Roadblocks in the Path of iPSC to the Clinic

Articular cartilage tissue engineering using genetically modified induced pluripotent stem cell lines

Mature hyaline cartilage has a low regenerative potential and its repair remains a complex clinical and research issue. Articular cartilage injuries often contribute to the development of osteoarthritis, resulting in loss of joint function and patient disability. Surgical techniques for repairing articular surfaces, such as mosaic chondroplasty and microfracture, which are designed for small defects, cannot be used for degenerative and dystrophic cartilage lesions. Cell therapy using chondrocytes differentiated from induced pluripotent stem cells (iPSCs) is a promising approach to reconstruct articular cartilage tissue. iPSCs have high proliferative activity, which allows the harvesting of autologous cells in quantities necessary to repair a joint defect. CRISPR-Cas genome editing technology, based on the bacterial adaptive immune system, enables the genetic modification of iPSCs to obtain progenitor cells with specific characteristics and properties. This review describes specific research papers on the combined use of iPSC and CRISPR-Cas technologies for the evaluation of cartilage regenerative medicine. Papers were evaluated for the last twelve years since CRISPR-Cas technology was introduced to the global community. CRISPR-Cas is currently being used to address therapeutic issues in articular cartilage regeneration by increasing the efficiency of chondrogenic differentiation of iPSC lines and harvesting a more homogeneous population of chondroprogenitor cells. Another approach is to remove the pro-inflammatory cytokine receptor sequence to produce inflammation-resistant cartilage. Finally, knocking out genes for components of the major histocompatibility complex allows harvesting chondrocytes that are invisible to the recipient's immune system. This kind of research contributes to personalized healthcare and can improve the quality of life of the world's population in the long term.

Transcriptome and epigenome dynamics of the clonal heterogeneity of human induced pluripotent stem cells for cardiac differentiation

Human induced pluripotent stem cells (hiPSCs) generate multiple clones with inherent heterogeneity, leading to variations in their differentiation capacity. Previous studies have primarily addressed line-to-line variations in differentiation capacity, leaving a gap in the comprehensive understanding of clonal heterogeneity. Here, we aimed to profile the heterogeneity of hiPSC clones and identify predictive biomarkers for cardiomyocyte (CM) differentiation capacity by integrating transcriptomic, epigenomic, endogenous retroelement, and protein kinase phosphorylation profiles. We generated multiple clones from a single donor and validated that these clones exhibited comparable levels of pluripotency markers. The clones were classified into two groups based on their differentiation efficiency to CMs-productive clone (PC) and non-productive clone (NPC). We performed RNA sequencing (RNA-seq) and assay for transposase-accessible chromatin with sequencing (ATAC-seq). NPC was enriched in vasculogenesis and cell adhesion, accompanied by elevated levels of phosphorylated ERK1/2. Conversely, PC exhibited enrichment in embryonic organ development and transcription factor activation, accompanied by increased chromatin accessibility near transcription start site (TSS) regions. Integrative analysis of RNA-seq and ATAC-seq revealed 14 candidate genes correlated with cardiac differentiation potential. Notably, TEK and SDR42E1 were upregulated in NPC. Our integrative profiles enhance the understanding of clonal heterogeneity and highlight two novel biomarkers associated with CM differentiation. This insight may facilitate the identification of suboptimal hiPSC clones, thereby mitigating adverse outcomes in clinical applications.

Advances in cartilage tissue regeneration: a review of stem cell therapies, tissue engineering, biomaterials, and clinical trials

Cartilage tissue, characterized by its limited regenerative capacity, presents significant challenges in clinical therapy. Recent advancements in cartilage regeneration have focused on integrating stem cell therapies, tissue engineering strategies, and advanced modeling techniques to overcome existing limitations. Stem cells, particularly Mesenchymal Stem Cells (MSCs) and induced pluripotent stem cells (iPSCs), hold promise for cartilage repair due to their ability to differentiate into chondrocytes, the key cells responsible for cartilage formation. Tissue engineering approaches, including 3D models, organ-on-a-chip systems, and organoids, offer innovative methods to mimic natural tissue microenvironments and evaluate potential treatments. MSC-based techniques, such as cell sheet tissue engineering, address challenges associated with traditional therapies, including cell availability and culture difficulties. Furthermore, advancements in 3D bioprinting enable the fabrication of complex tissue structures, while organ-on-a-chip systems provide microfluidic platforms for disease modeling and physiological mimicry. Organoids serve as simplified models of organs, capturing some complexity and enabling the monitoring of pathophysiological aspects of cartilage diseases. This comprehensive review underscores the transformative potential of integrating stem cell therapies, tissue engineering strategies, and advanced modeling techniques to improve cartilage regeneration and pave the way for more effective clinical treatments.

Challenges and perspectives of heart repair with pluripotent stem cell-derived cardiomyocytes

Here we aim at providing a concise but comprehensive overview of the perspectives and challenges of heart repair with pluripotent stem cell-derived cardiomyocytes. This Review comes at a time when consensus has been reached about the lack of relevant proliferative capacity of adult mammalian cardiomyocytes and the lack of new heart muscle formation with autologous cell sources. While alternatives to cell-based approaches will be shortly summarized, the focus lies on pluripotent stem cell-derived cardiomyocyte repair, which entered first clinical trials just 2 years ago. In the view of the authors, these early trials are important but have to be viewed as early proof-of-concept trials in humans that will hopefully provide first answers on feasibility, safety and the survival of allogeneic pluripotent stem cell-derived cardiomyocyte in the human heart. Better approaches have to be developed to make this approach clinically applicable.

Corneal Endothelial-like Cells Derived from Induced Pluripotent Stem Cells for Cell Therapy

Corneal endothelial dysfunction is one of the leading causes of corneal blindness, and the current conventional treatment option is corneal transplantation using a cadaveric donor cornea. However, there is a global shortage of suitable donor graft material, necessitating the exploration of novel therapeutic approaches. A stem cell-based regenerative medicine approach using induced pluripotent stem cells (iPSCs) offers a promising solution, as they possess self-renewal capabilities, can be derived from adult somatic cells, and can be differentiated into all cell types including corneal endothelial cells (CECs). This review discusses the progress and challenges in developing protocols to induce iPSCs into CECs, focusing on the different media formulations used to differentiate iPSCs to neural crest cells (NCCs) and subsequently to CECs, as well as the characterization methods and markers that define iPSC-derived CECs. The hurdles and solutions for the clinical application of iPSC-derived cell therapy are also addressed, including the establishment of protocols that adhere to good manufacturing practice (GMP) guidelines. The potential risks of genetic mutations in iPSC-derived CECs associated with long-term in vitro culture and the danger of potential tumorigenicity following transplantation are evaluated. In all, this review provides insights into the advancement and obstacles of using iPSC in the treatment of corneal endothelial dysfunction.

Current developments and therapeutic potentials of exosomes from induced pluripotent stem cells-derived mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells derived from adult human tissues that have the ability to proliferate in vitro and maintain their multipotency, making them attractive cell sources for regenerative medicine. However, MSCs reportedly show limited proliferative capacity with inconsistent therapeutic outcomes due to their heterogeneous nature. On the other hand, induced pluripotent stem cells (iPSC) have emerged as an alternative source for the production of various specialized cell types via their ability to differentiate from all three primary germ layers, leading to applications in regenerative medicine, disease modeling, and drug therapy. Notably, iPSCs can differentiate into MSCs in monolayer, commonly referred to as induced mesenchymal stem cells (iMSCs). These cells show superior therapeutic qualities compared with adult MSCs as the applications of the latter are restricted by passage number and autoimmune rejection when applied in tissue regeneration trials. Furthermore, increasing evidence shows that the therapeutic properties of stem cells are a consequence of the paracrine effects mediated by their secretome such as from exosomes, a type of extracellular vesicle secreted by most cell types. Several studies that investigated the potential of exosomes in regenerative medicine and therapy have revealed promising results. Therefore, this review focuses on the recent findings of exosomes secreted from iMSCs as a potential noncell-based therapy.

Stem cell sources and characterization in the development of cell-based products for treating retinal disease: An NEI Town Hall report

National Eye Institute recently issued a new Strategic Plan outlining priority research areas for the next 5 years. Starting cell source for deriving stem cell lines is as an area with gaps and opportunities for making progress in regenerative medicine, a key area of emphasis within the NEI Strategic Plan. There is a critical need to understand how starting cell source affects the cell therapy product and what specific manufacturing capabilities and quality control standards are required for autologous vs allogeneic stem cell sources. With the goal of addressing some of these questions, in discussion with the community-at-large, NEI hosted a Town Hall at the Association for Research in Vision and Ophthalmology annual meeting in May 2022. This session leveraged recent clinical advances in autologous and allogeneic RPE replacement strategies to develop guidance for upcoming cell therapies for photoreceptors, retinal ganglion cells, and other ocular cell types. Our focus on stem cell-based therapies for RPE underscores the relatively advanced stage of RPE cell therapies to patients with several ongoing clinical trials. Thus, this workshop encouraged lessons learned from the RPE field to help accelerate progress in developing stem cell-based therapies in other ocular tissues. This report provides a synthesis of the key points discussed at the Town Hall and highlights needs and opportunities in ocular regenerative medicine.

Novel strategies for designing regenerative skin products for accelerated wound healing

Healthy skin protects from pathogens, water loss, ultraviolet rays, and also maintains homeostasis conditions along with sensory perceptions in normal circumstances. Skin wound healing mechanism is a multi-phased biodynamic process that ultimately triggers intercellular and intracellular mechanisms. Failure to implement the normal and effective healing process may result in chronic injuries and aberrant scarring. Chronic wounds lead to substantial rising healthcare expenditure, and innovative methods to diagnose and control severe consequences are urgently needed. Skin tissue engineering (STE) has achieved several therapeutic accomplishments during the last few decades, demonstrating tremendous development. The engineered skin substitutes provide instant coverage for extensive wounds and facilitate the prevention of microbial infections and fluid loss; furthermore, they help in fighting inflammation and allow rapid neo-tissue formation. The current review primarily focused on the wound recovery and restoration process and the current conditions of STE with various advancements and complexities associated with different strategies such as cell sources, biopolymers, innovative fabrication techniques, and growth factors delivery systems.

The Structural and the Functional Aspects of Intercellular Communication in iPSC-Cardiomyocytes

Recent advances in the technology of producing novel cardiomyocytes from induced pluripotent stem cells (iPSC-cardiomyocytes) fuel new hope for future clinical applications. The use of iPSC-cardiomyocytes is particularly promising for the therapy of cardiac diseases such as myocardial infarction, where these cells could replace scar tissue and restore the functionality of the heart. Despite successful cardiogenic differentiation, medical applications of iPSC-cardiomyocytes are currently limited by their pronounced immature structural and functional phenotype. This review focuses on gap junction function in iPSC-cardiomyocytes and portrays our current understanding around the structural and the functional limitations of intercellular coupling and viable cardiac graft formation involving these novel cardiac muscle cells. We further highlight the role of the gap junction protein connexin 43 as a potential target for improving cell–cell communication and electrical signal propagation across cardiac tissue engineered from iPSC-cardiomyocytes. Better insight into the mechanisms that promote functional intercellular coupling is the foundation that will allow the development of novel strategies to combat the immaturity of iPSC-cardiomyocytes and pave the way toward cardiac tissue regeneration.

The Induced Pluripotent Stem Cells in Articular Cartilage Regeneration and Disease Modelling: Are We Ready for Their Clinical Use?

The development of induced pluripotent stem cells has brought unlimited possibilities to the field of regenerative medicine. This could be ideal for treating osteoarthritis and other skeletal diseases, because the current procedures tend to be short-term solutions. The usage of induced pluripotent stem cells in the cell-based regeneration of cartilage damages could replace or improve on the current techniques. The patient’s specific non-invasive collection of tissue for reprogramming purposes could also create a platform for drug screening and disease modelling for an overview of distinct skeletal abnormalities. In this review, we seek to summarise the latest achievements in the chondrogenic differentiation of pluripotent stem cells for regenerative purposes and disease modelling.

Downregulated Calcium-Binding Protein S100A16 and HSP27 in Placenta-Derived Multipotent Cells Induce Functional Astrocyte Differentiation

Little is known about genes that induce stem cells differentiation into astrocytes. We previously described that heat shock protein 27 (HSP27) downregulation is directly related to neural differentiation under chemical induction in placenta-derived multipotent stem cells (PDMCs). Using this neural differentiation cell model, we cross-compared transcriptomic and proteomic data and selected 26 candidate genes with the same expression trends in both omics analyses. Those genes were further compared with a transcriptomic database derived from Alzheimer’s disease (AD). Eighteen out of 26 candidates showed opposite expression trends between our data and the AD database. The mRNA and protein expression levels of those candidates showed downregulation of HSP27, S100 calcium-binding protein A16 (S100A16) and two other genes in our neural differentiation cell model. Silencing these four genes with various combinations showed that co-silencing HSP27 and S100A16 has stronger effects than other combinations for astrocyte differentiation. The induced astrocyte showed typical astrocytic star-shape and developed with ramified, stringy and filamentous processes as well as differentiated endfoot structures. Also, some of them connected with each other and formed continuous network. Immunofluorescence quantification of various neural markers indicated that HSP27 and S100A16 downregulation mainly drive PDMCs differentiation into astrocytes. Immunofluorescence and confocal microscopic images showed the classical star-like shape morphology and co-expression of crucial astrocyte markers in induced astrocytes, while electrophysiology and Ca2+ influx examination further confirmed their functional characteristics. In conclusion, co-silencing of S100A16 and HSP27 without chemical induction leads to PDMCs differentiation into functional astrocytes.

Graphical abstract

Neuroregenerative gene therapy to treat temporal lobe epilepsy in a rat model

Temporal lobe epilepsy (TLE) is a common drug-resistant epilepsy associated with abundant cell death in the hippocampus. Here, we develop a novel gene therapy-mediated cell therapy that regenerates GABAergic neurons using internal hippocampal astrocytes to suppress seizure activity in a rat TLE model. We discovered that TLE-induced reactive astrocytes in the hippocampal CA1 region can be efficiently converted into GABAergic neurons after overexpressing a neural transcription factor NeuroD1. The astrocyte-converted neurons showed typical markers of GABAergic interneurons, fired action potentials, and formed functional synaptic connections with other neurons. Following NeuroD1-mediated astrocyte-to-neuron conversion, the number of hippocampal interneurons was significantly increased, and the spontaneous recurrent seizure (SRS) activity was significantly decreased. Moreover, NeuroD1 gene therapy treatment rescued total neuronal loss in the CA1 region and ameliorated the cognitive and mood dysfunctions in the TLE rat model. These results suggest that regeneration of GABAergic interneurons through gene therapy approach may provide a novel therapeutic intervention to treat drug-resistant TLE.

Induced pluripotent stem cell-based disease modeling and prospective immune therapy for coronavirus disease 2019

The emergence of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic poses a never before seen challenge to human health and the economy. Considering its clinical impact, with no streamlined therapeutic strategies in sight, it is crucial to understand the infection process of SARS-CoV-2. Our limited knowledge of the mechanisms underlying SARS-CoV-2 infection impedes the development of alternative therapeutics to address the pandemic. This aspect can be addressed by modeling SARS-CoV-2 infection in the human context to facilitate drug screening and discovery. Human induced pluripotent stem cell (iPSC)-derived lung epithelial cells and organoids recapitulating the features and functionality of the alveolar cell types can serve as an in vitro human model and screening platform for SARS-CoV-2. Recent studies suggest an immune system asynchrony leading to compromised function and a decreased proportion of specific immune cell types in coronavirus disease 2019 (COVID-19) patients. Replenishing these specific immune cells may serve as useful treatment modality against SARS-CoV-2 infection. Here the authors review protocols for deriving lung epithelial cells, alveolar organoids and specific immune cell types, such as T lymphocytes and natural killer cells, from iPSCs with the aim to aid investigators in making relevant in vitro models of SARS-CoV-2 along with the possibility derive immune cell types to treat COVID-19.

Human Pluripotent Stem Cells Go Diabetic: A Glimpse on Monogenic Variants

Diabetes, as one of the major diseases in industrial countries, affects over 350 million people worldwide. Type 1 (T1D) and type 2 diabetes (T2D) are the most common forms with both types having invariable genetic influence. It is accepted that a subset of all diabetes patients, generally estimated to account for 1-2% of all diabetic cases, is attributed to mutations in single genes. As only a subset of these genes has been identified and fully characterized, there is a dramatic need to understand the pathophysiological impact of genetic determinants on β-cell function and pancreatic development but also on cell replacement therapies. Pluripotent stem cells differentiated along the pancreatic lineage provide a valuable research platform to study such genes. This review summarizes current perspectives in applying this platform to study monogenic diabetes variants.

Mitochondrial DNA Dynamics in Reprogramming to Pluripotency

Mammalian cells, with the exception of erythrocytes, harbor mitochondria, which are organelles that provide energy, intermediate metabolites, and additional activities to sustain cell viability, replication, and function. Mitochondria contain multiple copies of a circular genome called mitochondrial DNA (mtDNA), whose individual sequences are rarely identical (homoplasmy) because of inherited or sporadic mutations that result in multiple mtDNA genotypes (heteroplasmy). Here, we examine potential mechanisms for maintenance or shifts in heteroplasmy that occur in induced pluripotent stem cells (iPSCs) generated by cellular reprogramming, and further discuss manipulations that can alter heteroplasmy to impact stem and differentiated cell performance. This additional insight will assist in developing more robust iPSC-based models of disease and differentiated cell therapies.

Recent progress in translational engineered in vitro models of the central nervous system

The complexity of the human brain poses a substantial challenge for the development of models of the CNS. Current animal models lack many essential human characteristics (in addition to raising operational challenges and ethical concerns), and conventional in vitro models, in turn, are limited in their capacity to provide information regarding many functional and systemic responses. Indeed, these challenges may underlie the notoriously low success rates of CNS drug development efforts. During the past 5 years, there has been a leap in the complexity and functionality of in vitro systems of the CNS, which have the potential to overcome many of the limitations of traditional model systems. The availability of human-derived induced pluripotent stem cell technology has further increased the translational potential of these systems. Yet, the adoption of state-of-the-art in vitro platforms within the CNS research community is limited. This may be attributable to the high costs or the immaturity of the systems. Nevertheless, the costs of fabrication have decreased, and there are tremendous ongoing efforts to improve the quality of cell differentiation. Herein, we aim to raise awareness of the capabilities and accessibility of advanced in vitro CNS technologies. We provide an overview of some of the main recent developments (since 2015) in in vitro CNS models. In particular, we focus on engineered in vitro models based on cell culture systems combined with microfluidic platforms (e.g. 'organ-on-a-chip' systems). We delve into the fundamental principles underlying these systems and review several applications of these platforms for the study of the CNS in health and disease. Our discussion further addresses the challenges that hinder the implementation of advanced in vitro platforms in personalized medicine or in large-scale industrial settings, and outlines the existing differentiation protocols and industrial cell sources. We conclude by providing practical guidelines for laboratories that are considering adopting organ-on-a-chip technologies.

Diabetes Mellitus Is a Chronic Disease that Can Benefit from Therapy with Induced Pluripotent Stem Cells

Diabetes mellitus (DM) is one of the main causes of morbidity and mortality, with an increasing incidence worldwide. The impact of DM on public health in developing countries has triggered alarm due to the exaggerated costs of the treatment and monitoring of patients with this disease. Considerable efforts have been made to try to prevent the onset and reduce the complications of DM. However, because insulin-producing pancreatic β-cells progressively deteriorate, many people must receive insulin through subcutaneous injection. Additionally, current therapies do not have consistent results regarding the prevention of chronic complications. Leveraging the approval of real-time continuous glucose monitors and sophisticated algorithms that partially automate insulin infusion pumps has improved glycemic control, decreasing the burden of diabetes management. However, these advances are facing physiologic barriers. New findings in molecular and cellular biology have produced an extraordinary advancement in tissue development for the treatment of DM. Obtaining pancreatic β-cells from somatic cells is a great resource that currently exists for patients with DM. Although this therapeutic option has great prospects for patients, some challenges remain for this therapeutic plan to be used clinically. The purpose of this review is to describe the new techniques in cell biology and regenerative medicine as possible treatments for DM. In particular, this review highlights the origin of induced pluripotent cells (iPSCs) and how they have begun to emerge as a regenerative treatment that may mitigate the pathology of this disease.

Tumorigenic and Immunogenic Properties of Induced Pluripotent Stem Cells: a Promising Cancer Vaccine

Induced pluripotent stem cells (iPSCs) are mainly characterized by their unlimited proliferation abilities and potential to develop into almost any cell type. The creation of this technology has been of great interest to many scientific fields, especially regenerative biology. However, concerns about the safety of iPSC application in transplantation have arisen due to the tumorigenic and immunogenic properties of iPSCs. This review will briefly introduce the developing history of somatic reprogramming and applications of iPSC technology in regenerative medicine. In addition, the review will highlight two challenges to the efficient usage of iPSCs and the underlying mechanisms of these challenges. Finally, the review will discuss the expanding application of iPSC technology in cancer immunotherapy as a potential cancer vaccine and its advantages in auxiliary treatment compared with oncofetal antigen-based and embryonic stem cell (ESC)-based vaccines.

Overhauling CAR T Cells to Improve Efficacy, Safety and Cost

Gene therapy is now surpassing 30 years of clinical experience and in that time a variety of approaches has been applied for the treatment of a wide range of pathologies. While the promise of gene therapy was over-stated in the 1990’s, the following decades were met with polar extremes between demonstrable success and devastating setbacks. Currently, the field of gene therapy is enjoying the rewards of overcoming the hurdles that come with turning new ideas into safe and reliable treatments, including for cancer. Among these modalities, the modification of T cells with chimeric antigen receptors (CAR-T cells) has met with clear success and holds great promise for the future treatment of cancer. We detail a series of considerations for the improvement of the CAR-T cell approach, including the design of the CAR, routes of gene transfer, introduction of CARs in natural killer and other cell types, combining the CAR approach with checkpoint blockade or oncolytic viruses, improving pre-clinical models as well as means for reducing cost and, thus, making this technology more widely available. While CAR-T cells serve as a prime example of translating novel ideas into effective treatments, certainly the lessons learned will serve to accelerate the current and future development of gene therapy drugs.

Donor information in research and drug evaluation with induced pluripotent stem cells (iPSCs)

Background

The discovery of induced pluripotent stem cells (iPSCs) opened the possibilities for reprogramming cells back to a pluripotent state. Because of no apparent ethical issues connected with donation and derivation of biomaterial, iPSCs are considered as a research alternative to ethically highly disputed human embryonic stem cells (hESCs). However, the unique character of iPSCs leads to numerous ethical considerations, which mainly concern the issue of donor information and consent for the use of biospecimen in research and drug evaluation.

Methods

For the purpose of this analysis, we conducted a review of the literature in the PubMed/MEDLINE and Web of Science databases. The search algorithm led to the identification of 1461 results. After removing duplicates and screening of title and abstract, 90 articles were found to be relevant to the study’s objective. Full texts of these articles were apprised and 62 articles were excluded at this step for not properly addressing the study’s objective. In the final step, 28 articles were included in the analysis. Analyzed were both research and non-research manuscripts published in peer-reviewed journals.

Results

In the case of iPSC research, the information process should be guided by general frameworks established for research on human subjects but also by specific characteristics of iPSCs. We determined four main domains and 12 thematic subdomains that should be included in donor information. Our results show that majority of authors agree to the content of information with regard to the areas of general information, storage of cells, and protection of privacy. Two main issues that are discussed in the literature are donor’s consent for use in future studies and the process of donor information.

Conclusions

Given the unique character of iPSCs and the possibility of their various uses in the future, the content of donor information should contain specific information central to iPSC research. Effective methods of communicating information to donors should combine written and oral information with the possible use of multimedia.

Unprecedented Potential for Neural Drug Discovery Based on Self-Organizing hiPSC Platforms

Human induced pluripotent stem cells (hiPSCs) have transformed conventional drug discovery pathways in recent years. In particular, recent advances in hiPSC biology, including organoid technologies, have highlighted a new potential for neural drug discovery with clear advantages over the use of primary tissues. This is important considering the financial and social burden of neurological health care worldwide, directly impacting the life expectancy of many populations. Patient-derived iPSCs-neurons are invaluable tools for novel drug-screening and precision medicine approaches directly aimed at reducing the burden imposed by the increasing prevalence of neurological disorders in an aging population. 3-Dimensional self-assembled or so-called ‘organoid’ hiPSCs cultures offer key advantages over traditional 2D ones and may well be gamechangers in the drug-discovery quest for neurological disorders in the coming years.

Genomic Instability of iPSCs and Challenges in Their Clinical Applications

Generation of human-induced pluripotent stem cells (iPSCs) from somatic cells has opened the possibility to design novel therapeutic approaches. In 2014, the first-in-human clinical trial of iPSC-based therapy was conducted. However, the transplantation for the second patient was discontinued at least in part due to genetic aberrations detected in iPSCs. Moreover, many studies have reported genetic aberrations in iPSCs with the rapid progress in genomic technologies. The presence of genomic instability raises serious safety concerns and can hamper the advancement of iPSC-based therapies. Here, we summarize our current knowledge on genomic instability of iPSCs and challenges in their clinical applications. In view of the recent expansion of stem cell therapies, it is crucial to gain deeper mechanistic insights into the genetic aberrations, ranging from chromosomal aberrations, copy number variations to point mutations. On the basis of their origin, these genetic aberrations in iPSCs can be classified as (i) preexisting mutations in parental somatic cells, (ii) reprogramming-induced mutations, and (iii) mutations that arise during in vitro culture. However, it is still unknown whether these genetic aberrations in iPSCs can be an actual risk factor for adverse effects. Intersection of the genomic data on iPSCs with the patients' clinical follow-up data will help to produce evidence-based criteria for clinical application. Furthermore, we discuss novel approaches to generate iPSCs with fewer genetic aberrations. Better understanding of iPSCs from both basic and clinical aspects will pave the way for iPSC-based therapies.

Human induced pluripotent stem cells technology in treatment resistant depression: novel strategies and opportunities to unravel ketamine's fast-acting antidepressant mechanisms

Approximately 30% of Major Depressive Disorder (MDD) patients develop treatment-resistant depression (TRD). Among the different causes that make TRD so challenging in both clinical and research contexts, major roles are played by the inadequate understanding of MDD pathophysiology and the limitations of current pharmacological treatments. Nevertheless, the field of psychiatry is facing exciting times. Combined with recent advances in genome editing techniques, human induced pluripotent stem cell (hiPSC) technology is offering novel and unique opportunities in both disease modelling and drug discovery. This technology has allowed innovative disease-relevant patient-specific in vitro models to be set up for many psychiatric disorders. Such models hold great potential in enhancing our understanding of MDD pathophysiology and overcoming many of the well-known practical limitations inherent to animal and post-mortem models. Moreover, the field is approaching the advent of (es)ketamine, a glutamate N-methyl-d-aspartate (NMDA) receptor antagonist, claimed as one of the first and exemplary agents with rapid (in hours) antidepressant effects, even in TRD patients. Although ketamine seems poised to transform the treatment of depression, its exact mechanisms of action are still unclear but greatly demanded, as the resulting knowledge may provide a model to understand the mechanisms behind rapid-acting antidepressants, which may lead to the discovery of novel compounds for the treatment of depression. After reviewing insights into ketamine's mechanisms of action (derived from preclinical animal studies) and depicting the current state of the art of hiPSC technology below, we will consider the implementation of an hiPSC technology-based TRD model for the study of ketamine's fast acting antidepressant mechanisms of action.

Generation and comprehensive characterization of induced pluripotent stem cells for translational research

Induced pluripotent stem cells (iPSCs) hold immense potential in disease modeling, drug discovery and regenerative medicine. Despite advances in reprogramming methods, generation of clinical-grade iPSCs remains a challenge. Reported here is the first off-the-shelf reprogramming kit, CTS CytoTune-iPS 2.1, specifically designed for clinical and translational research. Workflow gaps were identified, and methods developed were used to consistently generate iPSC from multiple cell types. Resulting clones were subjected to characterization that included confirmation of pluripotency, preservation of genomic integrity and authentication of cell banks via an array of molecular methods including high resolution microarray and next-generation sequencing. Development of integrated xeno-free workflows combined with comprehensive characterization offers generation of high-quality iPSCs that are suited for clinical and translational research.

Current Challenges of iPSC-Based Disease Modeling and Therapeutic Implications

Induced pluripotent stem cell (iPSC)-based disease modelling and the cell replacement therapy approach have proven to be very powerful and instrumental in biomedical research and personalized regenerative medicine as evidenced in the past decade by unraveling novel pathological mechanisms of a multitude of monogenic diseases at the cellular level and the ongoing and emerging clinical trials with iPSC-derived cell products. iPSC-based disease modelling has sparked widespread enthusiasm and has presented an unprecedented opportunity in high throughput drug discovery platforms and safety pharmacology in association with three-dimensional multicellular organoids such as personalized organs-on-chips, gene/base editing, artificial intelligence and high throughput "omics" methodologies. This critical review summarizes the progress made in the past decade with the advent of iPSC discovery in biomedical applications and regenerative medicine with case examples and the current major challenges that need to be addressed to unleash the full potential of iPSCs in clinical settings and pharmacology for more effective and safer regenerative therapy.

Progress in understanding Friedreich's ataxia using human induced pluripotent stem cells

Introduction

Friedreich's ataxia (FRDA) is an autosomal recessive multisystem disease mainly affecting the peripheral and central nervous systems, and heart. FRDA is caused by a GAA repeat expansion in the first intron of the frataxin (FXN) gene, that leads to reduced expression of FXN mRNA and frataxin protein. Neuronal and cardiac cells are primary targets of frataxin deficiency and generating models via differentiation of induced pluripotent stem cells (iPSCs) into these cell types is essential for progress towards developing therapies for FRDA.

Areas covered

This review is focused on modeling FRDA using human iPSCs and various iPSC-differentiated cell types. We emphasized the importance of patient and corrected isogenic cell line pairs to minimize effects caused by biological variability between individuals.

Expert opinion

The versatility of iPSC-derived cellular models of FRDA is advantageous for developing new therapeutic strategies, and rigorous testing in such models will be critical for approval of the first treatment for FRDA. Creating a well-characterized and diverse set of iPSC lines, including appropriate isogenic controls, will facilitate achieving this goal. Also, improvement of differentiation protocols, especially towards proprioceptive sensory neurons and organoid generation, is necessary to utilize the full potential of iPSC technology in the drug discovery process.