Myeloid Mcpip1/Regnase-1 regulates intestinal homeostasis by modulating epithelial cell differentiation

BACKGROUND: MCPIP1/Regnase-1 is a negative regulator of the inflammatory response, and its protective role against the development of various pathological conditions, including intestinal diseases, has been documented. Importantly, the biological effects of MCPIP1 are cell-specific. METHODS: Myeloid-specific Zc3h12a knockout (Mcpip1MKO) mice were generated using the Cre-loxP system. Acute colitis was induced with 3% DSS, and disease severity was assessed by DAI scoring, histology, and intestinal permeability assays. Colon tissues and bone marrow-derived monocytes were analyzed via qRT-PCR, immunostaining, and confocal microscopy. RESULTS: In this study, we focused on its role in submucosal macrophages, which serve as key sentinels of the intestinal immune system. Using macrophage-specific Mcpip1-deficient mice, we report that myeloid MCPIP1 controls the homeostasis of intestinal secretory cells through negative regulation of the Notch signaling pathway. The underlying molecular mechanism involves MCPIP1-dependent repression of Notch ligands in macrophages, including Jagged1, Dll3, and Dll4, which control proper differentiation of intestinal stem cells (ISCs). Depletion of MCPIP1 enhances epithelial proliferation and the number of Lgr5⁺ stem cells in colon, but fails to maintain their differentiation into secretory lineages. Moreover, in Mcpip1-deficient macrophages, activation of the Notch pathway is further enhanced in response to bacterial components and microorganisms penetrating from the gut lumen. In consequence, mucosal barrier integrity is compromised due to defective differentiation of secretory cells, leading to a significant reduction in the mucus layer and severe colitis, highlighting the physiological significance of our findings. CONCLUSIONS: Our study provides novel mechanistic insight into the role of macrophages in ISC differentiation and establish MCPIP1 as a key immune regulator of intestinal stem cell fate via macrophage-derived Notch signaling. An immune - epithelial axis that links innate immune regulation to epithelial barrier function and colitis pathogenesis, thereby opening new avenues for therapeutic intervention in intestinal inflammatory disorders.