Immunohistochemical characterization of Renaut bodies in superficial digital nerves: further evidence supporting their perineurial cell origin.

Renaut bodies are well-demarcated cylindrical (circular in cross section) hyaline structures attached to the inner layer of the perineurium that can be found in normal and pathological nerves of various animals and humans. They are composed of spidery fibroblasts and perineurial cells immersed in an extracellular matrix that contains randomly oriented collagen fibers and elastin precursors but not axons or Schwann cells. Frequently, they are associated with thickened subperineurial capillaries. As Renaut bodies are mainly located at sites of nerve compression, it is hypothesized they may act as 'protective cushions' for endoneurial components, and that they may be formed as a secondary reaction to trauma. Herein, we report the presence of Renaut bodies within numerous small dermal nerve trunks in an amputated finger. By immunohistochemistry, Renaut bodies expressed markers identical to those of perineurial cells (epithelial membrane antigen, Glut-1, and claudin-1), supporting the concept of a closely associated perineurial but not endoneurial origin. In addition, expression of hypoxia-inducible factor 1 alpha (which has been shown to increase Glut-1 transcription), neurofibromatosis 1 gene related product and NF-2, were also detected in these peripheral nerve structures.