Milk-derived small extracellular vesicles promote intestinal epithelial and immune development in suckling mice

Milk-derived small extracellular vesicles (M-sEVs) represent a key bioactive component of breast milk, demonstrating multifaceted benefits for intestinal health, including preservation of intestinal barrier integrity, modulation of gut microbiota composition, immunoregulatory functions, and amelioration of colitis. However, their regulatory roles in early-life intestinal and immune development remain incompletely elucidated. Here, M-sEVs derived from human breast milk significantly enhanced body weight, body length, and small intestinal length in suckling mice. Further analysis revealed that M-sEVs potently stimulated intestinal epithelial regenerative capacity and increased the population of secretory lineage epithelial cells (including goblet cells, Paneth cells, and enteroendocrine cells). In addition, M-sEVs administration regulated immune programming in the intestinal lamina propria, enhanced the differentiation of IgA⁺ plasma cells, upregulated the proportions of CD4⁺ and CD8⁺ T cells, and exerted regulatory effects on overall immune development. Finally, we identified that M-sEVs upregulated genes and pathways associated with immune regulation, proliferation and differentiation, as well as digestion and absorption, thereby playing a pivotal role in intestinal maturation during infancy. Overall, this study provides novel insights into the potential role of M-sEVs in modulating intestinal epithelial and immune development during infancy, thereby establishing a scientific foundation for developing early-life nutritional intervention strategies.