Gene expression in cumulus cells and oocyte quality

Infertility is a worldwide growing issue, and female factors account for about 30 % of the total cases of infertility. The majority of couples affected by infertility undergo in vitro fertilization (IVF) protocols following women hormonal hyperstimulation cycles to obtain mature oocytes to fertilize in vitro. Nowadays, the oocyte/embryo quality is mainly assessed by morphokinetic parameters even if these approaches have low objective prediction value. The rate of live newborns after IVF is relatively low, ranging from about 30 % in younger women to 10 % in the older ones. Aging, in fact, is a well-known critical factor for the success of IVF protocols. As a consequence, a primary goal in older women is to increase the pregnancy rate, with a crucial point represented by the selection of the oocytes to fertilize in vitro and transfer in women. In this view, transcriptomic information about granulosa cells (GCs) might shed light on the oocyte viability, thereby providing a non-invasive method of oocyte/embryo selection. The nutritional support and trafficking of macromolecules that this system allows may be particularly important for oocytes due to the avascular nature of the granulose layer. The signaling between GCs and oocyte via cytoplasmic processes penetrating the zona pellucid and forming gap junctions at the oocyte surface is a key means of disseminating local and endocrine signals to the oocyte. In fact, GCs functionality is a key determinant of the oocyte quality and competence, since GCs are the somatic cells strictly connected to the growing oocyte by a bidirectional communication ensuring the environment for its correct development. It is clear that the role of the oocyte extends far beyond its functions in the transmission of genetic information and supply of raw materials to the early embryo. It also has a critical part to play in mammalian follicular control and the regulation of oogenesis, ovulation rate, and fecundity. This chapter is aimed to explore the GCs gene activity in physiological and pathological conditions.