title: Regulation of type-II collagen gene expression during human chondrocyte de-differentiation and recovery of chondrocyte-specific phenotype in culture involves Sry-type high-mobility-group box (SOX) transcription factors.
abstract: During ex vivo growth as monolayer cultures, chondrocytes proliferate and undergo a process of de-differentiation. This process involves a change in morphology and a change from expression of chondrocyte-specific genes to that of genes that are normally expressed in fibroblasts. Transfer of the monolayer chondrocyte culture to three-dimensional culture systems induces the cells to re-acquire a chondrocyte-specific phenotype and produce a cartilaginous-like tissue in vitro. We investigated mechanisms involved in the control of the de-differentiation and re-differentiation process in vitro. De-differentiated chondrocytes re-acquired their chondrocyte-specific phenotype when cultured on poly-(2-hydroxyethyl methacrylate) (polyHEMA) as assayed by morphology, reverse transcriptase PCR of chondrocyte-specific mRNA, Western-blot analysis and chondrocyte-specific promoter activity. Essentially, full recovery of the chondrocyte-specific phenotype was observed when cells that had been cultured for 4 weeks on plastic were transferred to culture on polyHEMA. However, after subsequent passages on plastic, the phenotype recovery was incomplete or did not occur. The activity of a gene reporter construct containing the promoter and enhancer from the human type-II collagen gene (COL2A1) was modulated by the culture conditions, so that its transcriptional activity was repressed in monolayer cultures and rescued to some extent when the cells were switched to polyHEMA cultures. The binding of Sry-type high-mobility-group box (SOX) transcription factors to the enhancer region was modulated by the culture conditions, as were the mRNA levels for SOX9. A transfected human type-II collagen reporter construct was activated in de-differentiated cells by ectopic expression of SOX transcription factors. These results underscore the overt change in phenotype that occurs when chondrocytes are cultured as monolayers on tissue-culture plastic substrata.
authors.affiliation: Department of Medicine, Division of Rheumatology, 233 S. 10th Street, Thomas Jefferson University, Philadelphia, PA 19107, USA.
authors.forename: D G
authors.initials: DG
authors.lastname: Stokes
authors.forename: G
authors.initials: G
authors.lastname: Liu
authors.forename: R
authors.initials: R
authors.lastname: Dharmavaram
authors.forename: D
authors.initials: D
authors.lastname: Hawkins
authors.forename: S
authors.initials: S
authors.lastname: Piera-Velazquez
authors.forename: S A
authors.initials: SA
authors.lastname: Jimenez
mesh_terms: D000818:Animals; D001483:Base Sequence; D002417:Cattle; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology / Q000378:metabolism*; D024043:Collagen Type II / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D004742:Enhancer Elements, Genetic; D005333:Fetus; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D006609:High Mobility Group Proteins / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011485:Protein Binding / Q000235:genetics; D055758:SOX9 Transcription Factor; D055755:SOXD Transcription Factors; D019849:Sex Determination Processes; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D015854:Up-Regulation / Q000235:genetics; D014998:Y Chromosome / Q000235:genetics
chemical_list: D024043:Collagen Type II; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D009687:Nuclear Proteins; C490301:SOX5 protein, human; C486270:SOX6 protein, human; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; D055755:SOXD Transcription Factors; C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors