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Modification of mesenchymal stem cells for cardiac regeneration.
Song, Heesang,Song, Byeong-Wook,Cha, Min-Ji,Choi, In-Geol,Hwang, Ki-Chul Ashley Publications Ltd 2010 Expert opinion on biological therapy Vol.10 No.3
<P>Mesenchymal stem cells (MSCs) have the greatest potential for use in cell-based therapy of human heart diseases, especially in myocardial infarcts. The therapeutic potential of MSCs in myocardial repair is based on the ability of MSCs to directly differentiate into cardiac tissue and on the paracrine actions of factors released from MSCs. However, the major obstacle in the clinical application of MSC-based therapy is the poor viability of the transplanted cells due to harsh microenvironments like ischemia, inflammation and/or anoikis in the infarcted myocardium. Recently, various approaches have been implemented in an effort to improve the survival of implanted MSCs through ex vivo manipulation of MSCs.</P>
Song, Heesang,Hwang, Hye Jin,Chang, Woochul,Song, Byeong-Wook,Cha, Min-Ji,Kim, Il-Kwon,Lim, Soyeon,Choi, Eun Ju,Ham, Onju,Lee, Chang Youn,Park, Jun-Hee,Lee, Se-Yeon,Choi, Eunmi,Lee, Chungkeun,Lee, Myo National Academy of Sciences 2011 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.108 No.1
<P>Despite the safety and feasibility of mesenchymal stem cell (MSC) therapy, an optimal cell type has not yet emerged in terms of electromechanical integration in infarcted myocardium. We found that poor to moderate survival benefits of MSC-implanted rats were caused by incomplete electromechanical integration induced by tissue heterogeneity between myocytes and engrafted MSCs in the infarcted myocardium. Here, we report the development of cardiogenic cells from rat MSCs activated by phorbol myristate acetate, a PKC activator, that exhibited high expressions of cardiac-specific markers and Ca(2+) homeostasis-related proteins and showed adrenergic receptor signaling by norepinephrine. Histological analysis showed high connexin 43 coupling, few inflammatory cells, and low fibrotic markers in myocardium implanted with these phorbol myristate acetate-activated MSCs. Infarct hearts implanted with these cells exhibited restoration of conduction velocity through decreased tissue heterogeneity and improved myocardial contractility. These findings have major implications for the development of better cell types for electromechanical integration of cell-based treatment for infarcted myocardium.</P>
Tissue transglutaminase 2 promotes apoptosis of rat neonatal cardiomyocytes under oxidative stress
Song, Heesang,Kim, Byoung-Keuk,Chang, Woochul,Lim, Soyeon,Song, Byeong-Wook,Cha, Min-Ji,Jang, Yangsoo,Hwang, Ki-Chul Informa Healthcare 2011 Journal of receptors and signal transduction Vol.31 No.1
<P>The role of tissue transglutaminase 2 (TG2) in cardiac myocyte apoptosis under oxidative stress induced by ischemic injury remains unclear. Here, we investigated the effects of TG2 on apoptosis of cardiomyocytes under oxidative stress. Ectopic expression of TG2 increased caspase-3 activity and calcium overload in cardiomyocytes. Expression levels of TG2 were significantly increased in H<SUB>2</SUB>O<SUB>2</SUB>-treated cardiomyocytes. Caspase-3 activity assay demonstrated its considerable correlation with TG2 expression, which supported that caspase-3 inhibitor inhibited the apoptosis induced by the ectopic overexpression of TG2. In addition, the other apoptotic signals, such as caspase-8, cytochrome <I>c</I>, and Bax, were increased dependent with TG2 expression in H<SUB>2</SUB>O<SUB>2</SUB>-treated cardiomyocytes. These results indicated that apoptotic signals had a positive correlation with TG2 expression. The decreased expression of phospholipase C (PLC)-δ1 and phospho-PKC in H<SUB>2</SUB>O<SUB>2</SUB>-treated cardiomyocytes were rescued by TG2 silencing. Together, our data strongly suggest that oxidative stress up-regulates TG2 expression in cardiomyocytes, leading to apoptosis.</P>
Song, Heesang,Chang, Woochul,Lim, Soyeon,Seo, Hye-Sun,Shim, Chi Young,Park, Sungha,Yoo, Kyung-Jong,Kim, Byung-Soo,Min, Byoung-Hyun,Lee, Hakbae,Jang, Yangsoo,Chung, Namsik,Hwang, Ki-Chul Wiley (John WileySons) 2007 Stem Cells Vol.25 No.6
<P>Autologous mesenchymal stem cell (MSC) transplantation therapy for repair of myocardial injury has inherent limitations due to the poor viability of the stem cells after cell transplantation. Adhesion is a prerequisite for cell survival and also a key factor for the differentiation of MSCs. As a novel prosurvival modification strategy, we genetically engineered MSCs to overexpress tissue transglutaminase (tTG), with intention to enhance adhesion and ultimately cell survival after implantation. tTG-transfected MSCs (tTG-MSCs) showed a 2.7-fold and greater than a twofold increase of tTG expression and surface tTG activity, respectively, leading to a 20% increased adhesion of MSCs on fibronectin (Fn). Spreading and migration of tTG-MSCs were increased 4.75% and 2.52%, respectively. Adhesion of tTG-MSCs on cardiogel, a cardiac fibroblast-derived three-dimensional matrix, showed a 33.1% increase. Downregulation of tTG by transfection of small interfering RNA specific to the tTG resulted in markedly decreased adhesion and spread of MSCs on Fn or cardiogel. tTG-MSCs on Fn significantly increased phosphorylation of focal adhesion related kinases FAK, Src, and PI3K. tTG-MSCs showed significant retention in infarcted myocardium by forming a focal adhesion complex and developed into cardiac myocyte-like cells by the expression of cardiac-specific proteins. Transplantation of 1 x 10(6) MSCs transduced with tTG into the ischemic rat myocardium restored normalized systolic and diastolic cardiac function. tTG-MSCs further restored cardiac function of infarcted myocardium as compared with MSC transplantation alone. These findings suggested that tTG may play an important role in integrin-mediated adhesion of MSCs in implanted tissues. Disclosure of potential conflicts of interest is found at the end of this article.</P>
[기타] 대향류형 보텍스 튜브에서의 입구조건 변화에 따른 온도 분리 효율에 관한 연구
황승식(Seungsik Hwang),선영택(Youngtaek Sun),전운학(Unhack Chun),김종철(Jongchul Kim),이희상(Heesang Lee) 한국자동차공학회 2000 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The aim of this study is to provide fundamental informations that make it possible to use a cool stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and the efficiency. From the study, following conclusive remarks can be made. As inlet pressure increases temperature distribution to increase. But, efficiency not to change. As a number of nozzle increases efficiency enlarge.
황해수(Haesu Hwang),이희상(Heesang Lee) 한국정보보호학회 2015 정보보호학회논문지 Vol.25 No.3
최근 IT환경의 변화와 해킹공격의 발전은 기업의 보안사고 발생위험을 높이고 있다. 특정 사건이 기업에 미치는 주가변화를 측정할 수 있는 사건연구방법론은 보안사고 기업의 시장가치의 피해비용을 분석하기 위한 대표적인 방법론으로 주로 사용되어 왔다. 그러나 기업의 일시적인 주가변화 분석은 모든 기업들에게 공통된 시사점으로 활용하는데 제약이 있고, 기업에 발생한 평판의 손실분석에 대한 필요성 또한 강조되고 있다. 본 연구는 국내에서 최근 10년간 발생된 상장기업의 보안사고 52건을 대상으로 기업의 가치평가 방법론인 Tobin’s q가 제시한 기업의 기준을 세분화함으로써, 보안사고로 인한 평판손실이 유의하게 발생함을 정량분석하였다. 이러한 접근방법은 q로 분류된 기업 별 피해범위에 해당하는 정보보호 투자예산 책정과 효율적인 리소스 투입 산정의 판단기준으로 활용 가능할 것이다. Recently, the risk of security incidents has been increased due to change of IT environment and development of new hacking methods. Event study methodology that measures the effect of a specific security incident on the stock price is widely adopted to analyze the damage cost of security incidents on market value. However, analysis of company’s temporary stock price change is limited to immediate practical implication, and reputation loss should be considered as a collateral damage caused by security incidents. We analyzed 52 security incidents of listed Korean companies in the last decade; by refining the criteria presented by Tobin’s q, we quantitatively showed that the companies has significantly higher reputation loss due to security loss than the other companies. Our research findings can be used in order that the companies can efficiently allocate its resource and investment for information security.