title: Milrinone treatment of bovine oocytes during in vitro maturation benefits production of nuclear transfer embryos by improving enucleation rate and developmental competence.
abstract: In the production of cattle nuclear transfer embryos, the production efficiency is affected by the oocyte developmental competence and successful enucleation rate. This study investigated the effect of treating oocytes with milrinone, a phosphodiesterase inhibitor, on these two characteristics. When cumulus-oocyte complexes (COCs) were cultured for 19 h with 0, 50 or 100 μM of milrinone, the enucleation rate was significantly improved by 100 μM milrinone. However, milrinone treatment during in vitro maturation (IVM) also delayed meiotic progression by at least 2 h, which would affect the examination of enucleation rate and developmental competence of oocytes. Thus, in the second experiment, meiotic resumption was temporarily inhibited with butyrolactone I (BL-I; 100 μM, 18 h) to decrease the delayed maturation caused by milrinone; this enabled a more accurate comparison of the effects of milrinone after oocyte maturation. In nuclear transfer embryo production, oocytes treated with milrinone (100 μM, 20 h) showed a significantly higher rate of enucleation compared with that of control oocytes. This improved enucleation rate was associated with a closer location of the metaphase plate to the first polar body in the treated oocytes compared with that in control oocytes. Furthermore, milrinone improved the frequency of development to the blastocyst stage in the resulting embryos. In conclusion, milrinone supplementation during IVM improved enucleation rates by rendering the metaphase plate in close proximity to the first polar body, and this treatment also improved oocyte developmental competence. These benefits additively improved the yield of cloned embryos that developed to the blastocyst stage.
authors.affiliation: NARO Tohoku Agricultural Research Center, Iwate 020-0198, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Naruse
authors.forename: Kosuke
authors.initials: K
authors.lastname: Iga
authors.forename: Manabu
authors.initials: M
authors.lastname: Shimizu
authors.forename: Naoki
authors.initials: N
authors.lastname: Takenouchi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Akagi
authors.forename: Tamas
authors.initials: T
authors.lastname: Somfai
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hirao
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001755:Blastocyst / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D002417:Cattle; D065150:Cellular Reprogramming / Q000187:drug effects*; D054885:Cumulus Cells / Q000502:physiology; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D003599:Cytoskeleton / Q000187:drug effects / Q000648:ultrastructure; D004477:Ectogenesis / Q000187:drug effects*; D004624:Embryo Transfer / Q000662:veterinary; D005260:Female; D059471:In Vitro Oocyte Maturation Techniques / Q000662:veterinary*; D008677:Metaphase / Q000187:drug effects; D020105:Milrinone / Q000494:pharmacology*; D053652:Nuclear Transfer Techniques / Q000662:veterinary*; D009865:Oocytes / Q000166:cytology / Q000187:drug effects* / Q000648:ultrastructure; D009994:Osmolar Concentration; D058987:Phosphodiesterase 3 Inhibitors / Q000494:pharmacology*; D059705:Polar Bodies / Q000187:drug effects / Q000648:ultrastructure; D047428:Protein Kinase Inhibitors / Q000494:pharmacology
chemical_list: D058987:Phosphodiesterase 3 Inhibitors; D047428:Protein Kinase Inhibitors; C082868:butyrolactone I; D018844:Cyclin-Dependent Kinases; D020105:Milrinone; D015107:4-Butyrolactone