Exposure of Bovine Granulosa Cells to Lipopolysaccharide Reduces Progesterone Secretion During Luteinization.

Abstract

Uterine disease reduces fertility in dairy cows and is caused by pathogenic bacteria. During disease, lipopolysaccharide (LPS) accumulates in follicular fluid and triggers granulosa cell inflammation via the Toll-like receptor 4 pathway. Follicle growth and plasma estradiol are reduced in cows with uterine disease, and treatment of bovine granulosa cells with LPS reduces CYP19A1 expression and estradiol synthesis. It is unclear if the effects of LPS on the steroidogenic capacity of granulosa cells persist in cells during luteinization. We hypothesized that acute exposure of granulosa cells to LPS would alter progesterone synthesis during luteinization. Here, we demonstrate that acute exposure of granulosa cells to LPS reduces progesterone synthesis during a 9-day period of luteinization after LPS treatment. We show that exposure of granulosa cells to LPS does not alter the gene expression of STAR, HSD3B1 or CYP11A1, or cellular respiration during luteinization. However, acute exposure of granulosa cells to LPS reduces the abundance of intracellular lipid, mitochondria density and cholesterol uptake during luteinization, suggesting a potential mechanism of altered steroidogenesis after acute inflammation. Collectively, these findings show that exposure of granulosa cells to LPS reduces progesterone synthesis during luteinization which is associated with altered lipid droplets and mitochondria accumulation required for steroidogenesis. Perturbations to granulosa cell physiology during uterine disease may have prolonged effects on ovarian function that contribute to reduced fertility of cows. Understanding the effects of uterine disease on corpus luteum function after disease resolution can help explain disease associated subfertility in cattle.