Open AccessAggrecanase cleavage in juvenile idiopathic arthritis patients is minimally detected in the aggrecan interglobular domain but robust at the aggrecan C‐terminus
Author(s) -
Struglics André,
Lohmander L. Stefan,
Last Karena,
Akikusa Jonathan,
Allen Roger,
Fosang Amanda J.
Publication year - 2012
Publication title -
arthritis & rheumatism
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/art.34665
Subject(s) - aggrecan , aggrecanase , synovial fluid , osteoarthritis , arthritis , chondroitin sulfate , western blot , chemistry , medicine , microbiology and biotechnology , glycosaminoglycan , pathology , biochemistry , articular cartilage , biology , alternative medicine , gene
Objective To investigate aggrecan degradation in juvenile idiopathic arthritis (JIA). Methods The pattern and abundance of aggrecan fragments in synovial fluid (SF) aspirates from JIA patients were analyzed and compared with aggrecan fragments in SF from patients with other arthritides, children with knee injury, and a knee‐healthy reference group. Concentrations of sulfated glycosaminoglycan (sGAG) in SF were measured by Alcian blue precipitation assay. Aggrecan fragments were purified by dissociative CsCl density‐gradient centrifugation, deglycosylated, and analyzed by Western blot using antibodies specific for either aggrecanase‐derived ARGS, SELE, and KEEE neoepitopes or the aggrecan G3 domain. Results The concentration of sGAG in SF from patients with JIA was significantly lower compared with that in SF from patients with osteoarthritis (OA) ( P < 0.001), patients with juvenile knee injury ( P = 0.006), and knee‐healthy controls ( P = 0.022). Western blot analysis revealed KEEE, SELE, and G3 fragments generated by aggrecanase cleavage in the chondroitin sulfate–rich region of aggrecan in patients with JIA. The pattern of aggrecan fragments in JIA patients was not identical to that in pooled OA SF, although there were notable similarities. Surprisingly, aggrecanase‐derived ARGS fragments were barely detectable in JIA SF, in marked contrast to levels in OA SF. Conclusion Aggrecanases appear to cleave minimally in the interglobular domain of aggrecan in JIA patients despite robust levels of cleavage in the chondroitin sulfate–rich region. These results suggest that in JIA, unlike other arthritides, aggrecanase cleavage in the aggrecan interglobular domain might not be a major pathogenic event.