Induced pluripotent stem cells from homozygous Runx2-deficient mice show poor response to vitamin D during osteoblastic differentiation.

Cleidocranial dysplasia (CCD) is a hereditary disorder associated with skeletal dysplasia and dental abnormalities. CCD arises from heterozygous loss of function mutations in the Runt-related transcription factor 2 (RUNX2) gene. Osteoporosis is often observed in CCD patients and conventional vitamin D supplementation is recommended. However, sufficient evidences have not been presented yet. This study investigated the role of RUNX2 in osteoblastic differentiation and sought to identify potential target genes for the treatment of osteoporosis associated with CCD, using induced pluripotent stem cell (iPSC) technology. We successfully established Runx2-/-, Runx2+/- and wild-type miPSCs from litter-matched mice and found poor Vdr expression in Runx2-/-cells. Significant down-regulation of osteoblastic differentiation in Runx2-/- miPSCs was observed. Gene expression array revealed unexpected results such as remarkable increase of Rankl expression and decrease of Vdr in Runx2-/- cells. Insufficient response to vitamin D in Runx2-/- cells was also observed. Our results suggest that RUNX2 functions as a regulator of Rankl and Vdr and thereby controls bone density. These findings also suggest that conventional vitamin D supplementation may not be as effective as previously expected, in the treatment of osteoporosis associated with CCD, and that inhibiting RANKL function might be worth considering as an alternative treatment strategy.

Downregulation of Odd-Skipped Related 2, a Novel Regulator of Epithelial-Mesenchymal Transition, Enables Efficient Somatic Cell Reprogramming.

Somatic cell reprogramming proceeds through a series of events to generate induced pluripotent stem cells (iPSCs). The early stage of reprogramming of mouse embryonic fibroblasts is characterized by rapid cell proliferation and morphological changes, which are accompanied by downregulation of mesenchyme-associated genes. However, the functional relevance of their downregulation to reprogramming remains poorly defined. In this study, we have screened transcriptional regulators that are downregulated immediately upon reprogramming, presumably through direct targeting by reprogramming factors. To test if these transcriptional regulators impact reprogramming when expressed continuously, we generated an expression vector that harbors human cytomegalovirus upstream open reading frame 2 (uORF2), which reduces translation to minimize the detrimental effect of an expressed protein. Screening of transcriptional regulators with this expression vector revealed that downregulation of (odd-skipped related 2 [Osr2]) is crucial for efficient reprogramming. Using a cell-based model for epithelial-mesenchymal transition (EMT), we show that Osr2 is a novel EMT regulator that acts through induction of transforming growth factor-ß (TGF-ß) signaling. During reprogramming, Osr2 downregulation not only diminishes TGF-ß signaling but also allows activation of Wnt signaling, thus promoting mesenchymal-epithelial transition (MET) toward acquisition of pluripotency. Our results illuminate the functional significance of Osr2 downregulation in erasing the mesenchymal phenotype at an early stage of somatic cell reprogramming.

Dual-antigen targeted iPSC-derived chimeric antigen receptor-T cell therapy for refractory lymphoma.

We generated dual-antigen receptor (DR) T cells from induced pluripotent stem cells (iPSCs) to mitigate tumor antigen escape. These cells were engineered to express a chimeric antigen receptor (CAR) for the antigen cell surface latent membrane protein 1 (LMP1; LMP1-CAR) and a T cell receptor directed to cell surface latent membrane protein 2 (LMP2), in association with human leucocyte antigen A24, to treat therapy-refractory Epstein-Barr virus-associated lymphomas. We introduced LMP1-CAR into iPSCs derived from LMP2-specific cytotoxic T lymphocytes (CTLs) to generate rejuvenated CTLs (rejTs) active against LMP1 and LMP2, or DRrejTs. All DRrejT-treated mice survived >100 days. Furthermore, DRrejTs rejected follow-up inocula of lymphoma cells, demonstrating that DRrejTs persisted long-term. We also demonstrated that DRrejTs targeting CD19 and LMP2 antigens exhibited a robust tumor suppressive effect and conferred a clear survival advantage. Co-operative antitumor effect and in vivo persistence, with unlimited availability of DRrejT therapy, will provide powerful and sustainable T cell immunotherapy.

Generation of a control human induced pluripotent stem cell line using the defective and persistent Sendai virus vector system.

The defective and persistent Sendai virus (SeVdp) vector system allows efficient generation of transgene-free induced pluripotent stem cells (iPSCs) from human somatic cells. By leveraging the system, here we report the generation of an iPSC line from somatic fibroblasts of a healthy control donner (female), named KEIOi002-A (also named YG-iPS). The control iPSC line would be a useful resource for stem cell research and regenerative medicine.

Generation of disease-specific and CRISPR/Cas9-mediated gene-corrected iPS cells from a patient with adult progeria Werner syndrome.

Adult progeria Werner syndrome (WS), a rare autosomal recessive disorder, is characterized by accelerated aging symptoms after puberty. The causative gene, WRN, is a member of the RecQ DNA helicase family and is predominantly involved in DNA replication, repair, and telomere maintenance. Here, we report the generation of iPS cells from a patient with WS and correction of the WRN gene by the CRISPR/Cas9-mediated method. These iPSC lines would be a valuable resource for deciphering the pathogenesis of WS.

Canine induced pluripotent stem cell maintenance under feeder-free and chemically-defined conditions.

Canine induced pluripotent stem cells (ciPSCs) provide a platform for regenerative veterinary medicine, disease modeling, and drug discovery. However, in the conventional method, ciPSCs are maintained using chemically-undefined media containing unknown animal components under on-murine embryonic fibroblast feeder conditions, which were reported to modify cell surface of iPSCs and increases the risk of immune rejection when the cells are transplanted into patients. Moreover, in the conventional method, ciPSCs are mechanically passaged, which requires much time and effort. Therefore, the large-scale expansion of ciPSCs is difficult, which should be resolved for using ciPSCs in clinical application and research. Here, it was shown that StemFit® AK02N and iMatrix-511 could maintain the pluripotency of ciPSCs using conventional culture method. Furthermore, it was demonstrated that the feeder-free and chemically-defined ciPSC culture systems using StemFit® AK02N and iMatrix-511 could stably maintain and allow the easy expansion of ciPSCs generated using N2B27 and StemFit® AK02N, without causing karyotype abnormalities. ciPSCs expressed several pluripotency markers and formed teratomas, including cells derived from three germ layers.

Efficient Reprogramming of Canine Peripheral Blood Mononuclear Cells into Induced Pluripotent Stem Cells.

Forced coexpression of the transcription factors Oct3/4, Klf4, Sox2, and c-Myc reprograms somatic cells into pluripotent stem cells (PSCs). Such induced PSCs (iPSCs) can generate any cell type of the adult body or indefinitely proliferate without losing their potential. Accordingly, iPSCs can serve as an unlimited cell source for the development of various disease models and regenerative therapies for animals and humans. Although canine peripheral blood mononuclear cells (PBMCs) can be easily obtained, they have a very low iPSC reprogramming efficiency. In this study, we determined the reprogramming efficiency of canine PBMCs under several conditions involving three types of media supplemented with small-molecule compounds. We found that canine iPSCs (ciPSCs) could be efficiently generated from PBMCs using N2B27 medium supplemented with leukemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF), and a small-molecule cocktail (Y-27632, PD0325901, CHIR99021, A-83-01, Forskolin, and l-ascorbic acid). We generated five ciPSC lines that could be maintained in StemFit® medium supplemented with LIF. The SeVdp(KOSM)302L vectors were appropriately silenced in four ciPSC lines. Of the two lines characterized, both were positive for alkaline phosphatase activity and expressed pluripotency markers, including the Oct3/4, Sox2, and Nanog transcripts, as well as the octamer-binding transcription factor (OCT) 3/4 and NANOG proteins, and the SSEA-1 carbohydrate antigen. The ciPSCs could form embryoid bodies and differentiate into the three germ layers, as indicated by marker gene and protein expression. Furthermore, one ciPSC line formed teratomas comprising several tissues from every germ layer. Our ciPSC lines maintained a normal karyotype even after multiple passages. Moreover, our new reprogramming method was able to generate ciPSCs from multiple donor PBMCs. In conclusion, we developed an easy and efficient strategy for the generation of footprint-free ciPSCs from PBMCs. We believe that this strategy can be useful for disease modeling and regenerative medicine in the veterinary field.

Induction of Noonan syndrome-specific human-induced pluripotent stem cells under serum-, feeder-, and integration-free conditions.

Noonan syndrome is an autosomal dominant developmental disorder. Although it is relatively common, and its phenotypical variability is well documented, its pathophysiology is not fully understood. Previously, with the aim of revealing the pathogenesis of genetic disorders, we reported the induction of cleidocranial dysplasia-specific human-induced pluripotent stem cells (hiPSCs) from patient's dental pulp cells (DPCs) under serum-free, feeder-free, and integration-free conditions. Notably, these cells showed potential for application to genetic disorder disease models. Furthermore, using similar procedures, we reported the induction of hiPSCs derived from peripheral blood mononuclear cells (PBMCs) of healthy volunteers. These methods are beneficial, because they are carried out without invasive and painful biopsies. Using those procedures, we reprogrammed DPCs and PBMCs that were derived from a patient with Noonan syndrome (NS) to establish NS-specific hiPSCs (NS-DPC-hiPSCs and NS-PBMC-hiPSCs, respectively). The induction efficiency of NS-hiPSCs was higher than that of WT-hiPSCs. We hypothesize that this was caused by high NANOG expression. Here, we describe the experimental results and findings related to NS-hiPSCs. This is the first report on the establishment of NS-hiPSCs and their disease modeling.

Regeneration of Tumor-Antigen-Specific Cytotoxic T Lymphocytes from iPSCs Transduced with Exogenous TCR Genes.

In the current adoptive T cell therapy, T cells from a patient are given back to that patient after ex vivo activation, expansion, or genetic manipulation. However, such strategy depends on the quality of the patient's T cells, sometimes leading to treatment failure. It would therefore be ideal to use allogeneic T cells as "off-the-shelf" T cells. To this aim, we have been developing a strategy where potent tumor-antigen-specific cytotoxic T lymphocytes (CTLs) are regenerated from T-cell-derived induced pluripotent stem cells (T-iPSCs). However, certain issues still remain that make it difficult to establish highly potent T-iPSCs: poor reprogramming efficiency of T cells into iPSCs and high variability in the differentiation capability of each T-iPSC clone. To expand the versatility of this approach, we thought of a method to produce iPSCs equivalent to T-iPSCs, namely, iPSCs transduced with exogenous T cell receptor (TCR) genes (TCR-iPSCs). To test this idea, we first cloned TCR genes from WT1-specific CTLs regenerated from T-iPSCs and then established WT1-TCR-iPSCs. We show that the regenerated CTLs from TCR-iPSCs exerted cytotoxic activity comparable to those from T-iPSCs against WT1 peptide-loaded cell line in in vitro model. These results collectively demonstrate the feasibility of the TCR-iPSC strategy.

4-Phenylbutyrate ameliorates apoptotic neural cell death in Down syndrome by reducing protein aggregates.

Individuals with Down syndrome (DS) commonly show unique pathological phenotypes throughout their life span. Besides the specific effects of dosage-sensitive genes on chromosome 21, recent studies have demonstrated that the gain of a chromosome exerts an adverse impact on cell physiology, regardless of the karyotype. Although dysregulated transcription and perturbed protein homeostasis are observed in common in human fibroblasts with trisomy 21, 18, and 13, whether and how this aneuploidy-associated stress acts on other cell lineages and affects the pathophysiology are unknown. Here, we investigated cellular stress responses in human trisomy 21 and 13 neurons differentiated from patient-derived induced pluripotent stem cells. Neurons of both trisomies showed increased vulnerability to apoptotic cell death, accompanied by dysregulated protein homeostasis and upregulation of the endoplasmic reticulum stress pathway. In addition, misfolded protein aggregates, comprising various types of neurodegenerative disease-related proteins, were abnormally accumulated in trisomic neurons. Intriguingly, treatment with sodium 4-phenylbutyrate, a chemical chaperone, successfully decreased the formation of protein aggregates and prevented the progression of cell apoptosis in trisomic neurons. These results suggest that aneuploidy-associated stress might be a therapeutic target for the neurodegenerative phenotypes in DS.

Sustainable Tumor-Suppressive Effect of iPSC-Derived Rejuvenated T Cells Targeting Cervical Cancers.

Immunotherapy utilizing induced pluripotent stem cell (iPSC) technology has great potential. Functionally rejuvenated cytotoxic T lymphocytes (CTLs) can survive long-term as young memory T cells in vivo, with continuous tumor eradication. Banking of iPSCs as an unlimited "off-the-shelf" source of therapeutic T cells may be feasible. To generate safer iPSCs, we reprogrammed human papilloma virus type 16 (HPV16) E6-specific CTLs by Sendai virus vector without cotransduction of SV40 large T antigen. The iPSCs efficiently differentiated into HPV16-specific rejuvenated CTLs that demonstrated robust cytotoxicity against cervical cancer. The tumor-suppressive effect of rejuvenated CTLs was stronger and more persistent than that of original peripheral blood CTLs. These rejuvenated HPV16-specific CTLs provide a sustained tumor-suppressive effect even for epithelial cancers and constitute promising immunotherapy for cervical cancer.

Generation of Footprint-Free Canine Induced Pluripotent Stem Cells from Peripheral Blood Mononuclear Cells Using Sendai Virus Vector.

Using auto-erasable Sendai virus vector, we generated ciPSC line. After several passages, virus was not present in ciPSCs by RT-PCR. ciPSCs from canine PBMCs had pluripotent state, differentiated all three germ layers in vitro, and had normal 78 XX karyotype. These results proved that PBMCs were one of the good cell sources to generate ciPSC lines from companion and patient dogs.

High Frequency Production of T Cell-Derived iPSC Clones Capable of Generating Potent Cytotoxic T Cells.

Current adoptive T cell therapies conducted in an autologous setting are costly, time-consuming, and depend on the quality of the patient's T cells, and thus it would be highly beneficial to develop an allogeneic strategy. To this aim, we have developed a method by which cytotoxic T lymphocytes (CTLs) are regenerated from induced pluripotent stem cells that are originally derived from T cells (T-iPSCs). In order to assess the feasibility of this strategy, we investigated the frequency of usable T-iPSC clones in terms of their T cell-generating capability and T cell receptor (TCR) affinity. We first established eight clones of T-iPSCs bearing different MART-1-specific TCRs from a healthy volunteer. Whereas all clones were able to give rise to mature CTLs, cell yield varied greatly, and five clones were considered to be usable. TCR affinity in the regenerated CTLs showed a large variance among the eight clones, but functional avidities measured by cytotoxic activity were almost equivalent among three selected clones representing high, medium, and low TCR affinity. In a total of 50 alloreactivity tests using five CTL clones versus ten target cells, alloreactivity was seen in only three cases. These findings collectively support the feasibility of this T-iPSC strategy.

Induction of integration-free human-induced pluripotent stem cells under serum- and feeder-free conditions.

Human-induced pluripotent stem cells (hiPSCs) have shown great potential toward practical and scientific applications. We previously reported the generation of human dental pulp stem cells using non-integrating replication-defective Sendai virus (SeVdp) vector in feeder-free culture with serum-free medium hESF9. This study describes the generation of hiPSCs from peripheral blood mononuclear cells to increase the donor population, while reducing biopsy invasiveness. From 6-d-old primary culture of peripheral blood mononuclear cells (PBMCs) with IL-2, hiPSCs were established using SeVdp(KOSM)302L with recombinant Laminin-511 E8 fragments under serum-free condition. The established PBMC-derived hiPSCs showed pluripotency and differentiation ability both in vivo and in vitro. In addition, we evaluated microarray data from PBMC- and dental pulp-derived hiPSCs. These hiPSCs will be beneficial for characterizing the molecular mechanisms of cellular differentiation and may provide useful substrates for developing cellular therapeutics.

A Sendai Virus-Based Cytoplasmic RNA Vector as a Novel Platform for Long-Term Expression of MicroRNAs.

Cytoplasmic RNA virus-derived vectors have emerged as attractive vehicles for microRNA (miRNA) delivery as they possess no potential risk of chromosomal insertion. However, their relatively short-term expression limits their use in biological applications that require long-term miRNA manipulation, such as somatic cell reprogramming. Here, we show that a cytoplasmic RNA virus vector based on a replication-defective and persistent Sendai virus (SeVdp) serves as an effective platform for long-term production of miRNAs capable of inducing sequence-specific target suppression. The SeVdp vector was able to simultaneously deliver embryonic stem cell-enriched miRNAs, as well as multiple transcription factors, into fibroblasts, resulting in effective reprogramming into induced pluripotent stem cells. Furthermore, we report that the murine miR-367 hairpin produced elevated levels of mature miRNA when it was incorporated into the SeVdp vector and served as an effective backbone for production of artificial miRNAs. These SeVdp vector-derived artificial miRNAs efficiently inhibited expression of target genes. Our findings provide novel insights into a powerful tool for long-term and targeted gene silencing in areas such as regenerative medicine, gene therapy, and cell therapy.

Elimination of protein aggregates prevents premature senescence in human trisomy 21 fibroblasts.

Chromosome abnormalities induces profound alterations in gene expression, leading to various disease phenotypes. Recent studies on yeast and mammalian cells have demonstrated that aneuploidy exerts detrimental effects on organismal growth and development, regardless of the karyotype, suggesting that aneuploidy-associated stress plays an important role in disease pathogenesis. However, whether and how this effect alters cellular homeostasis and long-term features of human disease are not fully understood. Here, we aimed to investigate cellular stress responses in human trisomy syndromes, using fibroblasts and induced pluripotent stem cells (iPSCs). Dermal fibroblasts derived from patients with trisomy 21, 18 and 13 showed a severe impairment of cell proliferation and enhanced premature senescence. These phenomena were accompanied by perturbation of protein homeostasis, leading to the accumulation of protein aggregates. We found that treatment with sodium 4-phenylbutyrate (4-PBA), a chemical chaperone, decreased the protein aggregates in trisomy fibroblasts. Notably, 4-PBA treatment successfully prevented the progression of premature senescence in secondary fibroblasts derived from trisomy 21 iPSCs. Our study reveals aneuploidy-associated stress as a potential therapeutic target for human trisomies, including Down syndrome.

Generation of three induced pluripotent stem cell lines from postmortem tissue derived following sudden death of a young patient with STXBP1 mutation.

We established three iPSC lines from postmortem-cultured fibroblasts derived following the sudden unexpected death of an 8-year-old girl with Lennox-Gastaut syndrome, who turned out to have the R551H-mutant STXBP1 gene. These iPSC clones showed pluripotent characteristics while retaining the genotype and demonstrated trilineage differentiation capability, indicating their utility in disease-modeling studies, i.e., STXBP1-encephalopathy. This is the first report on the establishment of iPSCs from a sudden death child, suggesting the possible use of postmortem-iPSC technologies as an epoch-making approach for precise identification of the cause of sudden death.

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.

Sufficiency for inducible Caspase-9 safety switch in human pluripotent stem cells and disease cells.

Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) have promising potential for opening new avenues in regenerative medicine. However, since the tumorigenic potential of undifferentiated pluripotent stem cells (PSCs) is a major safety concern for clinical transplantation, inducible Caspase-9 (iC9) is under consideration for use as a fail-safe system. Here, we used targeted gene editing to introduce the iC9 system into human iPSCs, and then interrogated the efficiency of inducible apoptosis with normal iPSCs as well as diseased iPSCs derived from patients with acute myeloid leukemia (AML-iPSCs). The iC9 system induced quick and efficient apoptosis to iPSCs in vitro. More importantly, complete eradication of malignant cells without AML recurrence was shown in disease mouse models by using AML-iPSCs. In parallel, it shed light on several limitations of the iC9 system usage. Our results suggest that careful use of the iC9 system will serve as an important countermeasure against posttransplantation adverse events in stem cell transplantation therapies.

Epigenetic-scale comparison of human iPSCs generated by retrovirus, Sendai virus or episomal vectors.

Human induced pluripotent stem cells (iPSCs) are established by introducing several reprogramming factors, such as OCT3/4, SOX2, KLF4, c-MYC. Because of their pluripotency and immortality, iPSCs are considered to be a powerful tool for regenerative medicine. To date, iPSCs have been established all over the world by various gene delivery methods. All methods induced high-quality iPSCs, but epigenetic analysis of abnormalities derived from differences in the gene delivery methods has not yet been performed. Here, we generated genetically matched human iPSCs from menstrual blood cells by using three kinds of vectors, i.e., retrovirus, Sendai virus, and episomal vectors, and compared genome-wide DNA methylation profiles among them. Although comparison of aberrant methylation revealed that iPSCs generated by Sendai virus vector have lowest number of aberrant methylation sites among the three vectors, the iPSCs generated by non-integrating methods did not show vector-specific aberrant methylation. However, the differences between the iPSC lines were determined to be the number of random aberrant hypermethylated regions compared with embryonic stem cells. These random aberrant hypermethylations might be a cause of the differences in the properties of each of the iPSC lines.