Assessment of Formaldehyde-Induced Arthritis (FIA) using Modified Rheumatoid Arthritis Disease Activity Index (RADAI) on Adult Male Wistar Rats

Rheumatoid Arthritis (RA) is an autoimmune inflammatory and degenerative disease affecting the joints and joint cartilage, with extra-articular manifestations. The chronicity of RA causes irreversible damage to the skeletal system and with a poorly understood pathogenesis, current management modalities are grossly limited. Pre-clinical studies on RA in Africa are plagued with scarcity and inaccessibility of research grants and funding, and this has negatively impacted interest in research. Also, inducting agents that mimic the true pathogenesis of diseases such as RA are limited. Therefore, there is a need to find readily available alternatives to promote research studies on RA in our environment. This study aimed to evaluate the rheumatoid arthritis disease activity index (RADAI) of formaldehyde induction (FIA) in comparison to collagen induction (CIA) of arthritis using twenty adult male Wistar rats which were grouped into 5 (A-E) (n=4). Group A, the control group had feed and water only. Groups B, C, and D had two doses of 0.1% formaldehyde (50µl, 100µl, and 200µl, respectively). Group E had 200µl of bovine CII-CFA emulsion (0.2mg/ml). Booster dosage was performed 9 days later by injecting 100µl of bovine CII-CFA emulsion (0.1mg/ml). Body weights, ankle measurements, and blood samples were taken on days 1, 16, and 48, before sacrificing the animals by cervical dislocation. Both ankles were rapidly dissected and processed for histological assessment using Modified Mankin System. We recorded a 100% mortality rate on high-dose formaldehyde administration (Group D), but no mortalities were seen in other groups. In low and moderate dosages of formaldehyde, RA induction was achieved and when compared to Collagen Induced Arthritis (CIA), there was no significant difference noted. We postulate that Formaldehyde Induced Arthritis (FIA) models can serve as a substitute for CIA mimicking the true pathogenesis seen in rheumatoid arthritis.