Expression of lncRNA and mRNA in the cumulus-oocyte complex of rabbits exposed to ammonia
Background: Ammonia (NH3) is an environmental pollutant and a potent reproductive stressor widely found in rabbit houses. Exposure to ammonia can result in follicle atresia, affect oocyte maturation and cause cumulus cell apoptosis. Long non-coding RNA (lncRNA) is an important factor in the regulation of cumulus cell development and oocyte maturation. The potential molecular mechanism of NH3 in the induction of cumulus-oocyte complex (COCs) toxicity and the regulatory role of lncRNA in COCs are currently unclear. Methods: A total of 150 female IRA rabbits (35 days old) were randomly divided into three groups, and kept in environmental control rooms for four weeks. The rabbits in the control group (CG) were kept under an NH3 concentration of < 3 ppm. The two treatment groups were kept under NH3 concentrations of 10 ppm (low ammonia concentration, LAC) and 30 ppm (high ammonia concentration, HAC). We used a combination of RNA deep sequencing, quantitative real-time polymerase chain reaction (qRT-PCR), and bioinformatic analysis to explore the regulatory mechanism of lncRNA and messenger RNA (mRNA) in COCs. Results: The results from Gene Ontology (GO) items showed that female meiosis sister chromatid cohesion and the regulation of follicle-stimulating hormone secretion were involved in the mechanism of rabbits exposed to NH3. The results demonstrated that the mammalian target of the rapamycin (mTOR) signaling pathway and the transforming growth factor-beta (TGF-beta) signaling pathway inhibits germ cell development and follicular growth in the LAC versus the CG group. LncRNAs were involved in the apoptosis of female germ cells via the hypoxia-inducible factor (HIF-1) signaling pathway in the HAC versus the CG group. Co-expression analysis found that lncRNA MAPK3 and lncRNA SHC1 were correlated with changes in cumulus cell and oocyte function after NH3 exposure. Conclusions: These results indicate that NH3 affected the development and function of COCs by influencing lncRNA expression. Overall design: A total of 150 female IRA rabbits (35-days-old) were randomly divided into three groups, and were kept in environment control rooms for four weeks.  The rabbits in the control group (CG) were kept under NH3 concentration of < 3 ppm.  The two treatment groups were kept under NH3 concentration of 10 ppm (low ammonia concentration, LAC) and 30 ppm (high ammonia concentration, HAC).  Then we used a combination of RNA deep sequencing, quantitative real-time polymerase chain reaction (qRT-PCR), and bioinformatic analysis to explore the regulatory mechanism of lncRNA and messenger RNA (mRNA) in cumulus-oocyte complex.