Exosomes from dairy cows of divergent fertility; Action on endometrial cells.

Abnormalities in endometrial function contribute to poor fertility and reproductive failure. Exosomes are small lipid vesicles that contain transferable bioactive substances; they participate in intercellular signaling and may have critical roles in reproductive mechanisms, including endometrial remodeling in preparation for pregnancy. In this study, we evaluated the effects of exosomes from heifers with high and low genetic merit for fertility on inflammatory mediator expression by bovine endometrial epithelial and stromal cell lines. Co-incubation of exosomes from low, compared with high, fertility heifers upregulated the gene expression of pro-inflammatory IL1A and IL8 (CXCL8) but downregulated IL4 gene expression in epithelial cells. In contrast, stromal cells co-incubated with exosomes from low, compared with high, fertility heifers downregulated the gene expression of CXCL9, CXCL10, and CX3CL1. Our findings demonstrated that circulating exosomes from high fertility heifers did not alter endometrial inflammatory mediator gene expression. In contrast, circulating exosomes from low fertility heifers enhanced endometrial expression of inflammatory mediators, which may contribute to aberrant inflammation, leading to a reduced fertility in low fertility heifers. However, an in-depth investigation is required to elucidate the role of exosomes in regulating endometrial remodeling events required for enhanced reproductive performance and fertility in dairy cows.