Inflammation-induced leukocyte accumulation in injured skeletal muscle: role of mast cells

Inflammation consequent to muscle damage is characterized by an accumulation of leukocytes. Our aim in this study was to determine whether mast cells can modulate inflammation-induced leukocyte trafficking. One approach consisted of giving rats a mast cell-degranulating agent, CMP 48/80, prior to a protocol of lengthening contractions inducing inflammation without neutrophil accumulation; in parallel, other rats were given the mast cell-stabilizing agent, cromolyn, prior to injecting muscle with bupivacaine, which induces neutrophil accumulation. Damage was evaluated through measurement of contractile force and inflammation using histochemical and immunohistochemical methods. Stimulation with CMP 48/80 increased the proportion of degranulated mast cells significantly and neutrophil accumulation occurred with lengthening contractions. With bupivacaine, accumulation of neutrophils decreased by 70% when degranulation was inhibited. These results indicate that mast cells are important in the process governing leukocyte trafficking in skeletal muscle trauma and that targeting their inhibition could be an attractive alternative for control of inflammation.