Neuron-like activity identified in skin cells.
It is known that melanocytes are skin cells located in the skin’s epidermis layer that produce the protective skin-darkening pigment melanin. Melanin pigment is made by melanosomes contained within melanocytes and transferred, via melanocytic dendrites, to neighboring epithelial cells known as keratinocytes. Despite this knowledge, the physiology of communication between melanocytes and keratinocytes is still poorly understood. Now, a study from researchers at the Rockefeller University identifies compartmentalized neuron-like activity taking place outside the nervous system in certain skin cells, with compartmentalized signaling a recognized hallmark of localized cell-to-cell communication within the nervous system. The team states they observed melanocyte skin cell’s dendritic extensions communicating with neighboring cells, providing a new model system for studying compartmentalized signaling in dendritic structures. The opensource study is published in the Journal of Cell Biology.
Previous studies show melanocytes produce UV-absorbing pigment, known as melanin, to protect keratinocytes, which constitute 90% of the cells of the outermost layer of the skin. It has been observed that one melanocyte can physically interact with multiple keratinocytes across different layers of the epidermis via its dendritic extensions. In turn, keratinocytes are known to be the master regulators of melanocyte behavior, with much work undertaken to decipher how keratinocytes control melanocyte production and transfer of pigment throughout the skin. The current study investigates how melanocytes make physical contact with keratinocytes to receive information from them.
The current study uses a co-culture of melanocytes with an integrated calcium sensor, with keratinocytes present to show how these skin cells interact. Results show keratinocytes wrap around the melanocytes, forming connections similar to those seen in neural cells. Data findings show keratinocytes have small projections made up of cytoplasm that wraps around individual melanocyte dendrites to exchange pooled vesicles in the keratinocyte protrusions adjacent to the melanocyte spines.
The lab observed that endothelin and acetylcholine are then secreted by keratinocytes which causes a localized calcium response from the melanocytic dendrites. They state that this secretion causes the melanocytes to produce compartmentalized bursts of calcium. They stress that although dendritic morphologies are not unique to the nervous system, it is still unclear if non-neuronal dendrites, such as those seen on melanocytes, are also capable of compartmentalizing signals received from adjacent cells.
The team surmises they have detected neuron-like activity in skin cells resulting in a calcium transient. For the future, the researchers state they plan to decode these signals, focusing on how the transfer of melanin pigment is coordinated.
Source: The Rockefeller University