Myocardial Regenerative Therapy Research Articles

Abstract We049: Cell-Specific Metabolic Labelling Identifies hiPSC-CM Proteome In Vitro and In Vivo Post-Transplantation

Background: Human induced pluripotent stem cells (hiPSCs) and their derived cardiomyocytes (hiPSC-CMs) have been used for cell-based therapies for myocardial regeneration. Underlying paracrine signals derived from these hiPSC-CMs have been shown to play a critical role in improving the function of the ischemic myocardium. However, characterization of the transplanted cell proteome in vivo has been challenging due to the lack of tools to distinguish cell-specific proteome in a complex multicellular microenvironment. Methods: To establish cell-specific proteome labelling, we adopted the biorthogonal non-canonical amino acid tagging (BONCAT) system in hiPSCs. We expressed the mutant mouse tRNA synthetase gene, “L274GmMetRS” in hiPSCs (L274G-hiPSCs) using lentiviral transduction to enable incorporation of the non-canonical amino acid azidonorleucine (Anl) in these cells. We assessed the pluripotency and trilineage differentiation potential of the L274G-hiPSCs in vitro and in vivo (teratoma formation assay). Furthermore, we validated the cell-specific Anl incorporation in the L274G-hiPSC-CMs both in vitro (co-culture) and in vivo (post-transplantation). Results: Our studies showed that the L274G-hiPSCs could efficiently differentiate into all the three germ lineages and can be used to track the cell-specific proteome in their differentiated progenies, including L274G-hiPSC-CMs. Furthermore, immunostaining and western blots showed cell-specific BONCAT in L274G-hiPSC-CMs both in co-cultures (in vitro) and post-transplantation (in vivo). Conclusion: The newly-established L274G-hiPSC line can be used to track cell-specific proteome of hiPSC-CMs in vitro and in vivo, to characterize cell-specific proteomic responses and delineate mechanisms underlying cell therapies.

Abstract We041: In vitro characterization of different human-induced pluripotent stem cell-derived cardiac progenitors

Introduction: Myocardial Infarction (MI) is the number one cause of death in the United States. The heart undergoes severe trauma during MI, which results in the death of cardiac cells. Although the cardiac tissue cannot regenerate on its own, regenerative medicine approaches involving cell transplantation have been shown to improve the cardiac function. Among different cell types, human induced pluripotent stem cell-derived cardiac progenitor cells (hiPSCs) have been shown to have the ability to proliferate and differentiate into cardiac lineage cells and therefore, are a promising source for myocardial repair. Here, we characterized two distinct populations of hiPSC-CPCs and assessed their differentiation potential. Methods: We compared hiPSC-CPCs differentiated using the small molecule, isoxazole-9 (ISX-9), ISX9-hiPSC-CPCs with the commercially acquired iCell hiPSC-CPCs (Fujifilm Cellular Dynamics Int.). The expression of different cardiac lineage markers were assessed via immunostaining, qPCR and flow cytometry. Furthermore, we assessed the proliferation of the cells using immunostaining and XTT assays. We also evaluated their in vitro differentiation to cardiomyocytes, via immunostaining and qPCR analysis. Results: Our studies showed similar expression of different cardiac progentior markers (Nkx2.5, GATA4, KFL-4, ISL-1, BRY-T, MESP-1, MYH-6, CTnT) in the two hiPSC-CPC populations. However, while the iCell hiPSC-CPCs predominantly expressed the cell surface marker KDR, the ISX-9-hiPSC-CPCs predominantly expressed SSEA-1. The iCell-hiPSC-CPCs showed higher proliferation rates when compared to the ISX-9-hiPSC-CPCs. However, >95% of both the cell populations expressed the proliferation marker, ki67. Finally, the while both the CPC populations could differentiate into cardiomyocytes (cTNT + ), only a few of these differentiated cardiomyocytes showed spontaneous contractility in vitro. Conclusion: In our study, we have compared and characterized two distinct populations of hiPSC-CPCs to identify a promising candidate for myocardial regeneration therapies.

Current Status of Cardiac Regenerative Therapy Using Induced Pluripotent Stem Cells.

Heart failure (HF) is a life-threatening disorder and is treated by drug therapies and surgical interventions such as heart transplantation and left ventricular assist device (LVAD). However, these treatments can lack effectiveness in the long term and are associated with issues such as donor shortage in heart transplantation, and infection, stroke, or gastrointestinal bleeding in LVADs. Therefore, alternative therapeutic strategies are still needed. In this respect, stem cell therapy has been introduced for the treatment of HF and numerous preclinical and clinical studies are employing a range of stem cell varieties. These stem cells, such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), have been shown to improve cardiac function and attenuate left ventricular remodeling. IPSCs, which have a capacity for unlimited proliferation and differentiation into cardiomyocytes, are a promising cell source for myocardial regeneration therapy. In this review, we discuss the following topics: (1) what are iPSCs; (2) the limitations and solutions for the translation of iPSC-CMs practically; and (3) the current therapeutic clinical trials.

Assessment of the feasibility of human amniotic membrane stem cell-derived cardiomyocytes in vitro

Myocardial infarction (MI) is a leading cause of death worldwide, resulting in extensive loss of cardiomyocytes and subsequent heart failure. Inducing cardiac differentiation of stem cells is a potential approach for myocardial regeneration therapy to improve post-MI prognosis. Mesenchymal stem cells (MSCs) have several advantages, including immune privilege and multipotent differentiation potential. This study aimed to explore the feasibility of chemically inducing human amniotic membrane MSCs (hAMSCs) to differentiate into cardiomyocytes in vitro. Human amniotic membrane (AM) samples were obtained from routine cesarean sections at Far Eastern Memorial Hospital. The isolated cells exhibited spindle-shaped morphology and expressed surface antigens CD73, CD90, CD105, and CD44, while lacking expression of CD19, CD11b, CD19, CD45, and HLA-DR. The SSEA-1, SSEA-3, and SSEA-4 markers were also positive, and the cells displayed the ability for tri-lineage differentiation into adipocytes, chondrocytes, and osteoblasts. The expression levels of MLC2v, Nkx2.5, and MyoD were analyzed using qPCR after applying various protocols for chemical induction, including BMP4, ActivinA, 5-azacytidine, CHIR99021, and IWP2 on hAMSCs. The group treated with 5 ng/ml BMP4, 10 ng/ml Activin A, 10 μM 5-azacytidine, 7.5 μM CHIR99021, and 5 μM IWP 2 expressed the highest levels of these genes. Furthermore, immunofluorescence staining demonstrated the expression of α-actinin and Troponin T in this group. In conclusion, this study demonstrated that hAMSCs can be chemically induced to differentiate into cardiomyocyte-like cells in vitro. However, to improve the functionality of the differentiated cells, further investigation of inductive protocols and regimens is needed.

Abstract 15721: CRISPR Activates Heterochromatic Cardiac Genes in Fibroblasts to Initiate Lineage Conversion Into Cardiac Progenitors

Introduction: Our previous studies have demonstrated that CRISPR activation (CRISPRa) of endogenous genes was sufficient to convert fibroblasts into induced cardiovascular progenitor cells (iCPCs) for myocardial regenerative therapy. However, reprogramming efficiency remains a challenge and little has been elucidated about the epigenetic mechanisms of cellular reprogramming, which will be important for methodological improvements or refinements. Hypothesis: CRISPRa complex can alter the chromatin accessibility and activity of heterochromatic cardiac genes in fibroblasts, directly initiating cardiac reprogramming. Methods: A fibroblast-specific CRISPRa mice model (Pdgfra-cre/ERT; ROSA-dCas9-SunTag) was generated. SgRNAs targeting the promoter region of Gata4, Isl1, Nkx2-5, Baf60c, or Tbx5 genes were transduced through an AAV system in cardiac fibroblast isolated from transgenic mice. iCPCs were confirmed via immunostaining of CPC markers and cardiac electrophysiological assays. iCPCs were collected for RNA-seq, ATAC-seq, and ChIP-seq after reprogramming induction to reveal the epigenetic landscape modulated by CRISPRa. Results: The CRISPRa system was activated in ~80% of fibroblasts after tamoxifen induction and AAV-sgRNA transfection. The reprogrammed iCPCs were characterized by immunostaining of proliferative markers (Ki67 and Pcna), progenitor surface markers (Flk1 and Ssea1), and markers of cardiac tri-lineage cells after induced differentiation. RNA-seq data showed the upregulation of genes associated with cell cycling (Cdkn1b, Aurkb, etc.) and heart development (Myh6, Irx4, etc.) in CRISPRa-induced cells. ATAC-seq showed increased chromatin accessibility at the loci of cardiogenic genes targeted by CRISPRa in fibroblasts. Furthermore, ChIP-seq of Gata4, Nkx2.5, and Tbx5 associated DNA shows that these factors can bind to their own promoter regions in fibroblasts after CRISPRa induction. Conclusions: CRISPRa complexes open the chromatin of the targeted genes in fibroblasts and establish an endogenous autoregulatory loop to ensure stable reprogramming into cardiac progenitors.

Cardiac Regeneration Using Pluripotent Stem Cells and Controlling Immune Responses.

Pluripotent stem cell (PSC)-derived cardiomyocytes are a promising source of cells in myocardial regeneration therapy for end-stage heart failure. Because most previous reports have focussed on xenotransplantation models using immunocompromised animals, studies on immune rejection in allogeneic transplantation models are needed for preclinical and clinical applications. Human leukocyte antigen (HLA) plays an important role in allogeneic transplantation, and cell bank projects are currently underway worldwide to stock induced pluripotent stem cells (iPSCs) generated from healthy individuals with homozygous HLA haplotypes. However, it is difficult to stock iPSCs that match the entire population in these cell banks; thus, several groups have produced hypoimmunogenic PSCs by knocking out HLA. These HLA-knockout PSCs were able to avoid rejection by T cells but still suffered rejection by natural killer(NK) cells caused by 'missing self-recognition'. Recent studies have attempted to generate hypoimmunogenic PSCs with gene editing to inhibit NK cell activation. Regenerative medicine using autologous iPSCs can be an ideal transplantation therapy, but, currently, there are major hurdles to its practical application. Hopefully, further research will resolve these issues. This review provides an overview of the current understanding and progress in this field.

Modified mRNA as a Treatment for Myocardial Infarction

Myocardial infarction (MI) is a severe disease with high mortality worldwide. However, regenerative approaches remain limited and with poor efficacy. The major difficulty during MI is the substantial loss of cardiomyocytes (CMs) with limited capacity to regenerate. As a result, for decades, researchers have been engaged in developing useful therapies for myocardial regeneration. Gene therapy is an emerging approach for promoting myocardial regeneration. Modified mRNA (modRNA) is a highly potential delivery vector for gene transfer with its properties of efficiency, non-immunogenicity, transiency, and relative safety. Here, we discuss the optimization of modRNA-based therapy, including gene modification and delivery vectors of modRNA. Moreover, the effective of modRNA in animal MI treatment is also discussed. We conclude that modRNA-based therapy with appropriate therapeutical genes can potentially treat MI by directly promoting proliferation and differentiation, inhibiting apoptosis of CMs, as well as enhancing paracrine effects in terms of promoting angiogenesis and inhibiting fibrosis in heart milieu. Finally, we summarize the current challenges of modRNA-based cardiac treatment and look forward to the future direction of such treatment for MI. Further advanced clinical trials incorporating more MI patients should be conducted in order for modRNA therapy to become practical and feasible in real-world treatment.

P16INK4a Regulates ROS-Related Autophagy and CDK4/6-Mediated Proliferation: A New Target of Myocardial Regeneration Therapy.

Neonatal mice achieve complete cardiac repair through endogenous myocardial regeneration after apical resection (AR), but this capacity is rapidly lost 7 days after birth. As an upstream inhibitor of cyclin-dependent kinase 4/6- (CDK4/6-) mediated cell cycle activity, p16INK4a is widely involved in regulating tumor and senescence. Given that p16INK4a had a significant negative regulation on cell proliferation, targeting cardiomyocytes (CMs) to inhibit p16INK4a seems to be a promising attempt at myocardial regeneration therapy. The p16INK4a expression was upregulated during perimyocardial regeneration time. Knockdown of p16INK4a stimulated CM proliferation, while p16INK4a overexpression had the opposite effect. In addition, p16INK4a knockdown prolonged the proliferation time window of newborn myocardium. And p16INK4a overexpression inhibited cell cycle activity and deteriorated myocardial regeneration after AR. The quantitative proteomic analysis showed that p16INK4a knockdown mediated the cell cycle progression and intervened in energy metabolism homeostasis. Mechanistically, overexpression of p16INK4a causes abnormal accumulation of reactive oxygen species (ROS) to induce autophagy, while scavenging ROS with N-acetylcysteine can alleviate autophagy and regulate p16INK4a, CDK4/6, and CyclinD1 in a covering manner. And the effect of inhibiting the proliferation of p16INK4a-activated CMs was significantly blocked by the CDK4/6 inhibitor Palbociclib. In summary, p16INK4a regulated CM proliferation progression through CDK4/6 and ROS-related autophagy to jointly affect myocardial regeneration repair. Our study revealed that p16INK4a might be a potential therapeutic target for myocardial regeneration after injury.

Cell-Based and Selected Cell-Free Therapies for Myocardial Infarction: How Do They Compare to the Current Treatment Options?

Because of cardiomyocyte death or dysfunction frequently caused by myocardial infarction (MI), heart failure is a leading cause of morbidity and mortality in modern society. Paradoxically, only limited and non-curative therapies for heart failure or MI are currently available. As a result, over the past two decades research has focused on developing cell-based approaches promoting the regeneration of infarcted tissue. Cell-based therapies for myocardial regeneration include powerful candidates, such as multipotent stem cells (mesenchymal stem cells (MSCs), bone-marrow-derived stem cells, endothelial progenitor cells, and hematopoietic stem cells) and induced pluripotent stem cells (iPSCs). These possess unique properties, such as potency to differentiate into desired cell types, proliferation capacity, and patient specificity. Preclinical and clinical studies have demonstrated modest improvement in the myocardial regeneration and reduced infarcted areas upon transplantation of pluripotent or multipotent stem cells. Another cell population that need to be considered as a potential source for cardiac regeneration are telocytes found in different organs, including the heart. Their therapeutic effect has been studied in various heart pathologies, such as MI, arrhythmias, or atrial amyloidosis. The most recent cell-free therapeutic tool relies on the cardioprotective effect of complex cargo carried by small membrane-bound vesicles—exosomes—released from stem cells via exocytosis. The MSC/iPSC-derived exosomes could be considered a novel exosome-based therapy for cardiovascular diseases thanks to their unique content. There are also other cell-free approaches, e.g., gene therapy, or acellular cardiac patches. Therefore, our review provides the most recent insights into the novel strategies for myocardial repair based on the regenerative potential of different cell types and cell-free approaches.

A 3D mathematical model of coupled stem cell-nutrient dynamics in myocardial regeneration therapy

Stem cell therapy is a promising treatment for the regeneration of myocardial tissue injured by an ischemic event. Mathematical modeling of myocardial regeneration via stem cell therapy is a challenging task, since the mechanisms underlying the processes involved in the treatment are not yet fully understood. Many aspects must be accounted for, such as the spread of stem cells and nutrients, chemoattraction, cell proliferation, stages of cell maturation, differentiation, angiogenesis, stochastic effects, just to name a few. In this paper we propose a 3D mathematical model with a free boundary that aims to provide a qualitative description of some main aspects of the stem cell regenerative therapy in a simplified scenario. The paper mainly focuses on the description of the shrinking of the necrotic core during treatment. The stem cell and nutrients dynamics are described through coupled reaction-diffusion problems. Proliferation, chemoattraction, tissue regeneration and nutrient consumption are included in the model.

Single-photon emission computed tomography as a fundamental tool in evaluation of myocardial reparation and regeneration therapies.

Despite unquestionable progress in interventional and pharmacologic therapies of ischemic heart disease, the number of patients with chronic ischemic heart failure is increasing and the prognosis remains poor. Repair/restoration of functional myocardium through progenitor cell-mediated (PCs) healing and renovation of injured myocardium is one of the pivotal directions in biomedical research. PCs release numerous pro-angiogenic and anti-apoptotic factors. Moreover, they have self-renewal capability and may differentiate into specialized cells that include endothelial cells and cardiomyocytes. Uptake and homing of PCs in the zone(s) of ischaemic injury (i.e., their effective transplantation to the target zone) is an essential pre-requisite for any potential therapeutic effect; thus effective cell tracking is fundamental in pre-clinical and early clinical studies. Another crucial requirement in rigorous research is quantification of the infarct zone, including the amount of non-perfused and hypo-perfused myocardium. Quantitative and reproducible evaluation of global and regional myocardial contractility and left ventricular remodeling is particularly relevant in clinical studies. Using SPECT, our earlier work has addressed several critical questions in cardiac regenerative medicine including optimizing transcoronary cell delivery, determination of the zone(s) of myocardial cell uptake, and late functional improvement in relation to the magnitude of cell uptake. Here, we review the role of single-photon emission computed tomography (SPECT), a technique that offers high-sensitivity, quantitative cell tracking on top of its ability to evaluate myocardial perfusion and function on both cross-sectional and longitudinal bases. SPECT, with its direct relevance to routine clinical practice, is a fundamental tool in evaluation of myocardial reparation and regeneration therapies.

Efficient Method to Dissociate Induced Pluripotent Stem Cell-Derived Cardiomyocyte Aggregates into Single Cells.

The human adult heart consists of approximately fourbillion cardiomyocytes, which do not possess self-renewal abilities. Severe myocardial infarction and dilated cardiomyopathy result in the loss of more than a billion cardiomyocytes. Induced pluripotent stem cells (iPSCs) can differentiate into various types of cells. Due to this ability, these cells could potentially serve as a new resource for cell therapy. Many studies have utilized cardiomyocytes derived from iPSCs for myocardial regeneration therapy. To obtain large number of cardiomyocytes for transplantation, we need to develop effective methods that would allow us to dissociate multiple cardiomyocyte aggregates simultaneously. Here, we describe a method to efficiently dissociate large number of iPSC-derived cardiomyocyte aggregates.

Safety profiling of genetically engineered Pim-1 kinase overexpression for oncogenicity risk in human c-kit+ cardiac interstitial cells.

Advancement of stem cell-based treatment will involve next-generation approaches to enhance therapeutic efficacy which is often modest, particularly in the context of myocardial regenerative therapy. Our group has previously demonstrated the beneficial effect of genetic modification of cardiac stem cells with Pim-1 kinase overexpression to rejuvenate aged cells as well as potentiate myocardial repair. Despite these encouraging findings, concerns were raised regarding potential for oncogenic risk associated with Pim-1 kinase overexpression. Testing of Pim-1 engineered c-kit+ cardiac interstitial cells (cCIC) derived from heart failure patient samples for indices of oncogenic risk was undertaken using multiple assessments including soft agar colony formation, micronucleation, gamma-Histone 2AX foci, and transcriptome profiling. Collectively, findings demonstrate comparable phenotypic and biological properties of cCIC following Pim-1 overexpression compared with using baseline control cells with no evidence for oncogenic phenotype. Using a highly selective and continuous sensor for quantitative assessment of PIM1 kinase activity revealed a sevenfold increase in Pim-1 engineered vs. control cells. Kinase activity profiling using a panel of sensors for other kinases demonstrates elevation of IKKs), AKT/SGK, CDK1-3, p38, and ERK1/2 in addition to Pim-1 consistent with heightened kinase activity correlating with Pim-1 overexpression that may contribute to Pim-1-mediated effects. Enhancement of cellular survival, proliferation, and other beneficial properties to augment stem cell-mediated repair without oncogenic risk is a feasible, logical, and safe approach to improve efficacy and overcome current limitations inherent to cellular adoptive transfer therapeutic interventions.

Regulation of Cardiomyocyte Differentiation, Angiogenesis, and Inflammation by the Delta Opioid Signaling in Human Mesenchymal Stem Cells

Lack of angiogenesis, inflammation, and low differentiation of MSCs upon transplantation to ischemic site are major drawbacks in cell therapies for myocardial tissue regeneration. To overcome these problems, this study aimed to increase the angiogenesis, anti-inflammation, and differentiation of human umbilical cord MSCs (hMSCs) into cardiomyocytes by activating the delta opioid pathway by its agonist SNC80 with the combination of zebularine, activin A and oxytocin. Human umbilical cord MSCs were seeded on gelatin-coated plates by using alpha MEM. MSCs were treated with SNC80 and the combination of zebularine, activin A and oxytocin. Media and inducers were changed every 3 days once until 21 days. Spent media collected from day 7 and day 21 was used to estimate angiogenic (VEGF) and anti- or pro-inflammatory cytokines (IL-10, IL1b, IL-6) levels by ELISA. The effect of spent media on in vitro endothelial tube formation and anti-inflammatory effect on inflammation induced with LPS on macrophages was also studied along with cytokine levels. Proteins that were isolated from day 7 and day 21 were used to study for cardiomyocyte markers (GATA4, MEF2C, connexin 43, and KCNJ2) and NOTCH1 involved in cardiomyocyte differentiation using Western blot. Activation of DOR increases the VEGF secretion levels estimated by ELISA and increases the in vitro tube formation in terms of number of loops and total length. Delta opioid receptor (DOR)-activated conditioned media secreted anti-inflammatory cytokine IL-10, which could prevent the secretion of pro-inflammatory cytokines IL-1b and IL-6 from LPS induced macrophages. DOR activated MSCs upregulated the early and late cardiomyocytes markers (GATA4, MEF2C and connexin 43, KCNJ43) via NOTCH1 signaling. Activation of DOR on hMSCs plays a vital role in angiogenesis, anti-inflammation, and cardiomyocyte differentiation by regulating the NOTCH1 signaling pathway. Our results indicate that, upon activation of delta opioid receptors on human umbilical cord derived mesenchymal stem cells, they can differentiate into heart cells (by expressing specific markers GATA4, MEF2C, Connexin43), show enhanced formation of blood vessels and anti-inflammatory activity. This approach may help to treat pateints post heart attack.

A New Era of Cardiac Cell Therapy: Opportunities and Challenges.

Myocardial infarction (MI), caused by coronary heart disease (CHD), remains one of the most common causes of death in the United States. Over the last few decades, scientists have invested considerable resources on the study and development of cell therapies for myocardial regeneration after MI. However, due to a number of limitations, they are not yet readily available for clinical applications. Mounting evidence supports the theory that paracrine products are the main contributors to the regenerative effects attributed to these cell therapies. The next generation of cell-based MI therapies will identify and isolate cell products and derivatives, integrate them with biocompatible materials and technologies, and use them for the regeneration of damaged myocardial tissue. This review discusses the progress made thus far in pursuit of this new generation of cell therapies. Their fundamental regenerative mechanisms, their potential to combine with other therapeutic products, and their role in shaping new clinical approaches for heart tissue engineering, are addressed.

Cell therapy and left ventricular restoration for ischemic cardiomyopathy: long-term results of a perspective, randomized study.

Aim of this study is to verify the potential advantages and benefits of bone-marrow derived autologous stem cells implantation associated to surgical left ventricular restoration (SVR), to report a new modality of cell delivery to myocardium, and to identify possible side effects of this procedure. Between March 2007 and March 2013, 30 patients affected by ischemic dilative cardiomyopathy who received a SVR operation were enrolled in the study. The population was divided in two groups:16 patients were randomly assigned to receive stem cells therapy in addition to SVR (groupA), 14 patients received a placebo (group B). The two groups were homogeneous in respect of age, gender, preoperative NYHA class, mitral incompetence and left ventricular sizes and volumes. The patients were evaluated by echo and pet-scan before surgery and at 6 months follow-up, and by echo at subsequent follow-up. Overall 30 days-in hospital mortality was 0 for the entire cohort. At last follow-up ejection fraction increased from 25.3% before surgery to 36.3% in group A, and from 31.8% to 45.6% in group B. Reduction of LVEDD was 6% in group A, 9% in group B. ESLVV and EDLVD decreased more significantly in patients receiving stem cells (55% vs. 35%). Late cardiac mortality at 9 years follow-up was similar in the two groups of patients. No early or late adverse reaction nor cases of infections were observed. Patients affected by ischemic cardiomyopathy have a favourable outcome after SVR. A higher reduction of LVEDV and LVESV assessed by CT-Scan evaluation in patients receiving cell therapy, when compared to control group, encourages the evolution and refinement of myocardial regenerative therapy added to SVR.

Development of a vitrification method for preserving human myoblast cell sheets for myocardial regeneration therapy

BackgroundTissue-engineered cardiac constructs have potential in the functional recovery of heart failure; however, the preservation of these constructs is crucial for the development and widespread application of this treatment. We hypothesized that tissue-engineered skeletal myoblast (SMB) constructs may be preserved by vitrification to conserve biological function and structure.ResultsScaffold-free cardiac cell-sheet constructs were prepared from SMBs and immersed in a vitrification solution containing ethylene glycol, sucrose, and carboxyl poly-l-lysine. The cell sheet was wrapped in a thin film and frozen rapidly above liquid nitrogen to achieve vitrification (vitrification group, n = 8); fresh, untreated SMB sheets (fresh group, n = 8) were used as the control. The cryopreserved SMB sheets were thawed at 2 days, 1 week, 1 month, and 3 months after cryopreservation for assessment. Thawed, cryopreserved SMB sheets were transplanted into rat hearts in a myocardial infarction nude rat model, and their effects on cardiac function were evaluated. Cell viability in the cardiac constructs of the vitrification group was comparable to that of the fresh group, independent of the period of cryopreservation (p > 0.05). The structures of the cell-sheet constructs, including cell-cell junctions such as desmosomes, extracellular matrix, and cell membranes, were maintained in the vitrification group for 3 months. The expression of cytokine genes and extracellular matrix proteins (fibronectin, collagen I, N-cadherin, and integrin α5) showed similar levels in the vitrification and fresh groups. Moreover, in an in vivo experiment, the ejection fraction was significantly improved in animals treated with the fresh or cryopreserved constructs as compared to that in the sham-treated group (p < 0.05).ConclusionsOverall, these results show that the vitrification method proposed here preserves the functionality and structure of scaffold-free cardiac cell-sheet constructs using human SMBs after thawing, suggesting the potential clinical application of this method in cell-sheet therapy.

Contemporary Perspective on Myocardial Regeneration Therapy in Children with Cardiomyopathy

Contemporary Perspective on Myocardial Regeneration Therapy in Children with Cardiomyopathy

Myocardial regeneration therapy in heart failure: Current status and future therapeutic implications in clinical practice

Despite multiple treatment regimens the morbidity and mortality of patients with advanced heart failure (HF) have reached pandemic proportions. In an effort to address the root cause of the problem, curative strategies are increasingly being considered. A case in point is the evolution of regenerative medicine technologies aiming to halt or even reverse progressive organ deterioration in the HF setting.The prevailing unmet clinical needs in HF therapy have provided a major incentive for the development of cell-based treatment strategies, which have shown encouraging results in experimental studies. In turn, this has led to a significant international effort in cell-based clinical trials. In order to translate the promise of biotherapies into clinical benefit many more questions need to be addressed.In this review we analyze current clinical experience regarding cell therapy in the setting of ischemic/nonischemic HF and address key issues that could be a guide for future successful cell-based therapeutic application in HF patients in clinical practice.

Pivotal Role of Non-cardiomyocytes in Electromechanical and Therapeutic Potential of Induced Pluripotent Stem Cell-Derived Engineered Cardiac Tissue.

Although engineered cardiac tissues (ECTs) derived from induced pluripotent stem cells (iPSCs) are promising for myocardial regenerative therapy, the appropriate ratio of cardiomyocytes to non-cardiomyocytes is not fully understood. Here, we determined whether ECT-cell content is a key determinant of its structure/function, thereby affecting ECT therapeutic potential for advanced heart failure. Scaffold-free ECTs containing different ratios (25%, 50%, 70%, or 90%) of iPSC-derived cardiomyocytes were generated by magnetic-activated cell sorting by using cardiac-specific markers. Notably, ECTs showed synchronized spontaneous beating when cardiomyocytes constituted ≥50% of total cells, with the electrical-conduction velocity increasing depending on cardiomyocyte ratio; however, ECTs containing 90% cardiomyocytes failed to form stable structures. ECTs containing 25% or 50% cardiomyocytes predominantly expressed collagen and fibronectin, whereas ECTs containing 70% cardiomyocytes predominantly expressed laminin and exhibited the highest contractile/relaxation properties. Furthermore, transplantation of ECTs containing 50% or 70% cardiomyocytes into a rat chronic myocardial infarction model led to a more profound functional recovery as compared with controls. Notably, transplanted ECTs showed electrical synchronization with the native heart under Langendorff perfusion. Collectively, these results indicate that the quantity of non-cardiomyocytes is critical in generating functional iPSC-derived ECTs as grafts for cardiac-regeneration therapy, with ECTs containing 50–70% cardiomyocytes exhibiting stable structures and increased cardiotherapeutic potential.