3.3. Vit D treatment augments IL-22 production in the intestine
Studies in mice showed that intestinal ILC3s development and IL-22 production are regulated by Vit D, and its receptor (VDR) signaling. On one hand, Vit D or VDR deficiency thus reduced intestinal ILC3s and IL-22.11,12 On the other hand, exposure of human ILC3s to Vit D was shown to reduce IL-23R expression and IL-22 production.20 Given the regenerative roles of IL-22 on intestinal epithelia, we assessed the impact of intraperitoneal Vit D or IL-22 overexpression on intestinal tissue IL-22 levels along with other Th17-signature cytokines (Fig 3). Intestinal tissue cultures showed elevated IL-22 production in both Vit D treated and IL-22 overexpressed mice groups compared with control group. The increase in Vit D group was more profound compared with IL-22 overexpression group. IL-17A or GM-CSF cytokines were not statistically significant across the mice groups.
Levels of IL-23, IFN-γ, TNF-α and IL-10 was measured by real-time qPCR in intestinal biopsies obtained at the end of the experiment (Fig 4). Although IL-23 was elevated post methotrexate, none of the cytokines were statistically different across the groups. Finally, we quantified the numbers of B cells, neutrophils and total ILC in the lamina propria of all mice groups on 5th day of mucositis (Fig 5, Supp Fig 1 and 2). Neutrophils appeared to increase in number after methotrexate treatment, however, across all animal groups, numbers were comparable (Fig 5).