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Koshiro Monzen

Publications and source records attributed to Koshiro Monzen.

10 recordsLinked to original sources
PubMed2005

The use of a supercooling refrigerator improves the preservation of organ grafts.

Current medical transplantation confronts major problems such as the shortage of donors and geographical restrictions that inhibit efficient utilization of finite donor organs within their storage lives. To overcome these issues, expanding organ preservation time has become a major concern. We investigated whether a strategy which best preserves organ grafts can be achieved by the use of a newly developed refrigerating chamber, which is capable of establishing a supercooled and unfrozen state stably by generating an electrostatic field in its inside. When adult rat organs such as heart, liver, and kidneys were stored in the supercooled conditions, the levels of major biochemical markers leaked from the preserved organs were significantly lower than in the ordinary hypothermic storage. No apparent tissue damages were observed histologically after the supercooled preservation. Our results suggest that the use of this supercooling refrigerator improves organ preservation and may provide an innovative technique for human organ transplantation.

Animals↗
PubMed2005

Genetic analysis in a patient with recurrent cardiac myxoma and endocrinopathy.

A 60 year-old male was referred for treatment of a cardiac myxoma in the right atrium. He had a past history of left atrial cardiac myxoma at age 49 and pituitary microadenoma related to acromegaly at age 55. He did not have a family history of cardiac neoplasm or endocrinopathy. The intracardiac tumor was resected and its pathology was compatible with myxoma. A diagnosis of Carney complex (CNC) was made because the diagnostic criteria of this neoplastic syndrome were satisfied by the presence of recurrent cardiac myxoma, endocrine tumor and spotty skin pigmentation. In genetic analysis novel frame shift mutation was detected in exon 2 in a heterozygous fashion in the causative gene of CNC, protein kinase A regulatory subunit 1 alpha (PRKAR1A). This genetic mutation is thought to cause haplo-insufficiency of PRKAR1A resulting in tumorigenesis. Although it is the most common, usually benign, cardiac tumor, myxoma can cause a critical clinical situation and thus detecting the PRKAR1A mutation can assist with prognosis.

Acromegaly↗
PubMed2004

Atrial natriuretic peptide inhibits cardiomyocyte hypertrophy through mitogen-activated protein kinase phosphatase-1.

Cardiac hypertrophy is formed in response to hemodynamic overload. Although a variety of factors such as catecholamines, angiotensin II (AngII), and endothelin-1 (ET-1) have been reported to induce cardiac hypertrophy, little is known regarding the factors that inhibit the development of cardiac hypertrophy. Production of atrial natriuretic peptide (ANP) is increased in the hypertrophied heart and ANP has recently been reported to inhibit the growth of various cell types. We therefore examined whether ANP inhibits the development of cardiac hypertrophy. Pretreatment of cultured cardiomyocytes with ANP inhibited the AngII- or ET-1-induced increase in the cell size and the protein synthesis. ANP also inhibited the AngII- or ET-1-induced hypertrophic responses such as activation of mitogen-activated protein kinase (MAPK) and induction of immediate early response genes and fetal type genes. To determine how ANP inhibits cardiomyocyte hypertrophy, we examined the mechanism of ANP-induced suppression of the MAPK activation. ANP strongly induced expression of MAPK phosphatase-1 (MKP-1) and overexpression of MKP-1 inhibited AngII- or ET-1-induced hypertrophic responses. These growth-inhibitory actions of ANP were mimicked by a cyclic GMP analog 8-bromo-cyclic GMP. Taken together, ANP directly inhibits the growth factor-induced cardiomyocyte hypertrophy at least partly via induction of MKP-1. Our present study suggests that the formation of cardiac hypertrophy is regulated not only by positive but by negative factors in response to hemodynamic load.

Animals↗
PubMed2004

Development of a pioneering clinical support system utilizing information technology.

Nowadays, evidence-based medicine has entered the mainstream of clinical judgement and the human genome has been completely decoded. Even the concept of individually designed medicine, that is, tailor-made medicine, is now being discussed. Due to their complexity, however, management methods for clinical information have yet to be established. We have conducted a study on a universal technique which enables one to select or produce by employing information processing technology clinical findings from various clinical information generated in vast quantity in day-to-day clinical practice, and to share such information and/or the results of analysis between two or more institutions. In this study, clinically useful findings have been successfully obtained by systematizing actual clinical information and genomic information obtained by an appropriate collecting and management method of information with due consideration to ethical issues. We report here these medical achievements as well as technological ones which will play a role in propagating such medical achievements.

Artificial Intelligence↗
PubMed2003

Early stage-specific inhibitions of cardiomyocyte differentiation and expression of Csx/Nkx-2.5 and GATA-4 by phosphatidylinositol 3-kinase inhibitor LY294002.

Inhibition of phosphatidylinositol 3-kinase (PI3-kinase) has been reported to block cardiomyocyte differentiation. However, at which stage PI3-kinase plays this important role and what its molecular targets are remain unknown. To answer these questions, we induced cardiomyocyte differentiation of P19CL6 mouse embryonal carcinoma cells and investigated the activation of PI3-kinase by analyzing phospho-Akt. We also treated P19CL6 cells with the PI3-kinase-specific inhibitor LY294002 either continuously or at various time points and monitored the expression of cardiac contractile proteins and transcription factors. Most cells differentiated into sarcomeric myosin heavy chain (MHC)-positive cardiomyocytes on day 16 after induction. An increase in phospho-Akt was observed after induction and was maintained throughout the differentiation. LY294002 treatment restricted to the phase from days 0 to 4 was sufficient to inhibit cardiomyocyte differentiation in a dose-dependent manner. In contrast, LY294002 treatment either from days 4 to 8 or from days 8 to 12 did not cause significant changes in sarcomeric MHC expression. LY294002 treatment from days 0 to 4 also suppressed Csx/Nkx-2.5 and GATA-4 expression. These results demonstrate that PI3-kinase becomes activated and plays a pivotal role at a very early stage of cardiomyocyte differentiation, possibly by modulating the expression of the cardiac transcription factors.

Animals↗
PubMed2003

Sox6 regulation of cardiac myocyte development.

A mouse mutation (p100H/p100H) has been identified that is associated with cardioskeletal myopathy, heart block, delayed growth and early postnatal death. The gene that is disrupted in this mutation encodes the transcription factor Sox6. P19CL6 cells were used as an in vitro cardiomyocyte differentiation system and revealed that Sox6 is expressed exclusively when the cells are committed to differentiate to beating cardiac myocytes. We used the yeast two-hybrid system to identify the Prtb (Proline-rich transcript of the brain) protein as a Sox6 interactor, and subsequently confirmed the interaction by co-immunoprecipitation. Prtb expression in P19CL6 cells increased with differentiation to beating cardiomyocytes. Using the P19CL6 cells stably transfected with noggin, an antagonist of BMP (Bone Morphogenic Protein), we found that BMP expression is required for Sox6 expression in cardiomyocyte differentiation. Surprisingly, the expression of the alpha1c-subunit gene of the L-type Ca2+ channel decreased in P19CL6 cells as they differentiated to beating cardiac cells. Ectopic expression of Sox6 or Prtb alone in P19CL6 cells caused down-regulation of L-type Ca2+ alpha1c expression, but when Sox6 and Prtb were co-transfected to the cells, L-type Ca2+ alpha1c remained at basal levels. A similar relationship of Sox6 and L-type Ca2+ alpha1c expression was seen in vivo (comparing wild-type and p(100H)/p(100H) mutant mice). Thus, Sox6 is within the BMP pathway in cardiac differentiation, interacts with Prtb and may play a critical role in the regulation of a cardiac L-type Ca2+ channel.

Animals↗
PubMed2003

A common Ile 823 Met variant of ATP-binding cassette transporter A1 gene (ABCA1) alters high density lipoprotein cholesterol level in Japanese population.

Recently, variants in ATP-binding cassette transporter A1 (ABCA1) were demonstrated to be associated with increased level of high density lipoprotein cholesterol (HDL-C) and decreased risk of coronary artery disease (CAD) in Caucasians. However, this is not universally applicable due to the ethnic or environmental differences. In this context, to clarify the effect of ABCA1 in Japanese, we evaluated the phenotypic effects of I/M 823 and R/K 219 variants on the plasma level of HDL-C in 410 patients recruited in our hospital. Subjects with M 823 allele had significantly higher level of HDL-C than those without M823 allele (49.0+/-15.1 vs. 44.9+/-11.5 mg/dl, respectively, P<0.05). This statistical significance did not change even after multiple regression analysis. In contrast, there was no difference in HDL-C level among the genotypes in R/K 219 polymorphism. Further, in our study population an inverse relationship was shown to exist between HDL-C level and incidence of CAD. However, no positive association was observed between those variants and susceptibility to CAD. In this study, we provide evidence that I/M 823 variant, not R/K 219 variant, in ABCA1 is one of the determinants of HDL-C level, suggesting the importance of this gene on lipid metabolism in Japanese.

ATP Binding Cassette Transporter 1↗
PubMed2002

Dual effects of the homeobox transcription factor Csx/Nkx2-5 on cardiomyocytes.

A homeobox-containing transcription factor Csx/Nkx2-5 is an important regulator of cardiac development. Many different human CSX/NKX2-5 mutations have been reported to cause congenital heart disease. We here examined the effects of three representative CSX/NKX2-5 mutations on cardiomyocyte differentiation and death with the use of the P19CL6 cardiomyogenic cell lines. Stable overexpression of wild-type CSX/NKX2-5 enhanced expression of cardiac-specific genes such as MEF2C and MLC2v, the promoter activity of the atrial natriuretic peptide gene, and the terminal differentiation of P19CL6 into cardiomyocytes, while all CSX/NKX2-5 mutants attenuated them by different degrees. When exposed to H(2)O(2) or cultured without change of the medium, many differentiated P19CL6 cells overexpressing the mutants, especially the mutant which lacks the carboxyl terminal region just after the homeodomain, were dead, while most of the cells overexpressing wild-type CSX/NKX2-5 survived. Overexpression of the carboxyl terminus-deleted mutant down-regulated expression of an anti-apoptotic protein Bcl-x(L) and up-regulated that of a pro-apoptotic protein CAS, while in the cells overexpressing wild-type CSX/NKX2-5, expression of a pro-apoptotic protein RIP was reduced. Furthermore, overexpression of wild-type CSX/NKX2-5 decreased the number of H(2)O(2)-induced TUNEL-positive cultured cardiomyocytes of neonatal rats, whereas overexpression of the mutants enhanced it. These results suggest that Csx/Nkx2-5 not only regulates expression of cardiac-specific genes but protects cardiomyocytes from stresses and that cell death may be another cause for the cardiac defects induced by human CSX/NKX2-5 mutations.

Animals↗
PubMed2002

A role for bone morphogenetic protein signaling in cardiomyocyte differentiation.

Elucidating molecular mechanisms that regulate induction of cardiomyocyte differentiation is important because it may lead to practical therapeutic application for tissue regeneration in various heart diseases. Recent studies have demonstrated that some growth factors regulate expression of cardiac transcription factors and play a pivotal role in cardiac development. This study investigated the roles of bone morphogenetic proteins (BMPs) and their downstream molecules, using P19CL6 cardiomyogenic cell lines. Several lines of evidence show that BMPs are indispensable for cardiomyocyte differentiation and induce differentiation through two cardiac transcription factors, Csx/Nkx2-5 and GATA-4. Furthermore, it was demonstrated that not only Smads and TAK1, important mediators of transforming growth factor-beta signaling, but also their common target, ATF-2 transcription factor, play a critical role in cardiomyocyte differentiation.

Animals↗