Myocardial Regeneration and Stem Cell Repair

Stem cells-derived exosomes as cardiac regenerative agents

Heart failure is a root cause of morbidity and mortality worldwide. Due to the limited regenerative capacity of the heart following myocardial injury, stem cell-based therapies have been considered a hopeful approach for improving cardiac regeneration. In recent years, different kinds of cell products have been investigated regarding their potential to treat patients with heart failure. Despite special attention to cell therapy and its products, therapeutic efficacy has been disappointing, and clinical application is not affordable. In the past few years, a subset of small extracellular vehicles (EVs), commonly known as "exosomes," was reported to grant regenerative and cardioprotective signals at a value similar to their donor cells. The conceptual advantage is that they may be ideally used without evoking a relevant recipient immune response or other adverse effects associated with viable cells. The evidence related to their beneficial effects in animal models of heart failure is rapidly growing. However, there is remarkable heterogeneity regarding source cells, isolation process, effective dosage, and delivery mode. This brief review will focus on the latest research and debates on regenerative potential and cardiac repair of exosomes from different sources, such as cardiac/non-cardiac stem, somatic cells, and progenitor cells. Overall, the current state of research on exosomes as an experimental therapy for heart diseases will be discussed.

Differences in Mitochondrial Membrane Potential Identify Distinct Populations of Human Cardiac Mesenchymal Progenitor Cells

Adult human cardiac mesenchymal progenitor cells (hCmPC) are multipotent resident populations involved in cardiac homeostasis and heart repair. Even if the mechanisms have not yet been fully elucidated, the stem cell differentiation is guided by the mitochondrial metabolism; however, mitochondrial approaches to identify hCmPC with enhanced stemness and/or differentiation capability for cellular therapy are not established. Here we demonstrated that hCmPCs sorted for low and high mitochondrial membrane potential (using a lipophilic cationic dye tetramethylrhodamine methyl ester, TMRM), presented differences in energy metabolism from preferential glycolysis to oxidative rates. TMRM-high cells are highly efficient in terms of oxygen consumption rate, basal and maximal respiration, and spare respiratory capacity compared to TMRM-low cells. TMRM-high cells showed characteristics of pre-committed cells and were associated with higher in vitro differentiation capacity through endothelial, cardiac-like, and, to a lesser extent, adipogenic and chondro/osteogenic cell lineage, when compared with TMRM-low cells. Conversely, TMRM-low showed higher self-renewal potential. To conclude, we identified two hCmPC populations with different metabolic profile, stemness maturity, and differentiation potential. Our findings suggest that metabolic sorting can isolate cells with higher regenerative capacity and/or long-term survival. This metabolism-based strategy to select cells may be broadly applicable to therapies.

Tissue evacuated during joint replacement procedure as a source of mononuclear cells

Background

Different cell populations from bone marrow were used in various clinical trials for cardiac diseases during last decade. Four clinical studies are ongoing in our institution and enroll patients with cardiac diseases, coronary disease, type 2 diabetes, and osteoarthritis. The density gradient is used to separate bone marrow mononuclear cells. Joint replacement procedures were associated with significant loss of tissue. Usually, excess tissue as bone marrow, peripheral blood and fat are removed to clean operation site. The aim of this study is to prove whether removed tissue during joint replacement procedure can be considered as a significant source of mononuclear cells.

Methods

Excised tissue obtained during joint replacement procedure was collected by AutoLog system. Bone marrow tissue was collected by iliac crest puncture. Mononuclear cells from both sources were isolated by using Ficoll density gradient centrifugation. Flow cytometry was used to detect mononuclear cell, CD34+ population counts and cell viability. Tissue processing yields between the group of joint replacement and iliac crest puncture group were compared.

Results

Together, 34 bone marrow tissue processings were performed. On average, samples contained 46.31 ± 9.35 ml of bone marrow solution. Average cell yield in final product was 28.64 ± 9.35 × 10⁶ MNCs and 0.77 ± 1.51 × 10⁶ CD34+ population. In case of tissue removed during joint replacement nine processings were performed. On average samples contained 450 ± 157.69 ml of tissue solution. Average cell yield in final product was 76.67 ± 35.42 × 10⁶ MNCs and 1.33 ± 0.97 × 10⁶ CD34+ population.

Conclusions

Tissue processing analysis shows that tissue removed during joint replacement procedure can be assumed as a significant source of mononuclear cells. Methods used for bone marrow-derived mononuclear cell extraction can be applied to the excess tissue.

Synergistic induction of cardiomyocyte differentiation from human bone marrow mesenchymal stem cells by interleukin 1β and 5-azacytidine

Interleukin-1β (IL-1β) is a cytokine protein expressed by cardiomyocyte in myocardial damage-associated inflammation. Although several methods are currently available for treatment of heart diseases none of them are completely successful. Recently, stem cells have gained enormous attention and are expected to play a significant role for treating heart diseases. 5-Azacytidine (5-aza) has recently been found to cause stimulation of stem cells to differentiate into cardiomyocytes. Here we present the determination of whether IL-1β can induce the differentiation of mesenchymal stem cells (MSCs) to cardiomyocytes. MSCs were derived from bone marrow, propagated and then cultured in differentiation medium supplemented with 5-aza and IL-1β (at two levels, 5 and 10 ng/ml). After 21 days, total RNA was extracted and cDNA synthesis was carried out. Quantitative polymerase chain reaction (Q-PCR) was performed for detecting cardiac-specific markers. Besides, to investigate the expression of cardiac markers in protein levels, immunocytochemistry was done by specific antibodies. Ultimately, cardiac markers expression suggested that IL-1β and 5-aza synergistically induces the cardiomyocyte differentiation.

Human Umbilical Cord Mesenchymal Stromal Cell Transplantation in Myocardial Ischemia (HUC-HEART Trial). A Study Protocol of a Phase 1/2, Controlled and Randomized Trial in Combination with Coronary Artery Bypass Grafting

Mesenchymal stem cells (MSCs), which may be obtained from the bone marrow, have been studied for more than a decade in the setting of coronary artery disease (CAD). Adipose tissue-derived MSCs have recently come into focus and are being tested in a series of clinical trials. MSC-like cells have also been derived from a variety of sources, including umbilical cord stroma, or HUC-MSCs. The HUC-HEART trail (ClinicalTrials.gov Identifier: NCT02323477) is a phase 1/2, controlled, multicenter, randomized clinical study of the intramyocardial delivery of allogeneic HUC-MSCs in patients with chronic ischemic cardiomyopathy. A total of 79 patients (ages 30-80) with left ventricle ejection fractions ranging between 25 and 45% will be randomized in a 2:1:1 pattern in order to receive an intramyocardial injection of either HUC-MSCs or autologous bone marrow-derived mononuclear cells (BM-MNCs) in combination with coronary arterial bypass grafting (CABG) surgery. The control group of patients will receive no cells and undergo CABG alone. Human HUC-MSCs will be isolated, propagated and banked in accordance with a cGMP protocol, whereas the autologous BM-MNCs will be isolated via aspiration from the iliac crest and subsequently process in a closed-circuit cell purification system shortly before cell transplantation. The cell injections will be implemented in 10 peri-infarct areas. Baseline and post-transplantation outcome measures will be primarily utilized to test both the safety and the efficacy of the administered cells for up to 12 months.

Assessment of Retrograde Coronary Venous Infusion of Mesenchymal Stem Cells Combined with Basic Fibroblast Growth Factor in Canine Myocardial Infarction Using Strain Values Derived from Speckle-Tracking Echocardiography

Speckle-tracking echocardiography was used to assess retrograde coronary venous infusion of mesenchymal stem cells (MSCs) combined with basic fibroblast growth factor (bFGF) in a canine model of acute myocardial infarction (AMI). AMI was induced by ligation of the left anterior descending coronary artery. Coronary venous retroperfusion was performed at 1 wk after AMI. Twenty-eight animals were randomized into four groups: saline, bFGF+saline, saline+MSCs and bFGF+MSCs. Echocardiography was performed before AMI, at 7 d post-AMI and 40 d after retroperfusion. Apoptotic cardiomyocytes in the border zone of the ischemic region were evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling. Vascular endothelial growth factor and factor VIII concentrations were measured by western blotting. The left ventricular end-systolic volume increased significantly, whereas the left ventricular ejection fraction and global and segmental strain values decreased significantly after AMI. After retroperfusion, the strain values of the infarct zone, but not conventional echocardiographic parameters, were significantly different between control and bFGF+MSC groups. Cardiomyocyte apoptosis decreased, whereas vascular endothelial growth factor and factor VIII concentrations were higher in the bFGF+MSC, bFGF and MSC groups. Cardiomyocyte apoptosis was well correlated with the strain values. Although retrograde coronary venous infusion of bFGF and MSCs promoted neo-vascularization of the infarcted myocardium and inhibited apoptosis, there was only a slight strain improvement without a substantial increase in global cardiac functions.

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.

Cell lineage tracing in human epithelial tissues using mitochondrial DNA mutations as clonal markers

The study of cell lineages through heritable genetic lineage tracing is well established in experimental animals, particularly mice. While such techniques are not feasible in humans, we have taken advantage of the fact that the mitochondrial genome is highly prone to nonpathogenic mutations and such mutations can be used as clonal markers to identify stem cell derived clonal populations in human tissue sections. A mitochondrial DNA (mtDNA) mutation can spread by a stochastic process through the several copies of the circular genome in a single mitochondrion, and then through the many mitochondria in a single cell, a process called 'genetic drift.' This process takes many years and so is likely to occur only in stem cells, but once established, the fate of stem cell progeny can be followed. A cell having at least 80% of its mtDNA genomes bearing the mutation results in a demonstrable deficiency in mtDNA-encoded cytochrome c oxidase (CCO), optimally detected in frozen tissue sections by dual-color histochemistry, whereby CCO activity stains brown and CCO deficiency is highlighted by subsequent succinate dehydrogenase activity, staining the CCO-deficient areas blue. Cells with CCO deficiency can be laser captured and subsequent mtDNA sequencing can ascertain the nature of the mutation. If all cells in a CCO-deficient area have an identical mutation, then a clonal population has been identified; the chances of the same mutation initially arising in separate cells are highly improbable. The technique lends itself to the study of both normal epithelia and can answer several questions in tumor biology. WIREs Dev Biol 2016, 5:103-117. doi: 10.1002/wdev.203 For further resources related to this article, please visit the WIREs website.

Adult Stem Cell Responses to Nanostimuli

Adult or mesenchymal stem cells (MSCs) have been found in different tissues in the body, residing in stem cell microenvironments called "stem cell niches". They play different roles but their main activity is to maintain tissue homeostasis and repair throughout the lifetime of an organism. Their ability to differentiate into different cell types makes them an ideal tool to study tissue development and to use them in cell-based therapies. This differentiation process is subject to both internal and external forces at the nanoscale level and this response of stem cells to nanostimuli is the focus of this review.

Activation of Notch1 signalling promotes multi-lineage differentiation of c-Kit(POS)/NKX2.5(POS) bone marrow stem cells: implication in stem cell translational medicine

Introduction

Transplantation of bone marrow mesenchymal stem cells (BMSCs) can repair injured hearts. However, whether BMSC populations contain cells with cardiac stem cell characteristics is ill-defined. We report here that Notch signalling can promote differentiation of c-Kit^POS/NKX2.5^POS BMSCs into cardiomyocyte-like cells.

Methods

Total BMSCs were isolated from Sprague–Dawley rat femurs and c-Kit^POS cells were purified. c-Kit^POS/NKX2.5^POS cells were isolated by single-cell cloning, and the presence of cardiomyocyte, smooth muscle cell (SMC), and endothelial cell differentiation markers assessed by immunofluorescence staining and semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR) analysis. Levels of c-Kit and Notch1–4 in total BMSCs and c-Kit^POS/NKX2.5^POS BMSCs were quantitated by flow cytometry. Following infection with an adenovirus over-expressing Notch1 intracellular domain (NICD), total BMSCs and c-Kit^POS/NKX2.5^POS cells were assessed for differentiation to cardiomyocyte, SMC, and endothelial cell lineages by immunofluorescence staining and real-time quantitative RT-PCR. Total BMSCs and c-Kit^POS/NKX2.5^POS cells were treated with the Notch1 ligand Jagged1 and markers of cardiomyocyte, SMC, and endothelial cell differentiation were examined by immunofluorescence staining and real-time quantitative RT-PCR analysis.

Results

c-Kit^POS/NKX2.5^POS cells were present among total BMSC populations, and these cells did not express markers of adult cardiomyocyte, SMC, or endothelial cell lineages. c-Kit^POS/NKX2.5^POS BMSCs exhibited a multi-lineage differentiation potential similar to total BMSCs. Following sorting, the c-Kit level in c-Kit^POS/NKX2.5^POS BMSCs was 84.4%. Flow cytometry revealed that Notch1 was the predominant Notch receptor present in total BMSCs and c-Kit^POS/NKX2.5^POS BMSCs. Total BMSCs and c-Kit^POS/NKX2.5^POS BMSCs overexpressing NICD had active Notch1 signalling accompanied by differentiation into cardiomyocyte, SMC, and endothelial cell lineages. Treatment of total BMSCs and c-Kit^POS/NKX2.5^POS BMSCs with exogenous Jagged1 activated Notch1 signalling and drove multi-lineage differentiation, with a tendency towards cardiac lineage differentiation in c-Kit^POS/NKX2.5^POS BMSCs.

Conclusions

c-Kit^POS/NKX2.5^POS cells exist in total BMSC pools. Activation of Notch1 signalling contributed to multi-lineage differentiation of c-Kit^POS/NKX2.5^POS BMSCs, favouring differentiation into cardiomyocytes. These findings suggest that modulation of Notch1 signalling may have potential utility in stem cell translational medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0085-2) contains supplementary material, which is available to authorized users.

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.

Stem cells in the management of heart failure: what have we learned from clinical trials?

Research shows that various types of stem cells (SCs) have the ability to rebuild damaged heart tissue. The TIME and Late TIME human trials shed light on the optimum timing of SC therapy administration after myocardial damage. The FOCUS study failed to show a substantial positive effect of bone marrow-derived mononuclear cells in patients suffering from ischemic heart failure; however, some completed human trials do show promise, with improvement in cardiac function. Recent clinical trials have identified a subset of marrow cells that was able to stimulate endogenous adult cardiac SCs where cardiac SCs administration showed promise in the SCIPIO trial. This review addresses some of the lessons learned from clinical trials with SC therapy in ischemic heart failure.

The potential and challenges of using stem cells for cardiovascular repair and regeneration

Recent progress in using stem cells for tissue repair and functional restoration has aroused much attention due to its potential to provide a cue for many diseases such as myocardial infarction. Stem cell therapy for cardiovascular disease has been studied extensively at both experimental and clinical levels. Pluripotent stem cells and mesenchymal stem cells were proven to be effective for myocardial regeneration, angiogenesis, and cardiac functional restoration. In this review, we will concisely discuss advantages and disadvantages of currently-used stem cells for cardiovascular repair and regeneration. The limitations and uniqueness of some types of stem cells will also be discussed. Although substantial progress has been made over the last decade about stem cells in cardiovascular regeneration, many challenges lie ahead before the therapeutic potentials of stem cells can be fully recognized.

Macroscopic fluorescence imaging: a novel technique to monitor retention and distribution of injected microspheres in an experimental model of ischemic heart failure

Background

The limited effectiveness of cardiac cell therapy has generated concern regarding its clinical relevance. Experimental studies show that cell retention and engraftment are low after injection into ischemic myocardium, which may restrict therapy effectiveness significantly. Surgical aspects and mechanical loss are suspected to be the main culprits behind this phenomenon. As current techniques of monitoring intramyocardial injections are complex and time-consuming, the aim of the study was to develop a fast and simple model to study cardiac retention and distribution following intramyocardial injections. For this purpose, our main hypothesis was that macroscopic fluorescence imaging could adequately serve as a detection method for intramyocardial injections.

Methods and Results

A total of 20 mice underwent ligation of the left anterior descending artery (LAD) for myocardial infarction. Fluorescent microspheres with cellular dimensions were used as cell surrogates. Particles (5×10⁵) were injected into the infarcted area of explanted resting hearts (Ex vivo myocardial injetions EVMI, n = 10) and in vivo into beating hearts (In vivo myocardial injections IVMI, n = 10). Microsphere quantification was performed by fluorescence imaging of explanted organs. Measurements were repeated after a reduction to homogenate dilutions. Cardiac microsphere retention was 2.78×10⁵±0.31×10⁵ in the EVMI group. In the IVMI group, cardiac retention of microspheres was significantly lower (0.74×10⁵±0.18×10⁵; p<0.05). Direct fluorescence imaging revealed venous drainage through the coronary sinus, resulting in a microsphere accumulation in the left (0.90×10⁵±0.20×10⁵) and the right (1.07×10⁵±0.17×10⁵) lung. Processing to homogenates involved further particle loss (p<0.05) in both groups.

Conclusions

We developed a fast and simple direct fluorescence imaging method for biodistribution analysis which enabled the quantification of fluorescent microspheres after intramyocardial delivery using macroscopic fluorescence imaging. This new technique showed massive early particle loss and venous drainage into the right atrium leading to substantial accumulation of graft particles in both lungs.

Cell therapy with human MSCs isolated from the umbilical cord Wharton jelly associated to a PVA membrane in the treatment of chronic skin wounds

The healing process of the skin is a dynamic procedure mediated through a complex feedback of growth factors secreted by a variety of cells types. Despite the most recent advances in wound healing management and surgical procedures, these techniques still fail up to 50%, so cellular therapies involving mesenchymal stem cells (MSCs) are nowadays a promising treatment of skin ulcers which are a cause of high morbidity. The MSCs modulate the inflammatory local response and induce cell replacing, by a paracrine mode of action, being an important cell therapy for the impaired wound healing. The local application of human MSCs (hMSCs) isolated from the umbilical cord Wharton's jelly together with a poly(vinyl alcohol) hydrogel (PVA) membrane, was tested to promote wound healing in two dogs that were referred for clinical examination at UPVET Hospital, showing non-healing large skin lesions by the standard treatments. The wounds were infiltrated with 1000 cells/µl hMSCs in a total volume of 100 µl per cm(2) of lesion area. A PVA membrane was applied to completely cover the wound to prevent its dehydration. Both animals after the treatment demonstrated a significant progress in skin regeneration with decreased extent of ulcerated areas confirmed by histological analysis. The use of Wharton's jelly MSCs associated with a PVA membrane showed promising clinical results for future application in the treatment of chronic wounds in companion animals and humans.

Cell shape and cardiosphere differentiation: a revelation by proteomic profiling

Stem cells (embryonic stem cells, somatic stem cells such as neural stem cells, and cardiac stem cells) and cancer cells are known to aggregate and form spheroid structures. This behavior is common in undifferentiated cells and may be necessary for adapting to certain conditions such as low-oxygen levels or to maintain undifferentiated status in microenvironments including stem cell niches. In order to decipher the meaning of this spheroid structure, we established a cardiosphere clone (CSC-21E) derived from the rat heart which can switch its morphology between spheroid and nonspheroid. Two forms, floating cardiospheres and dish-attached flat cells, could be switched reversibly by changing the cell culture condition. We performed differential proteome analysis studies and obtained protein profiles distinct between spherical forms and flat cells. From protein profiling analysis, we found upregulation of glycolytic enzymes in spheroids with some stress proteins switched in expression levels between these two forms. Evidence has been accumulating that certain chaperone/stress proteins are upregulated in concert with cellular changes including proliferation and differentiation. We would like to discuss the possible mechanism of how these aggregates affect cell differentiation and/or other cellular functions.

Satellite cells and the muscle stem cell niche

Adult skeletal muscle in mammals is a stable tissue under normal circumstances but has remarkable ability to repair after injury. Skeletal muscle regeneration is a highly orchestrated process involving the activation of various cellular and molecular responses. As skeletal muscle stem cells, satellite cells play an indispensible role in this process. The self-renewing proliferation of satellite cells not only maintains the stem cell population but also provides numerous myogenic cells, which proliferate, differentiate, fuse, and lead to new myofiber formation and reconstitution of a functional contractile apparatus. The complex behavior of satellite cells during skeletal muscle regeneration is tightly regulated through the dynamic interplay between intrinsic factors within satellite cells and extrinsic factors constituting the muscle stem cell niche/microenvironment. For the last half century, the advance of molecular biology, cell biology, and genetics has greatly improved our understanding of skeletal muscle biology. Here, we review some recent advances, with focuses on functions of satellite cells and their niche during the process of skeletal muscle regeneration.

Cardiomyocyte regeneration

The heart was initially believed to be a terminally differentiated organ; once the cardiomyocytes died, no recovery could be made to replace the dead cells. However, around a decade ago, the concept of cardiac stem cells (CSCs) in adult hearts was proposed. CSCs differentiate into cardiomyocytes, keeping the heart functioning. Studies have proved the existence of stem cells in the heart. These somatic stem cells have been studied for use in cardiac regeneration. Moreover, recently, induced pluripotent stem cells (iPSCs) were invented, and methodologies have now been developed to induce stable cardiomyocyte differentiation and purification of mature cardiomyocytes. A reprogramming method has also been applied to direct reprogramming using cardiac fibroblasts into cardiomyocytes. Here, we address cardiomyocyte differentiation of CSCs and iPSCs. Furthermore, we describe the potential of CSCs in regenerative biology and regenerative medicine.

Trophic actions of bone marrow-derived mesenchymal stromal cells for muscle repair/regeneration

Bone marrow-derived mesenchymal stromal cells (BM-MSCs) represent the leading candidate cell in tissue engineering and regenerative medicine. These cells can be easily isolated, expanded in vitro and are capable of providing significant functional benefits after implantation in the damaged muscle tissues. Despite their plasticity, the participation of BM-MSCs to new muscle fiber formation is controversial; in fact, emerging evidence indicates that their therapeutic effects occur without signs of long-term tissue engraftment and involve the paracrine secretion of cytokines and growth factors with multiple effects on the injured tissue, including modulation of inflammation and immune reaction, positive extracellular matrix (ECM) remodeling, angiogenesis and protection from apoptosis. Recently, a new role for BM-MSCs in the stimulation of muscle progenitor cells proliferation has been demonstrated, suggesting the potential ability of these cells to influence the fate of local stem cells and augment the endogenous mechanisms of repair/regeneration in the damaged tissues.

Ventricular systolic reserve in asymptomatic children previously treated with low doses of anthracyclines: a longitudinal, prospective exercise echocardiography study

BACKGROUND

The time course of mild cardiotoxicity induced by anthracycline remains unknown. The aim of this study was to evaluate the long-term evolution of decreased myocardial reserve in children previously treated with a cumulative dose of anthracycline up to 100 mg/m(2).

PATIENTS AND METHODS

Twenty-seven asymptomatic cancer survival patients (25 with lymphoblastic leukemia), in continuous remission and off treatment for >12 months with no alterations in conventional echocardiograms were evaluated by exercise echocardiography at 37 ± 15.4 months (T1) and 101 ± 24 months (T2) after finishing treatment (ADRIA group). This group was compared with 25 healthy individuals (control group) similar to the ADRIA group with respect to age and body surface area (BSA). All individuals underwent treadmill exercise testing according to Bruce protocol. Echocardiograms were performed before and immediately after exercise.

RESULTS

The groups were similar regarding cardiac structure and left ventricular (LV) systolic function at rest at T1 and T2. The growth of LV posterior wall thickness related to BSA was lower in the ADRIA group at T2. Post exercise, smaller LV ejection indexes and attenuated changes in the afterload in ADRIA group were observed at T1 and T2.

CONCLUSION

The decreased systolic reserve induced by a low dose of anthracycline in asymptomatic children and adolescents remains unaffected over a 5-year period, suggesting that positive outcomes in chronic cardiotoxicity would be expected in patients with mild impairment after anthracycline treatment.

Ablation of MMP9 induces survival and differentiation of cardiac stem cells into cardiomyocytes in the heart of diabetics: a role of extracellular matrix

The contribution of extracellular matrix (ECM) to stem cell survival and differentiation is unequivocal, and matrix metalloproteinase-9 (MMP9) induces ECM turn over; however, the role of MMP9 in the survival and differentiation of cardiac stem cells is unclear. We hypothesize that ablation of MMP9 enhances the survival and differentiation of cardiac stem cells into cardiomyocytes in diabetics. To test our hypothesis, Ins2(+/-) Akita, C57 BL/6J, and double knock out (DKO: Ins2(+/-)/MMP9(-/-)) mice were used. We created the DKO mice by deleting the MMP9 gene from Ins2(+/-). The above 3 groups of mice were genotyped. The activity and expression of MMP9 in the 3 groups were determined by in-gel gelatin zymography, Western blotting, and confocal microscopy. To determine the role of MMP9 in ECM stiffness (fibrosis), we measured collagen deposition in the histological sections of hearts using Masson's trichrome staining. The role of MMP9 in cardiac stem cell survival and differentiation was determined by co-immunoprecipitation (co-IP) of MMP9 with c-kit (a marker of stem cells) and measuring the level of troponin I (a marker of cardiomyocytes) by confocal microscopy in the 3 groups. Our results revealed that ablation of MMP9 (i) reduces the stiffness of ECM by decreasing collagen accumulation (fibrosis), and (ii) enhances the survival (elevated c-kit level) and differentiation of cardiac stem cells into cardiomyocytes (increased troponin I) in diabetes. We conclude that inhibition of MMP9 ameliorates stem cell survival and their differentiation into cardiomyocytes in diabetes.

Stem cell treatment for acute myocardial infarction

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

This Cochrane review is an update of a previous one (published in 2008). MEDLINE (1950 to January 2011), EMBASE (1974 to January 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 1, 2011), CINAHL (1982 to January 2011) and the Transfusion Evidence Library (1980 to January 2011) were searched. In addition, several international and ongoing trial databases were searched and handsearching of relevant conference proceedings undertaken to January 2011.

SELECTION CRITERIA

RCTs comparing autologous stem/progenitor cells with no autologous stem/progenitor cells in patients diagnosed with AMI were eligible.

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

Thirty-three RCTs (1765 participants) were eligible for inclusion. Stem/progenitor cell treatment was not associated with statistically significant changes in the incidence of mortality (RR 0.70, 95% CI 0.40 to 1.21) or morbidity (the latter measured by re-infarction, hospital re-admission, restenosis and target vessel revascularisation). A considerably high degree of heterogeneity has been observed among the included trials. In short-term follow up, stem cell treatment was observed to improve left ventricular ejection fraction (LVEF) significantly (WMD 2.87, 95% CI 2.00 to 3.73). This improvement in LVEF was maintained over long-term follow up of 12 to 61 months (WMD 3.75, 95% CI 2.57 to 4.93). With certain measurements and at certain times, stem cell treatment was observed to reduce left ventricular end systolic and end diastolic volumes (LVESV & LVEDV) and infarct size significantly in long-term follow up. There was a positive correlation between mononuclear cell dose infused and the effect on LVEF measured by magnetic resonance imaging. A correlation between timing of stem cell treatment and effect on LVEF measured by left ventricular angiography was also observed.

AUTHORS' CONCLUSIONS

Despite the high degree of heterogeneity observed, the results of this systematic review suggest that moderate improvement in global heart function is significant and sustained long-term. However, because mortality rates after successful revascularization of the culprit arteries are very low, larger number of participants would be required to assess the full clinical effect of this treatment. Standardisation of methodology, cell dosing and cell product formulation, timing of cell transplantation and patient selection may also be required in order to reduce the substantial heterogeneity observed among the included studies.

Optimising human mesenchymal stem cell numbers for clinical application: a literature review

Adult mesenchymal stem cells (MSCs) are being investigated further for their use in stem cell therapies. However, as they are found in very low numbers in adult tissue, expansion in vitro is required to produce desired MSC numbers for clinical application. The need for effective cell-based therapies is increasing due to a rise in the ageing population, increasing the prevalence of musculoskeletal disorders. This review investigates how factors, age and gender of donor, as well as seeding density can affect MSC expansion. Age and gender of donor have received mixed results from studies, whereas seeding density studies have produced consistent results for numerous MSC sources, favouring lower seeding densities. Further research is required to reduce the risk of infection, loss of cell characterisation in cell culture, and making cell-based therapies more cost effective through creating rapid expansion of MSCs regardless of patient factors.

The novel DPP-4 inhibitors linagliptin and BI 14361 reduce infarct size after myocardial ischemia/reperfusion in rats

BACKGROUND

Dipeptidylpeptidase-4 inhibition is reported to have beneficial effects on myocardial ischemia. Mechanisms might include a reduced degradation of stromal cell-derived factor-1 alpha with subsequent increased recruitment of circulating stem cells and/or incretin receptor-dependent pathways. This study evaluated the novel xanthine-based dipeptidylpeptidase-4 inhibitors linagliptin (BI 1356) and BI 14361 in cardiac ischemia.

METHODS

Male Wistar rats were pretreated with linagliptin or BI 14361 and subjected to ligation of the left anterior descending coronary artery for 30 min.

RESULTS

Dipeptidylpeptidase-4 inhibition significantly reduced the infarct size after 7 days (-27.7%, p<0.05) and 8 weeks (-18.0%, p<0.05). There was a significantly improved maximum rate of left ventricular pressure decline (dP/dt min) in linagliptin-treated animals 8 weeks after ischemia/reperfusion. Apart from that, treatment did not improve cardiac function as determined by echocardiography and cardiac catheterization. Immunohistological staining revealed an increased number of cells positive for stromal cell-derived factor-1 alpha, CXCR-4 and CD34 within and around the infarcted area of BI 14361-treated animals.

CONCLUSIONS

Linagliptin and BI 14361 are able to reduce infarct size after myocardial ischemia. The immunohistological findings support the hypothesis that dipeptidylpeptidase-4 inhibition via reduced cleavage of stromal cell-derived factor-1 alpha might lead to an enhanced recruitment of CXCR-4+ circulating progenitor cells.

Characterization of rat very small embryonic-like stem cells and cardiac repair after cell transplantation for myocardial infarction

Stem cell therapy is a promising therapeutic strategy for treating myocardial infarction (MI). However, it is necessary to identify ideal adult stem cells for transplantation and explore mechanisms of the transplanted cells in improving cardiac functions after MI. In this study, a population of embryonic-like stem cells (ELSCs) was isolated from rat bone marrow. The cells express pluripotent stem cell transcriptional factors and present high proliferative activity on mouse embryonic fibroblast feeder. ELSCs retain clonal expansion and may form embryoid-like bodies in soft agarose containing leukemia inhibitory factor and basic fibroblast growth factor. The cells of the embryoid-like bodies can differentiate into the cells from 3 germ layers. Under induction, the cells can differentiate into cardiomyocytes and endothelial cells. In MI models of female rats, the transplantation of preinduced ELSCs of male rats reduce scar area and improve cardiac function significantly. Comparing with marrow-derived mesenchymal stem cells and ELSCs without induction, effects of the preinduced ELSCs on myocardial repair and improvement of cardiac function are greater. Survival of the transplanted cells in the peri-infarcted and infarcted regions was examined by fluorescence in situ hybridization. Y chromosome-positive cells may differentiate toward cardiomyocytes and express cTnT and Cx43. Cx43 expression was observed at conjunction of Y chromosome-positive cells and recipient cardiomyocytes. Some Y chromosome-positive cells express CD31 and incorporate into the microvessels in the infarcted tissue. These results suggest that a population of ELSCs resides in rat bone marrow and display similar biological characteristics of ESCs. ELSCs can differentiate into cardiomyocytes and endothelial cells and contribute to cardiomyogenesis and angiogenesis in vivo. Cardiac function after MI may be significantly improved with transplantation of the preinduced ELSCs. Therefore, ELSCs are novel seed cells for stem cell transplantation in regenerative medicine.

Stem cell microenvironments--unveiling the secret of how stem cell fate is defined

Stem cells are defined as unspecialized cells that are capable of long term self-renewal and differentiation into specialized cell types. These unique properties make them an attractive cell source for regenerative medicine applications. Although the functions of various stem cells have been extensively studied in the development of organisms and in diseases, the specific factors and conditions that control stem cell fate, specifically the conditions that allow them to remain unspecialized, are not well studied. It has been suggested that adult stem cell survival and maintenance, as well as proliferation and differentiation, are controlled by the three-dimensional (3D) microenvironment, the so-called niche. Major functional niche components include supporting niche cells, growth-modulating soluble factors stored within the niches, and the extracellular matrix (ECM). In this article, we review work highlighting the growing complexity of stem cell-ECM interactions and their impact on the fields of biomaterials research and regenerative medicine.

Heterogeneity in SDF-1 expression defines the vasculogenic potential of adult cardiac progenitor cells

Rationale

The adult myocardium has been reported to harbor several classes of multipotent progenitor cells (CPCs) with tri-lineage differentiation potential. It is not clear whether c-kit+CPCs represent a uniform precursor population or a more complex mixture of cell types.

Objective

To characterize and understand vasculogenic heterogeneity within c-kit+presumptive cardiac progenitor cell populations.

Methods and Results

c-kit+, sca-1+ CPCs obtained from adult mouse left ventricle expressed stem cell-associated genes, including Oct-4 and Myc, and were self-renewing, pluripotent and clonogenic. Detailed single cell clonal analysis of 17 clones revealed that most (14/17) exhibited trilineage differentiation potential. However, striking morphological differences were observed among clones that were heritable and stable in long-term culture. 3 major groups were identified: round (7/17), flat or spindle-shaped (5/17) and stellate (5/17). Stellate morphology was predictive of vasculogenic differentiation in Matrigel. Genome-wide expression studies and bioinformatic analysis revealed clonally stable, heritable differences in stromal cell-derived factor-1 (SDF-1) expression that correlated strongly with stellate morphology and vasculogenic capacity. Endogenous SDF-1 production contributed directly to vasculogenic differentiation: both shRNA-mediated knockdown of SDF-1 and AMD3100, an antagonist of the SDF-1 receptor CXC chemokine Receptor-4 (CXCR4), reduced tube-forming capacity, while exogenous SDF-1 induced tube formation by 2 non-vasculogenic clones. CPCs producing SDF-1 were able to vascularize Matrigel dermal implants in vivo, while CPCs with low SDF-1 production were not.

Conclusions

Clonogenic c-kit+, sca-1+ CPCs are heterogeneous in morphology, gene expression patterns and differentiation potential. Clone-specific levels of SDF-1 expression both predict and promote development of a vasculogenic phenotype via a previously unreported autocrine mechanism.

Mesenchymal stromal cells for cardiovascular disease

The fields of regenerative medicine and cellular therapy have been the subject of tremendous hype and hope. In particular, the perceived usage of somatic cells like mesenchymal stromal cells (MSCs) has captured the imagination of many. MSCs are a rare population of cells found in multiple regions within the body that can be readily expanded ex vivo and utilized clinically. Originally, it was hypothesized that transplantation of MSCs to sites of injury would lead to de novo tissue-specific differentiation and thereby replace damaged tissue. Now, it is generally agreed that MSC home to sites of injury and direct positive remodeling via the secretion of paracrine factors. Consequently, their clinical utilization has largely revolved around their abilities to promote neovascularization for ischemic disorders and modulate overly exuberant inflammatory responses for autoimmune and alloimmune conditions. One of the major issues surrounding the development of somatic cell therapies like MSCs is that despite evoking a positive response, long-term engraftment and persistence of these cells is rare. Consequently, very large cell doses need be administered for raising production, delivery, and efficacy issues. In this review, we will outline the field of MSC in the context of ischemia and discuss causes for their lack of persistence. In addition, some of the methodologies be used to enhance their therapeutic potential will be highlighted.

Functionalized scaffold-mediated interleukin 10 gene delivery significantly improves survival rates of stem cells in vivo

While stem cell transplantation could potentially treat a variety of disorders, clinical studies have not yet demonstrated conclusive benefits. This may be partly because transplanted stem cells have low survival rates, potentially due to host inflammation. The system described herein used two different gene therapy techniques to improve retention of rat mesenchymal stem cells. In the first, stem cells were transfected with interleukin-10 (IL-10) before being loaded into a collagen scaffold. In the second, unmodified stem cells were loaded into a collagen scaffold along with polymer-complexed IL-10 plasmids. The scaffolds were surgically implanted into the dorsum of syngeneic rats. At each endpoint, the scaffolds were explanted and cell retention, IL-10 level and inflammatory response were quantified. All treatment groups had statistically significant increases in cell retention after 7 days, but the group treated with 2 µg of IL-10 polyplexes had a significant improvement even at 21 days. This cell retention was associated with increased IL-10 and decreased levels of proinflammatory cytokines and apoptosis. The primary effect on the inflammatory response appeared to be on macrophage differentiation, encouraging the regulatory phenotype over the cytotoxic lineage. Improving cell survival may be an important step toward realization of the therapeutic potential of stem cells.

Cardiac progenitor cell commitment is inhibited by nuclear Akt expression

RATIONALE

Stem cell therapies to regenerate damaged cardiac tissue represent a novel approach to treat heart disease. However, the majority of adoptively transferred stem cells delivered to damaged myocardium do not survive long enough to impart protective benefits, resulting in modest functional improvements. Strategies to improve survival and proliferation of stem cells show promise for significantly enhancing cardiac function and regeneration.

OBJECTIVE

To determine whether injected cardiac progenitor cells (CPCs) genetically modified to overexpress nuclear Akt (CPCeA) increase structural and functional benefits to infarcted myocardium relative to control CPCs.

METHODS AND RESULTS

CPCeA exhibit significantly increased proliferation and secretion of paracrine factors compared with CPCs. However, CPCeA exhibit impaired capacity for lineage commitment in vitro. Infarcted hearts receiving intramyocardial injection of CPCeA have increased recruitment of endogenous c-kit cells compared with CPCs, but neither population provides long-term functional and structural improvements compared with saline-injected controls. Pharmacological inhibition of Akt alleviated blockade of lineage commitment in CPCeA.

CONCLUSIONS

Although overexpression of nuclear Akt promotes rapid proliferation and secretion of protective paracrine factors, the inability of CPCeA to undergo lineage commitment hinders their capacity to provide functional or structural benefits to infarcted hearts. Despite enhanced recruitment of endogenous CPCs, lack of functional improvement in CPCeA-treated hearts demonstrates CPC lineage commitment is essential to the regenerative response. Effective stem cell therapies must promote cellular survival and proliferation without inhibiting lineage commitment. Because CPCeA exhibit remarkable proliferative potential, an inducible system mediating nuclear Akt expression could be useful to augment cell therapy approaches.

High-resolution X-ray microtomography for three-dimensional imaging of cardiac progenitor cell homing in infarcted rat hearts

The recent introduction of stem cells in cardiology provides new tools in understanding the regenerative processes of the normal and pathological heart and has opened a search for new therapeutic strategies. Recent published reports have contributed to identifying possible cellular therapy approaches to generate new myocardium, involving transcoronary and intramyocardial injection of progenitor cells. However, one of the limiting factors in the overall interpretation of clinical results obtained by cell therapy is represented by the lack of three-dimensional (3D) high-resolution methods for the visualization of the injected cells and their fate within the myocardium. This work shows that X-ray computed microtomography may offer the unique possibility of detecting, with high definition and resolution and in ex vivo conditions, the 3D spatial distribution of rat cardiac progenitor cells, labelled with iron oxide nanoparticles, inside the infarcted rat heart early after injection. The obtained 3D images represent a very innovative progress as compared to experimental two-dimensional (2D) histological analysis, which requires time-consuming energies for image reconstruction in order to provide the overall distribution of rat clonogenic cells within the heart. Through microtomography, we were able to observe in 3D the presence of these cells within damaged cardiac tissue, with important structural details that are difficult to visualize by conventional bidimensional imaging techniques. This new 3D-imaging approach appears to be an important way to investigate the cellular events involved in cardiac regeneration and represents a promising tool for future clinical applications.

Recapitulation of the embryonic cardiovascular progenitor cell niche

Stem or progenitor cell populations are often established in unique niche microenvironments that regulate cell fate decisions. Although niches have been shown to be critical for the normal development of several tissues, their role in the cardiovascular system is poorly understood. In this study, we characterized the cardiovascular progenitor cell (CPC) niche in developing human and mouse hearts, identifying signaling pathways and extracellular matrix (ECM) proteins that are crucial for CPC maintenance and expansion. We demonstrate that collagen IV (ColIV) and β-catenin-dependent signaling are essential for maintaining and expanding undifferentiated CPCs. Since niches are three-dimensional (3D) structures, we investigated the impact of a 3D microenvironment that mimics the in vivo niche ECM. Employing electrospinning technologies, 3D in vitro niche substrates were bioengineered to serve as culture inserts. The three-dimensionality of these structures increased mouse embryonic stem cell differentiation into CPCs when compared to 2D control cultures, which was further enhanced by incorporation of ColIV into the substrates. Inhibiting p300-dependent β-catenin signals with the small molecule IQ1 facilitated further expansion of CPCs. Our study represents an innovative approach to bioengineer cardiac niches that can serve as unique 3D in vitro systems to facilitate CPC expansion and study CPC biology.

Knockdown of cyclin-dependent kinase inhibitors induces cardiomyocyte re-entry in the cell cycle

Proliferation of mammalian cardiomyocytes stops rapidly after birth and injured hearts do not regenerate adequately. High cyclin-dependent kinase inhibitor (CKI) levels have been observed in cardiomyocytes, but their role in maintaining cardiomyocytes in a post-mitotic state is still unknown. In this report, it was investigated whether CKI knockdown by RNA interference induced cardiomyocyte proliferation. We found that triple transfection with p21(Waf1), p27(Kip1), and p57(Kip2) siRNAs induced both neonatal and adult cardiomyocyte to enter S phase and increased the nuclei/cardiomyocyte ratio; furthermore, a subpopulation of cardiomyocytes progressed beyond karyokynesis, as assessed by the detection of mid-body structures and by straight cardiomyocyte counting. Intriguingly, cardiomyocyte proliferation occurred in the absence of overt DNA damage and aberrant mitotic figures. Finally, CKI knockdown and DNA synthesis reactivation correlated with a dramatic change in adult cardiomyocyte morphology that may be a prerequisite for cell division. In conclusion, CKI expression plays an active role in maintaining cardiomyocyte withdrawal from the cell cycle.

Basement membrane components are key players in specialized extracellular matrices

More than three decades ago, basement membranes (BMs) were described as membrane-like structures capable of isolating a cell from and connecting a cell to its environment. Since this time, it has been revealed that BMs are specialized extracellular matrices (sECMs) with unique components that support important functions including differentiation, proliferation, migration, and chemotaxis of cells during development. The composition of these sECM is as unique as the tissues to which they are localized, opening the possibility that such matrices can fulfill distinct functions. Changes in BM composition play significant roles in facilitating the development of various diseases. Furthermore, tissues have to provide sECM for their stem cells during development and for their adult life. Here, we briefly review the latest research on these unique sECM and their components with a special emphasis on embryonic and adult stem cells and their niches.

Divergent effects of losartan and metoprolol on cardiac remodeling, c-kit+ cells, proliferation and apoptosis in the left ventricle after myocardial infarction

There is strong evidence for the use of angiotensin converting enzyme inhibitors and beta-blockers to reduce morbidity and mortality in patients with myocardial infarction (MI), whereas the effect of angiotensin receptor blockers is less clear. We evaluated the effects of an angiotensin receptor blocker losartan and a beta-blocker metoprolol on left ventricular (LV) remodeling, c-kit+ cells, proliferation, fibrosis, apoptosis, and angiogenesis using a model of coronary ligation in rats. Metoprolol treatment for 2 weeks improved LV systolic function. In contrast, losartan triggered deleterious structural remodeling and functional deterioration of LV systolic function, ejection fraction being 41% and fractional shortening 47% lower in losartan group than in controls 2 weeks after MI. The number of c-kit+ cells as well as expression of Ki-67 was increased by metoprolol. Losartan-induced thinning of the anterior wall and ventricular dilation were associated with increased apoptosis and fibrosis, while losartan had no effect on the expression of c-kit or Ki-67. Metoprolol or losartan had no effect on microvessel density. These results demonstrate that beta-blocker treatment attenuated adverse remodeling via c-kit+ cells and proliferation, whereas angiotensin receptor blocker-induced worsening of LV systolic function was associated with increased apoptosis and fibrosis in the peri-infarct region.

Toward clinical application of stem cells for cardiac regeneration

Heart failure affects more than 10% of the Australian population over age 65, and the ageing population will ensure continued growth of this significant problem. There are various treatment options available, but the growing field of regenerative therapy offers promise to restore or replace tissue lost in those with either congenital or acquired cardiac defects. Stem cells have many potential properties, but they need multiple discussed qualities to succeed in this field such as ease of harvest and multiplication, and most importantly minimal ethical concerns. There are multiple cell types available and one of the challenges will be to find the most appropriate cell type for cardiac regeneration. Cardiac tissue engineering is being explored using both in vitro and in vivo techniques. In vitro methods are primarily limited in terms of the vascularisation and size of the construct. In vivo engineered constructs overcome these limitations in early models, but they are still not ready for human trials. This review aims to provide the reader with an outline of the cell-based and tissue engineering therapies currently being used and developed for cardiac regeneration, as well as some insight into the potential problems that may hamper its progress in the future.

Myogenic differentiation in atrium-derived adult cardiac pluripotent cells and the transcriptional regulation of GATA4 and myogenin on ANP promoter

We established cardiac pluripotent stem-like cells from the left atrium (LA-PCs) of adult rat hearts. These cells could differentiate not only into beating myocytes but also into cells of other lineages, including adipocytes and endothelial cells in the methylcellulose-based medium containing interleukin-3 (IL-3), interleukin-6 (IL-6), and stem cell factor (SCF). In particular, IL-3 and SCF contributed to the differentiation into cardiac troponin I-positive cells. Notably, small population of LA-PCs coexpressed GATA4 and myogenin, which are markers specific to cardiomyocytes and skeletal myocytes, respectively, and could differentiate into both cardiac and skeletal myocytes. Therefore, we investigated the involvement of these two tissue-specific transcription factors in the cardiac transcriptional activity. Coexpression of GATA4 and myogenin synergistically activated GATA4-specific promoter of the atrial natriuretic peptide gene. This combinatorial function was shown to be dependant on the GATA site, but independent of the E-box. The results of chromatin immunoprecipitation and electrophoretic mobility shift assays suggested that myogenin bound to GATA4 on the GATA elements and the C-terminal Zn-finger domain of GATA4 and the N-terminal region of myogenin were required for this synergistic activation of transcription. Taken together, these two transcription factors could be involved in the myogenesis of LA-PCs.