Unifying theory of adult resting follicle recruitment and fetal oocyte arrest

Abstract

One of the biggest mysteries of ovarian physiology is what controls the emergence of adult primordial follicles from the resting stage, and their steady depletion over the woman's lifetime. A related mystery is why do early oogonia begin meiosis in the fetus and then suddenly arrest for most of fetal and adult life. If fetal oocyte arrest did not occur after meiotic activation, there would be no oocytes left in the female baby by the time she is born. Similarly, without a steady controlled release in the adult ovary of resting follicles, the adult woman would run out of her eggs prematurely and have an early menopause. Could there be a similarity between what causes fetal oocyte arrest and what causes adult oocyte recruitment? The answer begins with the observation of a sudden massive recruitment of primordial follicles after human ovarian transplantation, and the embryologic discoveries about oocyte activation and the time of differentiation of cortex and medulla. The unifying theory is that ovarian cortical tissue pressure controls both fetal oocyte arrest and adult oocyte recruitment.