| dc.description.abstract | Nothing extraordinary that fully grown oocytes derived from large antral follicles can
obtain complete nuclear and cytoplasmic maturation and achieve both high quality
and quantity of blastocyst formation after in vitro development but it is a difficulty for
oocytes from small antral follicles. Therefore, the pre-in vitro maturation (pre-IVM)
process was established to support the oocytes' growth and meiotic arrested capacity
to prepare materials to enter maturation phase. The objective of this study is to
investigate optimal time for pre-IVM before in vitro maturation (IVM) of immature
oocytes derived from small antral follicles (2-3 mm in diameter) and its effect on the
developmental competence of embryo upon being subjected to different pre-IVM
durations. There were four potential timing examined, including pre-IVM in 0 h, 6 h,
8 h, and 10 h for oocyte from small follicles compare to positive control as fully grown
oocytes from large antral follicles (4-6 mm in diameter). The result indicated that
after 8 h pre-IVM, most of the oocytes from small follicles were reached at GVI-I’
stage which as quite like the oocytes collected from large follicles (83%, 80%,
respectively). In addition, after IVM, oocyte from small follicle obtained full meiotic
competence to reach to metaphase II (MII) was significantly higher in pre-IVM 8 h
and 10 h compared to 0 h and 6 h (77.67%, 79.73% vs 50.65%, 50.38%,
respectively). Especially, the blastocyst formation rate of pre-IVM 8 h was highest
compared to the other groups 0 h, 6 h, and 10 h (36.64% vs 14.14%, 22.49%,
27.32%, respectively), although it was still lower than control group from the large
follicle (59.4%). Study on the quality of the embryo, we found that the total cell
number in the blastocyst of group pre-IVM 8 h was also highest compared to the other
groups 0 h, 6 h, and 10 h (118 cells vs 44, 39, and 72 cells, respectively). Besides
that, the increasing the levels of acetylation of histone H3 at lysine 9 (Ac-H3-K9) in
blastocyst derived from group pre-IVM 8 h was significantly higher than other preIVM groups, although it was still lower than the group of large antral follicles. In
conclusion, we found that the pre-IVM of oocytes from small follicles for 8 h in our
culture condition, which reached the highest meiotic resumption at MII, lead to a
significant positive effect on the developmental competence of bovine oocytes and
improvement in the quality of blastocysts | en_US |
