Use Of hiPSCs Research Articles

Public attitudes toward the use of human induced pluripotent stem cells: insights from an Italian adult population

IntroductionHuman induced pluripotent stem cells (hiPSCs), derived from reprogrammed adult somatic cells, hold significant promise for disease modelling, personalized medicine, drug discovery, and regenerative therapies. Public awareness and understanding of hiPSCs are crucial for advancing research in this field. However, limited data exists on the general population’s knowledge and attitudes toward their use.MethodsThis study aimed to assess the awareness and perceptions of hiPSCs among Italian adults through a web-based survey conducted via the EUSurvey platform, using a snowball sampling approach. The survey included demographic information and mandatory questions on knowledge, awareness, and concerns regarding hiPSC technology, with responses collected on a 3-point scale. Statistical analysis was performed using chi-squared tests, with significance set at p ≤ 0.05.ResultsOut of 1874 respondents, the majority were aged 18–35 years (40.5%), female (63.4%), and university-educated (67.2%). Among those familiar with hiPSCs (54.1%, n = 1,201), 95.3% expressed willingness to donate blood samples for hiPSC generation to treat individuals with incurable diseases. Concerns about current research and therapeutic applications were low (less than 20%), but nearly half of the respondents were hesitant or opposed to the use of hiPSCs in animal experiments and their commercialization by pharmaceutical companies. Increased skepticism was observed in older, less educated, religious individuals, and those who were not blood donors. Overall, the Italian public shows strong support for hiPSC-based therapies, though reservations exist around specific ethical and economic issues.DiscussionThese findings underscore the importance of addressing public concerns through targeted educational campaigns, not only in Italy but globally, to foster a more informed and supportive environment for advancing stem cell research and its clinical applications worldwide. Similar studies have been conducted in Japan, the United States, and Sweden, but there remains a need for all countries to engage with their citizens to better understand how stem cell research is perceived locally. Such engagement is crucial for guiding international strategies in personalized medicine and regenerative therapies, ensuring that emerging technologies are met with both ethical integrity and public trust.

Human-Induced Pluripotent Stem Cells in Plastic and Reconstructive Surgery.

A hallmark of plastic and reconstructive surgery is restoring form and function. Historically, tissue procured from healthy portions of a patient's body has been used to fill defects, but this is limited by tissue availability. Human-induced pluripotent stem cells (hiPSCs) are stem cells derived from the de-differentiation of mature somatic cells. hiPSCs are of particular interest in plastic surgery as they have the capacity to be re-differentiated into more mature cells, and cultured to grow tissues. This review aims to evaluate the applications of hiPSCs in the plastic surgery context, with a focus on recent advances and limitations. The use of hiPSCs and non-human iPSCs has been researched in the context of skin, nerve, vasculature, skeletal muscle, cartilage, and bone regeneration. hiPSCs offer a future for regenerated autologous skin grafts, flaps comprised of various tissue types, and whole functional units such as the face and limbs. Also, they can be used to model diseases affecting tissues of interest in plastic surgery, such as skin cancers, epidermolysis bullosa, and scleroderma. Tumorigenicity, immunogenicity and pragmatism still pose significant limitations. Further research is required to identify appropriate somatic origin and induction techniques to harness the epigenetic memory of hiPSCs or identify methods to manipulate epigenetic memory.

#5919 PATIENT-SPECIFIC HUMAN INDUCED PLURIPOTENT STEM CELL (HIPSC)-DERIVED PODOCYTES

Abstract Background and Aims Podocytes typically represent a distinct morphology with long, interdigitating primary and secondary foot processes wrapping around glomerular capillaries forming the filtration unit of the kidney. In glomerular diseases like genetic focal segmental glomerulosclerosis (FSGS), podocyte alterations are often related to dysfunction of the glomerular filtration barrier and the development of proteinuria. Genetic mutations in podocyte relevant genes, important for foot process or actin cytoskeleton dynamics, are known to induce severe podocyte injury. Analysis of podocyte alterations ex vivo is limited because of their inability to proliferate due to their terminal differentiated state and limited access to primary podocytes. Instead, immortalized podocytes regained proliferation capacity by insertion of a thermosensitive SV40 large T antigen and are useful for many research questions. However, these podocytes usually do not express all podocyte marker and foot process development is often restricted. Since we aim to characterize personalized podocytes from patients suffering from genetic FSGS ex vivo, we generated podocytes from dermal fibroblasts via reprogramming into hiPSCs and subsequent differentiation into hiPSC-derived podocytes keeping the patients’ genetic background. Method Dermal fibroblasts were outgrown from a skin punch biopsy from a patient or a healthy donor and subsequently reprogrammed into hiPSCs by electroporation of the common OKSM plasmids and finally differentiated into podocytes. Cells were characterized phenotypically regarding morphology and marker expression using RNA bulk sequencing, western blot, qPCR and immunofluorescence staining. Potential functional alterations of diseased podocytes regarding actin cytoskeleton were assessed by actin polymerization assay. Results Patient-specific podocytes could be generated ex vivo by reprogramming dermal fibroblasts into hiPSCs and subsequently differentiating them into mature podocytes representing the patients’ background. During this process, cell morphology changed from spindle-like fibroblasts to small and round hiPSCs growing in colonies and representing a high nuclei-to body ratio as well as high proliferation rate. During differentiation, hiPSCs were induced into intermediate mesoderm, resulting in increased cell size and decreased proliferation rate terminating in 300 nm large star-shaped podocytes developing a distinct network of long primary and secondary foot processes. Patient-derived hiPSC-podocytes with a mutation in the INF2 gene lacked filamentous actin and only develop a limited number of only short foot processes compared to hiPSC-podocytes derived from a healthy control donor. Moreover, expression of actin cytoskeleton associated genes like SYNPO, ACTN4 and CD2AP was decreased while other actin isoforms, cortactin and the GTPase RhoA were increased in diseased patient-specific podocytes. Actin polymerization assay showed that polymerization process itself was not altered in healthy and diseased hiPSC-podocytes. Conclusion Analysis of patient-specific podocytes is possible ex vivo via differentiation of hiPSCs, generated from patients’ dermal fibroblasts by episomal reprogramming, into hiPSC-derived podocytes, with the potential to study alterations of disease-specific mutations regarding phenotypical and functional behavior in a personalized manner. The use of hiPSCs bypasses the limitation of restricted podocyte cell number and has the advantage of maintaining the patients’ genetic background at podocyte cell level. This enables future large-scale experiments regarding intercell-cell communication and interaction in glomerular three-dimensional co-cultures or via treatment with therapeutic substances or stress factors.

CRISPR-Cas9 in hiPSCs: A new era in personalized treatment for Stargardt disease

CRISPR-Cas9 in hiPSCs: A new era in personalized treatment for Stargardt disease

Arrhythmogenic cardiomyopathy as a myogenic disease: highlights from cardiomyocytes derived from human induced pluripotent stem cells.

Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiomyopathy characterized by the replacement of myocardium by fibro-fatty infiltration and cardiomyocyte loss. ACM predisposes to a high risk for ventricular arrhythmias. ACM has initially been defined as a desmosomal disease because most of the known variants causing the disease concern genes encoding desmosomal proteins. Studying this pathology is complex, in particular because human samples are rare and, when available, reflect the most advanced stages of the disease. Usual cellular and animal models cannot reproduce all the hallmarks of human pathology. In the last decade, human-induced pluripotent stem cells (hiPSC) have been proposed as an innovative human cellular model. The differentiation of hiPSCs into cardiomyocytes (hiPSC-CM) is now well-controlled and widely used in many laboratories. This hiPSC-CM model recapitulates critical features of the pathology and enables a cardiomyocyte-centered comprehensive approach to the disease and the screening of anti-arrhythmic drugs (AAD) prescribed sometimes empirically to the patient. In this regard, this model provides unique opportunities to explore and develop new therapeutic approaches. The use of hiPSC-CMs will undoubtedly help the development of precision medicine to better cure patients suffering from ACM. This review aims to summarize the recent advances allowing the use of hiPSCs in the ACM context.

Research Progress towards the Effects of Fatty Acids on the Differentiation and Maturation of Human Induced Pluripotent Stem Cells into Cardiomyocytes.

The incidence of cardiovascular disease has been continuously increasing. Because cardiomyocytes (CM) are non-renewable cells, it is difficult to find appropriate CM sources to repair injured hearts. Research of human induced pluripotent stem cell (hiPSC) differentiation and maturation into CM has been invaluable for the treatment of heart diseases. The use of hiPSCs as regenerative therapy allows for the treatment of many diseases that cannot be cured, including progressive heart failure. This review contributes to the study of cardiac repair and targeted treatment of cardiovascular diseases at the cytological level. Recent studies have shown that for differentiation and maturation of hiPSCs into CMs, fatty acids have a strong influence on cellular metabolism, organelle development, expression of specific genes, and functional performance. This review describes the recent research progress on how fatty acids affect the differentiation of hiPSCs into CMs and their maturation.

Functional genomics and the future of iPSCs in disease modeling.

SummaryInduced pluripotent stem cells (iPSCs) are valuable in disease modeling because of their potential to expand and differentiate into virtually any cell type and recapitulate key aspects of human biology. Functional genomics are genome-wide studies that aim to discover genotype-phenotype relationships, thereby revealing the impact of human genetic diversity on normal and pathophysiology. In this review, we make the case that human iPSCs (hiPSCs) are a powerful tool for functional genomics, since they provide an in vitro platform for the study of population genetics. We describe cutting-edge tools and strategies now available to researchers, including multi-omics technologies, advances in hiPSC culture techniques, and innovations in drug development. Functional genomics approaches based on hiPSCs hold great promise for advancing drug discovery, disease etiology, and the impact of genetic variation on human biology.

Generation of neuronal/glial mixed cultures from human induced pluripotent stem cells (hiPSCs).

For a long time, the understanding of neurological diseases has been limited by the lack of representative experimental models able to recapitulate essential features of the human pathologies. Human induced pluripotent stem cells (hiPSCs) have emerged as a powerful tool for disease modeling, drug screening, and the development of novel cell and gene therapies. A critical issue for the prospective use of hiPSCs in basic and translational research for central nervous system (CNS) disorders is to validate robust protocols able to efficiently differentiate pluripotent cells into neurons and glial cells of interest, specifically those that are most affected in pathological conditions. We describe here a three-step differentiation protocol optimized for feeder-free hiPSCs. The protocol includes a first step of neural induction mediated by dual SMAD inhibition to generate homogeneous populations of neural progenitor cells (NPCs), a second step of NPCs expansion, and a third phase of NPCs differentiation into a mixed culture of neurons, oligodendrocytes, and astrocytes. This experimental platform is relevant to recapitulate the neural induction of hiPSCs and to monitor NPC lineage specification and neuronal/glial differentiation in physiological conditions as well as in the context of CNS diseases. The protocol allows monitoring early pathological hallmarks in the different CNS cell types, also offering a simplified in vitro model to study the neuronal-glial crosstalk.

Induction of Neural Crest Stem Cells From Bardet-Biedl Syndrome Patient Derived hiPSCs.

Neural crest cells arise in the embryo from the neural plate border and migrate throughout the body, giving rise to many different tissue types such as bones and cartilage of the face, smooth muscles, neurons, and melanocytes. While studied extensively in animal models, neural crest development and disease have been poorly described in humans due to the challenges in accessing embryonic tissues. In recent years, patient-derived human induced pluripotent stem cells (hiPSCs) have become easier to generate, and several streamlined protocols have enabled robust differentiation of hiPSCs to the neural crest lineage. Thus, a unique opportunity is offered for modeling neurocristopathies using patient specific stem cell lines. In this work, we make use of hiPSCs derived from patients affected by the Bardet–Biedl Syndrome (BBS) ciliopathy. BBS patients often exhibit subclinical craniofacial dysmorphisms that are likely to be associated with the neural crest-derived facial skeleton. We focus on hiPSCs carrying variants in the BBS10 gene, which encodes a protein forming part of a chaperonin-like complex associated with the cilium. Here, we establish a pipeline for profiling hiPSCs during differentiation toward the neural crest stem cell fate. This can be used to characterize the differentiation properties of the neural crest-like cells. Two different BBS10 mutant lines showed a reduction in expression of the characteristic neural crest gene expression profile. Further analysis of both BBS10 mutant lines highlighted the inability of these mutant lines to differentiate toward a neural crest fate, which was also characterized by a decreased WNT and BMP response. Altogether, our study suggests a requirement for wild-type BBS10 in human neural crest development. In the long term, approaches such as the one we describe will allow direct comparison of disease-specific cell lines. This will provide valuable insights into the relationships between genetic background and heterogeneity in cellular models. The possibility of integrating laboratory data with clinical phenotypes will move us toward precision medicine approaches.

How Does Reprogramming to Pluripotency Affect Genomic Imprinting?

Human induced Pluripotent Stem Cells (hiPSCs) have the capacity to generate a wide range of somatic cells, thus representing an ideal tool for regenerative medicine. Patient-derived hiPSCs are also used for in vitro disease modeling and drug screenings. Several studies focused on the identification of DNA mutations generated, or selected, during the derivation of hiPSCs, some of which are known to drive cancer formation. Avoiding such stable genomic aberrations is paramount for successful use of hiPSCs, but it is equally important to ensure that their epigenetic information is correct, given the critical role of epigenetics in transcriptional regulation and its involvement in a plethora of pathologic conditions. In this review we will focus on genomic imprinting, a prototypical epigenetic mechanism whereby a gene is expressed in a parent-of-origin specific manner, thanks to the differential methylation of specific DNA sequences. Conventional hiPSCs are thought to be in a pluripotent state primed for differentiation. They display a hypermethylated genome with an unexpected loss of DNA methylation at imprinted loci. Several groups recently reported the generation of hiPSCs in a more primitive developmental stage, called naïve pluripotency. Naïve hiPSCs share several features with early human embryos, such as a global genome hypomethylation, which is also accompanied by a widespread loss of DNA methylation at imprinted loci. Given that loss of imprinting has been observed in genetic developmental disorders as well as in a wide range of cancers, it is fundamental to make sure that hiPSCs do not show such epigenetic aberrations. We will discuss what specific imprinted genes, associated with human pathologies, have been found commonly misregulated in hiPSCs and suggest strategies to effectively detect and avoid such undesirable epigenetic abnormalities.

The paracrine effects of human induced pluripotent stem cells promote bone-like structures via the upregulation of BMP expression in a mouse ectopic model

Use of human induced pluripotent stem cells (h-iPSCs) for bone tissue engineering is most appealing, because h-iPSCs are an inexhaustible source of osteocompetent cells. The present study investigated the contribution of undifferentiated h-iPSCs and elucidated aspects of the underlying mechanism(s) of the involvement of these cells to new bone formation. Implantation of undifferentiated h-iPSCs seeded on coral particles in ectopic sites of mice resulted in expression of osteocalcin and DMP-1, and in mineral content similar to that of the murine bone. The number of the implanted h-iPSCs decreased with time and disappeared by 30 days post-implantation. In contrast, expression of the murine osteogenic genes at day 15 and 30 post-implantation provided, for the first time, evidence that the implanted h-iPSCs affected the observed outcomes via paracrine mechanisms. Supporting evidence was provided because supernatant conditioned media from h-iPSCs (h-iPSC CM), promoted the osteogenic differentiation of human mesenchymal stem cells (h-MSCs) in vitro. Specifically, h-iPSC CM induced upregulation of the BMP-2, BMP-4 and BMP-6 genes, and promoted mineralization of the extracellular matrix. Given the current interest in the use of h-iPSCs for regenerative medicine applications, our study contributes new insights into aspects of the mechanism underlying the bone promoting capability of h-iPSCs.

Endogenous Protein Tagging in Human Induced Pluripotent Stem Cells Using CRISPR/Cas9.

A protocol is presented for generating human induced pluripotent stem cells (hiPSCs) that express endogenous proteins fused to in-frame N- or C-terminal fluorescent tags. The prokaryotic CRISPR/Cas9 system (clustered regularly interspaced short palindromic repeats/CRISPR-associated 9) may be used to introduce large exogenous sequences into genomic loci via homology directed repair (HDR). To achieve the desired knock-in, this protocol employs the ribonucleoprotein (RNP)-based approach where wild type Streptococcus pyogenes Cas9 protein, synthetic 2-part guide RNA (gRNA), and a donor template plasmid are delivered to the cells via electroporation. Putatively edited cells expressing the fluorescently tagged proteins are enriched by fluorescence activated cell sorting (FACS). Clonal lines are then generated and can be analyzed for precise editing outcomes. By introducing the fluorescent tag at the genomic locus of the gene of interest, the resulting subcellular localization and dynamics of the fusion protein can be studied under endogenous regulatory control, a key improvement over conventional overexpression systems. The use of hiPSCs as a model system for gene tagging provides the opportunity to study the tagged proteins in diploid, nontransformed cells. Since hiPSCs can be differentiated into multiple cell types, this approach provides the opportunity to create and study tagged proteins in a variety of isogenic cellular contexts.

Endogenous Protein Tagging in Human Induced Pluripotent Stem Cells Using CRISPR/Cas9

A protocol is presented for generating human induced pluripotent stem cells (hiPSCs) that express endogenous proteins fused to in-frame N- or C-terminal fluorescent tags. The prokaryotic CRISPR/Cas9 system (clustered regularly interspaced short palindromic repeats/CRISPR-associated 9) may be used to introduce large exogenous sequences into genomic loci via homology directed repair (HDR). To achieve the desired knock-in, this protocol employs the ribonucleoprotein (RNP)-based approach where wild type Streptococcus pyogenes Cas9 protein, synthetic 2-part guide RNA (gRNA), and a donor template plasmid are delivered to the cells via electroporation. Putatively edited cells expressing the fluorescently tagged proteins are enriched by fluorescence activated cell sorting (FACS). Clonal lines are then generated and can be analyzed for precise editing outcomes. By introducing the fluorescent tag at the genomic locus of the gene of interest, the resulting subcellular localization and dynamics of the fusion protein can be studied under endogenous regulatory control, a key improvement over conventional overexpression systems. The use of hiPSCs as a model system for gene tagging provides the opportunity to study the tagged proteins in diploid, nontransformed cells. Since hiPSCs can be differentiated into multiple cell types, this approach provides the opportunity to create and study tagged proteins in a variety of isogenic cellular contexts.

Human-Induced Pluripotent Stem Cell Technology and Cardiomyocyte Generation: Progress and Clinical Applications.

Human-induced pluripotent stem cells (hiPSCs) are reprogrammed cells that have hallmarks similar to embryonic stem cells including the capacity of self-renewal and differentiation into cardiac myocytes. The improvements in reprogramming and differentiating methods achieved in the past 10 years widened the use of hiPSCs, especially in cardiac research. hiPSC-derived cardiac myocytes (CMs) recapitulate phenotypic differences caused by genetic variations, making them attractive human disease models and useful tools for drug discovery and toxicology testing. In addition, hiPSCs can be used as sources of cells for cardiac regeneration in animal models. Here, we review the advances in the genetic and epigenetic control of cardiomyogenesis that underlies the significant improvement of the induced reprogramming of somatic cells to CMs; the methods used to improve scalability of throughput assays for functional screening and drug testing in vitro; the phenotypic characteristics of hiPSCs-derived CMs and their ability to rescue injured CMs through paracrine effects; we also cover the novel approaches in tissue engineering for hiPSC-derived cardiac tissue generation, and finally, their immunological features and the potential use in biomedical applications.

Expansion of human midbrain floor plate progenitors from induced pluripotent stem cells increases dopaminergic neuron differentiation potential

Human induced pluripotent stem cells (hiPSCs) are invaluable to study developmental processes and disease mechanisms particularly in the brain. hiPSCs can be differentiated into mature and functional dopaminergic (DA) neurons. Having robust protocols for the generation of differentiated DA neurons from pluripotent cells is a prerequisite for the use of hiPSCs to study disease mechanisms, for drug discovery, and eventually for cell replacement therapy. Here, we describe a protocol for generating and expanding large numbers of homogeneous midbrain floor plate progenitors (mFPPs) that retain efficient DA neurogenic potential over multiple passages and can be cryobanked. We demonstrate that expanded mFPPs have increased DA neuron potential and differentiate more efficiently and rapidly than progenitors generated by standard protocols. In addition, this novel method results in increased numbers of DA neurons that in vitro show characteristic electrophysiological properties of nigrostriatal DA neurons, produce high levels of dopamine, and integrate into host mice when grafted in vivo. Thus, we describe a robust method for producing human mesencephalic DA neurons from hiPSCs.

Gene expression profile in human induced pluripotent stem cells: Chondrogenic differentiation in vitro, part A.

Human induced pluripotent stem cells (hiPSCs) offer promise in regenerative medicine, however more data are required to improve understanding of key aspects of the cell differentiation process, including how specific chondrogenic processes affect the gene expression profile of chondrocyte-like cells and the relative value of cell differentiation markers. The main aims of the present study were as follows: To determine the gene expression profile of chondrogenic-like cells derived from hiPSCs cultured in mediums conditioned with HC-402-05a cells or supplemented with transforming growth factor β3 (TGF-β3), and to assess the relative utility of the most commonly used chondrogenic markers as indicators of cell differentiation. These issues are relevant with regard to the use of human fibroblasts in the reprogramming process to obtain hiPSCs. Human fibroblasts are derived from the mesoderm and thus share a wide range of properties with chondrocytes, which also originate from the mesenchyme. Thus, the exclusion of dedifferentiation instead of chondrogenic differentiation is crucial. The hiPSCs were obtained from human primary dermal fibroblasts during a reprogramming process. Two methods, both involving embryoid bodies (EB), were used to obtain chondrocytes from the hiPSCs: EBs formed in a chondrogenic medium supplemented with TGF-β3 (10 ng/ml) and EBs formed in a medium conditioned with growth factors from HC-402-05a cells. Based on immunofluorescence and reverse transcription-quantiative polymerase chain reaction analysis, the results indicated that hiPSCs have the capacity for effective chondrogenic differentiation, in particular cells differentiated in the HC-402-05a-conditioned medium, which present morphological features and markers that are characteristic of mature human chondrocytes. By contrast, cells differentiated in the presence of TGF-β3 may demonstrate hypertrophic characteristics. Several genes [paired box 9, sex determining region Y-box (SOX) 5, SOX6, SOX9 and cartilage oligomeric matrix protein] were demonstrated to be good markers of early hiPSC chondrogenic differentiation: Insulin-like growth factor 1, Tenascin-C, and β-catenin were less valuable. These observations provide valuable data on the use of hiPSCs in cartilage tissue regeneration.

Perspectives and Challenges of Pluripotent Stem Cells in Cardiac Arrhythmia Research.

The promises of human-induced pluripotent stem cells (hiPSCs) for modeling arrhythmogenic disease, but also for drug discovery and toxicity tests, are straightforward and exciting. However, the full potential of this new technology has not been fully realized yet. The purpose of this review is to provide an overview of the state-of-the-art research in arrhythmogenic disease modeling and drug discovery and an outlook of what can be expected from the second decade of hiPSC-based arrhythmia research. Remarkable advances in genomic discoveries, stem cell biology, and genome editing via sequence-specific nucleases have been made in recent years. Together, these breakthroughs have allowed us to progress from studying monogenetic diseases with a direct genotype-phenotype relationship to genetically more complex diseases such as arrhythmogenic right ventricular dysplasia and atrial fibrillation. In addition, newly developed tools for arrhythmia research such as optical action potential recordings have facilitated the use of hiPSCs for drug and toxicity screening and their eventual clinical use. These advances in in vitro assay development, genome editing, and stem cell biology will soon enable the implementation of hiPSC-based findings into clinical practice and provide us with unprecedented insights into mechanisms of complex arrhythmogenic diseases.

Actual strategies in human induced pluripotent stem cells (hiPSCs) differentiation – perspectives and challenges

The application of stem cells (SCs) in regenerative medicine has recently become a rapidly growing field, holding promise for combating a number of currently incurable disorders: including diabetes, neurodegenerative, retinal and cardiac diseases, as well as muscular dystrophy. The search for alternative approaches led to the development of human induced pluripotent stem cells (hiPSCs) which have unrestricted proliferative activity and pluripotency – the capacity to differentiation into derivatives of three germ layers (meso-, ecto – and endoderm). Because hiPSCs are developed from adult human cells throughout the forced expression of pluripotency factors, they are free from the ethical concerns associated with human embryonic stem cells (hESCs), that creation involves the destruction of human embryos. Moreover, the use of hiPSCs contributes to the development of personalized medicine that exploits patient-specific cells extremely useful in autologous grafts. In the present study the methods of hiPSCs differentiation into stem cell-derived neurons, cardiomyocytes, chondrocytes and osteocytes were summarized and evaluated having regard to their most important aspects.

DNA methylation dynamics in human induced pluripotent stem cells.

Indeed human induced pluripotent stem cells (hiPSCs) are considered to be powerful tools in regenerative medicine. To enable the use of hiPSCs in the field of regenerative medicine, it is necessary to understand the mechanisms of reprogramming during the transformation of somatic cells into hiPSCs. Genome-wide epigenetic modification constitutes a critical event in the generation of iPSCs. In other words, to analyze epigenetic changes in iPSCs means to elucidate reprogramming processes. We have established a large number of hiPSCs derived from various human tissues and have obtained their DNA methylation profiles. Comparison analyses indicated that the epigenetic patterns of various hiPSCs, irrespective of their source tissue, were very similar to one another and were similar to those of human embryonic stem cells (hESCs). However, the profiles of hiPSCs and hESCs exhibited epigenetic differences, which were caused by random aberrant hypermethylation at early passages. Interestingly, continuous passaging of the hiPSCs diminished the differences between DNA methylation profiles of hiPSCs and hESCs. The number of aberrant DNA methylation regions may thus represent a useful epigenetic index for evaluating hiPSCs in the context of therapeutic applications.

A Single CRISPR-Cas9 Deletion Strategy that Targets the Majority of DMD Patients Restores Dystrophin Function in hiPSC-Derived Muscle Cells

Mutations in DMD disrupt the reading frame, prevent dystrophin translation, and cause Duchenne muscular dystrophy (DMD). Here we describe a CRISPR/Cas9 platform applicable to 60% of DMD patient mutations. We applied the platform to DMD-derived hiPSCs where successful deletion and non-homologous end joining of up to 725 kb reframed the DMD gene. This is the largest CRISPR/Cas9-mediated deletion shown to date in DMD. Use of hiPSCs allowed evaluation of dystrophin in disease-relevant cell types. Cardiomyocytes and skeletal muscle myotubes derived from reframed hiPSC clonal lines had restored dystrophin protein. The internally deleted dystrophin was functional as demonstrated by improved membrane integrity and restoration of the dystrophin glycoprotein complex in vitro and in vivo. Furthermore, miR31 was reduced upon reframing, similar to observations in Becker muscular dystrophy. This work demonstrates the feasibility of using a single CRISPR pair to correct the reading frame for the majority of DMD patients.