Eggmodning

Eggmodning is the biological process by which immature oocytes mature into fertilization-ready eggs. The term refers to the developmental steps that prepare an egg for meiosis completion and potential fertilization. It is a central concept in reproductive biology and is studied across vertebrates, with particular focus on human oocyte maturation for natural and assisted conception.

In female mammals, oocyte development begins before birth when primordial germ cells form oogonia that enter meiosis and arrest as primary oocytes in prophase I. At puberty, cyclic follicular growth is driven by follicle-stimulating hormone (FSH). The oocyte resumes meiosis, completing meiosis I to form a secondary oocyte and the first polar body, then arrests again at metaphase II until fertilization. Ovulation releases the mature oocyte surrounded by cumulus cells; meiosis II is completed only after sperm entry.

Regulation of eggmodning involves a network of signals. The maturation-promoting factor (MPF, a complex of Cyclin B and Cdc2) drives meiotic progression. Growth factors produced by surrounding granulosa cells, such as GDF9 and BMP15, support oocyte development and cumulus expansion. Hormonal cues, particularly the luteinizing hormone (LH) surge, coordinate ovulation and resumption of meiosis, while gap junction communication provides metabolic support from follicular cells.

Clinical and research relevance is significant. In vitro maturation (IVM) allows immature oocytes to reach a mature state outside the body, offering options for certain infertility cases. Oocyte cryopreservation preserves eggs before maturation or during a resting stage, aiding fertility preservation. Age-related decline in egg quality raises aneuploidy risk and affects outcomes of assisted reproduction.

Cross-species differences exist, but the core aim of eggmodning remains to render an oocyte competent for fertilization and development.