Cartilage-derived retinoic acid-sensitive protein in equine synovial fluid from healthy and diseased joints.
BACKGROUND
More sensitive and specific diagnostic methods for early detection of changes in the joint cartilage are needed. Cartilage-derived retinoic acid-sensitive protein (CD-RAP) is a potential marker of cartilage synthesis and regeneration. This is the first study on equine CD-RAP.


OBJECTIVE
To evaluate the ability of a commercially available human sandwich ELISA assay to detect equine CD-RAP in synovial fluid from healthy and diseased joints.


METHODS
Synovial fluid was collected from 28 horses with no signs of joint disease and from 5 with induced inflammatory arthritis. CD-RAP concentrations were measured using a human CD-RAP ELISA. Intra- and interassay imprecision of the assay were evaluated by multiple measurements on pools of equine synovial fluid. Assay inaccuracy was determined by linearity under dilution.


RESULTS
The assay showed moderate to large intra- and interassay variation when applied to equine synovial fluid. Equine CD-RAP was detected in synovial fluid from healthy horses ranged at 8.2-52 ng/ml. Repeated arthrocentesis (after injection of isotonic saline), age, joint or gender did not significantly affect CD-RAP concentrations. Twelve hours after intra-articular injection of lipopolysaccharide, concentrations of CD-RAP were significantly lower than after injection of isotonic saline and remained significantly lower until the end of the study at 144 h.


CONCLUSIONS
The assay is suitable for longitudinal monitoring of CD-RAP concentration in individual horses. Disease significantly influenced CD-RAP levels. Similar to previous results obtained in man, CD-RAP seems to be a marker of cartilage synthesis and/or regeneration in horses.
Berg
L C
LC
Faculty of Life Sciences, Department of Animal and Veterinary Basic Sciences, University of Copenhagen, Groennegaardsvej 7, DK-1870 Frederiksberg C, Denmark.
Lenz
J
J
Kjelgaard-Hansen
M
M
Thomsen
P D
PD
Jacobsen
S
S
D000818:Animals; D001168:Arthritis / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D015415:Biomarkers / Q000378:metabolism; D002358:Cartilage, Articular / Q000378:metabolism* / Q000473:pathology; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000662:veterinary; D016326:Extracellular Matrix Proteins / Q000378:metabolism*; D005260:Female; D006734:Horse Diseases / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D006736:Horses / Q000378:metabolism*; D007592:Joint Diseases / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D008297:Male; D012680:Sensitivity and Specificity; D013582:Synovial Fluid / Q000166:cytology / Q000378:metabolism*
D015415:Biomarkers; D016326:Extracellular Matrix Proteins