The Effect of Preincubation Time on Oocyte Qual-ity and Fertilization Potential of Mouse MII Oocytes in The Simple and Myo-Inositol Supplemented Media

Background: It is demonstrated that non–optimal preincuba-tion time in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles can lead to reduction in the oocyte qual-ity, regarding to oxidative stress condition and mitochondrial alteration, and consequently can decrease the oocyte fertili-zation potential. Nevertheless, there is not any explanation of standard preincubation time in ART guidelines. Myo-inositole, as an antioxidant, exists naturally in the follicular fluid and is a marker of good quality in the oocytes. This study evaluated the oxidative stress condition, mitochondrial alterations and ferti-lization potential in mouse MII oocytes following 0, 4 and 8 hours preincubation time in the simple and myo-inositol sup-plemented media.Materials and Methods: Cumulus Oocyte Complexes (COCs) which were retrieved from 6-8 weeks-old superovulated female NMRI mice were pooled and divided randomly in five experi-mental groups: (1) control, (2) 4 hours preincubation in simple medium, (3) 4 hours preincubation in 20 mmol/l of myo-inosi-tol supplemented medium, (4) 8 hours preincubation in simple medium, (5) 8 hours preincubation in 20 mmol/l of myo-inosi-tol supplemented medium. COCs in each group were denuded and intracellular reactive oxygen species (ROS), glutathione (GSH), mitochondrial membrane potential (MMP) and mito-chondrial distribution were measured by a fluorometric assay. ATP content of oocytes also was measured using the ELISA method. 2PN rate was calculated to assess oocytes fertilization potential.Results: Results showed that intracellular H2O2 and glutathione levels, mitochondrial distribution, mitochondrial membrane potential, ATP content, as well as fertilization rate were differ-ent between groups. Nonetheless, myo-inositol supplementa-tion could improve levels of H2O2, glutathione, mitochondrial distribution, ATP content and fertilization rate. Unlike other variables, mitochondrial membrane potential of oocytes was not reduced after 4 hours of preincubation in either simple or supplemented medium, but 8 hours of preincubation time could decrease it significantly. Addition of myo-inositol to the me-dium could not ameliorate mitochondrial membrane potential in oocytes preincubated for 4 and 8 hours. While, ATP content did not decline in oocytes preincubated for 4 and 8 hours, sup-plementation of myo-inositol in medium could increase it in both groups.Conclusion: Finally, the analysis addressed that 4 hours or more preincubation time can influence the oocyte quality re-lated to alternation in H2O2, glutathione, mitochondrial integrity and mitochondrial membrane potential which ultimatelty leads to reduced oocyte fertilization potential. Supplementation of myo-inositol in medium improves the oocyte quality in com-parison to the simple medium and saves 4 hours for preincu-bated oocytes.

کلیدواژه ها:

Oocyte Preincubation Time ، Myo-Inositole Supple-ment ، Oocyte Quality ، Fertilization Potential