Differential miRNAs analysis of colostrum and normal milk exosomes in Bamei and Landrace pigs

Breast milk is an indispensable source of nutrition for the growth and development of newborn mammals. The exosomes in breast milk have potential regulatory effects on the growth, development, and immunity of newborn piglets. We isolated two types of exosomes from porcine colostrum and normal milk by density gradient centrifugation and characterized them by transmission electron microscopy (TEM) and particle size analysis. Furthermore, the expression profiles of miRNAs in the two types of exosomes were investigated by miRNA-Seq and bioinformatics analysis. The sequencing results identified a total of 480 known miRNAs, 601 conservative miRNAs, and 2311 novel miRNAs in porcine milk exosomes from Bamei and Landrace pigs. The differential miRNA target genes were significantly enriched in the endocytosis, T-cell receptor signaling pathway and Th17 cell differentiation signaling pathways. Differentially expressed miRNAs (DE-miRNAs) were closely associated with processes such as cell signaling, cell physiology, and immune system development. Differential expression profiles of miRNAs in milk exosomes from different lactation stages in two breeds of pigs identified some immune-related miRNA-mRNA negative regulatory networks and KEGG pathways. Our findings provide a theoretical basis for further studies on the functions of miRNAs in milk exosomes.