We also observed that the expression of MMP9 was dramatically upregulated at both the mRNA and protein levels in the cellular and mouse models of colitis (Figure 4C-4F), and knockout of Olfm4 further upregulated the expression of MMP9 in LPS-stimulated cells and in the colon of DSS-treated mice (Figure 4G-4I; Figure S5B). Here, MMP9 is linked to colitis.