Impact of preovulatory follicle maturity treatment during in vitro oocyte maturation on the transcriptome of resulting blastocysts.

Reproductive success is multi-faceted; however, the oocyte’s competency to develop into a quality embryo is necessary for pregnancy. Appropriate preparation of the oocyte to support early embryo development is heavily influenced by intercellular communication between the maturing oocyte and preovulatory follicle. Variations in preovulatory follicle maturity have been linked to profound differences in pregnancy success, follicular fluid metabolite milieu, cumulus-oocyte metabolism, and oocyte competency for embryo development. Such relationships indicate metabolic and developmental programming of the oocyte based on follicle maturity, but the impact of preovulatory follicle maturity on the molecular signature of resulting blastocysts has not been examined. We hypothesized that supplementing in vitro maturing oocytes with follicular fluid originating from preovulatory follicles of greater or lesser physiological maturity would impact the transcriptome of resulting blastocysts. The objective was to investigate the impact of follicle maturity on metabolic preparation of the oocyte by examining alterations in the functional genome of resulting blastocysts. In vitro maturing oocytes were supplemented with follicular fluid collected from preovulatory follicles categorized as greater or lesser follicle maturity based on estradiol production. In vitro fertilization and embryo culture were performed identically between treatments and RNA-sequencing was performed on pools of two blastocysts from each treatment (Greater, n = 12; Lesser, n = 15). One hundred thirteen transcripts differed in abundance between blastocysts of greater and lesser follicle maturity treatments. Differentially abundant transcripts indicated improved Wnt/β-catenin signaling, metabolism, and protection from oxidative stress in blastocysts resulting from oocytes matured in the presence of follicular fluid of preovulatory follicles of greater maturity. Alternatively, demonstration of unregulated cell growth presented in blastocysts from oocytes of the lesser follicle maturity treatment. Follicular fluid milieu from preovulatory follicles of greater physiological maturity may better prepare maturing oocytes for early embryo development. Oocytes matured in follicular fluid of lesser mature follicles appear to attempt to overcompensate for lack of nutrients during oocyte maturation, thus leading to uncontrolled cellular growth, poorer Wnt signaling, less efficient metabolism, and increased oxidative stress.