Modulation of the inflammatory response in the rat TMJ with increasing doses of complete Freund's adjuvant

Objectives: Acute inflammation stresses the physiological system, which mus t respond in order to reestablish homeostasis. The purpose of this study wa s to determine whether bilateral temporomandibular joint (TMJ) injections o f different doses of Complete Freund's Adjuvant (CFA) produced dose-depende nt changes in biologic markers of acute inflammation. The ability to establ ish an animal model with varying degrees of joint inflammation would allow evaluation of agents or conditions that could modulate the severity of the disease. Design: The TMJs of three groups of male Sprague-Dawley rats were injected with CFA containing varying doses of Mycobacterium tuberculosis (MT). A gro up of non-injected and a group of saline injected rats were used as control s, Food intake, body weights, swelling and chromodacryorrhea were recorded daily. Interleukin-1 beta (IL-1 beta) and corticosterone levels were assaye d and condylar cartilage thickness was measured 48 h after injections. Results: Twenty-four hours post-injection, bilateral TMJ swelling and chrom odacryorrhea were significantly (P <0.05) increased following 10 mug of MT and further increased with elevated MT dose. In the CFA groups food intake was attenuated (P <0.01) 24 and 48 h post-injection and negatively correlat ed with dose at 24 h. Body weight was also negatively correlated, with dose . TMJ retrodiscal tissues IL-1 beta was increased (P <0.05) in a dose-depen dent manner. CFA increased corticosterone (P <0.05), but this elevation was not dose dependent. Condylar cartilage thickness was decreased in a dose-d ependent manner. Conclusions: These data suggest that an intermediate dose of CFA can be use d to effect submaximal levels of TMJ inflammation that will allow experimen tal modulation in future studies. (C) 2001 OsteoArthritis Research Society International.