Promise of Blood- and Bone Marrow-Derived Stem Cell Transplantation for Functional Cardiac Repair

The effect of intracoronary infusion of bone marrow-derived mononuclear cells on all-cause mortality in acute myocardial infarction: the BAMI trial

Aims 

Bone marrow-derived mononuclear cell (BM-MNC) therapy may improve myocardial recovery in patients following acute myocardial infarction (AMI), though existing trial results are inconsistent.

Methods and results 

Originally an open-label, multicentre Phase III trial, BAMI was designed to demonstrate the safety and efficacy of intracoronary infusion of BM-MNCs in reducing the time to all-cause mortality in patients with reduced left ventricular ejection fraction (LVEF, ≤45%) after primary angioplasty (PPCI) for ST-elevation AMI. Unexpectedly low recruitment means the trial no longer qualifies as a hypothesis-testing trial, but is instead an observational study with no definitive conclusions possible from statistical analysis. In total, 375 patients were recruited: 185 patients were randomized to the treatment arm (intracoronary infusion of BM-MNCs 2–8 days after PPCI) and 190 patients to the control arm (optimal medical therapy). All-cause mortality at 2 years was 3.26% [6 deaths; 95% confidence interval (CI): 1.48–7.12%] in the BM-MNC group and 3.82% (7 deaths; 95% CI: 1.84–7.84%) in the control group. Five patients (2.7%, 95% CI: 1.0–5.9%) in the BM-MNC group and 15 patients (8.1%, CI : 4.7–12.5%) in the control group were hospitalized for heart failure during 2 years of follow-up. Neither adverse events nor serious adverse events differed between the two groups. There were no patients hospitalized for stroke in the control group and 4 (2.2%) patients hospitalized for stroke in the BM-MNC group.

Conclusions 

Although BAMI is the largest trial of autologous cell-based therapy in the treatment of AMI, unexpectedly low recruitment and event rates preclude any meaningful group comparisons and interpretation of the observed results.

G-CSF for Extensive STEMI

RATIONALE

In the exploratory Phase II STEM-AMI (Stem Cells Mobilization in Acute Myocardial Infarction) trial, we reported that early administration of G-CSF (granulocyte colony-stimulating factor), in patients with anterior ST-segment-elevation myocardial infarction and left ventricular (LV) dysfunction after successful percutaneous coronary intervention, had the potential to significantly attenuate LV adverse remodeling in the long-term.

OBJECTIVE

The STEM-AMI OUTCOME CMR (Stem Cells Mobilization in Acute Myocardial Infarction Outcome Cardiac Magnetic Resonance) Substudy was adequately powered to evaluate, in a population showing LV ejection fraction ≤45% after percutaneous coronary intervention for extensive ST-segment-elevation myocardial infarction, the effects of early administration of G-CSF in terms of LV remodeling and function, infarct size assessed by late gadolinium enhancement, and myocardial strain.

METHODS AND RESULTS

Within the Italian, multicenter, prospective, randomized, Phase III STEM-AMI OUTCOME trial, 161 ST-segment-elevation myocardial infarction patients were enrolled in the CMR Substudy and assigned to standard of care (SOC) plus G-CSF or SOC alone. In 119 patients (61 G-CSF and 58 SOC, respectively), CMR was available at baseline and 6-month follow-up. Paired imaging data were independently analyzed by 2 blinded experts in a core CMR lab. The 2 groups were similar for clinical characteristics, cardiovascular risk factors, and pharmacological treatment, except for a trend towards a larger infarct size and longer symptom-to-balloon time in G-CSF patients. ANCOVA showed that the improvement of LV ejection fraction from baseline to 6 months was 5.1% higher in G-CSF patients versus SOC (P=0.01); concurrently, there was a significant between-group difference of 6.7 mL/m² in the change of indexed LV end-systolic volume in favor of G-CSF group (P=0.02). Indexed late gadolinium enhancement significantly decreased in G-CSF group only (P=0.04). Moreover, over time improvement of global longitudinal strain was 2.4% higher in G-CSF patients versus SOC (P=0.04). Global circumferential strain significantly improved in G-CSF group only (P=0.006).

CONCLUSIONS

Early administration of G-CSF exerted a beneficial effect on top of SOC in patients with LV dysfunction after extensive ST-segment-elevation myocardial infarction in terms of global systolic function, adverse remodeling, scar size, and myocardial strain.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov. Unique identifier: NCT01969890.

Mineralocorticoid receptor deficiency improves the therapeutic effects of mesenchymal stem cells for myocardial infarction via enhanced cell survival

The poor survival of stem cells seriously limits their therapeutic efficacy for myocardial infarction (MI). Mineralocorticoid receptor (MR) activation plays an important role in the pathogenesis of multiple cardiovascular diseases. Here, we examined whether MR silencing in bone marrow derived mesenchymal stem cells (MSCs) could improve MSCs’ survival and enhance their cardioprotective effects in MI. MSCs from male Sprague‐Dawley rats were transfected with adenoviral small interfering RNA to silence MR (siRNA‐MR). MR silencing decreased hypoxia‐induced MSCs’ apoptosis, as demonstrated by Annexin V/7‐AAD staining. The mechanisms contributing to the beneficial effects of MR depletion were associated with inhibiting intracellular reactive oxygen species production and increased Bcl‐2/Bax ratio. In vivo study, 1 × 10⁶ of MSCs with or without siRNA‐MR were injected into rat hearts immediately after MI. Depletion of MR could improve the MSCs’ survival significantly in infarcted myocardium, associated with more cardiac function improvement and smaller infarct size. Capillary density were also significantly higher in siRNA group with increased expression of vascular endothelial growth factor. Our study demonstrated that silencing MR promoted MSCs’ survival and repair efficacy in ischaemic hearts. MR might be a potential target for enhancing the efficacy of cell therapy in ischaemic heart disease.

Mechanistic effects of mesenchymal and hematopoietic stem cells: New therapeutic targets in myocardial infarction

Myocardial infarction (MI) results in dysfunction and irreversible loss of cardiomyocytes and is of the most serious health threats today. Mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) have been explored as promising cell therapy in MI and regenerative therapy. Recently, reports investigated the potential therapeutic effects of MSCs or HSCs transplantation after MI in numerous experimental and clinical studies; however, their results are controversy and needs more explorations. The current review is an attempt to clarify the therapeutic potentials of MSCs and HSCs in MI therapy, as well as their possible effects; especially the paracrine one and the exosome-derived stem cell among animal models as well as clinical trials conducted within the last 10 years. In this context, various sources of MSCs and HSCs have been addressed in helping cardiac regeneration by either revitalizing the cardiac stem cells niche or revascularizing the arteries and veins of the heart. In addition, both MSCs and HSCs could produce paracrine mediators and growth factors which led to cardiomyocytes protection, angiogenesis, immunemodulation, antioxidants, anti-apoptotic, anti-inflammatory, antifibrotic, as well as increasing cardiac contractility. Recently, microRNAs (miRNAs), post-transcriptional regulators of gene expression, and long non-coding RNA (lncRNA), a miRNA sponge, are recent stem cell-derived mediators can be promising targets of MSCs and HSCs through their paracrine effects. Although MSCs and HSCs have achieved considerable achievements, however, some challenges still remain that need to be overcome in order to establish it as a successful technique. The present review clarified the mechanistic potentials of MSCs and HSCs especially paracrine effects involved in MI including human and animal studies and the challenges challenges regarding type, differentiation, route, and number of injections.

Mechanical and Chemical Predifferentiation of Mesenchymal Stem Cells Into Cardiomyocytes and Their Effectiveness on Acute Myocardial Infarction

Myocardial infarction is one of the leading causes of death all over the world. Mesenchymal stem cells (MSCs) transplantation has shown a promising potential to recovery of ischemic heart disease due to their capability in differentiating into cardiac cells. However, various investigations have been performed to optimize the efficacy of cardiac cell therapy in recent years. Here, we sought to interrogate the effect of autologous transplantation of undifferentiated and predifferentiated adipose and bone marrow-derived MSCs in a rabbit model of myocardial infarction and also to investigate whether cardiac function could be improved by mechanically induced MSCs via equiaxial cyclic strain. The two sources of MSCs were induced toward cardiomyocyte phenotype using mechanical loading and chemical factors and thereafter injected into the infarcted myocardium of 35 rabbits. Echocardiography and histopathology studies were used to evaluate cardiac function after 2 months. The results demonstrated significant scar size reduction and greater recovery of left ventricle ejection fraction after transplantation of predifferentiated cells, though the differences were not significant when comparing mechanically with chemically predifferentiated MSCs. Thus, although there was no significant improvement in infarcted myocardium between chemically and mechanically predifferentiated MSCs, mechanically induced cells are more preferred due to lack of any chemical intervention and cost reasonableness in their preparation method. Outcomes of this study may be useful for developing future therapeutic strategies, however long-term assessments are still required to further examine their effectiveness.

Mesenchymal stem cell therapy: A promising cell-based therapy for treatment of myocardial infarction

For decades, mesenchymal stem (MSCs) cells have been used for cardiovascular diseases as regenerative therapy. This review is an attempt to summarize the types of MSCs involved in myocardial infarction (MI) therapy, as well as its possible mechanisms effects, especially the paracrine one in MI focusing on the studies (human and animal) conducted within the last 10 years. Recently, reports showed that MSC therapy could have infarct-limiting effects after MI in both experimental and clinical trials. In this context, various types of MSCs can help cardiac regeneration by either revitalizing the cardiac stem cells or revascularizing the arteries and veins of the heart. Furthermore, MSCs could produce paracrine growth factors that increase the survival of nearby cardiomyocytes, as well as increase angiogenesis through recruitment of stem cell from bone marrow or inducing vessel growth from existing capillaries. Recent research suggests that the paracrine effects of MSCs could be mediated by extracellular vesicles including exosomes. Exosomal microRNAs (miRNAs) released by MSCs are promising therapeutic hotspot target for MI. This could be attributed to the role of miRNA in cardiac biology, including cardiac regeneration, stem cell differentiation, apoptosis, neovascularization, cardiac contractility and cardiac remodeling. Furthermore, gene-modified MSCs could be a recent promising therapy for MI to enhance the paracrine effects of MSCs, including better homing and effective cell targeted tissue regeneration. Although MSC therapy has achieved considerable attention and progress, there are critical challenges that remains to be overcome to achieve the most effective successful cell-based therapy in MI.

The effect of intracoronary infusion of bone marrow-derived mononuclear cells on all-cause mortality in acute myocardial infarction: rationale and design of the BAMI trial

Over the past 13 years bone marrow‐derived mononuclear cells (BM‐MNCs) have been widely investigated for clinical efficacy in patients following acute myocardial infarction (AMI). These early phase II trials have used various surrogate markers to judge efficacy and, although promising, the results have been inconsistent. The phase III BAMI trial has therefore been designed to demonstrate that intracoronary infusion of BM‐MNCs is safe and will significantly reduce the time to first occurrence of all‐cause death in patients with reduced left ventricular ejection fraction after successful reperfusion for ST‐elevation AMI (powered with the aim of detecting a 25% reduction in all‐cause mortality). This is a multinational, multicentre, randomized, open‐label, controlled, parallel‐group phase III study aiming to enrol approximately 3000 patients in 11 European countries with at least 17 sites. Eligible patients who have impaired left ventricular ejection (≤45%) following successful reperfusion for AMI will be randomized to treatment or control group in a 1:1 ratio. The treatment group will receive intracoronary infusion of BM‐MNCs 2–8 days after successful reperfusion for AMI added on top of optimal standard of care. The control group will receive optimal standard of care. The primary endpoint is time from randomization to all‐cause death. The BAMI trial is pivotal and the largest trial to date of BM‐MNCs in patients with impaired left ventricular function following AMI. The aim of the trial is to provide a definitive answer as to whether BM‐MNCs reduce all‐cause mortality in this group of patients.

An exploratory randomized control study of combination cytokine and adult autologous bone marrow progenitor cell administration in patients with ischaemic cardiomyopathy: the REGENERATE-IHD clinical trial

Aims

The effect of combined cytokine and cell therapy in ischaemic cardiomyopathy is unknown. Meta‐analyses suggest improved cardiac function with cell therapy. The optimal cell delivery route remains unclear. We investigated whether granulocyte colony‐stimulating factor (G‐CSF) alone or in combination with intracoronary (i.c.) or intramyocardial (i.m.) injection of autologous bone marrow‐derived cells (BMCs) improves cardiac function.

Methods and results

Ninety patients with symptomatic ischaemic cardiomyopathy and no further treatment options were enrolled in the randomized, placebo‐controlled, single‐centre REGENERATE‐IHD study. Randomization was to one of three arms: peripheral, i.c., or i.m. In each arm, patients were randomized to active treatment or placebo. All patients, apart from the peripheral placebo group (saline only) received G‐CSF for 5 days. The i.c. and i.m. arms received either BMCs or serum (placebo). The primary endpoint was change in LVEF at 1 year assessed by cardiac magnetic resonance imaging/computed tomography. The i.m. BMC group showed a significant improvement in LVEF of 4.99% (95% confidence interval 0.33–9.6%; P = 0.038) at 1 year. This group also showed a reduction in NYHA class at 1 year and NT‐proBNP at 6 months. No other group showed a significant change in LVEF. This finding is supported by post‐hoc between‐group comparisons.

Conclusion

We have shown that G‐CSF combined with autologous i.m. BMCs has a beneficial effect on cardiac function and symptoms. However, this result should be considered preliminary in support of a clinical benefit of i.m. stem cell infusion in ‘no option’ patients and needs further exploration in a larger study.

Preconditioning of mesenchymal stem cells with 2,4-dinitrophenol improves cardiac function in infarcted rats

AIMS

The aim of this study is to determine if preconditioning of bone marrow derived mesenchymal stem cells (MSCs) with 2,4-dinitrophenol (DNP) improves survival of transplanted stem cells in a rat model of myocardial infarction (MI), and to asses if this strategy has measurable impact on cardiac function.

MAIN METHODS

MSCs were preconditioned with DNP. In vitro cell adhesion assay and qRT-PCR were performed to analyze the expression of genes involved in cardiomyogenesis, cell adhesion and angiogenesis. MI was produced by occlusion of left anterior descending coronary artery. One million cells were transplanted by intramyocardial injection into the infarcted myocardium. Echocardiography was performed after two and four weeks of cellular transplantation. Hearts were harvested after four weeks and processed for histological analysis.

KEY FINDINGS

DNP treated MSCs adhered to the surface more (p<0.001) as compared to the normal MSCs. Gene expression levels were significantly upregulated in case of DNP treatment. The number of viable MSCs was more (p<0.001) in animals that received DNP treated MSCs, leading to significant improvement in cardiac function. Histological analysis revealed significant reduction in scar formation (p<0.001), maintenance of left ventricular wall thickness (p<0.001), and increased angiogenesis (p<0.01).

SIGNIFICANCE

The study evidenced for the first time that MSCs preconditioned with DNP improved cardiac function after transplantation. This can be attributed to improved survival, homing, adhesion, and cardiomyogenic and angiogenic differentiation of DNP treated MSCs in vivo.

Bendavia, a mitochondria-targeting peptide, improves postinfarction cardiac function, prevents adverse left ventricular remodeling, and restores mitochondria-related gene expression in rats

AB We evaluated the post-myocardial infarction (MI) therapeutic effects of Bendavia. Two hours after coronary artery ligation, rats were randomized to receive chronic Bendavia treatment (n = 28) or water (n = 26). Six weeks later, Bendavia significantly reduced scar circumference (39.7% +/- 2.2%) compared with water treatment (47.4% +/- 0.03%, P = 0.024) and reduced left ventricular (LV) volume by 8.9% (P = 0.019). LV fractional shortening was significantly improved by Bendavia (28.8% +/- 1.7%) compared with water treatment (23.8% +/- 1.8%, P = 0.047). LV ejection fraction was higher with Bendavia (55.3% +/- 1.4%) than water treatment (49.3% +/- 1.4%, P = 0.005). Apoptosis, within the MI border zone, was significantly less in the Bendavia group (32% +/- 3%, n = 12) compared with the water group (41% +/- 2%, n = 12; P = 0.029). Bendavia reversed mitochondrial function-related gene expression in the MI border, which was largely reduced in water-treated rats. Bendavia improved complex-I and -IV activity, and reduced production of reactive oxygen species and cytosolic cytochrome c level in the peri-infarcted region. Bendavia improved post-MI cardiac function, prevented infarct expansion and adverse LV remodeling, and restored mitochondria-related gene expression, complex-I and -IV activity, and reduced reactive oxygen species and cardiomyocyte apoptosis in the noninfarcted MI border.

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.

Long-term outcomes of complete versus incomplete revascularization for patients with multivessel coronary artery disease and left ventricular systolic dysfunction in drug-eluting stent era

We aimed to investigate that complete revascularization (CR) would be associated with a decreased mortality in patients with multivessel disease (MVD) and reduced left ventricular ejection fraction (LVEF). We enrolled a total of 263 patients with MVD and LVEF <50% who had undergone percutaneous coronary intervention with drug-eluting stent between March 2003 and December 2010. We compared major adverse cardiac and cerebrovascular accident (MACCE) including all-cause death, myocardial infarction, any revascularization, and cerebrovascular accident between CR and incomplete revascularization (IR). CR was achieved in 150 patients. During median follow-up of 40 months, MACCE occurred in 52 (34.7%) patients in the CR group versus 51 (45.1%) patients in the IR group (P=0.06). After a Cox regression model with inverse-probability-of-treatment-weighting using propensity score, the incidence of MACCE of the CR group were lower than those of the IR group (34.7% vs. 45.1%; adjusted hazard ratio [HR], 0.65; 95% confidence interval [CI], 0.44-0.95, P=0.03). The rate of all-cause death was significantly lower in patients with CR than in those with IR (adjusted HR, 0.48; 95% CI, 0.29-0.80, P<0.01). In conclusion, the achievement of CR with drug-eluting stent reduces long-term MACCE in patients with MVD and reduced LVEF.

Translating stem cell research to cardiac disease therapies: pitfalls and prospects for improvement

Over the past 2 decades, there have been numerous stem cell studies focused on cardiac diseases, ranging from proof-of-concept to phase 2 trials. This series of papers focuses on the legacy of these studies and the outlook for future treatment of cardiac diseases with stem cell therapies. The first section by Drs. Rosen and Myerburg is an independent review that analyzes the basic science and translational strategies supporting the rapid advance of stem cell technology to the clinic, the philosophies behind them, trial designs, and means for going forward that may impact favorably on progress. The second and third sections were collected as responses to the initial section of this review. The commentary by Drs. Francis and Cole discusses the review by Drs. Rosen and Myerburg and details how trial outcomes can be affected by noise, poor trial design (particularly the absence of blinding), and normal human tendencies toward optimism and denial. The final, independent paper by Dr. Marbán takes a different perspective concerning the potential for positive impact of stem cell research applied to heart disease and future prospects for its clinical application. (Compiled by the JACC editors).

Breakthroughs in cell therapy for heart disease: focus on cardiosphere-derived cells

The clinical reality of cell therapy for heart disease dates back to the 1990 s, when autologous skeletal myoblasts were first transplanted into failing hearts during open-chest surgery. Since then, the focus has shifted to bone marrow-derived cells and, more recently, cells extracted from the heart itself. Although progress has been nonlinear and often disheartening, the field has nevertheless made remarkable progress. Six major breakthroughs are notable: (1) the establishment of safety with intracoronary delivery; (2) the finding that therapeutic regeneration is possible; (3) the increase in allogeneic cell therapy; (4) the effect of increasing mechanistic insights; (5) glimmers of clinical efficacy; and (6) the progression to phase 2 and 3 studies. This article individually reviews these landmark developments in detail and concludes that the field has reached a new phase of maturity where the prospect of clinical impact is increasingly imminent.

The promise and challenges of cardiac stem cell therapy

After an extensive myocardial infarction, restoration of heart function depends on the ability of the heart to promote regeneration and prevent adverse ventricular remodeling. Preclinical research demonstrated that the transplantation of healthy stem cells restored heart function, but the stem cells obtained from older animals or patients were not as efficacious as those from younger individuals. In this paper, we review the successes and limitations discovered in preclinical studies and clinical trials examining cell therapy for damaged hearts. After the modest successes of the early clinical trials, research is now exploring the benefits of enhanced stem cell therapy. Cell based gene therapy markedly improves the angiogenesis achieved. Rejuvenating aged stems cells prior to transplantation restores the functional benefits attained. Transplanting healthy allogeneic stem cells from young donors into aged individuals can restore function if rejection can be prevented. Finally, modulating the cellular environment in aged individuals permits the full functional benefits of stem cell therapy to be realized. Significant challenges remain, but these approaches show promise that cell therapy may become routine therapy to improve functional recovery of older patients after an extensive myocardial infarction.

Long-term clinical outcome after intracoronary application of bone marrow-derived mononuclear cells for acute myocardial infarction: migratory capacity of administered cells determines event-free survival

BACKGROUND

In the REPAIR-AMI trial, intracoronary infusion of bone marrow-derived cells (BMCs) was associated with a significantly greater recovery of contractile function in patients with acute myocardial infarction (AMI) at 4-month follow-up than placebo infusion. The current analysis investigates clinical outcome and predictors of event-free survival at 5 years.

METHODS AND RESULTS

In the multicentre, placebo-controlled, double-blind REPAIR-AMI trial, 204 patients received intracoronary infusion of BMCs (n = 101) or placebo (n = 103) into the infarct vessel 3-7 days following successful percutaneous coronary intervention. Fifteen patients died in the placebo group compared with seven patients in the BMC group (P = 0.08). Nine placebo-treated patients and five BMC-treated patients required rehospitalization for chronic heart failure (P = 0.23). The combined endpoint cardiac/cardiovascular/unknown death or rehospitalisation for heart failure was more frequent in the placebo compared with the BMC group (18 vs. 10 events; P = 0.10). Univariate predictors of adverse outcomes were age, the CADILLAC risk score, aldosterone antagonist and diuretic treatment, changes in left ventricular ejection fraction, left ventricular end-systolic volume, and N-terminal pro-Brain Natriuretic Peptide (all P < 0.01) at 4 months in the entire cohort and in the placebo group. In contrast, in the BMC group, only the basal (P = 0.02) and the stromal cell-derived factor-1-induced (P = 0.05) migratory capacity of the administered BMC were associated with improved clinical outcome.

CONCLUSION

In patients of the REPAIR-AMI trial, established clinical parameters are associated with adverse outcome at 5 years exclusively in the placebo group, whereas the migratory capacity of the administered BMC determines event-free survival in the BMC-treated patients. These data disclose a potency-effect relationship between cell therapy and long-term outcome in patients with AMI.

Impact of intracoronary bone marrow cell therapy on left ventricular function in the setting of ST-segment elevation myocardial infarction: a collaborative meta-analysis

AIMS

The objective of the present analysis was to systematically examine the effect of intracoronary bone marrow cell (BMC) therapy on left ventricular (LV) function after ST-segment elevation myocardial infarction in various subgroups of patients by performing a collaborative meta-analysis of randomized controlled trials.

METHODS AND RESULTS

We identified all randomized controlled trials comparing intracoronary BMC infusion as treatment for ST-segment elevation myocardial infarction. We contacted the principal investigator for each participating trial to provide summary data with regard to different pre-specified subgroups [age, diabetes mellitus, time from symptoms to percutaneous coronary intervention, infarct-related artery, LV end-diastolic volume index (EDVI), LV ejection fraction (EF), infarct size, presence of microvascular obstruction, timing of cell infusion, and injected cell number] and three different endpoints [change in LVEF, LVEDVI, and LV end-systolic volume index (ESVI)]. Data from 16 studies were combined including 1641 patients (984 cell therapy, 657 controls). The absolute improvement in LVEF was greater among BMC-treated patients compared with controls: [2.55% increase, 95% confidence interval (CI) 1.83-3.26, P < 0.001]. Cell therapy significantly reduced LVEDVI and LVESVI (-3.17 mL/m², 95% CI: -4.86 to -1.47, P < 0.001; -2.60 mL/m², 95% CI -3.84 to -1.35, P < 0.001, respectively). Treatment benefit in terms of LVEF improvement was more pronounced in younger patients (age <55, 3.38%, 95% CI: 2.36-4.39) compared with older patients (age ≥ 55 years, 1.77%, 95% CI: 0.80-2.74, P = 0.03). This heterogeneity in treatment effect was also observed with respect to the reduction in LVEDVI and LVESVI. Moreover, patients with baseline LVEF <40% derived more benefit from intracoronary BMC therapy. LVEF improvement was 5.30%, 95% CI: 4.27-6.33 in patients with LVEF <40% compared with 1.45%, 95% CI: 0.60 to 2.31 in LVEF ≥ 40%, P < 0.001. No clear interaction was observed between other subgroups and outcomes.

CONCLUSION

Intracoronary BMC infusion is associated with improvement of LV function and remodelling in patients after ST-segment elevation myocardial infarction. Younger patients and patients with a more severely depressed LVEF at baseline derived most benefit from this adjunctive therapy.

Grafts enriched with subamnion-cord-lining mesenchymal stem cell angiogenic spheroids induce post-ischemic myocardial revascularization and preserve cardiac function in failing rat hearts

A crucial question in post-ischemic cell therapy refers to the ideal method of cell delivery to the heart. We hypothesized that epicardial implantation of subamnion-cord-lining mesenchymal stem cells (CL-MSC) angiogenic spheroids embedded within fibrin grafts (SASG) facilitates donor cell survival and enhances cardiac function in failing rat hearts. Furthermore, we compared the efficacy of this approach applied through two delivery methods. Spheroids made of 1.5×10(4) human CL-MSC coated with 2×10(3) human umbilical vein endothelial cells were self-assembled in hanging drops. SASG were constructed by embedding 150 spheroids in fibrin matrix. Except for untreated rats (MI, n=8), grafts were implanted 2 weeks after myocardial infarction upon confirmation of ensued heart failure through thoracotomy: SASG (n=8) and fibrin graft (FG, n=8); or video-assisted thoracoscopic surgery (VATS): SASG-VATS (n=8) and FG-VATS (n=7). In vivo CL-MSC survival was comparable between both SASG-treated groups throughout the study. SASG and SASG-VATS animals had decreased left ventricular end-diastolic pressure relative to untreated animals, and increased fractional shortening compared to MI and FG controls, 4 weeks after treatment. A 14.1% and 6.2% enhancement in ejection fraction from week 2 to 6 after injury was observed in SASG/SASG-VATS, paralleled by improvement in cardiac output. Treated hearts had smaller scar size, and more blood vessels than MI, while donor CL-MSC contributed to arteriogenesis within the graft and infarct areas. Taken together, our data suggest that SASG treatment has the potential to restore failing hearts by preserving cardiac function and inducing myocardial revascularization, while attenuating cardiac fibrosis. Furthermore, we introduce a method for minimally invasive in situ graft assembly.

Almanac 2012: Cell therapy in cardiovascular disease. The national society journals present selected research that has driven recent advances in clinical cardiology

The rapid translation from bench to bedside that has been seen in the application of regenerative medicine to cardiology has led to exciting new advances in our understanding of some of the fundamental mechanisms related to human biology. The first generation of cells used in phase I-II trials (mainly bone marrow mononuclear cells) are now entering phase III clinical trials with the goal of producing a cell based therapeutic that can change the outcome of cardiac disease. First generation cell therapy appears to have addressed safety concerns as well as showing 'activity' in numerous published meta-analyses. With the knowledge gained to date, the field is moving towards the next generation of cells-the 'engineered' cell-that have been developed to display a phenotype that will further enhance the myocardial repair/salvage process. This almanac review covers the latest basic research that may soon have application to humans as well as the results of the latest clinical trials.

Establishment and characterization of the reversibly immortalized mouse fetal heart progenitors

OBJECTIVE

Progenitor cell-based cardiomyocyte regeneration holds great promise of repairing an injured heart. Although cardiomyogenic differentiation has been reported for a variety of progenitor cell types, the biological factors that regulate effective cardiomyogenesis remain largely undefined. Primary cardiomyogenic progenitors (CPs) have a limited life span in culture, hampering the CPs' in vitro and in vivo studies. The objective of this study is to investigate if primary CPs isolated from fetal mouse heart can be reversibly immortalized with SV40 large T and maintain long-term cell proliferation without compromising cardiomyogenic differentiation potential.

METHODS

Primary cardiomyocytes were isolated from mouse E15.5 fetal heart, and immortalized retrovirally with the expression of SV40 large T antigen flanked with loxP sites. Expression of cardiomyogenic markers were determined by quantitative RT-PCR and immunofluorescence staining. The immortalization phenotype was reversed by using an adenovirus-mediated expression of the Cre reconbinase. Cardiomyogenic differentiation induced by retinoids or dexamethasone was assessed by an α-myosin heavy chain (MyHC) promoter-driven reporter.

RESULTS

We demonstrate that the CPs derived from mouse E15.5 fetal heart can be efficiently immortalized by SV40 T antigen. The conditionally immortalized CPs (iCP15 clones) exhibit an increased proliferative activity and are able to maintain long-term proliferation, which can be reversed by Cre recombinase. The iCP15 cells express cardiomyogenic markers and retain differentiation potential as they can undergo terminal differentiate into cardiomyctes under appropriate differentiation conditions although the iCP15 clones represent a large repertoire of CPs at various differentiation stages. The removal of SV40 large T increases the iCPs' differentiation potential. Thus, the iCPs not only maintain long-term cell proliferative activity but also retain cardiomyogenic differentiation potential.

CONCLUSIONS

Our results suggest that the reported reversible SV40 T antigen-mediated immortalization represents an efficient approach for establishing long-term culture of primary cardiomyogenic progenitors for basic and translational research.

Xenografted human amniotic fluid-derived stem cell as a cell source in therapeutic angiogenesis

BACKGROUND

Amniotic fluid-derived stem cells (AFSCs) are pluripotent with high renewal capacity and are not tumorigenic. We tested whether AFSCs can function as a cell source for therapeutic angiogenesis in a mouse hindlimb ischemia model.

METHODS

Using a defined culture medium for endothelial lineage cells (ECs), we differentiated human AFSCs into AFSC-derived ECs (AFSC-ECs) in vitro, as evidenced by expression of EC markers, and capillary-like network formation on Matrigel. We assessed the in vivo therapeutic angiogenesis efficacy of AFSC-ECs in an athymic nude mouse model of hindlimb ischemia. One day after high ligation of the external iliac artery in athymic nude mice, AFSC-ECs were intramuscularly injected into ischemic limbs.

RESULTS

The AFSC-ECs demonstrated endothelial cell characteristics in vitro. Four weeks later, AFSC-ECs transplantation significantly increased limb salvage (85%), compared to AFSCs (56%), human umbilical vein endothelial cells (HUVECs; 25%), or medium (0%). Laser Doppler perfusion analysis revealed that the ischemic/normal limb blood perfusion ratio significantly improved in the AFSC-EC group. AFSC-EC transplantation significantly increased capillary and arteriole densities as compared to AFSCs, HUVECs, and medium. Transplanted AFSC-ECs were incorporated into vessels in the ischemic region, as confirmed by immunofluorescent staining for human smooth muscle 22α or von Willebrand factor. Matrix metalloproteinase (MMP)-3 and MMP-9 expressions were significantly higher in AFSC-ECs. MMP-9 might activate angiogenesis by regulation of vascular endothelial growth factor.

CONCLUSIONS

Our study indicated that AFSC-EC transplantation improved limb salvage and blood perfusion by promoting neovascularization. Therefore, AFSC-ECs possess the potential for therapeutic angiogenesis.

[Cell therapy for ischemic heart disease]

Ischemic heart disease is the leading cause of death and heart failure worldwide. That is why it is important to develop new therapeutic modalities to decrease mortality and long-term complications in these patients. One of the main lines of research worldwide is myocardial regeneration, using progenitor cells in order to improve systolic and diastolic function in patients with ischemic heart disease, as well as to increase their survival. There have been carried out, with great enthusiasm worldwide, human and animal studies to define the usefulness of stem cells in the management of patients with ischemic heart disease. Today, regenerative therapy in ischemic heart disease is considered a novel therapeutic tool, with substantial theoretical benefits and few side effects. Here we present the scientific principles that support the use of this therapy, discuss the current clinical evidence available; and point out the controversial issues still not clarified on its use and usefulness in the short and long term.

Ephrin-B2-activated peripheral blood mononuclear cells from diabetic patients restore diabetes-induced impairment of postischemic neovascularization

We hypothesized that in vitro treatment of peripheral blood mononuclear cells (PB-MNCs) from diabetic patients with ephrin-B2/Fc (EFNB2) improves their proangiogenic therapeutic potential in diabetic ischemic experimental models. Diabetes was induced in nude athymic mice by streptozotocin injections. At 9 weeks after hyperglycemia, 10(5) PB-MNCs from diabetic patients, pretreated by EFNB2, were intravenously injected in diabetic mice with hindlimb ischemia. Two weeks later, the postischemic neovascularization was evaluated. The mechanisms involved were investigated by flow cytometry analysis and in vitro cell biological assays. Paw skin blood flow, angiographic score, and capillary density were significantly increased in ischemic leg of diabetic mice receiving EFNB2-activated diabetic PB-MNCs versus those receiving nontreated diabetic PB-MNCs. EFNB2 bound to PB-MNCs and increased the adhesion and transmigration of PB-MNCs. Finally, EFNB2-activated PB-MNCs raised the number of circulating vascular progenitor cells in diabetic nude mice and increased the ability of endogenous bone marrow MNCs to differentiate into cells with endothelial phenotype and enhanced their proangiogenic potential. Therefore, EFNB2 treatment of PB-MNCs abrogates the diabetes-induced stem/progenitor cell dysfunction and opens a new avenue for the clinical development of an innovative and accessible strategy in diabetic patients with critical ischemic diseases.

Cardiac stem cell therapy: stemness or commitment?

Cardiac stem cell therapy to promote engraftment of de novo beating cardiac muscle cells in cardiomyopathies could potentially improve clinical outcomes for many patients with congestive heart failure. Clinical trials carried out over the last decade for cardiac regeneration have revealed inadequacy of current approaches in cell therapy. Chief among them is the choice of stem cells to achieve the desired outcomes. Initial enthusiasm of adult bone marrow stems cells for myocyte regeneration has largely been relegated to paracrine-driven, donor cell-independent, endogenous cardiac repair. However, true functional restoration in heart failure is likely to require considerable myocyte replacement. In order to match stem cell application to various clinical scenarios, we review the necessity to preprime stem cells towards cardiac fate before myocardial transplantation and if these differentiated stem cells could confer added advantage over current choice of undifferentiated stem cells. We explore differentiation ability of various stem cells to cardiac progenitors/cardiomyocytes and compare their applicability in providing targeted recovery in light of current clinical challenges of cell therapy.

Cardiomyogenic differentiation-independent improvement of cardiac function by human cardiomyocyte progenitor cell injection in ischaemic mouse hearts

We previously showed that human cardiomyocyte progenitor cells (hCMPCs) injected after myocardial infarction (MI) had differentiated into cardiomyocytes in vivo 3 months after MI. Here, we investigated the short-term (2 weeks) effects of hCMPCs on the infarcted mouse myocardium. MI was induced in immunocompromised (NOD/scid) mice, immediately followed by intramyocardial injection of hCMPCs labelled with enhanced green fluorescent protein (hCMPC group) or vehicle only (control group). Sham-operated mice served as reference. Cardiac performance was measured 2 and 14 days after MI by magnetic resonance imaging at 9.4 T. Left ventricular (LV) pressure-volume measurements were performed at day 15 followed by extensive immunohistological analysis. Animals injected with hCMPCs demonstrated a higher LV ejection fraction, lower LV end-systolic volume and smaller relaxation time constant than control animals 14 days after MI. hCMPCs engrafted in the infarcted myocardium, did not differentiate into cardiomyocytes, but increased vascular density and proliferation rate in the infarcted and border zone area of the hCMPC group. Injected hCMPCs engraft into murine infarcted myocardium where they improve LV systolic function and attenuate the ventricular remodelling process 2 weeks after MI. Since no cardiac differentiation of hCMPCs was evident after 2 weeks, the observed beneficial effects were most likely mediated by paracrine factors, targeting amongst others vascular homeostasis. These results demonstrate that hCMPCs can be applied to repair infarcted myocardium without the need to undergo differentiation into cardiomyocytes.

Adult bone marrow cell therapy improves survival and induces long-term improvement in cardiac parameters: a systematic review and meta-analysis

BACKGROUND

Despite rapid clinical translation and widespread enthusiasm, the therapeutic benefits of adult bone marrow cell (BMC) transplantation in patients with ischemic heart disease continue to remain controversial. A synthesis of the available data is critical to appreciate and underscore the true impact of this promising approach.

METHODS AND RESULTS

A total of 50 studies (enrolling 2625 patients) identified by database searches through January 2012 were included. Weighted mean differences for changes in left ventricular (LV) ejection fraction, infarct size, LV end-systolic volume, and LV end-diastolic volume were estimated with random-effects meta-analysis. Compared with control subjects, BMC-treated patients exhibited greater LV ejection fraction (3.96%; 95% confidence interval, 2.90-5.02; P<0.00001) and smaller infarct size (-4.03%, 95% confidence interval, -5.47 to -2.59; P<0.00001), LV end-systolic volume (-8.91 mL; 95% confidence interval, -11.57 to -6.25; P<0.00001), and LV end-diastolic volume (-5.23 mL; 95% confidence interval, -7.60 to -2.86; P<0.0001). These benefits were noted regardless of the study design (randomized controlled study versus cohort study) and the type of ischemic heart disease (acute myocardial infarction versus chronic ischemic heart disease) and persisted during long-term follow-up. Importantly, all-cause mortality, cardiac mortality, and the incidence of recurrent myocardial infarction and stent thrombosis were significantly lower in BMC-treated patients compared with control subjects.

CONCLUSIONS

Transplantation of adult BMCs improves LV function, infarct size, and remodeling in patients with ischemic heart disease compared with standard therapy, and these benefits persist during long-term follow-up. BMC transplantation also reduces the incidence of death, recurrent myocardial infarction, and stent thrombosis in patients with ischemic heart disease.

Reconstitution of aged bone marrow with young cells repopulates cardiac-resident bone marrow-derived progenitor cells and prevents cardiac dysfunction after a myocardial infarction

AIMS

The study was designed to evaluate the mechanisms of cardiac regeneration after injury and to determine how to restore that capacity in aged individuals. The adult heart retains a small population of nascent cells that have myeloid, mesenchymal, and mesodermal capabilities, which play an essential role in the recovery of ventricular function after injury. In aged individuals, these cells are diminished and dysfunctional. We evaluated the derivation of some of these cardiac progenitors and a method to restore their number and function.

METHODS AND RESULTS

We first demonstrated that aged mice have fewer progenitors in both the bone marrow (BM) and the myocardium, which correlated with the extent of cardiac dysfunction after injury. Bone marrow chimerism established in aged mice with young BM donors restored both myocardial progenitors and cardiac function, but neither was restored with aged BM donors. Cardiac micro-chimerism in aged mice was established with young BM cells, which restored cardiac function after injury, even with old peripheral BM cells. The young cardiac-resident BM-derived progenitor cells in the aged myocardium persisted for at least a year, and after myocardial infarction they actively proliferated and enhanced cardiac repair through paracrine mechanisms.

CONCLUSION

Bone marrow reconstitution with young BM cells in aged recipients restored progenitors in both the BM and, most importantly, the myocardium. The number and function of cardiac-resident BM-derived progenitor cells in the aged myocardium prior to injury was the major determinant for successful recovery of cardiac function. The aged heart was rejuvenated with young BM cells.

Quantification of myocardial segmental function in acute and chronic ischemic heart disease and implications for cardiovascular cell therapy trials: a review from the NHLBI-Cardiovascular Cell Therapy Research Network

Global left ventricular (LV) ejection fraction (LVEF) has been used as a measure of improvement in LV function following cell therapy. Although the impact of cell therapy on LVEF in short- and long-term follow-up has been generally positive, there is concern that research evaluating regional therapeutics (e.g., cell or gene therapy) may require analysis of regional LV function localized to the site of intervention. Regional LV assessment is traditionally performed with qualitative or quantitative analysis of wall thickening within 16 myocardial segments, but advances in noninvasive imaging permit an increasingly more detailed and accurate evaluation of LV function. Wall-thickness measurements can now include evaluation of over 1,000 myocardial segments. In addition to higher resolution measures of wall thickening, automated assessments of myocardial segment deformation, such as strain imaging, exist. Strain imaging allows for direct evaluation of the mechanical properties that may improve following regional therapeutic intervention. Improvements in regional LV function may also be assessed by determining regional ejection fraction (EF). Regional EF offers the advantage of summarizing the end result of all of the complex deformations in the adjacent myocardial segments. Although regional EF and strain imaging, as compared with wall thickening, enhance detection of improvement in complex measures of regional myocardial function, it remains unclear whether such measures are better able to predict meaningful improvement in clinical outcomes.

Stem cells and regenerative medicine - future perspectives

Stem cell research has expanded at an exponential rate, but its therapeutic applications have progressed much more slowly. Currently, the research focuses on understanding embryonic, adult, and inducible pluripotent stem cells. Translation of adult stem cell research has established a definitive benefit that is greater than that of the current standard of care in the field of cardiovascular medicine. The future of stem cell research and therapy will continue to provide novel avenues of diagnostics, therapeutics, and tissue regeneration. Here we discuss a brief history of stem cell research as it transitioned from the 20th to the 21st century. We address lessons learned in the first decade of the new millennium that could help guide others to translate research into therapy across disciplines. Finally, we highlight future goals and challenges that must be overcome and offer some perspective on the bright future of stem cell research and therapy.

Stem cell mediated cardiovascular repair

Recent increase in the interest in stem and progenitor cells may be attributed to their behavioural characteristics. A consensus has been reached that embryonic or adult stem cells have therapeutic potential. As cardiovascular health issues are still the major culprits in many developed countries, stem and progenitor cell driven approaches may give the clinicians a new arsenal to tackle many significant health issues. However, stem and progenitor cell mediated cardiovascular regeneration can be achieved via complex and dynamic molecular mechanisms involving a variety of cells, growth factors, cytokines, and genes. Functional contributions of transplanted cells on target organs and their survival are still critical problems waiting to be resolved. Moreover, the regeneration of contracting myocardial tissue has controversial results in human trials. Thus, moderately favourable clinical results should be interpreted carefully. Determining the behavioural programs, genetic and transcriptional control of stem cells, mechanisms that determine cell fate, and functional characteristics are the primary targets. In addition, ensuring the long-term follow-up of cells with efficient imaging techniques in human clinical studies may provide a resurgence of the initial enthusiasm, which has faded over time. Here, we provide a brief historical perspective on stem cell driven cardiac regeneration and discuss cardiac and vascular repair in the context of translational science.

Bone marrow mononuclear cells and acute myocardial infarction

Stem cell transplantation is emerging as a potential therapy to treat heart diseases. Promising results from early animal studies led to an explosion of small, non-controlled clinical trials that created even further excitement by showing that stem cell transplantation improved left ventricular systolic function and enhanced remodelling. However, the specific mechanisms by which these cells improve heart function remain largely unknown. A large variety of cell types have been considered to possess the regenerative ability needed to repair the damaged heart. One of the most studied cell types is the bone marrow-derived mononuclear cells and these form the focus of this review. This review article aims to provide an overview of their use in the setting of acute myocardial infarction, the challenges it faces and the future of stem cell therapy in heart disease.

Progenitor cell mobilization and recruitment: SDF-1, CXCR4, α4-integrin, and c-kit

Progenitor cell retention and release are largely governed by the binding of stromal-cell-derived factor 1 (SDF-1) to CXC chemokine receptor 4 (CXCR4) and by α4-integrin signaling. Both of these pathways are dependent on c-kit activity: the mobilization of progenitor cells in response to either CXCR4 antagonism or α4-integrin blockade is impaired by the loss of c-kit kinase activity; and c-kit-kinase inactivation blocks the retention of CXCR4-positive progenitor cells in the bone marrow. SDF-1/CXCR4 and α4-integrin signaling are also crucial for the retention of progenitor cells in the ischemic region, which may explain, at least in part, why clinical trials of progenitor cell therapy have failed to display the efficacy observed in preclinical investigations. The lack of effectiveness is often attributed to poor retention of the transplanted cells and, to date, most of the trial protocols have mobilized cells with injections of granulocyte colony-stimulating factor (G-CSF), which activates extracellular proteases that irreversibly cleave cell-surface adhesion molecules, including α4-integrin and CXCR4. Thus, the retention of G-CSF-mobilized cells in the ischemic region may be impaired, and the mobilization of agents that reversibly disrupt SDF-1/CXCR4 binding, such as AMD3100, may improve patient response. Efforts to supplement SDF-1 levels in the ischemic region may also improve progenitor cell recruitment and the effectiveness of stem cell therapy.

Mesenchymal stem cells for cardiovascular regeneration

Despite recent studies suggesting that the heart has instrinsic mechanisms of self-regeneration following myocardial infarction, it cannot regenerate itself to an optimal level. Mesenchymal stem cells (MSCs) are currently being investigated for regeneration of mesenchyme-derived tissues, such as bone, cartilage and tendon. In vitro evidence suggests that MSCs can also differentiate into cardiomyogenic and vasculogenic lineages, offering another cell source for cardiovascular regeneration. In vivo, MSCs may contribute to the re-growth and protection of vasculature and cardiomyocytes, mediated by paracrine actions, and/or persist within the myocardium in a differentiated state; although proof of cardiomyocytic phenotype and functional integration remains elusive. Herein, we review the evidence of MSCs as a cell source for cardiovascular regeneration, as well as their limitations that may prevent them from being effectively used in the clinic.

Stem cell therapy in cardiology

Cell therapy provides one of the most important solutions to the unmet need for new treatments in cardiovascular disease. This area of research has undergone a rapid translation into humans, with the bone marrow mononuclear cell predominating as the cell type with most clinical data. Confidence in the use of this cell type has grown over the last year with the publication of the results of Phase II/III trials in the setting of acute and chronic ischemia confirming safety and biological activity. A large pan-European outcome study is now being planned, which will definitely address the therapeutic potential of this cell type with respect to mortality. Data for the use of selected populations of cells, bioengineered cells/scaffolds and the resident stem cell population continue to grow, with some of these approaches reported in Phase I clinical trials with promising results. There is still some way to go and these more complicated cell therapy products will need to undergo the same scrutiny that has been applied to the results of the bone marrow mononuclear cell trials to date. Ultimately, these engineered biologics will have to justify the costs involved in producing them by significantly improving on results obtained by using bone marrow mononuclear cells for cardiovascular repair. The continued success of this area of translational medicine relies on the ongoing partnership between clinicians and scientists, who have thus far demonstrated a determined and pragmatic approach to solving some of the complexities of moving from bench to bedside. The next 5-years will see this partnership reach fruition as the long-awaited results of outcome studies of cell therapy in the treatment of cardiovascular disease are published.

Bone marrow-derived cell transplantation therapy for myocardial infarction: lessons learned and future questions

Over the last decade, many investigators have utilized bone marrow-derived cells for cell transplantation therapy in animal studies and in patients with acute myocardial infarction and chronic heart failure. In those experimental and clinical studies, various doses and types of bone marrow-derived cells have been transplanted to the injured myocardium using a variety of approaches, such as intracoronary infusion or catheter-based direct endomyocardial injection, and at different time points after successful coronary reperfusion. The reported treatment effects are variable, which may be related to differences in cell type and quantity of transplanted cells, timing and approach of cell transplantation and patient selection. In this review, we summarize and discuss the controversies and questions related to the clinical use of bone marrow-derived cells.

The stuttering progress of cell therapy for heart disease

Stem cell therapy has emerged as a potential therapeutic strategy for myocardial infarction (MI). Multiple cell types used to regenerate the injured heart have been tested in clinical trials. The results of studies of skeletal myoblasts (SKMs) have been resoundingly negative, and the bone marrow-derived-cell experience leaves much to be desired. A number of lessons arise from the large-scale bone marrow-derived-cell trials: (i) efficacy has been inconsistent and, overall, modest; however, unexpectedly meaningful benefits on clinical end points have been reported; (ii) cardiac engraftment of cells is disappointingly low, and delivery methods need to be optimized and combined with strategies to boost retention; (iii) the cardiomyogenic potential of bone marrow cells is low; however, functional benefit can be achieved through indirect pathways; and (iv) autologous cell therapy has severe limitations; highly standardized allogeneic cell products are attractive. Given the spotty trajectory of cell therapy to date, a more systematic approach to product development and preclinical optimization will facilitate more effective clinical translation.

Perfusion defect size predicts engraftment but not early retention of intra-myocardially injected cardiosphere-derived cells after acute myocardial infarction

Therapeutic cell retention and engraftment are critical for myocardial regeneration. Underlying mechanisms, including the role of tissue perfusion, are not well understood. In Wistar Kyoto rats, syngeneic cardiosphere-derived cells (CDCs) were injected intramyocardially, after experimental myocardial infarction. CDCs were labeled with [¹⁸F]-FDG (n = 7), for quantification of 1-h retention, or with sodium-iodide-symporter gene (NIS; n = 8), for detection of 24-h engraftment by reporter imaging. Perfusion was imaged simultaneously. Infarct size was 37 ± 9 and 38 ± 9% of LV in FDG and NIS groups. Cell signal was located in the infarct border zone in all animals. No significant relationship was observed between infarct size and 1-h CDC retention (r = −0.65; P = 0.11). However, infarct size correlated significantly with 24-h engraftment (r = 0.75; P = 0.03). Residual perfusion at the injection site was not related to cell retention/engraftment. Larger infarcts are associated with improved CDC engraftment. This observation encourages further investigation of microenvironmental conditions after ischemic damage and their role in therapeutic cell survival.