Intracoronary transplantation of non-expanded peripheral blood-derived mononuclear cells promotes improvement of cardiac function in patients with acute myocardial infarction

Regeneration-associated cells improve recovery from myocardial infarction through enhanced vasculogenesis, anti-inflammation, and cardiomyogenesis

Background

Considering the impaired function of regenerative cells in myocardial infarction (MI) patients with comorbidities and associated risk factors, cell therapy to enhance the regenerative microenvironment was designed using regeneration-associated cells (RACs), including endothelial progenitor cells (EPCs) and anti-inflammatory cells.

Methods

RACs were prepared by quality and quantity control culture of blood mononuclear cells (QQMNCs). Peripheral blood mononuclear cells (PBMNCs) were isolated from Lewis rats and conditioned for 5 days using a medium containing stem cell factors, thrombopoietin, Flt-3 ligand, vascular endothelial growth factor, and interleukin-6 to generate QQMNCs.

Results

A 5.3-fold increase in the definitive colony-forming EPCs and vasculogenic EPCs was observed, in comparison to naïve PBMNCs. QQMNCs were enriched with EPCs (28.9-fold, P<0.0019) and M2 macrophages (160.3-fold, P<0.0002). Genes involved in angiogenesis (angpt1, angpt2, and vegfb), stem/progenitors (c-kit and sca-1), and anti-inflammation (arg-1, erg-2, tgfb, and foxp3) were upregulated in QQMNCs. For in vivo experiments, cells were administered into syngeneic rat models of MI. QQMNC-transplanted group (QQ-Tx) preserved cardiac function and fraction shortening 28 days post-MI in comparison with PBMNCs-transplanted (PB-Tx) (P<0.0001) and Control (P<0.0008) groups. QQ-Tx showed enhanced angiogenesis and reduced interstitial left ventricular fibrosis, along with a decrease in neutrophils and an increase in M2 macrophages in the acute phase of MI. Cell tracing studies revealed that intravenously administered QQMNCs preferentially homed to ischemic tissues via blood circulation. QQ-Tx showed markedly upregulated early cardiac transcriptional cofactors (Nkx2-5, 29.8-fold, and Gata-4, 5.2-fold) as well as c-kit (4.5-fold) while these markers were downregulated in PB-Tx. In QQ-Tx animals, de novo blood vessels formed a “Biological Bypass”, observed macroscopically and microscopically, while PB-Tx and Control-Tx groups showed severe fibrotic adhesion to the surrounding tissues, but no epicardial blood vessels.

Conclusion

QQMNCs conferred potent angiogenic and anti-inflammatory properties to the regenerative microenvironment, enhancing myocardiogenesis and functional recovery of rat MI hearts.

Stem cells and heart disease - Brake or accelerator?

After two decades of intensive research and attempts of clinical translation, stem cell based therapies for cardiac diseases are not getting closer to clinical success. This review tries to unravel the obstacles and focuses on underlying mechanisms as the target for regenerative therapies. At present, the principal outcome in clinical therapy does not reflect experimental evidence. It seems that the scientific obstacle is a lack of integration of knowledge from tissue repair and disease mechanisms. Recent insights from clinical trials delineate mechanisms of stem cell dysfunction and gene defects in repair mechanisms as cause of atherosclerosis and heart disease. These findings require a redirection of current practice of stem cell therapy and a reset using more detailed analysis of stem cell function interfering with disease mechanisms. To accelerate scientific development the authors suggest intensifying unified computational data analysis and shared data knowledge by using open-access data platforms.

Platelet-Targeted Delivery of Peripheral Blood Mononuclear Cells to the Ischemic Heart Restores Cardiac Function after Ischemia-Reperfusion Injury

One of the major hurdles in intravenous regenerative cell therapy is the low homing efficiency to the area where these cells are needed. To increase cell homing toward areas of myocardial damage, we developed a bispecific tandem single-chain antibody (Tand-scFv_{Sca-1+GPIIb/IIIa}) that binds with high affinity to activated platelets via the activated glycoprotein (GP)IIb/IIIa receptor, and to a subset of peripheral blood mononuclear cells (PBMC) which express the stem cell antigen-1 (Sca-1) receptor. Methods: The Tand-scFv_{Sca-1+GPIIb/IIIa} was engineered, characterized and tested in a mouse model of ischemia-reperfusion (IR) injury applying left coronary artery occlusion for 60 min. Fluorescence cell tracking, cell infiltration studies, echocardiographic and histological analyses were performed. Results: Treatment of mice undergoing myocardial infarction with targeted-PBMCs led to successful cell delivery to the ischemic-reperfused myocardium, followed by a significant decrease in infiltration of inflammatory cells. Homing of targeted-PBMCs as shown by fluorescence cell tracking ultimately decreased fibrosis, increased capillary density, and restored cardiac function 4 weeks after ischemia-reperfusion injury. Conclusion: Tand-scFv_{Sca-1+GPIIb/IIIa} is a promising candidate to enhance therapeutic cell delivery in order to promote myocardial regeneration and thereby preventing heart failure.

A systematic review of randomised controlled trials examining the therapeutic effects of adult bone marrow-derived stem cells for non-ischaemic dilated cardiomyopathy

BACKGROUND

Certain early-phase clinical trials have suggested that bone marrow-derived stem cell transplantation might improve left ventricular function in patients with non-ischaemic dilated cardiomyopathy (NIDCM), whereas others trials have revealed no benefit from this approach. We sought to evaluate the therapeutic effects of bone marrow-derived stem cell therapy on NIDCM.

METHODS

We searched the PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases (through February 2016) for randomised controlled clinical trials that reported on bone marrow-derived stem cell transplantation for patients with NIDCM with a follow-up period ≥12 months. The co-primary endpoints were changes in mortality rate and left ventricular ejection fraction (LVEF); the secondary endpoints were changes in the 6-minute-walk test (6MWT) and left ventricular chamber size. Seven trials involving bone marrow-derived stem cell therapy that included 482 patients satisfied the inclusion and exclusion criteria.

RESULTS

Subjects who received bone marrow-derived stem cell therapy exhibited a significant reduction in mortality rate (19.7% in the cell group vs. 27.1% in the control group; 95% confidence interval (CI) -0.16 to -0.00, I 2 = 52%, p = 0.04). Bone marrow-derived stem cell therapy tended to produce LVEF improvement within 6 months (1.83% increase; 95% CI -0.27 to 3.94, I 2 = 74%, p = 0.09) and significantly improved LVEF after mid-term (6-12 months) follow-up (3.53% increase; 95% CI 0.76 to 6.29, I 2 = 88%, p = 0.01). However, this therapy produced no significant benefit in the 6MWT (p = 0.18). Finally, the transplantation of increased numbers of stem cells resulted in no observable additional benefit with respect to LVEF.

CONCLUSIONS

Bone marrow-derived stem cell therapy might have improved prognoses and appeared to provide moderate benefits in cardiac systolic function at mid-term follow-up. However, this therapy produced no observed improvement in exercise tolerance.

Circulating Progenitor Cells and Childhood Cardiovascular Disease

Circulating progenitor cells have been extensively studied in the context of heart disease in adults. In these patients, they have been demonstrated to be markers of myocardial injury and recovery as well as potential therapeutic agents. However, studies in children are much more limited. Here we review current knowledge pertaining to circulating progenitor cells in the context of childhood cardiovascular disease. Priorities for further research are also highlighted.

Revisiting cardiovascular regeneration with bone marrow-derived angiogenic and vasculogenic cells

Cell-based therapy has emerged as a promising therapy for cardiovascular disease. Particularly, bone marrow (BM)-derived cells have been most extensively investigated and have shown encouraging results in preclinical studies. Clinical trials, however, have demonstrated split results in post-myocardial infarction cardiac repair. Mechanistically, transdifferentiation of BM-derived cells into cardiovascular tissue demonstrated by earlier studies is now known to play a minor role in functional recovery, and humoral and paracrine effects turned out to be main mechanisms responsible for tissue regeneration and functional recovery. With this advancement in the mechanistic insight of BM-derived cells, new efforts have been made to identify cell population, which can be readily isolated and obtained in sufficient quantity without mobilization and have higher therapeutic potential. Recently, haematopoietic CD31(+) cells, which are more prevalent in bone marrow and peripheral blood, have been revealed to have angiogenic and vasculogenic activities and strong potential for therapeutic neovascularization in ischaemic tissues. This article will cover the recent advances in BM-derived cell-based therapy and implication of CD31(+) cells.

A combined prognostic serum interleukin-8 and interleukin-6 classifier for stage 1 lung cancer in the prostate, lung, colorectal, and ovarian cancer screening trial

BACKGROUND

The advent of low-dose helical computed tomography for lung cancer screening will likely lead to an increase in the detection of stage I lung cancer. Presently, these patients are primarily treated with surgery alone and approximately 30% will develop recurrence and die. Biomarkers that can identify patients for whom adjuvant chemotherapy would be a benefit could significantly reduce both patient morbidity and mortality. Herein, we sought to build a prognostic inflammatory-based classifier for stage I lung cancer.

METHODS

We performed a retrospective analysis of 548 European American lung cancer cases prospectively enrolled in the Prostate, Lung, Colorectal and Ovarian study. C-reactive protein, interleukin (IL)-6, IL-8, tumor necrosis factor-α, and IL-1β were measured using an ultrasensitive electrochemiluminescence immunoassay in serum samples collected at the time of study entry.

RESULTS

IL-6 and IL-8 were each associated with significantly shorter survival (hazard ratio [HR], 1.33; 95% confidence interval [CI], 1.08-1.64; p = 0.007; and HR, 1.3; 95% CI, 1.09-1.67; p = 0.005, respectively). Moreover, a combined classifier of IL-6 and IL-8 were significantly associated with poor outcome in stage I lung cancer patients (HR, 3.39; 95% CI, 1.54-7.48, p = 0.002) and in stage 1 patients with more than or equal to 30 pack-years of smoking (HR, 3.15; 95% CI, 1.54-6.46, p = 0.002).

CONCLUSIONS

These results further support the association between inflammatory markers and lung cancer outcome and suggest that a combined serum IL-6/IL-8 classifier could be a useful tool for guiding therapeutic decisions in patients with stage I lung cancer.

Role of formyl peptide receptor 2 in homing of endothelial progenitor cells and therapeutic angiogenesis

Endothelial progenitor cells (EPCs) hold a great promise as a therapeutic mediator in treatment of ischemic disease conditions. The discovery of EPCs in adult blood has been a cause of significant enthusiasm in the field of endothelial cell research and numerous clinical trials have been expedited. After more than a decade of research in basic science and clinical applications, limitations and new strategies of EPC therapeutics have emerged. With various phenotypes, vague definitions, and uncertain distinction from hematopoietic cells, understanding EPC biology remains challenging. However, EPCs, still hold great hope for treatment of critical ischemic injury as low concern regarding safety can accelerate the clinical applications from basic findings. This review provides an introduction to EPC as cellular therapeutics, which highlights a recent finding that EPC homing was promoted through FPR2 signaling.

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

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

Regeneration through autologous hypoxia preconditioned plasma

Cellular hypoxic preconditioning is being employed to obtain complex, yet physiological, secretomes rich is angiogenic factors. We previously proposed exposing peripheral blood cells (PBCs) to hypoxic stress stimulation, and demonstrated that controlled release of PBC-derived factor mixtures induces directional microvessel growth in vitro. Hypoxia therefore provides a useful tool for enhancing the angiogenic potential of blood plasma, by generating compositions based on PBCs' natural responses to a wound-like microenvironment. Here, we discuss various methods for preparing and delivering Hypoxia Preconditioned Plasma (HPP), i.e., plasma derived after extracorporeal conditioning of anticoagulated blood under physiological temperature and hypoxia. Special emphasis is given to those approaches that will likely facilitate the clinical translation of HPP-based therapies. We finally draw a comparison between HPP and other, currently available blood-based products, and present the case that its arrival paves the way for developing next-generation autologous therapies toward angiogenesis-supported tissue repair and regeneration.

Cardiovascular repair with bone marrow-derived cells

While bone marrow (BM)-derived cells have been comprehensively studied for their propitious pre-clinical results, clinical trials have shown controversial outcomes. Unlike previously acknowledged, more recent studies have now confirmed that humoral and paracrine effects are the key mechanisms for tissue regeneration and functional recovery, instead of transdifferentiation of BM-derived cells into cardiovascular tissues. The progression of the understanding of BM-derived cells has further led to exploring efficient methods to isolate and obtain, without mobilization, sufficient number of cell populations that would eventually have a higher therapeutic potential. As such, hematopoietic CD31⁺ cells, prevalent in both bone marrow and peripheral blood, have been discovered, in recent studies, to have angiogenic and vasculogenic activities and to show strong potential for therapeutic neovascularization in ischemic tissues. This article will discuss recent advancement on BM-derived cell therapy and the implication of newly discovered CD31⁺ cells.

Genetic engineering of somatic cells to study and improve cardiac function

AIMS

To demonstrate the utility of genetically engineered excitable cells for studies of basic electrophysiology and cardiac cell therapy.

METHODS AND RESULTS

'Zig-zag' networks of neonatal rat ventricular myocytes (NRVMs) were micropatterned onto thin elastomeric films to mimic the slow action potential (AP) conduction found in fibrotic myocardium. Addition of genetically engineered excitable human embryonic kidney cells (HEK-293 cells) ('Ex-293' cells stably expressing Kir2.1, Na(v)1.5, and Cx43 channels) increased both cardiac conduction velocity by 370% and twitch force amplitude by 64%. Furthermore, we stably expressed mutant Na(v)1.5 [A1924T (fast sodium channel mutant (substitution of alanine by threonine at amino acid 1924)] channels with hyperpolarized steady-state activation and showed that, despite a 71.6% reduction in peak I(Na), these cells propagated APs at the same velocity as the wild-type Na(v)1.5-expressing Ex-293 cells. Stable expression of Ca(v)3.3 (T-type voltage-gated calcium) channels in Ex-293 cells (to generate an 'ExCa-293' line) significantly increased their AP duration and reduced repolarization gradients in cocultures of these cells and NRVMs. Additional expression of an optogenetic construct [ChIEF (light-gated Channelrhodopsin mutant)]enabled light-based control of AP firing in ExCa-293 cells.

CONCLUSION

We show that, despite being non-contractile, genetically engineered excitable cells can significantly improve both electrical and mechanical function of engineered cardiac tissues in vitro. We further demonstrate the utility of engineered cells for tissue-level studies of basic electrophysiology and cardiac channelopathies. In the future, this novel platform could be utilized in the high-throughput design of new genetically encoded indicators of cell electrical function, validation, and improvement of computer models of AP conduction, and development of novel engineered somatic cell therapies for the treatment of cardiac infarction and arrhythmias.

Cell-free carrier system for localized delivery of peripheral blood cell-derived engineered factor signaling: towards development of a one-step device for autologous angiogenic therapy

Spatiotemporally-controlled delivery of hypoxia-induced angiogenic factor mixtures has been identified by this group as a promising strategy for overcoming the limited ability of chronically ischemic tissues to generate adaptive angiogenesis. We previously developed an implantable, as well as an injectable system for delivering fibroblast-produced factors in vivo. Here, we identify peripheral blood cells (PBCs) as the ideal factor-providing candidates, due to their autologous nature, ease of harvest and ample supply, and investigate wound-simulating biochemical and biophysical environmental parameters that can be controlled to optimize PBC angiogenic activity. It was found that hypoxia (3% O₂) significantly affected the expression of a range of angiogenesis-related factors including VEGF, angiogenin and thrombospondin-1, relative to the normoxic baseline. While all three factors underwent down-regulation over time under hypoxia, there was significant variation in the temporal profile of their expression. VEGF expression was also found to be dependent on cell-scaffold material composition, with fibrin stimulating production the most, followed by collagen and polystyrene. Cell-scaffold matrix stiffness was an additional important factor, as shown by higher VEGF protein levels when PBCs were cultured on stiff vs. compliant collagen hydrogel scaffolds. Engineered PBC-derived factor mixtures could be harvested within cell-free gel and microsphere carriers. The angiogenic effectiveness of factor-loaded carriers could be demonstrated by the ability of their releasates to induce endothelial cell tubule formation and directional migration in in vitro Matrigel assays, and microvessel sprouting in the aortic ring assay. To aid the clinical translation of this approach, we propose a device design that integrates this system, and enables one-step harvesting and delivering of angiogenic factor protein mixtures from autologous peripheral blood. This will facilitate the controlled release of these factors both at the bed-side, as an angiogenic therapy in wounds and peripheral ischemic tissue, as well as pre-, intra- and post-operatively as angiogenic support for central ischemic tissue, grafts, flaps and tissue engineered implants.

Clinical trials of cardiac repair with adult bone marrow- derived cells

The past decade has witnessed a marked increase in the number of clinical trials of cardiac repair with adult bone marrow cells (BMCs). These trials included patients with acute myocardial infarction (MI) as well as chronic ischemic heart disease (IHD) and utilized different types of BMCs with variable numbers, routes of administration, and timings after MI. Given these differences in methods, the outcomes from these trials have been often disparate and controversial. However, analysis of pooled data suggests that BMC injection enhances left ventricular function, reduces infarct scar size, and improves remodeling in patients with acute MI as well as chronic IHD. BMC therapy also improves clinical outcomes during follow-up without any increase in adverse effects. Although the underlying mechanisms of heart repair are difficult to elucidate in human studies, valuable insights may be gleaned from subgroup analysis of key variables. This information may be utilized to design future randomized controlled trials to carefully determine the long-term safety and benefits of BMC therapy.

Current stem cell delivery methods for myocardial repair

Heart failure commonly results from an irreparable damage due to cardiovascular diseases (CVDs), the leading cause of morbidity and mortality in the United States. In recent years, the rapid advancements in stem cell research have garnered much praise for paving the way to novel therapies in reversing myocardial injuries. Cell types currently investigated for cellular delivery include embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and adult stem cell lineages such as skeletal myoblasts, bone-marrow-derived stem cells (BMSCs), mesenchymal stem cells (MSCs), and cardiac stem cells (CSCs). To engraft these cells into patients' damaged myocardium, a variety of approaches (intramyocardial, transendocardial, transcoronary, venous, intravenous, intracoronary artery and retrograde venous administrations and bioengineered tissue transplantation) have been developed and explored. In this paper, we will discuss the pros and cons of these delivery modalities, the current state of their therapeutic potentials, and a multifaceted evaluation of their reported clinical feasibility, safety, and efficacy. While the issues of optimal delivery approach, the best progenitor stem cell type, the most effective dose, and timing of administration remain to be addressed, we are highly optimistic that stem cell therapy will provide a clinically viable option for myocardial regeneration.

Pharmacological preconditioning with erythropoietin attenuates the organ injury and dysfunction induced in a rat model of hemorrhagic shock

Pre-treatment with erythropoietin (EPO) has been demonstrated to exert tissue-protective effects against 'ischemia-reperfusion'-type injuries. This protection might be mediated by mobilization of bone marrow endothelial progenitor cells (EPCs), which are thought to secrete paracrine factors. These effects could be exploited to protect against tissue injury induced in cases where hemorrhage is foreseeable, for example, prior to major surgery. Here, we investigate the effects of EPO pre-treatment on the organ injury and dysfunction induced by hemorrhagic shock (HS). Recombinant human EPO (1000 IU/kg/day i.p.) was administered to rats for 3 days. Rats were subjected to HS on day 4 (pre-treatment protocol). Mean arterial pressure was reduced to 35 ± 5 mmHg for 90 minutes, followed by resuscitation with 20 ml/kg Ringer's lactate for 10 minutes and 50% of the shed blood for 50 minutes. Rats were sacrificed 4 hours after the onset of resuscitation. EPC (CD34(+)/flk-1(+) cell) mobilization was measured following the 3-day pre-treatment with EPO and was significantly increased compared with rats pre-treated with phosphate-buffered saline. EPO pre-treatment significantly attenuated organ injury and dysfunction (renal, hepatic and neuromuscular) caused by HS. In livers from rats subjected to HS, EPO enhanced the phosphorylation of Akt (activation), glycogen synthase kinase-3β (GSK-3β; inhibition) and endothelial nitric oxide synthase (eNOS; activation). In the liver, HS also caused an increase in nuclear translocation of p65 (activation of NF-κB), which was attenuated by EPO. This data suggests that repetitive dosing with EPO prior to injury might protect against the organ injury and dysfunction induced by HS, by a mechanism that might involve mobilization of CD34(+)/flk-1(+) cells, resulting in the activation of the Akt-eNOS survival pathway and inhibition of activation of GSK-3β and NF-κB.

The need for standardized protocols for future clinical trials of cell therapy

Multiple clinical trials have been conducted to determine the outcome of stem cell transplantation on cardiac function. However, marked variability in design across these trials has generated ambiguity in interpretation of their results. This review systematically evaluates the currently available protocols to illustrate the need for a standardized protocol for future trials.

Periprocedural adverse events in cell therapy trials in myocardial infarction and cardiomyopathy: a systematic review

BACKGROUND

Cell therapy (CTh) is a promising novel therapy for myocardial infarction (MI) and ischemic cardiomyopathy (iCMP). Recognizing adverse events (AE) is important for safety evaluation, harm prevention and may aid in the design of future trials.

OBJECTIVE

To define the prevalence of periprocedural AE in CTh trials in MI and iCMP.

METHODS

A literature search was conducted using the MEDLINE database from January 1990 to October 2010. Controlled clinical trials that compared CTh with standard treatment in the setting of MI and/or iCMP were selected. AE related to CTh were analyzed.

RESULTS

A total of 2,472 patients from 35 trials were included. There were 26 trials including 1,796 patients that used CTh in MI and 9 trials including 676 patients that used CTh in iCMP. Periprocedural arrhythmia monitoring protocols were heterogeneous and follow-up was short in most of the trials. In MI trials, the incidence of periprocedural adverse events (AE) related to intracoronary cell transplantation was 7.5 % (95 % CI 6.04-8.96 %). AE related to granulocyte colony-stimulating factor (GCS-F) used for cell mobilization for peripheral apheresis was 16 % (95 % CI 9.44-22.56 %). During intracoronary transplantation in iCMP, the incidence of periprocedural AE incidence was 2.6 % (95 % CI 0.53-4.67 %). There were no AE reported during transepicardial transplantation and AE were rare during transendocardial transplantation.

CONCLUSIONS

The majority of periprocedural AE in CTh trials in MI occurred during intracoronary transplantation and GCS-F administration. In iCMP, periprocedural AE were uncommon. Avoiding intracoronary route for CTh implantation may decrease the burden of periprocedural AE. Standardization of AE definition in CTh trials is needed.

Cell delivery routes for stem cell therapy to the heart: current and future approaches

An important factor to determine the success of stem cell therapy to the heart is the choice of cell delivery route. This will affect the fate of donor cells and subsequently influence the outcome of treatment; however, there is currently no optimum cell delivery route appropriate for every disease condition or every donor cell type. This review summarises currently available approaches for administering cells to the heart, with a particular focus on cell retention/survival and the therapeutic benefits seen in preclinical and clinical studies. Two major approaches are intracoronary and intramyocardial injection, which have been widely used for the delivery of various types of cells. Although there are advantages to both approaches, donor cell retention and survival are poor using these methods, potentially limiting therapeutic effects. Various attempts to improve current approaches, along with the development of emerging new approaches, are also described and discussed in this review.

Endothelial progenitor cells and left ventricle function in patients with acute myocardial infarction: potential therapeutic considertions

Endothelial progenitor cells (EPCs) play a key role in angiogenesis and vascular repair, although their exact functions are still disputable. The impact of EPC on left ventricular ejection fraction (LVEF) during acute myocardial infarction (MI) in patients treated with primary percutaneous coronary intervention (PCI) is also under investigation. The aim of this study was to assess the impact of different populations of EPC on LVEF during and 6 months after acute MI treated with primary PCI. The study included 34 patients with documented acute anterior wall MI. The control group consisted of 19 apparently healthy subjects. Blood for EPC assessments was obtained during the first 24 hours after MI and at 7 days and 6 months after PCI. CD34⁺/CD133⁺/CD45⁻, CD34⁺/CD31⁺/CD45⁻, CD34⁺/CD105⁺/CD45⁻, and CD31⁺/CD133⁺/CD45⁻ cell types were studied by flow cytometry. Echocardiography has been performed simultaneously with the EPC measurements. We observed a significant elevation of CD34⁺/CD133⁺/CD45⁻, CD34⁺/CD105⁺/CD45⁻, and CD31⁺/CD133⁺/CD45⁻ EPC at 7 days after PCI in comparison with 24 hours and 6 months after the MI. Patients with preserved LVEF at 7 days after PCI had also higher levels of CD31⁺/CD133⁺/CD45⁻. Acute anterior wall MI treated with primary PCI is followed by enhanced mobilization of EPC among which a high level of CD31⁺/CD133⁺/CD45⁻ subtype was strongly associated with the most preserved LVEF for up to 6 months after the index event. These data may provide some insight for future therapeutic strategies.

Nitric oxide-donating statin improves multiple functions of circulating angiogenic cells

BACKGROUND AND PURPOSE

Statins, a major component of the prevention of cardiovascular disease, aid progenitor cell functions in vivo and in vitro. Statins bearing a NO-releasing moiety were developed for their enhanced anti-inflammatory/anti-thrombotic properties. Here, we investigated if the NO-donating atorvastatin (NCX 547) improved the functions of circulating angiogenic cells (CACs).

EXPERIMENTAL APPROACH

Circulating angiogenic cells (CACs) were prepared from peripheral blood monocytes of healthy volunteers and type-2 diabetic patients and were cultured in low (LG) or high glucose (HG) conditions, in presence of atorvastatin or NCX 547 (both at 0.1 µM) or vehicle. Functional assays (outgrowth, proliferation, viability, senescence and apoptosis) were performed in presence of the endothelial NOS inhibitor L-NIO, the NO scavenger c-PTIO or vehicle.

KEY RESULTS

Culturing in HG conditions lowered NO in CACs, inhibited outgrowth, proliferation, viability and migration, and induced cell senescence and apoptosis. NCX 547 fully restored NO levels and functions of HG-cultured CACs, while atorvastatin prevented only apoptosis in CACs. The activity of Akt, a pro-survival kinase, was increased by atorvastatin in LG-cultured but not in HG-cultured CACs, whereas NCX 547 increased Akt activity in both conditions. L-NIO partially blunted and c-PTIO prevented NCX 547-induced improvements in CAC functions. Finally, NCX 547 improved outgrowth and migration of CACs prepared from patients with type 2 diabetes.

CONCLUSIONS AND IMPLICATIONS

NCX 547 was more effective than atorvastatin in preserving functions of CACs. This property adds to the spectrum of favourable actions that would make NO-releasing statins more effective agents for treating cardiovascular disease.

Advances in bone marrow-derived cell therapy: CD31-expressing cells as next generation cardiovascular cell therapy

In the past few years, bone marrow (BM)-derived cells have been used to regenerate damaged cardiovascular tissues post-myocardial infarction. Recent clinical trials have shown controversial results in recovering damaged cardiac tissue. New progress has shown that the underlying mechanisms of cell-based therapy relies more heavily on humoral and paracrine effects rather than on new tissue generation. However, studies have also reported the potential of new endothelial cell generation from BM cells. Thus, efforts have been made to identify cells having higher humoral or therapeutic effects as well as their surface markers. Specifically, BM-derived CD31+ cells were isolated by a surface marker and demonstrated high angio-vasculogenic effects. This article will describe recent advances in the therapeutic use of BM-derived cells and the usefulness of CD31+ cells.

In vivo tracking of transplanted mononuclear cells using manganese-enhanced magnetic resonance imaging (MEMRI)

BACKGROUND

Transplantation of mononuclear cells (MNCs) has previously been tested as a method to induce therapeutic angiogenesis to treat limb ischemia in clinical trials. Non-invasive high resolution imaging is required to track the cells and evaluate clinical relevance after cell transplantation. The hypothesis that MRI can provide in vivo detection and long-term observation of MNCs labeled with manganese contrast-agent was investigated in ischemic rat legs.

METHODS AND FINDINGS

The Mn-labeled MNCs were evaluated using 7-tesla high-field magnetic resonance imaging (MRI). Intramuscular transplanted Mn-labeled MNCs were visualized with MRI for at least 7 and up to 21 days after transplantation in the ischemic leg. The distribution of Mn-labeled MNCs was similar to that of ¹¹¹In-labeled MNCs measured with single-photon emission computed tomography (SPECT) and DiI-dyed MNCs with fluorescence microscopy. In addition, at 1-2 days after transplantation the volume of the site injected with intact Mn-labeled MNCs was significantly larger than that injected with dead MNCs, although the dead Mn-labeled MNCs were also found for approximately 2 weeks in the ischemic legs. The area covered by CD31-positive cells (as a marker of capillary endothelial cells) in the intact Mn-MNCs implanted site at 43 days was significantly larger than that at a site implanted with dead Mn-MNCs.

CONCLUSIONS

The present Mn-enhanced MRI method enabled visualization of the transplanted area with a 150-175 µm in-plane spatial resolution and allowed the migration of labeled-MNCs to be observed for long periods in the same subject. After further optimization, MRI-based Mn-enhanced cell-tracking could be a useful technique for evaluation of cell therapy both in research and clinical applications.

Endothelial progenitor cells: a novel tool for the therapy of ischemic diseases

Circulating endothelial progenitor cells (EPCs) are believed to home to sites of neovascularization, contributing to vascular regeneration either directly via incorporation into newly forming vascular structures or indirectly via the secretion of pro-angiogenic growth factors, thereby enhancing the overall vascular and hemodynamic recovery of ischemic tissues. The therapeutic application of EPCs has been shown to be effective in animal models of ischemia, and we as well as other groups involved in clinical trials have demonstrated that the use of EPCs was safe and feasible for the treatment of critical limb ischemia and cardiovascular diseases. However, many issues in the field of EPC biology, especially in regard to the proper and unambiguous molecular characterization of these cells, still remain unresolved, hampering not only basic research but also the effective therapeutic use and widespread application of these cells. Further, recent evidence suggests that several diseases and pathological conditions are correlated with a reduction in the number and biological activity of EPCs, making the development of novel strategies to overcome the current limitations and shortcomings of this promising but still limited therapeutic tool by refinement and improvement of EPC purification, expansion, and administration techniques, a rather pressing issue.

Adult stem cells in the treatment of acute myocardial infarction

Stem cell therapy has emerged as a novel therapeutic treatment alternative for early and end stage LV dysfunction. The rapid translation into clinical trials has left many questions unanswered. Moreover, results of randomized trials in the setting of acute myocardial infarction are controversial, emphasizing a need for further basic and translational research to improve understanding of cell functionality. This review attempts to summarize some of the functional issues related to cell therapy and also evaluate the current status of stem cell clinical trials. Although results to date have shown modest improvement in left ventricular function, the progress should follow a coordinated, multidisciplinary, and well designed path to address issues of cell homing, cell retention, and also look at outcomes beyond physiological parameters.

A novel and simplified method of culture of human blood-derived early endothelial progenitor cells for the treatment of ischemic vascular disease

Endothelial progenitor cells (EPCs) consist of two different subpopulations named early (eEPCs) and late EPCs (lEPCs) that are derived from CD14(+) and CD14(-) circulating cells, respectively. These cells are regularly cultured over fibronectin-coated surfaces in endothelial basal medium (EBM)-2 supplemented with insulin-like growth factor (IGF-1), vascular endothelial growth factor (VEGF), epidermal growth factor (EGF), and fibroblast growth factor (FGF). We have developed a new and simplified method for culturing human EPCs obtained from peripheral blood and tested their ability to preserve cardiac function following infarction. We first demonstrated that eEPCs derived from human peripheral blood mononuclear cells (PBMCs) and cultured in EBM-2 medium supplemented with autologous serum (10%) over fibronectin-coated surfaces (10 μg/ml) in the presence of IGF-1 (50 ng/ml) only, have a secretome similar to eEPCs cultured under regular conditions with IGF-1, VEGF, EGF, and FGF. Our data also indicate that IGF-1 modulates PBMC secretome in a dose-dependent manner. In another series of experiments, we showed that PBMCs cultured in suspension in bags (S-PBMCs) in basal medium supplemented with fibronectin and IGF-1 secrete significant amounts of stem cell factor (SCF, 31.3 ± 3.1 pg/ml)), hepatocyte growth factor (HGF, 438.6 ± 41.4 pg/ml), soluble tumor necrosis factor receptor 1 (sTNFR1, 127.1 ± 9.9 pg/ml), VEGF (139.3 ± 9.6 pg/ml), and IGF-1 (147.2 ± 46.1 pg/ml) but very low levels of TNF-α (13.4 ± 2.5 pg/ml). S-PBMCs injected intravenously into NOD SCID mice migrated to the injured myocardium, reduced cardiac fibrosis, enhanced angiogenesis, and preserved cardiac function after myocardial infarction (MI) in a manner similar to eEPCs cultured under standard conditions. In conclusion, we show in this study a refined and optimized method for culturing eEPCs. Our data indicate that S-PBMCs are composed of several cell populations including eEPCs and that they secrete high amounts of antiapoptotic, anti-inflammatory, and proangiogenic factors capable of preserving cardiac function following MI.

The role of PET with 13N-ammonia and 18F-FDG in the assessment of myocardial perfusion and metabolism in patients with recent AMI and intracoronary stem cell injection

Over the last decade, the effects of stem cell therapy on cardiac repair after acute myocardial infarction (AMI) have been investigated with different imaging techniques. We evaluated a new imaging approach using (13)N-ammonia and (18)F-FDG PET for a combined analysis of cardiac perfusion, metabolism, and function in patients treated with intracoronary injection of endothelial progenitors or with conventional therapy for AMI.

METHODS

A total of 15 patients were randomly assigned to 3 groups based on different treatments (group A: bone marrow-derived stem cells; group B: peripheral blood-derived stem cells; group C: standard therapy alone). The number of scarred and viable segments, along with the infarct size and the extent of the viable area, were determined on a 9-segment (13)N-ammonia/(18)F-FDG PET polar map. Myocardial blood flow (MBF) was calculated for each segment on the ammonia polar map, whereas a global evaluation of left ventricular function was obtained by estimating left ventricular ejection fraction (LVEF) and end-diastolic volume, both derived from electrocardiography-gated (18)F-FDG images. Both intragroup and intergroup comparative analyses of the mean values of each parameter were performed at baseline and 3, 6, and 12 mo after AMI. During follow-up, major cardiac events were also registered.

RESULTS

A significant decrease (P < 0.05) in the number of scarred segments and infarct size was observed in group A, along with an increase in MBF (P < 0.05) and a mild improvement in cardiac function. Lack of infarct size shrinkage in group B was associated with a marked impairment of MBF (P = 0.01) and cardiac dysfunction. Ambiguous changes in infarct size, MBF, and LVEF were found in group C. No differences in number of viable segments or in extent of viable area were found among the groups. At clinical follow-up, no major cardiac events occurred in group A patients, whereas 2 patients of group B experienced in-stent occlusion and one patient of group C received a transplant for heart failure.

CONCLUSION

Our data suggest that a single nuclear imaging technique accurately analyzes changes in myocardial perfusion and metabolism occurring after stem cell transplantation.

Age, gender and diabetic status are associated with effects of bone marrow cell therapy on recovery of left ventricular function after acute myocardial infarction: a systematic review and meta-analysis

Clinical studies on intracoronary bone marrow cell (BMCs) infusion in patients with acute myocardial infarction (AMI) revealed mixed results. Recently, meta-analysis on this topic have been conducted and found that there was marked heterogeneity between trials. The objective of this systematic review is to have a retrospection of the efficacy of cell therapy and explore whether the study design or characteristics of subjects may have influenced the effects of cell therapy on recovery of left ventricular function after AMI. Trials were identified in ClinicalTrial, mRCT, Cochrane Library, EMBASE, and PubMed databases, reviews, and reference lists of relevant papers. The weighted mean difference (WMD) was calculated for net changes in left ventricular ejection fraction (LVEF) by using random-effect models. Meta-regression analyses were performed to explore the influence of study characteristics. Ten randomized controlled trials (12 comparisons) with a total of 814 participants were included. In an overall pooled estimate, compared with the control group, BMCs therapy significantly improved the LVEF change from baseline to follow-up (WMD: 3.79%, 95% CI: 2.4-5.7%, P<0.001; heterogeneity test: I(2)=82.7%, P<0.001). A multivariate meta-regression analysis was conducted to investigate the potential sources of heterogeneity. The model including age (coefficient=21%, P=0.04), male proportion (coefficient=-14%, P=0.001) and diabetic patients' proportion (coefficient=17%, P=0.002) explained most of the identified heterogeneity. The present systematic review and meta-analysis suggest that (1) BMCs therapy is effective at improving the LVEF; (2) BMCs therapy is more effective in ageing and diabetic individuals, whereas less effective in males.

Bone marrow and circulating stem/progenitor cells for regenerative cardiovascular therapy

Cardiovascular disease is the leading cause of death and disability in the Western world. In addition to the advancement of current therapeutic approaches to reduce the associated morbidity and mortality, regenerative medicine and cell-based therapy have been areas of continuous investigation. Circulating and bone-marrow-derived stem or endothelial progenitor cells are an attractive source for regenerative therapy in the cardiovascular field. In this review, we highlight the advantages and limitations of this approach with a focus on key observations from animal studies and clinical trials.

Clinical potential of adult vascular progenitor cells

Cell therapy to treat vascular and cardiovascular diseases has evolved over the past decade with improved understanding of progenitor cell mobilization, recruitment, and differentiation. The beneficial effects seen in several preclinical studies have prompted translation of adult vascular progenitor therapy to clinical trials. To date, progenitor cells isolated from bone marrow and peripheral blood have been tested in the context of acute myocardial infarction and chronic ischemic cardiomyopathy, with moderate benefit. This therapeutic effect occurs despite a relatively small number of injected progenitor cells and short-term residence in the target zone. Thus, indirect benefits, such as paracrine factors released from these cells, have been suggested as significant contributors to therapeutic efficacy. Several additional vascular progenitors of endothelial, smooth muscle, mesenchymal, and cardiac origin have been identified that may contribute to vasculogenesis. Indeed, a unifying paradigm for the most effective cell therapy strategies to date appears to be robust support of angiogenesis. Here we discuss a number of progenitor cells that currently show potential as cardiovascular therapeutics, either singly or in combination. We look at emerging cell types and disease targets that may be exploited for therapeutic benefit and future strategies that may maximize clinical efficacy.

Characterizing functional stem cell-cardiomyocyte interactions

Despite the progress in traditional pharmacological and organ transplantation therapies, heart failure still afflicts 5.3 million Americans. Since June 2000, stem cell-based approaches for the prevention and treatment of heart failure have been pursued in clinics with great excitement; however, the exact mechanisms of how transplanted cells improve heart function remain elusive. One of the main difficulties in answering these questions is the limited ability to directly access and study interactions between implanted cells and host cardiomyocytes in situ. With the growing number of candidate cell types for potential clinical use, it is becoming increasingly more important to establish standardized, well-controlled in vitro and in situ assays to compare the efficacy and safety of different stem cells in cardiac repair. This article describes recent innovative methodologies to characterize direct functional interactions between stem cells and cardiomyocytes, aimed to facilitate the rational design of future cell-based therapies for heart disease.

Stem cell therapy for the treatment of acute myocardial infarction

The last decade has been accompanied by great optimism and interest in the concept of cell or tissue regeneration in the postinfarction myocardium. However, despite the promise, progress was slow. Data derived from multiple controlled studies in hundreds of patients postmyocardial infarction have shown hints of potential benefit but not of the magnitude anticipated. The complexity and hurdles to repair the damaged myocardium have been more daunting than originally estimated. In the end analysis, progress will be made incrementally. The promise for cell therapy continues to be significant, but so are the challenges ahead. This article takes a fresh look at the progress in myocardial regeneration. The authors look at the postmyocardial environment for cues that may guide repair and they look closely at the clinical data for evidence of cardiac regeneration. This evidence is used for suggestions on how to best proceed with future work.

Role of the SDF-1/CXCR4 system in myocardial infarction

Myocardial infarction (MI) is accompanied by an inflammatory response, leading to the recruitment of leukocytes and subsequent myocardial injury and healing. Chemokines are potent chemoattractant cytokines that regulate leukocyte trafficking in inflammatory processes. Recent evidence indicates that chemokines play a role not only in leukocyte trafficking but also in angiogenesis and cardioprotection. In particular, stromal cell-derived factor-1alpha (SDF-1alpha) has generated considerable interest for its role in the pathophysiology of MI. This review will focus on the role of SDF-1 and its receptor CXC chemokine receptor 4 (CXCR4; ie, the SDF-1/CXCR4 system) in the pathophysiology of MI and discuss their potential as therapeutic targets for MI.

Stem cell therapy in acute myocardial infarction: a review of clinical trials

Stem cells (SCs) possess the ability to differentiate into cells of various tissues. Although the differentiation of SCs into functional cardiomyocytes has been difficult to demonstrate in humans, clinical trials using SCs in the setting of acute myocardial infarction (AMI) have demonstrated variable results. Interpretation of these trials has been difficult because of multiple variables, which include differences in trial design, cell type, timing of cell delivery, and outcome measurements. Herein, a summary of all clinical trials in subgroups of direct injection, indirect mobilization, and combination approaches of SC therapy in AMI is provided with significant findings in each group.

Ex-vivo expanded umbilical cord blood stem cells retain capacity for myocardial regeneration

BACKGROUND

Umbilical cord blood (UCB) is a source of human hematopoietic precursor cells (HPCs), a stem cell (SC) type that has been used in several trials for myocardial repair. A certain minimal number of cells is required for measurable regeneration and a major challenge of SC-based regenerative therapy constitutes ex-vivo expansion of the primitive cell compartment. The aim of this study was to investigate the ex-vivo expansion potential of UCB-derived HPCs and the ability of these expanded cells to migrate to the site of damage and improve ventricular function in a rodent model of myocardial infarction (MI).

METHODS AND RESULTS

UCB-derived HPCs, defined by coexpression of CD133 and CD34, were expanded using various cytokine combinations. MI was induced by left anterior descending artery ligation in nude rats. Cells were injected intravenously 2 days after infarction. The combination of SC factor, thrombopoietin, flt3-ligand and interleukin-6 was found to be the most effective for inducing proliferation of HPCs. The migratory capacity of expanded HPCs was similar to that of non-expanded HPCs and improvement of ejection fraction was significant in both groups, with a relative increase of >60%.

CONCLUSIONS

UCB-derived HPCs can be reproducibly expanded ex-vivo and retain their potential to improve cardiac function post-MI. (Circ J 2010; 74: 188 - 194).

Stem cell-related therapies for vascular diseases

The therapeutic potential of 'adult' or at least non-embryonic stem cells and their progeny has developed gradually over the past half century as a consequence of the wealth of knowledge derived from stem cell research. Translational research coupled with clinical trials and derived from basic research has led the way to the clinic. This commenced with the use of haematopoietic stem cell transplantation (HSCT), to treat haematological malignancies, to be followed by the most recent clinical trials to treat a variety of coronary and peripheral artery diseases. Stem cells and their progeny isolated from bone marrow or blood appear to exert an ameliorating effect in certain vascular disorders. Although promising, some of these treatments remain controversial and further research and, where indicated, appropriately powered trials are required to confirm the safety and determine the efficacy of these novel therapies.

Endothelial progenitor cells and cardiovascular cell-based therapies

Since their initial discovery more than a decade ago, bone marrow (BM)-derived circulating endothelial progenitor cells (EPC) have been reported to play a role in postnatal vasculogenesis through vessel regeneration and remodeling. These cells have been reported to mobilize into the blood stream in response to vascular injury, and differentiate into cells expressing a host of endothelial cell (EC) markers in vitro. Because of demonstrable regenerative capacity in animal models of human disease, EPC are thought to represent a novel treatment option for problematic cardiovascular conditions such as myocardial infarction (MI) and peripheral vascular disease (PVD). Various studies have been performed to test the clinical efficacy of EPC in patients with cardiovascular disease (CVD), including the mobilization of EPC with pharmacologic agents in patients with heart disease, and harvesting of cells from the circulation and BM for autologous reinfusion in affected patients. The outcomes of these trials have been mixed and not as robust as predicted from the animal models, partly because of the variation in the definition of human EPC and the resulting heterogeneity in cell populations used in the treatments. This review will decipher a number of published studies that have been conducted to examine cell therapies for treatment of CVD, will attempt to explain why efficacy of treatment with putative EPC has been inconsistent, and predict which aspects of these trials may need to be redesigned for future successful treatment of CVD.

Transplantation of Endothelial Progenitor Cells as Therapeutics for Cardiovascular Diseases

With better understanding of endothelial progenitor cells (EPCs), many therapeutic approaches to cardiovascular diseases have been developed. This article will review novel research of EPCs in promoting angiogenesis, vasculogenesis, and endothelialization, as a design for future clinical treatment. Cell therapy has the potential to supply stem/progenitor cells and multiple angiogenic factors to the region of ischemia. The efficacy of EPC transplantation may be impaired by low survival rate, insufficient cell number, and impaired function in aging and diseases. Combination of EPCs or cells primed with growth factors or genetic modification may improve the therapeutic efficacy. The molecular mechanism involved in EPC repairing processes is essential. Thus, we have also addressed the molecular mechanism of mobilization, homing, and differentiation of EPCs. The potential of therapeutic neovascularization, angiogenic factor therapy, and cell transplantation have been elucidated. Based on past experience and actual knowledge, future strategies for EPC therapy will be proposed in order to fully exploit the potential of EPC transplantation with clinical relevance for cardiovascular disease applications.

Erythropoietin in patients with acute coronary syndrome and its cardioprotective action after percutaneous coronary intervention

BACKGROUND

Erythropoietin (EPO) has been shown to have effects beyond hematopoiesis, such as prevention of cardiac apoptosis. The purpose of the current study is to examine the influence of the time-course change in the serum concentration of endogenous EPO on cardiac functions in the chronic phase in patients with acute coronary syndrome, who successfully achieved reperfusion by primary percutaneous coronary intervention (PCI).

METHODS AND RESULTS

The prospective study included 34 patients with angiographically documented coronary artery disease, including 24 patients with acute myocardial infarction (AMI) and 10 patients with unstable angina pectoris (UAP) who underwent successful PCI within 24 h from the onset. Serum EPO concentration significantly increased at Day 3 and Day 7 compared with that at Day 1 in the AMI group, and the level at Day 3 was significantly higher in the AMI group than in the UAP group. There were significant correlations between DeltaEPO and Delta left ventricular ejection fraction (LVEF) or Delta left ventricular end-diastolic volume index and between peak EPO concentration and DeltaLVEF.

CONCLUSIONS

These data showed the time-dependent increase of serum EPO in AMI patients after primary PCI, indicating its possible contribution to cardioprotective effect in the chronic phase.

Cardiac repair with adult bone marrow-derived cells: the clinical evidence

On the basis of strong evidence from animal studies, numerous clinical trials of cardiac repair with adult bone marrow-derived cells (BMC) have been completed. These relatively smaller studies employed different BMC types with highly variable numbers, routes, and timings of transplantation, and included patients with acute myocardial infarction (MI), chronic ischemic heart disease (IHD), as well as ischemic cardiomyopathy. Although the outcomes have been predictably disparate, analysis of pooled data indicates that BMC therapy in patients with acute MI and chronic IHD results in modest improvements in left ventricular function and infarct scar size without any increase in untoward effects. However, the precise mechanisms underlying these benefits remain to be ascertained, and the specific advantages of one BMC type over another remain to be determined. The long-term benefit and safety issues with different BMC types are currently being evaluated critically in larger randomized controlled trials with a view to applying this novel therapeutic strategy to broader patient populations. The purpose of this review is to summarize the available clinical evidence regarding the efficacy and safety of therapeutic cardiac repair with different types of adult BMCs, and to discuss the key variables that need optimization to further enhance the benefits of BMC therapy.

The BALANCE Study: clinical benefit and long-term outcome after intracoronary autologous bone marrow cell transplantation in patients with acute myocardial infarction

OBJECTIVES

The aim of this study was to investigate the quantitative amount of improvement of ventricular hemodynamic status, geometry, and contractility as well as the long-term clinical outcome of cell-treated patients after acute myocardial infarction (AMI).

BACKGROUND

Animal experiments as well as clinical studies have demonstrated that autologous bone marrow cell (BMC) transplantation might improve ventricular function and prevent remodeling.

METHODS

Sixty-two patients underwent intracoronary autologous BMC transplantation 7 +/- 2 days after AMI. Cells were infused directly into the infarct-related artery. The control group consisted of 62 patients with comparable left ventricular (LV) ejection fraction (EF) and diagnosis. All patients had several examinations (e.g., coronary angiography, right heart catheterization, biplane left ventriculography, electrocardiogram [ECG] at rest and exercise, echocardiography, late potential [LP], heart rate variability [HRV], and 24-h Holter ECG). The therapeutic follow-up was performed 3, 12, and 60 months after BMC therapy.

RESULTS

Three months after BMC therapy there was significant improvement of EF and stroke volume index. The infarct size was significantly reduced by 8%. Contraction velocities (lengths/second, volumes/second) increased significantly and the slope of the ventricular function curve (systolic pressure/end-systolic volume) became steeper. There was significant improvement of contractility in the infarct zone, as evidenced by a 31% increase of LV velocity of shortening (VCF), preferably in the border zone of the infarct zone. In contrast, the noninfarcted area showed no difference in VCF before and after BMC therapy. Furthermore, decreases of abnormal HRV, LP, and ectopic beats were documented after BMC therapy. Twelve and 60 months after BMC therapy the parameters of contractility, hemodynamic status, and geometry of the LV were stable. The exercise capacity of treated patients was significantly augmented, and the mortality was significantly reduced in comparison with the control group.

CONCLUSIONS

BMC therapy leads to significant and longstanding improvements of LV performance as well as quality of life and mortality of patients after AMI. After BMC therapy, no side effects were observed, showing that BMC therapy is safe.

Cardiac repair and regeneration: the Rubik's cube of cell therapy for heart disease

Acute ischemic injury and chronic cardiomyopathies damage healthy heart tissue. Dead cells are gradually replaced by a fibrotic scar, which disrupts the normal electromechanical continuum of the ventricular muscle and compromises its pumping capacity. Recent studies in animal models of ischemic cardiomyopathy suggest that transplantation of various stem cell preparations can improve heart recovery after injury. The first clinical trials in patients produced some encouraging results, showing modest benefits. Most of the positive effects are probably because of a favorable paracrine influence of stem cells on the disease microenvironment. Stem cell therapy attenuates inflammation, reduces apoptosis of surrounding cells, induces angiogenesis, and lessens the extent of fibrosis. However, little new heart tissue is formed. The current challenge is to find ways to improve the engraftment, long-term survival and appropriate differentiation of transplanted stem cells within the cardiovascular tissue. Hence, there has been a surge of interest in pluripotent stem cells with robust cardiogenic potential, as well as in the inherent repair and regenerative mechanisms of the heart. Recent discoveries on the biology of adult stem cells could have relevance for cardiac regeneration. Here, we discuss current developments in the field of cardiac repair and regeneration, and present our ideas about the future of stem cell therapy.