Galectin-3 surface expression on human adult chondrocytes: a potential substrate for collagenase-3.
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-beta1 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.


CONCLUSIONS
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.
Guévremont
M
M
Unité de Recherche en Arthrose, Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, Québec, Canada.
Martel-Pelletier
J
J
Boileau
C
C
Liu
F-T
FT
Richard
M
M
Fernandes
J-C
JC
Pelletier
J-P
JP
Reboul
P
P
D000368:Aged; D002358:Cartilage, Articular / Q000737:chemistry / Q000378:metabolism; D002458:Cell Fractionation / Q000379:methods; D002478:Cells, Cultured; D019902:Chondrocytes / Q000737:chemistry*; D017364:Collagenases / Q000378:metabolism*; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D037502:Galectin 3 / Q000032:analysis* / Q000378:metabolism; D018093:Gelatinases / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D019012:Integrin beta1 / Q000032:analysis; D008297:Male; D053509:Matrix Metalloproteinase 13; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000378:metabolism*; D016133:Polymerase Chain Reaction / Q000379:methods
D037502:Galectin 3; D019012:Integrin beta1; D017364:Collagenases; D018093:Gelatinases; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13