A Simple Immunofluorescence Technique for Simultaneous Visualization of Mast Cells and Nerve Fibers Reveals Selectivity and Hair Cycle-Dependent Changes in Mast Cell-Nerve Fiber Contacts in Murine Skin

The study developed a novel triple-staining immunofluorescence technique to simultaneously visualize mast cells (MCs) and nerve fibers in murine skin, revealing that MC-nerve associations were highly selective for specific nerve fiber types and varied with the hair cycle. In telogen and early anagen phases, MCs predominantly contacted CGRP-immunoreactive (IR) or SP/CGRP-IR double-labelled nerve fibers. During late anagen, there was a significant increase in contacts between MCs and tyrosine hydroxylase-IR fibers, while in catagen, increased contacts were observed with peptide histidine-methionine-IR and choline acetyl transferase-IR fibers. This contradicted previous suggestions and highlighted the dynamic nature of MC-nerve interactions in relation to the hair cycle.