In livestock, most of the follicles on the ovarian surface are small follicles. A procedure that supports the in vitro growth and maturation of these small follicle-derived oocytes may offer a new source of useable oocytes for both biotechnological and fundamental research purposes. The objective of the current study was to test the hypothesis that providing a more growth-supporting and less maturation-promoting environment during the first phase of small follicle-derived oocyte maturation may improve oocyte competence for meiosis and embryo development upon activation. In our small follicle-derived oocyte growth-maturation system (SGM group), cumulus-oocyte complexes (COCs) from small follicles (1–3 mm) were first cultured in oocyte growth medium for 24 h, then in oocyte maturation medium for 20 h. As controls, COCs from small (SM group) and large (LM group) follicles were cultured using a conventional in vitro maturation (IVM) approach in which they were directly cultured in oocyte maturation medium. At 24 h of culture, the percentage of small follicle-derived oocytes that underwent germinal vesicle breakdown (GVBD) in the SGM group was comparable to that of large follicle-derived oocytes (LM group) but was significantly higher than that of the SM group (P < 0.05). At 44 h of culture, compared to 36% in the SM group, 55% of the SGM group oocytes reached metaphase II (MII; P < 0.05). In addition, the level of cyclin B in oocytes of the SGM group was comparable to that of oocytes from LM group and was significantly higher than that of oocytes from the SM group (P < 0.05). When activated and in vitro fertilized (IVF), 7.3 and 9.0 times more parthenogenetic and IVF embryos developed to blastocyst stage in the SGM group than in the SM group (P < 0.05). The mRNA expression levels of three developmentally important genes—DNA-methyltransferase 1, Pou domain class 5 transcription factor 1, and Fibroblast growth factor receptor 2—in embryos of the SGM group were comparable to those of embryos developed from the LM group, whereas they were significantly lower in those of the SM group (P < 0.05). Our data suggest that the oocyte growth-maturation system facilitates the final stage of oocyte growth and thus resulted in better oocyte nuclear, cytoplasmic maturation, and developmental competency compared with the conventional direct oocyte maturation system.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.