THU0545 Characterising a mouse model of temporomandibular joint (TMJ) arthritis to study orofacial pain and inflammation

Background The temporomandibular joints (TMJ) encompass the jawbones (mandibular condyle) and the skull region (temporal bone)1. Dysfunctions in these joints and surrounding muscles result in a condition known as TMJ disorder (TMD), which include mastication-related pain. 16%–59% of patients reported painful symptoms while 33%–86% of these patients showed clinical signs1. Currently, the etiology of TMD is unknown, although lavage samples from patients showed signs of synovitis, which may lead to the development of degenerative disorders, such as TMJ arthritis2. There are only a few murine models available, as the most commonly used animal model is TMJ arthritis in rats. Objectives We aimed to characterise a mouse model of TMJ arthritis by mimicking the formation of synovitis using zymosan. We sought to characterise the development of orofacial pain by performing various behavioural measurements and measure joint inflammation. Methods All in vivo procedures were carried out according to the UK Home Office Animals (Scientific Procedure) .Act 1986 Male CD1 mice (6–8 weeks) were anaesthetised transiently using 2% isoflurane. Zymosan (10, 30, or 100 µg; 10 µl), or saline was administered unilaterally into the TMJ as previously described3. Spontaneous pain behaviours were observed by counting the number of unilateral cheek wipes. All studies were terminated by cervical dislocation and the tissue was collected for ex vivo analyses. Mean ±SEM was calculated and data were analysed by unpaired Student’s T-test or 2-way repeated measures ANOVA with Bonferroni’s post hoc test. p Results A dose response study showed that 30 µg, but not 10 µg and 100 µg of zymosan, resulted in a maximal wiping response at 2 hours, which was maintained at 4 hours (table 1; ***p Table 1 A summary of zymosan-mediated spontaneous orofacial pain behaviours and inflammation. Conclusions We have established a mouse model of TMJ arthritis, which showed significant orofacial pain responses in vivo. Our data highlights an inflammatory profile typical of zymosan and shows a potential use for this model to investigate novel TMD treatments. References [1] Millam. J Musculoskel Neuron Interact2003;3(4):382–390. [2] Cheng and Israel. J Maxillofac Surg2005;63(6):761–765. [3] Kramer, et al. Physiol Behav2010;99(5):669–678. Acknowledgements XK and JV were funded by Arthritis Research UK. Disclosure of Interest None declared