Research of cardiomyocyte precursors in adult rat heart

Recent reports supported the existence of stem cells in adult hearts. However, phenotype and localization of these cells have not been completely described and it is unknown if cardiac regenerative potential differs from one subject to another. The aims of our work were to identify different populations of cardiac stem cells by the analysis of specific markers and to evaluate the expression variability of these markers in 12 adult rat hearts. The expression of CD9, taube nuss and nanog suggests the presence of stem cells from the earliest stages of embryogenesis in adult myocardium. Their different expression could be associated to the degree of stem cell differentiation. CD34 and c-Kit antibodies were used to detect stem cells committed to one or more specific tissue lineages and we found a strong immunoreactivity for CD34 exclusively in the endothelial cells and a low positivity for c-Kit in the interstitium and next to the vessels. Moreover, as c-Kit expression highly differed within all examined hearts, we suggest that cardiomyogenic potential is different among the various subjects. Undifferentiated cells with myogenic-committed phenotype expressing GATA-4 and nestin were found, respectively, in the interstitial and myocardial cells and in few interstitial cells. Therefore, the physiologic turn over of cardiomyocytes may occur in adult hearts as it has been shown in many others organs. The study of myogenic potential could be important to identify markers specific of stem cells in in vivo adult myocardium that may be used to purify these cells and evaluate their regenerative ability.     

Adult stem cell therapy for the heart

The purpose of this review is to summarize current data leading to and arising from recent clinical application of cellular therapy for acute myocardial infarct (heart attack) and congestive heart failure. We specifically focus on use of adult stem cells and compare and contrast bone marrow and adipose tissue; two different sources from which stem cells can be harvested in substantial numbers with limited morbidity. Cellular therapy is the latest in a series of strategies applied in an effort to prevent or mitigate the progressive and otherwise irreversible loss of cardiac function that frequently follows a heart attack. Unlike surgical, pharmacologic, and gene transfer approaches, cellular therapy has the potential to restore cardiac function by providing cells capable of regenerating damaged myocardium and/or myocardial function. Skeletal muscle myoblast expansion and transfer allows delivery of cells with contractile function, albeit without any evidence of cardiomyogenesis or electrical coupling to remaining healthy myocardium. Delivery of endothelial progenitor cells (EPCs) which drive reperfusion of infarct zone tissues is also promising, although this mechanism is directed at halting ongoing degeneration rather than initiating a regenerative process. By contrast, demonstration of the ability of adult stem cells to undergo cardiomyocyte differentiation both in vitro and in vivo suggests a potential for regenerative medicine. This potential is being examined in early clinical studies.     

Progenitor cell therapy for heart disease

Many cell types are currently being studied as potential sources of cardiomyocytes for cell transplantation therapy to repair and regenerate damaged myocardium. The question remains as to which progenitor cell represents the best candidate. Bone marrow-derived cells and endothelial progenitor cells have been tested in clinical studies. These cells are safe, but their cardiogenic potential is controversial. The functional benefits observed are probably due to enhanced angiogenesis, reduced ventricular remodeling, or to cytokine-mediated effects that promote the survival of endogenous cells. Human embryonic stem cells represent an unlimited source of cardiomyocytes due to their great differentiation potential, but each step of differentiation must be tightly controlled due to the high risk of teratoma formation. These cells, however, confront ethical barriers and there is a risk of graft rejection. These last two problems can be avoided by using induced pluripotent stem cells (iPS), which can be autologously derived, but the high risk of teratoma formation remains. Cardiac progenitor cells have the advantage of being cardiac committed, but important questions remain unanswered, such as what is the best marker to identify and isolate these cells? To date the different markers used to identify adult cardiac progenitor cells also recognize progenitor cells that are outside the heart. Thus, it cannot be determined whether the cardiac progenitor cells identified in the adult heart represent resident cells present since fetal life or extracardiac cells that colonized the heart after cardiac injury. Developmental studies have identified markers of multipotent progenitors, but it is unknown whether these markers are specific for adult progenitors when expressed in the adult myocardium. Cardiac regeneration is dependent on the stability of the cells transplanted into the host myocardium and on the electromechanical coupling with the endogenous cells. Finally, the promotion of endogenous regenerative processes by mobilizing endogenous progenitors represents a complementary approach to cell transplantation therapy.     

Bmi‐1 high‐expressing cells enrich cardiac stem/progenitor cells and respond to heart injury

Bmi‐1 gene is well recognized as an oncogene, but has been recently demonstrated to play a role in the self‐renewal of tissue‐specific stem cells. By using Bmi‐1^GFP/+ mice, we investigated the role of Bmi‐1 in cardiac stem/progenitor cells and myocardial repair. RT‐PCR and flow cytometry analysis indicated that the expression of Bmi‐1 was significantly higher in cardiac side population than the main population from CD45^?Ter119^?CD31^? heart cells. More Sca‐1⁺ cardiac stem/progenitor cells were found in Bmi‐1 GFP^hi subpopulation, and these Bmi‐1 GFP^hi heart cells showed the potential of differentiation into SMM⁺ smooth muscle‐like cells and TnT⁺ cardiomyocyte‐like cells in vitro. The silencing of Bmi‐1 significantly inhibited the proliferation and differentiation of heart cells. Otherwise, myocardial infarction induced a significantly increase (2.7‐folds) of Bmi‐1 GFP^hi population, mainly within the infarction and border zones. These preliminary data suggest that Bmi‐1^hi heart cells are enriched in cardiac stem/progenitor cells and may play a role in myocardial repair.     

Functional Cardiomyocytes Derived from Isl1 Cardiac Progenitors via Bmp4 Stimulation

As heart failure due to myocardial infarction remains a leading cause of morbidity worldwide, cell-based cardiac regenerative therapy using cardiac progenitor cells (CPCs) could provide a potential treatment for the repair of injured myocardium. As adult CPCs may have limitations regarding tissue accessibility and proliferative ability, CPCs derived from embryonic stem cells (ESCs) could serve as an unlimited source of cells with high proliferative ability. As one of the CPCs that can be derived from embryonic stem cells, Isl1 expressing cardiac progenitor cells (Isl1-CPCs) may serve as a valuable source of cells for cardiac repair due to their high cardiac differentiation potential and authentic cardiac origin. In order to generate an unlimited number of Isl1-CPCs, we used a previously established an ESC line that allows for isolation of Isl1-CPCs by green fluorescent protein (GFP) expression that is directed by the mef2c gene, specifically expressed in the Isl1 domain of the anterior heart field. To improve the efficiency of cardiac differentiation of Isl1-CPCs, we studied the role of Bmp4 in cardiogenesis of Isl1-CPCs. We show an inductive role of Bmp directly on cardiac progenitors and its enhancement on early cardiac differentiation of CPCs. Upon induction of Bmp4 to Isl1-CPCs during differentiation, the cTnT+ cardiomyocyte population was enhanced 2.8±0.4 fold for Bmp4 treated CPC cultures compared to that detected for vehicle treated cultures. Both Bmp4 treated and untreated cardiomyocytes exhibit proper electrophysiological and calcium signaling properties. In addition, we observed a significant increase in Tbx5 and Tbx20 expression in differentiation cultures treated with Bmp4 compared to the untreated control, suggesting a link between Bmp4 and Tbx genes which may contribute to the enhanced cardiac differentiation in Bmp4 treated cultures. Collectively these findings suggest a cardiomyogenic role for Bmp4 directly on a pure population of Isl1 expressing cardiac progenitors, which could lead to enhancement of cardiac differentiation and engraftment, holding a significant therapeutic value for cardiac repair in the future.     

Chemical and physical stimuli induce cardiomyocyte differentiation from stem cells

In this study we investigated cardiomyocyte differentiation of rat bone marrow-mesenchymal stem cells (BM-MSCs) by treating the stem cells with conditions mimicking that of myocardial infarction. The extract from infarcted rat myocardium contained the biochemical factors arising after infarction. The cardiac contraction and relaxation were simulated by applying 4% strain at 1 Hz to the stem cells. We found that the extract from infarcted myocardium or 4% strain each alone could induce cardiomyocyte differentiation of BM-MSCs, as shown by expression of cardiomyocyte-specific genes including α-actin, connexin 43, Nkx2.5, MEF2c, GATA4, α-MHC, and Troponin I. Furthermore, a combination of the extract and 4% strain had stronger effects on cardiomyocyte differentiation than what either treatment alone had. Our results suggest that this in vitro model system simulates the local cardiac environment cues after infarction and may be useful in identifying the biochemical and physical factors involved in cardiomyocyte differentiation.     

Pluripotent stem cell‐based heart regeneration: From the developmental and immunological perspectives

Heart diseases such as myocardial infarction cause massive loss of cardiomyocytes, but the human heart lacks the innate ability to regenerate. In the adult mammalian heart, a resident progenitor cell population, termed epicardial progenitors, has been identified and reported to stay quiescent under uninjured conditions; however, myocardial infarction induces their proliferation and de novo differentiation into cardiac cells. It is conceivable to develop novel therapeutic approaches for myocardial repair by targeting such expandable sources of cardiac progenitors, thereby giving rise to new muscle and vasculatures. Human pluripotent stem cells such as embryonic stem cells and induced pluripotent stem cells can self‐renew and differentiate into the three major cell types of the heart, namely cardiomyocytes, smooth muscle, and endothelial cells. In this review, we describe our current knowledge of the therapeutic potential and challenges associated with the use of pluripotent stem cell and progenitor biology in cell therapy. An emphasis is placed on the contribution of paracrine factors in the growth of myocardium and neovascularization as well as the role of immunogenicity in cell survival and engraftment. (Part C) 96:98–107, 2012. © 2012 Wiley Periodicals, Inc.     

胚胎干细胞的心脏应用

心肌梗死期间死亡的心肌细胞将由没有收缩功能的疤痕组织替代,因而极可能引起心力衰竭。对治疗心衰来说,修复死亡或损伤的心肌以及改善心功能仍面临着极大挑战。干细胞移植已在近年来的实验中用于修复损失的心肌。本文总结了近期在心肌损伤动物中实施胚胎干细胞移植的实验结果,并着重介绍对这类特定细胞的研究进展。胚胎干细胞取源于早期哺乳类胚胎的胚芽细胞,属于多功能干细胞。这类细胞具有长期增殖而不分化的能力,或台色够在培养过程中分化成包括心肌细胞在内的所有特殊体细胞。由于胚胎干细胞具有极大的增殖和分化为成熟组织的能力,它们可能成为一种潜在的很有实用价值的细胞来源,可用于对病态心脏的功能心肌再生的细胞治疗。新近的研究表明,在心肌梗死动物模型中,心肌内移植胚胎干细胞或由其分化成的心肌样细胞,能导致已损伤心肌的再生,并改善心脏功能。另外,在病毒性心肌炎小鼠中,静脉输入胚胎干细胞可明显提高生存率和减轻心肌损伤。有关人类胚胎干细胞在体外分化成心肌细胞以及这些细胞的特性,近来已有报道。然而,要在临床能应用人类胚胎干细胞或由其分化成的心肌细胞来治疗晚期心脏疾病,还必须越过大量的伦理、法律和科学上的障碍。     

Mobilization of bone marrow-derived progenitor cells in acute coronary syndromes

Two hypotheses explain the role of adult progenitor cells in myocardial regeneration. Stem cell plasticity which involves mobilization of stem cells from the bone marrow and other niches, homing to the area of tissue injury and transdifferentiation into functional cardiomyocytes. Alternative hypothesis is based on the observations that bone marrow harbors a heterogenous population of cells positive for CXCR4 - receptor for chemokine SDF-1. This population of non-hematopoietic cells expresses genes specific for early muscle, myocardial and endothelial progenitor cells (EPC). These tissue-committed stem cells circulate in the peripheral blood at low numbers and can be mobilized by hematopoietic cytokines in the setting of myocardial ischemia. Endothelial precursors capable of transforming into mature, functional endothelial cells are present in the pool of peripheral mononuclear cells in circulation. Their number significantly increases in acute myocardial infarction (AMI) with subsequent decrease after 1 month, as well as in patients with unstable angina in comparison to stable coronary heart disease (CHD). There are numerous physiological and pathological stimuli which influence the number of circulating EPC such as regular physical activity, medications (statins, PPAR-gamma agonists, estrogens), as well as numerous inflammatory and hematopoietic cytokines. Mobilization of stem cells in AMI involves not only the endothelial progenitors but also hematopoietic, non-hematopoietic stem cells and most probably the mesenchymal cells. In healthy subjects and patients with stable CHD, small number of circulating CD34+, CXCR4+, CD117+, c-met+ and CD34/CD117+ stem cells can be detected. In patients with AMI, a significant increase in CD34+/CXCR4+, CD117+, c-met+ and CD34/CD117+ stem cell number the in peripheral blood was demonstrated with parallel increase in mRNA expression for early cardiac, muscle and endothelial markers in peripheral blood mononuclear cells. The maximum number of stem cells was found early in ST-segment elevation myocardial infarction (<12 hours) with subsequent decrease through the 7-day follow-up and with concomitant changes in the levels of cytokines involved in the inflammatory response and stem cell recruitment. Moreover, peak expression of cardiac muscle and endothelial markers occurred at the same time as the most significant increase in CD34/CXCR4+ stem cell number. The SDF-1/CXCR-4 axis seems particularly important in stem/muscle progenitor cell homing, chemotaxis, engraftment and retention in ischaemic myocardium. The significance of autologous stem cells mobilization in terms of cardiac salvage and regeneration needs to be proved in humans but it seems to be a reparative mechanism triggered early in the course of acute coronary syndromes.     

Human endometrial stem cells confer enhanced myocardial salvage and regeneration by paracrine mechanisms

Human endometrial stem cells (EnSCs) have the potential to be ‘off the shelf’ clinical reagents for the treatment of heart failure. Here, using an immunocompetent rat model of myocardial infarction (MI), we provide evidence that the functional benefits of EnSC transplantation are principally and possibly exclusively through a paracrine effect. Human EnSCs were delivered by intramyocardial injection into rats 30 min. after coronary ligation. EnSC therapy significantly preserved viable myocardium in the infarct zone and improved cardiac function at 28 days. Despite increased viable myocardium and vascular density, there was scant evidence of differentiation of EnSCs into any cardiovascular cell type. Cultured human EnSCs expressed a distinctive profile of cytokines that enhanced the survival, proliferation and function of endothelial cells in vitro. When injected into the peri‐infarct zone, human EnSCs activated AKT, ERK1/2 and STAT3 and inhibited the p38 signalling pathway. EnSC therapy decreased apoptosis and promoted cell proliferation and c‐kit+ cell recruitment in vivo. Myocardial protection and enhanced post‐infarction regeneration by EnSCs is mediated primarily by paracrine effects conferred by secreted cytokines that activate survival pathways and recruit endogenous progenitor stem cells. Menstrual blood provides a potentially limitless source of biologically competent ‘off the shelf’ EnSCs for allogeneic myocardial regenerative medicine.     

Cardiomyocyte progenitor cell‐derived exosomes stimulate migration of endothelial cells

Patients suffering from heart failure as a result of myocardial infarction are in need of heart transplantation. Unfortunately the number of donor hearts is very low and therefore new therapies are subject of investigation. Cell transplantation therapy upon myocardial infarction is a very promising strategy to replace the dead myocardium with viable cardiomyocytes, smooth muscle cells and endothelial cells, thereby reducing scarring and improving cardiac performance. Despite promising results, resulting in reduced infarct size and improved cardiac function on short term, only a few cells survive the ischemic milieu and are retained in the heart, thereby minimizing long-term effects. Although new capillaries and cardiomyocytes are formed around the infarcted area, only a small percentage of the transplanted cells can be detected months after myocardial infarction. This suggests the stimulation of an endogenous regenerative capacity of the heart upon cell transplantation, resulting from release of growth factor, cytokine and other paracrine molecules by the progenitor cells – the so-called paracrine hypothesis. Here, we focus on a relative new component of paracrine signalling, i.e. exosomes. We are interested in the release and function of exosomes derived from cardiac progenitor cells and studied their effects on the migratory capacity of endothelial cells.     

Cloning and expression pattern of dog SDF-1 and the implications of altered expression of SDF-1 in ischemic myocardium

Stromal cell derived factor-1 (SDF-1) plays a pivotal role in the mobilization and homing of stem cells, indicative of its potential in myocardial regeneration after heart damage. The use of large animal models in cardiac surgery research plays an essential role in the translation of results from basic studies into clinical trials. Considering the aforesaid two reasons, for the first time, we cloned dog SDF-1 cDNA and characterized the constitutive expression pattern of SDF-1 gene in normal dog tissues and the dynamic expression pattern in a dog model of myocardial infarction (MI) by means of ELISA test, real-time RT-PCR, and Western blotting. In a dog model of MI, We also examined and compared the differentially expressed pattern of SDF-1 between infarct area and border zone of myocardium in order to explore the implication of differentially distribution of SDF-1 in the mobilization and homing of stem cells to the damaged heart. Our results provide insights into expression pattern and pathophysiologic significance of dog SDF-1 in normal and heart-damaged dogs.     

Cell therapy for ischaemic heart disease: focus on the role of resident cardiac stem cells

Myocardial infarction results in loss of cardiomyocytes, scar formation, ventricular remodelling, and eventually heart failure. In recent years, cell therapy has emerged as a potential new strategy for patients with ischaemic heart disease. This includes embryonic and bone marrow derived stem cells. Recent clinical studies showed ostensibly conflicting results of intracoronary infusion of autologous bone marrow derived stem cells in patients with acute or chronic myocardial infarction. Anyway, these results have stimulated additional clinical and pre-clinical studies to further enhance the beneficial effects of stem cell therapy. Recently, the existence of cardiac stem cells that reside in the heart itself was demonstrated. Their discovery has sparked intense hope for myocardial regeneration with cells that are obtained from the heart itself and are thereby inherently programmed to reconstitute cardiac tissue. These cells can be detected by several surface markers (e.g. c-kit, Sca-1, MDR1, Isl-1). Both in vitro and in vivo differentiation into cardiomyocytes, endothelial cells and vascular smooth muscle cells has been demonstrated, and animal studies showed promising results on improvement of left ventricular function. This review will discuss current views regarding the feasibility of cardiac repair, and focus on the potential role of the resident cardiac stem and progenitor cells. (Neth Heart J 2009;17:199–207.)     

Stem cell engineering for treatment of heart diseases: Potentials and challenges

Heart disorders are a major health concern worldwide responsible for millions of deaths every year. Among the many disorders of the heart, myocardial infarction, which can lead to the development of congestive heart failure, arrhythmias, or even death, has the most severe social and economic ramifications. Lack of sufficient available donor hearts for heart transplantation, the only currently viable treatment for heart failure other than medical management options (ACE inhibition, beta blockade, use of AICDs, etc.) that improve the survival of patients with heart failure emphasises the need for alternative therapies. One promising alternative replaces cardiac muscle damaged by myocardial infarction with new contractile cardiomyocytes and vessels obtained through stem cell-based regeneration.We report on the state of the art of recovery of cardiac functions by using stem cell engineering. Current research focuses on (a) inducing stem cells into becoming cardiac cells before or after injection into a host, (b) growing replacement heart tissue in vitro, and (c) stimulating the proliferation of the post-mitotic cardiomyocytes in situ. The most promising treatment option for patients is the engineering of new heart tissue that can be implanted into damaged areas. Engineering of cardiac tissue currently employs the use of co-culture of stem cells with scaffold microenvironments engineered to improve tissue survival and enhance differentiation. Growth of heart tissue in vitro using scaffolds, soluble collagen, and cell sheets has unique advantages. To compensate for the loss of ventricular mass and contractility of the injured cardiomyocytes, different stem cell populations have been extensively studied as potential sources of new cells to ameliorate the injured myocardium and eventually restore cardiac function. Unresolved issues including insufficient cell generation survival, growth, and differentiation have led to mixed results in preclinical and clinical studies. Addressing these limitations should ensure the successful production of replacement heart tissue to benefit cardiac patients.     

Myocardial regeneration potential of adipose tissue-derived stem cells

Various tissue resident stem cells are receiving attention from basic scientists and clinicians as they hold promise for myocardial regeneration. For practical reasons, adipose tissue-derived stem cells (ASCs) are attractive cells for clinical application in repairing damaged myocardium based on the following advantages: abundant adipose tissue in most patients and easy accessibility with minimally invasive lipoaspiration procedure. Several recent studies have demonstrated that both cultured and freshly isolated ASCs could improve cardiac function in animal model of myocardial infarction. The mechanisms underlying the beneficial effect of ASCs on myocardial regeneration are not fully understood. Growing evidence indicates that transplantation of ASCs improve cardiac function via the differentiation into cardiomyocytes and vascular cells, and through paracrine pathways. Paracrine factors secreted by injected ASCs enhance angiogenesis, reduce cell apoptosis rates, and promote neuron sprouts in damaged myocardium. In addition, Injection of ASCs increases electrical stability of the injured heart. Furthermore, there are no reported cases of arrhythmia or tumorigenesis in any studies regarding myocardial regeneration with ASCs. This review summarizes the characteristics of both cultured and freshly isolated stem cells obtained from adipose tissue, their myocardial regeneration potential, and the underlying mechanisms for beneficial effect on cardiac function, and safety issues.     

Cardiac potential of stem cells from whole human umbilical cord tissue

We investigated the role of stem cells from human umbilical cord tissue in cardiomyocyte regeneration. The umbilical cord stem cells were initially characterized and differentiated in a myocardial differentiation medium containing 5‐azacytidine for 24 h. Differentiation into cardiomyocytes was determined by expression of cardiac specific markers, like cardiac α‐actin, connexin43, myosin, Troponin T, and ultrastructural analysis. In vivo, the transplanted umbilical cord stem cells were sprouting from local injection and differentiated into cardiomyocyte‐like cells in a rat myocardial infarction model. Echocardiography revealed increasing left ventricular function after umbilical cord stem cell transplantation. These results demonstrate that umbilical cord stem cells can differentiate into cardiomyocyte‐like cells both in vitro and in vivo. Therefore, human umbilical cord might represent a source of stem cells useful for cellular therapy and myocardial tissue engineering. Future studies are required to determine the molecular signaling mechanisms responsible for this phenomenon. J. Cell. Biochem. 107: 926–932, 2009. © 2009 Wiley‐Liss, Inc.     

Exosomes derived from adipose tissue,bone marrow,and umbilical cord blood for cardioprotection after myocardial infarction

Human mesenchymal stem cells (MSCs) have the potential for improving cardiac function following myocardial infarction (MI). This study was performed to explore the cardioprotection of bone marrow mesenchymal stem cells (BMMSCs), adipose tissue-derived mesenchymal stem cells (ADMSCs), and umbilical cord blood-derived mesenchymal stem cells (UCBMSCs) for myocardium in rats after MI. MI models were established in rats, which were injected with PBS, BMMSCs, ADMSCs, and UCMSCs. Cardiac function was detected by ultrasonic cardiogram. TTC staining, TUNEL staining, and immunohistochemistry were adopted to determine infarction area, cardiomyocyte apoptosis, and microvascular density (MVD), respectively. Exosomes were derived from BMMSCs, ADMSCs, and UCBMSCs, and identified by morphological observation and CD63 expression detection. Neonatal rat cardiomyocytes (NRCMs) were isolated and cultured with hypoxia, subjected to PBS and exosomes derived from BMMSCs, ADMSCs, and UCMSCs. Flow cytometry and enzyme-linked immunosorbent assay were used to determine NRCM apoptosis and the levels of angiogenesis-related markers (VEGF, bFGF, and HGF). According to ultrasonic cardiogram, BMMSCs, ADMSCs, and UCMSCs facilitated the cardiac function of MI rats. Furthermore, three kinds of MSCs inhibited cardiomyocyte apoptosis, infarction area, and increased MVD. NRCMs treated with exosomes derived from BMMSCs, ADMSCs, and UCMSCs reduced the NRCM apoptosis and promoted angiogenesis by increasing levels of VEGF, bFGF, and HGF. Notably, exosomes from ADMSCs had the most significant effect. On the basis of the results obtained from this study, exosomes derived from BMMSCs, ADMSCs, and UCBMSCs inhibited the cardiomyocyte apoptosis and promoted angiogenesis, thereby improving cardiac function and protecting myocardium. Notably, exosomes from ADMSCs stimulated most of the cardioprotection factors.     

MicroRNA-1 transfected embryonic stem cells enhance cardiac myocyte differentiation and inhibit apoptosis by modulating the PTEN/Akt pathway in the infarcted heart

microRNAs (miRs) have emerged as critical modulators of various physiological processes including stem cell differentiation. Indeed, miR-1 has been reported to play an integral role in the regulation of cardiac muscle progenitor cell differentiation. However, whether overexpression of miR-1 in embryonic stem (ES) cells (miR-1-ES cells) will enhance cardiac myocyte differentiation following transplantation into the infarcted myocardium is unknown. In the present study, myocardial infarction (MI) was produced in C57BL/6 mice by left anterior descending artery ligation. miR-1-ES cells, ES cells, or culture medium (control) was transplanted into the border zone of the infarcted heart, and 2 wk post-MI, cardiac myocyte differentiation, adverse ventricular remodeling, and cardiac function were assessed. We provide evidence demonstrating enhanced cardiac myocyte commitment of transplanted miR-1-ES cells in the mouse infarcted heart as compared with ES cells. Assessment of apoptosis revealed that overexpression of miR-1 in transplanted ES cells protected host myocardium from MI-induced apoptosis through activation of p-AKT and inhibition of caspase-3, phosphatase and tensin homolog, and superoxide production. A significant reduction in interstitial and vascular fibrosis was quantified in miR-1-ES cell and ES cell transplanted groups compared with control MI. However, no statistical significance between miR-1-ES cell and ES cell groups was observed. Finally, mice receiving miR-1-ES cell transplantation post-MI had significantly improved heart function compared with respective controls (P < 0.05). Our data suggest miR-1 drives cardiac myocyte differentiation from transplanted ES cells and inhibits apoptosis post-MI, ultimately giving rise to enhanced cardiac repair, regeneration, and function.     

Isolation and characterization of cardiac progenitor cells from myocardial right atrial appendage tissue

Resident cardiac stem cells, known as “cardiogenic progenitor cells” (CPCs), are a heterogeneous population of immature cells residing in the myocardium and capable of self-renewal and differentiation into cardiomyocyte-like and vascular-like cells. CPCs are usually isolated by long enzymatic digestion of heart tissue and selection with stem cell markers. However, long exposure to enzymatic digestion and the small size of a myocardial sample significantly hinder acquiring a large number of viable cells. To avoid these problems, we developed a method based on CPC growth ex vivo and subsequent immunomagnetic selection.