Malcolm Maden, Abigail Nunez
Myofibroblasts are considered to be the villains of regeneration, causing scarring and fibrosis after damage in many systems of the body, including the skin. They are induced by the action of pro-fibrotic cytokines released from various immune cells and express α-smooth muscle actin (α-SMA). Acomys, the spiny mouse, does not fibrose after full-thickness skin injury, it instead will regenerate all the tissues removed. We compared the appearance and behavior of myofibroblasts after skin injury in Mus (scarring) and Acomys (regenerating). In Mus, myofibroblasts appear soon after wounding, remain in the wound bed for 2 weeks, and then disappear. In contrast, Acomys myofibroblasts initially appear at the same time and location as Mus, but they disappear from the wound bed earlier. Strikingly, Acomys myofibroblasts, intensely expressing α-SMA, form a bridge between the two ends of the panniculus muscle, which remains for many weeks as the muscle regenerates completely. We suggest that this myofibroblast scaffold may be responsible for the regeneration of the panniculus carnosus, which occurs following full-thickness skin injuries in Acomys.