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.
Eighteen DBA/1J mice were divided into 3 groups and were used to study fibroproliferative changes in paws elicited by immunization.
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.
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.
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).
The present results demonstrate increases in MCs and chymase in fibroproliferative paws of collagen-induced arthritic mice.