Effects of Granulocyte Colony Stimulating Factor on Functional Activities of Endothelial Progenitor Cells in Patients With Chronic Ischemic Heart Disease

Role of Stromal Cell-Derived Factor-1 in Endothelial Progenitor Cell-Mediated Vascular Repair and Regeneration

Endothelial progenitor cells (EPCs) are immature endothelial cells that participate in vascular repair and postnatal neovascularization and provide a novel and promising therapy for the treatment of vascular disease. Studies in different animal models have shown that EPC mobilization through pharmacological agents and autologous EPC transplantation contribute to restoring blood supply and tissue regeneration after ischemic injury. However, these effects of the progenitor cells in clinical studies exhibit mixed results. The therapeutic efficacy of EPCs is closely associated with the number of the progenitor cells recruited into ischemic regions and their functional abilities and survival in injury tissues. In this review, we discussed the regulating role of stromal cell-derived factor-1 (also known CXCL12, SDF-1) in EPC mobilization, recruitment, homing, vascular repair and neovascularization, and analyzed the underlying machemisms of these functions. Application of SDF-1 to improve the regenerative function of EPCs following vascular injury was also discussed. SDF-1 plays a crucial role in mobilizing EPC from bone marrow into peripheral circulation, recruiting the progenitor cells to target tissue and protecting against cell death under pathological conditions; thus improve EPC regenerative capacity. SDF-1 are crucial for regulating EPC regenerative function, and provide a potential target for improve therapeutic efficacy of the progenitor cells in treatment of vascular disease.

Autologous Bone-Marrow vs. Peripheral Blood Mononuclear Cells Therapy for Peripheral Artery Disease in Diabetic Patients

Diabetes mellitus (DM) remains one of the most important risk factors for peripheral artery disease (PAD), with approximately 20% of DM patients older than 40 years old are affected with PAD. The current standard management for severe PAD is endovascular intervention with or without surgical bypass. Unfortunately, up to 40% of patients are unable to undergo these revascularization therapies due to excessive surgical risk or adverse vascular side effects. Stem cell therapy has emerged as a novel therapeutic strategy for these ‘no-option’ patients. Several types of stem cells are utilized for PAD therapy, including bone marrow mononuclear cells (BMMNC) and peripheral blood mononuclear cells (PBMNC). Many studies have reported the safety of BMMNC and PBMNC, as well as its efficacy in reducing ischemic pain, ulcer size, pain-free walking distance, ankle-brachial index (ABI), and transcutaneous oxygen pressure (TcPO2). However, the capacity to establish the efficacy of reducing major amputation rates, amputation free survival, and all-cause mortality is limited, as shown by several randomized placebo-controlled trials. The present literature review will focus on comparing safety and efficacy between BMMNC and PBMNC as cell-based management in diabetic patients with PAD who are not suitable for revascularization therapy.

Autologous cells derived from different sources and administered using different regimens for 'no-option' critical lower limb ischaemia patients

BACKGROUND

Revascularisation is the gold standard therapy for patients with critical limb ischaemia (CLI). In over 30% of patients who are not suitable for or have failed previous revascularisation therapy (the 'no-option' CLI patients), limb amputation is eventually unavoidable. Preliminary studies have reported encouraging outcomes with autologous cell-based therapy for the treatment of CLI in these 'no-option' patients. However, studies comparing the angiogenic potency and clinical effects of autologous cells derived from different sources have yielded limited data. Data regarding cell doses and routes of administration are also limited.

OBJECTIVES

To compare the efficacy and safety of autologous cells derived from different sources, prepared using different protocols, administered at different doses, and delivered via different routes for the treatment of 'no-option' CLI patients.

SEARCH METHODS

The Cochrane Vascular Information Specialist (CIS) searched the Cochrane Vascular Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE Ovid, Embase Ovid, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Allied and Complementary Medicine Database (AMED), and trials registries (16 May 2018). Review authors searched PubMed until February 2017.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) involving 'no-option' CLI patients comparing a particular source or regimen of autologous cell-based therapy against another source or regimen of autologous cell-based therapy.

DATA COLLECTION AND ANALYSIS

Three review authors independently assessed the eligibility and methodological quality of the trials. We extracted outcome data from each trial and pooled them for meta-analysis. We calculated effect estimates using a risk ratio (RR) with 95% confidence interval (CI), or a mean difference (MD) with 95% CI.

MAIN RESULTS

We included seven RCTs with a total of 359 participants. These studies compared bone marrow-mononuclear cells (BM-MNCs) versus mobilised peripheral blood stem cells (mPBSCs), BM-MNCs versus bone marrow-mesenchymal stem cells (BM-MSCs), high cell dose versus low cell dose, and intramuscular (IM) versus intra-arterial (IA) routes of cell implantation. We identified no other comparisons in these studies. We considered most studies to be at low risk of bias in random sequence generation, incomplete outcome data, and selective outcome reporting; at high risk of bias in blinding of patients and personnel; and at unclear risk of bias in allocation concealment and blinding of outcome assessors. The quality of evidence was most often low to very low, with risk of bias, imprecision, and indirectness of outcomes the major downgrading factors.Three RCTs (100 participants) reported a total of nine deaths during the study follow-up period. These studies did not report deaths according to treatment group.Results show no clear difference in amputation rates between IM and IA routes (RR 0.80, 95% CI 0.54 to 1.18; three RCTs, 95 participants; low-quality evidence). Single-study data show no clear difference in amputation rates between BM-MNC- and mPBSC-treated groups (RR 1.54, 95% CI 0.45 to 5.24; 150 participants; low-quality evidence) and between high and low cell dose (RR 3.21, 95% CI 0.87 to 11.90; 16 participants; very low-quality evidence). The study comparing BM-MNCs versus BM-MSCs reported no amputations.Single-study data with low-quality evidence show similar numbers of participants with healing ulcers between BM-MNCs and mPBSCs (RR 0.89, 95% CI 0.44 to 1.83; 49 participants) and between IM and IA routes (RR 1.13, 95% CI 0.73 to 1.76; 41 participants). In contrast, more participants appeared to have healing ulcers in the BM-MSC group than in the BM-MNC group (RR 2.00, 95% CI 1.02 to 3.92; one RCT, 22 participants; moderate-quality evidence). Researchers comparing high versus low cell doses did not report ulcer healing.Single-study data show similar numbers of participants with reduction in rest pain between BM-MNCs and mPBSCs (RR 0.99, 95% CI 0.93 to 1.06; 104 participants; moderate-quality evidence) and between IM and IA routes (RR 1.22, 95% CI 0.91 to 1.64; 32 participants; low-quality evidence). One study reported no clear difference in rest pain scores between BM-MNC and BM-MSC (MD 0.00, 95% CI -0.61 to 0.61; 37 participants; moderate-quality evidence). Trials comparing high versus low cell doses did not report rest pain.Single-study data show no clear difference in the number of participants with increased ankle-brachial index (ABI; increase of > 0.1 from pretreatment), between BM-MNCs and mPBSCs (RR 1.00, 95% CI 0.71 to 1.40; 104 participants; moderate-quality evidence), and between IM and IA routes (RR 0.93, 95% CI 0.43 to 2.00; 35 participants; very low-quality evidence). In contrast, ABI scores appeared higher in BM-MSC versus BM-MNC groups (MD 0.05, 95% CI 0.01 to 0.09; one RCT, 37 participants; low-quality evidence). ABI was not reported in the high versus low cell dose comparison.Similar numbers of participants had improved transcutaneous oxygen tension (TcO₂) with IM versus IA routes (RR 1.22, 95% CI 0.86 to 1.72; two RCTs, 62 participants; very low-quality evidence). Single-study data with low-quality evidence show a higher TcO₂ reading in BM-MSC versus BM-MNC groups (MD 8.00, 95% CI 3.46 to 12.54; 37 participants) and in mPBSC- versus BM-MNC-treated groups (MD 1.70, 95% CI 0.41 to 2.99; 150 participants). TcO₂ was not reported in the high versus low cell dose comparison.Study authors reported no significant short-term adverse effects attributed to autologous cell implantation.

AUTHORS' CONCLUSIONS

Mostly low- and very low-quality evidence suggests no clear differences between different stem cell sources and different treatment regimens of autologous cell implantation for outcomes such as all-cause mortality, amputation rate, ulcer healing, and rest pain for 'no-option' CLI patients. Pooled analyses did not show a clear difference in clinical outcomes whether cells were administered via IM or IA routes. High-quality evidence is lacking; therefore the efficacy and long-term safety of autologous cells derived from different sources, prepared using different protocols, administered at different doses, and delivered via different routes for the treatment of 'no-option' CLI patients, remain to be confirmed.Future RCTs with larger numbers of participants are needed to determine the efficacy of cell-based therapy for CLI patients, along with the optimal cell source, phenotype, dose, and route of implantation. Longer follow-up is needed to confirm the durability of angiogenic potential and the long-term safety of cell-based therapy.

Reloadable multidrug capturing delivery system for targeted ischemic disease treatment

Human clinical trials of protein therapy for ischemic diseases have shown disappointing outcomes so far, mainly because of the poor circulatory half-life of growth factors in circulation and their low uptake and retention by the targeted injury site. The attachment of polyethylene glycol (PEG) extends the circulatory half-lives of protein drugs but reduces their extravasation and retention at the target site. To address this issue, we have developed a drug capture system using a mixture of hyaluronic acid (HA) hydrogel and anti-PEG immunoglobulin M antibodies, which, when injected at a target body site, can capture and retain a variety of systemically injected PEGylated therapeutics at that site. Furthermore, repeated systemic injections permit "reloading" of the capture depot, allowing the use of complex multistage therapies. This study demonstrates this capture system in both murine and porcine models of critical limb ischemia. The results show that the reloadable HA/anti-PEG system has the potential to be clinically applied to patients with ischemic diseases, who require sequential administration of protein drugs for optimal outcomes.

The lack of increases in circulating endothelial progenitor cell as a negative predictor for pathological response to neoadjuvant chemotherapy in breast cancer patients

Circulating endothelial progenitor cells are a potential surrogate marker for angiogenesis. Little is known about the alteration of circulating endothelial progenitor cell counts during neoadjuvant chemotherapy. Our goal was to reveal the alteration in CEP counts in association with response to neoadjuvant chemotherapy in patients with breast cancer. We measured the number of circulating endothelial progenitor cells (CD31⁺CD34⁺CD133⁺CD45^dim) by four-color flow cytometry using blood samples from 57 patients with breast cancer who received neoadjuvant chemotherapy (5-fluorouracil + epirubicin + cyclophosphamide (FEC), docetaxel + cyclophosphamide (TC), cisplatin + docetaxel (TP)). There was no significant difference in the baseline circulating endothelial progenitor cell counts with respect to the clinical and pathological background factors. Circulating endothelial progenitor cell counts increased after the initiation of chemotherapy (pre-1st vs. pre-2nd cycle, p = 0.0035; pre-1st vs. pre-4th cycle, p = 0.047). An increase of circulating endothelial progenitor cell counts from pre-1st to pre-2nd cycle was associated with pCR (p = 0.013 for χ² test). A multivariate analysis, including subtype, and clinical response showed that the lack of circulating endothelial progenitor cell increases from pre-1st to pre-2nd cycle was an independent negative predictor of pCR (p = 0.002). Our data suggest that alterations in circulating endothelial progenitor cell counts are associated with treatment response. The circulating endothelial progenitor cell count could be a useful biomarker for monitoring chemotherapeutic response.

Breast cancer patients do better after preoperative chemotherapy if their numbers of circulating endothelial progenitor cells (CEPs) go up. A team from Japan led by Takayuki Ueno from the Kyorin University School of Medicine in Tokyo studied 57 women who underwent neoadjuvant chemotherapy to shrink the size of their tumors before surgery. The researchers measured the number of CEPs—cells that derive from the bone marrow and can help build new blood vessels around tumors—both before and during chemotherapy. They found no link between overall CEP counts and treatment response. However, patients whose CEP numbers went up between cycles of chemotherapy had better outcomes. The authors suggest that CEP counts could be used as a diagnostic tool for predicting responses to neoadjuvant chemotherapy, although larger studies are needed to confirm their initial findings

Granulocyte-colony stimulating factor for large anterior ST-elevation myocardial infarction: rationale and design of the prospective randomized phase III STEM-AMI OUTCOME trial

BACKGROUND

Granulocyte-colony stimulating factor (G-CSF) has been clinically tested in ST-elevation myocardial infarction (STEMI) with mixed results. Our 3-year follow-up data from STEM-AMI trial documented a sustained benefit of G-CSF on adverse ventricular remodeling after large anterior STEMI, when administered early and at a high-dose in patients with left ventricular (LV) dysfunction. The Aim of the present trial is to establish whether G-CSF improves hard clinical long-term outcomes.

METHODS

The STEM-AMI OUTCOME is a prospective, multicenter, randomized, open-label, phase III trial. It will include 1,530 patients with anterior STEMI undergoing primary percutaneous coronary intervention 2 to 24 hours after symptoms onset and with LV ejection fraction ≤45% after successful reperfusion. Patients will be randomized 1:1 to G-CSF and/or standard treatment. The primary end point is a reduced occurrence of all-cause death, recurrence of myocardial infarction, or hospitalization due to heart failure in G-CSF-treated patients. Left ventricular remodeling will be assessed via cardiac ultrasound and a substudy with cardiac magnetic resonance will be carried out in 120 subjects. Accrual and follow-up periods will last 3 and 2 years, respectively.

CONCLUSIONS

The STEM-AMI OUTCOME study is designed to be a rigorous controlled phase III trial with adequate statistical power to conclusively assess efficacy of G-CSF treatment in STEMI.

Cell Therapy in Patients with Critical Limb Ischemia

Critical limb ischemia (CLI) represents the most advanced stage of peripheral arterial obstructive disease (PAOD) with a severe obstruction of the arteries which markedly reduces blood flow to the extremities and has progressed to the point of severe rest pain and/or even tissue loss. Recent therapeutic strategies have focused on restoring this balance in favor of tissue survival using exogenous molecular and cellular agents to promote regeneration of the vasculature. These are based on stimulation of angiogenesis by extracellular and cellular components. This review article carries out a systematic analysis of the most recent scientific literature on the application of stem cells in patients with CLI. The results obtained from the detailed analysis of the recent literature data have confirmed the beneficial role of cell therapy in reducing the rate of major amputations in patients with CLI and improving their quality of life.

Progress and prospects of endothelial progenitor cell therapy in coronary stent implantation

Drug-eluting stents (DES) have been widely used to treat coronary artery disease (CAD) since their clinical use has significantly reduced the occurrence of in-stent restenosis (ISR) as compared with the initially applied bare-metal stents (BMS). However, analyses of long-term clinical outcome have raised concerns about the serious safety problem of DES, such as ISR caused by late or very late thrombosis. Various studies showed that those complications were associated with vascular endothelial injury/dysfunction or endothelialization delaying. Recently, through biological characterization of endothelial progenitor cells (EPCs), mechanistic understanding of rapid re-endothelialization of the vascular injury sites after coronary stenting has become possible and is a new research hotspot in the prevention of ISR and late/very late stent thrombosis. It has been well recognized that the formation of a functional endothelial layer from EPCs requires a coordinated sequence of multistep and signaling events, which includes cell mobilization, adhesion, migration and finally the differentiation to vascular endothelial cells (VECs). In this review, we summarize and discuss the currently relevant information about EPCs, the mechanism of DES interfering with the natural vascular healing process in preventing or delaying the formation of a functional endothelial layer, and EPCs-mediated acceleration of re-endothelialization at vascular injury sites. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1237-1247, 2016.

Safety and feasibility of intramyocardial versus intracoronary delivery of autologous cell therapy in advanced heart failure: the REGENERATE-IHD pilot study

AIM

This study presents an interim safety and feasibility analysis of the REGENERATE-IHD randomized controlled trial, which is examining the safety and efficacy of three different delivery routes of bone marrow-derived stem cells (BMSCs) in patients with ischemic heart failure.

METHODS & RESULTS

The first 58 patients recruited to the REGENERATE-IHD study are included in this interim analysis (pilot). Symptomatic patients with ischemic heart failure were randomized to receive subcutaneous granulocyte colony-stimulating factor or saline injections only; or subcutaneous granulocyte colony-stimulating factor injections followed by intracoronary or intramyocardial injections of BMSCs or serum (control). No significant differences were found in terms of safety and feasibility between the different delivery routes, with no significant difference in procedural complications or major adverse cardiac events. There was a signal towards improved heart failure symptoms in the patients treated with intramyocardial injection of mobilized BMSCs.

CONCLUSION

Peripheral mobilization of BMSCs with or without subsequent direct myocardial delivery appears safe and feasible in patients with chronic ischemic heart failure.

Correlation of restenosis after rabbit carotid endarterectomy and inflammatory cytokines

OBJECTIVE

To establish rabbit model of restenosis after carotid endarterectomy surgery, and to study tissue inflammatory cytokines (TNF-α, IL-6) involved in restenosis.

METHODS

A total of 32 rabbits were randomly divided into two groups: model group and control group. The right common carotid artery in rabbits was damaged by carotid endar terectomy in model group. The tissues were harvested at different time points respectively, the pathological changes of the vascular wall after operation were observed at different time points. The changes of expression of tissue vascular wall inflammatory cytokines (TNF-α, IL-6) at different time points after the surgery was observed by RT-PCR, and the changes of serum inflammatory cytokines (TNF-α, IL -6) were detected by ELISA.

RESULTS

The new intima appeared after 7 days of the injury and reached the peak on 28 d which is uneven and significantly thicker than the control group (P<0.01). The tissue inflammatory cytokines (TNF-α, IL-6) were significantly increased after the rabbit common carotid artery injury, which was significant difference compared with normal control group (P<0.05).

CONCLUSIONS

The tissue inflammatory factors significantly increase after the rabbit carotid artery injury, which suggests the mutual concurrent effects of inflammatory cytokines can result in the proliferation of vascular restenosis.

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.

Incidence and clinical significance of cardiac biomarker elevation during stem cell mobilization, apheresis, and intramyocardial delivery: an analysis from ACT34-CMI

BACKGROUND

Cell therapy is a promising therapeutic for a variety of cardiovascular conditions including refractory angina. Elevation of cardiac biomarkers during cell delivery has been frequently described, but the clinical implications have never been studied.

METHODS

ACT34-CMI was a randomized double-blind study assessing the use of intramyocardial delivery of autologous CD34(+) cells for the treatment of refractory angina. Patients (n = 167) underwent G-CSF-mediated (5 μg/[kg day] × 5 days) stem cell mobilization, apheresis, and intramyocardial injection of 1 × 10(5)/kg or 5 × 10(5)/kg CD34(+) cells or placebo. Troponin and creatinine kinase MB were assessed at baseline (n = 161), after cell mobilization and apheresis (n = 153 and 143, respectively), and post-intramyocardial injection (n = 155 and 141, respectively). Major adverse cardiac events (MACE) included death, myocardial infarction, acute congestive heart failure, urgent revascularization, or sustained ventricular arrhythmia.

RESULTS

Seven (4.3%) subjects had troponin above the upper limits of normal (ULN) at baseline. Thirty-four (22.2%) and 11 (7.2%) subjects had troponin levels > ULN or >3× ULN after cell mobilization and apheresis, whereas 72 (46.1%) and 39 (25.2%) subjects had troponin elevations > ULN or >3× ULN, respectively, after intramyocardial injections. Age, but no other preprocedural factors, was predictive of troponin elevation. Periprocedural troponin elevation was not associated with an increased risk of MACE during 1 year, especially in cell therapy-treated patients.

CONCLUSIONS

Troponin elevation is common during stem cell harvesting and intramyocardial administration, is usually asymptomatic, and does not appear to be associated with long-term MACE in subjects undergoing stem cell mobilization and intramyocardial injection.

Cell-based interventions for therapeutic angiogenesis: review of potential cell sources

Alternative therapies are currently being developed to treat patients with chronic limb ischemia who are unable to be revascularized in order to avoid amputation. Cell-based therapy using mononuclear cells is gaining attention as many clinical trials are currently underway. We review cell differentiation along with the different potential cell sources for use in therapeutic angiogenesis.

Circulating apoptotic endothelial cells and apoptotic endothelial microparticles independently predict the presence of cardiac allograft vasculopathy

OBJECTIVES

Maintenance of endothelial homeostasis may prevent the development of cardiac allograft vasculopathy (CAV). This study investigated whether biomarkers related to endothelial injury and endothelial repair discriminate between CAV-negative and CAV-positive heart transplant recipients.

BACKGROUND

CAV is the most important determinant of cardiac allograft survival and a major cause of death after heart transplantation.

METHODS

Fifty-two patients undergoing coronary angiography between 5 and 15 years after heart transplantation were recruited in this study. Flow cytometry was applied to quantify endothelial progenitor cells (EPCs), circulating endothelial cells (CECs), and endothelial microparticles. Cell culture was used for quantification of circulating EPC number and hematopoietic progenitor cell number and for analysis of EPC function.

RESULTS

The EPC number and function did not differ between CAV-negative and CAV-positive patients. In univariable models, age, creatinine, steroid dose, granulocyte colony-forming units, apoptotic CECs, and apoptotic endothelial microparticles discriminated between CAV-positive and CAV-negative patients. The logistic regression model containing apoptotic CECs and apoptotic endothelial microparticles as independent predictors provided high discrimination between CAV-positive and CAV-negative patients (C-statistic 0.812; 95% confidence interval: 0.692 to 0.932). In a logistic regression model with age and creatinine as covariates, apoptotic CECs (p = 0.0112) and apoptotic endothelial microparticles (p = 0.0141) were independent predictors (C-statistic 0.855; 95% confidence interval: 0.756 to 0.953). These 2 biomarkers remained independent predictors when steroid dose was introduced in the model.

CONCLUSIONS

The high discriminative ability of apoptotic CECs and apoptotic endothelial microparticles is a solid foundation for the development of clinical prediction models of CAV.

G-CSF stimulation and coronary reinfusion of mobilized circulating mononuclear proangiogenic cells in patients with chronic ischemic heart disease:five-year results of the TOPCARE-G-CSF trial

Prognosis of patients with heart failure remains poor despite improved conventional and interventional treatment regimens. The improvement of neovascularization and repair processes by administration of bone marrow-derived cells modestly improved the recovery after acute myocardial infarction. However, circulating patient-derived cells are reduced in number and function particularly in chronic heart failure. Therefore, we tested the hypothesis whether the mobilization of circulating mononuclear proangiogenic cells (CPCs) by G-CSF may overcome some of these limitations. In the present pilot study, 32 patients with at least 3-month-old myocardial infarction were randomized to G-CSF alone (G-CSF group) or intracoronary infusion of G-CSF-mobilized and cultured CPCs into the infarct-related artery (G-CSF/CPC group). Primary endpoint of the study was safety. Efficacy parameters included serial assessment of LV function, NT-proBNP levels, and cardiopulmonary exercise testing. G-CSF effectively mobilized circulating CD34(+)CD45(+) cells after 5 days in all patients (408 ± 64%) without serious adverse events. At 3 months, NYHA class and global LV function did not show significant improvements in both treatment groups (G-CSF: ΔLVEF 1.6 ± 2.4%; p = 0.10; G-CSF/CPC: ΔLVEF 1.4 ± 4.1%; p = 0.16). In contrast, target area contractility improved significantly in the G-CSF/CPC group. During 5-year follow-up, one patient died after rehospitalization for worsening heart failure. Eleven patients underwent further revascularization procedures. NT-proBNP levels, cardiopulmonary exercise capacity, and NYHA class remained stable in both treatment groups. The results from our pilot trial indicate that administration of G-CSF alone or G-CSF-mobilized and cultured CPCs can be performed safely in patients with chronic ischemic heart disease. However, only minor effects on LV function, NT-proBNP levels, and NYHA classification were observed during follow-up, suggesting that the enhancement of CPCs by G-CSF alone does not substantially improve intracoronary cell therapy effects in patients with chronic ischemic heart failure.

Endothelial progenitor cells in atherosclerosis

Endothelial progenitor cells (EPCs) are involved in the maintenance of endothelial homoeostasis and in the process of new vessel formation. Experimental and clinical studies have shown that atherosclerosis is associated with reduced numbers and dysfunction of EPCs; and that medications alone are able to partially reverse the impairment of EPCs in patients with atherosclerosis. Therefore, novel EPC-based therapies may provide enhancement in restoring EPCs' population and improvement of vascular function. Here, for a better understanding of the molecular mechanisms underlying EPC impairment in atherosclerosis, we provide a comprehensive overview on EPC characteristics, phenotypes, and the signaling pathways underlying EPC impairment in atherosclerosis.

α1AMP-activated protein kinase mediates vascular protective effects of exercise

OBJECTIVE

We investigated whether AMP-activated protein kinase (AMPK) may be involved in the signaling processes leading to exercise-mediated vascular protection.

METHODS AND RESULTS

The effects of voluntary exercise on AMPK activity, endothelial NO synthase expression and phosphorylation, vascular reactive oxygen species formation, and cell senescence were tested in α1AMPK knockout and corresponding wild-type mice. Exercise significantly improved endothelial function, and increased plasma nitrite production in wild-type mice, associated with an activation of aortic AMPK assessed by its phosphorylation at threonine 172. In addition, regular physical activity resulted in an upregulation of endothelial NO synthase protein, serine 1177 endothelial NO synthase phosphorylation, and an increase of circulating Tie-2(+)Sca-1(+)Flk-1(+) myeloid progenitor cells. All these changes were absent after α1AMPK deletion. In addition, exercise increased the expression of important regulators of the antioxidative defense including heme oxygenase-1 and peroxisome proliferator-activated receptor γ coactivator 1α, decreased aortic reactive oxygen species levels, and prevented endothelial cell senescence in an α1AMPK-dependent manner.

CONCLUSIONS

Intact α1AMPK signaling is required for the signaling events leading to the manifestation of vascular protective effects during exercise. Pharmacological AMPK activation might be a novel approach in the near future to simulate the beneficial vascular effects of physical activity.

Cotreatment with darbepoetin and granulocyte colony-stimulating factor is efficient to recruit proangiogenic cell populations in patients with acute myocardial infarction

To determine whether newer combination cytokine treatment with granulocyte colony-stimulating factor (G-CSF) and darbepoetin can improve efficacy of stem cell therapy, we evaluated safety and peripheral blood stem/progenitor cell (PBSC) mobilizing effects of combination cytokine in comparison with G-CSF alone in patients with acute myocardial infarction (AMI). We randomized 60 patients with AMI into two groups under 2:1 ratio; combination treatment with darbepoetin and G-CSF (n = 41: Combicytokine group) and the G-CSF alone (n = 19: G-CSF group). After coronary angioplasty, G-CSF was treated for 3 days with dose of 10 μg/kg/day in both groups. Only in the combicytokine group, additional single intravenous injection of 4.5 μg/kg of darbepoetin was administrated immediate after coronary angioplasty. Combination cytokine treatment was well tolerated as was G-CSF alone. PBSCs were obtained by apheresis for intracoronary infusion after completion of cytokine treatment and were analyzed by flow cytometry. The purity of proangiogenic cells was higher in combination cytokine group than the G-CSF group. Specifically, proportion of CD34(+)/KDR(+) endothelial progenitor cells, CD3(+)/CD31(+) angiogenic T cells and Tie2(+)/CXCR4(+) cells in apheresis products were higher in the combicytokine group. These meant that the combicytokine treatment recruited PBSCs in higher purity and fewer unwanted inflammatory cells than G-CSF alone in apheresis products. Combination treatment with darbepoetin and G-CSF is safe and more efficient to mobilize and recruit proangiogenic cells than G-CSF alone in patients with AMI. (

TRIAL REGISTRATION

www.ClinicalTrials. gov identifier: NCT00501917).

The cardioprotective effects of parathyroid hormone are independent of endogenous granulocyte-colony stimulating factor release

AIMS

Parathyroid hormone (PTH) administration after myocardial infarction (MI) is known to attenuate ischaemic cardiomyopathy. This effect mainly resulted from an increase in mobilization and homing of CD34+/CD45+ cells into the ischaemic myocardium. PTH-related stem cell mobilization was shown to be related to endogenous granulocyte-colony stimulating factor (G-CSF) release. The aim of our study is to determine the role of G-CSF on the cardioprotective effects of PTH.

METHODS AND RESULTS

G-CSF +/+ (C57BL/6) and G-CSF -/- mice were treated with PTH for 6 days after inducing a MI. The myocardial homing factor stromal cell-derived factor-1 (SDF-1) was analysed on day 2 with enzyme-linked immunosorbent assay. Stem cell populations in peripheral blood and hearts were examined by FACS on days 6 and 2, respectively. Cardiac function and immunohistochemistry were investigated on day 6 and day 30. PTH treatment resulted in a significant increase in CD45+/CD34+ cells in peripheral blood in G-CSF +/+ but not in G-CSF -/- mice. However, a significant increase in SDF-1 and enhanced migration of CD45+/CD34+ cells into the ischaemic myocardium was revealed after PTH administration in both G-CSF +/+ and G-CSF -/- mice. Enhanced stem cell homing was associated with improved cardiac function and post-MI survival after PTH treatment. Furthermore, infarct size, wall thickness, and neovascularization showed a significant improvement in both groups 30 days after MI.

CONCLUSION

The cardioprotective effects of PTH were shown to be independent of endogenous G-CSF release and therefore from stem cell mobilization. This puts more emphasis on the role of stem cell homing into ischaemic myocardium.

Interleukin-10 deficiency impairs bone marrow-derived endothelial progenitor cell survival and function in ischemic myocardium

RATIONALE

Endothelial progenitor cell (EPC) survival and function in the injured myocardium is adversely influenced by hostile microenvironment such as ischemia, hypoxia, and inflammatory response, thereby compromising full benefits of EPC-mediated myocardial repair.

OBJECTIVE

We hypothesized that interleukin-10 (IL-10) modulates EPC biology leading to enhanced survival and function after transplantation in the ischemic myocardium.

METHODS AND RESULTS

Myocardial infarction (MI)-induced mobilization of bone marrow EPC (Sca-1+Flk1+cells) into the circulation was significantly impaired in IL-10 knockout (KO) mice. Bone marrow transplantation to replace IL-10 KO marrow with wild-type (WT) marrow attenuated these effects. Impaired mobilization was associated with lower stromal cell-derived factor (SDF)-1 expression levels in the myocardium of KO mice. Interestingly, SDF-1 administration reversed mobilization defect in KO mice. In vitro, hypoxia-mediated increases in CXCR4 expression and cell survival were lower in IL-10-deficient EPCs. Furthermore, SDF-1-induced migration of WT EPCs was inhibited by AMD3100, an inhibitor of CXCR4. To further study the effect of IL-10 on in vivo EPC survival and engraftment into vascular structures, GFP-labeled EPC were injected intramyocardially after induction of MI, and the mice were treated with either saline or recombinant IL-10. The IL-10-treated group showed increased retention of transplanted EPCs in the myocardium and was associated with significantly reduced EPC apoptosis after MI. Interestingly, increased EPC retention and their association with the vascular structures was observed in IL-10-treated mice. Increased EPC survival and angiogenesis in the myocardium of IL-10-treated mice corroborated with improved left ventricular function, reduced infarct size, and fibrosis in the myocardium. In vitro, IL-10-induced increase in VEGF expression in WT EPC was abrogated by STAT3 inhibitor, suggesting IL-10 signals through STAT3 activation.

CONCLUSIONS

Taken together, our studies demonstrate that MI-induced EPC mobilization was impaired in IL-10 KO mice and that IL-10 increases EPC survival and function possibly through activation of STAT3/VEGF signaling cascades, leading to attenuation of MI-induced left ventricular dysfunction and remodeling.

Hematopoietic cytokines for cardiac repair: mobilization of bone marrow cells and beyond

Hematopoietic cytokines, traditionally known to influence cellular proliferation, differentiation, maturation, and lineage commitment in the bone marrow, include granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor, stem cell factor, Flt-3 ligand, and erythropoietin among others. Emerging evidence suggests that these cytokines also exert multifarious biological effects on diverse nonhematopoietic organs and tissues. Although the precise mechanisms remain unclear, numerous studies in animal models of myocardial infarction (MI) and heart failure indicate that hematopoietic cytokines confer potent cardiovascular benefits, possibly through mobilization and subsequent homing of bone marrow-derived cells into the infarcted heart with consequent induction of myocardial repair involving multifarious mechanisms. In addition, these cytokines are also known to exert direct cytoprotective effects. However, results from small-scale clinical trials of G-CSF therapy as a single agent after acute MI have been discordant and largely disappointing. It is likely that cardiac repair following cytokine therapy depends on a number of known and unknown variables, and further experimental and clinical studies are certainly warranted to accurately determine the true therapeutic potential of such therapy. In this review, we discuss the biological features of several key hematopoietic cytokines and present the basic and clinical evidence pertaining to cardiac repair with hematopoietic cytokine therapy.

Myocardial blood flow and infarct size after CD133+ cell injection in large myocardial infarction with good recanalization and poor reperfusion: results from a randomized controlled trial

OBJECTIVE

Large acute ST-elevation myocardial infarction (STEMI) sometimes leaves extensive ischemic damage despite timely and successful primary angioplasty. This clinical picture of good recanalization with incomplete reperfusion represents a good model to assess the reparative potential of locally administered cell therapy. Thus, we conducted a randomized controlled trial aimed at evaluating the effect of intracoronary administration of CD133 stem cells on myocardial blood flow and function in this setting.

METHODS

Fifteen patients with large anterior STEMI, myocardial blush grade 0-1 and more than 50% ST-elevation recovery after optimal coronary recanalization (TIMI 3 flow) with stenting were randomly assigned to receive CD133 cells from either bone marrow (group A) or peripheral blood (group B), or to stay on drug therapy alone (group C). The cells were intracoronary injected within 10-14 days of STEMI. Infarct-related myocardial blood flow (MBF) was evaluated by NH positron emission tomography 2-5 days before cell administration and after 1 year.

RESULTS

MBF increased in the infarct area from 0.419 (0.390-0.623) to 0.544 (0.371-0.729) ml/min per g in group A, decreased from 0.547 (0.505-0.683) to 0.295 (0.237-0.472) ml/min per g in group B and only slightly changed from 0.554 (0.413-0.662) to 0.491 (0.453-0.717) ml/min per g in group C (A vs. C: P = 0.023; B vs. C: P = 0.066). Left ventricular volume tended to increase more in groups B and C than in group A, ejection fraction and wall motion score index remained stable in the three groups.

CONCLUSION

These findings support the hypothesis that intracoronary administration of bone marrow-derived, but not peripheral blood-derived CD133 cells 10-14 days after STEMI may improve long-term perfusion.

17β-Estradiol enhances the recruitment of bone marrow-derived endothelial progenitor cells into infarcted myocardium by inducing CXCR4 expression

BACKGROUND

17β-Estradiol (E2) has been thought to produce cardioprotective effects by mediating bone marrow-derived endothelial progenitor cells (EPC) for cardiac repair in the setting of acute myocardial infarction (AMI). However, the underlying mechanism of action of E2 on EPC remains unclear. CXCR4 is a critical modulator in homing of EPC. Accordingly, we hypothesized that E2 exerts beneficial effects through enhancing EPC homing to infarcted myocardium via mediating CXCR4 pathway.

METHODS AND RESULTS

Migratory capacity and CXCR4 expression of EPC from ovariectomized BALB/C mice were detected after being incubated with various E2 concentrations for various incubation times. For in vivo studies, EPC were labeled with superparamagnetic ion oxide (SPIO) for tracing, and ovariectomized mice were grouped (n=11) after inducing AMI to receive saline without cells or with 3 × 10(6) non-preconditioned EPC, 100 nmol/L E2 preconditioned EPC, CXCR4 inhibitor AMD3100 (5 μg/mL) preconditioned EPC, or EPC pretreated with E2 plus AMD3100. The number of homing EPC in infarcted myocardium and left ventricular (LV) function, dimensions and fibrosis were measured. In vitro data showed that E2 increased migratory activity and functional CXCR4 expression of EPC. However, these effects were completely blocked by AMD3100. In vivo data in E2 group displayed a greater number of homing EPC, decreased fibrosis of LV, and significant improvement in cardiac function. Nevertheless, effects of E2 preconditioning were abrogated by AMD3100.

CONCLUSIONS

We conclude that E2 enhances the recruitment of EPC into infarcted myocardium by up-regulating functional CXCR4 expression, resulting in improving recovery after myocardial infarction.

Cd34+ progenitor cells likely are involved in the good functional recovery after intracerebral hemorrhage in humans

Bone marrow-derived stem/progenitor cells (CD34(+) progenitor cells) were demonstrated to play an important role in the regeneration of damaged brain tissue. Our aim was to study the influence of CD34(+) progenitor cells in the outcome of intracerebral hemorrhage (ICH). Thirty-two patients with primary ICH (64.0% male, mean age 67.1 ± 10.8 years) were prospectively included in the study within 12 hr of symptom onset. The main outcome variable was good functional outcome at 3 months (modified Rankin scale ≤ 2). Circulating CD34(+) progenitor cell levels were measured by flow cytometry at admission and at 7 ± 1 days, and serum levels of growth factors (determined by ELISA) were measured at admission and at 24 and 72 hr. Circulating levels of CD34(+) progenitor cells at day 7 were independently associated with good functional outcome at 3 months (OR 1.17, CI95% 1.06-1.39, P = 0.012). On the other hand, CD34(+) progenitor cells at day 7 were negatively correlated with residual cavity volume at 3 months (r = -0.607, P = 0.001). Serum levels of vascular endothelial growth factor (r = 0.386), angiopoietin 1 (r = 0.518), brain-derived neurotrophic factor (r = 0.484), and stromal cell-derived factor-1α (r = 0.837) but not granulocyte-colony stimulating factor (r = -0.038) at 72 hr showed a strong correlation with CD34(+) progenitor cell levels at day 7. These findings suggest that CD34(+) progenitor cells may participate in the functional recovery of ICH patients.

Functional effects of adiponectin on endothelial progenitor cells

Adiponectin is an adipokine whose plasma levels are inversely correlated to metabolic syndrome components. Adiponectin protects against atherosclerosis and decreases risks in myocardial infarction. Endothelial progenitor cells (EPCs) are a heterogeneous population of circulating cells involved in vascular repair and neovascularization. EPCs number is reduced in patients with cardiovascular disease. We hypothesize that the positive effects of adiponectin against atherosclerosis are explained in part by its interactions with EPCs. Cells were obtained from healthy volunteers' blood by mononuclear cell isolation and plating on collagen-coated dishes. Three sub-populations of EPCs were identified and characterized using flow cytometry. EPCs' expression of adiponectin receptors, AdipoR1, and AdipoR2 was evaluated by quantitative PCR. The effects of recombinant adiponectin on EPCs' susceptibility to apoptosis were assessed. Finally, expression of neutrophil elastase by EPCs and activity of this enzyme on adiponectin processing were assessed. Quantitative PCR analysis of EPCs mRNAs showed that AdipoR1 mRNA is expressed at higher levels than AdipoR2. Expression of AdipoR1 protein was confirmed by western blot. Adiponectin significantly increased survival of two sub-populations of EPCs in conditions of serum deprivation. Such effect could not be demonstrated in the third EPCs sub-population. We also demonstrated that EPCs, particularly one sub-population, express neutrophil elastase. Neutrophil elastase activity was confirmed in EPCs' conditioned media. Adiponectin protects some EPCs sub-populations against apoptosis and therefore could modulate EPCs ability to induce repair of vascular damage. Neutrophil elastase activity of EPCs could locally modulate adiponectin activity by its involvement in the generation of the globular form of adiponectin.

Downregulation of the CXC chemokine receptor 4/stromal cell-derived factor 1 pathway enhances myocardial neovascularization, cardiomyocyte survival, and functional recovery after myocardial infarction

OBJECTIVES

Although adequate numbers of hematopoietic progenitor cells reside in the human bone marrow, the extent of endogenous neovascularization after myocardial infarction remains insufficient. The aim of this study was to identify the role of the CXC chemokine receptor 4/stromal cell-derived factor 1 axis in the mobilization and homing of hematopoietic progenitor cells in the ischemic heart.

METHODS

Human bone marrow-derived hematopoietic progenitor cells or saline were injected systemically into athymic nude rats 48 hours after myocardial infarction. Myocardial and bone marrow expression of stromal cell-derived factor 1 and chemotaxis of hematopoietic progenitor cells were measured in vitro in the presence or absence of stromal cell-derived factor 1. The role of the CXC chemokine receptor 4/stromal cell-derived factor 1 axis was investigated by means of antibody blockade or systemic administration of granulocyte colony-stimulating factor. Morphologic analysis included measurement of the infarct area, capillary density, and apoptosis, whereas left ventricular function was measured by means of echocardiographic analysis.

RESULTS

Expression of postinfarct stromal cell-derived factor 1 was increased by 67% in the bone marrow and decreased by 43% in myocardium. Disruption of bone marrow stromal cell-derived factor 1/CXC chemokine receptor 4 interactions by antibody blockade resulted in a redirection of human hematopoietic progenitor cells from the bone marrow to the ischemic heart and augmented neovascularization and cardiomyocyte survival. Similarly, systemic administration of granulocyte colony-stimulating factor to block CXC chemokine receptor 4/stromal cell-derived factor 1 interaction resulted in increased mobilization and homing of hematopoietic progenitor cells to the ischemic heart, which translated to augmented myocardial neovascularization, prevention of apoptosis, and improved cardiac function.

CONCLUSIONS

Bone marrow stromal cell-derived factor 1 upregulation after myocardial ischemia prevents mobilization of endogenous hematopoietic progenitor cells. We provide evidence that disruption of stromal cell-derived factor 1/CXC chemokine receptor 4 interactions allows redirection of hematopoietic progenitor cells to ischemic myocardium and enhances recovery of left ventricular function.

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

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

A multicenter, prospective, randomized, controlled trial evaluating the safety and efficacy of intracoronary cell infusion mobilized with granulocyte colony-stimulating factor and darbepoetin after acute myocardial infarction: study design and rationale of the 'MAGIC cell-5-combination cytokine trial'

Background

Bone marrow derived stem/progenitor cell transplantation after acute myocardial infarction is safe and effective for improving left ventricular systolic function. However, the improvement of left ventricular systolic function is limited. This study will evaluate novel stem/progenitor cell therapy with combination cytokine treatment of the long-acting erythropoietin analogue, darbepoetin, and granulocyte colony-stimulating factor (G-CSF) in patients with acute myocardial infarction.

Methods

The 'MAGIC Cell-5-Combination Cytokine Trial' is a multicenter, prospective, randomized, 3-arm, controlled trial with blind evaluation of the endpoints. A total of 116 patients will randomly receive one of the following three treatments: an intravenous darbepoetin infusion and intracoronary infusion of peripheral blood stem cells mobilized with G-CSF (n = 58), an intracoronary infusion of peripheral blood stem cells mobilized with G-CSF alone (n = 29), or conventional therapy (n = 29) at phase I. Patients with left ventricular ejection fraction < 45% at 6 months, in the patients who received stem cell therapy at phase I, will receive repeated cell therapy at phase II. The objectives of this study are to evaluate the safety and efficacy of combination cytokine therapy with erythropoietin and G-CSF (phase I) and repeated progenitor/stem cell treatment (phase II).

Discussion

This is the first study to evaluate the safety and efficacy of combination cytokine based progenitor/stem cell treatment.

Trial registration

http://www.ClinicalTrials.gov identifier: NCT00501917.

Evaluation of the efficacy of granulocyte colony-stimulating factor for the treatment of experimental myocardial destruction in mice

We studied the effects of recombinant granulocytic CSF on heart remodeling in BALB/c mice after cryodestruction. Administration of granulocytic CSF was started 1 day after cryodestruction (subcutaneously, 10 μg/kg/day, for 4 days). As early as after the first injection, leukocytosis in the peripheral blood started to develop, leukocyte count peaked on days 4-6 and returned to normal on day 14. Treatment with granulocytic CSF significantly increased the content of progenitor cells in the bone marrow and led to rapid development of the inflammatory reaction and myocardium infiltration with mononuclear cells. Injections of granulocytic CSF did not reduce scar area, but provided significantly less pronounced heart hypertrophy, which attests to its better functional properties. By day 30 after cryodestruction, control animals and animals receiving granulocytic CSF exhibited similar morphological picture at the site of damage. Thus, our regimen of granulocytic CSF administration produced a mobilizing effect on bone marrow progenitor cells and postinfarction heart remodeling. Direct effects of granulocytic CSF on the heart have to be established for its use in the treatment of myocardial infarction.

The role of PET with 13N-ammonia and 18F-FDG in the assessment of myocardial perfusion and metabolism in patients with recent AMI and intracoronary stem cell injection

Over the last decade, the effects of stem cell therapy on cardiac repair after acute myocardial infarction (AMI) have been investigated with different imaging techniques. We evaluated a new imaging approach using (13)N-ammonia and (18)F-FDG PET for a combined analysis of cardiac perfusion, metabolism, and function in patients treated with intracoronary injection of endothelial progenitors or with conventional therapy for AMI.

METHODS

A total of 15 patients were randomly assigned to 3 groups based on different treatments (group A: bone marrow-derived stem cells; group B: peripheral blood-derived stem cells; group C: standard therapy alone). The number of scarred and viable segments, along with the infarct size and the extent of the viable area, were determined on a 9-segment (13)N-ammonia/(18)F-FDG PET polar map. Myocardial blood flow (MBF) was calculated for each segment on the ammonia polar map, whereas a global evaluation of left ventricular function was obtained by estimating left ventricular ejection fraction (LVEF) and end-diastolic volume, both derived from electrocardiography-gated (18)F-FDG images. Both intragroup and intergroup comparative analyses of the mean values of each parameter were performed at baseline and 3, 6, and 12 mo after AMI. During follow-up, major cardiac events were also registered.

RESULTS

A significant decrease (P < 0.05) in the number of scarred segments and infarct size was observed in group A, along with an increase in MBF (P < 0.05) and a mild improvement in cardiac function. Lack of infarct size shrinkage in group B was associated with a marked impairment of MBF (P = 0.01) and cardiac dysfunction. Ambiguous changes in infarct size, MBF, and LVEF were found in group C. No differences in number of viable segments or in extent of viable area were found among the groups. At clinical follow-up, no major cardiac events occurred in group A patients, whereas 2 patients of group B experienced in-stent occlusion and one patient of group C received a transplant for heart failure.

CONCLUSION

Our data suggest that a single nuclear imaging technique accurately analyzes changes in myocardial perfusion and metabolism occurring after stem cell transplantation.

Endothelial and cardiac progenitors: boosting, conditioning and (re)programming for cardiovascular repair

Preclinical studies performed in cell culture and animal systems have shown the outstanding ability of stem cells to repair ischemic heart and lower limbs by promoting the formation of new blood vessels and new myocytes. In contrast, clinical studies of stem cell administration in patients with myocardial ischemia have revealed only modest, although promising, results. Basic investigations have shown the feasibility of adult cells reprogramming into pluripotent cells by defined factors, thus opening the way to the devise of protocols to ex vivo derive virtually unexhausted cellular pools. In contrast, cellular and molecular studies have indicated that risk factors limit adult-derived stem cell survival, proliferation and engraftment in ischemic tissues. The use of fully reprogrammed cells raises safety concerns; therefore, adult cells remain a primary option for clinicians interested in therapeutic cardiovascular repair. Pharmacologic approaches have been devised to restore the cardiovascular repair ability of failing progenitors from patients at risk. In the present contribution, the most advanced pharmacologic approaches to (re)program, boost, and condition endothelial and cardiac progenitor cells to enhance cardiovascular regeneration are discussed.

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.

Association of growth factors with arterial recanalization and clinical outcome in patients with ischemic stroke treated with tPA

SUMMARY BACKGROUND

Growth factors (GF) such as vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and granulocyte-colony stimulating factor (G-CSF) have been associated with greater efficacy of tissue plasminogen activator (tPA) in experimental studies.

OBJECTIVES

To study the association of these GF with arterial recanalization and clinical outcome in patients with acute ischemic stroke treated with tPA.

METHODS

We prospectively studied 79 patients with ischemic stroke attributable to MCA occlusion treated with i.v. tPA within the first 3 h from onset of symptoms. Continuous transcranial color-coded sonography (TCCS) was performed during the first 2 h after tPA bolus to assess early MCA recanalization. Hemorrhagic transformation (HT) was classified according to ECASS II definitions. Good functional outcome was defined as a Rankin scale score of 0-2 at 90 days. GF levels were determined by ELISA.

RESULTS

Mean serum levels of VEGF, G-CSF and Ang-1 at baseline were significantly higher in patients with early MCA recanalization (n = 30) (all P < 0.0001). In the multivariate analysis, serum levels of VEGF (OR, 1.03), G-CSF (OR, 1.02) and Ang-1 (OR, 1.07) were independently associated with early MCA recanalization (all P < 0.0001). On the other hand, patients with parenchymal hematoma (PH) (n = 20) showed higher levels of Ang-1 (P < 0.0001). Ang-1 (OR, 1.12; P < 0.0001) was independently associated with PH, whereas patients with good outcome (n = 38) had higher levels of G-CSF (P < 0.0001). G-CSF was independently associated with good outcome (OR, 1.12; P = 0.036).

CONCLUSIONS

These findings suggest that GF may enhance arterial recanalization in patients with ischemic stroke treated with t-PA, although they might increase the HT.

Granulocyte colony-stimulating factor (G-CSF) depresses angiogenesis in vivo and in vitro: implications for sourcing cells for vascular regeneration therapy

SUMMARY BACKGROUND

The most common source of hematopoietic progenitor cells (HPCs) for hematopoietic reconstitution comprises granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood stem cells (PBSCs). It has been proposed that endothelial progenitor cells (EPCs) share precursors with HPCs, and that EPC release may accompany HPC mobilization to the circulation following G-CSF administration.

OBJECTIVE

To investigate EPC activity following HPC mobilization, and the direct effects of exogenous G-CSF administration on human umbilical vein endothelial cells (HUVECs) and endothelial outgrowth cells (EOCs), using in vitro and in vivo correlates of angiogenesis.

PATIENTS/METHODS

Heparinized venous blood samples were collected from healthy volunteers and from cord blood at parturition. G-CSF-mobilized samples were collected before administration, at apheresis harvest, and at follow-up. PBSCs were phenotyped by flow cytometry, and cultured in standard colony-forming unit (CFU)-EPC and EOC assays. The effect of exogenous G-CSF was investigated by addition of it to HUVECs and EOCs in standard tubule formation and aortic ring assays, and in an in vivo sponge implantation model.

RESULTS

Our data show that G-CSF mobilization of PBSCs produces a profound, reversible depression of circulating CFU-EPCs. Furthermore, G-CSF administration did not mobilize CD34+CD133- cells, which include precursors of EOCs. No EOCs were cultured from any mobilized PBSCs studied. Exogenous G-CSF inhibited CFU-EPC generation, HUVEC and EOC tubule formation, microvessel outgrowth, and implanted sponge vascularization in mice.

CONCLUSIONS

G-CSF administration depresses both endothelial cell angiogenesis and monocyte proangiogenic activity, and we suggest that any angiogenic benefit observed following implantation of cells mobilized by G-CSF may come only from a paracrine effect from HPCs.

Regulation of bone marrow-derived vascular progenitor cell mobilization and maintenance

Cell therapy is a promising option for treating ischemic diseases and heart failure. Bone marrow-derived vasculogenic cells, including progenitor cells and proangiogenic cells, have been shown to augment the functional recovery after ischemia. However, cardiovascular diseases affect the functional activity of the endogenous progenitor cell pools. The local microenvironment, also termed the stem cell niche, provides essential cues that maintain stem and progenitor cell functions and direct cell fate decisions in the bone marrow. A disturbed niche might lead to cell dysfunction (eg, by exhaustion). In addition, the niche controls mobilization of the cells into the circulation. This review will discuss the impact of cardiovascular disease on stem cell niches and summarize strategies targeting the niche for mobilization of vasculogenic cells.

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.

The promise of cell-based therapies for diabetic complications: challenges and solutions

The discovery of endothelial progenitor cells (EPCs) in human peripheral blood advanced the field of cell-based therapeutics for many pathological conditions. Despite the lack of agreement about the existence and characteristics of EPCs, autologous EPC populations represent a novel treatment option for complications requiring therapeutic revascularization and vascular repair. Patients with diabetic complications represent a population of patients that may benefit from cellular therapy yet their broadly dysfunctional cells may limit the feasibility of this approach. Diabetic EPCs have decreased migratory prowess and reduced proliferative capacity and an altered cytokine/growth factor secretory profile that can accelerate deleterious repair mechanisms rather than support proper vascular repair. Furthermore, the diabetic environment poses additional challenges for the autologous transplantation of cells. The present review is focused on correcting diabetic EPC dysfunction and the challenges involved in the application of cell-based therapies for treatment of diabetic vascular complications. In addition, ex vivo and in vivo functional manipulation(s) of EPCs to overcome these hurdles are discussed.

Granulocyte-colony stimulating factor treatment of chronic myocardial infarction

PURPOSE

The aim of this study was to investigate the impact of granulocyte-colony stimulating factor (G-CSF) administration on cardiac function of rats with chronic myocardial infarction through two different protocols: high dose short term and low dose long term protocols.

METHODS

Wistar rats were submitted to MI surgery and after 4 weeks they received recombinant human G-CSF (Filgrastim) or vehicle subcutaneously. We tested the classical protocol (50 microg/kg/day during 7 days) and the long term low dose treatment (four cycles of 5 days of 10 microg/kg/day). Cardiac performance was evaluated before, 4 and 6 weeks after G-CSF injections by electro- and echocardiography, hemodynamic and treadmill exercise test.

RESULTS

All infarcted groups exhibited impaired function compared to sham operated animals. Moreover, all cardiac functional parameter were not different between G-CSF and Vehicle group at resting conditions as well as after treadmill exercise stress test, despite intense white blood cell mobilization in both protocols at all time points. Hypertrophy was not different and infarct size was similar in histological analysis

CONCLUSIONS

These data clearly show that G-CSF treatment was unable to restore cardiac function impaired by myocardial infarction either with classical approach or long term low dose administration.

Comparison between Culture Conditions Improving Growth and Differentiation of Blood and Bone Marrow Cells Committed to the Endothelial Cell Lineage

The aim of this study was to compare different cell sources and culture conditions to obtain endothelial progenitor cells (EPCs) with predictable antigen pattern, proliferation potential and in vitro vasculogenesis. Pig mononuclear cells were isolated from blood (PBMCs) and bone marrow (BMMCs). Mesenchymal stem cells (MSCs) were also derived from pig bone marrow. Cells were cultured on fibronectin in the presence of a high concentration of VEGF and low IGF-1 and FGF-2 levels, or on gelatin with a lower amount of VEGF and higher IGF-1 and FGF-2 concentrations. Endothelial commitment was relieved in almost all PBMCs and BMMCs irrespective of the protocol used, whilst MSCs did not express a reliable pattern of EPC markers under these conditions. BMMCs were more prone to expand on gelatin and showed a better viability than PBMCs. Moreover, about 90% of the BMMCs pre-cultured on gelatin could adhere to a hyaluronan-based scaffold and proliferate on it up to 3 days. Pre-treatment of BMMCs on fibronectin generated well-shaped tubular structures on Matrigel, whilst BMMCs exposed to the gelatin culture condition were less prone to form vessel-like structures. MSCs formed rough tubule-like structures, irrespective of the differentiating condition used. In a relative short time, pig BMMCs could be expanded on gelatin better than PBMCs, in the presence of a low amount of VEGF. BMMCs could better specialize for capillary formation in the presence of fibronectin and an elevated concentration of VEGF, whilst pig MSCs anyway showed a limited capability to differentiate into the endothelial cell lineage.

Decreased in the number and function of circulation endothelial progenitor cells in patients with avascular necrosis of the femoral head

INTRODUCTION

Once non-traumatic avascular necrosis of the femoral head (ANFH) happened, vascular impairment and feeble collateral circulation are followed by poor outcomes. Circulating endothelial progenitor cells (EPCs) may substantially contribute to vascular homeostasis such as vascular repair and new blood vessel growth. We investigated whether abnormalities in EPCs levels and functions are present in ANFH patients.

METHODS

54 ANFH patients were enrolled, including steroid-induced (n=21), alcohol-induced (n=15) and idiopathic ANFH (n=18), and 30 healthy subjects as control (HC). The numbers of circulation EPCs were determined by fluorescence-activated cell-sorting (FACS) analysis. EPCs cultured from peripheral blood mononuclear cells on fibronectin to induce the expression of receptors for acetylated low-density lipoprotein and ulex-lectin. EPCs colony-forming units (CFUs) were observed from 54 patients and 30 healthy controls. Migratory capacity to chemo-attractants (vascular endothelial growth factor) cellular senescence levels and in vitro angiogenesis ability were assessed in age-matched subjects (n=10 per groups).

RESULTS

Mean numbers of circulating EPC were 1460+/-265 cells/ml in HC, 545+/-177 in ANFH, (P<0.001). Mean numbers of CFUs were 26.2+/-6.2 in HC, 19.6+/-7.7 in ANFH,(P<0.001). Although there were not significant differences in circulating EPC and CFUs among the steroid-induced, alcohol-induced or idiopathic three groups, all these risk factors contributed to the decreased circulating EPCs numbers and CFUs. In addition, EPCs from ANFH patients showed reduced migratory capacity and increased cellular senescence compared with EPCs from normal subjects, furthermore the ability of angiogenesis in vitro was also impaired.

CONCLUSION

Circulating endothelial progenitor cells (EPCs) numbers and functions are reduced in ANFH patients, suggesting that risk factors of ANFH may alter EPCs biology in angiogenesis and vascular repair.

Clinical application of stem cells in the cardiovascular system

Regenerative medicine encompasses "tissue engineering" - the in vitro fabrication of tissues and/or organs using scaffold material and viable cells - and "cell therapy" - the transplantation or manipulation of cells in diseased tissue in vivo. In the cardiovascular system, tissue engineering strategies are being pursued for the development of viable replacement blood vessels, heart valves, patch material, cardiac pacemakers and contractile myocardium. Anecdotal clinical applications of such vessels, valves and patches have been described, but information on systematic studies of the performance of such implants is not available, yet. Cell therapy for cardiovascular regeneration, however, has been performed in large series of patients, and numerous clinical studies have produced sometimes conflicting results. The purpose of this chapter is to summarize the clinical experience with cell therapy for diseases of the cardiovascular system, and to analyse possible factors that may influence its outcome.

High serum levels of growth factors are associated with good outcome in intracerebral hemorrhage

In experimental models, growth factors (GFs) such as vascular endothelial growth factor (VEGF), Angiopoietin 1 (Ang-1), or granulocyte-colony stimulating factor (G-CSF) mediate brain recovery after intracerebral hemorrhage (ICH). Our aim was to study the association between serum levels of GF and clinical outcome in patients with ICH. A total of 95 patients with primary ICH (male, 66.3%; mean age, 67.8+/-9.8 years) were prospectively included in the study within 12 h from symptoms onset. The main outcome variable was good functional outcome at 3 months (modified Rankin scale < or =2). Median serum levels of GF at 72 h from stroke onset were significantly higher in patients with good outcome (n=39) compared with those with poor outcome (all P<0.0001). Serum levels of VEGF > or =330 pg/mL, G-CSF > or =413 pg/mL, and Ang-1 > or =35 ng/mL at 72 h were independently associated with good functional outcome (odds ratio (OR), 11.2; 95% confidence interval (CI): 2.9 to 43.0; OR, 19.6; 95% CI: 3.9 to 97.9; and OR, 14.7; 95% CI: 3.6 to 60.0, respectively), neurologic improvement (all P<0.0001) and reduced residual cavity at 3 months (all P<0.01). These results illustrate that high serum levels of GF are associated with good functional outcome and reduced lesion volume in ICH.

Priming with angiopoietin-1 augments the vasculogenic potential of the peripheral blood stem cells mobilized with granulocyte colony-stimulating factor through a novel Tie2/Ets-1 pathway

BACKGROUND

The low engraftment rate of stem/progenitor cells infused via the intracoronary route to the ischemic myocardium is one of the most important factors limiting the efficacy of cell therapy. We investigated the concept of priming peripheral blood stem cells enriched by granulocyte colony-stimulating factor mobilization and apheresis ((mob)PBSCs) with angiopoietin-1 (Ang1), to enhance the engraftment into the ischemic tissue and neovasculogenic potential.

METHODS AND RESULTS

The expression of Tie2, the Ang1 receptor, was significantly higher in (mob)PBSCs than naïve peripheral blood mononuclear cells (19.2+/-3.0% versus 1.2+/-0.8% versus 1.2+/-0.2%; P<0.001 for (mob)PBSCs from acute myocardial infarction (AMI) patients with granulocyte colony-stimulating factor treatment for 3 days versus peripheral blood mononuclear cells from AMI patients versus peripheral blood mononuclear cells from stable angina patients). After 4 hours of cartilage oligomeric matrix protein (COMP)-Ang1 stimulation, (mob)PBSCs committed to the endothelial lineage with the induction of CD31 and VE-cadherin expression, mediated by Tie2/Ets-1 pathway. Priming of (mob)PBSCs with COMP-Ang1 induced the expression of alpha4beta1 and alpha5beta1 integrins, which are also Ets-1 downstream molecules, leading to enhanced adhesion to endothelial cells or fibronectin. In a rabbit ear ischemia/reperfusion model, priming of (mob)PBSCs with COMP-Ang1 improved first-pass engraftment to the distal vascular bed after intraarterial delivery. In a murine ischemic hind-limb model, intravascular delivery of primed (mob)PBSCs enhanced both engraftment and neovascularization.

CONCLUSIONS

The short-term priming with COMP-Ang1 may be a feasible and promising option to activate (mob)PBSCs by enhancing differentiation and adhesiveness and to improve the efficacy of cell therapy for ischemic diseases.

Effect of granulocyte colony-stimulating factor on the incidence of threshold retinopathy of prematurity

PURPOSE

To study the effect of granulocyte colony-stimulating factor (GCSF) on the incidence of threshold retinopathy of prematurity (ROP).

METHODS

A retrospective chart review of all neonates who received GCSF at our neonatal intensive care unit over a period ranging from January 2003 to September 2007 was performed. Of the 213 patients identified, 50 patients with birth weight <1,500 g and gestational age <32 weeks were included in this study. The incidence of threshold ROP in this subset was compared to a control group (n = 161) obtained from Vermont Oxford Network ROP database over the same time period. The two data sets were cross-referenced to exclude any patient receiving GCSF from the control data.

RESULTS

The average birth weight was 913 g in GCSF patients and 847 g in controls. The average dose of GCSF was 10.4 microg (range, 1.2-21.6 microg). The average age at administration of GCSF was 12 days after birth (range, 0-34 days). Out of 50 patients in the GCSF group, 5 (10%) required laser treatment, whereas in the contol group, 30 (18.6 %) required laser treatment; this difference was not statistically significant.

CONCLUSIONS

There was a suggestion of a decreased incidence of threshold ROP, leading to reduced need for laser treatment, in patients who received GCSF, but the observed differences were not statistically significant. The authors anticipate that these findings will lead to further study of the upstream regulators of neovascularization.