Expression of estrogen receptor related protein (p29) and estradiol binding in human arthritic synovium

Abstract

Objective: We investigated the expression of estrogen receptors (ER) and the presence of estradiol in human synovial tissues from subjects without arthritis and patients with traumatic arthritis, osteoarthritis, and rheumatoid arthritis.

Methods: Synovial tissues were immunostained using ER-D5 monoclonal antibody (Mab) directed toward an ER related protein (p29), ER-ICA Mab directed toward nuclear ER, and antiestradiol serum. Fluorescent estradiol was used to demonstrate specific estradiol binding to ER.

Results: (1) p29 was present predominantly in hyperplastic synovial lining cells and smooth muscles of blood vessels. (2) Exogenous estradiol bound to synoviocytes and sublining macrophage-like cells in the inflamed synovium. (3) Endogenous estradiol was also detected in hyperplastic lining cells and macrophage-like cells in arthritic synovium.

Conclusion: Our study demonstrated the expression of ER in arthritic synovium and suggested that estrogen modulates local inflammation in various joint diseases via synoviocytes as well as sublining macrophage-like cells.