uPA is expressed by macrophages and satellite cells after muscle injury.

Double-immunohistochemical staining of cross-sections from regenerating muscle of wild-type mice visualizing uPA, together with Mac-1, Gr-1, and M-cadherin, respectively. uPA is expressed by macrophages, but not by neutrophils, because abundant uPA– and Mac-1–double-positive cells were found 2 days after injury, whereas no uPA– or Gr-1–double-positive cells were found 12 hours after injury. uPA is expressed in satellite cells because it was detected in M-cadherin–positive cells 5 days after injury.