Reduced numbers of circulating endothelial progenitor cells in patients with coronary artery disease associated with long-term statin treatment

Endogenous PCSK9 may influence circulating CD45neg/CD34bright and CD45neg/CD34bright/CD146neg cells in patients with type 2 diabetes mellitus

Protease proprotein convertase subtilisin/kexin type 9 (PCSK9) is a regulator of LDL cholesterol clearance and has been associated with cardiovascular risk. PCSK9 inhibitors increase in vivo circulating endothelial progenitor cells (EPCs), a subtype of immature cells involved in ongoing endothelial repair. We hypothesized that the effect of PCSK9 on vascular homeostasis may be mediated by EPCs in patients with or without type 2 diabetes mellitus (T2DM). Eighty-two patients (45 with, 37 without T2DM) at high cardiovascular risk were enrolled in this observational study. Statin treatment was associated with higher circulating levels of PCSK9 in patients with and without T2DM (p < 0.001 and p = 0.036) and with reduced CD45neg/CD34bright (total EPC compartment) (p = 0.016) and CD45neg/CD34bright/CD146neg (early EPC) (p = 0.040) only among patients with T2DM. In the whole group of patients, statin treatment was the only independent predictor of low number of CD45neg/CD34bright (β = - 0.230; p = 0.038, adjusted R2 = 0.041). Among T2DM patients, PCSK9 circulating levels were inversely related and predicted both the number of CD45neg/CD34bright (β = - 0.438; p = 0.003, adjusted R2 = 0.173), and CD45neg/CD34bright/CD146neg (β = - 0.458; p = 0.002, adjusted R2 = 0.191) independently of age, gender, BMI and statin treatment. In high-risk T2DM patients, high endogenous levels of PCSK9 may have a detrimental effect on EPCs by reducing the endothelial repair and worsening the progression of atherothrombosis.

Phototunable interpenetrating polymer network hydrogels to stimulate the vasculogenesis of stem cell-derived endothelial progenitors

Vascularization of engineered scaffolds remains a critical obstacle hindering the translation of tissue engineering from the bench to the clinic. We previously demonstrated the robust micro-vascularization of collagen hydrogels with induced pluripotent stem cell (iPSC)-derived endothelial progenitors; however, physically cross-linked collagen hydrogels compact rapidly and exhibit limited strength. We have synthesized an interpenetrating polymer network (IPN) hydrogel comprised of collagen and norbornene-modified hyaluronic acid (NorHA) to address these challenges. This dual-network hydrogel combines the natural cues presented by collagen's binding sites and extracellular matrix (ECM)-mimicking fibrous architecture with the in situ modularity and chemical cross-linking of NorHA. We modulated the IPN hydrogel's stiffness and degradability by varying the concentration and sequence, respectively, of the NorHA peptide cross-linker. Rheological characterization of the photo-mediated gelation process revealed that the IPN hydrogel's stiffness increased with cross-linker concentration and was decoupled from the bulk NorHA content. Conversely, the swelling of the IPN hydrogel decreased linearly with increasing cross-linker concentration. Collagen microarchitecture remained relatively unchanged across cross-linking conditions, although the addition of NorHA delayed collagen fibrillogenesis. Upon iPSC-derived endothelial progenitor encapsulation, robust, lumenized microvascular networks developed in IPN hydrogels over two weeks. Subsequent computational analysis showed that an initial rise in stiffness increased the number of branch points and vessels, but vascular growth was suppressed in high stiffness IPN hydrogels. These results suggest that an IPN hydrogel consisting of collagen and NorHA is highly tunable, compaction resistant, and capable of supporting vasculogenesis.

Androgens Stimulate EPC-Mediated Neovascularization and Are Associated with Increased Coronary Collateralization

Endothelial progenitor cells (EPCs) play a key role in neovascularization and have been linked to improved cardiovascular outcomes. Although there is a well-established inverse relationship between androgen levels and cardiovascular mortality in men, the role of androgens in EPC function is not fully understood. In this study, we investigated the effects of androgens on 2 subpopulations of EPCs, early EPCs (EEPCs) and late outgrowth EPCs (OECs), and their relationships with coronary collateralization. Early EPCs and OECs were isolated from the peripheral blood of young healthy men and treated with dihydrotestosterone (DHT) with or without androgen receptor (AR) antagonist, hydroxyflutamide, in vitro. Dihydrotestosterone treatment enhanced AR-mediated proliferation, migration, and tubulogenesis of EEPCs and OECs in a dose-dependent manner. Furthermore, DHT augmented EPC sensitivity to extracellular stimulation by vascular endothelial growth factor (VEGF) via increased surface VEGF receptor expression and AKT activation. In vivo, xenotransplantation of DHT pretreated human EPCs augmented blood flow recovery and angiogenesis in BALB/c nude male mice, compared to mice receiving untreated EPCs, following hindlimb ischemia. In particular, DHT pretreated human OECs exhibited higher reparative potential than EEPCs in augmenting postischemic blood flow recovery in mice. Furthermore, whole blood was collected from the coronary sinus of men with single vessel coronary artery disease (CAD) who underwent elective percutaneous intervention (n = 23). Coronary collateralization was assessed using the collateral flow index. Serum testosterone and EPC levels were measured. In men with CAD, circulating testosterone was positively associated with the extent of coronary collateralization and the levels of OECs. In conclusion, androgens enhance EPC function and promote neovascularization after ischemia in mice and are associated with coronary collateralization in men.

Atorvastatin and Conditioned Media from Atorvastatin-Treated Human Hematopoietic Stem/Progenitor-Derived Cells Show Proangiogenic Activity In Vitro but Not In Vivo

Myeloid angiogenic cells (MAC) derive from hematopoietic stem/progenitor cells (HSPCs) that are mobilized from the bone marrow. They home to sites of neovascularization and contribute to angiogenesis by production of paracrine factors. The number and function of proangiogenic cells are impaired in patients with diabetes or cardiovascular diseases. Both conditions can be accompanied by decreased levels of heme oxygenase-1 (HMOX1), cytoprotective, heme-degrading enzyme. Our study is aimed at investigating whether precursors of myeloid angiogenic cells (PACs) treated with known pharmaceuticals would produce media with better proangiogenic activity in vitro and if such media can be used to stimulate blood vessel growth in vivo. We used G-CSF-mobilized CD34⁺ HSPCs, FACS-sorted from healthy donor peripheral blood mononuclear cells (PBMCs). Sorted cells were predominantly CD133⁺. CD34⁺ cells after six days in culture were stimulated with atorvastatin (AT), acetylsalicylic acid (ASA), sulforaphane (SR), resveratrol (RV), or metformin (Met) for 48 h. Conditioned media from such cells were then used to stimulate human aortic endothelial cells (HAoECs) to enhance tube-like structure formation in a Matrigel assay. The only stimulant that enhanced PAC paracrine angiogenic activity was atorvastatin, which also had ability to stabilize endothelial tubes in vitro. On the other hand, the only one that induced heme oxygenase-1 expression was sulforaphane, a known activator of a HMOX1 inducer—NRF2. None of the stimulants changed significantly the levels of 30 cytokines and growth factors tested with the multiplex test. Then, we used atorvastatin-stimulated cells or conditioned media from them in the Matrigel plug in vivo angiogenic assay. Neither AT alone in control media nor conditioned media nor AT-stimulated cells affected numbers of endothelial cells in the plug or plug's vascularization. Concluding, high concentrations of atorvastatin stabilize tubes and enhance the paracrine angiogenic activity of human PAC cells in vitro. However, the effect was not observed in vivo. Therefore, the use of conditioned media from atorvastatin-treated PAC is not a promising therapeutic strategy to enhance angiogenesis.

Quantifying the Vasculogenic Potential of Induced Pluripotent Stem Cell-Derived Endothelial Progenitors in Collagen Hydrogels

IMPACT STATEMENT

Our work reinforces the role of extracellular matrix (ECM) density and matrix metalloprotease activity on the formation of microvasculature from induced pluripotent stem cell (iPSC)-derived vascular cells. The cell-matrix interactions discussed in this study underscore the importance of understanding the role of mechanoregulation and matrix degradation on vasculogenesis and can potentially drive the development of ECM-mimicking angiogenic biomaterials. Furthermore, our work has broader implications concerning the response of iPSC-derived cells to the mechanics of engineered microenvironments. An understanding of these interactions will be critical to creating physiologically relevant transplantable tissue replacements.

Improving Arterial Wall Characteristics in Patients After Myocardial Infarction with a Very Low Dose of Fluvastatin and Valsartan: A Proof-of-Concept Study

Background

We tested the concept of improving arterial wall characteristics by treatment with a very low-dose combination of fluvastatin and valsartan (low-flu/val) in stable, post-myocardial infarction (MI) patients.

Material/Methods

We enrolled 36 post-MI middle-aged males in the treatment (n=20) or control (n=16) group receiving low-flu/val (10 mg/20 mg) or placebo, respectively. The parameters of endothelial function (flow-mediated dilatation (FMD), reactive hyperemia index), and arterial stiffness (carotid-femoral pulse wave velocity (cf-PWV), local carotid PWV, and beta stiffness coefficient) were measured before and after 30 days of therapy, and 10 weeks later.

Results

Treatment with low-flu/val improved FMD from 3.1±1.3% to 4.8±1.5% (p<0.001; by 54.8%) and cf-PWV from 7.8±1.1 to 6.7±1.5 m/s (p<0.01; by 14.1%) without affecting either lipids or blood pressure. In the treatment group, FMD and/or cf-PWV significantly improved in 17 patients, but the improvements did not correlate. The benefits obtained were still detectable 10 weeks after complete treatment cessation. No changes were obtained in the control group. No other vascular parameters changed.

Conclusions

Low-flu/val added “on top of” optimal therapy substantially improves endothelial function and arterial stiffness in post-MI patients. Since these improved parameters are well-known predictors of future coronary events, such treatment could decrease cardiovascular risk. Further studies are therefore warranted.

Effect of intensive multifactorial treatment on vascular progenitor cells in hypertensive patients

Background

Most hypertensive patients, despite a proper control of their cardiovascular risk factors, have cardiovascular complications, evidencing the importance of controlling and/or reversing target-organ damage. In this sense, endothelial dysfunction has been associated with the presence of cardiovascular risk factors and related cardiovascular outcomes. Since hypertension often clusters with other risk factors such as dyslipemia, diabetes and obesity, in this study we have investigated the effect of intensive multifactorial treatment on circulating vascular progenitor cell levels on high-risk hypertensive patients.

Design

We included108 hypertensive patients receiving intensive multifactorial pharmacologic treatment and dietary recommendations targeting blood pressure, dyslipemia, hyperglycemia and weight for 12 months. After the treatment period, blood samples were collected and circulating levels of endothelial (CD34+/KDR+, CD34+/VE-cadherin+) and smooth muscle (CD14+/endoglin+) progenitor cells were identified by flow cytometry. Additionally, plasma concentration of vascular endothelial growth factor (VEGF) was determined by ELISA.

Results

Most hypertensive patients (61±12 years, 47% men) showed cardiovascular parameters within normal ranges at baseline. Moreover, body mass index and the majority of the biochemical parameters (systolic and diastolic blood pressure, fasting glucose, total cholesterol, HDL-c, LDL-c, creatinine and hs-CRP) significantly decreased overtime. After 12 months of intensive treatment, CD34+/KDR+ and CD14+/endoglin+ levels did not change, but CD34+/VE-cadherin+ cells increased significantly at month 12 [0.9(0.05–0.14)% vs 0.05(0.02–0.09)% P<0.05]. However, VEGF plasma concentration decreased significantly overtime [89.1(53.9–218.7) vs [66.2(47.5–104.6) pg/mL, P<0.05].

Conclusions

Long-term intensive treatment in hypertensive patients further improves cardiovascular risk and increases circulating EPCs, suggesting that these cells could be a therapeutic target.

Stabilisation of atherosclerotic plaques

Plaque rupture and subsequent thrombotic occlusion of the coronary artery account for as many as three quarters of myocardial infarctions. The concept of plaque stabilisation emerged about 20 years ago to explain the discrepancy between the reduction of cardiovascular events in patients receiving lipid lowering therapy and the small decrease seen in angiographic evaluation of atherosclerosis. Since then, the concept of a vulnerable plaque has received a lot of attention in basic and clinical research leading to a better understanding of the pathophysiology of the vulnerable plaque and acute coronary syndromes. From pathological and clinical observations, plaques that have recently ruptured have thin fibrous caps, large lipid cores, exhibit outward remodelling and invasion by vasa vasorum. Ruptured plaques are also focally inflamed and this may be a common denominator of the other pathological features. Plaques with similar characteristics, but which have not yet ruptured, are believed to be vulnerable to rupture. Experimental studies strongly support the validity of anti-inflammatory approaches to promote plaque stability. Unfortunately, reliable non-invasive methods for imaging and detection of such plaques are not yet readily available. There is a strong biological basis and supportive clinical evidence that low-density lipoprotein lowering with statins is useful for the stabilisation of vulnerable plaques. There is also some clinical evidence for the usefulness of antiplatelet agents, beta blockers and renin-angiotensin-aldosterone system inhibitors for plaque stabilisation. Determining the causes of plaque rupture and designing diagnostics and interventions to prevent them are urgent priorities for current basic and clinical research in cardiovascular area.

Endothelial Progenitor Cells for the Vascularization of Engineered Tissues

Self-assembled microvasculature from cocultures of endothelial cells (ECs) and stromal cells has significantly advanced efforts to vascularize engineered tissues by enhancing perfusion rates in vivo and producing investigative platforms for microvascular morphogenesis in vitro. However, to clinically translate prevascularized constructs, the issue of EC source must be resolved. Endothelial progenitor cells (EPCs) can be noninvasively supplied from the recipient through adult peripheral and umbilical cord blood, as well as derived from induced pluripotent stem cells, alleviating antigenicity issues. EPCs can also differentiate into all tissue endothelium, and have demonstrated potential for therapeutic vascularization. Yet, EPCs are not the standard EC choice to vascularize tissue constructs in vitro. Possible reasons include unresolved issues with EPC identity and characterization, as well as uncertainty in the selection of coculture, scaffold, and culture media combinations that promote EPC microvessel formation. This review addresses these issues through a summary of EPC vascular biology and the effects of tissue engineering design parameters upon EPC microvessel formation. Also included are perspectives to integrate EPCs with emerging technologies to produce functional, organotypic vascularized tissues.

The acute impact of high-dose lipid-lowering treatment on endothelial progenitor cells in patients with coronary artery disease-The REMEDY-EPC early substudy

RATIONALE AND OBJECTIVE

Endothelial progenitor cells (EPCs) play a role in vascular repair, while circulating endothelial cells (CECs) are biomarkers of vascular damage and regeneration. Statins may promote EPC/CEC mobilization in the peripheral blood. We evaluated whether pre-procedural exposure to different lipid-lowering drugs (statins±ezetimibe) can acutely increase levels/activity of EPCs/CECs in patients with stable coronary artery disease (CAD).

METHODS

In a planned sub-analysis of the Rosuvastatin For REduction Of Myocardial DamagE During Coronary AngioplastY (REMEDY) trial, 38 patients with stable CAD on chronic low-dose statin therapy were randomized, in a double-blind, placebo-controlled design, into 4 groups before PCI: i. placebo (n = 11); ii. atorvastatin (80 mg+40 mg, n = 9); iii. rosuvastatin (40 mg twice, n = 9); and iv. rosuvastatin (5 mg) and ezetimibe (10 mg) twice, (n = 9). At baseline and 24 h after treatment-before PCI-, patients underwent blinded analyses of EPCs [colony forming units-endothelial cells (CFU-ECs), endothelial colony-forming cells (ECFCs) and tubulization activity] and CECs in peripheral blood.

RESULTS

We found no significant treatment effects on parameters investigated such as number of CECs [Median (IQR): i. 0(0), ii. 4.5(27), iii. 1.9(2.3), iv. 1.9(2.3)], CFU-ECs [Median (IQR): i. 27(11), ii. 19(31), iii. 47(36), iv. 30(98)], and ECFCs [Median (IQR): i. 86(84), ii. 7(84), iii. 8/(42.5), iv. 5(2)], as well as tubulization activity [total tubuli (well), Median (IQR): i. 19(7), ii. 5(4), iii. 25(13), iv. 15(24)].

CONCLUSIONS

In this study, we found no evidence of acute changes in levels or activity of EPCs and CECs after high-dose lipid-lowering therapy in stable CAD patients.

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.

Short-term atorvastatin therapy improves arterial stiffness of middle-aged systemic lupus erythematosus patients with pathological pulse wave velocity

Objectives Statins have been proposed as a potential treatment for systemic lupus erythematosus (SLE) due to their immunomodulatory properties, their role restoring endothelial function and preventing atherosclerosis. We evaluate the effect of a short period treatment with a low dose of atorvastatin and its withdrawal on early stage subclinical atherosclerosis. Methods Thirty-seven SLE females received 20 mg/day atorvastatin during eight weeks. At baseline, at the end of treatment and six months after atorvastatin withdrawal, disease activity, subclinical atherosclerosis -assessed by measuring carotid-femoral pulse wave velocity (PWV) - and quantification of circulating endothelial progenitor cells (EPC) - as a surrogate biological marker of subclinical atherosclerosis - were carried out. Results The group of SLE patients with baseline pathological arterial stiffness showed a significant decrease of PWV after atorvastatin therapy (8.43 ± 1.45 m/s vs 7.42 ± 1.06 m/s; p = 0.002) that is maintained six months after treatment finished. Only patients of the middle-aged group showed a nearly significant decrease in the PWV measured along the study (7.16 ± 1.23 m/s vs 6.76 ± 0.82 m/s; p = 0.05). Atorvastatin induced a significant decrease in the circulating EPC percentage (0.65 ± 0.67 vs 0.40 ± 0.31; p = 0.023) as well as a downward trend of disease activity that it is observed by a decrease in SLE disease activity index simultaneously with an increase in C3 complement and significant decrease in serum concentration of vascular endothelial grow factor (VEGF) and sVCAM-1. Conclusions Short-term atorvastatin therapy reduces arterial stiffness of SLE patients with baseline pathological PWV, who are mainly in the group of middle-aged patients. Further studies are needed to determine whether these patients would benefit from statin therapy in preventing cardiovascular events.

Endothelial progenitor cells (EPCs) in ageing and age-related diseases: How currently available treatment modalities affect EPC biology, atherosclerosis, and cardiovascular outcomes

Endothelial progenitor cells (EPCs) are mononuclear cells that circulate in the blood and are derived from different tissues, expressing cell surface markers that are similar to mature endothelial cells. The discovery of EPCs has lead to new insights in vascular repair and atherosclerosis and also a new theory for ageing. EPCs from the bone marrow and some other organs aid in vascular repair by migrating to distant vessels where they differentiate into mature endothelial cells and replace old and injured endothelial cells. The ability of EPCs to repair vascular damage depends on their number and functionality. Currently marketed drugs used in a variety of diseases can modulate these characteristics. In this review, the effect of currently available treatment options for cardiovascular and metabolic disorders on EPC biology will be discussed. The various EPC-based therapies that will be discussed include lipid-lowering agents, antihypertensive agents, antidiabetic drugs, phosphodiesteraze inhibitors, hormones, as well as EPC capturing stents.

Measurements of CD34+/CD45-dim Stem Cells Predict Healing of Diabetic Neuropathic Wounds

Management of neuropathic foot ulcers in patients with diabetes (DFUs) has changed little over the past decade, and there is currently no objective method to gauge probability of successful healing. We hypothesized that studies of stem/progenitor cells (SPCs) in the early weeks of standard wound management could predict who will heal within 16 weeks. Blood and debrided wound margins were collected for 8 weeks from 100 patients undergoing weekly evaluations and treatment. SPC number and intracellular content of hypoxia-inducible factors (HIFs) were evaluated by flow cytometry and immunohistochemistry. More SPCs entered the bloodstream in the first 2 weeks of care in patients who healed (n = 37) than in those who did not (n = 63). Logistic regression demonstrated that the number of blood-borne SPCs and the cellular content of HIFs at study entry and the first-week follow-up visit predicted healing. Strong correlations were found among week-to-week assessments of blood-borne SPC HIF factors. We conclude that assays of SPCs during the first weeks of care in patients with DFUs can provide insight into how well wounds will respond and may aid with decisions on the use of adjunctive measures.

Effect of High-Dose Atorvastatin Reload on the Release of Endothelial Progenitor Cells in Patients on Long-Term Statin Treatment Who Underwent Percutaneous Coronary Intervention (from the ARMYDA-EPC Study)

Endothelial progenitor cells (EPCs) may concur to endogenous vascular repair. Previous studies have reported that statin treatment increases EPC levels. We investigated whether this occurs in patients on long-term statin treatment who underwent percutaneous coronary interventions (PCIs). In a phase A study, 53 patients (atorvastatin reload [AR] 80 mg 12 hours before + 40 mg 2 hours before PCI, n = 27; placebo [P], n = 26) were evaluated for EPC mobilization as CD45dim/CD34+/CD133+/KDR+ cell number by flow cytometry. Assays were run at randomization (12 hours before PCI, R), immediately before PCI (T0) at 8 (T8) and 24 hours (T24). In phase B study, 50 patients (AR, n = 25; P, n = 25) were evaluated for early colony formation by Hill colony forming unit (CFU) assay, with sampling at randomization and 24 hours later. In phase A, EPCs levels were similar at randomization between 2 arms (0.23% [0.14 to 0.54] of total events in AR vs 0.22% [0.04 to 0.37] in P group; p = 0.33). At PCI, EPC levels were higher in AR arm (0.42% [0.06 to 0.30] vs 0.19% [0.06 to 030]; p = 0.009). Higher EPC levels in AR group were also found at 8 and 24 hours. In phase B, EPC CFUs/well numbers at randomization were similar in the 2 arms (8 [6 to 12] in AR vs 12 [6 to 20] in P group, p = 0.109). EPC CFU/well at 24 hours became significantly higher in AR arm (17 [10 to 23] vs 5 [2 to 13], p = 0.002). In conclusion, high-dose AR before PCI in patients on long-term statin therapy promptly increases EPCs mobilization, which are capable of early colony formation and may contribute to cardioprotection.

Residential Proximity to Major Roadways Is Associated With Increased Levels of AC133+ Circulating Angiogenic Cells

OBJECTIVES

Previous studies have shown that residential proximity to a roadway is associated with increased cardiovascular disease risk. Yet, the nature of this association remains unclear, and its effect on individual cardiovascular disease risk factors has not been assessed. The objective of this study was to determine whether residential proximity to roadways influences systemic inflammation and the levels of circulating angiogenic cells.

APPROACH AND RESULTS

In a cross-sectional study, cardiovascular disease risk factors, blood levels of C-reactive protein, and 15 antigenically defined circulating angiogenic cell populations were measured in participants (n=316) with moderate-to-high cardiovascular disease risk. Attributes of roadways surrounding residential locations were assessed using geographic information systems. Associations between road proximity and cardiovascular indices were analyzed using generalized linear models. Close proximity (<50 m) to a major roadway was associated with lower income and higher rates of smoking but not C-reactive protein levels. After adjustment for potential confounders, the levels of circulating angiogenic cells in peripheral blood were significantly elevated in people living in close proximity to a major roadway (CD31(+)/AC133(+), AC133(+), CD34(+)/AC133(+), and CD34(+)/45(dim)/AC133(+) cells) and positively associated with road segment distance (CD31(+)/AC133(+), AC133(+), and CD34(+)/AC133(+) cells), traffic intensity (CD31(+)/AC133(+) and AC133(+) cells), and distance-weighted traffic intensity (CD31(+)/34(+)/45(+)/AC133(+) cells).

CONCLUSIONS

Living close to a major roadway is associated with elevated levels of circulating cells positive for the early stem marker AC133(+). This may reflect an increased need for vascular repair. Levels of these cells in peripheral blood may be a sensitive index of cardiovascular injury because of residential proximity to roadways.

Large platelets but not putative endothelial progenitor cells are associated with low strut coverage after drug-eluting stent implantation

OBJECTIVES

This study assessed whether different subsets of circulating endothelial and putative endothelial progenitor cells (CEC and EPC) correlate with stent strut coverage (SSC) using second generation optical coherence tomography (OCT).

BACKGROUND

Due to the lack of imaging modalities with a resolution down to the magnitude of a few cells, the influence of EPC on endothelialisation of drug-eluting stents has not been assessed in patients.

METHODS

In 37 patients, SSC of everolimus-eluting stents was assessed by OCT 5-7months after stent implantation. Different subsets of EPC (CD34(+)KDR(+), CD34(+)KDR(+)CD45(dim), CD133(+), CD3(+)CD31(+)), CEC (CD31(+)CD45(-)CD146(+)), and CD31(+)CD45(-)CD146(-) representing large platelets were analysed by flow cytometry, including viability analyses with 7-AAD. Statistical analysis comprised univariate regression analysis and multivariable models integrating OCT and flow cytometry data as well as clinical variables.

RESULTS

SSC and frequency of different cell types were highly comparable with previously published data. EPC defined in part by KDR expression were mostly non-viable. On univariate and in multivariable models, no association between EPC counts and strut coverage was detected. For CD31(+)CD45(-)CD146(-) counts, representing large platelets, an inverse relationship with strut coverage was identified by a multivariable regression model adjusting for age, sex, diabetes mellitus, NYHA and CCS class, CRP, serum triglycerides, glucose and creatinine (beta=-9.42, p=0.006).

CONCLUSIONS

There was no significant association between EPC or CEC and healing after drug-eluting stent implantation. Yet, CD31(+)CD45(-)CD146(-) cells were associated with low SSC. These data suggest that large platelets may represent a more important mediator of late stent endothelialisation than EPC.

Diabetes, Endothelial Dysfunction, and Vascular Repair: What Should a Diabetologist Keep His Eye on?

Cardiovascular complications are the most common complications of diabetes mellitus. A prominent attribute of diabetic cardiovascular complications is accelerated atherosclerosis, considered as a still incurable disease, at least at more advanced stages. The discovery of endothelial progenitor cells (EPCs), able to replace old and injured mature endothelial cells and capable of differentiating into healthy and functional endothelial cells, has offered the prospect of merging the traditional theories on the pathogenesis of atherosclerosis with evolving concepts of vascular biology. The literature supports the notion that EPC alterations are involved in the pathogenesis of vascular diseases in diabetics, but at present many questions remain unanswered. In this review the aspects linking endothelial progenitor cells to the altered vascular biology in diabetes mellitus are discussed.

Short-term statin discontinuation increases endothelial progenitor cells without inflammatory rebound in type 2 diabetic patients

Type 2 diabetes (T2D) is characterized by impaired vascular regeneration owing to reduced endothelial progenitor cells (EPCs). While statins are known to increase EPCs, the effects of statin withdrawal on EPCs are unknown. Herein, we evaluated the effects of statin discontinuation on EPCs, inflammation and in vivo angiogenesis. Thirty-four T2D patients were randomized to 5-day discontinuation or continuation of statin treatment. At baseline and at day 5, we determined lipid profile, EPC levels, monocyte-macrophage polarization, and concentrations of hsCRP, VEGF, SDF-1α, and G-CSF. Angiogenesis by human circulating cells was assessed in vivo. At day 5, patients who stopped statins showed raised total and LDL cholesterol and EPCs compared to baseline, while no changes were observed in patients who continued statins. No changes were observed in hsCRP, VEGF, SDF-1α, G-CSF, M1 and M2 macrophages and classical, intermediate and nonclassical monocytes in both groups. In vivo angiogenesis by circulating cells was increased in patients who stopped statin treatment. In vitro, cholesterol supplementation stimulated mobilizing signals in human bone marrow mesenchymal stem cells. In conclusion, a brief statin withdrawal increases circulating EPCs and functional proangiogenic cells in T2D. These findings identify statin-sensitive pathways as reverse target mechanisms to stimulate vascular repair in diabetes.

Endothelial progenitor cells--potential new avenues to improve neoangiogenesis and reendothelialization

The term endothelial progenitor cell (EPC) was established more than 10 years ago and is used to refer to a group of circulating cells that display endothelial lineage qualities and are able to home to areas of ischemia or vascular injury and to facilitate the repair of damaged blood vessels or develop new vessels as needed. This chapter reviews the current lineage relationships among all the cells called EPC and will clear the terminology used in EPC research. Furthermore, an overview of the clinical and in vitro research, as well as cytokine and drug interactions and potential EPC applications, is given.

Endothelial progenitor cells in cardiovascular diseases

Endothelial dysfunction has been associated with the development of atherosclerosis and cardiovascular diseases. Adult endothelial progenitor cells (EPCs) are derived from hematopoietic stem cells and are capable of forming new blood vessels through a process of vasculogenesis. There are studies which report correlations between circulating EPCs and cardiovascular risk factors. There are also studies on how pharmacotherapies may influence levels of circulating EPCs. In this review, we discuss the potential role of endothelial progenitor cells as both diagnostic and prognostic biomarkers. In addition, we look at the interaction between cardiovascular pharmacotherapies and endothelial progenitor cells. We also discuss how EPCs can be used directly and indirectly as a therapeutic agent. Finally, we evaluate the challenges facing EPC research and how these may be overcome.

Endothelial progenitor cells in diabetic patients with myocardial infarction - can statins improve their function?

The effect of statins on endothelial progenitor cells (EPCs) function derived from diabetic patients (DMpts) with acute myocardial infarction (AMI) is unknown. In this study we assess the response of early and late EPCs from diabetic versus non-diabetic patients (NDMpts) with AMI to statins. EPCs were obtained from 10 diabetic and 10 age-matched non-diabetic male patients with AMI. For each patient, cultures of early and late EPCs were performed under 4 different conditions: normal glucose concentration (control); high glucose concentration; normal glucose concentration with atorvastatin supplementation and normal glucose concentration with pravastatin supplementation. To compare the effect of these treatments on EPC function in DMpts versus NDMpts, we performed in vitro: EPC colony-forming units (CFU) assay; cell cycle analysis; viability assessment and expression of the surface markers CXCR4, CD133, CD34 and KDR. Under control conditions, CFU numbers were reduced in DMpts-derived EPCs when compared to those of NDMpts (1.4±0.8 vs 2.6±1.2 CFU/well, P=0.021). When early EPCs from DMpts were cultured in the presence of statins, CFU capacity was restored, surmounting that of NDMpts under control conditions. Statins significantly improved viability of early EPCs and delayed the onset of late EPCs senescence, even in cells from DMpts. In addition, statins induced approximately a 2-fold increase in the proportion of late EPCs in S-phase of the cell cycle (P<0.05). Statins have a beneficial effect on both early and late EPCs from DMpts with AMI. Despite the functional impairment of EPCs from DMpts, they exhibit similar responsiveness to statins as equivalent cells from NDMpts.

CD34+/CD45-dim stem cell mobilization by hyperbaric oxygen - changes with oxygen dosage

Because hyperbaric oxygen treatment mobilizes bone marrow derived-stem/progenitor cells by a free radical mediated mechanism, we hypothesized that there may be differences in mobilization efficiency based on exposure to different oxygen partial pressures. Blood from twenty consecutive patients was obtained before and after the 1st, 10th and 20th treatment at two clinical centers using protocols involving exposures to oxygen at either 2.0 or 2.5 atmospheres absolute (ATA). Post-treatment values of CD34+, CD45-dim leukocytes were always 2-fold greater than the pre-treatment values for both protocols. Values for those treated at 2.5 ATA were significantly greater than those treated at 2.0 ATA by factors of 1.9 to 3-fold after the 10th and before and after the 20th treatments. Intracellular content of hypoxia inducible factors -1, -2, and -3, thioredoxin-1 and poly-ADP-ribose polymerase assessed in permeabilized CD34+ cells with fluorophore-conjugated antibodies were twice as high in all post- versus pre-treatment samples with no significant differences between 2.0 and 2.5 ATA protocols. We conclude that putative progenitor cell mobilization is higher with 2.5 versus 2.0 ATA treatments, and all newly mobilized cells exhibit higher concentrations of an array of regulatory proteins.

Mobilization of CD133+ progenitor cells in patients with acute cerebral infarction

Progenitor cells (PCs) contribute to the endogenous repair mechanism after ischemic events. Interleukin-8 (IL-8) as part of the acute inflammatory reaction may enhance PC mobilization. Also, statins are supposed to alter number and function of circulating PCs. We aimed to investigate PC mobilization after acute ischemic stroke as well as its association with inflammatory markers and statin therapy. Sixty-five patients with ischemic stroke were enrolled in the study. The number of CD133⁺ PCs was analyzed by flow cytometry. Blood samples were drawn within 24 hours after symptom onset and after 5 days. The number of CD133⁺ PCs increased significantly within 5 days (p<0.001). We found no correlation between CD133⁺ PCs and the serum levels of IL-8, IL-6, or C-reactive protein (CRP). Multivariate analysis revealed that preexisting statin therapy correlated independently with the increase of CD133⁺ PCs (p = 0.001). This study showed a mobilization of CD133⁺ PCs in patients with acute cerebral infarction within 5 days after symptom onset. The early systemic inflammatory response did not seem to be a decisive factor in the mobilization of PCs. Preexisting statin therapy was associated with the increase in CD133⁺ PCs, suggesting a potentially beneficial effect of statin therapy in patients with stroke.

Distinct CD11b+-monocyte subsets accelerate endothelial cell recovery after acute and chronic endothelial cell damage

BACKGROUND

Endothelial cell recovery requires replenishment of primary cells from the endothelial lineage. However, recent evidence suggests that cells of the innate immune system enhance endothelial regeneration.

METHODS AND RESULTS

Focusing on mature CD11b+-monocytes, we analyzed the fate and the effect of transfused CD11b+-monocytes after endothelial injury in vivo. CD11b-diphtheria-toxin-receptor-mice--a mouse model in which administration of diphtheria toxin selectively eliminates endogenous monocytes and macrophages--were treated with WT-derived CD11b+-monocytes from age-matched mice. CD11b+-monocytes improved endothelium-dependent vasoreactivity after 7 days while transfusion of WT-derived CD11b--cells had no beneficial effect on endothelial function. In ApoE-/--CD11b-DTR-mice with a hypercholesterolemia-induced chronic endothelial injury transfusion of WT-derived CD11b+-monocytes stimulated by interferon-γ (IFNγ) decreased endothelial function, whereas interleukin-4-stimulated (IL4) monocytes had no detectable effect on vascular function. Bioluminescent imaging revealed restriction of transfused CD11b+-monocytes to the endothelial injury site in CD11b-DTR-mice depleted of endogenous monocytes. In vitro co-culture experiments revealed significantly enhanced regeneration properties of human endothelial outgrowth cells (EOCs) when cultured with preconditioned-media (PCM) or monocytes of IL4-stimulated-subsets compared to the effects of IFNγ-stimulated monocytes.

CONCLUSION

CD11b+-monocytes play an important role in endothelial cell recovery after endothelial injury by homing to the site of vascular injury, enhancing reendothelialization and improving endothelial function. In vitro experiments suggest that IL4-stimulated monocytes enhance EOC regeneration properties most likely by paracrine induction of proliferation and cellular promotion of differentiation. These results underline novel insights in the biology of endothelial regeneration and provide additional information for the treatment of vascular dysfunction.

Controlled intramyocardial release of engineered chemokines by biodegradable hydrogels as a treatment approach of myocardial infarction

Myocardial infarction (MI) induces a complex inflammatory immune response, followed by the remodelling of the heart muscle and scar formation. The rapid regeneration of the blood vessel network system by the attraction of hematopoietic stem cells is beneficial for heart function. Despite the important role of chemokines in these processes, their use in clinical practice has so far been limited by their limited availability over a long time-span in vivo. Here, a method is presented to increase physiological availability of chemokines at the site of injury over a defined time-span and simultaneously control their release using biodegradable hydrogels. Two different biodegradable hydrogels were implemented, a fast degradable hydrogel (FDH) for delivering Met-CCL5 over 24 hrs and a slow degradable hydrogel (SDH) for a gradual release of protease-resistant CXCL12 (S4V) over 4 weeks. We demonstrate that the time-controlled release using Met-CCL5-FDH and CXCL12 (S4V)-SDH suppressed initial neutrophil infiltration, promoted neovascularization and reduced apoptosis in the infarcted myocardium. Thus, we were able to significantly preserve the cardiac function after MI. This study demonstrates that time-controlled, biopolymer-mediated delivery of chemokines represents a novel and feasible strategy to support the endogenous reparatory mechanisms after MI and may compliment cell-based therapies.

High-dose atorvastatin reloading before percutaneous coronary intervention increased circulating endothelial progenitor cells and reduced inflammatory cytokine expression during the perioperative period

OBJECTIVE

We investigated atorvastatin reloading effects on endothelial progenitor cell (EPC) count and inflammatory cytokine expression after percutaneous coronary intervention (PCI) in patients with stable angina pectoris who had previously received long-term statin treatments.

METHODS

Patients with stable angina pectoris were treated with 80 mg atorvastatin 12 hours and 40 mg atorvastatin 2 hours before coronary angioplasty (n = 15) or preoperatively with 40 mg/d atorvastatin for 7 days (n = 15) or did not receive atorvastatin (n = 15). CD45-/133+/34+, CD45-/CD34+/kinase insert domain receptor (KDR)+, and CD45-/CD144+/KDR+ EPCs in the peripheral blood were determined by flow cytometry 1 hour before as well as 1 hour, 6 hours, and 24 hours after PCI. Soluble intercellular adhesion molecule 1 (sICAM-1), hypersensitive C-reactive protein (hCRP), and troponin-I (TnI) serum concentrations were analyzed immediately prior to and 24 hours after PCI.

RESULTS

In the 40mg Atorvastatin and control groups, none of the analyzed EPC blood concentrations changed significantly from 1h before operation to 1h and 6 h postoperative values. In contrast, the number of circulating early differentiation stage EPCs CD45-/133+/34+ and CD45-/CD34+/ KDR+ raised significantly from 1 h preoperative values (57.3±9.3; 57.3 ± 10.7) to 1 h postoperative ((74.4 ± 11.4; 78.8 ± 16.2), (p < 0.05)) and 6 h postoperative ((93 ± 16.9; 99.7 ± 11.9), (p < 0.05)) concentrations after coronary angioplasty in the 80mg Atorvastatin medication patients. In the control group, the sICAM-1 (174.55 ± 38.91 vs 204.11 ± 58.24) and hCRP (1.89 ± 1.93 vs 9.0 ± 11.1) serum concentrations at 24 hours after PCI were significantly elevated (P < .05) compared to preoperative values, whereas the increases in the 2 groups treated with atorvastatin were not significant. In addition, the rise in serum TnI concentration level from pre- to postoperative in the 80-mg (0.02 ± 0.02 vs 0.09 ± 0.08) and the 40-mg (0.01 ± 0.03 vs 1.2 ± 2.59) reloading groups was less than that of the controls (0.01 ± 0.02 vs 1.75 ± 3.09) (p < 0.05).

CONCLUSION

Our results suggested that high-dose atorvastatin application before PCI triggered early EPC circulation. Furthermore, postoperative inflammatory cytokine sICAM-1 as well as hCRP serum levels were reduced, while postinterventional myocardial injury marker TnI elevations were inversely correlated with statin reloadings.

Improving cardiovascular outcomes in rheumatic diseases: therapeutic potential of circulating endothelial progenitor cells

Patients with Rheumatoid Arthritis (RA) and Systemic Lupus Erythematosus (SLE) have a significantly increased risk of cardiovascular disease (CVD). The reason for this is unclear but may be due, at least in part, to the failure of endothelial repair mechanisms. Over the last 15 years there has been much interest in the mechanisms of endothelial renewal and its potential as a therapy for CVD. In the circulation there are two distinct populations of cells; myeloid angiogenic cells (MACs) which augment repair by the paracrine secretion of angiogenic factors, and outgrowth endothelial cells (OECs) which are true endothelial progenitor cells (EPCs) and promote vasculogenesis by differentiating into mature endothelium. There are marked abnormalities in the number and function of these cells in patients with RA and SLE. Inflammatory cytokines including interferon-alpha (IFNα) and tumour-necrosis factor alpha (TNFα) both impair MAC and OEC function ex vivo and may therefore contribute to the CVD risk in these patients. Whilst administration of mononuclear cells, MACs and other progenitors has improved cardiovascular outcomes in the acute setting, this is not a viable option in chronic disease. The pharmacological manipulation of MAC/OEC function in vivo however has the potential to significantly improve endothelial repair and thus reduce CVD in this high risk population.

The effect of statin therapy withdrawal on monocyte subsets

BACKGROUND

Three functionally distinct monocyte subsets have been identified. Statins are of undoubted effect in atherosclerosis and have numerous pleiotropic effects that contribute to their clinical success, but the effect of these drugs on monocyte subsets is unclear. We hypothesised a beneficial effect of statins on key receptor expression by monocyte subsets.

MATERIAL AND METHODS

Effects of temporal (2 weeks) cessation of statin therapy by 66 patients with stable coronary artery disease on monocyte subsets [CD14++CD16-CCR2+ (Mon1), CD14++CD16+CCR2+ (Mon2) and CD14+CD16++CCR2- (Mon3)], their aggregates with platelets and their expression of a number of receptors involved in inflammation (IL-6 receptor), adhesion [vascular cell adhesion molecule (VCAM)], angiogenesis [vascular endothelial growth factor (VEGF)] and repair were assessed by flow cytometry.

RESULTS

Statin cessation did not lead to any significant changes in absolute numbers of monocyte subsets or the degree of their aggregation with platelets. All monocyte subsets showed significant downregulation of expression of vascular endothelial factor receptor 2, Tie2 and Toll-like receptor-4 (TLR4; all changes P < 0·01). Expression of CXCR4 was only reduced in Mon1 cells (P = 0·013). There was no significant change in the expression of CD14, CD16, CCR4, IL6 receptor and VCAM (all P = NS).

CONCLUSIONS

Statin withdrawal does not affect counts of any of monocyte subsets, but leads to downregulation of expression of TLR4 and receptors related to angiogenesis on all subsets, as well as a decrease in density of CXCR4 expression on 'classical' Mon1. These data provide further support of pleiotropic effects of statins and their effects on monocyte pro-angiogenic and proreparative characteristics.

Endothelial progenitor cells in acute ischemic stroke

OBJECTIVES

The levels of circulating endothelial progenitor cells (EPCs) in ischemic stroke have not been studied extensively and reported results are inconsistent. We aimed to investigate the time course, the prognostic relevance, and the variables associated with EPC counts in patients with ischemic stroke at different time points.

MATERIAL AND METHODS

We studied prospectively 146 consecutive patients with ischemic stroke within the first 48 h from the onset of symptoms (baseline). We evaluated demographic data, classical vascular risk factors, treatment with thrombolysis and statins, stroke etiology, National Institute of Health and Stroke Scale score and outcome (favorable when Rankin scale score 0-2). Blood samples were collected at baseline, at day 7 after stroke (n = 121) and at 3 months (n = 92). The EPC were measured by flow cytometry.

RESULTS

We included 146 patients with a mean age of 70.8 ± 12.2 years. The circulating EPC levels were higher on day 7 than at baseline or at 3 months (P = 0.045). Pretreatment with statins (odds ratio [OR] 3.11, P = 0.008) and stroke etiology (P = 0.032) were predictive of EPC counts in the baseline sample. EPC counts were not associated with stroke severity or functional outcome in all the patients. However, using multivariate analyses, a better functional outcome was found in patients with higher EPC counts in large-artery atherosclerosis and small-vessel disease etiologic subtypes.

CONCLUSIONS

After acute ischemic stroke, circulating EPC counts peaked at day 7. Pretreatment with statins increased the levels of EPC. In patients with large-artery atherosclerosis and small-vessel disease subtypes, higher counts were related to better outcome at 3 months.

Increasing doses of simvastatin versus combined ezetimibe/simvastatin: effect on circulating endothelial progenitor cells

BACKGROUND

Patients with coronary artery disease (CAD) should be treated with statins to attain very low cholesterol levels, in order to reduce cardiovascular adverse events. More than 70% of these patients do not reach the appropriate cholesterol goal despite moderate statin doses. However, it is not known whether therapeutic uptitration with different lipid-lowering strategies has a similar "pleiotropic" effect on atherosclerotic endothelial dysfunction evaluated by measurement of endothelial progenitor cells (EPCs).

OBJECTIVE

We sought to compare, in patients with stable CAD and with a low-density lipoprotein cholesterol (LDL-C) >70 mg/dL on treatment with simvastatin 20 mg, the effects on EPCs by increasing simvastatin to 80 mg versus adding ezetimibe 10 mg.

METHODS

Patients (n = 68, 63 ± 9 years, 39% men) were randomly allocated to receive ezetimibe 10/simvastatin 20 mg or simvastatin 80 mg for 6 weeks. Circulating EPCs were measured by flow cytometry before and after the treatment.

RESULTS

Both strategies presented similar effects on metabolic parameters. The LDLs were equally reduced by ezetimibe 10/simvastatin 20 mg and simvastatin 80 mg (28.9% ± 13% vs 21.1% ± 33%; P = .46, respectively). The levels of EPCs were unaffected by ezetimibe 10/simvastatin 20 mg (median [25th, 75th]: pre- vs posttreatment, 7.0 [2.3; 13.3] vs 3.1 [0.1; 13.2] EPCs/10(4) mononuclear cells; P = .43) or simvastatin 80 mg (pre- vs posttreatment, 6.1 [2.9; 15.2] vs 4.0 [1.4; 10.7] EPCs/10(4) mononuclear cells; P = .5), and there were no differences between the groups on treatment effects (P = .9).

CONCLUSIONS

Among stable patients with CAD and with an LDL-C >70 mg/dL on simvastatin 20 mg, increasing simvastatin dose to 80 mg or adding ezetimibe 10 mg promoted similar further cholesterol reduction but did not have incremental effects on circulating EPCs. These data suggest that the effects of simvastatin moderate doses on EPCs are not increased by intensive lipid-lowering strategies (clinicaltrials.gov: NCT00474123).

Statin use and peripheral blood progenitor cells mobilization in patients with multiple myeloma

PURPOSE

Statins have beneficial effects in patients after myocardial infarction and at least part of the benefit results from mobilization of marrow endothelial progenitors to repopulate damaged myocardial tissues. This study examines if statins may have the same effect in mobilizing marrow progenitors to be harvested and subsequently used in high-dose chemotherapy with progenitor cell rescue in multiple myeloma.

METHODS

From 2006 to 2012, 86 patients with multiple myeloma were mobilized with the use of G-CSF and were retrospectively analyzed. Patients with other malignancies or mobilized with the use of chemotherapy or with plerixafor were excluded.

RESULTS

The median age of the patients was 60 years. 72 patients had received one line of chemotherapy and 14 patients two or more lines of chemotherapy. Twenty patients were taking statins at the time of the harvest while 66 patients were not. In the group of patients taking statins the success rate of first leukapheresis (obtaining the target number of 4 × 10(6) CD34+ cells/kg) was 85 % while in the group not taking statins this rate was 63.6 %. Despite the comparatively small number of patients this difference approached statistical significance (χ (2) = 0.07).

CONCLUSION

This retrospective analysis of 86 patients shows for the first time a possible benefit of statins for peripheral blood progenitor cells mobilization in patients with multiple myeloma. Larger studies would be required to clarify the issue. If their effectiveness is confirmed, statins could be a safe and cheaper addition to chemotherapy and plerixafor for peripheral hematopoietic stem cell mobilization.

Effect of vitamin D receptor activator therapy on vitamin D receptor and osteocalcin expression in circulating endothelial progenitor cells of hemodialysis patients

BACKGROUND

The effects of vitamin D receptor (VDR) and osteocalcin (OC) expression as well as VDR agonist (VDRA) therapy on circulating endothelial progenitor cells (EPCs) has not been elucidated yet.

METHODS

We therefore analyzed EPCs in 30 healthy controls and 82 patients undergoing dialysis (no VDRA therapy: 28; oral calcitriol: 30, and intravenous paricalcitol, PCTA: 24). The percentage of EPCs (CD34+/CD133-/KDR+/CD45-) expressing VDR or OC, and VDR and OC expression defined by mean fluorescence intensity (MFI) were analyzed using flow cytometry. The in vitro effect of VDRAs was evaluated in EPCs isolated from each patient group.

RESULTS

The percentage of VDR+ EPCs correlated positively with VDRA therapy and 25(OH)D, and negatively with diabetes, C-reactive protein, hemoglobin and osteopontin. VDR-MFI correlated positively with VDRA therapy, parathyroid hormone (PTH) and 25(OH)D, and negatively with diabetes and osteopontin. The percentage of OC+ EPCs correlated positively with the calcium score, PTH and phosphate, and negatively with 25(OH)D. OC-MFI correlated positively with calcium score, PTH, phosphate and hemoglobin, and negatively with albumin, 25(OH)D and osteopontin. Cell cultures from patients without VDRA therapy had the highest levels of calcium deposition and OC expression, which both significantly decreased following in vitro VDRA administration: in particular extracellular calcium deposition was only reduced by adding PCTA.

CONCLUSIONS

Our data suggest that 25(OH)D serum levels and VDRA therapy influence VDR and OC expression on circulating EPCs. Since OC expression may contribute to vascular calcification, we hypothesize a putative protective role of VDRA therapy.

Association of HIV-Infection and antiretroviral therapy with levels of endothelial progenitor cells and subclinical atherosclerosis

BACKGROUND

Although in the general population circulating vascular progenitor cell levels have been implicated in the homeostasis of the vascular wall through differentiation into endothelium and/or smooth muscle cells, it has not yet been assessed in HIV-infected patients. We herein investigated the number of progenitor cell subpopulations in HIV-infected patients and its relationship to carotid intima-media thickness (c-IMT).

METHODS

Blood samples were collected from 200 HIV-infected patients and CD34/KDR, CD34/VE-cadherin, and CD14/Endoglin progenitor cells were identified by flow cytometry. c-IMT was determined by ultrasonography. A group of 27 healthy subjects was used as control group.

RESULTS

In our population (20 ART-naive patients and 180 treated patients), traditional cardiovascular risk factors were not found predictive of vascular progenitor cell levels. However, antiretroviral therapy (ART)-treatment was identified as the main predictive value for low CD34/KDR cells and high CD14/Endoglin cells after adjustment by cardiovascular risk factors (age, sex, hypertension, diabetes, and hyperlipidaemia) and HIV-related characteristics (HIV duration and ART treatment). Low levels of circulating CD34/KDR or CD34/VE-cadherin endothelial progenitor cells tended to be associated with increased c-IMT. However, a positive association was found between CD14/Endoglin cells and c-IMT. Low number of CD34/KDR cells was also associated with the longest exposure to nucleoside reverse transcriptase inhibitors and/or protease inhibitors.

CONCLUSIONS

ART exposure is the main predictor of circulating vascular progenitor cell levels. However, their levels are only partially associated with high c-IMT in HIV-infected patients. ART has already been found to have proatherogenic effect, but our data first describe its relationship with vascular progenitor cells and c-IMT.

Restoring stem cell mobilization to promote vascular repair in diabetes

Diabetes triggers endothelial dysfunction, which is linked to increased risk of cardiovascular diseases. Stem and progenitor cells from the bone marrow are involved in the maintenance of vascular integrity. Diabetic patients show a dysfunction of these cells, which might represent a novel pathophysiological mechanism of vascular disease. Specifically, stem and progenitor cells fail to egress from the bone marrow (BM) due to BM pathological alterations and unresponsiveness to mobilizing stimuli. In this review, we describe impaired stem cell mobilization in diabetes as a mechanism of failed vascular repair and we provide evidence that pharmacological strategies can restore mobilization. We discuss recent advances in the knowledge of aberrant organization of the diabetic BM and its implications for impaired mobilization. Finally, we describe in detail the pharmacological exploitation of the G-CSF/DPP-4(CD26)/SDF-1α axis as a novel strategy to improve mobilization and attain vascular repair in diabetes.

Circulating CD34(+) progenitor cell frequency is associated with clinical and genetic factors

Circulating blood CD34(+) cells consist of hematopoietic stem/progenitor cells, angiogenic cells, and endothelial cells. In addition to their clinical use in hematopoietic stem cell transplantation, CD34(+) cells may also promote therapeutic neovascularization. Therefore, understanding the factors that influence circulating CD34(+) cell frequency has wide implications for vascular biology in addition to stem cell transplantation. In the present study, we examined the clinical and genetic characteristics associated with circulating CD34(+) cell frequency in a large, community-based sample of 1786 Framingham Heart Study participants.Among subjects without cardiovascular disease (n = 1595), CD34(+) frequency was inversely related to older age, female sex, and smoking. CD34(+) frequency was positively related to weight, serum total cholesterol, and statin therapy. Clinical covariates accounted for 6.3% of CD34(+) variability. CD34(+) frequency was highly heritable (h(2) = 54%; P < .0001). Genome-wide association analysis of CD34(+) frequency identified suggestive associations at several loci, including OR4C12 (chromosome 11; P = 6.7 × 10(-7)) and ENO1 and RERE (chromosome 1; P = 8.8 × 10(-7)). CD34(+) cell frequency is reduced in older subjects and is influenced by environmental factors including smoking and statin use. CD34(+) frequency is highly heritable. The results of the present study have implications for therapies that use CD34(+) cell populations and support efforts to better understand the genetic mechanisms that underlie CD34(+) frequency.

Statins and stem cell modulation

Stem cell-based therapy is a promising option for the treatment of ischemic heart diseases. As to a successful stem cell-based therapy, one of the most important issues is that the stable engraftment and survival of implanted stem cells in cardiac microenvironment. There are evidences suggest that pharmacological treatment devoted to regulate stem cell function might represent a potential new therapeutic strategy and are drawing nearer to becoming a part of treatment in clinical settings. Statins could exert cholesterol-independent or pleiotropic effects to cardiovascular system. Recent studies have shown that statins could modulate the biological characteristics and function of various stem cells, thus could be an effective method to facilitate stem cell therapy. This review will focus on statins and their modulation effects on various stem cells.

Effects of preoperative short term use of atorvastatin on endothelial progenitor cells after coronary surgery: a randomized, controlled trial

OBJECTIVES

We investigated the effects of short-term use of atorvastatin on CD34+/VEGF-R2+/CD133+/CD45- endothelial progenitor cell (EPC) count after on-pump coronary artery bypass surgery (CABG).

METHODS

Between Feb-2010 and May-2010, we randomly assigned, in a placebo-controlled, double-blind study, 60 consecutive patients who underwent isolated, first-time CABG to receive either 14-day atorvastatin (40 mg/day) or placebo preoperatively. Urgent CABG and recent myocardial infarction were excluded. EPCs were quantified (cells/μl) by flow cytometric phenotyping obtained from venous blood samples collected preoperatively (T(1)), 6-hours (T(2)), and on the 5th day postoperatively (T(3)). Levels of markers of inflammation and serum cardiac troponin I were also measured preoperatively and daily until day-5 after surgery.

RESULTS

There were no differences in baseline risk factors including cholesterol profiles, and EuroSCORES between the groups. The composite primary end-point, favored statin group with higher amount of circulating, early EPC count (cells/μl) at all time points compared with placebo (T(1), 2.30±0.02 versus 1.58±0.03, p<0.001; T(2), 5.00±0.06 versus 2.19±0.06, p<0.001; T(3), 3.03±0.08 versus 1.78±0.02, p<0.001). Postoperative hsCRP rise were inversely correlated with EPC count, and were significantly lower in the statin group (T(1), 0.8 ± 0.1 versus 2.2±1.5, p<0.001; T(2), 72.9±3.2 versus 96.0±3.6, p<0.001; T(3), 4.3±1.2 versus 11.4±4.1, p<0.001). Furthermore, the incidence of postoperative atrial fibrillation was significantly lower in the statin group compared to placebo (3.3% versus 23%, p=0.02).

CONCLUSIONS

Short-term atorvastatin use increases circulating early EPCs both pre- and post-operatively and is associated with better preservation of sinus rhythm and reduced hsCRP levels. (ClinicalTrials.gov number, NCT01096875).

Decreased pre-surgical CD34+/CD144+ cell number in patients undergoing coronary artery bypass grafting compared to coronary artery disease-free valvular patients

BACKGROUND

Cardiovascular disease has been linked to endothelial progenitor cell (EPC) depletion and functional impairment in atherosclerosis and aortic stenosis. EPCs may play a pivotal role in vascular grafting. However, the EPC depletion in coronary artery bypass grafting (CABG) patients has not been compared to coronary artery disease-free valvular replacement patients with aortic stenosis.

METHODS

We aimed to assess the basal number of CD34+/KDR+ and CD34+/CD144+ cells in CABG patients, compared to aortic stenosis valvular replacement patients. 100 patients (51 CABG and 49 valvular surgery ones) were included in the present study. All CABG or valvular patients had angiographic demonstration of the presence or the absence of coronary artery disease, respectively. Numbers of CD34+/KDR+ and CD34+/CD144+ were assessed by flow cytometry of pre-surgical blood samples.

RESULTS

We found a lower number of CD34+/CD144+ cells in CABG patients compared to valvular patients (0.21 ± 0.03% vs. 0.47 ± 0.08%), and this difference remained statistically significant after the P was adjusted for multiple comparisons (P = 0.01428). Both groups had more EPCs than healthy controls.

CONCLUSIONS

Pre-surgical CD34+/CD144+ numbers are decreased in CABG patients, compared to valvular patients with absence of coronary disease.

Pharmacological actions of statins: a critical appraisal in the management of cancer

Statins, among the most commonly prescribed drugs worldwide, are cholesterol-lowering agents used to manage and prevent cardiovascular and coronary heart diseases. Recently, a multifaceted action in different physiological and pathological conditions has been also proposed for statins, beyond anti-inflammation and neuroprotection. Statins have been shown to act through cholesterol-dependent and -independent mechanisms and are able to affect several tissue functions and modulate specific signal transduction pathways that could account for statin pleiotropic effects. Typically, statins are prescribed in middle-aged or elderly patients in a therapeutic regimen covering a long life span during which metabolic processes, aging, and concomitant novel diseases, including cancer, could occur. In this context, safety, toxicity, interaction with other drugs, and the state of health have to be taken into account in subjects treated with statins. Some evidence has shown a dichotomous effect of statins with either cancer-inhibiting or -promoting effects. To date, clinical trials failed to demonstrate a reduced cancer occurrence in statin users and no sufficient data are available to define the long-term effects of statin use over a period of 10 years. Moreover, results from clinical trials performed to evaluate the therapeutic efficacy of statins in cancer did not suggest statin use as chemotherapeutic or adjuvant agents. Here, we reviewed the pharmacology of the statins, providing a comprehensive update of the current knowledge of their effects on tissues, biological processes, and pathological conditions, and we dissected the disappointing evidence on the possible future use of statin-based drugs in cancer therapy.

Testosterone and phosphodiesterase type-5 inhibitors: new strategy for preventing endothelial damage in internal and sexual medicine?

Normal vascular endothelium is essential for the synthesis and release of substances affecting vascular tone (e.g. nitric oxide; NO), cell adhesion (e.g. endothelins, interleukins), and the homeostasis of clotting and fibrinolysis (e.g. plasminogen inhibitors, von Willebrand factor). The degeneration of endothelial integrity promotes adverse events (AEs) leading to increased atherogenesis and to the development of vascular systemic and penile end-organ disease. Testosterone (T) is an important player in the regulation of vascular tone through non-genomic actions exerted via blockade of extracellular-calcium entry or activation of potassium channels; also, adequate T concentrations are paramount for the regulation of phosphodiesterase type-5 (PDE5) expression and finally, for the actions exerted by hydrogen sulphide, a gas involved in the alternative pathway controlling vasodilator responses in penile tissue. It is known that an age-related decline of serum T is reported in approximately 20 to 30% of men whereas T deficiency is reported in up to 50% of men with metabolic syndrome or diabetes. A number of laboratory and human studies have shown the combination of T and other treatments for erectile dysfunction (ED), such as PDE5 inhibitors, to be more beneficial in patients with ED and hypogonadism, who fail monotherapy for sexual disturbances.The aim of this review is to show evidence on the role of T and PDE5 inhibitors, alone or in combination, as potential boosters of endothelial function in internal medicine diseases associated with reduced T or NO bioavailability, i.e. metabolic syndrome, obesity, diabetes, coronary artery disease, hyperhomocysteinemia, that share common risk factors with ED. Furthermore, the possibility of such a strategy to prevent endothelial dysfunction in men at increased cardiovascular risk is discussed.

Differential role of monocyte subsets in atherosclerosis

Endothelial dysfunction and inflammation of the arterial wall continuously drive the development of atherosclerosis. Details regarding the sequential involvement of different monocyte subsets in the pathology of this disease have recently emerged. This review concentrates on major monocyte subpopulations in mouse and men and specifically addresses their phenotype, function and recruitment during primary atherosclerosis as well as their contribution to angiogenesis and tissue regeneration secondary to plaque rupture.

A new strategy of promoting vascularization of skin substitutes by capturing endothelial progenitor cells automatically

How to promote vascularization of a skin substitute is the key to successful skin transplantation. Current methods are mainly through releasing angiogenesis-related factors (ARF) or seeding angiogenesis-related cells (ARC), but the efficacy of these methods is not satisfactory, because angiogenesis needs participation of multiple factors, extracellular matrix and related cells. The latest research has demonstrated that endothelial progenitor cells (EPCs) originating from bone marrow and existing in peripheral blood are the key element participating in revascularization of adult tissues. They directly participate in both stem cell vasculogenesis of ischemic tissues and local angiogenesis. We therefore hypothesize whether it is possible to construct a new skin substitute and use it to mobilize EPCs in bone marrow to peripheral circulation and capture EPCs automatically as a simple and effective method of promoting vascularization of the skin substitute for the sake of improving its post-transplant survival.

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

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