Circadian actin dynamics drive rhythmic fibroblast mobilization during wound healing

Fibroblasts are primary cellular protagonists of wound healing. They also exhibit circadian timekeeping, which imparts an approximately 24-hour rhythm to their biological function. We interrogated the functional consequences of the cell-autonomous clockwork in fibroblasts using a proteome-wide screen for rhythmically expressed proteins. We observed temporal coordination of actin regulators that drives cell-intrinsic rhythms in actin dynamics. In consequence, the cellular clock modulates the efficiency of actin-dependent processes such as cell migration and adhesion, which ultimately affect the efficacy of wound healing. Accordingly, skin wounds incurred during a mouse's active phase exhibited increased fibroblast invasion in vivo and ex vivo, as well as in cultured fibroblasts and keratinocytes. Our experimental results correlate with the observation that the time of injury significantly affects healing after burns in humans, with daytime wounds healing ~60% faster than nighttime wounds. We suggest that circadian regulation of the cytoskeleton influences wound-healing efficacy from the cellular to the organismal scale.