Decline after immobilisation and recovery after remobilisation of synovialfluid IL1, TIMP, and chondroitin sulphate levels in young beagle dogs

Objective-To monitor the concentration of markers of cartilage and synovium metabolism in the knee (stifle) joint synovial fluid of young beagles subj ected to immobilisation and subsequent remobilisation. Methods-The right hind limb of 17 dogs was immobilised in flexion for 11 we eks. Simultaneously, the contralateral left knee was exposed to increased w eight bearing. The remobilisation period lasted 50 weeks. Litter mates serv ed as controls. The concentration in joint lavage fluid of interleukin 1 al pha (IL1 alpha) was measured by immunoassay, the activity of phospholipase A, (PLA,) was determined by an extraction method, chondroitin sulphate (CS) concentration by precipitation with Alcian blue, hyaluronan (HA) by an ELI SA-like assay using biotinylated HA-binding complexes,matrix metalloprotein ase 3 (MMP-3), and tissue inhibitor of metalloproteinases 1 (TIMP-1) by san dwich ELISA, and synovitis was scored by light microscopy. Results-Synovitis or effusion was absent in all experimental and control gr oups. Immobilisation decreased the joint lavage fluid levels of IL1 alpha ( p<0.05), TIMP (p< 0.05), and the concentration of CS down to 38% (p<0.05) i n comparison with untreated Litter mates with normal weight bearing. Immobi lisation did not affect the activity of PLA,, or the concentration of MMP-3 or HA in synovial fluid. Joint remobilisation restored the decreased conce ntrations of markers to control levels. Increased weight bearing did not ch ange the concentrations of markers in comparison with the control joints wi th normal weight bearing. Conclusions-11 weeks' joint immobilisation decreased the concentration of m arkers of cartilage and synovium metabolism in the synovial fluid, and remo bilisation restored the concentrations to control levels. The changes in jo int metabolism induced by immobilisation, as reflected by the markers, are thus different from those found in osteoarthritis, where increased levels o f these markers are associated with enhanced degradation and synthesis. The se findings suggest that the change induced in joint metabolism by immobili sation is reversible in its early stages.