Whole-body exposure to cigarette smoke alters oocyte miRNAs expression in C57BL/6 mice

Cigarette smoke is toxic for the female reproductive system with particular reference to the ovary. The purpose of the study was to investigate if the microRNAs (miRNAs) pattern could be altered by cigarette smoke exposure in mouse oocytes. For this purpose, C57BL/6 mice were whole-body exposed to three cigarettes daily, 7 days/week, for 2 or 4 months by a specific rodent ventilator. Mice were then superovulated and oocytes collected. MII oocytes pools obtained by single animals were deprived of cumulus cells and used to extract total RNA including miRNAs. TaqMan (TM) Rodent MicroRNA A Array v2.0 was used to analyze the miRNAs expression profile. The biological functions and the functional networks of the identified up- and downregulated miRNAs were analyzed by ingenuity pathway analysis software. The gene expression of deregulated-miRNAs targets was evaluated. For the first time, the global miRNAs changes in mouse oocyte in response to cigarette smoke exposure were disclosed. Our results revealed significant modulation of miRNAs mainly involved in inflammatory processes, cellular proliferation, and apoptosis. miRNAs expression was altered in a time-dependent manner. Smoke exposure induced an early downregulation of Dicer1. Transcriptional alterations of the modulated miRNAs major targets, estrogen receptor 1, peroxisome proliferator-activated receptor-alpha, and tumor protein 53, as well as that of other key regulatory genes, were evidenced. Cigarette smoke represents a stimulus able to alter miRNAs pattern in mouse oocyte. This study increases our understanding of the ovarian toxicity profile of cigarette smoke, and open new roads toward the identification of biomarkers of oocyte toxicity and dysregulation.