Transcriptomic Analysis of Cumulus and Granulosa Cells as a Marker of Embryo Viability

Abstract

As well as contributing the female genetic component to the developing embryo, oocytes also provide a store of mRNAs, proteins and other resources needed to sustain the embryo through the first few mitoses, until activation of its own genome takes place at the 4–8 cell stage. The build up of essential molecules in the oocyte is dependent not only on the oocyte itself but also on other cells within the ovary. Maturing oocytes are enclosed in follicles and are surrounded by multiple layers of somatic cells. These cells protect and support the oocyte and participate in events that regulate its nuclear and cytoplasmic maturation and subsequent ovulation. The cells associated with the oocyte can be divided into two groups, the mural granulosa cells (GCs) which line the wall of the follicle, and the cumulus cells (CCs). The CCs are differentiated GCs that enclose the oocyte, creating what is known as the cumulus-oocyte-complex (COC). The CCs and oocyte have a particularly intimate association, establishing a bi-directional communication involving, but not limited to, exchange of proteins and metabolites through gap junctions that link the two types of cells (Hum Reprod 22:3069–3077, 2007). These connections allow the CCs to fulfil vital roles in the support and resourcing of the maturing oocyte.