Comparison of Cardiomyocyte Differentiation Potential Between Type 1 Diabetic Donor- and Nondiabetic Donor-Derived Induced Pluripotent Stem Cells

Research progress of autoimmune diseases based on induced pluripotent stem cells

Autoimmune diseases can damage specific or multiple organs and tissues, influence the quality of life, and even cause disability and death. A 'disease in a dish' can be developed based on patients-derived induced pluripotent stem cells (iPSCs) and iPSCs-derived disease-relevant cell types to provide a platform for pathogenesis research, phenotypical assays, cell therapy, and drug discovery. With rapid progress in molecular biology research methods including genome-sequencing technology, epigenetic analysis, '-omics' analysis and organoid technology, large amount of data represents an opportunity to help in gaining an in-depth understanding of pathological mechanisms and developing novel therapeutic strategies for these diseases. This paper aimed to review the iPSCs-based research on phenotype confirmation, mechanism exploration, drug discovery, and cell therapy for autoimmune diseases, especially multiple sclerosis, inflammatory bowel disease, and type 1 diabetes using iPSCs and iPSCs-derived cells.

Bilirubin-Induced Neurological Damage: Current and Emerging iPSC-Derived Brain Organoid Models

Bilirubin-induced neurological damage (BIND) has been a subject of studies for decades, yet the molecular mechanisms at the core of this damage remain largely unknown. Throughout the years, many in vivo chronic bilirubin encephalopathy models, such as the Gunn rat and transgenic mice, have further elucidated the molecular basis of bilirubin neurotoxicity as well as the correlations between high levels of unconjugated bilirubin (UCB) and brain damage. Regardless of being invaluable, these models cannot accurately recapitulate the human brain and liver system; therefore, establishing a physiologically recapitulating in vitro model has become a prerequisite to unveil the breadth of complexities that accompany the detrimental effects of UCB on the liver and developing human brain. Stem-cell-derived 3D brain organoid models offer a promising platform as they bear more resemblance to the human brain system compared to existing models. This review provides an explicit picture of the current state of the art, advancements, and challenges faced by the various models as well as the possibilities of using stem-cell-derived 3D organoids as an efficient tool to be included in research, drug screening, and therapeutic strategies for future clinical applications.

Identification of a dihydropyridine scaffold that blocks ryanodine receptors

Ryanodine receptors (RyRs) are large, intracellular ion channels that control Ca²⁺ release from the sarco/endoplasmic reticulum. Dysregulation of RyRs in skeletal muscle, heart, and brain has been implicated in various muscle pathologies, arrhythmia, heart failure, and Alzheimer's disease. Therefore, there is considerable interest in therapeutically targeting RyRs to normalize Ca²⁺ homeostasis in scenarios involving RyR dysfunction. Here, a simple invertebrate screening platform was used to discover new chemotypes targeting RyRs. The approach measured Ca²⁺ signals evoked by cyclic adenosine 5′-diphosphate ribose, a second messenger that sensitizes RyRs. From a 1,534-compound screen, FLI-06 (currently described as a Notch “inhibitor”) was identified as a potent blocker of RyR activity. Two closely related tyrosine kinase inhibitors that stimulate and inhibit Ca²⁺ release through RyRs were also resolved. Therefore, this simple screen yielded RyR scaffolds tractable for development and revealed an unexpected linkage between RyRs and trafficking events in the early secretory pathway.

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FLI-06 inhibits transport in the secretory pathway via an unknown mechanism

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An invertebrate screening platform revealed FLI-06 blocks intracellular Ca²⁺ release

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FLI-06 acts as a potent, cell-permeable ryanodine receptor (RyR) blocker

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The para-substituted dihydropyridine chemotype is a new scaffold for RyR modulation

Disease Modeling of Mitochondrial Cardiomyopathy Using Patient-Specific Induced Pluripotent Stem Cells

Mitochondrial cardiomyopathy (MCM) is characterized as an oxidative phosphorylation disorder of the heart. More than 100 genetic variants in nuclear or mitochondrial DNA have been associated with MCM. However, the underlying molecular mechanisms linking genetic variants to MCM are not fully understood due to the lack of appropriate cellular and animal models. Patient-specific induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs) provide an attractive experimental platform for modeling cardiovascular diseases and predicting drug efficacy to such diseases. Here we introduce the pathological and therapeutic studies of MCM using iPSC-CMs and discuss the questions and latest strategies for research using iPSC-CMs.

Biphasic effect of metformin on human cardiac energetics

Metformin is the first-line medication for treatment of type 2 diabetes and has been shown to reduce heart damage and death. However, mechanisms by which metformin protects human heart remain debated. The aim of the study was to evaluate the cardioprotective effect of metformin on cardiomyocytes derived from human-induced pluripotent stem cells (hiPSC-CMs) and mitochondria isolated from human cardiac tissue. At concentrations ≤2.5 mM, metformin significantly increased oxygen consumption rate (OCR) in the hiPSC-CMs by activating adenosine monophosphate activated protein kinase (AMPK)-dependent signaling and enhancing mitochondrial biogenesis. This effect was abrogated by compound C, an inhibitor of AMPK. At concentrations >5 mM, metformin inhibited the cellular OCR and triggered metabolic reprogramming by enhancing glycolysis and glutaminolysis in the cardiomyocytes. In isolated cardiac mitochondria, metformin did not increase the OCR at any concentrations but inhibited the OCR starting at 1 mM through direct inhibition of electron-transport chain complex I. This was associated with reduction of superoxide production and attenuation of Ca2+-induced mitochondrial permeability transition pore (mPTP) opening in the mitochondria. Thus, in human heart, metformin might improve cardioprotection due to its biphasic effect on mitochondria: at low concentrations, it activates mitochondrial biogenesis via AMPK signaling and increases the OCR; at high concentrations, it inhibits the respiration by directly affecting the activity of complex I, reduces oxidative stress and delays mPTP formation. Moreover, metformin at high concentrations causes metabolic reprogramming by enhancing glycolysis and glutaminolysis. These effects can be a beneficial adjunct to patients with impaired endogenous cardioprotective responses.

Human Induced Pluripotent Stem Cells as a Disease Model System for Heart Failure

PURPOSE OF REVIEW

Heart failure is among the most prevalent disease complexes overall and is associated with high morbidity and mortality. The underlying aetiology is manifold including coronary artery disease, genetic alterations and mutations, viral infections, adverse immune responses, and cardiac toxicity. To date, no specific therapies have been developed despite notable efforts. This can especially be attributed to hurdles in translational research, mainly due to the lack of proficient models of heart failure limited translation of therapeutic approaches from bench to bedside.

RECENT FINDINGS

Human induced pluripotent stem cells (hiPSCs) are rising in popularity, granting the ability to divide infinitely, to hold human, patient-specific genome, and to differentiate into any human cell, including cardiomyocytes (hiPSC-CMs). This brings magnificent promise to cardiological research, providing the possibility to recapitulate cardiac diseases in a dish. Advances in yield, maturity, and in vivo resemblance due to straightforward, low-cost protocols, high-throughput approaches, and complex 3D cultures have made this tool widely applicable. In recent years, hiPSC-CMs have been used to model a wide variety of cardiac diseases, bringing along the possibility to not only elucidate molecular mechanisms but also to test novel therapeutic approaches in the dish. Within the last decade, hiPSC-CMs have been exponentially employed to model heart failure. Constant advancements are aiming at improvements of differentiation protocols, hiPSC-CM maturity, and assays to elucidate molecular mechanisms and cellular functions. However, hiPSC-CMs are remaining relatively immature, and in vitro models can only partially recapitulate the complex interactions in vivo. Nevertheless, hiPSC-CMs have evolved as an essential model system in cardiovascular research.

A Concise Review on Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Personalized Regenerative Medicine

The induced pluripotent stem cells (iPSCs) are derived from somatic cells by using reprogramming factors such as Oct4, Sox2, Klf4, and c-Myc (OSKM) or Oct4, Sox2, Nanog and Lin28 (OSNL). They resemble embryonic stem cells (ESCs) and have the ability to differentiate into cell lineage of all three germ-layer, including cardiomyocytes (CMs). The CMs can be generated from iPSCs by inducing embryoid bodies (EBs) formation and treatment with activin A, bone morphogenic protein 4 (BMP4), and inhibitors of Wnt signaling. However, these iPSC-derived CMs are a heterogeneous population of cells and require purification and maturation to mimic the in vivo CMs. The matured CMs can be used for various therapeutic purposes in regenerative medicine by cardiomyoplasty or through the development of tissue-engineered cardiac patches. In recent years, significant advancements have been made in the isolation of iPSC and their differentiation, purification, and maturation into clinically usable CMs. Newer small molecules have also been identified to substitute the reprogramming factors for iPSC generation as well as for direct differentiation of somatic cells into CMs without an intermediary pluripotent state. This review provides a concise update on the generation of iPSC-derived CMs and their application in personalized cardiac regenerative medicine. It also discusses the current limitations and challenges in the application of iPSC-derived CMs. Graphical abstract.

Modeling alcohol-induced neurotoxicity using human induced pluripotent stem cell-derived three-dimensional cerebral organoids

Maternal alcohol exposure during pregnancy can substantially impact the development of the fetus, causing a range of symptoms, known as fetal alcohol spectrum disorders (FASDs), such as cognitive dysfunction and psychiatric disorders, with the pathophysiology and mechanisms largely unknown. Recently developed human cerebral organoids from induced pluripotent stem cells are similar to fetal brains in the aspects of development and structure. These models allow more relevant in vitro systems to be developed for studying FASDs than animal models. Modeling binge drinking using human cerebral organoids, we sought to quantify the downstream toxic effects of alcohol (ethanol) on neural pathology phenotypes and signaling pathways within the organoids. The results revealed that alcohol exposure resulted in unhealthy organoids at cellular, subcellular, bioenergetic metabolism, and gene expression levels. Alcohol induced apoptosis on organoids. The apoptotic effects of alcohol on the organoids depended on the alcohol concentration and varied between cell types. Specifically, neurons were more vulnerable to alcohol-induced apoptosis than astrocytes. The alcohol-treated organoids exhibit ultrastructural changes such as disruption of mitochondria cristae, decreased intensity of mitochondrial matrix, and disorganized cytoskeleton. Alcohol exposure also resulted in mitochondrial dysfunction and metabolic stress in the organoids as evidenced by (1) decreased mitochondrial oxygen consumption rates being linked to basal respiration, ATP production, proton leak, maximal respiration and spare respiratory capacity, and (2) increase of non-mitochondrial respiration in alcohol-treated organoids compared with control groups. Furthermore, we found that alcohol treatment affected the expression of 199 genes out of 17,195 genes analyzed. Bioinformatic analyses showed the association of these dysregulated genes with 37 pathways related to clinically relevant pathologies such as psychiatric disorders, behavior, nervous system development and function, organismal injury and abnormalities, and cellular development. Notably, 187 of these genes are critically involved in neurodevelopment, and/or implicated in nervous system physiology and neurodegeneration. Furthermore, the identified genes are key regulators of multiple pathways linked in networks. This study extends for the first time animal models of binge drinking-related FASDs to a human model, allowing in-depth analyses of neurotoxicity at tissue, cellular, subcellular, metabolism, and gene levels. Hereby, we provide novel insights into alcohol-induced pathologic phenotypes, cell type-specific vulnerability, and affected signaling pathways and molecular networks, that can contribute to a better understanding of the developmental neurotoxic effects of binge drinking during pregnancy.

Diabetic Cardiomyopathy Modelling Using Induced Pluripotent Stem Cell Derived Cardiomyocytes: Recent Advances and Emerging Models

The global burden of diabetes has drastically increased over the past decades and in 2017 approximately 4 million deaths were caused by diabetes and cardiovascular complications. Diabetic cardiomyopathy is a common complication of diabetes with early manifestations of diastolic dysfunction and left ventricular hypertrophy with subsequent progression to systolic dysfunction and ultimately heart failure. An in vitro model accurately recapitulating key processes of diabetic cardiomyopathy would provide a useful tool for investigations of underlying disease mechanisms to further our understanding of the disease and thereby potentially advance treatment strategies for patients. With their proliferative capacity and differentiation potential, human induced pluripotent stem cells (iPSCs) represent an appealing cell source for such a model system and cardiomyocytes derived from induced pluripotent stem cells have been used to establish other cardiovascular related disease models. Here we review recently made advances and discuss challenges still to be overcome with regard to diabetic cardiomyopathy models, with a special focus on iPSC-based systems. Recent publications as well as preliminary data presented here demonstrate the feasibility of generating cardiomyocytes with a diabetic phenotype, displaying insulin resistance, impaired calcium handling and hypertrophy. However, capturing the full metabolic- and functional phenotype of the diabetic cardiomyocyte remains to be accomplished.

Dynamic Characterization of Structural, Molecular, and Electrophysiological Phenotypes of Human-Induced Pluripotent Stem Cell-Derived Cerebral Organoids, and Comparison with Fetal and Adult Gene Profiles

BACKGROUND

The development of 3D cerebral organoid technology using human-induced pluripotent stem cells (iPSCs) provides a promising platform to study how brain diseases are appropriately modeled and treated. So far, understanding of the characteristics of organoids is still in its infancy. The current study profiled, for the first time, the electrophysiological properties of organoids at molecular and cellular levels and dissected the potential age equivalency of 2-month-old organoids to human ones by a comparison of gene expression profiles among cerebral organoids, human fetal and adult brains.

RESULTS

Cerebral organoids exhibit heterogeneous gene and protein markers of various brain cells, such as neurons, astrocytes, and vascular cells (endothelial cells and smooth muscle cells) at 2 months, and increases in neural, glial, vascular, and channel-related gene expression over a 2-month differentiation course. Two-month organoids exhibited action potentials, multiple channel activities, and functional electrophysiological responses to the anesthetic agent propofol. A bioinformatics analysis of 20,723 gene expression profiles showed the similar distance of gene profiles in cerebral organoids to fetal and adult brain tissues. The subsequent Ingenuity Pathway Analysis (IPA) of select canonical pathways related to neural development, network formation, and electrophysiological signaling, revealed that only calcium signaling, cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) signaling in neurons, glutamate receptor signaling, and synaptogenesis signaling were predicted to be downregulated in cerebral organoids relative to fetal samples. Nearly all cerebral organoid and fetal pathway phenotypes were predicted to be downregulated compared with adult tissue.

CONCLUSIONS

This novel study highlights dynamic development, cellular heterogeneity and electrophysiological activity. In particular, for the first time, electrophysiological drug response recapitulates what occurs in vivo, and neural characteristics are predicted to be highly similar to the human brain, further supporting the promising application of the cerebral organoid system for the modeling of the human brain in health and disease. Additionally, the studies from these characterizations of cerebral organoids in multiple levels and the findings from gene comparisons between cerebral organoids and humans (fetuses and adults) help us better understand this cerebral organoid-based cutting-edge platform and its wide uses in modeling human brain in terms of health and disease, development, and testing drug efficacy and toxicity.

A Brief Review of Current Maturation Methods for Human Induced Pluripotent Stem Cells-Derived Cardiomyocytes

Cardiovascular diseases are the leading cause of death worldwide. Therefore, the discovery of induced pluripotent stem cells (iPSCs) and the subsequent generation of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) was a pivotal point in regenerative medicine and cardiovascular research. They constituted an appealing tool for replacing dead and dysfunctional cardiac tissue, screening cardiac drugs and toxins, and studying inherited cardiac diseases. The problem is that these cells remain largely immature, and in order to utilize them, they must reach a functional degree of maturity. To attempt to mimic in vivo environment, various methods including prolonging culture time, co-culture and modulations of chemical, electrical, mechanical culture conditions have been tried. In addition to that, changing the topology of the culture made huge progress with the introduction of the 3D culture that closely resembles the in vivo cardiac topology and overcomes many of the limitations of the conventionally used 2D models. Nonetheless, 3D culture alone is not enough, and using a combination of these methods is being explored. In this review, we summarize the main differences between immature, fetal-like hiPSC-CMs and adult cardiomyocytes, then glance at the current approaches used to promote hiPSC-CMs maturation. In the second part, we focus on the evolving 3D culture model - it's structure, the effect on hiPSC-CMs maturation, incorporation with different maturation methods, limitations and future prospects.

Vascular progenitors generated from tankyrase inhibitor-regulated naïve diabetic human iPSC potentiate efficient revascularization of ischemic retina

Here, we report that the functionality of vascular progenitors (VP) generated from normal and disease-primed conventional human induced pluripotent stem cells (hiPSC) can be significantly improved by reversion to a tankyrase inhibitor-regulated human naïve epiblast-like pluripotent state. Naïve diabetic vascular progenitors (N-DVP) differentiated from patient-specific naïve diabetic hiPSC (N-DhiPSC) possessed higher vascular functionality, maintained greater genomic stability, harbored decreased lineage-primed gene expression, and were more efficient in migrating to and re-vascularizing the deep neural layers of the ischemic retina than isogenic diabetic vascular progenitors (DVP). These findings suggest that reprogramming to a stable naïve human pluripotent stem cell state may effectively erase dysfunctional epigenetic donor cell memory or disease-associated aberrations in patient-specific hiPSC. More broadly, tankyrase inhibitor-regulated naïve hiPSC (N-hiPSC) represent a class of human stem cells with high epigenetic plasticity, improved multi-lineage functionality, and potentially high impact for regenerative medicine.

Isolation and Culture of Human-Induced Pluripotent Stem Cell-Derived Cerebral Organoid Cells

The advent of human-induced pluripotent stem cell (iPSC)-derived three-dimensional (3D) cerebral organoids provides unprecedented opportunities of modeling human brains in states of health and disorder. Emerging data supports that cerebral organoids allow for more relevant in vitro systems for studying the human brain system and diseases than the current widely used 2D monolayer cell culture. Thus, the ability to isolate, culture, and maintain human brain cells from cerebral organoids is highly needed, particularly for studies on organoid-derived cell-type-specific signaling and their electrophysiological properties. Here we present a protocol to isolate and culture brain cells from 2-month human iPSC-derived cerebral organoids. The dissociation and plating of cells from organoids takes 3-4 h. The dissociated cells can be maintained in culture for up to at least 3 weeks. Some cells expressed the neuron-specific marker microtubule-associated protein 2 and exhibited spontaneous action potentials.

Fatty Acid-Treated Induced Pluripotent Stem Cell-Derived Human Cardiomyocytes Exhibit Adult Cardiomyocyte-Like Energy Metabolism Phenotypes

Human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) (iPSC-CMs) are a promising cell source for myocardial regeneration, disease modeling and drug assessment. However, iPSC-CMs exhibit immature fetal CM-like characteristics that are different from adult CMs in several aspects, including cellular structure and metabolism. As an example, glycolysis is a major energy source for immature CMs. As CMs mature, the mitochondrial oxidative capacity increases, with fatty acid β-oxidation becoming a key energy source to meet the heart’s high energy demand. The immaturity of iPSC-CMs thereby limits their applications. The aim of this study was to investigate whether the energy substrate fatty acid-treated iPSC-CMs exhibit adult CM-like metabolic properties. After 20 days of differentiation from human iPSCs, iPSC-CMs were sequentially cultured with CM purification medium (lactate+/glucose-) for 7 days and maturation medium (fatty acids+/glucose-) for 3–7 days by mimicking the adult CM’s preference of utilizing fatty acids as a major metabolic substrate. The purity and maturity of iPSC-CMs were characterized via the analysis of: (1) Expression of CM-specific markers (e.g., troponin T, and sodium and potassium channels) using RT-qPCR, Western blot or immunofluorescence staining and electron microscopy imaging; and (2) cell energy metabolic profiles using the XF96 Extracellular Flux Analyzer. iPSCs-CMs (98% purity) cultured in maturation medium exhibited enhanced elongation, increased mitochondrial numbers with more aligned Z-lines, and increased expression of matured CM-related genes, suggesting that fatty acid-contained medium promotes iPSC-CMs to undergo maturation. In addition, the oxygen consumption rate (OCR) linked to basal respiration, ATP production, and maximal respiration and spare respiratory capacity (representing mitochondrial function) was increased in matured iPSC-CMs. Mature iPSC-CMs also displayed a larger change in basal and maximum respirations due to the utilization of exogenous fatty acids (palmitate) compared with non-matured control iPSC-CMs. Etomoxir (a carnitine palmitoyltransferase 1 inhibitor) but not 2-deoxyglucose (an inhibitor of glycolysis) abolished the palmitate pretreatment-mediated OCR increases in mature iPSC-CMs. Collectively, our data demonstrate for the first time that fatty acid treatment promotes metabolic maturation of iPSC-CMs (as evidenced by enhanced mitochondrial oxidative function and strong capacity of utilizing fatty acids as energy source). These matured iPSC-CMs might be a promising human CM source for broad biomedical application.

Compromised Barrier Function in Human Induced Pluripotent Stem-Cell-Derived Retinal Pigment Epithelial Cells from Type 2 Diabetic Patients

In diabetic patients, high blood glucose induces alterations in retinal function and can lead to visual impairment due to diabetic retinopathy. In immortalized retinal pigment epithelial (RPE) cultures, high glucose concentrations are shown to lead to impairment in epithelial barrier properties. For the first time, the induced pluripotent stem-cell-derived retinal pigment epithelium (hiPSC-RPE) cell lines derived from type 2 diabetics and healthy control patients were utilized to assess the effects of glucose concentration on the cellular functionality. We show that both type 2 diabetic and healthy control hiPSC-RPE lines differentiate and mature well, both in high and normal glucose concentrations, express RPE specific genes, secrete pigment epithelium derived factor, and form a polarized cell layer. Here, type 2 diabetic hiPSC-RPE cells had a decreased barrier function compared to controls. Added insulin increased the epithelial cell layer tightness in normal glucose concentrations, and the effect was more evident in type 2 diabetics than in healthy control hiPSC-RPE cells. In addition, the preliminary functionality assessments showed that type 2 diabetic hiPSC-RPE cells had attenuated autophagy detected via ubiquitin-binding protein p62/Sequestosome-1 (p62/SQSTM1) accumulation, and lowered pro- matrix metalloproteinase 2 (proMMP2) as well as increased pro-MMP9 secretion. These results suggest that the cellular ability to tolerate stress is possibly decreased in type 2 diabetic RPE cells.

Studying Human Neurological Disorders Using Induced Pluripotent Stem Cells: From 2D Monolayer to 3D Organoid and Blood Brain Barrier Models

Neurological disorders have emerged as a predominant healthcare concern in recent years due to their severe consequences on quality of life and prevalence throughout the world. Understanding the underlying mechanisms of these diseases and the interactions between different brain cell types is essential for the development of new therapeutics. Induced pluripotent stem cells (iPSCs) are invaluable tools for neurological disease modeling, as they have unlimited self-renewal and differentiation capacity. Mounting evidence shows: (i) various brain cells can be generated from iPSCs in two-dimensional (2D) monolayer cultures; and (ii) further advances in 3D culture systems have led to the differentiation of iPSCs into organoids with multiple brain cell types and specific brain regions. These 3D organoids have gained widespread attention as in vitro tools to recapitulate complex features of the brain, and (iii) complex interactions between iPSC-derived brain cell types can recapitulate physiological and pathological conditions of blood-brain barrier (BBB). As iPSCs can be generated from diverse patient populations, researchers have effectively applied 2D, 3D, and BBB models to recapitulate genetically complex neurological disorders and reveal novel insights into molecular and genetic mechanisms of neurological disorders. In this review, we describe recent progress in the generation of 2D, 3D, and BBB models from iPSCs and further discuss their limitations, advantages, and future ventures. This review also covers the current status of applications of 2D, 3D, and BBB models in drug screening, precision medicine, and modeling a wide range of neurological diseases (e.g., neurodegenerative diseases, neurodevelopmental disorders, brain injury, and neuropsychiatric disorders). © 2019 American Physiological Society. Compr Physiol 9:565-611, 2019.

Can Human Pluripotent Stem Cell-Derived Cardiomyocytes Advance Understanding of Muscular Dystrophies?

Muscular dystrophies (MDs) are clinically and molecularly a highly heterogeneous group of single-gene disorders that primarily affect striated muscles. Cardiac disease is present in several MDs where it is an important contributor to morbidity and mortality. Careful monitoring of cardiac issues is necessary but current management of cardiac involvement does not effectively protect from disease progression and cardiac failure. There is a critical need to gain new knowledge on the diverse molecular underpinnings of cardiac disease in MDs in order to guide cardiac treatment development and assist in reaching a clearer consensus on cardiac disease management in the clinic. Animal models are available for the majority of MDs and have been invaluable tools in probing disease mechanisms and in pre-clinical screens. However, there are recognized genetic, physiological, and structural differences between human and animal hearts that impact disease progression, manifestation, and response to pharmacological interventions. Therefore, there is a need to develop parallel human systems to model cardiac disease in MDs. This review discusses the current status of cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSC) to model cardiac disease, with a focus on Duchenne muscular dystrophy (DMD) and myotonic dystrophy (DM1). We seek to provide a balanced view of opportunities and limitations offered by this system in elucidating disease mechanisms pertinent to human cardiac physiology and as a platform for treatment development or refinement.

iPSC technology-based regenerative therapy for diabetes

The directed differentiation of human pluripotent stem cells, such as embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs), into pancreatic endocrine lineages has been vigorously examined by reproducing the in vivo developmental processes of the pancreas. Recent advances in this research field have enabled the generation from hESCs/iPSCs of functionally mature β-like cells in vitro that show glucose-responsive insulin secretion ability. The therapeutic potentials of hESC/iPSC-derived pancreatic cells have been evaluated using diabetic animal models, and transplantation methods including immunoprotective devices that prevent immune responses from hosts to the implanted pancreatic cells have been investigated towards the development of regenerative therapies against diabetes. These efforts led to the start of a clinical trial that involves the implantation of hESC-derived pancreatic progenitors into type 1 diabetes patients. In addition, patient-derived iPSCs have been generated from diabetes-related disorders towards the creation of novel in vitro disease models and drug discovery, although few reports so far have analyzed the disease mechanisms. Considering recent advances in differentiation methods that generate pancreatic endocrine lineages, we will see the development of novel cell therapies and therapeutic drugs against diabetes based on iPSC technology-based research in the next decade.

Concise Review: Challenges in Regenerating the Diabetic Heart: A Comprehensive Review

Stem cell therapy is one of the promising regenerative strategies developed to improve cardiac function in patients with ischemic heart diseases (IHD). However, this approach is limited in IHD patients with diabetes due to a progressive decline in the regenerative capacity of stem cells. This decline is mainly attributed to the metabolic memory incurred by diabetes on stem cell niche and their systemic cues. Understanding the molecular pathways involved in the diabetes-induced deterioration of stem cell function will be critical for developing new cardiac regeneration therapies. In this review, we first discuss the most common molecular alterations occurring in the diabetic stem cells/progenitor cells. Next, we highlight the key signaling pathways that can be dysregulated in a diabetic environment and impair the mobilization of stem/progenitor cells, which is essential for the transplanted/endogenous stem cells to reach the site of injury. We further discuss the possible methods of preconditioning the diabetic cardiac progenitor cell (CPC) with an aim to enrich the availability of efficient stem cells to regenerate the diseased diabetic heart. Finally, we propose new modalities for enriching the diabetic CPC through genetic or tissue engineering that would aid in developing autologous therapeutic strategies, improving the proliferative, angiogenic, and cardiogenic properties of diabetic stem/progenitor cells. Stem Cells 2017;35:2009-2026.

Cardiomyocytes from human pluripotent stem cells: From laboratory curiosity to industrial biomedical platform

Cardiomyocytes from human pluripotent stem cells (hPSCs-CMs) could revolutionise biomedicine. Global burden of heart failure will soon reach USD $90bn, while unexpected cardiotoxicity underlies 28% of drug withdrawals. Advances in hPSC isolation, Cas9/CRISPR genome engineering and hPSC-CM differentiation have improved patient care, progressed drugs to clinic and opened a new era in safety pharmacology. Nevertheless, predictive cardiotoxicity using hPSC-CMs contrasts from failure to almost total success. Since this likely relates to cell immaturity, efforts are underway to use biochemical and biophysical cues to improve many of the ~30 structural and functional properties of hPSC-CMs towards those seen in adult CMs. Other developments needed for widespread hPSC-CM utility include subtype specification, cost reduction of large scale differentiation and elimination of the phenotyping bottleneck. This review will consider these factors in the evolution of hPSC-CM technologies, as well as their integration into high content industrial platforms that assess structure, mitochondrial function, electrophysiology, calcium transients and contractility. This article is part of a Special Issue entitled: Cardiomyocyte Biology: Integration of Developmental and Environmental Cues in the Heart edited by Marcus Schaub and Hughes Abriel.