The cardiac stem cell compartment is indispensable for myocardial cell homeostasis, repair and regeneration in the adult

Resveratrol activates endogenous cardiac stem cells and improves myocardial regeneration following acute myocardial infarction

Stem cell antigen-1-positive (Sca-1+) cardiac stem cells (CSCs) therapy for myocardial regeneration following acute myocardial infarction (AMI) is limited by insufficient cell viability and a high rate of apoptosis, due to the poor regional microenvironment. Resveratrol, which is a compound extracted from red wine, has been reported to protect myocardial tissue post‑AMI by increasing the expression of angiogenic and chemotactic factors. The present study aimed to investigate the effects of resveratrol on Sca‑1+ CSCs, and to optimize Sca‑1+ CSCs therapy for myocardial regeneration post‑AMI. C57/BL6 mice (age, 6 weeks) were divided into two groups, which received intragastric administration of PBS or 2.5 mg/kg.d resveratrol. The endogenous expression of Sca‑1+ CSCs in the heart was assessed on day 7. Furthermore, C57/BL6 mice underwent left anterior descending coronary artery ligation for the construction of an AMI model, and received an injection of 1x106 CSCs into the peri‑ischemic area (n=8/group). Mice received intragastric administration of PBS or resveratrol (2.5 mg/kg.d) for 4 weeks after cell transplantation. Echocardiography was used to evaluate cardiac function 4 weeks after cell transplantation. Capillary density and cardiomyocyte apoptosis in the peri‑ischemic myocardium were assessed by cluster of differentiation 31 immunofluorescent staining and terminal deoxynucleotidyl transferase‑mediated dUTP nick end labeling assay, respectively. Western blot analysis was conducted to detect the protein expression levels of vascular endothelial growth factor (VEGF) and stromal cell‑derived factor (SDF)‑1α in the myocardium. Treatment with resveratrol increased the number of endogenous Sca‑1+ CSCs in heart tissue after 7 days (PBS vs. Res, 1.85±0.41/field vs. 3.14±0.26/field, P<0.05). Furthermore, intragastric administration of resveratrol significantly increased left ventricle (LV) function 4 weeks after AMI, as determined by an increase in LV fractional shortening (CSCs vs. Res + CSCs, 28.82±1.58% vs. 31.18±2.02%, P<0.05), reduced LV end‑diastolic diameter (CSCs vs. Res + CSCs, 0.37±0.01 mm vs. 0.35±0.02 mm, P<0.05), and reduced LV end‑systolic diameter (CSCs vs. Res + CSCs, 0.26±0.01 mm vs. 0.23±0.02 mm, P<0.05). These protective effects were predominantly achieved via an increase in capillary density (CSCs vs. Res + CSCs, 281.02±24.08/field vs. 329.75±36.69/field, P<0.05) and a reduction in cardiomyocyte apoptosis (CSCs vs. Res + CSCs, 1.5±0.54/field vs. 0.83±0.40/field, P<0.05) in peri‑ischemic myocardium. Western blot analysis indicated that VEGF and SDF‑1α were upregulated in resveratrol‑treated myocardium after a 7 day treatment or 4 weeks after AMI (7 days VEGF PBS vs. Res, 0.89±0.07 vs. 1.21±0.02, P<0.05; SDF‑1α PBS vs. Res, 0.66±0.04 vs. 1.33±0.04, P<0.05; 4 weeks VEGF CSCs vs. Res + CSCs, 0.54±0.03 vs. 0.93±0.13, P<0.05; SDF‑1α CSCs vs. Res + CSCs, 0.53±0.03 vs. 0.93±0.03, P<0.05). Resveratrol activated endogenous CSCs, increased capillary density and decreased cardiomyocyte apoptosis in the peri‑ischemic myocardium, and augmented the effects of CSCs transplantation. These effects may be caused by the upregulation of VEGF and SDF‑1α.

A New Method to Stabilize C-Kit Expression in Reparative Cardiac Mesenchymal Cells

Cell therapy improves cardiac function. Few cells have been investigated more extensively or consistently shown to be more effective than c-kit sorted cells; however, c-kit expression is easily lost during passage. Here, our primary goal was to develop an improved method to isolate c-kit(pos) cells and maintain c-kit expression after passaging. Cardiac mesenchymal cells (CMCs) from wild-type mice were selected by polystyrene adherence properties. CMCs adhering within the first hours are referred to as rapidly adherent (RA); CMCs adhering subsequently are dubbed slowly adherent (SA). Both RA and SA CMCs were c-kit sorted. SA CMCs maintained significantly higher c-kit expression than RA cells; SA CMCs also had higher expression endothelial markers. We subsequently tested the relative efficacy of SA vs. RA CMCs in the setting of post-infarct adoptive transfer. Two days after coronary occlusion, vehicle, RA CMCs, or SA CMCs were delivered percutaneously with echocardiographic guidance. SA CMCs, but not RA CMCs, significantly improved cardiac function compared to vehicle treatment. Although the mechanism remains to be elucidated, the more pronounced endothelial phenotype of the SA CMCs coupled with the finding of increased vascular density suggest a potential pro-vasculogenic action. This new method of isolating CMCs better preserves c-kit expression during passage. SA CMCs, but not RA CMCs, were effective in reducing cardiac dysfunction. Although c-kit expression was maintained, it is unclear whether maintenance of c-kit expression per se was responsible for improved function, or whether the differential adherence property itself confers a reparative phenotype independently of c-kit.

Secretome from resident cardiac stromal cells stimulates proliferation, cardiomyogenesis and angiogenesis of progenitor cells

In the heart, tissue-derived signals play a central role on recruiting/activating stem cell sources to induce cardiac lineage specification for maintenance of tissue homeostasis and repair. Cardiac resident stromal cells (CRSCs) may play a pivotal role in cardiac repair throughout their secretome. Here, we performed the characterization of CRSCs and their secretome by analyzing the composition of their culture-derived extracellular matrix (ECM) and conditioned medium (CM) and by investigating their potential effect on adipose-derived stem cell (ADSC) and progenitor cell behavior. We confirmed that CRSCs are a heterogeneous cell population whose secretome is composed by proteins related to cellular growth, immune response and cardiovascular development and function. We also observed that CRSC secretome was unable to change the behavior of ADSCs, except for proliferation. Additionally, CM from CRSCs demonstrated the potential to drive proliferation and cardiac differentiation of H9c2 cells and also the ability to induce angiogenesis in vitro. Our data suggest that the CRSCs can be a source of important modulating signals for cardiac progenitor cell recruitment/activation.

In vitro expansion of human cardiac progenitor cells: exploring 'omics tools for characterization of cell-based allogeneic products

Human cardiac stem/progenitor cells (hCPCs) have been shown to be capable to regenerate contractile myocardium. However, because of their relative low abundance in the heart, in vitro expansion of hCPC is mandatory to achieve necessary quantities for allogeneic or autologous cardiac regeneration therapy applications (10(6)-10(9) cells/patient). Up to now, cell number requirements of ongoing phase I/IIa trials have been fulfilled with production in static monolayer cultures. However, this manufacturing process poses critical limitations when moving to the following clinical phases where hundreds of patients will be enrolled. For this, increased process yield is required, while guaranteeing the quality of the cell-based products. In this work, we developed and validated a robust, scalable, and good manufacturing practice (GMP)-compatible bioprocess for the expansion of high-quality hCPC. We applied platforms extensively used by the biopharmaceutical industry, such as microcarrier technology and stirred systems, and assessed culture conditions' impact on hCPC's quality and potency, as required by regulatory agencies. Complementary analytical assays including gene expression microarrays and mass spectrometry-based approaches were explored to compare transcriptome, proteome, surface markers, and secretion profiles of hCPC cultured in static monolayers and in stirred microcarrier-based systems. Our results show that stirred microcarrier-based culture systems enabled achieving more than 3-fold increase in hCPC expansion, when compared with traditional static monolayers, while retaining cell's phenotype and similar "omics" profiles. These findings demonstrate that this change in the production process does not affect cell's identity and quality, with potential to be translated into a transversal production platform for clinical development of stem-cell therapies.

G9a histone methyltransferase inhibitor BIX01294 promotes expansion of adult cardiac progenitor cells without changing their phenotype or differentiation potential

OBJECTIVES

As a follow-up to our previous reports showing that the G9a histone methyltransferase-specific inhibitor BIX01294 enhances bone marrow cell cardiac potential, this drug was examined for its effects on cardiomyocytes and mouse cardiac progenitor cells (CPCs).

MATERIALS AND METHODS

Cardiomyocytes and cardiac explants were cultured ± BIX01294, and examined for changes in cardiac function, protein and gene expression. Additionally, enriched populations of CPCs, contained in the 'phase bright cell' component of explants, were harvested from non-treated and BIX01294-treated cardiac tissue, and assayed for differences in cell phenotype and differentiation potential. Mouse CPCs were cultured with rat cardiomyocytes to allow differentiation of the progenitors to be assayed using species-specific PCR primers.

RESULTS

While BIX01294 had no discernible effect on myocyte function and sarcomeric organization, treatment with this drug significantly increased CPC proliferation, as indicated by enhanced MTT metabolization and BrdUrd incorporation (4.1- and 2.0-fold, respectively, P < 0.001) after 48 h labelling, and increased Ki67 expression (4.8-fold, P < 0.001) after 7 days culture. Heart explants exposed to BIX01294 generated 3.6-fold (P < 0.005) greater yields of CPCs by 2 weeks culture. Importantly, CPCs obtained from non-treated and BIX01294-treated cultures did not differ in phenotype or differentiation potential.

CONCLUSIONS

These data indicate that BIX01294 can expand CPCs without undermining their capacity as cardiac progenitors, and suggest that this drug may have utility for generating large numbers of CPCs for cardiac repair.

Antiarrhythmic effect of growth factor-supplemented cardiac progenitor cells in chronic infarcted heart

c-Kit(pos) cardiac progenitor cells (CPCs) represent a successful approach in healing the infarcted heart and rescuing its mechanical function, but electrophysiological consequences are uncertain. CPC mobilization promoted by hepatocyte growth factor (HGF) and IGF-1 improved electrogenesis in myocardial infarction (MI). We hypothesized that locally delivered CPCs supplemented with HGF + IGF-1 (GFs) can concur in ameliorating electrical stability of the regenerated heart. Adult male Wistar rats (139 rats) with 4-wk-old MI or sham conditions were randomized to receive intramyocardial injection of GFs, CPCs, CPCs + GFs, or vehicle (V). Enhanced green fluorescent protein-tagged CPCs were used for cell tracking. Vulnerability to stress-induced arrhythmia was assessed by telemetry-ECG. Basic cardiac electrophysiological properties were examined by epicardial multiple-lead recording. Hemodynamic function was measured invasively. Hearts were subjected to anatomical, morphometric, immunohistochemical, and molecular biology analyses. Compared with V and at variance with individual CPCs, CPCs + GFs approximately halved arrhythmias in all animals, restoring cardiac anisotropy toward sham values. GFs alone reduced arrhythmias by less than CPCs + GFs, prolonging ventricular refractoriness without affecting conduction velocity. Concomitantly, CPCs + GFs reactivated the expression levels of Connexin-43 and Connexin-40 as well as channel proteins of key depolarizing and repolarizing ion currents differently than sole GFs. Mechanical function and anatomical remodeling were equally improved by all regenerative treatments, thus exhibiting a divergent behavior relative to electrical aspects. Conclusively, we provided evidence of distinctive antiarrhythmic action of locally injected GF-supplemented CPCs, likely attributable to retrieval of Connexin-43, Connexin-40, and Cav1.2 expression, favoring intercellular coupling and spread of excitation in mended heart.

Systems-based technologies in profiling the stem cell molecular framework for cardioregenerative medicine

Over the last decade, advancements in stem cell biology have yielded a variety of sources for stem cell-based cardiovascular investigation. Stem cell behavior, whether to maintain its stable state of pluripotency or to prime toward the cardiovascular lineage is governed by a set of coordinated interactions between epigenetic, transcriptional, and translational mechanisms. The science of incorporating genes (genomics), RNA (transcriptomics), proteins (proteomics), and metabolites (metabolomics) data in a specific biological sample is known as systems biology. Integrating systems biology in progression with stem cell biologics can contribute to our knowledge of mechanisms that underlie pluripotency maintenance and guarantee fidelity of cardiac lineage specification. This review provides a brief summarization of OMICS-based strategies including transcriptomics, proteomics, and metabolomics used to understand stem cell fate and to outline molecular processes involved in heart development. Additionally, current efforts in cardioregeneration based on the "one-size-fits-all" principle limit the potential of individualized therapy in regenerative medicine. Here, we summarize recent studies that introduced systems biology into cardiovascular clinical outcomes analysis, allowing for predictive assessment for disease recurrence and patient-specific therapeutic response.

Cellular and molecular characterization of human cardiac stem cells reveals key features essential for their function and safety

Cell therapy of heart diseases is emerging as one of the most promising known treatments in recent years. Transplantation of cardiac stem cells (CSCs) may be one of the best strategies to cure adult or pediatric heart diseases. As these patient-derived stem cells need to be isolated from small heart biopsies, it is important to select the best isolation method and CSC subpopulation with the best cardiogenic functionality. We employed three different protocols including c-KIT(+) cell sorting, clonogenic expansion, and explants culture to isolate c-KIT(+) cells, clonogenic expansion-derived cells (CEDCs), and cardiosphere-derived cells (CDCs), respectively. Evaluation of isolated CSC characteristics in vitro and after rat myocardial infarction (MI) model transplantation revealed that although c-KIT(+) and CDCs had higher MI regenerative potential, CEDCs had more commitment into cardiomyocytes and needed lower passages that were essential to reach a definite cell count. Furthermore, genome-wide expression analysis showed that subsequent passages caused changes in characteristics of cells, downregulation of cell cycle-related genes, and upregulation of differentiation and carcinogenic genes, which might lead to senescence, commitment, and possible tumorigenicity of the cells. Because of different properties of CSC subpopulations, we suggest that appropriate CSCs subpopulation should be chosen based on their experimental or clinical use.

Self-assembling peptide-based delivery of therapeutics for myocardial infarction

Cardiovascular disease, including myocardial infarction, is the number one cause of death. Current treatments are palliative and slow the progression toward heart failure, but to not regenerate healthy tissue. Self-assembling peptides are biomimietic, readily produced, non-immunogenic and non-cytotoxic. They do not assemble into hydrogels until triggered, allowing them to be injected into the myocardium and providing opportunities for minimally invasive therapies. The ability to tune the mechanical and bioactive properties of self-assembling peptides will continue to make them readily adaptable for mimicking natural microenvironments. To date, a variety of growth factors and signaling moieties have been incorporated into self-assembling peptide hydrogels, enhancing cell behavior and tissue function. Furthermore, the hydrogels serve as delivery vehicles for cells in vivo and platforms for improved cell culture. In addition to a brief review of self-assembling peptides, we will discuss a variety of their approaches for myocardial infarction therapy. Moreover, we will assess approaches taken in other tissue and discuss how these could benefit therapies for myocardial infarction.

Rejuvenating the senescent heart

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the cardiac stem cell field with an emphasis on aging and to suggest some relevant strategies directed toward rejuvenation of the senescent heart.

RECENT FINDINGS

Stem cells were long considered as a fountain of youth and were assumed to be equipped against any form of aging effect. However, it is now clear that stem cells suffer the consequences of aging as well. With the discovery that cardiac stem cells reside in the heart comes the question whether these cells are also impaired upon aging. As cardiac stem cell properties are also altered with age, autologous stem cell-based therapy to treat heart failure will benefit from new improved strategies.

SUMMARY

With the goal to improve stem cell properties that are impaired upon aging, some strategies are highlighted. Genetic modification of adult human cardiac progenitor cells prior to autologous stem cell-based therapy, delivery of the next generation of stem cells such as CardioChimeras and CardioClusters, and improvement of the myocardial environment with rejuvenating factors constitute some of the possibilities and are discussed in more detail in this review.

FDG-PET reveals improved cardiac regeneration and attenuated adverse remodelling following Sitagliptin + G-CSF therapy after acute myocardial infarction

AIMS

Dual therapy comprising G-CSF for mobilization of bone marrow-derived progenitor cells (BMPCs), with simultaneous pharmacological inhibition of dipeptidylpeptidase-IV for enhanced myocardial recruitment of circulating BMPC via the SDF-1α/CXCR4-axis, has been shown to improve survival after acute myocardial infarction (AMI). Using an innovative method to provide non-invasive serial in vivo measurements and information on metabolic processes, we aimed to substantiate the possible effects of this therapeutic concept on cardiac remodelling after AMI using 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography (FDG-PET).

METHODS AND RESULTS

AMI was induced in C57BL/6 mice by performing surgical ligation of the left anterior descending artery in these mice. Animals were then treated with granulocyte-colony stimulating factor + Sitagliptin (GS) or placebo for a duration of 5 days following AMI. From serial PET scans, we verified that the infarct size in GS-treated mice (n = 13) was significantly reduced at Day 30 after AMI when compared with the mice receiving placebo (n = 10). Analyses showed a normalized FDG uptake on Day 6 in GS-treated mice, indicating an attenuation of the cardiac inflammatory response to AMI in treated animals. Furthermore, flow cytometry showed a significant increase in the anti-inflammatory M2-macrophages subpopulation in GS-treated animals. In comparing GS treated with placebo animals, those receiving GS-therapy showed a reduction in myocardial hypertrophy and left ventricular dilatation, which indicates the beneficial effect of GS treatment on cardiac remodelling. Remarkably, flow cytometry and immunohistochemistry showed an increase of myocardial c-kit positive cells in treated mice (n = 12 in both groups).

CONCLUSION

Using the innovative method of micro-PET for non-invasive serial in vivo measurements of metabolic myocardial processes in mice, we were able to provide mechanistic evidence that GS therapy improves cardiac regeneration and reduces adverse remodelling after AMI.

Biomimetic approaches for cell implantation to the restoration of infarcted myocardium

Compelling evidences accumulated over the years have proven stem cells as a promising source for regenerative medicine. However, the inadequacy with the design of delivery modalities has prolonged the research in realizing an ideal cell-based approach for the regeneration of infarcted myocardium. Currently, some modest improvements in cardiac function have been documented in clinical trials with stem cell treatments, although regenerating a fully functional myocardium remains a dream for cardiac surgeons. This review provides an overview on the significance of stem cell therapy, the current attempts to resolve the drawbacks with the cell implantation approach and the various stratagems adopted with electrospun hybrid nanofibers for implementation in myocardial regenerative therapy.

Heart-on-a-chip based on stem cell biology

Heart diseases are one of the main causes of death around the world. The great challenge for scientists is to develop new therapeutic methods for these types of ailments. Stem cells (SCs) therapy could be one of a promising technique used for renewal of cardiac cells and treatment of heart diseases. Conventional in vitro techniques utilized for investigation of heart regeneration do not mimic natural cardiac physiology. Lab-on-a-chip systems may be the solution which could allow the creation of a heart muscle model, enabling the growth of cardiac cells in conditions similar to in vivo conditions. Microsystems can be also used for differentiation of stem cells into heart cells, successfully. It will help better understand of proliferation and regeneration ability of these cells. In this review, we present Heart-on-a-chip systems based on cardiac cell culture and stem cell biology. This review begins with the description of the physiological environment and the functions of the heart. Next, we shortly described conventional techniques of stem cells differentiation into the cardiac cells. This review is mostly focused on describing Lab-on-a-chip systems for cardiac tissue engineering. Therefore, in the next part of this article, the microsystems for both cardiac cell culture and SCs differentiation into cardiac cells are described. The section about SCs differentiation into the heart cells is divided in sections describing biochemical, physical and mechanical stimulations. Finally, we outline present challenges and future research concerning Heart-on-a-chip based on stem cell biology.

Contemporary perspective on endogenous myocardial regeneration

Considering the complex nature of the adult heart, it is no wonder that innate regenerative processes, while maintaining adequate cardiac function, fall short in myocardial jeopardy. In spite of these enchaining limitations, cardiac rejuvenation occurs as well as restricted regeneration. In this review, the background as well as potential mechanisms of endogenous myocardial regeneration are summarized. We present and analyze the available evidence in three subsequent steps. First, we examine the experimental research data that provide insights into the mechanisms and origins of the replicating cardiac myocytes, including cell populations referred to as cardiac progenitor cells (i.e., c-kit+ cells). Second, we describe the role of clinical settings such as acute or chronic myocardial ischemia, as initiators of pathways of endogenous myocardial regeneration. Third, the hitherto conducted clinical studies that examined different approaches of initiating endogenous myocardial regeneration in failing human hearts are analyzed. In conclusion, we present the evidence in support of the notion that regaining cardiac function beyond cellular replacement of dysfunctional myocardium via initiation of innate regenerative pathways could create a new perspective and a paradigm change in heart failure therapeutics. Reinitiating cardiac morphogenesis by reintroducing developmental pathways in the adult failing heart might provide a feasible way of tissue regeneration. Based on our hypothesis “embryonic recall”, we present first supporting evidence on regenerative impulses in the myocardium, as induced by developmental processes.

Inhibition of G9a Histone Methyltransferase Converts Bone Marrow Mesenchymal Stem Cells to Cardiac Competent Progenitors

The G9a histone methyltransferase inhibitor BIX01294 was examined for its ability to expand the cardiac capacity of bone marrow cells. Inhibition of G9a histone methyltransferase by gene specific knockdown or BIX01294 treatment was sufficient to induce expression of precardiac markers Mesp1 and brachyury in bone marrow cells. BIX01294 treatment also allowed bone marrow mesenchymal stem cells (MSCs) to express the cardiac transcription factors Nkx2.5, GATA4, and myocardin when subsequently exposed to the cardiogenic stimulating factor Wnt11. Incubation of BIX01294-treated MSCs with cardiac conditioned media provoked formation of phase bright cells that exhibited a morphology and molecular profile resembling similar cells that normally form from cultured atrial tissue. Subsequent aggregation and differentiation of BIX01294-induced, MSC-derived phase bright cells provoked their cardiomyogenesis. This latter outcome was indicated by their widespread expression of the primary sarcomeric proteins muscle α-actinin and titin. MSC-derived cultures that were not initially treated with BIX01294 exhibited neither a commensurate burst of phase bright cells nor stimulation of sarcomeric protein expression. Collectively, these data indicate that BIX01294 has utility as a pharmacological agent that could enhance the ability of an abundant and accessible stem cell population to regenerate new myocytes for cardiac repair.

Cardiac tissue engineering and regeneration using cell-based therapy

Stem cell therapy and tissue engineering represent a forefront of current research in the treatment of heart disease. With these technologies, advancements are being made into therapies for acute ischemic myocardial injury and chronic, otherwise nonreversible, myocardial failure. The current clinical management of cardiac ischemia deals with reestablishing perfusion to the heart but not dealing with the irreversible damage caused by the occlusion or stenosis of the supplying vessels. The applications of these new technologies are not yet fully established as part of the management of cardiac diseases but will become so in the near future. The discussion presented here reviews some of the pioneering works at this new frontier. Key results of allogeneic and autologous stem cell trials are presented, including the use of embryonic, bone marrow-derived, adipose-derived, and resident cardiac stem cells.

“Second-generation” stem cells for cardiac repair

Over the last years, stem cell therapy has emerged as an inspiring alternative to restore cardiac function after myocardial infarction. A large body of evidence has been obtained in this field but there is no conclusive data on the efficacy of these treatments. Preclinical studies and early reports in humans have been encouraging and have fostered a rapid clinical translation, but positive results have not been uniformly observed and when present, they have been modest. Several types of stem cells, manufacturing methods and delivery routes have been tested in different clinical settings but direct comparison between them is challenging and hinders further research. Despite enormous achievements, major barriers have been found and many fundamental issues remain to be resolved. A better knowledge of the molecular mechanisms implicated in cardiac development and myocardial regeneration is critically needed to overcome some of these hurdles. Genetic and pharmacological priming together with the discovery of new sources of cells have led to a “second generation” of cell products that holds an encouraging promise in cardiovascular regenerative medicine. In this report, we review recent advances in this field focusing on the new types of stem cells that are currently being tested in human beings and on the novel strategies employed to boost cell performance in order to improve cardiac function and outcomes after myocardial infarction.

The Role of MicroRNAs in Cardiac Stem Cells

Stem cells are considered as the next generation drug treatment in patients with cardiovascular disease who are resistant to conventional treatment. Among several stem cells used in the clinical setting, cardiac stem cells (CSCs) which reside in the myocardium and epicardium of the heart have been shown to be an effective option for the source of stem cells. In normal circumstances, CSCs primarily function as a cell store to replace the physiologically depleted cardiovascular cells, while under the diseased condition they have been shown to experimentally regenerate the diseased myocardium. In spite of their major functional role, molecular mechanisms regulating the CSCs proliferation and differentiation are still unknown. MicroRNAs (miRs) are small, noncoding RNA molecules that regulate gene expression at the posttranscriptional level. Recent studies have demonstrated the important role of miRs in regulating stem cell proliferation and differentiation, as well as other physiological and pathological processes related to stem cell function. This review summarises the current understanding of the role of miRs in CSCs. A deeper understanding of the mechanisms by which miRs regulate CSCs may lead to advances in the mode of stem cell therapies for the treatment of cardiovascular diseases.

VEGF-A promotes cardiac stem cell engraftment and myocardial repair in the infarcted heart

BACKGROUND

The objective of this study was to determine whether vascular endothelial growth factor (VEGF)-A subtypes improve cardiac stem cell (CSC) engraftment and promote CSC-mediated myocardial repair in the infarcted heart.

METHODS

CSCs were treated with VEGF receptor (VEGFR) inhibitors, VCAM-1 antibody (VCAM-1-Ab), or PKC-α inhibitor followed by the treatment with VEGF-A. CSC adhesion assays were performed in vitro. In vivo, the PKH26-labeled and VCAM-1-Ab or PKC-α inhibitor pre-treated CSCs were treated with VEGF-A followed by implantation into infarcted rat hearts. The hearts were then collected for measuring CSC engraftment and evaluating cardiac fibrosis and function 3 or 28days after the CSC transplantation.

RESULTS

All three VEGF-A subtypes promoted CSC adhesion to extracellular matrix and endothelial cells. VEGF-A-mediated CSC adhesion required VEGFR and PKCα signaling. Importantly, VEGF-A induced VCAM-1, but not ICAM-1 expression in CSCs through PKCα signaling. In vivo, VEGF-A promoted the engraftment of CSCs in infarcted hearts, which was attenuated by PKCα inhibitor or VCAM-1-Ab. Moreover, VEGF-A-mediated CSC engraftment resulted in a reduction in infarct size and fibrosis. Functional studies showed that the transplantation of the VEGF-A-treated CSCs stimulated extensive angiomyogenesis in infarcted hearts as indicated by the expression of cardiac troponin T and von Willebrand factor, leading to an improved performance of left ventricle. Blockade of PKCα signaling or VCAM-1 significantly diminished the beneficial effects of CSCs treated with VEGF-A.

CONCLUSION

VEGF-A promotes myocardial repair through, at least in part, enhancing the engraftment of CSCs mediated by PKCα/VCAM-1 pathway.

Cardiac stem cells: translation to human studies

The discovery of multiple classes of cardiac progenitor cells in the adult mammalian heart has generated hope for their use as a therapeutic in heart failure. However, successful results from animal models have not always yielded similar findings in human studies. Recent Phase I/II trials of c-Kit (SCIPIO) and cardiosphere-based (CADUCEUS) cardiac progenitor cells have demonstrated safety and some therapeutic efficacy. Gaps remain in our understanding of the origins, function and relationships between the different progenitor cell families, many of which are heterogeneous populations with overlapping definitions. Another challenge lies in the limitations of small animal models in replicating the human heart. Cryopreserved human cardiac tissue provides a readily available source of cardiac progenitor cells and may help address these questions. We review important findings and relative unknowns of the main classes of cardiac progenitor cells, highlighting differences between animal and human studies.

Bone marrow-derived mesenchymal cell differentiation toward myogenic lineages: facts and perspectives

Bone marrow-derived mesenchymal stem cells (BM-MSCs) are valuable platforms for new therapies based on regenerative medicine. BM-MSCs era is coming of age since the potential of these cells is increasingly demonstrated. In fact, these cells give origin to osteoblasts, chondroblasts, and adipocyte precursors in vitro, and they can also differentiate versus other mesodermal cell types like skeletal muscle precursors and cardiomyocytes. In our short review, we focus on the more recent manipulations of BM-MSCs toward skeletal and heart muscle differentiation, a growing field of obvious relevance considering the toll of muscle disease (i.e., muscular dystrophies), the heavier toll of heart disease in developed countries, and the still not completely understood mechanisms of muscle differentiation and repair.