Peribulbar Innervation and Substance P Expression Following Nonpermanent Injury to the Human Scalp Hair Follicle

The hair pluck procedure alters the anatomy of the anagen hair bulb. Hemmorhage can occur in the mesenchymal sheath and breaks at the proximal epithelium, above or around the upper third of the dermal papilla, have been reported. We hypothesized that innervation, as identified with protein gene product 9.5 (PGP 9.5), and expression of the neuropeptide Substance P (SP) within the dermal papilla would also be altered following plucking. We focused on studying SP as this neuropeptide has been associated with several cellular responses, including anagen hair growth in the C57BL/6 mouse model. Four millimeter punch biopsies were obtained from the occipital scalp of two healthy adults. Hair was then plucked and additional biopsies were obtained immediately, and at 1 d, 1 wk, and 1 mo after plucking. Each set was processed for immunohistochemical analyses and in-focus optical sections of the dermal papilla were captured by laser scanning confocal microscopy and later reconstructed into single images. Following injury, SP was expressed in a disorganized pattern below the dermal papilla. There was also a significant reduction in labeled neuronal cells, and SP expression was enhanced within peribulbar blood vessels at 1 d and 1 wk. By 1 mo, peribulbar nerves, vessels, and SP expression were similar to baseline observations. It remains to be ascertained whether PGP 9.5, also known as unbiquitin hydrolase, and SP are involved in the proliferation of new matrix cells in the human scalp hair follicle following injury