Contusion of skeletal muscle increases leukocyte-endothelial cell interactions: an intravital-microscopy study in rats.

OBJECTIVE

To investigate the relationship between secondary muscle damage after contusion and the interactions between leukocytes and endothelial cells, which are essential steps in secondary inflammatory response.

METHODS

In a randomized animal study, rats were chronically instrumented with dorsal skinfold microvascular chambers and exposed to standardized contusion or sham contusion. Leukocyte rolling and adherence in postcapillary venules before and after muscle contusion or sham contusion were quantitated using in vivo microscopy.

RESULTS

The number of rolling leukocytes in the postcapillary venules before contusion was low. At 300 minutes after contusion, the number of rolling and adherent leukocytes in the striated muscle microvasculature was increased significantly (p < or = 0.05) compared with either the baseline precontusion condition or the control group at the same time.

CONCLUSION

In the mid-term to long-term stages of skeletal muscle injury associated with contusion, a significant portion of tissue damage is secondary to leukocyte-endothelial cell interactions.