Expression of factor-1 in the mouse cumulus-oocyte complex is negatively related with oocyte maturation

Objective: We found previously that $interferon$ $regulatory$ factor ($Irf$)-1 is a germinal vesicle (GV)-selective gene that highly expressed in GV as compared to metaphase II oocytes. To our knowledge, the function of $Irf-1$ in oocytes has yet to be examined. The present study was conducted to determine the relationship between retinoic acid (RA) and RA-mediated expression of $Irf-1$ and the mouse oocyte maturation. Methods: Immature cumulus-oocyte-complexes (COCs) were collected from 17-day-old female mice and cultured $in$ $vitro$ for 16 hours in the presence of varying concentrations of RA (0-10 ${\mu}M$). Rate of oocyte maturation and activation was measured. Gene expression was measured by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) and cytokine secretion in the medium was measured by Bio-Plex analysis. Apoptosis was analyzed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Results: The rates of oocyte maturation to metaphase II and oocyte activation increased significantly with RA treatment (10 nM-1 ${\mu}M$). With 100 nM RA treatment, lowest level of $Irf-1$ mRNA and cumulus cell's apoptosis was found. Among 23 cytokines measured by Bio-Plex system, the substantial changes in secretion of tumor necrosis factor-${\alpha}$, macrophage inflammatory protein-$1{\beta}$, eotaxin and interleukin-12 (p40) from COCs in response to RA were detected. Conclusion: We concluded that the maturation of oocytes and $Irf-1$ expression are negatively correlated, and RA enhances the developmental competence of mouse immature oocytes $in$ $vitro$ by suppressing apoptosis of cumulus cells. Using a mouse model, results of the present study provide insights into improved culture conditions for $in$ $vitro$ oocyte maturation and relevant cytokine production and secretion in assisted reproductive technology.