The role of mast cells and fibre type in ischaemia reperfusion injury of murine skeletal muscles

BACKGROUND: Ischaemia reperfusion (IR) injury of skeletal muscle, is a significant cause of morbidity following trauma and surgical procedures, in which muscle fibre types exhibit different susceptibilities. The relative degree of mast cell mediated injury, within different muscle types, is not known. METHODS: In this study we compared susceptibility of the fast-twitch, extensor digitorum longus (EDL), mixed fast/slow-twitch gastrocnemius and the predominately slow-twitch soleus, muscles to ischemia reperfusion (IR) injury in four groups of mice that harbour different mast cell densities; C57/DBA mast cell depleted (W(f)/W(f)), their heterozygous (W(f)/+) and normal littermates (+/+) and control C57BL/6 mice. We determined whether susceptibility to IR injury is associated with mast cell content and/or fibre type and/or mouse strain. In experimental groups, the hind limbs of mice were subjected to 70 minutes warm tourniquet ischemia, followed by 24 h reperfusion, and the muscle viability was assessed on fresh whole-mount slices by the nitroblue tetrazolium (NBT) histochemical assay. RESULTS: Viability was remarkably higher in the W(f)/W(f )strain irrespective of muscle type. With respect to muscle type, the predominately slow-twitch soleus muscle was significantly more resistant to IR injury than gastrocnemius and the EDL muscles in all groups. Mast cell density was inversely correlated to muscle viability in all types of muscle. CONCLUSION: These results show that in skeletal muscle, IR injury is dependent upon both the presence of mast cells and on fibre type and suggest that a combination of preventative therapies may need to be implemented to optimally protect muscles from IR injury.