Efficient generation of transgene-free human induced pluripotent stem cells (iPSCs) by temperature-sensitive Sendai virus vectors. Proc Natl Acad Sci U S A. 2011;108:14234-14239. [PMID: 21821793 DOI: 10.1073/pnas.1103509108]

Human Motor Neurons With SOD1-G93A Mutation Generated From CRISPR/Cas9 Gene-Edited iPSCs Develop Pathological Features of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by gradual degeneration and elimination of motor neurons (MNs) in the motor cortex, brainstem, and spinal cord. Some familial forms of ALS are caused by genetic mutations in superoxide dismutase 1 (SOD1) but the mechanisms driving MN disease are unclear. Identifying the naturally occurring pathology and understanding how this mutant SOD1 can affect MNs in translationally meaningful ways in a valid and reliable human cell model remains to be established. Here, using CRISPR/Cas9 genome editing system and human induced pluripotent stem cells (iPSCs), we generated highly pure, iPSC-derived MNs with a SOD1-G93A missense mutation. With the wild-type cell line serving as an isogenic control and MNs from a patient-derived iPSC line with an SOD1-A4V mutation as a comparator, we identified pathological phenotypes relevant to ALS. The mutant MNs accumulated misfolded and aggregated forms of SOD1 in cell bodies and processes, including axons. They also developed distinctive axonal pathologies. Mutants had axonal swellings with shorter axon length and less numbers of branch points. Moreover, structural and molecular abnormalities in presynaptic and postsynaptic size and density were found in the mutants. Finally, functional studies with microelectrode array demonstrated that the individual mutant MNs exhibited decreased number of spikes and diminished network bursting, but increased burst duration. Taken together, we identified spontaneous disease phenotypes relevant to ALS in mutant SOD1 MNs from genome-edited and patient-derived iPSCs. Our findings demonstrate that SOD1 mutations in human MNs cause cell-autonomous proteinopathy, axonopathy, synaptic pathology, and aberrant neurotransmission.

Human sensory neurons derived from pluripotent stem cells for disease modelling and personalized medicine

•

New techniques emerge to study peripheral sensory neurons in iPS-cell derived models.

•

Genetic pain syndromes, e.g. gain- and loss-of-function mutations in Nav-channels are helpful.

•

Individualized treatment for neuropathic pain can be identified with iPS-cell derived nociceptors.

In this concise Mini-Review we will summarize ongoing developments of new techniques to study physiology and pathophysiology of the peripheral sensory nervous system in human stem cell derived models. We will focus on recent developments of reprogramming somatic cells into induced pluripotent stem cells, neural differentiation towards neuronal progenitors and human sensory neurons.

We will sum up the high potential of this new technique for disease modelling of human neuropathies with a focus on genetic pain syndromes, such as gain- and loss-of-function mutations in voltage-gated sodium channels. The stem cell derived human sensory neurons are used for drug testing and we will summarize their usefulness for individualized treatment identification in patients with neuropathic pain. The review will give an outlook on potential application of this technique as companion diagnostics and for personalized medicine.

Human iPSC-Derived Neuronal Cells From CTBP1-Mutated Patients Reveal Altered Expression of Neurodevelopmental Gene Networks

A recurrent de novo mutation in the transcriptional corepressor CTBP1 is associated with neurodevelopmental disabilities in children (Beck et al., 2016, 2019; Sommerville et al., 2017). All reported patients harbor a single recurrent de novo heterozygous missense mutation (p.R342W) within the cofactor recruitment domain of CtBP1. To investigate the transcriptional activity of the pathogenic CTBP1 mutant allele in physiologically relevant human cell models, we generated induced pluripotent stem cells (iPSC) from the dermal fibroblasts derived from patients and normal donors. The transcriptional profiles of the iPSC-derived “early” neurons were determined by RNA-sequencing. Comparison of the RNA-seq data of the neurons from patients and normal donors revealed down regulation of gene networks involved in neurodevelopment, synaptic adhesion and anti-viral (interferon) response. Consistent with the altered gene expression patterns, the patient-derived neurons exhibited morphological and electrophysiological abnormalities, and susceptibility to viral infection. Taken together, our studies using iPSC-derived neuron models provide novel insights into the pathological activities of the CTBP1 p.R342W allele.

Insulin/Glucose-Responsive Cells Derived from Induced Pluripotent Stem Cells: Disease Modeling and Treatment of Diabetes

Type 2 diabetes, characterized by dysfunction of pancreatic β-cells and insulin resistance in peripheral organs, accounts for more than 90% of all diabetes. Despite current developments of new drugs and strategies to prevent/treat diabetes, there is no ideal therapy targeting all aspects of the disease. Restoration, however, of insulin-producing β-cells, as well as insulin-responsive cells, would be a logical strategy for the treatment of diabetes. In recent years, generation of transplantable cells derived from stem cells in vitro has emerged as an important research area. Pluripotent stem cells, either embryonic or induced, are alternative and feasible sources of insulin-secreting and glucose-responsive cells. This notwithstanding, consistent generation of robust glucose/insulin-responsive cells remains challenging. In this review, we describe basic concepts of the generation of induced pluripotent stem cells and subsequent differentiation of these into pancreatic β-like cells, myotubes, as well as adipocyte- and hepatocyte-like cells. Use of these for modeling of human disease is now feasible, while development of replacement therapies requires continued efforts.

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.

Development of a High-Efficacy Reprogramming Method for Generating Human Induced Pluripotent Stem (iPS) Cells from Pathologic and Senescent Somatic Cells

Induced pluripotent stem (iPS) cells are a type of artificial pluripotent stem cell induced by the epigenetic silencing of somatic cells by the Yamanaka factors. Advances in iPS cell reprogramming technology will allow aging or damaged cells to be replaced by a patient's own rejuvenated cells. However, tissue that is senescent or pathologic has a relatively low reprogramming efficiency as compared with juvenile or robust tissue, resulting in incomplete reprogramming; iPS cells generated from such tissue types do not have sufficient differentiation ability and are therefore difficult to apply clinically. Here, we develop a new reprogramming method and examine it using myofibroblasts, which are pathologic somatic cells, from patient skin tissue and from each of the four heart chambers of a recipient heart in heart transplant surgery. By adjusting the type and amount of vectors containing transcriptional factors for iPS cell reprogramming, as well as adjusting the transfection load and culture medium, the efficiency of iPS cell induction from aged patient skin-derived fibroblasts was increased, and we successfully induced iPS cells from myocardial fibroblasts isolated from the pathologic heart of a heart transplant recipient.

Mutations in the Heterotopia Gene Eml1/EML1 Severely Disrupt the Formation of Primary Cilia

Apical radial glia (aRGs) are predominant progenitors during corticogenesis. Perturbing their function leads to cortical malformations, including subcortical heterotopia (SH), characterized by the presence of neurons below the cortex. EML1/Eml1 mutations lead to SH in patients, as well as to heterotopic cortex (HeCo) mutant mice. In HeCo mice, some aRGs are abnormally positioned away from the ventricular zone (VZ). Thus, unraveling EML1/Eml1 function will clarify mechanisms maintaining aRGs in the VZ. We pinpoint an unknown EML1/Eml1 function in primary cilium formation. In HeCo aRGs, cilia are shorter, less numerous, and often found aberrantly oriented within vesicles. Patient fibroblasts and human cortical progenitors show similar defects. EML1 interacts with RPGRIP1L, a ciliary protein, and RPGRIP1L mutations were revealed in a heterotopia patient. We also identify Golgi apparatus abnormalities in EML1/Eml1 mutant cells, potentially upstream of the cilia phenotype. We thus reveal primary cilia mechanisms impacting aRG dynamics in physiological and pathological conditions.

Induced Pluripotent Stem Cells: Hope in the Treatment of Diseases, including Muscular Dystrophies

Induced pluripotent stem (iPS) cells are laboratory-produced cells that combine the biological advantages of somatic adult and stem cells for cell-based therapy. The reprogramming of cells, such as fibroblasts, to an embryonic stem cell-like state is done by the ectopic expression of transcription factors responsible for generating embryonic stem cell properties. These primary factors are octamer-binding transcription factor 4 (Oct3/4), sex-determining region Y-box 2 (Sox2), Krüppel-like factor 4 (Klf4), and the proto-oncogene protein homolog of avian myelocytomatosis (c-Myc). The somatic cells can be easily obtained from the patient who will be subjected to cellular therapy and be reprogrammed to acquire the necessary high plasticity of embryonic stem cells. These cells have no ethical limitations involved, as in the case of embryonic stem cells, and display minimal immunological rejection risks after transplant. Currently, several clinical trials are in progress, most of them in phase I or II. Still, some inherent risks, such as chromosomal instability, insertional tumors, and teratoma formation, must be overcome to reach full clinical translation. However, with the clinical trials and extensive basic research studying the biology of these cells, a promising future for human cell-based therapies using iPS cells seems to be increasingly clear and close.

An Insight into DNA-free Reprogramming Approaches to Generate Integration-free Induced Pluripotent Stem Cells for Prospective Biomedical Applications

More than a decade ago, a pioneering study reported generation of induced Pluripotent Stem Cells (iPSCs) by ectopic expression of a cocktail of reprogramming factors in fibroblasts. This study has revolutionized stem cell research and has garnered immense interest from the scientific community globally. iPSCs hold tremendous potential for understanding human developmental biology, disease modeling, drug screening and discovery, and personalized cell-based therapeutic applications. The seminal study identified Oct4, Sox2, Klf4 and c-Myc as a potent combination of genes to induce reprogramming. Subsequently, various reprogramming factors were identified by numerous groups. Most of these studies have used integrating viral vectors to overexpress reprogramming factors in somatic cells to derive iPSCs. However, these techniques restrict the clinical applicability of these cells as they may alter the genome due to random viral integration resulting in insertional mutagenesis and tumorigenicity. To circumvent this issue, alternative integration-free reprogramming approaches are continuously developed that eliminate the risk of genomic modifications and improve the prospects of iPSCs from lab to clinic. These methods establish that integration of transgenes into the genome is not essential to induce pluripotency in somatic cells. This review provides a comprehensive overview of the most promising DNA-free reprogramming techniques that have the potential to derive integration-free iPSCs without genomic manipulation, such as sendai virus, recombinant proteins, microRNAs, synthetic messenger RNA and small molecules. The understanding of these approaches shall pave a way for the generation of clinical-grade iPSCs. Subsequently, these iPSCs can be differentiated into desired cell type(s) for various biomedical applications.

Generation of HIV-1-infected patients' gene-edited induced pluripotent stem cells using feeder-free culture conditions

OBJECTIVES

The discovery of induced pluripotent stem cells (iPSC) has brought promise to regenerative medicine as it breaks the ethical barrier of using embryonic stem cells. Such cell culture-derived patient-specific autologous stem cells are needed for transplantation. Here we report deriving HIV-1-infected patients' iPSC lines under transgene-free methods and under feeder-free and xeno-free culture conditions to meet the requirement for clinical application.

METHODS AND RESULTS

We have reprogrammed patients' peripheral blood mononuclear cells with EBNA1/OriP episomal vectors, or a defective and persistent Sendai virus vector (SeVdp) to ensure a nonintegrating iPSC generation. Both single picked and pooled iPSC lines demonstrated high pluripotency and were able to differentiate into various lineage cells in vivo. The established cell lines could be modified by genetic editing using the TALENs or CRISPR/Cas 9 technology to have a bi-allelic CCR5Δ32 mutations seamlessly. All generated iPSC lines and modified cell lines had no evidence of HIV integration and maintained normal karyotype after expansion.

CONCLUSIONS

This study provides a reproducible simple procedure for generating therapeutic grade iPSCs from HIV-infected patients and for engineering these cells to possess a naturally occurring genotype for resistance to HIV-1 infection when differentiated into immune cells.

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 and transdifferentiation - two key processes for regenerative medicine

Regenerative medicine based on transplants obtained from donors or foetal and new-born mesenchymal stem cells, encounter important obstacles such as limited availability of organs, ethical issues and immune rejection. The growing demand for therapeutic methods for patients being treated after serious accidents, severe organ dysfunction and an increasing number of cancer surgeries, exceeds the possibilities of the therapies that are currently available. Reprogramming and transdifferentiation provide powerful bioengineering tools. Both procedures are based on the somatic differentiated cells, which are easily and unlimitedly available, like for example: fibroblasts. During the reprogramming procedure mature cells are converted into pluripotent cells - which are capable to differentiate into almost any kind of desired cells. Transdifferentiation directly converts differentiated cells of one type into another differentiated cells type. Both procedures allow to obtained patient's dedicated cells for therapeutic purpose in regenerative medicine. In combination with biomaterials, it is possible to obtain even whole anatomical structures. Those patient's dedicated structures may serve for them upon serious accidents with massive tissue damage but also upon cancer surgeries as a replacement of damaged organ. Detailed information about reprogramming and transdifferentiation procedures as well as the current state of the art are presented in our review.

Establishment of two induced pluripotent stem cell line from healthy elderly (IPTi005-A and IPTi007-A)

Two healthy elderly donated their peripheral blood mononuclear cells (PBMCs). The induced pluripotent stem cell lines (IPTi005-A and IPTi007-A) were reprogrammed by episomal vector system with Yamanaka factors OCT4, SOX2, C-MYC and KLF4. Both the two iPSC lines can differentiate into three germ layers determined by embryoid bodies (EBs) differentiation. Flow cytometry analysis showed that more than 90% cells expressed NANOG, OCT4 and SSEA4. Besides, the iPSC lines of IPTi005-A and IPTi007-A were confirmed to exhibit a normal karyotype. In the studies of age-related disease, the iPSC lines can be used as controls.

Establishment of SIAISi002-A, an induced pluripotent stem cell (iPSC) line from 39-year old healthy female donor with a family history of Alzheimer's disease (AD) and two copies of APOE4 gene

A 39-year old healthy female with a family history of Alzheimer's disease (AD) and two copies of apolipoprotein E(APOE) ε4 allele donated her Peripheral blood mononuclear cells (PBMC). The non-integrative Sendai viral vectors used to reprogram PBMCs with the human OKSM transcription factors. The pluripotency of iPSCs was confirmed by immunocytochemistry and ability of differentiation spontaneously into 3 germ layers. Furthermore, the iPSC line displayed a normal karyotype. The APOE gene is currently considered to be the most relevant gene for sporadic AD. Our model might offer a platform to study the pathological mechanisms and drug testing studies in AD.

Human induced pluripotent stem cell-derived cardiomyocytes reveal abnormal TGFβ signaling in type 2 diabetes mellitus

Diabetes mellitus is a serious metabolic condition associated with a multitude of cardiovascular complications. Moreover, the prevalence of diabetes in heart failure populations is higher than that in control populations. However, the role of cardiomyocyte alterations in type 2 diabetes mellitus (T2DM) has not been well characterized and the underlying mechanisms remain elusive. In this study, two patients who were diagnosed as T2DM were recruited and patient-specific induced pluripotent stem cells (iPSCs) were generated from urine epithelial cells using nonintegrated Sendai virus. The iPSC lines derived from five healthy subjects were used as controls. All iPSCs were differentiated into cardiomyocytes (iPSC-CMs) using the monolayer-based differentiation protocol. T2DM iPSC-CMs exhibited various disease phenotypes, including cellular hypertrophy and lipid accumulation. Moreover, T2DM iPSC-CMs exhibited higher susceptibility to high-glucose/high-lipid challenge than control iPSC-CMs, manifesting an increase in apoptosis. RNA-Sequencing analysis revealed a differential transcriptome profile and abnormal activation of TGFβ signaling pathway in T2DM iPSC-CMs. We went on to show that inhibition of TGFβ significantly rescued the hypertrophic phenotype in T2DM iPSC-CMs. In conclusion, we demonstrate that the iPSC-CM model is able to recapitulate cellular phenotype of T2DM. Our results indicate that iPSC-CMs can therefore serve as a suitable model for investigating molecular mechanisms underlying diabetic cardiomyopathies and for screening therapeutic drugs.

Advances in Transcription Factors Related to Neuroglial Cell Reprogramming

Neuroglial cells have a high level of plasticity, and many types of these cells are present in the nervous system. Neuroglial cells provide diverse therapeutic targets for neurological diseases and injury repair. Cell reprogramming technology provides an efficient pathway for cell transformation during neural regeneration, while transcription factor-mediated reprogramming can facilitate the understanding of how neuroglial cells mature into functional neurons and promote neurological function recovery.

Establishment of SIAISi001-A, an induced pluripotent stem cell (iPSC) line from 66-year old mild cognitive impairment (MCI) with two copies of APOE4 gene

A 66-year old mild cognitive impairment (MCI) female patient donated her Peripheral blood mononuclear cells (PBMC). PBMC was reprogrammed using non-integrative Sendai viral vectors containing reprogramming factors OCT4, KLF4, SOX2 and C-MYC. The pluripotency of transgene-free iPSCs was confirmed by immunocytochemistry and ability of differentiation spontaneously into 3 germ layers in vitro. Moreover, the iPSC line displayed a normal karyotype. The apolipoprotein E (APOE) ε4 allele, is considered to be the strongest genetic risk factor for Sporadic Alzheimer's disease (AD). Our model might offer a good platform to study the pathological mechanisms and drug testing studies in AD and MCI.

Generation of a human induced pluripotent stem cell line from an epilepsy patient carrying mutations in the PIK3R2 gene

A 48-year-old female epilepsy patient of Han Chinese genetic descent carrying heterozygous mutations in PIK3R2 donated her peripheral blood mononuclear cells (PBMCs). The PBMCs were reprogrammed by the nonintegrating vector system with human OKSM transcription factors. The generated iPSCs contained congenital mutations in an exon of PIK3R2 and expressed endogenous pluripotency markers. They had a normal karyotype and were able to differentiate into all three germ layers. This new iPSC line will contribute to a better understanding of the pathology of epilepsy, enabling the identification of early biomarkers and the screening of small molecule drugs.

Reprogramming of Primary Human Cells to Induced Pluripotent Stem Cells Using Sendai Virus

Induced pluripotent stem (iPS) cells are important tools for studying differentiation and for use in patient-specific disease modeling. We present a detailed method for the reprogramming of primary human fibroblasts to induced pluripotent stem cells using Sendai virus. These procedures allow for the efficient generation of multiple high-quality feeder-independent iPS cell lines for a given human fibroblast line. The iPS cell lines generated by this protocol can be used in a variety of differentiation and gene expression studies, as well as in genetic manipulations.

Gene Correction of LGMD2A Patient-Specific iPSCs for the Development of Targeted Autologous Cell Therapy

Limb girdle muscular dystrophy type 2A (LGMD2A), caused by mutations in the Calpain 3 (CAPN3) gene, is an incurable autosomal recessive disorder that results in muscle wasting and loss of ambulation. To test the feasibility of an autologous induced pluripotent stem cell (iPSC)-based therapy for LGMD2A, here we applied CRISPR-Cas9-mediated genome editing to iPSCs from three LGMD2A patients to enable correction of mutations in the CAPN3 gene. Using a gene knockin approach, we genome edited iPSCs carrying three different CAPN3 mutations, and we demonstrated the rescue of CAPN3 protein in myotube derivatives in vitro. Transplantation of gene-corrected LGMD2A myogenic progenitors in a novel mouse model combining immunodeficiency and a lack of CAPN3 resulted in muscle engraftment and rescue of the CAPN3 mRNA. Thus, we provide here proof of concept for the integration of genome editing and iPSC technologies to develop a novel autologous cell therapy for LGMD2A.

Application of Human Induced Pluripotent Stem Cells in Generating Tissue-Engineered Blood Vessels as Vascular Grafts

In pace with the advancement of tissue engineering during recent decades, tissue-engineered blood vessels (TEBVs) have been generated using primary seed cells, and their impressive success in clinical trials have demonstrated the great potential of these TEBVs as implantable vascular grafts in human regenerative medicine. However, the production, therapeutic efficacy, and readiness in emergencies of current TEBVs could be hindered by the accessibility, expandability, and donor-donor variation of patient-specific primary seed cells. Alternatively, using human induced pluripotent stem cells (hiPSCs) to derive seed vascular cells for vascular tissue engineering could fundamentally address this current dilemma in TEBV production. As an emerging research field with a promising future, the generation of hiPSC-based TEBVs has been reported recently with significant progress. Simultaneously, to further promote hiPSC-based TEBVs into vascular grafts for clinical use, several challenges related to the safety, readiness, and structural integrity of vascular tissue need to be addressed. Herein, this review will focus on the evolution and role of hiPSCs in vascular tissue engineering technology and summarize the current progress, challenges, and future directions of research on hiPSC-based TEBVs.

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.

Pathogenic Tau Impairs Axon Initial Segment Plasticity and Excitability Homeostasis

Dysregulation of neuronal excitability underlies the pathogenesis of tauopathies, including frontotemporal dementia (FTD) with tau inclusions. A majority of FTD-causing tau mutations are located in the microtubule-binding domain, but how these mutations alter neuronal excitability is largely unknown. Here, using CRISPR/Cas9-based gene editing in human pluripotent stem cell (iPSC)-derived neurons and isogenic controls, we show that the FTD-causing V337M tau mutation impairs activity-dependent plasticity of the cytoskeleton in the axon initial segment (AIS). Extracellular recordings by multi-electrode arrays (MEAs) revealed that the V337M tau mutation in human neurons leads to an abnormal increase in neuronal activity in response to chronic depolarization. Stochastic optical reconstruction microscopy of human neurons with this mutation showed that AIS plasticity is impaired by the abnormal accumulation of end-binding protein 3 (EB3) in the AIS submembrane region. These findings expand our understanding of how FTD-causing tau mutations dysregulate components of the neuronal cytoskeleton, leading to network dysfunction.

Generation of an induced pluripotent stem cell line (CIMAi001-A) from a compound heterozygous Primary Hyperoxaluria Type I (PH1) patient carrying p.G170R and p.R122* mutations in the AGXT gene

Primary Hyperoxaluria Type I (PH1) is a rare autosomal recessive metabolic disorder characterized by defects in enzymes involved in glyoxylate metabolism. PH1 is a life-threatening disease caused by the absence, deficiency or mistargeting of the hepatic alanine-glyoxylate aminotransferase (AGT) enzyme. A human induced pluripotent stem cell (iPSC) line was generated from dermal fibroblasts of a PH1 patient being compound heterozygous for the most common mutation c.508G>A (G170R), a mistargeting mutation, and c.364C>T (R122*), a previously reported nonsense mutation in AGTX. This iPSC line offers a useful resource to study the disease pathophysiology and a cell-based model for drug development.

Allele-specific NKX2-5 binding underlies multiple genetic associations with human electrocardiographic traits

The cardiac transcription factor (TF) gene NKX2-5 has been associated with electrocardiographic (EKG) traits through genome-wide association studies (GWASs), but the extent to which differential binding of NKX2-5 at common regulatory variants contributes to these traits has not yet been studied. We analyzed transcriptomic and epigenomic data from induced pluripotent stem cell-derived cardiomyocytes from seven related individuals, and identified ~2,000 single-nucleotide variants associated with allele-specific effects (ASE-SNVs) on NKX2-5 binding. NKX2-5 ASE-SNVs were enriched for altered TF motifs, for heart-specific expression quantitative trait loci and for EKG GWAS signals. Using fine-mapping combined with epigenomic data from induced pluripotent stem cell-derived cardiomyocytes, we prioritized candidate causal variants for EKG traits, many of which were NKX2-5 ASE-SNVs. Experimentally characterizing two NKX2-5 ASE-SNVs (rs3807989 and rs590041) showed that they modulate the expression of target genes via differential protein binding in cardiac cells, indicating that they are functional variants underlying EKG GWAS signals. Our results show that differential NKX2-5 binding at numerous regulatory variants across the genome contributes to EKG phenotypes.

Partially Reprogrammed Induced Pluripotent Stem Cells Using MicroRNA Cluster miR-302s in Guangxi Bama Minipig Fibroblasts

Pig-induced pluripotent stem cells (piPSCs) have great potential application in regenerative medicine. The miR-302s cluster alone has been shown to reprogram mouse and human somatic cells into induced pluripotent stem cells (iPSCs) without exogenous transcription factors. However, miR-302s alone have not been reported to reprogram cells in large livestock. In this study, we induced pig somatic cells into partially reprogrammed piPSCs using overexpression of the miR-302s cluster (miR-302s-piPSC) and investigated the early reprogramming events during the miRNA induction process. The results showed that miR-302s-piPSCs exhibited some characteristics of pluripotent stem cells including expression of pluripotency markers-particularly, efficient activation of endogenous OCT4-and differentiation to the three germ layers in vitro. During the early reprogramming process, somatic cells first underwent epithelial-mesenchymal transition and then mesenchymal-epithelial transition to eventually form miR-302s-piPSCs. These data show, for the first time, that single factor miR-302s successfully induced pig somatic cells into miR-302s-piPSCs. This study provides a new tool and research direction for the induction of pluripotent stem cells in a large livestock.

Clinical Trial in a Dish: Personalized Stem Cell-Derived Cardiomyocyte Assay Compared With Clinical Trial Results for Two QT-Prolonging Drugs

Induced pluripotent stem cells (iPSCs) have shown promise in investigating donor-specific phenotypes and pathologies. The iPSC-derived cardiomyocytes (iPSC-CMs) could potentially be utilized in personalized cardiotoxicity studies, assessing individual proarrhythmic risk. However, it is unclear how closely iPSC-CMs derived from healthy subjects can recapitulate a range of responses to drugs. It is well known that QT-prolonging drugs induce subject-specific clinical response and that all healthy subjects do not necessarily develop arrhythmias or exhibit similar amounts of QT prolongation. We previously reported this variability in a study of four human ether-a-go-go-related gene (hERG) potassium channel-blocking drugs in which each subject underwent intensive pharmacokinetic and pharmacodynamic sampling such that subjects had 15 time-matched plasma drug concentration and electrocardiogram measurements throughout 24 hours after dosing in a phase I clinical research unit. In this study, iPSC-CMs were generated from those subjects. Their drug-concentration-dependent QT prolongation response from the clinic was compared with in vitro drug-concentration-dependent action potential duration (APD) prolongation response to the same two hERG-blocking drugs, dofetilide and moxifloxacin. Comparative results showed no significant correlation between the subject-specific APD response slopes and clinical QT response slopes to either moxifloxacin (P = 0.75) or dofetilide (P = 0.69). Similarly, no significant correlation was found between baseline QT and baseline APD measurements (P = 0.93). This result advances our current understanding of subject-specific iPSC-CMs and facilitates discussion into factors obscuring correlation and considerations for future studies of subject-specific phenotypes in iPSC-CMs.

A High-Throughput Method as a Diagnostic Tool for HIV Detection in Patient-Specific Induced Pluripotent Stem Cells Generated by Different Reprogramming Methods

Induced pluripotent stem cells (iPSCs) provide a unique opportunity for generation of patient-specific cells for use in translational purposes. We aimed to compare iPSCs generated by different reprogramming methods regarding their reprogramming efficiency, pluripotency capacity, and the possibility to use high-throughput PCR-based methods for detection of human pathogenic viruses. iPSCs from skin fibroblasts (FB), peripheral blood mononuclear cells (PBMCs), or mesenchymal stem cells (MSCs) were generated by using three different reprogramming systems including chromosomal integrating and nonintegrating methods. Reprogramming efficiencies were in accordance with the literature, indicating that the parental cell type and the reprogramming method play a major role for the reprogramming efficiencies (FB: STEMCCA: 1.30 ± 0.18, Sendai virus: 1.37 ± 0.01, and episomal plasmids: 0.04 ± 0.02; PBMCs: Sendai virus: 0.002 ± 0.001, episomal plasmids: 0) but result in the same characteristics of pluripotency. We found the highest reprogramming efficiencies for MSC with 3.32 ± 1.2 by using episomal plasmids. Since GMP standard working procedures and screening units need virus contamination-free cell lines, we studied HIV-1 contamination in the generated iPSCs. We used the high-throughput cobas® 6800/8800 system, which is normally used for detection of HIV-1 in plasma of patients, and found that footprint-free reprogramming methods as episomal plasmids and Sendai virus are useful for the described virus detection method. This fast, cost-effective, robust, and reliable assay demonstrates the feasibility to use high-throughput PCR-based methods for detection of human pathogenic viruses in ps-iPSC lines that were generated with nongenome integrating reprogramming methods.

Generation of an integration-free induced pluripotent stem cell line (FDEENTi003-A) from a patient with pathological myopia

Pathological myopia (PM) is a major cause of irreversible vision impairment worldwide. We have successfully reprogrammed the peripheral blood mononuclear cells (PBMCs) from a PM patient to induced pluripotent stem cells and characterized their pluripotency and genetic stability, as well as the potential to differentiate to retinal pigment epithelium (RPE). This line may serve as a useful tool to explore the pathogenesis of PM.

Tau Kinetics in Neurons and the Human Central Nervous System

We developed stable isotope labeling and mass spectrometry approaches to measure the kinetics of multiple isoforms and fragments of tau in the human central nervous system (CNS) and in human induced pluripotent stem cell (iPSC)-derived neurons. Newly synthesized tau is truncated and released from human neurons in 3 days. Although most tau proteins have similar turnover, 4R tau isoforms and phosphorylated forms of tau exhibit faster turnover rates, suggesting unique processing of these forms that may have independent biological activities. The half-life of tau in control human iPSC-derived neurons is 6.74 ± 0.45 days and in human CNS is 23 ± 6.4 days. In cognitively normal and Alzheimer's disease participants, the production rate of tau positively correlates with the amount of amyloid plaques, indicating a biological link between amyloid plaques and tau physiology.

Establishment of an induced pluripotent stem cell line (FDEENTi002-A) from a patient with Best's disease carrying c.888C > A mutation in BEST1 gene

Best's disease (BD) is an inherited retinal degenerative disease caused by mutations in BEST1 gene. A human induced pluripotent stem cell (iPSC) line has been generated with integration-free Sendai virus method from peripheral blood mononuclear cells (PBMCs) of a BD patient carrying c.888C > A mutation in BEST1 gene. This cell line may serve as a model for the study of pathogenesis of BD.

Expression of mutant mRNA and protein in pancreatic cells derived from MODY3- iPS cells

Maturity-onset diabetes of the young (MODY) is a heterozygous monogenic diabetes; more than 14 disease genes have been identified. However, the pathogenesis of MODY is not fully understood because the patients' pancreatic beta cells are inaccessible. To elucidate the pathology of MODY, we established MODY3 patient-derived iPS (MODY3-iPS) cells using non-integrating Sendai virus (SeV) vector and examined the mutant mRNA and protein of HNF1A (Hepatocyte Nuclear factor 1A) after pancreatic lineage differentiation. Our patient had a cytosine insertion in the HNF1A gene (P291fsinsC) causing frameshift and making a premature termination codon (PTC). We confirmed these MODY3-iPS cells possessed the characteristics of pluripotent stem cells. After we differentiated them into pancreatic beta cells, transcripts of HNF1A gene were cloned and sequenced. We found that P291fsinsC mutant transcripts were much less frequent than wild ones, but they increased after adding cycloheximide (CHX) to the medium. These results suggested that mutant mRNA was destroyed by nonsense-mediated mRNA decay (NMD). Moreover, we were not able to detect any band of mutant proteins in pancreatic lineage cells which were differentiated from MODY3-iPSCs by western blot (WB) analysis. A scarcity of the truncated form of mutant protein may indicate that MODY3 might be caused by a haplo-insufficiency effect rather than a dominant negative manner.

Generation of induced pluripotent stem cells-derived hepatocyte-like cells for ex vivo gene therapy of primary hyperoxaluria type 1

Primary hyperoxaluria type 1 (PH1) is a rare autosomal recessive disorder of the liver metabolism due to functional deficiency of the peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT). AGT deficiency results in overproduction of oxalate which complexes with calcium to form insoluble calcium-oxalate salts in urinary tracts, ultimately leading to end-stage renal disease. Currently, the only curative treatment for PH1 is combined liver-kidney transplantation, which is limited by donor organ shortage and lifelong requirement for immunosuppression. Transplantation of genetically modified autologous hepatocytes is an attractive therapeutic option for PH1. However, the use of fresh primary hepatocytes suffers from limitations such as organ availability, insufficient cell proliferation, loss of function, and the risk of immune rejection. We developed patient-specific induced pluripotent stem cells (PH1-iPSCs) free of reprogramming factors as a source of renewable and genetically defined autologous PH1-hepatocytes. We then investigated additive gene therapy using a lentiviral vector encoding wild-type AGT under the control of the liver-specific transthyretin promoter. Genetically modified PH1-iPSCs successfully provided hepatocyte-like cells (HLCs) that exhibited significant AGT expression at both RNA and protein levels after liver-specific differentiation process. These results pave the way for cell-based therapy of PH1 by transplantation of genetically modified autologous HLCs derived from patient-specific iPSCs.

Recent Updates on Induced Pluripotent Stem Cells in Hematological Disorders

Over the past decade, enormous progress has been made in the field of induced pluripotent stem cells (iPSCs). Patients' somatic cells such as skin fibroblasts or blood cells can be used to generate disease-specific pluripotent stem cells, which have unlimited proliferation and can differentiate into all cell types of the body. Human iPSCs offer great promises and opportunities for treatments of degenerative diseases and studying disease pathology and drug screening. So far, many iPSC-derived disease models have led to the discovery of novel pathological mechanisms as well as new drugs in the pipeline that have been tested in the iPSC-derived cells for efficacy and potential toxicities. Furthermore, recent advances in genome editing technology in combination with the iPSC technology have provided a versatile platform for studying stem cell biology and regenerative medicine. In this review, an overview of iPSCs, patient-specific iPSCs for disease modeling and drug screening, applications of iPSCs and genome editing technology in hematological disorders, remaining challenges, and future perspectives of iPSCs in hematological diseases will be discussed.

Measles vector as a multigene delivery platform facilitating iPSC reprogramming

Induced pluripotent stem cells (iPSCs) provide a unique platform for individualized cell therapy approaches. Currently, episomal DNA, mRNA, and Sendai virus-based RNA reprogramming systems are widely used to generate iPSCs. However, they all rely on the use of multiple (three to six) components (vectors/plasmids/mRNAs) leading to the production of partially reprogrammed cells, reducing the efficiency of the systems. We produced a one-cycle measles virus (MV) vector by substituting the viral attachment protein gene with the green fluorescent protein (GFP) gene. Here, we present a highly efficient multi-transgene delivery system based on a vaccine strain of MV, a non-integrating RNA virus that has a long-standing safety record in humans. Introduction of the four reprogramming factors OCT4, SOX2, KLF4, and cMYC via a single, "one-cycle" MV vector efficiently reprogrammed human somatic cells into iPSCs, whereas MV vector genomes are rapidly eliminated in derived iPSCs. Our MV vector system offers a new reprogramming platform for genomic modification-free iPSCs amenable for clinical translation.

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.

Applying hydrodynamic pressure to efficiently generate induced pluripotent stem cells via reprogramming of centenarian skin fibroblasts

Induced pluripotent stem cell (iPSC)-technology is an important platform in medicine and disease modeling. Physiological degeneration and disease onset are common occurrences in the aging population. iPSCs could offer regenerative medical options for age-related degeneration and disease in the elderly. However, reprogramming somatic cells from the elderly is inefficient when successful at all. Perhaps due to their low rates of replication in culture, traditional transduction and reprogramming approaches with centenarian fibroblasts met with little success. A simple and reproducible reprogramming process is reported here which enhances interactions of the cells with the viral vectors that leads to improved iPSC generation. The improved methods efficiently generates fully reprogrammed iPSC lines from 105-107 years old subjects in feeder-free conditions using an episomal, Sendai-Virus (SeV) reprogramming vector expressing four reprogramming factors. In conclusion, dermal fibroblasts from human subjects older than 100 years can be efficiently and reproducibly reprogrammed to fully pluripotent cells with minor modifications to the standard reprogramming procedures. Efficient generation of iPSCs from the elderly may provide a source of cells for the regeneration of tissues and organs with autologous cells as well as cellular models for the study of aging, longevity and age-related diseases.

Concise Review: Application of Chemically Modified mRNA in Cell Fate Conversion and Tissue Engineering

Chemically modified RNA (cmRNA) has potential as a safe and efficient tool for nucleic acid‐based therapies and regenerative medicine. Modifications in the chemistry of mRNA can enhance stability, reduce immunogenicity, and thus facilitate mRNA‐based nucleic acid therapy, which eliminates risk of insertional mutagenesis. In addition to these valuable advantages, the mRNA‐based method showed significantly higher efficacy for reprogramming somatic cells to pluripotency compared with DNA‐ or protein‐based methods. These findings suggest cmRNA can provide a powerful and safe tool for cell programming and reprogramming. Delivery methods, particularly using lipid nanoparticles, provide strategies for cell and organ‐specific targeting. The present study comprehensively compares studies that have used cmRNAs for cell fate conversion and tissue engineering. The information should be useful for investigators looking to choose the most efficient and straightforward cmRNA‐based strategy and protocol for tissue engineering and regenerative medicine research. stem cells translational medicine2019;8:833&843

Subtle changes in chromatin loop contact propensity are associated with differential gene regulation and expression

While genetic variation at chromatin loops is relevant for human disease, the relationships between contact propensity (the probability that loci at loops physically interact), genetics, and gene regulation are unclear. We quantitatively interrogate these relationships by comparing Hi-C and molecular phenotype data across cell types and haplotypes. While chromatin loops consistently form across different cell types, they have subtle quantitative differences in contact frequency that are associated with larger changes in gene expression and H3K27ac. For the vast majority of loci with quantitative differences in contact frequency across haplotypes, the changes in magnitude are smaller than those across cell types; however, the proportional relationships between contact propensity, gene expression, and H3K27ac are consistent. These findings suggest that subtle changes in contact propensity have a biologically meaningful role in gene regulation and could be a mechanism by which regulatory genetic variants in loop anchors mediate effects on expression.

iPS-Cell Technology and the Problem of Genetic Instability-Can It Ever Be Safe for Clinical Use?

The use of induced Pluripotent Stem Cells (iPSC) as a source of autologous tissues shows great promise in regenerative medicine. Nevertheless, several major challenges remain to be addressed before iPSC-derived cells can be used in therapy, and experience of their clinical use is extremely limited. In this review, the factors affecting the safe translation of iPSC to the clinic are considered, together with an account of efforts being made to overcome these issues. The review draws upon experiences with pluripotent stem-cell therapeutics, including clinical trials involving human embryonic stem cells and the widely transplanted mesenchymal stem cells. The discussion covers concerns relating to: (i) the reprogramming process; (ii) the detection and removal of incompletely differentiated and pluripotent cells from the resulting medicinal products; and (iii) genomic and epigenetic changes, and the evolutionary and selective processes occurring during culture expansion, associated with production of iPSC-therapeutics. In addition, (iv) methods for the practical culture-at-scale and standardization required for routine clinical use are considered. Finally, (v) the potential of iPSC in the treatment of human disease is evaluated in the light of what is known about the reprogramming process, the behavior of cells in culture, and the performance of iPSC in pre-clinical studies.

Direct cell reprogramming for tissue engineering and regenerative medicine

Direct cell reprogramming, also called transdifferentiation, allows for the reprogramming of one somatic cell type directly into another, without the need to transition through an induced pluripotent state. Thus, it is an attractive approach to develop novel tissue engineering applications to treat diseases and injuries where there is a shortage of proliferating cells for tissue repair. In certain tissue damage, terminally differentiated somatic cells lose their ability to proliferate, as a result, damaged tissues cannot heal by themselves. Examples of these scenarios include myocardial infarctions, neurodegenerative diseases, and cartilage injuries. Transdifferentiation is capable of reprogramming cells that are abundant in the body into desired cell phenotypes that are able to restore tissue function in damaged areas. Therefore, direct cell reprogramming is a promising direction in the cell and tissue engineering and regenerative medicine fields.

In recent years, several methods for transdifferentiation have been developed, ranging from the overexpression of transcription factors via viral vectors, to small molecules, to clustered regularly interspaced short palindromic repeats (CRISPR) and its associated protein (Cas9) for both genetic and epigenetic reprogramming. Overexpressing transcription factors by use of a lentivirus is currently the most prevalent technique, however it lacks high reprogramming efficiencies and can pose problems when transitioning to human subjects and clinical trials. CRISPR/Cas9, fused with proteins that modulate transcription, has been shown to improve efficiencies greatly. Transdifferentiation has successfully generated many cell phenotypes, including endothelial cells, skeletal myocytes, neuronal cells, and more. These cells have been shown to emulate mature adult cells such that they are able to mimic major functions, and some are capable of promoting regeneration of damaged tissue in vivo. While transdifferentiated cells have not yet seen clinical use, they have had promise in mice models, showing success in treating liver disease and several brain-related diseases, while also being utilized as a cell source for tissue engineered vascular grafts to treat damaged blood vessels. Recently, localized transdifferentiated cells have been generated in situ, allowing for treatments without invasive surgeries and more complete transdifferentiation. In this review, we summarized the recent development in various cell reprogramming techniques, their applications in converting various somatic cells, their uses in tissue regeneration, and the challenges of transitioning to a clinical setting, accompanied with potential solutions.

Reprogramming Captures the Genetic and Tumorigenic Properties of Neurofibromatosis Type 1 Plexiform Neurofibromas

Neurofibromatosis type 1 (NF1) is a tumor predisposition genetic disease caused by mutations in the NF1 tumor suppressor gene. Plexiform neurofibromas (PNFs) are benign Schwann cell (SC) tumors of the peripheral nerve sheath that develop through NF1 inactivation and can progress toward a malignant soft tissue sarcoma. There is a lack of non-perishable model systems to investigate PNF development. We reprogrammed PNF-derived NF1(-/-) cells, descendants from the tumor originating cell. These NF1(-/-)-induced pluripotent stem cells (iPSCs) captured the genomic status of PNFs and were able to differentiate toward neural crest stem cells and further to SCs. iPSC-derived NF1(-/-) SCs exhibited a continuous high proliferation rate, poor myelination ability, and a tendency to form 3D spheres that expressed the same markers as their PNF-derived primary SC counterparts. They represent a valuable model to study and treat PNFs. PNF-derived iPSC lines were banked for making them available.

Establishment of TUSMi008-A, an induced pluripotent stem cell (iPSC) line from a 76-year old Alzheimer's disease (AD) patient with PAXIP1 gene mutation

A 76-year old Alzheimer's disease (AD) female patient donated her Peripheral blood mononuclear cells (PBMC). The non-integrating episomal vector system used to reprogram PBMCs with the human OKSM transcription factors. The pluripotency of transgene-free iPSCs was confirmed by immunocytochemistry for pluripotency markers and by the ability of the iPSCs to differentiate spontaneously into 3 germ layers in vitro. In addition, the iPSC line displayed a normal karyotype. Our model might offer a good platform to further study the pathological mechanisms, to identify early biomarkers, and also for drug testing studies in AD.

Establishment of an induced pluripotent stem cell line (FDEENTi001-A) from a patient with pathological myopia

Pathological myopia (PM) is a retinal degenerative disease with an increasing prevalence in Asia. The peripheral blood mononuclear cells (PBMCs) from a patient with PM were successfully reprogrammed to induced pluripotent stem cells (iPSCs) using integration-free method, Sendai viral (SeV) vectors expressing OCT4, SOX2, KLF4 and C-MYC. This line may provide a useful resource for exploring the pathogenesis of PM.

Use of a Sendai virus-based vector for effcient transduction of pinniped fbroblasts

Generation of induced pluripotent stem (iPS) cells expanded possibilities of pluripotency and early development studies. Generation of order Carnivora iPS cells from dog (Canis lupus familiaris), snow leopard (Panthera uncia), and American mink (Neovison vison) was previously reported. The aim of the current study was to examine conditions of pinniped fbroblast reprogramming. Pinnipeds are representatives of the suborder Caniformia sharing conservative genomes. There are several ways to deliver reprogramming transcription factors: RNA, proteins, plasmids, viral vectors etc. The most effective delivery systems for mouse and human cells are based on viral vectors. We compared a lentiviral vector which integrates into the genome and a Sendai virus­based vector, CytoTune EmGFP Sendai Fluorescence Reporter. The main advantage of Sendai virus­based vectors is that they do not integrate into the genome. We performed delivery of genetic constructions carrying fluorescent proteins to fbroblasts of seven Pinnipeds: northern fur seal (Callorhinus ursinus), Steller sea lion (Eumetopias jubatus), walrus (Odobenus rosmarus), bearded seal (Erignathus barbatus), Baikal seal (Pusa sibirica), ringed seal (Phoca hispida), and spotted seal (Phoca largha). We also transduced American mink (N. vison), human (Homo sapiens), and mouse (Mus musculus) fbroblasts as a control. We showed that the Sendai virus­based transduction system provides transgene expression one­two orders of magnitude higher than the lentiviral system at a comparable multiplicity of infection. Also, transgene expression after Sendai virus­based transduction is quite stable and changes only slightly at day four compared to day two. These data allow us to suggest that Sendai virus­based vectors are preferable for generation of Pinniped iPS cells.

Potential Clinical Applications of Stem Cells in Regenerative Medicine

The field of regenerative medicine is looking for a pluripotent/multipotent stem cell able to differentiate across germ layers and be safely employed in therapy. Unfortunately, with the exception of hematopoietic stem/progenitor cells (HSPCs) for hematological applications, the current clinical results with stem cells are somewhat disappointing. The potential clinical applications of the more primitive embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have so far been discouraging, as both have exhibited several problems, including genomic instability, a risk of teratoma formation, and the possibility of rejection. Therefore, the only safe stem cells that have so far been employed in regenerative medicine are monopotent stem cells, such as the abovementioned HSPCs or mesenchymal stem cells (MSCs) isolated from postnatal tissues. However, their monopotency, and therefore limited differentiation potential, is a barrier to their broader application in the clinic. Interestingly, results have accumulated indicating that adult tissues contain rare, early-development stem cells known as very small embryonic-like stem cells (VSELs), which can differentiate into cells from more than one germ layer. This chapter addresses different sources of stem cells for potential clinical application and their advantages and problems to be solved.

Application of induced pluripotent stem cell technology for the investigation of hematological disorders

Induced pluripotent stem cells (iPSCs) were first described over a decade ago and are currently used in various basic biology and clinical research fields. Recent advances in the field of human iPSCs have opened the way to a better understanding of the biology of human diseases. Disease-specific iPSCs provide an unparalleled opportunity to establish novel human cell-based disease models, with the potential to enhance our understanding of the molecular mechanisms underlying human malignancies, and to accelerate the identification of effective new drugs. When combined with genome editing technologies, iPSCs represent a new approach to study single or multiple disease-causing mutations and model specific diseases in vitro. In addition, genetically corrected patient-specific iPSCs could potentially be used for stem cell based therapy. Furthermore, the reprogrammed cells share patient-specific genetic background, offering a new platform to develop personalized therapy/medicine for patients. In this review we discuss the recent advances in iPSC research technology and their potential applications in hematological diseases. Somatic cell reprogramming has presented new routes for generating patient-derived iPSCs, which can be differentiated to hematopoietic stem cells and the various downstream hematopoietic lineages. iPSC technology shows promise in the modeling of both inherited and acquired hematological disorders. A direct reprogramming and differentiation strategy is able to recapitulate hematological disorder progression and capture the earliest molecular alterations that underlie the initiation of hematological malignancies.