Neo-oogenesis: Has its existence been proven?

It was long believed that mammals are born with a fixed number of primordial follicles, each of which encloses an oocyte arrested at the diplotene step of meiotic prophase. Arising at or after birth, small numbers of primordial follicles become activated each day and enter a folliculogenic growth phase during which follicles either degenerate by atresia or complete maturation, resulting in ovulation (1-7). The reserve of follicles is claimed to continue depletion by the process of atresia throughout adulthood to the point of exhaustion around menopausal age, driving ovarian failure (8, 9). Recently, the work of Johnson et al challenged the half century old dogma that the primordial follicle pool cannot be replenished after birth (10). Since then, the concept of neo-oogenesis has been a subject of vigorous experimentation and debate. Existing and challenging developments in female reproductive biology have led to a growing body of evidence that the ovarian follicle pool may be replenished during adult life.