Differential expression of GADD45β in normal and osteoarthritic cartilage: Potential role in homeostasis of articular chondrocytes

Hospital for Special Surgery, New York, New York, United States
Arthritis & Rheumatology (Impact Factor: 7.76). 07/2008; 58(7):2075-87. DOI: 10.1002/art.23504
Source: PubMed


Our previous study suggested that growth arrest and DNA damage–inducible protein 45β (GADD45β) prolonged the survival of hypertrophic chondrocytes in the developing mouse embryo. This study was undertaken, therefore, to investigate whether GADD45β plays a role in adult articular cartilage.
Gene expression profiles of cartilage from patients with late-stage osteoarthritis (OA) were compared with those from patients with early OA and normal controls in 2 separate microarray analyses. Histologic features of cartilage were graded using the Mankin scale, and GADD45β was localized by immunohistochemistry. Human chondrocytes were transduced with small interfering RNA (siRNA)–GADD45β or GADD45β-FLAG. GADD45β and COL2A1 messenger RNA (mRNA) levels were analyzed by real-time reverse transcriptase–polymerase chain reaction, and promoter activities were analyzed by transient transfection. Cell death was detected by Hoechst 33342 staining of condensed chromatin.
GADD45β was expressed at higher levels in cartilage from normal donors and patients with early OA than in cartilage from patients with late-stage OA. All chondrocyte nuclei in normal cartilage immunostained for GADD45β. In early OA cartilage, GADD45β was distributed variably in chondrocyte clusters, in middle and deep zone cells, and in osteophytes. In contrast, COL2A1, other collagen genes, and factors associated with skeletal development were up-regulated in late OA, compared with early OA or normal cartilage. In overexpression and knockdown experiments, GADD45β down-regulated COL2A1 mRNA and promoter activity. NF-κB overexpression increased GADD45β promoter activity, and siRNA-GADD45β decreased cell survival per se and enhanced tumor necrosis factor α–induced cell death in human articular chondrocytes.
These observations suggest that GADD45β might play an important role in regulating chondrocyte homeostasis by modulating collagen gene expression and promoting cell survival in normal adult cartilage and in early OA.

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Available from: Luiz Fernando Zerbini, May 16, 2014
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    • "During the more advanced stages of OA, the fibrocartilaginous cartilage contains collagens, such as type I and type III [43–45], while we find the amount of collagen type II decreases as seen by quantitative immunohistochemistry [44]. In contrast, microarray investigations demonstrate an overall increased anabolism and an up-regulation of mRNAs also of cartilage-specific collagens [46, 47]. In any case, the altered matrix composition seems to be one reason for the long-term failure of the repair tissue to initiate a restitutio ad integrim. "
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