TNFAIP6 and colitis: MSCs improve gastrointestinal inflammation and the severity of colitis by suppressing the polarization of M1 macrophages in the colon, mesenteric lymph nodes, spleen, and peritoneum, and shifting them to the M2 phenotype through the cyclooxygenase (COX)-2/PGE2 pathway [60,61], TNF-α induced gene/protein 6 (TSG-6) production [62], and microRNA transmission [63].