Nerve cells in the skin help wounds to heal. When an injury occurs, cells known as glial cells change into repair cells and disseminate into the wound, where they help the skin to regenerate, according to researchers.

An essential step in skin wound healing is wound closure, which is why shortly after an injury occurs, blood coagulates and seals the wound. For the injury to be able to heal permanently, however, the affected layers of the skin need to be newly formed. For that to happen, a complex, only partially understood interplay takes place between various cell types in our skin. Research group have now been able to show that peripheral nerve cells play a central role in this healing process.

There have long been indications that for optimal healing to occur, a tissue needs to be innervated (i.e. supplied with nerves). The reason, however, remained unclear. With the help of an animal model, the researchers from discovered that fine nerve bundles change drastically if they are injured when a skin wound occurs.

Cells along the injured nerve bundles, known as glial cells, change their original identity and are reprogrammed to "repair cells." They thereby lose their contact to the nerve bundles and disseminate into the wound bed. "There, they distribute a diverse cocktail of factors, which support the wound healing," explains the author.

Authors show that injury activates peripheral glia by promoting de-differentiation, cell-cycle re-entry and dissemination of the cells into the wound bed. Moreover, injury-activated glia upregulate the expression of many secreted factors previously associated with wound healing and promote myofibroblast differentiation by paracrine modulation of TGF-β signalling.

Accordingly, depletion of these cells impairs epithelial proliferation and wound closure through contraction, while their expansion promotes myofibroblast formation.  Through genetic experiments, authors were able to prove that, among other things, these repair cells were important to help the wound close as they support the necessary reconstitution of the dermis.

In older people or people with diabetes, for example, wounds often heal slowly or, in some cases, not at all. Such chronic wounds usually cause serious health problems and treatment is currently unsatisfactory. Interestingly, the researchers also found reprogrammed peripheral nerve cells in human skin wounds. "Now we want to work together with clinicians to better characterize the wound healing factors that are distributed by nerve cells," says Sommer. "This may lead to an effective treatment for chronic wounds in the future."

http://www.media.uzh.ch/en/Press-Releases/2018/Wound-Healing.html