For OEC‐CM treatment, at time 0, media conditioning (25%, 50% and 100%) obtained from OECs cultured for 24, 48 and 72 hrs were applied in the same experimental culture groups. To verify the status of hypoxia, the expression of hypoxia‐inducible factor 1‐alpha (HIF1A), a specific transcription factor of the hypoxic response, was analysed by immunofluorescence (data not shown).