Sheet Preparations Expose the Dermal Nerve Plexus of Human Skin and Render the Dermal Nerve End Organ Accessible to Extensive Analysis

Abstract

Since vertical tissue sections used for the study of the human cutaneous nervous system inherently allow visualization of only a small part of the mainly horizontally oriented cutaneous nerves, we searched for possibilities to extend this view. We now propose a method based on the immuno-staining of dermal sheet preparations for subsequent analysis by electron-, light- or laser scanning microscopy. Dermal sheet preparations for the first time allowed the imaging of the complex structure of the nerve end organ over several cm 2, and facilitated viewing of its topological relationship to other tissue components. We could visualize that the bulk of free ending nerve fibers ramified within 25 μm of the dermo-epidermal junction, whereas below that only larger nerve bundles were present. This method further allowed the detection and quantification of NCAM/CD56- non-myelinating Schwann cells which envelope terminal axons within the dermis. Depending on the body region, we detected between 140 to over 300 individual terminal Schwann cells per mm2 skin surface. Our method should allow the acquisition of new insights into the highly organized architecture of the skin nerve end organ. Its further application will give new impetus in the investigation of alterations of this skin compartment under pathological conditions.