Didier Hannouche, Dominique Come, Nathalie Busso, Christelle Nguyen, Arnaud Bianchi, Michel Daudon, Aurore Chatron-Colliet, Frédéric Lioté, Dominique Bazin, Alexander So, Hang-Korng Ea, BMC, Ed., Os et articulations, Université Paris Diderot - Paris 7 (UPD7)-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), CHU Tenon [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU), Service de chirurgie orthopédique, Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Lariboisière-Fernand-Widal [APHP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Université Paris Diderot - Paris 7 (UPD7)-Faculté de Médecine, Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Service de Rhumatologie, Université de Lausanne = University of Lausanne (UNIL)-Centre Hospitalier Universitaire Vaudois [Lausanne] (CHUV)-Département de l'Appareil Locomoteur (DAL), Service de Rhumatologie [Lariboisière], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), This work was supported by grants from the Fondation pour la Recherche Médicale (FRM DV020081013483, call for bids Vieillissement, 2008 to 2011), INSERM, University Paris Diderot, Sorbonne Paris Cité, Association pour la Recherche en Pathologie Synoviale (ARPS), Prévention et Traitement des Décalcifications - Cristaux et Cartilage, and ART. Part of the work presented was supported by a CNRS grant as a part of the Longévité et Vieillissement 2010 interdisciplinary program (CALARTHROS project)., Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Collège de France (CdF (institution))-Institut de Chimie du CNRS (INC), Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL), and Université de Lausanne (UNIL)-Centre Hospitalier Universitaire Vaudois [Lausanne] (CHUV)-Département de l'Appareil Locomoteur (DAL)
International audience; INTRODUCTION: Calcium-containing (CaC) crystals, including basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate (CPP), are associated with destructive forms of osteoarthritis (OA). We assessed their distribution and biochemical and morphologic features in human knee OA cartilage. METHODS: We prospectively included 20 patients who underwent total knee replacement (TKR) for primary OA. CaC crystal characterization and identification involved Fourier-transform infra-red spectrometry and scanning electron microscopy of 8 to 10 cartilage zones of each knee, including medial and lateral femoral condyles and tibial plateaux and the intercondyle zone. Differential expression of genes involved in the mineralization process between cartilage with and without calcification was assessed in samples from 8 different patients by RT-PCR. Immunohistochemistry and histology studies were performed in 6 different patients. RESULTS: Mean (SEM) age and body mass index of patients at the time of TKR was 74.6 (1.7) years and 28.1 (1.6) kg/m², respectively. Preoperative X-rays showed joint calcifications (chondrocalcinosis) in 4 cases only. The medial femoro-tibial compartment was the most severely affected in all cases, and mean (SEM) Kellgren-Lawrence score was 3.8 (0.1). All 20 OA cartilages showed CaC crystals. The mineral content represented 7.7% (8.1%) of the cartilage weight. All patients showed BCP crystals, which were associated with CPP crystals for 8 joints. CaC crystals were present in all knee joint compartments and in a mean of 4.6 (1.7) of the 8 studied areas. Crystal content was similar between superficial and deep layers and between medial and femoral compartments. BCP samples showed spherical structures, typical of biological apatite, and CPP samples showed rod-shaped or cubic structures. The expression of several genes involved in mineralization, including human homolog of progressive ankylosis, plasma-cell-membrane glycoprotein 1 and tissue-nonspecific alkaline phosphatase, was upregulated in OA chondrocytes isolated from CaC crystal-containing cartilages. CONCLUSIONS: CaC crystal deposition is a widespread phenomenon in human OA articular cartilage involving the entire knee cartilage including macroscopically normal and less weight-bearing zones. Cartilage calcification is associated with altered expression of genes involved in the mineralisation process.