This study was conducted to examine the oocyte recovery efficiency through having an OPU session once and twice a week. Also, the oocyte recovery efficiency was examined by using OPU after two and three months of rest period. Six cows were used for oocytes collection and were randomly divided into two groups. In experiment 1, OPU sessions were conducted once and twice a week to collect oocytes. The collected oocytes between once and twice OPU groups were classified into four groups (grade 1, 2, 3 and 4) according to the quality of cumulus cells and ooplasm. Based on the result, the percentage of collected oocytes per aspirated follicle number was similar between once and twice OPU session groups (65.5 ± 1.9 and 68.7 ± 1.4 vs.). However, the percentage of grade 1 oocytes from the twice OPU session group was significantly high compared with that of the once a week OPU session group (25.3 ± 0.9 and 32.5 ± 1.2% vs. once and twice session group, respectively, p < 0.05). In experiment 2, the group with three months of rest period tended to have a high percentage of collected oocyte compared with the group with two months of rest period (64.6 and 70.9% vs. 2 and 3 months rest group, respectively, p = 0.62). The percentage of grade 4 in the group with three months of rest period was significantly low compared with the group with two months of rest period group (27.3 and 36.5% vs. two and three months rest group, respectively, p = 0.05). In conclusion, twice a week OPU session is suitable for collection of high quality oocytes by using OPU, and three months of rest period is needed for the recovery of oocyte quality of a donor cow.

Ganglioside GM3 is known as an inhibition factor of cell differentiation and proliferation via inhibition of epidermal growth factor receptor (EGFR) phosphorylation. Our previous study showed that the exogenous ganglioside GM3 reduced the meiotic maturation of porcine oocytes and induced apoptosis at 44 h of in vitro maturation (IVM). However, the role of ganglioside GM3 in the relationship between EGFR signaling and apoptosis during porcine oocyte maturation has not yet been studied. First, porcine cumulus-oocyte complexes (COCs) were cultured in the NCSU-23 medium with exogenous ganglioside GM3 according to maturation periods (non-treated, only IVM I: 0 - 22 h, only IVM II: 22 - 44 h and IVM I & II: 0 - 44 h). We confirmed that the proportion of germinal vesicle breakdown (GVBD) increased significantly in the IVM I treated group than in the control group. We also confirmed that the meiotic maturation until M II stage and polar body formation decreased significantly in the only IVM I treated group. Cumulus cell expansion and mRNA levels of the expansion-related factors (HAS2, TNFAIP6 and PTX3) decreased significantly in the IVM I treated group than in the control group. Protein levels of EGFR, p-EGFR, ERK1/2, and p-ERK1/2 decreased significantly in the GM3-treated groups, during the IVM I period. In addition, cellular apoptosis, determined using TUNEL assay, and protein levels of Cleaved caspase 3, were increased significantly in the GM3-treated COCs during the IVM I period. Based on these results, ganglioside GM3 exposure of porcine COCs during the IVM I period reduced meiotic maturation and cumulus cell expansion via inhibition of EGFR activity in pigs.

Oocyte is the central factor in the bi-directional communication axis in the ovarian follicles. It controls the cumulus or granulosa cells to perform functions which are beneficial for its own development via secreting paracrine growth factors, including GDF9 and BMP15. The aim of this study was to investigate whether the recombinant GDF9 and BMP15 are able to promote meiotic resumption and cumulus expansion of canine COCs during IVM, as well as to demonstrate the actions of GDF9 and BMP15 in regulating the expression of connexin transcripts in the ovarian granulosa cells. As results, GDF9 and BMP15 significantly improved the meiotic resumption rate and cumulus expansion by activating ERK1/2 signaling. Treatments with GDF9 significantly improved the expression of CyclinB1 but inhibited the expression of Cx43 transcripts. In addition, cumulus expansion genes (MAPK1, Ptgs2, Tnfaip6 and Ptx3) were differentially improved by GDF9 and BMP15. In the ovarian granulosa cells, GDF9 suppressed the expression of Cx43 transcripts by binding ALK4/5/7 receptors and activation Smad2/3 signaling, whereas, BMP15 stimulated the expression of Cx43 transcripts by binding ALK2/3/6 receptors and activating Smad1/5/8 signaling. In conclusion, by regulating functions of granulosa/cumulus cells, oocyte has the potential to enhance the growth and maturation of itself.

Oocyte is the central factor in the bi-directional communication axis in the ovarian follicles. It controls the cumulus or granulosa cells to perform functions which are beneficial for its own development via secreting paracrine growth factors, including GDF9 and BMP15. The aim of this study was to investigate whether the recombinant GDF9 and BMP15 are able to promote meiotic resumption and cumulus expansion of canine COCs during IVM, as well as to demonstrate the actions of GDF9 and BMP15 in regulating the expression of connexin transcripts in the ovarian granulosa cells. As results, GDF9 and BMP15 significantly improved the meiotic resumption rate and cumulus expansion by activating ERK1/2 signaling. Treatments with GDF9 significantly improved the expression of CyclinB1 but inhibited the expression of Cx43 transcripts. In addition, cumulus expansion genes (MAPK1, Ptgs2, Tnfaip6 and Ptx3) were differentially improved by GDF9 and BMP15. In the ovarian granulosa cells, GDF9 suppressed the expression of Cx43 transcripts by binding ALK4/5/7 receptors and activation Smad2/3 signaling, whereas, BMP15 stimulated the expression of Cx43 transcripts by binding ALK2/3/6 receptors and activating Smad1/5/8 signaling. In conclusion, by regulating functions of granulosa/cumulus cells, oocyte has the potential to enhance the growth and maturation of itself.