Co-culture of iNeurons with primary human skin cells provides a reliable model to examine intercellular communication

The skin is a sensory organ, densely innervated with various types of sensory nerve endings, capable of discriminating touch, environmental sensations, proprioception, and physical affection. Neurons communication with skin cells confer to the tissue the ability to undergo adaptive modifications during response to environmental changes or wound healing after injury. Thought for a long time to be dedicated to the central nervous system, the glutamatergic neuromodulation is increasingly described in peripheral tissues. Glutamate receptors and transporters have been identified in the skin. There is a strong interest in understanding the communication between keratinocytes and neurons, as the close contacts with intra-epidermal nerve fibers is a favorable site for efficient communication. To date, various coculture models have been described. However, these models were based on non-human or immortalized cell line. Even the use of induced pluripotent stem cells (iPSCs) is posing limitations because of epigenetic variations during the reprogramming process.

In this study, we performed small molecule-driven direct conversion of human skin primary fibroblasts into induced neurons (iNeurons).

The resulting iNeurons were mature, showed pan-neuronal markers, and exhibited a glutamatergic subtype and C-type fibers characteristics. Autologous coculture of iNeurons with human primary keratinocytes, fibroblasts, and melanocytes was performed and remained healthy for many days, making possible to study the establishment of intercellular interactions.

Here, we report that iNeurons and primary skin cells established contacts, with neurite ensheathment by keratinocytes, and demonstrated that iNeurons cocultured with primary skin cells provide a reliable model to examine intercellular communication.