19 Effects of recombinant equine intra-articular IL-1 on synovial fluid PGE2 and movement asymmetry: A pilot study (Abstract only)

Synovitis is a common feature of osteoarthritis (OA). Exogeneous intra-articular inflammatory compounds such as lipopolysaccharide or interleukin 1β (human or equine) produce a convenient, self-limiting, and reversible synovitis in horses, which can be useful to evaluate putative OA interventions. Although biochemical responses to this minimally invasive synovitis model have been described, its effects on functional adaptations in movement remains unclear. The aim of this pilot study was to correlate synovial fluid biochemical responses to intra-articular injection of recombinant equine IL-1b (IL-1) with objective measures of movement asymmetry. Horses (n = 3) randomly received 0, 50 or 75ng reIL-1 in 500μL of sterile saline into the left or right intercarpal joint in a 3-way crossover design, with 50 and 75ng treatments applied to the contralateral carpus and 24 h between treatments. Synovial fluid was collected by aseptic arthrocentesis at 0 (before IL-1 injection), 6, 12 and 24 h after IL-1 injection and analyzed for prostaglandin E2 (PGE2) by ELISA. To quantify movement asymmetry, MinDiff was calculated using withersvertical displacement data (2000 Hz) acquired from an inertial measurement unit (IMU) (Delsys Trigno) during in-hand trot trials at each time point/condition. PGE2 and MinDiff data were analyzed using 2-way repeated measures ANOVA with respect to IL-1 challenge dose and time. Correlations between variables were determined using the Spearman correlation. PGE2 significantly increased at 6 h (314.4 ± 136.4 pg/mL) compared with 0 h (128.0 ± 43.2 pg/mL) following challenge with 75ng IL-1 (P = 0.04). An increase in MinDiff 6 h following 75ng challenge was not significant (P = 0.13). MinDiff and PGE2 peaked simultaneously at 6 h after injection of 75ng IL-1, but the correlation was not significant (P = 0.27). Data from this small pilot study indicate that low intra-articular dose of reIL-1b induces measurable increase in local synovial fluid PGE2, which is a key pro-inflammatory biomarker. Effects on adaptations in gait asymmetry warrant further investigation