A pilot trial of autologous bone marrow mononuclear cell transplantation through grafting artery: a sub-study focused on segmental left ventricular function recovery and scar reduction

Cardiac regeneration - Past advancements, current challenges, and future directions

Cardiovascular disease is the leading cause of mortality and morbidity worldwide. Despite improvements in the standard of care for patients with heart diseases, including innovation in pharmacotherapy and surgical interventions, none have yet been proven effective to prevent the progression to heart failure. Cardiac transplantation is the last resort for patients with severe heart failure, but donor shortages remain a roadblock. Cardiac regenerative strategies include cell-based therapeutics, gene therapy, direct reprogramming of non-cardiac cells, acellular biologics, and tissue engineering methods to restore damaged hearts. Significant advancements have been made over the past several decades within each of these fields. This review focuses on the advancements of: 1) cell-based cardiac regenerative therapies, 2) the use of noncoding RNA to induce endogenous cell proliferation, and 3) application of bioengineering methods to promote retention and integration of engrafted cells. Different cell sources have been investigated, including adult stem cells derived from bone marrow and adipose cells, cardiosphere-derived cells, skeletal myoblasts, and pluripotent stem cells. In addition to cell-based transplantation approaches, there have been accumulating interest over the past decade in inducing endogenous CM proliferation for heart regeneration, particularly with the use of noncoding RNAs such as miRNAs and lncRNAs. Bioengineering applications have focused on combining cell-transplantation approaches with fabrication of a porous, vascularized scaffold using biomaterials and advanced bio-fabrication techniques that may offer enhanced retention of transplanted cells, with the hope that these cells would better engraft with host tissue to improve cardiac function. This review summarizes the present status and future challenges of cardiac regenerative therapies.

Unlocking the Pragmatic Potential of Regenerative Therapies in Heart Failure with Next-Generation Treatments

Patients with chronic heart failure (HF) have a poor prognosis due to irreversible impairment of left ventricular function, with 5-year survival rates <60%. Despite advances in conventional medicines for HF, prognosis remains poor, and there is a need to improve treatment further. Cell-based therapies to restore the myocardium offer a pragmatic approach that provides hope for the treatment of HF. Although first-generation cell-based therapies using multipotent cells (bone marrow-derived mononuclear cells, mesenchymal stem cells, adipose-derived regenerative cells, and c-kit-positive cardiac cells) demonstrated safety in preclinical models of HF, poor engraftment rates, and a limited ability to form mature cardiomyocytes (CMs) and to couple electrically with existing CMs, meant that improvements in cardiac function in double-blind clinical trials were limited and largely attributable to paracrine effects. The next generation of stem cell therapies uses CMs derived from human embryonic stem cells or, increasingly, from human-induced pluripotent stem cells (hiPSCs). These cell therapies have shown the ability to engraft more successfully and improve electromechanical function of the heart in preclinical studies, including in non-human primates. Advances in cell culture and delivery techniques promise to further improve the engraftment and integration of hiPSC-derived CMs (hiPSC-CMs), while the use of metabolic selection to eliminate undifferentiated cells will help minimize the risk of teratomas. Clinical trials of allogeneic hiPSC-CMs in HF are now ongoing, providing hope for vast numbers of patients with few other options available.

Clinical Outcomes by Consolidation of Bone Marrow Stem Cell Therapy and Coronary Artery Bypass Graft in Patients With Heart Failure With Reduced Ejection Fraction: A Meta-analysis

Bone marrow stem cell (BMSC) transplantation during coronary artery bypass graft (CABG) is an innovative treatment for ischemic heart disease (IHD). We conduct a meta-analysis to examine whether patients with IHD presenting heart failure with reduced ejection fraction (HFrEF) can be beneficent from CABG with additional BMSC transplantation. Electronic searches were performed on PubMed, EMBASE, Cochrane Library, and ClinicalTrials.gov from their inception to July 2021. The efficacy was based on left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD), left ventricular end-diastolic volume (LVEDV), left ventricular end-diastolic volume index (LVEDVi), left ventricular end-systolic volume index (LVESVi), and 6-min walk test (6MWT) change after treatment. Eight randomized-controlled trials (RCTs) were included in this meta-analysis, with a total of 350 patients. Results showed BMSC transplantation significantly improved the LVEF [mean difference (MD) = 6.23%, 95% confidence interval (CI): 3.22%-9.24%, P < 0.0001], LVEDVi (MD = -20.15 ml/m2, 95% CI: -30.49 to -9.82 ml/m2, P < 0.00001), and LVESVi (MD = -17.69 ml/m2, 95% CI: -25.24 to -10.14 ml/m2, P < 0.00001). There was no statistically significant difference in the improvement of LVEDD, LVEDV, and 6MWT between the cell transplantation group and control groups. Subgroup analysis revealed that the intervention for control group could affect the efficacy of BMSC transplantation. Sensitivity analysis found the conclusion of LVEDD, LVEDV, and 6MWT changes was not stable. Therefore, among patients with IHD presenting HFrEF, BMSC transplantation during CABG is promising to be beneficial for postoperative left ventricular (LV) function improvement. However, according to the unstable results of the sensitivity analysis, it cannot be concluded whether the extra step has a positive effect on left ventricular remodeling and exercise capacity. RCTs with larger cohorts and more strict protocols are needed to validate these conclusions.

Autologous bone marrow stem cell transplantation for patients undergoing coronary artery bypass grafting: a meta-analysis of 22 randomized controlled trials

Background

Although the safety and feasibility of coronary artery bypass grafting (CABG) and bone marrow stem cell (BMSC) transplantation have been established, the effectiveness of this approach compared with CABG alone remains controversial. The aim of this updated meta-analysis of randomized controlled trials was to evaluate the efficacy of this procedure.

Methods

A random-effects meta-analysis was conducted using studies sourced from the PubMed, Embase, and Cochrane literature databases to compare patients who received isolated CABG (CABG group) and BMSC transplantation with CABG (BMSC group). 22 studies were included.

Results

A total of 22 relevant publications with 820 patients were included. 432 patients received BMSC transplantation with CABG and 388 patients received isolated CABG. Compared with the CABG group, the BMSC transplantation group exhibited an improvement in the left ventricular (LV) ejection fraction (mean difference (MD) = 3.87%; 95% confidence interval (CI): 1.93–5.80%; P < 0.001).

Conclusion

The present evidence suggests that autologous BMSC transplantation for patients undergoing CABG appears to be associated with an improvement in LV function compared with CABG alone. However, heterogeneity in the data suggests that patients respond differently to this therapy. Further research is needed to understand these differences.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13019-022-01838-2.

The Role of MSC Therapy in Attenuating the Damaging Effects of the Cytokine Storm Induced by COVID-19 on the Heart and Cardiovascular System

The global pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes coronavirus disease 2019 (COVID-19) has led to 47 m infected cases and 1. 2 m (2.6%) deaths. A hallmark of more severe cases of SARS-CoV-2 in patients with acute respiratory distress syndrome (ARDS) appears to be a virally-induced over-activation or unregulated response of the immune system, termed a "cytokine storm," featuring elevated levels of pro-inflammatory cytokines such as IL-2, IL-6, IL-7, IL-22, CXCL10, and TNFα. Whilst the lungs are the primary site of infection for SARS-CoV-2, in more severe cases its effects can be detected in multiple organ systems. Indeed, many COVID-19 positive patients develop cardiovascular complications, such as myocardial injury, myocarditis, cardiac arrhythmia, and thromboembolism, which are associated with higher mortality. Drug and cell therapies targeting immunosuppression have been suggested to help combat the cytokine storm. In particular, mesenchymal stromal cells (MSCs), owing to their powerful immunomodulatory ability, have shown promise in early clinical studies to avoid, prevent or attenuate the cytokine storm. In this review, we will discuss the mechanistic underpinnings of the cytokine storm on the cardiovascular system, and how MSCs potentially attenuate the damage caused by the cytokine storm induced by COVID-19. We will also address how MSC transplantation could alleviate the long-term complications seen in some COVID-19 patients, such as improving tissue repair and regeneration.

Robust Cardiac Regeneration: Fulfilling the Promise of Cardiac Cell Therapy

PURPOSE

We review the history of cardiac cell therapy, highlighting lessons learned from initial adult stem cell (ASC) clinical trials. We present pluripotent stem cell-derived cardiomyocytes (PSC-CMs) as a leading candidate for robust regeneration of infarcted myocardium but identify several issues that must be addressed before successful clinical translation.

METHODS

We conducted an unstructured literature review of PubMed-listed articles, selecting the most comprehensive and relevant research articles, review articles, clinical trials, and basic or translation articles in the field of cardiac cell therapy. Articles were identified using the search terms adult stem cells, pluripotent stem cells, cardiac stem cell, and cardiac regeneration or from references of relevant articles, Articles were prioritized and selected based on their impact, originality, or potential clinical applicability.

FINDINGS

Since its inception, the ASC therapy field has been troubled by conflicting preclinical data, academic controversies, and inconsistent trial designs. These issues have damaged perceptions of cardiac cell therapy among investors, the academic community, health care professionals, and, importantly, patients. In hindsight, the key issue underpinning these problems was the inability of these cell types to differentiate directly into genuine cardiomyocytes, rendering them unable to replace damaged myocardium. Despite this, beneficial effects through indirect paracrine or immunomodulatory effects remain possible and continue to be investigated. However, in preclinical models, PSC-CMs have robustly remuscularized infarcted myocardium with functional, force-generating cardiomyocytes. Hence, PSC-CMs have now emerged as a leading candidate for cardiac regeneration, and unpublished reports of first-in-human delivery of these cells have recently surfaced. However, the cardiac cell therapy field's history should serve as a cautionary tale, and we identify several translational hurdles that still remain. Preclinical solutions to issues such as arrhythmogenicity, immunogenicity, and poor engraftment rates are needed, and next-generation clinical trials must draw on robust knowledge of mechanistic principles of the therapy.

IMPLICATIONS

The clinical transplantation of functional stem cell-derived heart tissue with seamless integration into native myocardium is a lofty goal. However, considerable advances have been made during the past 2 decades. Currently, PSC-CMs appear to be the best prospect to reach this goal, but several hurdles remain. The history of adult stem cell trials has taught us that shortcuts cannot be taken without dire consequences, and it is essential that progress not be hurried and that a worldwide, cross-disciplinary approach be used to ensure safe and effective clinical translation.

Systemic and local delivery of mesenchymal stem cells for heart renovation: Challenges and innovations

In the beginning stage of heart disease, the blockage of blood flow frequently occurs due to the persistent damage and even death of myocardium. Cicatricial tissue developed after the death of myocardium can affect heart function, which ultimately leads to heart failure. In recent years, several studies carried out about the use of stem cells such as embryonic, pluripotent, cardiac and bone marrow-derived stem cells as well as myoblasts to repair injured myocardium. Current studies focus more on finding appropriate measures to enhance cell homing and survival in order to increase paracrine function. Until now, there is no universal delivery route for mesenchymal stem cells (MSCs) for different diseases. In this review, we summarize the advantages and challenges of the systemic and local pathways of MSC delivery. In addition, we also describe some advanced measures of cell delivery to improve the efficiency of transplantation. The combination of cells and therapeutic substances could be the most reliable method, which allows donor cells to deliver sufficient amounts of paracrine factors and provide long-lasting effects. The cardiac support devices or tissue engineering techniques have the potential to facilitate the controlled release of stem cells on local tissue for a sustained period. A novel promising epicardial drug delivery system is highlighted here, which not only provides MSCs with a favorable environment to promote retention but also increases the contact area and a number of cells recruited in the heart muscle.

Clot-Derived Contaminants in Transplanted Bone Marrow Mononuclear Cells Impair the Therapeutic Effect in Stroke

Background and Purpose—

The beneficial effects of bone marrow mononuclear cell (BM-MNC) transplantation in preclinical experimental stroke have been reliably demonstrated. However, only overall modest effects in clinical trials were observed. We have investigated and reported a cause of the discrepancy between the preclinical and clinical studies.

Methods—

To investigate the possible cause of low efficacy of BM-MNC transplantation in experimental stroke, we have focused on blood clot formation, which is not uncommon in human bone marrow aspirates. To evaluate the effects of clot-derived contaminants in transplanted BM-MNC on stroke outcome, a murine stroke model was used.

Results—

We show that BM-MNC separated by an automatic cell isolator (Sepax2), which does not have the ability to remove clots, did not attenuate brain atrophy after stroke. In contrast, manually isolated, clot-free BM-MNC exerted therapeutic effects. Clot-derived contaminants were also transplanted intravenously to poststroke mice. We found that the transplanted contaminants were trapped at the peristroke area, which were associated with microglial/macrophage activation.

Conclusions—

Clot-derived contaminants in transplanted BM-MNC nullify therapeutic effects in experimental stroke. This may explain neutral results in clinical trials, especially in those using automated stem cell separators that lack the ability to remove clot-derived contaminants.

Visual Overview—

An online visual overview is available for this article.

Combined Coronary Artery Bypass Surgery With Bone Marrow Stem Cell Transplantation: Are We There Yet?

BACKGROUND

Although the safety and feasibility of combined coronary artery bypass grafting (CABG) and bone marrow stem cell (BMSC) transplantation have been proven, the efficacy of this approach remains controversial. Therefore, we conducted an updated meta-analysis of randomized controlled trials to evaluate the efficacy of this procedure.

METHODS

Electronic databases were systematically searched for randomized trials comparing 4-month to 6-month follow-up outcomes in patients who underwent isolated CABG (CABG group) and patients who received BMSC transplantation with CABG (BMSC group). A random-effects meta-analysis was conducted across eligible studies. Meta-regression and subgroup analyses were utilized to identify sources of data heterogeneity.

RESULTS

Thirteen trials were eligible, with a total number of 292 patients in the BMSC group and 247 patients in the CABG group. Compared with the CABG group, the BMSC group showed significant improvement of follow-up left ventricular ejection fraction (n = 539, 4.8%; 95% confidence interval [CI], 2.3%-7.3%; P = .001). The analyzed data showed significant heterogeneity (I² = 74.2%, P < .001). The reduction in scar size (n = 120; -2.2 mL; 95% CI, -18.2 mL to 13.7 mL; P = .44) and the improvement in the 6-minute walk test (n = 212; 41 m; 95% CI, -13 m to 95 m; P = .10) did not reach statistical significance. No significant correlation was found between the number of the injected BMSCs or the method of injection and the change in ejection fraction.

CONCLUSIONS

The present evidence suggests that combined CABG and BMSC transplantation is associated with improvement of left ventricular ejection fraction. However, the heterogeneity in the data suggests variations in patient response to this therapy. Further studies are required to understand these variations.

Autologous bone marrow stem cell therapy for patients undergoing coronary artery bypass grafting: A meta-analysis of 14 randomized controlled trials

Autologous bone marrow stem cell (BMSC) therapy is a novel option for regenerative therapy in patients with ischemic heart disease. The aim of the present meta-analysis was to evaluate the effectiveness of BMSCs combined with coronary artery bypass grafting (CABG). The PubMed, Cochrane Library, EMBASE and Web of Science databases were searched from inception to November 22, 2017 for randomized controlled trials on BMSC therapy combined with CABG. Finally, 14 trials with a total of 596 participants were included. Data were analyzed using a random-effects model. Compared with the control group, the BMSC therapy group exhibited an improvement in the left ventricular (LV) ejection fraction from baseline to follow-up [mean difference (MD)=4.36%; 95% confidence interval (CI): 1.90–6.81%; P<0.01]. Analysis of the pooled results revealed non-significant differences in the LV end-diastolic volume (MD=−6.27 ml; 95% CI: −22.34 to 9.80 ml; P=0.44), LV end-diastolic volume index (MD=−15.11 ml/m²; 95% CI: −31.53 to 1.30 ml/m²; P=0.07), LV end-systolic volume (MD=−11.52 ml; 95% CI: −26.97 to 3.93 ml; P=0.14) and LV end-systolic volume index (MD=−16.56 ml/m²; 95% CI: −37.75 to 4.63 ml/m²; P=0.13) between the BMSC and CABG alone groups. Therefore, autologous BMSC therapy for patients undergoing CABG appears to be associated with an improvement in LV function compared with CABG alone.

Effects of bone marrow mononuclear cells delivered through a graft vessel in patients with previous myocardial infarction and chronic heart failure: An echocardiographic study of left ventricular dyssynchrony

OBJECTIVES

Several trials are investigating the delivery of stem cells to treat ischemic cardiomyopathy. The aim of this study was the echocardiographic evaluation of the effectiveness of isolated coronary artery bypass graft (CABG) combined with bone marrow mononuclear cells (BMMNC) delivered through the graft vessels to improve left ventricular dyssynchrony in patients with previous myocardial infarction and chronic heart failure.

METHODS

42 patients with previous myocardial infarction and chronic heart failure were randomly allocated to either the CABG only group (n = 18) or the CABG with BMMNC graft group (n = 24group). We used 2D strain imaging to measure the absolute difference in time-to-peak radial strain between the earliest and the latest activated segments on LV short-axis images at the apical (RSTa), at the mitral annulus (RSTb), and at the papillary muscle (RSTm) level.

RESULTS

The effective rate of LV dyssynchrony improvement was significantly higher in the CABG + BMMNC than in the CABG only group (RSTb: 91.7% vs 50%, P < .05; RSTm: 78.6% vs 35.7%, P < .05; RSTa: 92.3% vs 50%, P < .05). The deterioration rate of LV synchrony was significantly lower in the CABG + BMMNC than in the CABG only group for RSTb (8.3% vs 70%, P < .05;) and RSTm (0 vs 50%, P < .05), but not for RSTa (18.2% vs 37.5%, P > .05).

CONCLUSIONS

Combining CABG with BMMNC delivering provided a better improvement of left ventricular dyssynchrony than CABG only.

Left ventricular ejection fraction as therapeutic target: is it the ideal marker?

Heart failure (HF) consists the fastest growing clinical cardiac disease. HF patients are categorized on the basis of underlying left ventricular ejection fraction (LVEF) into HF with preserved EF (HFpEF), reduced LVEF (HFrEF), and mid-range LVEF (HFmrEF). While LVEF is the most commonly used surrogate marker of left ventricular (LV) systolic function, the implementation of two-dimensional echocardiography in estimating this parameter imposes certain caveats on current HF classification. Most importantly, LVEF could fluctuate in repeated measurements or even recover after treatment, thus blunting the borders between proposed categories of HF and enabling upward classification of patients. Under this prism, we sought to summarize possible procedures to improve systolic function in patients with HFrEF either naturally or by the means of pharmacologic and non-pharmacologic treatment and devices. Therefore, we reviewed established pharmacotherapy, including beta-blockers, inhibitors of renin-angiotensin-aldosterone axis, statins, and digoxin as well as novel treatments like sacubitril-valsartan, ranolazine, and ivabradine. In addition, we assessed evidence in favor of cardiac resynchronization therapy and exercise training programs. Finally, innovative therapeutic strategies, including stem cells, xanthine oxidase inhibitors, antibiotic regimens, and omega-3 polyunsaturated fatty acids, were also taken into consideration. We concluded that LVEF is subject to changes in HF after intervention and besides the aforementioned HFrEF, HFpEF, and HFmrEF categories, a new entity of HF patients with recovered LVEF should be acknowledged. An improved global and refined LV function assessment by sophisticated imaging modalities and circulating biomarkers is expected to render HF classification more accurate and indicate patients with viable-yet dysfunctional-myocardium and favorable characteristics as the ideal candidates for LVEF recovery by individualized HF therapy.

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.

Myocardial late gadolinium enhancement: a head-to-head comparison of motion-corrected balanced steady-state free precession with segmented turbo fast low angle shot

AIM

To evaluate the image quality and diagnostic agreement with a head-to-head comparison of late gadolinium enhancement (LGE) images acquired by the motion-corrected (MOCO) balanced steady-state free precession (bSSFP) phase sensitivity inversion recovery (PSIR) and conventional segmented fast low angle shot (FLASH) PSIR methods^15,16 in a patient cohort with a wide spectrum of cardiovascular disease.

MATERIALS AND METHODS

In 59 consecutive patients, signal-to-noise ratios (SNRs), contrast-to-noise ratios (CNRs) of the normal myocardium (NM), LGE, and blood pool (BP) were pair-wise compared between the two different sequences. A further semi-qualitative score system (graded 1 -4) was used to compare the overall image quality (OIQ). The diagnostic agreement of the two techniques were evaluated by both transmural severity and absolutely quantitative size of LGE.

RESULTS

The SNRs of the NM, LGE, and BP of MOCO bSSFP were 4.8±3.4, 53.6±35.6 and 43.2±29.3, compared with 3.9±3.6 (p=0.126), 27.7±18.5 (p<0.001) and 24.3±13.4 (p<0.001) of FLASH LGE, respectively. The CNRs of LGE to NM, LGE to BP, and BP to NM were 48.3±33.1 versus 23.8±16.7 (p<0.001), 6.5±21.6 versus 3.8±10.8 (p<0.001), and 38.3±27.2 versus 20.3±10.7 (p=0.448), respectively. The OIQ of MOCO bSSFP was higher than that of segmented FLASH (median 4 versus median 3, p<0.001). For quantification of LGE size, there is good agreement and high correlation (r=0.992, p<0.001) between the two methods.

CONCLUSIONS

MOCO bSSFP is a feasible, robust sequence for LGE imaging, especially for patients with arrhythmia and those incapable of breath-holding due to severe heart failure.

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.

Clinical Benefits of Stem Cells for Chronic Symptomatic Systolic Heart Failure: A Systematic Review of the Existing Data and Ongoing Trials

The benefits of stem cell therapy for patients with chronic symptomatic systolic heart failure due to ischemic and nonischemic cardiomyopathy (ICM and NICM, respectively) are unclear. We performed a systematic review of major published and ongoing trials of stem cell therapy for systolic heart failure and compared measured clinical outcomes for both types of cardiomyopathy. The majority of the 29 published studies demonstrated clinical benefits of autologous bone marrow-derived mesenchymal stem cells (BM-MSCs). Left ventricular ejection fraction (LVEF) was improved in the majority of trials after therapy. Cell delivery combined with coronary artery bypass grafting was associated with the greatest improvement in LVEF. Left ventricular end-systolic volume (or diameter), New York Heart Association functional classification, quality of life, and exercise capacity were also improved in most studies after cell therapy. Most ICM trials demonstrated a significant improvement in perfusion defects, infarct size, and myocardial viability. Several larger clinical trials that are in progress employ alternative delivery modes, cell types, and longer follow-up periods. Stem cells are a promising therapeutic modality for patients with heart failure due to ICM or NICM. More data are required from larger blinded trials to determine which combination of cell type and delivery mode will yield the most benefit with avoidance of harm in these patient populations.

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.

Cell therapy for heart disease after 15 years: Unmet expectations

Over the past two decades cardiac cell therapy (CCT) has emerged as a promising new strategy to cure heart diseases at high unmet need. Thousands of patients have entered clinical trials for acute or chronic heart conditions testing different cell types, including autologous or allogeneic bone marrow (BM)-derived mononuclear or selected cells, BM- or adipose tissue-derived mesenchymal cells, or cardiac resident progenitors based on their potential ability to regenerate scarred or dysfunctional myocardium. Nowadays, the original enthusiasm surrounding the regenerative medicine field has been cushioned by a cumulative body of evidence indicating an inefficient or modest efficacy of CCT in improving cardiac function, along with the continued lack of indisputable proof for long-term prognostic benefit. In this review, we have firstly comprehensively outlined the positive and negative results of cell therapy studies in patients with acute myocardial infarction, refractory angina and chronic heart failure. Next, we have discussed cell therapy- and patient-related variables (e.g. cell intrinsic and extrinsic characteristics as well as criteria of patient selection and proposed methodologies) that might have dampened the efficacy of past cell therapy trials. Finally, we have addressed critical factors to be considered before embarking on further clinical trials.

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.

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.

Meta-analysis of coronary artery bypass graft surgery combined with stem cell transplantation in the treatment of ischemic heart diseases

OBJECTIVE

The use of bone marrow cells (BMCs) to regenerate the myocardium and vessels is a new treatment for ischemic heart diseases (IHD) that has been receiving attention. In this study, a meta-analysis was used to analyze the efficacy of combining coronary artery bypass graft (CABG) surgery with BMC transplantation in the treatment of IHD.

METHODS AND RESULTS

MEDLINE, EMBASE, Cochrane, CNKI, WAN-FANG, and WEI-PU databases were searched. The main inclusion criteria were as follows: (a) studies that analyzed patients diagnosed with chronic IHD. (b) Studies that had randomized-controlled trials. (c) Studies that included research comparing the efficacy of CABG and CABG combined with bone BMC transplantation in the treatment of IHD. (d) Studies with specific enumeration data at the end of the follow-up with a follow-up time of at least 3 months. Nine randomized trials were included. There were 158 patients in the group that received the treatment of CABG surgery as well as stem cell transplantation, referred to as the 'cell transplantation group.' A total of 147 patients were in the group that only received the treatment of CABG surgery, referred to as the 'CABG group'. Our data show that not only did stem cell transplantation significantly improve left ventricular ejection fraction (odds ratio=11.7, 95% confidence interval: 4.04-19.36; P=0.003) but it also significantly reduced the left ventricular end-diastolic volume and left ventricular end-systolic volume (P<0.001).

CONCLUSION

BMC transplantation is associated with a significant improvement in left ventricular ejection fraction and the attenuation of left ventricular remodeling.

Adult Bone Marrow Cell Therapy for Ischemic Heart Disease: Evidence and Insights From Randomized Controlled Trials

RATIONALE

Notwithstanding the uncertainties about the outcomes of bone marrow cell (BMC) therapy for heart repair, further insights are critically needed to improve this promising approach.

OBJECTIVE

To delineate the true effect of BMC therapy for cardiac repair and gain insights for future trials through systematic review and meta-analysis of data from eligible randomized controlled trials.

METHODS AND RESULTS

Database searches through August 2014 identified 48 eligible randomized controlled trials (enrolling 2602 patients). Weighted mean differences for changes in left ventricular (LV) ejection fraction, infarct size, LV end-systolic volume, and LV end-diastolic volume were analyzed with random-effects meta-analysis. Compared with standard therapy, BMC transplantation improved LV ejection fraction (2.92%; 95% confidence interval, 1.91-3.92; P<0.00001), reduced infarct size (-2.25%; 95% confidence interval, -3.55 to -0.95; P=0.0007) and LV end-systolic volume (-6.37 mL; 95% confidence interval, -8.95 to -3.80; P<0.00001), and tended to reduce LV end-diastolic volume (-2.26 mL; 95% confidence interval, -4.59 to 0.07; P=0.06). Similar effects were noted when data were analyzed after excluding studies with discrepancies in reporting of outcomes. The benefits also persisted when cardiac catheterization was performed in control patients as well. Although imaging modalities partly influenced the outcomes, LV ejection fraction improved in BMC-treated patients when assessed by magnetic resonance imaging. Early (<48 hours) BMC injection after myocardial Infarction was more effective in reducing infarct size, whereas BMC injection between 3 and 10 days proved superior toward improving systolic function. A minimum of 50 million BMCs seemed to be necessary, with limited additional benefits seen with increasing cell numbers. BMC therapy was safe and improved clinical outcomes, including all-cause mortality, recurrent myocardial Infarction, ventricular arrhythmia, and cerebrovascular accident during follow-up, albeit with differences between acute myocardial Infarction and chronic ischemic heart disease subgroups.

CONCLUSIONS

Transplantation of adult BMCs improves LV ejection fraction, reduces infarct size, and ameliorates remodeling in patients with ischemic heart disease. These effects are upheld in the analyses of studies using magnetic resonance imaging and also after excluding studies with discrepant reporting of outcomes. BMC transplantation may also reduce the incidence of death, recurrent myocardial Infarction, ventricular arrhythmia, and cerebrovascular accident during follow-up.

Effects of Bone Marrow Mononuclear Cells Delivered through a Graft Vessel for Patients with Previous Myocardial Infarction and Chronic Heart Failure: An Echocardiographic Study of Left Ventricular Function

OBJECTIVES

The graft of stem cells to treat ischemic cardiomyopathy is popular in many clinical trials. The aim of this study was to evaluate the effectiveness of isolated coronary artery bypass graft combined with bone marrow mononuclear cells (BMMNC) delivered through graft vessels to improve left ventricular function of patients with previous myocardial infarction and chronic heart failure using echocardiography.

METHODS

Forty-two patients with previous myocardial infarction and chronic heart failure were randomly allocated to one of the two groups: CABG only (18 in CABG group), or CABG with BMMNC transplantation (24 in CABG + BMMNC group). Echocardiographic parameters of systolic function were measured on B-mode imaging, tissue Doppler imaging (TDI), two-dimensional (2D) strain imaging, and 8 parameters were measured totally. Echocardiographic parameters of diastolic function were measured on pulsed-wave Doppler imaging, TDI, and 2D strain rate imaging; 17 parameters were measured totally.

RESULTS

Postoperative left ventricular ejection fraction (LVEF) versus preoperative LVEF were 49.083 ± 1.914% versus 36.042 ± 1.185% (P < 0.05) in CABG + BMMMNC group and 41.389 ± 2.210% versus 34.667 ± 1.369% (P < 0.05) in CABG group, global longitudinal strain were -12.542 ± 0.512% versus -7.083 ± 0.583% (P < 0.05) in CABG + BMMMNC group and -9.278 ± 0.591% versus -7.000 ± 0.673% (P < 0.05) in CABG group, mLsr1 were -0.108 ± 0.018/sec versus -0.039 ± 0.017/sec (P < 0.05) in CABG+BMMMNC group and -0.048 ± 0.021/sec versus 0.004 ± 0.020/sec (P < 0.05) in CABG group, mLsr2 were -0.055 ± 0.013/sec versus -0.009 ± 0.015/sec (P < 0.05) in CABG + BMMMNC group and 0.004 ± 0.015/sec versus 0.024 ± 0.017/sec (P < 0.05) in CABG group, and Aa1 were 7.303 ± 0.479 cm/sec versus 5.131 ± 0.381 cm/sec (P < 0.05) in CABG + BMMMNC group and 7.908 ± 0.553 cm/sec versus 6.764 ± 0.440 cm/sec (P < 0.05) in CABG group. Parameters above were significantly improved postoperatively in both groups. The degree of the improvement was significantly different between the two groups with the CABG + BMMNC group improved more versus the group of CABG only (P < 0.05).

CONCLUSIONS

The improvement of left ventricular function in CABG + BMMNC group is better than CABG group. 2D strain and strain rate imaging is a more sensitive tool to evaluate left ventricular function.

Efficacy and safety of bone marrow cell transplantation for chronic ischemic heart disease: a meta-analysis

Background

Although bone marrow-derived cells (BMCs) have shown great therapeutic potential in patients with chronic ischemic heart disease (CIHD), the exact efficacy and safety of BMCs therapy is still not completely defined.

Material/Methods

We searched PubMed, OVID, EMBASE, the Cochrane Library, and ClinicalTrials.gov and finally identified 20 qualified trials in this meta-analysis. Assessment of efficacy was based on left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), and left ventricular end-diastolic volume (LVEDV) improvement, by weighted mean difference (WMD) with 95% confidence intervals (CIs). Results of all-cause death, ventricular arrhythmia, recurrent myocardial infarction, and cerebrovascular accident were pooled to assess safety. Subgroup analysis was performed by stratifying RCTs into 2 subgroups of those with revascularization and without revascularization.

Results

BMC transplantation significantly improved LVEF in patients with revascularization (3.35%, 95% CI 0.72% to 5.97%, p=0.01; I²=85%) and without revascularization (3.05%, 95% CI 0.65% to 5.45%, p=0.01; I²=86%). In patients without revascularization, BMC transplantation was associated with significantly decreased LVESV (−11.75 ml, 95% CI −17.81 ml to −5.69 ml, p=0.0001; I²=81%), and LVEDV (−7.80 ml, 95% CI −15.31 ml to −0.29 ml, p=0.04; I²=39%). Subgroup analysis showed that the route of transplantation, baseline LVEF, and type of cells delivered could influence the efficacy of BMC transplantation.

Conclusions

Autologous transplantation of BMCs was safe and effective for patients who were candidates for revascularization with CABG/PCI and those who were not. However, large clinical trials and long-term follow-up are required to confirm these benefits.

Autologous mesenchymal stem cells produce concordant improvements in regional function, tissue perfusion, and fibrotic burden when administered to patients undergoing coronary artery bypass grafting: The Prospective Randomized Study of Mesenchymal Stem Cell Therapy in Patients Undergoing Cardiac Surgery (PROMETHEUS) trial

RATIONALE

Although accumulating data support the efficacy of intramyocardial cell-based therapy to improve left ventricular (LV) function in patients with chronic ischemic cardiomyopathy undergoing CABG, the underlying mechanism and impact of cell injection site remain controversial. Mesenchymal stem cells (MSCs) improve LV structure and function through several effects including reducing fibrosis, neoangiogenesis, and neomyogenesis.

OBJECTIVE

To test the hypothesis that the impact on cardiac structure and function after intramyocardial injections of autologous MSCs results from a concordance of prorecovery phenotypic effects.

METHODS AND RESULTS

Six patients were injected with autologous MSCs into akinetic/hypokinetic myocardial territories not receiving bypass graft for clinical reasons. MRI was used to measure scar, perfusion, wall thickness, and contractility at baseline, at 3, 6, and 18 months and to compare structural and functional recovery in regions that received MSC injections alone, revascularization alone, or neither. A composite score of MRI variables was used to assess concordance of antifibrotic effects, perfusion, and contraction at different regions. After 18 months, subjects receiving MSCs exhibited increased LV ejection fraction (+9.4 ± 1.7%, P=0.0002) and decreased scar mass (-47.5 ± 8.1%; P<0.0001) compared with baseline. MSC-injected segments had concordant reduction in scar size, perfusion, and contractile improvement (concordant score: 2.93 ± 0.07), whereas revascularized (0.5 ± 0.21) and nontreated segments (-0.07 ± 0.34) demonstrated nonconcordant changes (P<0.0001 versus injected segments).

CONCLUSIONS

Intramyocardial injection of autologous MSCs into akinetic yet nonrevascularized segments produces comprehensive regional functional restitution, which in turn drives improvement in global LV function. These findings, although inconclusive because of lack of placebo group, have important therapeutic and mechanistic hypothesis-generating implications.

CLINICAL TRIAL REGISTRATION URL

http://clinicaltrials.gov/show/NCT00587990. Unique identifier: NCT00587990.

Autologous transplantation of bone marrow/blood-derived cells for chronic ischemic heart disease: a systematic review and meta-analysis

BACKGROUND

Studies focused on cell therapy for chronic ischemic heart disease (CIHD) have been published with conflicting results. In this meta-analysis, we aimed to assess the effectiveness and safety of autologous bone marrow/blood-derived cell transplantation in patients with CIHD.

METHODS

Randomized controlled trials (RCTs) were identified in PubMed, OVID, EMBASE, and Cochrane Library reviews and reference lists of relevant articles. Weighted mean difference was calculated for changes in left ventricular ejection fraction (LVEF), left ventricular end-systolic volume (LVESV), and left ventricular end-diastolic volume (LVEDV) using a random-effects model.

RESULTS

Nineteen trials with a total of 886 patients were included. Compared with controls, patients who received transplantation of bone marrow/blood-derived cells had significantly improved LVEF (3.54%; 95% confidence interval [CI], 1.92%-5.17%; P < 0.001) and LVESV (-8.96 mL; 95% CI, -13.64 to -4.28 mL; P < 0.001). No significant improvement in LVEDV (-0.75 mL; 95% CI, -9.80-8.30 mL; P = 0.22) was detected. Subgroup analysis revealed that significant improvement in LVEDV was observed in patients with lower baseline LVEF. Moreover, there were trends in favor of a benefit for LV function and remodelling when intramyocardial cells were injected during coronary bypass surgery and the bone marrow mononuclear cell number was ≤ 1 × 10(8). Furthermore, cell therapy was associated with a significant decrease in all-cause death (relative risk: 0.49; 95% CI, 0.29-0.84; P = 0.01).

CONCLUSIONS

Current evidence showed that cell therapy moderately improved left ventricle function and significantly decreased all-cause death in patients with CIHD and supports further RCTs with larger sample size and longer follow-up.