MMP9 and keloid: NOX-mediated ROS have been reported to stimulate the expression of MMP-1 and MMP-9, both highly active during scar maturation [181].Of interest, it has been recently shown that NOX2 siRNA suppresses collagen production in primary keloid dermal fibroblasts, suggesting that NOX2 plays a causal role in the overproduction of collagen in keloids [128].