Characterisation of a Freund's complete adjuvant-induced model of chronic arthritis in mice

Freund's complete adjuvant (FCA)-induced arthritis is a commonly used model in the rat. Use of FCA to induce arthritis in mice has been only occasionally reported, and most attempts to use this model have met with little success. Subdermal injection of FCA at multiple sites around the tibiotarsal joint of male C57Bl6 mice caused a localised inflammatory reaction to develop in 24 h. Significant swelling occurred around the injected tibiotarsal joint within 24 h (P<0.001), with joint circumferences increasing from 10.9 +/- 0.1 to 21 +/- 0.3 mm. This swelling showed no signs of resolution over 20 days. Unilateral joint swelling was accompanied by significant unilateral mechanical allodynia (P<0.001) and thermal hyperalgesia (P<0.001). At no point were changes in nociceptive thresholds observed in the contralateral paw. Although mice exhibited profound inflammation and showed significant alteration in nociceptive thresholds, the mobility of the mice remained generally unchanged. Histologically the tibiotarsal joints showed changes indicative of arthritis, including pannus formation. Subdermal injection of FCA around the tibiotarsal joint of the mouse provides a useful model to investigate inflammatory-induced nociceptive behaviours, which can be used in genetically manipulated mouse lines that use C57Bl6 as a background strain.