The control of oocyte survival by intrinsic and extrinsic factors

Abstract

The duration that ovaries function is, as is intuitive, controlled by the number of remaining oocytes within follicles. Once the number of follicles drops beneath a threshold number, ovarian function ceases. Thus, understanding mechanisms that control oocyte survival is paramount as we consider strategies to protect or prolong ovarian function in women. It is often assumed that physiological oocyte survival is entirely controlled by "oocyte- intrinsic" factors, such as poor genetic quality or accumulated damage to the oocyte itself. Oocytes that have poor genetic quality due to development or accumulated damage would then die sooner than those of higher "quality." Indeed, new data suggest that oocyte-intrinsic genetic quality as determined by the ability to repair double-stranded DNA breaks is a signifi cant contributor to oocyte survival and the duration of ovarian function. However, the nature of the follicle, where the oocyte and surrounding granulosa cells exist in intimate contact and rely upon each other for survival signals and metabolic function, makes it unlikely that oocyte-intrinsic factors entirely control oocyte survival. We and others are assessing the role of adjacent somatic (granulosa) cells in follicle survival, determining the relative importance of "oocyte-extrinsic" factors. © Springer Science+Business Media New York 2013.