Insulin-like growth factor 1 improves the efficacy of mesenchymal stem cells transplantation in a rat model of myocardial infarction

Background Previous study demonstrated the improvement of cardiac function was proportional to the number of cells implanted. Therefore, increasing cell survival in the infarcted myocardium might contribute to the improvement of the functional benefit of cell transplantation. Methods and results MSCs were treated with IGF-1 in vitro and infused into the acute myocardial infarction rats via the tail vein. After treatment of MSCs with IGF-1 for 48 h, flow cytometric analysis showed marked enhancement of expression of CXCR4 in the cell surface. After 4 weeks of transplantation, we found 1) a greater number of engrafted MSCs arrived and survived in the peri-infarct region; 2) TnT protein expression and capillary density were enhanced; 3) LV cavitary dilation, transmural infarct thinning, deposition of total collagen in the peri-infarct region and cardiac dysfunction were attenuated. Conclusion 1) IGF-1 treatment has time-dependent and dose-dependent effects on CXCR4 expression in MSCs in vitro. 2) IGF-1 improves the efficacy of MSCs transplantation in a rat model of myocardial infarction mainly via enhancement of the number of cells attracted into the infarcted heart. These findings provide a novel stem cell therapeutic avenue against ischemic heart disease.     

Effects of hepatocyte growth factor overexpressed bone marrow‐derived mesenchymal stem cells on prevention from left ventricular remodelling and functional improvement in infarcted rat hearts

Bone marrow‐derived mesenchymal stem cells (BM‐MSCs ) transplantation has been reported to be a promising therapy for myocardial infarction (MI). However, low survival rate of BM‐MSCs in infarcted heart is one of the major limitations for the perspective clinical application. In this study, we aimed to investigate the effect of hepatocyte growth factor (HGF) on left ventricular function improvement of HGF gene‐modified BM‐MSCs (HGF‐MSCs) after its delivery into the infarcted rat hearts. BM‐MSCs were isolated with fibroblast‐like morphology and expressed CD44+CD29+CD90+/CD34‐CD45‐CD31‐CD11a. After 5‐azacytidine induction in vitro, 20%–30% of the cells were positively stained for desmin, cardiac‐specific cardiac troponin I and connexin‐43. Histological staining revealed that 2 weeks after MI is an optimal time point with decreased neutrophil infiltration and increased vascular number. Minimal infarct size and best haemodynamic analysis were also observed after cell injection at 2 weeks compared with that of 1 h, 1 week or 4 weeks. Echocardiogram confirmed that transplantation with HGF‐MSCs significantly improved left ventricular function compared with other groups in rat MI models. MSCs and HGF‐MSCslabelled with DAPI were detected 4 weeks after MI in the infarcted area. Decreased infarcted scar area and increased angiogenesis formation could be found in HGF‐MSCs group than in other groups as demonstrated by hematoxylin and eosin (H&E) staining and factor VIII staining. These results indicate that HGF‐MSCs transplantation could enhance the contractile function and attenuate left ventricular remodelling efficiently in rats with MI. Copyright © 2012 John Wiley & Sons, Ltd.     

Local activation of cardiac stem cells for post‐myocardial infarction cardiac repair

The prognosis of patients with myocardial infarction (MI) and resultant chronic heart failure remains extremely poor despite continuous advancements in optimal medical therapy and interventional procedures. Animal experiments and clinical trials using adult stem cell therapy following MI have shown a global improvement of myocardial function. The emergence of stem cell transplantation approaches has recently represented promising alternatives to stimulate myocardial regeneration. Regarding their tissue‐specific properties, cardiac stem cells (CSCs) residing within the heart have advantages over other stem cell types to be the best cell source for cell transplantation. However, time‐consuming and costly procedures to expanse cells prior to cell transplantation and the reliability of cell culture and expansion may both be major obstacles in the clinical application of CSC‐based transplantation therapy after MI. The recognition that the adult heart possesses endogenous CSCs that can regenerate cardiomyocytes and vascular cells has raised the unique therapeutic strategy to reconstitute dead myocardium via activating these cells post‐MI. Several strategies, such as growth factors, mircoRNAs and drugs, may be implemented to potentiate endogenous CSCs to repair infarcted heart without cell transplantation. Most molecular and cellular mechanism involved in the process of CSC‐based endogenous regeneration after MI is far from understanding. This article reviews current knowledge opening up the possibilities of cardiac repair through CSCs activation in situ in the setting of MI.     

Myocardial regeneration by transplantation of modified endothelial progenitor cells expressing SDF-1 in a rat model

Cell based therapy has been shown to attenuate myocardial dysfunction after myocardial infarction (MI) in different acute and chronic animal models. It has been further shown that stromal‐cell derived factor‐1α (SDF‐1α) facilitates proliferation and migration of endogenous progenitor cells into injured tissue. The aim of the present study was to investigate the role of exogenously applied and endogenously mobilized cells in a regenerative strategy for MI therapy. Lentivirally SDF‐1α‐infected endothelial progenitor cells (EPCs) were injected after 90 min. of ligation and reperfusion of the left anterior descending artery (LAD) intramyocardial and intracoronary using a new rodent catheter system. Eight weeks after transplantation, echocardiography and isolated heart studies revealed a significant improvement of LV function after intramyocardial application of lentiviral with SDF‐1 infected EPCs compared to medium control. Intracoronary application of cells did not lead to significant differences compared to medium injected control hearts. Histology showed a significantly elevated rate of apoptotic cells and augmented proliferation after transplantation of EPCs and EPCs + SDF‐1α in infarcted myocardium. In addition, a significant increased density of CD31⁺ vessel structures, a lower collagen content and higher numbers of inflammatory cells after transplantation of SDF‐1 transgenic cells were detectable. Intramyocardial application of lentiviral‐infected EPCs is associated with a significant improvement of myocardial function after infarction, in contrast to an intracoronary application. Histological results revealed a significant augmentation of neovascularization, lower collagen content, higher numbers of inflammatory cells and remarkable alterations of apoptotic/proliferative processes in infarcted areas after cell transplantation.     

Mesenchymal stem cells conditioned with glucose depletion augments their ability to repair-infarcted myocardium

Mesenchymal stem cells (MSCs) are an attractive candidate for autologous cell therapy, but their ability to repair damaged myocardium is severely compromised with advanced age. Development of viable autologous cell therapy for treatment of heart failure in the elderly requires the need to address MSC ageing. In this study, MSCs from young (2 months) and aged (24 months) C57BL/6 mice were characterized for gene expression of IGF‐1, FGF‐2, VEGF, SIRT‐1, AKT, p16^INK4a, p21 and p53 along with measurements of population doubling (PD), superoxide dismutase (SOD) activity and apoptosis. Aged MSCs displayed senescent features compared with cells isolated from young animals and therefore were pre‐conditioned with glucose depletion to enhance age affected function. Pre‐conditioning of aged MSCs led to an increase in expression of IGF‐1, AKT and SIRT‐1 concomitant with enhanced viability, proliferation and delayed senescence. To determine the myocardial repair capability of pre‐conditioned aged MSCs, myocardial infarction (MI) was induced in 24 months old C57BL/6 wild type mice and GFP expressing untreated and pre‐conditioned aged MSCs were transplanted. Hearts transplanted with pre‐conditioned aged MSCs showed increased expression of paracrine factors, such as IGF‐1, FGF‐2, VEGF and SDF‐1α. This was associated with significantly improved cardiac performance as measured by dp/dt_max, dp/dt_min, LVEDP and LVDP, declined left ventricle (LV) fibrosis and apoptosis as measured by Masson's Trichrome and TUNEL assays, respectively, after 30 days of transplantation. In conclusion, pre‐conditioning of aged MSCs with glucose depletion can enhance proliferation, delay senescence and restore the ability of aged cells to repair senescent infarcted myocardium.     

Bone marrow mesenchymal stem cells for post-myocardial infarction cardiac repair: microRNAs as novel regulators

Transplantation of bone marrow-derived mesenchymal stem cells (MSCs) is safe and may improve cardiac function and structural remodelling in patients following myocardial infarction (MI). Cardiovascular cell differentiation and paracrine effects to promote endogenous cardiac regeneration, neovascularization, anti-inflammation, anti-apoptosis, anti-remodelling and cardiac contractility, may contribute to MSC-based cardiac repair following MI. However, current evidence indicates that the efficacy of MSC transplantation was unsatisfactory, due to the poor viability and massive death of the engrafted MSCs in the infarcted myocardium. MicroRNAs are short endogenous, conserved, non-coding RNAs and important regulators involved in numerous facets of cardiac pathophysiologic processes. There is an obvious involvement of microRNAs in almost every facet of putative repair mechanisms of MSC-based therapy in MI, such as stem cell differentiation, neovascularization, apoptosis, cardiac remodelling, cardiac contractility and arrhythmias, and others. It is proposed that therapeutic modulation of individual cardiovascular microRNA of MSCs, either mimicking or antagonizing microRNA actions, will hopefully enhance MSC therapeutic efficacy. In addition, MSCs may be manipulated to enhance functional microRNA expression or to inhibit aberrant microRNA levels in a paracrine manner. We hypothesize that microRNAs may be used as novel regulators in MSC-based therapy in MI and MSC transplantation by microRNA regulation may represent promising therapeutic strategy for MI patients in the future.     

Combination of CD34‐positive cell subsets with infarcted myocardium‐like matrix stiffness: a potential solution to cell‐based cardiac repair

Detection of the optimal cell transplantation strategy for myocardial infarction (MI) has attracted a great deal of attention. Commitment of engrafted cells to angiogenesis within damaged myocardium is regarded as one of the major targets in cell‐based cardiac repair. Bone marrow–derived CD34‐positive cells, a well‐characterized population of stem cells, might represent highly functional endothelial progenitor cells and result in the formation of new blood vessels. Recently, physical microenvironment (extracellular matrix stiffness) around the engrafted cells was found to exert an essential impact on their fate. Stem cells are able to feel and respond to the tissue‐like matrix stiffness to commit to a relevant lineage. Notably, the infarct area after MI experiences a time‐dependent stiffness change from flexible to rigid. Our previous observations demonstrated myocardial stiffness‐dependent differentiation of the unselected bone marrow–derived mononuclear cells (BMMNCs) along endothelial lineage cells. Myocardial stiffness (~42 kPa) within the optimal time domain of cell engraftment (at week 1 to 2) after MI provided a more favourable physical microenvironment for cell specification and cell‐based cardiac repair. However, the difference in tissue stiffness‐dependent cell differentiation between the specific cell subsets expressing and no expressing CD34 phenotype remains uncertain. We presumed that CD34‐positive cell subsets facilitated angiogenesis and subsequently resulted in cardiac repair under induction of infarcted myocardium‐like matrix stiffness compared with CD34‐negative cells. If the hypothesis were true, it would contribute greatly to detect the optimal cell subsets for cell therapy and to establish an optimized therapy strategy for cell‐based cardiac repair.     

Mineralocorticoid receptor deficiency improves the therapeutic effects of mesenchymal stem cells for myocardial infarction via enhanced cell survival

The poor survival of stem cells seriously limits their therapeutic efficacy for myocardial infarction (MI). Mineralocorticoid receptor (MR) activation plays an important role in the pathogenesis of multiple cardiovascular diseases. Here, we examined whether MR silencing in bone marrow derived mesenchymal stem cells (MSCs) could improve MSCs’ survival and enhance their cardioprotective effects in MI. MSCs from male Sprague‐Dawley rats were transfected with adenoviral small interfering RNA to silence MR (siRNA‐MR). MR silencing decreased hypoxia‐induced MSCs’ apoptosis, as demonstrated by Annexin V/7‐AAD staining. The mechanisms contributing to the beneficial effects of MR depletion were associated with inhibiting intracellular reactive oxygen species production and increased Bcl‐2/Bax ratio. In vivo study, 1 × 10⁶ of MSCs with or without siRNA‐MR were injected into rat hearts immediately after MI. Depletion of MR could improve the MSCs’ survival significantly in infarcted myocardium, associated with more cardiac function improvement and smaller infarct size. Capillary density were also significantly higher in siRNA group with increased expression of vascular endothelial growth factor. Our study demonstrated that silencing MR promoted MSCs’ survival and repair efficacy in ischaemic hearts. MR might be a potential target for enhancing the efficacy of cell therapy in ischaemic heart disease.     

Transplantation of embryonic stem cells improves cardiac function in postinfarcted rats.

Massive loss of cardiac myocytes after myocardial infarction (MI) is a common cause of heart failure. The present study was designed to investigate the improvement of cardiac function in MI rats after embryonic stem (ES) cell transplantation. MI in rats was induced by ligation of the left anterior descending coronary artery. Cultured ES cells used for cell transplantation were transfected with the marker green fluorescent protein (GFP). Animals in the treated group received intramyocardial injection of ES cells in injured myocardium. Compared with the MI control group injected with an equivalent volume of the cell-free medium, cardiac function in ES cell-implanted MI animals was significantly improved 6 wk after cell transplantation. The characteristic phenotype of engrafted ES cells was identified in implanted myocardium by strong positive staining to sarcomeric alpha-actin, cardiac alpha-myosin heavy chain, and troponin I. GFP-positive cells in myocardium sectioned from MI hearts confirmed the survival and differentiation of engrafted cells. In addition, single cells isolated from cell-transplanted MI hearts showed rod-shaped GFP-positive myocytes with typical striations. The present data demonstrate that ES cell transplantation is a feasible and novel approach to improve ventricular function in infarcted failing hearts.     

The bifunctional SDF‐1‐AnxA5 fusion protein protects cardiac function after myocardial infarction

Stromal cell‐derived factor‐1 (SDF‐1) is a well‐characterized cytokine that protects heart from ischaemic injury. However, the beneficial effects of native SDF‐1, in terms of promoting myocardial repair, are limited by its low concentration in the ischaemic myocardium. Annexin V (AnxA5) can precisely detect dead cells in vivo. As massive cardiomyocytes die after MI, we hypothesize that AnxA5 can be used as an anchor to carry SDF‐1 to the ischaemic myocardium. In this study, we constructed a fusion protein consisting of SDF‐1 and AnxA5 domains. The receptor competition assay revealed that SDF‐1‐AnxA5 had high binding affinity to SDF‐1 receptor CXCR4. The treatment of SDF‐1‐AnxA5 could significantly promote phosphorylation of AKT and ERK and induce chemotactic response, angiogenesis and cell survival in vitro. The binding membrane assay and immunofluorescence revealed that AnxA5 domain had the ability to specifically recognize and bind to cells injured by hypoxia. Furthermore, SDF‐1‐AnxA5 administered via peripheral vein could accumulate at the infarcted myocardium in vivo. The treatment with SDF‐1‐AnxA5 attenuated cell apoptosis, enhanced angiogenesis, reduced infarcted size and improved cardiac function after mouse myocardial infarction. Our results suggest that the bifunctional SDF‐1‐AnxA5 can specifically bind to dead cells. The systemic administration of bifunctional SDF‐1‐AnxA5 effectively provides cardioprotection after myocardial infarction.     

培养于生物降解支架膜内的胚胎干细胞可修复小鼠的梗塞心肌

我们以往的研究表明,直接在心肌梗塞（myocardial infarction,MI）动物的心脏缺血区注射胚胎干细胞（embryonic stemceils,ESCs）可以提高其心肌功能,干细胞组织工程学可以使组织再生、修复。本研究旨在观察将ESCs接种到生物降解膜内并移植到梗塞部位的效果。通过结扎小鼠左冠状动脉制作MI模型,将培养3d的带有小鼠ESCs的聚羟基乙酸膜（polyglycolicacid,PGA）移植到心肌缺血及边缘区表面。实验小鼠分成4组：假手术组、MI组、MI＋PGA组、MI＋ESC组,移植操作8周后检测血流动力学和心肌功能。MI组的血压和左心室功能显著降低。与MI组和MI＋PGA组相比,MI＋ESC组的血压和心室功能显著改善,存活率也显著增高,在梗塞区检测到GFP阳性组织,表明ESCs存活,并可能有心肌再生。以上结果表明,移植生物降解膜内的ESCs可修复小鼠梗塞区心肌细胞并提高心脏功能。将ESCs和生物降解材料联合运用可能为修复受损心脏提供一个新的治疗方法。     

Implanted bone marrow-derived mesenchymal stem cells fail to metabolically stabilize or recover electromechanical function in infarcted hearts

Mesenchymal stem cells (MSCs) have been used with success in several clinical applications for clinical treatment of ischemic hearts. However, the reported effects of MSC-based therapy on myocardial infarction (MI) are inconsistent. In particular, the preventive effects of MSC-based therapy on arrhythmic sudden death and metabolic disorders after infarction remain controversial. Here, we investigated the effects of MSCs on reverse remodeling in an infarcted myocardium, and found that MSC-therapy failed to achieve the complete regeneration of infarcted myocardium. Histological analyses showed that although infarct size and interstitial fibrosis induced by MI recovered significantly after MSC treatment, these improvements were marginal, indicating that a significant amount of damaged tissue was still present. Furthermore, transplanted MSCs had slight anti-apoptotic and anti-inflammatory effects in MSC-implanted regions and no significant improvements in cardiac function were observed, suggesting that naïve MSCs might not be the right cell type to treat myocardial infarction. Furthermore, small ion profiling using ToF-SIMS revealed that the metabolic stabilization provided by the MSCs implantation was not significant compared to the sham group. Together, these results indicate that pretreatment of MSCs is needed to enhance the benefits of MSCs, particularly when MSCs are used to treat arrhythmogenicity and metabolically stabilize infarcted myocardium.     

The similar effect of transplantation of marrow-derived mesenchymal stem cells with or without prior differentiation induction in experimental myocardial infarction

Marrow-derived mesenchymal stem cells (MSCs) have been heralded as a source of great promise for the regeneration of the infarcted heart. There is no clear data indicating whether or not in vitro differentiation of MSCs into major myocardial cells can increase the beneficial effects of MSCs. The aim of this study is to address this issue. To induce MSCs to transdifferentiate into cardiomyocyte-like and endothelial-like cells, 5-azacytidine and vascular endothelial growth factor (VEGF) were used, respectively. Myocardial infarction in rabbits was generated by ligating the left anterior descending coronary artery. Animals were divided into three experimental groups: I, control group; II, undifferentiated mesenchymal stem cell transplantation group; III, differentiated mesenchymal stem cell transplantation group; which respectively received peri-infarct injections of culture media, autologous undifferentiated MSCs and autologous differentiated MSCs. General pathology, immunohistochemistry, electron microscopy and echocardiography were performed in order to search for myocardial regeneration and improvement of cardiac function. In Groups II and III, implanted cells transdifferentiate into myocardial cells within 28 days post injection in a similar manner, and well-developed ultra structures formed within transplanted cells. Improvements in left ventricular function and reductions in infarcted area were observed in both cell-transplanted groups to the same degree. Vascular density was similar in Groups II and III and significantly higher in these groups compared with the control group. There is no need for prior differentiation induction of marrow-derived MSCs before transplantation and peri-infarct implantation of MSCs can efficiently regenerate the infarcted myocardium and improve cardiac function.     

Low level laser irradiation precondition to create friendly milieu of infarcted myocardium and enhance early survival of transplanted bone marrow cells

We suggested that low‐level laser irradiation (LLLI) precondition prior to cell transplantation might remodel the hostile milieu of infarcted myocardium and subsequently enhance early survival and therapeutic potential of implanted bone marrow mesenchymal stem cells (BMSCs). Therefore, in this study we wanted to address: (1) whether LLLI pre‐treatment change the local cardiac micro‐environment after myocardial infarction (MI) and (2) whether the LLLI preconditions enhance early cell survival and thus improve therapeutic angiogenesis and heart function. MI was induced by left anterior descending artery ligation in female rats. A 635 nm, 5 mW diode laser was performed with energy density of 0.96 J/cm² for 150 sec. for the purpose of myocardial precondition. Three weeks later, qualified rats were randomly received with LLLI precondition (n= 26) or without LLLI precondition (n= 27) for LLLI precondition study. Rats that received thoracotomy without coronary ligation were served as sham group (n= 24). In the cell survival study, rats were randomly divided into 4 groups: serum‐free culture media injection (n= 8), LLLI precondition and culture media injection (n= 8), 2 million male BMSCs transplantation without LLLI pre‐treatment (n= 26) and 2 million male BMSCs transplantation with LLLI precondition (n= 25) group, respectively. Vascular endothelial growth factor (VEGF), glucose‐regulated protein 78 (GRP78), superoxide dismutase (SOD) and malondialdehyde (MDA) in the infarcted myocardium were evaluated by Western blotting, real‐time PCR and colorimetry, respectively, at 1 hr, 1 day and 1 week after laser irradiation. Cell survival was assayed with quantitative real‐time PCR to identify Y chromosome gene and apoptosis was assayed with transferase‐mediated dUTP end labelling staining. Capillary density, myogenic differentiation and left ventricular function were tested by immunohistochemistry and echocardiography, respectively, at 1 week. After LLLI precondition, increased VEGF and GRP78 expression, as well as the enhanced SOD activity and inhibited MDA production, was observed. Compared with BMSC transplantation and culture media injection group, although there was no difference in the improved heart function and myogenic differentiation, LLLI precondition significantly enhanced early cell survival rate by 2‐fold, decreased the apoptotic percentage of implanted BMSCs in infarcted myocardium and thus increased the number of newly formed capillaries. Taken together, LLLI precondition could be a novel non‐invasive approach for intraoperative cell transplantation to enhance cell early survival and therapeutic potential.     

Use of human embryonic stem cell derived-mesenchymal cells for cardiac repair

Human mesenchymal stem cells (hMSC) have proven beneficial in the repair and preservation of infarcted myocardium. Unfortunately, MSCs represent a small portion of the bone marrow and require ex vivo expansion. To further advance the clinical usefulness of cellular cardiomyoplasty, derivation of "MSC-like" cells that can be made available "off-the-shelf" are desirable. Recently, human embryonic stem cell-derived mesenchymal cells (hESC-MC) were described. We investigated the efficacy of hESC-MC for cardiac repair after myocardial infarction (MI) compared to hMSC. Because of increased efficacy of cell delivery, cells were embedded into collagen patches and delivered to infarcted myocardium. Culture of hMSC and hESC-MCs in collagen patches did not induce differentiation or significant loss in viability. Transplantation of hMSC and hES-MC patches onto infarcted myocardium of athymic nude rats prevented adverse changes in infarct wall thickness and fractional area change compared to a non-viable patch control. Hemodynamic assessment showed that hMSCs and hES-MC patch application improved end diastolic pressure equivalently. There were no changes in systolic function. hES-MC and hMSC construct application enhanced neovessel formation compared to a non-viable control, and each cell type had similar efficacy in stimulating endothelial cell growth in vitro. In summary, the use of hES-MC provides similar efficacy for cellular cardiomyoplasty as compared to hMSC and may be considered a suitable alternative for cell therapy.     

Pan-epicardial lineage tracing reveals that epicardium derived cells give rise to myofibroblasts and perivascular cells during zebrafish heart regeneration

Myocardial infarction (MI) leads to a severe loss of cardiomyocytes, which in mammals are replaced by scar tissue. Epicardial derived cells (EPDCs) have been reported to differentiate into cardiomyocytes during development, and proposed to have cardiomyogenic potential in the adult heart. However, mouse MI models reveal little if any contribution of EPDCs to myocardium. In contrast to adult mammals, teleosts possess a high myocardial regenerative capacity. To test if this advantage relates to the properties of their epicardium, we studied the fate of EPDCs in cryoinjured zebrafish hearts. To avoid the limitations of genetic labelling, which might trace only a subpopulation of EPDCs, we used cell transplantation to track all EPDCs during regeneration. EPDCs migrated to the injured myocardium, where they differentiated into myofibroblasts and perivascular fibroblasts. However, we did not detect any differentiation of EPDCs nor any other non-cardiomyocyte population into cardiomyocytes, even in a context of impaired cardiomyocyte proliferation. Our results support a model in which the epicardium promotes myocardial regeneration by forming a cellular scaffold, and suggests that it might induce cardiomyocyte proliferation and contribute to neoangiogenesis in a paracrine manner.     

VEGF enhances functional improvement of postinfarcted hearts by transplantation of ESC-differentiated cells.

Despite considerable advances in medicine, the incidence of heart failure remains high in patients after myocardial infarction (MI). This study investigated the effects of engrafted early-differentiated cells (EDCs) from mouse embryonic stem cells, with or without transfection of vascular endothelial growth factor (VEGF) cDNA (phVEGF(165)), on cardiac function in postinfarcted mice. EDCs were transfected with green fluorescent protein (GFP) cDNA and transplanted into infarcted myocardium. Compared with the MI mice receiving cell-free medium, cardiac function was significantly improved in the MI mice 6 wk after transplantation of EDCs. Moreover, improvement of heart function was significantly greater in the mice implanted with EDCs overexpressing VEGF (EDCs-VEGF) than with EDCs alone. Frozen sections of infarcted myocardium with EDCs or EDCs-VEGF transplantation showed GFP-positive tissue. The area with positive immunostaining for cardiac troponin I and alpha-myosin heavy chain was larger in injured myocardium with EDCs or EDCs-VEGF transplantation than with medium injection. Transplantation of EDCs or EDCs-VEGF significantly increased the number of blood vessels in the MI area. However, the density of capillaries was significantly higher in the EDCs-VEGF animals than in the EDC mice. Double staining for GFP and connexin-43 was positive in injured myocardium with EDC transplantation. Our data demonstrate that engrafted EDCs or EDCs-VEGF regenerated cardiac tissue and significantly improved cardiac function in postinfarcted hearts. The novel EDCs-VEGF synergistic approach may have an important impact on future cell therapy for patients experiencing MI or heart failure.     

Cardiac telocytes were decreased during myocardial infarction and their therapeutic effects for ischaemic heart in rat

Recently, cardiac telocytes were found in the myocardium. However, the functional role of cardiac telocytes and possible changes in the cardiac telocyte population during myocardial infarction in the myocardium are not known. In this study, the role of the recently identified cardiac telocytes in myocardial infarction (MI) was investigated. Cardiac telocytes were distributed longitudinally and within the cross network of the myocardium, which was impaired during MI. Cardiac telocytes in the infarction zone were undetectable from approximately 4 days to 4 weeks after an experimental coronary occlusion was used to induce MI. Although cardiac telocytes in the non‐ischaemic area of the ischaemic heart experienced cell death, the cell density increased approximately 2 weeks after experimental coronary occlusion. The cell density was then maintained at a level similar to that observed 1–4 days after left anterior descending coronary artery (LAD)‐ligation, but was still lower than normal after 2 weeks. We also found that simultaneous transplantation of cardiac telocytes in the infarcted and border zones of the heart decreased the infarction size and improved myocardial function. These data indicate that cardiac telocytes, their secreted factors and microvesicles, and the microenvironment may be structurally and functionally important for maintenance of the physiological integrity of the myocardium. Rebuilding the cardiac telocyte network in the infarcted zone following MI may be beneficial for functional regeneration of the infarcted myocardium.     

Epicardium‐derived cells (EPDCs) in development,cardiac disease and repair of ischemia

The proepicardial-derived epicardium covers the myocardium and after a process of epithelial–mesenchymal transition (EMT) forms epicardium-derived cells (EPDCs). These cells migrate into the myocardium and show an essential role in the induction of the ventricular compact myocardium and the differentiation of the Purkinje fibres. EPDCs are furthermore the source of the interstitial fibroblast, the coronary smooth muscle cell and the adventitial fibroblast. The possible differentiation into cardiomyocytes, endothelial cells and the recently described telocyte and other cells in the cardiac stem cell niche needs further investigation. Surgically or genetically disturbed epicardial and EPDC differentiation leads to a spectrum of abnormalities varying from thin undifferentiated myocardium, which can be embryonic lethal, to a diminished coronary vascular bed with even absent main coronary arteries. The embryonic potential of EPDCs has been translated to both structural and functional congenital malformations and adult cardiac disease, like development of Ebstein’s malformation, arrhythmia and cardiomyopathies. Furthermore, the use of adult EPDCs as a stem cell source has been explored, showing in an animal model of myocardial ischemia the recapitulation of the embryonic program with improved function, angiogenesis and less adverse remodeling. Combining EPDCs and adult cardiomyocyte progenitor cells synergistically improved these results. The contribution of injected EPDCs was instructive rather than constructive. The finding of reactivation of the endogenous epicardium in ischemia with re-expression of developmental genes and renewed EMT marks the onset of a novel therapeutic focus.     

Bone marrow mesenchymal stem cells protected post‐infarcted myocardium against arrhythmias via reversing potassium channels remodelling

Bone marrow mesenchymal stem cells (BMSCs) emerge as a promising approach for treating heart diseases. However, the effects of BMSCs‐based therapy on cardiac electrophysiology disorders after myocardial infarction were largely unclear. This study was aimed to investigate whether BMSCs transplantation prevents cardiac arrhythmias and reverses potassium channels remodelling in post‐infarcted hearts. Myocardial infarction was established in male SD rats, and BMSCs were then intramyocardially transplanted into the infarcted hearts after 3 days. Cardiac electrophysiological properties in the border zone were evaluated by western blotting and whole‐cell patch clamp technique after 2 weeks. We found that BMSCs transplantation ameliorated the increased heart weight index and the impaired LV function. The survival of infarcted rats was also improved after BMSCs transplantation. Importantly, electrical stimulation‐induced arrhythmias were less observed in BMSCs‐transplanted infarcted rats compared with rats without BMSCs treatment. Furthermore, BMSCs transplantation effectively inhibited the prolongation of action potential duration and the reduction of transient and sustained outward potassium currents in ventricular myocytes in post‐infarcted rats. Consistently, BMSCs‐transplanted infarcted hearts exhibited the increased expression of K_V4.2, K_V4.3, K_V1.5 and K_V2.1 proteins when compared to infarcted hearts. Moreover, intracellular free calcium level, calcineurin and nuclear NFATc3 protein expression were shown to be increased in infarcted hearts, which was inhibited by BMSCs transplantation. Collectively, BMSCs transplantation prevented ventricular arrhythmias by reversing cardiac potassium channels remodelling in post‐infarcted hearts.