ARBs) have become an important drug class in the treatment of hypertension and heart failure and the protection from diabetic nephropathy. Eight ARBs are clinically available [azilsartan, candesartan, eprosartan, irbesartan, losartan, olmesartan, telmisartan, valsartan]. Azilsartan (in some countries), candesartan, and olmesartan are orally administered as prodrugs, whereas the blocking action of some is mediated through active metabolites. On the basis of their chemical structures, ARBs use different binding pockets in the receptor, which are associated with differences in dissociation times and, in most cases, apparently insurmountable antagonism. The physicochemical differences between ARBs also manifest in different tissue penetration, including passage through the blood-brain barrier. Differences in binding mode and tissue penetration are also associated with differences in pharmacokinetic profile, particularly duration of action. Although generally highly specific for angiotensin II type 1 receptors, some ARBs, particularly telmisartan, are partial agonists at peroxisome proliferator-activated receptor-γ. All of these properties are comprehensively reviewed in this article. Although there is general consensus that a continuous receptor blockade over a 24-hour period is desirable, the clinical relevance of other pharmacological differences between individual ARBs remains to be assessed.

Atorvastatin-induced increase in progenitor cell levels is rather caused by enhanced receptor activator of NF-kappaB ligand (RANKL) cell proliferation than by bone marrow mobilization

BACKGROUND

Statins have been shown to increase the level of circulating progenitor cells in peripheral blood supposedly due to a mobilization of progenitor cells from the bone marrow niche. Osteoclast/osteoblast interaction has been associated with progenitor cell mobilization. Here, we investigated the role of statins on progenitor cell mobilization with a focus on bone metabolism.

METHODS AND RESULTS

FGF2(-/-) and wild type (wt) mice were treated with atorvastatin or placebo. In contrast to wt mice, the number of sca-1/flk-1 positive progenitor cells in peripheral blood (PB) of atorvastatin treated FGF2(-/-) mice did not increase, and was accompanied by a defective reendothelialization after perielectric injury of the common carotid artery. In wt, but not FGF2(-/-) mice, statin treatment was associated with increased levels of receptor activator of NF-κB ligand (RANKL) in bone marrow (BM) supernatant. Treatment with recombinant RANKL increased sca-1/flk-1 positive progenitors in FGF2(-/-) mice. Interestingly, osteoclast activation was not altered. To measure the egress of sca-1/flk-1 positive progenitor cells from the bone marrow, we performed in-situ perfusion experiments of isolated hind limbs. Mobilization was not significantly affected by atorvastatin in both wt and FGF2(-/-) mice. Furthermore, RANK - the specific receptor to RANKL - is expressed on progenitor cells, and RANKL stimulation increases cell proliferation in vitro and in vivo.

CONCLUSIONS

Atorvastatin treatment increases RANKL levels with no measurable effect on bone metabolism and mobilization of progenitor cells from BM to PB. RANKL is essential for the statin-mediated increase of progenitor cell levels but predominantly due to a RANKL-induced stimulation of cell proliferation.

Making sense in antisense: therapeutic potential of noncoding RNAs in diabetes-induced vascular dysfunction

The rapid rise of type II diabetes mellitus and its accompanying vascular complications call for novel approaches in unravelling its pathophysiological mechanisms and designing new treatment modalities. Noncoding RNAs represent a class of previously unknown molecular modulators of this disease. The most important features of diabetes-induced vascular disease, which include metabolic deregulation, increased oxidative stress, release of inflammatory mediators like adipokines, and pathologic changes in vascular cells, all are depicted and governed by a certain set of noncoding RNAs. While these mechanisms are being unravelled, new diagnostic and therapeutic opportunities to treat diabetes-induced vascular disease emerge.

Angiotensin-converting enzyme 2 priming enhances the function of endothelial progenitor cells and their therapeutic efficacy

Angiotensin-converting enzyme 2 (ACE2) is a lately discovered enzyme catalyzing Angiotensin II into Angiotensin 1-7. Angiotensin II has been reported to impair endothelial progenitor cell (EPC) function and is detrimental to stroke. Here, we studied the role of ACE2 in regulating EPC function in vitro and in vivo. EPCs were cultured from human renin and angiotensinogen transgenic (R+A+) mice and their controls (R-A-). In in vitro experiments, EPCs were transduced with lentivirus-ACE2 or lentivirus-green fluorescence protein. The effects of ACE2 overexpression on EPC function and endothelial NO synthase (eNOS)/nicotinamide adenine dinucleotide phosphate oxidase (Nox) expression were determined. ACE2, eNOS, and Nox inhibitors were used for pathway validation. In in vivo studies, the therapeutic efficacy of EPCs overexpressing ACE2 was determined at day 7 after ischemic stroke induced by middle cerebral artery occlusion. We found that (1) lentivirus-ACE2 transduction resulted in a 4-fold increase of ACE2 expression in EPCs. This was accompanied with an increase in eNOS expression and NO production, and a decrease in Nox2 and -4 expression and reactive oxygen species production. (2) ACE2 overexpression improved the abilities of EPC migration and tube formation, which were impaired in R+A+ mice. These effects were inhibited by ACE2 or eNOS inhibitor and further enhanced by Nox inhibitor. (3) Transfusion of lentivirus-ACE2-primed EPCs reduced cerebral infarct volume and neurological deficits, and increased cerebral microvascular density and angiogenesis. Our data demonstrate that ACE2 improves EPC function, via regulating eNOS and Nox pathways, and enhances the efficacy of EPC-based therapy for ischemic stroke.

The renin–angiotensin system, bone marrow and progenitor cells

Modulation of the RAS (renin–angiotensin system), in particular of the function of the hormones AngII (angiotensin II) and Ang-(1–7) [angiotensin-(1–7)], is an important target for pharmacotherapy in the cardiovascular system. In the classical view, such modulation affects cardiovascular cells to decrease hypertrophy, fibrosis and endothelial dysfunction, and improves diuresis. In this view, excessive stimulation of AT1 receptors (AngII type 1 receptors) fulfils a detrimental role, as it promotes cardiovascular pathogenesis, and this is opposed by stimulation of the AT2 receptor (angiotensin II type 2 receptor) and the Ang-(1–7) receptor encoded by the Mas proto-oncogene. In recent years, this view has been broadened with the observation that the RAS regulates bone marrow stromal cells and stem cells, thus involving haematopoiesis and tissue regeneration by progenitor cells. This change of paradigm has enlarged the field of perspectives for therapeutic application of existing as well as newly developed medicines that alter angiotensin signalling, which now stretches beyond cardiovascular therapy. In the present article, we review the role of AngII and Ang-(1–7) and their respective receptors in haematopoietic and mesenchymal stem cells, and discuss possible pharmacotherapeutical implications.

Effects of the renin angiotensin system on vasculogenesis-related progenitor cells

The current concept is that there are both cells that integrate into the vasculature, true endothelial progenitor cells (EPC), and cells with hematopoietic markers that support neovascularisation. As identification of the EPC is controversial and studies refer cells that might fall into either pools, we will use the term, vasculogenesis-related progenitor cells (VRPC), for this review. VRPC are considered to be an important target for the treatment of cardiovascular diseases (CVD). Angiotensin II is known to be an important player in neovascularisation and the modulation of renin angiotensin system (RAS) is one of the major pharmacotherapeutic strategies for the treatment of CVD. We will review the effects of different components of the RAS on such VRPC under physiological conditions and in CVD. The reviewed research strongly supports a critical role of the RAS in vasculogenesis and vascular regeneration. Therefore, pharmacological intervention on the components of the RAS does not only target directly end-organ remodelling and blood pressure but also influence tissue healing and/or regeneration by influencing specific progenitor cells. Thus, the interrogation of RAS effects on VRPC will be important in the optimisation of RAS intervention or regenerative therapy.

Endothelial cells (EC) and endothelial precursor cells (EPC) kinetics in hematological patients undergoing chemotherapy or autologous stem cell transplantation (ASCT)

Our objective was to study the kinetics of circulating endothelial cells (EC) and endothelial precursor cells (EPC) in hematological patients during chemotherapy and autologous stem cell transplantion (ASCT). Eighteen newly diagnosed patients and 17 patients undergoing ASCT were studied and compared to healthy controls. ECs were evaluated as CD146+CD31+Lin- cells, while EPCs were evaluated as CD34+CD133+Lin-, or CD34+VEGFR2+Lin- cells, or CFU-En colony forming units. Numbers of these cells were evaluated before and after treatment, and, in patients treated with ASCT, during mobilization of hematopoietic progenitors. Both newly diagnosed patients and patients before ASCT had significantly higher number of CD146+CD31+Lin- cells and significantly lower number of CFU-En colonies than healthy controls. These parameters did not return to normal for at least 3 months after chemotherapy or ASCT. Numbers of CFU-En did not correlate either with numbers of CD34+CD133+Lin- cells or with numbers of CD34+VEGFR2+Lin- cells but they did correlate with numbers of CD4+ lymphocytes and NK cells. In conclusion, we have found that hematological patients have higher number of EC and lower numbers of CFU-En than healthy controls and that these parameters do not return to normal after short-term follow-up. Furthermore, our observations support emerging data that CFU-En represent cell population different from flowcytometrically defined EC and endothelial precursors and that their development requires cooperation of monocytes and CD4+ lymphocytes. However, cells forming CFU-En express endothelial surface markers and can contribute to proper endothelial function by NO production.

The renin inhibitor aliskiren upregulates pro-angiogenic cells and reduces atherogenesis in mice

Sca-1 and VEGFR-2 positive pro-angiogenic cells (PAC) predict outcome of patients with vascular disease. Activation of the renin-angiotensin-aldosterone system impairs PAC function. The effects of the direct renin inhibitor aliskiren on PAC numbers and function are not known. Treatment of C57Bl/6 mice and Apo E(-/-) mice on high-cholesterol diet with aliskiren, 25 mg/kg/day s.c. for 3-6 weeks, reduced systolic and diastolic blood pressure by -11.5 and -13.7% compared to vehicle. Aliskiren increased Sca-1/VEGFR-2 positive PAC in the blood (159 ± 14%) and spleen-derived DiLDL/lectin positive PAC (180 ± 21%). Migratory capacity of PAC was increased to 165 ± 16%. In cultured human PAC, aliskiren dose-dependently increased the number of colony forming units to 152 ± 9% (1 μmol/l) and 187 ± 7% (10 μmol/l), which was prevented by the eNOS inhibitor LNMA. H₂O₂-induced apoptosis of cultured human PAC was reduced to 77 ± 23%. In Apo E(-/-) mice, aliskiren reduced atherosclerotic plaque area in the aortic sinus by 58 ± 4%. Circulating Sca-1/VEGFR-2 positive PAC were upregulated to 180 ± 25% and migratory capacity of PAC was increased to 127 ± 7%. Aliskiren reduced vascular NADPH oxidase activity to 41.6 ± 6.7%. Despite similar blood pressure lowering, treatment with hydralazine (25 mg/kg/day) did not significantly influence atherogenesis or PAC. Treatment of C57Bl/6 mice with a lower dose of aliskiren (15 mg/kg/day) did not affect blood pressure but increased cultured DiLDL/lectin positive PAC to 229 ± 30% and their migratory capacity to 214 ± 24%. Aliskiren increased number and function of PAC in mice and prevented atherosclerotic lesion formation. The effects were observed independent of blood pressure lowering.