Combination of the angiotensin-converting enzyme inhibitor perindopril and the diuretic indapamide activate postnatal vasculogenesis in spontaneously hypertensive rats

Enhancement of EPC migration by high-dose lisinopril is superior compared to captopril and ramipril

Background: Angiotensin-converting enzyme (ACE) inhibitors have been shown to promote endothelial progenitor cell (EPC) function. However, the efficacies of different ACE inhibitors in improving the migratory capabilities of ECPs in coronary artery disease (CAD) patients is unclear. This study compared the effectiveness of captopril, lisinopril, and ramipril toward the migration capability of impaired EPCs from CAD patients. Methods: We isolated peripheral blood mononuclear cells (PBMCs), separated EPCs from PBMCs, and divided them into an untreated group (control) and treated groups of captopril, lisinopril, and ramipril at doses of 1mM, 10mM, and 100mM. EPC migration was evaluated using the Boyden chamber assay. Analysis of variance (ANOVA) was performed using SPSS 25.0. Results: This study showed that treatment with captopril, lisinopril, and ramipril starting at the lowest dose (1 mM) increased EPC migration (65,250 ± 6,750 cells; 60,750± 5,030 cells; and 49,500 ± 8,400 cells, respectively) compared to control (43,714 ± 7,216 cells). Increased migration of EPCs was observed by increasing the treatment dose to 10 mM with captopril, lisinopril, and ramipril (90,000 ± 16,837 cells; 79,071 ± 2,043 cells; and 64,285 ± 11,824 cells, respectively). The highest EPC migration was shown for lisinopril 100 mM (150,750 ± 16,380 cells), compared to captopril and ramipril at the same dose (105,750 ± 8112 cells and 86,625 ± 5,845 cells, respectively). Conclusions: Captopril, ramipril, and lisinopril were shown to increase EPC migration in a dose-dependent manner. Low-dose (1 mM) and medium-dose (10 mM) captopril had a larger effect on ECP migration than lisinopril and ramipril. Meanwhile, high-dose lisinopril (100mM) had the highest migration effect, suggesting it may be preferable for promoting EPC migration in CAD patients.

Targeting Angiotensin-Converting Enzyme-2/Angiotensin-(1-7)/Mas Receptor Axis in the Vascular Progenitor Cells for Cardiovascular Diseases

Bone marrow-derived hematopoietic stem/progenitor cells are vasculogenic and play an important role in endothelial health and vascular homeostasis by participating in postnatal vasculogenesis. Progenitor cells are mobilized from bone marrow niches in response to remote ischemic injury and migrate to the areas of damage and stimulate revascularization largely by paracrine activation of angiogenic functions in the peri-ischemic vasculature. This innate vasoprotective mechanism is impaired in certain chronic clinical conditions, which leads to the development of cardiovascular complications. Members of the renin-angiotensin system-angiotensin-converting enzymes (ACEs) ACE and ACE2, angiotensin II (Ang II), Ang-(1-7), and receptors AT1 and Mas-are expressed in vasculogenic progenitor cells derived from humans and rodents. Ang-(1-7), generated by ACE2, is known to produce cardiovascular protective effects by acting on Mas receptor and is considered as a counter-regulatory mechanism to the detrimental effects of Ang II. Evidence has now been accumulating in support of the activation of the ACE2/Ang-(1-7)/Mas receptor pathway by pharmacologic or molecular maneuvers, which stimulates mobilization of progenitor cells from bone marrow, migration to areas of vascular damage, and revascularization of ischemic areas in pathologic conditions. This minireview summarizes recent studies that have enhanced our understanding of the physiology and pharmacology of vasoprotective axis in bone marrow-derived progenitor cells in health and disease. SIGNIFICANCE STATEMENT: Hematopoietic stem progenitor cells (HSPCs) stimulate revascularization of ischemic areas. However, the reparative potential is diminished in certain chronic clinical conditions, leading to the development of cardiovascular diseases. ACE2 and Mas receptor are key members of the alternative axis of the renin-angiotensin system and are expressed in HSPCs. Accumulating evidence points to activation of ACE2 or Mas receptor as a promising approach for restoring the reparative potential, thereby preventing the development of ischemic vascular diseases.

Antihypertensive properties of a traditional Chinese medicine GAO-ZI-YAO in elderly spontaneous hypertensive rats

AIM

The present study aims to investigate the antihypertensive effect and the underlying mechanism of GAO-ZI-YAO, one of the traditional Chinese medicines, in elderly spontaneous hypertensive rats (SHR).

METHODS

12-month-old male SHRs were randomly divided into five groups on the basis of treatment with different doses of GAO-ZI-YAO or angiotensin II receptor-1 blocker (ARB, Irbesartan) for four weeks. Systolic blood pressure (SBP), and serum levels of nitric oxide (NO), endothelin-1 (ET-1), angiotensin II (Ang II), vascular endothelial growth factor (VEGF), interleukin (IL)-1β, IL-2, IL-6, and tumor necrotic factor (TNF)-α were measured. The pathological changes of ventricular muscle and thoracic aorta were observed by hematoxylin-eosin staining (H&E).

RESULTS

GAO-ZI-YAO treatment reduced SBP in a dose-dependent manner accompanied by the inhibition of the development of cardiovascular remodeling. Although GAO-ZI-YAO treatment markedly increased serum levels of NO and suppressed serum levels of Ang II, this medicine did not affect the serum levels of ET-1 and VEGF. In addition, GAO-ZI-YAO also inhibited inflammatory response parameters (inflammatory cell infiltration in cardiac tissues and serum levels of IL-1β, IL-2, IL-6, and TNF-α) in a dose-dependent manner.

CONCLUSION

GAO-ZI-YAO exerts antihypertensive and anti-cardiovascular-remodeling effects in elderly SHR, which may be through regulation of NO, Ang II production, and inflammation.

Elevated Inflammatory Parameter Levels Negatively Impact Populations of Circulating Stem Cells (CD133+), Early Endothelial Progenitor Cells (CD133+/VEGFR2+), and Fibroblast Growth Factor in Stroke Patients

BACKGROUND

Endothelial Progenitor Cells (EPCs) are important players in neovascularization, mobilized through signalling by Angiogenic Growth Factors (AGFs) such as Vascular Endothelial Growth Factor (VEGF) and fibroblast growth factor (FGF). In vitro, inflammatory parameters impair the function and influence of EPCs on AGFs. However, this connection is not clear in vivo. To understand the mechanisms of augmented arteriogenesis and angiogenesis in acute ischemic stroke (AIS) patients, we investigated whether circulating stem cells (CD133+), early endothelial progenitor cells (CD133+/VEGFR2+), and endothelial cells (ECs; CD34¯/CD133¯/VEGFR2+) were increasingly mobilized during AIS, and whether there were correlations between EPC levels, growth factor levels and inflammatory parameters.

METHODS

Data on demographics, classical vascular risk factors, neurological deficit information (assessed using the National Institutes of Health Stroke Scale), and treatment were collected from 43 consecutive AIS patients (group I). Risk factor control patients (group II) included 22 nonstroke subjects matched by age, gender, and traditional vascular risk factors. EPCs were measured by flow cytometry and the populations of circulating stem cells (CD133+), early EPCs (CD133+/VEGFR2+), and ECs (CD34¯/CD133¯/VEGFR2+) were analysed. Correlations between EPC levels and VEGF and FGF vascular growth factor levels as well as the influence of inflammatory parameters on EPCs and AGFs were assessed.

RESULTS

Patient ages ranged from 54 to 92 years (mean age 75.2 ± 11.3 years). The number of circulating CD34¯/CD133¯/VEGF-R2+ cells was significantly higher in AIS patients than in control patients (p < 0.05). VEGF plasma levels were also significantly higher in AIS patients compared to control patients on day 7 (p < 0.05). FGF plasma levels in patients with AIS were significantly higher than those in the control group on day 3 (p < 0.05). There were no correlations between increased VEGF and FGF levels and the number of CD133+, CD133+/VEGFR2+, or CD34¯/CD133¯/VEGFR2+ cells. Leukocyte levels, FGF plasma levels, and the number of early EPCs were negatively correlated on day 3. High sensitivity C-reactive protein levels and the number of CD133+ and CD133+/VEGFR2+ cells were negatively correlated on day 7. In addition, there was a negative correlation between fibrinogen levels and FGF plasma levels as well as the number of early EPCs (CD133+/VEGFR2+).

CONCLUSION

AIS patients exhibited increased numbers of early EPCs (CD133+/VEGFR2+) and AGF (VEGF and FGF) levels. A negative correlation between inflammatory parameters and AGFs and EPCs indicated the unfavourable influence of inflammatory factors on EPC differentiation and survival. Moreover, these correlations represented an important mechanism linking inflammation to vascular disease.

Vascular legacy beyond blood pressure control: benefits of perindopril/indapamide combination in hypertensive patients with diabetes

OBJECTIVES

Much of the chronic care of patients with type 2 diabetes mellitus and hypertension involves the prevention of diabetic complications. Renin-angiotensin system inhibitors are recommended as first-line therapies because of their nephroprotective properties. Their combination with metabolically neutral diuretics is recommended to reduce blood pressure, morbidity and mortality. Our objective was to review the mechanisms by which the combination of the angiotensin-converting enzyme inhibitor, perindopril, and metabolically neutral thiazide-like diuretic, indapamide, targets the pathways involved in microvascular and macrovascular diabetic complications.

METHODS

For this narrative review, extensive literature searches were performed using PubMed/Medline. Articles published in English describing clinical trials and mechanism of action studies that were relevant to the treatment of patients with perindopril and/or indapamide were included.

RESULTS

Perindopril/indapamide treatment has been shown to reduce blood pressure and to have significant beneficial effects on arterial distensibility, kidney structure and function, and endothelial function. Recent data also suggests that perindopril may reduce the deleterious accumulation of advanced glycation end products in diabetic tissue. In the Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation diabetes trial, perindopril/indapamide treatment significantly reduced the relative risk of microvascular and macrovascular events by 9%, cardiovascular mortality by 18%, and all-cause mortality by 14%. Interestingly, 6 years after the end of the double-blind period, follow-up data showed that the beneficial effects on mortality continued to be significant even though differences in blood pressure and glycated hemoglobin levels had not been significant for several years. Together this data suggests that treatment with perindopril/indapamide has microvascular and macrovascular effects that extend beyond blood pressure lowering and that this treatment might confer a long-lasting beneficial vascular legacy.

CONCLUSION

Moving forward, understanding the pathophysiological bases of the effects that extend beyond those of blood pressure control will help us differentiate between anti-hypertensive choices.

Effects of Angiotensin-Converting Enzyme Inhibition on Circulating Endothelial Progenitor Cells in Patients with Acute Ischemic Stroke

Background

Therapeutic neovascularization might represent an important strategy to salvage tissue after ischemia. Circulating bone marrow-derived endothelial progenitor cells (EPCs) were previously shown to augment the neovascularization of ischemic tissue. Angiotensin-converting enzyme inhibitors (ACEIs) might modulate EPC mobilization. We evaluated populations of circulating stem cells and early EPCs in acute ischemic stroke (AIS) patients and the effect of ACEI on circulating EPCs in these patients with respect to aspects of stroke pathogenesis.

Methods

We studied 43 AIS patients (group I), comprising 33 treated with ACEI (group Ia) and 10 untreated (group Ib). Risk factor controls (group II) included 22 subjects. EPCs were measured by flow cytometry.

Results

In AIS patients, the number of circulating stem cells and early EPCs upon admission was similar to that in control group individuals. There were no significant differences in the numbers of stem cells and early EPCs over subsequent days after AIS. There were also no significant differences in stem cell and early EPC numbers over the first 3 days between group Ia and group Ib. However, on day 7, these numbers were significantly higher in group Ib than in group Ia (p < 0.05). In AIS patients chronically treated with ACEI, there was a negative correlation between CD133⁺ cell number and neurological deficit on the first, third, and seventh days (p < 0.005).

Conclusions

An increased number of circulating stem cells and early EPCs were not observed in stroke patients chronically treated with ACEI. In patients chronically treated with ACEI, a significant correlation was observed between decreased neurological deficit and higher levels of CD133⁺ cells; this could be due to the positive influence of these cells on the regeneration of the endothelium and improved circulation in the ischemic penumbra.

Role of angiotensin II in stem cell therapy of cardiac disease

INTRODUCTION

The renin angiotensin system (RAS) is closely related to the cardiovascular system, body fluid regulation and homeostasis.

MATERIALS AND METHODS

Despite common therapeutic methods, stem cell/progenitor cell therapy is daily increasing as a term of regenerative medicine. RAS and its pharmacological inhibitors are not only involved in physiological and pathological aspects of the cardiovascular system, but also affect the different stages of stem cell proliferation, differentiation and function, via interfering cell signaling pathways.

RESULTS

This study reviews the new role of RAS, in particular Ang II distinct from other common roles, by considering its regulating impact on the different signaling pathways involved in the cardiac and endothelial tissue, as well as in stem cell transplantation.

CONCLUSIONS

This review focuses on the impact of stem cell therapy on the cardiovascular system, the role of RAS in stem cell differentiation, and the role of RAS inhibition in cardiac stem cell growth and development.

Postischemic revascularization: from cellular and molecular mechanisms to clinical applications

After the onset of ischemia, cardiac or skeletal muscle undergoes a continuum of molecular, cellular, and extracellular responses that determine the function and the remodeling of the ischemic tissue. Hypoxia-related pathways, immunoinflammatory balance, circulating or local vascular progenitor cells, as well as changes in hemodynamical forces within vascular wall trigger all the processes regulating vascular homeostasis, including vasculogenesis, angiogenesis, arteriogenesis, and collateral growth, which act in concert to establish a functional vascular network in ischemic zones. In patients with ischemic diseases, most of the cellular (mainly those involving bone marrow-derived cells and local stem/progenitor cells) and molecular mechanisms involved in the activation of vessel growth and vascular remodeling are markedly impaired by the deleterious microenvironment characterized by fibrosis, inflammation, hypoperfusion, and inhibition of endogenous angiogenic and regenerative programs. Furthermore, cardiovascular risk factors, including diabetes, hypercholesterolemia, hypertension, diabetes, and aging, constitute a deleterious macroenvironment that participates to the abrogation of postischemic revascularization and tissue regeneration observed in these patient populations. Thus stimulation of vessel growth and/or remodeling has emerged as a new therapeutic option in patients with ischemic diseases. Many strategies of therapeutic revascularization, based on the administration of growth factors or stem/progenitor cells from diverse sources, have been proposed and are currently tested in patients with peripheral arterial disease or cardiac diseases. This review provides an overview from our current knowledge regarding molecular and cellular mechanisms involved in postischemic revascularization, as well as advances in the clinical application of such strategies of therapeutic revascularization.

The role of renin-angiotensin system in cellular differentiation: implications in pancreatic islet cell development and islet transplantation

In addition to the well-characterized circulating renin-angiotensin system (RAS), local RAS has been identified recently in diverse tissues and organs. The presence of key components of the RAS in local tissues is important for our understanding of the patho-physiological mechanism(s) of several metabolic diseases, and may serve as a major therapeutic target for cardiometabolic syndromes. Locally generated and physiologically active RAS components have functions that are distinct from the classical vasoconstriction and fluid homeostasis actions of systemic RAS and cater specifically for local tissues. Local RAS can affect islet-cell function and structure in the adult pancreas as well as proliferation and differentiation of pancreatic stem/progenitor cells during development. Differentiation of stem/progenitor cells into insulin-expressing cells suitable for therapeutic transplantation offers a desperately needed new approach for replacement of glucose-responsive insulin producing cells in diabetic patients. Given that the generation of functional and transplantable islet cells has proven to be difficult, elucidation of RAS involvement in cellular regeneration and differentiation may propel pancreatic stem/progenitor cell development and thus β-cell regeneration forward. This review provides a critical appraisal of current research progress on the role of the RAS, including the newly characterized ACE2/Ang-(1-7)/Mas axis in the proliferation, differentiation, and maturation of pancreatic stem/progenitor cells. It is thus plausible to propose that the AT1 stimulation could be a repair mechanism involving the AT2R as well as the ACE2/Ang-(1-7)/Mas axis in directing β-cell development in diabetic patients using genetic and pharmaceutical manipulation of the RAS.

Pro-angiogenic cell-based therapy for the treatment of ischemic cardiovascular diseases

Pro-angiogenic cell therapy has emerged as a promising option to treat patients with acute myocardial infarction or with critical limb ischemia. Exciting pre-clinical studies have prompted the initiation of numerous clinical trials based on administration of stem/progenitor cells with pro-angiogenic potential. Most of the clinical studies performed so far have used bone marrow-derived or peripheral blood-derived mononuclear cells and showed, overall, a modest but significant benefit on tissue remodeling and function in patients with ischemic diseases. These mixed results pave the way for the development of strategies to overcome the limitation of autologous cell therapy and to propose more efficient approaches. Such strategies include pretreatment of cells with activators to augment cell recruitment and survival in the ischemic target area and/or the improvement of cell functions such as their paracrine ability to release proangiogenic factors and vasoactive molecules. In addition, efforts should be directed towards stimulation of both angiogenesis and vessel maturation, the development of a composite product consisting of stem/progenitor cells encapsulated in a biomaterial and the use of additional sources of regenerative cells.

Effects of ACE inhibition on endothelial progenitor cell mobilization and prognosis after acute myocardial infarction in type 2 diabetic patients

OBJECTIVE

We aimed to assess the chemotactic response of endothelial progenitor cells to angiotensin-converting enzyme inhibitors in T2DM patients after acute myocardial infarction, as well as the associated prognosis.

METHODS

Sixty-eight T2DM patients with acute myocardial infarction were randomized to either receive or not receive daily oral perindopril 4 mg, and 36 non-diabetic patients with acute myocardial infarction were enrolled as controls. The numbers of circulating CD45-/low+CD34+CD133+KDR+ endothelial progenitor cells, as well as the stromal cell-derived factor-α and high-sensitivity C reactive protein levels, were measured before acute percutaneous coronary intervention and on days 1, 3, 5, 7, 14, and 28 after percutaneous coronary intervention. Patients were followed up for 6 months. Chinese Clinical Trial Registry: ChiCTR-TRC-12002599.

RESULTS

T2DM patients had lower circulating endothelial progenitor cell counts, decreased plasma vascular endothelial growth factor and α levels, and higher plasma high-sensitivity C reactive protein levels compared with non-diabetic controls. After receiving perindopril, the number of circulating endothelial progenitor cells increased from day 3 to 7, as did the plasma levels of vascular endothelial growth factor and stromal cell-derived factor-α, compared with the levels in T2DM controls. Plasma high-sensitivity C reactive protein levels in the treated group decreased to the same levels as those in non-diabetic controls. Furthermore, compared with T2DM controls, the perindopril-treated T2DM patients had lower cardiovascular mortality and occurrence of heart failure symptoms (p<0.05) and better left ventricle function (p<0.01).

CONCLUSIONS

The use of angiotensin-converting enzyme inhibitors represents a novel approach for improving cardiovascular repair after acute myocardial infarction in T2DM patients.

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 ACE inhibition on circulating endothelial progenitor cells, vascular damage, and oxidative stress in hypertensive patients

PURPOSE

The pathogenic role of angiotensin-converting enzyme (ACE) inhibition in hypertensive patients regarding endothelial progenitor-cell (EPC) function is still poorly understood. The aim of the study was to evaluate EPC number, function, and relationship to carotid intima media thickness (IMT) progression.

METHODS

We studied 36 newly diagnosed mildly hypertensive patients free of cardiovascular disease and related risk factors without prior or concurrent therapy with ACE inhibitors. Patients were randomized to receive enalapril 20 mg/day (n = 18) or zofenopril 30 mg/day (n = 18). EPC number and migrating capacity, plasma nitrite and nitrate (NOx), and isoprostane concentrations were evaluated. Carotid IMT was determined by ultrasonography at baseline and after 1 and 5 years of follow-up.

RESULTS

EPC number increased during the follow-up, with no statistical differences between treatment groups. There was an inverse correlation between circulating EPCs and IMT increase over time. Plasma NOx decreased during the study without evident differences between treatment groups. Isoprostanes decreased more markedly in zofenopril-treated patients. Multiple linear regression model demonstrated that carotid IMT was significantly inversely correlated with EPC but not with migratory cells after adjusting for confounders.

CONCLUSIONS

The study demonstrated that EPC levels increased during the follow-up in both groups of newly diagnosed hypertensive patients treated with ACE inhibitors. These drugs prevented progression of vascular damage, with an inverse correlation between circulating EPC levels and IMT values.

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.

Targeting stem cell niches and trafficking for cardiovascular therapy

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

Role of the renin angiotensin system on bone marrow-derived stem cell function and its impact on skeletal muscle angiogenesis

Autologous bone marrow cell (BMC) transplantation has been shown as a potential approach to treat various ischemic diseases. However, under many conditions BMC dysfunction has been reported, leading to poor cell engraftment and a failure of tissue revascularization. We have previously shown that skeletal muscle angiogenesis induced by electrical stimulation (ES) is impaired in the SS/Mcwi rats and that this effect is related to a dysregulation of the renin angiotensin system (RAS) that is normalized by the replacement of chromosome 13 derived from the Brown Norway rat (SS-13(BN)/Mcwi consomic rats). The present study explored bone marrow-derived endothelial cell (BM-EC) function in the SS/Mcwi rat and its impact on skeletal muscle angiogenesis induced by ES. SS/Mcwi rats were randomized to receive BMC from: SS/Mcwi; SS-13(BN)/Mcwi; SS/Mcwi rats infused with saline or ANG II (3 ng kg(-1) min(-1)). BMC were injected in the stimulated tibialis anterior muscle of SS/Mcwi rats. Vessel density was evaluated in unstimulated and stimulated muscles after 7 days of ES. BMC isolated from SS/Mcwi or SS/Mcwi rats infused with saline failed to restore angiogenesis induced by ES. However, BMC isolated from SS-13(BN)/Mcwi and SS/Mcwi rats infused with ANG II effectively restored the angiogenesis response in the SS/Mcwi recipient. Furthermore, ANG II infusion increased the capacity of BM-EC to induce endothelial cell tube formation in vitro and slightly increased VEGF protein expression. This study suggests that dysregulation of the RAS in the SS/Mcwi rat contributes to impaired BM-EC function and could impact the angiogenic therapeutic potential of BMC.

Current perspective of pathophysiological and interventional effects on endothelial progenitor cell biology: focus on PI3K/AKT/eNOS pathway

For more than a decade, endothelial progenitor cells (EPCs) have been implicated in cardiovascular homeostasis. EPCs are believed to reside within the bone marrow in close contact with surrounding stromal cells, and, under stimulation of pro-inflammatory cytokines, EPCs are mobilized out of the bone marrow. Hereafter circulating EPCs home to peripheral tissues, undergoing further proliferation and differentiation. Under certain pathophysiologic conditions this process seems to be blunted, resulting in a reduced capacity of EPCs to engage in vasculogenesis at sites of endothelial injury or tissue ischemia. In this review, we focus on the effects of traditional cardiovascular risk factors on EPC biology and we explore whether pharmacological, dietary and lifestyle interventions can favorably restore EPC mobilization, differentiation, homing and angiogenic properties. Because the PI3K/Akt/eNOS pathway plays a pivotal role in the process of EPC mobilization, migration and homing, we specifically emphasize the involvement of PI3K, Akt and eNOS in EPC biology under these different (patho)physiologic conditions. (Pre)clinically used drugs or lifestyle interventions that have been shown to ameliorate EPC biology are reviewed. These treatment strategies remain attractive targets to restore the regenerative capacity of EPCs in cardiovascular diseases.

Stimulation of endothelial progenitor cells: a new putative effect of several cardiovascular drugs

The role of vascular endothelium in cardiovascular disorders is well recognized. Mature endothelial cells contribute to the repair of endothelial injury, but they only have a limited capacity to do so. This has led to growing interest and further investigation into circulating endothelial progenitor cells (EPCs) and their role in vascular healing, repair, and postnatal neovascularization. The current perception of vascular health is that of a balance between ongoing injury and resultant vascular repair, mediated at least in part by circulating EPCs. Circulating EPCs play an important role in accelerating endothelialization at areas of vascular damage, and EPC enumeration is a viable strategy for assessing reparative capacity. Recent studies have shown that EPCs are affected both in number and function by several cardiovascular risk factors as well as various cardiovascular disease states, such as hypertension, hypercholesterolemia, and coronary artery disease. The present review summarizes the most relevant studies on the effects of cardiovascular drugs on vascular function and EPCs, focusing on their mechanisms of action.

Endothelial-regenerating cells: an expanding universe

Atherosclerosis is the most common cause for cardiovascular diseases and is based on endothelial dysfunction. A growing body of evidence suggests the contribution of bone marrow-derived endothelial progenitor cells, monocytic cells, and mature endothelial cells to vessel formation and endothelial rejuvenation. To this day, various subsets of these endothelial-regenerating cells have been identified according to cellular origin, phenotype, and properties in vivo and in vitro. However, the definition and biology, especially of endothelial progenitor cells, is complex and under heavy debate. In this review, we focus on current definitions of endothelial progenitor cells, highlight the clinical relevance of endothelial-regenerating cells, and provide new insights into cell-cell interactions involved in endothelial cell rejuvenation.

[Proangiogenic cell-based therapy for treatment of ischemic diseases]

The application of endothelial progenitor cells (EPC) cell-based therapy for regenerative medicine constitutes a promising therapeutic avenue for the treatment of cardiovascular diseases. Based on experimental studies demonstrating that bone marrow-, blood- or tissue-derived stem/progenitor cells improve the functional recovery after ischemia, clinical trials were initiated to address this new therapeutic concept. Although autolougous cell therapy was shown to improve perfusion and function of ischemic tissues, a number of issues remain to be adressed. The nature of the mobilizing, migratory and homing signals, and the mechanisms of action need to be identified and further defined. In addition, strategies to enhance homing, survival and therapeutic potential of EPC need to be developped to improve therapeutic effect and counteract EPC dysfunction in aged patients with cardiovascular risk factors. The present review article will discuss the mechanisms of action of different types of adult stem cells and several approaches to improve their therapeutic efficiency.

The role of the renin-angiotensin-aldosterone system in cardiovascular progenitor cell function

Intervention in the RAAS (renin-angiotensin-aldosterone system) is one of the leading pharmacotherapeutic strategies, among others, used for the treatment of cardiovascular disease to improve the prognosis after myocardial infarction and to reduce hypertension. Recently, regenerative progenitor cell therapy has emerged as a possible alternative for pharmacotherapy in patients after myocardial infarction or ischaemic events elsewhere, e.g. in the limbs. Angiogenic cell therapy to restore the vascular bed in ischaemic tissues is currently being tested in a multitude of clinical studies. This has prompted researchers to investigate the effect of modulation of the RAAS on progenitor cells. Furthermore, the relationship between hypertension and endothelial progenitor cell function is being studied. Pharmacotherapy by means of angiotensin II type 1 receptor antagonists or angiotensin-converting enzyme inhibitors has varying effects on progenitor cell levels and function. These controversial effects may be explained by involvement of multiple mediators, e.g. angiotensin II and angiotensin-(1-7), that have differential effects on mesenchymal stem cells, haematopoietic progenitor cells and endothelial progenitor cells. Importantly, angiotensin II can either stimulate endothelial progenitor cells by improvement of vascular endothelial growth factor signalling, or invoke excessive production of reactive oxygen species causing premature senescence of these cells. On the other hand, angiotensin-(1-7) stimulates haematopoietic cells and possibly also endothelial progenitor cells. Furthermore, aldosterone, bradykinin and Ac-SDKP (N-acetyl-Ser-Asp-Lys-Pro) may also affect progenitor cell populations. Alternatively, the variability in effects of angiotensin II type 1 receptor and angiotensin-converting enzyme inhibition on cardiovascular progenitor cells might reflect differences between the various models or diseases with respect to circulating and local tissue RAAS activation. In the present review we discuss what is currently known with respect to the role of the RAAS in the regulation of cardiovascular progenitor cells.

Telmisartan induces proliferation of human endothelial progenitor cells via PPARgamma-dependent PI3K/Akt pathway

OBJECTIVE

Although recent clinical trials have suggested that angiotensin II type 1 receptor blockers (ARBs) reduced cardiovascular events, the precise mechanisms involved are still unknown. Telmisartan, an ARB, has recently been identified as a ligand of peroxisome proliferator-activated receptor-gamma (PPARgamma). On the other hand, since endothelial progenitor cells (EPCs) are thought to play a critical role in ischemic diseases, we investigated effects of telmisartan on proliferation of EPCs.

METHODS AND RESULTS

Human peripheral blood mononuclear cells were isolated from healthy volunteers, and cultured on fibronectin-coated dishes in the presence or absence of telmisartan. Four days after starting culture, adherent cells were collected, and equal numbers of cells were reseeded into methylcellulose medium with or without telmisartan. In the presence of telmisartan, numbers of colonies increased in a dose-dependent manner. DiI-AcLDL uptake and lectin and CD31, CD34 staining revealed that these colonies were EPCs. Increase in colony number by treatment with telmisartan was absolutely inhibited when cultured with a specific inhibitor of PPARgamma. In addition, we observed that specific inhibitors of phosphoinositide-3 kinase (PI3K) abolished telmisartan-stimulated increase of monocytic EPC-like cells and telmisartan induced phosphorylation of Akt. Furthermore, mRNA expression of p21 was downregulated in a dose dependent manner, suggesting that growth inductive effects of telmisartan might be regulated by the PI3K/Akt and p21 signaling pathway.

CONCLUSIONS

These findings suggest that telmisartan might contribute to endothelial integrity and vasculogenesis in ischemic regions by increasing numbers of EPCs.

Pharmacological approaches to improve endothelial repair mechanisms

Endothelial injury is thought to play a pivotal role in the development and progression of vascular diseases, such as atherosclerosis, hypertension or restenosis, as well as their complications, including myocardial infarction or stroke. Accumulating evidence suggests that bone marrow-derived endothelial progenitor cells (EPCs) promote endothelial repair and contribute to ischemia-induced neovascularization. Coronary artery disease and its risk factors, such as diabetes, hypercholesterolemia, hypertension and smoking, are associated with a reduced number and impaired functional activity of circulating EPCs. Moreover, initial data suggest that reduced EPC levels are associated with endothelial dysfunction and an increased risk of cardiovascular events, compatible with the concept that impaired EPC-mediated vascular repair promotes progression of vascular disease. In this review we summarize recent data on the effects of pharmacological agents on mobilization and functional activity of EPCs. In particular, several experimental and clinical studies have suggested that statins, angiotensin-converting enzyme inhibitors, angiotensin II type 1 receptor blockers, PPAR-gamma agonists and erythropoietin increase the number and functional activity of EPCs. The underlying mechanisms remain largely to be defined; however, they likely include activation of the PI3-kinase/Akt pathway and endothelial nitric oxide synthase, as well as inhibition of NAD(P)H oxidase activity of progenitor cells.