Objective and design: To investigate whether mast cells (MCs) and chymase, the major protease of murine MCs, were involved in a chronic fibroproliferative disorder of the paws associated with type II collagen (CII)-induced arthritis.
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 intradermally 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 received 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 determined with a chromogenic peptide substrate.
Results: In CII-immunized group, collagen bundles accumulated around the destructed joints. In accordance with the pathological findings, MC density in the affected paws was increased (154.8+/-13.3/mm2; p<0.05 vs. control) 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 in fibroproliferative paws of collagen-induced arthritic mice.