Profile of circular RNAs in bovine mammary tissues infected with Staphylococcus aureus.

Mastitis is one of the most common diseases in cattle. The causes are complex, and the disease tends to recur and its difficult to cure, resulting in significant economic losses to the global dairy industry each year. Circular RNAs (circRNAs), a class of endogenous non-coding RNAs (ncRNAs), have recently been recognized as key regulators in inflammatory diseases. However, little is known about the roles of circRNAs in mastitis caused by Staphylococcus aureus (S. aureus) infection. In this study, bovine mammary gland tissue was treated with S. aureus (105 CFU/ml, M_S) and PBS (control, M_C) and RNA-sequencing was used to explore the effect of S. aureus on circRNA expression in the tissue. The results showed that compared with the M_C group, 202 differentially expressed circRNAs (DE circRNAs) were identified in the M_S group, including 105 up-regulated and 97 down-regulated circRNAs. Gene Ontology (GO) analysis showed that most of the DE circRNAs were enriched in categories such as transcription by RNA polymerase II, transcription factor complexes, and oxidoreductase activity, while Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed significant enrichment in pathways involved in thyroid hormone, FoxO, and cell cycle functions. Seven circRNAs associated with bovine mastitis were also identified (novel_circ_0016953, novel_circ_0001266, novel_circ_0015099, novel_circ_0008169, novel_circ_0001807, novel_circ_0016220, and novel_circ_0009731). The results of this study lay a theoretical foundation for further investigation into the mechanism underlying bovine mastitis and provide valuable references for subsequent research on bovine mastitis.