Meiotic arrest with roscovitine and follicular fluid improves cytoplasmic maturation of porcine oocytes by promoting chromatin de-condensation and gene transcription

The developmental capacity of in vitro matured oocytes is inferior to that of the in vivo matured ones due to insufficient cytoplasmic maturation. Although great efforts were made to accomplish better cytoplasmic maturation by meiotic arrest maintenance (MAM) before in vitro maturation (IVM), limited progress has been achieved in various species. This study showed that MAM of porcine oocytes was better achieved with roscovitine than with dibutyryl cyclic adenosine monophosphate (db-cAMP) or 3-isobutyl-1-methylxanthine. Oocyte developmental competence after IVM was significantly improved following MAM in 199 + FF medium (TCM-199 containing 10% porcine follicular fluid and 25 µM roscovitine) to a level even higher than that in control oocytes matured without pre-MAM. Observations on other markers further confirmed the positive effects of MAM in 199 + FF on oocyte cytoplasmic maturation. During MAM culture in 199 + FF, re-decondensation (RDC) of condensed chromatin occurred, and transcription of genes beneficial to cytoplasmic maturation was evident in some of the oocytes with surrounded nucleoli (SN). However, MAM with db-cAMP neither induced RDC nor improved oocyte developmental potential. Together, the results suggest that MAM in the presence of FF and roscovitine improved the developmental competence of porcine oocytes by promoting a pre-GVBD chromatin de-condensation and expression of beneficial genes.