The urinary COMP assay with mAb 14G4 is useful for discriminating horses with osteoarthritis. The higher COMP levels in urine from such horses would be indicative of enhanced proteolytic activity, in addition to the increased COMP levels in the diseased joints.

The histologic diversity of epidermal laminae from hooves of Thoroughbreds was attributable to the combined morphology of PEL and SEL. Detection of hyperplastic changes in the laminar interface does not justify a diagnosis of laminitis because such changes can develop independent of clinical disease. The classification system used here should aid investigators in making a more accurate histologic evaluation of laminae.

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ABSTRACT. We investigated the relationship between cartilage oligomeric matrix protein (COMP) levels in synovial fluid (SF), serum and urine and the development of osteochondral damage and osteophyte (OP) formation following intraarticular fractures of the carpus in racehorses in order to assess the clinical usefulness of COMP as a diagnostic biomarker of developmental osteoarthritis (OA). Two monoclonal antibodies (mAb clones 2A11 and 3C8) raised against equine COMP were shown to be capable of detecting the molecule in serum and urine as well as SF. Fifty-one samples were obtained from 26 OP-positive (OP(+)) and 25 OP-negative (OP(-)) racehorses with carpal bone fracture, in whom OP was ascertained arthroscopically and radiographically. The COMP measurements obtained using the two mAbs were highly correlated with each other in SF, serum, or urine. Horses with OP(+) showed a significantly higher [urinary COMP (µg)]/[urinary creatinine (mg)] ratio (4.94 ± 5.10 and 1.46 ± 1.19, using mAbs 2A11 and 3C8, respectively) than OP(-) horses (2.80 ± 1.72 and 0.93 ± 0.49, respectively). The relationship between serum and urine COMP levels and the period from injury to surgery were extrapolated using a polynomial expression. Measurement of COMP, especially in urine, has potential as a predictive marker of advanced OA following carpal bone fractures in racehorses. KEY WORDS: COMP, equine, fracture, osteoarthritis, urine.J. Vet. Med. Sci. 70(9): 915-921, 2008 Cartilage oligomeric matrix protein (COMP), an abundant non-collagenous extracellular matrix protein in cartilage [1], plays an important role in the construction of collagen bundles and networks, being likely involved in determination of fibril diameter and/or orientation [2,3] and interaction with other extracellular matrix molecules [4]. A recent study has also suggested that association of COMP with granulin-epithelin precursor could be required for chondrocyte proliferation [5]. COMP may also play a role in the pathogenesis of osteoarthritis (OA) as a factor secreted by chondrocytes to ameliorate matrix breakdown at the late stage of OA [6]. In human OA, measurement of COMP in serum and synovial fluid (SF) has been proposed as a helpful biomarker for predicting disease-mediated damage to joint cartilage [7,8]. The serum COMP level is reportedly higher in patients with OA than in healthy volunteers [9]. The serum level of COMP is significantly correlated with the Western Ontario and McMaster Universities index pain scale for the lower limbs, and is higher in patients with bilateral knee OA than in unilaterally affected patients [10]. Another study has suggested that serum COMP level at the baseline could be useful for predicting the course of OA, progressors showing higher average values than nonprogressors [11].In studies of horses, we have demonstrated enhanced degradation of COMP in SF, and suggested that COMP fragmentation in SF could be useful for monitoring equine OA in combination with ELISA measurements [12]. Subsequently, we investigated the clinical use...

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