xylosyltransferase-i regulates glycosaminoglycan synthesis during the pathogenic process of human osteoarthritisxylosyltransferase-i调节人类骨关节炎的致病过程中粘多糖的合成.pdfVIP

Xylosyltransferase-I Regulates Glycosaminoglycan Synthesis during the Pathogenic Process of Human Osteoarthritis ´ Narayanan Venkatesan, Lydia Barre, Mustapha Bourhim, Jacques Magdalou, Didier Mainard, Patrick Netter, Sylvie Fournel-Gigleux, Mohamed Ouzzine* ´ ´ ´ ` UMR 7561 CNRS-Universite Nancy 1, Faculte de Medecine, Vandœuvre-les-Nancy, France Abstract Loss of glycosaminoglycan (GAG) chains of proteoglycans (PGs) is an early event of osteoarthritis (OA) resulting in cartilage degradation that has been previously demonstrated in both huma and experimental OA models. However, the mechanism of GAG loss and the role of xylosyltransferase-I (XT-I) that initiates GAG biosynthesis onto PG molecules in the pathogenic process of human OA are unknown. In this study, we have characterized XT-I expression and activity together with GAG synthesis in human OA cartilage obtained from different regions of the same joint, defined as ‘‘normal’’, ‘‘late-stage’’ or adjacent to ‘‘late-stage’’. The results showed that GAG synthesis and content increased in cartilage from areas flanking OA lesions compared to cartilage from macroscopically ‘‘normal’’ unaffected regions, while decreased in ‘‘late-stage’’ OA cartilage lesions. This increase in anabolic state was associated with a marked upregulation of XT-I expression and activity in cartilage ‘‘next to lesion’’ while a decrease in the ‘‘late-stage’’ OA cartilage. Importantly, XT-I inhibition by shRNA or forced- expression with a pCMV-XT-I construct correlated with the modulation of GAG anabolism in human cartilage explants. The observation that XT-I gene expression was down-regulated by IL-1b and up-regulated by TGF-b1 indicates that these cytokines may play a role in regulating GA