Autologous bone marrow-derived stem-cell transfer in patients with ST-segment elevation myocardial infarction: double-blind, randomised controlled trial

Stem cells to repair the broken heart: much ado about nothing?

The long promised benefits of using stem cells for myocardial repair are still awaited.

Cardiac repair--fact or fancy?

Patients with ischemic cardiomyopathy have a poor prognosis despite all pharmacological, interventional and surgical treatment modalities currently applied. Heart transplantation remains the ideal treatment for this group of patients but the scarcity of donors hinders its widespread application. The autologous transplantation of stem cells (SCs) for cardiac repair is emerging as a new therapy for patients with myocardial dysfunction early after an acute infarction or ischemic cardiomyopathy. The rationale of this novel method is the enhancement of the repair mechanisms achieved by tissue-specific and circulating stem/progenitor cells. SCs assist naturally occurring myocardial repair by contributing to increased myocardial perfusion and contractile performance especially in the setting of acute myocardial infarction (AMI), but also in patients with chronic ischemic heart failure and advanced, diffuse coronary artery disease. The exact mechanism of their action has not been fully elucidated. Few studies continue to suggest a formation of few new contractile tissue. The majority if investigators believe that these cells do not persist long in the myocardium but that they secrete vascular growth and other cardioprotective factors.

Low-energy shock wave for enhancing recruitment of endothelial progenitor cells: a new modality to increase efficacy of cell therapy in chronic hind limb ischemia

BACKGROUND

Stem and progenitor cell therapy is a novel approach to improve neovascularization and function of ischemic tissue. Enhanced tissue expression of chemoattractant factors such as stromal cell-derived factor 1 and vascular endothelial growth factor is crucial for the recruitment of circulating endothelial progenitor cells (EPCs) during acute ischemia. In chronic ischemia, however, expression of these chemoattractants is less pronounced, which results in insufficient EPC recruitment into the target tissue. Therefore, we investigated the effect of targeted extracorporeal shock wave (SW) application in order to facilitate EPC recruitment into nonischemic and chronic ischemic tissue.

METHODS AND RESULTS

Hind limb adductor muscles of nude rats were treated with 500, 1000, and 2000 impulses of focused low-energy SW (flux density level: 0.05 mJ/mm2). Twenty-four hours later, mRNA expression of the chemoattractant stromal cell-derived factor 1 was significantly increased with 1000 impulses (stromal cell-derived factor 1/GAPDH: 0.95+/-0.09) and 2000 impulses (stromal cell-derived factor 1/GAPDH: 1.17+/-0.24; both P<0.05 versus untreated). Histologically, the number of vascular endothelial growth factor-positive endothelial cells per myocyte was significantly increased with 2000 impulses (0.24+/-0.05 versus 0.09+/-0.02; P<0.01). This preconditioning effect resulted in significantly enhanced recruitment and homing of EPCs that were intravenously infused 24 hours after SW treatment (P<0.05). In a rat model of chronic hind limb ischemia, SW-facilitated EPC treatment resulted in a significant increase in relative blood flow recovery as assessed by laser Doppler imaging (P<0.05).

CONCLUSIONS

Preconditioning of both nonischemic and chronic ischemic tissue with low-energy SW improves recruitment of circulating EPCs via enhanced expression of chemoattractant factors. Thus, SW-facilitated cell therapy may improve the efficacy of EPC treatment in patients with chronic ischemia.

Nuclear imaging in cardiac cell therapy

Cardiac stem cell therapy is an innovative and promising therapeutic approach for heart failure. However, despite an increasing body of existing experimental and human data, it still presents a substantial challenge for basic scientists and clinical researchers. Several issues concerning biologic mechanisms of therapy remain to be answered, and unequivocal proof of clinical efficacy is needed. The variety of different available cell types and different methods for cell delivery to the myocardium raises further questions about the most useful therapeutic approach. Nuclear imaging not only provides accurate noninvasive information about myocardial perfusion, contractile function and viability, which enables assessment of clinical benefits of therapy. The rapidly developing field of molecular imaging has also brought up more specific tracers targeting cellular and subcellular biologic events, which are expected to shed more light upon mechanisms of cell therapy. Moreover, nuclear imaging is well suited for tracking of transplanted cells by use of direct radionuclide labeling or genetic labeling with reporter genes that can be targeted by radioactive reporter probes. Such a broad spectrum of available in vivo information is expected to significantly impact the future development of cell therapy towards a clinically accepted treatment.

Targeting angiogenesis versus myogenesis with cardiac cell therapy

Considerable hope has been vested in cell therapy strategies designed to augment the endogenous neovascularization response to obstructive coronary artery disease, and to replace cardiomyocyte loss caused by myocardial infarction. Conceptually, the relative importance of targeting angiogenesis versus myogenesis in this scheme will vary depending on the clinical context (the predominance of ischemia versus ventricular dysfunction and scarring). Although the evidence so far is encouraging, whether these processes can be effectively targeted in a selective fashion with cell therapy is still unclear. Intriguingly, data are now emerging suggesting that the beneficial effects of cardiac cell therapies in a variety of clinical settings may be accounted for by a greater interaction of angiogenesis, myocardial salvage and myogenesis than heretofore appreciated, and through mechanisms that may include both cellular and paracrine effects. Greater understanding of these mechanisms should accelerate the development of effective cell therapies for the growing number of patients with advanced, and in many cases 'no-option', cardiovascular disease. Possible clinical targets for angiogenic and myogenic cardiac cell therapy, the scientific rationale for this therapeutic approach and future directions in this field are discussed here.

Technology insight: in vivo cell tracking by use of MRI

Animal studies have shown some success in the use of stem cells of diverse origins to treat heart failure and ventricular dysfunction secondary to ischemic injury. The clinical use of these cells is, therefore, promising. In order to develop effective cell therapies, the location, distribution and long-term viability of these cells must be evaluated in a noninvasive manner. MRI of cells labeled with magnetically visible contrast agents after either direct injection or local or intravenous infusion has the potential to fulfill this goal. In this Review, techniques for labeling and imaging a variety of cells will be discussed. Particular attention will be given to the advantages and limitations of various contrast agents and passive and facilitated cell-labeling methods, as well as to imaging techniques that produce negative and positive contrast, and the effect on image quantification of compartmentalization of contrast agents within the cell.

Bone marrow cell transfer in acute myocardial infarction

Permanent loss of cardiomyocytes after ischemic injury often initiates the development of heart failure and adversely affects clinical outcome. The concept of progenitor-cell transfer for enhancing cardiac repair has raised new therapeutic prospects. Promising results have been reported in early studies in rodents, using various modalities of progenitor-cell transfer in the dysfunctional heart, although underlying mechanisms remain ill defined. Despite ongoing controversies over whether or not stem cells can autonomously adapt cardiomyocyte-like behavior after genetic reprogramming or whether they merely fuse with native host cardiomyocytes, early-phase clinical trials have shown a reassuring safety profile and suggest a functional benefit. However, identification of the intrinsic value of stem cell transfer in patients after myocardial infarction will require carefully designed randomized, placebo-controlled, blinded studies. While these are becoming available, a number of critical questions about the choice of progenitor-cell type, dosage regimen, and timing of administration need to be considered, and end points for future clinical trials need to be chosen carefully. There is great enthusiasm for this novel treatment paradigm in patients with ischemic cardiomyopathy, but only carefully conducted clinical trials paralleled by preclinical studies in relevant animal models will ultimately identify the best conditions and indications for cell transfer.

Cell-based therapies after myocardial injury

Recent translational research into the emerging field of cardiac cell therapy has paved the way for novel clinical treatment strategies. However, neither the ideal source and type of cell nor the critical quantity and mode of application have yet been defined. In patients who have undergone acute myocardial infarction, several cell-based approaches are currently being evaluated, such as intracoronary delivery of autologous mononuclear bone marrow cells or enriched hematopoietic progenitor cell products; systemic cytokine stimulation with release of bone marrow progenitor cells into the systemic circulation; and both intravenous and intracoronary delivery of allogenic marrow stroma cell-derived cells. There are potentially encouraging data for each of these strategies, based to date on small cohorts with conflicting or equivocal recovery of function. Taken together, it is too early to consider cell therapy for heart disease to be effective. Future setbacks are likely, but both clinicians and basic scientists will eventually introduce more potent cell-based strategies into the clinical arena.

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.

Autologous transplantation of mononuclear bone marrow cells in patients with acute myocardial infarction: the effect of the dose of transplanted cells on myocardial function

BACKGROUND

Despite the reports on successful treatment of acute myocardial infarction using autologous mononuclear bone marrow cell transplantation, many unresolved questions still remain. We studied the impact of the dose of transplanted cells on myocardial function and perfusion.

METHODS

Sixty-six patients with a first acute myocardial infarction were randomized into 3 groups. Two groups were intracoronarily given mononuclear bone marrow cells in either higher (10(8) cells, higher cell dose [HD] group, n = 22) or lower (10(7) cells, lower cell dose [LD] group, n = 22) doses. Twenty-two patients without cell transplantation served as a control (C) group.

RESULTS

At 3 months of follow-up, the baseline peak systolic velocities of longitudinal contraction of the infarcted wall of 5.2, 4.5, and 4.3 cm/s in C, LD, and HD groups increased by 0.0, 0.5 (P < .05 vs C group), and 0.9 cm/s (P < .05 vs LD group, P < .01 vs C group), respectively, as demonstrated by Doppler tissue imaging. Baseline left ventricular ejection fractions of 42%, 42%, and 41% in C, LD, and HD groups increased by 2%, 3%, and by 5% (P < .05 vs group C), respectively, as assessed by the gated technetium Tc 99m sestamibi single photon emission computed tomography.

CONCLUSIONS

Mononuclear bone marrow cell transplantation improves regional myocardial function of the infarcted wall in a dose-dependent manner.

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.

The mechanistic basis of infarct healing

Myocardial infarction triggers an inflammatory cascade that results in healing and replacement of the damaged tissue with scar. Cardiomyocyte necrosis triggers innate immune mechanisms eliciting Toll-like receptor- mediated responses, activating the complement cascade and generating reactive oxygen species. Subsequent activation of NF-kappaB is a critical element in the regulation of cytokine, chemokine, and adhesion molecule expression in the ischemic myocardium. Chemokine induction mediates leukocyte recruitment in the myocardium. Pleiotropic proinflammatory cytokines, such as TNF-alpha, IL-1, and IL-6, are also upregulated in the infarct and exert a wide range of effects on a variety of cell types. Timely repression of proinflammatory gene synthesis is crucial for optimal healing; IL-10 and TGF-beta-mediated pathways may be important for suppression of chemokine and cytokine expression and for resolution of the leukocytic infiltrate. In addition, TGF-beta may be critically involved in inducing myofibroblast differentiation and activation, promoting extracellular matrix protein deposition in the infarcted area. The composition of the extracellular matrix plays an important role in regulating cell behavior. Both structural and matricellular proteins modulate cell signaling through interactions with specific surface receptors. The molecular and cellular changes associated with infarct healing directly influence ventricular remodeling and affect prognosis in patients with myocardial infarction.

Regenerative Therapien in der Kardiologie

During acute myocardial infarction, ischemia causes progressive loss of contractile tissue. Subsequently, structural changes lead to left ventricular remodeling finally resulting in the development of heart failure. In addition to an optimal reperfusion and pharmacologinal post-infarction therapy, increased neovascularization and regeneration of cardiomyocytes could reduce or even abolish the ongoing left ventricular remodeling processes within the infarct area. Experimental studies have demonstrated that transplantation of adult progenitor cells leads to increased neovascularization, reduced fibrosis and, therefore, increased left ventricular function after acute myocardial infarction. In contrast to current treatment strategies, progenitor cell therapy offers a new regenerative approach for myocardial tissue. Initial clinical studies have demonstrated, apart from safety and feasibility of intracoronary infusion of adult autologous progenitor cells, a significant improvement of left ventricular function, geometry and vascularization in patients with acute myocardial infarction receiving intracoronary infusion of progenitor cells. However, in patients with chronic ischemic cardiomyopathy, the improvement in contractility is less pronounced. Finally, whether intracoronary infusion of adult progenitor cells can also reduce morbidity and mortality due to heart failure, remains to be investigated.

Multipotent Adult Progenitor Cells from Swine Bone Marrow

We show that multipotent adult progenitor cells (MAPCs) can be derived from both postnatal and fetal swine bone marrow (BM). Although swine MAPC (swMAPC) cultures are initially mixed, cultures are phenotypically homogenous by 50 population doublings (PDs) and can be maintained as such for more than 100 PDs. swMAPCs are negative for CD44, CD45, and major histocompatibility complex (MHC) classes I and II; express octamer binding transcription factor 3a (Oct3a) mRNA and protein at levels close to those seen in human ESCs (hESCs); and have telomerase activity preventing telomere shortening even after 100 PDs. Using quantitative-reverse transcription-polymerase chain reaction (Q-RT-PCR), immunofluorescence, and functional assays, we demonstrate that swMAPCs differentiate into chondrocytes, adipocytes, osteoblasts, smooth muscle cells, endothelium, hepatocyte-like cells, and neuron-like cells. Consistent with what we have shown for human and rodent MAPCs, Q-RT-PCR demonstrated a significant upregulation of transcription factors and other lineage-specific transcripts in a time-dependent fashion similar to development. When swMAPCs were passaged for 3-6 passages at high density (2,000-8,000 cells per cm(2)), Oct3a mRNA levels were no longer detectable, cells acquired the phenotype of mesenchymal stem cells (CD44(+), MHC class I(+)), and could differentiate into typical mesenchymal lineages (adipocytes, osteoblasts, and chondroblasts), but not endothelium, hepatocyte-like cells, or neuron-like cells. Even if cultures were subsequently replated at low density (approximately 100-500 cells per cm(2)) for >20 PDs, Oct3a was not re-expressed, nor were cells capable of differentiating to cells other than mesenchymal-type cells. This suggests that the phenotype and functional characteristics of swMAPCs may not be an in vitro culture phenomenon.

Engraftment of engineered ES cell-derived cardiomyocytes but not BM cells restores contractile function to the infarcted myocardium

Cellular cardiomyoplasty is an attractive option for the treatment of severe heart failure. It is, however, still unclear and controversial which is the most promising cell source. Therefore, we investigated and examined the fate and functional impact of bone marrow (BM) cells and embryonic stem cell (ES cell)-derived cardiomyocytes after transplantation into the infarcted mouse heart. This proved particularly challenging for the ES cells, as their enrichment into cardiomyocytes and their long-term engraftment and tumorigenicity are still poorly understood. We generated transgenic ES cells expressing puromycin resistance and enhanced green fluorescent protein cassettes under control of a cardiac-specific promoter. Puromycin selection resulted in a highly purified (>99%) cardiomyocyte population, and the yield of cardiomyocytes increased 6-10-fold because of induction of proliferation on purification. Long-term engraftment (4-5 months) was observed when co-transplanting selected ES cell-derived cardiomyocytes and fibroblasts into the injured heart of syngeneic mice, and no teratoma formation was found (n = 60). Although transplantation of ES cell-derived cardiomyocytes improved heart function, BM cells had no positive effects. Furthermore, no contribution of BM cells to cardiac, endothelial, or smooth muscle neogenesis was detected. Hence, our results demonstrate that ES-based cell therapy is a promising approach for the treatment of impaired myocardial function and provides better results than BM-derived cells.

Heart repair and stem cells

Of the medical conditions currently being discussed in the context of possible treatments based on cell transplantation therapy, few have received more attention than the heart. Much focus has been on the potential application of bone marrow-derived cell preparations, which have already been introduced into double-blind, placebo-controlled clinical trials. The consensus is that bone marrow may have therapeutic benefit but that this is not based on the ability of bone marrow cells to transdifferentiate into cardiac myocytes. Are there potential stem cell sources of cardiac myocytes that may be useful in replacing those lost or dysfunctional after myocardial infarction? Here, this question is addressed with a review of the recent literature.

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.

Intracoronary bone marrow-derived progenitor cells in acute myocardial infarction

BACKGROUND

Pilot trials suggest that the intracoronary administration of autologous progenitor cells may improve left ventricular function after acute myocardial infarction.

METHODS

In a multicenter trial, we randomly assigned 204 patients with acute myocardial infarction to receive an intracoronary infusion of progenitor cells derived from bone marrow (BMC) or placebo medium into the infarct artery 3 to 7 days after successful reperfusion therapy.

RESULTS

At 4 months, the absolute improvement in the global left ventricular ejection fraction (LVEF) was significantly greater in the BMC group than in the placebo group (mean [+/-SD] increase, 5.5+/-7.3% vs. 3.0+/-6.5%; P=0.01). Patients with a baseline LVEF at or below the median value of 48.9% derived the most benefit (absolute improvement in LVEF, 5.0%; 95% confidence interval, 2.0 to 8.1). At 1 year, intracoronary infusion of BMC was associated with a reduction in the prespecified combined clinical end point of death, recurrence of myocardial infarction, and any revascularization procedure (P=0.01).

CONCLUSIONS

Intracoronary administration of BMC is associated with improved recovery of left ventricular contractile function in patients with acute myocardial infarction. Large-scale studies are warranted to examine the potential effects of progenitor-cell administration on morbidity and mortality.

Overview of stem cells and imaging modalities for cardiovascular diseases

Stem cell therapy is emerging as a promising approach to treat heart diseases. Considerable evidence from experimental studies and initial clinical trials suggests that stem cell transplantation promotes systolic function and prevent ventricular remodeling. However, the specific mechanisms by which stem cells improve heart function remain largely unknown. In addition, interpreting the long-term effects of stem cell therapy is difficult because of the limitations of conventional techniques. The recent development of molecular imaging techniques offers great potential to address these critical issues by noninvasively tracking the fate of the transplanted cells. This review offers a focused discussion on the use of stem cell therapy and imaging in the context of cardiology.

Intracoronary infusion of autologous mononuclear bone marrow cells or peripheral mononuclear blood cells after primary percutaneous coronary intervention: rationale and design of the HEBE trial--a prospective, multicenter, randomized trial

BACKGROUND

Recently, several preliminary reports have demonstrated that cell transplantation after acute myocardial infarction in humans is safe and leads to better preserved left ventricular function and improved myocardial perfusion and coronary flow reserve.

METHODS

The HEBE trial is a multicenter, prospective, randomized, 3-arm open trial with blinded evaluation of end points. Patients with acute large myocardial infarction treated with primary percutaneous coronary intervention (PCI) will undergo magnetic resonance imaging (MRI) and echocardiography. A total of 200 patients are randomized to treatment with (1) intracoronary infusion of autologous mononuclear bone marrow cells, (2) intracoronary infusion of peripheral mononuclear blood cells, or (3) standard therapy. Mononuclear cells are isolated from bone marrow aspirate or venous blood by density gradient centrifugation. Within 7 days after PCI and within 24 hours after bone marrow aspiration or blood collection, a catheterization for intracoronary infusion of the mononuclear cells in the infarct-related artery is performed. In all patients, follow-up will be obtained at 1, 4, and 12 months. MRI and catheterization are repeated at 4 months, and all images are analyzed by a core laboratory blinded to randomization. The primary end point of the study is the change in regional myocardial function in dysfunctional segments at 4 months relative to baseline, based on segmental analysis as measured by MRI.

IMPLICATIONS

If intracoronary infusion of autologous mononuclear bone marrow cells or peripheral mononuclear blood cells is proven to be beneficial after primary PCI; it could be a valuable tool in preventing heart failure-related morbidity and mortality after myocardial infarction.

Acute ST-elevation myocardial infarction

Acute ST-elevation myocardial infarction (STEMI) remains the leading cause of death in industrialized countries. For many patients, a myocardial infarction is the first presentation of atherosclerotic coronary artery disease. This often results in delays in obtaining medical attention and subsequently poorer outcome, certainly because symptoms are often misinterpreted. Furthermore, a large proportion of STEMI patients die from lethal arrhythmias even before reaching medical facilities. Numerous studies during the past decades have firmly established the paradigm of achieving early, complete and sustained infarct-related artery patency. Because of a more aggressive therapy and rapid revascularization using either fibrinolysis or primary PCI, many patients do remarkably well after STEMI. Unfortunately, adherence to treatment guidelines is often suboptimal, leading to less favourable outcome. Also, more efficient care for patients with myocardial infarction has led to a rapidly growing population of patients with chronic heart failure.

From cardiac repair to cardiac regeneration – ready to translate?

Cardiovascular disease is a major public health challenge in the western world. Mortality of acute events has improved, but more patients develop HF--a condition affecting up to 22 million people worldwide. Cell transplantation is the first therapy to attempt replacement of lost cardiomyocytes and vasculature to restore lost contractile function. Since the first reported functional repair after injection of autologous skeletal myoblasts into the injured heart in 1998, a variety of cell types have been proposed for transplantation in different stages of cardiovascular disease. Fifteen years of preclinical research and the rapid move into clinical studies have left us with promising results and a better understanding of cells as a potential clinical tool. Cell-based cardiac repair has been the first step, but cardiac regeneration remains the more ambitious goal. Promising new cell types and the rapidly evolving concept of adult stem and progenitor cell fate may enable us to move towards regenerating viable and functional myocardium. Meeting a multidisciplinary consensus will be required to translate these findings into safe and applicable clinical tools.

Recovery of regional but not global contractile function by the direct intramyocardial autologous bone marrow transplantation: results from a randomized controlled clinical trial

BACKGROUND

Recent trials have shown that intracoronary infusion of bone marrow cells (BMCs) improves functional recovery after acute myocardial infarction. However, whether this treatment is effective in heart failure as a consequence of remodeling after organized infarcts remains unclear. In this randomized trial, we assessed the hypothesis that direct intramyocardial injection of autologous mononuclear bone marrow cells during coronary artery bypass graft (CABG) could improve global and regional left ventricular ejection fraction (LVEF) at 4-month follow-up.

METHODS AND RESULTS

Twenty patients (age 64.8+/-8.7; 17 male, 3 female) with a postinfarction nonviable scar, as assessed by thallium (Tl) scintigraphy and cardiac magnetic resonance imaging (MRI), scheduled for elective CABG, were included. They were randomized to a control group (n =10, CABG only) or a BMC group (CABG and injection of 60.10(6)+/-31.10(6) BMC). Primary end points were global LVEF change and wall thickening changes in the infarct area from baseline to 4-month follow-up, as measured by MRI. Changes in metabolic activity were measured by Tl scintigraphy and expressed as a score with a range from 0 to 4, corresponding to percent of maximal myocardial Tl uptake (4 indicates <50%, nonviable scar; 3, 50% to 60%; 2, 60% to 70%; 1, 70% to 80%; 0>80%). Global LVEF at baseline was 39.5+/-5.5% in controls and 42.9+/-10.3% in the BMC group (P=0.38). At 4 months, LVEF had increased to 43.1+/-10.9% in the control group and to 48.9+/-9.5% in the BMC group (P=0.23). Systolic thickening had improved from -0.6+/-1.3 mm at baseline to 1.8+/-2.6 mm at 4 months in the cell-implanted scars, whereas nontreated scars remained largely akinetic (-0.5+/-2.0 mm at baseline compared with 0.4+/-1.7 mm at 4 months, P=0.007 control versus BMC-treated group at 4 months). Defect score decreased from 4 to 3.3+/-0.9 in the BMC group and to 3.7+/-0.4 in the control group (P=0.18).

CONCLUSIONS

At 4 months, there was no significant difference in global LVEF between both groups, but a recovery of regional contractile function in previously nonviable scar was observed in the BMC group.

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.

Potential of stem-cell-based therapies for heart disease

The use of stem cells to generate replacement cells for damaged heart muscle, valves, vessels and conduction cells holds great potential. Recent identification of multipotent progenitor cells in the heart and improved understanding of developmental processes relevant to pluripotent embryonic stem cells may facilitate the generation of specific types of cell that can be used to treat human heart disease. Secreted factors from circulating progenitor cells that localize to sites of damage may also be useful for tissue protection or neovascularization. The exciting discoveries in basic science will require rigorous testing in animal models to determine those most worthy of future clinical trials.

Efficacy of emergent transcatheter transplantation of stem cells for treatment of acute myocardial infarction (TCT-STAMI)

OBJECTIVE

To study whether emergent intracoronary autologous bone marrow cell transplantation (BMT) is applicable for the treatment of acute myocardial infarction (AMI).

METHODS

20 patients admitted within 24 h after the onset of a first AMI were randomly allocated to receive intracoronary autologous BMT (n = 10) or bone marrow supernatant (controls, n = 10) immediately after primary percutaneous coronary intervention. Left ventricular ejection fraction (LVEF), left ventricular end diastolic internal diameter (LVDd) and myocardial perfusion defect scores were examined respectively by echocardiography and single-photon emission computed tomography at one week and six months after AMI.

RESULTS

From one week to six months after AMI, LVEF was enhanced from mean 53.8 (SD 9.2)% to 58.6 (9.9)% (p < 0.05) in the BMT group but was unchanged in the control group (58.2 (7.5)% v 56.3 (3.5)%, p > 0.05); LVDd remained unchanged (52.5 (2.8) v 52.1 (3.2) mm, p > 0.05) in the BMT group but was significantly enlarged in the control group (50.4 (6.0) v 55.2 (7.1) mm, p < 0.05). Additionally, myocardial perfusion defect scores decreased from 21 (11) to 13 (10) (p < 0.01) in the BMT group but were unchanged in the control group (20 (14) v 17 (15), p > 0.05).

CONCLUSION

Emergent intracoronary transplantation of bone marrow mononuclear cells after AMI is practicable, and it improved cardiac function, prevented myocardial remodelling and increased myocardial perfusion at six months' follow up.

Magnetic resonance imaging and its role in myocardial regenerative therapy

There has been extensive interest recently in cardiac stem cell therapy. Current research has been hampered by differences in cell type, methods of delivery and efficacy evaluation. In this article we review the use of magnetic resonance imaging in this growing area and argue that it is well suited to all areas of myocardial regeneration: from patient identification, through cell delivery and tracking of appropriately labeled cells, to evaluation of therapeutic effect. Potential future advances are discussed including magnetic resonance imaging-guided intervention suites and the use of higher field strength magnets for cell tracking.

Regeneration gaps: observations on stem cells and cardiac repair

Substantial evidence indicates that cell transplantation can improve function of the infarcted heart. A surprisingly wide range of non-myogenic cell types improves ventricular function, suggesting that benefit may result in part from mechanisms that are distinct from true myocardial regeneration. While clinical trials explore cells derived from skeletal muscle and bone marrow, basic researchers are investigating sources of new cardiomyocytes, such as resident myocardial progenitors and embryonic stem cells. In this commentary, we briefly review the evolution of cell-based cardiac repair, discuss the current state of clinical research, and offer some thoughts on how newcomers can critically evaluate this emerging field.

Stem cells for the ischaemic heart

The discovery of adult progenitor cells capable of generating new vascular and myocardial tissue offers the promise of salvage of ischaemically threatened or irreversibly damaged cardiac tissue. Not surprisingly, great interest has focused on the use of a variety of cell types to treat both acute myocardial infarction and chronic ischaemic heart disease. This review focuses on the treatment of these two categories of disease, the cell types being considered, our understanding of timing and methods of cellular administration, and possible mechanisms of myocardial salvage.

Controversies in ventricular remodelling

Ventricular remodelling describes structural changes in the left ventricle in response to chronic alterations in loading conditions, with three major patterns: concentric remodelling, when a pressure load leads to growth in cardiomyocyte thickness; eccentric hypertrophy, when a volume load produces myocyte lengthening; and myocardial infarction, an amalgam of patterns in which stretched and dilated infarcted tissue increases left-ventricular volume with a combined volume and pressure load on non-infarcted areas. Whether left-ventricular hypertrophy is adaptive or maladaptive is controversial, as suggested by patterns of signalling pathways, transgenic models, and clinical findings in aortic stenosis. The transition from apparently compensated hypertrophy to the failing heart indicates a changing balance between metalloproteinases and their inhibitors, effects of reactive oxygen species, and death-promoting and profibrotic neurohumoral responses. These processes are evasive therapeutic targets. Here, we discuss potential novel therapies for these disorders, including: sildenafil, an unexpected option for anti-transition therapy; surgery for increased sphericity caused by chronic volume overload of mitral regurgitation; an antifibrotic peptide to inhibit the fibrogenic effects of transforming growth factor beta; mechanical intervention in advanced heart failure; and stem-cell therapy.