The Effect of Granulosa Cells Co-culture and Retinoic Acid on Maturation and Development of Immature Mouse Oocytes in Vitro

Purpose: The purpose of this study was to develop an appropriate medium for in vitro maturation (IVM) of immature mouse oocytes. Materials and Methods: Germinal vesicle of female NMRI mouse oocytes (6-8 weeks old) were collected from ovaries and cultured in maturation medium MEM-a, supplemented with: 100 mlIU/ml rFSH+7.5 IU/ml hCG+5% FCS (Control group) and 2mM all- trans retinoic acid (t-RA) in presence or absent of granulose cells. Ethanol (Sham group) 0.2% (v/v) used as solvent. After 24 hours the matured oocytes were fertilized with spermatozoa in T6 medium and cultured for 5 days. Cultured immature oocytes development to the morula and blastocyst stages was studied. Results: The retinoic acid supported progression and resumption of meiosis and also increased advancing the oocytes to Metaphase II, formation of morula and blastocyst compared to control group. When there were not 2mM t-RA and granulose cells in IVM medium, significantly lower maturation rates were observed, followed by a decrease in the percentage of embryos reaching the blastocyst stage. Whereas, when 2mM t- RA and granulose cells monolayer were present in the IVM medium, better results in comparison with control group were obtained. Conclusion: Results attest that co-culture of granulose cells with 2mM all-trance retinoic acid during in vitro maturation enhanced mouse oocytes maturation and improved embryonic development.