title: Repression of anti-proliferative factor Tob1 in osteoarthritic cartilage.
abstract: Osteoarthritis is the most common degenerative disorder of the modern world. However, many basic cellular features and molecular processes of the disease are poorly understood. In the present study we used oligonucleotide-based microarray analysis of genes of known or assumed relevance to the cellular phenotype to screen for relevant differences in gene expression between normal and osteoarthritic chondrocytes. Custom made oligonucleotide DNA arrays were used to screen for differentially expressed genes in normal (n = 9) and osteoarthritic (n = 10) cartilage samples. Real-time polymerase chain reaction (PCR) with gene-specific primers was used for quantification. Primary human adult articular chondrocytes and chondrosarcoma cell line HCS-2/8 were used to study changes in gene expression levels after stimulation with interleukin-1beta and bone morphogenetic protein, as well as the dependence on cell differentiation. In situ hybridization with a gene-specific probe was applied to detect mRNA expression levels in fetal growth plate cartilage. Overall, more than 200 significantly regulated genes were detected between normal and osteoarthritic cartilage (P < 0.01). One of the significantly repressed genes, Tob1, encodes a protein belonging to a family involved in silencing cells in terms of proliferation and functional activity. The repression of Tob1 was confirmed by quantitative PCR and correlated to markers of chondrocyte activity and proliferation in vivo. Tob1 expression was also detected at a decreased level in isolated chondrocytes and in the chondrosarcoma cell line HCS-2/8. Again, in these cells it was negatively correlated with proliferative activity and positively with cellular differentiation. Altogether, the downregulation of the expression of Tob1 in osteoarthritic chondrocytes might be an important aspect of the cellular processes taking place during osteoarthritic cartilage degeneration. Activation, the reinitiation of proliferative activity and the loss of a stable phenotype are three major changes in osteoarthritic chondrocytes that are highly significantly correlated with the repression of Tob1 expression.
authors.affiliation: Aventis Pharma Deutschland, Functional Genomics, Sanofi-Aventis, Frankfurt, Germany. mathias.gebauer@aventis.com
authors.forename: Mathias
authors.initials: M
authors.lastname: Gebauer
authors.forename: Joachim
authors.initials: J
authors.lastname: Saas
authors.forename: Jochen
authors.initials: J
authors.lastname: Haag
authors.forename: Uwe
authors.initials: U
authors.lastname: Dietz
authors.forename: Masaharu
authors.initials: M
authors.lastname: Takigawa
authors.forename: Eckart
authors.initials: E
authors.lastname: Bartnik
authors.forename: Thomas
authors.initials: T
authors.lastname: Aigner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002358:Cartilage, Articular / Q000378:metabolism*; D002454:Cell Differentiation; D002455:Cell Division; D045744:Cell Line, Tumor / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism; D002813:Chondrosarcoma / Q000473:pathology; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D017403:In Situ Hybridization; D007375:Interleukin-1 / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000502:physiology*; D019394:Ki-67 Antigen / Q000032:analysis; D008297:Male; D008875:Middle Aged; D020411:Oligonucleotide Array Sequence Analysis; D010003:Osteoarthritis / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
chemical_list: C525819:BMP7 protein, human; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D007375:Interleukin-1; D047908:Intracellular Signaling Peptides and Proteins; D019394:Ki-67 Antigen; D012333:RNA, Messenger; C098669:TOB1 protein, human; D016212:Transforming Growth Factor beta; D025521:Tumor Suppressor Proteins
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