Fertilization and Early Embryogenesis
(T299) DEVELOPMENTAL COMPETENCE OF IN VITRO AND IN VIVO MATURED OOCYTES: MOUSE MODEL STUDY.
Wang, Yue1, Chian, Ri-Cheng1, 1 McGill University, Montreal, QC, Canada
ABSTRACT- The objective of present study is to determine the developmental competence of two populations of oocytes matured in vitro and in vivo primed with or without gonadotropins, using mouse model. There were four groups of oocytes used: 1) In vivo nature: matured oocytes collected from nature cycle ovaries; 2) In vivo stimulation: matured oocytes collected from ovaries treated with super-ovulation; 3) In vitro nature: immature oocytes collected from nature cycle ovaries and then matured in vitro; 4) In vitro stimulation: In vitro matured oocytes collected 48 h after priming with eCG and followed by IVM. In vitro maturation (IVM), in vitro fertilization (IVF) and in vitro culture (IVC) were performed using standard laboratory protocol. The status of DNA damage in individual metaphase II oocyte was detected by Comet assay. The two cell cleavage rates and the blastocysts formation rates of in vitro matured oocytes was significantly lower than that of in vivo matured oocytes (Two cell cleavage rates: In vitro nature 60.5%, In vivo nature 87.7%, p<0.05; blastocysts formation rates: In vitro nature 18.7%, in vivo nature 81.10%, p<0.05). The two cell cleavage rates and the blastocysts formation rates of in vitro matured oocytes collected 48 h after priming with eCG followed by IVM were significantly higher than the no treatment group (Two cell cleavage rates: In vitro stimulation 64.9 %, In vitro nature 45.9%, p<0.05; blastocysts formation rates: In vitro stimulation 38.5%, in vitro nature 19.3%, p<0.05). After IVM, In vitro matured oocytes have more DNA fragmentation compared to in vivo matured oocytes (The length of comet tail: in vitro nature, 27.38±12.3 mm vs. in vivo nature 14.2±6.95mm, p<0.05). These results indicate that eCG priming can improve the developmental competence of oocytes matured in vitro. The low developmental competence of in vitro matured oocytes may be related to oocyte DNA fragmentation during culture in vitro. This work was a part of the Program on Oocyte Health funded under the Healthy Gametes and Great Embryos Strategic Initiative of the Canadian Institutes of Health Research (CIHR), Institute of Human development, Child and Youth Health (IHDCYH), grant number HGG62293.
KEY WORDS: IVM, developmental competence, DNA fragmentation