Aggrecanase- and matrix metalloproteinase-mediated aggrecan degradation is associated with different molecular characteristics of aggrecan and separated in time ex vivo

Abstract

Aggrecan is one of the first proteins to be depleted from articular cartilage in early osteoarthritis. We investigated the molecular differences between matrix metalloproteinase (MMP)- and aggrecanase-mediated aggrecan degradation, as a consequence of their distinct time-dependent degradation profiles. Cartilage degradation was induced by cytokine stimulation in bovine articular cartilage explants and quantified by a dye-binding assay and immunoassays. The size of degradation fragments was analysed by Western blot. Cytokine stimulation resulted in the early release of aggrecanase-mediated aggrecan degradation fragments. In contrast, MMP-mediated aggrecan degradation began only at day 16 and continued to day 21. Western blot analysis showed that glycosylated high-molecular-weight 374ARGSVI fragments appeared at day 7, in contrast to deglycosylated low-molecular-weight 342FFGVG fragments which were detected at day 21. Aggrecan degradation may be divided into two different pools, a high-molecular-weight aggrecanase-mediated pool, and a low-molecular-weight MMP-mediated pool. This may have implications for the development of intervention strategies for OA.