Oxidative Stress-Related Signaling Pathways Predict Oocytes' Fertilization In Vitro and Embryo Quality

Oocyte development and fertilization are largely influenced by the microenvironment of the follicular fluid (FF), and the exploration of its molecular/metabolic composition may help in improving in vitro fertilization (IVF) outcomes. Here, the concentrations of molecules related to oxidative stress/inflammation were measured in FF from follicles at oocyte retrieval during IVF. Here, the FF antioxidant potential was correlated with the number of retrieved/mature oocytes and the number of fertilized ones. FF collected from the follicles of normal fertilized oocytes presented an elevated antioxidant capability, lower levels of pro-inflammatory molecules (i.e., IL-6, IL-8, IL-12, TGF-beta, and HIF-1 alpha), and a higher IL-10 concentration. FF samples from follicles at oocyte retrieval that resulted in top-quality embryos displayed a peculiar antioxidant capability and a further decrease in proinflammatory molecules when compared with FF, giving rise to poor-quality embryos. Finally, pro-inflammatory molecules were lower and accompanied by a high antioxidant capability in samples giving rise to successful embryo implantation. The antioxidant capability and IL-10 displayed a good predictive ability for fertilization and embryo quality. Overall, our data showed the great influence of oxidative stress on the oocytes' fertilization, and shed light on the importance of controlling the inflammatory and oxidative status of FF to obtain good-quality embryos with significant implantation potential.

Automated summary

The molecular/metabolic composition of follicular fluid (FF) has a significant impact on oocyte development and fertilization. The antioxidant potential of FF is correlated with the number of retrieved/mature oocytes and fertilized ones. FF from normal fertilized oocytes exhibits elevated antioxidant capability, lower levels of pro-inflammatory molecules, and higher IL-10 concentration. Samples giving rise to top-quality embryos display a unique antioxidant capability and further decrease in pro-inflammatory molecules compared to FF from poor-quality embryos. Successful embryo implantation is associated with lower pro-inflammatory molecules and high antioxidant capability. Antioxidant capability and IL-10 show good predictive ability for fertilization and embryo quality.