The nerve endings inside the epidermis convey pain, touch, and itching. Recent studies show that even keratinocytes in the epidermis have a role. Their contact with sensory neurons has a synaptic like character. The underlying communication mechanism is not well understood.

This study demonstrates keratinocyte contact with intraepidermal nerve endings.

The study tries to establish the synaptic character of keratinocytes-sensory neurons contact. The co-cultures of both these cells were used for assessment. The contacts were explored using molecular, morphological, and functional approaches. The in vitro structures were observed for indications in human epidermis. Skin biopsies were studied during this process.

The epidermal keratinocytes have an en passant synaptic-like contact with sensory neurons. Their features are ultrastructural with molecular hallmarks of chemical contacts. These include narrow intercellular cleft, syntaxin1, vesicle release, and SNARE-mediated for sensory data transfer. And the keratinocyte synaptic vesicles express synaptotagmin 1 and synaptophysin. The synaptic-like contacts form the primary spots of two-site receptors.

The identification of selective communication has been delayed by high plasticity. En passant structure and epidermal turnover also misled researchers into the nerve endings concept. This discovery questions such basic assumptions of cutaneous sensory perception. It also improves knowledge of the pathophysiology of pain, itch, and touch sensations.

Ref: https://onlinelibrary.wiley.com/doi/10.1002/ana.25912