Angiogenesis in ischaemic myocardium by intramyocardial autologous bone marrow mononuclear cell implantation

Identification of a distinct subpopulation of fibroblasts from murine dermis: CD73(-) CD105(+) as potential marker of dermal fibroblasts subset with multipotency

Skin dermis includes various types of multipotent stromal cells (MSCs) and a subpopulation of dermal fibroblasts that exhibit the ability to differentiate. However, characterization of this dermal fibroblast subtype remains less understood. In this study, we isolated dermal cells from the skin of newborn C57/B6 mice and investigated their characteristics. Isolated murine dermal cells exhibited a fibroblast phenotype as judged by accepted criteria including a lack of MSC-related antigens and the differentiation potential of MSCs, and the positive expression of fibroblast markers. A comparative analysis demonstrated that CD73(-) CD105(+) but not CD73(-) CD105(-) dermal fibroblasts exhibited some of the functional properties of MSCs. Furthermore, the multipotent phenotype of CD73(-) CD105(+) cells was diminished by treatment of CD105 siRNA and shRNA, indicating that CD105 expression was critical for the retention of differentiation potential of those cells. Overall, these results suggest that CD73(-) CD105(+) cells are a distinct subset of dermal fibroblasts with multipotency and that their surface antigens could help to classify this subpopulation. These cells may contribute to the regeneration of damaged tissue.

Therapeutic Angiogenesis With Bone Marrow—Derived Stem Cells

Despite that advances in medical treatment and interventional procedures have reduced the mortality rate in patients with coronary artery disease, the number of patients with refractory myocardial ischemia and congestive heart failure is rapidly increasing. Experimental studies have demonstrated that bone marrow (BM) contains adult stem cells that can induce neovascularization and improve heart function in ischemic myocardium. Recent insights into the understanding of the mechanisms involved in proliferation, recruitment, mobilization, and incorporation of BM-derived stem cells into the myocardium and blood vessels have prompted development of cellular transplantation therapy for heart diseases refractory to conventional therapy. Initial preliminary clinical studies indicated potential clinical benefit of BM therapy in patients with acute myocardial infarction and chronic myocardial ischemia. Nevertheless, many obstacles remain, such as long-term safety and optimal timing and treatment strategies for BM cell therapy, and these issues need to be addressed in rationally designed, randomized clinical trials.

Challenges to success in heart failure: Cardiac cell therapies in patients with heart diseases

Heart failure remains the leading cause of death worldwide, and is a burgeoning problem in public health due to the limited capacity of postnatal hearts to self-renew. The pathophysiological changes in injured hearts can sometimes be manifested as scar formation or myocardial degradation, rather than supplemental muscle regeneration to replenish lost tissue during the healing processes. Stem cell therapies have been investigated as a possible treatment approach for children and adults with potentially fatal cardiovascular disease that does not respond to current medical therapies. Although the heart is one of the least regenerative organs in mammals, discoveries made during the past few decades have improved our understanding of cardiac development and resident stem/progenitor pools, which may be lineage-restricted subpopulations during the post-neonatal stage of cardiac morphogenesis. Recently, investigation has specifically focused on factors that activate either endogenous progenitor cells or preexisting cardiomyocytes, to regenerate cardiovascular cells and replace the damaged heart tissues. The discovery of induced pluripotent stem cells has advanced our technological capability to direct cardiac reprogramming by essential factors that are crucial for heart field completion in each stage. Cardiac tissue engineering technology has recently shown progress in generating myocardial tissue on human native cardiac extracellular matrix scaffolds. This review summarizes recent advances in the field of cardiac cell therapies with an emphasis on cellular mechanisms, such as bone marrow stem cells and cardiac progenitor cells, which show the high potential for success in preclinical and clinical meta-analysis studies. Expanding our current understanding of mechanisms of self-renewal in the neonatal mammalian heart may lead to the development of novel cardiovascular regenerative medicines for pediatric heart diseases.

Repeated Intramyocardial Bone Marrow Cell Injection in Previously Responding Patients With Refractory Angina Again Improves Myocardial Perfusion, Anginal Complaints, and Quality of Life

BACKGROUND

Intramyocardial bone marrow cell injection is associated with improvements in myocardial perfusion and anginal symptoms in patients with refractory angina pectoris. This study evaluates the effect of repeated intramyocardial bone marrow cell injection in patients with residual or recurrent myocardial ischemia.

METHODS AND RESULTS

Twenty-three patients (17 men; 69±9 years) who had improved myocardial perfusion after the first injection but had residual or recurrent angina and ischemia on single-photon emission computed tomographic myocardial perfusion imaging were included. Patients again received intramyocardial injection of 100×10(6) autologous bone marrow mononuclear cells, 4.6±2.5 years after their first injection. No periprocedural complications occurred. Myocardial perfusion assessed using single-photon emission computed tomographic myocardial perfusion imaging improved from a summed stress score of 27.3±5.8 at baseline to 24.5±4.4 at 3 months (P=0.002) and 25.4±4.9 at 12 months of follow-up (P=0.002). Perfusion improvement after 3 months was comparable with the effect of the first injection (P=0.379). Anginal complaints improved ≤12 months after cell injection in Canadian Cardiovascular Society score (mean change at 3, 6, and 12 months: 0.6±0.9%, 0.5±0.9%, and 0.6±0.9%, respectively; Pslope=0.007, first versus repeated; P=0.188) and in quality of life score as measured by Seattle Angina Questionnaire (mean change at 3, 6, and 12 months: 7±14%, 8±14%, and 7±15%, respectively; Pslope=0.020, first versus repeated; P=0.126).

CONCLUSIONS

Repeated bone marrow cell injection in previously responding patients with refractory angina is associated with improvements in myocardial perfusion, anginal complaints, and quality of life score ≤12 months of follow-up.

CLINICAL TRIAL REGISTRATION

URL: http://www.trialregister.nl. Unique identifier: NTR2664.

Fibrin, the preferred scaffold for cell transplantation after myocardial infarction? An old molecule with a new life

Fibrin is a topical haemostat, sealant and tissue glue, which consists of concentrated fibrinogen and thrombin. It has broad medical and research uses. Recently, several studies have shown that engineered patches comprising mixtures of biological or synthetic materials and progenitor cells showed therapeutic promise for regenerating damaged tissues. In that context, fibrin maintains cell adherence at the site of injury, where cells are required for tissue repair, and offers a nurturing environment that protects implanted cells without interfering with their expected benefit. Here we review the past, present and future uses of fibrin, with a focus on its use as a scaffold material for cardiac repair. Fibrin patches filled with regenerative cells can be placed over the scarring myocardium; this methodology avoids many of the drawbacks of conventional cell-infusion systems. Advantages of using fibrin also include extraction from the patient's blood, an easy readjustment and implantation procedure, increase in viability and early proliferation of delivered cells, and benefits even with the patch alone. In line with this, we discuss the numerous preclinical studies that have used fibrin-cell patches, the practical issues inherent in their generation, and the necessary process of scaling-up from animal models to patients. In the light of the data presented, fibrin stands out as a valuable biomaterial for delivering cells to damaged tissue and for promoting beneficial effects. However, before the fibrin scaffold can be translated from bench to bedside, many issues must be explored further, including suboptimal survival and limited migration of the implanted cells to underlying ischaemic myocardium. Copyright © 2016 John Wiley & Sons, Ltd.

MicroRNA-133a engineered mesenchymal stem cells augment cardiac function and cell survival in the infarct heart

: Cardiovascular disease is the number 1 cause of morbidity and mortality in the United States. The most common manifestation of cardiovascular disease is myocardial infarction (MI), which can ultimately lead to congestive heart failure. Cell therapy (cardiomyoplasty) is a new potential therapeutic treatment alternative for the damaged heart. Recent preclinical and clinical studies have shown that mesenchymal stem cells (MSCs) are a promising cell type for cardiomyoplasty applications. However, a major limitation is the poor survival rate of transplanted stem cells in the infarcted heart. miR-133a is an abundantly expressed microRNA (miRNA) in the cardiac muscle and is downregulated in patients with MI. We hypothesized that reprogramming MSCs using miRNA mimics (double-stranded oligonucleotides) will improve survival of stem cells in the damaged heart. MSCs were transfected with miR-133a mimic and antagomirs, and the levels of miR-133a were measured by quantitative real-time polymerase chain reaction. Rat hearts were subjected to MI and MSCs transfected with miR-133a mimic or antagomir were implanted in the ischemic hearts. Four weeks after MI, cardiac function, cardiac fibrosis, miR-133a levels, and apoptosis-related genes (Apaf-1, Caspase-9, and Caspase-3) were measured in the heart. We found that transfecting MSCs with miR-133a mimic improves survival of MSCs as determined by the MTT assay. Similarly, transplantation of miR-133a mimic transfected MSCs in rat hearts subjected to MI led to a significant increase in cell engraftment, cardiac function, and decreased fibrosis when compared with MSCs only or MI groups. At the molecular level, quantitative real-time polymerase chain reaction data demonstrated a significant decrease in expression of the proapoptotic genes; Apaf-1, caspase-9, and caspase-3 in the miR-133a mimic transplanted group. Furthermore, luciferase reporter assay confirmed that miR-133a is a direct target for Apaf-1. Overall, bioengineering of stem cells through miRNAs manipulation could potentially improve the therapeutic outcome of patients undergoing stem cell transplantation for MI.

Attenuation of cardiac dysfunction and remodeling of myocardial infarction by microRNA-130a are mediated by suppression of PTEN and activation of PI3K dependent signaling

OBJECTIVE

Activation of PI3K/Akt signaling protects the myocardium from ischemia/reperfusion injury. MicroRNAs have been demonstrated to play an important role in the regulation of gene expression at the post-transcriptional level. In this study, we examined whether miR-130a will attenuate cardiac dysfunction and remodeling after myocardial infarction (MI) via PI3K/Akt dependent mechanism.

APPROACHES AND RESULTS

To determine the role of miR-130a in the proliferation and migration of endothelial cells, HUVECs were transfected with miR-130a mimics before the cells were subjected to scratch-induced wound injury. Transfection of miR-130a mimics stimulated the migration of endothelial cells into the wound area and increased phospho-Akt levels. To examine the effect of miR-130a on cardiac dysfunction and remodeling after MI, Lentivirus expressing miR-130a (LmiR-130a) was delivered into mouse hearts seven days before the mice were subjected to MI. Cardiac function was assessed by echocardiography before and for up to 21 days after MI. Ejection fraction (EF%) and fractional shortening (FS%) in the LmiR-130a transfected MI hearts were significantly greater than in LmiR-control and untransfected control MI groups. LmiR-130a transfection increased capillary number and VEGF expression, and decreased collagen deposition in the infarcted myocardium. Importantly, LmiR-130a transfection significantly suppressed PTEN expression and increased the levels of phosphorylated Akt in the myocardium. However, treatment of LmiR-130a-transfected mice with LY294002, a PI3K inhibitor, completely abolished miR-130a-induced attenuation of cardiac dysfunction after MI.

CONCLUSIONS

miR-130a plays a critical role in attenuation of cardiac dysfunction and remodeling after MI. The mechanisms involve activation of PI3K/Akt signaling via suppression of PTEN expression.

Are Endothelial Progenitor Cells the Real Solution for Cardiovascular Diseases? Focus on Controversies and Perspectives

Advanced knowledge in the field of stem cell biology and their ability to provide a cue for counteracting several diseases are leading numerous researchers to focus their attention on “regenerative medicine” as possible solutions for cardiovascular diseases (CVDs). However, the lack of consistent evidence in this arena has hampered the clinical application. The same condition affects the research on endothelial progenitor cells (EPCs), creating more confusion than comprehension. In this review, this aspect is discussed with particular emphasis. In particular, we describe biology and physiology of EPCs, outline their clinical relevance as both new predictive, diagnostic, and prognostic CVD biomarkers and therapeutic agents, discuss advantages, disadvantages, and conflicting data about their use as possible solutions for vascular impairment and clinical applications, and finally underline a very crucial aspect of EPCs “characterization and definition,” which seems to be the real cause of large heterogeneity existing in literature data on this topic.

Stem cell treatment for acute myocardial infarction

BACKGROUND

Cell transplantation offers a potential therapeutic approach to the repair and regeneration of damaged vascular and cardiac tissue after acute myocardial infarction (AMI). This has resulted in multiple randomised controlled trials (RCTs) across the world.

OBJECTIVES

To determine the safety and efficacy of autologous adult bone marrow stem cells as a treatment for acute myocardial infarction (AMI), focusing on clinical outcomes.

SEARCH METHODS

This Cochrane review is an update of a previous version (published in 2012). We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2015, Issue 2), MEDLINE (1950 to March 2015), EMBASE (1974 to March 2015), CINAHL (1982 to March 2015) and the Transfusion Evidence Library (1980 to March 2015). In addition, we searched several international and ongoing trial databases in March 2015 and handsearched relevant conference proceedings to January 2011.

SELECTION CRITERIA

RCTs comparing autologous bone marrow-derived cells with no cells in patients diagnosed with AMI were eligible.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all references, assessed the risk of bias of the included trials and extracted data. We conducted meta-analyses using random-effects models throughout. We analysed outcomes at short-term (less than 12 months) and long-term (12 months or more) follow-up. Dichotomous outcomes are reported as risk ratio (RR) and continuous outcomes are reported as mean difference (MD) or standardised MD (SMD). We performed sensitivity analyses to evaluate the results in the context of the risk of selection, performance and attrition bias. Exploratory subgroup analysis investigated the effects of baseline cardiac function (left ventricular ejection fraction, LVEF) and cell dose, type and timing of administration, as well as the use of heparin in the final cell solution.

MAIN RESULTS

Forty-one RCTs with a total of 2732 participants (1564 cell therapy, 1168 controls) were eligible for inclusion. Cell treatment was not associated with any changes in the risk of all-cause mortality (34/538 versus 32/458; RR 0.93, 95% CI 0.58 to 1.50; 996 participants; 14 studies; moderate quality evidence), cardiovascular mortality (23/277 versus 18/250; RR 1.04, 95% CI 0.54 to 1.99; 527 participants; nine studies; moderate quality evidence) or a composite measure of mortality, reinfarction and re-hospitalisation for heart failure (24/262 versus 33/235; RR 0.63, 95% CI 0.36 to 1.10; 497 participants; six studies; moderate quality evidence) at long-term follow-up. Statistical heterogeneity was low (I(2) = 0% to 12%). Serious periprocedural adverse events were rare and were generally unlikely to be related to cell therapy. Additionally, cell therapy had no effect on morbidity, quality of life/performance or LVEF measured by magnetic resonance imaging. Meta-analyses of LVEF measured by echocardiography, single photon emission computed tomography and left ventricular angiography showed evidence of differences in mean LVEF between treatment groups although the mean differences ranged between 2% and 5%, which are accepted not to be clinically relevant. Results were robust to the risk of selection, performance and attrition bias from individual studies.

AUTHORS' CONCLUSIONS

The results of this review suggest that there is insufficient evidence for a beneficial effect of cell therapy for AMI patients. However, most of the evidence comes from small trials that showed no difference in clinically relevant outcomes. Further adequately powered trials are needed and until then the efficacy of this intervention remains unproven.

Activation of NRG1-ERBB4 signaling potentiates mesenchymal stem cell-mediated myocardial repairs following myocardial infarction

Mesenchymal stem cell (MSC) transplantation has achieved only modest success in the treatment of ischemic heart disease owing to poor cell viability in the diseased microenvironment. Activation of the NRG1 (neuregulin1)-ERBB4 (v-erb-b2 avian erythroblastic leukemia viral oncogene homolog 4) signaling pathway has been shown to stimulate mature cardiomyocyte cell cycle re-entry and cell division. In this connection, we aimed to determine whether overexpression of ERBB4 in MSCs can enhance their cardio-protective effects following myocardial infarction. NRG1, MSCs or MSC-ERBB4 (MSC with ERBB4 overexpression), were transplanted into mice following myocardial infarction. Superior to that of MSCs and solely NRG1, MSC-ERBB4 transplantation significantly preserved heart functions accompanied with reduced infarct size, enhanced cardiomyocyte division and less apoptosis during early phase of infarction. The transduction of ERBB4 into MSCs indeed increased cell mobility and apoptotic resistance under hypoxic and glucose-deprived conditions via a PI3K/Akt signaling pathway in the presence of NRG1. Unexpectedly, introduction of ERBB4 into MSC in turn potentiates NRG1 synthesis and secretion, thus forming a novel NRG1-ERBB4-NRG1 autocrine loop. Conditioned medium of MSC-ERBB4 containing elevated NRG1, promoted cardiomyocyte growth and division, whereas neutralization of NRG1 blunted this proliferation. These findings collectively suggest that ERBB4 overexpression potentiates MSC survival in the infarcted heart, enhances NRG1 generation to restore declining NRG1 in the infarcted region and stimulates cardiomyocyte division. ERBB4 has an important role in MSC-mediated myocardial repairs.

Paracrine mechanisms of mesenchymal stem cell-based therapy: current status and perspectives

Mesenchymal stem cells (MSCs) are one of a few stem cell types to be applied in clinical practice as therapeutic agents for immunomodulation and ischemic tissue repair. In addition to their multipotent differentiation potential, a strong paracrine capacity has been proposed as the principal mechanism that contributes to tissue repair. Apart from cytokine/chemokine secretion, MSCs also display a strong capacity for mitochondrial transfer and microvesicle (exosomes) secretion in response to injury with subsequent promotion of tissue regeneration. These unique properties of MSCs make them an invaluable cell type to repair damaged tissues/organs. Although MSCs offer great promise in the treatment of degenerative diseases and inflammatory disorders, there are still many challenges to overcome prior to their widespread clinical application. Particularly, their in-depth paracrine mechanisms remain a matter for debate and exploration. This review will highlight the discovery of the paracrine mechanism of MSCs, regulation of the paracrine biology of MSCs, important paracrine factors of MSCs in modulation of tissue repair, exosome and mitochondrial transfer for tissue repair, and the future perspective for MSC-based therapy.

Cardiac Repair and Regeneration: The Value of Cell Therapies

Ischaemic heart disease is the predominant contributor to cardiovascular morbidity and mortality; one million myocardial Infarctions occur per year in the USA, while more than five million patients suffer from chronic heart failure. Recently, heart failure has been singled out as an epidemic and is a staggering clinical and public health problem associated with significant mortality, morbidity and healthcare expenditures, particularly among those aged ≥65 years. Death rates have improved dramatically over the last four decades, but new approaches are nevertheless urgently needed for those patients who go on to develop ventricular dysfunction and chronic heart failure. Over the past decade, stem cell transplantation has emerged as a promising therapeutic strategy for acute or chronic ischaemic cardiomyopathy. Multiple candidate cell types have been used in preclinical animal models and in humans to repair or regenerate the injured heart, either directly or indirectly (through paracrine effects), including: embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), neonatal cardiomyocytes, skeletal myoblasts (SKMs), endothelial progenitor cells, bone marrow mononuclear cells (BMMNCs), mesenchymal stem cells (MSCs) and, most recently, cardiac stem cells (CSCs). Although no consensus has emerged yet, the ideal cell type for the treatment of heart disease should: (a) improve heart function; (b) create healthy and functional cardiac muscle and vasculature, integrated into the host tissue; (c) be amenable to delivery by minimally invasive clinical methods; (d) be available 'off the shelf' as a standardised reagent; (e) be tolerated by the immune system; (f) be safe oncologically, i.e. not create tumours; and (g) circumvent societal ethical concerns. At present, it is not clear whether such a 'perfect' stem cell exists; what is apparent, however, is that some cell types are more promising than others. In this brief review, we provide ongoing data on agreement and controversy arising from clinical trials and touch upon the future directions of cell therapy for heart disease.

Combination treatment of biomechanical support and targeted intra-arterial infusion of peripheral blood stem cells mobilized by granulocyte-colony stimulating factor for the osteonecrosis of the femoral head: a randomized controlled clinical trial

The objective of this study was to determine the benefits of combination treatment with mechanical support and targeted intra-arterial infusion of peripheral blood stem cells (PBSCs) mobilized by granulocyte-colony stimulating factor (G-CSF) via the medial circumflex femoral artery on the progression of osteonecrosis of the femoral head (ONFH). Fifty-five patients (89 hips) with early and intermediate stage ONFH were recruited and randomly assigned to combination treatment or mechanical support treatment (control group). All hips received mechanical support treatment (porous tantalum rod implantation). Then, hips in the combination treatment group were performed targeted intra-arterial infusion of PBSCs. At each follow-up, Harris hip score (HHS) and Association Research Circulation Osseous (ARCO) classification were used to evaluate the symptoms and progression of osteonecrosis. Total hip arthroplasty (THA) was assessed as an endpoint at each follow-up. At 36 months, 9 of the 41 hips (21.95%) in the control group progressed to clinical failure and underwent THA whereas only 3 of the 48 hips (6.25%) in the combination treatment group required THA (p = 0.031). Kaplan-Meier survival analysis showed a significant difference in the survival time between the two groups (log-rank test; p = 0.025). Compared to the control group, combination treatment significantly improved the HHS at 36 months (p = 0.003). At the final follow-up examination, radiological progression was noted in 13 of 41 hips (31.71%) for the control group, but in only 4 of 48 hips (8.33%) for the combination treatment group (p = 0.005). The overall collapse rates were 15.15% (5/33 hips) and 8.11% (3/37 hips) in the control and combination treatment groups, respectively. Targeted intra-arterial infusion of PBSCs is capable of enhancing the efficacy of biomechanical support in the treatment of ONFH. This clinical trial confirmed that the combination treatment might be a safe and feasible choice for the treatment of early or intermediate stages of ONFH.

Neurogenic differentiation from adipose-derived stem cells and application for autologous transplantation in spinal cord injury

Mesenchymal stem cells derived from adipose tissue have the capacity to differentiate into endodermal, mesoderm and ectodermal cell lineages in vitro, which are an ideal engraft in tissue-engineered repair. In this study, mouse adipose-derived stem cells (ADSCs) were isolated from subcutaneous fat. The markers of ADSCs, CD13, CD29, CD44, CD71, CD73, CD90, CD105, CD166, Nestin, GFAP and MAP-2 were detected by immunofluorescence assays. The ADSCs were cultured in cocktail factors (including ATRA, GGF-2, bFGF, PDGF and forskolin) for neurogenic differentiation. The neurogenic cells markers, Nestin, GFAP and MAP-2 were analyzed using immunofluorescence and real-time PCR after dramatic changes in morphology. Neurogenic cells from ADSCs were autologous transplanted into the mouse of spinal cord injury for observation neurogenic cells colonization in spinal cord. The result demonstrated that the mouse ADSCs were positive for the CD13, CD29, CD44, CD71, CD73, CD90, CD105 and CD166 but negative for neurogenic cell markers, MAP-2, GFAP and Nestin. After neurogenic differentiation, the neurogenic cells were positive for neurogenic cell special markers, gene expression level showed a time-lapse increase, and the cells were successful colonized into spinal cord. In conclusion, our research shows that a population of neuronal cells can be specifically generated from ADSCs and that induced cells may allow for participation in tissue-repair.

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.

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.

Intravenous administration of bone marrow mononuclear cells alleviates hearing loss after transient cochlear ischemia through paracrine effects

Bone marrow mononuclear cells (BMMCs) are known to enhance recovery from ischemic insults by secreting angiogenic factors and inducing the expression of angiogenic factors from host tissues. Therefore, the transplantation of BMMCs is considered a potential approach to promoting the repair of ischemic damaged organs. Here, we investigated the influence of BMMCs on progressive hair cell degeneration after transient cochlear ischemia in gerbils. Transient cochlear ischemia was produced by extracranial occlusion of the bilateral vertebral arteries immediately before their entry into the transverse foramen of the cervical vertebra. An intravenous injection of BMMCs prevented ischemia-induced hair cell degeneration and ameliorated hearing impairment. A tracking study showed that BMMCs injected into the femoral vein were limited in the spiral artery of the cochlea, suggesting that, although transplanted BMMCs were retained within the spiral ganglion area of the cochlea, they were neither transdifferentiated into cochlear cells nor fused with the injured hair cells and supporting cells in the organ of Corti to restore their functions. We also showed that the protein level of neurotrophin-3 and glial cell line-derived neurotrophic factor in the organ of Corti was upregulated after treatment with BMMCs. These results suggested that BMMCs have therapeutic potential possibly through paracrine effects. Thus, we propose the use of BMMCs as a potential new therapeutic strategy for hearing loss.

The potential of stem cells in the treatment of cardiovascular diseases

Although the adult mammalian heart was once believed to be a post-mitotic organ without any capacity for regeneration, recent findings have challenged this dogma. A modified view assigns to the mammalian heart a measurable capacity for regeneration throughout life. The ultimate goals of the cardiac regeneration field have been pursued by multiple strategies, including understanding the developmental biology of cardiomyocytes and cardiac stem and progenitor cells, applying chemical genetics, and engineering biomaterials and delivery methods that facilitate cell transplantation. Successful stimulation of endogenous regenerative capacity in injured adult mammalian hearts can benefit from studies of natural cardiac regeneration.

Prompt bone marrow-derived mesenchymal stem cell therapy enables early porcine heart function recovery from acute myocardial infarction

Impact of early bone marrow-derived mesenchymal stem cell (BMDMSC) implantation on left ventricular (LV) function after AMI was studied.Twelve mini-pigs were equally divided into placebo (AMI through left coronary artery ligation) and cell-treated groups [BMDMSCs (3.0 × 10(7)) implanted into infarct area (IA)] with myocardium harvested by post-AMI day 90. Six healthy animals served as controls.On post-AMI day 90, magnetic resonance imaging showed a lower LV ejection fraction but higher LV dimensions in the placebo group (P < 0.003) that also had increased IAs but reduced wall thickness (P < 0.005). Pro-apoptotic gene expressions (Bax, caspase-3) and apoptotic nucleus number in IAs and peri-IAs were highest in the placebo group (P < 0.001). Inflammatory biomarker expressions (MMP-9, oxidized protein, CD40+ cells) were highest, whereas those of angiogenesis (VEGF, CD31+ cells, SDF-1α, CXCR4) and myocardium-preservation (connexin43, troponin-I, cytochrome-C) were lowest in the placebo group (P < 0.01).BMDMSC implantation preserved LV function and alleviated remodeling at post-AMI day 90.

Long-Term and Sustained Therapeutic Results of a Specific Promonocyte Cell Formulation in Refractory Angina: ReACT(®) (Refractory Angina Cell Therapy) Clinical Update and Cost-Effective Analysis

Mononuclear stem cells have been studied for their potential in myocardial ischemia. In our previous published article, ReACT(®) phase I/II clinical trial, our results suggest that a certain cell population, promonocytes, directly correlated with the perceived angiogenesis in refractory angina patients. This study is ReACT's clinical update, assessing long-term sustained efficacy. The ReACT phase IIA/B noncontrolled, open-label, clinical trial enrolled 14 patients with refractory angina and viable ischemic myocardium, without ventricular dysfunction, who were not suitable for myocardial revascularization. The procedure consisted of direct myocardial injection of a specific mononuclear cell formulation, with a certain percentage of promonocytes, in a single series of multiple injections (24-90; 0.2 ml each) into specific areas of the left ventricle. Primary endpoints were Canadian Cardiovascular Society Angina Classification (CCSAC) improvement at the 12-month follow-up and ischemic area reduction (scintigraphic analysis) at the 12-month follow-up, in correlation with ReACT's formulation. A recovery index (for patients with more than 1 year follow-up) was created to evaluate CCSAC over time, until April 2011. Almost all patients presented progressive improvement in CCSAC beginning 3 months (p=0.002) postprocedure, which was sustained at the 12-month follow-up (p=0.002), as well as objective myocardium ischemic area reduction at 6 months (decrease of 15%, p<0.024) and 12 months (decrease of 100%, p<0.004) The recovery index (n=10) showed that the patients were graded less than CCSAC 4 for 73.9 ± 24.2% over a median follow-up time of 46.8 months. After characterization, ReACT's promonocyte concentration suggested a positive correlation with CCSAC improvement (r=-0.575, p=0.082). Quality of life (SF-36 questionnaire) improved significantly in almost all domains. Cost-effectiveness analysis showed decrease in angina-related direct costs. Refractory angina patients presented a sustained long-term improvement in CCSAC and myocardium ischemic areas after the procedure. The long-term follow-up and strong improvement in quality of life reinforce effectiveness. Promonocytes may play a key role in myocardial neoangiogenesis. ReACT dramatically decreased direct costs.

Bone marrow cells for cardiac regeneration and repair: current status and issues

Extensive studies in experimental animal heart models and patients have shown the promise of bone marrow cell (BMC) transplantation as an alternative strategy to the conventional treatment modalities for cardiac repair. 'Stemness' of BMC to adopt cardiac phenotype, their potential as carriers of exogenous therapeutic genes and an inherent ability to express growth factors and cytokines to exert paracrine effects have been especially focused until recently. These findings suggest that locally delivered BMCs are capable of regenerating de novo myocardium. Others have shown that extensive neovascularization due to paracrine effects of the engrafted cells resulted in improved regional blood flow and reduced infarct size. Despite initial success, there are multiple fundamental issues that remain contentious. Indeed, resolving these issues will optimize future heart cell therapy protocols to achieve better prognosis in the clinical settings. This review is a concise, in-depth and critical appreciation of the role of BMCs in heart cell therapy and builds a conceptual framework to elaborate their significance as a possible source of donor cells. Moreover, it discusses the current status of BMC transplantation as a clinical modality and the relevant issues confronting this approach in light of the published data with clinical relevance.

Cell transplantation for treatment of left-ventricular dysfunction due to ischemic heart failure: from bench to bedside

Cell transplantation is an innovative technology that involves the implantation of a variety of myogenic and angiogenic cell types. The transplanted cells proliferate and augment left ventricular performance and therein ameliorate the heart failure symptoms. The concept of cell transplantation has followed the footsteps of angiogenesis starting as bench side research. The latter half of the decade saw the transformation of this potential mechanism to a promising therapy for ischemic heart failure. More than 150 patients have been treated with cellular transplantation worldwide. This novel application has the potential to revolutionize alternative therapeutic approaches to management of heart failure.

Therapeutic angiogenesis for myocardial ischemia

Therapeutic angiogenesis offers promise as a novel treatment for ischemic heart disease, particularly for patients who are not candidates for current methods of revascularization. The goal of treatment is both relief of symptoms of coronary artery disease and improvement of cardiac function by increasing perfusion to the ischemic region. Protein-based therapy with cytokines including vascular endothelial growth factor and fibroblast growth factor demonstrated functionally significant angiogenesis in several animal models. However, clinical trials have yielded largely disappointing results. The attenuated angiogenic response seen in clinical trials of patients with coronary artery disease may be due to multiple factors including endothelial dysfunction, particularly in the context of advanced atherosclerotic disease and associated comorbid conditions, regimens of single agents, as well as inefficiencies of current delivery methods. Gene therapy has several advantages over protein therapy and recent advances in gene transfer techniques have improved the feasibility of this approach. The safety and tolerability of therapeutic angiogenesis by gene transfer has been demonstrated in phase I clinical trials. The utility of therapeutic angiogenesis by gene transfer as a treatment option for ischemic cardiovascular disease will be determined by adequately powered, randomized, placebo-controlled Phase II and III clinical trials. Cell-based therapies offer yet another approach to therapeutic angiogenesis. Although it is a promising therapeutic strategy, additional preclinical studies are warranted to determine the optimal cell type to be administered, as well as the optimal delivery method. It is likely the optimal treatment will involve multiple agents as angiogenesis is a complex process involving a large cascade of cytokines, as well as cells and extracellular matrix, and administration of a single factor may be insufficient. The promise of therapeutic angiogenesis as a novel treatment for no-option patients should be approached with cautious optimism as the field progresses.

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.

Perspective and challenges of mesenchymal stem cells for cardiovascular regeneration

Mesenchymal stem cells (MSCs) exhibit multipotent differentiation potential and can be derived from embryonic, neonatal and adult differentiation stage III tissue sources. While increasing preclinical studies and clinical trials have indicated that MSC-based therapy is a promising strategy for cardiovascular regeneration, there are major challenges to overcome before this stem-cell technology can be widely applied in clinical settings. In this review, the following important issues will be addressed. First, optimal sources of MSC derivation suitable for myocardial repair are not determined. Second, assessments for preclinical and clinical studies of MSCs require more scientific data analysis. Third, mechanisms of MSC-based therapy for cardiovascular regeneration have not been fully understood yet. Finally, the potential benefit-risk ratio of MSC therapy needs to be evaluated systematically. Additionally, future development of MSC therapy will be discussed.

Stem cell therapy for heart disease

Coronary artery disease is the leading cause of death in Americans. After myocardial infarction, significant ventricular damage persists despite timely reperfusion and pharmacological management. Treatment is limited, as current modalities do not cure this damage. In the past decade, stem cell therapy has emerged as a promising therapeutic solution to restore myocardial function. Clinical trials have demonstrated safety and beneficial effects in patients suffering from acute myocardial infarction, heart failure, and dilated cardiomyopathy. These benefits include improved ventricular function, increased ejection fraction, and decreased infarct size. Mechanisms of therapy are still not clearly understood. However, it is believed that paracrine factors, including stromal cell-derived factor-1, contribute significantly to stem cell benefits. The purpose of this article is to provide medical professionals with an overview on stem cell therapy for the heart and to discuss potential future directions.

Intramyocardial injection of autologous bone marrow-derived ex vivo expanded mesenchymal stem cells in acute myocardial infarction patients is feasible and safe up to 5 years of follow-up

In experimental studies, mesenchymal stem cell (MSC) transplantation in acute myocardial infarction (AMI) models has been associated with enhanced neovascularization and myogenesis. Clinical data however, are scarce. Therefore, the present study evaluates the safety and feasibility of intramyocardial MSC injection in nine patients, shortly after AMI during short-term and 5-year follow-up. Periprocedural safety analysis demonstrated one transient ischemic attack. No other adverse events related to MSC treatment were observed during 5-year follow-up. Clinical events were compared to a nonrandomized control group comprising 45 matched controls. A 5-year event-free survival after MSC-treatment was comparable to controls (89 vs. 91 %, P = 0.87). Echocardiographic imaging for evaluation of left ventricular function demonstrated improvements up to 5 years after MSC treatment. These findings were not significantly different when compared to controls. The present safety and feasibility study suggest that intramyocardial injection of MSC in patients shortly after AMI is feasible and safe up to 5-year follow-up.

Influence of in vitro biomimicked stem cell 'niche' for regulation of proliferation and differentiation of human bone marrow-derived mesenchymal stem cells to myocardial phenotypes: serum starvation without aid of chemical agents and prevention of spontaneous stem cell transformation enhanced by the matrix environment

Niche appears important for preventing the spontaneous differentiation or senescence that cells undergo during in vitro expansion. In the present study, it was revealed that human bone marrow-derived mesenchymal stem cells (hBM-MSCs) undergo senescence-related differentiation into the myocardial lineage in vitro without any induction treatment. This phenomenon occurred over the whole population of MCSs, much different from conventional differentiation with limited frequency of occurrence, and was accompanied by a change of morphology into large, flat cells with impeded proliferation, which are the representative indications of MSC senescence. By culturing MSCs under several culture conditions, it was determined that induction treatment with 5-azacytidine was not associated with the phenomenon, but the serum-starvation condition, under which proliferation is severely hampered, caused senescence progression and upregulation of cardiac markers. Nevertheless, MSCs gradually developed a myocardial phenotype under normal culture conditions over a prolonged culture period and heterogeneous populations were formed. In perspectives of clinical applications, this must be prevented for fair and consistent outcomes. Hence, the biomimetic 'niche' was constituted for hBM-MSCs by cultivating on a conventionally available extracellular matrix (ECM). Consequently, cells on ECM regained a spindle-shape morphology, increased in proliferation rate by two-fold and showed decreased expression of cardiac markers at both the mRNA and protein levels. In conclusion, the outcome indicates that progression of MSC senescence may occur via myocardial differentiation during in vitro polystyrene culture, and this can be overcome by employing appropriate ECM culture techniques.

The challenges for cardiac vascular precursor cell therapy: lessons from a very elusive precursor

There is compelling evidence that cardiovascular disorders arise and/or progress due mainly to endothelial dysfunction. Novel therapeutic strategies aim to generate new myocardial tissue using cells with regenerative potential, either alone or in combination with biomaterials, cytokines and advanced monitoring devices. Among the human adult progenitor cells used in such methods, those historically termed 'endothelial progenitor cells' show promise for vascular growth and repair. Asahara et al. [Science 1997;275:964-967] initially described putative endothelial cell precursors in 1997. Subsequently, distinct cell populations termed endothelial colony-forming units-Hill, circulating angiogenic cells and endothelial colony-forming cells were identified that varied in terms of phenotype, vascular homeostasis contribution and purity. Notably, most of these cells are not genuine vascular precursor cells belonging to the endothelial lineage. This review provides a broad overview of the main properties of the endothelium, focusing on the basis governing its growth and repair. We discuss efforts to identify true vascular precursors, a matter of debate for the past 15 years, as well as recent methodological advances in identifying new hierarchies of more homogeneous, clonogenic and proliferative vascular endothelial-lineage precursors. Consideration of these issues provides insights that may help develop more effective therapies against human diseases that involve vascular deficits.

Combined delivery of bone marrow-derived mononuclear cells in chronic ischemic heart disease: rationale and study design

BACKGROUND

Treatment with bone marrow-derived mononuclear cells (BM-MNC) may improve left ventricular (LV) function in patients with chronic ischemic heart disease (IHD). Delivery method of the cell product may be crucial for efficacy.

HYPOTHESIS

We aimed to demonstrate that the combination of intramyocardial and intracoronary injection of BM-MNC is safe and improves LV function in patients with chronic IHD.

METHODS

After a safety/feasibility phase of 10 patients, 54 patients will be randomly assigned in a 1:1:1 pattern to 1 control and 2 BM-MNC treatment groups. The control group will be treated with state-of-the-art medical management. The treatment groups will receive either exclusively intramyocardial injection or a combination of intramyocardial and intracoronary injection of autologous BM-MNC. Left ventricular function as well as scar size, transmural extension, and regional wall-motion score will be assessed by cardiac magnetic resonance imaging studies at baseline and after 6 months. The primary endpoint is the change in global LV ejection fraction by cardiac magnetic resonance from 6 months to baseline.

RESULTS

The results, it is hoped, will have important clinical impact and provide essential information to improve the design of future regenerative-medicine protocols in cardiology.

CONCLUSIONS

As cell delivery may play an important role in chronic IHD, we aim to demonstrate feasibility and efficacy of a combined cell-delivery approach in patients with decreased LV function.

Impacts of bone marrow aspirate and peripheral blood derived platelet-rich plasma on the wound healing in chronic ischaemic limb

Platelet rich plasma (PRP) has attracted attention as a safe and cost-effective source of growth factors that stimulate cells to regenerate tissue. Bone marrow cells are also estimated as an effective material for treating chronic ulcers. With the same technique to concentrate PRP from peripheral blood, bone marrow aspirate was processed and marrow cells were concentrated as well as platelets. Impact of PRP derived from bone marrow aspirate (bm-PRP) and that from peripheral blood (pb-PRP) on wound healing of persistent ischaemic rabbits' limbs were observed. Full thickness skin defects were made on the thighs, which had been treated to be persistent ischaemic status 3 weeks previously. Saline, pb-PRP, and bm-PRP were injected into the wound floor, respectively. Skin defected areas on ischaemic limbs were significantly wider than those on non-ischaemic limbs. bm-PRP injected wounds showed a significantly smaller skin defect area compared with pb-PRP and ischaemic-saline wounds at all time points. Fluorescently dyed cells of bm-PRP, injected into the wounds, could be traced 4 weeks after, whereas those of pb-PRP could be traced no more than 2 weeks. Wound healing on an ischaemic limb was accelerated with bm-PRP, whereas pb-PRP could not show any significance from saline. This difference can be attributed to the kind of cells contained in the PRPs. Injection of bm-PRP is a good candidate for treating wounds on ischaemic limbs.

Autologous serum enhances cardiomyocyte differentiation of rat bone marrow mesenchymal stem cells in the presence of transforming growth factor-β1 (TGF-β1)

In spite of previous reports, the role of transforming growth factor-β1 (TGF-β1) on cardiomyocyte differentiation, especially in the present autologous serum (AS) in culture medium, is still unclear. So, the purpose of this study was to investigate the potential of rat bone marrow mesenchymal stem cells (rBMSCs) to proliferate and differentiate towards cardiomyocyte lineage with the use of AS. Most expansion protocols use a medium supplemented with fetal bovine serum (FBS) as nutritional supplement. FBS is an adverse additive to cells that are proliferated for therapeutic purposes in humans because the use of FBS carries the risk of transmitting viral and bacterial infections and proteins that may initiate xenogeneic immune responses. Therefore, bone marrow cells were cultured in a medium supplemented with 10% AS, 10% FBS, and serum free medium (SFM). Then, rBMSCs were cultured with TGF-β1 (10 ng/ml) for 2 wk. The number of viable cells in AS and FBS groups were measured with MTT assay. Beating areas frequency, up to fourth week after plating, were monitored and evaluated daily. The characteristics of cardiomyocytes were assessed by semi-quantitative reverse transcription polymerase chain reaction and western blot. MTT result indicated that rBMSCs in AS proliferated markedly faster than FBS and SFM. The number of beating areas significantly increased in AS compared to FBS medium. A noticeable increase in the cardiac genes expression was observed in AS. Moreover, western blot analysis confirmed that cardiac proteins were increased in the AS condition. In conclusion, the present study could be extended toward the safe culture of MSCs for the treatment of heart defects.

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.

Attenuation of hind-limb ischemia in mice with endothelial-like cells derived from different sources of human stem cells

Functional endothelial-like cells (EC) have been successfully derived from different cell sources and potentially used for treatment of cardiovascular diseases; however, their relative therapeutic efficacy remains unclear. We differentiated functional EC from human bone marrow mononuclear cells (BM-EC), human embryonic stem cells (hESC-EC) and human induced pluripotent stem cells (hiPSC-EC), and compared their in-vitro tube formation, migration and cytokine expression profiles, and in-vivo capacity to attenuate hind-limb ischemia in mice. Successful differentiation of BM-EC was only achieved in 1/6 patient with severe coronary artery disease. Nevertheless, BM-EC, hESC-EC and hiPSC-EC exhibited typical cobblestone morphology, had the ability of uptaking DiI-labeled acetylated low-density-lipoprotein, and binding of Ulex europaeus lectin. In-vitro functional assay demonstrated that hiPSC-EC and hESC-EC had similar capacity for tube formation and migration as human umbilical cord endothelial cells (HUVEC) and BM-EC (P>0.05). While increased expression of major angiogenic factors including epidermal growth factor, hepatocyte growth factor, vascular endothelial growth factor, placental growth factor and stromal derived factor-1 were observed in all EC cultures during hypoxia compared with normoxia (P<0.05), the magnitudes of cytokine up-regulation upon hypoxic were more dramatic in hiPSC-EC and hESC-EC (P<0.05). Compared with medium, transplanting BM-EC (n = 6), HUVEC (n = 6), hESC-EC (n = 8) or hiPSC-EC (n = 8) significantly attenuated severe hind-limb ischemia in mice via enhancement of neovascularization. In conclusion, functional EC can be generated from hECS and hiPSC with similar therapeutic efficacy for attenuation of severe hind-limb ischemia. Differentiation of functional BM-EC was more difficult to achieve in patients with cardiovascular diseases, and hESC-EC or iPSC-EC are readily available as "off-the-shelf" format for the treatment of tissue ischemia.

Human embryonic stem cell derived mesenchymal progenitors express cardiac markers but do not form contractile cardiomyocytes

Mesenchymal progenitors or stromal cells have shown promise as a therapeutic strategy for a range of diseases including heart failure. In this context, we explored the growth and differentiation potential of mesenchymal progenitors (MPs) derived in vitro from human embryonic stem cells (hESCs). Similar to MPs isolated from bone marrow, hESC derived MPs (hESC-MPs) efficiently differentiated into archetypical mesenchymal derivatives such as chondrocytes and adipocytes. Upon treatment with 5-Azacytidine or TGF-β1, hESC-MPs modified their morphology and up-regulated expression of key cardiac transcription factors such as NKX2-5, MEF2C, HAND2 and MYOCD. Nevertheless, NKX2-5⁺ hESC-MP derivatives did not form contractile cardiomyocytes, raising questions concerning the suitability of these cells as a platform for cardiomyocyte replacement therapy. Gene profiling experiments revealed that, although hESC-MP derived cells expressed a suite of cardiac related genes, they lacked the complete repertoire of genes associated with bona fide cardiomyocytes. Our results suggest that whilst agents such as TGF-β1 and 5-Azacytidine can induce expression of cardiac related genes, but treated cells retain a mesenchymal like phenotype.

Activity of mesenchymal stem cells in a nonperfused cardiac explant model

Stem cell therapy represents a potential novel additional therapy for acute myocardial infarction. Cardiac applications of stem cell therapy are now undergoing clinical trials though many properties, including localization, possible adhesion, and infiltration of the injected stem cells in the myocardium, have not been studied in detail even in vitro. To study these mechanisms in a controlled microenvironment, we developed a model where mesenchymal stem cells (MSCs) were transported into live, cultured cardiac explants for further co-culture. About 10×10(3) porcine MSCs were injected into freshly excised and isolated cardiac explants of the pig. The explants were present in the culture medium for up to 7 days, with the time course of viability of the myocardial tissue, and the migration and the localization of the injected MSCs were analyzed with histological and immunohistological stainings. The myocyte structure was observed to be well preserved, and proliferation of capillaries and myofibroblasts was detected at the explant periphery. There were injected MSCs localized in the capillaries and in contact with the endothelial cells. The migration range and the number of adherent MSCs increased over time, suggesting active movement of MSCs in the explant. Our results suggest that this cardiac explant culture model is a feasible method for studying the effects of stem cells in the myocardium in vitro.

Stem cell therapy for chronic heart failure: an updated appraisal

INTRODUCTION

Significant advances have been made to understand the mechanisms involved in cardiac cell-based therapies. The early translational application of basic science knowledge has led to several animal and human clinical trials. The initial promising beneficial effect of stem cells on cardiac function restoration has been eclipsed by the inability of animal studies to translate into sustained clinical improvements in human clinical trials.

AREAS COVERED

In this review, the authors cover an updated overview of various stem cell populations used in chronic heart failure. A critical review of clinical trials conducted in advanced heart failure patients is proposed, and finally promising avenues for developments in the field of cardiac cell-based therapies are presented.

EXPERT OPINION

Several questions remain unanswered, and this limits our ability to understand basic mechanisms involved in stem cell therapeutics. Human studies have revealed critical unresolved issues. Further elucidation of the proper timing, mode delivery and prosurvival factors is imperative, if the field is to advance. The limited benefits seen to date are simply not enough if the potential for substantial recovery of nonfunctioning myocardium is to be realized.

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.