Choice of cell-delivery route for skeletal myoblast transplantation for treating post-infarction chronic heart failure in rat

Stem cell and exosome therapies for regenerating damaged myocardium in heart failure

Finding novel treatments for cardiovascular diseases (CVDs) is a hot topic in medicine; cell-based therapies have reported promising news for controlling dangerous complications of heart disease such as myocardial infarction (MI) and heart failure (HF). Various progenitor/stem cells were tested in various in-vivo, in-vitro, and clinical studies for regeneration or repairing the injured tissue in the myocardial to accelerate the healing. Fetal, adult, embryonic, and induced pluripotent stem cells (iPSC) have revealed the proper potency for cardiac tissue repair. As an essential communicator among cells, exosomes with specific contacts (proteins, lncRNAs, and miRNAs) greatly promote cardiac rehabilitation. Interestingly, stem cell-derived exosomes have more efficiency than stem cell transplantation. Therefore, stem cells induced pluripotent stem cells (iPSCs), embryonic stem cells (ESCs), cardiac stem cells (CDC), and skeletal myoblasts) and their-derived exosomes will probably be considered an alternative therapy for CVDs remedy. In addition, stem cell-derived exosomes have been used in the diagnosis/prognosis of heart diseases. In this review, we explained the advances of stem cells/exosome-based treatment, their beneficial effects, and underlying mechanisms, which will present new insights in the clinical field in the future.

The Progress of Stem Cell Therapy in Myocardial-Infarcted Heart Regeneration: Cell Sheet Technology

Various tissues, including the heart, cornea, bone, esophagus, bladder and liver, have been vascularized using the cell sheet technique. It overcomes the limitations of existing techniques by allowing small layers of the cell sheet to generate capillaries on their own, and it can also be used to vascularize tissue-engineered transplants. Cell sheets eliminate the need for traditional tissue engineering procedures such as isolated cell injections and scaffold-based technologies, which have limited applicability. While cell sheet engineering can eliminate many of the drawbacks, there are still a few challenges that need to be addressed. The number of cell sheets that can be layered without triggering core ischemia or hypoxia is limited. Even when scaffold-based technologies are disregarded, strategies to tackle this problem remain a substantial impediment to the efficient regeneration of thick, living three-dimensional cell sheets. In this review, we summarize the cell sheet technology in myocardial infarcted tissue regeneration.

Optimal Delivery Route of Mesenchymal Stem Cells for Cardiac Repair: The Path to Good Clinical Practice

Research has shown that mesenchymal stem cells (MSCs) could be a promising therapy for treating progressive heart disease. However, translation into clinics efficiently and successfully has proven to be much more complicated. Many questions remain for optimizing treatment. Application method influences destiny of MSCs and afterwards impacts results of procedure, yet there is no general agreement about most suitable method of MSC delivery in the clinical setting. Herein, we explain principle of most-frequent MSCs delivery techniques in cardiology. This chapter summarizes crucial translational obstacles of clinical employment of MSCs for cardiac repair when analysed trough a prism of latest research centred on different techniques of MSCs application.

Engineered cell-degradable poly(2-alkyl-2-oxazoline) hydrogel for epicardial placement of mesenchymal stem cells for myocardial repair

Epicardial placement of mesenchymal stromal cells (MSCs) is a promising strategy for cardiac repair post-myocardial infarction, but requires the design of biomaterials to maximise the retention of donor cells on the heart surface and control their phenotype. To this end, we propose the use of a poly(2-alkyl-2-oxazoline) (POx) derivative, based on 2-ethyl-2-oxazoline and 2-butenyl-2-oxazoline. This POx polymer can be cured rapidly (less than 2 min) via photo-irradiation due to the use of di-cysteine cell degradable peptides. We report that the cell-degradable properties of the resulting POx hydrogels enables the regulation of cell protrusion in corresponding 3D matrices and that this, in turn, regulates the secretory phenotype of MSCs. In particular, the expression of pro-angiogenic genes was upregulated in partially cell-degradable POx hydrogels. Improved angiogenesis was confirmed in an in vitro microfluidic assay. Finally, we confirmed that, owing to the excellent tissue adhesive properties of thiol-ene crosslinked hydrogels, the epicardial placement of MSC-loaded POx hydrogels promoted the recovery of cardiac function and structure with reduced interstitial fibrosis and improved neovascular formation in a rat myocardial infarction model. This report demonstrates that engineered synthetic hydrogels displaying controlled mechanical, cell degradable and bioactive properties are particularly attractive candidates for the epicardial placement of stem cells to promote cardiac repair post myocardial infarction.

Therapeutic approach for global myocardial injury using bone marrow-derived mesenchymal stem cells by cardiac support device in rats

Bone marrow-derived mesenchymal stem cells (BMSCs) have been considered a promising therapeutic approach to cardiovascular disease. This study intends to compare the effect of BMSCs through a standard active cardiac support device (ASD) and intravenous injection on global myocardial injury induced by isoproterenol. BMSCs were cultured in vitro, and the transplanted cells were labeled with a fluorescent dye CM-Dil. Isoproterenol (ISO) was injected into the rats; 2 weeks later, the labeled cells were transplanted into ISO-induced heart-jury rats through the tail vein or ASD device for 5 days. The rats were sacrificed on the first day, the third day, and the fifth day after transplantation to observe the distribution of cells in the myocardium by fluorescence microscopy. The hemodynamic indexes of the left ventricle were measured before sacrificing. H&E staining and Masson's trichrome staining were used to evaluate the cardiac histopathology. In the ASD groups, after 3 days of transplantation, there were a large number of BMSCs on the epicardial surface, and after 5 days of transplantation, BMSCs were widely distributed in the ventricular muscle. But in the intravenous injection group, there were no labeled-BMSCs distributed. In the ASD + BMSCs-three days treated group and ASD + BMSCs -five days-treated group, left ventricular systolic pressure (LVSP), the maximum rate of left ventricular pressure rise (+dP/dt), the maximum rate of left ventricular pressure decline (-dP/dt) increased compared with model group and intravenous injection group (P < 0.05). By giving BMSCs through ASD device, cells can rapidly and widely distribute in the myocardium and significantly improve heart function.

Mending a broken heart: current strategies and limitations of cell-based therapy

The versatility of pluripotent stem cells, attributable to their unlimited self-renewal capacity and plasticity, has sparked a considerable interest for potential application in regenerative medicine. Over the past decade, the concept of replenishing the lost cardiomyocytes, the crux of the matter in ischemic heart disease, with pluripotent stem cell-derived cardiomyocytes (PSC-CM) has been validated with promising pre-clinical results. Nevertheless, clinical translation was hemmed in by limitations such as immature cardiac properties, long-term engraftment, graft-associated arrhythmias, immunogenicity, and risk of tumorigenicity. The continuous progress of stem cell-based cardiac therapy, incorporated with tissue engineering strategies and delivery of cardio-protective exosomes, provides an optimistic outlook on the development of curative treatment for heart failure. This review provides an overview and current status of stem cell-based therapy for heart regeneration, with particular focus on the use of PSC-CM. In addition, we also highlight the associated challenges in clinical application and discuss the potential strategies in developing successful cardiac-regenerative therapy.

Systemic and local delivery of mesenchymal stem cells for heart renovation: Challenges and innovations

In the beginning stage of heart disease, the blockage of blood flow frequently occurs due to the persistent damage and even death of myocardium. Cicatricial tissue developed after the death of myocardium can affect heart function, which ultimately leads to heart failure. In recent years, several studies carried out about the use of stem cells such as embryonic, pluripotent, cardiac and bone marrow-derived stem cells as well as myoblasts to repair injured myocardium. Current studies focus more on finding appropriate measures to enhance cell homing and survival in order to increase paracrine function. Until now, there is no universal delivery route for mesenchymal stem cells (MSCs) for different diseases. In this review, we summarize the advantages and challenges of the systemic and local pathways of MSC delivery. In addition, we also describe some advanced measures of cell delivery to improve the efficiency of transplantation. The combination of cells and therapeutic substances could be the most reliable method, which allows donor cells to deliver sufficient amounts of paracrine factors and provide long-lasting effects. The cardiac support devices or tissue engineering techniques have the potential to facilitate the controlled release of stem cells on local tissue for a sustained period. A novel promising epicardial drug delivery system is highlighted here, which not only provides MSCs with a favorable environment to promote retention but also increases the contact area and a number of cells recruited in the heart muscle.

On-site fabrication of Bi-layered adhesive mesenchymal stromal cell-dressings for the treatment of heart failure

Mesenchymal stromal/stem cell (MSC)-based therapy is a promising approach for the treatment of heart failure. However, current MSC-delivery methods result in poor donor cell engraftment, limiting the therapeutic efficacy. To address this issue, we introduce here a novel technique, epicardial placement of bi-layered, adhesive dressings incorporating MSCs (MSC-dressing), which can be easily fabricated from a fibrin sealant film and MSC suspension at the site of treatment. The inner layer of the MSC dressing, an MSC-fibrin complex, promptly and firmly adheres to the heart surface without sutures or extra glues. We revealed that fibrin improves the potential of integrated MSCs through amplifying their tissue-repair abilities and activating the Akt/PI3K self-protection pathway. Outer collagen-sheets protect the MSC-fibrin complex from abrasion by surrounding tissues and also facilitates easy handling. As such, the MSC-dressing technique not only improves initial retention and subsequent maintenance of donor MSCs but also augment MSC's reparative functions. As a result, this technique results in enhanced cardiac function recovery with improved myocardial tissue repair in a rat ischemic cardiomyopathy model, compared to the current method. Dose-dependent therapeutic effects by this therapy is also exhibited. This user-friendly, highly-effective bioengineering technique will contribute to future success of MSC-based therapy.

Stem cells as therapy for heart disease: iPSCs, ESCs, CSCs, and skeletal myoblasts

Heart Diseases are serious and global public health concern. In spite of remarkable therapeutic developments, the prediction of patients with Heart Failure (HF) is weak, and present therapeutic attitudes do not report the fundamental problem of the cardiac tissue loss. Innovative therapies are required to reduce mortality and limit or abolish the necessity for cardiac transplantation. Stem cell-based therapies applied to the treatment of heart disease is according to the understanding that natural self-renewing procedures are inherent to the myocardium, nonetheless may not be adequate to recover the infarcted heart muscle. Following the first account of cell therapy in heart diseases, examination has kept up to rapidity; besides, several animals and human clinical trials have been conducted to preserve the capacity of numerous stem cell population in advance cardiac function and decrease infarct size. The purpose of this study was to censoriously evaluate the works performed regarding the usage of four major subgroups of stem cells, including induced Pluripotent Stem Cells (iPSC), Embryonic Stem Cells (ESCs), Cardiac Stem Cells (CDC), and Skeletal Myoblasts, in heart diseases, at the preclinical and clinical studies. Moreover, it is aimed to argue the existing disagreements, unsolved problems, and prospect directions.

Self-assembling peptide hydrogel enables instant epicardial coating of the heart with mesenchymal stromal cells for the treatment of heart failure

Transplantation of mesenchymal stromal cells (MSCs) is an emerging therapy for the treatment of heart failure. However, the delivery method of MSC is currently suboptimal. The use of self-assembling peptide hydrogels, including PuraMatrix® (PM; 3-D Matrix, Ltd), has been reported for clinical hemostasis and in research models. This study demonstrates the feasibility and efficacy of an advanced approach for MSC-therapy, that is coating of the epicardium with the instantly-produced PM hydrogel incorporating MSCs (epicardial PM-MSC therapy). We optimized the conditions/procedure to produce "instant" 2PM-MSC complexes. After spreading on the epicardium by easy pipetting, the PM-MSC complex promptly and stably adhere to the beating heart. Of note, this treatment achieved more extensive improvement of cardiac function, with greater initial retention and survival of donor MSCs, compared to intramyocardial MSC injection in rat heart failure models. This enhanced efficacy was underpinned by amplified myocardial upregulation of a group of tissue repair-related genes, which led to enhanced repair of the damaged myocardium, i.e. augmented microvascular formation and reduced interstitial fibrosis. These data suggest a potential for epicardial PM-MSC therapy to be a widely-adopted treatment of heart failure. This approach may also be useful for treating diseases in other organs than the heart.

Retrograde Coronary Venous Infusion as a Delivery Strategy in Regenerative Cardiac Therapy: an Overview of Preclinical and Clinical Data

An important aspect of cell therapy in the field of cardiac disease is safe and effective delivery of cells. Commonly used delivery strategies such as intramyocardial injection and intracoronary infusion both present with advantages and disadvantages. Therefore, alternative delivery routes are explored, such as retrograde coronary venous infusion (RCVI). Our aim is to evaluate safety and efficiency of RCVI by providing a complete overview of preclinical and clinical studies applying RCVI in a broad range of disease types and experimental models. Available data on technical and safety aspects of RCVI are incomplete and insufficient. Improvement of cardiac function is seen after cell delivery via RCVI. However, cell retention in the heart after RCVI appears inferior compared to intracoronary infusion and intramyocardial injection. Adequately powered confirmatory studies on retention rates and safety are needed to proceed with RCVI in the future.

Myoblast transplantation improves cardiac function after myocardial infarction through attenuating inflammatory responses

Myocardial infarction (MI) is a highly prevalent cardiac emergency, which results in adverse cardiac remodeling and then exacerbates progressive heart failure. Inflammatory responses in cardiac tissue after MI is necessary for myocardium repair and wound healing. However, the excessive inflammation is also a key component of subsequent heart failure pathology. Myoblast transplantation after MI have been fulfilled attractive effects on cardiac repair, but the complications of transplantation and the underlying mechanisms have not been fully elucidated. Here, we found that human myoblast transplantation into minipig myocardium decreased the infiltration of inflammatory cells, the expression levels of many pro-inflammatory genes and the activation of inflammation-related signal pathways, while upregulated the expression levels of anti-inflammatory genes such as IL-10 in cardiac tissue of minipig post-MI, which was contributed to the improved cardiac function, the decreased infarct area and the attenuated myocardial fibrosis. Moreover, co-culture of human myoblasts inhibited the production of IL-1β and TNF-α as well as activation of MAPK and NF-κB signaling pathway induced by damage-associated molecular patterns such as HMGB1 and HSP60 in human THP-1 cells, which was partially attributed to the up-regulated production of IL-10. Collectively, these results indicate that myoblast transplantation ameliorates heart injury and improves cardiac function post-MI through inhibiting the inflammatory response, which provides the novel mechanism for myoblast transplantation therapy of MI.

Skeletal Myoblast Cell Sheet Implantation Ameliorates Both Systolic and Diastolic Cardiac Performance in Canine Dilated Cardiomyopathy Model

Background

Improving both systolic and diastolic function may be the most important factor in treating heart failure. In this study, we hypothesized that cell-sheet transplantation could improve these function in the damaged heart.

Methods

We generated a dilated cardiomyopathy model in beagles by continuous ventricle pacing at 240 beats per minute. After 4 weeks, the beagles underwent skeletal myoblast cell sheet transplantation (SMCST) or a sham operation, and rapid ventricle pacing continued for an additional 4 weeks. Six of the e8 beagles treated by SMCST were still alive 4 weeks after the procedure. We evaluated SMCST's cardiotherapeutic effects by comparing beagles treated by SMCST with beagles that underwent a sham operation (control, n = 5).

Results

Diastolic function, as well as systolic function improved significantly in the SMCST group as compared with the sham group (control vs SMCST group, median [interquartile range]: E/E', 16 [0.9] vs 11 [1.0]; P < 0.001; tau, 47 [6.0] vs 36 [4.4] ms: P = 0.005. Ejection fraction, 22 (6.0) versus 46 (7.5) %, P < 0.001; end-systolic elastance, 2.5 (0.4) versus 8.2 (3.5) mm Hg/ml, P = 0.001). Histological examination revealed that the volume of collagen I and the collagen I/III ratio in the myocardium were significantly higher in the control than that in the SMCST group (collagen I, 6.0 [0.8] vs 2.6 [1.3]; P = 0.006; collagen I/III ratio, 4.8 [1.7] vs 1.2 [0.4]; P = 0.010).

Conclusions

The potential of SMCST to ameliorate both systolic and diastolic performance was proven. The SMCST may be an alternative therapy of conventional medical treatment in the dilated cardiomyopathy heart.

Bioengineered uterine tissue supports pregnancy in a rat model

OBJECTIVE

To create a bioengineered uterine patch for uterine repair of a partially defect uterus.

DESIGN

Three different decellularized uterine scaffolds were recellularized in vitro with primary uterine cells and green fluorescent protein- (GPF-) labeled bone marrow-derived mesenchymal stem cells (GFP-MSCs). The patches were transplanted in vivo to investigate their tissue adaptation and supporting capacity during pregnancy.

SETTING

Research laboratory.

ANIMAL(S)

Female Lewis rats (n = 9) as donors to generate whole-uterus scaffolds using three different protocols (n = 3 per protocol); Sprague Dawley rats (n = 40) for primary uterus cell isolation procedures (n = 10) and for transplantation/pregnancy studies (n = 30); and male Sprague Dawley rats (n = 12) for mating.

INTERVENTION(S)

Decellularization was achieved by whole-uterus perfusion with buffered or nonbuffered Triton-X100 and dimethyl sulfoxide (DMSO; group P1/P2) or with sodium deoxycholate (group P3). Primary uterine cells and GFP-MSCs were used to develop uterine tissue constructs, which were grafted to uteri with partial tissue defects.

MAIN OUTCOME MEASURE(S)

Recellularization efficiency and graft quality were analyzed morphologically, immunohistochemically, and by real-time quantitative polymerase chain reaction (PCR). The location and number of fetuses were documented during pregnancy days 16-20.

RESULT(S)

Pregnancy and fetal development were normal in groups P1 and P2, with fetal development over patched areas. Group P3 showed significant reduction of fetal numbers, and embryos were not seen in the grafted area. Quantitative PCR and immunohistochemistry revealed uterus-like tissue in the patches, which had been further reconstructed by infiltrating host cells after transplantation.

CONCLUSION(S)

Primary uterine cells and MSCs can be used to reconstruct decellularized uterine tissue. The bioengineered patches made from triton-X100+DMSO-generated scaffolds were supportive during pregnancy. These protocols should be explored further to develop suitable grafting material to repair partially defect uteri and possibly to create a complete bioengineered uterus.

Stem cell therapy for heart failure

"During the past decade, studies in animals and humans have suggested that cell therapy has positive effects for the treatment of heart failure. This clinical effect may be mediated by angiogenesis and reduction in fibrosis rather than by regeneration of myocytes. Increased microvasculature and decreased scar also likely lead to improved cardiac function in the failing heart. The effects of cell therapy are not limited to one type of cell or delivery technique. Well-designed, large-scale, randomized clinical trials with objective end points will help to fully realize the therapeutic potential of cell-based therapy for treating heart failure."

Xenotransplantation of Human Cardiomyocyte Progenitor Cells Does Not Improve Cardiac Function in a Porcine Model of Chronic Ischemic Heart Failure. Results from a Randomized, Blinded, Placebo Controlled Trial

BACKGROUND

Recently cardiomyocyte progenitor cells (CMPCs) were successfully isolated from fetal and adult human hearts. Direct intramyocardial injection of human CMPCs (hCMPCs) in experimental mouse models of acute myocardial infarction significantly improved cardiac function compared to controls.

AIM

Here, our aim was to investigate whether xenotransplantation via intracoronary infusion of fetal hCMPCs in a pig model of chronic myocardial infarction is safe and efficacious, in view of translation purposes.

METHODS & RESULTS

We performed a randomized, blinded, placebo controlled trial. Four weeks after ischemia/reperfusion injury by 90 minutes of percutaneous left anterior descending artery occlusion, pigs (n = 16, 68.5 ± 5.4 kg) received intracoronary infusion of 10 million fetal hCMPCs or placebo. All animals were immunosuppressed by cyclosporin (CsA). Four weeks after infusion, endpoint analysis by MRI displayed no difference in left ventricular ejection fraction, left ventricular end diastolic and left ventricular end systolic volumes between both groups. Serial pressure volume (PV-)loop and echocardiography showed no differences in functional parameters between groups at any timepoint. Infarct size at follow-up, measured by late gadolinium enhancement MRI showed no difference between groups. Intracoronary pressure and flow measurements showed no signs of coronary obstruction 30 minutes after cell infusion. No premature death occurred in cell treated animals.

CONCLUSION

Xenotransplantation via intracoronary infusion of hCMPCs is feasible and safe, but not associated with improved left ventricular performance and infarct size compared to placebo in a porcine model of chronic myocardial infarction.

Bone marrow-derived mesenchymal stem cells for the treatment of heart failure

Heart failure remains a major cause of death and disability, requiring rapid development of new therapies. Bone marrow-derived mesenchymal stem cell (MSC)-based therapy is an emerging approach for the treatment of both acute and chronic heart failure. Following successful experimental studies in a range of models, more than 40 clinical trials of MSC-based therapy for heart failure have now been registered, and the results of completed clinical trials so far have shown feasibility and safety of this approach with therapeutic potential suggested (though preliminarily). However, there appear to be several critical issues to be solved before this treatment could become a widespread standard therapy for heart failure. In this review, we comprehensively and systemically summarize a total of 73 preclinical studies and 11 clinical trial reports published to date. By analyzing the data in these reports, (1) improvement in the cell delivery method to the heart in order to enhance donor cell engraftment, (2) elucidation of mechanisms underpinning the therapeutic effects of the treatment differentiation and/or treatment secretion, and (3) validation of the utility of allogeneic MSCs which could enhance the efficacy and expand the application/indication of this therapeutic approach are highlighted as future perspectives. These important respects are further discussed in this review article with referencing latest scientific and clinical information.

Mesenchymal Stem Cells for Cardiac Regenerative Therapy: Optimization of Cell Differentiation Strategy

With the high mortality rate, coronary heart disease (CHD) has currently become a major life-threatening disease. The main pathological change of myocardial infarction (MI) is the induction of myocardial necrosis in infarction area which finally causes heart failure. Conventional treatments cannot regenerate the functional cell efficiently. Recent researches suggest that mesenchymal stem cells (MSCs) are able to differentiate into multiple lineages, including cardiomyocyte-like cells in vitro and in vivo, and they have been used for the treatment of MI to repair the injured myocardium and improve cardiac function. In this review, we will focus on the recent progress on MSCs derived cardiomyocytes for cardiac regeneration after MI.

Comparison of arrhythmogenicity and proinflammatory activity induced by intramyocardial or epicardial myoblast sheet delivery in a rat model of ischemic heart failure

Although cell therapy of the failing heart by intramyocardial injections of myoblasts to results in regenerative benefit, it has also been associated with undesired and prospectively fatal arrhythmias. We hypothesized that intramyocardial injections of myoblasts could enhance inflammatory reactivity and facilitate electrical cardiac abnormalities that can be reduced by epicardial myoblast sheet delivery. In a rat model of ischemic heart failure, myoblast therapy either by intramyocardial injections or epicardial cell sheets was given 2 weeks after occlusion of the coronary artery. Ventricular premature contractions (VPCs) were assessed, using an implanted three-lead electrocardiograph at 1, 7, and 14 days after therapy, and 16-point epicardial electropotential mapping (EEPM) was used to evaluate ventricular arrhythmogenicity under isoproterenol stress. Cardiac functioning was assessed by echocardiography. Both transplantation groups showed therapeutic benefit over sham therapy. However, VPCs were more frequent in the Injection group on day 1 and day 14 after therapy than in animals receiving epicardial or sham therapy (p < 0.05 and p < 0.01, respectively). EEPM under isoproterenol stress showed macroreentry at the infarct border area, leading to ventricular tachycardias in the Injection group, but not in the myoblast sheet- or sham-treated groups (p = 0.045). Both transplantation types modified the myocardial cytokine expression profile. In animals receiving epicardial myoblast therapy, selective reductions in the expressions of interferon gamma, interleukin (IL)-1β and IL12 were observed, accompanied by reduced infiltration of inflammatory CD11b- and CD68-positive leukocytes, compared with animals receiving myoblasts as intramyocardial injections. Intramyocardial myoblast delivery was associated with enhanced inflammatory and immunomodulatory reactivity and increased frequency of VPCs. In comparison to intramyocardial injection, the epicardial route may serve as the preferred method of skeletal myoblast transplantation to treat heart failure.

Central Sympathetic Activation and Arrhythmogenesis during Acute Myocardial Infarction: Modulating Effects of Endothelin-B Receptors

Sympathetic activation during acute myocardial infarction (MI) is an important arrhythmogenic mechanism, but the role of central autonomic inputs and their modulating factors remain unclear. Using the in vivo rat-model, we examined the effects of clonidine, a centrally acting sympatholytic agent, in the presence or absence of myocardial endothelin-B (ETB) receptors. We studied wild-type (n = 20) and ETB-deficient rats (n = 20) after permanent coronary ligation, with or without pretreatment with clonidine. Cardiac rhythm was continuously recorded for 24 h by implantable telemetry devices, coupled by the assessment of autonomic and heart failure indices. Sympathetic activation and arrhythmogenesis were more prominent in ETB-deficient rats during the early phase post-ligation. Clonidine improved these outcomes throughout the observation period in ETB-deficient rats, but only during the delayed phase in wild-type rats. However, this benefit was counterbalanced by atrioventricular conduction abnormalities and by higher incidence of heart failure, the latter particularly evident in ETB-deficient rats. Myocardial ETB-receptors attenuate the arrhythmogenic effects of central sympathetic activation during acute MI. ETB-receptor deficiency potentiates the sympatholytic effects of clonidine and aggravates heart failure. The interaction between endothelin and sympathetic responses during myocardial ischemia/infarction and its impact on arrhythmogenesis and left ventricular dysfunction merits further investigation.

Functional and Electrical Integration of Induced Pluripotent Stem Cell-Derived Cardiomyocytes in a Myocardial Infarction Rat Heart

In vitro expanded beating cardiac myocytes derived from induced pluripotent stem cells (iPSC-CMs) are a promising source of therapy for cardiac regeneration. Meanwhile, the cell sheet method has been shown to potentially maximize survival, functionality, and integration of the transplanted cells into the heart. It is thus hypothesized that transplanted iPSC-CMs in a cell sheet manner may contribute to functional recovery via direct mechanical effects on the myocardial infarction (MI) heart. F344/NJcl-rnu/rnu rats were left coronary artery ligated (n = 30), followed by transplantation of Dsred-labeled iPSC-CM cell sheets of murine origin over the infarct heart surface. Effects of the treatment were assessed, including in vivo molecular/cellular evaluations using a synchrotron radiation scattering technique. Ejection fraction and activation recovery interval were significantly greater from day 3 onward after iPSC-CM transplantation compared to those after sham operation. A number of transplanted iPSC-CMs were present on the heart surface expressing cardiac myosin or connexin 43 over 2 weeks, assessed by immunoconfocal microscopy, while mitochondria in the transplanted iPSC-CMs gradually showed mature structure as assessed by electron microscopy. Of note, X-ray diffraction identified 1,0 and 1,1 equatorial reflections attributable to myosin and actin-myosin lattice planes typical of organized cardiac muscle fibers within the transplanted cell sheets at 4 weeks, suggesting cyclic systolic myosin mass transfer to actin filaments in the transplanted iPSC-CMs. Transplantation of iPSC-CM cell sheets into the heart yielded functional and electrical recovery with cyclic contraction of transplanted cells in the rat MI heart, indicating that this strategy may be a promising cardiac muscle replacement therapy.

Stem cell therapy and breast cancer treatment: review of stem cell research and potential therapeutic impact against cardiotoxicities due to breast cancer treatment

A new problem has emerged with the ever-increasing number of breast cancer survivors. While early screening and advances in treatment have allowed these patients to overcome their cancer, these treatments often have adverse cardiovascular side effects that can produce abnormal cardiovascular function. Chemotherapeutic and radiation therapy have both been linked to cardiotoxicity; these therapeutics can cause a loss of cardiac muscle and deterioration of vascular structure that can eventually lead to heart failure (HF). This cardiomyocyte toxicity can leave the breast cancer survivor with a probable diagnosis of dilated or restrictive cardiomyopathy (DCM or RCM). While current HF standard of care can alleviate symptoms, other than heart transplantation, there is no therapy that replaces cardiac myocytes that are killed during cancer therapies. There is a need to develop novel therapeutics that can either prevent or reverse the cardiac injury caused by cancer therapeutics. These new therapeutics should promote the regeneration of lost or deteriorating myocardium. Over the last several decades, the therapeutic potential of cell-based therapy has been investigated for HF patients. In this review, we discuss the progress of pre-clinical and clinical stem cell research for the diseased heart and discuss the possibility of utilizing these novel therapies to combat cardiotoxicity observed in breast cancer survivors.

Magnetic targeting enhances retrograde cell retention in a rat model of myocardial infarction

Introduction

Retrograde coronary venous infusion is a promising delivery method for cellular cardiomyoplasty. Poor cell retention is the major obstacle to the establishment of this method as the preferred route for cell delivery. Here, we explored whether magnetic targeting could enhance retrograde cell retention in a rat model of myocardial infarction.

Methods

Rat mesenchymal stem cells were labeled with superparamagnetic oxide nanoparticles. The magnetic responsiveness of MSCs was observed while cells flowed through a tube that served as a model of blood vessels in a 0.6-Tesla magnetic field. In a Sprague–Dawley rat model of acute myocardial infarction, 1 × 10⁶ magnetic mesenchymal stem cells were transjugularly injected into the left cardiac vein while a 0.6-Tesla magnet was placed above the heart. The cardiac retention of transplanted cells was assessed by using quantitative Y chromosome-specific polymerase chain reaction, cardiac magnetic resonance imaging, and optical imaging. Cardiac function was measured by using echocardiography, and histologic analyses of infarct morphology and angiogenesis were obtained.

Results

The flowing iron oxide-labeled mesenchymal stem cells were effectively attracted to the area where the magnet was positioned. Twenty-four hours after cellular retrocoronary delivery, magnetic targeting significantly increased the cardiac retention of transplanted cells by 2.73- to 2.87-fold. Histologic analyses showed that more transplanted cells were distributed in the anterior wall of the left ventricle. The enhanced cell engraftment persisted for at least 3 weeks, at which time, left ventricular remodeling was attenuated, and cardiac function benefit was improved.

Conclusions

These results suggest that magnetic targeting offers new perspectives for retrograde coronary venous delivery to enhance cell retention and subsequent functional benefit in heart diseases.

Retrograde coronary vein infusion of cardiac explant-derived c-Kit+ cells improves function in ischemic heart failure

BACKGROUND

Progenitor cells isolated from cardiac explant-derived cells improve cardiac function after myocardial infarction (MI). To fully realize the therapeutic potential of these cells, it is essential to develop a safe and efficient delivery method. Therefore, the objective of this study was to determine the efficacy of our newly developed approach to retrograde coronary vein (RCV) infusion of cardiac c-Kit(+) cells in a small-animal model of congestive heart failure (CHF).

METHODS

Sprague-Dawley rats underwent experimental MI. After 21 days, cardiac explant-derived c-Kit(+) cells were delivered to both sham and CHF animals using RCV delivery. Vehicle-treated (serum-free medium) sham and CHF animals were used as controls. Cardiac function and heart tissues were evaluated 21 days post-transplantation.

RESULTS

RCV-delivered cells were retained in infarcted hearts for at least 21 days after transplantation. At 21 days post-RCV infusion, the majority of transplanted c-Kit(+)/GFP(+) cells were localized in the left ventricle. Compared with vehicle-treated CHF animals, RCV-treated rats showed a significant improvement in cardiac function. Furthermore, RCV-treated rats exhibited an increase in capillary density, a decrease in total heart collagen, and a reduction in both infarct size and cardiomyocyte hypertrophy when compared with vehicle-treated CHF rats.

CONCLUSIONS

Our study showed that the RCV infusion approach is an efficient technique for targeted cell delivery to the infarcted myocardium. Cardiac c-Kit(+) cells, delivered using RCV infusion ameliorated progression of heart failure, improved cardiac function and retarded myocardial remodeling in heart failure rats.

New coronary retroinfusion technique in the Rat infarct model: transjugular cardiac vein catheterization

Cell delivery via the retrograde coronary route boasts less vessel embolism, myocardial injury, and arrhythmogenicity when compared with those via antegrade coronary administration or myocardial injection. However, conventional insertion into the coronary sinus and consequent bleeding complication prevent its application in small animals. To overcome the complication of bleeding, we described a modified coronary retroinfusion technique via the jugular vein route in rats with myocardial infarction (MI). A flexible wire with a bent end was inserted into the left internal jugular vein and advanced slowly along the left superior vena cava. Under direct vision, the wire was run into the left cardiac vein by rotating the wire and changing the position of its tip. A fine tube was then advanced along the wire to the left cardiac vein. This modified technique showed less lethal hemorrhage than the conventional technique. Retroinfusion via transjugular catheter enabled efficient fluid or cell dissemination to the majority areas of the free wall of the left ventricle, covering the infarcted anterior wall. In conclusion, transjugular cardiac vein catheterization may make retrocoronary infusion a more safe and practical route for delivering cell, drug, and gene therapy into the infarcted myocardium of rats.

Cell therapy for heart failure: a comprehensive overview of experimental and clinical studies, current challenges, and future directions

Despite significant therapeutic advances, the prognosis of patients with heart failure (HF) remains poor, and current therapeutic approaches are palliative in the sense that they do not address the underlying problem of the loss of cardiac tissue. Stem cell-based therapies have the potential to fundamentally transform the treatment of HF by achieving what would have been unthinkable only a few years ago-myocardial regeneration. For the first time since cardiac transplantation, a therapy is being developed to eliminate the underlying cause of HF, not just to achieve damage control. Since the initial report of cell therapy (skeletal myoblasts) in HF in 1998, research has proceeded at lightning speed, and numerous preclinical and clinical studies have been performed that support the ability of various stem cell populations to improve cardiac function and reduce infarct size in both ischemic and nonischemic cardiomyopathy. Nevertheless, we are still at the dawn of this therapeutic revolution. Many important issues (eg, mechanism(s) of action of stem cells, long-term engraftment, optimal cell type(s), and dose, route, and frequency of cell administration) remain to be resolved, and no cell therapy has been conclusively shown to be effective. The purpose of this article is to critically review the large body of work performed with respect to the use of stem/progenitor cells in HF, both at the experimental and clinical levels, and to discuss current controversies, unresolved issues, challenges, and future directions. The review focuses specifically on chronic HF; other settings (eg, acute myocardial infarction, refractory angina) are not discussed.

Choice of cell-delivery route for successful cell transplantation therapy for the heart

The cell-delivery route is one of the major factors influencing the therapeutic effect and complications of cell transplantation therapy for cardiac diseases. There are four major clinically practical routes, with each method having its own advantages and disadvantages. First, intramyocardial injection allows targeted cell delivery into the areas of interest, although this induces mechanical injury, inflammation and islet-like donor cell clusters, leading to limited donor cell survival and arrhythmogenicity. Second, intracoronary injection is less likely to induce inflammation, whereas poor initial cell retention in the heart is a concern. Third, intravenous injection is easy and economical, but cell recruitment into the heart is not frequent. Finally, epicardial placement of 'cell sheets' enables higher efficiency of cell engraftment, but poor integration into the myocardium may be an issue. This review summarizes up-to-date clinical and preclinical knowledge regarding these cell-delivery methods. We further discuss the ways to refine these methods towards optimizing cell transplantation therapy for the heart.

Muscle-derived stem cell sheets support pump function and prevent cardiac arrhythmias in a model of chronic myocardial infarction

Direct intracardiac cell injection for heart repair is hindered by numerous limitations including: cell death, poor spreading of the injected cells, arrhythmia, needle injury, etc. Tissue-engineered cell sheet implantation has the potential to overcome some of these limitations. We evaluated whether the transplantation of a muscle-derived stem cell (MDSC) sheet could improve the regenerative capacity of MDSCs in a chronic model of myocardial infarction. MDSC sheet-implanted mice displayed a reduction in left ventricle (LV) dilation and sustained LV contraction compared with the other groups. The MDSC sheet formed aligned myotubes and produced a significant increase in capillary density and a reduction of myocardial fibrosis compared with the other groups. Hearts transplanted with the MDSC sheets did not display any significant arrhythmias and the donor MDSC survival rate was higher than the direct myocardial MDSC injection group. MDSC sheet implantation yielded better functional recovery of chronic infarcted myocardium without any significant arrhythmic events compared with direct MDSC injection, suggesting this cell sheet delivery system could significantly improve the myocardial regenerative potential of the MDSCs.

Human coronary venous anatomy: implications for interventions

The coronary venous system is a highly variable network of veins that drain the deoxygenated blood from the myocardium. The system is made up of the greater cardiac system, which carries the majority of the deoxygenated blood to the right atrium, and the smaller cardiac system, which drains the blood directly into the heart chambers. The coronary veins are currently being used for several biomedical applications, including but not limited to cardiac resynchronization therapy, ablation therapy, defibrillation, perfusion therapy, and annuloplasty. Knowledge of the details of the coronary venous anatomy is essential for optimal development and delivery of treatments using this vasculature. This article is part of a JCTR special issue on Cardiac Anatomy.

Guiding Differentiation of Stem Cells in Vivo by Tetracycline-Controlled Expression of Key Transcription Factors

Transplantation of stem or progenitor cells is an attractive strategy for cell replacement therapy. However, poor long-term survival and insufficiently reproducible differentiation to functionally appropriate cells in vivo still present major obstacles for translation of this methodology to clinical applications. Numerous experimental studies have revealed that the expression of just a few transcription factors can be sufficient to drive stem cell differentiation toward a specific cell type, to transdifferentiate cells from one fate to another, or to dedifferentiate mature cells to pluripotent stem/progenitor cells (iPSCs). We thus propose here to apply the strategy of expressing the relevant key transcription factors to guide the differentiation of transplanted cells to the desired cell fate in vivo. To achieve this requires tools allowing us to control the expression of these genes in the transplant. Here, we describe drug-inducible systems that allow us to sequentially and timely activate gene expression from the outside, with a particular emphasis on the Tet system, which has been widely and successfully used in stem cells. These regulatory systems offer a tool for strictly limiting gene expression to the respective optimal stage after transplantation. This approach will direct the differentiation of the immature stem/progenitor cells in vivo to the desired cell type.

The use of cell-sheet technique eliminates arrhythmogenicity of skeletal myoblast-based therapy to the heart with enhanced therapeutic effects

BACKGROUND

Clinical application of skeletal myoblast transplantation has been curtailed due to arrhythmogenicity and inconsistent therapeutic benefits observed in previous studies. However, these issues may be solved by the use of a new cell-delivery mode. It is now possible to generate "cell-sheets" using temperature-responsive dishes without artificial scaffolds. This study aimed to validate the safety and efficacy of epicardial placement of myoblast-sheets (myoblast-sheet therapy) in treating heart failure.

METHODS AND RESULTS

After coronary artery ligation in rats, the same numbers of syngeneic myoblasts were transplanted by intramyocardial injection or cell-sheet placement. Continuous radio-telemetry monitoring detected increased ventricular arrhythmias, including ventricular tachycardia, after intramyocardial injection compared to the sham-control, while these were abolished in myoblast-sheet therapy. This effect was conjunct with avoidance of islet-like cell-cluster formation that disrupts electrical conduction, and with prevention of increased arrhythmogenic substrates due to exaggerated inflammation. Persistent ectopic donor cells were found in the lung only after intramyocardial injection, strengthening the improved safety of myoblast-sheet therapy. In addition, myoblast-sheet therapy enhanced cardiac function, corresponding to a 9.2-fold increase in donor cell survival, compared to intramyocardial injection. Both methods achieved reduced infarct size, decreased fibrosis, attenuated cardiomyocyte hypertrophy, and increased neovascular formation, in association with myocardial upregulation of a group of relevant molecules. The pattern of these beneficial changes was similar between two methods, but the degree was more substantial after myoblast-sheet therapy.

CONCLUSION

The cell-sheet technique enhanced safety and therapeutic efficacy of myoblast-based therapy, compared to the current method, thereby paving the way for clinical application.

Gene and cell therapies for the failing heart to prevent sudden arrhythmic death

Current therapies for treatment and prevention of sudden cardiac death have certain limitations, and a search for new therapeutic approaches is desirable to reduce the burden of sudden arrhythmic death. Gene therapy and stem cell therapy have been investigated as new, valuable tools in treating cardiac diseases such as arrhythmias. In this review, the basics of each modality, important related experimental and clinical studies, and potential advantages and limitations of these treatments will be discussed. The future success of gene and cell therapy to become practical clinical tools greatly depends on our understanding of the mechanisms of ventricular arrhythmia and the mechanisms of action of gene and cell therapy.

Update on cardiac stem cell therapy in heart failure

PURPOSE OF REVIEW

Presentation of the current status of cardiac stem cell therapy for the treatment of ischaemic heart failure by highlighting recent clinical results and introducing ongoing trials. Furthermore, necessary upcoming procedural adjustments are discussed.

RECENT FINDINGS

During the last decade, stem cell application in the setting of ischaemic heart failure has been evaluated in phase I and II clinical trials, proving safety and feasibility of this approach. Functional results gained so far indicate moderate benefits. However, conclusive evaluation of cell therapy will not be possible before completion of ongoing phase III multicentre trials. Moreover, questions regarding the optimal cell population for treatment in a chronic setting and the favourable time-point of cell delivery have not been ultimately answered.

SUMMARY

Cell therapy for the treatment of ischaemic heart failure needs to be evaluated separately from the setting of acute myocardial infarction. In parallel with upcoming clinical evaluation in large-scale trials, further optimization of the 'cell product' regarding the favourable cell type and periprocedural processing, as well as route and time-point of application, is mandatory.

Cell delivery routes for stem cell therapy to the heart: current and future approaches

An important factor to determine the success of stem cell therapy to the heart is the choice of cell delivery route. This will affect the fate of donor cells and subsequently influence the outcome of treatment; however, there is currently no optimum cell delivery route appropriate for every disease condition or every donor cell type. This review summarises currently available approaches for administering cells to the heart, with a particular focus on cell retention/survival and the therapeutic benefits seen in preclinical and clinical studies. Two major approaches are intracoronary and intramyocardial injection, which have been widely used for the delivery of various types of cells. Although there are advantages to both approaches, donor cell retention and survival are poor using these methods, potentially limiting therapeutic effects. Various attempts to improve current approaches, along with the development of emerging new approaches, are also described and discussed in this review.

Role of GATA-4 in differentiation and survival of bone marrow mesenchymal stem cells

Cell and tissue regeneration is a relatively new research field and it incorporates a novel application of molecular genetics. Combinatorial approaches for stem-cell-based therapies wherein guided differentiation into cardiac lineage cells and cells secreting paracrine factors may be necessary to overcome the limitations and shortcomings of a singular approach. GATA-4, a GATA zinc-finger transcription factor family member, has been shown to regulate differentiation, growth, and survival of a wide range of cell types. In this chapter, we discuss whether overexpression of GATA-4 increases mesenchymal stem cell (MSC) transdifferentiation into cardiac phenotype and enhances the MSC secretome, thereby increasing cell survival and promoting postinfarction cardiac angiogenesis. MSCs engineered with GATA-4 enhance their capacity to differentiate into cardiac cell phenotypes, improve survival of the cardiac progenitor cells and their offspring, and modulate the paracrine activity of stem cells to support their angiomyogenic potential and cardioprotective effects.

Cardiac cell therapy: pre-conditioning effects in cell-delivery strategies

Stem-cell therapy holds great promise for the treatment of ischemic heart disease. However, the benefit of cardiac cell therapy has not yet been proven in long-term clinical trials. Poor engraftment and survival of transplanted cells is one of the major concerns for the successful application of stem cells in cardiac cell therapy. Cell and cardiac pre-conditioning are now being explored as new approaches to support cell survival and enhance the therapeutic efficacy. In this paper, we summarize the state-of-the-art methods of cell delivery and cell survival post-delivery, with a focus on the pre-conditioning approaches that have been attempted to support the survival of transplanted cells.

Retrograde delivery of stem cells: promising delivery strategy for myocardial regenerative therapy

Heart failure is a leading cause of morbidity and mortality worldwide. The current strategies for treatment are limited, and new therapeutic approaches are needed. Experimental studies and clinical trials suggest that stem cell transplantation may improve cardiac function and prevent cardiac remodeling of the injured heart. Although the results of the studies were exciting, many problems remain to be resolved such as the best method of delivering the targeted cells. Direct injection into the myocardium and intracoronary artery infusion are the two most used methods of delivery in clinical settings. However, in a portion of patients with occluded coronary arteries and poor collaterals, transplanted cells may not reach the target ischemic lesion. To resolve this problem, we hypothesize that retrograde coronary venous delivery of stem cells may be a promising therapeutic strategy for the patients with occluded coronary arteries and poor collaterals.

Skeletal myoblasts for cardiac repair

Stem cells provide an alternative curative intervention for the infarcted heart by compensating for the cardiomyocyte loss subsequent to myocardial injury. The presence of resident stem and progenitor cell populations in the heart, and nuclear reprogramming of somatic cells with genetic induction of pluripotency markers are the emerging new developments in stem cell-based regenerative medicine. However, until safety and feasibility of these cells are established by extensive experimentation in in vitro and in vivo experimental models, skeletal muscle-derived myoblasts, and bone marrow cells remain the most well-studied donor cell types for myocardial regeneration and repair. This article provides a critical review of skeletal myoblasts as donor cells for transplantation in the light of published experimental and clinical data, and indepth discussion of the advantages and disadvantages of skeletal myoblast-based therapeutic intervention for augmentation of myocardial function in the infarcted heart. Furthermore, strategies to overcome the problems of arrhythmogenicity and failure of the transplanted skeletal myoblasts to integrate with the host cardiomyocytes are discussed.

Stem cell therapy for chronic myocardial infarction

Although recent advances for the treatment of myocardial infarction have dramatically increased the rate of survival after the ischemic event, this has also led to a rise in the number of chronic patients, making the finding of a suitable therapy a compulsory subject for modern medicine. Over the last decade, stem cells have been a promise for the cure of several diseases not only due to their plasticity but also to their capacity to act in a paracrine manner and influence the affected tissue, prompting the launching of several clinical trials. In spite of the knowledge already acquired, stem cell application to chronically infarcted hearts has been much less approached than its acute counterpart. Through this review, we will focus in stem cell therapy in animal models of chronic myocardial infarction: cell types employed, functional results, mechanisms analyzed, and questions raised.

Lost in translation: what is limiting cardiomyoplasty and can tissue engineering help?

Heart failure accounts for more deaths in the United States than any other detrimental human pathology. Recently, repairing the heart after seemingly irreversible injury leading to heart failure appears to have come within reach. Cellular cardiomyoplasty, transplanting viable cell alternatives into the diseased myocardium, has emerged as a promising possible solution. Translating this approach from the laboratory to the clinic, however, has been met with several challenges, leaving many questions unanswered. This review assesses the state of investigation of several progenitor cell sources, including induced pluripotent stem cells, embryonic stem cells, bone marrow stem cells, adipose-derived adult stem cells, amniotic fluid stem cells, skeletal muscle progenitors, induced pluripotent stem cells and cardiac progenitors. Several current roadblocks to maximum success are discussed. These include understanding the need for cardiomyocyte differentiation, appreciating the role of paracrine factors, and addressing the low engraftment rates using current techniques. Tissue engineering strategies to address these obstacles and to help maximize cellular cardiomyoplasty success are reviewed.

Donor cell-type specific paracrine effects of cell transplantation for post-infarction heart failure

Cell transplantation is an emerging therapy for treating post-infarction heart failure. Although the paracrine effect has been proposed to be an important mechanism for the therapeutic benefits, details remain largely unknown. This study compared various aspects of the paracrine effect after transplantation of either bone marrow mononuclear cells (BMC) or skeletal myoblasts (SMB) into the post-infarction chronically failing heart. Three weeks after left coronary artery ligation, adult rats received intramyocardial injection of either BMC, SMB or PBS only. Echocardiography demonstrated that injection of either cell type improved cardiac function compared to PBS injection. Interestingly, BMC injection markedly improved neovascularization in the border areas surrounding infarcts, while SMB injection decreased fibrosis in both the border and remote areas. Injection of either cell type similarly reduced hypertrophy of cardiomyocytes as assessed by cell-size planimetry using isolated cardiomyocytes. Quantitative RT-PCR revealed that, among 15 candidate mediators of paracrine effects studied, Fgf2 and Hgf were upregulated only after BMC injection, while Mmp2 and Timp4 were modulated after SMB injection. Additional investigations of signalling pathways relevant to heart failure by western blotting showed that p38 and STAT3 were temporarily activated after BMC injection, in contrast, ERK1/2 and JNK were activated after SMB injection. There was no difference in activation of Akt, PKD or Smad3 among groups. These data suggest that paracrine effects observed after cell transplantation in post-infarction heart failure were noticeably different between cell types in terms of mediators, signal transductions and consequent effects.

Knockdown of microRNA-181 by lentivirus mediated siRNA expression vector decreases the arrhythmogenic effect of skeletal myoblast transplantation in rat with myocardial infarction

The arrhythmogenic effect of intracardiac skeletal myoblast (SKM) transplantation may be related to the differentiation state of SKMs. We tested the hypothesis that lentivirus mediated siRNA against the loop region of miRNA-181a could upregulate the SKMs differentiation repressor homeobox protein A11 (Hox-A11) and reduce the arrhythmias post SKM transplantation into ischemic myocardium of rats. Primary cultured SKMs were transfected with Lenti-siR-miR-181 (recombined lentivirus expressing the unique siRNA against miR-181a, LV group). Real-time PCR showed that miRNA-181a level was significantly decreased and Hox-A11 protein level significantly increased in LV group than in control group at days 5 and days 7 post Lentivirus transfection. Knockdown of miRNA-181a significantly promoted SKMs' growth and attenuated the connexin43 downregulation in SKMs in vitro. Seven days after left coronary artery ligation, rats were randomized to receive intramyocardial injection of either 5x10(6) SKMs transfected with Lenti-siR-miR-181 (MI-SKMLV), 5x10(6) Lenti-siLUC SKMs (MI-SKM) or PBS (MI-PBS). Systolic function was significantly improved in both MI-SKM and MI-SKMLV groups fourteen days after injection. Incidence of inducible self-terminating ventricular tachycardia was significantly lower in MI-SKMLV than that in MI-SKM group. Engraftments of SKMs with knockdowned miRNA-181a similarly improved cardiac function as SKM transplantation but significantly decreased the arrhythmogenic effect of SKM transplantation in rats with experimental myocardial infarction.

Stem cell therapy for heart failure: are arrhythmias a real safety concern?

So far, the major safety issue raised by the use of stem cells for cardiac repair has been the occurrence of ventricular arrhythmias, particularly after skeletal myoblast transplantation. Although one cannot refute a potential intrinsic arrhythmogenicity of stem cells, primarily related to their common lack of electromechanical integration into the recipient myocardium, it is also important to recognize that patients eligible for cell replacement therapy are prone to develop arrhythmias because of their underlying ischemic heart disease. Another confounding factor is the method used for the intramyocardial delivery of the cells, which can cause enough inflammatory tissue damage to further increase ventricular irritability on top of an already high baseline level. Thus any strategy designed to minimize the risk of stem cell-associated ventricular arrhythmias should take into account, besides the cell-specific ability to appropriately couple with host cardiomyocytes, the method of cell transfer and the nature of the myocardial environment targeted for cell engraftment. A more accurate characterization of the baseline risk of arrhythmias in these patients would thus be helpful for better assessing the respective contribution of the donor cells and the host myocardium to these complications. The risk-to-benefit ratio of stem cell therapy will finally have to be revisited in light of the fact that because this baseline risk is usually high, most of these patients will in any way be fitted with an implantable defibrillator.