Differential Expression of miR-223-3p and miR-26-5p According 2 to Different Stages of Mastitis in Dairy Cows

Mastitis is the leading cause of economic losses in dairy farming, significantly impairing 14 animal welfare and the quality and quantity of milk production. MicroRNAs are increasingly gain- 15 ing attention, in both human and veterinary medicine, as biomarkers for various diseases. This 16 study evaluated the diagnostic potential of four circulating microRNAs (miR-26-5p, miR-142-5p, 17 miR-146a, and miR-223-3p) by examining changes in their expression in milk samples from dairy 18 cows at different immune cells subpopulations correlated to different stage of mastitis in validated 19 method. Additionally, the study has analysed the possible source of these circulating microRNA by 20 the measurement of their secretion from activated immune cells (lymphocytes, monocytes, and neu- 21 trophils). miR-223-3p has been significantly expressed in acute stage of mastitis (p<0.01) but not in 22 the chronic or susceptible stages. Conversely, mir-26-5p has been significantly reduced in acute, 23 chronic and susceptible groups of animals. In immune cell cultures miR-26 has been shown to 24 downregulated in Lypopolysaccharide (LPS)-stimulated neutrophils while miR-223 has been 25 shown to be upregulated in Phytohaemagglutinin (PHA)-stimulated lymphocytes. The differential 26 expression of miR-223-3p and miR-26-5p, combined with differential and total somatic cell count, 27 could serve as a useful tool for identifying the evolutionary stage of mastitis-related inflammatory 28 pathology