Expression of clusterin in the superficial zone of bovine articular cartilage

• Published in: Arthritis and rheumatism 2001-08, Vol.44 (8), p.1795-1799
• Main Authors: Khan, Ilyas M., Salter, Donald M., Bayliss, Mike T., Thomson, Brian M., Archer, Charles W.
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Blotting, Northern; Cartilage, Articular - metabolism; Cattle; Cells, Cultured; Chondrocytes - metabolism; Cloning, Molecular; Clusterin; Glycoproteins - biosynthesis; Glycoproteins - genetics; In Situ Hybridization; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Molecular Chaperones - biosynthesis; Molecular Chaperones - genetics; Osteoarticular system. Muscles; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; RNA, Messenger - biosynthesis; Transcription, Genetic
• ISSN: 0004-3591; 1529-0131
• DOI: 10.1002/1529-0131(200108)44:8<1795::AID-ART316>3.0.CO;2-K

Objective To investigate the differences between chondrocytes of the superficial and underlying zones of articular cartilage at the level of gene expression. Methods Messenger RNA (mRNA) was isolated from chondrocytes harvested from the superficial and deep zones of immature bovine articular cartilage. This mRNA was reverse transcribed, radiolabeled, and then each complementary DNA (cDNA) sample was used to screen duplicate filters of a bovine chondrocyte cDNA library. By comparing autoradiographic signals on matching filter sets, clones exclusively expressed in the superficial zone of articular cartilage were isolated and characterized further. Results Of the superficial‐specific gene clones isolated, 25% were found to be a single gene product, clusterin. Northern hybridization was used to show that clusterin is expressed specifically in the superficial zone of articular cartilage and that its expression is up‐regulated in mature cartilage. In situ hybridization was used to precisely localize clusterin transcripts in articular cartilage, where it was found that clusterin expression was confined to the articular surface in both immature and mature samples. Conclusion The discovery of clusterin expression at the articular cartilage surface extends previous observations that superficial articular chondrocytes are highly specialized cells. Clusterin is a multifunctional, secreted glycoprotein that has been shown to be expressed in diverse locations that have in common a tissue–fluid boundary. Additionally, clusterin has been implicated in regulating complement activation and cell death in injured and degenerating tissues.