In recent years, exciting progress was made to improve the embryo outcome after ovarian stimulation in domestic animals. The practice of follicle-stimulating hormone (FSH) withdrawal, which is defined as the period of time between the last injection of FSH and oocyte retrieval, resulted in embryo yields significantly superior. Since then, specific changes in the transcriptome of granulosa cells were associated with the increase and also the decline in oocyte developmental competence following the FSH decline. In this study, we integrated large datasets from a public depository using a meta-analysis in order to elucidate the molecular changes occurring in granulosa cells following FSH decline in association with oocyte developmental competence. The meta-analysis revealed that the gene expression patterns observed during this period resulted from the downregulation of proliferative signals, and the upregulation of differentiation signals and early apoptotic signals. Additionally, FSH decline induced cellular hypoxia and triggered the expression of proinflammatory molecules which resulted in early atresia and mimicked the luteinizing hormone (LH) surge signaling to ovulation. To characterize this unique differentiation period, we suggest using the term “follicle capacitation” to refer to the functional changes occurring within the follicle in order to prepare the molecular machinery for the LH surge and ovulation following FSH decline. During this period, the follicle confers the oocyte with developmental competence to become a viable embryo. However, if this period is not rapidly followed by an LH surge, apoptosis signals are increased to generate follicular atresia and decrease oocyte quality.

Summary Sentence

Follicle capacitation occurs following FSH decline or withdrawal in order to prepare the molecular machinery for the LH surge and confer the oocyte with developmental competence.