Effect of methylparaben on the expression of genes involved in the in vitro maturation of porcine oocytes

Abstract

Background Parabens (PBs) are widely used due to their antimicrobial properties in drugs, cosmetics, and food; however, previous studies have reported that methylparaben (MePB) may adversely interfere with female reproduction. MePB decreases oocyte in vitro maturation (IVM) at a maturation inhibition concentration 50 (MIC50) of 780.31 µM but also their viability at a lethal concentration 50 (LC50) of 2028.38 µM. It was reported that PBs are endocrine disruptors (EDs), affecting steroidogenesis as well as the cumulus cells (CC) expansion. Therefore, the aim of this study was to elucidate some of the mechanisms by which MePB alters CC expansion and decreases oocyte maturation through the evaluation of gene expression, Has2 for CC expansion, and Stard1, Cyp11a1, Hsd3b1, and Pr, for progesterone (P4) synthesis. Also, CC expansion and P4 concentrations in culture media were evaluated. Methods Oocytes were exposed to different MePB concentrations of 0 (control), 650, 780 and 1000 µM during 20 and 44 h of IVM. After 44 h of IVM, CC expansion, and IVM rates were evaluated. Gene expression of Has2, Stard1, Cyp11a1, Hsd3b1, and Pr were evaluated by qPCR at 20 and 44 h. P4 concentrations in culture media were evaluated at 20 and 44 h of IVM. Results MePB decreased CC expansion and the IVM of porcine oocytes. The expression of genes involved in steroidogenesis and CC expansion were also altered by MePB, as well as P4 concentrations in culture media, suggesting its potential role as ED. Conclusions This study provides insights into the mechanisms underlying MePB influence on IVM of porcine oocytes. Maturation is an important event that provides the oocyte the capacity to be fertilized, so any alteration produced during this period can impair fertility. Porcine oocytes are P4-dependent and require the CC expansion to reach the metaphase II (MII) stage. At sublethal concentrations of MePB, subexpression of Has2 resulted in decreased CC expansion and IVM. Also, MePB altered the expression of the genes involved in the first step of steroidogenesis from cholesterol to P4, suggesting its role as ED. These findings could partially explain some of the mechanisms by which MePB alters female fertility.