Cumulus co-culture system does not improve the in-vitro maturation (IVM) of oocytes in mice

Objective: To examine the effect of co-culture system with CCs on the in vitro maturation (IVM) of immature oocytes retrieved from mice. Design: This is an experimental study. Setting: Research and Clinical Center for Infertility of Yazd. Sample: A total of 144 oocytes from 5 to 6 weeks mice. Material: After dissecting ovaries, denuded GVs (DGVs) were considered as control group and put in IVM medium. In cumulus oocyte complexes (COCs) as exp I, intact COCs were put in IVM medium and observed for maturation after 24 h and 48 h. In exp II, GVs were co-cultured with mature CCs. For exp II, COCs were incubated for 30 min before removing oocytes. Then, denuded mature oocytes were removed and the remaining CCs were used to culture denuded GVs recovered from ovaries. Main outcome measures: Maturation rates of oocytes after 24 h and 48 h. Results: The rate of oocyte maturation was 77.36 ± 14.4 in control group. In exp I and exp II, the rates of maturation were 91.32 ± 22.5 and 63.33 ± 7.4, respectively (P = 0.04). However, maturation rate did not increase after 24 h. The maturation rate in metaphase I (MI) oocytes was as low as 15% in different groups at 24 h and did not increase by 48 h. Degeneration rate was increased from time 0 to 48 h, but not significant in different times. Conclusion: Presence of intact COCs significantly improved the oocyte maturation rates in animal model. However, co-culture of GVs with mature CCs did not improve IVM program in mice.