Randomized controlled trials on the therapeutic effects of adult progenitor cells for myocardial infarction: meta-analysis

Adipose-PAS interactions in the context of its localised bio-engineering potential (Review)

Adipocytes are a known source of stem cells. They are easy to harvest, and are a suitable candidate for autogenous grafts. Adipose derived stem cells (ADSCs) have multiple target tissues which they can differentiate into, including bone and cartilage. In adipose tissue, ADSCs are able to differentiate, as well as providing energy and a supply of cytokines/hormones to manage the hypoxic and lipid/hormone saturated adipose environment. The plasminogen activation system (PAS) controls the majority of proteolytic activities in both adipose and wound healing environments, allowing for rapid cellular migration and tissue remodelling. While the primary activation pathway for PAS occurs through the urokinase plasminogen activator (uPA), which is highly expressed by endothelial cells, its function is not limited to enabling revascularisation. Proteolytic activity is dependent on protease activation, localisation, recycling mechanisms and substrate availability. uPA and uPA activated plasminogen allows pluripotent cells to arrive to new local environments and fulfil the niche demands. However, overstimulation, the acquisition of a migratory phenotype and constant protein turnover can be unconducive to the formation of structured hard and soft tissues. To maintain a suitable healing pattern, the proteolytic activity stimulated by uPA is modulated by plasminogen activator inhibitor 1. Depending on the physiological settings, different parts of the remodelling mechanism are activated with varying results. Utilising the differences within each microenvironment to recreate a desired niche is a valid therapeutic bio-engineering approach. By controlling the rate of protein turnover combined with a receptive stem cell lineage, such as ADSC, a novel avenue on the therapeutic opportunities may be identified, which can overcome limitations, such as scarcity of stem cells, low angiogenic potential or poor host tissue adaptation.

Meta-Analysis of Cell Therapy Studies in Heart Failure and Acute Myocardial Infarction

Heart failure (HF) is one of the leading causes of death worldwide and has reached epidemic proportions in most industrialized nations. Despite major improvements in the treatment and management of the disease, the prognosis for patients with HF remains poor with approximately only half of patients surviving for 5 years or longer after diagnosis. The poor prognosis of HF patients is in part because of irreparable damage to cardiac tissue and concomitant maladaptive changes associated with the disease. Cell-based therapies may have the potential to transform the treatment and prognosis of HF through regeneration or repair of damaged cardiac tissue. Accordingly, numerous phase I and II randomized clinical trials have tested the clinical benefits of cell transplant, mostly autologous bone marrow-derived mononuclear cells, in patients with HF, ischemic heart disease, and acute myocardial infarction. Although many of these trials were relatively small, meta-analyses of cell-based therapies have attempted to apply rigorous statistical methodology to assess the potential clinical benefits of the intervention. As a prelude to larger phase III trials, meta-analyses, therefore, remain the obvious means of evaluating the available clinical evidence. Here, we review the different meta-analyses of randomized clinical trials that evaluate the safety and potential beneficial effect of cell therapies in HF and acute myocardial infarction spanning nearly 2 decades since the first pioneering trials were conducted.

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.

Pursuing meaningful end-points for stem cell therapy assessment in ischemic cardiac disease

Despite optimal interventional and medical therapy, ischemic heart disease is still an important cause of morbidity and mortality worldwide. Although not included in standard of care rehabilitation, stem cell therapy (SCT) could be a solution for prompting cardiac regeneration. Multiple studies have been published from the beginning of SCT until now, but overall no unanimous conclusion could be drawn in part due to the lack of appropriate end-points. In order to appreciate the impact of SCT, multiple markers from different categories should be considered: Structural, biological, functional, physiological, but also major adverse cardiac events or quality of life. Imaging end-points are among the most used - especially left ventricle ejection fraction (LVEF) measured through different methods. Other imaging parameters are infarct size, myocardial viability and perfusion. The impact of SCT on all of the aforementioned end-points is controversial and debatable. 2D-echocardiography is widely exploited, but new approaches such as tissue Doppler, strain/strain rate or 3D-echocardiography are more accurate, especially since the latter one is comparable with the MRI gold standard estimation of LVEF. Apart from the objective parameters, there are also patient-centered evaluations to reveal the benefits of SCT, such as quality of life and performance status, the most valuable from the patient point of view. Emerging parameters investigating molecular pathways such as non-coding RNAs or inflammation cytokines have a high potential as prognostic factors. Due to the disadvantages of current techniques, new imaging methods with labelled cells tracked along their lifetime seem promising, but until now only pre-clinical trials have been conducted in humans. Overall, SCT is characterized by high heterogeneity not only in preparation, administration and type of cells, but also in quantification of therapy effects.

Therapeutic Application of Pluripotent Stem Cells: Challenges and Risks

Stem-cell-based therapies are considered to be promising and innovative but complex approaches. Induced pluripotent stem cells (iPSCs) combine the advantages of adult stem cells with the hitherto unique characteristics of embryonic stem cells (ESCs). Major progress has already been achieved with regard to reprogramming technology, but also regarding targeted genome editing and scalable expansion and differentiation of iPSCs and ESCs, in some cases yielding highly enriched preparations of well-defined cell lineages at clinically required dimensions. It is noteworthy, however, that for many applications critical requirements such as the targeted specification into distinct cellular subpopulations and a proper cell maturation remain to be achieved. Moreover, current hurdles such as low survival rates and insufficient functional integration of cellular transplants remain to be overcome. Nevertheless, PSC technologies obviously have come of age and matured to a stage where various clinical applications of PSC-based cellular therapies have been initiated and are conducted.

Translational cardiac stem cell therapy: advancing from first-generation to next-generation cell types

Acute myocardial infarction and chronic heart failure rank among the major causes of morbidity and mortality worldwide. Except for heart transplantation, current therapy options only treat the symptoms but do not cure the disease. Stem cell-based therapies represent a possible paradigm shift for cardiac repair. However, most of the first-generation approaches displayed heterogeneous clinical outcomes regarding efficacy. Stemming from the desire to closely match the target organ, second-generation cell types were introduced and rapidly moved from bench to bedside. Unfortunately, debates remain around the benefit of stem cell therapy, optimal trial design parameters, and the ideal cell type. Aiming at highlighting controversies, this article provides a critical overview of the translation of first-generation and second-generation cell types. It further emphasizes the importance of understanding the mechanisms of cardiac repair and the lessons learned from first-generation trials, in order to improve cell-based therapies and to potentially finally implement cell-free therapies.

Interleukin-3 greatly expands non-adherent endothelial forming cells with pro-angiogenic properties

Circulating endothelial progenitor cells (EPCs) provide revascularisation for cardiovascular disease and the expansion of these cells opens up the possibility of their use as a cell therapy. Herein we show that interleukin-3 (IL3) strongly expands a population of human non-adherent endothelial forming cells (EXnaEFCs) with low immunogenicity as well as pro-angiogenic capabilities in vivo, making their therapeutic utilisation a realistic option. Non-adherent CD133(+) EFCs isolated from human umbilical cord blood and cultured under different conditions were maximally expanded by day 12 in the presence of IL3 at which time a 350-fold increase in cell number was obtained. Cell surface marker phenotyping confirmed expression of the hematopoietic progenitor cell markers CD133, CD117 and CD34, vascular cell markers VEGFR2 and CD31, dim expression of CD45 and absence of myeloid markers CD14 and CD11b. Functional experiments revealed that EXnaEFCs exhibited classical properties of endothelial cells (ECs), namely binding of Ulex europaeus lectin, up-take of acetylated-low density lipoprotein and contribution to EC tube formation in vitro. These EXnaEFCs demonstrated a pro-angiogenic phenotype within two independent in vivo rodent models. Firstly, a Matrigel plug assay showed increased vascularisation in mice. Secondly, a rat model of acute myocardial infarction demonstrated reduced heart damage as determined by lower levels of serum creatinine and a modest increase in heart functionality. Taken together, these studies show IL3 as a potent growth factor for human CD133(+) cell expansion with clear pro-angiogenic properties (in vitro and in vivo) and thus may provide clinical utility for humans in the future.

Current evidence of the efficacy of cell-based therapies in heart failure

Heart failure (HF) is the major cause of mortality worldwide. For more than a decade, cell-based therapies have been developed as treatment for heart disease as an alternative to current therapies. Trials and systematic reviews have assessed the safety and efficacy of cell therapies in a diverse number of participants and clinical settings. The present study collated and synthesized evidence from all systematic reviews related to cell-based therapies and HF. A total of 11 systematic reviews were identified through searches of electronic databases up to June 2014. We set out to answer 2 key questions on the efficacy of cell therapies in HF: (1) What is the overall effect of cell therapies on primary outcomes such as left ventricular ejection fraction (LVEF) and mortality? (2) How important is it to define the clinical setting and length of follow-up when assessing cell therapies and HF? There seems to be enough evidence to suggest that cell therapies have a moderate, long-lasting effect on LVEF, but the reduction on the risk of mortality observed by some systematic reviews needs to be confirmed in larger, statistically powered clinical trials. Additionally, and in order to strengthen conclusions, it is important to assess clinical evidence for defined clinical settings and to standardize the length of follow-up when comparing outcome data across several trials and systematic reviews.

[Effects of long-term exercise training on left ventricular function and remodeling in patients with anterior wall myocardial infarction]

OBJECTIVE

To assess the effects of long-term exercise training on the function and remodeling of the left ventricle after myocardial infarction.

METHODS

We studied 90 patients with a first acute anterior-wall myocardial infarction, all received conventional medical treatment. Symptom-limited maximal exercise stress tests, echocardiograms and effort-rest isotopic ventriculographies at 2, 6 and 12 months after myocardial infarction were performed; the follow-up time averaged 36.3±17 months. All patients joined a cardiac rehabilitation program with moderate or intense exercise training lasting at least a year. Of all patients, 41.1% suffered severe left ventricle dysfunction.

RESULTS

Ergometric parameters that expressed functional capacity increased significantly (P<.0005) at the sixth month evaluation and remained unchanged after a year. There was significant decrease (P<.01) of exercise myocardial ischemia at 6 months. The variables that measured size and function of left ventricle did not change during evolution. Morbidity amounted to 16.7% and total mortality of the series was 13.3%, with 8.9% of cardiovascular cause.

CONCLUSIONS

Long-term exercise training showed no deleterious effects on left ventricle function or remodeling and beneficial functional and clinical effects were obtained in these rehabilitated postinfarction patients.

Stem cell therapy for cardiovascular disease: the demise of alchemy and rise of pharmacology

Regenerative medicine holds great promise as a way of addressing the limitations of current treatments of ischaemic disease. In preclinical models, transplantation of different types of stem cells or progenitor cells results in improved recovery from ischaemia. Furthermore, experimental studies indicate that cell therapy influences a spectrum of processes, including neovascularization and cardiomyogenesis as well as inflammation, apoptosis and interstitial fibrosis. Thus, distinct strategies might be required for specific regenerative needs. Nonetheless, clinical studies have so far investigated a relatively small number of options, focusing mainly on the use of bone marrow-derived cells. Rapid clinical translation resulted in a number of small clinical trials that do not have sufficient power to address the therapeutic potential of the new approach. Moreover, full exploitation has been hindered so far by the absence of a solid theoretical framework and inadequate development plans. This article reviews the current knowledge on cell therapy and proposes a model theory for interpretation of experimental and clinical outcomes from a pharmacological perspective. Eventually, with an increased association between cell therapy and traditional pharmacotherapy, we will soon need to adopt a unified theory for understanding how the two practices additively interact for a patient's benefit.

Reprogramming for cardiac regeneration

Treatment of cardiovascular diseases remains challenging considering the limited regeneration capacity of the heart muscle. Developments of reprogramming strategies to create in vitro and in vivo cardiomyocytes have been the focus point of a considerable amount of research in the past decades. The choice of cells to employ, the state-of-the-art methods for different reprogramming strategies, and their promises and future challenges before clinical entry, are all discussed here.

Myoblasts and embryonic stem cells differentially engraft in a mouse model of genetic dilated cardiomyopathy

The functional and architectural benefits of embryonic stem cells (ESC) and myoblasts (Mb) transplantations into infarcted myocardium have been investigated extensively. Whereas ESC repopulated fibrotic areas and contributed to myocardial regeneration, Mb exerted their effects through paracrine secretions and scar remodeling. This therapeutic perspective, however, has been less explored in the setting of nonischemic dilated cardiomyopathies (DCMs). Our aim was to compare the integration and functional efficacy of ESC committed to cardiac fate by bone morphogenic protein 2 (BMP-2) pretreatment and Mb used as gold standard following their transplantation into the myocardium of a mouse model of laminopathy exhibiting a progressive and lethal DCM. After 4 and 8 weeks of transplantation, stabilization was observed in Mb-transplanted mice (P = 0.008) but not in groups of ESC-transplanted or medium-injected animals, where the left ventricular fractional shortening (LVFS) decreased by 32 ± 8% and 41 ± 8% respectively. Engrafted differentiated cells were consistently detected in myocardia of mice receiving Mb, whereas few or no cells were detected in the hearts of mice receiving ESC, except in two cases where teratomas were formed. These data suggest that committed ESC fail to integrate in DCM where scar tissue is absent to provide the appropriate niche, whereas the functional benefits of Mb transplantation might extend to nonischemic cardiomyopathy.

Myocyte proliferation in the developing heart

Regulation of organ growth is critical during embryogenesis. At the cellular level, mechanisms controlling the size of individual embryonic organs include cell proliferation, differentiation, migration, and attrition through cell death. All these mechanisms play a role in cardiac morphogenesis, but experimental studies have shown that the major determinant of cardiac size during prenatal development is myocyte proliferation. As this proliferative capacity becomes severely restricted after birth, the number of cell divisions that occur during embryogenesis limits the growth potential of the postnatal heart. We summarize here current knowledge concerning regional control of myocyte proliferation as related to cardiac morphogenesis and dysmorphogenesis. There are significant spatial and temporal differences in rates of cell division, peaking during the preseptation period and then gradually decreasing toward birth. Analysis of regional rates of proliferation helps to explain the mechanics of ventricular septation, chamber morphogenesis, and the development of the cardiac conduction system. Proliferation rates are influenced by hemodynamic loading, and transduced by autocrine and paracrine signaling by means of growth factors. Understanding the biological response of the developing heart to such factors and physical forces will further our progress in engineering artificial myocardial tissues for heart repair and designing optimal treatment strategies for congenital heart disease.

Comparison of in leakage from labeled endocardial and epicardial cells: impact on modeling viability of cells to be transplanted into myocardium

Introduction. Previously we proposed a cellular imaging technique to determine the surviving fraction of transplanted cells in vivo. Epicardial kinetics using Indium-111 determined the Debris Impulse Response Function (DIRF) and leakage coefficient parameters. Convolution-based modeling which corrected for these signal contributions indicated that ¹¹¹In activity was quantitative of cell viability with half-lives within 20 hrs to 37 days. We determine if the 37-day upper limit remains valid for endocardial injections by comparing previous epicardial cell leakage parameter estimates to those for endocardial cells. Methods. Normal canine myocardium was injected (¹¹¹In-tropolone) epicardially (9 injections) or endocardially (10 injections). Continuous whole body and SPECT scans for 5 hours were acquired with three weekly follow-up imaging sessions up to 20–26 days. Time-activity curves evaluated each injection type. Results. The epicardial and endocardial kinetics were not significantly different (Epi: 1286 ± 253; Endo: 1567 ± 470 hours P = .62). Conclusion. The original epicardial estimate of leakage kinetics has been validated for use in endocardial injections.

Nitric oxide synthase gene transfer restores activity of circulating angiogenic cells from patients with coronary artery disease

Circulating angiogenic cells (CACs), represent a potential new therapeutic tool for the treatment of cardiovascular diseases, but their regenerative function is impaired in patients with coronary artery disease (CAD) and cardiac risk factors. The objective of this study is to assess the effect of lentiviral overexpression of endothelial nitric oxide synthase (eNOS) on the activity of CACs from patients with CAD and cardiac risk factors. In vitro and in vivo assays were employed to evaluate the regenerative capacity of the cells compared to CACs derived from healthy volunteers. Lentiviral eNOS transduction of cells from CAD patients significantly improved chemotactic migration compared with sham transduction, and increased the ability of CACs to induce angiogenic tube formation when cocultured with human umbilical vein endothelial cells (HUVECs) on Matrigel. In addition, eNOS transduction restored the ability of patient-derived CACs to enhance neovascularization and improve ischemic hind limb perfusion, approaching the efficacy of cells from healthy donors. These data indicate that CAC dysfunction seen in high-risk patients can be partially reversed by eNOS overexpression, suggesting that ex vivo gene delivery may improve the efficacy of autologous cell therapy for cardiovascular disease.

Cardiac regeneration: different cells same goal

Cardiovascular diseases are the leading cause of mortality, morbidity, hospitalization and impaired quality of life. In most, if not all, pathologic cardiac ischemia ensues triggering a succession of events leading to massive death of cardiomyocytes, fibroblast and extracellular matrix accumulation, cardiomyocyte hypertrophy which culminates in heart failure and eventually death. Though current pharmacological treatment is able to delay the succession of events and as a consequence the development of heart failure, the only currently available and effective treatment of end-stage heart failure is heart transplantation. However, donor heart availability and immunorejection upon transplantation seriously limit the applicability. Cardiac regeneration could provide a solution, making real a dream of both scientist and clinician in the previous century and ending an ongoing challenge for this century. In this review, we present a basic overview of the various cell types that have been used in both the clinical and research setting with respect to myocardial differentiation.

Direct autologous bone marrow-derived stem cell transplantation for ischemic heart disease: a meta-analysis

OBJECTIVE

Previous evaluation of intracoronary autologous bone marrow-derived stem cell (BMSCs) therapy following ischemic heart disease (IHD) suggested improvement of cardiac functional parameters. We performed a meta-analysis to provide systematic assessment of the safety and efficacy of direct (intramyocardial or endomyocardial) BMSCs transplantation in patients with IHD.

RESEARCH DESIGN AND METHODS

Randomized controlled Trials (RCTs) were identified in the MEDLINE (approximately Oct. 2010), the Cochrane Central Register of Controlled Trials (Central) (approximately Oct. 2010), EMBASE (approximately Oct. 2010), and EBSCO (approximately Oct. 2010), reviews, and reference lists of relevant articles. Weighted mean difference (WMD) was calculated for changes in left ventricular ejection fraction (LVEF), left ventricular end-diastolic and end-systolic volumes (LVEDV and LVESV) by using a fixed effects model.

RESULTS

Eight RCTs with 307 participants were eligible. Compared with controls, direct BMSCs transplantation improved LVEF (8.4%, 95% CI, 6.49 to 10.31%; p < 0.01), reduced LVESV and LVEDV (-14.85 ml, 95% CI, -27.29 to -2.41 ml, p = 0.02 and -12.79 ml, 95% CI, -24.94 to -0.65 ml, p = 0.04, respectively).

CONCLUSIONS

This meta-analysis suggests that direct BMSCs transplantation is associated with moderate but significant improvements over regular therapy in cardiac functional parameters in patients with IHD, and supports conducting further RCTs of a higher quality.