Disease modeling and lentiviral gene transfer in patient-specific induced pluripotent stem cells from late-onset Pompe disease patient

Mitochondrial dysfunction is associated with hypertrophic cardiomyopathy in Pompe disease-specific induced pluripotent stem cell-derived cardiomyocytes

Pompe disease (PD) is a rare autosomal recessive disorder that presents with progressive hypertrophic cardiomyopathy. However, the detailed mechanism remains clarified. Herein, PD patient-specific induced pluripotent stem cells were differentiated into cardiomyocytes (PD-iCMs) that exhibited cardiomyopathic features of PD, including decreased acid alpha-glucosidase activity, lysosomal glycogen accumulation and hypertrophy. The defective mitochondria were involved in the cardiac pathology as shown by the significantly decreased number of mitochondria and impaired respiratory function and ATP production in PD-iCMs, which was partially due to elevated levels of intracellular reactive oxygen species produced from depolarized mitochondria. Further analysis showed that impaired fusion and autophagy of mitochondria and declined expression of mitochondrial complexes underlies the mechanism of dysfunctional mitochondria. This was alleviated by supplementation with recombinant human acid alpha-glucosidase that improved the mitochondrial function and concomitantly mitigated the cardiac pathology. Therefore, this study suggests that defective mitochondria underlie the pathogenesis of cardiomyopathy in patients with PD.

Targeted genetic therapies for inherited disorders that affect both cardiac and skeletal muscle

Skeletal myopathies and ataxias with secondary cardiac involvement are complex, progressive and debilitating conditions. As life expectancy increases across these conditions, cardiac involvement often becomes more prominent. This highlights the need for targeted therapies that address these evolving cardiac pathologies. Musculopathies by and large lack cures that directly target the genetic basis of the diseases; however, as our understanding of the genetic causes of these conditions has evolved, it has become tractable to develop targeted therapies using biologics, to design precision approaches to target the primary genetic causes of these varied diseases. Using the examples of Duchenne muscular dystrophy, Friedreich ataxia and Pompe disease, we discuss how the genetic causes of such diseases derail diverse homeostatic, energetic and signalling pathways, which span multiple cellular systems in varied tissues across the body. We outline existing therapeutics and treatments in the context of emerging novel genetic approaches. We discuss the hurdles that the field must overcome to deliver targeted therapies across the many tissue types affected in primary myopathies.

Isotopic Tracing of Nucleotide Sugar Metabolism in Human Pluripotent Stem Cells

Metabolism not only produces energy necessary for the cell but is also a key regulator of several cellular functions, including pluripotency and self-renewal. Nucleotide sugars (NSs) are activated sugars that link glucose metabolism with cellular functions via protein N-glycosylation and O-GlcNAcylation. Thus, understanding how different metabolic pathways converge in the synthesis of NSs is critical to explore new opportunities for metabolic interference and modulation of stem cell functions. Tracer-based metabolomics is suited for this challenge, however chemically-defined, customizable media for stem cell culture in which nutrients can be replaced with isotopically labeled analogs are scarcely available. Here, we established a customizable flux-conditioned E8 (FC-E8) medium that enables stem cell culture with stable isotopes for metabolic tracing, and a dedicated liquid chromatography mass-spectrometry (LC-MS/MS) method targeting metabolic pathways converging in NS biosynthesis. By 13C6-glucose feeding, we successfully traced the time-course of carbon incorporation into NSs directly via glucose, and indirectly via other pathways, such as glycolysis and pentose phosphate pathways, in induced pluripotent stem cells (hiPSCs) and embryonic stem cells. Then, we applied these tools to investigate the NS biosynthesis in hiPSC lines from a patient affected by deficiency of phosphoglucomutase 1 (PGM1), an enzyme regulating the synthesis of the two most abundant NSs, UDP-glucose and UDP-galactose.

Induced pluripotent stem cell for modeling Pompe disease

Pompe disease (PD) is a rare, autosomal recessive, inherited, and progressive metabolic disorder caused by α-glucosidase defect in lysosomes, resulting in abnormal glycogen accumulation. Patients with PD characteristically have multisystem pathological disorders, particularly hypertrophic cardiomyopathy, muscle weakness, and hepatomegaly. Although the pathogenesis and clinical outcomes of PD are well-established, disease-modeling ability, mechanism elucidation, and drug development targeting PD have been substantially limited by the unavailable PD-relevant cell models. This obstacle has been overcome with the help of induced pluripotent stem cell (iPSC) reprogramming technology, thus providing a powerful tool for cell replacement therapy, disease modeling, drug screening, and drug toxicity assessment. This review focused on the exciting achievement of PD disease modeling and mechanism exploration using iPSC.

Human Induced Pluripotent Stem Cell as a Disease Modeling and Drug Development Platform-A Cardiac Perspective

A comprehensive understanding of the pathophysiology and cellular responses to drugs in human heart disease is limited by species differences between humans and experimental animals. In addition, isolation of human cardiomyocytes (CMs) is complicated because cells obtained by biopsy do not proliferate to provide sufficient numbers of cells for preclinical studies in vitro. Interestingly, the discovery of human-induced pluripotent stem cell (hiPSC) has opened up the possibility of generating and studying heart disease in a culture dish. The combination of reprogramming and genome editing technologies to generate a broad spectrum of human heart diseases in vitro offers a great opportunity to elucidate gene function and mechanisms. However, to exploit the potential applications of hiPSC-derived-CMs for drug testing and studying adult-onset cardiac disease, a full functional characterization of maturation and metabolic traits is required. In this review, we focus on methods to reprogram somatic cells into hiPSC and the solutions for overcome immaturity of the hiPSC-derived-CMs to mimic the structure and physiological properties of the adult human CMs to accurately model disease and test drug safety. Finally, we discuss how to improve the culture, differentiation, and purification of CMs to obtain sufficient numbers of desired types of hiPSC-derived-CMs for disease modeling and drug development platform.

Inborn errors of metabolism: Lessons from iPSC models

The possibility of reprogramming human somatic cells to pluripotency has opened unprecedented opportunities for creating genuinely human experimental models of disease. Inborn errors of metabolism (IEMs) constitute a greatly heterogeneous class of diseases that appear, in principle, especially suited to be modeled by iPSC-based technology. Indeed, dozens of IEMs have already been modeled to some extent using patient-specific iPSCs. Here, we review the advantages and disadvantages of iPSC-based disease modeling in the context of IEMs, as well as particular challenges associated to this approach, together with solutions researchers have proposed to tackle them. We have structured this review around six lessons that we have learnt from those previous modeling efforts, and that we believe should be carefully considered by researchers wishing to embark in future iPSC-based models of IEMs.

Gaining Insight into Mitochondrial Genetic Variation and Downstream Pathophysiology: What Can i(PSCs) Do?

Mitochondria are specialized organelles involved in energy production that have retained their own genome throughout evolutionary history. The mitochondrial genome (mtDNA) is maternally inherited and requires coordinated regulation with nuclear genes to produce functional enzyme complexes that drive energy production. Each mitochondrion contains 5-10 copies of mtDNA and consequently, each cell has several hundreds to thousands of mtDNAs. Due to the presence of multiple copies of mtDNA in a mitochondrion, mtDNAs with different variants may co-exist, a condition called heteroplasmy. Heteroplasmic variants can be clonally expanded, even in post-mitotic cells, as replication of mtDNA is not tied to the cell-division cycle. Heteroplasmic variants can also segregate during germ cell formation, underlying the inheritance of some mitochondrial mutations. Moreover, the uneven segregation of heteroplasmic variants is thought to underlie the heterogeneity of mitochondrial variation across adult tissues and resultant differences in the clinical presentation of mitochondrial disease. Until recently, however, the mechanisms mediating the relation between mitochondrial genetic variation and disease remained a mystery, largely due to difficulties in modeling human mitochondrial genetic variation and diseases. The advent of induced pluripotent stem cells (iPSCs) and targeted gene editing of the nuclear, and more recently mitochondrial, genomes now provides the ability to dissect how genetic variation in mitochondrial genes alter cellular function across a variety of human tissue types. This review will examine the origins of mitochondrial heteroplasmic variation and propagation, and the tools used to model mitochondrial genetic diseases. Additionally, we discuss how iPSC technologies represent an opportunity to advance our understanding of human mitochondrial genetics in disease.

Modified Spirulina maxima Pectin Nanoparticles Improve the Developmental Competence of In Vitro Matured Porcine Oocytes

Simple Summary

Poor in vitro embryo development is a major obstacle in porcine assisted reproduction. In the current study, we utilized modified Spirulina maxima pectin nanoparticles as a supplement to improve porcine in vitro maturation medium. Results showed that modified Spirulina maxima pectin nanoparticles at 2.5 µg/mL improved oocyte maturation in form of first polar body extrusion, reduced oxidative stress, and increased the developmental competence of the oocytes after parthenogenetic activation and somatic cell nuclear transfer. Moreover, the relative transcripts quantification showed significant increase in the pluripotency-associated transcripts in the resultant cloned embryos after modified Spirulina maxima pectin nanoparticles supplementation. Therefore, we provide an optimum in vitro maturation condition to improve the in vitro embryo production in porcine.

Abstract

Molecular approaches have been used to determine metabolic substrates involved in the early embryonic processes to provide adequate culture conditions. To investigate the effect of modified Spirulina maxima pectin nanoparticles (MSmPNPs) on oocyte developmental competence, cumulus–oocyte complexes (COCs) retrieved from pig slaughterhouse ovaries were subjected to various concentrations of MSmPNPs (0, 2.5, 5.0, and 10 µg/mL) during in vitro maturation (IVM). In comparison to the control, MSmPNPs-5.0, and MSmPNPs-10 groups, oocytes treated with 2.5 µg/mL MSmPNPs had significantly increased glutathione (GSH) levels and lower levels of reactive oxygen species (ROS). Following parthenogenetic activation, the MSmPNPs-2.5 group had a considerably higher maturation and cleavage rates, blastocyst development, total cell number, and ratio of inner cell mass/trophectoderm (ICM:TE) cells, when compared with those in the control and all other treated groups. Furthermore, similar findings were reported for the developmental competence of somatic cell nuclear transfer (SCNT)-derived embryos. Additionally, the relative quantification of POU5F1, DPPA2, and NDP52 mRNA transcript levels were significantly higher in the MSmPNPs-2.5 group than in the control and other treated groups. Taken together, the current findings suggest that MSmPNP treatment alleviates oxidative stress and enhances the developmental competence of porcine in vitro matured oocytes after parthenogenetic activation and SCNT.

Stem Cell Applications in Lysosomal Storage Disorders: Progress and Ongoing Challenges

Lysosomal storage disorders (LSDs) are rare inborn errors of metabolism caused by defects in lysosomal function. These diseases are characterized by accumulation of completely or partially degraded substrates in the lysosomes leading to cellular dysfunction of the affected cells. Currently, enzyme replacement therapies (ERTs), treatments directed at substrate reduction (SRT), and hematopoietic stem cell (HSC) transplantation are the only treatment options for LSDs, and the effects of these treatments depend strongly on the type of LSD and the time of initiation of treatment. However, some of the LSDs still lack a durable and curative treatment. Therefore, a variety of novel treatments for LSD patients has been developed in the past few years. However, despite significant progress, the efficacy of some of these treatments remains limited because these therapies are often initiated after irreversible organ damage has occurred.Here, we provide an overview of the known effects of LSDs on stem cell function, as well as a synopsis of available stem cell-based cell and gene therapies that have been/are being developed for the treatment of LSDs. We discuss the advantages and disadvantages of use of hematopoietic stem cell (HSC), mesenchymal stem cell (MSC), and induced pluripotent stem cell (iPSC)-related (gene) therapies. An overview of current research data indicates that when stem cell and/or gene therapy applications are used in combination with existing therapies such as ERT, SRT, and chaperone therapies, promising results can be achieved, showing that these treatments may result in alleviation of existing symptoms and/or prevention of progression of the disease. All together, these studies offer some insight in LSD stem cell biology and provide a hopeful perspective for the use of stem cells. Further development and improvement of these stem cell (gene) combination therapies may greatly improve the current treatment options and outcomes of patients with a LSD.

Modeling CNS Involvement in Pompe Disease Using Neural Stem Cells Generated from Patient-Derived Induced Pluripotent Stem Cells

Pompe disease is a lysosomal storage disorder caused by autosomal recessive mutations in the acid alpha-glucosidase (GAA) gene. Acid alpha-glucosidase deficiency leads to abnormal glycogen accumulation in patient cells. Given the increasing evidence of central nervous system (CNS) involvement in classic infantile Pompe disease, we used neural stem cells, differentiated from patient induced pluripotent stem cells, to model the neuronal phenotype of Pompe disease. These Pompe neural stem cells exhibited disease-related phenotypes including glycogen accumulation, increased lysosomal staining, and secondary lipid buildup. These morphological phenotypes in patient neural stem cells provided a tool for drug efficacy evaluation. Two potential therapeutic agents, hydroxypropyl-β-cyclodextrin and δ-tocopherol, were tested along with recombinant human acid alpha-glucosidase (rhGAA) in this cell-based Pompe model. Treatment with rhGAA reduced LysoTracker staining in Pompe neural stem cells, indicating reduced lysosome size. Additionally, treatment of diseased neural stem cells with the combination of hydroxypropyl-β-cyclodextrin and δ-tocopherol significantly reduced the disease phenotypes. These results demonstrated patient-derived Pompe neural stem cells could be used as a model to study disease pathogenesis, to evaluate drug efficacy, and to screen compounds for drug discovery in the context of correcting CNS defects.

hiPSC-Derived Cardiac Tissue for Disease Modeling and Drug Discovery

Relevant, predictive normal, or disease model systems are of vital importance for drug development. The difference between nonhuman models and humans could contribute to clinical trial failures despite ideal nonhuman results. As a potential substitute for animal models, human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs) provide a powerful tool for drug toxicity screening, modeling cardiovascular diseases, and drug discovery. Here, we review recent hiPSC-CM disease models and discuss the features of hiPSC-CMs, including subtype and maturation and the tissue engineering technologies for drug assessment. Updates from the international multisite collaborators/administrations for development of novel drug discovery paradigms are also summarized.

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.

Human pluripotent stem cell-derived cardiomyocytes for studying energy metabolism

Cardiomyocyte energy metabolism is altered in heart failure, and primary defects of metabolic pathways can cause heart failure. Studying cardiac energetics in rodent models has principal shortcomings, raising the question to which extent human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CM) can provide an alternative. As metabolic maturation of CM occurs mostly after birth during developmental hypertrophy, the immaturity of hiPSC-CM is an important limitation. Here we shortly review the physiological drivers of metabolic maturation and concentrate on methods to mature hiPSC-CM with the goal to benchmark the metabolic state of hiPSC-CM against in vivo data and to see how far known abnormalities in inherited metabolic disorders can be modeled in hiPSC-CM. The current data indicate that hiPSC-CM, despite their immature, approximately mid-fetal state of energy metabolism, faithfully recapitulate some basic metabolic disease mechanisms. Efforts to improve their metabolic maturity are underway and shall improve the validity of this model.

DeepNEU: Artificially Induced Stem Cell (aiPSC) and Differentiated Skeletal Muscle Cell (aiSkMC) Simulations of Infantile Onset POMPE Disease (IOPD) for Potential Biomarker Identification and Drug Discovery

Infantile onset Pompe disease (IOPD) is a rare and lethal genetic disorder caused by the deletion of the acid alpha-glucosidase (GAA) gene. This gene encodes an essential lysosomal enzyme that converts glycogen to glucose. While enzyme replacement therapy helps some, our understanding of disease pathophysiology is limited. In this project we develop computer simulated stem cells (aiPSC) and differentiated skeletal muscle cells (aiSkMC) to empower IOPD research and drug discovery. Our Artificial Intelligence (AI) platform, DeepNEU v3.6 was used to generate aiPSC and aiSkMC simulations with and without GAA expression. These simulations were validated using peer reviewed results from the recent literature. Once the aiSkMC simulations (IOPD and WT) were validated they were used to evaluate calcium homeostasis and mitochondrial function in IOPD. Lastly, we used aiSkMC IOPD simulations to identify known and novel biomarkers and potential therapeutic targets. The aiSkMC simulations of IOPD correctly predicted genotypic and phenotypic features that were reported in recent literature. The probability that these features were accurately predicted by chance alone using the binomial test is 0.0025. The aiSkMC IOPD simulation correctly identified L-type calcium channels (VDCC) as a biomarker and confirmed the positive effects of calcium channel blockade (CCB) on calcium homeostasis and mitochondrial function. These published data were extended by the aiSkMC simulations to identify calpain(s) as a novel potential biomarker and therapeutic target for IOPD. This is the first time that computer simulations of iPSC and differentiated skeletal muscle cells have been used to study IOPD. The simulations are robust and accurate based on available published literature. We also demonstrated that the IOPD simulations can be used for potential biomarker identification leading to targeted drug discovery. We will continue to explore the potential for calpain inhibitors with and without CCB as effective therapy for IOPD.

Molecular Approaches for the Treatment of Pompe Disease

Glycogen storage disease type II (GSDII, Pompe disease) is a rare metabolic disorder caused by a deficiency of acid alpha-glucosidase (GAA), an enzyme localized within lysosomes that is solely responsible for glycogen degradation in this compartment. The manifestations of GSDII are heterogeneous but are classified as early or late onset. The natural course of early-onset Pompe disease (EOPD) is severe and rapidly fatal if left untreated. Currently, one therapeutic approach, namely, enzyme replacement therapy, is available, but advances in molecular medicine approaches hold promise for even more effective therapeutic strategies. These approaches, which we review here, comprise splicing modification by antisense oligonucleotides, chaperone therapy, stop codon readthrough therapy, and the use of viral vectors to introduce wild-type genes. Considering the high rate at which innovations are translated from bench to bedside, it is reasonable to expect substantial improvements in the treatment of this illness in the foreseeable future.

Modelling inherited cardiac disease using human induced pluripotent stem cell-derived cardiomyocytes: progress, pitfalls, and potential

In the past few years, the use of specific cell types derived from induced pluripotent stem cells (iPSCs) has developed into a powerful approach to investigate the cellular pathophysiology of numerous diseases. Despite advances in therapy, heart disease continues to be one of the leading causes of death in the developed world. A major difficulty in unravelling the underlying cellular processes of heart disease is the extremely limited availability of viable human cardiac cells reflecting the pathological phenotype of the disease at various stages. Thus, the development of methods for directed differentiation of iPSCs to cardiomyocytes (iPSC-CMs) has provided an intriguing option for the generation of patient-specific cardiac cells. In this review, a comprehensive overview of the currently published iPSC-CM models for hereditary heart disease is compiled and analysed. Besides the major findings of individual studies, detailed methodological information on iPSC generation, iPSC-CM differentiation, characterization, and maturation is included. Both, current advances in the field and challenges yet to overcome emphasize the potential of using patient-derived cell models to mimic genetic cardiac diseases.

Cardiomyopathy phenotypes in human-induced pluripotent stem cell-derived cardiomyocytes-a systematic review

Human-induced pluripotent stem cells (hiPSC) can be differentiated to cardiomyocytes at high efficiency and are increasingly used to study cardiac disease in a human context. This review evaluated 38 studies on hypertrophic (HCM) and dilated cardiomyopathy (DCM) of different genetic causes asking to which extent published data allow the definition of an in vitro HCM/DCM hiPSC-CM phenotype. The data are put in context with the prevailing hypotheses on HCM/DCM dysfunction and pathophysiology. Relatively consistent findings in HCM not reported in DCM were larger cell size (156 ± 85%, n = 15), more nuclear localization of nuclear factor of activated T cells (NFAT; 175 ± 65%, n = 3), and higher β-myosin heavy chain gene expression levels (500 ± 547%, n = 8) than respective controls. Conversely, DCM lines showed consistently less force development than controls (47 ± 23%, n = 9), while HCM forces scattered without clear trend. Both HCM and DCM lines often showed sarcomere disorganization, higher NPPA/NPPB expression levels, and arrhythmic beating behaviour. The data have to be taken with the caveat that reporting frequencies of the various parameters (e.g. cell size, NFAT expression) differ widely between HCM and DCM lines, in which data scatter is large and that only 9/38 studies used isogenic controls. Taken together, the current data provide interesting suggestions for disease-specific phenotypes in HCM/DCM hiPSC-CM but indicate that the field is still in its early days. Systematic, quantitative comparisons and robust, high content assays are warranted to advance the field.

Pompe Disease: From Basic Science to Therapy

Pompe disease is a rare and deadly muscle disorder. As a clinical entity, the disease has been known for over 75 years. While an optimist might be excited about the advances made during this time, a pessimist would note that we have yet to find a cure. However, both sides would agree that many findings in basic science-such as the Nobel prize-winning discoveries of glycogen metabolism, the lysosome, and autophagy-have become the foundation of our understanding of Pompe disease. The disease is a glycogen storage disorder, a lysosomal disorder, and an autophagic myopathy. In this review, we will discuss how these past discoveries have guided Pompe research and impacted recent therapeutic developments.

Modeling rare diseases with induced pluripotent stem cell technology

Rare diseases, in totality, affect a significant proportion of the population and represent an unmet medical need facing the scientific community. However, the treatment of individuals affected by rare diseases is hampered by poorly understood mechanisms preventing the development of viable therapeutics. The discovery and application of cellular reprogramming to create novel induced pluripotent stem cell models of rare diseases has revolutionized the rare disease community. Through developmental and functional analysis of differentiated cell types, these stem cell models carrying patient-specific mutations have become an invaluable tool for rare disease research. In this review article, we discuss the reprogramming of samples from individuals affected with rare diseases to induced pluripotent stem cells, current and future applications for this technology, and how integration of genome editing to rare disease research will help to improve our understanding of disease pathogenesis and lead to patient therapies.

Human pluripotent stem cell models of cardiac disease: from mechanisms to therapies

It is now a decade since human induced pluripotent stem cells (hiPSCs) were first described. The reprogramming of adult somatic cells to a pluripotent state has become a robust technology that has revolutionised our ability to study human diseases. Crucially, these cells capture all the genetic aspects of the patient from which they were derived. Combined with advances in generating the different cell types present in the human heart, this has opened up new avenues to study cardiac disease in humans and investigate novel therapeutic approaches to treat these pathologies. Here, we provide an overview of the current state of the field regarding the generation of cardiomyocytes from human pluripotent stem cells and methods to assess them functionally, an essential requirement when investigating disease and therapeutic outcomes. We critically evaluate whether treatments suggested by these in vitro models could be translated to clinical practice. Finally, we consider current shortcomings of these models and propose methods by which they could be further improved.

Induced pluripotent stem cell models of lysosomal storage disorders

Induced pluripotent stem cells (iPSCs) have provided new opportunities to explore the cell biology and pathophysiology of human diseases, and the lysosomal storage disorder research community has been quick to adopt this technology. Patient-derived iPSC models have been generated for a number of lysosomal storage disorders, including Gaucher disease, Pompe disease, Fabry disease, metachromatic leukodystrophy, the neuronal ceroid lipofuscinoses, Niemann-Pick types A and C1, and several of the mucopolysaccharidoses. Here, we review the strategies employed for reprogramming and differentiation, as well as insights into disease etiology gleaned from the currently available models. Examples are provided to illustrate how iPSC-derived models can be employed to develop new therapeutic strategies for these disorders. We also discuss how models of these rare diseases could contribute to an enhanced understanding of more common neurodegenerative disorders such as Parkinson’s disease, and discuss key challenges and opportunities in this area of research.

Summary: This Review discusses how induced pluripotent stem cells (iPSCs) provide new opportunities to explore the biology and pathophysiology of lysosomal storage diseases, and how iPSCs have illuminated the role of lysosomes in more common disorders.

Interleukin-18 deteriorates Fabry cardiomyopathy and contributes to the development of left ventricular hypertrophy in Fabry patients with GLA IVS4+919 G>A mutation

RATIONALE

A high incidence of GLA IVS4+919 G>A mutation in patients with Fabry disease of the later-onset cardiac phenotype, has been reported in Taiwan. However, suitable biomarkers or potential therapeutic surrogates for Fabry cardiomyopathy (FC) in such patients under enzyme replacement treatment (ERT) remain unknown.

OBJECTIVE

Using FC patients carrying IVS4+919 G>A mutation, we constructed an induced pluripotent stem cell (iPSC)-based disease model to investigate the pathogenetic biomarkers and potential therapeutic targets in ERT-treated FC.

RESULTS AND METHODS

The iPSC-differentiated cardiomyocytes derived from FC-patients (FC-iPSC-CMs) carried IVS4+919 G>A mutation recapitulating FC characteristics, including low α-galactosidase A enzyme activity, cellular hypertrophy, and massive globotriaosylceramide accumulation. Microarray analysis revealed that interleukin-18 (IL-18), a pleiotropic cytokine involved in various myocardial diseases, was the most highly upregulated marker in FC-iPSC-CMs. Meanwhile, IL-18 levels were found to be significantly elevated in the culture media of FC-iPSC-CMs and patients' sera. Notably, the serum IL-18 levels were highly paralleled with the progression of left ventricular hypertrophy in Fabry patients receiving ERT. Finally, using FC-iPSC-CMs as in vitro FC model, neutralization of IL-18 with specific antibodies combined with ERT synergistically reduced the secretion of IL-18 and the progression of cardiomyocyte hypertrophy in FC-iPSC-CMs.

CONCLUSION

Our data demonstrated that cardiac IL-18 and circulating IL-18 are involved in the pathogenesis of FC and LVH. IL-18 may be a novel marker for evaluating ERT efficacy, and targeting IL-18 might be a potential adjunctive therapy combined with ERT for the treatment of advanced cardiomyopathy in FC patients with IVS4+919 G>A mutation.

Human-Induced Pluripotent Stem Cell-Based Modeling of Cardiac Storage Disorders

PURPOSE OF REVIEW

The aim of this study is to review the published human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) models of cardiac storage disorders and to evaluate the limitations and future applications of this technology.

RECENT FINDINGS

Several cardiac storage disorders (CSDs) have been modeled using patient-specific hiPSC-CMs, including Anderson-Fabry disease, Danon disease, and Pompe disease. These models have shown that patient-specific hiPSC-CMs faithfully recapitulate key phenotypic features of CSDs and respond predictably to pharmacologic manipulation. hiPSC-CMs generated from patients with CSDs are representative models of the patient disease state and can be used as an in vitro system for the study of human cardiomyocytes. While these models suffer from several limitations, they are likely to play an important role in future mechanistic studies of cardiac storage disorders and the development of targeted therapeutics for these diseases.

A Skeletal Muscle Model of Infantile-onset Pompe Disease with Patient-specific iPS Cells

Pompe disease is caused by an inborn defect of lysosomal acid α-glucosidase (GAA) and is characterized by lysosomal glycogen accumulation primarily in the skeletal muscle and heart. Patients with the severe type of the disease, infantile-onset Pompe disease (IOPD), show generalized muscle weakness and heart failure in early infancy. They cannot survive over two years. Enzyme replacement therapy with recombinant human GAA (rhGAA) improves the survival rate, but its effect on skeletal muscle is insufficient compared to other organs. Moreover, the patho-mechanism of skeletal muscle damage in IOPD is still unclear. Here we generated induced pluripotent stem cells (iPSCs) from patients with IOPD and differentiated them into myocytes. Differentiated myocytes showed lysosomal glycogen accumulation, which was dose-dependently rescued by rhGAA. We further demonstrated that mammalian/mechanistic target of rapamycin complex 1 (mTORC1) activity was impaired in IOPD iPSC-derived myocytes. Comprehensive metabolomic and transcriptomic analyses suggested the disturbance of mTORC1-related signaling, including deteriorated energy status and suppressed mitochondrial oxidative function. In summary, we successfully established an in vitro skeletal muscle model of IOPD using patient-specific iPSCs. Disturbed mTORC1 signaling may contribute to the pathogenesis of skeletal muscle damage in IOPD, and may be a potential therapeutic target for Pompe disease.

Human heart disease: lessons from human pluripotent stem cell-derived cardiomyocytes

Technical advances in generating and phenotyping cardiomyocytes from human pluripotent stem cells (hPSC-CMs) are now driving their wider acceptance as in vitro models to understand human heart disease and discover therapeutic targets that may lead to new compounds for clinical use. Current literature clearly shows that hPSC-CMs recapitulate many molecular, cellular, and functional aspects of human heart pathophysiology and their responses to cardioactive drugs. Here, we provide a comprehensive overview of hPSC-CMs models that have been described to date and highlight their most recent and remarkable contributions to research on cardiovascular diseases and disorders with cardiac traits. We conclude discussing immediate challenges, limitations, and emerging solutions.

Induced pluripotent stem cell: A headway in reprogramming with promising approach in regenerative biology

Since the embryonic stem cells have knocked the doorsteps, they have proved themselves in the field of science, research, and medicines, but the hovered restrictions confine their application in human welfare. Alternate approaches used to reprogram the cells to the pluripotent state were not up to par, but the innovation of induced pluripotent stem cells (iPSCs) paved a new hope for the researchers. Soon after the discovery, iPSCs technology is undergoing renaissance day by day, i.e., from the use of genetic material to recombinant proteins and now only chemicals are employed to convert somatic cells to iPSCs. Thus, this technique is moving straightforward and productive at an astonishing pace. Here, we provide a brief introduction to iPSCs, the mechanism and methods for their generation, their prevailing and prospective applications and the future opportunities that can be expected from them.

Translation of Human-Induced Pluripotent Stem Cells: From Clinical Trial in a Dish to Precision Medicine

The prospect of changing the plasticity of terminally differentiated cells toward pluripotency has completely altered the outlook for biomedical research. Human-induced pluripotent stem cells (iPSCs) provide a new source of therapeutic cells free from the ethical issues or immune barriers of human embryonic stem cells. iPSCs also confer considerable advantages over conventional methods of studying human diseases. Since its advent, iPSC technology has expanded with 3 major applications: disease modeling, regenerative therapy, and drug discovery. Here we discuss, in a comprehensive manner, the recent advances in iPSC technology in relation to basic, clinical, and population health.

Shortcomings of Animal Models and the Rise of Engineered Human Cardiac Tissue

We provide here an historical context of how studies utilizing engineered human cardiac muscle can complement and in some cases substitute animal and cell models for studies of disease and drug testing. We give an overview of the development of animal models and discuss the ability of novel human tissue models to overcome limited predictive power of cell culture and animal models in studies of drug efficacy and safety. The in vitro generation of cardiac tissue is discussed in the context of state of the art in the field. Finally we describe the assembly of multitissue platforms for more accurate representation of integrated human cardiac physiology and consider the advantages of in silico drug trials to augment our ability to predict drug-drug and organ-organ interactions in humans.

Human-induced pluripotent stem cell approaches to model inborn and acquired metabolic heart diseases

PURPOSE OF REVIEW

The article provides an overview of advances in the induced pluripotent stem cell field to model cardiomyopathies of inherited inborn errors of metabolism and acquired metabolic syndromes in vitro.

RECENT FINDINGS

Several inborn errors of metabolism have been studied using 'disease in a dish' models, including Pompe disease, Danon disease, Fabry disease, and Barth syndrome. Disease phenotypes of complex metabolic syndromes, such as diabetes mellitus and aldehyde dehydrogenase 2 deficiency, have also been observed.

SUMMARY

Differentiation of patient and disease-specific induced pluripotent stem cell-derived cardiomyocytes has provided the capacity to model deleterious cardiometabolic diseases to understand molecular mechanisms, perform drug screens, and identify novel drug targets.

Metabolomic Profiling of Pompe Disease-Induced Pluripotent Stem Cell-Derived Cardiomyocytes Reveals That Oxidative Stress Is Associated with Cardiac and Skeletal Muscle Pathology

Pompe disease (PD) is a lysosomal storage disease that is caused by a deficiency of the acid α‐glucosidase, which results in glycogen accumulation in the lysosome. The major clinical symptoms of PD include skeletal muscle weakness, respiratory failure, and cardiac hypertrophy. Based on its severity and symptom onset, PD is classified into infantile and late‐onset forms. Lysosomal accumulation of glycogen can promote many types of cellular dysfunction, such as autophagic dysfunction, endoplasmic reticulum stress, and abnormal calcium signaling within skeletal muscle. However, the disease mechanism underlying PD cardiomyopathy is not fully understood. Several researchers have shown that PD induced pluripotent stem cell (iPSC)‐derived cardiomyocytes successfully replicate the disease phenotype and are useful disease models. We have analyzed the metabolomic profile of late‐onset PD iPSC‐derived cardiomyocytes and found that oxidative stress and mitochondrial dysfunction are likely associated with cardiac complications. Furthermore, we have validated that these disease‐specific changes were also observed in the cardiomyocytes and skeletal muscle of a genetically engineered murine PD model. Oxidative stress may contribute to skeletal muscle and cardiomyocyte dysfunction in PD mice; however, NF‐E2‐related factor 2 was downregulated in cardiomyocytes and skeletal muscle, despite evidence of oxidative stress. We hypothesized that oxidative stress and an impaired antioxidative stress response mechanism may underlie the molecular pathology of late‐onset PD. Stem Cells Translational Medicine2017;6:31–39

TFEB overexpression promotes glycogen clearance of Pompe disease iPSC-derived skeletal muscle

Pompe disease (PD) is a lysosomal disorder caused by acid α-glucosidase (GAA) deficiency. Progressive muscular weakness is the major symptom of PD, and enzyme replacement therapy can improve the clinical outcome. However, to achieve a better clinical outcome, alternative therapeutic strategies are being investigated, including gene therapy and pharmacological chaperones. We previously used lentiviral vector-mediated GAA gene transfer in PD patient-specific induced pluripotent stem cells. Some therapeutic efficacy was observed, although glycogen accumulation was not normalized. Transcription factor EB is a master regulator of lysosomal biogenesis and autophagy that has recently been associated with muscular pathology, and is now a potential therapeutic target in PD model mice. Here, we differentiated skeletal muscle from PD patient-specific induced pluripotent stem cells by forced MyoD expression. Lentiviral vector-mediated GAA and transcription factor EB gene transfer independently improved GAA enzyme activity and reduced glycogen content in skeletal muscle derived from PD-induced pluripotent stem cells. Interestingly, GAA and transcription factor EB cooperatively improved skeletal muscle pathology, both biochemically and morphologically. Thus, our findings show that abnormal lysosomal biogenesis is associated with the muscular pathology of PD, and transcription factor EB gene transfer is effective as an add-on strategy to GAA gene transfer.

Human Induced Pluripotent Stem Cells as a Platform for Personalized and Precision Cardiovascular Medicine

Human induced pluripotent stem cells (hiPSCs) have revolutionized the field of human disease modeling, with an enormous potential to serve as paradigm shifting platforms for preclinical trials, personalized clinical diagnosis, and drug treatment. In this review, we describe how hiPSCs could transition cardiac healthcare away from simple disease diagnosis to prediction and prevention, bridging the gap between basic and clinical research to bring the best science to every patient.

Disease models for the development of therapies for lysosomal storage diseases

Lysosomal storage diseases (LSDs) are a group of rare diseases in which the function of the lysosome is disrupted by the accumulation of macromolecules. The complexity underlying the pathogenesis of LSDs and the small, often pediatric, population of patients make the development of therapies for these diseases challenging. Current treatments are only available for a small subset of LSDs and have not been effective at treating neurological symptoms. Disease-relevant cellular and animal models with high clinical predictability are critical for the discovery and development of new treatments for LSDs. In this paper, we review how LSD patient primary cells and induced pluripotent stem cell-derived cellular models are providing novel assay systems in which phenotypes are more similar to those of the human LSD physiology. Furthermore, larger animal disease models are providing additional tools for evaluation of the efficacy of drug candidates. Early predictors of efficacy and better understanding of disease biology can significantly affect the translational process by focusing efforts on those therapies with the higher probability of success, thus decreasing overall time and cost spent in clinical development and increasing the overall positive outcomes in clinical trials.

Induced pluripotent stem cells: at the heart of cardiovascular precision medicine

The advent of human induced pluripotent stem cell (hiPSC) technology has revitalized the efforts in the past decade to realize more fully the potential of human embryonic stem cells for scientific research. Adding to the possibility of generating an unlimited amount of any cell type of interest, hiPSC technology now enables the derivation of cells with patient-specific phenotypes. Given the introduction and implementation of the large-scale Precision Medicine Initiative, hiPSC technology will undoubtedly have a vital role in the advancement of cardiovascular research and medicine. In this Review, we summarize the progress that has been made in the field of hiPSC technology, with particular emphasis on cardiovascular disease modelling and drug development. The growing roles of hiPSC technology in the practice of precision medicine will also be discussed.

Targeted approaches to induce immune tolerance for Pompe disease therapy

Enzyme and gene replacement strategies have developed into viable therapeutic approaches for the treatment of Pompe disease (acid α-glucosidase (GAA) deficiency). Unfortunately, the introduction of GAA and viral vectors encoding the enzyme can lead to detrimental immune responses that attenuate treatment benefits and can impact patient safety. Preclinical and clinical experience in addressing humoral responses toward enzyme and gene therapy for Pompe disease have provided greater understanding of the immunological consequences of the provided therapy. B- and T-cell modulation has been shown to be effective in preventing infusion-associated reactions during enzyme replacement therapy in patients and has shown similar success in the context of gene therapy. Additional techniques to induce humoral tolerance for Pompe disease have been the targeted expression or delivery of GAA to discrete cell types or tissues such as the gut-associated lymphoid tissues, red blood cells, hematopoietic stem cells, and the liver. Research into overcoming preexisting immunity through immunomodulation and gene transfer are becoming increasingly important to achieve long-term efficacy. This review highlights the advances in therapies as well as the improved understanding of the molecular mechanisms involved in the humoral immune response with emphasis on methods employed to overcome responses associated with enzyme and gene therapies for Pompe disease.