title: Mechanisms involved in inhibition of chondrogenesis by activin-A.
abstract: OBJECTIVE
  Activin-A, a member of the TGF-β family, is known to be present in bone and cartilage. Although, involvement of the TGF-β family in chondrogenesis has been reported, the mechanism by which activin-A regulates chondrogenesis has not been fully elucidated. The aim of this study was to investigate the effects of activin-A on chondrocyte differentiation in vitro.
  
  
  METHODS
  Monolayer cultures of mouse chondrocyte ATDC cells were pretreated with a variety of inhibitors of major signaling pathways prior to addition of activin-A. The expressions of sox9, runx2, and osterix mRNA were detected using real-time PCR. To determine chondrocyte differentiation, sulfated glycosaminoglycans were stained with Alcian blue. To further elucidate the role of activin-A on chondrogenesis regulation, phosphorylation of Smad2/3, ERK, JNK, and Akt proteins was determined by western blotting.
  
  
  RESULTS
  Activin-A suppressed the transcription of sox9, runx2, and osterix mRNA, as well as sulfated glycosaminoglycans accumulation. Activin-A also inhibited constitutive phosphorylation of JNK and Akt proteins. Furthermore, inhibition of the JNK and PI3K-Akt pathways by chemical inhibitors suppressed chondrogenesis in ATDC5 cells.
  
  
  CONCLUSIONS
  These results indicate that activin-A may suppress chondrocyte differentiation in ATDC5 cells via down-regulation of JNK and Akt phosphorylation.
authors.affiliation: Division of Oral and Maxillofacial Reconstructive Surgery, Department of Oral and Maxillofacial Surgery, Kyushu Dental College, Kitakyushu 803-8580, Japan.
authors.forename: Sho
authors.initials: S
authors.lastname: Mitsugi
authors.forename: Wataru
authors.initials: W
authors.lastname: Ariyoshi
authors.forename: Toshinori
authors.initials: T
authors.lastname: Okinaga
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kaneuji
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kataoka
authors.forename: Tetsu
authors.initials: T
authors.lastname: Takahashi
authors.forename: Tatsuji
authors.initials: T
authors.lastname: Nishihara
mesh_terms: D028341:Activins / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D020219:Chondrogenesis / Q000187:drug effects; D050659:Core Binding Factor Alpha 1 Subunit / Q000096:biosynthesis; D051379:Mice; D018125:Receptors, Transforming Growth Factor beta / Q000037:antagonists & inhibitors; D055758:SOX9 Transcription Factor / Q000096:biosynthesis; D000076182:Sp7 Transcription Factor; D014157:Transcription Factors / Q000096:biosynthesis
chemical_list: D050659:Core Binding Factor Alpha 1 Subunit; D018125:Receptors, Transforming Growth Factor beta; C493716:Runx2 protein, mouse; D055758:SOX9 Transcription Factor; C527933:Sox9 protein, mouse; D000076182:Sp7 Transcription Factor; C479466:Sp7 protein, mouse; D014157:Transcription Factors; C422405:activin A; D028341:Activins