Perineurium talin immunoreactivity decreases in diabetic neuropathy

We studied the immunolocalization of Dp116 (a 116 kDa protein product of the dystrophin gene), vinculin, talin, vimentin, desmin, spectrin and titin in the sural nerve biopsies of 25 patients with peripheral neuropathies of different origin. 4 patients presented with HMSN type 1, 4 with HMSN type 2, 2 with HNPP, 4 with CIDP, 5 with chronic axonal neuropathy of unknown origin, 3 with vasculitic neuropathy, 3 with diabetic neuropathy. Expression and localization of Dp116, vinculin, vimentin, desmin, spectrin and titin did not differ from normal control cases. Spectrin and titin immunoreactivities were absent and desmin was occasionally found in few epineurial vessels. A thin rim of Dp116 binding surrounded the outermost layer of myelin sheaths. Perineurium and epineurial vessels stained deeply for vinculin. Vimentin immunoreactivity was seen in all endoneurial, perineurial and epineurial cells. Immunoreactivity for talin was normally found at endoneurial and epineurial vessel walls, perineurial cells and epineurial fibroblasts in all the sural nerves except diabetic nerves. In the latter, whereas talin binding was normal in the vessel walls and epineurial fibroblasts, it was markedly reduced in the perineurium. On immunoblot, two bands at 235 and 190 kDa were found in the sural nerves with the antibody anti-talin, and both were reduced only in the patients with diabetic neuropathy. We postulate that decreased perineurium talin in diabetic polyneuropathy may be related to the known alterations of the tight junctions of the perineurial cells, which have been proposed to be a contributory factor to impaired permeability barrier properties.