Meeting Abstract
In mammals, the discourse over the existence and functionality of oocyte-stem cells (OSCs) within the postnatal ovary is well into its second decade, with the vast majority of studies on both sides of the debate limited to few species exhibiting variant reproductive strategies. Owing to their exceptionally long reproductive lifespan relative to body size, we hypothesized that the naked mole rat (NMR, Heterocephalus glaber) might maintain continuous renewal of oocytes through OSCs. Our initial investigations have provided some support for this hypothesis. We found a substantial number of germ cells within postnatal NMR ovaries that were immuno-reactive for the pluripotency markers OCT4 and SOX2. In addition, germ cells marked by DDX4 (VASA) demonstrated evidence for recent mitotic activity, either by their co-labeling with phospho-histone H3 or by incorporation of the thymidine analog EdU. Chromosome spreads from NMR ovaries at postnatal day 28 (P28) revealed oocytes in all stages of prophase I, which coexist with cells that expressed markers of pluripotency. In contrast to mice, for which follicle formation is complete by P5, the breakdown of germ cell cysts and formation of primordial follicles are markedly delayed in NMRs. Whereas the ovarian reserve of follicles is nearly exhausted by a year of age in mice, we have observed an abundance of primordial follicles in the ovaries of a 10-year-old NMR. Ongoing research will determine how the NMR establishes its unusually large ovarian reserve and maintains it over an exceptionally long reproductive lifespan, including experiments to test whether OSCs in the postnatal ovary contribute to the NMR’s protracted fertility.
