Determinants of oocytes reserve and depletion

Farook Al-Azzawi (GB)

[Al-Azzawi] University Hospitals of Leicester, Leicester

Early menopause before the age of 45 affects about 10% of women and about 1% would have reached the menopause before the age of 40 (Primary Ovarian Insufficiency –POI). The journey of primordial germ cells from the epiblasts layer to the genital ridge and associated mitotic divisions are controlled by a number of orderly expressed genes. In the absence of Y chromosome, a specific set of gene expression together with the encapsulation by somatic cells signal the commitment of primordial germ cells to meiosis and the primordial follicles are formed. These follicles consist of an oocyte arrested in the diplotene stage of meiotic prophase I encased by a layer of somatic pregranulosa cells. This pool of non-growing primordial follicles (NGF) while remains quiescence, sustains a continuous process of apoptosis and follicular atresia in utero, during childhood and adult life until the reserve reaches a nadir that becomes unresponsive to recruitment and growth signals. It is the dynamics of conserving the NGF pool that determines the time of the menopause. In this presentation, regulatory factors that maintain the dormancy and integrity of NGFs are discussed. Also discussed; the potential role of ovarian germ stem cells in the reconstruction of the oocytes pool immediately post-natally and beyond.