Novel follicular fluid factors influencing oocyte developmental potential in IVF: a review

The aim of IVF centres today is to obtain high quality, developmentally competent embryos, and thus increase live birth rates. Apoptosis in the patient's follicles is among the factors that will determine IVF outcome. Follicular fluid constitutes an important microenvironment, containing apoptotic factors and others, which influence oocyte growth. The sFas–sFas ligand system is present in the follicular fluid and may play a role in preventing oocyte atresia during folliculogenesis. Levels of the anti-apoptotic molecule sFas may be related positively to oocyte maturation and negatively to fertilization and embryo quality. Reactive oxygen species exert a toxic effect when found in high concentrations in the follicular fluid, whereas in low concentrations they might be indispensable for pregnancy and therefore serve as a potential marker for successful IVF outcome. Nitric oxide plays a dual role; in some cells promoting and in others inhibiting apoptosis. Nitric oxide production is stimulated by TNF-α, so the latter is also implicated in the apoptotic process. Hyaluronan, a disaccharide, whose functions have not been fully elucidated, is a valuable predictor of oocyte fertilization. Gelatinases are responsible for remodelling during follicular atresia. In conclusion, a number of factors found in the follicular fluid, some involved in apoptosis, can influence assisted reproduction.