title: Integrity of the cortical actin ring is required for activation of the PI3K/Akt and p38 MAPK signaling pathways in redifferentiation of chondrocytes on chitosan.
abstract: Cell shape alterations and accompanying cytoskeletal changes have diverse effects on cell function. We have already shown that dedifferentiated chondrocytes have a round cell morphology and undergo redifferentiation when cultured on chitosan membrane. In the present study, we investigate the role of the cytoskeleton in chondrocyte redifferentiation. Chondrocytes obtained from a micromass culture of chick limb bud mesenchymal cells were subcultured four times. Immunofluorescence analysis of F-actin showed cortical distribution of the actin cytoskeleton upon subculture of dedifferentiated chondrocytes on chitosan membrane. Treatment with cytochalasin D disrupted the cortical actin ring formed during cultivation of chondrocytes on the chitosan membrane, and inhibited chondrocyte redifferentiation. Moreover, cytochalasin D inhibited the phosphorylation of Akt and p38 mitogen activated protein kinase (MAPK), induced during redifferentiation on chitosan membrane. LY294002, an inhibitor of phosphatidylinositol-3-OH-kinase (PI3K), suppressed chondrocyte redifferentiation. These findings suggest that integrity of the actin cytoskeleton is a crucial requirement for PI3K/Akt and p38 MAPK in chondrocyte redifferentiation.
authors.affiliation: Department of Biology, College of Natural Sciences, Kyungpook National University, 1370 Sankyuck-dong, Buk-gu, Daegu 702-701, South Korea.
authors.forename: Eun Hee
authors.initials: EH
authors.lastname: Park
authors.forename: Shin-Sung
authors.initials: SS
authors.lastname: Kang
authors.forename: Young-Sup
authors.initials: YS
authors.lastname: Lee
authors.forename: Song-Ja
authors.initials: SJ
authors.lastname: Kim
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Jin
authors.forename: Eun Nam
authors.initials: EN
authors.lastname: Tak
authors.forename: Jong Kyung
authors.initials: JK
authors.lastname: Sonn
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D048430:Cell Shape; D002478:Cells, Cultured; D002642:Chick Embryo; D048271:Chitosan / Q000378:metabolism*; D019902:Chondrocytes / Q000166:cytology / Q000502:physiology; D015638:Cytochalasin D / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D000199:Actins; D004791:Enzyme Inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; D015638:Cytochalasin D; D048271:Chitosan; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases