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Fibroblasts (red) invading a wound (blood clot, in blue) in mouse skin. Photo: MRC Laboratory of Molecular Biology

The time of day you sustain a skin wound may influence how quickly it heals, according to a new study.

A team of researchers found that our circadian clock influences the rate at which skin cells repair damage and begin to heal scrapes and cuts.

Recent research has proven that biological clocks are in every individual cell in the human body, not just in the brain as previously thought. The latest research – led by John O’Neill, from the Medical Research Council (MRC) Laboratory of Molecular Biology in Cambridge, England, in collaboration with NHS colleagues Ken Funn, from the Manchester Burns and Plastic Surgery Service, and John Blaikley, from the Centre for Respiratory Medicine and Allergy in Manchester – demonstrates for the first time how these clocks also influence how wounds heal.

Fibroblasts are the skin cells responsible for wound healing. A protein known as actin triggers fibroblasts to invade the area of a wound, where they produce restorative proteins like collagen to repair the damage and grow new skin.

The proteins in the skin cells appear to prefer to work “daytime shifts,” the study found. Data from 118 burn patients showed that patients who suffered from a burn injury during nighttime hours took an average of 11 days longer to heal than patients who sustained similar wounds during the day.

To further confirm the findings, the team observed skin cells grown in a petri dish, as well as living skin. Wounds were produced at different times of the day, and the researchers noted the rate at which skin cells migrated to the vulnerable area.

Injuries that occurred during the day healed faster than those at night. The second phase of the study investigated how wounds healed in mice, which produced similar results. The team reported that nearly twice as many fibroblasts moved to the spot of a wound compared to movement at night.

However, the findings were reversed in nocturnal mice, where skin cells moved more quickly and wounds healed faster when injuries occurred at night as the mice were most active.

The study implies that patients may recover from surgery faster if they schedule it based on the patient’s circadian rhythms, which vary slightly by individual. The findings could also lead to the development of new medications that prompt actin to “get motivated” regardless of the time of day.

The study was published in Science Translational Medicine.

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