Ryusuke Nakatsuka

Kansai Medical University, Moriguchi, Ōsaka, Japan

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Publications (11)48.85 Total impact

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    ABSTRACT: The identification of human CD34-negative (CD34(-)) hematopoietic stem cells (HSCs) provides a new concept for the hierarchy in the human HSC compartment. Previous studies demonstrated that CD34(-) SCID-repopulating cells (SRCs) are a distinct class of primitive HSCs in comparison to the well-characterized CD34(+)CD38(-) SRCs. However, the purification level of rare CD34(-) SRCs in 18 lineage-negative (Lin(-)) CD34(-) cells (1/1,000) is still very low compared to that of CD34(+)CD38(-) SRCs (1/40). As in the mouse, it will be necessary to identify useful positive markers for a high degree of purification of rare human CD34(-) SRCs. Using 18Lin(-)CD34(-) cells, we analyzed the expression of candidate positive markers by FCM. We finally identified CD133 as a reliable positive marker of human CB-derived CD34(-) SRCs and succeeded in highly purifying primitive human CD34(-) HSCs. The limiting dilution analysis demonstrated that the incidence of CD34(-) SRCs in 18Lin(-)CD34(-)CD133(+) cells was 1/142, which is the highest level of purification of these unique CD34(-) HSCs to date. Furthermore, CD133 expression clearly segregated the SRC activities of 18Lin(-)CD34(-) cells, as well as 18Lin(-)CD34(+) cells, in their positive fractions, indicating its functional significance as a common cell surface maker to effectively isolate both CD34(+) and CD34(-) SRCs.Leukemia accepted article preview online, 5 November 2013; doi:10.1038/leu.2013.326.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 11/2013; · 10.16 Impact Factor
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    ABSTRACT: It is well documented that specialized mesenchymal stem/stromal cells (MSCs) constitute the hematopoietic stem cell (HSCs) niche in the bone marrow (BM), and these MSCs support/maintain the HSCs in an undifferentiated state. A number of studies have demonstrated that BM-derived MSCs (BM-MSCs) can support HSCs in vitro. However, it remains unclear whether non-hematopoietic tissue-derived MSClike cells, such as dental pulp stem cells(DPSCs), have an HSC-supporting activity. In this study, we prospectively isolated DPSCs from mouse mandibular incisors by fluorescence-activated cell sorting (FACS)using the BM-MSC markers, such as PDGFR? and Sca-1. The PDGFR? and Sca-1 double-positive DPSCs and BMMSCs showed similar morphologies and expression patterns of MSC markers. The ability of the DPSCs to support hematopoietic stem/progenitor cells (HSPCs) was then analyzed by an in vitro co-culture system. Moreover, their HSC-supporting activity was evaluated by in vivo xenotransplantation assays using NOD/Shi-scid/IL-2R?c(null) (NOG) mice. Interestingly, the DPSCs supported human cord blood (CB)-derived CD34-positive (CD34(+)), as well as CD34-negative (CD34(-)), HSCs. The supporting activities of DPSCs for human CB-derived CD34(+)and CD34(-)HSCs were comparable to those of BM-MSCs. The results of the present study demonstrated, for the first time, that prospectively isolated murine PDGFR? and Sca-1 double-positive DPSCs could support primitive human CD34(+) and CD34(-)HSCs in vitro.
    Cell Transplantation 10/2013; · 4.42 Impact Factor
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    ABSTRACT: Although c-kit is expressed highly on murine hematopoietic stem cells (HSCs) and essential for bone marrow (BM) hematopoiesis, the significance of the high level of expression of c-kit on HSCs was not well determined. We show here that CD150(+) CD48(-) Lineage(-) Sca-1(+) c-kit(+) HSCs in adult BM are distributed within the range of roughly a 20-fold difference in the expression level of c-kit, and that c-kit density correlates with the cycling status of the HSC population. This predisposition is more evident in the BM of mice older than 30 weeks. The HSCs in G(0) phase express a lower level of c-kit both on the cell surface and inside the cells, which cannot be explained by ligand receptor binding and internalization. It is more likely that the low level of c-kit expression is a unique property of HSCs in G(0). Despite functional differences in the c-kit gradient, the HSCs are uniformly hypoxic and accessible to blood perfusion. Therefore, our data indicate the possibility that the hypoxic state of the HSCs is actively regulated, rather than them being passively hypoxic through a simple anatomical isolation from the circulation.
    Stem Cells 09/2011; 29(11):1783-91. · 7.70 Impact Factor
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    ABSTRACT: We have successfully identified human cord blood (CB)-derived CD34-negative (CD34(-)) severe combined immunodeficiency (SCID)-repopulating cells (SRCs) with extensive lymphomyeloid repopulating ability using the intrabone marrow injection method. In our previous study, a limiting dilution analysis demonstrated the frequency of CD34(-) SRCs in CB-derived 13lineage-negative (Lin(-)) CD34(-) cells to be approximately 1/25,000. In this study, we intended to develop a high-resolution purification method to obtain highly purified CD34(-) SRCs. The pooled CB-derived Lin(-) cells were stained with 13 reported Lin monoclonal antibodies (mAbs) and 5 more Lin mAb, against CD11b, CD33, CD66c, CD45RA, and CD127. Then 18Lin(-)CD34(high), 18Lin(-)CD34(-), and 13Lin(-)CD34(high)CD38(-) cells were sorted by fluorescence-activated cell sorting. Stem cell characteristics of these three fractions of cells were analyzed by in vitro cultures and in vivo repopulation assays for evaluation of this new purification method. A limiting dilution analysis demonstrated the frequency of CD34(-) SRCs in these 18Lin(-)CD34(-) cells to be approximately 1/1,000, which is associated with a seeding efficiency 25 times greater than the previous method. All primary recipient nonobese diabetic/Shi-scid/IL-2Rγc(null) mice that received transplants of only two CD34(-) SRCs were highly engrafted with human lymphomyeloid cells at 24 weeks after primary transplantation and showed secondary multilineage repopulating abilities. We succeeded to highly purify the CD34(-) SRCs using 18Lin mAbs and the intrabone marrow injection technique. This newly developed high-resolution purification method is indispensable to precisely characterize a distinct class of primitive human CB-derived CD34(-) hematopoietic stem cells.
    Experimental hematology 02/2011; 39(2):203-213.e1. · 3.11 Impact Factor
  • International journal of hematology 01/2011; 93(1):123-5. · 1.17 Impact Factor
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    ABSTRACT: OECs (outgrowth endothelial cells), also known as late-EPCs (late-endothelial progenitor cells), have a high proliferation potential in addition to in vitro tube formation capability. In ischaemic animal models, injected OECs were integrated into regenerating blood vessels and improved neovascularization. Previous reports have demonstrated the expression of CXCL8 to be up-regulated in ischaemic tissues. It has also been documented that CXCL8 stimulates the angiogenic activity of mature ECs (endothelial cells). Therefore, it has been suggested that CXCL8 plays an important role in neovascularization in ischaemic tissues. However, it is still uncertain whether CXCL8 also stimulates the angiogenic activity of OECs. This study evaluated the effects of CXCL8 on the angiogenic activity of OECs in vitro. OECs were isolated from human UCB (umbilical cord blood)-derived mononuclear cells. Phenotypes of the OECs were assessed by flow cytometry, immunostaining, and real-time RT (reverse transcription)-PCR. The effects of CXCL8 on OECs were investigated by transwell migration assay and capillary tube formation assay on Matrigel. The OEC clones isolated from UCB expressed OEC phenotypes. In addition, CXCL8 receptors (CXCR1 and CXCR2) were expressed on these OEC clones. CXCL8 significantly stimulated the transwell migration and capillary tube formation of OECs. Neutralizing antibody against CXCR2, but not CXCR1, abolished a transwell migration of OECs induced by CXCL8, suggesting the involvement of CXCL8/CXCR2 axis in transwell migration. These results demonstrate that CXCL8 stimulates the angiogenic activity of UCB-derived OECs in vitro.
    Cell Biology International 10/2010; 35(3):201-8. · 1.64 Impact Factor
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    ABSTRACT: Tissue stem cells in dental pulp are assumed to possess differentiation potentials similar to mesenchymal stem cells (MSCs). The aim of this in vitro study is to examine the differentiation potentials of mouse dental pulp stem cells (DPSCs) and develop the appropriate differentiation assay systems for skeletal myogenic differentiation of these cells. Dental pulps were extracted from mandible sections of C57/BL6 mice, and adherent dental pulp cells were isolated in culture. These cells were cultured in osteogenic or adipogenic induction medium to induce osteogenic and adipogenic differentiation. On the other hand, the skeletal myogenic differentiation potential of these cells was investigated using different conditions, such as serum-free medium, Myod1 overexpression, or 5-Aza-2'-deoxycytidine (5-Aza) treatment for DNA demethylation. Muscle-specific transcriptional factor expression was evaluated by RT-PCR, and myotube formation and myosin heavy chain expression were evaluated by phase-contrast microscopy and immunofluorescence staining, respectively. The adherent dental pulp cells exhibited a proliferative capacity and they showed osteogenic and adipogenic differentiation as seen in previous studies. Although the expression of Myod1 mRNA and myotube formation was not detected in serum-free conditions, the forced expression of Myod1 up-regulated the expression of Myogenin and Pax7 mRNA. However, myotube formation was not confirmed. Interestingly, myosin heavy chain expression and myotube formation were observed following 5-Aza treatment of these cells. These results demonstrated that mouse DPSCs possess MSC-like differentiation potential. DNA demethylation induced by 5-Aza treatment resulted in the skeletal muscle differentiation in mouse DPSCs, suggesting that DNA demethylation might trigger this differential induction of mouse DPSCs.
    Archives of oral biology 03/2010; 55(5):350-7. · 1.65 Impact Factor
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    ABSTRACT: Dilazep dihydrochloride (dilazep) is used to treat ischemic dysfunction, although the mechanisms underlying the anti-inflammatory effects of the drug have not yet been elucidated. The present study evaluated the anti-inflammatory effect of dilazep. Dilazep suppressed the production of nitric oxide (NO) and the expression of TNF-alpha mRNA by lipopolysaccharide (LPS) in RAW 264 cells. However, 1400W, an inducible NO synthase inhibitor, suppressed the production of NO but did not suppress the expression of TNF-alpha mRNA following treatment with LPS. Caffeine, an adenosine antagonist, restored LPS-stimulated NO synthesis, which is suppressed by dilazep. Therefore, these observations may suggest that the suppression of NO synthesis after dilazep treatment in RAW 264 cells is caused by the inhibition of TNF-alpha expression via adenosine receptors.
    Journal of Pharmacological Sciences 01/2010; 113(3):271-5. · 2.15 Impact Factor
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    ABSTRACT: Stromal cell-derived factor 1 (SDF-1) and its receptor CXCR4 are the key regulatory molecules of hematopoietic stem cell (HSC) migration and engraftment to the bone marrow (BM) microenvironment. However, the significance of the ligand-receptor complex on HSC in steady-state BM is not clear. There is currently a lack of information as to how CXCR4 is expressed on HSCs. We herein demonstrate that c-kit(+)Sca-1(+)Lineage(-) (KSL) cells freshly isolated from BM expressed very low to undetectable levels of CXCR4. Two hours of incubation at 37 degrees C quickly up-modulated the receptor expression on KSL cells. Protein synthesis was not required for this early stage up-regulation, thus suggesting the emergence of intracellularly pooled receptors to the cell surface. However, protein synthesis was involved at the later stage of up-regulation. The up-regulated CXCR4 was functional, as evidenced by the fact that the incubated KSL cells more efficiently migrated to the SDF-1 gradient in vitro. Therefore, although KSL cells are able to express functional CXCR4, the receptors are only marginally expressed in the steady-state BM microenvironment. These observations therefore indicate the limited role of the SDF-1-CXCR4 axis on HSC functionality in a static BM environment.
    International journal of hematology 11/2009; 90(5):553-60. · 1.17 Impact Factor
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    ABSTRACT: The identification of human CD34-negative (CD34(-)) hematopoietic stem cells (HSCs) provides a new concept for the hierarchy in the human HSC compartment. This study investigated the long-term repopulating capacity and redistribution kinetics of human cord blood-derived CD34(-) severe combined immunodeficiency (SCID)-repopulating cells (SRCs) and compared them with those of CD34(+)CD38(+) and CD34(+)CD38(-) SRCs using the intra-bone marrow injection (IBMI) to clarify the characteristics of CD34(-) SRCs. On the basis of the limiting dilution analyses data, estimated numbers of CD34(+)CD38(+), CD34(+)CD38(-), and CD34(-) SRCs were transplanted to NOD/SCID mice by IBMI. The human cell repopulation at the site of injection and the other bones were serially investigated. Interestingly, CD34(+)CD38(+), CD34(+)CD38(-), and CD34(-) SRCs began to migrate to other bones 2 and 5 weeks after the transplantation, respectively. Accordingly, the initiation of migration seemed to differ between the CD34(+) and CD34(-) SRCs. In addition, CD34(+)CD38(+) SRCs only sustained a short-term repopulation. However, both CD34(+)CD38(-) and CD34(-) SRCs had longer-term repopulation capacity. Taken together, these findings showed that CD34(-) SRCs show different in vivo kinetics, thus suggesting that the identified CD34(-) SRCs are a distinct class of primitive HSCs in comparison to the CD34(+)CD38(+) and CD34(+)CD38(-) SRCs.
    Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 10/2009; 24(1):162-8. · 10.16 Impact Factor
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    ABSTRACT: CD1d-restricted invariant NKT (iNKT) cells play crucial roles in various types of immune responses, including autoimmune diseases, infectious diseases and tumor surveillance. The mechanisms underlying their adjuvant functions are well understood. Nevertheless, although IL-4 and IL-10 production characterize iNKT cells able to prevent or ameliorate some autoimmune diseases and inflammatory conditions, the precise mechanisms by which iNKT cells exert immune regulatory function remain elusive. This study demonstrates that the activation of human iNKT cells by their specific ligand alpha-galactosylceramide enhances IL-12p70 while inhibiting the IL-23 production by monocyte-derived dendritic cells, and in turn down-regulating the IL-17 production by memory CD4(+) Th cells. The ability of the iNKT cells to regulate the differential production of IL-12p70/IL-23 is mainly mediated by a remarkable hallmark of their function to produce both Th1 and Th2 cytokines. In particular, the down-regulation of IL-23 is markedly associated with a production of IL-4 and IL-10 from iNKT cells. Moreover, Th2 cytokines, such as IL-4 and IL-13 play a crucial role in defining the biased production of IL-12p70/IL-23 by enhancement of IL-12p70 in synergy with IFN-gamma, whereas inhibition of the IFN-gamma-promoted IL-23 production. Collectively, the results suggest that iNKT cells modify the IL-12p70/IL-23 balance to enhance the IL-12p70-induced cell-mediated immunity and suppress the IL-23-dependent inflammatory pathologies. These results may account for the long-appreciated contrasting beneficial and adverse consequence of ligand activation of iNKT cells.
    The Journal of Immunology 08/2009; 183(1):201-8. · 5.52 Impact Factor