Increases in mast cells and chymase in fibroproliferative paws of collagen-induced arthritic mice

Objective and Design: To investigate whether mast cells (MCs) and chymase, the major protease of murine MCs, were involved in a chronic fibroprolifera tive disorder of the paws associated with type II collagen (CII)-induced ar thritis. Materials: Eighteen DBA/1J mice were divided into 3 groups and were used to study fibroproliferative changes in paws elicited by immunization. Treatment: Arthritis was induced by immunization with CII, which was intrad ermally injected as an emulsion made with adjuvant. A booster shot was done 3 weeks after the initial shot. A group with no treatment and that receive d adjuvant alone served as control. Methods: Twelve weeks after the booster shot, inflammation of the paws was evaluated for pathological and biochemical indices. Chymase activity was de termined with a chromogenic peptide substrate. Results: In CII-immunized group, collagen bundles accumulated around the de structed joints. In accordance with the pathological findings, MC density i n the affected paws was increased (154.8 +/- 13.3/mm(2); p < 0.05 vs, contr ol) and chymase activity was also increased (29.5 +/- 2.8 mU/mg protein; p < 0.01 vs. control). Conclusions: The present results demonstrate increases in MCs and chymase i n fibroproliferative paws of collagen-induced arthritic mice.