Regenerated cutaneous nerves in human epidermal and subepidermal regions. An electron microscopy study

To elucidate the regeneration of cutaneous nerves in human skin, biopsy specimens were taken from the regenerated skin of extremities of five adult men with third degree burns that had occurred about 3 weeks previously. Numerous subepidermal nerves could be detected in the newly formed granulation tissue, independent of the blood vessels. These nerves were axon-Schwann's cell complexes. Some axons were packed with small clear vesicles 40-60 nm in diameter or large dense-cored vesicles 70-100 nm in diameter and large dense bodies. Schwann's cell components showed a relatively abundant cytoplasm and many microfilaments. Intraepidermal nerves were frequently encountered in the interspace between the basal lamina and the cytomembrane of basal keratinocytes in most cases or in the intercellular spaces between basal keratinocytes; however, they were never seen in and beyond spinous layers. They were seen as axon-Schwann's cell complexes or naked axons. In one case a Schwann's cell containing axons migrated into the epidermis. These findings suggest that cutaneous nerves may show hyperregeneration in very early stages of wound healing.