Kohyama, Jun

写真a

Affiliation

School of Medicine, Department of Physiology （Shinanomachi）

Position

Associate Professor
Page Top ▲
 

Papers 【 Display / hide 】

  • Fail-Safe System against Potential Tumorigenicity after Transplantation of iPSC Derivatives

    Itakura Go, Kawabata Soya, Ando Miki, Nishiyama Yuichiro, Sugai Keiko, Ozaki Masahiro, Iida Tsuyoshi, Ookubo Toshiki, Kojima Kota, Kashiwagi Rei, Yasutake Kaori, Nakauchi Hiromitsu, Miyoshi Hiroyuki, Nagoshi Narihito, Kohyama Jun, Iwanami Akio, Matsumoto Morio, Nakamura Masaya, Okano Hideyuki

    Stem Cell Reports 8 （ 3 ） 673 - 684 2017.03

    ISSN  2213-6711

    　View Summary

    <p>Human induced pluripotent stem cells (iPSCs) are promising in regenerative medicine. However, the risks of teratoma formation and the overgrowth of the transplanted cells continue to be major hurdles that must be overcome. Here, we examined the efficacy of the inducible caspase-9 (iCaspase9) gene as a fail-safe against undesired tumorigenic transformation of iPSC-derived somatic cells. We used a lentiviral vector to transduce iCaspase9 into two iPSC lines and assessed its efficacy in vitro and in vivo. In vitro, the iCaspase9 system induced apoptosis in approximately 95% of both iPSCs and iPSC-derived neural stem/progenitor cells (iPSC-NS/PCs). To determine in vivo function, we transplanted iPSC-NS/PCs into the injured spinal cord of NOD/SCID mice. All transplanted cells whose mass effect was hindering motor function recovery were ablated upon transduction of iCaspase9. Our results suggest that the iCaspase9 system may serve as an important countermeasure against post-transplantation adverse events in stem cell transplant therapies.</p>

  • Evaluation of the immunogenicity of human iPS cell-derived neural stem/progenitor cells in vitro

    Ozaki Masahiro, Iwanami Akio, Nagoshi Narihito, Kohyama Jun, Itakura Go, Iwai Hiroki, Nishimura Soraya, Nishiyama Yuichiro, Kawabata Soya, Sugai Keiko, Iida Tsuyoshi, Matsubayashi Kohei, Isoda Miho, Kashiwagi Rei, Toyama Yoshiaki, Matsumoto Morio, Okano Hideyuki, Nakamura Masaya

    Stem Cell Research 19   128 - 138 2017.03

    ISSN  1873-5061

    　View Summary

    <p>To achieve the goal of a first-in-human trial for human induced pluripotent stem cell (hiPSC)-based transplantation for the treatment of various diseases, allogeneic human leukocyte antigen (HLA)-matched hiPSC cell banks represent a realistic tool from the perspective of quality control and cost performance. Furthermore, considering the limited therapeutic time-window for acute injuries, including neurotraumatic injuries, an iPS cell bank is of potential interest. However, due to the relatively immunoprivileged environment of the central nervous system, it is unclear whether HLA matching is required in hiPSC-derived neural stem/progenitor cell (hiPSC-NS/PC) transplantation for the treatment of neurodegenerative diseases and neurotraumatic injuries. In this study, we evaluated the significance of HLA matching in hiPSC-NS/PC transplantation by performing modified mixed lymphocyte reaction (MLR) assays with hiPSC-NS/PCs. Compared to fetus-derived NS/PCs, the expression levels of human leukocyte antigen-antigen D related (HLA-DR) and co-stimulatory molecules on hiPSC-NS/PCs were significantly low, even with the addition of tumor necrosis factor-α (TNFα) and/or interferon-γ (IFNγ) to mimic the inflammatory environment surrounding transplanted hiPSC-NS/PCs in injured tissues. Interestingly, both the allogeneic HLA-matched and the HLA-mismatched responses were similarly low in the modified MLR assay. Furthermore, the autologous response was also similar to the allogeneic response. hiPSC-NS/PCs suppressed the proliferative responses of allogeneic HLA-mismatched peripheral blood mononuclear cells (PBMCs) in a dose-dependent manner. Thus, the low antigen-presenting function and immunosuppressive effects of hiPSC-NS/PCs result in a depressed immune response, even in an allogeneic HLA-mismatched setting. It is crucial to verify whether these in vitro results are reproducible in a clinical setting.</p>

  • Changeability of the fully methylated status of the 15q11.2 region in induced pluripotent stem cells derived from a patient with Prader-Willi syndrome

    Okuno Hironobu, Nakabayashi Kazuhiko, Abe Kousei, Ando Takayuki, Sanosaka Tsukasa, Kohyama Jun, Akamatsu Wado, Ohyama Manabu, Takahashi Takao, Kosaki Kenjiro, Okano Hideyuki

    Congenital Anomalies  2017

    ISSN  0914-3505

    　View Summary

    <p>Prader-Will syndrome (PWS) is characterized by hyperphagia, growth hormone deficiency and central hypogonadism caused by the dysfunction of the hypothalamus. Patients with PWS present with methylation abnormalities of the PWS-imprinting control region in chromosome 15q11.2, subject to parent-of-origin-specific methylation and controlling the parent-of-origin-specific expression of other paternally expressed genes flanking the region. In theory, the reversal of hypermethylation in the hypothalamic cells could be a promising strategy for the treatment of PWS patients, since cardinal symptoms of PWS patients are correlated with dysfunction of the hypothalamus. The genome-wide methylation status dramatically changes during the reprograming of somatic cells into induced pluripotent stem cells (iPSCs) and during the in vitro culture of iPSCs. Here, we tested the methylation status of the chromosome 15q11.2 region in iPSCs from a PWS patient using pyrosequencing and a more detailed method of genome-wide DNA methylation profiling to reveal whether iPSCs with a partially unmethylated status for the chromosome 15q11.2 region exhibit global methylation aberrations. As a result, we were able to show that a fully methylated status for chromosome 15q11.2 in a PWS patient could be reversed to a partially unmethylated status in at least some of the PWS-iPSC lines. Genome-wide DNA methylation profiling revealed that the partial unmethylation occurred at differentially methylated regions located in chromosome 15q11.2, but not at other differentially methylated regions associated with genome imprinting. The present data potentially opens a door to cell-based therapy for PWS patients and, possibly, patients with other disorders associated with genomic imprinting.</p>

  • Whole-Genome DNA Methylation Analyses Revealed Epigenetic Instability in Tumorigenic Human iPS Cell-Derived Neural Stem/Progenitor Cells

    Iida Tsuyoshi, Iwanami Akio, Sanosaka Tsukasa, Kohyama Jun, Miyoshi Hiroyuki, Nagoshi Narihito, Kashiwagi Rei, Toyama Yoshiaki, Matsumoto Morio, Nakamura Masaya, Okano Hideyuki

    Stem Cells  2017

    ISSN  1066-5099

    　View Summary

    <p>Although human induced pluripotent stem cell (hiPSC) derivatives are considered promising cellular resources for regenerative medicine, their tumorigenicity potentially limits their clinical application in hiPSC technologies. We previously demonstrated that oncogenic hiPSC-derived neural stem/progenitor cells (hiPSC-NS/PCs) produced tumor-like tissues that were distinct from teratomas. To gain insight into the mechanisms underlying the regulation of tumorigenicity in hiPSC-NS/PCs, we performed an integrated analysis using the Infinium HumanMethylation450 BeadChip array and the HumanHT-12 v4.0 Expression BeadChip array to compare the comprehensive DNA methylation and gene expression profiles of tumorigenic hiPSC-NS/PCs (253G1-NS/PCs) and non-tumorigenic cells (201B7-NS/PCs). Although the DNA methylation profiles of 253G1-hiPSCs and 201B7-hiPSCs were similar regardless of passage number, the methylation status of the global DNA methylation profiles of 253G1-NS/PCs and 201B7-NS/PCs differed; the genomic regions surrounding the transcriptional start site of the CAT and PSMD5 genes were hypermethylated in 253G1-NS/PCs but not in 201B7-NS/PCs. Interestingly, the aberrant DNA methylation profile was more pronounced in 253G1-NS/PCs that had been passaged more than 15 times. In addition, we identified aberrations in DNA methylation at the RBP1 gene locus; the DNA methylation frequency in RBP1 changed as 253G1-NS/PCs were sequentially passaged. These results indicate that different NS/PC clones have different DNA methylomes and that DNA methylation patterns are unstable as cells are passaged. Therefore, DNA methylation profiles should be included in the criteria used to evaluate the tumorigenicity of hiPSC-NS/PCs in the clinical setting.</p>

  • Functional Comparison of Neuronal Cells Differentiated from Human Induced Pluripotent Stem Cell-Derived Neural Stem Cells under Different Oxygen and Medium Conditions

    Yamazaki Kazuto, Fukushima Kazuyuki, Sugawara Michiko, Tabata Yoshikuni, Imaizumi Yoichi, Ishihara Yasuharu, Ito Masashi, Tsukahara Kappei, Kohyama Jun, Okano Hideyuki

    Journal of Biomolecular Screening 21 （ 10 ） 1054 - 1064 2016.12

    ISSN  1087-0571

    　View Summary

    <p>Because neurons are difficult to obtain from humans, generating functional neurons from human induced pluripotent stem cells (hiPSCs) is important for establishing physiological or disease-relevant screening systems for drug discovery. To examine the culture conditions leading to efficient differentiation of functional neural cells, we investigated the effects of oxygen stress (2% or 20% O2) and differentiation medium (DMEM/F12:Neurobasal-based [DN] or commercial [PhoenixSongs Biologicals; PS]) on the expression of genes related to neural differentiation, glutamate receptor function, and the formation of networks of neurons differentiated from hiPSCs (201B7) via long-term self-renewing neuroepithelial-like stem (lt-NES) cells. Expression of genes related to neural differentiation occurred more quickly in PS and/or 2% O2 than in DN and/or 20% O2, resulting in high responsiveness of neural cells to glutamate, N-methyl-d-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), and (S)-3,5-dihydroxyphenylglycine (an agonist for mGluR1/5), as revealed by calcium imaging assays. NMDA receptors, AMPA receptors, mGluR1, and mGluR5 were functionally validated by using the specific antagonists MK-801, NBQX, JNJ16259685, and 2-methyl-6-(phenylethynyl)-pyridine, respectively. Multielectrode array analysis showed that spontaneous firing occurred earlier in cells cultured in 2% O2 than in 20% O2. Optimization of O2 tension and culture medium for neural differentiation of hiPSCs can efficiently generate physiologically relevant cells for screening systems.</p>

display all >>

Page Top ▲

Papers, etc., Registered in KOARA 【 Display / hide 】

Page Top ▲

Research Projects of Competitive Funds, etc. 【 Display / hide 】

  • Unraveling mechanism of pathogenesis in CHAREGE syndrome using iPSC-derived brain organoid

    2019.04
    -
    2024.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Principal investigator

  • Development of new technology to analyze cellular interaction between neuron and glial cells

    2016.04
    -
    2018.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Challenging Exploratory Research, Principal investigator

  • Crosstalk between immune system and nervous system in the pathogenesis of spinal cord injury

    2014.04
    -
    2018.03

    MEXT,JSPS, Grant-in-Aid for Scientific Research, Grant-in-Aid for Young Scientists (A), Principal investigator

Page Top ▲
 

Courses Taught 【 Display / hide 】

  • PHYSIOLOGY 2

    2024

  • MCB(MOLECULAR CELL BIOLOGY)

    2024

  • PHYSIOLOGY 2

    2023

  • MCB(MOLECULAR CELL BIOLOGY)

    2023

  • HUMAN ANATOMY AND PHYSIOLOGY

    2023

display all >>

Page Top ▲