Dynamics of focal adhesions and reorganization of F‐actin in VEGF‐stimulated NSCs under varying differentiation states

Precise migration of neural stem/progenitor cells (NSCs) is crucially important for neurogenesis and repair in the nervous system. However, the detailed mechanisms are not clear. Our previous results showed that NSCs in varying differentiation states possess different migratory ability to vascular endothelial growth factor (VEGF). In this study, we demonstrate the different dynamics of focal adhesions (FAs) and reorganization of F‐actin in NSCs during spreading and migration stimulated by VEGF. We found that the migrating NSCs of 0.5 and 1 day differentiation possess more FAs at leading edge than cells of other states. Moreover, the phosphorylation of focal adhesion kinase (FAK) and paxillin in NSCs correlates closely with their differentiation states. VEGF promotes FA formation with broad lamellipodium generation at the leading edge in chemotaxing cells of 0, 0.5, and 1 day differentiation, but not in cells of 3 days differentiation. Furthermore, cells of 1 day differentiation show a maximal asymmetry of FAs between lamella and cell rear, orchestrating cell polarization and directional migration. Time‐lapse video analysis shows that the disassembly of FAs and the cell tail detachment in NSCs of 1 day differentiation are more rapid, along with the concurrent enlarged size of FAs at the leading edge, leading to the most effective chemotactic response to VEGF. Collectively, these results indicate that the dynamics of FAs and reorganization of F‐actin in NSCs that undergo directional migration correlate closely with their differentiation states, contributing to the different chemotactic responses of these cells to VEGF. J. Cell. Biochem. 114: 1744–1759, 2013. © 2013 Wiley Periodicals, Inc.     

Growth differentiation factor‐15 (GDF‐15) suppresses in vitro angiogenesis through a novel interaction with connective tissue growth factor (CCN2)

Growth differentiation factor‐15 (GDF‐15) and the CCN family member, connective tissue growth factor (CCN2), are associated with cardiac disease, inflammation, and cancer. The precise role and signaling mechanism for these factors in normal and diseased tissues remains elusive. Here we demonstrate an interaction between GDF‐15 and CCN2 using yeast two‐hybrid assays and have mapped the domain of interaction to the von Willebrand factor type C domain of CCN2. Biochemical pull down assays using secreted GDF‐15 and His‐tagged CCN2 produced in PC‐3 prostate cancer cells confirmed a direct interaction between these proteins. To investigate the functional consequences of this interaction, in vitro angiogenesis assays were performed. We demonstrate that GDF‐15 blocks CCN2‐mediated tube formation in human umbilical vein endothelial (HUVEC) cells. To examine the molecular mechanism whereby GDF‐15 inhibits CCN2‐mediated angiogenesis, activation of α_Vβ₃ integrins and focal adhesion kinase (FAK) was examined. CCN2‐mediated FAK activation was inhibited by GDF‐15 and was accompanied by a decrease in α_Vβ₃ integrin clustering in HUVEC cells. These results demonstrate, for the first time, a novel signaling pathway for GDF‐15 through interaction with the matricellular signaling molecule CCN2. Furthermore, antagonism of CCN2 mediated angiogenesis by GDF‐15 may provide insight into the functional role of GDF‐15 in disease states. J. Cell. Biochem. 114: 1424–1433, 2013. © 2012 Wiley Periodicals, Inc.     

Comparative study of myocytes from normal and mdx mice iPS cells

Recently, induced pluripotent stem cells (iPS cells) have been derived from various techniques and show great potential for therapy of human diseases. Furthermore, the iPS technique can be used to provide cell models to explore pathological mechanisms of many human diseases in vitro, such as Duchenne muscular dystrophy (DMD), which is a severe recessive X-linked form of muscular dystrophy without effective treatment. In this study, we try to determine whether there are different characteristics of myocytes from mdx iPS cells and C57BL/10 iPS cells. Our results showed that both of mdx and C57BL/10 cells could be induced into iPS cells in vitro, whereas colony-forming ability of mdx iPS cells was much weaker than that of C57BL/10 iPS cells. Meanwhile, mdx iPS cells could be induced to differentiate into myocytes, whereas their differentiation efficiency was much lower than that of C57BL/10 iPS cells. And, the number of apoptotic cells in differentiated myocytes from mdx iPS cells was significantly higher than that from C57BL/10 iPS cells. More importantly, treatment of a pan-caspase inhibitor (Z-VAD) produced a significant decrease in apoptotic cells. This study might add some insight to the biology study of dystrophin gene.     

The Role of Epigenetic Regulation and Pluripotency‐Related MicroRNAs in Differentiation of Pancreatic Stem Cells to Beta Cells

In this study, we aimed to research the effects of class‐I HDACs and glucose on differentiation of pancreatic islet derived mesenchymal stem cells (PI‐MSCs) to beta cells. Beta cell differentiation determined by flow cytometric analysis and gene expression levels of PDX1, PAX4, PAX6, NKX6.1, NGN3, INS2, and GLUT2. As a result the valproic acid, is an inhibitor of class‐I HDACs, caused the highest beta cell differentiation in PI‐MSCs. However, the cells in this group were at early stages of differentiation. Glucose co‐administration to this group carried the differentiation to higher levels, but these newly formed beta cells were not functional. Moreover, reduction in the levels of pluripotency factors that Oct3/4, c‐Myc, and Nanog were parallel to beta cell differentiation. Also, the levels of HDAC1 and acetylated H3/H4 were increased and methylated H3 was decreased by VPA treatment. In addition, we have detected over expression in genes of miR‐18a‐5p, miR‐19b‐5p, miR‐30d‐3p, miR‐124, miR‐146a‐5p, miR‐184, miR‐335, and miR‐433‐5p in parallel to beta cell differentiation. As the conclusion, this study is important for understanding the epigenetic mechanism that controls the beta cell differentation and it suggests new molecules that can be used for diagnosis, and treatment of diabetes. J. Cell. Biochem. 119: 455–467, 2018. © 2017 Wiley Periodicals, Inc.