title: c-fos oncogene expression in dexamethasone stimulated osteogenic cells in chick embryo periosteal cultures.
abstract: Although the complex effects of glucocorticoids on bone cells have been studied extensively in vitro, little is known about the molecular mechanisms of glucocorticoid responses in osteogenic cells. As c-fos and its protein product are believed to play a key role in intracellular signal transduction, and since their role in regulation of bone formation is well-recognized, we studied the effect of the glucocorticoid analogue dexamethasone (DEX) on the expression of c-fos oncogene in the chick periosteal osteogenesis (CPO) model. C-fos mRNA expression was determined by in situ hybridization at various time points after 10(-7) M DEX treatment. Prior to DEX treatment, the cultures had been synchronized with 2 mM thymidine. The mean area of positively hybridized cells in experimental (DEX-treated) and control (DEX-free) cultures was quantitated by computer assisted morphometry. In DEX-treated cultures c-fos mRNA could be detected transiently and mainly in the osteogenic layer at 30, 45 and 60 min after treatment whereas no c-fos expression could be detected above background level in the control groups. Differences between experimental and control groups were significant (P less than 0.01) as determined by a general linear model (GLM) analysis of variance. These data indicate that in the CPO culture system, DEX (10(-7) M) induces c-fos expression. The findings are compatible with the hypothesis which states that glucocorticoid-induced phenotypic changes in osteogenic cells may be mediated by c-fos.
authors.affiliation: Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Birek
authors.forename: H Z
authors.initials: HZ
authors.lastname: Huang
authors.forename: P
authors.initials: P
authors.lastname: Birek
authors.forename: H C
authors.initials: HC
authors.lastname: Tenenbaum
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D002642:Chick Embryo; D003907:Dexamethasone / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos; D066298:In Vitro Techniques; D009693:Nucleic Acid Hybridization; D010012:Osteogenesis; D010521:Periosteum / Q000166:cytology / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D003907:Dexamethasone; D000469:Alkaline Phosphatase