Background: To identify capsular components of neuromuscular spindles in man by means of immunohistochemistry.
Methods: Investigation of histologically observed neuromuscular spindles in surgical specimens with the use of markers for sheath cells and basement membranes.
Results: Epithelial membrane antigen and CD34 immunoreactivities were found in the outer and inner capsular layers, respectively. S-100 protein was not expressed in the capsules and there was more collagen type IV than laminin.
Conclusions: Cells resembling perineurial cells and endoneurial fibroblasts, and basement membrane rich in collagen type IV comprise the capsules of neuromuscular spindles.