Effects of transendocardial CD34+ cell transplantation in patients with ischemic cardiomyopathy

The Long Telling Story of "Endothelial Progenitor Cells": Where Are We at Now?

Endothelial progenitor cells (EPCs): The name embodies years of research and clinical expectations, but where are we now? Do these cells really represent the El Dorado of regenerative medicine? Here, past and recent literature about this eclectic, still unknown and therefore fascinating cell population will be discussed. This review will take the reader through a temporal journey that, from the first discovery, will pass through years of research devoted to attempts at their definition and understanding their biology in health and disease, ending with the most recent evidence about their pathobiological role in cardiovascular disease and their recent applications in regenerative medicine.

Therapeutic Angiogenesis Using Autologous CD34-Positive Cells for Vascular Diseases

CD34 is a cell surface marker, which is expressed in various somatic stem/progenitor cells such as bone marrow (BM)-derived hematopoietic stem cells and endothelial progenitor cells (EPCs), skeletal muscle satellite cells, epithelial hair follicle stem cells, and adipose tissue mesenchymal stem cells. CD34+ cells in BM and peripheral blood are known as a rich source of EPCs. Thus, vascular regeneration therapy using granulocyte colony stimulating factor (G-CSF) mobilized- or BM CD34+ cells has been carried out in patients with various vascular diseases such as chronic severe lower limb ischemia, acute myocardial infarction, refractory angina, ischemic cardiomyopathy, and dilated cardiomyopathy as well as ischemic stroke. Pilot and randomized clinical trials demonstrated the safety, feasibility, and effectiveness of the CD34+ cell therapy in peripheral arterial, cardiovascular, and cerebrovascular diseases. This review provides an overview of the preclinical and clinical reports of CD34+ cell therapy for vascular regeneration.

Cell administration routes for heart failure: a comparative re-evaluation of the REGENERATE-DCM and REGENERATE-IHD trials

Aims: Given the logistical issues surrounding intramyocardial cell delivery, we sought to address the efficacy of the simpler, more accessible intracoronary route by re-evaluating REGENERATE-DCM and REGENERATE-IHD (autologous cell therapy trials for heart failure; n = 150). Methods: A retrospective statistical analysis was performed on the trials' combined data. The following end points were evaluated: left ventricular ejection fraction (LVEF), N-terminal pro brain natriuretic peptide concentration (NT-proBNP), New York Heart Association class (NYHA) and quality of life. Results: This demonstrated a new efficacy signal for intracoronary delivery, with significant benefits to: LVEF (3.7%; p = 0.01), NT-proBNP (median -76 pg/ml; p = 0.04), NYHA class (48% patients; p = 0.01) and quality of life (12 ± 19; p = 0.006). The improvements in LVEF, NYHA and quality of life scores remained significant compared to the control group. Conclusion: The efficacy and logistical simplicity of intracoronary delivery should be taken into consideration for future trials.

Impact of procedural variability and study design quality on the efficacy of cell-based therapies for heart failure - a meta-analysis

Background

Cell-based therapy has long been considered a promising strategy for the treatment of heart failure (HF). However, its effectiveness in the clinical setting is now doubted. Because previous meta-analyses provided conflicting results, we sought to review all available data focusing on cell type and trial design.

Methods and findings

The electronic databases PubMed, Cochrane library, ClinicalTrials.gov, and EudraCT were searched for randomized controlled trials (RCTs) utilizing cell therapy for HF patients from January 1, 2000 to December 31, 2020. Forty-three RCTs with 2855 participants were identified. The quality of the reported study design was assessed by evaluating the risk-of-bias (ROB). Primary outcomes were defined as mortality rate and left ventricular ejection fraction (LVEF) change from baseline. Secondary outcomes included both heart function data and clinical symptoms/events. Between-study heterogeneity was assessed using the I2 index. Subgroup analysis was performed based on HF type, cell source, cell origin, cell type, cell processing, type of surgical intervention, cell delivery routes, cell dose, and follow-up duration. Only 10 of the 43 studies had a low ROB for all method- and outcome parameters. A higher ROB was associated with a greater increase in LVEF. Overall, there was no impact on mortality for up to 12 months follow-up, and a clinically irrelevant average LVEF increase by LVEF (2.4%, 95% CI = 0.75−4.05, p = 0.004). Freshly isolated, primary cells tended to produce better outcomes than cultured cell products, but there was no clear impact of the cell source tissue, bone marrow cell phenotype or cell chricdose (raw or normalized for CD34+ cells). A meaningful increase in LVEF was only observed when cell therapy was combined with myocardial revascularization.

Conclusions

The published results suggest a small increase in LVEF following cell therapy for heart failure, but publication bias and methodologic shortcomings need to be taken into account. Given that cardiac cell therapy has now been pursued for 20 years without real progress, further efforts should not be made.

Study registry number

This meta-analysis is registered at the international prospective register of systematic reviews, number CRD42019118872.

Endothelial repair by stem and progenitor cells

The integrity of the endothelial barrier is required to maintain vascular homeostasis and fluid balance between the circulatory system and surrounding tissues and to prevent the development of vascular disease. However, the origin of the newly developed endothelial cells is still controversial. Stem and progenitor cells have the potential to differentiate into endothelial cell lines and stimulate vascular regeneration in a paracrine/autocrine fashion. The one source of new endothelial cells was believed to come from the bone marrow, which was challenged by the recent findings. By administration of new techniques, including genetic cell lineage tracing and single cell RNA sequencing, more solid data were obtained that support the concept of stem/progenitor cells for regenerating damaged endothelium. Specifically, it was found that tissue resident endothelial progenitors located in the vessel wall were crucial for endothelial repair. In this review, we summarized the latest advances in stem and progenitor cell research in endothelial regeneration through findings from animal models and discussed clinical data to indicate the future direction of stem cell therapy.

Circulating Progenitor Cells Are Associated With Plaque Progression And Long-Term Outcomes In Heart Transplant Patients

AIMS

Circulating progenitor cells (CPCs) play a role in vascular repair and plaque stability, while osteocalcin (OC) expressing CPCs have been linked to unstable plaque and adverse cardiovascular outcomes. However, their role in cardiac allograft vasculopathy (CAV) has not been elucidated. This cohort study aimed to investigate the contribution of CPCs on CAV progression and cardiovascular events after heart transplantation.

METHODS AND RESULTS

A total of 80 heart transplant patients (mean age 55 ± 14 years, 72% male) undergoing annual intravascular ultrasound (IVUS) had fresh CPCs marked by CD34, CD133, and OC counted in peripheral blood using flow cytometry, on the same day as baseline IVUS. CAV progression was assessed by IVUS as the change (Δ) in plaque volume divided by segment length (PV/SL), adjusted for the time between IVUS measurements (median 3.0, interquartile range (IQR) [2.8, 3.1] years), and was defined as ΔPV/SL that is above the median ΔPV/SL of study population. Major adverse cardiac events (MACE) was defined as any incident of revascularization, myocardial infarction, heart failure admission, re-transplantation, stroke and death. Patients with higher CD34+CD133+ CPCs had a decreased risk of CAV progression (odds ratio 0.58, 95% confidence interval [CI] [0.37, 0.92], p = 0.01) and MACE (hazard ratio [HR] 0.79, 95% CI [0.66, 0.99], p = 0.05) during a median (IQR) follow up of 8.0 years (7.2, 8.3). Contrarily, higher OC+ cell counts were associated with an increased risk of MACE (HR 1.26, 95% CI [1.03, 1.57], p = 0.02).

CONCLUSIONS

Lower levels of CD34+CD133+ CPCs are associated with plaque progression and adverse long-term outcomes in patients who underwent allograft heart transplantation. In contrast, higher circulating OC+ levels are associated with adverse long term outcomes. Thus, CPCs might play a role in amelioration of transplant vasculopathy, while OC expression by these cells might play a role in progression.

TRANSLATIONAL PERSPECTIVE

The results of the current study suggest lower levels of circulating CD34+CD133+ cell levels are associated with cardiac allograft vasculopathy progression and future adverse cardiovascular events, while higher OC+ cell levels are associated with a greater risk of future cardiovascular events. Further studies confirming our findings might elucidate the role of circulating progenitor cells in the pathophysiology of CAV. Moreover, our findings might support the use of circulating progenitors as biomarkers, as well as the notion of cell therapy as potential treatment option for CAV, a disease with severe burden and limited treatment options.

Transplantation of CD34+ cells for myocardial ischemia

CD34+ cells are multipotent hematopoietic stem cells also known as endothelial progenitor cells and are useful in regenerative medicine. Naturally, these cells are mobilized from the bone marrow into peripheral circulation in response to ischemic tissue injury. CD34+ cells are known for their high proliferative and differentiation capacities that play a crucial role in the repair process of myocardial damage. They have an important paracrine activity in secreting factors to stimulate vasculogenesis, reduce endothelial cells and cardiomyocytes apoptosis, remodel extracellular matrix and activate additional progenitor cells. Once they migrate to the target site, they enhance angiogenesis, neovascularization and tissue regeneration. Several trials have demonstrated the safety and efficacy of CD34+ cell therapy in different settings, such as peripheral limb ischemia, stroke and cardiovascular disease. Herein, we review the potential utility of CD34+ cell transplantation in acute myocardial infarction, refractory angina and ischemic heart failure.

Promise of autologous CD34+ stem/progenitor cell therapy for treatment of cardiovascular disease

CD34+ cells are haematopoietic stem cells used therapeutically in patients undergoing radiation or chemotherapy due to their regenerative potential and ability to restore the haematopoietic system. In animal models, CD34+ cells have been associated with therapeutic angiogenesis in response to ischaemia. Several trials have shown the potential safety and efficacy of CD34+ cell delivery in various cardiovascular diseases. Moreover, Phase III trials have now begun to explore the potential role of CD34+ cells in treatment of both myocardial and peripheral ischaemia. CD34+ cells have been shown to be safe and well-tolerated in the acute myocardial infarction (AMI), heart failure, and angina models. Several studies have suggested potential benefit of CD34+ cell therapy in patients with coronary microvascular disease as well. In this review, we will discuss the therapeutic potential of CD34+ cells, and describe the pertinent trials that have used autologous CD34+ cells in no-options refractory angina, AMI, and heart failure. Lastly, we will review the potential utility of autologous CD34+ cells in coronary endothelial and microvascular dysfunction.

State of the art of stem cell therapy for ischaemic cardiomyopathy. Part 2

Ischemic cardiomyopathy is becoming a leading cause of morbidity and mortality in the whole world. Stem cell-based therapy is emerging as a promising option for treatment of ischemic cardiomyopathy. Several stem cell types, including cardiac-derived stem cells, bone marrow-derived stem cells, mesenchymal stem cells, skeletal myoblasts, CD34+ and CD133+ stem cells have been used in clinical trials. Clinical effects mostly depend on transdifferentiation and paracrine factors. One important issue is that a low survival and residential rate of transferred stem cells blocks the effective advances in cardiac improvement. Many other factors associated with the efficacy of cell replacement therapy for ischemic cardiomyopathy mainly including the route of delivery, the type and number of stem cell infusion, the timing of injection, patient's physical conditions, the particular microenvironment onto which the cells are delivered, and clinical conditions remain to be addressed. Here we provide an overview of modern methods of stem cell delivery, types of stem cells and discuss the current state of their therapeutic potential.

Favorable Response to CD34+ Cell Therapy Is Associated with a Decrease of Galectin-3 Levels in Patients with Chronic Heart Failure

Background

Galectin-3 plasma levels (gal-3) were shown to correlate with the scar burden in chronic heart failure (CHF) setting. As scar burden predicts response to stem cell therapy, we sought to explore a correlation between gal-3 and response to CD34+ cell transplantation in patients with CHF.

Methods

We performed a post hoc analysis of patients, enrolled in 2 prospective trials investigating the clinical effects of CD34+ cell therapy in patients with ischemic cardiomyopathy (ICMP) and nonischemic dilated cardiomyopathy (DCMP). CD34+ cells were mobilized by G-CSF, collected via apheresis, and injected transendocardially using NOGA system. Patients were followed for 3 months and demographic, echocardiographic, and biochemical parameters and gal-3 were analyzed at baseline and at follow-up. Response to cell therapy was defined as an LVEF increase of ≥5%.

Results

61 patients were included in the analysis. The mean age of patients was 52 years and 83% were male. DCMP and ICMP were present in 69% and 31% of patients, respectively. The average serum creatinine was 86 ± 23 μmol/L, NT-proBNP 1132 (IQR 350-2279) pg/mL, and LVEF 30 ± 6%. Gal-3 at baseline and at 3 months did not differ significantly (13.4 ± 5.5 ng/mL vs. 13.1 ± 5.8 ng/mL; p = 0.72), and there were no differences in baseline gal-3 with respect to heart failure etiology (15.1 ± 7.2 ng/mL in ICMP vs. 12.7 ± 4.3 ng/mL in DCMP; p = 0.12). Comparing responders (N = 49) to nonresponders (N = 18), we found no differences in baseline gal-3 (13.6 ± 5.7 ng/mL vs. 13.2 ± 4.9 ng/mL; p = 0.80). However, responders had significantly lower gal-3 at 3-month follow-up (12.1 ± 4.0 ng/mL vs. 15.7 ± 8.4 ng/mL; p < 0.05). Also, responders demonstrated a significant decrease in gal-3 over 3 months, while in nonresponders, an increase in gal-3 occurred (−1.5 ± 5.4 ng/mL vs. +2.7 ± 4.3 ng/mL; p = 0.01).

Conclusions

In patients with chronic heart failure undergoing CD34+ cell therapy, a decrease in galectin-3 plasma levels is associated with beneficial response to this treatment modality. Further prospective data is warranted to confirm our findings and to deepen our understanding of the role of gal-3 in the field of stem cell therapy.

Fenofibrate Reverses Dysfunction of EPCs Caused by Chronic Heart Failure

The enhanced activity of endothelial progenitor cells (EPCs) by AMP-activated protein kinase (AMPK) agonists might explain the reversal of chronic heart failure (CHF)-mediated endothelial dysfunction. We studied baseline circulating EPC numbers in patients with heart failure and clarified the effect of fenofibrate on both circulating angiogenic cell (CAC) and late EPC activity. The numbers of circulating EPCs in CHF patients were quantified by flow cytometry. Blood-derived mononuclear cells were cultured, and CAC and late EPC functions, including fibronectin adhesion, tube formation, and migration, were evaluated. We focused on the effect of fenofibrate, an AMPK agonist, on EPC function and Akt/eNOS cascade activation in vitro. The number of circulating EPCs (CD34⁺/KDR⁺) was significantly lower in CHF patients (ischemic cardiomyopathy (ICMP): 0.07%, dilated cardiomyopathy (DCMP): 0.068%; p < 0.05) than in healthy subjects (0.102% of the gating region). In CACs, fibronectin adhesion function was reversed by fenofibrate treatment (p < 0.05). Similar results were also found for tube formation and migration in late EPCs, which were significantly improved by fenofibrate in an AMPK-dependent manner (p < 0.05), suggesting that fenofibrate reversed CACs and late EPC dysfunction in CHF patients. The present findings reveal the potential application of the AMPK agonist fenofibrate to reverse endothelial dysfunction in CHF patients.

CD34+ Stem Cells: Promising Roles in Cardiac Repair and Regeneration

Cell therapy has received significant attention as a novel therapeutic approach to restore cardiac function after injury. CD34-positive (CD34⁺) stem cells have been investigated for their ability to promote angiogenesis and contribute to the prevention of remodelling after infarct. However, there are significant differences between murine and human CD34⁺ cells; understanding these differences might benefit the therapeutic use of these cells. Herein we discuss the function of the CD34 cell and highlight the similarities and differences between murine and human CD34 cell function, which might explain some of the differences between the animal and human evolutions. We also summarize the studies that report the application of murine and human CD34⁺ cells in preclinical studies and clinical trials and current limitations with the application of cell therapy for cardiac repair. Finally, to overcome these limitations we discuss the application of novel humanized rodent models that can bridge the gap between preclinical and clinical studies as well as rejuvenation strategies for improving the quality of old CD34⁺ cells for future clinical trials of autologous cell transplantation.

Transendocardial CD34+ Cell Therapy does not Increase the Risk of Ventricular Arrhythmias in Patients with Chronic Heart Failure

Ventricular arrhythmias (VA) are of major concern in the field of cell therapy, potentially limiting its safety and efficacy. We sought to investigate the effects of CD34⁺ cell therapy on VA burden in patients with chronic heart failure (CHF). We performed registry data analysis of patients with CHF and implanted ICD/CRT devices treated with transendocardial CD 34⁺ cell therapy. Demographic, echocardiographic, and biochemical parameters were analyzed. Device records were reviewed and the number and type of VA 1 year prior to and 1 year after cell therapy were analyzed. All patients underwent electroanatomical mapping, and myocardial scar was defined as unipolar voltage (UV) <8.3 mV and linear local shortening (LLS) <6%. Of 209 patients screened, 48 met inclusion criteria. The mean age of the patients was 52 years and 88% were male. Nonischemic and ischemic cardiomyopathy were present in 55% and 45% of patients. The average serum creatinine was 91±26 µmol/L, serum bilirubin 18±9 µmol/L, NT-proBNP 1767 (468, 2446) pg/mL, LVEF 27±9% and 6’ walk test 442±123 m. The average scar burden in patients with nonischemic and ischemic DCM was 58±15% and 51±25% (P=0.48). No significant difference in VA burden was observed before and after cell therapy (48% vs. 44%; P=0.68). ICD activation occurred in 19% and 27% of patients before and after cell therapy (P=0.33). According to our results, transendocardial CD34⁺ cell therapy does not appear to increase the risk of VA in chronic heart failure patients.

CD34+ enriched cell products intended for autologous transendocardial CD34+ cell transplantation release significant amounts of angiopoietin-1

OBJECTIVES

Cell-based therapy has emerged as a promising strategy for the treatment of patients with heart failure. Increasing evidence supports the hypothesis that paracrine mechanisms mediated by soluble factors released by the cells play a predominate role in reparative processes. The aim of our study was to analyze which cytokines are released by CD34⁺ enriched cell products intended for autologous transendocardial CD34⁺ cell transplantation in patients with cardiomyopathy.

MATERIAL AND METHODS

The peripheral blood CD34⁺ cells from 12 patients were mobilized with granulocyte colony-stimulating factor, collected via apheresis and enriched by immunoselection.

RESULTS

In CD34⁺ enriched cell population, hematopoietic, but not mesenchymal or endothelial, progenitors were detected. Except for angiopoietin-1, other measured cytokines (FGF1, FGF2, VEGF, PDGF, IL-6, HGH, SDF-1α/CXCL12, NRG1) were not released by CD34⁺ cells. The average concentration of angiopoietin-1 released by 5×10⁶ CD34⁺ cells grown in neutral DMEM medium was 213.6±130.0pg/mL (range: 74-448pg/mL). Angiopoietin-1 secretion correlated well with CD34⁺ cell's capacity for generating colonies derived from hematopoietic progenitors (Pearson's correlation=0.964; P<0.001).

CONCLUSION

Our study presents angiopoietin-1 as an interesting candidate and suggests future studies to explore how its release by CD34⁺ cells might impact the success of autologous CD34⁺ cell transplantation.

Potential clinical benefits of cell therapy in coronary heart disease: an update

Cell therapy is a central issue of regenerative medicine and is raising a growing interest in the scientific community, but its full therapeutic potential in coronary heart disease (CHD) has not been reached yet. Several different methods, cell types, delivery routes, and supporting techniques have been attempted and improved to elicit cardiac regeneration in CHD, but only some of them showed a really convincing potential for the use in clinical practice. Here we provide an update on approaches and clinical trials of cell therapy applied to CHD, which are ongoing or that have been realized in the last 5 years. Moreover, we discuss the evidence collected so far in favor or against the validity of stem cell therapy for CHD. In particular, we review and comment the recent advances in cell therapy applied to CHD, the most promising cell types, delivery strategies, biochemical and engineering techniques that have been adopted in this context.

Stem cell therapy targeting the right ventricle in pulmonary arterial hypertension: is it a potential avenue of therapy?

Pulmonary arterial hypertension (PAH) is an incurable disease characterized by an increase in pulmonary arterial pressure due to pathological changes to the pulmonary vascular bed. As a result, the right ventricle (RV) is subject to an increased afterload and undergoes multiple changes, including a decrease in capillary density. All of these dysfunctions lead to RV failure. A number of studies have shown that RV function is one of the main prognostic factors for PAH patients. Many stem cell therapies targeting the left ventricle are currently undergoing development. The promising results observed in animal models have led to clinical trials that have shown an improvement of cardiac function. In contrast to left heart disease, stem cell therapy applied to the RV has remained poorly studied, even though it too may provide a therapeutic benefit. In this review, we discuss stem cell therapy as a treatment for RV failure in PAH. We provide an overview of the results of preclinical and clinical studies for RV cell therapies. Although a large number of studies have targeted the pulmonary circulation rather than the RV directly, there are nonetheless encouraging results in the literature that indicate that cell therapies may have a direct beneficial effect on RV function. This cell therapy strategy may therefore hold great promise and warrants further studies in PAH patients.

Cellular therapies for chronic ischemic heart failure

The development of stem cell therapies for chronic ischemic heart failure is highly sought after to attempt to improve morbidity and mortality of this prevalent disease. This article reviews clinical trials that investigate stem cell therapy for chronic ischemic heart failure. To generate this review article, PubMed was searched using keywords "stem cell therapy heart failure" with the article type "Clinical Trial" selected on 10/04/2016. The raw search yielded 156 articles; 53 articles were selected for inclusion in the review between the original literature search and manual research/cross-referencing. Additional reviews and original articles were also manually researched and cross-referenced. Cellular-based therapies utilizing peripheral blood progenitor cells, bone marrow cells, mesenchymal stem cells, cells of cardiac origin, and embryonic stem cells have yielded mixed results, but some studies have shown modest efficacy. Skeletal myoblasts raised concerns about safety due to arrhythmias. Optimizing cell type and delivery method will be of critical importance in enhancing efficacy of therapy within various subsets of chronic ischemic heart failure patients. Although much more work needs to be done to optimize treatment strategies, developing stem cell therapies for chronic ischemic heart failure could be of critical importance to lessen the impactful health burden that heart failure has on patients and society.

Stem cells and heart disease - Brake or accelerator?

After two decades of intensive research and attempts of clinical translation, stem cell based therapies for cardiac diseases are not getting closer to clinical success. This review tries to unravel the obstacles and focuses on underlying mechanisms as the target for regenerative therapies. At present, the principal outcome in clinical therapy does not reflect experimental evidence. It seems that the scientific obstacle is a lack of integration of knowledge from tissue repair and disease mechanisms. Recent insights from clinical trials delineate mechanisms of stem cell dysfunction and gene defects in repair mechanisms as cause of atherosclerosis and heart disease. These findings require a redirection of current practice of stem cell therapy and a reset using more detailed analysis of stem cell function interfering with disease mechanisms. To accelerate scientific development the authors suggest intensifying unified computational data analysis and shared data knowledge by using open-access data platforms.

Dose Comparison Study of Allogeneic Mesenchymal Stem Cells in Patients With Ischemic Cardiomyopathy (The TRIDENT Study)

RATIONALE

Cell dose and concentration play crucial roles in phenotypic responses to cell-based therapy for heart failure.

OBJECTIVE

To compare the safety and efficacy of 2 doses of allogeneic bone marrow-derived human mesenchymal stem cells identically delivered in patients with ischemic cardiomyopathy.

METHODS AND RESULTS

Thirty patients with ischemic cardiomyopathy received in a blinded manner either 20 million (n=15) or 100 million (n=15) allogeneic human mesenchymal stem cells via transendocardial injection (0.5 cc per injection × 10 injections per patient). Patients were followed for 12 months for safety and efficacy end points. There were no treatment-emergent serious adverse events at 30 days or treatment-related serious adverse events at 12 months. The Major Adverse Cardiac Event rate was 20.0% (95% confidence interval [CI], 6.9% to 50.0%) in 20 million and 13.3% (95% CI, 3.5% to 43.6%) in 100 million (P=0.58). Worsening heart failure rehospitalization was 20.0% (95% CI, 6.9% to 50.0%) in 20 million and 7.1% (95% CI, 1.0% to 40.9%) in 100 million (P=0.27). Whereas scar size reduced to a similar degree in both groups: 20 million by -6.4 g (interquartile range, -13.5 to -3.4 g; P=0.001) and 100 million by -6.1 g (interquartile range, -8.1 to -4.6 g; P=0.0002), the ejection fraction improved only with 100 million by 3.7 U (interquartile range, 1.1 to 6.1; P=0.04). New York Heart Association class improved at 12 months in 35.7% (95% CI, 12.7% to 64.9%) in 20 million and 42.9% (95% CI, 17.7% to 71.1%) in 100 million. Importantly, proBNP (pro-brain natriuretic peptide) increased at 12 months in 20 million by 0.32 log pg/mL (95% CI, 0.02 to 0.62; P=0.039), but not in 100 million (-0.07 log pg/mL; 95% CI, -0.36 to 0.23; P=0.65; between group P=0.07).

CONCLUSIONS

Although both cell doses reduced scar size, only the 100 million dose increased ejection fraction. This study highlights the crucial role of cell dose in the responses to cell therapy. Determining optimal dose and delivery is essential to advance the field, decipher mechanism(s) of action and enhance planning of pivotal Phase III trials.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02013674.

Cellular mechanisms underlying cardiac engraftment of stem cells

INTRODUCTION

Over the past decade, it has become clear that long-term engraftment of any ex vivo expanded cell product transplanted into injured myocardium is modest and all therapeutic regeneration is mediated by stimulation of endogenous repair rather than differentiation of transplanted cells into working myocardium. Given that increasing the retention of transplanted cells boosts myocardial function, focus on the fundamental mechanisms limiting retention and survival of transplanted cells may enable strategies to help to restore normal cardiac function. Areas covered: This review outlines the challenges confronting cardiac engraftment of ex vivo expanded cells and explores means of enhancing cell-mediated repair of injured myocardium. Expert opinion: Stem cell therapy has already come a long way in terms of regenerating damaged hearts though the poor retention of transplanted cells limits the full potential of truly cardiotrophic cell products. Multifaceted strategies directed towards fundamental mechanisms limiting the long-term survival of transplanted cells will be needed to enhance transplanted cell retention and cell-mediated repair of damaged myocardium for cardiac cell therapy to reach its full potential.

DNA Methylation and Hydroxymethylation Profile of CD34+-Enriched Cell Products Intended for Autologous CD34+ Cell Transplantation

Epigenetic dysregulation has been shown to limit functional capacity of aging hematopoietic stem cells, which may contribute to impaired outcome of hematopoietic stem cell-based therapies. The aim of our study was to gain better insight into the epigenetic profile of CD34⁺-enriched cell products intended for autologous CD34⁺ cell transplantation in patients with cardiomyopathy. We found global DNA methylation content significantly higher in immunoselected CD34⁺ cells compared to leukocytes in leukapheresis products (2.33 ± 1.03% vs. 1.84 ± 0.86%, p = 0.04). Global DNA hydroxymethylation content did not differ between CD34⁺ cells and leukocytes (p = 0.30). By measuring methylation levels of 94 stem cell transcription factors on a ready-to-use array, we identified 15 factors in which average promoter methylation was significantly different between leukocytes and CD34⁺ cells. The difference was highest for HOXC12 (58.18 ± 6.47% vs. 13.34 ± 24.18%, p = 0.0009) and NR2F2 (51.65 ± 25.89% vs. 7.66 ± 21.43%, p = 0.0045) genes. Our findings suggest that global DNA methylation and hydroxymethylation patterns as well as target methylation profile of selected genes in CD34⁺-enriched cell products do not differ significantly compared to leukapheresis products and, thus, can tell us little about the functional capacity and regenerative properties of CD34⁺ cells. Future studies should examine other CD34⁺ cell graft characteristics, which may serve as prognostic tools for autologous CD34⁺ cell transplantation.

Benefit of cardiopoietic mesenchymal stem cell therapy on left ventricular remodelling: results from the Congestive Heart Failure Cardiopoietic Regenerative Therapy (CHART-1) study

AIMS

Left ventricular (LV) reverse remodelling is an important marker of improved outcomes in patients with advanced heart failure (HF). We examined the impact of the intramyocardial administration of bone-marrow-derived, lineage-directed, autologous cardiopoietic mesenchymal stem cells (C3BS-CQR-1) on LV remodelling in patients with advanced HF enrolled in the CHART-1 study.

METHODS AND RESULTS

Patients (n=351) with symptomatic advanced HF secondary to ischaemic heart disease, and reduced LV ejection fraction (LVEF <35%) were randomized to receive C3BS-CQR-1 or a sham procedure. In a post hoc analysis we examined the effect of C3BS-CQR-1 on LV reverse remodelling within 1 year of the procedure and the influence of C3BS-CQR-1 dosing in the 271 patients treated as randomized. Delivery of C3BS-CQR-1 was associated with a progressive decrease in both LV end-diastolic volume (LVEDV) and end-systolic volume (LVESV) within 52 weeks after treatment. At 1 year, the LVEDV and LVESV of treated patients decreased by 17.0 mL and 12.8 mL greater than controls (P=0.006 and P=0.017, respectively). The effect on LVEDV was maintained after multivariable adjustment for baseline age, systolic blood pressure, LVEDV, LVEF and history of myocardial infarction. The largest reverse remodelling was evident in the patients receiving a moderate number of injections (<20).

CONCLUSION

In CHART-1, intramyocardial administration of cardiopoietic stem cells led to reverse remodelling as evidenced by significant progressive decreases in LVEDV and LVESV through the 52 weeks of follow-up. Further studies are needed to explore the dose response with regard to cell number and injected volume, and reverse remodelling.

PreSERVE-AMI: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial of Intracoronary Administration of Autologous CD34+ Cells in Patients With Left Ventricular Dysfunction Post STEMI

RATIONALE

Despite direct immediate intervention and therapy, ST-segment-elevation myocardial infarction (STEMI) victims remain at risk for infarct expansion, heart failure, reinfarction, repeat revascularization, and death.

OBJECTIVE

To evaluate the safety and bioactivity of autologous CD34+ cell (CLBS10) intracoronary infusion in patients with left ventricular dysfunction post STEMI.

METHODS AND RESULTS

Patients who underwent successful stenting for STEMI and had left ventricular dysfunction (ejection fraction≤48%) ≥4 days poststent were eligible for enrollment. Subjects (N=161) underwent mini bone marrow harvest and were randomized 1:1 to receive (1) autologous CD34+ cells (minimum 10 mol/L±20% cells; N=78) or (2) diluent alone (N=83), via intracoronary infusion. The primary safety end point was adverse events, serious adverse events, and major adverse cardiac event. The primary efficacy end point was change in resting myocardial perfusion over 6 months. No differences in myocardial perfusion or adverse events were observed between the control and treatment groups, although increased perfusion was observed within each group from baseline to 6 months (P<0.001). In secondary analyses, when adjusted for time of ischemia, a consistently favorable cell dose-dependent effect was observed in the change in left ventricular ejection fraction and infarct size, and the duration of time subjects was alive and out of hospital (P=0.05). At 1 year, 3.6% (N=3) and 0% deaths were observed in the control and treatment group, respectively.

CONCLUSIONS

This PreSERVE-AMI (Phase 2, randomized, double-blind, placebo-controlled trial) represents the largest study of cell-based therapy for STEMI completed in the United States and provides evidence supporting safety and potential efficacy in patients with left ventricular dysfunction post STEMI who are at risk for death and major morbidity.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01495364.

Stem cell therapy for chronic ischaemic heart disease and congestive heart failure

BACKGROUND

A promising approach to the treatment of chronic ischaemic heart disease and congestive heart failure is the use of stem cells. The last decade has seen a plethora of randomised controlled trials developed worldwide, which have generated conflicting results.

OBJECTIVES

The critical evaluation of clinical evidence on the safety and efficacy of autologous adult bone marrow-derived stem/progenitor cells as a treatment for chronic ischaemic heart disease and congestive heart failure.

SEARCH METHODS

We searched CENTRAL in the Cochrane Library, MEDLINE, Embase, CINAHL, LILACS, and four ongoing trial databases for relevant trials up to 14 December 2015.

SELECTION CRITERIA

Eligible studies were randomised controlled trials comparing autologous adult stem/progenitor cells with no cells in people with chronic ischaemic heart disease and congestive heart failure. We included co-interventions, such as primary angioplasty, surgery, or administration of stem cell mobilising agents, when administered to treatment and control arms equally.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all references for eligibility, assessed trial quality, and extracted data. We undertook a quantitative evaluation of data using random-effects meta-analyses. We evaluated heterogeneity using the I2 statistic and explored substantial heterogeneity (I2 greater than 50%) through subgroup analyses. We assessed the quality of the evidence using the GRADE approach. We created a 'Summary of findings' table using GRADEprofiler (GRADEpro), excluding studies with a high or unclear risk of selection bias. We focused our summary of findings on long-term follow-up of mortality, morbidity outcomes, and left ventricular ejection fraction measured by magnetic resonance imaging.

MAIN RESULTS

We included 38 randomised controlled trials involving 1907 participants (1114 cell therapy, 793 controls) in this review update. Twenty-three trials were at high or unclear risk of selection bias. Other sources of potential bias included lack of blinding of participants (12 trials) and full or partial commercial sponsorship (13 trials).Cell therapy reduced the incidence of long-term mortality (≥ 12 months) (risk ratio (RR) 0.42, 95% confidence interval (CI) 0.21 to 0.87; participants = 491; studies = 9; I2 = 0%; low-quality evidence). Periprocedural adverse events associated with the mapping or cell/placebo injection procedure were infrequent. Cell therapy was also associated with a long-term reduction in the incidence of non-fatal myocardial infarction (RR 0.38, 95% CI 0.15 to 0.97; participants = 345; studies = 5; I2 = 0%; low-quality evidence) and incidence of arrhythmias (RR 0.42, 95% CI 0.18 to 0.99; participants = 82; studies = 1; low-quality evidence). However, we found no evidence that cell therapy affects the risk of rehospitalisation for heart failure (RR 0.63, 95% CI 0.36 to 1.09; participants = 375; studies = 6; I2 = 0%; low-quality evidence) or composite incidence of mortality, non-fatal myocardial infarction, and/or rehospitalisation for heart failure (RR 0.64, 95% CI 0.38 to 1.08; participants = 141; studies = 3; I2 = 0%; low-quality evidence), or long-term left ventricular ejection fraction when measured by magnetic resonance imaging (mean difference -1.60, 95% CI -8.70 to 5.50; participants = 25; studies = 1; low-quality evidence).

AUTHORS' CONCLUSIONS

This systematic review and meta-analysis found low-quality evidence that treatment with bone marrow-derived stem/progenitor cells reduces mortality and improves left ventricular ejection fraction over short- and long-term follow-up and may reduce the incidence of non-fatal myocardial infarction and improve New York Heart Association (NYHA) Functional Classification in people with chronic ischaemic heart disease and congestive heart failure. These findings should be interpreted with caution, as event rates were generally low, leading to a lack of precision.

Cellular Therapy for Heart Failure

The pathogenesis of cardiomyopathy and heart failure (HF) is underpinned by complex changes at subcellular, cellular and extracellular levels in the ventricular myocardium. For all of the gains that conventional treatments for HF have brought to mortality and morbidity, they do not adequately address the loss of cardiomyocyte numbers in the remodeling ventricle. Originally conceived to address this problem, cellular transplantation for HF has already gone through several stages of evolution over the past two decades. Various cell types and delivery routes have been implemented to positive effect in preclinical models of ischemic and nonischemic cardiomyopathy, with pleiotropic benefits observed in terms of myocardial remodeling, systolic and diastolic performance, perfusion, fibrosis, inflammation, metabolism and electrophysiology. To a large extent, these salubrious effects are now attributed to the indirect, paracrine capacity of transplanted stem cells to facilitate endogenous cardiac repair processes. Promising results have also followed in early phase human studies, although these have been relatively modest and somewhat inconsistent. This review details the preclinical and clinical evidence currently available regarding the use of pluripotent stem cells and adult-derived progenitor cells for cardiomyopathy and HF. It outlines the important lessons that have been learned to this point in time, and balances the promise of this exciting field against the key challenges and questions that still need to be addressed at all levels of research, to ensure that cell therapy realizes its full potential by adding to the armamentarium of HF management.

Towards the standardization of stem cell therapy studies for ischemic heart diseases: Bridging the gap between animal models and the clinical setting

Today there is an increasing demand for heart transplantations for patients diagnosed with heart failure. Though, shortage of donors as well as the large number of ineligible patients hurdle such treatment option. This, in addition to the considerable number of transplant rejections, has driven the clinical research towards the field of regenerative medicine. Nonetheless, to date, several stem cell therapies tested in animal models fall by the wayside and when they meet the criteria to clinical trials, subjects often exhibit modest improvements. A main issue slowing down the admission of such therapies in the domain of human trials is the lack of protocol standardization between research groups, which hampers comparison between different approaches as well as the lack of thought regarding the clinical translation. In this sense, given the large amount of reports on stem cell therapy studies in animal models reported in the last 3years, we sought to evaluate their advantages and limitations towards the clinical setting and provide some suggestions for the forthcoming investigations. We expect, with this review, to start a new paradigm on regenerative medicine, by evoking the debate on how to plan novel stem cell therapy studies with animal models in order to achieve more consistent scientific production and accelerate the admission of stem cell therapies in the clinical setting.

Thrombospondin-1-Derived Peptide RFYVVMWK Improves the Adhesive Phenotype of CD34+ Cells From Atherosclerotic Patients With Type 2 Diabetes

CD34+ progenitor cells are growing in use for vascular repair. However, in diabetic individuals with cardiovascular diseases, these cells have dysfunctional engraftment capabilities, which compromise their use for autologous cell therapy. The thrombospondin-1-derived peptide RFYVVMWK has previously been reported to stimulate cell adhesiveness through CD47 and integrin activation pathways. Our aim was to test whether RFYVVMWK preconditioning could modulate CD34+ cell phenotype and enhance its proadhesive properties in diabetic patients. Peripheral blood mononuclear CD34+ cells isolated from 40 atherosclerotic patients with type 2 diabetes (T2D; n = 20) or without (non-T2D; n = 20) were preconditioned with 30 μM RFYVVMWK or truncated peptide RFYVVM. CD34+ cell adhesion was assessed on a vitronectin-collagen matrix and on TNF-α or IL-1β-stimulated HUVEC monolayers. Adhesion receptors, platelet/CD34+ cell conjugates, and cell viability were analyzed by flow cytometry and confocal microscopy. RFYVVMWK increased the adhesion of T2D CD34+ cells by eightfold to the vitronectin-collagen matrix (p < 0.001) corresponding to a threefold increase compared to unstimulated non-T2D CD34+ cells. The peptide induced the formation of platelet/CD34+ conjugates and increased the expression of TSP-1, CD29, CD51/CD61, and CD62P in both T2D and non-T2D cells. However, RFYVVMWK treatment did not affect the viability/apoptosis of CD34+ progenitor cells. In conclusion, priming CD34+ cells with RFYVVMWK may enhance their vascular engraftment during autologous proangiogenic cell therapy.

Transplantation of hematopoietic stem cells: intra-arterial versus intravenous administration impacts stroke outcomes in a murine model

Based on results of hematopoietic stem cell transplantation in animal models of stroke, clinical trials with hematopoietic stem cells administered intra-arterially or intravenously have been initiated in patients. Although intra-arterial injection is expected to deliver transplanted cells more directly to the ischemic tissue, the optimal route for enhancing clinical outcomes has not been identified in the setting of stroke. In this study, we compared the therapeutic potential of intra-arterial versus intravenous injection of bone marrow derived-mononuclear cells (BM-MNCs) and CD133-positive (CD133(+)) cells in a murine stroke model. We have found that intra-arterial injection of BM-MNCs exaggerates inflammation with accompanying loss of microvascular structures in poststroke brain and no improvement in cortical function. In contrast, intravenous injection of BM-MNCs did not similarly enhance inflammation and improved cortical function. Our results indicate that the optimal route of cell transplantation can vary with different cell populations and highlight possible issues that might arise with intra-arterial cell administration for acute ischemic cerebrovascular disease.

Stem cell therapy for chronic heart failure

PURPOSE OF REVIEW

The aim of this review was to discuss recent advances in clinical aspects of stem cell therapy in heart failure with emphasis on patient selection, stem cell types and delivery methods.

RECENT FINDINGS

Several stem cell types have been considered for the treatment of patients with heart failure. In nonischemic heart failure, transplantation of CD34 cells improved myocardial performance, functional capacity and neurohumoral activation. In ischemic heart failure, cardiosphere-derived cells were shown to reduce myocardial scar burden with concomitant increase in viable tissue and regional systolic wall thickening. Both autologous and allogeneic mesenchymal stem cells were shown to be effective in improving heart function in patients with ischemic heart failure; this may represent an important step toward the development of a standardized stem cell product for widespread clinical use.

SUMMARY

Although trials of stem cell therapy in heart failure have shown promising results, the findings are not consistent. Given the wide spectrum of heart failure, it may be difficult to define a uniform stem cell therapy for all subsets of patients; instead, future stem cell therapeutic strategies should aim for a more personalized approach by establishing optimal stem cell type, dose and delivery method for an individual patient and disease state.

Stem cell therapy for heart failure

"During the past decade, studies in animals and humans have suggested that cell therapy has positive effects for the treatment of heart failure. This clinical effect may be mediated by angiogenesis and reduction in fibrosis rather than by regeneration of myocytes. Increased microvasculature and decreased scar also likely lead to improved cardiac function in the failing heart. The effects of cell therapy are not limited to one type of cell or delivery technique. Well-designed, large-scale, randomized clinical trials with objective end points will help to fully realize the therapeutic potential of cell-based therapy for treating heart failure."

Endpoints in stem cell trials in ischemic heart failure

Despite multimodal regimens and diverse treatment options alleviating disease symptoms, morbidity and mortality associated with advanced ischemic heart failure remain high. Recently, technological innovation has led to the development of regenerative therapeutic interventions aimed at halting or reversing the vicious cycle of heart failure progression. Driven by the unmet patient need and fueled by encouraging experimental studies, stem cell-based clinical trials have been launched over the past decade. Collectively, these trials have enrolled several thousand patients and demonstrated the clinical feasibility and safety of cell-based interventions. However, the totality of evidence supporting their efficacy in ischemic heart failure remains limited. Experience from the early randomized stem cell clinical trials underscores the key points in trial design ranging from adequate hypothesis formulation to selection of the optimal patient population, cell type and delivery route. Importantly, to translate the unprecedented promise of regenerative biotherapies into clinical benefit, it is crucial to ensure the appropriate choice of endpoints along the regulatory path. Accordingly, we here provide considerations relevant to the choice of endpoints for regenerative clinical trials in the ischemic heart failure setting.

The Clinical Status of Stem Cell Therapy for Ischemic Cardiomyopathy

Ischemic cardiomyopathy (ICM) is becoming a leading cause of morbidity and mortality in the whole world. Stem cell-based therapy is emerging as a promising option for treatment of ICM. Several stem cell types including cardiac-derived stem cells (CSCs), bone marrow-derived stem cells, mesenchymal stem cells (MSCs), skeletal myoblasts (SMs), and CD34(+) and CD 133(+) stem cells have been applied in clinical researches. The clinical effect produced by stem cell administration in ICM mainly depends on the transdifferentiation and paracrine effect. One important issue is that low survival and residential rate of transferred stem cells in the infracted myocardium blocks the effective advances in cardiac improvement. Many other factors associated with the efficacy of cell replacement therapy for ICM mainly including the route of delivery, the type and number of stem cell infusion, the timing of injection, patient's physical condition, the particular microenvironment onto which the cells are delivered, and clinical condition remain to be addressed. Here we provide an overview of the pros and cons of these transferred cells and discuss the current state of their therapeutic potential. We believe that stem cell translation will be an ideal option for patients following ischemic heart disease in the future.