Cellular and molecular mechanisms of various types of oocyte aging

Abstract

It is well established that age-related decline of a woman's fertility is related to the poor developmental potential of her gametes. The age-associated decline in female fertility is largely attributable to the oocyte aging caused by ovarian aging. Age-associated oocyte aging results in a decrease in oocyte quality. In contrast to ovarian aging, there is a concept of postovulatory oocyte aging. Postovulatory aging of oocytes, not being fertilized for a prolonged time after ovulation, is known to significantly affect the development of oocytes. Both categories of oocyte aging have similar phenotypes of reproductive failure. However, the mechanisms of the decline in oocyte quality are not necessarily equivalent. An age-dependent increase in aneuploidy is a key determinant of oocyte quality. The reduced expression of molecules regulating cell cycle control during meiosis might be involved in the age-dependent increase in aneuploidy. The mechanism of age-associated oocyte aging might be involved in mitochondrial dysfunction, whose etiologies are still unknown. Alternatively, the mechanism of postovulatory oocyte aging might be involved in reactive oxygen species-induced mitochondrial injury pathways followed by abnormal intracellular Ca regulation of the endoplasmic reticulum. We suggest that future research into the mechanism of oocyte aging will be necessary to develop a method to rescue the poor developmental potential of aged oocytes.

Molecular mechanism of poor embryo development in postovulatory aged oocytes: Mini review

“…Postovulatory oocyte aging is classified into two types: in vivo ‐ and in vitro ‐postovulatory oocyte aging. If fertilization does not occur during the optimal period after ovulation, an unfertilized oocyte that remains in the oviduct ( in vivo ‐postovulatory oocyte aging) or in vitro culture ( in vitro ‐postovulatory oocyte aging) goes through a time‐dependent aging process . We and numerous other investigators have reported that in vivo‐ and in vitro ‐aged oocytes frequently show lower fertilization and blastocyst formation rates (Fig.…”

“…There are several problems associated with the study of oocyte aging with respect to ovarian aging: it takes more than 1 year to obtain experimental animals that are old enough, and there are only a few available oocytes. Moreover, there is no appropriate animal model analogous to the one that is used in ovarian aging studies …”

“…Moreover, there is no appropriate animal model analogous to the one that is used in ovarian aging studies. 6 In contrast to ovarian aging, there is a concept of postovulatory oocyte aging. In mammals, ovulated oocytes are arrested at the metaphase stage of the second meiotic division until fertilization.…”

Cellular and molecular changes associated with fish oocyte ageing

“…Takahashi et al . () reviewed two categories of oocyte ageing caused by ovarian ageing or post‐ovulatory ageing. The authors concluded that both categories of oocyte ageing have similar phenotypes of reproductive failure.…”

Inhibition of the NLRP3 inflammasome prevents ovarian aging

“…Female infertility is exacerbated by socioeconomic changes in developed countries, which enable women to progressively delay the age at which they have their first child. As a consequence, there is increased demand for the treatment of infertility (3).…”