Lipopolysaccharide Impairs The In Vitro Growth, Steroidogenesis, and Maturation of Oocyte-Cumulus-Granulosa Cell Complexes Derived from Bovine Early Antral Follicles

Abstract

In postpartum dairy cows, lipopolysaccharide (LPS) derived from gram-negative bacteria causes uterine or mammary inflammation, resulting in low fertility. The present study aimed to investigate the effect of LPS on the in vitro growth (IVG), steroidogenesis, and maturation of oocyte-cumulus-granulosa cell complexes (OCGCs) derived from bovine early antral follicles. OCGCs were isolated from bovine early antral follicles (0.5 to 1 mm in diameter) and cultured in vitro for 12 days using media containing 0 (control), 0.01, or 1 µg/mL of LPS. The viability and antrum formation of OCGCs, oocyte diameter, and estradiol (E2) and progesterone (P4) concentrations in the media were determined. After IVG culture, oocytes collected from viable OCGCs were matured in vitro (IVM) in a medium without LPS. The nuclear maturation rate and the mitochondrial membrane potential of oocytes were determined. The viability and antrum formation of OCGCs were lower in the 0.01 and 1 µg/mL LPS groups than in the control group. No significant difference in oocyte diameter was observed between the treatment groups throughout the culture period. Moreover, E2 production from Days 4 to 8 was suppressed in the 0.01 and 1 µg/mL LPS groups, whereas P4 production from Days 0 to 8 increased in the 1 µg/mL LPS group. The nuclear maturation rate after IVM was lower in the 0.01 and 1 µg/mL LPS groups than in the control group. The mitochondrial membrane potential of post-IVM oocytes was lower in the 0.01 and 1 µg/mL LPS group than in the control group. Taken together, these results indicate that LPS inhibited the growth and steroidogenesis of OCGCs and impaired the nuclear and cytoplasmic maturation of oocytes derived from early antral follicles. This study suggests that the detrimental effects of LPS on developing oocytes may contribute to the long-term decreased fertility in postpartum dairy cows.

Keywords: dairy cows, LPS, OCGCs, maturation, steroidogenesis