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Watch a wound close with the help of fat cells

Fat gets a bad rap, but it may be critical to wound healing, a new study suggests. Researchers fluorescently labeled fat cells in fruit fly pupae—the developmental stage between larva and adult—and then cut a small hole in the pupae with a laser. Within an hour, the fat cells had swum toward the wound, the team reports today in Developmental Cell. Actomyosin, a protein complex responsible for cellular contractions, was responsible for the fat cells’ wormlike propulsion, called peristalsis, the scientists found. The researchers also discovered that immune cells known as hemocytes arrive at the wound first, and when the fat cells follow they brush the hemocytes aside. Fat cells continued to show up at the wound even when the researchers deactivated the hemocytes, indicating that hemocytes aren’t signaling the location of the wound. But both cell types worked together to heal the injury, with hemocytes removing cellular debris and the fat cells tightly plugging the wound until new tissue could grow. How the fat cells know where to go remains a mystery. Fat cells likely play a role in wound healing in humans and other vertebrates, too, the researchers say, though whether the process is the same as it is in flies remains to be seen.