Effects of colloidal silicon dioxide on intestinal barrier and mucosal immunity in childhood mice

This study aimed to investigate the effects of colloidal silica nanoparticles Aerosil 200 (A200) on intestinal barrier and mucosal immunity in childhood mice. Three-week-old BALB/c mice were administered A200 (20, 50, 200 mg·kg^-1) via gavage for 7 days. Intestinal morphology, barrier function, immune cell phenotypes, and oral tolerance were systematically evaluated. Histopathological analysis of intestinal morphology revealed that no obvious pathological damage in the intestine. However, 200 mg·kg^-1 A200 increased ileal villus length, reduced crypt depth. Functional assessments of the intestinal barrier demonstrated that 200 mg·kg^-1 A200 upregulated ZO-1 in the ileum but downregulated it in the colon; The intestinal stem cell marker Lgr5 remained unchanged, while Mucin-2 increased and lysozyme decreased in the ileum. Analysis of immune cell phenotypes revealed that the 200 mg·kg^-1 group exhibited elevated proportions of Treg and Th2 cells in the mesenteric lymph nodes, while serum and intestinal levels of TNF-α and IL-6 remained unaffected. Oral tolerance assays revealed no alteration in OVA-specific IgG, IgG1, or IgG2a antibody levels. Animal welfare and the animal experimental protocols were strictly consistent with related ethics regulations of Peking University Health Science Center (Approval No.: BCJB0076). In conclusion, A200 is generally safe for childhood mice but may modulate epithelial barrier proteins and immune cell phenotypes at high doses, which may provide insights into its pediatric application.