Harnessing neuroendocrine controls of keratin expression: a new therapeutic strategy for skin diseases?

Human skin produces numerous neurohormones and neuropeptides. Recent evidence has shown that the neuroendocrine regulation of human skin biology also extends to keratins, the major structural components of epithelial cells. For example, thyrotropin-releasing hormone, thyrotropin, opioids, prolactin, and cannabinoid receptor 1-ligands profoundly modulate human keratin gene and protein expression in human epidermis and/or hair follicle epithelium in situ. Since selected keratins are now understood to exert important regulatory functions beyond mechanical stability, we argue that neuroendocrine pathways of keratin regulation are important for maintaining skin and hair follicle homeostasis. This invites innovative neuroendocrine therapeutic interventions for skin disorders characterized by abnormal keratin expression, ranging from psoriasis to genodermatoses, and for promoting skin wound healing and hair growth. This strategy can be probed in simple, but instructive and readily available human skin and hair follicle organ culture assays as ideal models for exploring this new neuroendocrine frontier in translational epithelial biology.