G.P.128 The effect of non-severe dorsal burn injury on the contractile properties of fast-twitch hind limb skeletal muscle of the mouse

Abstract

Abstract Loss of skeletal muscle function is cited as the most common reason preventing burn patients from returning to work. However, the effect of non-severe burn injury on muscle function has not been investigated, despite this type of burn accounting for >90% of all burn injuries. We examined the effect of non-severe burn injury on muscle mass and contractile function in the mouse extensor digitorum longus (EDL) muscle. Anaesthetised mice (4% isoflurane in O 2 ) received a full-thickness burn to 6% of total body surface area. Analgesics (buprenorphine (0.1 mg/kg) and paracetamol (0.01 mg/mL)) were administered post-injury. At 7, 28 or 84 days after burn injury, mice were anaesthetised with pentobarbitone (40 mg/kg) and EDL muscles were excised for assessment of contractile function. The effects of burn-injury on the contractile filaments were also determined using the skinned fibre technique. The muscle mass from burn-injured and control mice were not significantly different at any time point. The maximum specific force (N/cm 2 ) in EDL muscles from burn-injured mice was significantly higher than controls at day 7 (by 16%), but significantly lower at days 28 and 84 (by 18% and 14%, respectively). Skinned fibres from burn injured muscles exhibited significantly greater maximum force at day 7, but were not significantly different from controls at day 28 or day 84 post-injury. Non-severe burn injuries caused significant long-term contractile dysfunction in remotely located hind-limb muscles. These effects were independent of muscle atrophy or direct effects on the contractile apparatus. Therefore, non-severe burn injury-related muscle weakness may be an important factor impeding patient recovery. If similar effects occur in humans, non-severe burn injury-related muscle weakness may be an important factor impeding patient recovery.