• Journal of Animal Reproduction and Biotechnology
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• v.38 no.2
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• pp.70-76
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• 2023

Background: Despite considerable technological advancements, polyspermy remains a significant challenge in in vitro fertilization (IVF) procedures in pigs, disrupting normal embryonic development. Here, we aimed to determine whether optimal fertilization conditions reduce the polyspermy incidence in pigs. Methods: In vitro-matured oocytes were co-incubated with sperm according to a modified two-step culture system. Results: In the first experiment, oocytes were briefly co-incubated with sperm, washed in IVF medium, and then moved to fresh IVF medium for 5 or 6 h. Although the 6 h sperm-free cultured group had a higher penetration rate than the 5 h cultured group, the polyspermy rate significantly increased in the 6 h sperm-free cultured group. The gamete co-incubation period was either 20 or 40 min. The 40 min cultured group had a higher rate of blastocyst formation and number of total cells in blastocysts than the 20 min cultured group. In experiment 2, oocytes were inseminated with sperm separated by Pecroll treatment. Percoll treatment increased the rate of oocyte penetration and blastocyst formation compared to the control. In experiment 3, fertilized oocytes were cultured in 25 µL microdroplets (10 gametes/drop) or 500 µL (100 gametes/well) of culture medium in 4-well plates. The large volume of medium significantly reduced the number of dead oocytes and increased the rate of blastocyst formation compared to the small volume. Conclusions: Collectively, these results demonstrate that various fertilization conditions, including modified co-culture period, active sperm separation, and culture medium volume, enhance fertilization efficiency and subsequent embryonic development by decreasing polyspermy occurrence.

• Journal of Embryo Transfer
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• v.22 no.1
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• pp.1-7
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• 2007

This study was conducted to examine the role of intact cumulus cells during in vitro fertilization (IVF) on sperm penetration, male pronuclear (MPN) formation and subsequent embryo development of oocytes matured and fertilized in vitro. Cumulus-oocyte complexes obtained from the slaughtered gilt ovaries were matured for 44 h in TCM199 containing 10% porcine follicular fluid, epidermal growth factor and hormones. After maturation culture, denuded oocytes or oocytes with intact cumulus cells were coincubated with frozen-thawed boar semen for 8h in a modified tris-buffered medium containing 5mM caffeine and 10mM calcium chloride. Putative zygotes were fixed and examined for sperm penetration and MPN formation (Experiments $1{\sim}3$), or cultured in North Carolina State University-23 medium fo. 156 h (Experiment 3). In Experiment 1, sperm penetration was examined after insemination of denuded oocytes and oocytes with intact cumulus cells at the concentration of $7.5{\times}10^5$ sperm/ml. Optimal sperm concentration for IVF of cumulus-intact oocytes was determined in Experiment 2 by inseminating intact oocytes with $2{\sim}5{\times}10^6$ sperm/ml. In Experiment 3, denuded or intact oocytes were inseminated at the concentrations of $7.5{\times}10^5$ and $4.0{\times}10^6$ sperm/ml, respectively, and in vitro embryo development was compared. Sperm penetration was significantly (p<0.01) decreased in cumulus-intact oocytes compared to denuded oocytes (35.2% vs. 77.4%). Based on the rates of sperm penetration and normal fertilization, the concentration of $4.0{\times}10^6$ sperm/ml was optimal for the IVF of intact oocytes compared to other sperm concentrations. The presence of intact cumulus cells during IVF significantly (p<0.05) improved embryo cleavage (48.8% vs. 58.9%), blastocyst (BL) formation (11.0% vs. 22.8%) and embryo cell number $(22{\pm}2\;vs.\;29{\pm}2\;cells)$ compared to denuded oocytes. In conclusion, these results suggest that intact cumulus cells during IVF inhibit sperm penetration but improve embryo cleavage, BL formation and embryo cell number of porcine embryos produced in vitro.

• Asian-Australasian Journal of Animal Sciences
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• v.31 no.6
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• pp.827-834
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• 2018

Objective: The aim of this study was to compare the effects of $36.5^{\circ}C$ and $38.5^{\circ}C$ incubation temperatures on the maturation of bovine oocytes and developmental competence of embryos. Methods: In experiment 1, oocytes were maturated in bicarbonate-buffered TCM-199 for 22 hours in a humidified atmosphere of 5% $CO_2$ in the air at either $36.5^{\circ}C$ or $38.5^{\circ}C$ and nuclear maturation status were determined. In experiment 2, in vitro fertilized oocytes were allocated randomly into synthetic oviductal fluid medium with or without a mixture of 1 mM L-glutathione reduced and 1,500 IU superoxide dismutase and cultured in a humidified atmosphere of 5% $CO_2$, 5% $O_2$, and 90% $N_2$ in the air at $38.5^{\circ}C$ for 8 days. Results: There were no significant differences between incubation temperatures in terms of oocyte maturation parameters such as cumulus expansion, first polar body extrusion and nuclear maturation. Incubation temperatures during in vitro maturation had no effects on developmental competence of embryos, but supplementation of antioxidants increased (p<0.05) developmental competence of the embryos. Blastocysts from oocytes matured at $38.5^{\circ}C$ had comparatively higher inner cell mass, but low overall and trophectoderm cell numbers (p<0.05). Conclusion: The results of present study showed that maturation of bovine oocytes at $36.5^{\circ}C$ may provide a suitable thermal environment for nuclear maturation and subsequent embryo development.

• Journal of Embryo Transfer
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• v.19 no.3
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• pp.229-237
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• 2004

The main objective of this study was to examine the effects of serum and gonadotropins supplement during in vitro maturation(IVM) of bovine oocytes on nuclear maturation and embryo development, and we also examine the cell number. 1 . The first polar body(PB) extrusion rates of Korean native cow(KNC) oocytes matured in medium with FBS or gonadotropins were similar among treatment groups. The development rate to the blastocyst stage was significantly higher in the group of both supplement FBS and gonadotropins(26.0％) than in the group of non-supplement(9.9％) and gonadotropins (12.0％). The numbers of inner cell mass (ICM) and trophectoderm (TE) cells and total cell numbers of blastocysts were highest in the group of both supplement FBS and gonadotropins, and the number of ICM cells was increased by FBS supplementation (p<0.05). 2. The PB extrusion rates of KNC oocytes matured in medium with FBS in the different duration of IVM was significantly higher in the 0-18hr(63.1％) and in the 9-18hr(63.4％) group than in the 0-9hr.(37.4％) group (p<0.05). The embryo development rates did not differ among treatment groups. The numbers of TE cells and total cell numbers of blastocysts were similar among treatment groups, but the number of ICM cells of the 0-18h. group were significantly higher than the other treatment groups (p<0.05). The results indicate that although TCM199 alone can support bovine oocyte maturation and development to the blastocyst stage, a high quality of blastocysts can be produced from oocytes matured in medium containing serum and gonadotropins.

• Clinical and Experimental Reproductive Medicine
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• v.27 no.1
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• pp.23-29
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• 2000

Objective: Zona pellucida (ZP) has been thought to be the barrier of egg to sperm penetration before and after fertilization. The phenomenon of ZP hardening has been considered as a post-fertilization event until now, and it is generally accepted that it is caused by the secretory products of cortical granules released during the cortical reaction. Hardening of ZP could occur "spontaneously" in mammalian oocytes in standard culture conditions, and that it is probably not a consequence of cortical reaction. The purpose of our study was to investigate the effect of human amniotic fluid (HAF) on nuclear maturation (NM) and fertilization ability of mouse immature oocytes. Methods: HAF was obtained from patients undergoing amniocentesis at $16{\sim}20$ weeks of gestation. HAF from five to ten patients was centrifuged and the supernatants was pooled. Cumulusenclosed mouse immature oocytes were incubated in the medium containing HAF, and examined to confirm NM and fertilization. Female ICR mice (about 3 weeks old) were stimulated with 7.5 IU PMSG. Immature oocytes were isolated at $48{\sim}52$ hrs post PMSG injection and cultured in TCM-199 supplemented with 20% HAF for 18 hrs. FBS was used as a control for the examination. Matured oocytes (MII) were fertilized with sperms collected from the epididymis of male mice (over 10 weeks old). Fertilization was in conducted T6 medium containing 15 mg/ml BSA, and confirmed at 6 hrs post-insemination. Fertilization rate was assessed in zona-intact or zona-free oocytes (denuded by trypsin). Evaluation of NM and fertilization was carried out by rapid staining method. ZP hardening was evaluated by incubating cumulus cell-free mature oocytes in 0.001% chymotrypsin at $37^{\circ}C$ for 10 min. Results: There was no significant difference between the effects of HAF (86.6%) and FBS (87.7%) supplements on NM of immature oocytes. When maturation medium was supplemented with HAF, total fertilization rates (7%) were significantly lower (p<0.01) than that of FBS (85.1%). In HAF group, fertilization rate was increased (p<0.01) in zona-free oocytes (7% versus 100%). The resistance of mouse oocyte ZP to digestion by chymotrypsin after maturation in vitro was significantly higher (p<0.01) in HAF group (86.7%) than in FBS (6.7%). To culture oocytes in FBS were very effective in preventing ZP hardening. However cultured oocytes in HAF showed high rate of ZP hardening (p<0.01). Conclusions: These results suggest that HAF can be used as a supplement for the NM of mouse immature oocytes in vitro. However, HAF induces spontaneous hardening of ZP of mouse immaure oocytes during maturation in vitro.

• Korean Journal of Animal Reproduction
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• v.25 no.1
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• pp.1-7
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• 2001

This study was to test whether in vitro matured Hanwoo oocytes can be successfully cryopreserved by a new vitrification procedure using MVC method. For the vitrification, oocytes were pretreated in 10% ethylene glycol (EG10) for 5~10 min, exposed in EG30 for 30 sec, each oocyte was individually put on the inner wall of 0.25 $m\ell$ straw, and then straws were directly plunged into L$N_2$. Thawing was taken by 4-step procedures 〔1.0 M sucrose (MS), 0.5 MS, 0.25 MS, and 0.125 MS〕 at 37$^{\circ}C$. In vitro developmental capacity (survival, cleavage ($\geq$2-cell) and blastocyst rates) in vitrified group was no significant difference compared to that in other treatment groups (exposed; 100.0, 74.4, 32.3% and control; 100.0, 78.3, 36.3%): high mean percentage of oocytes (91.2%) was survived, 69.4% of them were cleaved and 27.9% of cleaved embryos were developed to blastocyst. Especially, after transfer of in vitro developed embryos in vitrified group, four of six recipient animals were pregnant and three of them were ongoing-pregnant by manual palpation at 250 days after transfer. This result demonstrates that MVC method is very appropriate freezing method for the Hanwoo in vitro matured oocytes and that ovum bank can be maintained efficiently by MVC cryopreservation method.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.10
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• pp.1369-1373
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• 2004

The percentages of sperm motility and normal acrosome on the liquid boar semen diluted and preserved at $4^{\circ}C$ with lactose hydrate, egg yolk and N-acetyl-D-glucosamine (LEN) diluent were significant differences according to preservation day and incubation time, respectively. The sperm motility steadily declined from 96.9% at 0.5 h incubation to 78.8% at 6 h incubation at 1 day of preservation. However, the sperm motility rapidly declined after 4 day of preservation during incubation. The normal acrosome steadily declined from 93.3% at 0.5 h incubation to 73.8% at 6 h incubation at 1 day of preservation. However, the normal acrosome rapidly declined after 3 day of preservation during incubation. The rates of sperm penetration and polyspermy were higher in 5 and $10{\times}10^6$ sperm/ml than in 0.2 and $1{\times}10^6$ sperm/ml. Mean numbers of sperm in penetrated oocyte were highest in $10{\times}10^6$ sperm/ml compared with other sperm concentrations. The rates of blastocysts from the cleaved oocytes (2-4 cell stage) were highest in $1{\times}10^6$sperm/ml compared with other sperm concentrations. In conclusion, we found out that liquid boar sperm stored at $4^{\circ}C$ could be used for in vitro fertilization of pig oocytes matured in vitro. Also, we recommend $1{\times}10^6$sperm/ml concentration for in vitro fertilization of pig oocytes.

• Journal of Embryo Transfer
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• v.24 no.2
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• pp.97-104
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• 2009

The objective of this study was to examine the effect of macromolecule in a maturation medium on nuclear maturation, intracellular glutathione (GSH) level of oocytes, and embryonic development after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT) in pigs. Immature pig oocytes were cultured in maturation medium that was supplemented with each polyvinyl alcohol (PVA), pig follicular fluid (pFF) or newborn calf serum (NBCS) during the first 22 h and the second 22 h. Oocyte maturation was not influenced by the source of macromolecules during in vitro maturation (IVM). Embryo cleavage and cell number in blastocyst after PA was altered by the source of macromolecule but no difference was observed in blastocyst formation among treatments. Oocytes matured in PVA-PVA medium showed lower rates of oocyte-cell fusion (70.4% vs. 77${\sim}$82%) and embryo cleavage (75% vs. 86${\sim}$90%) after SCNT than those matured in other media but blastocyst formation was not altered (13${\sim}$27%) by different macromolecules. pFF added to IVM medium significantly increased the intracellular GSH level of oocytes compared to PVA and NBCS, particularly when pFF was supplemented during the first 22 h of IVM. Our results demonstrate that source of macromolecule in IVM medium influences developmental competence of oocytes after PA and SCNT, and that pFF supplementation during the early period (first 22 h) of IVM increases intracellular GSH level of oocytes.

• Journal of Embryo Transfer
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• v.12 no.3
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• pp.307-313
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• 1997

Experiments were conducted to assess the effect of quality and viability of bovine blastocysts derived from in-vitro culture(IVC) of in vitro matured and fertilized(IVM-IVF) oocytes during their transport 2 hours. Follicular oocytes were collected form ovaries obtained at a slaughterhouse and were cultured for 24 hours in TCM-199. The IVM oocytes were fertilized in vitro with caudal epididymis spermatozoa. Fertilized oocytes were cultured for 7 to 9 days, and embryos that developed to the blastocyst stage were used for the experiment. The blastocysts, packed in straws with storage medium that consisted TCM-199 with HEPES equilibratd in air and supplemented with 10% FCS were transported at 39~(2.0 h). The quality of blastocysts was assessed and ranked as A(excel-lent), B(Good), fair or poor after transportation. The percentages of A and B grade blastocysts after transport duration for < 1 hours(97.7%) were similar to the result from transport duration for 1~2 hours (92.9%) and 2~3 hours(89.6%), but significantly(P<0.05) higher than transpot duration for 3~4 hours(76.3%). The percentages of A and B grade blastocysts after transport duration for two hours from developed blastocyst at 7day(100%) and 8day(85.0%) were higher 9day(96.6%) and >9day (40.0%). And early to expanded blastocyst produced in vitro were transferred to recipient cow by additional embryos at 7 and 8th day after AI. Three of them were pregnant to term and produced four twin calves, and two calves was premature birth. The gestation lengths of male to female and female to female twin were 282 and 281 days, respectively. And birth weight of twin calves were male to female(22.Skg) and female to female twin(20.3Okg), respectively.

• Journal of Embryo Transfer
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• v.13 no.3
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• pp.245-249
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• 1998

The purpose of this study was to evaluate the effects of growth factors such as epidermal growth factor (EGF) and insulin-like growth factor-1 (IGF-1) on maturation of bovine follicular oocytes in vitro. Oocytes were recovered from the ovaries of slaughtered Hanwoos. The oocytes were matured in TCM 199 at 39$^{\circ}C$, 5% $CO_2$ in air. Growth factors were added to maturation medium as follows: control (no serum), EGF (10ng/m1, 50ng/ml or 100ng/m1), IGF-1 (100ng/m1) and EGF (50ng/ml) + IGF-1 (100ng/m1). The oocytes were placed onto a slide and stained with aceto-orcein dye. Nuclear maturation was evaluated and classified as germinal vesicle breakdown (GVBD), metaphase-I (MI) or metaphase-ll(Mll). Maturation rates were 37.9% (control), 45.8% (EGF, 10ng/m1), 55.8% (EGF, 50ng/ml), 44.4% (EGF, 100ng/m1), 46.7% (IGF-1, 100ng/m1) and 67.0% (IGF-1+EGF). The highest group developed to Mll stage was IGF-1+EGF treatment group (p<0.05). Therefore, nuclear maturation of bovine oocytes were affected by both of growth factors, and it seems to have a mutual activity between them.