Description
Female germ cells, oocytes, are localised in the ovaries and form ovarian reserve of the individual. Their development comprises primordial germ cells specification, migration to gonadal ridge, rounds of mitotic divisions and germ cell nests formation, in which germ cells stop dividing, exit pluripotency and enter meiosis while nests are broken apart into individual early oocytes. It was assumed that all oocytes are created only during embryonic development as a finite pool. However, it was found out that in a naked mole-rat (Heterocephalus glaber), germ cell development is delayed and occurs postnatally. Moreover, ovaries of adult naked mole-rat comprise germ cell nests, as well as mitotically dividing primordial germ cells, suggesting that adult de novo oogenesis may take place in this species, replenishing ovarian reserve and thus contributing to the long reproductive span.
We studied ovarian reserve of naked mole-rat and other rodents from Hystricognathi and Myomorpha lineages, with a focus on whether germ cell nests and dividing primordial germ cells occur in other species, and whether the ovarian reserve is eventually depleted in aged African mole-rats, despite potential replenishment. Using histology staining and imaging, we observed formations resembling germ cell nests in a blind mole rat (Nannospalax galili), a long-lived Myomorpha rodent, and we demonstrated that ovarian reserve substantially depletes in aged African mole-rats. For further research we will obtain more individuals of the same species in different age categories for a more precise comparison and characterization.
