Impact of Two‐step <i>in vitro</i> Culture Systems on Developmental Potency of Oocytes

Abstract

Contents Proper conditions for the successful induction of a functional two step in vitro culture system for agricultural or clinical applications are hereby described in form of a two‐step protocol. The first inhibitory culture of oocytes in media supplemented with specific cdk inhibitors (roscovitine, BL I) appears essential to promote appropriate oocyte‐cumulus cell interactions and ensure production of ova competent to undergo normal embryogenesis. This inhibitory period should last for several days, depending on the origin of the follicles, and the degree of accumulation and storage of mRNAs and proteins essential for the acquisition of developmental competence in the oocytes. The full reversibility of the inhibitory step secures that during the second maturation step, oocytes reach metaphase II with correctly arranged microtubuli in the meiotic spindle and well‐expanded cumuli.