Enhanced Therapeutic Effects of Human iPS Cell Derived-Cardiomyocyte by Combined Cell-Sheets with Omental Flap Technique in Porcine Ischemic Cardiomyopathy Model

Monoclonal antibodies specific for podocalyxin expressed on human induced pluripotent stem cells

Human induced pluripotent stem cells (hiPSCs) are useful starting materials for the generation of cell therapy products, due to their pluripotency and ability to self-renew. Quality control of hiPSCs is extremely important in creating a stable supply of hPSC-derived products. Previously we identified an hiPSC-specific lectin probe, rBC2LCN, which binds specifically to α1,2-fucosylated glycan and recognizes podocalyxin (PODXL) as a glycoprotein ligand. In this study, we produced monoclonal antibodies (mAbs) specific for α1,2-fucosylated PODXL expressed on hiPSCs. PODXL was recombinantly expressed in fucosyltransferase 1 (FUT1)-transfected HEK293, followed by immunization into mice. Monoclonal antibodies, which bind to PODXL/FUT1-transfected cells, but not to cells transfected with only one of PODXL or FUT1, were screened by flow cytometry. The two mAbs generated (179-6B8C9 and 179-7E12E10), termed α1,2-fucosylated PODXL-specific mAbs (FpMabs), showed binding specificity to PODXL/FUT1-transfected cells. The FpMabs bound to hiPSCs but never to human adipose-derived mesenchymal stem cells, human dermal fibroblasts, or hiPSC-derived mesoderm. Altogether, FpMabs are highly specific probes for hiPSCs, which might be a powerful tool for the characterization of hiPSCs used in regenerative medicine.

Optimizing the Use of iPSC-CMs for Cardiac Regeneration in Animal Models

Simple Summary

In 2006, the first induced pluripotent stem cells were generated by reprogramming skin cells. Induced pluripotent stem cells undergo fast cell division, can differentiate into many different cell types, can be patient-specific, and do not raise ethical issues. Thus, they offer great promise as in vitro disease models, drug toxicity testing platforms, and for autologous tissue regeneration. Heart failure is one of the major causes of death worldwide. It occurs when the heart cannot meet the body’s metabolic demands. Induced pluripotent stem cells can be differentiated into cardiac myocytes, can form patches resembling native cardiac tissue, and can engraft to the damaged heart. However, despite correct host/graft coupling, most animal studies demonstrate an arrhythmogenicity of the engrafted tissue and variable survival. This is partially because of the heterogeneity and immaturity of the cells. New evidence suggests that by modulating induced pluripotent stem cells-cardiac myocytes (iPSC-CM) metabolism by switching substrates and changing metabolic pathways, you can decrease iPSC-CM heterogeneity and arrhythmogenicity. Novel culture methods and tissue engineering along with animal models of heart failure are needed to fully unlock the potential of cardiac myocytes derived from induced pluripotent stem cells for cardiac regeneration.

Abstract

Heart failure (HF) is a common disease in which the heart cannot meet the metabolic demands of the body. It mostly occurs in individuals 65 years or older. Cardiac transplantation is the best option for patients with advanced HF. High numbers of patient-specific cardiac myocytes (CMs) can be generated from induced pluripotent stem cells (iPSCs) and can possibly be used to treat HF. While some studies found iPSC-CMS can couple efficiently to the damaged heart and restore cardiac contractility, almost all found iPSC-CM transplantation is arrhythmogenic, thus hampering the use of iPSC-CMs for cardiac regeneration. Studies show that iPSC-CM cultures are highly heterogeneous containing atrial-, ventricular- and nodal-like CMs. Furthermore, they have an immature phenotype, resembling more fetal than adult CMs. There is an urgent need to overcome these issues. To this end, a novel and interesting avenue to increase CM maturation consists of modulating their metabolism. Combined with careful engineering and animal models of HF, iPSC-CMs can be assessed for their potential for cardiac regeneration and a cure for HF.

Cells, Materials, and Fabrication Processes for Cardiac Tissue Engineering

Cardiovascular disease is the number one killer worldwide, with myocardial infarction (MI) responsible for approximately 1 in 6 deaths. The lack of endogenous regenerative capacity, added to the deleterious remodelling programme set into motion by myocardial necrosis, turns MI into a progressively debilitating disease, which current pharmacological therapy cannot halt. The advent of Regenerative Therapies over 2 decades ago kick-started a whole new scientific field whose aim was to prevent or even reverse the pathological processes of MI. As a highly dynamic organ, the heart displays a tight association between 3D structure and function, with the non-cellular components, mainly the cardiac extracellular matrix (ECM), playing both fundamental active and passive roles. Tissue engineering aims to reproduce this tissue architecture and function in order to fabricate replicas able to mimic or even substitute damaged organs. Recent advances in cell reprogramming and refinement of methods for additive manufacturing have played a critical role in the development of clinically relevant engineered cardiovascular tissues. This review focuses on the generation of human cardiac tissues for therapy, paying special attention to human pluripotent stem cells and their derivatives. We provide a perspective on progress in regenerative medicine from the early stages of cell therapy to the present day, as well as an overview of cellular processes, materials and fabrication strategies currently under investigation. Finally, we summarise current clinical applications and reflect on the most urgent needs and gaps to be filled for efficient translation to the clinical arena.

Modeling Cardiac Disease Mechanisms Using Induced Pluripotent Stem Cell-Derived Cardiomyocytes: Progress, Promises and Challenges

Cardiovascular diseases (CVDs) are a class of disorders affecting the heart or blood vessels. Despite progress in clinical research and therapy, CVDs still represent the leading cause of mortality and morbidity worldwide. The hallmarks of cardiac diseases include heart dysfunction and cardiomyocyte death, inflammation, fibrosis, scar tissue, hyperplasia, hypertrophy, and abnormal ventricular remodeling. The loss of cardiomyocytes is an irreversible process that leads to fibrosis and scar formation, which, in turn, induce heart failure with progressive and dramatic consequences. Both genetic and environmental factors pathologically contribute to the development of CVDs, but the precise causes that trigger cardiac diseases and their progression are still largely unknown. The lack of reliable human model systems for such diseases has hampered the unraveling of the underlying molecular mechanisms and cellular processes involved in heart diseases at their initial stage and during their progression. Over the past decade, significant scientific advances in the field of stem cell biology have literally revolutionized the study of human disease in vitro. Remarkably, the possibility to generate disease-relevant cell types from induced pluripotent stem cells (iPSCs) has developed into an unprecedented and powerful opportunity to achieve the long-standing ambition to investigate human diseases at a cellular level, uncovering their molecular mechanisms, and finally to translate bench discoveries into potential new therapeutic strategies. This review provides an update on previous and current research in the field of iPSC-driven cardiovascular disease modeling, with the aim of underlining the potential of stem-cell biology-based approaches in the elucidation of the pathophysiology of these life-threatening diseases.

Requirements for Proper Immunosuppressive Regimens to Limit Translational Failure of Cardiac Cell Therapy in Preclinical Large Animal Models

Various cell-based therapies are currently investigated in an attempt to tackle the high morbidity and mortality associated with heart failure. The need for these therapies to move towards the clinic is pressing. Therefore, preclinical large animal studies that use non-autologous cells are needed to evaluate their potential. However, non-autologous cells are highly immunogenic and trigger immune rejection responses resulting in potential loss of efficacy. To overcome this issue, adequate immunosuppressive regimens are of imminent importance but clear guidelines are currently lacking. In this review, we assess the immunological barriers regarding non-autologous cell transplantation and immune modulation with immunosuppressive drugs. In addition, we provide recommendations with respect to immunosuppressive regimens in preclinical cardiac cell-replacement studies.

Extracellular matrix-based biomaterials for cardiac regeneration and repair

The spectrum of ischemic heart diseases, encompassing acute myocardial infarction to heart failure, represents the leading cause of death worldwide. Although extensive progress in cardiovascular diagnoses and therapy has been made, the prevalence of the disease continues to increase. Cardiac regeneration has a promising perspective for the therapy of heart failure. Recently, extracellular matrix (ECM) has been shown to play an important role in cardiac regeneration and repair after cardiac injury. There is also evidence that the ECM could be directly used as a drug to promote cardiomyocyte proliferation and cardiac regeneration. Increasing evidence supports that applying ECM biomaterials to maintain heart function recovery is an important approach to apply the concept of cardiac regenerative medicine to clinical practice in the future. Here, we will introduce the essential role of cardiac ECM in cardiac regeneration and summarize the approaches of delivering ECM biomaterials to promote cardiac repair in this review.

Stem cell-derived cell sheet transplantation for heart tissue repair in myocardial infarction

Stem cell-derived sheet engineering has been developed as the next-generation treatment for myocardial infarction (MI) and offers attractive advantages in comparison with direct stem cell transplantation and scaffold tissue engineering. Furthermore, induced pluripotent stem cell-derived cell sheets have been indicated to possess higher potential for MI therapy than other stem cell-derived sheets because of their capacity to form vascularized networks for fabricating thickened human cardiac tissue and their long-term therapeutic effects after transplantation in MI. To date, stem cell sheet transplantation has exhibited a dramatic role in attenuating cardiac dysfunction and improving clinical manifestations of heart failure in MI. In this review, we retrospectively summarized the current applications and strategy of stem cell-derived cell sheet technology for heart tissue repair in MI.

Pigs with δ-sarcoglycan deficiency exhibit traits of genetic cardiomyopathy

Genetic cardiomyopathy is a group of intractable cardiovascular disorders involving heterogeneous genetic contribution. This heterogeneity has hindered the development of life-saving therapies for this serious disease. Genetic mutations in dystrophin and its associated glycoproteins cause cardiomuscular dysfunction. Large animal models incorporating these genetic defects are crucial for developing effective medical treatments, such as tissue regeneration and gene therapy. In the present study, we knocked out the δ-sarcoglycan (δ-SG) gene (SGCD) in domestic pig by using a combination of efficient de novo gene editing and somatic cell nuclear transfer. Loss of δ-SG expression in the SGCD knockout pigs caused a concomitant reduction in the levels of α-, β-, and γ-SG in the cardiac and skeletal sarcolemma, resulting in systolic dysfunction, myocardial tissue degeneration, and sudden death. These animals exhibited symptoms resembling human genetic cardiomyopathy and are thus promising for use in preclinical studies of next-generation therapies.

Targeting cell plasticity for regeneration: From in vitro to in vivo reprogramming

The discovery of induced pluripotent stem cells (iPSCs), reprogrammed to pluripotency from somatic cells, has transformed the landscape of regenerative medicine, disease modelling and drug discovery pipelines. Since the first generation of iPSCs in 2006, there has been enormous effort to develop new methods that increase reprogramming efficiency, and obviate the need for viral vectors. In parallel to this, the promise of in vivo reprogramming to convert cells into a desired cell type to repair damage in the body, constitutes a new paradigm in approaches for tissue regeneration. This review article explores the current state of reprogramming techniques for iPSC generation with a specific focus on alternative methods that use biophysical and biochemical stimuli to reduce or eliminate exogenous factors, thereby overcoming the epigenetic barrier towards vector-free approaches with improved clinical viability. We then focus on application of iPSC for therapeutic approaches, by giving an overview of ongoing clinical trials using iPSCs for a variety of health conditions and discuss future scope for using materials and reagents to reprogram cells in the body.

The Challenge of Bringing iPSCs to the Patient

The implementation of induced pluripotent stem cells (iPSCs) in biomedical research more than a decade ago, resulted in a huge leap forward in the highly promising area of personalized medicine. Nowadays, we are even closer to the patient than ever. To date, there are multiple examples of iPSCs applications in clinical trials and drug screening. However, there are still many obstacles to overcome. In this review, we will focus our attention on the advantages of implementing induced pluripotent stem cells technology into the clinics but also commenting on all the current drawbacks that could hinder this promising path towards the patient.

Multi-layer pre-vascularized magnetic cell sheets for bone regeneration

The lack of effective strategies to produce vascularized 3D bone transplants in vitro, hampers the development of thick-constructed bone, limiting the translational of lab-based engineered system to clinical practices. Cell sheet (CS) engineering techniques provide an excellent microenvironment for vascularization since the technique can maintain the intact cell matrix, crucial for angiogenesis. In an attempt to develop hierarchical vascularized 3D cellular constructs, we herein propose the construction of stratified magnetic responsive heterotypic CSs by making use of iron oxide nanoparticles previously internalized within cells. Magnetic force-based CS engineering allows for the construction of thick cellular multilayers. Results show that osteogenesis is achieved due to a synergic effect of human umbilical vein endothelial cells (HUVECs) and adipose-derived stromal cells (ASCs), even in the absence of osteogenic differentiating factors. Increased ALP activity, matrix mineralization, osteopontin and osteocalcin detection were achieved over a period of 21 days for the heterotypic CS conformation (ASCs/HUVECs/ASCs), over the homotypic one (ASCs/ASCs), corroborating our findings. Moreover, the validated crosstalk between BMP-2 and VEGF releases triggers not only the recruitment of blood vessels, as demonstrated in an in vivo CAM assay, as well as the osteogenesis of the 3D cell construct. The in vivo angiogenic profile also demonstrated preserved human vascular structures and human cells showed the ability to migrate and integrate within the chick vasculature.

Stem Cells in Cardiovascular Medicine: Historical Overview and Future Prospects

Cardiovascular diseases remain the leading cause of death in the developed world, accounting for more than 30% of all deaths. In a large proportion of these patients, acute myocardial infarction is usually the first manifestation, which might further progress to heart failure. In addition, the human heart displays a low regenerative capacity, leading to a loss of cardiomyocytes and persistent tissue scaring, which entails a morbid pathologic sequela. Novel therapeutic approaches are urgently needed. Stem cells, such as induced pluripotent stem cells or embryonic stem cells, exhibit great potential for cell-replacement therapy and an excellent tool for disease modeling, as well as pharmaceutical screening of novel drugs and their cardiac side effects. This review article covers not only the origin of stem cells but tries to summarize their translational potential, as well as potential risks and clinical translation.

Moving forward on the pathway of cell-based therapies in ischemic heart disease and heart failure - time for new recommendations?

Although substantial advances have been made in treating ischemic heart disease and subsequent heart failure, the overall morbidity and mortality from these conditions remain high. Stem cell-based therapy has emerged as a promising approach for prompting cardiac rejuvenation. Various cell types have been tested in the clinical arena, proving consistent safety results. As for efficiency outcomes, contradictory findings have been reported, partly due to inconsistency in study protocols but also due to poor survival, engraftment and differentiation of transplanted cells in the hostile milieu of the ischemic host tissue. Studies have varied in terms of route of delivery, type and dose of implanted stem cells, patient selection and randomization, and assessment of therapeutic effect. Founded on the main achievements and challenges within almost 20 years of research, a number of official documents have been published by leading experts in the field. Core recommendations have focused on developing and optimizing effective strategies to enrich cell retention and their regenerative potential. Issued consensus and position papers have stemmed from an unmet need to provide a harmonized framework for future research, resulting in improved therapeutic application of cell-based therapies for cardiac regeneration and repair.

Cardiac regeneration with pluripotent stem cell-derived cardiomyocytes and direct cardiac reprogramming

Cardiovascular disease is the leading cause of death globally. Cardiomyocytes (CMs) have poor regenerative capacity, and pharmacological therapies have limited efficacy in severe heart failure. Currently, there are several promising strategies for cardiac regeneration. The most promising approach to remuscularize failing hearts is cell transplantation therapy using newly generated CMs from exogenous sources, such as pluripotent stem cells. Alternatively, approaches to generate new CMs from endogenous cell sources in situ may also repair the injured heart and improve cardiac function. Direct cardiac reprogramming has emerged as a novel therapeutic approach to regenerate injured hearts by directly converting endogenous cardiac fibroblasts into CM-like cells. Through cell transplantation and direct cardiac reprogramming, new CMs can be generated and scar tissue reduced to improve cardiac function; therefore, cardiac regeneration may serve as a powerful strategy for treatment of severe heart failure. While substantial progress has been made in these two strategies for cardiac regeneration over the past several years, challenges remain for clinical translation. This review provide an overview of previous reports and current challenges in this field.

Multi-cellularity in cardiac tissue engineering, how close are we to native heart tissue?

Tissue engineering is a complex field where the elements of biology and engineering are combined in an attempt to recapitulate the native environment of the body. Tissue engineering has shown one thing categorically; that the human body is extremely complex and it is truly a difficult task to generate this in the lab. There have been varied attempts at trying to generate a model for the heart with numerous cell types and different scaffolds or materials. The common underlying theme in these approaches is to combine together matrix material and different cell types to make something similar to heart tissue. Multi-cellularity is an essential aspect of the heart and therefore critical to any approach which would try to mimic such a complex tissue. The heart is made up of many cell types that combine to form complex structures like: deformable chambers, a tri-layered heart muscle, and vessels. Thus, in this review we will summarise how tissue engineering has progressed in modelling the heart and what gaps still exist in this dynamic field.

Nanotechnology Approaches in Tackling Cardiovascular Diseases

Cardiovascular diseases have continued to remain a leading cause of mortality and morbidity worldwide. Poor proliferation capability of adult cardiomyocytes disables the heart from regenerating new myocardium after a myocardial ischaemia event and therefore weakens the heart in the long term, which may result in heart failure and death. Delivery of cardioprotective therapeutics soon after the event can help to protect the heart from further cell death and improve cardiac function, but delivery methods and potential side effects of these therapeutics may be an issue. Advances in nanotechnology, particularly nanoparticles for drug delivery, have enabled researchers to obtain better drug targeting capability, thus increasing the therapeutic outcome. Detailed study of nanoparticles in vivo is useful as it can provide insight for future treatments. Nanogel can help to create a more favourable environment, not only for a sustained delivery of therapeutics, but also for a better navigation of the therapeutics to the targeted sites. Finally, if the damage to the myocardium is too severe for drug treatment, nanopatch can help to improve cardiac function and healing by becoming a platform for pluripotent stem cell-derived cardiomyocytes to grow for the purpose of cell-based regenerative therapy.

Biomaterializing the promise of cardiac tissue engineering

During an average individual's lifespan, the human heart pumps nearly 200 million liters of blood delivered by approximately 3 billion heartbeats. Therefore, it is not surprising that native myocardium under this incredible demand is extraordinarily complex, both structurally and functionally. As a result, successful engineering of adult-mimetic functional cardiac tissues is likely to require utilization of highly specialized biomaterials representative of the native extracellular microenvironment. There is currently no single biomaterial that fully recapitulates the architecture or the biochemical and biomechanical properties of adult myocardium. However, significant effort has gone toward designing highly functional materials and tissue constructs that may one day provide a ready source of cardiac tissue grafts to address the overwhelming burden of cardiomyopathic disease. In the near term, biomaterial-based scaffolds are helping to generate in vitro systems for querying the mechanisms underlying human heart homeostasis and disease and discovering new, patient-specific therapeutics. When combined with advances in minimally-invasive cardiac delivery, ongoing efforts will likely lead to scalable cell and biomaterial technologies for use in clinical practice. In this review, we describe recent progress in the field of cardiac tissue engineering with particular emphasis on use of biomaterials for therapeutic tissue design and delivery.

Protein-Engineered Large Area Adipose-derived Stem Cell Sheets for Wound Healing

Human adipose-derived stem cells (hADSCs) formed robust cell sheets by engineering the cells with soluble cell adhesive molecules (CAMs), which enabled unique approaches to harvest large area hADSC sheets. As a soluble CAM, fibronectin (FN) (100 pg/ml) enhanced the cell proliferation rate and control both cell-to-cell and cell-to-substrate interactions. Through this engineering of FN, a transferrable hADSC sheet was obtained as a free-stranding sheet (122.6 mm²) by a photothermal method. During the harvesting of hADSC sheets by the photothermal method, a collagen layer in-between cells and conductive polymer film (CP) was dissociated, to protect cells from direct exposure to a near infrared (NIR) source. The hADSC sheets were applied to chronic wound of genetically diabetic db/db mice in vivo, to accelerate 30% faster wound closure with a high closure effect (ε_wc) than that of control groups. These results indicated that the engineering of CAM and collagens allow hADSC sheet harvesting, which could be extended to engineer various stem cell sheets for efficient therapies.

Therapeutic approaches for cardiac regeneration and repair

Ischaemic heart disease is a leading cause of death worldwide. Injury to the heart is followed by loss of the damaged cardiomyocytes, which are replaced with fibrotic scar tissue. Depletion of cardiomyocytes results in decreased cardiac contraction, which leads to pathological cardiac dilatation, additional cardiomyocyte loss, and mechanical dysfunction, culminating in heart failure. This sequential reaction is defined as cardiac remodelling. Many therapies have focused on preventing the progressive process of cardiac remodelling to heart failure. However, after patients have developed end-stage heart failure, intervention is limited to heart transplantation. One of the main reasons for the dramatic injurious effect of cardiomyocyte loss is that the adult human heart has minimal regenerative capacity. In the past 2 decades, several strategies to repair the injured heart and improve heart function have been pursued, including cellular and noncellular therapies. In this Review, we discuss current therapeutic approaches for cardiac repair and regeneration, describing outcomes, limitations, and future prospects of preclinical and clinical trials of heart regeneration. Substantial progress has been made towards understanding the cellular and molecular mechanisms regulating heart regeneration, offering the potential to control cardiac remodelling and redirect the adult heart to a regenerative state.

Building a new strategy for treating heart failure using Induced Pluripotent Stem Cells

Although cell therapy using myoblasts, bone marrow cells, or other stem cells appears to improve functional recovery of the failing heart, mainly by cytokine paracrine effects, its effectiveness in severely damaged myocardium is limited, probably because there are too few residual myocytes to promote cytokine-induced angiogenesis. Recently, cardiogenic stem cells, such as c-kit-positive cells, were reported to generate cardiomyogenic lineages, and basic research experiments showed that implanting these cells, which can differentiate into cardiomyocytes, improves heart function. However, this functional recovery may have also mainly depended on cytokine paracrine effects, because the differentiation to cardiomyocytes in vivo was poor. In contrast, while Induced Pluripotent Stem Cell-derived cardiomyocytes have paracrine effects, they also have the potential to supply newly born myocytes that can function synchronously with the recipient myocardium as "mechanically working cells" in severely damaged myocardium. Thus, they could represent a "true" myocardial regeneration therapy that can actually regenerate severely damaged myocardium. In addition, iPS cells, especially disease-specific iPS cells, have other applications in regenerative medicine such as in drug screening. In this report, we present the state of basic research in the field of cardiac iPS cells.

Human iPS cell-derived cardiac tissue sheets for functional restoration of infarcted porcine hearts

To realize human induced pluripotent stem cell (hiPSC)-based cardiac regenerative therapy, evidence of therapeutic advantages in human-sized diseased hearts are indispensable. In combination with an efficient and simultaneous differentiation of various cardiac lineages from hiPSCs and cell sheet technology, we aimed to generate clinical-sized large cardiac tissue sheets (L-CTSs) and to evaluate the therapeutic potential in porcine infarct heart. We simultaneously induced cardiomyocytes (CMs) and vascular cells [vascular endothelial cells (ECs) and vascular mural cells (MCs)] from hiPSCs. We generated L-CTSs using 10cm-sized temperature-responsive culture dishes. We induced myocardial infarction (MI) in micromini-pigs (15–25 kg) and transplanted the L-CTSs (Tx) 2 weeks after MI induction (4 sheets/recipient) under immunosuppression (Tx: n = 5, Sham: n = 5). Self-pulsating L-CTSs were approximately 3.5cm in diameter with 6.8×10⁶±0.8 of cells containing cTnT⁺-CMs (45.6±13.2%), VE-cadherin⁺-ECs (5.3±4.4%) and PDGFRβ⁺-MCs (14.4±20.7%), respectively (n = 5). In Tx group, echocardiogram indicated a significantly higher systolic function of the left ventricle (LV) compared to that in sham control (Sham vs Tx: fractional shortening: 24.2±8.6 vs 40.5±9.7%; p<0.05). Ejection fraction evaluated by left ventriculogram was significantly higher in Tx group (25.3±6.2% vs 39.8±4.2%; p<0.01). Speckle tracking echocardiogram showed a significant increase of circumference strain in infarct and border regions after transplantation. Fibrotic area was significantly lower in Tx group (23.8±4.5 vs 15.9±3.8%; P<0.001). Capillary density in the border region was significantly higher in Tx group (75.9±42.6/mm² vs 137.4±44.8/mm², p<0.001). These data indicate that the L-CTS transplantation attenuated LV remodeling. L-CTSs potentially restore cardiac dysfunction of human-sized infarct heart.

Endoscopic Transplantation of Mesenchymal Stem Cell Sheets in Experimental Colitis in Rats

Owing to the recent progress in regenerative medicine technology, clinical trials that harnessed the regeneration and immune modulation potentiality of stem cells for treating IBD have shown promising results. We investigated the feasibility and utility of intraluminal endoscopic transplantation of rat MSC sheets in murine models of experimental colitis for targeted delivery of stem cells to lesions. We isolated adipose-derived mesenchymal stem cells (AD-MSC) and bone marrow-derived mesenchymal stem cells (BM-MSC) from EGFP-transgenic rats and fabricated the cells in sheet forms using temperature-responsive culture dishes. The MSC sheets were endoscopically transplanted to the inflamed area in electrocoagulation and DNBS colitis model. The effect of the transplantation was verified using endoscopic scoring and histological analysis. In the electrocoagulation model, the AD-MSC group showed significantly decreased ulcer size in the transplanted regions. In the DNBS colitis model, the AD-MSC group showed decreased inflammation and colitis in the transplanted regions. Histologic analysis showed that the MSC sheets had successfully attached to the inflamed mucosa in both the electrocoagulation and DNBS colitis model. Our results show that endoscopic transplantation of MSC sheets could be a new effective mode of stem cell therapy for IBD treatment.

Transplantation of Endothelial Progenitor Cells Overexpressing miR-126-3p Improves Heart Function in Ischemic Cardiomyopathy

BACKGROUND

In a previous study, a low level of miR-126-3p in endothelial progenitor cells (EPCs) was linked to the outcome of ischemic cardiomyopathy (ICM) patients. However, it remains unclear whether transplantation with miR-126-3p-overexpressing EPCs (MO-EPCs) can improve the cardiac function of ICM animal models. Methods and Results: miR-126-3p overexpression by lentiviral vector significantly increased migration and tube-like structures of EPCs from ICM patients. MO-EPCs or non-modified EPCs (NM-EPCs) were transplanted into nude rats with ICM induced by coronary artery ligation. MO-EPC transplantation increased capillary density and EPC survival rate in myocardial tissues of nude rats. Cytokines were also assessed by antibody array and real-time RT-PCR. G-CSF, VEGF-A, IL-3, IL-10, IGF-1, angiogenin, HGF, TIMP-1 and TIMP-2 were upregulated, and IL-8, MCP-1, MCP-2, TNF-α, TNF-β and MIP-1β were downregulated after miR-126-3p overexpression in EPCs. The same results were obtained in infarction tissues of nude rats after MO-EPC transplantation. Eight weeks after MO-EPC transplantation, left ventricular function improved significantly with clearly decreased infarction size, increased anterior wall thickness, and inhibition of inflammation compared with the results for NM-EPC transplantation. However, MO-EPC transplantation showed no increase in survival time of nude rats with ICM during 8 weeks of observation.

CONCLUSIONS

miR-126-3p can restore the biology of EPCs from ICM patients. Moreover, MO-EPC transplantation improves cardiac function effectively, representing a promising future treatment for ICM.

Pluripotent Stem Cell-Derived Cardiomyocytes as a Platform for Cell Therapy Applications: Progress and Hurdles for Clinical Translation

Cardiovascular diseases are the leading cause of morbidity and mortality worldwide. Regenerative therapy has been applied to restore lost cardiac muscle and cardiac performance. Induced pluripotent stem cells (iPSCs) can provide an unlimited source of cardiomyocytes and therefore play a key role in cardiac regeneration. Despite initial encouraging results from pre-clinical studies, progress toward clinical applications has been hampered by issues such as tumorigenesis, arrhythmogenesis, immune rejection, scalability, low graft-cell survival, and poor engraftment. Here, we review recent developments in iPSC research on regenerating injured heart tissue, including novel advances in cell therapy and potential strategies to overcome current obstacles in the field.

Bioengineered tissue solutions for repair, correction and reconstruction in cardiovascular surgery

The treatment of cardiac alterations is still nowadays a dramatic issue in the cardiosurgical practice. Synthetic materials applied in this surgery have failed in their long-term therapeutic efficacy due to low biocompatibility and compliance, especially when used in contractile sites. In order to overcome these treatment pitfalls, novel solutions have been developed based on biological tissues. Patches in pericardium, small intestinal submucosa, as well as engineered tissues of myocardium, heart valves and blood vessels have undergone a large preclinical investigation in regenerative medicine studies. Clinical translation has been started or reached by several of these new bioengineered treatment alternatives. This review will describe the preclinical and clinical experiences realized so far with the application of biological tissues in cardiovascular surgery. It will depict the progressive steps realized in the evolution of this research, as well as it will point out the challenges yet to face in order to generate the ideal biomaterial for cardiovascular repair, corrective and reconstructive surgery.

iPSCs-based generation of vascular cells: reprogramming approaches and applications

Recent advances in the field of induced pluripotent stem cells (iPSCs) research have opened a new avenue for stem cell-based generation of vascular cells. Based on their growth and differentiation potential, human iPSCs constitute a well-characterized, generally unlimited cell source for the mass generation of lineage- and patient-specific vascular cells without any ethical concerns. Human iPSCs-derived vascular cells are perfectly suited for vascular disease modeling studies because patient-derived iPSCs possess the disease-causing mutation, which might be decisive for full expression of the disease phenotype. The application of vascular cells for autologous cell replacement therapy or vascular engineering derived from immune-compatible iPSCs possesses huge clinical potential, but the large-scale production of vascular-specific lineages for regenerative cell therapies depends on well-defined, highly reproducible culture and differentiation conditions. This review will focus on the different strategies to derive vascular cells from human iPSCs and their applications in regenerative therapy, disease modeling and drug discovery approaches.

Cardiac Regeneration with Human Pluripotent Stem Cell-Derived Cardiomyocytes

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), which are collectively called pluripotent stem cells (PSCs), have emerged as a promising source for regenerative medicine. Particularly, human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) have shown robust potential for regenerating injured heart. Over the past two decades, protocols to differentiate hPSCs into CMs at high efficiency have been developed, opening the door for clinical application. Studies further demonstrated therapeutic effects of hPSC-CMs in small and large animal models and the underlying mechanisms of cardiac repair. However, gaps remain in explanations of the therapeutic effects of engrafted hPSC-CMs. In addition, bioengineering technologies improved survival and therapeutic effects of hPSC-CMs in vivo. While most of the original concerns associated with the use of hPSCs have been addressed, several issues remain to be resolved such as immaturity of transplanted cells, lack of electrical integration leading to arrhythmogenic risk, and tumorigenicity. Cell therapy with hPSC-CMs has shown great potential for biological therapy of injured heart; however, more studies are needed to ensure the therapeutic effects, underlying mechanisms, and safety, before this technology can be applied clinically.