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Galectin-3 surface expression on human adult chondrocytes: a potential substrate for collagenase-3

M Guévremont¹, J Martel-Pelletier¹, C Boileau¹, F-T Liu², M Richard³, J-C Fernandes¹, J-P Pelletier¹, P Reboul¹

¹ Unité de Recherche en Arthrose, Centre de Recherche du Centre Hospitalier de l’Université de Montréal, Montréal, Québec, Canada
² Department of Dermatology, Sacramento, University of California-Davis, California, USA
³ Département de Biochimie, Faculté de Médecine Lyon-Sud, Lyon, France

Correspondence to:
Correspondence to:
Dr P Reboul
Osteoarthritis Research Unit, CR-CHUM, Y2604, 1560 Sherbrooke Street East, Montreal, Quebec, Canada H2L 4M1; pascal.reboul{at}umontreal.ca

Background: Galectin-3 is a lectin detected in mature and early hypertrophic chondrocytes; osteoarthritic (OA) chondrocytes can re-express hypertrophic markers.

Objective: To investigate the synthesis and subcellular localisation of galectin-3 in adult chondrocytes as well as the possibility of cleavage of galectin-3 by collagenase-1 and -3.

Methods: Galectin-3 was assessed by immunohistochemistry and real time polymerase chain reaction (PCR) in normal and OA cartilage. Its localisation was investigated by subcellular fractionation, immunocytology, and flow cytometry. Proteolysis of galectin-3 by collagenase-1 and -3 was determined by in vitro assay.

Results: Galectin-3 expression was increased 2.4-fold as measured by reverse transcriptase (RT)-PCR (p<0.05, n = 5) and threefold by immunohistochemistry (p<0.003 n = 6) in OA cartilage compared with normal cartilage. In adult chondrocytes, galectin-3 was found in the cytosol and membrane enriched fractions. Both immunocytology and flow cytometry confirmed the presence of galectin-3 at the surface of chondrocytes. A strong correlation was found between integrin-ß1 and galectin-3 expression at the surface of chondrocytes. Moreover, collagenase-3 cleaved galectin-3 with a higher activity than collagenase-1. The proteolysed sites generated were identical to those produced by gelatinases A and B.

Conclusion: Galectin-3 may play a part in OA, having two roles, one intracellular and not yet identified, and another at the cell surface, possibly related to the interaction of chondrocytes and the cartilage matrix.

Keywords: galectin-3; osteoarthritis; chondrocytes; collagenase-3; integrin-ß1

Abbreviations: 7-AAD, 7-aminoactinomycin D; ECM, extracellular matrix; MMP, matrix metalloproteinase; OA, osteoarthritis/osteoarthritic; PBS, phosphate buffered saline; PCR, polymerase chain reaction; RT-PCR, reverse transcriptase-polymerase chain reaction; SDS-PAGE, sodium dodecyl sulphate-polyacrylamide gel electrophoresis

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