Use of synovial fluid markers of cartilage synthesis and turnover to studyeffects of repeated intra-articular administration of methylprednisolone acetate on articular cartilage in vivo

In vivo the effects of intra-articular (IA) corticosteroids on articular ca rtilage remain controversial. This study was designed to examine this issue using synovial fluid (SF) markers of cartilage metabolism Paired radiocarp al joints. without clinical or radiographic signs of joint disease, were st udied in 10 adult horses. Aseptic arthrocentesis was performed weekly for 1 3 weeks. IA injections of methylprednisolone acetate (MPA) into the treatme nt joint and the vehicle into the control joint were performed at weeks 3, 5 and 7. We used radioimmunoassays on SF samples which measure a keratan su lfate epitope (KS) and the 846 epitope on cartilage aggrecan (PG) and the C -propeptile (CPII) of cartilage type II procollagen which is released follo wing synthesis of this molecule. Gel chromatography was performed on select ed SF samples to evaluate the sizes of SF PG molecules. The total joint KS and the 846 epitopes were both present on a heterogeneous population of mai nly molecules which, from chromotographic analysis, appeared to be mainly f ragments of the articular cartilage aggrecan. They were significantly eleva ted in MPA joints whereas CPII mas significantly reduced compared to the co ntrol during the treatment period. These results indicate that the repeated use of IA MPA leads to a potentially harmful inhibition of procollagen II synthesis and an increased release of degradation products of the PG aggrec an from articular cartilage. (C) 2001 Orthopaedic Research Society. Publish ed by Elsevier Sciene Ltd. All rights reserved.