Objective: To investigate the expression of discoidin domain receptor 2 (DDR2) of fibroblast-like synovial cells in improved adjuvant-induced animal (AIA) model for rheumatoid arthritis (RA) and to provide evidence for DDR2's antagonist use clinically.
Methods: AIA was modified by administrating 0.1 mL of complete Freund's adjuvant (CFA, mixed with 5 mg Bacillus Calmette-Guerin vaccine/mL) into rats' right hind paws and 0.125 mL tumor necrosis factor-alpha (2 U/mL) into right ankles and subpatellar fatty tissue. The expression of DDR2 in fibroblast-like synovial cells was assessed using immunohistochemistry, immunofluorescence histochemistry, and in situ hybridization methods. Levels of anti-collagen II antibody were measured using enzyme-linked immunosorbent assay.
Results: Given the terms mentioned above, we found a more practical rat model, apparently decreasing immunization time (average 3-5 days). DDR2 can be detected upon the 15th day of immunization; expression gradually increased with time going on, and reaching a peak 35 days after immunization before gradually decreasing. Serum anti-collagen II antibody showed similar expression patterns as DDR2, but reached peak later than DDR2, about 40 days after immunization.
Conclusion: Regular expression of DDR2 in animal models infers its important role in the pathological process of RA.