Matrix Gla-protein (MGP) is a calcification inhibitor produced by cartilage and vessel walls. Arthritis is defined by inflammation, cartilage and bone destruction/formation and articular calcifications. Our objectives were to evaluate ucMGP levels in synovial fluid (SF) in arthritis patients and to investigate the relationship between local and circulating ucMGP and their association with age and inflammation.
Arthritis patients (n=26) with knee joint effusion and controls (n=30) underwent an ultrasonographic knee examination for articular calcifications assessment. Patients were divided into inflammatory and non-inflammatory groups. ucMGP levels were determined in serum and SF using a competitive ELISA assay.
Within the arthritis patients, the inflammatory group had the lowest ucMGP serum levels, and the highest levels of synovial ucMGP. Furthermore, the inflammatory group had significantly (p<0.05) higher RucMGP (synovial ucMGP/serum ucMGP*100) than the non-inflammatory group [36 (17-69) vs. 24 (5-55)], and this parameter positively correlated (r=0.4; p<0.05) with the erythrocyte sedimentation rate (ESR). No correlation was found between age and local or circulating ucMGP in patients and controls.
The ucMGP assay can be used for determination of MGP in SF, and combined assessment of ucMGP in serum and SF could potentially serve as a joint inflammatory marker in arthritis patients.