Spatial and Temporal Localization of the Melanocortin 1 Receptor and Its Ligand α–Melanocyte-Stimulating Hormone during Cutaneous Wound Repair

Growing evidence indicates that the melanocortin 1 receptor (MC1R) and its ligand α–melanocyte-stimulating hormone (α-MSH) have other functions in the skin in addition to pigment production. Activation of the MC1R/α-MSH signaling pathway has been implicated in the regulation of both inflammation and extracellular matrix homeostasis. However, little is known about the role of MC1R/α-MSH signaling in the regulation of inflammatory and fibroproliferative responses to cutaneous injury. Although MC1R and α-MSH localization has been described in uninjured skin, their spatial and temporal expression during cutaneous wound repair has not been investigated. In this study, the authors report the localization of MC1R and α-MSH in murine cutaneous wounds, human acute burns, and hypertrophic scars. During murine wound repair, MC1R and α-MSH were detected in inflammatory cells and suprabasal keratinocytes at the leading edge of the migrating epithelial tongue. MC1R and α-MSH protein levels were upregulated in human burn wounds and hypertrophic scars compared to uninjured human skin, where receptor and ligand were absent. In burn wounds and hypertrophic scars, MC1R and α-MSH localized to epidermal keratinocytes and dermal fibroblasts. This spatiotemporal localization of MC1R and α-MSH in cutaneous wounds warrants future investigation into the role of MC1R/α-MSH signaling in the inflammatory and fibroproliferative responses to cutaneous injury. This article contains online supplemental material at http://www.jhc.org . Please visit this article online to view these materials.