Reprogramming of T cells from human peripheral blood

Current status and new avenues of stem cell-based preclinical and therapeutic approaches in amyotrophic lateral sclerosis

INTRODUCTION

Cell therapy development represents a critical challenge in amyotrophic lateral sclerosis (ALS) research. Despite more than 20 years of basic and clinical research, no definitive safety and efficacy results of cell-based therapies for ALS have been published.

AREAS COVERED

This review summarizes advances using stem cells (SCs) in pre-clinical studies to promote clinical translation and in clinical trials to treat ALS. New technologies have been developed and new experimental in vitro and animal models are now available to facilitate pre-clinical research in this field and to determine the most promising approaches to pursue in patients. New clinical trial designs aimed at developing personalized SC-based treatment with biological endpoints are being defined.

EXPERT OPINION

Knowledge of the basic biology of ALS and on the use of SCs to study and potentially treat ALS continues to grow. However, a consensus has yet to emerge on how best to translate these results into therapeutic applications. The selection and follow-up of patients should be based on clinical, biological, and molecular criteria. Planning of SC-based clinical trials should be coordinated with patient profiling genetically and molecularly to achieve personalized treatment. Much work within basic and clinical research is still needed to successfully transition SC therapy in ALS.

Generation of immune cells from induced pluripotent stem cells (iPSCs): Their potential for adoptive cell therapy

Advances in human stem cell technologies enable induced pluripotent stem cells (iPSCs) to be explored as potent candidates for treating various diseases, such as malignancies, autoimmunity, immunodeficiencies, and allergic reactions. iPSCs with infinite self-renewal ability can be derived from different types of somatic cells without the ethical issues associated with embryonic stem cells. To date, numerous cell types, including various immune cell subsets [CD4+ and CD8+ T cells, gamma delta T (γδ T) cells, regulatory T cells, dendritic cells, natural killer cells, macrophages, and neutrophils] have successfully been generated from iPSCs paving the way for effective adoptive cell transfer therapy, drug development, and disease modeling. Herein, we review various iPSC-derived immune cells and their possible application in immunotherapy.

Hypoxia Increases the Efficiencies of Cellular Reprogramming and Oncogenic Transformation in Human Blood Cell Subpopulations In Vitro and In Vivo

Patients with chronic hypoxia show a higher tumor incidence; however, no primary common cause has been recognized. Given the similarities between cellular reprogramming and oncogenic transformation, we directly compared these processes in human cells subjected to hypoxia. Mouse embryonic fibroblasts were employed as controls to compare transfection and reprogramming efficiency; human adipose-derived mesenchymal stem cells were employed as controls in human cells. Easily obtainable human peripheral blood mononuclear cells (PBMCs) were chosen to establish a standard protocol to compare cell reprogramming (into induced pluripotent stem cells (iPSCs)) and oncogenic focus formation efficiency. Cell reprogramming was achieved for all three cell types, generating actual pluripotent cells capable for differentiating into the three germ layers. The efficiencies of the cell reprogramming and oncogenic transformation were similar. Hypoxia slightly increased the reprogramming efficiency in all the cell types but with no statistical significance for PBMCs. Various PBMC types can respond to hypoxia differently; lymphocytes and monocytes were, therefore, reprogrammed separately, finding a significant difference between normoxia and hypoxia in monocytes in vitro. These differences were then searched for in vivo. The iPSCs and oncogenic foci were generated from healthy volunteers and patients with chronic obstructive pulmonary disease (COPD). Although higher iPSC generation efficiency in the patients with COPD was found for lymphocytes, this increase was not statistically significant for oncogenic foci. Remarkably, a higher statistically significant efficiency in COPD monocytes was demonstrated for both processes, suggesting that physiological hypoxia exerts an effect on cell reprogramming and oncogenic transformation in vivo in at least some cell types.

Bioprocessing considerations for generation of iPSCs intended for clinical application: perspectives from the ISCT Emerging Regenerative Medicine Technology working group

Approval of induced pluripotent stem cells (iPSCs) for the manufacture of cell therapies to support clinical trials is now becoming realized after 20 years of research and development. In 2022 the International Society for Cell and Gene Therapy (ISCT) established a Working Group on Emerging Regenerative Medicine Technologies, an area in which iPSCs-derived technologies are expected to play a key role. In this article, the Working Group surveys the steps that an end user should consider when generating iPSCs that are stable, well-characterised, pluripotent, and suitable for making differentiated cell types for allogeneic or autologous cell therapies. The objective is to provide the reader with a holistic view of how to achieve high-quality iPSCs from selection of the starting material through to cell banking. Key considerations include: (i) intellectual property licenses; (ii) selection of the raw materials and cell sources for creating iPSC intermediates and master cell banks; (iii) regulatory considerations for reprogramming methods; (iv) options for expansion in 2D vs. 3D cultures; and (v) available technologies and equipment for harvesting, washing, concentration, filling, cryopreservation, and storage. Some key process limitations are highlighted to help drive further improvement and innovation, and includes recommendations to close and automate current open and manual processes.

miRNA circuit modules for precise, tunable control of gene expression

The ability to express transgenes at specified levels is critical for understanding cellular behaviors, and for applications in gene and cell therapy. Transfection, viral vectors, and other gene delivery methods produce varying protein expression levels, with limited quantitative control, while targeted knock-in and stable selection are inefficient and slow. Active compensation mechanisms can improve precision, but the need for additional proteins or lack of tunability have prevented their widespread use. Here, we introduce a toolkit of compact, synthetic miRNA-based circuit modules that provide precise, tunable control of transgenes across diverse cell types. These circuits, termed DIMMERs (Dosage-Invariant miRNA-Mediated Expression Regulators) use multivalent miRNA regulatory interactions within an incoherent feed-forward loop architecture to achieve nearly uniform protein expression over more than two orders of magnitude variation in underlying gene dosages or transcription rates. They also allow coarse and fine control of expression, and are portable, functioning across diverse cell types. In addition, a heuristic miRNA design algorithm enables the creation of orthogonal circuit variants that independently control multiple genes in the same cell. These circuits allowed dramatically improved CRISPR imaging, and super-resolution imaging of EGFR receptors with transient transfections. The toolbox provided here should allow precise, tunable, dosage-invariant expression for research, gene therapy, and other biotechnology applications.

Induced Pluripotent Stem Cell-Derived Chimeric Antigen Receptor T Cells: The Intersection of Stem Cells and Immunotherapy

Chimeric antigen receptor (CAR) T cell therapy is a promising cell-based immunotherapy applicable to various cancers. High cost of production, immune rejection, heterogeneity of cell product, limited cell source, limited expandability, and relatively long production time have created the need to achieve a universal allogeneic CAR-T cell product for "off-the-shelf" application. Since the innovation of induced pluripotent stem cells (iPSCs) by Yamanaka et al., extensive efforts have been made to prepare an unlimited cell source for regenerative medicine, that is, immunotherapy. In the autologous grafting approach, iPSCs prepare the desired cell source for generating autologous CAR-T cells through more accessible and available sources. In addition, generating iPSC-derived CAR-T cells is a promising approach to achieving a suitable source for producing an allogeneic CAR-T cell product. In brief, the first step is reprogramming somatic cells (accessible from peripheral blood, skin, etc.) to iPSCs. In the next step, CAR expression and T cell lineage differentiation should be applied in different arrangements. In addition, in an allogeneic manner, human leukocyte antigen/T cell receptor (TCR) deficiency should be applied in iPSC colonies. The allogeneic iPSC-derived CAR-T cell experiments showed that simultaneous performance of HLA/TCR deficiency, CAR expression, and T cell lineage differentiation could bring the production to the highest efficacy in generating allogeneic iPSC-derived CAR-T cells.

Generating hematopoietic cells from human pluripotent stem cells: approaches, progress and challenges

Human pluripotent stem cells (hPSCs) have been suggested as a potential source for the production of blood cells for clinical application. In two decades, almost all types of blood cells can be successfully generated from hPSCs through various differentiated strategies. Meanwhile, with a deeper understanding of hematopoiesis, higher efficiency of generating progenitors and precursors of blood cells from hPSCs is achieved. However, how to generate large-scale mature functional cells from hPSCs for clinical use is still difficult. In this review, we summarized recent approaches that generated both hematopoietic stem cells and mature lineage cells from hPSCs, and remarked their efficiency and mechanisms in producing mature functional cells. We also discussed the major challenges in hPSC-derived products of blood cells and provided some potential solutions. Our review summarized efficient, simple, and defined methodologies for developing good manufacturing practice standards for hPSC-derived blood cells, which will facilitate the translation of these products into the clinic.

Identifying Cancer Type-Specific Transcriptional Programs through Network Analysis

Identifying cancer type-specific genes that define cell states is important to develop effective therapies for patients and methods for detection, early diagnosis, and prevention. While molecular mechanisms that drive malignancy have been identified for various cancers, the identification of cell-type defining transcription factors (TFs) that distinguish normal cells from cancer cells has not been fully elucidated. Here, we utilized a network biology framework, which assesses the fidelity of cell fate conversions, to identify cancer type-specific gene regulatory networks (GRN) for 17 types of cancer. Through an integrative analysis of a compendium of expression data, we elucidated core TFs and GRNs for multiple cancer types. Moreover, by comparing normal tissues and cells to cancer type-specific GRNs, we found that the expression of key network-influencing TFs can be utilized as a survival prognostic indicator for a diverse cohort of cancer patients. These findings offer a valuable resource for exploring cancer type-specific networks across a broad range of cancer types.

Apoptosis inhibition enhances induced pluripotent stem cell generation during T cell reprogramming

The widespread adoption of chimeric antigen receptor (CAR)-T cell therapy has been hindered by its complex and costly manufacturing process. Induced pluripotent stem cells (iPSCs) have shown promise as a cellular immunotherapy alternative, due to their unlimited self-renewal potential in culture and capacity to differentiate into functional immune cell types. However, it is imperative to carefully select the original cell for iPSC seed preparation, as iPSCs have been found to retain the epigenetic imprint of the original somatic cells. Additionally, the efficiency of reprogramming terminal differentiated cells for immunotherapy must be addressed. Our research highlights the superiority of lymphocyte-origin cells over embryonic stem cells in functional immune cell differentiation. Furthermore, blocking Fas-FasL induced apoptosis in T cells significantly improves iPSC generation. Interestingly, transient Fas suppression in T cells does not alter the expression of Fas in the resulting iPSCs or affect their differentiation potential. This finding brings up new avenues in the field of cellular immunotherapy and provides a solution for creating high-quality and suitable iPSCs for lymphocyte differentiation for immunotherapy purposes.

Analysis of causes for poor persistence of CAR-T cell therapy in vivo

Chimeric antigen receptor T-cell (CAR-T-cell) therapy has been well researched to date because of its ability to target malignant tumor cells. The most common CAR-T cells are CD19 CAR-T cells, which play a large role in B-cell leukemia treatment. However, most CAR-T cells are associated with relapse after clinical treatment, so the quality and persistence of CAR-T cells need to be improved. With continuous optimization, there have been four generations of CARs and each generation of CARs has better quality and durability than the previous generation. In addition, it is important to increase the proportion of memory cells in CAR-T cells. Studies have shown that an immunosuppressive tumor microenvironment (TME) can lead to dysfunction of CAR-T cells, resulting in decreased cell proliferation and poor persistence. Thus, overcoming the challenges of immunosuppressive molecules and targeting cytokines in the TME can also improve CAR-T cell persistence. In this paper, we explored how to improve the durability of CAR-T cell therapy by improving the structure of CARs, increasing the proportion of memory CAR-T cells and improving the TME.

Generation of CD34+CD43+ Hematopoietic Progenitors to Induce Thymocytes from Human Pluripotent Stem Cells

Immunotherapy using primary T cells has revolutionized medical care in some pathologies in recent years, but limitations associated to challenging cell genome edition, insufficient cell number production, the use of only autologous cells, and the lack of product standardization have limited its clinical use. The alternative use of T cells generated in vitro from human pluripotent stem cells (hPSCs) offers great advantages by providing a self-renewing source of T cells that can be readily genetically modified and facilitate the use of standardized universal off-the-shelf allogeneic cell products and rapid clinical access. However, despite their potential, a better understanding of the feasibility and functionality of T cells differentiated from hPSCs is necessary before moving into clinical settings. In this study, we generated human-induced pluripotent stem cells from T cells (T-iPSCs), allowing for the preservation of already recombined TCR, with the same properties as human embryonic stem cells (hESCs). Based on these cells, we differentiated, with high efficiency, hematopoietic progenitor stem cells (HPSCs) capable of self-renewal and differentiation into any cell blood type, in addition to DN3a thymic progenitors from several T-iPSC lines. In order to better comprehend the differentiation, we analyzed the transcriptomic profiles of the different cell types and demonstrated that HPSCs differentiated from hiPSCs had very similar profiles to cord blood hematopoietic stem cells (HSCs). Furthermore, differentiated T-cell progenitors had a similar profile to thymocytes at the DN3a stage of thymic lymphopoiesis. Therefore, utilizing this approach, we were able to regenerate precursors of therapeutic human T cells in order to potentially treat a wide range of diseases.

Scalable Generation of Nanovesicles from Human-Induced Pluripotent Stem Cells for Cardiac Repair

Extracellular vesicles (EVs) from stem cells have shown significant therapeutic potential to repair injured cardiac tissues and regulate pathological fibrosis. However, scalable generation of stem cells and derived EVs for clinical utility remains a huge technical challenge. Here, we report a rapid size-based extrusion strategy to generate EV-like membranous nanovesicles (NVs) from easily sourced human iPSCs in large quantities (yield 900× natural EVs). NVs isolated using density-gradient separation (buoyant density 1.13 g/mL) are spherical in shape and morphologically intact and readily internalised by human cardiomyocytes, primary cardiac fibroblasts, and endothelial cells. NVs captured the dynamic proteome of parental cells and include pluripotency markers (LIN28A, OCT4) and regulators of cardiac repair processes, including tissue repair (GJA1, HSP20/27/70, HMGB1), wound healing (FLNA, MYH9, ACTC1, ILK), stress response/translation initiation (eIF2S1/S2/S3/B4), hypoxia response (HMOX2, HSP90, GNB1), and extracellular matrix organization (ITGA6, MFGE8, ITGB1). Functionally, NVs significantly promoted tubule formation of endothelial cells (angiogenesis) (p < 0.05) and survival of cardiomyocytes exposed to low oxygen conditions (hypoxia) (p < 0.0001), as well as attenuated TGF-β mediated activation of cardiac fibroblasts (p < 0.0001). Quantitative proteome profiling of target cell proteome following NV treatments revealed upregulation of angiogenic proteins (MFGE8, MYH10, VDAC2) in endothelial cells and pro-survival proteins (CNN2, THBS1, IGF2R) in cardiomyocytes. In contrast, NVs attenuated TGF-β-driven extracellular matrix remodelling capacity in cardiac fibroblasts (ACTN1, COL1A1/2/4A2/12A1, ITGA1/11, THBS1). This study presents a scalable approach to generating functional NVs for cardiac repair.

Building in vitro models of the brain to understand the role of APOE in Alzheimer's disease

Alzheimer's disease (AD) is a devastating, complex, and incurable disease that represents an increasingly problematic global health issue. The etiology of sporadic AD that accounts for a vast majority of cases remains poorly understood, with no effective therapeutic interventions. Genetic studies have identified AD risk genes including the most prominent, APOE, of which the ɛ4 allele increases risk in a dose-dependent manner. A breakthrough discovery enabled the creation of human induced pluripotent stem cells (hiPSCs) that can be differentiated into various brain cell types, facilitating AD research in genetically human models. Herein, we provide a brief background on AD in the context of APOE susceptibility and feature work employing hiPSC-derived brain cell and tissue models to interrogate the contribution of APOE in driving AD pathology. Such models have delivered crucial insights into cellular mechanisms and cell type-specific roles underlying the perturbed biological functions that trigger pathogenic cascades and propagate neurodegeneration. Collectively, hiPSC-based models are envisioned to be an impactful platform for uncovering fundamental AD understanding, with high translational value toward AD drug discovery and testing.

A protocol for the generation of patient-specific iPSC lines from peripheral blood mononuclear cells

The current procedure thoroughly explains how to reprogram induced pluripotent stem cells (iPSCs) from the patient’s peripheral blood mononuclear cells (PBMCs), a less invasive source; e.g., somatic cells. We describe how to isolate PBMCs and reprogram them into iPSCs by electroporation. Furthermore, we provide an alternative approach to generating iPSC using Geltrex or Matrigel matrix to replace MEF-feeder. The challenge of this process is the relatively lower cell survival rates of PBMCs due to the damage of electroporation.

For complete details on the use and execution of this protocol, please refer to Hu et al. (2021).

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Protocol to induce iPSC from patient-derived PBMCs

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Protocol to isolate PBMC from patients

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Alternative feeder approach to generating iPSC by Geltrex or Matrigel matrix

Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics.

Stem-like T cells and niches: Implications in human health and disease

Recently, accumulating evidence has elucidated the important role of T cells with stem-like characteristics in long-term maintenance of T cell responses and better patient outcomes after immunotherapy. The fate of TSL cells has been correlated with many physiological and pathological human processes. In this review, we described present advances demonstrating that stem-like T (TSL) cells are central players in human health and disease. We interpreted the evolutionary characteristics, mechanism and functions of TSL cells. Moreover, we discuss the import role of distinct niches and how they affect the stemness of TSL cells. Furthermore, we also outlined currently available strategies to generate TSL cells and associated affecting factors. Moreover, we summarized implication of TSL cells in therapies in two areas: stemness enhancement for vaccines, ICB, and adoptive T cell therapies, and stemness disruption for autoimmune disorders.

CELLoGeNe - An energy landscape framework for logical networks controlling cell decisions

Experimental and computational efforts are constantly made to elucidate mechanisms controlling cell fate decisions during development and reprogramming. One powerful computational method is to consider cell commitment and reprogramming as movements in an energy landscape. Here, we develop Computation of Energy Landscapes of Logical Gene Networks (CELLoGeNe), which maps Boolean implementation of gene regulatory networks (GRNs) into energy landscapes. CELLoGeNe removes inadvertent symmetries in the energy landscapes normally arising from standard Boolean operators. Furthermore, CELLoGeNe provides tools to visualize and stochastically analyze the shapes of multi-dimensional energy landscapes corresponding to epigenetic landscapes for development and reprogramming. We demonstrate CELLoGeNe on two GRNs governing different aspects of induced pluripotent stem cells, identifying experimentally validated attractors and revealing potential reprogramming roadblocks. CELLoGeNe is a general framework that can be applied to various biological systems offering a broad picture of intracellular dynamics otherwise inaccessible with existing methods.

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CELLoGeNe – Computation of Energy Landscapes of Logical Gene Networks

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Cell states as landscape attractors

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Maintenance and acquisition of cell pluripotency applications

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Single cell stochastic landscape navigation and visualization tool

The Potential Applications of Stem Cells for Cancer Treatment

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Scientists encounter many obstacles in traditional cancer therapies, including the side effects on the healthy cells, drug resistance, tumor relapse, the short half-life of employed drugs in the blood circulation, and the improper delivery of drugs toward the tumor site. The unique traits of stem cells (SCs) such as self-renewal, differentiation, tumor tropism, the release of bioactive molecules, and immunosuppression have opened a new window for utilizing SCs as a novel tool in cancer treatment. In this regard, engineered SCs can secrete anti-cancer proteins or express enzymes used in suicide gene therapy which locally induce apoptosis in neoplastic cells via the bystander effect. These cells also stand as proper candidates to serve as careers for drug-loaded nanoparticles or to play suitable hosts for oncolytic viruses. Moreover, they harbor great potential to be employed in immunotherapy and combination therapy. However, tactful strategies should be devised to allow easier transplantation and protection of SCs from in vivo immune responses. In spite of the great hope concerning SCs application in cancer therapy, there are shortcomings and challenges to be addressed. This review tends to elaborate on recent advances on the various applications of SCs in cancer therapy and existing challenges in this regard.

Using hiPSC-CMs to Examine Mechanisms of Catecholaminergic Polymorphic Ventricular Tachycardia

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a potentially lethal inherited cardiac arrhythmia condition, triggered by physical or acute emotional stress, that predominantly expresses early in life. Gain-of-function mutations in the cardiac ryanodine receptor gene (RYR2) account for the majority of CPVT cases, causing substantial disruption of intracellular calcium (Ca²⁺ ) homeostasis particularly during the periods of β-adrenergic receptor stimulation. However, the highly variable penetrance, patient outcomes, and drug responses observed in clinical practice remain unexplained, even for patients with well-established founder RyR2 mutations. Therefore, investigation of the electrophysiological consequences of CPVT-causing RyR2 mutations is crucial to better understand the pathophysiology of the disease. The development of strategies for reprogramming human somatic cells to human induced pluripotent stem cells (hiPSCs) has provided a unique opportunity to study inherited arrhythmias, due to the ability of hiPSCs to differentiate down a cardiac lineage. Employment of genome editing enables generation of disease-specific cell lines from healthy and diseased patient-derived hiPSCs, which subsequently can be differentiated into cardiomyocytes. This paper describes the means for establishing an hiPSC-based model of CPVT in order to recapitulate the disease phenotype in vitro and investigate underlying pathophysiological mechanisms. The framework of this approach has the potential to contribute to disease modeling and personalized medicine using hiPSC-derived cardiomyocytes. © 2021 Wiley Periodicals LLC.

Epigenetics and CD8+ T cell memory

Following antigen recognition, CD8⁺ T lymphocytes can follow different patterns of differentiation, with the generation of different subsets characterized by distinct phenotypes, functions, and migration properties. The changes of transcription factors activity and chromatin structure dynamics drive the functional differentiation and phenotypic heterogeneity of these T cell subsets, which include short-lived effectors, long-term survival of memory, and also dysfunctional exhausted T cells. Recent progress in the field has shed light on the key contribution of chromatin organization to control the T cell fate specification. In fact, the understanding of these processes has important implications for the development of new immunotherapy protocols and to design new vaccination strategies. Here, we review the current understanding of the contribution of chromatin architecture and transcription factor activity orchestrating the gene expression programs guiding the CD8⁺ T cell subset commitment. We will focus on epigenetic changes, acting sequentially or in combination, which control the transcriptional programs governing T cell plasticity, stability, and memory. New molecular insights into the mechanisms of maintenance of cellular memory and identity, favoring or impeding the reprogramming, will be discussed in the context of T cell memory differentiation in infection and cancer.

Prospects for Development of Induced Pluripotent Stem Cell-Derived CAR-Targeted Immunotherapies

Technologies required to generate induced pluripotent stem cells (iPSC) were first described 15 years ago, providing a strong impetus to the field of regenerative medicine. In parallel, immunotherapy has finally emerged as a clinically meaningful modality of cancer therapy. In particular, impressive efficacy has been achieved in patients with selected haematological malignancies using ex vivo expanded autologous T cells engineered to express chimeric antigen receptors (CARs). While solid tumours account for over 90% of human cancer, they currently are largely refractory to this therapeutic approach. Nonetheless, given the considerable innovation taking place worldwide in the CAR field, it is likely that effective solutions for common solid tumours will emerge in the near future. Such a development will create significant new challenges in the scalable delivery of these complex, costly and individualised therapies. CAR-engineered immune cell products that originate from iPSCs offer the potential to generate unlimited numbers of homogeneous, standardised cell products in which multiple defined gene modification events have been introduced to ensure safety, potency and reproducibility. Here, we review some of the emerging strategies in use to engineer CAR-expressing iPSC-derived drug products.

Application of the Pluripotent Stem Cells and Genomics in Cardiovascular Research-What We Have Learnt and Not Learnt until Now

Personalized regenerative medicine and biomedical research have been galvanized and revolutionized by human pluripotent stem cells in combination with recent advances in genomics, artificial intelligence, and genome engineering. More recently, we have witnessed the unprecedented breakthrough life-saving translation of mRNA-based vaccines for COVID-19 to contain the global pandemic and the investment in billions of US dollars in space exploration projects and the blooming space-tourism industry fueled by the latest reusable space vessels. Now, it is time to examine where the translation of pluripotent stem cell research stands currently, which has been touted for more than the last two decades to cure and treat millions of patients with severe debilitating degenerative diseases and tissue injuries. This review attempts to highlight the accomplishments of pluripotent stem cell research together with cutting-edge genomics and genome editing tools and, also, the promises that have still not been transformed into clinical applications, with cardiovascular research as a case example. This review also brings to our attention the scientific and socioeconomic challenges that need to be effectively addressed to see the full potential of pluripotent stem cells at the clinical bedside.

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

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

Induced Pluripotent Stem Cells to Model Juvenile Myelomonocytic Leukemia: New Perspectives for Preclinical Research

Juvenile myelomonocytic leukemia (JMML) is a malignant myeloproliferative disorder arising in infants and young children. The origin of this neoplasm is attributed to an early deregulation of the Ras signaling pathway in multipotent hematopoietic stem/progenitor cells. Since JMML is notoriously refractory to conventional cytostatic therapy, allogeneic hematopoietic stem cell transplantation remains the mainstay of curative therapy for most cases. However, alternative therapeutic approaches with small epigenetic molecules have recently entered the stage and show surprising efficacy at least in specific subsets of patients. Hence, the establishment of preclinical models to test novel agents is a priority. Induced pluripotent stem cells (IPSCs) offer an opportunity to imitate JMML ex vivo, after attempts to generate immortalized cell lines from primary JMML material have largely failed in the past. Several research groups have previously generated patient-derived JMML IPSCs and successfully differentiated these into myeloid cells with extensive phenotypic similarities to primary JMML cells. With infinite self-renewal and the capability to differentiate into multiple cell types, JMML IPSCs are a promising resource to advance the development of treatment modalities targeting specific vulnerabilities. This review discusses current reprogramming techniques for JMML stem/progenitor cells, related clinical applications, and the challenges involved.

Early-phenotype CAR-T cells for the treatment of pediatric cancers

Chimeric antigen receptor (CAR) T cell therapy is a promising approach for the treatment of childhood cancers, particularly high-risk tumors that fail to respond to standard therapies. CAR-T cells have been highly successful in treating some types of hematological malignancies. However, CAR-T cells targeting solid cancers have had limited success so far for multiple reasons, including their poor long-term persistence and proliferation. Evidence is emerging to show that maintaining CAR-T cells in an early, less differentiated state in vitro results in superior persistence, proliferation, and anti-tumor effects in vivo. Children are ideal candidates for receiving less-differentiated CAR-T cells, because their peripheral T cell pool primarily comprises naïve cells that could readily be harvested in large numbers to generate early-phenotype CAR-T cells. Although several studies have reported different approaches to successfully generate early CAR-T cells, there are only a few clinical trials testing these in adult patients. No trials are currently testing early CAR-T cells in children. Here, we summarize the different strategies used to maintain CAR-T cells in an early phenotypic stage, and present evidence suggesting that this approach may be particularly relevant to treating childhood cancers.

Clinically compatible advances in blood-derived endothelial progenitor cell isolation and reprogramming for translational applications

The promise of using induced pluripotent stem cells (iPSCs) for cellular therapies has been hampered by the lack of easily isolatable and well characterized source cells whose genomes have undergone minimal changes during their processing. Blood-derived late-outgrowth endothelial progenitor cells (EPCs) are used for disease modeling and have potential therapeutic uses including cell transplantation and the translation of induced pluripotent stem cell (iPSC) derivatives. However, the current isolation of EPCs has been inconsistent and requires at least 40-80 mL of blood, limiting their wider use. In addition, previous EPC reprogramming methods precluded the translation of EPC-derived iPSCs to the clinic. Here a series of clinically-compatible advances in the isolation and reprogramming of EPCs is presented, including a reduction of blood sampling volumes to 10 mL and use of highly efficient RNA-based reprogramming methods together with autologous human serum, resulting in clinically relevant iPSCs carrying minimal copy number variations (CNVs) compared to their parent line.

Cell Fate Reprogramming in the Era of Cancer Immunotherapy

Advances in understanding how cancer cells interact with the immune system allowed the development of immunotherapeutic strategies, harnessing patients' immune system to fight cancer. Dendritic cell-based vaccines are being explored to reactivate anti-tumor adaptive immunity. Immune checkpoint inhibitors and chimeric antigen receptor T-cells (CAR T) were however the main approaches that catapulted the therapeutic success of immunotherapy. Despite their success across a broad range of human cancers, many challenges remain for basic understanding and clinical progress as only a minority of patients benefit from immunotherapy. In addition, cellular immunotherapies face important limitations imposed by the availability and quality of immune cells isolated from donors. Cell fate reprogramming is offering interesting alternatives to meet these challenges. Induced pluripotent stem cell (iPSC) technology not only enables studying immune cell specification but also serves as a platform for the differentiation of a myriad of clinically useful immune cells including T-cells, NK cells, or monocytes at scale. Moreover, the utilization of iPSCs allows introduction of genetic modifications and generation of T/NK cells with enhanced anti-tumor properties. Immune cells, such as macrophages and dendritic cells, can also be generated by direct cellular reprogramming employing lineage-specific master regulators bypassing the pluripotent stage. Thus, the cellular reprogramming toolbox is now providing the means to address the potential of patient-tailored immune cell types for cancer immunotherapy. In parallel, development of viral vectors for gene delivery has opened the door for in vivo reprogramming in regenerative medicine, an elegant strategy circumventing the current limitations of in vitro cell manipulation. An analogous paradigm has been recently developed in cancer immunotherapy by the generation of CAR T-cells in vivo. These new ideas on endogenous reprogramming, cross-fertilized from the fields of regenerative medicine and gene therapy, are opening exciting avenues for direct modulation of immune or tumor cells in situ, widening our strategies to remove cancer immunotherapy roadblocks. Here, we review current strategies for cancer immunotherapy, summarize technologies for generation of immune cells by cell fate reprogramming as well as highlight the future potential of inducing these unique cell identities in vivo, providing new and exciting tools for the fast-paced field of cancer immunotherapy.

Induced Pluripotent Stem Cells (iPSCs) Provide a Potentially Unlimited T Cell Source for CAR-T Cell Development and Off-the-Shelf Products

Chimeric antigen receptor T (CAR-T) cell therapy has been increasingly conducted for cancer patients in clinical settings. Progress in this therapeutic approach is hampered by the lack of a solid manufacturing process, T lymphocytes, and tumor-specific antigens. T cell source used in CAR-T cell therapy is derived predominantly from the patient's own T lymphocytes, which makes this approach impracticable to patients with progressive diseases and T leukemia. The generation of autologous CAR-T cells is time-consuming due to the lack of readily available T lymphocytes and is not applicable for third-party patients. Pluripotent stem cells, such as human induced pluripotent stem cells (hiPSCs), can provide an unlimited T cell source for CAR-T cell development with the potential of generating off-the-shelf T cell products. T-iPSCs (iPSC-derived T cells) are phenotypically defined, expandable, and as functional as physiological T cells. The combination of iPSC and CAR technologies provides an exciting opportunity to oncology and greatly facilitates cell-based therapy for cancer patients. However, T-iPSCs, in combination with CARs, are at the early stage of development and need further pre-clinical and clinical studies. This review will critically discuss the progress made in iPSC-derived T cells and provides a roadmap for the development of CAR iPSC-derived T cells and off-the-shelf T-iPSCs.

An Overview on Promising Somatic Cell Sources Utilized for the Efficient Generation of Induced Pluripotent Stem Cells

Human induced Pluripotent Stem Cells (iPSCs) have enormous potential in understanding developmental biology, disease modeling, drug discovery, and regenerative medicine. The initial human iPSC studies used fibroblasts as a starting cell source to reprogram them; however, it has been identified to be a less appealing somatic cell source by numerous studies due to various reasons. One of the important criteria to achieve efficient reprogramming is determining an appropriate starting somatic cell type to induce pluripotency since the cellular source has a major influence on the reprogramming efficiency, kinetics, and quality of iPSCs. Therefore, numerous groups have explored various somatic cell sources to identify the promising sources for reprogramming into iPSCs with different reprogramming factor combinations. This review provides an overview of promising easily accessible somatic cell sources isolated in non-invasive or minimally invasive manner such as keratinocytes, urine cells, and peripheral blood mononuclear cells used for the generation of human iPSCs derived from healthy and diseased subjects. Notably, iPSCs generated from one of these cell types derived from the patient will offer ethical and clinical advantages. In addition, these promising somatic cell sources have the potential to efficiently generate bona fide iPSCs with improved reprogramming efficiency and faster kinetics. This knowledge will help in establishing strategies for safe and efficient reprogramming and the generation of patient-specific iPSCs from these cell types.

The therapeutic potential of multiclonal tumoricidal T cells derived from tumor infiltrating lymphocyte-1derived iPS cells

Tumor-infiltrating lymphocytes (TIL), which include tumor-specific T lymphocytes with frequency, are used for adoptive cell transfer therapy (ACT) in clinical practice. The optimization of TIL preparation has been investigated to reduce the senescence and increase the abundance of TIL, as both the quality and quantity of the transferred cells have great influence on the outcome of TIL-based ACT (TIL-ACT). Considering the effects of cell reprogramming on senescence, we expected that the anti-tumor effect could be enhanced by TIL regeneration. To confirm this hypothesis, we established tumor-specific TIL-derived iPS cells (TIL-iPSC) with human colorectal cancer specimens. T cells differentiated from TIL-iPSC (TIL-iPS-T) retained not only intrinsic T cell functions and tumor specificity, but also exhibited improved proliferation capacity and additional killing activity. Moreover, less differentiated profiles and prolonged persistency were seen in TIL-iPS-T compared with primary cells. Our findings imply that iPSC technology has great potential for TIL-ACT.

Modeling leukemia with pediatric acute leukemia patient-derived iPSCs

OBJECTIVE

ediatric acute leukemia (AL) is the most common hematological malignancy in childhood. However, the limitation of clinical specimens hindered the progress of research. Therefore, new research platforms are urgently needed to establish and clarify the pathogenesis of pediatric AL, and it is necessary to try to find novel targeted therapies for the clinical use. Here, the induced pluripotent stem cells (iPSCs) derived from AL provide a reliable model for basic research.

METHODS

eukemia cells were sorted by flow cytometry and then reprogrammed into iPSCs by Sendai virus. Cell cycle assay was used to analyze cell proliferation.

RESULTS

iPS cell lines from T cell acute lymphoblastic leukemia (T-ALL) and acute myeloid leukemia (AML) cells were successfully established. The reprogramming efficiency of AML cells was much higher than that of ALL cells. Disease iPS cells switched off the expression of the disease marker genes at iPS and HPC stage. When different subtypes of AML-iPSCs were differentiated into hematopoietic progenitor cells, iPS derived from acute megakaryocytic leukemia was more readily differentiated into megakaryocyte-erythroid progenitors. Whereas, the differentiation of multipotent lymphoid progenitor (MLP) and granulocyte macrophage progenitor (GMP) were blocked. The iPS derived from acute monocyte leukemia (AMCL) also showed the differentiation of common myeloid progenitors (CMP), GMP and monocytes significantly increased but MLP differentiation was inhibited. The AML-iPSC could form teratomas and we could obverse three germ layers in vivo, indicating that the AML-iPSCs have full pluripotency. However, there were not enough blood cells in teratoma to identify the leukemia.

CONCLUSIONS

Our results provide a novel platform for AL research and critical insight into the difference of hematopoietic differentiation between ALL and AML.

Role of SHH in Patterning Human Pluripotent Cells towards Ventral Forebrain Fates

The complexities of human neurodevelopment have historically been challenging to decipher but continue to be of great interest in the contexts of healthy neurobiology and disease. The classic animal models and monolayer in vitro systems have limited the types of questions scientists can strive to answer in addition to the technical ability to answer them. However, the tridimensional human stem cell-derived organoid system provides the unique opportunity to model human development and mimic the diverse cellular composition of human organs. This strategy is adaptable and malleable, and these neural organoids possess the morphogenic sensitivity to be patterned in various ways to generate the different regions of the human brain. Furthermore, recapitulating human development provides a platform for disease modeling. One master regulator of human neurodevelopment in many regions of the human brain is sonic hedgehog (SHH), whose expression gradient and pathway activation are responsible for conferring ventral identity and shaping cellular phenotypes throughout the neural axis. This review first discusses the benefits, challenges, and limitations of using organoids for studying human neurodevelopment and disease, comparing advantages and disadvantages with other in vivo and in vitro model systems. Next, we explore the range of control that SHH exhibits on human neurodevelopment, and the application of SHH to various stem cell methodologies, including organoids, to expand our understanding of human development and disease. We outline how this strategy will eventually bring us much closer to uncovering the intricacies of human neurodevelopment and biology.

MACMIC Reveals A Dual Role of CTCF in Epigenetic Regulation of Cell Identity Genes

Numerous studies of relationship between epigenomic features have focused on their strong correlation across the genome, likely because such relationship can be easily identified by many established methods for correlation analysis. However, two features with little correlation may still colocalize at many genomic sites to implement important functions. There is no bioinformatic tool for researchers to specifically identify such feature pairs. Here, we develop a method to identify feature pairs in which two features have maximal colocalization minimal correlation (MACMIC) across the genome. By MACMIC analysis of 3306 feature pairs in 16 human cell types, we reveal a dual role of CCCTC-binding factor (CTCF) in epigenetic regulation of cell identity genes. Although super-enhancers are associated with activation of target genes, only a subset of super-enhancers colocalized with CTCF regulate cell identity genes. At super-enhancers colocalized with CTCF, CTCF is required for the active marker H3K27ac in cell types requiring the activation, and also required for the repressive marker H3K27me3 in other cell types requiring repression. Our work demonstrates the biological utility of the MACMIC analysis and reveals a key role for CTCF in epigenetic regulation of cell identity. The code for MACMIC is available at https://github.com/bxia888/MACMIC.

Formaldehyde-induced hematopoietic stem and progenitor cell toxicity in mouse lung and nose

Formaldehyde (FA), an economically important and ubiquitous chemical, has been classified as a human carcinogen and myeloid leukemogen. However, the underlying mechanisms of leukemogenesis remain unclear. Unlike many classical leukemogens that damage hematopoietic stem/progenitor cells (HSC/HPC) directly in the bone marrow, FA-as the smallest, most reactive aldehyde-is thought to be incapable of reaching the bone marrow through inhalation exposure. A recent breakthrough study discovered that mouse lung contains functional HSC/HPC that can produce blood cells and travel bi-directionally between the lung and bone marrow, while another early study reported the presence of HSC/HPC in rat nose. Based on these findings, we hypothesized that FA inhalation could induce toxicity in HSC/HPC present in mouse lung and/or nose rather than in the bone marrow. To test this hypothesis, we adapted a commercially available protocol for culturing burst-forming unit-erythroid (BFU-E) and colony-forming unit-granulocyte, macrophage (CFU-GM) colonies from bone marrow and spleen to also enable culture of these colonies from mouse lung and nose, a novel application of this assay. We reported that in vivo exposure to FA at 3 mg/m3 or ex vivo exposure up to 400 µM FA decreased the formation of both colony types from mouse lung and nose as well as from bone marrow and spleen. These findings, to the best of our knowledge, are the first empirically to show that FA exposure can damage mouse pulmonary and olfactory HSC/HPC and provide potential biological plausibility for the induction of leukemia at the sites of entry rather than the bone marrow.

Hypothalamus and neuroendocrine diseases: The use of human-induced pluripotent stem cells for disease modeling

The hypothalamus, which is part of the brain of all vertebrate animals, is considered the link between the central nervous system (CNS) and (i) the endocrine system via the pituitary gland and (ii) with our organs via the autonomic nervous system. It synthesizes and releases neurohormones, which in turn stimulate or inhibit the secretion of other hormones within the CNS, and sends and receives signals to and from the peripheral nervous and endocrine systems. As the brain region responsible for energy homeostasis, the hypothalamus is the key regulator of thermoregulation, hunger and satiety, circadian rhythms, sleep and fatigue, memory and learning, arousal and reproductive cycling, blood pressure, and heart rate and thus orchestrates complex physiological responses in order to maintain metabolic homeostasis. These critical roles implicate the hypothalamus in neuroendocrine disorders such as obesity, diabetes, anorexia nervosa, bulimia, and others. In this chapter, we focus on the use of human-induced pluripotent stem cells (hiPSCs) and their differentiation into hypothalamic neurons in order to model neuroendocrine disorders such as extreme obesity in a dish. To do so, we discuss important steps of human hypothalamus development, neuroendocrine diseases related to the hypothalamus, multiple protocols to differentiate hiPSCs into hypothalamic neurons, and severe obesity modeling in vitro using hiPSCs-derived hypothalamic neurons.

Human stem cell models of polyglutamine diseases: Sources for disease models and cell therapy

Polyglutamine (polyQ) diseases are a group of neurodegenerative disorders involving expanded CAG repeats in pathogenic genes that are translated into extended polyQ tracts and lead to progressive neuronal degeneration in the affected brain. To date, there is no effective therapy for these diseases. Due to the complex pathologic mechanisms of these diseases, intensive research on the pathogenesis of their progression and potential treatment strategies is being conducted. However, animal models cannot recapitulate all aspects of neuronal degeneration. Pluripotent stem cells (PSCs), such as induced pluripotent stem cells (iPSCs) and embryonic stem cells (ESCs), can be used to study the pathological mechanisms of polyQ diseases, and the ability of autologous stem cell transplantation to treat these diseases. Differentiated PSCs, neuronal precursor cells/neural progenitor cells (NPCs) and mesenchymal stem cells (MSCs) are valuable resources for preclinical and clinical cell transplantation therapies. Here, we discuss diverse stem cell models and their ability to generate neurons involved in polyQ diseases, such as medium spiny neurons (MSNs), cortical neurons, cerebellar Purkinje cells (PCs) and motor neurons. In addition, we discuss potential therapeutic approaches, including stem cell replacement therapy and gene therapy.

An Efficient Culture Method of CD3-Positive T Cells from Human Cryopreserved Buffy Coat Specimens

Context: In the National Cerebral and Cardiovascular Center (NCVC) Biobank, buffy coats have been collected from patients and stored with cryoprotective agents as a possible source for viable blood cells, using cost-efficient methods for storage. However, whether viable cells for in vitro studies can be recovered from these biospecimens has not been verified. Objective: To investigate whether T cells can be collected and expanded as viable cells from cryopreserved human buffy coats. Design: After thawing of cryopreserved buffy coat specimens, CD3-positive cells were isolated from the cell suspension using a leukocyte separation filter coated with an anti-CD3 antibody, and the filter-attached cells were cultured in T cell culture medium. To analyze the characteristics of these cultured cells, histocytological analyses of Giemsa staining, immunocytochemical (ICC) staining for CD3, and flow cytometry for CD3 in live cells were conducted. Results: A few days after starting cell culture, cell clusters were observed, and they gradually grew in size. Using Giemsa staining, the expanded cells were found to be ∼15 μm in diameter, having round nuclei, a high nucleus/cytoplasm ratio, and cytoplasm stained light blue, which is characteristic of lymphocytes. From ICC staining, these cells were CD3 positive, a pan-T cell marker among lymphocytes. Furthermore, CD3 immunoreactivity in live cells was detected in a flow cytometry assay, though that for CD19 was not detected, which is a marker of pan-B cells. Conclusions: These results suggest that T cells can be expanded from buffy coats cryopreserved at -180°C as an adequate method of NCVC Biobank, highlighting these biospecimens as a possible useful source for future in vitro studies.

GMP-grade CD34+ selection from HLA-homozygous licensed cord blood units and short-term expansion under European ATMP regulations

BACKGROUND

Based on a synergistic consortium, the cord blood (CB) bank Düsseldorf was responsible for the selection of HLA-homozygous (HLA-h) donors, contacting/re-consenting the mothers, Good Manufacturing Practice (GMP)-grade CD34⁺ enrichment, followed by short-term expansion of CD34⁺ cells and qualification of the resulting CD34⁺ population as advanced therapy medicinal product (ATMP)-starting material. Among 20 639 licensed Düsseldorf cord blood units (CBUs), 139 potential HLA-h donors were identified with the most frequent 10 German haplotypes. 100% of the donors were contacted, and for 47·5%, consent was obtained. HLA-A, -B, -C, -DR, -DQ and -DP were determined by sequencing.

METHODS

Thawing/washing of the CBUs was performed in the presence of Volulyte/HSA with Sepax^® , CD34⁺ selection by automated CliniMACS^® -system (Miltenyi), expansion with qualified GMP-grade cytokines and media in the GMP facility.

RESULTS

Here, we specify minimal criteria (≥5 x 10⁵ viable CD34⁺ -count, ≥80% CD34⁺ -purity and ≥70% viability) and confirm that n = 10 CB units (max storage time 16 years) could be qualified for an ATMP starting material. The mean fold change expansion of isolated CD34⁺ cells at Day 3/4 (d3/4) was 3·38 ± 3·02 with a mean purity of 86·90 ± 10·38% and a high viability of 96·07 ± 4·72%.

CONCLUSION

As of March 2019, approval was obtained by the Bezirksregierung Düsseldorf for the GMP-compliant production. The production of HLA-homozygous expanded CD34⁺ cells from cryopreserved CB under European ATMP regulations presented here describes the successful clinical translation and implementation of a qualified manufacturing process. This approach considers the main obstacle of rejection of transplanted cells (due to the immunological HLA barrier) by preselection of HLA-homozygous transplants.

Sweat gland regeneration: Current strategies and future opportunities

For patients with extensive skin defects, loss of sweat glands (SwGs) greatly decreases their quality of life. Indeed, difficulties in thermoregulation, ion reabsorption, and maintaining fluid balance might render them susceptible to hyperthermia, heatstroke, or even death. Despite extensive studies on the stem cell biology of the skin in recent years, in-situ regeneration of SwGs with both structural and functional fidelity is still challenging because of the limited regenerative capacity and cell fate control of resident progenitors. To overcome these challenges, one must consider both the intrinsic factors relevant to genetic and epigenetic regulation and cues from the cellular microenvironment. Here, we describe recent progress in molecular biology, developmental pathways, and cellular evolution associated with SwGdevelopment and maturation. This is followed by a summary of the current strategies used for cell-fate modulation, transmembrane drug delivery, and scaffold design associated with SwGregeneration. Finally, we offer perspectives for creating more sophisticated systems to accelerate patients' innate healing capacity and developing engineered skin constructs to treat or replace damaged tissues structurally and functionally.

Reprogramming fibroblasts and peripheral blood cells from a C9ORF72 patient: A proof-of-principle study

As for the majority of neurodegenerative diseases, pathological mechanisms of amyotrophic lateral sclerosis (ALS) have been challenging to study due to the difficult access to alive patients' cells. Induced pluripotent stem cells (iPSCs) offer a useful in vitro system for modelling human diseases. iPSCs can be theoretically obtained by reprogramming any somatic tissue although fibroblasts (FB) remain the most used cells. However, reprogramming peripheral blood cells (PB) may offer significant advantages. In order to investigate whether the choice of starting cells may affect reprogramming and motor neuron (MNs) differentiation potential, we used both FB and PB from a same C9ORF72-mutated ALS patient to obtain iPSCs and compared several hallmarks of the pathology. We found that both iPSCs and MNs derived from the two tissues showed identical properties and features and can therefore be used interchangeably, giving the opportunity to easily obtain iPSCs from a more manageable source of cells, such as PB.

Generation of Human-Induced Pluripotent Stem Cells From Anterior Cruciate Ligament

Human-induced pluripotent stem cells (hiPSCs) are reprogrammed somatic cells and are an excellent cell source for tissue engineering applications, disease modeling, and for understanding human development. HiPSC lines have now been generated from a diverse range of somatic cell types and have been reported to retain an epigenetic memory of their somatic origin. To date, the reprogramming of a true ligament has not been reported. The aim of this study is to generate iPSCs from human anterior cruciate ligament (ACL) cells. ACL cells from three above-knee amputation donors, with donor matched dermal fibroblasts (DFs) were tested for reprogramming using an existing DF reprogramming protocol. ACL cells were, however, more sensitive than donor matched DF to transforming growth factor-β (TGF-β); displaying marked contraction, increased proliferation and increased TNC and COMP expression in vitro, which hindered reprogramming to iPSCs. Modification of the protocol by scoring the cell monolayer or by removal of TGF-β during ACL reprogramming resulted in emerging colonies being easier to identify and extract, increasing reprogramming efficiency. Following 30 passages in culture, the generated ACL derived iPSCs displayed pluripotency markers, normal karyotype and can successfully differentiate to cells of the three embryonic germ layers. This study illustrates it is possible to generate hiPSCs from ligament and identifies optimized ligament reprogramming conditions. ACL derived iPSCs may provide a promising cell source for ligament and related tissue engineering applications. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 38:92-104, 2020.

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

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

iPSC modeling of rare pediatric disorders

Discerning the underlying pathological mechanisms and the identification of therapeutic strategies to treat individuals affected with rare neurological diseases has proven challenging due to a host of factors. For instance, rare diseases affecting the nervous system are inherently lacking in appropriate patient sample availability compared to more common diseases, while animal models often do not accurately recapitulate specific disease phenotypes. These challenges impede research that may otherwise illuminate aspects of disease initiation and progression, leading to the ultimate identification of potential therapeutics. The establishment of induced pluripotent stem cells (iPSCs) as a human cellular model with defined genetics has provided the unique opportunity to study rare diseases within a controlled environment. iPSC models enable researchers to define mutational effects on specific cell types and signaling pathways within increasingly complex systems. Among rare diseases, pediatric diseases affecting neurodevelopment and neurological function highlight the critical need for iPSC-based disease modeling due to the inherent difficulty associated with collecting human neural tissue and the complexity of the mammalian nervous system. Rare neurodevelopmental disorders are therefore ideal candidates for utilization of iPSC-based in vitro studies. In this review, we address both the state of the iPSC field in the context of their utility and limitations for neurodevelopmental studies, as well as speculating about the future applications and unmet uses for iPSCs in rare diseases.

Reprogramming of Cancer Cells into Induced Pluripotent Stem Cells Questioned

Background and Objectives

Several recent studies have claimed that cancer cells can be reprogrammed into induced pluripotent stem cells (iPSCs). However, in most cases, cancer cells seem to be resistant to cellular reprogramming. Furthermore, the underlying mechanisms of limited reprogramming in cancer cells are largely unknown. Here, we identified the candidate barrier genes and their target genes at the early stage of reprogramming for investigating cancer reprogramming.

Methods

We tried induction of pluripotency in normal human fibroblasts (BJ) and both human benign (MCF10A) and malignant (MCF7) breast cancer cell lines using a classical retroviral reprogramming method. We conducted RNA-sequencing analysis to compare the transcriptome of the three cell lines at early stage of reprogramming.

Results

We could generate iPSCs from BJ, whereas we were unable to obtain iPSCs from cancer cell lines. To address the underlying mechanism of limited reprogramming in cancer cells, we identified 29 the candidate barrier genes based on RNA-sequencing data. In addition, we found 40 their target genes using Cytoscape software.

Conclusions

Our data suggest that these genes might one of the roadblock for cancer cell reprogramming. Furthermore, we provide new insights into application of iPSCs technology in cancer cell field for therapeutic purposes.

Re-entering the pluripotent state from blood lineage: promises and pitfalls of blood reprogramming

Blood reprogramming, in which induced pluripotent stem cells (iPSCs) are derived from haematopoietic lineages, has rapidly advanced over the past decade. Since the first report using human blood, haematopoietic cell types from various sources, such as the peripheral bone marrow and cord blood, have been successfully reprogrammed. The volume of blood required has also decreased, from around tens of millilitres to a single finger-prick drop. Besides, while early studies were limited to reprogramming methods relying on viral integration, nonintegrating reprogramming systems for blood lineages have been subsequently established. Together, these improvements have made feasible the future clinical applications of blood-derived iPSCs. Here, we review the progress in blood reprogramming from various perspectives, including the starting materials and subsequent reprogramming strategies. We also discuss the downstream applications of blood-derived iPSCs, highlighting their clinical value in terms of disease modelling and therapeutic development.

Pluripotent Cell Models for Gonadal Research

Sex development is a complex process involving many genes and hormones. Defects in this process lead to Differences of Sex Development (DSD), a group of heterogeneous conditions not as rare as previously thought. Part of the obstacles in proper management of these patients is due to an incomplete understanding of the genetics programs and molecular pathways involved in sex development and DSD. Several challenges delay progress and the lack of a proper model system for the single patient severely hinders advances in understanding these diseases. The revolutionary techniques of cellular reprogramming and guided in vitro differentiation allow us now to exploit the versatility of induced pluripotent stem cells to create alternatives models for DSD, ideally on a patient-specific personalized basis.

Human iPSC banking: barriers and opportunities

The introduction of induced pluripotent stem cells (iPSCs) has opened up the potential for personalized cell therapies and ushered in new opportunities for regenerative medicine, disease modeling, iPSC-based drug discovery and toxicity assessment. Over the past 10 years, several initiatives have been established that aim to collect and generate a large amount of human iPSCs for scientific research purposes. In this review, we compare the construction and operation strategy of some iPSC banks as well as their ongoing development. We also introduce the technical challenges and offer future perspectives pertaining to the establishment and management of iPSC banks.

Preparation of Induced Pluripotent Stem Cells Using Human Peripheral Blood Monocytes

Since induced pluripotent stem (iPS) cells have been established, in recent years, clinical transplantation of cells differentiated from iPS cells derived from human skin fibroblasts is been in progress. On the contrary, monocytes have complete genome information without damage and gene recombination, they are contained in the peripheral blood by ∼3%–8% and differentiate into dendritic cells that are the type of control tower for immune cells. However, generation of monocyte-derived iPS cells has only been successful when special persistent Sendai virus vectors have been used. Therefore, in this study, as a preculture method for monocytes, a culture method for maintaining activity without using any cytokine was established, and using a commercially available vector without genetic toxicity without damaging the chromosome of the cell, iPS cells derived from monocytes were successfully produced. This cell has the ability to differentiate into three germ layers, and when compared with commercially available iPS cells, there was no significant difference between self-renewal and gene expression in the three germ layers. In future, we will compare the differentiation induction of monocyte-derived iPS cells with dendritic cells and investigate the production of dendritic cells that can cope with various antigens.

Non-transmissible MV Vector with Segmented RNA Genome Establishes Different Types of iPSCs from Hematopoietic Cells

Recent advances in gene therapy technologies have enabled the treatment of congenital disorders and cancers and facilitated the development of innovative methods, including induced pluripotent stem cell (iPSC) production and genome editing. We recently developed a novel non-transmissible and non-integrating measles virus (MV) vector capable of transferring multiple genes simultaneously into a wide range of cells through the CD46 and CD150 receptors. The MV vector expresses four genes for iPSC generation and the GFP gene for a period of time sufficient to establish iPSCs from human fibroblasts as well as peripheral blood T cells. The transgenes were expressed differentially depending on their gene order in the vector. Human hematopoietic stem/progenitor cells were directly and efficiently reprogrammed to naive-like cells that could proliferate and differentiate into primed iPSCs by the same method used to establish primed iPSCs from other cell types. The novel MV vector has several advantages for establishing iPSCs and potential future applications in gene therapy.

Applications of molecular engineering in T-cell-based immunotherapies

Harnessing an individual's immune cells to mediate antitumor and antiviral responses is a life-saving option for some patients with otherwise intractable forms of cancer and infectious disease. In particular, T-cell-based engineered immune cells are a powerful new class of therapeutics with remarkable efficacy. Clinical experience has helped to define some of the major challenges for reliable, safe, and effective deployment of T-cells against a broad range of diseases. While poised to revolutionize immunotherapy, scalable manufacturing, safety, specificity, and the development of resistance are potential roadblocks in their widespread usage. The development of molecular engineering tools to allow for the direct or indirect engineering of T-cells to enable one to troubleshoot delivery issues, amplify immunomodulatory effects, integrate the synergistic effects of different molecules, and home to the target cells in vivo. In this review, we will analyze thus-far developed cell- and material-based tools for enhancing T-cell therapies, including methods to improve safety and specificity, enhancing efficacy, and overcoming limitations in scalable manufacturing. We summarize the potential of T-cells as immune modulating therapies and the potential future directions for enabling their adoption for a broad range of diseases. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Cells at the Nanoscale.