Characterization of the First Coculture Between Human Primary Keratinocytes and the Dorsal Root Ganglion-Derived Neuronal Cell Line F-11

The epidermis can be considered as a sensory organ. Sensory neurons of the peripheral nervous system send many primary afferent fibers to the skin, creating a dynamic communication with epidermal cells. However, little is known about the functional interactions between the sensory fibers and the keratinocytes. It is therefore difficult to reproduce these interactions in vitro. We have developed an in vitro model based on the coculture of primary human keratinocytes and the dorsal root ganglion cell line F-11. F-11 cells have been classically used to mimic authentic peptidergic nociceptive neurons. We first investigated the morphological and functional characteristics of F-11 cells cultured in basal keratinocyte medium and then analyzed the influence of keratinocytes on these properties. We found that F-11 cells survived and differentiated well in this medium. Therefore, the addition of neurotrophins did not enhance their survival or differentiation. These neurons expressed sensory neuron markers and were able to release neuropeptides after capsaicin activation. We noted that neuropeptides release were obtained even at a low calcium concentration and that axonal outgrowth was not influenced by external calcium (Ca(2+)) levels. These properties were reproduced when F-11 cells were cocultured with keratinocytes, but they had no significant influence on axonal development or neuropeptide release. In this study, we describe for the first time the culture of F-11 neurons with another cell type. This coculture model in which keratinocytes and neurons are maintained in low Ca(2+) concentrations may be a useful in vitro alternative for studying and characterizing the close communication between keratinocytes and sensory neurons.