Even low‐grade synovitis significantly accelerates the clearance of protein from the canine knee: implications for measurement of synovial fluid “markers” of osteoarthritis

Abstract

Objective. In recent studies, the synovial fluid concentration of molecules derived from the extracellular matrix of articular cartilage has been used to deduce the magnitude of cartilage destruction or repair in osteoarthritic (OA) joints. Because low-grade synovitis is often present in such joints, we assessed the effect of synovial inflammation on the clearance of a prototypical protein, albumin, from synovial fluid.Methods. '311-labeled albumin (RISA) was injected into 1 (control) knee of each of 14 dogs. The concentration of RISA in synovial fluid aspirated 7 hours after the injection and serial measurements of surface radioactivity were used to calculate the volume of distribution ( v d ) and clearance of RISA. One week later, synovitis was induced in the contralateral knee by intraarticular injection of various quantities of calcium pyrophosphate dihydrate (CPPD) crystals, after which RISA was injected into that joint and these measurements were repeated.Results. Intraarticular injection of 500 pg of CPPD crystals produced intense synovitis, with a mean synovial fluid white blood cell (WBC) count of 43,200 cells/mm3, and values for RISA v d and RISA clearance (36.5 ml and 33.7 pVminute) were much higher than those for saline-injected control knees (2.7 ml and 1.5 pl/minute, respectively). Injection of 0.5 pg of CPPD

Coll2-1, Coll2-1NO2 and myeloperoxidase concentrations in the synovial fluid of equine tarsocrural joints affected with osteochondrosis

“…The absence of different MPO concentration in the synovial fluid of the affected tarsocrural joints compared to the controls could corroborate this conclusion. On the other hand, since the variance in MPO within the non-affected group is large and different from the affected group, the absence of a mean increase of the inflammatory markers used could also be the effect of clearance from the joint (Myers et al 1995) or dilution in the synovial fluid as a cause of effusion that can be present even in cases of mild synovitis. Any mean difference in Coll2-1NO 2 or MPO concentration between the affected and non affected joints may therefore have been undetectable.…”

Role of S100A8 and S100A9 in neutrophil recruitment in response to monosodium urate monohydrate crystals in the air‐pouch model of acute gouty arthritis

“…All of these chemokines had previously been shown to play a role in neutrophil migration in the air-pouch model in response to both TNF␣ and SEA (39,40). The air-pouch model was selected since it has been used extensively in the past as a model of the synovial environment to study the mechanism of inflammation induced by different proinflammatory factors, including MSU (45)(46)(47)(48)(49)(50)(51). Designed to replicate the synovial lining, this model allows for the identification and study of emigrated leukocytes and molecules produced during an inflammatory response, although several features of the synovial environment are missing in air-pouch fibroblasts (52,53).…”

Intraarticular injection of hyaluronan as treatment for knee osteoarthritis: What is the evidence?

“…A constant flow of HA occurs through the normal joint, with a half-life of 12 hours in rabbits and 1 day in sheep (13,14). Although it has been reported that synovial fluid flow is diminished in osteoarthritis (OA) (2), most measurements indicate more rapid clearance of both HA and protein from joints with synovitis, even when it is as mild as that commonly seen in OA (15,16). Others have suggested that HA acts as a chemical sponge, binding or entangling both macromolecules and particulate debris in the diseased joint, and that the rapid clearance of injected HA results in removal of these deleterious substances from the joint space (17).…”