Thus, for example, shock waves have been shown to be capable of reducing the collagen fibers of keloids due to increases in the expression of MMP13 [25], while stem cell therapies attenuated the expression of tissue inhibitor of metalloproteinases 1 (TIMP-1) in keloid fibroblasts [34], which would promote the activity of MMPs. The gene discussed is MMP13; the disease is keloid.