Cardiac-derived Progenitor Cells Research Articles

The multi-lineage transcription factor ISL1 controls cardiomyocyte cell fate through interaction with NKX2.5

Congenital heart disease often arises from perturbations of transcription factors (TFs) that guide cardiac development. ISLET1 (ISL1) is a TF that influences early cardiac cell fate, as well as differentiation of other cell types including motor neuron progenitors (MNPs) and pancreatic islet cells. While lineage specificity of ISL1 function is likely achieved through combinatorial interactions, its essential cardiac interacting partners are unknown. By assaying ISL1 genomic occupancy in human induced pluripotent stem cell-derived cardiac progenitors (CPs) or MNPs and leveraging the deep learning approach BPNet, we identified motifs of other TFs that predicted ISL1 occupancy in each lineage, with NKX2.5 and GATA motifs being most closely associated to ISL1 in CPs. Experimentally, nearly two-thirds of ISL1-bound loci were co-occupied by NKX2.5 and/or GATA4. Removal of NKX2.5 from CPs led to widespread ISL1 redistribution, and overexpression of NKX2.5 in MNPs led to ISL1 occupancy of CP-specific loci. These results reveal how ISL1 guides lineage choices through a combinatorial code that dictates genomic occupancy and transcription.

Characterization of decellularized left and right ventricular myocardial matrix hydrogels and their effects on cardiac progenitor cells

Congenital heart defects are the leading cause of right heart failure in pediatric patients. Implantation of c-kit+ cardiac-derived progenitor cells (CPCs) is being clinically evaluated to treat the failing right ventricle (RV), but faces limitations due to reduced transplant cell survival, low engraftment rates, and low retention. These limitations have been exacerbated due to the nature of cell delivery (narrow needles) and the non-optimal recipient microenvironment (reactive oxygen species (ROS)). Extracellular matrix (ECM) hydrogels derived from porcine left ventricular (LV) myocardium have emerged as a potential therapy to treat the ischemic LV and have shown promise as a vehicle to deliver cells to injured myocardium. However, no studies have evaluated the combination of an injectable biomaterial, such as an ECM hydrogel, in combination with cell therapy for treating RV failure. In this study we characterized LV and RV myocardial matrix (MM) hydrogels and performed in vitro evaluations of their potential to enhance CPC delivery, including resistance to forces experienced during injection and exposure to ROS, as well as their potential to enhance angiogenic paracrine signaling. While physical properties of the two hydrogels are similar, the decellularized LV and RV have distinct protein signatures. Both materials were equally effective in protecting CPCs against needle forces and ROS. CPCs encapsulated in either the LV MM or RV MM exhibited similar enhanced potential for angiogenic paracrine signaling when compared to CPCs in collagen. The RV MM without cells, however, likewise improved tube formation, suggesting it should also be evaluated as a potential standalone treatment.

Autologous Cardiac Stem Cell Injection in Patients with Hypoplastic Left Heart Syndrome (CHILD Study).

Mortality in infants with hypoplastic left heart syndrome (HLHS) is strongly correlated with right ventricle (RV) dysfunction. Cell therapy has demonstrated potential improvements of RV dysfunction in animal models related to HLHS, and neonatal human derived c-kit+ cardiac-derived progenitor cells (CPCs) show superior efficacy when compared to adult human cardiac-derived CPCs (aCPCs). Neonatal CPCs (nCPCs) have yet to be investigated in humans. The CHILD trial (Autologous Cardiac Stem Cell Injection in Patients with Hypoplastic Left Heart Syndrome) is a Phase I/II trial aimed at investigating intramyocardial administration of autologous nCPCs in HLHS infants by assessing the feasibility, safety, and potential efficacy of CPC therapy. Using an open-label, multicenter design, CHILD investigates nCPC safety and feasibility in the first enrollment group (Group A/Phase I). In the second enrollment group, CHILD uses a randomized, double-blinded, multicenter design (Group B/Phase II), to assess nCPC efficacy based on RV functional and structural characteristics. The study plans to enroll 32 patients across 4 institutions: Group A will enroll 10 patients, and Group B will enroll 22 patients. CHILD will provide important insights into the therapeutic potential of nCPCs in patients with HLHS.Clinical Trial Registration https://clinicaltrials.gov/ct2/home NCT03406884, First posted January 23, 2018.

Comparative computational RNA analysis of cardiac-derived progenitor cells and their extracellular vesicles

Stem/progenitor cells, including cardiac-derived c-kit+ progenitor cells (CPCs), are under clinical evaluation for treatment of cardiac disease. Therapeutic efficacy of cardiac cell therapy can be attributed to paracrine signaling and the release of extracellular vesicles (EVs) carrying diverse cargo molecules. Despite some successes and demonstrated safety, large variation in cell populations and preclinical/clinical outcomes remains a problem. Here, we investigated this variability by sequencing coding and non-coding RNAs of CPCs and CPC-EVs from 30 congenital heart disease patients and used machine learning methods to determine potential mechanistic insights. CPCs retained RNAs related to extracellular matrix organization and exported RNAs related to various signaling pathways to CPC-EVs. CPC-EVs are enriched in miRNA clusters related to cell proliferation and angiogenesis. With network analyses, we identified differences in non-coding RNAs which give insight into age-dependent functionality of CPCs. By taking a quantitative computational approach, we aimed to uncover sources of CPC cell therapy variability.

Isolation and phenotyping of cardiac-derived progenitor cells from neonatal mice

Dysfunctions of resident progenitor cells play a significant role in the pathogenesis of decreased myocardial contractility in heart failure, so the most promising approaches for the treatment of heart disease are cardiac-derived stem/progenitor cells (CSCs). Materials and methods. Protocols for progenitor cell cultures from different parts of the heart of newborn FVB/N mice have been developed and their proliferative potential has been characterized. Comparative analysis of the expression of CD31, CD34, CD44, CD45, CD73, CD90, CD105, CD117, CD309 and troponin I by cells from native myocardial biopsies and in the obtained cultures was performed by flow cytometric immunophenotyping. Results. The expression of mesenchymal markers CD44 and CD90 in the absence of the hematopoietic marker CD45 was demonstrated in early passages in mouse myocardial progenitor cell cultures. Relatively high expression of CD34 and CD31 was found. The presence of a minor population of CD44+117+ cells which correspond to the phenotype of cardiac progenitor cells, was detected. Expression of troponin I as one of the key markers of cardiomyocytes as well as the vascular endothelial growth factor receptor has been confirmed in terminally differentiated cultures of cells with contractile activity. Conclusions. It was found that newborn mice in the myocardial tissue contain more cells with the expression of markers of cardiac progenitors than in adult animals. The relative content of such cells is higher in the atria than in the ventricles. Cardiac progenitor cells in neonatal mice derived from the atrial appendages have better proliferative potential than cell cultures isolated from the ventricles.

MicroRNAs and exosomes: Cardiac stem cells in heart diseases

Treating cardiovascular diseases with cardiac stem cells (CSCs) is a valid treatment among various stem cell-based therapies. With supplying the physiological need for cardiovascular cells as their main function, under pathological circumstances, CSCs can also reproduce the myocardial cells. Although studies have identified many of CSCs’ functions, our knowledge of molecular pathways that regulate these functions is not complete enough. Either physiological or pathological studies have shown, stem cells proliferation and differentiation could be regulated by microRNAs (miRNAs). How miRNAs regulate CSC behavior is an interesting area of research that can help us study and control the function of these cells in vitro; an achievement that may be beneficial for patients with cardiovascular diseases. The secretome of stem and progenitor cells has been studied and it has been determined that exosomes are the main source of their secretion which are very small vesicles at the nanoscale and originate from endosomes, which are secreted into the extracellular space and act as key signaling organelles in intercellular communication. Mesenchymal stem cells, cardiac-derived progenitor cells, embryonic stem cells, induced pluripotent stem cells (iPSCs), and iPSC-derived cardiomyocytes release exosomes that have been shown to have cardioprotective, immunomodulatory, and reparative effects. Herein, we summarize the regulation roles of miRNAs and exosomes in cardiac stem cells.

Characterization of βARKct engineered cellular extracellular vesicles and model specific cardioprotection.

Recent data supporting any benefit of stem cell therapy for ischemic heart disease have suggested paracrine-based mechanisms via extracellular vesicles (EVs) including exosomes. We have previously engineered cardiac-derived progenitor cells (CDCs) to express a peptide inhibitor, βARKct, of G protein-coupled receptor kinase 2, leading to improvements in cell proliferation, survival, and metabolism. In this study, we tested whether βARKct-CDC EVs would be efficacious when applied to stressed myocytes in vitro and in vivo. When isolated EVs from βARKct-CDCs and control GFP-CDCs were added to cardiomyocytes in culture, they both protected against hypoxia-induced apoptosis. We tested whether these EVs could protect the mouse heart in vivo, following exposure either to myocardial infarction (MI) or acute catecholamine toxicity. Both types of EVs significantly protected against ischemic injury and improved cardiac function after MI compared with mice treated with EVs from mouse embryonic fibroblasts; however, βARKct EVs treated mice did display some unique beneficial properties including significantly altered pro- and anti-inflammatory cytokines. Importantly, in a catecholamine toxicity model of heart failure (HF), myocardial injections of βARKct-containing EVs were superior at preventing HF compared with control EVs, and this catecholamine toxicity protection was recapitulated in vitro. Therefore, introduction of the βARKct into cellular EVs can have improved reparative properties in the heart especially against catecholamine damage, which is significant as sympathetic nervous system activity is increased in HF.NEW & NOTEWORTHY βARKct, the peptide inhibitor of GRK2, improves survival and metabolic functions of cardiac-derived progenitor cells. As any benefit of stem cells in the ischemic and injured heart suggests paracrine mechanisms via secreted EVs, we investigated whether CDC-βARKct engineered EVs would show any benefit over control CDC-EVs. Compared with control EVs, βARKct-containing EVs displayed some unique beneficial properties that may be due to altered pro- and anti-inflammatory cytokines within the vesicles.

Exosomes: Beyond stem cells for cardiac protection and repair.

The adult human heart has limited regenerative capacity; hence, stem cell therapy has been investigated as a potential approach for cardiac repair. However, a large part of the benefit of the injection of stem and progenitor cells into injured hearts is mediated by secreted factors. Exosomes-nano-sized secreted extracellular vesicles of endosomal origin-have emerged as key signaling organelles in intercellular communication, and are now viewed as the key regenerative constituent of the secretome of stem and progenitor cells. Exosomes released from mesenchymal stem cells, cardiac-derived progenitor cells, embryonic stem cells, induced pluripotent stem cells (iPSCs), and iPSC-derived cardiomyocytes exhibit cardioprotective, immunomodulatory, and reparative abilities. This concise review discusses the therapeutic benefit of exosomes secreted by stem and progenitor cells in preclinical models of ischemic heart disease.

P2586Cardiac progenitor cell exosome-associated periostin triggers reentry of cardiomyocytes into cell cycle

Abstract Introduction Nanovesicles known as exosomes (Exo) from cardiac-derived progenitor cells (CPCs) are cardioprotective and improve cardiac function after myocardial infarction; however the mechanisms of benefit are incompletely understood, especially with respect to endogenous cardiomyocytes (CM) renewal. Periostin (POSTN), a secreted extracellular matrix protein, is emerging as a matricellular factor that can trigger CM proliferation. We have identified POSTN as a protein secreted by CPC and enriched in their exosomal fraction. Purpose We sought to determine whether Exo-CPC can induce proliferation of CM and to explore the role of exosomal POSTN in inducing reentry of CM into the cell cycle. Methods Exo were isolated from CPC condioned medium by density gradient ultracentrifugation. Fractions were analyzed by Western blotting for the presence of POSTN as well as specific Exo markers (TSG101, CD9). POSTN-depleted Exo (ExoCPC_SiPOSTN) were obtained by transfecting CPC with specific siRNA. Active DNA synthesis was assessed on primary cell culture of rat neonatal CM by EdU incorporation. H9C2 cardiomyocytic cells were used to assess by real-time RT-PCR the expression of downstream genes Hippo/Yes-associated protein (YAP) signaling pathway. Results Western blotting analysis allowed to specifically determining the presence of Exo markers and POSTN in the different fractions of secreted vesicles. Smaller fractions (f1-f3) have the highest amount of TSG101 and CD9 as well as POSTN, thus suggesting that CPC secrete POSTN associated with Exo. The silencing of POSTN in cells resulted in a 60% reduction of Exo-associated POSTN compared to naïve ExoCPC. ExoCPC but not ExoCPC_SiPOSTN, were able to increase phosporylation of AKT and ERK in H9C2 cells. YAP phosporylation and its degradation was decreased resulting in the activation of the downstream gene AurBKinase. By real-time PCR, AurBKinase expression was increased by 2.6 folds with ExoCPC and 1.5 folds with ExoCPC_SiPOSTN compared to cells not exposed to Exo. ExoCPC were able to increase 1.5 fold EdU incorporation in cardiac troponin-positive primary rat CM. ExoCPC_SiPSTN did not affect proliferation. Schematic figure Conclusion These results suggest that POSTN may promote cardiomyocyte proliferation through the direct activation of the AKT/ERK/Hippo-Yap pathway. Exosomes released by CPC are an important source of POSTN and may have a potential for promoting cardiac regeneration. Acknowledgement/Funding This work has been supported by The Swiss National Science Foundation under grant n° 310030_169194

Dose-dependent improvement of cardiac function in a swine model of acute myocardial infarction after intracoronary administration of allogeneic heart-derived cells

BackgroundAllogeneic cardiac-derived progenitor cells (CPC) without immunosuppression could provide an effective ancillary therapy to improve cardiac function in reperfused myocardial infarction. We set out to perform a comprehensive preclinical feasibility and safety evaluation of porcine CPC (pCPC) in the infarcted porcine model, analyzing biodistribution and mid-term efficacy, as well as safety in healthy non-infarcted swine.MethodsThe expression profile of several pCPC isolates was compared with humans using both FACS and RT-qPCR. ELISA was used to compare the functional secretome. One week after infarction, female swine received an intracoronary (IC) infusion of vehicle (CON), 25 × 106 pCPC (25 M), or 50 × 106 pCPC (50 M). Animals were followed up for 10 weeks using serial cardiac magnetic resonance imaging to assess functional and structural remodeling (left ventricular ejection fraction (LVEF), systolic and diastolic volumes, and myocardial salvage index). Statistical comparisons were performed using Kruskal-Wallis and Mann-Whitney U tests. Biodistribution analysis of 18F-FDG-labeled pCPC was also performed 4 h after infarction in a different subset of animals.ResultsPhenotypic and functional characterization of pCPC revealed a gene expression profile comparable to their human counterparts as well as preliminary functional equivalence. Left ventricular functional and structural remodeling showed significantly increased LVEF 10 weeks after IC administration of 50 M pCPC, associated to the recovery of left ventricular volumes that returned to pre-infarction values (LVEF at 10 weeks was 42.1 ± 10.0% in CON, 46.5 ± 7.4% in 25 M, and 50.2 ± 4.9% in 50 M, p < 0.05). Infarct remodeling was also improved following pCPC infusion with a significantly higher myocardial salvage index in both treated groups (0.35 ± 0.20 in CON; 0.61 ± 0.20, p = 0.04, in 25 M; and 0.63 ± 0.17, p = 0.01, in 50 M). Biodistribution studies demonstrated cardiac tropism 4 h after IC administration, with substantial myocardial retention of pCPC-associated tracer activity (18% of labeled cells in the heart), and no obstruction of coronary flow, indicating their suitability as a cell therapy product.ConclusionsIC administration of allogeneic pCPC at 1 week after acute myocardial infarction is feasible, safe, and associated with marked structural and functional benefit. The robust cardiac tropism of pCPC and the paracrine effects on left ventricle post-infarction remodeling established the preclinical bases for the CAREMI clinical trial (NCT02439398).

Beneficial effects of exosomes secreted by cardiac-derived progenitor cells and other cell types in myocardial ischemia.

When injected into acutely infarcted rodent or pig hearts, naturally secreted nanovesicles known as exosomes from cardiac-derived progenitor cells (CPCs) reduce scar size and improve cardiac function. In this regard, exosomes fully mimic the benefits of injecting their parent cells. This recognition paves the way to the development of exosome-based, cell-free treatments for heart disease that could possibly supplant cell-based therapies. Mechanisms of benefit of these vesicles are incompletely understood but cytoprotection, stimulation of angiogenesis, induction of antifibrotic cardiac fibroblasts, and modulation of M1/M2 polarization of macrophages infiltrating the infarcted region can all play important roles. Accordingly, the beneficial molecules carried by CPC-secreted exosomes have been identified only in part but cytoprotective and proangiogenic microRNAs (miRNA) and proteins have been described. Besides CPC-secreted exosomes, vesicles released from other cell types including mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and induced pluripotent stem cells (iSPCs) have also been associated with cardioprotection. This review aims to discuss recent advances in our understanding of the role of secreted vesicles in cardiac repair, with a focus on CPC-derived exosomes.

In this Issue

HomeCirculation ResearchVol. 121, No. 11In this Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn this Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published10 Nov 2017https://doi.org/10.1161/RES.0000000000000186Circulation Research. 2017;121:1205P2Y2R Prompts Cardiac Progenitor Cell Activation (p 1224)Khalafalla et al rejuvenate cardiac progenitor cells via nucleotide receptor signaling.Download figureDownload PowerPointThe use of autologous cardiac progenitor cells (CPCs) for repairing failing hearts has shown promising results in animal models, but trials in patients with heart failure have provided modest, if any, clinical benefits. One reason for the limited efficacy of CPCs may be that CPCs from patients carry genetic predispositions for heart failure, or have reduced regenerative capacity because of patient’s age or other characteristics. Boosting the potency of autologous CPCs may, therefore, improve their clinical performance. Regeneration in a variety of tissues has been shown to be promoted by the nucleotide receptor P2Y2R, which is activated by extracellular UTP. Now, Khalafalla and colleagues have discovered that P2Y2R is more abundantly expressed in healthy, fast-growing human CPCs than in slow-growing, more senescent cells. Furthermore, UTP treatment of human CPCs increased their regenerative potency (proliferation and migration rates) as did overexpression of P2Y2R. Knockdown of the receptor had the opposite effect. The team went on to show that CPC activation via UTP and P2Y2R was dependent on the downstream signaling factor YAP (Yes-associated protein). Together, these results indicate that rejuvenating CPCs by activating the UTP–P2Y2R–YAP pathway may improve outcomes of CPC therapy.CBSCs Preserve Structure and Function After MI (p 1263)Sharp et al bring cortical bone stem cell therapy one step closer to the clinic.Download figureDownload PowerPointA variety of cell types have been tested in animals and patients for their potential to promote the regeneration of injured and failing hearts. Mesenchymal stem cells (MSCs) and cardiac-derived progenitor cells (CDCs), for example, are among the most commonly tested cells, but while these cells have given encouraging results in animals, clinical benefits in patients remain uncertain. Stem cells derived from the cortical region—the dense outer layer— of bone (CBSCs) have recently been shown to be more effective than CDCs at improving heart function and reducing scar size after myocardial infarction in mice. Now, Sharp and colleagues have tested these cells in a larger animal model, more comparable to human patients. After undergoing induced myocardial infarctions, a group of pigs was given transendocardial injections of allogenic CBSCs, while another group was given control injections. After 3 months, the hearts of the CBSC-treated pigs exhibited smaller infarct scars, less ventricular dilation, and better preservation of function than control pigs. Although the study did not compare CBSCs to other types of stem cells, the results warrant further investigations of CBSCs as a potential cell therapy option.Cell Dosing in Ischemic Cardiomyopathy (p 1279)Stem cell dose is critical to cell therapy outcomes, say Florea et al.Download figureDownload PowerPointMany preclinical studies and clinical trials of cell therapies for heart disease have focused on identifying the best cell type to use, but few have focused on determining the optimal dose. Even the studies that have investigated cell dosage have given complicated and seemingly contradictory results. Given the importance of resolving questions of dosage, Florea and colleagues tested the safety and efficacy of 2 different doses of human allogenic mesenchymal stem cells (hMSCs) in 30 patients with chronic ischemic left ventricle dysfunction following myocardial infarction. Fifteen of the patients were given transendocardial injections of 20-million hMSCs, while the other 15 were dosed with 100-million cells. All patients were then followed for 12 months during which time none experienced serious adverse events. While the size of the infarct scars and the presence of systemic inflammation was shown to decrease similarly in both treatment groups, only patients in the 100-million cell group experienced improvements in left ventricle function. The results show that cell dosage is an important determinant of the clinical outcome of cell therapies and highlight the need for further trials aimed at evaluating optimal dosage. Previous Back to top Next FiguresReferencesRelatedDetails November 10, 2017Vol 121, Issue 11 Advertisement Article InformationMetrics © 2017 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000186 Originally publishedNovember 10, 2017 PDF download Advertisement

Abstract 353: P2Y 2 Nucleotide Receptor Overexpression: Letting Blind Cardiac Progenitor Cells ‘See’ Again

Heart failure (HF) is a leading cause of death in the US due to limited capability of adult mammalian heart to regenerate after myocardial infarction (MI). Autologous stem cell therapy holds promise for promoting regeneration of injured heart but stem cells derived from diseased organs exhibit poor proliferative, migratory and survival capabilities. Empowering cardiac-derived progenitor cells (CPC) with prosurvival genes has been attempted. However, molecular mechanisms by which stem cells detect stress signals to subsequently initiate appropriate regenerative responses are poorly understood. In this regard, purinergic receptors represent a major detector for extracellular nucleotides released during injury/stress and serve as an intracellular platform harboring numerous signaling pathways that regulate proinflammatory and regenerative responses required for the healing process. Despite the established roles of purinergic signaling in cardiovascular diseases, it has not been well-defined in CPCs. This study shows, for the first time, that the majority of P2 purinergic receptors are expressed and exhibit functional responses to ATP and UTP in human CPCs (hCPC) isolated from HF patients. The G protein-coupled P2Y 2 R is a pivotal stress detector that senses ATP and UTP accumulated in extracellular space after injury and mediates regenerative responses in various injury models, including MI model, and in stem cells from diverse origins. Interestingly, hCPCs with relatively slower growth kinetics and enhanced senescence show dramatic decreases in P2Y 2 receptor (P2Y 2 R) expression compared to fast-growing hCPCs, consistent with our hypothesis that overexpressing P2Y 2 R enables diseased hCPCs to better detect stress stimuli and react with the proper regenerative responses. Along this line, P2Y 2 R stimulation with UTP enhances hCPC proliferation and migration. Interestingly, preliminary results demonstrate that UTP treatment induces YAP activation and nuclear shuttling. Moreover, inhibition of YAP/TEAD interaction impairs UTP-induced proliferation and migration revealing a novel link between extracellular nucleotides released during cardiac ischemia and Hippo signaling that has been recently implicated in cardiac regeneration.

Epicardial application of cardiac progenitor cells in a 3D-printed gelatin/hyaluronic acid patch preserves cardiac function after myocardial infarction

Cardiac cell therapy suffers from limitations related to poor engraftment and significant cell death after transplantation. In this regard, ex vivo tissue engineering is a tool that has been demonstrated to increase cell retention and survival. The aim of our study was to evaluate the therapeutic potential of a 3D-printed patch composed of human cardiac-derived progenitor cells (hCMPCs) in a hyaluronic acid/gelatin (HA/gel) based matrix. hCMPCs were printed in the HA/gel matrix (30 × 106 cells/ml) to form a biocomplex made of six perpendicularly printed layers with a surface of 2 × 2 cm and thickness of 400 μm, in which they retained their viability, proliferation and differentiation capability. The printed biocomplex was transplanted in a mouse model of myocardial infarction (MI). The application of the patch led to a significant reduction in adverse remodeling and preservation of cardiac performance as was shown by both MRI and histology. Furthermore, the matrix supported the long-term in vivo survival and engraftment of hCMPCs, which exhibited a temporal increase in cardiac and vascular differentiation markers over the course of the 4 week follow-up period. Overall, we developed an effective and translational approach to enhance hCMPC delivery and action in the heart.

Cardiosphere-derived Progenitor Cells for Myocardial Repair Following Myocardial Infarction

In the recent years, the existence of cardiac regeneration in mammalian models and even humans has been confirmed in several, carefully designed and executed studies. However, the intrinsic rate of cardiomyocyte renewal is not sufficient to replenish the large number of cells lost after a major injury in the heart, such as myocardial infarction. Therefore, exogenously administered cells with progenitor properties have been used in order to augment this process. From the several candidate cell populations, cardiac derived progenitor cells appear particularly attractive for this purpose, based on data from many experimental studies but also preliminary clinical applications. Cardiosphere-derived cells are a mixed cell population that has shown great potential in stimulating endogenous mechanisms of cardiac repair and attenuating adverse remodeling of the heart. In the present review, we discuss in detail the existing evidence regarding the therapeutic role of cardiosphere-derived progenitor cell administration in the post-myocardial infarction setting. Proof-of-concept studies in rodents, as well as more clinically relevant experiments in large animal models, have provided consistent results regarding the potential of these cells to improve cardiac structure and function after myocardial infarction. Existing data about the underlying mechanisms that are implicated in myocardial regeneration triggered by these cells are presented, as well as preliminary data from clinical applications and future perspectives of this novel therapeutic option.

Three-Dimensional Perfusion Cultivation of Human Cardiac-Derived Progenitors Facilitates Their Expansion While Maintaining Progenitor State

The therapeutic application of autologous cardiac-derived progenitor cells (CPCs) requires a large cell quantity generated under defined conditions. Herein, we investigated the applicability of a three-dimensional (3D) perfusion cultivation system to facilitate the expansion of CPCs harvested from human heart biopsies and characterized by a relatively high percentage of c-kit(+) cells. The cells were seeded in macroporous alginate scaffolds and after cultivation for 7 days under static conditions, some of the constructs were transferred into a perfusion bioreactor, which was operated for an additional 14 days. A robust and highly reproducible human CPC (hCPC) expansion of more than seven-fold was achieved under the 3D perfusion culture conditions, while under static conditions, the expansion of CPCs was limited only to the first 7 days, after which it leveled-off. On day 21 of perfusion cultivation, the expanded cells exhibited a higher expression level of the progenitor marker c-kit, suggesting that the c-kit-positive CPCs are the main cell population undergoing proliferation. The profile of the spontaneous differentiation in the perfused construct was different from that in the static cultivated constructs; genes typical for cardiac and endothelial cell lineages were more widely expressed in the perfused constructs. By contrast, the differentiation to osteogenic (Von Kossa staining and alkaline phosphatase activity) and adipogenic (Oil Red staining) lineages was reduced in the perfused constructs compared with static cultivated constructs. Collectively, our results indicate that 3D perfusion cultivation mode is an appropriate system for robust expansion of human CPCs while maintaining their progenitor state and differentiation potential into the cardiovascular cell lineages.

Cardiac Stem Cells in Patients with Ischemic Cardiomyopathy: Discovery, Translation, and Clinical Investigation

The increasing prevalence of heart failure, in the US and worldwide, poses a significant burden to patients, practitioners, and healthcare systems. Hence, there is a pressing need for alternative therapies to enhance the current treatment armamentarium. Accordingly, when considering heart failure of ischemic etiology, an intervention designed to regenerate the attending loss of myocardium could potentially result in improved cardiac function, functional status, and quality of life. Significant strides have been made by investigators in the study of stem cell therapy for cardiac repair; recently with cardiac-derived progenitor cells. These cells include cardiospheres, cardiosphere-derived cells, and c-kit positive cardiac stem cells. Herein, a review of both preclinical studies and phase I clinical trials of these cell types is presented. A detailed account of in vitro characterization, in vivo bioactivity, and safety and efficacy in humans is outlined. Thus far, encouraging results have been realized, although larger studies have yet to be undertaken.

Heart Cells with Regenerative Potential from Pediatric Patients with End Stage Heart Failure: A Translatable Method to Enrich and Propagate

Background. Human cardiac-derived progenitor cells (hCPCs) have shown promise in treating heart failure (HF) in adults. The purpose of this study was to describe derivation of hCPCs from pediatric patients with end-stage HF. Methods. At surgery, discarded right atrial tissues (hAA) were obtained from HF patients (n = 25; hAA-CHF). Minced tissues were suspended in complete (serum-containing) DMEM. Cells were selected for their tissue migration and expression of stem cell factor receptor (hc-kit). Characterization of hc-kitpositive cells included immunohistochemical screening with a panel of monoclonal antibodies. Results. Cells, including phase-bright cells identified as hc-kitpositive, spontaneously emigrated from hAA-CHF in suspended explant cultures (SEC) after Day 7. When cocultured with tissue, emigrated hc-kitpositive cells proliferated, first as loosely attached clones and later as multicellular clusters. At Day 21~5% of cells were hc-kitpositive. Between Days 14 and 28 hc-kitpositive cells exhibited mesodermal commitment (GATA-4positive and NKX2.5positive); then after Day 28 cardiac lineages (flk-1positive, smooth muscle actinpositive, troponin-Ipositive, and myosin light chainpositive). Conclusions. C-kitpositive hCPCs can be derived from atrial tissue of pediatric patients with end-stage HF. SEC is a novel culture method for derivation of migratory hc-kitpositive cells that favors clinical translation by reducing the need for exogenously added factors to expand hCPCs in vitro.

Letter by Sluijter et al Regarding Article, “Human Cardiac Stem Cell Differentiation Is Regulated by a Mircrine Mechanism”

To the Editor: We read with interest the article by Hosoda et al,1 “Human Cardiac Stem Cell Differentiation Is Regulated by a Mircrine Mechanism.” We are pleased to read that Hosoda et al were able to confirm our observations that miR-499 is involved in the differentiation of human cardiac-derived progenitor cells.2 Hosoda and colleagues acknowledged our previous observations in human cardiomyocyte progenitor cells (hCMPCs), but claimed that these cells were erroneously considered a class of cardiac progenitor cells. The authors suggest that our results demonstrated that miR-1 and 499 favor a more mature phenotype in fetal-neonatal cardiomyocytes. Although controversy still exists about different populations of progenitor and stem cells in the heart, we used an exceptionally profound …

Letter by van Mil et al Regarding, “Dynamic MicroRNA Expression Programs During Cardiac Differentiation of Human Embryonic Stem Cells: Role for miR-499”

To the Editor: With interest, we read the recent article by Wilson et al1 in Circulation: Cardiovascular Genetics describing the role for miR-499 in dynamic microRNA (miRNA) expression programs during cardiac differentiation of human embryonic stem cells (hESCs). The authors demonstrated that a signature group of miRNAs is present in hESCs, whose expression is significantly altered after cardiomyogenic differentiation. We agree that improved understanding of cardiomyogenic differentiation is important, thereby including miRNA regulation. However, we believe that to understand general miRNA regulation and to interpret in silico prediction analysis, further studies and confirmations are needed, including other available cell sources. In our previous study,2 we used undifferentiated human cardiac-derived progenitor cells (hCMPCs) and hCMPCs fully differentiated into …