VWF and t-PA are coexpressed by endothelial cells of human muscle.

Cryosections of control human skeletal muscle were immunolabeled with antibodies against VWF (panels B and E) and t-PA (panels C and F). Using an FITC-conjugated secondary antibody, most endothelial cells of large muscle vessels, identified by phase-contrast as arterioles (panel A) and venules (panel D), were found to express VWF (panels B and E). Using a Texas Red–conjugated secondary antibody, tPA was found to be also expressed by most endothelial cells of the same arterioles (panel C), whereas its distribution in venules was detected in only a few endothelial cells (panel F). No immunostaining of the striated muscle fiber cells or the capillaries was observed with the 2 antibody combinations tested (panels B, C, E, and F). The bar represents 25 μm.