Skin Cells Create Neuron-Like Electric Signals

Animal bodies are crackling with electrical signals. Even before development is complete, electric fields guide the movement and arrangement of embryonic cells.¹ In adults, neurons communicate with other cells through a zap of electricity, microfractures in bones create a tiny, but charged, field around them to attract repair cells, and cancer cells use bioelectricity to promote metastases. In fact, all cells in the body act like a tiny battery, maintaining an ion-driven voltage difference across the cell membrane. However, the presence of this membrane potential is not the only condition required to generate electric signals.² Some cells, such as skin cells, were thought to not generate any electrical signals of their own.

Now, in a study published today in the Proceedings of the National Academy of Sciences, scientists have overturned this assumption, showing that wounded skin cells produce spikes of electricity, much like neurons in the brain.³ A deeper understanding of these charged epithelial sparks could drive the development of improved bioelectric medical devices.

Epithelial cells are known to respond to external electric stimuli. Membrane potential of epithelial cells and bioelectric networks across tissues have emerged as crucial drivers of tissue morphogenesis and regeneration in animals like tadpoles, salamanders, and flatworms.¹ Scientists have observed the migration of skin cells placed in external electric fields, a property that has been used to develop wound-healing electronic bandages and other devices.⁴ While many of these studies allude to bioelectric signaling between skin cells, none reported a direct observation of the electrical spikes.

To fill this gap in knowledge, Steve Granick, a polymer scientist at the University of Massachusetts Amherst, and Sun-Min Yu, a postdoctoral researcher in Granick’s group, cultured canine epithelial cells on a chip and wounded them with a laser. When they recorded the electrophysiological activity of the cells 10 minutes after the wound stimulus, they observed spiking that lasted for at least five hours. The various phases of the electrical spikes looked similar to those of neurons, except that they were slower by one to two seconds. Yu also observed a propagation of the electrical signals at a speed of 10 millimeters per second and up to 500 micrometers away from the cell that generated them. The team repeated the experiments using human skin cells and observed the same results.

“When injured, [epithelial cells] 'scream' to their neighbors, slowly, persistently and over surprising distances. It's like a nerve's impulse, but 1,000 times slower,” said Granick in a statement.

Considering the essential roles played by neural spikes in cognition, memory formation, and complex computations, Granick and Yu found the similarity between epithelial and neural spikes provocative. However, there is much left to be uncovered. What are the ion channels involved in the generation of these spikes? Why are they only produced after the skin cells are wounded? How does their function differ from those of neuronal spikes? These are just some of the questions the team is keen on answering next, which could have diverse potential ripple effects. “Understanding these screams between wounded cells opens doors we didn’t know existed,” Yu said in a statement.