The surge in luteinizing hormone (LH) in preovulatory ovarian follicles triggers the resumption of oocyte meiosis accompanied by expansion of surrounding cumulus cells and ovulation of cumulus-oocyte complexes (COCs) into the oviduct. Over the last 15 years, substantial progress has been made in elucidating the key pathways by which the LH signal spreads within the preovulatory follicle and in identifying the molecules responsible for maintaining oocyte arrest and meiosis resumption. It is now clear that the adenylcyclase-mediated rise in intracellular cyclic adenosine monophosphate leads to activation of the epidermal growth factor receptor (EGFR) network in granulosa and cumulus cells. This signaling network can control the transcription of key genes required for cell metabolism, cumulus expansion, and oocyte meiosis resumption. In addition, EGFR signaling is involved in the regulation of gap junctional communication within follicular somatic cells, and in this way it can control the diffusion of meiosis-arresting molecules as well as energy substrates into the oocyte. Thus, the proper functioning of the follicular EGFR network is a vital precondition for the production of matured and developmentally competent oocytes. However, most current in vitro maturation systems are based on a culture of COCs isolated from growing follicles, in which function of the EGFR network may be insufficient for promoting oocyte meiotic and developmental competence. This review focuses on research identifying the importance of the EGFR signaling in somatic follicular cells for oocyte meiotic and developmental competence, and on special approaches to the culture of COCs isolated from growing follicles to promote oocyte quality.

Laboratory of Developmental Biology Institute of Animal Physiology and Genetics Czech Academy of Sciences Rumburska 89 277 21 Libechov Czech Republic

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Meiotic and developmental competence of growing pig oocytes derived from small antral follicles is enhanced in culture medium containing FGF2, LIF, and IGF1 (FLI medium)

The Role of MAPK3/1 and AKT in the Acquisition of High Meiotic and Developmental Competence of Porcine Oocytes Cultured In Vitro in FLI Medium