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* Institut Cochin, Département d’Immunologie, Paris, France;
Service de Rhumatologie, Hôpital La Cavale Blanche, Brest, France;
Institut National de la Santé et de la Recherche Médicale (INSERM), Unité 567, Paris, France;
Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8104, Paris, France;
¶ Université Paris Descartes, Faculté de Médecine René Descartes, Unité Mixte de Recherche et de Service 8104, Paris, France;
|| Service d’Anatomo-pathologie, Hôpital Cochin, Paris;
# INSERM Unité 36, Collège de France, Paris, France;
** Service d’Hématologie Biologique A, Hôpital Européen Georges Pompidou, Paris, France;
Service d’Orthopédie Hôpital Cochin, Paris, France;
* Service d’Orthopédie Hôpital Roger Salengro, Lille, France;
* Service d’Orthopédie Hôpital La Cavale Blanche, Brest, France;
* INSERM Unité 519, Rouen, France;
* Institut de Rhumatologie, Hôpital Cochin, Paris, France; and
* Hôpital Ambroise Paré, Boulogne-Billancourt, France
We previously compared by microarray analysis gene expression in rheumatoid arthritis (RA) and osteoarthritis (OA) tissues. Among the set of genes identified as a molecular signature of RA, clusterin (clu) was one of the most differentially expressed. In the present study we sought to assess the expression and the role of CLU (mRNA and protein) in the affected joints and in cultured fibroblast-like synoviocytes (FLS) and to determine its functional role. Quantitative RT-PCR, Northern blot, in situ hybridization, immunohistochemistry, and Western blot were used to specify and quantify the expression of CLU in ex vivo synovial tissue. In synovial tissue, the protein was predominantly expressed by synoviocytes and it was detected in synovial fluids. Both full-length and spliced isoform CLU mRNA levels of expression were lower in RA tissues compared with OA and healthy synovium. In synovium and in cultured FLS, the overexpression of CLU concerned all protein isoforms in OA whereas in RA, the intracellular forms of the protein were barely detectable. Transgenic overexpression of CLU in RA FLS promoted apoptosis within 24 h. We observed that CLU knockdown with small interfering RNA promoted IL-6 and IL-8 production. CLU interacted with phosphorylated I
B
. Differential expression of CLU by OA and RA FLS appeared to be an intrinsic property of the cells. Expression of intracellular isoforms of CLU is differentially regulated between OA and RA. We propose that in RA joints, high levels of extracellular CLU and low expression of intracellular CLU may enhance NF-B activation and survival of the synoviocytes.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 This work was supported in part by Institut National de la Santé et de la Recherche Médicale, the Société Française de Rhumatologie, the Association de Recherche sur la Polyarthrite Rhumatoïde, and by Wyeth Lederle Laboratories.
2 Address correspondence and reprint requests to Dr. Gilles Chiocchia, Département d’Immunologie, Pavillon Hardy A1, 27 rue du Faubourg Saint-Jacques, 75674 Paris Cedex 14, France. E-mail address: chiocchia{at}cochin.inserm.fr
3 Abbreviations used in this paper: RA, rheumatoid arthritis; OA, osteoarthritis; CLU, clusterin; sCLU, secreted CLU; nCLU, nuclear CLU; SF, synovial fluid; siRNA, small interfering RNA; QT-PCR, quantitative RT-PCR; FLS, fibroblast-like synoviocyte.
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