ACTA1 and colitis: In these cases, the submucosal layer of the constrictedcolonic tissues has increased levels of collagen as well as an increasein fibrosis-associated elements like α-SMA, collagen-I, andfibronectin.29,51,52 In this experiment, due to repeated stimulation by DSS, α-SMAand collagen-I proteins increased continuously in colitis mice, resultingin thickening of the intestinal wall.