University of California, Los Angeles, US, (UCLA) researchers Sandra Rieger and Alvaro Sagasti have discovered new information about how injured skin cells and touch-sensing nerve fibres coordinate their regeneration when healing wounds in the skin. The key component at work when the wounded skin cells release a chemical signal to initiate this cooperative rebuilding is hydrogen peroxide. In their study, published in the journal PLoS Biology, they used zebrafish larvae, a species commonly used for development and regeneration research due to their optical transparency.

Detection of touch stimuli is achieved by peripheral sensory axons which form highly branched networks in the skin. When the skin is wounded, skin cells migrate to heal the wound, and the peripheral sensory axons must also regenerate somehow to restore sensory function.  Previous experiments have suggested that the wounded skins cells stimulate this regeneration, but had been unable to identify the responsible mediator. Hydrogen peroxide was well-known to be a toxic by-product of cell damage, but until recently it had not been appreciated as an activator of molecular pathways that regulate cellular development.

In the study the scientists amputated the tip of a larval zebrafish tail and observed the behaviour of nearby peripheral sensory axons using time-lapsed fluorescent microscopy. They discovered that the amputation boosted axon growth, and that injuring the skin cells in the body promoted the growth of nearby axons, which shows that the injured skins cells are the source of the signal that spurs the axons into mobilising. They found that adding hydrogen peroxide to the uninjured larvae had the same effect as damaging the skin cells – it boosted axon growth. And conversely they found that inhibiting the production of hydrogen peroxide blocked this function.

Having found this to be the case, the scientists are now hoping to be able to determine the role of the hydrogen peroxide: is it perceive by the peripheral sensory axons directly or does it elicit a signal from keratinocytes (the predominant skin cell type in the outer layer of the skin), or does it modify the environment somehow to encourage axon growth? If these questions can be resolved then it will inform how skin wounds are healed and sensory function is fully restored.

Read Michelle Berriedale Johnson's article about the difference hydrogen peroxide has made to her ES.

Source: PLoS Biology

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First Published May 2011

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