Abstract
BACKGROUND AND AIMS: Inflammatory bowel disease (IBD) is characterized by intestinal barrier disruption and dysregulated interactions between host immunity and gut microbiota. Osteopontin (OPN) is considered a proinflammatory mediator in IBD, but nonhematopoietic cell-derived OPN may exert barrier-protective functions. This study aimed to determine the effects of OPN in a murine model of acute colitis. METHODS: We examined wild-type and OPN knockout mice under steady-state conditions and in dextran sulfate sodium-induced colitis, including bone marrow chimeras to distinguish the effects of hematopoietic and nonhematopoietic OPN. RESULTS: Overt colitis did not occur under steady-state conditions. Compared with wild-type mice, OPN knockout mice exhibited crypt elongation, goblet cell hyperplasia, and increased epithelial proliferation. Gene expression analysis revealed reduced interleukin (IL)-22, IL-23, and IL-13 levels alongside increased interferon-γ, IL-1β, and IL-17A levels. 16S rRNA sequencing revealed increased alpha diversity, expansion of Akkermansia and Prevotellaceae, and reduced Lactobacillus abundance. Functional prediction identified enrichment of microbial sulfur metabolism pathways, and metabolomic analysis demonstrated increased L-proline and L-(-)-fucose levels and reduced β-sitosterol levels. These shifts indicate enhanced mucinolytic activity and altered energy metabolism, consistent with a latent "preinflammatory state." Bone marrow chimera experiments demonstrated that OPN deficiency in the recipients reproduced changes in the microbiota composition and lipocalin-2 expression at the steady state and conferred heightened susceptibility to dextran sulfate sodium-induced acute colitis, irrespective of donor genotype. CONCLUSION: These findings indicate that nonhematopoietic cell-derived "guardian-type" OPN preserves barrier integrity, sustains IL-22/IL-23 production, and maintains microbiota-metabolome balance, whereas its loss induces a preinflammatory state that predisposes to acute mucosal injury. These findings provide a conceptual basis for stage- and source-specific therapeutic strategies in IBD.