Induction of RA in rabbits

RA was generated in a well‐established rabbit model. This protocol was approved by the animal experimentation committee of the Sun Yat‐sen Memorial Hospital, Sun Yat‐sen University. Briefly, 24 adult female New Zealand white (NZW) rabbits with an initial weight of 3·3–3·9 kg were immunized by intradermal injections of 5 mg of ovalbumin (OVA; Sigma‐Aldrich, St. Louis, Missouri, United States) in Freund’s complete adjuvant (Difco, Detroit, MI, USA). Animals were immunized again 3 weeks later in the absence of the adjuvant. Ten days after the second immunization (day 0), 5 mg of OVA dissolved in 0·5 ml sterile saline was injected into the knees of 18 rabbits to induce arthritis (RA group). The same volume of sterile saline was injected into the knees of the remaining six animals (sham group). Twenty‐four hours after injection (on day 1), hospitals in the RA group were randomized into three groups. One group was injected with 1 μM imatinib (2 ml/kg, imatinib group, n = 6); one group was injected with 1 μM imatinib (2 ml/kg) and 5 μg pcDNA3.1‐CSF1R (imatinib + pcDNA3.1‐CSF1R group, n = 6); and one group was injected with 0·5 ml sterile saline (NC group).