慢性関節リウマチ (RA) における副甲状腺ホルモン関連蛋白 (PTHrP) の発現について

Objective : In order to investigate the dynamics of PTHrP in the patients with rheumatoid arthritis (RA), we measured the PTHrP levels in serum, synovial fluid, and immunohistochemically examined the expression of this peptide in joint tissues including synovial and bony tissues in destructed regions.Method : Serum, synovial fluid and joint tissues were taken at operation of total knee replacement from the patients who met the criteria of RA proposed by ACR in 1987. Total number of RA patients was 12. As controls, we used 3 cases of osteoarthritic (OA) patients. PTHrP levels in serum and joint fluid were measured by radioimmunoassay. Immunohistochemical study was performed using anti-PTHrP antibody which was made by immunization of synthetic peptide of PTHrP.Result : PTHrP levels in RA was 54.2±33.4 (pMO1/1), while 50.5±15.2 in OA cases. PTHrP levels in synovial fluid was 183.2±77.8, while 86.4±35.3 in OA cases. There were no positive or negative correlations between PTHrP in serum and synovial fluid and major laboratory data such as blood sedimentation ratio (BSR), c-reactive protein (CRP) in serum.Many kinds of cells such as osteoclast and osteoblast neighboring to deteriorating bony tissues, synovial cells in superficial layer, macrophage in deeper layer, and endothelial cell in blood vessels, demonstrated PTHrP. In comparing the inflammatory grade of synovial tissues with PTHrP level in the synovial fluid, the severer the inflammatory grade, the higher the level of PTHrP.Conclusion : PTHrP was expressed in RA patients, probably suggesting some relation with inflammation including bony destruction or regeneration.