Kohei Johkura

Shinshu University, Shonai, Nagano, Japan

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Publications (45)138.39 Total impact

  • Mayo Yokoyama, Kohei Johkura, Takehiko Sato
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    ABSTRACT: Plasma irradiation generates many factors able to affect the cellular condition, and this feature has been studied for its application in the field of medicine. We previously reported that hydrogen peroxide (H2O2) was the major cause of HeLa cell death among the chemical species generated by high level irradiation of a culture medium by atmospheric plasma. To assess the effect of plasma-induced factors on the response of live cells, HeLa cells were exposed to a medium irradiated by a non-lethal plasma flow level, and their gene expression was broadly analyzed by DNA microarray in comparison with that in a corresponding concentration of 51 μM H2O2. As a result, though the cell viability was sufficiently maintained at more than 90% in both cases, the plasma-medium had a greater impact on it than the H2O2-medium. Hierarchical clustering analysis revealed fundamentally different cellular responses between these two media. A larger population of genes was upregulated in the plasma-medium, whereas genes were downregulated in the H2O2-medium. However, a part of the genes that showed prominent differential expression was shared by them, including an immediate early gene ID2. In gene ontology analysis of upregulated genes, the plasma-medium showed more diverse ontologies than the H2O2-medium, whereas ontologies such as "response to stimulus" were common, and several genes corresponded to "response to reactive oxygen species." Genes of AP-1 proteins, e.g., JUN and FOS, were detected and notably elevated in the plasma-medium. These results showed that the medium irradiated with a non-lethal level of plasma flow altered various gene expressions of HeLa cells by giving not only common effects with H2O2 but also some distinctive actions. This study suggests that in addition to H2O2, other chemical species able to affect the cellular responses exist in the plasma-irradiated medium and provide unique features for it, probably increasing the oxidative stress level.
    Biochemical and Biophysical Research Communications 07/2014; · 2.28 Impact Factor
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    ABSTRACT: Peroxisomes in three forms of vertebrate kidney (pronephros, mesonephros, and metanephros), as permanent or provisional kidney, are summarized concerning their ultrastructure and developmental changes. Because the peroxisome is known to be diverse in mammalian metanephros, and species difference is its distinctive feature among cell organelles, information should be obtained on each kidney of each species. The ultrastructural and biochemical features of peroxisomes have at least been partly delineated in the metanephros and mesonephros, but nothing is known about the pronephros. Ultrastructural studies of the metanephric peroxisomes are present in mammals, birds, and reptiles, but information on their development is restricted to mammals and birds. As for the mesonephric peroxisomes, both ultrastructural and developmental data have been accumulating on mammals and amphibians, and ultrastructural information is present on fishes, but not on birds and reptiles. At present, studies on peroxisomes of provisional kidney have been restricted to mammalian mesonephros. The common features of renal peroxisomes previously examined are that they are spherical cell organelles with a single limiting membrane in ultrastructure, and are positive for catalase. Information on the ultrastructure and enzymes is not sufficient at present for comparing the ontogenesis of renal peroxisomes with their phylogenesis.
    Cell Biochemistry and Biophysics 04/2012; 32(1):305-312. · 1.91 Impact Factor
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    Takehiko Sato, Mayo Yokoyama, Kohei Johkura
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    ABSTRACT: Recently, a plasma flow has been applied to medical treatment using effects of various kinds of stimuli such as chemical species, charged particles, heat, light, shock wave and electric fields. Among them, the chemical species are known to cause an inactivation of cell viability. However, the mechanisms and key factors of this event are not yet clear. In this study, we focused on the effect of H2O2 in plasma-treated culture medium because it is generated in the culture medium and it is also chemically stable compared with free radicals generated by the plasma flow. To elucidate the significance of H2O2, we assessed the differences in the effects of plasma-treated medium and H2O2-added medium against inactivation of HeLa cell viability. These two media showed comparable effects on HeLa cells in terms of the survival ratios, morphological features of damage processes, permeations of H2O2 into the cells, response to H2O2 decomposition by catalase and comprehensive gene expression. The results supported that among chemical species generated in a plasma-treated culture medium, H2O2 is one of the main factors responsible for inactivation of HeLa cell viability.
    Journal of Physics D Applied Physics 01/2011; 44(37). · 2.53 Impact Factor
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    ABSTRACT: Embryonic kidney development begins with the outgrowth of the ureteric bud (UB) from the Wolffian duct (WD) into the adjacent metanephric mesenchyme (MM). Both a GDNF-dependent and GDNF-independent (Maeshima et al., 2007) pathway have been identified. In vivo and in vitro, the GDNF-dependent pathway is inhibited by BMPs, one of the factors invoked to explain the limitation of UB formation in the unbudded regions of the WD surrounding the UB. However, the exact mechanism remains unknown. Here a previously described in vitro system that models UB budding from the WD was utilized to study this process. Because Protein kinase A (PKA) activation has been shown to prevent migration, morphogenesis and tubulogenesis of epithelial cells (Santos et al., 1993), its activity in budded and non-budded portions of the GDNF-induced WD was analyzed. The level of PKA activity was 15-fold higher in the unbudded portions of the WD compared to budded portions, suggesting that PKA activity plays a key role in controlling the site of UB emergence. Using well-characterized PKA agonists and antagonists, we demonstrated that at various levels of the PKA-signaling hierarchy, PKA regulates UB outgrowth from the WD by suppressing budding events. This process appeared to be PKA-2 isoform specific, and mediated by changes in the duct rather than the surrounding mesenchyme. In addition, it was not due to changes in either the sorting of junctional proteins, cell death, or cell proliferation. Furthermore, the suppressive effect of cAMP on budding did not appear to be mediated by spread to adjacent cells via gap junctions. Conversely, antagonism of PKA activity stimulated UB outgrowth from the WD and resulted in both an increase in the number of buds per unit length of WD as well as a larger surface area per bud. Using microarrays, analysis of gene expression in GDNF-treated WDs in which the PKA pathway had been activated revealed a nearly 14-fold decrease in Ret, a receptor for GDNF. A smaller decrease in GFRα1. a co-receptor for GDNF, was also observed. Using Ret-null WDs, we were able to demonstrate that PKA regulated GDNF-dependent budding but not GDNF-independent pathway for WD budding. We also found that BMP2 was higher in unbudded regions of the GDNF-stimulated WD. Treatment of isolated WDs with BMP2 suppressed budding and resulted in a 3-fold increase in PKA activity. The data suggests that the suppression of budding by BMPs and possibly other factors in non-budded zones of the WD may be regulated in part by increased PKA activity, probably partially through downregulation of Ret/GFRα1 coreceptor expression.
    Developmental Biology 11/2010; 347(2):337-47. · 3.87 Impact Factor
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    ABSTRACT: Bone marrow stromal cells (BMSCs) secrete soluble factors and display varied cell-biological functions. To confirm the ability and efficiency of BMSCs to induce embryonic stem cells (ESCs) into cardiomyocytes, mouse embryoid bodies (EBs) were co-cultured with rat BMSCs. After about 10 days, areas of rhythmically contracting cells in more solid aggregates became evident with bundle-like structures formed along borders between EB outgrowth and BMSC layer. ESC-derived cardiomyocytes exhibited sarcomeric striations when stained with troponin I (Trop I), organized in separated bundles. Besides, the staining for connexin 43 was detected in cell-cell junctions, which demonstrated that ESC-derived cardiomyocytes were coupled by gap junction in culture. The related genes of cardiomyocytes were found in these beating and no-beating EBs co-cultured with BMSCs. In addition, an improved efficiency of cardiomyocyte differentiation from ESC-BMSC co-culture was found in the serum-free medium: 5-fold up-regulation in the number of beating area compared with the serum medium. Effective cardiac differentiation was also recognized in transfer filter assay and in condition medium obtained from BMSC culture. A clear increase in the expression of cardiac genes and TropI protein confirmed further cardiac differentiation by BMP4 and Retinoic Acid (RA) treatment. These results demonstrate that BMSCs can induce cardiomyocyte differentiation from ESCs through soluble factors and enhance it with BMP4 or RA treatment. Serum-free ESC-BMSC co-culture represents a defined in vitro model for identifying the cardiomyocyte-inducing activity from BMSCs and, in addition, a straightforward experimental system for assessing clinical applications.
    Annals of anatomy = Anatomischer Anzeiger: official organ of the Anatomische Gesellschaft 09/2010; 192(5):314-21. · 1.96 Impact Factor
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    ABSTRACT: Photoreceptors cannot regenerate and recover their functions once disordered. Transplantation of retinal pigment epithelium (RPE) has recently become a possible therapeutic approach for retinal degeneration. In the present study, we investigated the induction of photoreceptors by coculturing primate embryonic stem cells (ESCs) with ESC-derived RPE cells. RPE cells were derived by coculturing ESCs and Sertoli cells. Photoreceptors were then induced by using ESC-derived RPE cells and retinoic acid (RA) RESULTS: RPE cell generation was confirmed by morphological analysis, which revealed highly pigmented polygonal cells with a compact cell-cell arrangement. After coculturing ESCs and RPE cells, some ESC derivatives became immunopositive for rhodopsin. RT-PCR analysis demonstrated the expression of retina-related gene markers such as Pax6, CRX, IRBP, rhodopsin, rhodopsin kinase, and Muschx10A. When RA was added, a distinct increase in the expression of photoreceptor-specific proteins and genes was found. In addition, the differentiation of bipolar horizontal cells was demonstrated by protein and gene expression. The ESCs that were cocultured with RPE cells and treated with RA were transplanted into the renal capsule or intra-vitreal space of nude mice. Grafted ESC derivatives demonstrated extensive rhodopsin expression, and they survived and organized into recipient tissues, although they formed teratomas. These results indicate that coculturing ESCs with ESC-derived RPE cells is a useful and efficient method for inducing photoreceptors and providing an insight into the use of ESCs for retina regeneration.
    Biochemical and Biophysical Research Communications 03/2010; 394(4):877-83. · 2.28 Impact Factor
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    ABSTRACT: The plausibility of constructing vascularized three-dimensional (3D) kidney tissue from cells was investigated. The kidney develops from mutual inductive interactions between cells of the ureteric bud (UB), derived from the Wolffian duct (WD), and the metanephric mesenchyme (MM). We found that isolated MMs were capable of inducing branching morphogenesis of the WD (an epithelial tube) in recombination cultures; suggesting that the isolated MM retains inductive capacity for WD-derived epithelial tubule cells other than those from the UB. Hanging drop aggregates of embryonic and adult renal epithelial cells from UB and mouse inner medullary collecting duct cell (IMCD) lines, which are ultimately of WD origin, were capable of inducing MM epithelialization and tubulogenesis with apparent connections (UB cells) and collecting duct-like tubules with lumens (IMCD). This supports the view that the collecting system can be constructed from certain epithelial cells (those ultimately of WD origin) when stimulated by MM. Although the functions of the MM could not be replaced by cultured mesenchymal cells, primary MM cells and one MM-derived cell line (BSN) produced factors that stimulate UB branching morphogenesis, whereas another, rat inducible metanephric mesenchyme (RIMM-18), supported WD budding as a feeder layer. This indicates that some MM functions can be recapitulated by cells. Although engineering of a kidney-like tissue from cultured cells alone remains to be achieved, these results suggest the feasibility of such an approach following the normal developmental progression of the UB and MM. Consistent with this notion, implants of kidney-like tissues constructed in vitro from recombinations of the UB and MM survived for over 5 weeks and achieved an apparently host-derived glomerular vasculature. Lastly, we addressed the issue of optimal macro- and micro-patterning of kidney-like tissue, which might be necessary for function of an organ assembled using a tissue engineering approach. To identify suitable conditions, 3D reconstructions of HoxB7-green fluorescent protein mouse rudiments (E12) cultured on a filter or suspended in a collagen gel (type I or type IV) revealed that type IV collagen 3D culture supports the deepest tissue growth (600 +/- 8 microm) and the largest kidney volume (0.22 +/- 0.02 mm(3)), and enabled the development of an umbrella-shaped collecting system such as occurs in vivo. Taken together with prior work (Rosines et al., 2007; Steer et al., 2002), these results support the plausibility of a developmental strategy for constructing and propagating vascularized 3D kidney-like tissues from recombinations of cultured renal progenitor cells and/or primordial tissue.
    Tissue Engineering Part A 03/2010; 16(8):2441-55. · 4.64 Impact Factor
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    ABSTRACT: Kidney organogenesis depends on reciprocal interactions between the ureteric bud (UB) and the metanephric mesenchyme (MM) to form the UB-derived collecting system and MM-derived nephron. With the advent of in vitro systems, it is clear that UB branching can occur independently of MM contact; however, little has been done to detail the role of MM cellular contact in this process. Here, a model system in which the cultured isolated UB is recombined with uninduced MM is used to isolate the effects of the MM progenitor tissue on the development and maturation of the collecting system. By morphometrics, we demonstrate that cellular contact with the MM is required for vectorial elongation of stalks and tapering of luminal caliber of UB-derived tubules. Expression analysis of developmentally significant genes indicates the cocultured tissue is most similar to an embryonic day 19 (E19) kidney. The likely major contributor to this is the functional maturation of the collecting duct and proximal nephron segments in the UB-induced MM, as measured by quantitative PCR, of the collecting duct-specific arginine vasopressin receptor and the nephron tubule segment-specific organic anion transporter OAT1, Na-P(i) type 2 cotransporter, and Tamm-Horsfall protein gene expressions. However, expression of aquaporin-2 is upregulated similarly in isolated UB and cocultured tissue, suggesting that some aspects of functional maturation can occur independently of MM cellular contact. In addition to its sculpting effects, the MM normalized a "branchless" UB morphology induced by FGF7 or heregulin in isolated UB culture. The morphological changes induced by the MM were accompanied by a reassignment of GFRalpha1 (a receptor for GDNF) to tips. Such "quality control" by the MM of UB morphology may provide resiliency to the branching program. This may help to explain a number of knockout phenotypes in which branching and/or cystic defects are less impressive than expected. A second hit in the MM may thus be necessary to make these defects fully apparent.
    AJP Renal Physiology 10/2009; 297(5):F1330-41. · 4.42 Impact Factor
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    ABSTRACT: Cardiomyocytes derived from human embryonic stem (ES) cells are a potential source for cell-based therapy for heart diseases. We studied the effect of bone morphogenetic protein (BMP)-4 in the presence of fetal bovine serum (FBS) on cardiac induction from human H1 ES cells during embryoid body (EB) development. Suspension culture for 4 days with 20% FBS produced the best results for the differentiation of early mesoderm and cardiomyocytes. The addition of Noggin reduced the incidence of beating EBs from 23.6% to 5.3%, which indicated the involvement of BMP signaling in the spontaneous cardiac differentiation. In this condition, treatment with 12.5-25 ng/ml BMP-4 during the 4-day suspension optimally promoted the cardiomyocyte differentiation. The incidence of beating EBs at 25 ng/ml BMP-4 reached 95.8% on day 6 of expansion and then plateaued until day 20. In real-time PCR analysis, the cardiac development-related genes MESP1 and Nkx2.5 were upregulated in the EB outgrowths by 25 ng/ml BMP-4. The activation of BMP signaling in EBs was confirmed by the increase in the phosphorylation of Smad1/5/8 and by the nuclear localization of phospho-Smad1/5/8 and Smad4. The addition of 150 ng/ml Noggin considerably decreased the incidence of beating EBs and Nkx2.5 expression, and Noggin alone increased Nestin expression and neural differentiation in EB outgrowths. The cardiomyocytes induced by 25 ng/ml BMP-4 showed proper cell biological characteristics and a course of differentiation as judged from isoproterenol administration, gene expression, protein assay, immunoreactivity, and subcellular structures. No remarkable change in the extent of apoptosis and proliferation in the cardiomyocytes was observed by BMP-4 treatment. These findings showed that BMP-4 in combination with FBS at the appropriate time and concentrations significantly promotes cardiomyocyte induction from human ES cells.
    AJP Heart and Circulatory Physiology 05/2009; 296(6):H1793-803. · 4.01 Impact Factor
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    ABSTRACT: The objective of this study was to establish Liv2, a surface marker of mouse immature hepatocytes (hepatoblasts), as a selection tool for embryonic stem (ES) cell-derived immature hepatocytes by acquiring basic data on Liv2 in normal mouse embryos and by confirming Liv2 expression in mouse ES-derived cells. The estimated molecular weight of Liv2 was 40-45 kDa, and immunoreactivity was definitively detected in the cell membrane of fetal hepatocytes on embryonic day (E) 9.5, declined gradually until E12.5,and subsequently became undetectable. Liv2 was localized on and close to the cell membrane. Embryoid bodies (EB) were formed from mouse ES cells whose undifferentiated state was confirmed with immunostaining of Nanog by the hanging drop method. A few Liv2-positive cells occurred as a cluster in EB outgrowth on day 7, but only some of these were albumin (ALB)-positive on day 13. These cells had the same pattern of immunoreactivity, i.e., localization on the cell membrane, as immature hepatocytes in the developing liver, although there were other types of cells with a different pattern of immunoreactivity that were seen only as a granular pattern in the cytoplasm and without ALB or the neuronal marker nestin. These results suggest thatLiv2 may be useful as a surface marker for immature hepatocytes derived from ES cells.This application would allow for the sole selection of immature hepatocytes and provide a useful tool for regenerative medicine.
    The Scientific World Journal 02/2009; 9:190-9. · 1.73 Impact Factor
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    ABSTRACT: Metanephric kidneys of nude mice were transplanted on embryonic day 12 into an adult kidney of the same strain, and the growth of the implants was analysed histochemically to investigate the ontogenesis, structure and function of the newly developed additional nephrons. By using a light microscope, developing nephrons at various stages were observed in the implants growing in the host kidney 7 days after transplantation. Immature nephrons, comprising the nephrogenic zone, were intensely positive for proliferating cell nuclear antigen (PCNA) immunostaining, but were no longer present 14 days after transplantation. Vascular integration was observed between the host and implant tissues. Electron microscopic observation 14 days after transplantation showed that the afferent arterioles together with juxtaglomerular cells had entered the gtomeruli. All of the cell types were identified in the vascularised glomeruli with erythrocytes. the visceral epithelial cells had differentiated foot processes, whereas the endothelium of the glomerular tufts was rather thick in parts, and most of the epithelial and endothelial basement membranes were not fused. Several parts of the uriniferous tubules, including proximal and distal tubules, could be identified, and it was found that many of them had remained immature. Some proximal tubules with well-developed brush-border microvilli reabsorbed the horseradish peroxidase (HRP) injected into the host inferior vena cava, thus providing evidence of glomerular ultrafiltration in the vascularised implants perfused by the host. These findings indicate that the nephrogenesis in the implants followed a nearly normal developmental route and showed marked vascularisation, which promoted the organogenesis of the implanted metanephros and nephron function.
    Nephrology 06/2008; 7(2):92 - 100. · 1.69 Impact Factor
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    ABSTRACT: The aim of this study was to induce organized layered tissues with characteristics of the urinary tract from embryonic stem (ES) cells alone. We seeded embryoid bodies (EBs) originating from mouse ES cells onto mono-layered collagen membranes and cultured them in four different media. Group 1 was grown in a mixed medium of keratinocyte serum-free medium (KSFM) and Medium 199, Group 2 in a mixed medium of KSFM and conditioned medium collected from 3T3 fibroblasts, Group 3 in an EB formation medium (control group), and Group 4 in KSFM only (control group). After 28 days, cultured tissues were transplanted into nude mice. Cultured tissues from Groups 1 and 2 formed four-layered structures comprising a stratified epithelium, a submucosal loose connective tissue layer, a smooth muscle cell layer identified immunohistochemically by alpha-smooth muscle actin, and a deep loose connective tissue layer identical to the adventitia. Immunohistochemistry showed that the epithelia were positive for cytokeratins. Tissues also expressed uroplakin as detected by reverse transcription/polymerase chain reaction. In contrast, specimens from Groups 3 and 4 demonstrated necrotic features. Uroplakin-positive (i.e., urothelium-like) cells developed only in Group 2 in the transplanted culture tissues in nude mice. In addition to inducing organized layered tissues from mouse ES cells directly in vitro, these findings demonstrate that tissues cultured in KSFM plus conditioned medium from 3T3 fibroblasts differentiate into luminal walls similar to those of urinary tract in vivo. These findings suggest a new approach to urinary tract regeneration.
    Cell and Tissue Research 04/2008; 331(3):605-15. · 3.68 Impact Factor
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    ABSTRACT: Hepatocyte differentiation markers were expressed in the cells differentiated from mouse embryonic stem (ES) cells. In the differentiating ES cells, Cyp1a1 mRNA was highly expressed during the early to middle stage; Cyp2c29, Cyp2e1, Cyp3a11 and Cyp7a1 mRNAs were expressed only at the late stage; Cyp7b1 mRNA was expressed throughout all stages. Alpha-fetoprotein and albumin were co-expressed with Cyp3a and Cyp1a, respectively. Aryl hydrocarbon receptor, aryl hydrocarbon receptor nuclear translocator and glucocorticoid receptor mRNAs were detected in differentiating ES cells throughout the culture period. Pregnane X receptor mRNA was detected only in cells cultured for more than 24 days. The expression levels of Cyp2c29, Cyp3a11 and Cyp7a1 and G6p mRNAs were increased in embryoid bodies that were cultured with culture medium containing acid fibroblast growth factor, hepatocyte growth factor (HGF) and oncostatin M for 12 or 18 days, then the medium was replaced by that without HGF. These findings suggested that the expression levels of Cyp genes in hepatocytes differentiated from ES cells were markedly changed in individual enzymes during the course of differentiation, and that the duration of incubation with the addition of HGF affected the expression of Cyps and hepatocytes marker proteins.
    Drug Metabolism and Pharmacokinetics 02/2008; 23(3):188-95. · 2.07 Impact Factor
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    ABSTRACT: A major hurdle for current xenogenic-based and other approaches aimed at engineering kidney tissues is reproducing the complex three-dimensional structure of the kidney. Here, a stepwise, in vitro method of engineering rat kidney-like tissue capable of being implanted is described. Based on the fact that the stages of kidney development are separable into in vitro modules, an approach was devised that sequentially induces an epithelial tubule (the Wolffian duct) to undergo in vitro budding, followed by branching of a single isolated bud and its recombination with metanephric mesenchyme. Implantation of the recombined tissue results in apparent early vascularization. Thus, in principle, an unbranched epithelial tubular structure (potentially constructed from cultured cells) can be induced to form kidney tissue such that this in vitro engineered tissue is capable of being implanted in host rats and developing glomeruli with evidence of early vascularization. Optimization studies (of growth factor and matrix) indicate multiple suitable combinations and suggest both a most robust and a minimal system. A whole-genome microarray analysis suggested that recombined tissue recapitulated gene expression changes that occur in vivo during later stages of kidney development, and a functional assay demonstrated that the recombined tissue was capable of transport characteristic of the differentiating nephron. The approach includes several points where tissue can be propagated. The data also show how functional, 3D kidney tissue can assemble by means of interactions of independent modules separable in vitro, potentially facilitating systems-level analyses of kidney development.
    Proceedings of the National Academy of Sciences 01/2008; 104(52):20938-43. · 9.81 Impact Factor
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    ABSTRACT: Cryopreservation of embryonic stem (ES) cells is essential to establish them as a resource for regenerative therapy. We evaluated survival adhesion rate, cell structure, gene expression, and multipotency of frozen and thawed embryoid bodies (EBs) derived from mouse ES cells. EBs were cryopreserved using the BICELL and the Program Freezer. After one week the EBs were thawed and cultured. EBs prepared in the Program Freezer had the highest survival adhesion (Program Freezer; 55-69%, BICELL; 30-38%). Though many cells in the thawed EBs were damaged, some were not, especially those prepared in the Program Freezer. RT-PCR analysis showed that genes characteristic of the three embryonic germ layers were expressed in thawed EBs cultured for one week. EBs transplanted into mice formed teratomas consisting of cells derived from the three germ layers. In conclusion, EBs frozen in the Program Freezer had higher survival adhesion rates compared to the BICELL and formed differentiated cells characteristic of the three embryonic germ layers.
    Cryobiology 07/2007; 54(3):290-3. · 2.14 Impact Factor
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    ABSTRACT: The proliferation, structural differentiation, and capacity of association of human ES cell-derived cardiomyocytes were assessed in culture and in extracardiac graft tissues. Embryoid body (EB) outgrowths having cardiomyocytes, and their transplants in mice retroperitoneum or renal subcapsular region were analyzed mainly by immunochemistry. During the culture of EB outgrowths, colonies of cardiomyocytes grew in size exhibiting synchronized beatings. Subcellular structures of those cardiomyocytes involved in the contraction, hormone production, and intercellular integration differentiated with distinct immunoreactivity for constituent proteins/peptides. Judging from PCNA staining, proliferation potential was maintained in part for more than 70 days. In teratoma tissues on post-transplantation Day 7, cardiomyocytes maintained their integration with connexin 43 and cadherin at their junctions. They partly exhibited strong PCNA reactivity. On Day 28, large part of the cardiomyocytes lost their association, dispersing among non-cardiac cells without discernible cadherin reactivity. Proliferation potential was generally low irrespective of their tissue diversity. From these results, structural differentiation and active proliferation of human ES cell-derived cardiomyocytes occurred in vitro, maintaining their association. When developed in extracardiac tissues, however, the cardiomyocytes showed low proliferation potential and reduced cellular integration. This leads to the proposal that some procedure will be necessary to accelerate or maintain the proliferation of cardiomyocytes in vivo.
    Journal of Structural Biology 07/2007; 158(3):307-17. · 3.36 Impact Factor
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    ABSTRACT: The present study was performed to determine whether glucagon-like peptide-1 (GLP-1) stimulates differentiation of nestin-selected embryonic stem cells into insulin-producing cells. Our experimental strategy began with the production of a highly enriched population of nestin-positive cells from embryoid bodies. These cells differentiated into insulin-producing cells after addition of GLP-1. Islet-like cell clusters (ICCs) formed in inducing culture. These nestin-positive cell-derived ICCs expressed numerous beta-cell lineage genes, including insulin; Glut-2; pancreatic duodenal homebox-1 protein (PDX-1); islet amyloid polypeptide (IAPP); neurogenin 3 (ngn3); and alpha, gamma, and delta cell gene markers. Cells of ICCs showed increased insulin protein expression, glucose-dependent insulin release, and coexpression of insulin and C-peptide. In addition, ICCs were characterized by coexpression of nestin/insulin and nestin/PDX-1. The levels of pancreas-related gene and protein expression and insulin secretion in the GLP-1 group were stronger than those in the normal controls. GLP-1 has been shown to be involved in stimulating the signaling pathways downstream of the transcription factor PDX-1, by increasing its protein and messenger RNA levels. In vivo, ICCs displayed the ability to reverse hyperglycemia in diabetic severe combined immunodeficiency (SCID) mice. We concluded that GLP-1 induced differentiation of nestin-positive progenitor embryonic stem cells into insulin-producing cells, which was achieved by upregulation of PDX-1 expression. This method may have future applications in stem cell therapy of diabetes.
    Tissue Engineering 09/2006; 12(8):2105-16. · 4.25 Impact Factor
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    ABSTRACT: The aim of this study was to produce dopaminergic neurons from primate embryonic stem (ES) cells following coculture with mouse Sertoli cells. After 3 weeks of induction, immunostaining revealed that 90% +/- 9% of the colonies contained tyrosine hydroxylase-positive (TH(+)) neurons, and 60% +/- 7% of the tubulin beta III-positive (Tuj III(+)) neurons were TH(+). Reverse transcription-polymerase chain reaction analyses showed that Sertoli-induced neurons expressed midbrain dopaminergic neuron markers, including TH, dopamine transporter, aromatic amino acid decarboxylase (AADC), receptors such as TrkB and TrkC, and transcription factors NurrI and Lmx1b. Neurons that had been differentiated on Sertoli cells were positive for Pax2, En1, and AADC, midbrain-related markers, and negative for dopamine-beta-hydroxylase, a marker of noradrenergic neurons. These Sertoli cell-induced dopaminergic cells can release dopamine when depolarized by high K(+). Sertoli cell-conditioned medium contained glial cell line-derived neurotrophic factor (GDNF) and supported neuronal differentiation. After pretreatment with anti-GDNF antibody, the percentage of Tuj III(+) colonies was reduced to 14%. Thus, GDNF contributed significantly to inducing primate ES cells into dopaminergic neurons. When transplanted into a 6-hydroxydopamine-treated Parkinson's disease model, primate-derived dopaminergic neurons integrated into the mouse striatum. Two weeks after transplantation, surviving TH(+) cells were present. These TH(+) cells survived for 2 months. Therefore, the induction method of coculture ES cells with Sertoli cells provides an unlimited source of primate cells for the study of pathogenesis and transplantation in Parkinson's disease.
    Stem Cells 08/2006; 24(7):1695-706. · 7.70 Impact Factor
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    ABSTRACT: To analyze the biocompatibility and O2 generation of TiO2 nanotubes via photodecomposition of water into O2 and H2 in vivo, samples were implanted under the inguinal skin of the nude mouse. Venous oxygen saturation (SvO2) of the inguinal skin over the implanted region was measured with a tissue oximeter and the ultrastructures were examined with an electron microscope. Four weeks after the implantation, SvO2 of the inguinal skin of the groups with TiO2 nanotubes was 30-40% higher than that of the opposite control region (54%). SvO2 of the other groups, comprising splenic autografts, fetal cardiac tissue transplantation and surgical procedure without TiO2 nanotubes, was roughly the same as that of controls. Ultrastructurally, TiO2 nanotubes were phagocytized by the macrophage and promoted filament formation in its cytoplasm. Neither death of the cell nor destruction of the tissue was recognized. These findings indicate excellent biocompatibility and O2 generation of TiO2 nanotubes in vivo.
    Annals of Anatomy - Anatomischer Anzeiger 04/2006; 188(2):137-42. · 1.96 Impact Factor
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    ABSTRACT: Ureteric bud epithelial cells and metanephric mesenchymal cells that comprise the metanephric kidney primordium are capable of producing nephrons and collecting ducts through reciprocal inductive interaction. Once these cells are induced from pluripotent embryonic stem (ES) cells, they have the potential to become powerful tools in the regeneration of kidney tissues. In this study, we investigated these renal primordial cells and structures in mouse ES cell outgrowths and their transplants. Gene expression essential for early kidney development was examined by RT-PCR in embryoid body (EB) outgrowths and their transplants in adult mice. Histochemical detection of kidney primordial structures and gene expression analysis coupled with laser microdissection were performed in transplant tissues. RT-PCR analysis detected gene expression of Pax-2, Lim-1, c-Ret, Emx2, Sall1, WT-1, Eya-1, GDNF, and Wnt-4 in the EB outgrowths from days 6-9 of expansion onward, and also in the teratoma tissues 14 and 28 days after transplantation. Histochemical analysis 14 days after transplantation showed that some ducts were positive for Pax-2, endo A cytokeratin, kidney-specific cadherin, and Dolichos biflorus agglutinin and that dichotomous branching of these ducts had occurred. These staining patterns and morphological features are intrinsic for mesonephric ducts and ureteric buds. In long-term survival of 28 days, Pax-2-immunoreactivity disappeared in some renal primordia-like structures, indicating their differentiation. Some ducts were accompanied by mesonephric nephron-like convoluted tubules. RT-PCR analysis of those structures collected by microdissection confirmed that they expressed kidney development-related genes. In conclusion, these data suggest the potential of ES cells to produce renal primordial duct structures and provides an insight into the regeneration of kidney tissues.
    American journal of physiology. Renal physiology 02/2006; 290(1):F52-60. · 3.61 Impact Factor

Publication Stats

648 Citations
138.39 Total Impact Points

Institutions

  • 1999–2014
    • Shinshu University
      • • Department of Histology and Embryology
      • • Department of Medicine
      Shonai, Nagano, Japan
  • 2009–2010
    • University of California, San Diego
      • • Department of Bioengineering
      • • Department of Medicine
      San Diego, CA, United States