Figure 4.

Oocytes are required for E2 maintenance of cumulus cell competence to undergo expansion. OOX cumulus cell complexes were cultured with E2 and/or oocytes (Oo), and their competence to undergo expansion (A and B) and expression levels of the cumulus expansion-related transcripts (C) were assessed. OOX cumulus cells without maintenance culture were used as control groups (Fresh). Note that oocytes are present in micrographs of all groups because they are added during the test period whether or not they were present during the maintenance culture. Bar, 200 μm. The values indicated by different alphabetical letters (a, b, and c) are significantly different (P < 0.05).