Hiroshi Akazawa

The University of Tokyo, Tōkyō, Japan

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Publications (114)646.17 Total impact

  • Takehiro Kamo, Hiroshi Akazawa, Issei Komuro
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    ABSTRACT: Most of the pathophysiological actions of angiotensin II (Ang II) are mediated through the Ang II type 1 (AT1) receptor, a member of the seven-transmembrane G protein-coupled receptor family. Essentially, AT1 receptor signaling is beneficial for organismal survival and procreation, because it is crucial for normal organ development, and blood pressure and electrolyte homeostasis. On the other hand, AT1 receptor signaling has detrimental effects, such as promoting various aging-related diseases that include cardiovascular diseases, diabetes, chronic kidney disease, dementia, osteoporosis, and cancer. Pharmacological or genetic blockade of AT1 receptor signaling in rodents has been shown to prevent the progression of aging-related phenotypes and promote longevity. In this way, AT1 receptor signaling exerts antagonistic and pleiotropic effects according to the ages and pathophysiological conditions. Here we review the pleiotropic effects of AT1 receptor signaling in cardiovascular homeostasis and aging.
    International Heart Journal 04/2015; DOI:10.1536/ihj.14-429 · 1.13 Impact Factor
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    ABSTRACT: Myocarditis is a critical inflammatory disorder which causes life-threatening conditions. No specific or effective treatment has been established. DPP-4 inhibitors have salutary effects not only on type 2 diabetes but also on certain cardiovascular diseases. However, the role of a DPP-4 inhibitor on myocarditis has not been investigated. To clarify the effects of a DPP-4 inhibitor on myocarditis, we used an experimental autoimmune myocarditis (EAM) model in Balb/c mice. EAM mice were assigned to the following groups: EAM mice group treated with a DPP-4 inhibitor (linagliptin) (n = 19) and those untreated (n = 22). Pathological analysis revealed that the myocardial fibrosis area ratio in the treated group was significantly lower than in the untreated group. RT-PCR analysis demonstrated that the levels of mRNA expression of IL-2, TNF-α, IL-1β and IL-6 were significantly lower in the treated group than in the untreated group. Lymphocyte proliferation assay showed that treatment with the DPP-4 inhibit
    PLoS ONE 03/2015; 10(3-3):e0119360. DOI:10.1371/journal.pone.0119360 · 3.53 Impact Factor
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    ABSTRACT: Hypertension induces structural remodelling of arteries, which leads to arteriosclerosis and end-organ damage. Hyperplasia of vascular smooth muscle cells (VSMCs) and infiltration of immune cells are the hallmark of hypertensive arterial remodelling. However, the precise molecular mechanisms of arterial remodelling remain elusive. We have recently reported that complement C1q activates β-catenin signalling independent of Wnts. Here, we show a critical role of complement C1-induced activation of β-catenin signalling in hypertensive arterial remodelling. Activation of β-catenin and proliferation of VSMCs were observed after blood-pressure elevation, which were prevented by genetic and chemical inhibition of β-catenin signalling. Macrophage depletion and C1qa gene deletion attenuated the hypertension-induced β-catenin signalling, proliferation of VSMCs and pathological arterial remodelling. Our findings unveil the link between complement C1 and arterial remodelling and suggest that C1-induced activation of β-catenin signalling becomes a novel therapeutic target to prevent arteriosclerosis in patients with hypertension.
    Nature Communications 01/2015; 6:6241. DOI:10.1038/ncomms7241 · 10.74 Impact Factor
  • Journal of Cardiac Failure 10/2014; 20(10):S183. DOI:10.1016/j.cardfail.2014.07.288 · 3.07 Impact Factor
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    ABSTRACT: Background-Increasing evidence suggests a critical role for mitochondrial aldehyde dehydrogenase 2 (ALDH2) in protection against cardiac injuries; however, the downstream cytosolic actions of this enzyme are largely undefined. Methods and Results-Proteomic analysis identified a significant downregulation of mitochondrial ALDH2 in the heart of a rat heart failure model after myocardial infarction. The mechanistic insights underlying ALDH2 action were elucidated using murine models overexpressing ALDH2 or its mutant or with the ablation of the ALDH2 gene (ALDH2 knockout) and neonatal cardiomyocytes undergoing altered expression and activity of ALDH2. Left ventricle dilation and dysfunction and cardiomyocyte death after myocardial infarction were exacerbated in ALDH2-knockout or ALDH2 mutant-overexpressing mice but were significantly attenuated in ALDH2-overexpressing mice. Using an anoxia model of cardiomyocytes with deficiency in ALDH2 activities, we observed prominent cardiomyocyte apoptosis and increased accumulation of the reactive aldehyde 4-hydroxy-2-nonenal (4-HNE). We subsequently examined the impacts of mitochondrial ALDH2 and 4-HNE on the relevant cytosolic protective pathways. Our data documented 4-HNE-stimulated p53 upregulation via the phosphorylation of JNK, accompanying increased cardiomyocyte apoptosis that was attenuated by inhibition of p53. Importantly, elevation of 4-HNE also triggered a reduction of the cytosolic HSP70, further corroborating cytosolic action of the 4-HNE instigated by downregulation of mitochondrial ALDH2. Conclusions-Downregulation of ALDH2 in the mitochondria induced an elevation of 4-HNE, leading to cardiomyocyte apoptosis by subsequent inhibition of HSP70, phosphorylation of JNK, and activation of p53. This chain of molecular events took place in both the mitochondria and the cytosol, contributing to the mechanism underlying heart failure.
    Journal of the American Heart Association 09/2014; 3(5). DOI:10.1161/JAHA.113.000779 · 2.88 Impact Factor
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    ABSTRACT: Engineering of three-dimensional (3D) cardiac tissues using decellularized extracellular matrix could be a new technique to create an "organ-like" structure of the heart. To engineer artificial hearts functionally comparable to native hearts, however, much remain to be solved including stable excitation-propagation. To elucidate the points, we examined conduction properties of engineered tissues. We repopulated the decellularized hearts with neonatal rat cardiac cells and then, we observed excitation-propagation of spontaneous beatings using high resolution cameras. We also conducted immunofluorescence staining to examine morphological aspects. Live tissue imaging revealed that GFP-labeled-isolated cardiac cells were migrated into interstitial spaces through extravasation from coronary arteries. Engineered hearts repopulated with Ca(2+)-indicating protein (GCaMP2)-expressing cardiac cells were subjected to optical imaging experiments. Although the engineered hearts generally showed well-organized stable excitation-propagation, the hearts also demonstrated arrhythmogenic propensity such as disorganized propagation. Immunofluorescence study revealed randomly-mixed alignment of cardiomyocytes, endothelial cells and smooth muscle cells. The recellularized hearts also showed disarray of cardiomyocytes and markedly decreased expression of connexin43. In conclusion, we successfully demonstrated that the recellularized hearts showed dynamic excitation-propagation as a "whole organ". Our strategy could provide prerequisite information to construct a 3D-engineered heart, functionally comparable to the native heart.
    Biomaterials 06/2014; DOI:10.1016/j.biomaterials.2014.05.080 · 8.31 Impact Factor
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    ABSTRACT: Enzymatic proteolysis by calpains, Ca(2+)-dependent intracellular cysteine proteases, has been implicated in pathological processes such as cellular degeneration or death. Here, we investigated the role of calpain activation in the hearts subjected to myocardial infarction. We produced myocardial infarction in Cast(-/-) mice deficient for calpastatin, the specific endogenous inhibitory protein for calpains, and Cast(+/+) mice. The activity of cardiac calpains in Cast(+/+) mice was not elevated within 1 day, but showed a gradual elevation after 7 days following myocardial infarction, which was further pronounced in Cast(-/-) mice. Although the prevalence of cardiomyocyte death was indistinguishable between Cast(-/-) and Cast(+/+) mice, Cast(-/-) mice exhibited profound contractile dysfunction and chamber dilatation and showed a significant reduction in survival rate after myocardial infarction, as compared with Cast(+/+) mice. Notably, immunofluorescence revealed that, at 28 days after myocardial infarction, calpains were activated in cardiomyocytes exclusively at the border zone, and that Cast(-/-) mice showed higher intensity and broader extent of calpain activation at the border zone than Cast(+/+) mice. In the border zone of Cast(-/-) mice, pronounced activation of calpains was associated with a decrease in N-cadherin expression and up-regulation of molecular markers for cardiac hypertrophy and fibrosis. In cultured rat neonatal cardiomyocytes, activation of calpains by treatment with ionomycin induced cleavage of N-cadherin, and decreased expression levels of β-catenin and connexin 43, which was attenuated by calpain inhibitor. These results thus demonstrate that activation of calpains disassembles cell-cell adhesion at intercalated discs by degrading N-cadherin, and thereby promotes left ventricular remodeling after myocardial infarction.
    Journal of Biological Chemistry 06/2014; 289(28). DOI:10.1074/jbc.M114.567206 · 4.60 Impact Factor
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    ABSTRACT: Periodontitis is known to be a risk factor for abdominal aortic aneurysm (AAA). However, the influence of periodontitis on AAA in Japanese patients has not yet been elucidated. The aim of this clinical investigation was to assess the relationship between periodontal bacterial burden in AAA patients.We studied 12 AAA patients and 24 age- and sex-matched non-AAA cardiovascular patients. We examined periodontitis and the presence of the periodontal pathogens Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Prevotella intermedia in oral samples using polymerase chain reaction assays.We found that the AAA patients had deeper pocket depth compared to the non-AAA patients (3.53 ± 0.38 mm versus 2.67 ± 0.17 mm, P < 0.05). However, the populations of periodontal bacteria were comparable between the two groups. Periodontitis may have a greater effect on aneurysm progression compared to other cardiovascular diseases.
    International Heart Journal 05/2014; DOI:10.1536/ihj.13-301 · 1.13 Impact Factor
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    ABSTRACT: Although periodontitis is a risk factor for cardiovascular disease (CVD), the influence of periodontitis on Marfan syndrome (MFS) with CVD is unclear. The aim of this study was to assess the relationship between periodontal bacterial burden and MSF with CVD. The subjects were patients with MFS with CVD (n = 47); age and gender matched non-MFS CVD patients (n = 48) were employed as controls. Full-mouth clinical measurements, including number of teeth, probing of pocket depth (PD), bleeding on probing (BOP) and community periodontal index (CPI) were recorded. We also evaluated the existence of three periodontal pathogens, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Prevotella intermedia using polymerase chain reaction assays. Serum antibody titers against the pathogens were also measured. We revealed that MFS with CVD patients had periodontitis more frequently than the age and gender matched non-MFS CVD control subjects. MFS with CVD patients had significantly severer periodontitis, fewer remaining teeth and deeper PD compared to the non-MFS CVD controls. Furthermore, the serum antibody titer level against Prevotella intermedia was significantly lower in MFS plus CVD patients compared to the non-MFS CVD patients. Periodontitis may influence the pathophysiology of cardiovascular complications in MFS patients. A specific periodontal pathogen might be a crucial therapeutic target to prevent CVD development.
    PLoS ONE 04/2014; 9(4):e95521. DOI:10.1371/journal.pone.0095521 · 3.53 Impact Factor
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    ABSTRACT: Although there is a link between periodontitis and cardiovascular disease (CVD), the influence of periodontitis on CVD is unclear. The aim of this study was to assess the relationship between periodontal bacterial burden and CVD. We studied 142 patients with tachyarrhythmia (TA) and 25 patients with abdominal aortic aneurysm (AAA). We examined periodontitis and the presence of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans and Prevotella intermedia in the patients' saliva and subgingival plaque using PCR. We also measured serum antibody titers against the pathogens using ELISA. We found that the patients with AAA had fewer remaining teeth (14.6 ± 2.0 vs. 20.9 ± 0.7, P < 0.05) and deeper pocket depth (3.01 ± 0.26 vs. 2.52 ± 0.05 mm, P < 0.05) compared to the TA patients. The existence of each periodontal bacterium in their saliva or subgingival plaque and serum antibody titers was comparable between the two groups. Periodontitis may have a larger affect on aneurysm progression compared to arrhythmia.
    Heart and Vessels 04/2014; DOI:10.1007/s00380-014-0507-6 · 2.11 Impact Factor
  • Hiroshi Akazawa, Issei Komuro
    Cardiovascular Research 03/2014; DOI:10.1093/cvr/cvu051 · 5.81 Impact Factor
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    ABSTRACT: Cardiac hypertrophy is an adaptive response to physiological and pathological overload. In response to the overload, individual cardiac myocytes become mechanically stretched and activate intracellular hypertrophic signaling pathways to re-use embryonic transcription factors and to increase the synthesis of various proteins, such as structural and contractile proteins. These hypertrophic responses increase oxygen demand and promote myocardial angiogenesis to dissolve the hypoxic situation and to maintain cardiac contractile function; thus, these responses suggest crosstalk between cardiac myocytes and microvasculature. However, sustained pathological overload induces maladaptation and cardiac remodeling, resulting in heart failure. In recent years, specific understanding has increased with regard to the molecular processes and cell-cell interactions that coordinate myocardial growth and angiogenesis. In this review, we summarize recent advances in understanding the regulatory mechanisms of coordinated myocardial growth and angiogenesis in the pathophysiology of cardiac hypertrophy and heart failure.
    Circulation Research 01/2014; 114(3):565-571. DOI:10.1161/CIRCRESAHA.114.300507 · 11.09 Impact Factor
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    ABSTRACT: Recent epidemiological studies suggest that periodontitis is a major risk factor for renal failure and cerebral infarction. The aim of this study was to evaluate the association among periodontitis, renal failure, and cerebral infarction, focusing on microbiological and immunological features. Twenty-one patients treated with hemodialysis (HD) were enrolled in this study. They were 8 with diabetic nephropathy and 13 with non-diabetic nephropathy. Blood examination, periodontal examination, brain magnetic resonance image (MRI), and dental radiography were performed on all patients. Subgingival plaque, saliva, and blood samples were analyzed for the periodontal pathogens, Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), Porphyromonas gingivalis (P. gingivalis), and Prevotella intermedia (P. intermedia) using quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA). We found that the patients with diabetic nephropathy had more A. actinomycetemcomitans compared with non-diabetic nephropathy (P = 0.038) in dental plaque. Furthermore, the patients with diabetic nephropathy showed a significantly higher incidence of cerebral infarction compared with those with non-diabetic nephropathy (P = 0.029). Clinical oral and radiographic scores tended to be higher among patients in the diabetic nephropathy group than in the non-diabetic nephropathy group. Periodontal pathogens, particularly A. actinomycetemcomitans, may play a role, at least a part, in the development of cerebral infarction in Japanese HD patients with diabetic nephropathy.
    BMC Infectious Diseases 11/2013; 13(1):557. DOI:10.1186/1471-2334-13-557 · 2.56 Impact Factor
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    ABSTRACT: Marfan syndrome (MFS) is a systemic connective tissue disorder caused by mutations in the extracellular matrix protein fibrillin-1. While it is known that patients with MFS are at high risk of dental disorders and cardiovascular diseases, little information has been provided to date. To clarify the prevalence of periodontitis in patients with MFS, their oral condition and cardiovascular complications were evaluated. The subjects were patients with MFS (n = 40) who attended the University of Tokyo hospital; age- and gender-matched healthy individuals (n = 14) constituted a control group. Cardiovascular complications and full-mouth clinical measurements, including number of teeth, probing of pocket depth (PD), bleeding on probing (BOP), and community periodontal index (CPI) were recorded. MFS patients had more frequent cardiovascular complications (95 %) compared with the controls (0 %). MFS patients had periodontitis (CPI 3 and 4) more frequently (87.5 %) than the age- and gender-matched control subjects (35.7 %). Furthermore, MFS patients had significantly more severe periodontitis (CPI 2.90 ± 0.12 vs 1.64 ± 0.32) and fewer remaining teeth (26.7 ± 0.4 vs 28.4 ± 0.4) compared with the controls. However, PD and BOP were comparable between MFS patients and the control group. A high incidence of periodontitis and cardiovascular complications was observed in Japanese MFS patients.
    Heart and Vessels 11/2013; DOI:10.1007/s00380-013-0434-y · 2.11 Impact Factor
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    ABSTRACT: Notch signaling is involved in an intercellular communication mechanism that is essential for coordinated cell fate determination and tissue morphogenesis. The biological effects of Notch signaling are context-dependent. We investigated the functional and hierarchical relationship between angiotensin (Ang) II receptor signaling and Notch signaling in vascular smooth muscle cells (VSMCs). A fluorogenic substrate assay revealed directly that the enzymatic activity of γ-secretase was enhanced after 10 min of Ang II stimulation in HEK293 cells expressing Ang II type 1 receptor. Notch cleavage by γ-secretase was consistently induced and peaked at 10 min after Ang II stimulation, and the Ang II-stimulated increase in Notch intracellular domain production was significantly suppressed by treatment with the γ-secretase inhibitor DAPT. Treatment with DAPT also significantly reduced the Ang II-stimulated proliferation and migration of human aortic VSMCs, as revealed by BrdU incorporation and the Boyden chamber assay, respectively. Systemic administration of the γ-secretase inhibitor dibenzazepine reduced Ang II-induced medial thickening and perivascular fibrosis in the aortas of wild-type mice. These findings suggest that the hierarchical Ang II receptor-Notch signaling pathway promotes the proliferation and migration of VSMCs, and thereby contributes to the progression of vascular remodeling.Hypertension Research advance online publication, 30 May 2013; doi:10.1038/hr.2013.52.
    Hypertension Research 05/2013; DOI:10.1038/hr.2013.52 · 2.94 Impact Factor
  • Yoko Sakamoto, Hiroshi Akazawa, Issei Komuro
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    ABSTRACT: Calpains are Ca(2 +) -dependent cysteine proteases. Fifteen gene products of calpains are expressed in mammals. Among them, Calpain 1 and Calpain 2 are ubiquitously expressed and have been investigated extensively. Under the physiological conditions, calpain activity is strictly regulated by endogenous inhibitory protein, Calpastatin. Calpains are activated in the various cardiovascular diseases and implicated in their pathogenesis by degrading numerous target proteins. Here we briefly summarize the physiological and pathological role of calpains in the cardiovascular diseases.
    Clinical calcium 04/2013; 23(4):519-25.
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    ABSTRACT: The octapeptide angiotensin II (Ang II) plays a homeostatic role in the regulation of blood pressure and water and electrolyte balance, and also contributes to the progression of cardiovascular remodeling. Ang II activates Ang II type 1 (AT1) receptor and type 2 (AT2) receptor, both of which belong to the seven-transmembrane, G protein-coupled receptor family. Most of the actions of Ang II such as promotion of cellular prolifaration, hypertrophy, and fibrosis are mediated by AT1 receptor. However, in some pathological situations, AT2 receptor shows an increase in tissue expression and functions to antagonize the actions induced by AT1 receptor. Recent studies have advanced our understanding of the molecular mechanisms underlying receptor activation and signal transduction of AT1 and AT2 receptor in the cardiovascular system.
    Current pharmaceutical design 11/2012; · 3.29 Impact Factor
  • Hiroshi Akazawa, Issei Komuro
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    ABSTRACT: A growing body of evidence indicates that activation of angiotensin II (Ang II) type 1 (AT1) receptor, a seven -transmembrane G protein -coupled receptor, is critically involved in the development of various cardiovascular diseases. Inherently, AT1 receptor is structurally unstable, and shows spontaneous constitutive activity in an Ang II-independent manner. The constitutive activity of AT1 receptor under basal conditions contributes to the cardiac remodeling even in the absence of Ang II, when AT1 receptor is up-regulated in the heart. Furthermore, mechanical stress can activate AT1 receptor by inducing conformational switch without the involvement of Ang II, and induce cardiac hypertrophy in vivo. These agonist-independent activities of AT1 receptor can be inhibited by inverse agonists, but not by neutral antagonists. Therefore, inverse agonism of AT1 receptor blockers provides therapeutic benefits in the prevention of cardiac remodeling, and thus has potential impact on long-term outcomes in patients with cardiovascular diseases.
    Nippon rinsho. Japanese journal of clinical medicine 09/2012; 70(9):1492-8.
  • Hiroshi Akazawa, Issei Komuro
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    ABSTRACT: Pharmacological inhibitions of the renin-angiotensin-aldosterone system (RAAS) are crowned with one of the greatest success in the current field of cardiovascular medicine. In addition to the systemic effects including elevation of blood pressure and retention of sodium and water, sustained and excessive RAAS activation has direct and deleterious effects on a wide variety of tissues. Recent studies have deciphered the regulatory mechanisms underlying tissue RAAS activation at cellular and molecular levels, and suggested pathogenic roles of RAAS activation in hitherto unanticipated disorders such as muscular dystrophy, osteoporosis, cancer, and aging itself. Novel drugs targeting RAAS are under research and development in search for further efficacy, specificity, and even multifunctionality. This review will discuss the current progress and future perspective of RAAS research.
    Nippon rinsho. Japanese journal of clinical medicine 09/2012; 70(9):1471-6.
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    ABSTRACT: Wnt signaling plays critical roles in development of various organs and pathogenesis of many diseases, and augmented Wnt signaling has recently been implicated in mammalian aging and aging-related phenotypes. We here report that complement C1q activates canonical Wnt signaling and promotes aging-associated decline in tissue regeneration. Serum C1q concentration is increased with aging, and Wnt signaling activity is augmented during aging in the serum and in multiple tissues of wild-type mice, but not in those of C1qa-deficient mice. C1q activates canonical Wnt signaling by binding to Frizzled receptors and subsequently inducing C1s-dependent cleavage of the ectodomain of Wnt coreceptor low-density lipoprotein receptor-related protein 6. Skeletal muscle regeneration in young mice is inhibited by exogenous C1q treatment, whereas aging-associated impairment of muscle regeneration is restored by C1s inhibition or C1qa gene disruption. Our findings therefore suggest the unexpected role of complement C1q in Wnt signal transduction and modulation of mammalian aging.
    Cell 06/2012; 149(6):1298-313. DOI:10.1016/j.cell.2012.03.047 · 33.12 Impact Factor

Publication Stats

4k Citations
646.17 Total Impact Points


  • 2014
    • The University of Tokyo
      Tōkyō, Japan
  • 2010–2013
    • Osaka City University
      • Department of Cardiovascular Medicine
      Ōsaka, Ōsaka, Japan
  • 2010–2012
    • Osaka University
      Suika, Ōsaka, Japan
  • 2003–2009
    • Chiba University
      Tiba, Chiba, Japan
  • 2008
    • Massachusetts General Hospital
      Boston, Massachusetts, United States
  • 2007
    • Seirei Yokohama Hospital
      Yokohama, Kanagawa, Japan
  • 2006
    • Hyogo Prefectural Amagasaki Hospital
      Amagasaki, Hyōgo, Japan
  • 2005
    • Gunma Children's Medical Center
      Shibukawa, Gunma Prefecture, Japan
  • 2004
    • Yamaguchi University
      Yamaguti, Yamaguchi, Japan
  • 2002
    • Shinshu University
      Shonai, Nagano, Japan
  • 2000–2002
    • Japanese Foundation for Cancer Research
      Edo, Tōkyō, Japan