Molecular mechanisms of oocyte maturation: the role of luteinizing hormone in meiosis regulation

In this review paper, the molecular mechanisms of mammalian oocyte meiotic maturation are considered in detail, with an emphasis on the role of luteinizing hormone and its interaction with signaling pathways regulating cyclic nucleotide levels (cAMP and cGMP). A structured analysis of the key stages of folliculogenesis, the mechanism of meiotic blocking and its removal, as well as the molecular components involved in regulating the permeability of gap junctions between somatic cells and the oocyte is presented. The contribution of various phosphodiesterases, receptors, and peptide mediators to initiation of meiosis is discussed. Special attention is paid to the dual role of the luteinizing hormone: as a trigger for a cascade of intracellular changes in granulosa and cumulus cells, and as an indirect initiator of meiosis resumption in the oocyte. The latest achievements in the field of visualizing and monitoring intracellular signaling events using FRET-sensors and molecular markers are considered. The review differs from previously published similar papers in that it does not limit itself to describing individual signaling components, but builds a holistic model of meiosis regulation, including both classical and recently discovered molecules. Besides, the work examines promising directions of modulating these processes within the framework of assisted reproductive technologies, suggesting potential targets for improving oocytic competence and the success of in vitro fertilization programs.