Comparative study and characterization of a murine experimental model of murine experimental model of arthritis using one of two doses of chicken type II collagen

Abstract

Rheumatoid arthritis is a progressive and chronic process characterized by systemic and local inflammation, which generates damage, articular destruction, and pain. We wanted to evaluate and comparatively characterize a model of collagen-induced arthritis (CIA) after one or two injections of chicken type II collagen (CII). For such purpose, 12-week-old C57BL6 mice received an intradermal tail injection with Freund´s complete adjuvant and purified CII (ACF+CII). At 14 days (d) a group of mice received a second injection of an emulsion of incomplete Freund´s adjuvant and purified CII (AIF+CII). The experiments included mice injected with saline solution as controls (C). CIA development was evaluated at 31 and 45 days post first injection (dpfi) by: a) swelling of legs and ankles (expressed in mm); b) body weight and peripheral blood: c) leukocyte and platelets counts; d) neutrophil peroxidase (Px) and e) serum antiCII IgG (IgG, IgG1, IgG2a). One and two injections of CII induced significant swelling of the ankles, but only mice from the ACF+CII group demonstrated significant swelling of the paws (right paw 31 dpfi, C=2.18±0.17mm, ACF+CII=2.98±0.50mm, AIF+CII=2.59±0.27mm, C vs ACF +CII p<0.001, ANOVA). Both CIA groups, had elevated anti-CII IgG levels (serum dilution 1/500, OD 450 nm at 31 dpfi, C=0.14±0.04, ACF+CII=0.45±0.05, AIF+CII=0.41±0.03, C vs ACF+CII p<0.0001, C vs AIF+CII p<0.0001, ANOVA) and anti-CII IgG1 and IgG2a subtypes, increased neutrophils, decreased Px, and total leukocyte and lymphocyte counts with respect to C without significant alterations in body weight and platelet counts. We conclude that a single injection of ACF+CII is enough to induce CIA, demonstrated by clinical parameters and increased anti-CII IgG and subtypes, among other parameters. The smaller number of injections reduces animal suffering and allows a better evaluation of the alterations caused by CIA.