Autologous stem cell transplantation in acute myocardial infarction: The ASTAMI randomized controlled trial. Intracoronary transplantation of autologous mononuclear bone marrow cells, study design and safety aspects

Bone marrow cell therapy after acute myocardial infarction: the HEBE trial in perspective, first results

During the last decennium, the role of bone marrow mononuclear cells (BMMC) has been underscored in the healing process after acute myocardial infarction (AMI). Although these cells improve left ventricular recovery after AMI in experimental studies, results from large-scale randomised trials investigating BMMC therapy in patients with AMI have shown contradictory results. To address this issue the HEBE study was designed, a multicentre, randomised trial, evaluating the effects of intracoronary infusion of BMMCs and the effects of intracoronary infusion of peripheral blood mononuclear cells after primary percutaneous coronary intervention. The primary endpoint of the HEBE trial is the change in regional myocardial function in dysfunctional segments at four months relative to baseline, based on segmental analysis as measured by magnetic resonance imaging. The results from the HEBE trial will provide detailed information about the effects of intracoronary BMMC therapy on post-infarct left ventricular recovery. In addition, further analysis of the data and material obtained may provide important mechanistic insights into the contribution of BMMCs to natural recovery from AMI as well as the response to cell therapy. This may significantly contribute to the development of improved cell-based therapies, aiming at optimising post-infarct recovery and preventing heart failure. (Neth Heart J 2008;16:436-9.).

Effects of intracoronary autologous bone marrow cells on left ventricular function in acute myocardial infarction: a systematic review and meta-analysis for randomized controlled trials

BACKGROUND

Experimental and clinical studies have suggested that intracoronary infusion of bone marrow-derived stem/progenitor cells (BMC) may improve left ventricular function after acute myocardial infarction (AMI). We conducted a systematic review and meta-analysis to investigate the efficacy and safety of BMC therapy on global left ventricular function in AMI.

METHODS

A systematic literature search of MEDLINE, Cochrane Controlled Trials Register, EMBASE, Science Citation Index, and PUBMED from their inception to March 2007 was conducted using specific search terms. Reference lists of papers and reviews on the topic were further searched. Finally, six randomized controlled trials that comprised 517 patients were eligible for further meta-analysis. We used a standardized protocol to extract information on the included studies.

RESULTS

Compared with the control groups, BMC therapy produced a slight improvement of the follow-up left ventricular ejection fraction (LVEF) [2.53%, 95% confidence interval (CI): 0.67-4.39, P=0.008] between 3 and 6 months. Similarly, BMC therapy also significantly improved the LVEF change from baseline to follow-up [2.88%, 95%CI: 1.69-4.08, P=0.000] compared to control groups, and the heterogeneity across the studies with regards to the follow-up LVEF (P=0.696) and the LVEF change (P=0.179). Major adverse cardiovascular events, including ventricular arrhythmia, rehospitalization for heart failure, and the composite of other cardiovascular events (cardiac death, recurrent myocardial infarction, infarct-vessel revascularization procedure, and stroke), were not significantly different between BMC therapy and control groups [relative risk (RR): 1.19, 95%CI: 0.68-2.06; RR: 1.79, 95%CI: 0.62-5.17; and RR: 1.05, 95%CI: 0.81-1.35, respectively].

CONCLUSION

On the basis of present evidence, intracoronary BMC infusion in patients with AMI seems to be safe and associated with slight improvement of the left ventricular ejection fraction at 3-6 months' follow-up.

Stem cell treatment for acute myocardial infarction

BACKGROUND

Stem cell therapy offers a promising approach to the regeneration of damaged vascular and cardiac tissue after myocardial infarction (MI). This has resulted in multiple randomised controlled trials (RCTs) worldwide.

OBJECTIVES

To critically evaluate evidence from RCTs on the effectiveness of adult bone marrow-derived stem cells (BMSC) to treat acute MI.

SEARCH STRATEGY

MEDLINE (1950 to August 2007), EMBASE (1974 to August 2007), The Cochrane Library (Issue 3 2007), and CINAHL (1982 to August 2007) were searched. In addition LILACS, KOREAMED, INMED, Current Controlled Trials Register, the UK National Research Register and other handsearching was undertaken to August 2007.

SELECTION CRITERIA

RCTs comparing autologous stem/progenitor cells with no autologous stem/progenitor cells in patients diagnosed with acute myocardial infarction (AMI) were eligible.

DATA COLLECTION AND ANALYSIS

Two reviewers independently screened all references, assessed trial quality and extracted data. Meta-analyses using a random-effects model were conducted and heterogeneity was explored using sub-group analyses.

MAIN RESULTS

Thirteen RCTs (811 participants) were included. There were insufficient events on clinical outcomes like mortality to draw clear conclusions. Stem/progenitor cell treatment does not appear to be associated with an increase in adverse events but again the data do not allow clear conclusions. Left ventricular ejection fraction (LVEF) was the outcome with most results and there was marked heterogeneity between trials. There was however a consistent pattern indicating that BMSC treatment generally improves short-term LVEF, with similar trends for left ventricular end systolic and end diastolic volumes (LVESV and LVEDV), infarct size or cardiac wall motion. There was a positive correlation between cell dose infused and the effect on LVEF measured by magnetic resonance imaging.

AUTHORS' CONCLUSIONS

The results of this systematic review suggest that there is little evidence to assess the clinical effects of this treatment. Larger trials using optimal dosing and more reliable, patient-centred outcomes are required. Several trials are ongoing but is unclear whether these will overcome the limitations of the current evidence base.

Biological approaches to ischemic tissue repair: gene- and cell-based strategies

Gene therapy is a potential therapeutic strategy for treatment of ischemic vascular diseases; however, the clinical application of gene therapy has met some anticipated challenges. Recent randomized, controlled trials suggest that patients with cardiovascular disease may also benefit from cell-based therapies, and the optimal treatment regimen may combine both approaches to take advantage of potential synergy between the underlying therapeutic mechanisms. This review discusses recent research into both gene and cell therapy and considers the potential application of a combined treatment approach for cardiovascular and cerebrovascular ischemic diseases.

Concentration of bone marrow total nucleated cells by a point-of-care device provides a high yield and preserves their functional activity

Stem and progenitor cell therapy is a novel strategy to enhance cardiovascular regeneration. Cell isolation procedures are crucial for the functional activity of the administered cellular product. Therefore, new isolation techniques have to be evaluated in comparison to the Ficoll isolation procedure as the current gold standard. Here we prospectively evaluated a novel point-of-care device (Harvest BMAC System) for the concentration of bone marrow total nucleated cells (TNC) in comparison to the Ficoll isolation procedure for bone marrow mononucleated cells (MNC). The yield in total numbers of TNC was 2.4-fold higher for Harvest compared to Ficoll. Despite significant differences in their cellular compositions, the colony-forming capacity was similar for both products. Intriguingly, the migratory capacity was significantly higher for the Harvest TNC (164 +/- 66%; p = 0.007). In a mouse model of hind limb ischemia, the increase in blood flow recovery was similar between Harvest BM-TNC and Ficoll BM-MNC (0.53 +/- 0.20 vs. 0.46 +/- 0.15; p = 0.88). However, adjustment of the injected cell number based on the higher yield of Harvest TNC resulted in a significant better recovery (0.64 +/- 0.16 vs. 0.46 +/- 0.15; p = 0.003). Cells concentrated by the Harvest point-of-care device show similar or greater functional activity compared to Ficoll isolation. However, the greater yield of cells and the wider range of cell types for the Harvest device may translate into an even greater therapeutic effect.

Separation of adult bone marrow mononuclear cells using the automated closed separation system Sepax

BACKGROUND

The Düsseldorf-based cardiologist Professor Strauer was the first to present a therapeutic concept for the repair of acute infarcted myocardium in 2001: the autologous intracoronary transplantation of unfractionated human bone marrow (BM) mononuclear cells (MNC). The Division of Cardiology, Pneumology and Angiology, University of Duesseldorf Medical School, Duesseldorf, Germany, was also able to show the regenerative potential of BM stem cell transplantation in patients with chronic heart disease (CHD) and peripheral arterial disease (PAD). In the mean time, several clinical trials have been set up worldwide, predominantly by using MNC isolated manually from BM aspirates via density-gradient centrifugation; 374 patients have been treated here with unselected BM MNC since 2001. Altogether 217 BM aspirates have been processed manually. In order to maintain the high standards required for cellular therapeutics, the Sepax cell-separation system was implemented into routine BM processing in 2006. The closed Sepax system provides a reproducible MNC isolation method, and 157 BM samples have been processed with the Sepax device. The results of manual MNC isolation were compared with the Sepax-mediated MNC isolation.

METHODS

The manual Ficoll separation method was compared with the Sepax density gradient-based separation (DGBS) protocol using Ficoll with the kit CS-900 and the Sepax S-100 main processing unit from Biosafe.

RESULTS

Nucleated cell and MNC recovery were significantly higher after Sepax processing (P<0.0001) whereas no significance was found for red blood cell depletion.

DISCUSSION

The Sepax cell-separation system is a time-saving method providing clinical-grade MNC isolated automatically from human BM by Ficoll density centrifugation.

Stem cell therapy: MRI guidance and monitoring

With the recent advances in magnetic resonance (MR) labeling of cellular therapeutics, it is natural that interventional MRI techniques for targeting would be developed. This review provides an overview of the current methods of stem cell labeling and the challenges that are created with respect to interventional MRI administration. In particular, stem cell therapies will require specialized, MR-compatible devices as well as integration of graphical user interfaces with pulse sequences designed for interactive, real-time delivery in many organs. Specific applications that are being developed will be reviewed as well as strategies for future translation to the clinical realm.

Stem cells for cardiovascular repair - the challenges of the aging heart

The discovery of extracardiac progenitor cells and resident cardiac stem cells in recent years has led to a great deal of interest in the development of therapeutic strategies that target these endogenous cell sources for promotion of cardiovascular repair mechanisms in the diseased heart. Cardiovascular risk increases with age and among many factors, the age-associated decline in cardiac and vascular regenerative capacity may contribute to the progressive deterioration of cardiovascular health. Thus, understanding the mechanisms which underlie the dysregulation of cardiac stem and progenitor cells may lead to the identification of novel targets and approaches to reverse this decline. In this review, we outline the current knowledge about cardiac stem and progenitor cells, their contribution to cardiovascular regenerative processes and factors that may affect their decreased function in aging individuals. Moreover, we describe the therapeutic strategies that are currently being tested in clinical trials as well as potential new avenues of investigation for the future.

Endothelial progenitor cell therapy for the treatment of coronary disease, acute MI, and pulmonary arterial hypertension: current perspectives

Since their identification in 1997, bone marrow derived endothelial progenitor cells (EPCs) have been studied for their role in the endogenous maintenance and repair of endothelium and their potential regenerative capacity beyond the endothelium. In particular, EPCs have been tested in cell therapy approaches with the aim of developing novel therapies for conditions currently lacking effective treatment options. In this review, we discuss the scientific background and clinical experience using EPC delivery or mobilization for the treatment of post-angioplasty restenosis, acute myocardial infarction and pulmonary arterial hypertension. Although these approaches are safe, efficacy has yet to be proven in large randomized clinical trials. Unfortunately, the biology of EPCs is still poorly understood. The success of future clinical trials depends on a better understanding of EPC biology and intelligent design.

Evaluation of acute coronary syndromes by cardiac magnetic resonance imaging

The use of cardiovascular magnetic resonance (CMR) imaging for the evaluation of patients with acute chest pain and acute coronary syndromes has great potential. The strength of CMR relies on its ability to provide information on anatomy, physiology, and function in a single scanning session in a noninvasive manner without the need for iodinated contrast, radiation, or the need to undergo invasive procedures. Specifically, with regard to imaging patients with acute chest pain and/or myocardial infarction (MI), CMR has the ability to qualitatively and quantitatively evaluate global and regional right and left ventricular systolic functions, myocardial edema, myocardial perfusion, and myocardial infarct size and transmurality/viability. This review will focus on CMR imaging for the following applications: (1) imaging for the evaluation of ventricular function and infarct size in patients with acute chest pain and/or acute MI, (2) for triage and prognosis of patients presenting to the emergency department with acute chest pain, (3) for evaluating patients after sustaining an acute MI, and (4) for stem cell research.

Inflammatory responses after intracoronary injection of autologous mononuclear bone marrow cells in patients with acute myocardial infarction

BACKGROUND

Inflammatory responses after intracoronary injection of autologous mononuclear bone marrow cells (mBMC) are not clarified. The aim of this study was to investigate the influence of intracoronary injection of mBMC on inflammatory mediators in patients with acute myocardial infarction (AMI).

METHODS

Patients with AMI in the ASTAMI trial (N = 100) treated with percutaneous coronary intervention were randomized to intracoronary injections of mBMC or control. Fasting blood samples were drawn the day before stem cell transplantation (baseline 4-5 days after AMI) and 1 day, 3 days, 2 to 3 weeks, and 3 months after transplantation for determination of circulating levels of selected inflammatory markers and mRNA levels in whole blood samples.

RESULTS

From baseline to day 1, the levels of interleukin 6 and the expression of tumor necrosis factor alpha mRNA increased significantly in the mBMC group compared to the control group (P < .05 for both). The decrease in interleukin 6 levels from baseline to 2 to 3 weeks in the mBMC group was less pronounced than in the controls (P < .05), as was also the decrease in C-reactive protein levels from baseline to day 1 and day 3 in the mBMC group (P < .05). However, from baseline to 3 months the levels of tumor necrosis factor alpha and monocyte chemoattractant protein 1 increased less in the mBMC group (P < .05 for both).

CONCLUSION

Intracoronary injection of mBMC in patients with AMI induces a marked short-term inflammatory response, but a slightly reduced inflammation after 3 months which may have implications for the timing of stem cell transplantation in AMI.

Cell-based therapy of myocardial infarction

Cell-based therapy is a promising option for treatment of ischemic diseases. Several cell types have experimentally been shown to increase the functional recovery of the heart after ischemia by physically forming new blood vessels, differentiating to cardiac myocytes and--additionally or alternatively--by providing proangiogenic and antiapoptotic factors promoting tissue repair in a paracrine manner. Clinical studies preferentially used adult bone marrow-derived cells for the treatment of patients with acute myocardial infarction. Most of the studies suggested that cell therapy reduced the infarct size and improved cardiac contractile function. However, cell therapy is in its early stages, and various questions remain. For example, the identification of those patients who benefit most from cell therapy, the optimal cell type and number for patient with acute and chronic diseases, the best time and way of cell delivery, and the mechanisms of action by which cells exhibit beneficial effects, need to be further evaluated. Although no major safety concerns were raised during the initial clinical trials, several potential side effects need to be carefully monitored. The present review article summarizes the results of the clinical studies and discusses the open issues.

Use of stem cells for the treatment of multiple sclerosis

The reported evidence of neurodegeneration in multiple sclerosis (MS) may explain the lack of efficacy of the currently used immunomodulating modalities and the irreversible axonal damage, which results in accumulating disability. To date, efforts for neuroprotective treatments have not been successful in clinical studies in other CNS diseases. Therefore, for MS, the use of stem cells may provide a logical solution, since these cells can migrate locally into the areas of white-matter lesions (plaques) and have the potential to support local neurogenesis and rebuilding of the affected myelin. This is achieved both by support of the resident CNS stem cell repertoire and by differentiation of the transplanted cells into neurons and myelin-producing cells (oligodendrocytes). Stem cells were also shown to possess immunomodulating properties, inducing systemic and local suppression of the myelin-targeting autoimmune lymphocytes. Several types of stem cells (embryonic and adult) have been described and extensively studied in animal models of CNS diseases and the various models of MS (experimental autoimmune encephalomyelitis [EAE]). In this review, we summarize the experience with the use of different types of stem cells in CNS disease models, focusing on the models of EAE and describe the advantages and disadvantages of each stem cell type for future clinical applications in MS.

Exercise capacity and quality of life after intracoronary injection of autologous mononuclear bone marrow cells in acute myocardial infarction: results from the Autologous Stem cell Transplantation in Acute Myocardial Infarction (ASTAMI) randomized controlled trial

BACKGROUND

The effects on left ventricular function of intracoronary injection of bone marrow cells in acute myocardial infarction (AMI) have been studied with conflicting results. The aim of this substudy of the ASTAMI trial was to examine the effects of this novel treatment on exercise capacity and quality of life.

METHODS

We studied 100 patients with anterior wall ST-elevation AMI. All had percutaneous coronary intervention with stent in the proximal or mid left anterior descending coronary artery 2 to 12 hours after start of symptoms. Patients were randomized to intracoronary injection of mononuclear bone marrow cells (mBMCs) in left anterior descending coronary artery 6 +/- 1.3 days after AMI (n = 50) or control (n = 50). Assessment of physical capacity by maximal symptom-limited bicycle ergometer exercise tests and quality of life by the Short Form 36 health survey was performed 2 to 3 weeks and 6 months after the AMI.

RESULTS

There was a significantly greater improvement in exercise time in the mBMC group than in the control group (treatment effect 0.9 minute, 95% CI 0.3-1.6, P < .01), and a similar improvement in peak oxygen consumption in the groups (2.8 +/- 3.9 mL/[kg min] in the mBMC group vs 2.4 +/- 3.5 mL/[kg min] in controls, P = .62). Peak heart rate and percentage of heart rate reserve increased significantly more in the treatment group than in the control group. Treatment with mBMCs did not influence quality of life.

CONCLUSIONS

In this randomized open-labeled study, the mBMC group significantly improved exercise time and heart rate responses to exercise compared with the control group. There was no treatment effect on peak oxygen consumption.

Arteriogenesis: basic mechanisms and therapeutic stimulation

Pharmacological attempts to stimulate the growth of collateral arteries (arteriogenesis) are evolving towards a new treatment option for patients with vascular occlusive diseases. This enlargement of small pre-existing anastomoses towards large conductance arteries takes place independent of local oxygen tension and is driven by changes in luminal shear stress and infiltration of circulating cells. With the increasing knowledge regarding the distinct differences between capillary sprouting (angiogenesis) and arteriogenesis, several cytokines and growth factors have been demonstrated to stimulate the growth of arterial blood vessels in preclinical models of vascular disease. However, the translation towards clinical practice remains difficult and first in-man trials show limited success. Intensive research especially regarding new drug delivery platforms and the potentially serious side effects of pro-arteriogenic therapeutics is warranted before stimulation of arteriogenesis could become a significant treatment option for vascular occlusive diseases. This review focuses on the recent advances in the field of collateral artery growth. In addition, possible means to overcome the hurdles that have hampered the clinical implementation of pro-arteriogenic therapies will be discussed.

STEM CELL MECHANISMS AND PARACRINE EFFECTS

Heart disease remains the leading cause of death in the industrialized world. Stem cell therapy is a promising treatment modality for injured cardiac tissue. A novel mechanism for this cardioprotection may include paracrine actions. Cardiac surgery represents the unique situation where preischemia and postischemia treatment modalities exist that may use stem cell paracrine protection. This review (1) recalls the history of stem cells in cardiac disease and the unraveling of its mechanistic basis for protection, (2) outlines the pathways for stem cell-mediated paracrine protection, (3) highlights the signaling factors expressed, (4) explores the potential of using stem cells clinically in cardiac surgery, and (5) summarizes all human stem cell studies in cardiac disease to date.

Do stem cells in the heart truly differentiate into cardiomyocytes?

Chronic congestive heart failure (CHF) is a common consequence of heart muscle or valve damage and remains a major cause of morbidity and mortality worldwide. There are increasing interests to treat cardiac failure by stem cell-based therapy. Many types of stem cells or progenitor cells have been suggested for cellular therapy of heart failure. While stem cell-based therapy was initially thought to be achieved by transdifferentiation of stem cells into myocardial cells including cardiomyocytes it has become clear that this may be rather an infrequent event. Instead cardiac regeneration may result from vascular differentiation of stem cells or even from stem cell-mediated reverse remodelling. Thus the term stem cell-mediated cardiac regeneration covers the spectrum from stem cell transdifferentiation into cardiomyocytes to cell-mediated pharmacotherapy. In this review we revise stem cell-based cardiac regeneration both in experimental models and in clinical application. We have limited our discussion on some selected types of stem cells, with particular emphasis on their differentiation potential, current status and perspectives on their future applications.

Therapeutic myocardial angiogenesis

Armed with an improved understanding of the mediators of angiogenesis, physicians and scientists have made significant efforts at harnessing this naturally occurring process in order to treat patients with a variety of peripheral vascular and coronary ischemic syndromes. There is a growing population of patients with end-stage coronary artery disease (CAD) who are no longer candidates for mechanical revascularization, yet suffer from chronic myocardial ischemia who may benefit from regeneration of the depleted microvasculature.

Bone marrow–derived mononuclear cell transplantation improves myocardial recovery by enhancing cellular recruitment and differentiation at the infarction site

OBJECTIVE

Stem cell therapy in myocardial infarction is under intensive investigation; however, the mechanisms of recovery and the optimal transplantation technique remain controversial. The goal of this controlled and randomized study was to test the hypothesis that locally injected bone marrow-derived mononuclear cells can focus in on the damaged myocardium and improve cardiac function by means of active participation in remodeling.

METHODS

Myocardial infarction was introduced through occlusion of the circumflex coronary artery for 90 minutes in 14 piglets (24.0 +/- 4.9 kg) that were randomized to a cell-therapy group (n = 7) and a control group (n = 7). At reperfusion, autologous purified prelabeled or unlabeled cells (10(8) cells/2 mL) or saline were injected into the myocardium. Cardiac function was measured by using echocardiography preoperatively and postoperatively and at 3 weeks, when hearts were collected for histopathologic examination.

RESULTS

The ejection fraction recovered in the cell-therapy group (P = .02) but failed to recover in the control group, and at 3 weeks, it remained at the lower level compared with that in the cell-therapy group (P = .067). The number of living cells in the necrotic area was significantly greater in the cell-therapy group (P < .001). Labeled cells were detected in the infarcted area, and they showed signs of myocyte differentiation. Furthermore, the proportional area of muscle actin-positive cells at the granulation area was higher in the cell-therapy group (P = .035).

CONCLUSIONS

Autologous bone marrow-derived mononuclear cells at the infarcted area localize in the myocardium. The exact mechanism of recovery remains to be determined, but our findings may give new information concerning the cellular events that occur during cell therapy-enhanced recovery.

The bone marrow--cardiac axis of myocardial regeneration

Congestive heart failure remains the leading cause of morbidity and mortality in the developed world. Current therapies do not address the underlying pathophysiology of this disease, namely, the progressive loss of functional cardiomyocytes. The notion of repairing or regenerating lost myocardium via cell-based therapies remains highly appealing. The recent identification of adult stem cells, including both cardiac stem/progenitor cells and bone marrow stem cells, has triggered an explosive interest in using these cells for physiologically relevant cardiomyogenesis. Enthusiasm for cardiac regeneration via cell therapy has further been fueled by the many encouraging reports in both animals and human studies. Further intensive research in basic science and clinical arenas are needed to make this next great frontier in cardiovascular regenerative medicine a reality. In this review, we focus on the role of bone marrow-derived stem cells and cardiac stem/progenitor cells in cardiomyocyte homeostasis and myocardial repair and regeneration, as well as provide a brief overview of current clinical trials using cell-based therapeutic approaches in patients with heart disease.

Transendocardial autologous bone marrow in chronic myocardial infarction using a helical needle catheter: 1-year follow-up in an open-label, nonrandomized, single-center pilot study (the TABMMI study)

BACKGROUND

Cell therapy has shown benefit in preclinical and clinical studies, although debate continues on the mechanism of action and the most appropriate methods for performing such therapies. We assessed the hypothesis that helical needle transendocardial (TE) delivery of autologous bone marrow (ABM) mononuclear cells around regions of hypo- or akinesia in patients after chronic myocardial infarction (MI) would be safe and possibly improve ejection fraction (EF).

METHODS AND RESULTS

Ten stable post-MI patients with an EF <40% were enrolled. Autologous bone marrow cells were aspirated from the iliac crest and delivered percutaneously with a TE helical needle catheter. A total of 86 x 10(6) cells were injected into 7.1 +/- 3.1 sites around the infarct to target the peri-infarct zones. Two-dimensional echocardiographic left ventricle EF measurements, 24-hour Holter, and exercise tolerance testing were performed at baseline, day of procedure, 1 and 12 weeks, and 6 and 12 months. There were no adverse events associated with the catheter-based cell transplantation procedure. At 6 and 12 months, all patients showed an improvement in left ventricle EF over baseline (35.2 +/- 4.6 to 40.8 +/- 4.5, P = .003 at 6 months; 35.2 +/- 4.6 to 42.3 +/- 5.1, P = .0001 at 12 months).

CONCLUSIONS

Autologous bone marrow cells delivered with the helical needle TE catheter was safe in this small uncontrolled study in patients with chronic MI. Increased EF and other positive data trends support continued development of this therapeutic strategy in larger controlled trials.

Bone marrow cell-mediated cardiovascular repair: potential of combined therapies

Recent evidence indicates that bone-marrow cells (BMCs) can contribute to the healing process of the injured cardiovascular system via the chemokine receptor CXCR4/SDF-1, thymosin beta(4) and integrin alpha(4)beta(1) molecular pathways. During tissue ischemia overwhelming numbers of detrimental oxygen radicals are generated, and therefore treatment with antioxidants and L-arginine, the precursor of nitric oxide (NO), could induce beneficial effects beyond those achieved by BMC transplantation alone. Recent studies have reported that BMCs have enhanced neovascularization capacity in cotreatment with alpha-tocopherol (vitamin E), ascorbic acid (vitamin C) and L-arginine. Moreover, BMC therapy can be combined with gene therapy. Clinical trials employing BMCs in the treatment of cardiovascular diseases have been completed with mixed or positive results, and several trials are ongoing. Here, we discuss the clinical potential of BMC transplantation alone and in combined therapy that aims to restore organ vascularization and function. We also consider the mechanisms of mobilization, differentiation and incorporation of BMCs.

Trans-coronary transplantation may be an optimal route in cellular cardiomyoplasty with stem cells

Myocardial infarction is the leading cause of congestive heart failure and death in the industrialized world. However, the intrinsic repair mechanism of the injured heart and current therapeutic means are inadequate to regenerate lost myocardium. Recent interests focused on cellular cardiomyoplasty which is an outside intervention to support the reparative process in the heart through transplantation of stem/progenitor cells. Cellular myocardioplasty with stem cells is a possible option to reverse the adverse hemodynamic and neurohormonal imbalance after myocardial infarction. Experimental studies and clinical trials suggest that cellular cardiomyoplasty with stem/progenitor cells may improve cardiac function and prevent ventricular remodeling of the injured heart. Although the mechanisms are still in intensive debate, cellular cardiomyoplasty with stem cells has already been introduced into the clinical settings. However, it is an important challenge how donor cells are delivered to the targeted area. In early studies in animals, intramyocardial injection of stem cells after thoracotomy is the main transplantation route which is not suitable to most patients in clinical settings. Then the catheter-based infusion of stem cells is clinically introduced and rapidly developed because of its safety, convenience and micro-invasion. We hypothesize that catheter-based transplantation with stem cells may be a promising means to treat ischemic heart diseases in the future in clinical settings.

Endothelial progenitor cells as therapeutic vectors in cardiovascular disorders: from experimental models to human trials

Cell-based therapy approaches for the restoration of blood flow in ischemic organs has recently received growing interest. A considerable number of reports have documented the presence of circulating, bone marrow-derived endothelial progenitor cells (EPC) in adult peripheral blood. These putative cells are thought to participate in postnatal growth of new blood vessels. Mounting evidence from animal studies point to potential therapeutic applications of EPCs in the treatment of a wide range of cardiovascular (CV) disorders, while preliminary results from the pilot clinical trials still remain equivocal. Here, we review the experimental data that has accumulated so far from animal and clinical studies regarding the potential importance of EPCs. In addition, we discuss the potential hurdles as well as future options of EPC-based therapy.

Effects of autologous bone marrow derived CD34+ stem cells on the left ventricular function following myocardial infarction

A kísérletes és az utóbbi 5 évben végzett humán klinikai vizsgálatok szerint a csontvelői eredetű sejtek részt vesznek a miokardiális infarktus gyógyulási folyamatában. Számos kisebb klinikai vizsgálatban mutattak ki enyhe vagy mérsékelt fokú kedvező hatást a miokardiális infarktus után intracoronariásan beadott csontvelői eredetű őssejtekkel. Mivel a legtöbb eddigi vizsgálatban mononukleáris frakciót használtak, a sejtpopuláció sokfélesége miatt nem volt ismert, hogy melyik a hatásos szubpopuláció. 8 miokardiális infarktust szenvedett, csökkent bal kamra funkciójú betegben vizsgáltuk az akut coronaria esemény után 12 ± 1 nappal intracoronariásan végzett CD34+ saját csontvelői őssejt beültetés biztonságosságát és hatékonyságát. 2D-echocardiographia, FDG-PET és MIBI-SPECT vizsgálatot végeztünk a beültetés előtt és 6 hónappal azt követően. A 6 hónapos követés során szignifikánsan javult a globális bal kamra funkció (alap EF 37,3 ± 2,9%, sejt kezelés után 44,8 ± 4,1%; p = 0,0041) és a regionális viabilitás / metabolizmus (17,6 ± 13,5%-kal; p < 0,05). A szívizom elhalt részének perfúziójában nem szignifikáns tendenciózus növekedést észleltünk. Eredményeinkkel elsőként mutattuk ki, hogy a CD34+ csontvelői sejt szubpopuláció javítja a bal kamra funkciót és a metabolizmust miokardiális infarktust követően.

Donor cell transplantation for myocardial disease: does it complement current pharmacological therapies?This paper is one of a selection of papers published in this Special Issue, entitled Young Investigators' Forum

Heart failure secondary to ischemic heart disease, hypertension, and myocardial infarction is a common cause of death in developed countries. Although pharmacological therapies are very effective, poor prognosis and shorter life expectancy of heart disease patients clearly indicate the need for alternative interventions to complement the present therapies. Since the progression of heart disease is associated with the loss of myocardial cells, the concept of donor cell transplantation into host myocardium is emerging as an attractive strategy to repopulate the damaged tissue. To this end, a number of donor cell types have been tested for their ability to increase the systolic function of diseased hearts in both experimental and clinical settings. Although initial clinical trials with bone marrow stem cells are encouraging, long-term consequences of such interventions are yet to be rigorously examined. While additional laboratory studies are required to address several issues in this field, there is also a clear need for further characterization of drug interactions with donor cells in these interventions. Here, we provide a brief summary of current pharmacological and cell-based therapies for heart disease. Further, we discuss the potential of various donor cell types in myocardial repair, mechanisms underlying functional improvement in cell-based therapies, as well as potential interactions between pharmacological and cell-based therapies.

Adult bone marrow–derived stem cells for organ regeneration and repair

Stem cells have been recognized as a potential tool for the development of innovative therapeutic strategies. There are in general two types of stem cells, embryonic and adult stem cells. While embryonic stem cell therapy has been riddled with problems of allogeneic rejection and ethical concerns, adult stem cells have long been used in the treatment of hematological malignancies. With the recognition of additional, potentially therapeutic characteristics, bone marrow-derived stem cells have become a tool in regenerative medicine. The bone marrow is an ideal source of stem cells because it is easily accessible and harbors two types of stem cells. Hematopoietic stem cells give rise to all blood cell types and have been shown to exhibit plasticity, while multipotent marrow stromal cells are the source of osteocytes, chondrocytes, and fat cells and have been shown to support and generate a large number of different cell types. This review describes the general characteristics of these stem cell populations and their current and potential future applications in regenerative medicine.

Cellular cardiomyoplasty by catheter-based infusion of stem cells in clinical settings

Myocardial infarction is the leading cause of congestive heart failure and death in the industrialized world. However, the intrinsic repair mechanism of the heart is inadequate. Current therapy is limited in preventing ventricular remodeling, but can not regenerate the lost cardiomyocytes. Recent interests have been focused on cellular cardiomyoplasty which is an outside intervention to support the reparative process in the heart through transplantation of stem/progenitor cells or cardiac cells. Cellular cardiomyoplasty with stem cells is a possible option to reverse the adverse hemodynamic and neurohormonal imbalance after myocardial infarction. Experimental studies and clinical trials suggest that cellular cardiomyoplasty may benefit tissue perfusion and contractile performance of the injured heart. Although the mechanisms are still intensively debated, cellular cardiomyoplasty with stem cells has already been introduced into the clinical settings. However, it is an important challenge how stem cells are delivered to targeted area. In early studies on animals, intramyocardial injection of stem cells after thoracotomy is the predominant transplantation route which is not suitable for most patients in clinical settings. Then the catheter-based infusion of stem cells is clinically introduced and rapidly developed in patients because of the safety, convenience and mini-invasion. We mainly review the progress in catheter-based transplantation with stem cells in order to fully understand the application of various intervention-based approaches to stem cells transplantation in clinical settings.

Imaging stem cells implanted in infarcted myocardium

Stem cell-based cellular cardiomyoplasty represents a promising therapy for myocardial infarction. Noninvasive imaging techniques would allow the evaluation of survival, migration, and differentiation status of implanted stem cells in the same subject over time. This review describes methods for cell visualization using several corresponding noninvasive imaging modalities, including magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, and bioluminescent imaging. Reporter-based cell visualization is compared with direct cell labeling for short- and long-term cell tracking.

Repair of the Damaged Heart by Bone Marrow Cells: From Experimental Evidence to Clinical Hope

Heart failure remains the leading cause of death in developed countries in spite of improvements in medical and surgical treatments. However, recent observations in experimental studies that bone marrow cells may repair cardiac tissue have offered renewed hopes for the treatment of heart failure. This optimism is further supported by encouraging results from some clinical trials, although the degree of benefits, the underlying mechanisms, and the cell types involved remain to be elucidated. This review summarizes the relevant experimental and clinical studies supporting the use of bone marrow cells in myocardial repair, as well as the controversies and challenges encountered.

Lost and found: cardiac stem cell therapy revisited

Several clinical trials of bone marrow stem cell therapy for myocardial infarction are ongoing, but the mechanistic basis for any potential therapeutic effect is currently unclear. A growing body of evidence suggests that the potential improvement in cardiac function is largely independent of cardiac muscle regeneration. A study by Fazel et al. in this issue of the JCI provides evidence that bone marrow-derived c-kit+ cells can lead to an improvement in cardiac function in mutant hypomorphic c-kit mice that is independent of transdifferentiation into either cardiac muscle or endothelial cells, but rather is associated with the release of angiogenic cytokines and associated neovascularization in the infarct border zone (see the related article beginning on page 1865). These findings suggest the potential therapeutic effect of specific paracrine pathways for angiogenesis in improving cardiac function in the injured heart.

Intracoronary injection of mononuclear bone marrow cells in acute myocardial infarction

BACKGROUND

Previous studies have shown improvement in left ventricular function after intracoronary injection of autologous cells derived from bone marrow (BMC) in the acute phase of myocardial infarction. We designed a randomized, controlled trial to further investigate the effects of this treatment.

METHODS

Patients with acute ST-elevation myocardial infarction of the anterior wall treated with percutaneous coronary intervention were randomly assigned to the group that underwent intracoronary injection of autologous mononuclear BMC or to the control group, in which neither aspiration nor sham injection was performed. Left ventricular function was assessed with the use of electrocardiogram-gated single-photon-emission computed tomography (SPECT) and echocardiography at baseline and magnetic resonance imaging (MRI) 2 to 3 weeks after the infarction. These procedures were repeated 6 months after the infarction. End points were changes in the left ventricular ejection fraction (LVEF), end-diastolic volume, and infarct size.

RESULTS

Of the 50 patients assigned to treatment with mononuclear BMC, 47 underwent intracoronary injection of the cells at a median of 6 days after myocardial infarction. There were 50 patients in the control group. The mean (+/-SD) change in LVEF, measured with the use of SPECT, between baseline and 6 months after infarction for all patients was 7.6+/-10.4 percentage points. The effect of BMC treatment on the change in LVEF was an increase of 0.6 percentage point (95% confidence interval [CI], -3.4 to 4.6; P=0.77) on SPECT, an increase of 0.6 percentage point (95% CI, -2.6 to 3.8; P=0.70) on echocardiography, and a decrease of 3.0 percentage points (95% CI, 0.1 to -6.1; P=0.054) on MRI. The two groups did not differ significantly in changes in left ventricular end-diastolic volume or infarct size and had similar rates of adverse events.

CONCLUSIONS

With the methods used, we found no effects of intracoronary injection of autologous mononuclear BMC on global left ventricular function.

Angiogenic cells can be rapidly mobilized and efficiently harvested from the blood following treatment with AMD3100

Circulating endothelial progenitor cells (EPCs) are thought to contribute to angiogenesis following vascular injury, stimulating interest in their ability to mediate therapeutic angiogenesis. However, the number of EPCs in the blood is low, limiting endogenous repair, and a method to rapidly mobilize EPCs has not been reported. In this study, healthy donors were mobilized sequentially with the CXCR4 antagonist, AMD3100, and G-CSF. The number of EPCs and circulating angiogenic cells (CACs) in the blood and pheresis product was determined and the angiogenic capacity of each cell population assessed. Compared with baseline, treatment with AMD3100 or G-CSF increased the number of blood CACs 10.0-fold +/- 4.4-fold and 8.8-fold +/- 3.7-fold, respectively. The number of EPCs in the blood increased 10.2-fold +/- 3.3-fold and 21.8-fold +/- 5.4-fold, respectively. On a percell basis, CACs harvested from G-CSF-mobilized blood displayed increased in vivo angiogenic potential compared with AMD3100-mobilized CACs. Mobilized EPCs displayed a greater proliferative capacity than EPCs isolated from baseline blood. Both CACs and EPCs were efficiently harvested by leukapheresis. Cryopreserved CACs but not EPCs retained functional activity after thawing. These data show that AMD3100 is a potent and rapid mobilizer of angiogenic cells and demonstrate the feasibility of obtaining and storing large numbers of angiogenic cells by leukapheresis.

Clinical trials update from the American Heart Association: REPAIR-AMI, ASTAMI, JELIS, MEGA, REVIVE-II, SURVIVE, and PROACTIVE

This article provides information and a commentary on trials presented at the American Heart Association meeting held in November 2005, relevant to the pathophysiology, prevention and treatment of heart failure. All reports should be considered as preliminary data, as analyses may change in the final publication. In REPAIR-AMI an improvement in ejection fraction was observed in post-MI patients following infusion of bone marrow stem cells. However, the ASTAMI study showed no benefit of stem cell implantation in a similar patient cohort. The JELIS study reported a reduction in major coronary events in patients receiving statins plus fish oil compared to statins alone. MEGA showed that low dose statins in a low risk population reduce the incidence of major cardiovascular events. Two studies of levosimendan in acute heart failure gave conflicting results, in the REVIVE-II study levosimendan was reported to have a superior effect on the composite primary outcome compared to placebo, however, in SURVIVE despite a trend to early benefit with levosimendan, there was no difference in effect on long-term outcome versus dobutamine. The PROACTIVE study showed encouraging results for the use of pioglitazone in post-myocardial infarction patients with concomitant type 2 diabetes.