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Disruptions in follicle cell functions in the ovaries of rhesus monkeys during summer.

ABSTRACT: Oocytes isolated from female rhesus monkeys following standard ovarian stimulation protocols during the summer months displayed a reduced capacity to mature compared with stimulation during the normal breeding season. Because the gene expression profiles of oocyte-associated cumulus cells and mural granulosa cells (CCs and GCs) are indicative of altered oocyte quality and can provide insight into intrafollicular processes that may be disrupted during oogenesis, we performed array-based transcriptome comparisons of CCs and GCs from summer and normal breeding season stimulation cycles. Summer CCs and GCs both display deficiencies in expression of mRNAs related to cell proliferation, angiogenesis, and endocrine signaling, as well as reduced expression of glycogen phosphorylase. Additionally, CCs display deficiencies in expression of mRNAs related to stress response. These results provide the first insight into the specific molecular pathways and processes that are disrupted in the follicles of rhesus macaque females during the summer season. Some of the changes seen in summer GCs and CCs have been reported in humans and in other model mammalian species. This suggests that the seasonal effects seen in the rhesus monkey may help us to understand better the mechanisms that contribute to reduced oocyte quality and fertility in humans.

SUBMITTER: VandeVoort CA

PROVIDER: S-EPMC4385968 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Women and other mammalian females are born with a finite supply of oocytes that determine their reproductive lifespan. During fetal development, individual oocytes are enclosed by a protective layer of granulosa cells to form primordial follicles that will grow, mature, and eventually release the oocyte for potential fertilization. Despite the knowledge that follicles are dysfunctional and will die without granulosa cell-oocyte interactions, the mechanisms by which these cells establish communication is unknown. We previously identified that two members of the Iroquois homeobox transcription factor gene family, Irx3 and Irx5, are expressed within developing ovaries but not testes. Deletion of both factors (Irx3-Irx5EGFP/Irx3-Irx5EGFP) disrupted granulosa cell-oocyte contact during early follicle development leading to oocyte death. Thus, we hypothesized that Irx3 and Irx5 are required to develop cell-cell communication networks to maintain follicle integrity and female fertility. A series of Irx3 and Irx5 mutant mouse models were generated to assess roles for each factor. While both Irx3 and Irx5 single mutant females were subfertile, their breeding outcomes and ovary histology indicated distinct causes. Careful analysis of Irx3- and Irx5-reporter mice linked the cause of this disparity to dynamic spatio-temporal changes in their expression patterns. Both factors marked the progenitor pre-granulosa cell population in fetal ovaries. At the critical phase of germline nest breakdown and primordial follicle formation however, Irx3 and Irx5 transitioned to oocyte- and granulosa cell-specific expression respectively. Further investigation into the cause of follicle death in Irx3-Irx5EGFP/Irx3-Irx5EGFP ovaries uncovered specific defects in both granulosa cells and oocytes. Granulosa cell defects included poor contributions to basement membrane deposition and mis-localization of gap junction proteins. Granulosa cells and oocytes both presented fewer cell projections resulting in compromised cell-cell communication. Altogether, we conclude that Irx3 and Irx5 first work together to define the pregranulosa cell population of germline nests. During primordial follicle formation, they transition to oocyte- and granulosa cell-specific expression patterns where they cooperate in neighboring cells to build the foundation for follicle integrity. This foundation is left as their legacy of the essential oocyte-granulosa cell communication network that ensures and ultimately optimizes the integrity of the ovarian reserve and therefore, the female reproductive lifespan.

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Disruptions in follicle cell functions in the ovaries of rhesus monkeys during summer.

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