Lipopolysaccharide reduces progesterone and cytokines in equine follicular fluid without affecting oocyte development in vitro

Lipopolysaccharide (LPS) in follicular fluid impairs steroid production and oocyte developmental competence in cows and mice. This study assessed LPS concentrations in equine follicular fluid and their association with steroid and some cytokine levels. Additionally, we evaluated whether LPS exposure during in vitro maturation (IVM) affects equine oocyte developmental competence. In experiment 1, follicular fluid from large follicles (>30 mm in diameter) was collected from 16 slaughterhouse mares, and concentrations of LPS, estradiol, progesterone, TNF-α, and IL-6 were measured. In experiment 2, cumulus-oocyte complexes (COCs) were held overnight, then matured in vitro with (1 ng LPS/1 mL; LPS group) or without LPS (control group), and mature oocytes (n = 47 and 45, respectively) were fertilized using ICSI. Follicular fluid concentrations of LPS ranged between 5.21 and 12.08 endotoxin unit (EU)/mL (10 EU = 1 ng) and were negatively correlated with progesterone, IL-6, and TNF-α levels. Compared to controls, LPS exposure during IVM did not significantly affect maturation (56 % vs. 61 %; P = 0.432), cleavage (71 % vs. 65 %; P = 0.873), or blastocyst rates (21 % vs. 19 %; P = 0.227). In conclusion, this is the first report detecting LPS in the follicular fluid of clinically healthy mares and showing its negative association with progesterone, IL-6, and TNF-α. Exposing equine COCs to 1 ng/mL LPS during in vitro maturation had no significant effect on blastocyst rates. However, further research is needed to determine whether blastocysts derived from oocytes matured under LPS exposure can establish pregnancy after transfer.