Effect of GM-CSF on diameters of cumulus in in vitro matured COC. (A) COC (n = 52-56/per group) were in vitro matured in SOF medium alone or supplemented with 1, 10 and 100 nM of GM-CSF. (B) Higher (P < 0.001) diameters were detected in COC matured in presence of 10 and 100 ng/ml of GM-CSF compared to untreated COC. Time 0 corresponds with the immature state of the oocytes. Parameters from oocytes in the immature state and matured in TCM were used as positive control and not included in the statistical analysis. (*) Indicate significant (P < 0.001) differences between treatments of 0, 1 and 100 ng/ml of GM-CSF.