OLFM4 and colitis: To explore whether MMP9 mediated the regulatory effects of OLFM4 on colitis in mice, we transfected Olfm4-/- mice and WT littermates with recombinant adeno-associated virus-shMMP9 (AAV-shMMP9) or control vectors (AAV-shNC) through tail vein injection (Figure 5C; Figure S8A-S8D).