Engineered Exosomes Delivering bta-miR-223 Alleviate Staphylococcus aureus-Induced Mastitis in Mice via the TLR4/NF-κB Signaling Pathway

Bovine mastitis is an inflammatory disease of the mammary gland, frequently associated with infection by Staphylococcus aureus. Effective delivery of the antiinflammatory microRNA bta-miR-223 remains a challenge. In this study, we constructed engineered exosomes loaded with bta-miR-223 and demonstrated their antiinflammatory effects both in vitro (Mac-T cells) and in vivo (mice). Overexpression of bta-miR-223 reduced the expression of IL-6 and IL-1β in a lipoteichoic acid-induced Mac-T cell inflammation model. Following tail vein injection in lactating mice, the engineered exosomes accumulated in the mammary gland, alleviated S. aureus-induced inflammation, and increased the expression of barrier-related proteins ZO-1, claudin-1, and occludin. Mechanistically, bta-miR-223 inhibited RHOB expression and modulated the TLR4/NF-κB pathway. These results demonstrate that exosome-mediated delivery of bta-miR-223 effectively alleviates mammary inflammation, providing a novel strategy for nucleic acid nanotherapy.