Lack of regeneration of myocardium by autologous intracoronary mononuclear bone marrow cell transplantation in humans with large anterior myocardial infarctions

An Overview on Current Issues and Challenges of Endothelial Progenitor Cell-Based Neovascularization in Patients with Diabetic Foot Ulcer

Diabetic foot ulcer's impaired wound healing, which leads to the development of chronic non-healing wounds and ultimately amputation, is a major problem worldwide. Although recently endothelial progenitor cell-derived cell therapy has been used as a therapeutic intervention to treat diabetic wounds, thereby promoting neovascularization, the results, however, are not satisfactory. In this article, we have discussed the several steps that are involved in the neovascularization process, which might be impaired during diabetes. In addition, we have also discussed the reported possible interventions to correct these impairments. Thus, we have summarized neovascularization as a process with a coordinated sequence of multiple steps and thus, there is the need of a combined therapeutic approach to achieve better treatment outcomes.

Effects of Intracoronary Administration of Autologous Adipose Tissue-Derived Stem Cells on Acute Myocardial Infarction in a Porcine Model

PURPOSE

Adipose-derived stem cells (ADSCs) are known to be potentially effective in regeneration of damaged tissue. We aimed to assess the effectiveness of intracoronary administration of ADSCs in reducing the infarction area and improving function after acute transmural myocardial infarction (MI) in a porcine model.

MATERIALS AND METHODS

ADSCs were obtained from each pig's abdominal subcutaneous fat tissue by simple liposuction. After 3 passages of 14-days culture, 2 million ADSCs were injected into the coronary artery 30 min after acute transmural MI. At baseline and 4 weeks after the ADSC injection, 99mTc methoxyisobutylisonitrile-single photon emission computed tomography (MIBISPECT) was performed to evaluate the left ventricular volume, left ventricular ejection fraction (LVEF; %), and perfusion defects as well as the myocardial salvage (%) and salvage index. At 4 weeks, each pig was sacrificed, and the heart was extracted and dissected. Gross and microscopic analyses with specific immunohistochemistry staining were then performed.

RESULTS

Analysis showed improvement in the perfusion defect, but not in the LVEF in the ADSC group (n=14), compared with the control group (n=14) (perfusion defect, -13.0±10.0 vs. -2.6±12.0, p=0.019; LVEF, -8.0±15.4 vs. -15.9±14.8, p=0.181). There was a tendency of reducing left ventricular volume in ADSC group. The ADSCs identified by stromal cell-derived factor-1 (SDF-1) staining were well co-localized by von Willebrand factor and Troponin T staining.

CONCLUSION

Intracoronary injection of cultured ADSCs improved myocardial perfusion in this porcine acute transmural MI model.

Intravenous Followed by X-ray Fused with MRI-Guided Transendocardial Mesenchymal Stem Cell Injection Improves Contractility Reserve in a Swine Model of Myocardial Infarction

The aim of this study is to determine the effects of early intravenous (IV) infusion later followed by transendocardial (TE) injection of allogeneic mesenchymal stem cells (MSCs) following myocardial infarction (MI). Twenty-four swine underwent balloon occlusion reperfusion MI and were randomized into 4 groups: IV MSC (or placebo) infusion (post-MI day 2) and TE MSC (or placebo) injection targeting the infarct border with 2D X-ray fluoroscopy fused to 3D magnetic resonance (XFM) co-registration (post-MI day 14). Continuous ECG recording, MRI, and invasive pressure-volume analyses were performed. IV MSC plus TE MSC treated group was superior to other groups for contractility reserve (p = 0.02) and freedom from VT (p = 0.03) but had more lymphocytic foci localized to the peri-infarct region (p = 0.002). No differences were observed in post-MI remodeling parameters. IV followed by XFM targeted TE MSC therapy improves contractility reserve and suppresses VT but does not affect post-MI remodeling and may cause an immune response.

Genome-wide epigenetic and proteomic analysis reveals altered Notch signaling in EPC dysfunction

Endothelial progenitor cells (EPCs) are bone-marrow-derived mononuclear cells that participate in tube formation in vitro and vessel formation in vivo. EPC transplantation, as a therapeutic approach in cardiovascular diseases, has produced mixed results likely due to underlying disease states and environmental factors affecting EPC function. In this study, we investigated the mechanisms by which a high-salt diet impairs EPC function. The number of endothelial progenitor cells (CD34(+), VEGFR2(+), CD133(+), and c-Kit(+)) was decreased in the bone marrow of Sprague-Dawley (SD) rats fed a high-salt diet (HSD; 4% NaCl) as compared to SD rats on a normal-salt diet (NSD; 0.4% NaCl). NSD EPCs augmented endothelial cell tube formation in vitro, whereas HSD EPCs did not. NSD EPCs were a potent therapeutic restoring electrical stimulation-induced angiogenesis in vivo. HSD EPCs were not able to restore angiogenesis in vivo. EPC DNA methylation was analyzed by reduced representative bisulfite sequencing and membrane proteins were analyzed using high accuracy liquid chromatography mass spectrometry. Differentially methylated genes and differentially abundant membrane proteins measured between the NSD and HSD EPCs, revealed a total of 886 gene-protein sets where reciprocal methylation and expression occurred. Based on stringent criteria, Notch4 was found to be hypermethylated in HSD EPCs and had corresponding decrease in protein expression. Suppression of Notch4 protein expression in EPCs using siRNA confirmed a role for Notch4 in EPC-mediated angiogenesis, suggesting Notch4 suppression as a mechanism by which high-salt diet inhibits EPC-mediated angiogenesis.

Clinical application of adult stem cells for therapy for cardiac disease

INTRODUCTION

Cardiovascular disease is a major cause of death worldwide. Different medical and surgical therapeutic options are well established, but a significant number of patients are not amenable to standard therapeutic options. Cell-based therapies after clinical application have shown different results in recent years. Here, we are giving a comprehensive overview on major available clinical data regarding cell therapy.

BACKGROUND

Cell-based therapies and tissue engineering provide new promising platforms to develop upcoming therapeutic options. Initial clinical trials were able to generate promising results. A variety of different stem cell types have been used for the clinical application. Different adult cardiac stem cells and progenitor cells, including mesenchymal, CD34(+) and CD133(+) autologous human bone marrow-derived stem cells (BMCs), human myoblasts, and peripheral blood-derived stem and progenitor cells (PBSCs) have been used for the therapy for end-stage heart failure. Future experiments will show the importance of novel cell populations and clarify the mechanism causing cell therapy-mediated observed effects.

CONCLUSION

Several clinical trials have reported on sole therapy, as well as combined application of autologous adult stem cells with conventional revascularization. The reported promising findings encourage further research in the field of the translational research.

Tracking of stem cells in vivo for cardiovascular applications

In the past ten years, the concept of injecting stem and progenitor cells to assist with rebuilding damaged blood vessels and myocardial tissue after injury in the heart and peripheral vasculature has moved from bench to bedside. Non-invasive imaging can not only provide a means to assess cardiac repair and, thereby, cellular therapy efficacy but also a means to confirm cell delivery and engraftment after administration. In this first of a two-part review, we will review the different types of cellular labeling techniques and the application of these techniques in cardiovascular magnetic resonance and ultrasound. In addition, we provide a synopsis of the cardiac cellular clinical trials that have been performed to-date.

Postischemic revascularization: from cellular and molecular mechanisms to clinical applications

After the onset of ischemia, cardiac or skeletal muscle undergoes a continuum of molecular, cellular, and extracellular responses that determine the function and the remodeling of the ischemic tissue. Hypoxia-related pathways, immunoinflammatory balance, circulating or local vascular progenitor cells, as well as changes in hemodynamical forces within vascular wall trigger all the processes regulating vascular homeostasis, including vasculogenesis, angiogenesis, arteriogenesis, and collateral growth, which act in concert to establish a functional vascular network in ischemic zones. In patients with ischemic diseases, most of the cellular (mainly those involving bone marrow-derived cells and local stem/progenitor cells) and molecular mechanisms involved in the activation of vessel growth and vascular remodeling are markedly impaired by the deleterious microenvironment characterized by fibrosis, inflammation, hypoperfusion, and inhibition of endogenous angiogenic and regenerative programs. Furthermore, cardiovascular risk factors, including diabetes, hypercholesterolemia, hypertension, diabetes, and aging, constitute a deleterious macroenvironment that participates to the abrogation of postischemic revascularization and tissue regeneration observed in these patient populations. Thus stimulation of vessel growth and/or remodeling has emerged as a new therapeutic option in patients with ischemic diseases. Many strategies of therapeutic revascularization, based on the administration of growth factors or stem/progenitor cells from diverse sources, have been proposed and are currently tested in patients with peripheral arterial disease or cardiac diseases. This review provides an overview from our current knowledge regarding molecular and cellular mechanisms involved in postischemic revascularization, as well as advances in the clinical application of such strategies of therapeutic revascularization.

Stem cell-derived endothelial cells for cardiovascular disease: a therapeutic perspective

Stem cell therapy and organ regeneration are therapeutic approaches that will, we suggest, become mainstream for the treatment of human disease. Endothelial cells, which line the luminal surface of every vessel in the body, are essential components in any organ regeneration programme. There are a number of potentially therapeutic endothelial cell types, including embryonic, adult progenitor and induced pluripotent stem cell-derived endothelial cells, as well as host vascular cells. The features (benefits as well as disadvantages) of each cell type that make them potentially useful in therapy are important to consider. The field of stem cell biology is well developed in terms of protocols for generating endothelium. However, where there is a distinct and urgent unmet need for knowledge concerning how the endothelial cells from these different sources function as endothelium and how susceptible they may be to inflammation and atherosclerosis. Furthermore, where stem cells have been used in clinical trials there is little commonality in protocols for deriving the cells (and thereby the specific phenotype of cells used), administering the cells, dosing the cells and/or in assessing efficacy attributed to the cells themselves. This review discusses these and other issues relating to stem cell-derived endothelial cells in cell therapy for cardiovascular disease.

A pilot trial of autologous bone marrow mononuclear cell transplantation through grafting artery: a sub-study focused on segmental left ventricular function recovery and scar reduction

BACKGROUND

Our preliminary study suggested that patients with chronic myocardial infarction (MI) and heart failure could potentially benefit from CABG combined with aBM-MNC by improving global left ventricular (LV) function. The purpose of this sub-study was to quantitatively evaluate the effectiveness of aBM-MNC transplantation during CABG in patients with chronic MI by intensively analyzing the global and segmental LV function, the scar, and the relationships between the function recovery and the scar transmural extent.

METHODS

A randomized, double-blinded, placebo-controlled study was performed in 50 patients with chronic MI. The patients were randomly allocated into CABG with stem cell transplantation (group A) and CABG only (group B) groups. CMR assessments of global and segmental left ventricular function and scar tissue were performed before surgery and repeated at 12 months after CABG and aBM-MNC transplantation.

RESULTS

The left ventricular ejection fraction (LVEF) improved by 13.5% and 8.0% in group A and B respectively (P=0.04). Segmental analysis of regional LV function recovery indicated that more improvement in contractility was found in group A within the same degree of the infarct transmurality (P=0.017) and showed a predominant interaction in the most severely affected segments (76-100%, P=0.016). Decrease in infarct size between the two groups did not reach statistical difference (9.4% vs. 6.0%, P=0.100).

CONCLUSIONS

CMR assessments revealed reversed ventricular remodeling and improved systolic function and scar reduction in patients who underwent aBM-MNC transplantation during CABG. And the conjunctional use of CABG and stem cell therapy could improve the left ventricular function in patients with chronic MI.

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.

A comprehensive study on optimization of proliferation and differentiation potency of bone marrow derived mesenchymal stem cells under prolonged culture condition

Bone marrow derived stem cells (BMSC) have paved way to clinical approaches for its utilization in a variety of diseases due to its ease of isolation combined with its multilineage differentiation capacity. However, the applicability of BMSC is not successful due to the lesser number of nucleated cells obtained from large samples. Hence, culture expansion of BMSC is a prerequisite, as high numbers of stem cells are needed to meet the standards of clinical advancement. There are attempts on optimizing culture condition for large scale production of BMSC. It was believed that, prolonged culture of BMSC is difficult since they tend to lose their characteristics and differentiation potential. Hence, our study aims to determine whether BMSCs could retain its proliferative and differentiation capacity in prolonged in vitro culture by a comparative study on extensive culturing of BMSC with the following four media, DMEM LG (DMEM-Low Glucose), DMEM KO (DMEM-Knock Out), Alpha MEM (Alpha Minimal Essential Medium), DMEM F 12. We found that two samples among the three cultured tend to lose their property in long term culturing. Besides, we also found that DMEM LG and Alpha MEM were the optimal media for in vitro culturing of BMSC. Overall, it was concluded that BMSC can be cultured until passage 15 without losing its characteristics. However, its potency beyond passage 15 has to be further elucidated for utilization of the ex vivo expanded BMSC for subsequent cellular therapies.

Surface antigenic profiling of stem cells from human omentum fat in comparison with subcutaneous fat and bone marrow

Omentum fat derived stem cells have emerged as an alternative and accessible therapeutic tool in recent years in contrast to the existing persuasive sources of stem cells, bone marrow and subcutaneous adipose tissue. However, there has been a scanty citation on human omentum fat derived stem cells. Furthermore, identification of specific cell surface markers among aforesaid sources is still controversial. In lieu of this existing perplexity, the current research work aims at signifying omentum fat as a ground-breaking source of stem cells by surface antigenic profiling of stem cell population. In this study, we examined and compared the profiling of cell surface antigenic expressions of hematopoietic stem cells, mesenchymal stem cells, cell adhesion molecules and other unique markers such as ABCG2, ALDH and CD 117 in whole cell population of human omentum fat, subcutaneous fat and bone marrow. The phenotypic characterization through flowcytometry revealed the positive expressions of CD 34, CD 45, CD 133, HLADR, CD 90, CD 105, CD 73, CD 29, CD 13, CD 44, CD 54, CD 31, ALDH and CD 117 in all sources. The similarities between the phenotypic expressions of omentum fat derived stem cells to that of subcutaneous fat and bone marrow substantiates that identification of ultimate source for curative therapeutics is arduous to assess. Nevertheless, these results support the potential therapeutic application of omentum fat derived stem cells.

Tracking stem cells for cardiovascular applications in vivo: focus on imaging techniques

Despite rapid translation of stem cell therapy into clinical practice, the treatment of cardiovascular disease using embryonic stem cells, adult stem and progenitor cells or induced pluripotent stem cells has not yielded satisfactory results to date. Noninvasive stem cell imaging techniques could provide greater insight into not only the therapeutic benefit, but also the fundamental mechanisms underlying stem cell fate, migration, survival and engraftment in vivo. This information could also assist in the appropriate choice of stem cell type(s), delivery routes and dosing regimes in clinical cardiovascular stem cell trials. Multiple imaging modalities, such as MRI, PET, SPECT and CT, have emerged, offering the ability to localize, monitor and track stem cells in vivo. This article discusses stem cell labeling approaches and highlights the latest cardiac stem cell imaging techniques that may help clinicians, research scientists or other healthcare professionals select the best cellular therapeutics for cardiovascular disease management.

Myocardial remodeling: cellular and extracellular events and targets

The focus of this review is on translational studies utilizing large-animal models and clinical studies that provide fundamental insight into cellular and extracellular pathways contributing to post-myocardial infarction (MI) left ventricle (LV) remodeling. Specifically, both large-animal and clinical studies have examined the potential role of endogenous and exogenous stem cells to alter the course of LV remodeling. Interestingly, there have been alterations in LV remodeling with stem cell treatment despite a lack of long-term cell engraftment. The translation of the full potential of stem cell treatments to clinical studies has yet to be realized. The modulation of proteolytic pathways that contribute to the post-MI remodeling process has also been examined. On the basis of recent large-animal studies, there appears to be a relationship between stem cell treatment post-MI and the modification of proteolytic pathways, generating the hypothesis that stem cells leave an echo effect that moderates LV remodeling.

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.

Randomized transcoronary delivery of CD34(+) cells with perfusion versus stop-flow method in patients with recent myocardial infarction: Early cardiac retention of ⁹⁹(m)Tc-labeled cells activity

BACKGROUND

For transcoronary progenitor cells' administration, injections under flow arrest (over-the-wire balloon technique, OTW) are used universally despite lack of evidence for being required for cell delivery or being effective in stimulating myocardial engraftment. Flow-mediated endothelial rolling is mandatory for subsequent cell adhesion and extravasation.

METHODS

To optimize cell directing toward the coronary endothelium under maintained flow, the authors developed a cell-delivery side-holed perfusion catheter (PC). Thirty-four patients (36-69 years, 30 men) with primary stent-assisted angioplasty-treated anterior MI (peak TnI 151 [53-356]ng/dL, mean[range]) were randomly assigned to OTW or PC autologous ⁹⁹Tc-extametazime-labeled bone marrow CD34(+) cells (4.34 [0.92-7.54] × 10⁶) administration at 6-14 days after pPCI (LVEF 37.1 [24-44]%). Myocardial perfusion (⁹⁹(m)Tc-MIBI) and labeled cells' activity were evaluated (SPECT) at, respectively, 36-48 h prior to and 60 min after delivery.

RESULTS

In contrast to OTW coronary occlusions, no intolerance or ventricular arrhythmia occurred with PC cells' administration (P < .001). One hour after delivery, 4.86 [1.7-7.6]% and 5.05 [2.2-9.9]% activity was detected in the myocardium (OTW and PC, respectively, P = .84). Labeled cell activity was clearly limited to the (viable) peri-infarct zone in 88% patients, indicating that the infarct core zone may be largely inaccessible to transcoronary-administered cells.

CONCLUSIONS

Irrespective of the transcoronary delivery method, only ≈ 5% of native (i.e., non-engineered) CD34(+) cells spontaneously home to the injured myocardium, and cell retention occurs preferentially in the viable peri-infarct zone. Although the efficacy of cell delivery is not increased with the perfusion method, by avoiding provoking ischemic episodes PC offers a rational alternative to the OTW delivery.

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.

Cell therapy for heart failure: the need for a new therapeutic strategy

Improvements in the treatment of ischemic heart disease have led to a significant growth in the numbers of patients with systolic heart failure secondary to myocardial injury. Current therapies fail to address the loss of contractile tissue due to myocardial injury. Cell therapy is singular in its promise of primarily treating this underlying issue through salvage of viable myocardium or generation of new contractile tissue. Multiple cell types have been used to target acute myocardial infarction, chronic ischemic heart disease and heart failure due to infarction. Bone marrow mononuclear cells have been used to increase myocardial salvage after acute infarction. Randomized trials of over 800 patients have demonstrated no safety issues, and meta-analyses have suggested an improvement in left ventricular function in treated patients with trends toward improvements in hard cardiac end points. Cell therapy for chronic ischemic heart disease with bone marrow angiogenic progenitors has shown similar safety and trends toward improvement in function. While these therapies have targeted patients with viable myocardium, myoblasts have been used to treat patients with left ventricular dysfunction secondary to transmural infarction. Cell types with cardiomyogenic potential, including induced pluripotent stem cells and cardiac progenitor cells, offer the promise of true myocardial regeneration. Future studies with these cells may open the door for true myocardial regeneration.

Role of the renin angiotensin system on bone marrow-derived stem cell function and its impact on skeletal muscle angiogenesis

Autologous bone marrow cell (BMC) transplantation has been shown as a potential approach to treat various ischemic diseases. However, under many conditions BMC dysfunction has been reported, leading to poor cell engraftment and a failure of tissue revascularization. We have previously shown that skeletal muscle angiogenesis induced by electrical stimulation (ES) is impaired in the SS/Mcwi rats and that this effect is related to a dysregulation of the renin angiotensin system (RAS) that is normalized by the replacement of chromosome 13 derived from the Brown Norway rat (SS-13(BN)/Mcwi consomic rats). The present study explored bone marrow-derived endothelial cell (BM-EC) function in the SS/Mcwi rat and its impact on skeletal muscle angiogenesis induced by ES. SS/Mcwi rats were randomized to receive BMC from: SS/Mcwi; SS-13(BN)/Mcwi; SS/Mcwi rats infused with saline or ANG II (3 ng kg(-1) min(-1)). BMC were injected in the stimulated tibialis anterior muscle of SS/Mcwi rats. Vessel density was evaluated in unstimulated and stimulated muscles after 7 days of ES. BMC isolated from SS/Mcwi or SS/Mcwi rats infused with saline failed to restore angiogenesis induced by ES. However, BMC isolated from SS-13(BN)/Mcwi and SS/Mcwi rats infused with ANG II effectively restored the angiogenesis response in the SS/Mcwi recipient. Furthermore, ANG II infusion increased the capacity of BM-EC to induce endothelial cell tube formation in vitro and slightly increased VEGF protein expression. This study suggests that dysregulation of the RAS in the SS/Mcwi rat contributes to impaired BM-EC function and could impact the angiogenic therapeutic potential of BMC.

Long-term benefit of intracardiac delivery of autologous granulocyte-colony-stimulating factor-mobilized blood CD34+ cells containing cardiac progenitors on regional heart structure and function after myocardial infarct

BACKGROUND AIMS

Starting from experimental data proposing hematopoietic stem cells as candidates for cardiac repair, we postulated that human peripheral blood (PB) CD34+ cells mobilized by hematopoietic growth-factor (G-CSF) would contain cell subpopulations capable of regenerating post-ischemic myocardial damages.

METHODS

In a phase I clinical assay enrolling seven patients with acute myocardial infarct, we directly delivered to the injured myocardium autologous PB CD34+ cells previously mobilized by G-CSF, collected by leukapheresis and purified by immunoselection. In parallel, we looked for the eventual presence of cardiomyocytic and endothelial progenitor cells in leukapheresis products of these patients and controls, using flow cytometry, reverse transcription-quantitative (RTQ)-polymerase chain reaction (PCR), cell cultures and immunofluorescence analyzes.

RESULTS

The whole clinical process was feasible and safe. All patients were alive at an average follow-up of 49 months (range 24-76 months). Improvement of heart function parameters became obvious from the third month following cell reinjection. Left ventricular ejection fraction values progressively and dramatically increased with time, associated with PetScan demonstration of myocardial structure regeneration and revascularization and New York Heart Association (NYHA) grade improvement. Furthermore, we identified PB CD34+ cell subpopulations expressing characteristics of both immature and mature endothelial and cardiomyocyte progenitor cells. In vitro CD34+ cell cultures on a specific medium induced development of adherent cells featuring morphologies, gene expression and immunocytochemistry characteristics of endothelial and cardiac muscle cells.

CONCLUSIONS

Mobilized CD34+ cells contain stem cells committed along endothelial and cardiac differentiation pathways, which could play a key role in a proposed two-phase mechanism of myocardial regeneration after direct intracardiac delivery, probably being responsible for the long-term clinical benefit observed.

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.

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.

Making stem cells infarct avid

A major factor limiting the engraftment of transplanted stem cells after myocardial infarction is the low rate of retention in the infarcted site. Our long-term objective is to improve engraftment by enabling stem cells to recognize and bind infarcted tissue. To this end, we proposed to modify the surface of embryonic stem cells (ESCs) with the C2A domain of synaptotagmin I; this allows the engineered stem cells to bind to dead and dying cardiac cells by recognizing phosphatidylserine (PS). The latter is a molecular marker for apoptotic and necrotic cells. The C2A domain of synaptotagmin I, which binds PS with high affinity and specificity, was attached to the surface of mouse ESCs using the biotin-avidin coupling mechanism. Binding of C2A-ESCs to dead and dying cardiomyocytes was tested in vitro. After the surface modification, cellular physiology was examined for viability, pluripotency, and differentiation potential. C2A covalently attached to the ESC surface at an average of about 1 million C2A molecules per cell under mild conjugation reaction conditions. C2A-ESCs avidly bound to dying, but not viable, cardiomyocytes in culture. The normal physiology of C2A-modified ESCs was maintained. The binding of C2A-ESCs to moribund cardiomyocytes demonstrates that the retention of transplanted cells may be improved by conferring these cells with the ability to bind infarcted tissue. Once established, this novel approach may be applicable to other types of transplanted therapeutic cells.

Neoangiogenesis after direct intramyocardial implantation of bone marrow-derived stem cells in a patient with severe coronary artery disease ineligible for percutaneous or surgical revascularization

Bone marrow-derived stem cells (BMSC) may be an alternative for the treatment of patients with severe coronary artery disease ineligible for either percutaneous or surgical revascularization. This case report presents a 65-year-old male patient with untreatable angina pectoris (Canadian Cardiovascular Society Class III) and severe coronary artery disease. A mixture of BMSC containing approximately 3×106 CD34+ cells was directly injected into preoperatively determined ischemic regions of the myocardium by median sternotomy. At baseline, at 3 months, and at 1 year of follow-up, echocardiography (demonstrating wall motions of 16 segments), single-photon emission computed tomography, and coronary angiography (at baseline and at 1 year) were performed to assess myocardial perfusion, left ventricular (LV) function and coronary anatomy. The patient reached Canadian Cardiovascular Society Class I after 6 months of cell implantation. The ejection fraction increased from 34% to 37% at the third month and 40% at 1 year of follow-up. At 1 year of follow-up, preoperatively akinetic mid-base septum and anteroseptal regions progressed to mild hipokinesia and severe hypokinetic mid-base-apical anterior regions and apical lateral-inferior regions became normokinesia. Single-photon emission computed tomography revealed a visible improvement in anterior and lateral segments at 1 year of follow-up. Coronary angiography showed newly developed collateral arteries at 1 year of follow-up. BMSC transplantation in a patient with severe coronary artery disease resulted in increase of LV ejection fraction, an increase of the perfusion of ischemic myocardial regions, and improvement in wall motion defects without any adverse events.

The relative potency and safety of endothelial progenitor cells and unselected mononuclear cells for recovery from myocardial infarction and ischemia

Endothelial progenitor cells (EPCs) are a subset of the total mononuclear cell population (tMNCs) that possess an enhanced potential for differentiation within the endothelial-cell lineage. Typically, EPCs are selected from tMNCs via the expression of both hematopoietic stem-cell markers and endothelial-cell markers, such as CD34, or by culturing tMNCs in media selective for endothelial cells. Both EPCs and tMNCs participate in vascular growth and regeneration, and their potential use for treatment of myocardial injury or disease has been evaluated in early-phase clinical studies. Direct comparisons between EPCs and tMNCs are rare, but the available evidence appears to favor EPCs, particularly CD34+ cells, and the potency of EPCs may be increased as much as 30-fold through genetic modification. However, these observations must be interpreted with caution because clinical investigations of EPC therapy are ongoing. We anticipate that with continued development, EPC therapy will become a safe and effective treatment option for patients with acute myocardial infarction or chronic ischemic disease.

Autologous bone marrow-derived stem cells for ischemic heart failure: REGENERATE-IHD trial

The field of autologous stem/progenitor cell transplantation for cardiovascular diseases has moved rapidly from basic science research to clinical trials. To date, only a handful of pilot studies have reported the use of this novel strategy for heart failure patients. Most of these studies have demonstrated encouraging safety and efficacy data. However, this will need to be validated in large, randomized trials. Here, we introduce the ongoing REGENERATE-IHD trial, which is the largest randomized, placebo-controlled trial in the UK investigating the use of granulocyte-colony stimulating factor and autologous bone marrow-derived stem/progenitor cells to improve cardiac function and symptoms in heart failure patients.

Endothelial progenitor cells in neovascularization of infarcted myocardium

Historically, revascularization of ischemic tissue was believed to occur through the migration and proliferation of endothelial cells in nearby tissues; however, evidence accumulated in recent years indicates that a subpopulation of adult, peripheral-blood cells, collectively referred to as endothelial progenitor cells (EPCs), can differentiate into mature endothelial cells. After ischemic insult, EPCs are believed to home to sites of neovascularization, where they contribute to vascular regeneration by forming a structural component of capillaries and by secreting angiogenic factors; new evidence indicates that EPCs can also differentiate into cardiomyocytes and smooth-muscle cells. These insights into the molecular and cellular processes of tissue formation suggest that cardiac function may be preserved after myocardial infarction by transplanting EPCs into ischemic heart tissue, thereby enhancing vascular and myocardial recovery. This therapeutic strategy has been effective in animal models of ischemic disorders, and results from randomized clinical trials suggest that cell-based strategies may be safe and feasible for treatment of myocardial infarction in humans and have provided early evidence of efficacy. However, the scarcity of EPCs in the peripheral blood and evidence that several disease states reduce EPC number and/or function have prompted the development of several strategies to overcome these limitations, such as the administration of genetically modified EPCs that overexpress angiogenic growth factors. To optimize therapeutic outcomes, researchers must continue to refine methods of EPC purification, expansion, and administration, and to develop techniques that overcome the intrinsic scarcity and phenotypic deficiencies of EPCs.

Intracoronary autologous bone marrow stem cells transfer for patients with acute myocardial infarction: a meta-analysis of randomised controlled trials

BACKGROUND

Conflicting results existed now on the clinical utility of intracoronary bone marrow stem cells (BMSC) transfer for acute myocardial infarction (AMI). This study sought to analyze the efficacy and safety of autologous BMSC transfer in patients with AMI by performing a meta-analysis based on published randomised controlled trials.

METHODS

A systematic literature search of PubMed, MEDLINE, BIOSIS, EMBASE, and Cochrane EBM databases during the period of 1990-2007 was made, objective being the randomised controlled trials in patients with AMI who underwent primary percutaneous coronary intervention (PCI) and received intracoronary BMSC transfer, and were followed up for at least 3 months.

RESULTS

A total of 6 trials with 525 patients were available for analysis. The pooled statistics showed the mean increase in left ventricular ejection fraction (LVEF) from baseline was 7.05% in BMSC group (p=0.01), whereas only 2.46% in control group (p=0.02), and the effect on the absolute change in LVEF was an increase of 4.77% compared with the control (95% confidence interval [CI] 1.42% to 8.12%; p=0.005). The similar effect on left ventricular (LV) end-diastolic dimensions was demonstrated in inter-group comparison (standardized mean difference [SMD]=-0.15, 95%CI -0.50 to 0.20; p=0.41). The incidence of major adverse cardiac events was also similar in two groups but in favor of BMSC group (relative risk [RR]=0.85, 95%CI, 0.61 to 1.19; p=0.34).

CONCLUSIONS

Post PCI BMSC transplantation in patients with AMI significantly increases LVEF but has no effects on LV remodeling, and there is not an incremental effect on the occurrence of major adverse cardiac events in the observed period.

Re-expression of nestin in the myocardium of postinfarcted patients

Intact cardiac muscle cells in the adult heart do not express intermediate filament nestin. In this study, we report on widespread expression of intermediate filament nestin in human myocardium of patients who died from the myocardial infarction. Nestin was detected in cardiomyocytes, endothelial cells, and few interstitial cells. Elevated levels of nestin were observed in cardiac muscle cells in all specimens, although the intensity of immunoreactivity and distribution of the signal differed. The strongest immunoreactivity was observed from 4 days after myocardial infarction in the infarction border zone where nestin was distributed homogeneously in the entire sarcoplasm of cardiac muscle cells. Within the following week, nestin in immunoreactive cardiomyocytes was redistributed and restricted to small subsarcolemmal foci and to intercalated discs. Angiogenic capillaries that grew between vital nestin-positive cardiomyocytes and entered the necrotic area expressed also high levels of nestin. Nestin-positive endothelial cells were often observed in mutual interactions with nestin-positive cardiac muscle cells. These findings document a crucial role of nestin in remodeling cytoskeleton of cells in the human postinfarcted myocardium.

Cell therapy in patients with left ventricular dysfunction due to myocardial infarction

OBJECTIVES

The purpose of this study was to determine the impact of autologous transplantation of mononuclear bone marrow cells on myocardial function in patients with left ventricular (LV) dysfunction due to an acute myocardial infarction.

METHODS

The randomized study included 82 patients with a first acute myocardial infarction treated with a stent implantation. This presentation is a subanalysis of 47 patients with left ventricular dysfunction-EF (ejection fraction) <or= 40%. Group H patients (n = 17) received higher number (100,000,000) of cells; Group L patients (n = 13) received lower number (10,000,000) of cells. The patients of control Group C (n = 17) were not treated with cells. The Doppler tissue imaging and single photon emission computed tomography were performed before cell transplantation and 3 months later.

RESULTS

At 3 months of follow-up, the baseline EF of 35%, 36%, 35% in Groups H, L, and C increased by 6% (P < 0.01 vs. baseline), 5% (P < 0.01 vs. baseline), and 4% (P = NS vs. baseline), respectively, as assessed by single photon emission computed tomography (P = NS between groups). The baseline number of akinetic segments of 6.9, 7.0, and 6.2 in H, L, and C groups decreased by 1.7 (P < 0.01 vs. baseline), 1.5 (P < 0.01 vs. baseline), and 0.7 (P = NS vs. baseline, P = NS between groups), respectively, as demonstrated by echocardiography.

CONCLUSION

In our study, the statistically important effect of transplantation of mononuclear bone marrow cells on myocardial function was not found. Only an insignificant trend toward the improvement of global LV EF fraction was found at 3-month follow-up.

Intracoronary infusion of autologous mononuclear bone marrow cells in patients with acute myocardial infarction treated with primary PCI: Pilot study of the multicenter HEBE trial

OBJECTIVE

This study was a pilot trial to determine safety and feasibility of intracoronary infusion of mononuclear bone marrow cells (MBMC) in patients with acute myocardial infarction (MI).

BACKGROUND

Studies reporting the effect of MBMC therapy on improvement of left ventricular (LV) function have shown variable results. The HEBE trial is a large multicenter, randomized trial that currently enrolls patients. Prior to this trial we performed a pilot study.

METHODS

Twenty-six patients with a first acute MI were prospectively enrolled in eight centers. Bone marrow aspiration was performed at a median of 6 days after primary PCI (interquartile range, 5-7 days). MBMC were isolated by gradient centrifugation and were infused intracoronary the same day. All patients underwent magnetic resonance imaging before cell infusion and after 4 months. Clinical events were assessed up to 12 months.

RESULTS

Within 10 hr after bone marrow aspiration, 246 +/- 133 x 10(6) MBMC were infused, of which 3.9 +/- 2.3 x 10(6) cells were CD34(+). In one patient, this procedure was complicated by local dissection. LV ejection fraction significantly increased from 45.0 +/- 6.3% to 47.2 +/- 6.5% (P = 0.03). Systolic wall thickening in dysfunctional segments at baseline improved with 0.9 +/- 0.7 mm (P < 0.001). Infarct size decreased 37% from 17.8 +/- 8.2 to 11.2 +/- 4.2 gram (P < 0.001). During 12-month follow-up, 3 additional revascularizations were performed and an ICD was implanted in one patient, 3 weeks after PCI.

CONCLUSION

In patients with acute MI, intracoronary infusion of MBMC is safe in a multicenter setting. At 4-month follow-up, a modest increase in global and regional LV function was observed, with a concomitant decrease in infarct size.

Therapeutic potential of adult progenitor cells in the management of chronic myocardial ischemia

Refractory angina as a result of chronic myocardial ischemia is a common and disabling condition. Adult progenitor cells have emerged as a potential revolutionary treatment for cardiovascular disease. Locally administered adult progenitor cells with particular vasculogenic potential may offer treatment hope for those with chronic ischemia; however, the optimal cell type, dose, delivery mode, and target patient population has not been defined. Preclinical cell therapy studies have shown safety and efficacy sufficient to warrant human trials. Early, small-scale human trials exploring various cell types and delivery modes have shown that most approaches are safe, with modest early efficacy. This overview discusses the rationale and early results for ongoing larger cardiovascular disease trials, with a special emphasis on refractory angina and chronic myocardial ischemia.

Three-, 6-, and 12-month results of autologous transplantation of mononuclear bone marrow cells in patients with acute myocardial infarction

BACKGROUND

There are only few data on long-term effectiveness of the stem cell therapy.

AIM

We studied the time course of global and regional left ventricular function in patients with acute myocardial infarction within 1 year after the autologous mononuclear bone marrow cell transplantation.

METHODS

Sixty patients with a first acute myocardial infarction, who had been randomized into 3 groups, completed a 12-month protocol. Two groups were intracoronarily given bone marrow cells in either higher (10(8) cells, HD group, n=20) or lower (10(7) cells, LD group, n=20) doses. Twenty patients without cell transplantation served as a control (C) group. Doppler tissue imaging and the gated technetium-99m sestamibi single photon emission computed tomography were performed before cell transplantation and at 3, 6, and 12 months later.

RESULTS

The baseline peak systolic velocities of longitudinal contraction of the infarcted wall (S(infarct)) of 5.2 cm/s, 4.6 cm/s, and 4.4 cm/s in C, LD, and HD groups increased by 0.0 cm/s, 0.3 cm/s (p=NS vs. C group), and by 0.7 cm/s (p<0.05 vs. C group), respectively, at 3 months. At 12 months, however, the corresponding changes from baseline values of 0.1 cm/s, 0.2 cm/s, and 0.6 cm/s did not differ significantly (all p=NS). In contrast, the post-transplant improvements in the left ventricular ejection fraction by 6%, 7%, and 7% at months 3, 6, and 12, respectively, were preserved in HD group patients during the whole 12-month follow-up and remained significantly better as compared to controls.

CONCLUSIONS

In our study, the autologous mononuclear bone marrow cell transplantation provided sustained improvement in global left ventricular systolic function in patients with acute myocardial infarction. However, when evaluating regional systolic function of the infarcted wall, the short-term benefit was partially lost during the 12-month follow-up.

Cell therapy for left ventricular remodeling

The increasing longevity of patients with heart failure (HF) and the rise in the incidence of HF has created an urgent need to effectively treat and prevent left ventricular remodeling. Within the past 6 years, skeletal myoblast and bone marrow mononuclear cell transplantation have been undertaken in over 200 patients with HF, geared to the underlying injury, not just its mechanisms. Early safety/feasibility studies showed promising but somewhat conflicting secondary symptomatic and functional improvements, and safety concerns have arisen. However, the patient population, cell type, dose, time, mode of delivery, and outcome measures differed-making comparisons problematic. It is now time to: 1) create a central registry of all patients treated with cells; 2) perform side-by-side comparisons of different types of cells in patients with similar HF states; 3) agree on standardized trial designs; and 4) define acceptable and unacceptable outcomes (and measures) compared with both standard of care and to other emerging therapies. By doing so, we can avoid the pitfalls that previous biologics (eg, angiogenic gene therapy) have suffered, increase the likelihood of success, shorten the time-to-presentation of cell-based algorithms to clinicians, and deliver these therapies to patients who await new ways of reduction of symptoms and improvement of quality of life.

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

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

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

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

UC blood hematopoietic stem cells and therapeutic angiogenesis

Studies suggest that mobilized hematopoietic stem cells (HSC) are recruited to ischemic tissue and stimulate angiogenesis. Critical observations in pre-clinical studies have identified an augmentation of endogenous microvascular collateralization that is beyond that directly attributable to anatomic incorporation and differentiation of infused human cells into the vascular endothelium. Evidence links age-associated reductions in the levels of circulating marrow-derived HSC characterized by expression of early HSC markers CD133 and CD34, with the occurrence of cardiovascular events and associated death. Utilizing the patient's own HSC to augment angiogenesis has several disadvantages, including reduced function of these cells and logistical issues related to cell collection from individual patients. Thus an available source of allogeneic HSC such as UC blood for cellular therapy may be optimal.

Stem Cell Therapy for the Heart

Cellular cardiomyoplasty is an expanding field of research that involves numerous types of immature cells administered via several modes of delivery. The purpose of this review is to investigate the benefits of different types of cells used in stem cell research as well as the most efficient mode of delivery. The authors also present data showing that stem cells isolated from bone marrow are present at both 2 weeks and 3 months after engraftment in a myocardial infarction. These cells express muscle markers at both time points, which suggests that they have begun to differentiate into cardiomyocytes. Several questions must be answered, however, before stem cells can be used routinely in the clinic. Once these questions have been addressed, the use of stem cells in clinical practice can be realized.

Comparison of intracardiac cell transplantation: autologous skeletal myoblasts versus bone marrow cells

An increasing number of patients living with cardiovascular disease (CVD) and still unacceptably high mortality created an urgent need to effectively treat and prevent disease-related events. Within the past 5 years, skeletal myoblasts (SKMBs) and bone marrow (or blood)-derived mononuclear cells (BMNCs) have demonstrated preclinical efficacy in reducing ischemia and salvaging already injured myocardium, and in preventing left ventricular (LV) remodeling, respectively. These findings have been translated into clinical trials, so far totaling over 200 patients for SKMBs and over 800 patients for BMNCs. These safety/feasibility and early phase II studies showed promising but somewhat conflicting symptomatic and functional improvements, and some safety concerns have arisen. However, the patient population, cell type, dose, time and mode of delivery, and outcome measures differed, making comparisons problematic. In addition, the mechanisms through which cells engraft and deliver their beneficial effects remain to be fully elucidated. It is now time to critically evaluate progress made and challenges encountered in order to select not only the most suitable cells for cardiac repair but also to define appropriate patient populations and outcome measures. Reiterations between bench and bedside will increase the likelihood of cell therapy success, reduce the time to development of combined of drug- and cell-based disease management algorithms, and offer these therapies to patients to achieve a greater reduction of symptoms and allow for a sustained improvement of quality of life.

Present and future of stem cells for cardiovascular therapy

In this review we summarize the available evidence regarding the application of stem cell therapy for human cardiovascular repair, going over the principal concepts that will help us understand the present and future of this therapy: first the different types of cells available in clinical practice, second the delivery approaches, and third highlighting the most important clinical studies and their efficacy and safety results. In addition, we also speculate on the value of current clinical data to gain an insight into the mechanism of stem cell-based cardiac repair and to design clinical trials in the future.