Woochul Chang

Reactive Oxygen Species Inhibit Adhesion of Mesenchymal Stem Cells Implanted into Ischemic Myocardium via Interference of Focal Adhesion Complex

The integrity of transplanted mesenchymal stem cells (MSCs) for cardiac regeneration is dependent on cell–cell or cell–matrix adhesion, which is inhibited by reactive oxygen species (ROS) generated in ischemic surroundings after myocardial infarction. Intracellular ROS play a key role in the regulation of cell adhesion, migration, and proliferation. This study was designed to investigate the role of ROS on MSC adhesion. In H2O2 treated MSCs, adhesion and spreading were inhibited and detachment was increased in a dose‐dependent manner, and these effects were significantly rescued by co‐treatment with the free radical scavenger, N‐acetyl‐L‐cysteine (NAC, 1 mM). A similar pattern was observed on plates coated with different matrices such as fibronectin and cardiogel. Hydrogen peroxide treatment resulted in a marked decrease in the level of focal adhesion‐related molecules, such as phospho‐FAK and p‐Src in MSCs. We also observed a significant decrease in the integrin‐related adhesion molecules, αV and β1, in H2O2 treated MSCs. When injected into infarcted hearts, the adhesion of MSCs co‐injected with NAC to the border region was significantly improved. Consequently, we observed that fibrosis and infarct size were reduced in MSC and NAC‐injected rat hearts compared to in MSC‐only injected hearts. These results indicate that ROS inhibit cellular adhesion of engrafted MSCs and provide evidence that the elimination of ROS might be a novel strategy for improving the survival of engrafted MSCs. STEM CELLS 2010;28:555–563

Mesenchymal Stem Cells Pretreated with Delivered Hph‐1‐Hsp70 Protein Are Protected from Hypoxia‐Mediated Cell Death and Rescue Heart Functions from Myocardial Injury

Mesenchymal stem cell (MSC) therapy for myocardial injury has inherent limitations due to the poor viability of MSCs after cell transplantation. In this study, we directly delivered Hsp70, a protein with protective functions against stress, into MSCs, using the Hph‐1 protein transduction domain ex vivo for high transfection efficiency and low cytotoxicity. Compared to control MSCs in in vitro hypoxic conditions, MSCs delivered with Hph‐1‐Hsp70 (Hph‐1‐Hsp70‐MSCs) displayed higher viability and anti‐apoptotic properties, including Bcl2 increase, reduction of Bax, JNK phosphorylation and caspase‐3 activity. Hsp70 delivery also attenuated cellular ATP‐depleting stress. Eight animals per group were used for in vivo experiments after occlusion of the left coronary artery. Transplantation of Hph‐1‐Hsp70‐MSCs led to a decrease in the fibrotic heart area, and significantly reduced the apoptotic positive index by 19.5 ± 2%, compared to no‐treatment controls. Hph‐1‐Hsp70‐MSCs were well‐integrated into the infarcted host myocardium. The mean microvessel count per field in the infarcted myocardium of the Hph‐1‐Hsp70‐MSC‐treated group (122.1 ± 13.5) increased relative to the MSC‐treated group (75.9 ± 10.4). By echocardiography, transplantation of Hph‐1‐Hsp70‐MSCs resulted in additional increases in heart function, compared to the MSCs‐transplanted group. Our results may help formulate better clinical strategies for in vivo MSC cell therapy for myocardial damage. STEM CELLS 2009;27:2283–2292

Tissue Transglutaminase Is Essential for Integrin-Mediated Survival of Bone Marrow-Derived Mesenchymal Stem Cells

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 × 106 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.

Integrin-Linked Kinase Is Required in Hypoxic Mesenchymal Stem Cells for Strengthening Cell Adhesion to Ischemic Myocardium†‡

Mesenchymal stem cells (MSCs) therapy has limitations due to the poor viability of MSCs after cell transplantation. Integrin‐mediated adhesion is a prerequisite for cell survival. As a novel anti‐death strategy to improve cell survival in the infarcted heart, MSCs were genetically modified to overexpress integrin‐linked kinase (ILK). The survival rate of ILK‐transfected MSCs (ILK‐MSCs) was augmented by about 1.5‐fold and the phosphorylation of ERK1/2 and Akt in ILK‐MSCs were increased by about three and twofold, respectively. ILK‐MSCs demonstrated an increase of twofold in the ratio of Bcl‐2/Bax and inhibited caspase‐3 activation, compared with hypoxic MSCs. The adhesion rate of ILK‐MSCs also had a 32.2% increase on the cardiac fibroblast‐derived three‐dimensional matrix and ILK‐MSCs showed higher retention by about fourfold compared to unmodified MSCs. Six animals per group were used for the in vivo experiments analyzed at 1 week after occlusion of the left coronary artery. ILK‐MSC transplanted rats had a 12.0% ± 3.1% smaller infarct size than MSC‐treated rats after ligation of left anterior descending coronary artery. Transplantation of ILK‐MSCs not only led to a 16.0% ± 0.4% decrease in the fibrotic heart area, but also significantly reduced the apoptotic positive index by two‐thirds when compared with ligation only. The mean microvessel count per field in the infarcted myocardium of ILK‐MSCs group was increased relative to the sham group and MSCs group. In conclusion, the ILK gene transduction of MSCs further assisted cell survival and adhesion, and improved myocardial damage when compared with MSC only after transplantation. STEM CELLS 2009;27:1358–1365

Cordycepin inhibits vascular smooth muscle cell proliferation

Percutaneous transluminal coronary angioplasty (PTCA) is a common procedure for treating atherosclerosis, but its efficacy is limited because of the occurrence of restenosis within 3-6 months after angioplasty. Restenosis is induced by the remodeling of the vessel wall and/or the accumulation of cells and extracellular matrix (ECM) in the intimal layer. Therefore, the matrix metalloproteinase (MMP) system may be a potential therapeutic target for the treatment of restenosis or atherosclerosis. Cordycepin is reported to possess many pharmacological activities including immunological stimulating, anti-cancer, antioxidant, and anti-inflammatory activities. The effect of cordycepin on restenosis has not yet been clearly elucidated. Therefore, in the present study, we tested the role of cordycepin on the MMP system in vascular smooth muscle cells. In the carotid artery of a balloon-injured Sprague-Dawley (SD) rat, neointimal formation was reduced by treatment with cordycepin (20 microM/day, i.p), which inhibited the proliferation of rat aortic smooth muscle cells (RaoSMCs). To investigate the mechanism by which cordycepin inhibits the remodeling of the vessel wall and/or the accumulation of cells and ECM, we examined the activation of MMP systems in collagen type I-activated RaoSMCs. Cordycepin markedly inhibited the activation of MMP-2 and -9 as well as the expression of extracellular matrix metalloproteinase inducer (EMMPRIN) in a dose-dependent manner in collagen type I-activated RaoSMCs. Moreover, cordycepin suppressed cycloxygenase-2 (COX-2) expression related to hyperplasia of RAoSMCs. Taken together, these data suggest that cordycepin may induce antiproliferation in RAoSMCs via the modulation of vessel wall remodeling. Therefore, cordycepin may be a potential therapeutic approach to treat restenosis.

The role of microRNA-23b in the differentiation of MSC into chondrocyte by targeting protein kinase A signaling

Chondrogenic differentiation of mesenchymal stem cells (MSCs) is critical for successful cartilage regeneration. Several methods have been developed to attempt to chondrogenic differentiation, because chondrogenic differentiated cells can form stable cartilage and induce expression of a cartilage-specific phenotype. In this study, we found that both H-89 and microRNA-23b induced differentiation into chondrocyte of hMSCs through down-regulation of protein kinase A (PKA) signaling. The small molecule, H-89, was identified by PCA analysis as a potential mediator of chondrogenic differentiation. H-89 induced the expression of the chondrocyte marker, aggrecan, as well as miR-23b. We searched that miR-23b regulates protein level of PKA. When miR-23b was transfected into hMSCs, chondrogenic differentiation was induced. We confirmed the target of miR-23b using a reporter gene assay. Furthermore, not only H-89 or miR-23b-treated cells, but also cell co-treated with H-89 and miR-23b differentiated into chondrocytes. Our results indicate that H-89 induces the expression of endogenous miR-23b, thereby inducing chondrogenic differentiation by negatively inhibition of PKA signaling.

Chemicals that modulate stem cell differentiation

Important cellular processes such as cell fate are likely to be controlled by an elaborate orchestration of multiple signaling pathways, many of which are still not well understood or known. Because protein kinases, the members of a large family of proteins involved in modulating many known signaling pathways, are likely to play important roles in balancing multiple signals to modulate cell fate, we focused our initial search for chemical reagents that regulate stem cell fate among known inhibitors of protein kinases. We have screened 41 characterized inhibitors of six major protein kinase subfamilies to alter the orchestration of multiple signaling pathways involved in differentiation of stem cells. We found that some of them cause recognizable changes in the differentiation rates of two types of stem cells, rat mesenchymal stem cells (MSCs) and mouse embryonic stem cells (ESCs). Among many, we describe the two most effective derivatives of the same scaffold compound, isoquinolinesulfonamide, on the stem cell differentiation: rat MSCs to chondrocytes and mouse ESCs to dopaminergic neurons.

Antiarrhythmic Potential of Mesenchymal Stem Cell Is Modulated by Hypoxic Environment

OBJECTIVES The purpose of this study was to evaluate the antiarrhythmic potential of mesenchymal stem cells (MSC) under a different environment. BACKGROUND Little is known about how environmental status affects antiarrhythmic potential of MSCs. METHODS To investigate the effect of paracrine factors secreted from MSCs under different circumstances on arrhythmogenicity in rats with myocardial infarction, we injected paracrine media (PM) secreted under hypoxic, normoxic conditions (hypoxic PM and normoxic PM), and MSC into the border zone of infarcted myocardium in rats. RESULTS We found that the injection of hypoxic PM, but not normoxic PM, markedly restored conduction velocities, suppressed focal activity, and prevented sudden arrhythmic deaths in rats. Underlying this electrophysiological alteration was a decrease in fibrosis, restoration of connexin 43, alleviation of Ca(2+) overload, and recovery of Ca(2+)-regulatory ion channels and proteins, all of which is supported by proteomic data showing that several paracrine factors including basic fibroblast growth factor, insulinlike growth factor 1, hepatocyte growth factor, and EF-hand domain-containing 2 are potential mediators. When compared with PM, MSC injection did not reduce or prevent arrhythmogenicity, suggesting that the antiarrhythmic or proarrhythmic potential of MSC is mainly dependent on paracrine factors. CONCLUSIONS A hypoxic or normoxic environment surrounding MSC affects the type and properties of the growth factors or cytokines, and these secreted molecules determine the characteristics of the electro-anatomical substrate of the surrounding myocardium.

Survival of hypoxic human mesenchymal stem cells is enhanced by a positive feedback loop involving miR-210 and hypoxia-inducible factor 1

The use of mesenchymal stem cells (MSCs) has emerged as a potential new treatment for myocardial infarction. However, the poor viability of MSCs after transplantation critically limits the efficacy of this new strategy. The expression of microRNA-210 (miR-210) is induced by hypoxia and is important for cell survival under hypoxic conditions. Hypoxia increases the levels of hypoxia inducible factor-1 (HIF-1) protein and miR-210 in human MSCs (hMSCs). miR-210 positively regulates HIF-1α activity. Furthermore, miR-210 expression is also induced by hypoxia through the regulation of HIF-1α. To investigate the effect of miR-210 on hMSC survival under hypoxic conditions, survival rates along with signaling related to cell survival were evaluated in hMSCs over-expressing miR-210 or ones that lacked HIF-1α expression. Elevated miR-210 expression increased survival rates along with Akt and ERK activity in hMSCs with hypoxia. These data demonstrated that a positive feedback loop involving miR-210 and HIF-1α was important for MSC survival under hypoxic conditions.

Cardiomyocytes from phorbol myristate acetate-activated mesenchymal stem cells restore electromechanical function in infarcted rat hearts

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 Ca2+ 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.