TNF and colitis: Previous studies have shown that MSCs ameliorate colitis by downregulating the pro-inflammatory cytokines TNF-α, IL-1β, IL-2, IL-6, IL-17, and IL-23; upregulating IL-4, IL-10, and other anti-inflammatory cytokines; and regulating the imbalance of T cell subsets, such as Th 1 cells, Th2 cells, Th17 cells, and Tregs (Ghannam et al., 2010; Chen et al., 2013; Yan et al., 2014; Gao et al., 2016; Fu et al., 2018; Alves et al., 2019).