The antidote to a bad scrape-up is usually a fairly simple recipe: antibiotics, bandages, and time. Now, a new study suggests that timing also matters.

Skin cells that help patch up wounds work more quickly in the daytime than they do at night, thanks to the workings of our circadian clock. The finding suggests patients might recover from injury more quickly if they have surgery during the right time of day.

Biologists and neuroscientists long thought the body’s time keeper, our circadian clock, resided only in the brain. In mammals, that place is a region of the hypothalamus called the suprachiasmatic nucleus, which receives signals from the eyes.

However, recent research demonstrated that cells in other parts of the body—including the lungs and liver—keep their own time. Researchers aren’t quite sure how they maintain their own 24-hour schedule, whereas other cells need external reminders.

To find out, John O’Neill, a biologist at the Medical Research Council’s Laboratory of Molecular Biology in Cambridge, U.K., and his team studied a type of skin cell known as fibroblasts that are essential for wound healing. Fibroblasts invade the void left by a scratch and lay the foundation for new skin to grow. The cells are also known to keep their own time. For example, cultured cells exhibit rhythmic oscillations in gene expression where there is no input from the master clock.

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