Sensory nerve-secreted factors regulate basal keratinocyte function in vitro

Basal keratinocytes in the skin epidermis respond to microenvironmental signals during homeostatic maintenance of the skin and following injury by proliferating, migrating, and differentiating to restore the epidermal barrier. Injuries to the skin can result in non-healing wounds, characterized by prolonged inflammation, failure to close, and chronic pain. The skin is densely innervated by peripheral sensory nerves, which contribute to the wound repair response. Although it is known that nerves are important for successful wound healing, the underlying cellular mechanisms of this phenomenon, and particularly the role of nerves in directing keratinocyte re-epithelialization, are poorly understood. To explore the relationship between sensory nerves and keratinocyte function in vitro, we cultured keratinocytes with conditioned media collected from dorsal root ganglia (DRG) in both homeostatic and post-wounding conditions and found that keratinocyte migration, proliferation, and phenotype, functions essential for re-epithelialization, were modulated by DRG conditioned media. Using a proteomic approach, we characterized the secretome of cultured DRG and identified key factors essential for wound healing, including extracellular matrix proteins, growth factors, and metabolic factors involved with ATP production, which was correlated with alternations in keratinocyte metabolism when cultured in DRG conditioned medium. Our results advance our understanding of the microenvironmental cues that direct keratinocyte function during normal cellular turnover and cutaneous wound healing in vitro, helping to drive the development of therapeutics that target dysregulated re-epithelialization.