Status of KRAS in iPSCs Impacts upon Self-Renewal and Differentiation Propensity

Monoallelic KRAS (G13C) mutation triggers dysregulated expansion in induced pluripotent stem cell-derived hematopoietic progenitor cells

BACKGROUND

Although oncogenic RAS mutants are thought to exert mutagenic effects upon blood cells, it remains uncertain how a single oncogenic RAS impacts non-transformed multipotent hematopoietic stem or progenitor cells (HPCs). Such potential pre-malignant status may characterize HPCs in patients with RAS-associated autoimmune lymphoproliferative syndrome-like disease (RALD). This study sought to elucidate the biological and molecular alterations in human HPCs carrying monoallelic mutant KRAS (G13C) with no other oncogene mutations.

METHODS

We utilized induced pluripotent stem cells (iPSCs) derived from two unrelated RALD patients. Isogenic HPC pairs harboring either wild-type KRAS or monoallelic KRAS (G13C) alone obtained following differentiation enabled reliable comparative analyses. The compound screening was conducted with an established platform using KRAS (G13C) iPSCs and differentiated HPCs.

RESULTS

Cell culture assays revealed that monoallelic KRAS (G13C) impacted both myeloid differentiation and expansion characteristics of iPSC-derived HPCs. Comprehensive RNA-sequencing analysis depicted close clustering of HPC samples within the isogenic group, warranting that comparative studies should be performed within the same genetic background. When compared with no stimulation, iPSC-derived KRAS (G13C)-HPCs showed marked similarity with the wild-type isogenic control in transcriptomic profiles. After stimulation with cytokines, however, KRAS (G13C)-HPCs exhibited obvious aberrant cell-cycle and apoptosis responses, compatible with "dysregulated expansion," demonstrated by molecular and biological assessment. Increased BCL-xL expression was identified amongst other molecular changes unique to mutant HPCs. With screening platforms established for therapeutic intervention, we observed selective activity against KRAS (G13C)-HPC expansion in several candidate compounds, most notably in a MEK- and a BCL-2/BCL-xL-inhibitor. These two compounds demonstrated selective inhibitory effects on KRAS (G13C)-HPCs even with primary patient samples when combined.

CONCLUSIONS

Our findings indicate that a monoallelic oncogenic KRAS can confer dysregulated expansion characteristics to non-transformed HPCs, which may constitute a pathological condition in RALD hematopoiesis. The use of iPSC-based screening platforms will lead to discovering treatments that enable selective inhibition of RAS-mutated HPC clones.

Lymph node macrophages drive innate immune responses to enhance the anti-tumor efficacy of mRNA vaccines

mRNA vaccines are promising for cancer treatment. Efficient delivery of mRNAs encoding tumor antigens to antigen-presenting cells (APCs) is critical to elicit anti-tumor immunity. Herein, we identified a novel lipid nanoparticle (LNP) formulation, L17-F05, for mRNA vaccines by screening 34 ionizable lipids and 28 LNP formulations using human primary APCs. Subcutaneous delivery of L17-F05 mRNA vaccine encoding Gp100 and Trp2 inhibited tumor growth and prolonged the survival of mice bearing B16F10 melanoma. L17-F05 efficiently delivered mRNAs to conventional dendritic cells (cDCs) and macrophages in draining lymph nodes (dLNs). cDCs functioned as the main APCs by presenting antigens along with enhanced expression of co-stimulatory molecules. Macrophages triggered innate immune responses centered on type-I interferon (IFN-I) in dLNs. Lymph node (LN) macrophage depletion attenuated APC maturation and anti-tumor activity of L17-F05 mRNA vaccines. Loss-of-function studies revealed that L17-F05 works as a self-adjuvant by activating the stimulator of interferon genes (STING) pathway in macrophages. Collectively, the self-adjuvanticity of L17-F05 triggered innate immune responses in LN macrophages via the STING-IFN-I pathway, contributing to APC maturation and potent anti-tumor activity of L17-F05 mRNA vaccines. Our findings provide strategies for further optimization of mRNA vaccines based on the innate immune response driven by LN macrophages.

The mesodermal and myogenic specification of hESCs depend on ZEB1 and are inhibited by ZEB2

Human embryonic stem cells (hESCs) can differentiate into any cell lineage. Here, we report that ZEB1 and ZEB2 promote and inhibit mesodermal-to-myogenic specification of hESCs, respectively. Knockdown and/or overexpression experiments of ZEB1, ZEB2, or PAX7 in hESCs indicate that ZEB1 is required for hESC Nodal/Activin-mediated mesodermal specification and PAX7+ human myogenic progenitor (hMuP) generation, while ZEB2 inhibits these processes. ZEB1 downregulation induces neural markers, while ZEB2 downregulation induces mesodermal/myogenic markers. Mechanistically, ZEB1 binds to and transcriptionally activates the PAX7 promoter, while ZEB2 binds to and activates the promoter of the neural OTX2 marker. Transplanting ZEB1 or ZEB2 knocked down hMuPs into the muscles of a muscular dystrophy mouse model, showing that hMuP engraftment and generation of dystrophin-positive myofibers depend on ZEB1 and are inhibited by ZEB2. The mouse model results suggest that ZEB1 expression and/or downregulating ZEB2 in hESCs may also enhance hESC regenerative capacity for human muscular dystrophy therapy.

The Role of ATP-Binding Cassette Proteins in Stem Cell Pluripotency

Pluripotent stem cells (PSCs) are highly proliferative cells that can self-renew indefinitely in vitro. Upon receiving appropriate signals, PSCs undergo differentiation and can generate every cell type in the body. These unique properties of PSCs require specific gene expression patterns that define stem cell identity and dynamic regulation of intracellular metabolism to support cell growth and cell fate transitions. PSCs are prone to DNA damage due to elevated replicative and transcriptional stress. Therefore, mechanisms to prevent deleterious mutations in PSCs that compromise stem cell function or increase the risk of tumor formation from becoming amplified and propagated to progenitor cells are essential for embryonic development and for using PSCs including induced PSCs (iPSCs) as a cell source for regenerative medicine. In this review, we discuss the role of the ATP-binding cassette (ABC) superfamily in maintaining PSC homeostasis, and propose how their activities can influence cellular signaling and stem cell fate decisions. Finally, we highlight recent discoveries that not all ABC family members perform only canonical metabolite and peptide transport functions in PSCs; rather, they can participate in diverse cellular processes from genome surveillance to gene transcription and mRNA translation, which are likely to maintain the pristine state of PSCs.

Reversibility and developmental neuropathology of linear nevus sebaceous syndrome caused by dysregulation of the RAS pathway

Linear nevus sebaceous syndrome (LNSS) is a neurocutaneous disorder caused by somatic gain-of-function mutations in KRAS or HRAS. LNSS brains have neurodevelopmental defects, including cerebral defects and epilepsy; however, its pathological mechanism and potentials for treatment are largely unclear. We show that introduction of KRAS^G12V in the developing mouse cortex results in subcortical nodular heterotopia and enhanced excitability, recapitulating major pathological manifestations of LNSS. Moreover, we show that decreased firing frequency of inhibitory neurons without KRAS^G12V expression leads to disrupted excitation and inhibition balance. Transcriptional profiling after destabilization domain-mediated clearance of KRAS^G12V in human neural progenitors and differentiating neurons identifies reversible functional networks underlying LNSS. Neurons expressing KRAS^G12V show molecular changes associated with delayed neuronal maturation, most of which are restored by KRAS^G12V clearance. These findings provide insights into the molecular networks underlying the reversibility of some of the neuropathologies observed in LNSS caused by dysregulation of the RAS pathway.

CRISPR single base editing, neuronal disease modelling and functional genomics for genetic variant analysis: pipeline validation using Kleefstra syndrome EHMT1 haploinsufficiency

Background

Over 400 million people worldwide are living with a rare disease. Next Generation Sequencing (NGS) identifies potential disease causative genetic variants. However, many are identified as variants of uncertain significance (VUS) and require functional laboratory validation to determine pathogenicity, and this creates major diagnostic delays.

Methods

In this study we test a rapid genetic variant assessment pipeline using CRISPR homology directed repair to introduce single nucleotide variants into inducible pluripotent stem cells (iPSCs), followed by neuronal disease modelling, and functional genomics on amplicon and RNA sequencing, to determine cellular changes to support patient diagnosis and identify disease mechanism.

Results

As proof-of-principle, we investigated an EHMT1 (Euchromatin histone methyltransferase 1; EHMT1 c.3430C > T; p.Gln1144*) genetic variant pathogenic for Kleefstra syndrome and determined changes in gene expression during neuronal progenitor cell differentiation. This pipeline rapidly identified Kleefstra syndrome in genetic variant cells compared to healthy cells, and revealed novel findings potentially implicating the key transcription factors REST and SP1 in disease pathogenesis.

Conclusion

The study pipeline is a rapid, robust method for genetic variant assessment that will support rare diseases patient diagnosis. The results also provide valuable information on genome wide perturbations key to disease mechanism that can be targeted for drug treatments.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02740-3.

Genomic and evolutionary classification of lung cancer in never smokers

Lung cancer in never smokers (LCINS) is a common cause of cancer mortality but its genomic landscape is poorly characterized. Here high-coverage whole-genome sequencing of 232 LCINS showed 3 subtypes defined by copy number aberrations. The dominant subtype (piano), which is rare in lung cancer in smokers, features somatic UBA1 mutations, germline AR variants and stem cell-like properties, including low mutational burden, high intratumor heterogeneity, long telomeres, frequent KRAS mutations and slow growth, as suggested by the occurrence of cancer drivers' progenitor cells many years before tumor diagnosis. The other subtypes are characterized by specific amplifications and EGFR mutations (mezzo-forte) and whole-genome doubling (forte). No strong tobacco smoking signatures were detected, even in cases with exposure to secondhand tobacco smoke. Genes within the receptor tyrosine kinase-Ras pathway had distinct impacts on survival; five genomic alterations independently doubled mortality. These findings create avenues for personalized treatment in LCINS.

RASopathies: from germline mutations to somatic and multigenic diseases

The RAS-RAF-MEK-ERK signaling pathway is vital for different cellular mechanisms including cell proliferation, differentiation and apoptosis. This importance is highlighted by the high prevalence of mutations in RAS or related proteins of the pathway in cancers. More recently, development abnormalities have been linked to various germline mutations in this pathway and called RASopathies. Interestingly, rare disorders such as RAS-associated leukoproliferative diseases and histiocytosis have also been recently linked to multiple mutations in the same pathway, sometimes with the same mutation. This review will focus on germline RASopathies and rare somatic RASopathies and focus on how gain-of-function mutations in the same pathway can lead to various diseases.

Heterozygous OAS1 gain-of-function variants cause an autoinflammatory immunodeficiency

Analysis of autoinflammatory and immunodeficiency disorders elucidates human immunity and fosters the development of targeted therapies. Oligoadenylate synthetase 1 is a type I interferon-induced, intracellular double-stranded RNA (dsRNA) sensor that generates 2'-5'-oligoadenylate to activate ribonuclease L (RNase L) as a means of antiviral defense. We identified four de novo heterozygous OAS1 gain-of-function variants in six patients with a polymorphic autoinflammatory immunodeficiency characterized by recurrent fever, dermatitis, inflammatory bowel disease, pulmonary alveolar proteinosis, and hypogammaglobulinemia. To establish causality, we applied genetic, molecular dynamics simulation, biochemical, and cellular functional analyses in heterologous, autologous, and inducible pluripotent stem cell-derived macrophages and/or monocytes and B cells. We found that upon interferon-induced expression, OAS1 variant proteins displayed dsRNA-independent activity, which resulted in RNase L-mediated RNA cleavage, transcriptomic alteration, translational arrest, and dysfunction and apoptosis of monocytes, macrophages, and B cells. RNase L inhibition with curcumin modulated and allogeneic hematopoietic cell transplantation cured the disorder. Together, these data suggest that human OAS1 is a regulator of interferon-induced hyperinflammatory monocyte, macrophage, and B cell pathophysiology.

Promotion of cancer cell stemness by Ras

Cancer stem cells (CSC) may be the most relevant and elusive cancer cell population, as they have the exquisite ability to seed new tumors. It is plausible, that highly mutated cancer genes, such as KRAS, are functionally associated with processes contributing to the emergence of stemness traits. In this review, we will summarize the evidence for a stemness driving activity of oncogenic Ras. This activity appears to differ by Ras isoform, with the highly mutated KRAS having a particularly profound impact. Next to established stemness pathways such as Wnt and Hedgehog (Hh), the precise, cell cycle dependent orchestration of the MAPK-pathway appears to relay Ras activation in this context. We will examine how non-canonical activities of K-Ras4B (hereafter K-Ras) could be enabled by its trafficking chaperones calmodulin and PDE6D/PDEδ. Both dynamically localize to the cellular machinery that is intimately linked to cell fate decisions, such as the primary cilium and the centrosome. Thus, it can be speculated that oncogenic K-Ras disrupts fundamental polarized signaling and asymmetric apportioning processes that are necessary during cell differentiation.

Clinical Spectrum of Ras-Associated Autoimmune Leukoproliferative Disorder (RALD)

Ras-associated autoimmune leukoproliferative disorder (RALD) is a clinical entity initially identified in patients evaluated for an autoimmune lymphoproliferative syndrome (ALPS)-like phenotype. It remains a matter of debate whether RALD is a chronic and benign lymphoproliferative disorder or a pre-malignant condition. We report the case of a 7-year-old girl diagnosed with RALD due to somatic KRAS mutation who progressed to a juvenile myelomonocytic leukemia phenotype and finally evolved into acute myeloid leukemia. The case report prompted a literature review by a search for all RALD cases published in PubMed and Embase. We identified 27 patients with RALD. The male-to-female ratio was 1:1 and median age at disease onset was 2 years (range 3 months-36 years). Sixteen patients (59%) harbored somatic mutations in KRAS and 11 patients (41%) somatic mutations in NRAS. The most common features were splenomegaly (26/27 patients), autoimmune cytopenia (15/16 patients), monocytosis (18/24 patients), pericarditis (6 patients), and skin involvement (4 patients). Two patients went on to develop a hematopoietic malignancy. In summary, the current case documents an additional warning about the long-term risk of malignancy in RALD.

Altering chromatin methylation patterns and the transcriptional network involved in regulation of hematopoietic stem cell fate

Hematopoietic stem cells (HSCs) are quiescent cells with self-renewal capacity and potential multilineage development. Various molecular regulatory mechanisms such as epigenetic modifications and transcription factor (TF) networks play crucial roles in establishing a balance between self-renewal and differentiation of HSCs. Histone/DNA methylations are important epigenetic modifications involved in transcriptional regulation of specific lineage HSCs via controlling chromatin structure and accessibility of DNA. Also, TFs contribute to either facilitation or inhibition of gene expression through binding to enhancer or promoter regions of DNA. As a result, epigenetic factors and TFs regulate the activation or repression of HSCs genes, playing a central role in normal hematopoiesis. Given the importance of histone/DNA methylation and TFs in gene expression regulation, their aberrations, including changes in HSCs-related methylation of histone/DNA and TFs (e.g., CCAAT-enhancer-binding protein α, phosphatase and tensin homolog deleted on the chromosome 10, Runt-related transcription factor 1, signal transducers and activators of transcription, and RAS family proteins) could disrupt HSCs fate. Herewith, we summarize how dysregulations in the expression of genes related to self-renewal, proliferation, and differentiation of HSCs caused by changes in epigenetic modifications and transcriptional networks lead to clonal expansion and leukemic transformation.

Functional Analysis of PTH1R Variants Found in Primary Failure of Eruption

Although many variants of the parathyroid hormone 1 receptor (PTH1R) gene are known to be associated with primary failure of eruption (PFE), the mechanisms underlying the link remains poorly understood. We here performed functional analyses of PTH1R variants reported in PFE patients-namely, 356C>T (P119L), 395C>T (P132L), 439C>T (R147C), and 1148G>A (R383Q)-using HeLa cells with a lentiviral vector-mediated genetic modification. Two particular variants, P119L and P132L, had severe reduction in a level of N-linked glycosylation when compared with wild-type PTH1R, whereas the other 2 showed modest alteration. PTH1R having P119L or P132L showed marked decrease in the affinity to PTH_1-34, which likely led to severely impaired cAMP accumulation upon stimulation in cells expressing these mutants, highlighting the importance of these 2 amino acid residues for ligand-mediated proper functioning of PTH1R. To further gain insights into PTH1R functions, we established the induced pluripotent stem cell (iPSC) lines from a patient with PFE and the heterozygous P132L mutation. When differentiated into osteoblastic-lineage cells, PFE-iPSCs showed no abnormality in mineralization. The mRNA expression of RUNX2, SP7, and BGLAP, the osteoblastic differentiation-related genes, and that of PTH1R were augmented in both PFE-iPSC-derived cells and control iPSC-derived cells in the presence of bone morphogenetic protein 2. Also, active vitamin D₃ induced the expression of RANKL, a major key factor for osteoclastogenesis, equally in osteoblastic cells derived from control and PFE-iPSCs. In sharp contrast, exposure to PTH_1-34 resulted in no induction of RANKL mRNA expression in the cells expressing P132L variant PTH1R, consistent with the idea that a type of heterozygous PTH1R gene mutation would spoil PTH-dependent response in osteoblasts. Collectively, this study demonstrates a link between PFE-associated genetic alteration and causative functional impairment of PTH1R, as well as a utility of iPSC-based disease modeling for future elucidation of pathogenesis in genetic disorders, including PFE.

Transcriptome meta-analysis reveals differences of immune profile between eutopic endometrium from stage I-II and III-IV endometriosis independently of hormonal milieu

Eutopic endometrium appears to be crucial for endometriosis development. Despite of the evident importance, data regarding the cellular microenvironment remain unclear. Our objective was to explore the tissue microenvironment heterogeneity, transcripts, and pathways that are enriched in all phases of the menstrual cycle by analysing publicly deposited data derived from whole transcriptome microarrays of eutopic endometria of women with and without endometriosis. A meta-analysis of the transcriptome microarrays was performed using raw data available from a public database. Eligibility criteria included eutopic endometrium samples from women with endometriosis and healthy controls without any pathological condition reported the presence of an adequately reported normal menstrual phase, and samples containing both glandular and stromal components. Raw data were processed using a robust multiarray average method to provide background correction, normalisation, and summarisation. The batch effect was estimated by principal variant component analysis and removed using an empirical Bayes method. Cellular tissue heterogeneity was inferred using the xCell package. Differentially expressed genes were identified based on a 5% adjusted p value and a 2.0-fold change. Pathways were identified by functional enrichment based on the Molecular Signatures Database, a p value of < 5%, and an FDR q value of ≤ 25%. Genes that were more frequently found in pathways were identified using leading edge analysis. In a manner independent of cycle phase, the subpopulations of activated dendritic cells, CD4 T effector memory phenotype cells, eosinophils, macrophages M1, and natural killer T cells (NKT) were all higher in stage I-II endometriosis compared to those in healthy controls. The subpopulations of M2 macrophages and natural killer T cells were elevated in eutopic endometriums from women with stage III-IV endometriosis, and smooth muscle cells were always more prevalent in healthy eutopic endometriums. Among the differently expressed genes, FOS, FOSB, JUNB, and EGR1 were the most frequently mapped within the interaction networks, and this was independent of stage and cycle phase. The enriched pathways were directly related to immune surveillance, stem cell self-renewal, and epithelial mesenchymal transition. PI3K AKT mTOR, TGF signalling, and interferon alpha/gamma responses were enriched exclusively in stage III-IV endometriosis. The cellular microenvironments and immune cell profiles were different between eutopic endometriums from women with stage I-II and stage III-IV endometriosis, and these differences were independent of the hormonal milieu. Specifically, a pro-inflammatory profile was predominant in stage I-II endometriosis, and M1-M2 polarization into eutopic endometrium may be crucial for the progression of the disease. The higher prevalence of NKT cells in eutopic endometriums from women with endometriosis that was independent of cycle phase or staging suggested a sustained stress and/or damage to these eutopic endometriums. Based on this, the results of this meta-analysis are important for identifying challenges and opportunities for future research.

Meta-Analysis of Human and Mouse Biliary Epithelial Cell Gene Profiles

BACKGROUND

Chronic liver diseases are frequently accompanied with activation of biliary epithelial cells (BECs) that can differentiate into hepatocytes and cholangiocytes, providing an endogenous back-up system. Functional studies on BECs often rely on isolations of an BEC cell population from healthy and/or injured livers. However, a consensus on the characterization of these cells has not yet been reached. The aim of this study was to compare the publicly available transcriptome profiles of human and mouse BECs and to establish gene signatures that can identify quiescent and activated human and mouse BECs.

METHODS

We used publicly available transcriptome data sets of human and mouse BECs, compared their profiles and analyzed co-expressed genes and pathways. By merging both human and mouse BEC-enriched genes, we obtained a quiescent and activation gene signature and tested them on BEC-like cells and different liver diseases using gene set enrichment analysis. In addition, we identified several genes from both gene signatures to identify BECs in a scRNA sequencing data set.

RESULTS

Comparison of mouse BEC transcriptome data sets showed that the isolation method and array platform strongly influences their general profile, still most populations are highly enriched in most genes currently associated with BECs. Pathway analysis on human and mouse BECs revealed the KRAS signaling as a new potential pathway in BEC activation. We established a quiescent and activated BEC gene signature that can be used to identify BEC-like cells and detect BEC enrichment in alcoholic hepatitis, non-alcoholic steatohepatitis (NASH) and peribiliary sclerotic livers. Finally, we identified a gene set that can distinguish BECs from other liver cells in mouse and human scRNAseq data.

CONCLUSIONS

Through a meta-analysis of human and mouse BEC gene profiles we identified new potential pathways in BEC activation and created unique gene signatures for quiescent and activated BECs. These signatures and pathways will help in the further characterization of this progenitor cell type in mouse and human liver development and disease.

Neurodevelopmental Aspects of RASopathies

RAS gene mutations are frequently found in one third of human cancers. Affecting approximately 1 in 1,000 newborns, germline and somatic gain-of-function mutations in the components of RAS/mitogen-activated protein kinase (RAS/MAPK) pathway has been shown to cause developmental disorders, known as RASopathies. Since RAS-MAPK pathway plays essential roles in proliferation, differentiation and migration involving developmental processes, individuals with RASopathies show abnormalities in various organ systems including central nervous system. The frequently seen neurological defects are developmental delay, macrocephaly, seizures, neurocognitive deficits, and structural malformations. Some of the defects stemmed from dysregulation of molecular and cellular processes affecting early neurodevelopmental processes. In this review, we will discuss the implications of RAS-MAPK pathway components in neurodevelopmental processes and pathogenesis of RASopathies.

Dynamic genetic regulation of gene expression during cellular differentiation

Genetic regulation of gene expression is dynamic, as transcription can change during cell differentiation and across cell types. We mapped expression quantitative trait loci (eQTLs) throughout differentiation to elucidate the dynamics of genetic effects on cell type-specific gene expression. We generated time-series RNA sequencing data, capturing 16 time points during the differentiation of induced pluripotent stem cells to cardiomyocytes, in 19 human cell lines. We identified hundreds of dynamic eQTLs that change over time, with enrichment in enhancers of relevant cell types. We also found nonlinear dynamic eQTLs, which affect only intermediate stages of differentiation and cannot be found by using data from mature tissues. These fleeting genetic associations with gene regulation may explain some of the components of complex traits and disease. We highlight one example of a nonlinear eQTL that is associated with body mass index.

Robust and highly efficient hiPSC generation from patient non-mobilized peripheral blood-derived CD34+ cells using the auto-erasable Sendai virus vector

BACKGROUND

Disease modeling with patient-derived induced pluripotent stem cells (iPSCs) is a powerful tool for elucidating the mechanisms underlying disease pathogenesis and developing safe and effective treatments. Patient peripheral blood (PB) cells are used for iPSC generation in many cases since they can be collected with minimum invasiveness. To derive iPSCs that lack immunoreceptor gene rearrangements, hematopoietic stem and progenitor cells (HSPCs) are often targeted as the reprogramming source. However, the current protocols generally require HSPC mobilization and/or ex vivo expansion owing to their sparsity at the steady state and low reprogramming efficiencies, making the overall procedure costly, laborious, and time-consuming.

METHODS

We have established a highly efficient method for generating iPSCs from non-mobilized PB-derived CD34+ HSPCs. The source PB mononuclear cells were obtained from 1 healthy donor and 15 patients and were kept frozen until the scheduled iPSC generation. CD34+ HSPC enrichment was done using immunomagnetic beads, with no ex vivo expansion culture. To reprogram the CD34+-rich cells to pluripotency, the Sendai virus vector SeVdp-302L was used to transfer four transcription factors: KLF4, OCT4, SOX2, and c-MYC. In this iPSC generation series, the reprogramming efficiencies, success rates of iPSC line establishment, and progression time were recorded. After generating the iPSC frozen stocks, the cell recovery and their residual transgenes, karyotypes, T cell receptor gene rearrangement, pluripotency markers, and differentiation capability were examined.

RESULTS

We succeeded in establishing 223 iPSC lines with high reprogramming efficiencies from 15 patients with 8 different disease types. Our method allowed the rapid appearance of primary colonies (~ 8 days), all of which were expandable under feeder-free conditions, enabling robust establishment steps with less workload. After thawing, the established iPSC lines were verified to be pluripotency marker-positive and of non-T cell origin. A majority of the iPSC lines were confirmed to be transgene-free, with normal karyotypes. Their trilineage differentiation capability was also verified in a defined in vitro assay.

CONCLUSION

This robust and highly efficient method enables the rapid and cost-effective establishment of transgene-free iPSC lines from a small volume of PB, thus facilitating the biobanking of patient-derived iPSCs and their use for the modeling of various diseases.