Is the measurement of left ventricular ejection fraction the proper end point for cell therapy trials? An analysis of the effect of bone marrow mononuclear stem cell administration on left ventricular ejection fraction after ST-segment elevation myocardial infarction when evaluated by cardiac magnetic resonance imaging

Intra-carotid arterial transfusion of circulatory-derived autologous endothelial progenitor cells in rodent after ischemic stroke-evaluating the impact of therapeutic time points on prognostic outcomes

Background

This study tested the optimal time point for left intra-carotid arterial (LICA) administration of circulatory-derived autologous endothelial progenitor cells (EPCs) for improving the outcome in rat after acute ischemic stroke (IS).

Methods and results

Adult male SD rats (n = 70) were equally categorized into group 1 (sham-operated control), group 2 (IS), group 3 (IS+EPCs/1.2 × 10⁶ cells/by LICA administration 3 h after IS), group 4 (IS+EPCs/LICA administration post-day-3 IS), group 5 (IS+EPCs/LICA administration post-day-7 IS), group 6 (IS+EPCs/LICA administration post-day-14 IS), and group 7 (IS+EPCs/LICA administration post-day-28 IS). The brain infarct volume (BIV) (at day 60/MRI) was lowest in group 1, highest in group 2, and significantly progressively increased from groups 3 to 7, whereas among the IS animals, the neurological function was significantly preserved in groups 3 to 6 than in groups 2 and 7 post-day-60 IS (all P < 0.0001). By day 60, the endothelial cell markers at protein and cellular levels and number of small vessels exhibited an opposite pattern of BIV among the groups (all P < 0.0001). The protein and cellular levels of inflammation, and protein levels of oxidative stress, autophagy, and apoptosis were highest in group 2, lowest in group 1, and progressively increased from groups 3 to 7 (all P < 0.0001). The angiogenesis biomarkers at protein and cellular levels were significantly progressively increased from groups 1 to 3, then significantly progressively decreased from groups 4 to 7 (all P < 0.0001).

Conclusion

Early EPC administration provided better benefits on improving functional/image/molecular-cellular outcomes after acute IS in rat.

Safety and Efficacy of Intracoronary Infusion of Allogeneic Human Cardiac Stem Cells in Patients With ST-Segment Elevation Myocardial Infarction and Left Ventricular Dysfunction

RATIONALE

Allogeneic cardiac stem cells (AlloCSC-01) have shown protective, immunoregulatory, and regenerative properties with a robust safety profile in large animal models of heart disease.

OBJECTIVE

To investigate the safety and feasibility of early administration of AlloCSC-01 in patients with ST-segment-elevation myocardial infarction.

METHODS AND RESULTS

CAREMI (Safety and Efficacy of Intracoronary Infusion of Allogeneic Human Cardiac Stem Cells in Patients With STEMI and Left Ventricular Dysfunction) was a phase I/II multicenter, randomized, double-blind, placebo-controlled trial in patients with ST-segment-elevation myocardial infarction, left ventricular ejection fraction ≤45%, and infarct size ≥25% of left ventricular mass by cardiac magnetic resonance, who were randomized (2:1) to receive AlloCSC-01 or placebo through the intracoronary route at days 5 to 7. The primary end point was safety and included all-cause death and major adverse cardiac events at 30 days (all-cause death, reinfarction, hospitalization because of heart failure, sustained ventricular tachycardia, ventricular fibrillation, and stroke). Secondary safety end points included major adverse cardiac events at 6 and 12 months, adverse events, and immunologic surveillance. Secondary exploratory efficacy end points were changes in infarct size (percentage of left ventricular mass) and indices of ventricular remodeling by magnetic resonance at 12 months. Forty-nine patients were included (92% male, 55±11 years), 33 randomized to AlloCSC-01 and 16 to placebo. No deaths or major adverse cardiac events were reported at 12 months. One severe adverse events in each group was considered possibly related to study treatment (allergic dermatitis and rash). AlloCSC-01 elicited low levels of donor-specific antibodies in 2 patients. No immune-related adverse events were found, and no differences between groups were observed in magnetic resonance-based efficacy parameters at 12 months. The estimated treatment effect of AlloCSC-01 on the absolute change from baseline in infarct size was -2.3% (95% confidence interval, -6.5% to 1.9%).

CONCLUSIONS

AlloCSC-01 can be safely administered in ST-segment-elevation myocardial infarction patients with left ventricular dysfunction early after revascularization. Low immunogenicity and absence of immune-mediated events will facilitate adequately powered studies to demonstrate their clinical efficacy in this setting.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov . Unique identifier: NCT02439398.

Clinical Studies of Cell Therapy in Cardiovascular Medicine: Recent Developments and Future Directions

Given the rising prevalence of cardiovascular disease worldwide and the limited therapeutic options for severe heart failure, novel technologies that harness the regenerative capacity of the heart are sorely needed. The therapeutic use of stem cells has the potential to reverse myocardial injury and improve cardiac function, in contrast to most current medical therapies that only mitigate heart failure symptoms. Nearly 2 decades and >200 trials for cardiovascular disease have revealed that most cell types are safe; however, their efficacy remains controversial, limiting the transition of this therapy from investigation to practice. Lessons learned from these initial studies are driving the design of new clinical trials; higher fidelity of cell isolation techniques, standardization of conditions, more consistent use of state of the art measurement techniques, and assessment of multiple end points to garner insights into the efficacy of stem cells. Translation to clinical trials has almost outpaced our mechanistic understanding, and individual patient factors likely play a large role in stem cell efficacy. Therefore, careful analysis of dosing, delivery methods, and the ideal patient populations is necessary to translate cell therapy from research to practice. We are at a pivotal stage in the field in which information from many relatively small clinical trials must guide carefully executed efficacy trials. Larger efficacy trials are being launched to answer questions about older, first-generation stem cell therapeutics, while novel, second-generation products are being introduced into the clinical realm. This review critically examines the current state of clinical research on cell-based therapies for cardiovascular disease, highlighting the controversies in the field, improvements in clinical trial design, and the application of exciting new cell products.

Efficacy and safety of stem cell therapy in patients with dilated cardiomyopathy: a systematic appraisal and meta-analysis

BACKGROUND

The clinical significance of stem cell therapy in the treatment of dilated cardiomyopathy remains unclear. This systemic appraisal and meta-analysis aimed to assess the efficacy and safety of stem cell therapy in patients with dilated cardiomyopathy. After searching the PubMed, Embase, and Cochrane library databases until November 2017, we conducted a meta-analysis to evaluate the efficacy and safety of stem cell therapy in patients with dilated cardiomyopathy.

METHODS

The weighted mean difference (WMD), standard mean difference (SMD), relative risk (RR), and 95% confidence interval (CI) were summarized in this meta-analysis. Both fixed effects and random effects models were used to combine the data. Sensitivity analyses were conducted to evaluate the impact of an individual dataset on the pooled results.

RESULTS

A total of eight randomized controlled trials, which involved 531 participants, met the inclusion criteria in this systematic appraisal and meta-analysis. Our meta-analysis showed that stem cell therapy improves left ventricular ejection fraction (SMD = 1.09, 95% CI 0.29 to 1.90, I2 = 92%) and reduces left ventricular end-systolic volume (SMD = - 0.36, 95% CI - 0.61 to - 0.10, I2 = 20.5%) and left ventricular end-diastolic chamber size (SMD = - 0.48, 95% CI - 0.89 to - 0.07, I2 = 64.8%) in patients with dilated cardiomyopathy. However, stem cell therapy has no effect on mortality (RR = 0.72, 95% CI 0.50 to 1.02, I2 = 30.2%) and 6-min-walk test (WMD = 51.52, 95% CI - 24.52 to 127.55, I2 = 94.8%).

CONCLUSIONS

This meta-analysis suggests that stem cell therapy improves left ventricular ejection fraction and reduces left ventricular end-systolic volume and left ventricular end-diastolic chamber size in patients with dilated cardiomyopathy. However, future well-designed large studies might be necessary to clarify the effect of stem cell therapy in patients with dilated cardiomyopathy.

TIME Trial: Effect of Timing of Stem Cell Delivery Following ST-Elevation Myocardial Infarction on the Recovery of Global and Regional Left Ventricular Function: Final 2-Year Analysis

RATIONALE

The TIME trial (Timing in Myocardial Infarction Evaluation) was the first cell therapy trial sufficiently powered to determine if timing of cell delivery after ST-segment-elevation myocardial infarction affects recovery of left ventricular (LV) function.

OBJECTIVE

To report the 2-year clinical and cardiac magnetic resonance imaging results and their modification by microvascular obstruction.

METHODS AND RESULTS

TIME was a randomized, double-blind, placebo-controlled trial comparing 150 million bone marrow mononuclear cells versus placebo in 120 patients with anterior ST-segment-elevation myocardial infarctions resulting in LV dysfunction. Primary end points included changes in global (LV ejection fraction) and regional (infarct and border zone) function. Secondary end points included changes in LV volumes, infarct size, and major adverse cardiac events. Here, we analyzed the continued trajectory of these measures out to 2 years and the influence of microvascular obstruction present at baseline on these long-term outcomes. At 2 years (n=85), LV ejection fraction was similar in the bone marrow mononuclear cells (48.7%) and placebo groups (51.6%) with no difference in regional LV function. Infarct size and LV mass decreased ≥30% in each group at 6 months and declined gradually to 2 years. LV volumes increased ≈10% at 6 months and remained stable to 2 years. Microvascular obstruction was present in 48 patients at baseline and was associated with significantly larger infarct size (56.5 versus 36.2 g), greater adverse LV remodeling, and marked reduction in LV ejection fraction recovery (0.2% versus 6.2%).

CONCLUSIONS

In one of the longest serial cardiac magnetic resonance imaging analyses of patients with large anterior ST-segment-elevation myocardial infarctions, bone marrow mononuclear cells administration did not improve recovery of LV function over 2 years. Microvascular obstruction was associated with reduced recovery of LV function, greater adverse LV remodeling, and more device implantations. The use of cardiac magnetic resonance imaging leads to greater dropout of patients over time because of device implantation in patients with more severe LV dysfunction resulting in overestimation of clinical stability of the cohort.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00684021.

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.

Meta-Analyses of Human Cell-Based Cardiac Regeneration Therapies: What Can Systematic Reviews Tell Us About Cell Therapies for Ischemic Heart Disease?

Controversies from basic science, discrepancies from clinical trials, and divergent results from meta-analyses have recently arisen in the field of cell therapies for cardiovascular repair and regeneration. Noticeably, there are almost as many systematic reviews and meta-analyses published as there are well-conducted clinical studies. But how do we disentangle the confusion they have raised? This article addresses why results obtained from systematic reviews and meta-analyses of human cell-based cardiac regeneration therapies are still valid to inform the design of future clinical trials. It also addresses how meta-analyses are not free from limitations and how important it is to assess the quality of the evidence and the quality of the systematic reviews and finally how stronger conclusions can be drawn when several pieces of evidence converge.

Harnessing the secretome of cardiac stem cells as therapy for ischemic heart disease

Adult stem cells continue to promise opportunities to repair damaged cardiac tissue. However, precisely how adult stem cells accomplish cardiac repair, especially after ischemic damage, remains controversial. It has been postulated that the clinical benefit of adult stem cells for cardiovascular disease results from the release of cytokines and growth factors by the transplanted cells. Studies in animal models of myocardial infarction have reported that such paracrine factors released from transplanted adult stem cells contribute to improved cardiac function by several processes. These include promoting neovascularization of damaged tissue, reducing inflammation, reducing fibrosis and scar formation, as well as protecting cardiomyocytes from apoptosis. In addition, these factors might also stimulate endogenous repair by activating cardiac stem cells. Interestingly, stem cells discovered to be resident in the heart appear to be functionally superior to extra-cardiac adult stem cells when transplanted for cardiac repair and regeneration. In this review, we discuss the therapeutic potential of cardiac stem cells and how the proteins secreted from these cells might be harnessed to promote repair and regeneration of damaged cardiac tissue. We also highlight how recent controversies about the efficacy of adult stem cells in clinical trials of ischemic heart disease have not dampened enthusiasm for the application of cardiac stem cells and their paracrine factors for cardiac repair: the latter have proved superior to the mesenchymal stem cells used in most clinical trials in the past, some of which appear to have been conducted with sub-optimal rigor.

Human Mesenchymal Stem Cell Delivery System Modulates Ischemic Cardiac Remodeling With an Increase of Coronary Artery Blood Flow

Ways for extending the longevity of stem cells are imperative to attain diverse expected therapeutic effects. Here, we constructed a three-dimentional (3D) scaffold system for human mesenchymal stem cell (hMSC) delivery. Intramyocardial injections of porous PEI1.8k blended with poly(lactic-co-glycolic acid) (PLGA) (PLGA/PEI1.8k) (PPP) microparticles by physical electrostatic conjugation and structural entrapment of hMSCs demonstrated enhanced functional and geometric improvements on post-infarct cardiac remodeling in rats. In the hMSC-loaded PPP delivery, increases of coronary artery blood flow rate and in vivo engraftment rate as well as time-dependent functional, geometric, and pathologic findings reversing post-infarct cardiac remodeling account for improved left ventricular (LV) systolic function up to the level of sham thoracotomy group. This study expands our understanding by proving that increase of coronary artery blood flow augmented functional recovery of hMSC-loaded PPP delivery system after myocardial infarction (MI).

Widespread Myocardial Delivery of Heart-Derived Stem Cells by Nonocclusive Triple-Vessel Intracoronary Infusion in Porcine Ischemic Cardiomyopathy: Superior Attenuation of Adverse Remodeling Documented by Magnetic Resonance Imaging and Histology

Single-vessel, intracoronary infusion of stem cells under stop-flow conditions has proven safe but achieves only limited myocardial coverage. Continuous flow intracoronary delivery to one or more coronary vessels may achieve broader coverage for treating cardiomyopathy, but has not been investigated. Using nonocclusive coronary guiding catheters, we infused allogeneic cardiosphere-derived cells (CDCs) either in a single vessel or sequentially in all three coronary arteries in porcine ischemic cardiomyopathy and used magnetic resonance imaging (MRI) to assess structural and physiological outcomes. Vehicle-infused animals served as controls. Single-vessel stop-flow and continuous-flow intracoronary infusion revealed equivalent effects on scar size and function. Sequential infusion into each of the three major coronary vessels under stop-flow or continuous-flow conditions revealed equal efficacy, but less elevation of necrotic biomarkers with continuous-flow delivery. In addition, multi-vessel delivery resulted in enhanced global and regional tissue function compared to a triple-vessel placebo-treated group. The functional benefits after global cell infusion were accompanied histologically by minimal inflammatory cellular infiltration, attenuated regional fibrosis and enhanced vessel density in the heart. Sequential multi-vessel non-occlusive delivery of CDCs is safe and provides enhanced preservation of left ventricular function and structure. The current findings provide preclinical validation of the delivery method currently undergoing clinical testing in the Dilated cardiomYopathy iNtervention With Allogeneic MyocardIally-regenerative Cells (DYNAMIC) trial of CDCs in heart failure patients.

An update on stem cell therapies for acute coronary syndrome

Well into the second decade since its conception, cell transplantation continues to undergo intensive evaluation for the treatment of myocardial infarction. At a mechanistic level, its objectives remain to replace lost cardiac cell mass with new functioning cardiomyocytes and vascular cells, thereby minimizing infarct size and scar formation, and improving clinical outcomes by preventing adverse left ventricular remodeling and recurrent ischemic events. Many different cell types, including pluripotent stem cells and various adult-derived progenitor cells, have been shown to have therapeutic potential in preclinical studies, while early phase human trial experience has provided divergent outcomes and fundamental lessons, emphasizing that there remain key issues to address and challenges to overcome before cell therapy can be applied to wider clinical practice. The purpose of this review is to provide a balanced update on recent seminal developments in this exciting field and look to the next important steps to ensure its forward progression.

Randomized, double-blind, phase I/II study of intravenous allogeneic mesenchymal stromal cells in acute myocardial infarction

BACKGROUND AIMS

Cell therapy is promising as an exploratory cardiovascular therapy. We have recently developed an investigational new drug named Stempeucel (bone marrow-derived allogeneic mesenchymal stromal cells) for patients with acute myocardial infarction (AMI) with ST-segment elevation. A phase I/II randomized, double-blind, single-dose study was conducted to assess the safety and efficacy of intravenous administration of Stempeucel versus placebo (multiple electrolytes injection).

METHODS

Twenty patients who had undergone percutaneous coronary intervention for AMI were randomly assigned (1:1) to receive intravenous Stempeucel or placebo and were followed for 2 years.

RESULTS

The number of treatment-emergent adverse events observed were 18 and 21 in the Stempeucel and placebo groups, respectively. None of the adverse events were related to Stempeucel according to the investigators and independent data safety monitoring board. There was no serious adverse event in the Stempeucel group and there were three serious adverse events in the placebo group, of which one had a fatal outcome. Ejection fraction determined by use of echocardiography showed improvement in both Stempeucel (43.06% to 47.80%) and placebo (43.44% to 45.33%) groups at 6 months (P = 0.26). Perfusion scores measured by use of single-photon emission tomography and infarct volume measured by use of magnetic resonance imaging showed no significant differences between the two groups at 6 months.

CONCLUSIONS

This study showed that Stempeucel was safe and well tolerated when administered intravenously in AMI patients 2 days after percutaneous coronary intervention. The optimal dose and route of administration needs further evaluation in larger clinical trials (http://clinicaltrials.gov/show/NCT00883727).

Cell therapy for human ischemic heart diseases: critical review and summary of the clinical experiences

A decade ago, stem or progenitor cells held the promise of tissue regeneration in human myocardium, with the expectation that these therapies could rescue ischemic myocyte damage, enhance vascular density and rebuild injured myocardium. The accumulated evidence in 2014 indicates, however, that the therapeutic success of these cells is modest and the tissue regeneration involves much more complex processes than cell-related biologics. As the quest for the ideal cell or combination of cells continues, alternative cell types, such as resident cardiac cells, adipose-derived or phenotypic modified stem or progenitor cells have also been applied, with the objective of increasing both the number and the retention of the reparative cells in the myocardium. Two main delivery routes (intracoronary and percutaneous intramyocardial) of stem cells are currently used preferably for patients with recent acute myocardial infarction or ischemic cardiomyopathy. Other delivery modes, such as surgical or intravenous via peripheral veins or coronary sinus have also been utilized with less success. Due to the difficult recruitment of patients within conceivable timeframe into cardiac regenerative trials, meta-analyses of human cardiac cell-based studies have tried to gather sufficient number of subjects to present a statistical compelling statement, reporting modest success with a mean increase of 0.9-6.1% in left ventricular global ejection fraction. Additionally, nearly half of the long-term studies reported the disappearance of the initial benefit of this treatment. Beside further extensive efforts to increase the efficacy of currently available methods, pre-clinical experiments using new techniques such as tissue engineering or exploiting paracrine effect hold promise to regenerate injured human cardiac tissue.

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

BACKGROUND

A promising approach to the treatment of chronic ischaemic heart disease (IHD) and heart failure is the use of stem cells. The last decade has seen a plethora of randomised controlled trials (RCTs) 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 cells (BMSC) as a treatment for chronic ischaemic heart disease (IHD) and heart failure.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, 2013, Issue 3), MEDLINE (from 1950), EMBASE (from 1974), CINAHL (from 1982) and the Transfusion Evidence Library (from 1980), together with ongoing trial databases, for relevant trials up to 31st March 2013.

SELECTION CRITERIA

Eligible studies included RCTs comparing autologous adult stem/progenitor cells with no autologous stem/progenitor cells in participants with chronic IHD and heart failure. Co-interventions such as primary angioplasty, surgery or administration of stem cell mobilising agents, were included where 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 fixed-effect meta-analyses. We evaluated heterogeneity using the I² statistic; we explored considerable heterogeneity (I² > 75%) using a random-effects model and subgroup analyses.

MAIN RESULTS

We include 23 RCTs involving 1255 participants in this review. Risk of bias was generally low, with the majority of studies reporting appropriate methods of randomisation and blinding, Autologous bone marrow stem cell treatment reduced the incidence of mortality (risk ratio (RR) 0.28, 95% confidence interval (CI) 0.14 to 0.53, P = 0.0001, 8 studies, 494 participants, low quality evidence) and rehospitalisation due to heart failure (RR 0.26, 95% CI 0.07 to 0.94, P = 0.04, 2 studies, 198 participants, low quality evidence) in the long term (≥12 months). The treatment had no clear effect on mortality (RR 0.68, 95% CI 0.32 to 1.41, P = 0.30, 21 studies, 1138 participants, low quality evidence) or rehospitalisation due to heart failure (RR 0.36, 95% CI 0.12 to 1.06, P = 0.06, 4 studies, 236 participants, low quality evidence) in the short term (< 12 months), which is compatible with benefit, no difference or harm. The treatment was also associated with a reduction in left ventricular end systolic volume (LVESV) (mean difference (MD) -14.64 ml, 95% CI -20.88 ml to -8.39 ml, P < 0.00001, 3 studies, 153 participants, moderate quality evidence) and stroke volume index (MD 6.52, 95% CI 1.51 to 11.54, P = 0.01, 2 studies, 62 participants, moderate quality evidence), and an improvement in left ventricular ejection fraction (LVEF) (MD 2.62%, 95% CI 0.50% to 4.73%, P = 0.02, 6 studies, 254 participants, moderate quality evidence), all at long-term follow-up. Overall, we observed a reduction in functional class (New York Heart Association (NYHA) class) in favour of BMSC treatment during short-term follow-up (MD -0.63, 95% CI -1.08 to -0.19, P = 0.005, 11 studies, 486 participants, moderate quality evidence) and long-term follow-up (MD -0.91, 95% CI -1.38 to -0.44, P = 0.0002, 4 studies, 196 participants, moderate quality evidence), as well as a difference in Canadian Cardiovascular Society score in favour of BMSC (MD -0.81, 95% CI -1.55 to -0.07, P = 0.03, 8 studies, 379 participants, moderate quality evidence). Of 19 trials in which adverse events were reported, adverse events relating to the BMSC treatment or procedure occurred in only four individuals. No long-term adverse events were reported. Subgroup analyses conducted for outcomes such as LVEF and NYHA class revealed that (i) route of administration, (ii) baseline LVEF, (iii) cell type, and (iv) clinical condition are important factors that may influence treatment effect.

AUTHORS' CONCLUSIONS

This systematic review and meta-analysis found moderate quality evidence that BMSC treatment improves LVEF. Unlike in trials where BMSC were administered following acute myocardial infarction (AMI), we found some evidence for a potential beneficial clinical effect in terms of mortality and performance status in the long term (after at least one year) in people who suffer from chronic IHD and heart failure, although the quality of evidence was low.

Intracoronary stem cell infusion after acute myocardial infarction: a meta-analysis and update on clinical trials

BACKGROUND

Several cell-based therapies for adjunctive treatment of acute myocardial infarction have been investigated in multiple clinical trials, but the benefits still remain controversial. This meta-analysis aims to evaluate the efficacy of bone marrow-derived mononuclear cell (BMMNC) therapy in patients with acute myocardial infarction, but also explores the effect of newer generations of stem cells.

METHODS AND RESULTS

A random-effects meta-analysis was performed on randomized controlled trials investigating the effects of stem cell therapy in patients with acute myocardial infarction that were published between January 2002 and September 2013. The defined end points were left ventricular (LV) ejection fraction, LV end-systolic and end-diastolic volumes, infarct size, and major adverse cardiac and cerebrovascular event rates. Also, several subgroup analyses were performed on BMMNC trials. Overall, combining the results of 22 randomized controlled trials (RCTs), LV ejection fraction increased by +2.10% (95% confidence interval [CI], 0.68-3.52; P=0.004) in the BMMNC group as compared with controls, evoked by a preservation of LV end-systolic volume (-4.05 mL; 95% CI, -6.91 to -1.18; P=0.006) and a reduction in infarct size (-2.69%; 95% CI, -4.83 to -0.56; P=0.01). However, there is no effect on cardiac function, volumes, or infarct size, when only RCTs (n=9) that used MRI-derived end points were analyzed. Moreover, no beneficial effect could be detected on major adverse cardiac and cerebrovascular event rates after BMMNC infusion after a median follow-up duration of 6 months.

CONCLUSIONS

Intracoronary infusion of BMMNC is safe, but does not enhance cardiac function on MRI-derived parameters, nor does it improve clinical outcome. New and possibly more potent stem cells are emerging in the field, but their clinical efficacy still needs to be defined in future trials.

Layer-specific radiofrequency ultrasound-based strain analysis in a porcine model of ischemic cardiomyopathy validated by a geometric model

Local layer-specific myocardial deformation after myocardial infarction (MI) has not been studied extensively although the sub-endocardium is more vulnerable to ischemia and interstitial fibrosis deposition. Radiofrequency (RF) ultrasound-based analysis could provide superior layer-specific radial strain estimation compared with clinically available deformation imaging techniques. In this study, we used RF-based myocardial deformation measurements to investigate layer-specific differences between healthy and damaged myocardium in a porcine model of chronic MI. RF data were acquired epicardially in healthy (n = 21) and infarcted (n = 5) regions of a porcine chronic MI model 12 wk post-MI. Radial and longitudinal strains were estimated in the sub-endocardial, mid-wall and sub-epicardial layers of the left ventricle. Collagen content was quantified in three layers of healthy and infarcted regions in five pigs. An analytical geometric model of the left ventricle was used to theoretically underpin the radial deformation estimated in different myocardial layers. Means ± standard errors of the peak radial and longitudinal strain estimates of the sub-endocardial, mid-wall and sub-epicardial layers of the healthy and infarcted tissue were: 82.7 ± 5.2% versus 39.9 ± 10.8% (p = 0.002), 63.6 ± 3.3% versus 38.8 ± 7.7% (p = 0.004) and 34.3 ± 3.0% versus 35.1 ± 5.2% (p = 0.9), respectively. The radial strain gradient between the sub-endocardium and the sub-epicardium had decreased 12 wk after MI, and histologic examination revealed the greatest increases in collagen in the sub-endocardial and mid-wall layers. Comparable normal peak radial strain values were found by geometric modeling when input values were derived from the in vivo measurements and literature. In conclusion, the estimated strain values are realistic and indicate that sub-endocardial radial strain in healthy tissue can amount to 80%. This high value can be explained by the cardiac geometry, as was illustrated by geometric modeling. After MI, strain values were decreased and collagen content was increased in the sub-endocardial and mid-wall layers. Layer-specific peak radial strain can be assessed by RF strain estimation and clearly differs between healthy and infarcted tissue. Although the relationship between tissue stiffness and tissue strain is not strictly local, this novel technique provides a valuable way to assess layer-specific regional cardiac function in a variety of myocardial diseases.

Assessing myocardial recovery following ST-segment elevation myocardial infarction: short- and long-term perspectives using cardiovascular magnetic resonance

Myocardial recovery after revascularization for ST-segment elevation myocardial infarction (STEMI) remains a significant diagnostic and, despite novel treatment strategies, a therapeutic challenge. Cardiovascular magnetic resonance (CMR) has emerged as a valuable clinical and research tool after acute STEMI. It represents the gold standard for functional and morphological evaluation of the left ventricle. Gadolinium-based perfusion and late-enhancement viability imaging has expanded our knowledge about the underlying pathologies of inadequate myocardial recovery. T2-weighted imaging of myocardial salvage after early reperfusion of the infarct-related artery underlines the effectiveness of current invasive treatment for STEMI. In the last decade, the number of publications on CMR after acute STEMI continued to rise, with no plateau in sight. Currently, CMR research is gathering robust prognostic data on standardized CMR protocols with the aim to substantially improve patient care and prognosis. Beyond established CMR protocols, more specific methods such as magnetic resonance relaxometry, myocardial tagging, 4D phase-contrast imaging and novel superparamagnetic contrast agents are emerging. This review will discuss the currently available data on the use of CMR after acute STEMI and take a brief look at developing new methods currently under investigation.

Human erythropoietin gene delivery for cardiac remodeling of myocardial infarction in rats

Considerable efforts have been made to exploit cardioprotective drugs and gene delivery systems for myocardial infarction (MI). The promising cardioprotective effects of recombinant human erythropoietin (rHuEPO) protein in animal experiments have not been consistently reproduced in clinical human trials of acute MI; however, the mechanisms underlying the inconsistent discrepancies are not yet fully understood. We hypothesized that the plasmid human erythropoietin gene (phEPO) delivered by our bioreducible polymer might produce cardioprotective effects on post-infarct cardiac remodeling. We demonstrated that intramyocardial delivery of phEPO by an arginine-grafted poly(disulfide amine) (ABP) polymer in infarcted rats preserves cardiac geometry and systolic function. The reduced infarct size of phEPO/ABP delivery was followed by decrease in fibrosis, protection from cardiomyocyte loss, and down-regulation of apoptotic activity. In addition, the increased angiogenesis and decreased myofibroblast density in the border zone of the infarct support the beneficial effects of phEPO/ABP administration. Furthermore, phEPO/ABP delivery induced prominent suppression on Ang II and TGF-β activity in all subdivisions of cardiac tissues except for the central zone of infarct. These results of phEPO gene therapy delivered by a bioreducible ABP polymer provide insight into the lack of phEPO gene therapy translation in the treatment of acute MI to human trials.

Assessment of Myocardial Contractile Function Using Global and Segmental Circumferential Strain following Intracoronary Stem Cell Infusion after Myocardial Infarction: MRI Feature Tracking Feasibility Study

Background. Magnetic resonance imaging (MRI) strain analysis is a sensitive method to assess myocardial function. Our objective was to define the feasibility of MRI circumferential strain (ε_cc) analysis in assessing subtle changes in myocardial function following stem cell therapy. Methods and Results. Patients in the Amorcyte Phase I trial were randomly assigned to treatment with either autologous bone-marrow-derived stem cells infused into the infarct-related artery 5 to 11 days following primary PCI or control. MRI studies were obtained at baseline, 3, and 6 months. ε_cc was measured in the short axis views at the base, mid and apical slices of the left ventricle (LV) for each patient (13 treatments and 10 controls). Mid-anterior LV ε_cc improved between baseline −18.5 ± 8.6 and 3 months −22.6 ± 7.0, P = 0.03. There were no significant changes in ε_cc at 3 months and 6 months compared to baseline for other segments. There was excellent intraobserver and interobserver agreement for basal and mid circumferential strain. Conclusion. MRI segmental strain analysis is feasible in assessment of regional myocardial function following cell therapy with excellent intra- and inter-observer variability's. Using this method, a modest interval change in segmental ε_cc was detected in treatment group.

Using biomaterials to improve the efficacy of cell therapy following acute myocardial infarction

Cardiovascular cell therapy has the potential to improve left ventricular (LV) function and alter the course of adverse LV remodeling following acute myocardial infarction (AMI). However, current therapy using autologous intracoronary bone marrow mononuclear cells results in only minimal recovery of LV function. A major impediment appears to be limited retention and engraftment of the transplanted cells, in part due to loss of the extracellular matrix (ECM) following AMI that can lead to apoptosis of the delivered cells through the mechanism of anoikis. Recent pre-clinical studies suggest that the delivery of ECM surrogates to the infarct zone following AMI significantly improves LV function through multiple mechanisms. The use of ECM surrogates in conjunction with stem cell administration may represent a new paradigm for cardiac repair following AMI. This review discusses the potential use of biologically based ECM surrogates in the clinical setting following STEMI.

Effect of intracoronary delivery of autologous bone marrow mononuclear cells 2 to 3 weeks following acute myocardial infarction on left ventricular function: the LateTIME randomized trial

CONTEXT

Clinical trial results suggest that intracoronary delivery of autologous bone marrow mononuclear cells (BMCs) may improve left ventricular (LV) function when administered within the first week following myocardial infarction (MI). However, because a substantial number of patients may not present for early cell delivery, the efficacy of autologous BMC delivery 2 to 3 weeks post-MI warrants investigation.

OBJECTIVE

To determine if intracoronary delivery of autologous BMCs improves global and regional LV function when delivered 2 to 3 weeks following first MI.

DESIGN, SETTING, AND PATIENTS

A randomized, double-blind, placebo-controlled trial (LateTIME) of the National Heart, Lung, and Blood Institute-sponsored Cardiovascular Cell Therapy Research Network of 87 patients with significant LV dysfunction (LV ejection fraction [LVEF] ≤45%) following successful primary percutaneous coronary intervention (PCI) between July 8, 2008, and February 28, 2011.

INTERVENTIONS

Intracoronary infusion of 150 × 10(6) autologous BMCs (total nucleated cells) or placebo (BMC:placebo, 2:1) was performed within 12 hours of bone marrow aspiration after local automated cell processing.

MAIN OUTCOME MEASURES

Changes in global (LVEF) and regional (wall motion) LV function in the infarct and border zone between baseline and 6 months, measured by cardiac magnetic resonance imaging. Secondary end points included changes in LV volumes and infarct size.

RESULTS

A total of 87 patients were randomized (mean [SD] age, 57 [11] years; 83% men). Harvesting, processing, and intracoronary delivery of BMCs in this setting was feasible. Change between baseline and 6 months in the BMC group vs placebo for mean LVEF (48.7% to 49.2% vs 45.3% to 48.8%; between-group mean difference, -3.00; 95% CI, -7.05 to 0.95), wall motion in the infarct zone (6.2 to 6.5 mm vs 4.9 to 5.9 mm; between-group mean difference, -0.70; 95% CI, -2.78 to 1.34), and wall motion in the border zone (16.0 to 16.6 mm vs 16.1 to 19.3 mm; between-group mean difference, -2.60; 95% CI, -6.03 to 0.77) were not statistically significant. No significant change in LV volumes and infarct volumes was observed; both groups decreased by a similar amount at 6 months vs baseline.

CONCLUSION

Among patients with MI and LV dysfunction following reperfusion with PCI, intracoronary infusion of autologous BMCs vs intracoronary placebo infusion, 2 to 3 weeks after PCI, did not improve global or regional function at 6 months.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00684060.