Mammalian neo-oogenesis and expression of meiosis-specific protein SCP3 in adult human and monkey ovaries

The concept of neo-oogenesis and follicular renewal during adulthood in mammalian females, including humans, is a novel concept with major significance for ovarian physiology and mammalian reproductive biology. Previous observations from our laboratory demonstrated that mesenchymal cells in the tunica albuginea are bipotent progenitors for both granulosa and germ cells in adult human ovaries. In the present studies, we demonstrate that the antibodies against meiotic entry synaptonemal complex protein 3 (SCP3)-a marker for meiosis, showed reactivity with segments of tunica albuginea and ovarian surface epithelium, and in oocytes of some primordial follicles in functional human and monkey ovaries. These observations suggest that SCP3 is expressed in adult human and monkey ovaries. Preparation for meiotic activity may have already occurred at the level of tunica albuginea stem cells, and meiotic prophase activity may continue and terminate in oocytes of newly formed primordial follicles.