Hiroshi Wakao

Hokkaido University, Sapporo-shi, Hokkaido, Japan

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Publications (60)358.68 Total impact

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    Hiroshi Wakao, Hiroyoshi Fujita
    Cell cycle (Georgetown, Tex.) 07/2013; 12(15). · 5.24 Impact Factor
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    ABSTRACT: Mucosal-associated invariant T (MAIT) cells play an important physiological role in host pathogen defense and may also be involved in inflammatory disorders and multiple sclerosis. The rarity and inefficient expansion of these cells have hampered detailed analysis and application. Here, we report an induced pluripotent stem cell (iPSC)-based reprogramming approach for the expansion of functional MAIT cells. We found that human MAIT cells can be reprogrammed into iPSCs using a Sendai virus harboring standard reprogramming factors. Under T cell-permissive conditions, these iPSCs efficiently redifferentiate into MAIT-like lymphocytes expressing the T cell receptor Vα7.2, CD161, and interleukin-18 receptor chain α. Upon incubation with bacteria-fed monocytes, the derived MAIT cells show enhanced production of a broad range of cytokines. Following adoptive transfer into immunocompromised mice, these cells migrate to the bone marrow, liver, spleen, and intestine and protect against Mycobacterium abscessus. Our findings pave the way for further functional analysis of MAIT cells and determination of their therapeutic potential.
    Cell stem cell 03/2013; · 23.56 Impact Factor
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    ABSTRACT: The metabolic syndrome is an important social problem affecting many people in developed countries. Obesity is a leading cause of this syndrome, hence understanding molecular mechanisms underlying obesity is of prime importance for preventive medicine to develop novel methods to alleviate the corresponding social cost as well as for pharmaceutical companies to develop antimetabolic drugs. Since adipocytes play an important role in obesity, we explored the signaling pathways leading to differentiation of adipocytes. We used a preadipocyte cell line to monitor the differentiation of adipocytes, and virus-mediated gene transfer to assess the role of the transcription factor Stat5 in adipogenesis. Adipocyte differentiation was assessed by Northern blot and Western blot analyses as well as accumulation of fat droplets in cells. Promoter activity of the proadipogenic transcription factor peroxisome proliferator-activated receptor-gamma (PPARγ) was evaluated by luciferase assay. Virus-mediated gene transfer of the constitutively active form of both Stat5A and Stat5B resulted in enhanced adipocyte differentiation in the absence of fetal bovine serum (FBS) as judged by expression of proadipogenic factors as well as accumulation of fat droplets in cells. Such a proadipogenic effect of Stat5 is, in part, mediated by its ability to enhance transcription of PPARγ, a master transcriptional regulator in adipogenesis. The constitutively active form of Stat5A and Stat5B promoted adipocyte differentiation in the absence of FBS via induction of PPARγ.
    Environmental Health and Preventive Medicine 12/2010; 16(4):247-52.
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    ABSTRACT: Leptin, the product of the ob gene, plays important roles in the regulation of food intake and body weight through its receptor in the hypothalamus. To identify novel transcripts induced by leptin, we performed cDNA subtraction based on selective suppression of the polymerase chain reaction by using mRNA prepared from the forebrain of leptin-injected ob/ob mice. One of the genes isolated was a mouse homolog of human negative regulatory element-binding protein (NREBP). Its expression was markedly increased by leptin in the growth hormone secretagogue-receptor (GHS-R)-positive neurons of the arcuate nucleus and ventromedial hypothalamic nucleus. The promoter region of GHS-R contains one NREBP binding sequence, suggesting that NREBP regulates GHS-R transcription. Luciferase reporter assays showed that NREBP repressed GHS-R promoter activity in a hypothalamic neuronal cell line, GT1-7, and its repressive activity was abolished by the replacement of negative regulatory element in GHS-R promoter. Overexpression of NREBP reduced the protein expression of endogenous GHS-R without affecting the expression of ob-Rb in GT1-7 cells. To determine the functional importance of NREBP in the hypothalamus, we assessed the effects of NREBP on ghrelin action. Although phosphorylation of AMP-activated protein kinase α (AMPKα) was induced by ghrelin in GT1-7 cells, NREBP repressed ghrelin-induced AMPKα phosphorylation. These results suggest that leptin-induced NREBP is an important regulator of GHS-R expression in the hypothalamus and provides a novel molecular link between leptin and ghrelin signaling.
    Journal of Biological Chemistry 09/2010; 285(48):37884-94. · 4.65 Impact Factor
  • Hiroshi Wakao
    Seikagaku. The Journal of Japanese Biochemical Society 05/2009; 81(4):277-89. · 0.04 Impact Factor
  • Hiroshi Wakao
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    ABSTRACT: The recent discovery that natural killer T (NKT) cell nuclei are totipotent opens a novel avenue for further understanding NKT cell function in normal and diseased states. The progeny of a cloned mouse harboring the in-frame rearranged Valpha14-Jalpha18 T cell receptor in one allele showed a significant increase in NKT cell number compared with wild-type or littermate control mice that possessed a different TCR. Importantly, NKT cells from such progeny produced both interferon-gamma and interleukin-4, a hallmark of NKT cells. In these progeny, NKT cell development appeared to be instructively, rather than permissively, determined. Using embryonic stem cells prepared via the somatic cell nuclear transfer of NKT nuclei, relatively mature NKT cells were induced under conditions permissible for T cell induction. Furthermore, these NKT cells matured autonomously upon injection into mice, resulting in an antigen-specific adjuvant effect.
    Archivum Immunologiae et Therapiae Experimentalis 01/2009; 57(2):117-28. · 2.38 Impact Factor
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    ABSTRACT: The ectopic expression of the Notch receptor ligand delta-like 1 on stromal cells allows the induction of T cells from embryonic stem cells (ESCs). However, these in vitro-generated T cells are not transplantable because they are too immature to mount an immune response in an immunocompromised animal. We efficiently generated a subset of T cells called invariant natural killer T (iNKT) cells from ESCs derived from peripheral iNKT cells using somatic cell nuclear transfer (ntESCs). These iNKT cells matured autonomously in vivo and exhibited an adjuvant effect accompanying the production of interferon-gamma in an antigen-specific manner. This adjuvant effect culminated in the inhibition of inoculated tumor cell growth. Our results indicate that ntESC-derived iNKT cells are transplantable lymphocytes that will be beneficial for the induction of immune tolerance and the treatment of autoimmune diseases, tumors, and infections.
    The FASEB Journal 08/2008; 22(7):2223-31. · 5.70 Impact Factor
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    ABSTRACT: We have generated a novel mouse model harboring the in-frame rearranged TCRValpha specific for invariant NKT (iNKT) cells (Valpha14-Jalpha18) on one allele by crossing the mouse cloned from NKT cells with wild-type mice. This genomic configuration would ensure further rearrangement and expression of TCRValpha14-Jalpha18 under the endogenous promoters and enhancers. Mice harboring such an in-frame rearranged TCRValpha (Valpha14-Jalpha18 mouse) possessed an increase in iNKT cells in the thymus, liver, spleen, and bone marrow. Intriguingly, both Th1- and Th2-type cytokines were produced upon stimulation with alphaGalactosylceramide, an agonist of iNKT cells, and the IgE level in the serum remained unaffected in the Valpha14-Jalpha18 mouse. These features markedly distinguish the nature of iNKT cells present in the Valpha14-Jalpha18 mouse from that of iNKT cells found in the Valpha14-Jalpha18 transgenic mouse. Besides these, the expression of TCRVgammadelta cells remained intact, and the use of the TCRVbeta repertoire in iNKT cells was highly biased to TCRVbeta8 in the Valpha14-Jalpha18 mouse. Furthermore, alphaGalactosylceramide-CD1d dimer-reactive immature iNKT cells expressed less Rag2 as compared with the conventional immature T cells at the positive selection stage. Cell cycle analysis on the thymocytes revealed that no particular subset proliferated more vigorously than the others. Crossing the Valpha14-Jalpha18 mouse with the CD1d knockout mouse revealed a novel population of iNKT cells whose coreceptor expression profile was similar to that assigned to iNKT precursor cells. These mice will be useful for the study on the development of iNKT cells as well as on their functions in the immune system.
    The Journal of Immunology 10/2007; 179(6):3888-95. · 5.52 Impact Factor
  • Hiroshi Wakao
    Seikagaku. The Journal of Japanese Biochemical Society 06/2007; 79(5):446-9. · 0.04 Impact Factor
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    ABSTRACT: In mouse liver transplantation, tolerance is readily inducible. Recent studies have revealed that CD25+ CD4+ regulatory T cells play an important role in regulating various immune responses, including transplant tolerance. However, the contribution of these cells to tolerance in mouse liver transplantation has not been elucidated. We showed here that depletion of CD25+ CD4+ T cells increased proliferative response of CD4+ T cells and cytotoxic T lymphocyte induction of CD8+ T cells. Depletion of these cells in the recipient but not in the donor before liver transplantation caused rejection. Furthermore, the number of CD25+ CD4+ population and forkhead/winged helix transcription factor expression in liver mononuclear lymphocytes derived from tolerant mice were higher than those from grafts undergoing rejection. In conclusion, these results indicate that CD25+ CD4+ regulatory T cells in the recipient but not in the donor of liver transplantation are important for the tolerance induction.
    Liver Transplantation 08/2006; 12(7):1112-8. · 3.94 Impact Factor
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    ABSTRACT: Valpha14 NKT cells exhibit various immune regulatory properties in vivo, but their precise mechanisms remain to be solved. In this study, we demonstrate the mechanisms of generation of regulatory dendritic cells (DCs) by stimulation of Valpha14 NKT cells in vivo. After repeated injection of alpha-galactosylceramide (alpha-GalCer) into mice, splenic DCs acquired properties of regulatory DCs in IL-10-dependent fashion, such as nonmatured phenotypes and increased IL-10 but reduced IL-12 production. The unique cytokine profile in these DCs appears to be regulated by ERK1/2 and IkappaB(NS). These DCs also showed an ability to suppress the development of experimental allergic encephalomyelitis by generating IL-10-producing regulatory CD4 T cells in vivo. These findings contribute to explaining how Valpha14 NKT cells regulate the immune responses in vivo.
    The Journal of Immunology 10/2005; 175(6):3648-55. · 5.52 Impact Factor
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    ABSTRACT: It is well-documented that certain chemokines or their receptors play important roles in the graft rejection. However, the roles of chemokines and their receptors in the maintenance of transplantation tolerance remain unclear. In this study, we demonstrate that blocking of the interaction between the chemokine receptor, CXCR6, highly expressed on V alpha14+ NKT cells and its ligand, CXCL16, resulted in the failure to maintain graft tolerance and thus in the induction of acceleration of graft rejection. In a mouse transplant tolerance model, the expression of CXCL16 was up-regulated in the tolerated allografts, and anti-CXCL16 mAb inhibited intragraft accumulation of NKT cells. In vitro experiments further showed that blocking of CXCL16/CXCR6 interaction significantly affected not only chemotaxis but also cell adhesion of NKT cells. These results demonstrate the unique role of CXCL16 and CXCR6 molecules in the maintenance of cardiac allograft tolerance mediated by NKT cells.
    The Journal of Immunology 09/2005; 175(4):2051-5. · 5.52 Impact Factor
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    ABSTRACT: Cloning mammals by nuclear transfer (NT) remains inefficient. One fundamental question is whether clones have really been derived from differentiated cells rather than from rare stem cells present in donor-cell samples. To date, cells, such as mature lymphocytes, with genetic differentiation markers have been cloned to generate mice only via a two-step NT involving embryonic stem (ES) cell generation and tetraploid complementation [1, 2 and 3]. Here, we show that the genome of a unique T-cell population, natural killer T (NKT) cells, can be fully reprogrammed by a single-step NT. The pups and their placentas possessed the rearranged TCR loci specific for NKT cells. The NKT-cell-cloned embryos had a high developmental potential in vitro: Most (71%) developed to the morula/blastocyst stage, in marked contrast to embryos from peripheral blood T cells (12%; p < 1 x 10(-25)). Furthermore, ES cell lines were efficiently established from these NKT-cell blastocysts. These findings clearly indicate a high level of plasticity in the NKT-cell genome. Thus, differentiation of the genome is not always a barrier to NT cloning for either reproductive or therapeutic purposes, so we can now postulate that at least some mammals cloned to date have indeed been derived from differentiated donor cells.
    Current Biology 07/2005; 15(12):1114-8. · 9.49 Impact Factor
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    ABSTRACT: Natural killer (NK) cells play a pivotal role in the immune reaction during the bone marrow allograft rejection. Little is known, however, about the molecular mechanisms underlying the NK cell-mediated allograft recognition and rejection. In this report, we assessed the role of a recently identified NK receptor, killer cell lectinlike receptor 1 (KLRE-1), by generating knock-out mice. KLRE-1-deficient mice were born at an expected frequency and showed no aberrant phenotype on growth and lymphoid development. Nevertheless, KLRE-1-deficient cells showed a severely compromised allogeneic cytotoxic activity compared with the wild-type cells. Furthermore, allogeneic bone marrow transfer culminated in colony formation in the spleen of KLRE-1-deficient mice, whereas no colony formation was observed in wild-type recipient mice. These results demonstrate that KLRE-1 is a receptor mediating recognition and rejection of allogeneic target cells in the host immune system.
    Blood 09/2004; 104(3):781-3. · 9.78 Impact Factor
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    ABSTRACT: NKT cells expressing the invariant Valpha14 antigen receptor constitute a novel lymphocyte subpopulation with immunoregulatory functions. Stimulation via their invariant Valpha14 receptor with anti-CD3 or a ligand, alpha-galactosylceramide (alpha-GalCer), triggers activation of Valpha14 NKT cells, resulting in a rapid cytokine production such as IFN-gamma and IL-4. Soon after their receptor activation, Valpha14 NKT cells disappeared as judged by staining with CD1d tetramer loaded with alpha-GalCer (alpha-GalCer/CD1d tetramer), which has been believed to be due to apoptotic cell death. Here we show that such a disappearance was largely attributed to down-regulation of the Valpha14 receptor. In fact, Valpha14 NKT cells were relatively resistant to apoptosis compared to the conventional T cells as evidenced by less staining with Annexin-V, a limited DNA fragmentation, and their preferential expression of anti-apoptotic genes such as NAIP and MyD118. Furthermore, they did not become tolerant, and maintained their proliferative capacity and cytokine production even after their receptor down-regulation. These as yet unrecognized facets of Valpha14 NKT cells are discussed in relation to their regulatory functions.
    International Immunology 03/2004; 16(2):241-7. · 3.14 Impact Factor
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    ABSTRACT: Sarcoidosis is a systemic disorder associated with granuloma characterized by an abnormal T(h)1-type cytokine production and accumulation of T(h)1 CD4 T cells in the granuloma lesions, suggesting an importance of T(h)1 responses in sarcoidosis. However, the pathogenesis of sarcoidosis remains to be solved. Here, we investigated the nature of V(alpha)24 NKT cells with immunoregulatory functions in sarcoidosis. Patients with non-remitting sarcoidosis displayed a decrease in the number of V(alpha)24 NKT cells in peripheral blood, but an accumulation of these cells in granulomatous lesions. When stimulated with the specific glycolipid ligand, alpha-galactosylceramide, peripheral blood V(alpha)24 NKT cells from patients with non-remitting disease produced significantly less IFN-gamma than those from healthy volunteers, but normal levels of IL-4. The reduced IFN-gamma production was observed only in V(alpha)24 NKT cells and not conventional CD4 T cells, but was normal in patients with remitting disease, suggesting that non-remitting sarcoidosis involves an insufficient IFN-gamma production of V(alpha)24 NKT cells which is well correlated with disease activity. Thus, these results suggest that V(alpha)24 NKT cells play a crucial role in the disease status of sarcoidosis.
    International Immunology 03/2004; 16(2):215-22. · 3.14 Impact Factor
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    ABSTRACT: Natural killer (NK) cells mediate bone marrow allograft rejection. However, the molecular mechanisms underlying such a rejection remain elusive. In previous analyses, it has been shown that NK cells recognize allogeneic target cells through Ly-49s and CD94/NKG2 heterodimers. Here, we describe identification and characterization of a novel murine NK receptor, NKG2I, belonging to the NKG2 family. NKG2I, which was composed of 226 amino acids, showed approximately 40% homology to the murine NKG2D and CD94 in the C-type lectin domain. Flow cytometric analysis with anti-NKG2I monoclonal antibody (mAb) revealed that expression of NKG2I was largely confined to NK and NKT cells, but was not seen in T cells. Furthermore, anti-NKG2I mAb inhibited NK cell-mediated cytotoxicity, whereas cross-linking of NKG2I enhanced interleukin 2- and interleukin 12-dependent interferon-gamma production. Similarly, the injection of anti-NKG2I mAb before the allogeneic bone marrow transfer in vivo impinged on the function of NKG2I, resulting in the enhanced colony formation in the spleen. NKG2I is a novel activating receptor mediating recognition and rejection of allogeneic target cells.
    Journal of Experimental Medicine 02/2004; 199(1):137-44. · 13.21 Impact Factor
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    ABSTRACT: Sarcoidosis is a systemic disorder associated with granuloma characterized by an abnormal Th1-type cytokine production and accumulation of Th1 CD4 T cells in the granuloma lesions, suggesting an importance of Th1 responses in sarcoidosis. However, the pathogenesis of sarcoidosis remains to be solved. Here, we investigated the nature of Va24 NKT cells with immunoregulatory functions in sarcoidosis. Patients with non-remitting sarcoidosis displayed a decrease in the number of Va24 NKT cells in peripheral blood, but an accumulation of these cells in granulomatous lesions. When stimulated with the specific glycolipid ligand, a-galactosylceramide, peripheral blood Va24 NKT cells from patients with non-remitting disease produced significantly less IFN-g than those from healthy volunteers, but normal levels of IL-4. The reduced IFN-g production was observed only in Va24 NKT cells and not conventional CD4 T cells, but was normal in patients with remitting disease, suggesting that non-remitting sarcoidosis involves an insufficient IFN-g production of Va24 NKT cells which is well correlated with disease activity. Thus, these results suggest that Va24 NKT cells play a crucial role in the disease status of
    International Immunology - INT IMMUNOL. 01/2004; 16(2):215-222.
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    ABSTRACT: NKT cells expressing the invariant Va14 antigen receptor constitute a novel lymphocyte subpopulation with immunoregulatory functions. Stimulation via their invariant Va14 receptor with anti-CD3 or a ligand, a-galactosylceramide (a-GalCer), triggers activation of Va14 NKT cells, resulting in a rapid cytokine production such as IFN-g and IL-4. Soon after their receptor activation, Va14 NKT cells disappeared as judged by staining with CD1d tetramer loaded with a-GalCer (a- GalCer/CD1d tetramer), which has been believed to be due to apoptotic cell death. Here we show that such a disappearance was largely attributed to down-regulation of the Va14 receptor. In fact, Va14 NKT cells were relatively resistant to apoptosis compared to the conventional T cells as evidenced by less staining with Annexin-V, a limited DNA fragmentation, and their preferential expression of anti-apoptotic genes such as NAIP and MyD118. Furthermore, they did not become tolerant, and maintained their proliferative capacity and cytokine production even after their receptor down-regulation. These as yet unrecognized facets of Va14 NKT cells are discussed in relation to their regulatory functions.
    International Immunology - INT IMMUNOL. 01/2004; 16(2):241-247.
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    ABSTRACT: Recombination-activating gene (RAG) 1 and 2 are essential for the gene rearrangement of antigen receptors of both T and B cells. To investigate RAG gene expression in peripheral lymphoid organs other than the thymus and bone marrow, we established mice in which a green fluorescent protein (GFP) gene is knocked-in the RAG2 gene locus (RAG2-GFP mice). In the thymus and bone marrow of heterozygous RAG2-GFP mice, as expected, GFP expression was detected in the appropriate stages of developing T and B cells. Interestingly, only a fraction of Thy-1.2(+) cells in the Peyer's patch were found to be GFP(+) amongst the peripheral lymphoid organs. The GFP(+) cells expressed high levels of surface TCRbeta and CD3, suggesting mature T cells with rearranged TCRalphabeta. However, they showed activated/memory phenotypes, i.e. CD45RB(low), CD69(high), CD44(high) and CD62L(low), and belonged to a CD4(+)CD8(+) population expressing c-kit, IL-7R and pTalpha characteristic of immature developing lymphocytes. Moreover, RAG(+) Peyer's patch T cells seem to be of thymic origin as judged by their expression of CD8alphabeta. These results show that there exists a fraction of mature T cells expressing RAG genes in the Peyer's patch, implying a potential for a secondary rearrangement of TCR in extrathymic tissues.
    International Immunology 04/2003; 15(3):393-402. · 3.14 Impact Factor

Publication Stats

3k Citations
358.68 Total Impact Points

Institutions

  • 2007–2013
    • Hokkaido University
      • Department of Environmental Biology
      Sapporo-shi, Hokkaido, Japan
  • 2003–2004
    • Chiba University
      • Graduate School of Medicine
      Chiba-shi, Chiba-ken, Japan
  • 2002
    • Hokkaido University Hospital
      Sapporo, Hokkaidō, Japan
  • 2000
    • Osaka University
      • Division of Hematology and Oncology
      Ōsaka-shi, Osaka-fu, Japan
  • 1998
    • The University of Tokyo
      • Institute of Molecular and Cellular Biosciences
      Tokyo, Tokyo-to, Japan
  • 1995
    • Palo Alto Institute for Research and Education
      Palo Alto, California, United States
  • 1994–1995
    • Clinic for Tumor Biology Freiburg
      Freiburg, Baden-Württemberg, Germany
  • 1992–1995
    • Friedrich Miescher Institute for Biomedical Research
      Bâle, Basel-City, Switzerland