Loss of Nonhematopoietic Osteopontin Weakens the Intestinal Barrier and Alters the Microbiome and Metabolome in Mice

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: 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.