Inflammation during oocyte maturation reduces developmental competence and increases apoptosis in blastocysts.

Abstract

Uterine infections cause ovarian dysfunction and infertility. The bacterial endotoxin, lipopolysaccharide (LPS), accumulates in the follicular fluid of dominant follicles of cows with uterine infections. Granulosa cells produce an innate inflammatory response to LPS, altering the follicular microenvironment of the oocyte. We hypothesized that developmental competence and embryo quality would be reduced when oocytes are matured in an inflammatory environment. Bovine mural granulosa cells were exposed to either 1 μg/mL of LPS or medium alone for 24 h to produce conditioned medium. Inflammatory responses of mural granulosa cells were confirmed by increased expression of CXCL8, IL1B, IL6 and TNF. Bovine cumulus-oocyte complexes were matured for 22 ± 1 h in medium supplemented with either 1 μg/mL of LPS, 10% v/v conditioned medium of granulosa cells treated with either LPS (LCM) or medium alone (CCM), or no supplementation (CON). In addition, polymyxin B (20 μg/mL) was added to maturation medium to sequester LPS. Following maturation, cumulus-oocyte complexes were fertilized and cultured for 7.5 days with no further treatment. Oocyte maturation using LPS or LCM impaired development to the blastocysts stage, reduced the number of total and CDX2 negative blastomeres and increased TUNEL positive cells in blastocysts. Polymyxin B could rescue these effects in the LPS group but not in the LCM group, indicating factors produced by granulosa cells and not LPS alone compromised oocyte development. These findings suggest that the inflammatory milieu produced by granulosa cells in response to LPS impairs oocyte competence and quality of resultant blastocyst-stage embryos.