Immunohistochemical localization of utrophin and other cytoskeletral proteins in skin smooth muscle in neuromuscular diseases

We investigated the immunohistochemical distribution of cytoskeletal proteins in smooth muscles of 15 patients with Duchenne muscular dystrophy (DMD), 8 patients with Becker muscular dystrophy (BMD), 28 patients with various neuromuscular diseases, and 2 normal controls, performing skin and muscle biopsies. Dystrophin immunostaining confirmed absent reaction in the arrector pili muscles of DMD patients, faint positive reaction in BMD patients, and strong dystrophin reaction in patients with other neuromuscular diseases and normal controls. Immunostaining of utrophin was positive with variable intensity in the arrector pili muscles in all DMD patients. In BMD patients, utrophin was faintly expressed in the arrector pili muscles in 2 cases, and negative in the other 5 patients. In the other cases of neuromuscular diseases and in normal controls, immunostaining for utrophin was negative in the arrector pili muscles. Staining of the capillary endothelial cells and muscular vessel walls was seen in normal controls, as well as in DMD, BMD, and other neuromuscular diseases. Vinculin, vimentin and desmin were expressed both in arrector pili smooth muscles and in vessel walls of patients with dystrophinopathy and other neuromuscular diseases, as well as in normal controls. Thus utrophin is normally expressed in the smooth muscle of the vessels and its expression does not vary in neuromuscular diseases. On the contrary, in the arrector pili smooth muscle utrophin is not expressed in normal controls but it is in dystrophinopathies, paralleling the findings in striated muscle, which expresses utrophin in a reciprocal manner with respect to dystrophin.