title: Effect of stretching on gene expression of beta1 integrin and focal adhesion kinase and on chondrogenesis through cell-extracellular matrix interactions.
abstract: Differentiation of skeletal tissues, such as bone, ligament and cartilage, is regulated by complex interaction between genetic and epigenetic factors. In the present study, we attempted to elucidate the possible role of cell-extracellular matrix (ECM) adhesion on the inhibitory regulation in chondrogenesis responding to the tension force. The midpalatal suture cartilages in rats were expanded by orthopedic force. In situ hybridization for type I and II collagens, immunohistochemical analysis for fibronectin, alpha5 and beta1 integrins, paxillin, and vinculin, and cytochemical staining for actin were used to demonstrate the phenotypic change of chondrocytes. Immunohistochemical analysis for phosphorylation and nuclear translocation of extracellular signal-regulated kinase (ERK)-1/2 was performed. The role of the cell-ECM adhesion in the response of the chondroprogenitor cells to mechanical stress and the regulation of gene expression of focal adhesion kinase (FAK) and integrins were analyzed by using an in vitro system. A fibrous suture tissue replaced the midpalatal suture cartilage by the expansive force application for 14 days. The active osteoblasts that line the surface of bone matrix in the newly formed suture tissue strongly expressed the type I collagen gene, whereas they did not express the type II collagen gene. Although the numbers of precartilaginous cells expressing alpha5 and beta1 integrin increased, the immunoreactivity of alpha5 integrin in each cell was maintained at the same level throughout the experimental period. During the early response of midpalatal suture cartilage cells to expansive stimulation, formation of stress fibers, reorganization of focal adhesion contacts immunoreactive to a vinculin-specific antibody, and phosphorylation and nuclear translocation of ERK-1/2 were observed. In vitro experiments were in agreement with the results from the in vivo study, i.e. the inhibited expression of type II collagen and upregulation in integrin expression. The arginine-glycine-aspartic acid-containing peptide completely rescued chondrogenesis from tension-mediated inhibition. Thus, we conclude that stretching activates gene expression of beta1 integrin and FAK and inhibits chondrogenesis through cell-ECM interactions of chondroprogenitor cells.
authors.affiliation: Division of Orthodontics and Dentofacial Orthopedics, Tohoku University Graduate School of Dentistry, Sendai, Japan. takahasi@mail.cc.tohoku.ac.jp
authors.forename: Ichiro
authors.initials: I
authors.lastname: Takahashi
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Onodera
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Sasano
authors.forename: Itaru
authors.initials: I
authors.lastname: Mizoguchi
authors.forename: Jin-Wan
authors.initials: JW
authors.lastname: Bae
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Mitani
authors.forename: Manabu
authors.initials: M
authors.lastname: Kagayama
authors.forename: Hideo
authors.initials: H
authors.lastname: Mitani
mesh_terms: D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism; D020219:Chondrogenesis / Q000187:drug effects / Q000502:physiology*; D024043:Collagen Type II / Q000235:genetics; D003393:Cranial Sutures / Q000378:metabolism / Q000503:physiopathology; D003599:Cytoskeleton / Q000378:metabolism; D005109:Extracellular Matrix / Q000502:physiology*; D005260:Female; D005353:Fibronectins / Q000032:analysis; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D005786:Gene Expression Regulation; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D066298:In Vitro Techniques; D039482:Integrin alpha5 / Q000235:genetics; D019012:Integrin beta1 / Q000235:genetics*; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D010155:Palatal Expansion Technique; D010159:Palate / Q000378:metabolism / Q000503:physiopathology; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical
chemical_list: D024043:Collagen Type II; D005353:Fibronectins; D039482:Integrin alpha5; D019012:Integrin beta1; D009842:Oligopeptides; C049554:glycyl-arginyl-glycyl-aspartyl-serine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496052:Ptk2 protein, rat; D020928:Mitogen-Activated Protein Kinases