100 SEQUENTIAL VERSUS SINGLE-STEP MEDIUM FOR RHESUS MACAQUE EMBRYO CULTURE

2016 ◽  
Vol 28 (2) ◽  
pp. 180

The nonhuman primate (NHP) is a valuable translational model for human health studies and is widely used to investigate pre-implantation embryo development. Central to these investigations is the dependency on in vitro embryo culture (IVC). Since 2001, the single-step hamster embryo culture medium (HECM) has been the accepted standard for NHP IVC. With recent advances in formula optimization for IVC in human clinics, a re-examination of optimal NHP IVC media is warranted. Thus, two types of commercially available IVC media routinely used in human applications were compared with HECM-9: Global (single-step; LifeGlobal Group, Guilford, CT, USA), and Quinns Advantage (sequential; SAGE, Trumbull, CT, USA). Normally cycling, adult rhesus monkeys (n = 3) underwent controlled ovarian stimulations, and follicles were aspirated via laparoscope. Recovered ova were fertilized in vitro and the resultant zygotes (n = 138) were cultured for 9 days in HECM-9, Global, or Quinns with 10% protein supplement at 37.5°C in humidified tri-gas (6% CO2, 5% O2, and 89% N). Single-step media (HECM-9 and Global) were refreshed every two days while embryos were cultured for Days 1–3 in Quinns Advantage Cleavage medium without being replaced and in Quinns Advantage Blastocyst medium for Days 4–9 with medium changes every 2 days. Embryos were observed for cleavage, compaction, and blastocyst development. Proportional data with equal variance and normal distribution were analysed by one-way ANOVA, and significance was determined post-hoc by the Holm-Sidak method with P < 0.05. Developmental stage data ± s.e.M are presented in Table 1; a change in superscript indicates a significant difference within the column. There was no difference in embryonic cleavage or morula compaction between the three culture media evaluated, indicating no obvious differences in their effects on embryonic development 1 to 3 days after fertilization. However, a greater proportion of blastocysts developed in Global medium compared with HECM-9, and though it was not statistically different, embryos cultured in Global tended to reach the blastocyst stage more frequently than those in Quinns. Although not significant due to large variances in each group, blastocyst expansion also tended to occur more frequently in Global medium than in HECM-9 or Quinns. Taken together, these data indicate that single-step Global is as supportive of early embryonic development as HECM-9 but is better formulated to facilitate later stage differentiation and would be better suited for use in updated standard NHP IVC protocols. Table 1.Cleavage, compaction, blastocysts, and expansion of embryos in HECM-9, Global, and Quinns media

2004 ◽  
Vol 16 (2) ◽  
pp. 195
Author(s):  
Y.H. Choi ◽  
D.D. Varner ◽  
K. Hinrichs

Research on in vitro culture of equine embryos has been scant, due to failure of equine in vitro fertilization to be repeatably successful. We have recently obtained high fertilization rates of equine oocytes via intracytoplasmic sperm injection (ICSI) using a piezo drill (Choi et al., 2002 Reproduction 123, 455–465). Culture of presumptive zygotes in G1.2/2.2 medium resulted in 63% cleavage and an average of 15 cells at 4d, but only 2 to 9% blastocyst development at 7 days (Choi et al., 2003 Theriogenology 59, 1219–1229). In the present study, we evaluated the effect of two different culture media, G1.3/G2.3 v. DMEM/F-12, with or without FBS, on blastocyst development after ICSI. Oocytes were collected from slaughterhouse-derived ovaries by follicular scraping and were matured in vitro for 24h in M199 with 10% FBS and 5μUmL−1 FSH. After culture, oocytes having a polar body (198/305; 65%) were fertilized by ICSI with frozen-thawed equine sperm using a piezo drill. Presumptive zygotes were cultured in 1 of 4 media: G1.3/G2.3 (which includes 0.8% BSA) with or without 10% FBS, or in DMEM/F-12 with 0.5% BSA, with or without 10% FBS. Culture was performed in microdroplets at 5μL/zygote under oil at 38.2°C in an atmosphere of 5% CO2, 5% O2 and 90% N2 for 7.5 days. In G1.3/2.3 treatments, G1.3 media were completely refreshed at 48h, zygotes were transferred to G2.3 (with or without FBS as per the first stage) at 96h, and were completely refreshed with the same media at 144h. In DMEM/F-12 treatments, media were completely refreshed every other day. Three to 5 replicates were performed in each treatment, and data were analyzed by chi-square test. There were no significant differences in cleavage rates (59–64%) among treatments. The rate of development to blastocyst, per oocyte injected, in G1.3/G2.3/BSA (1/49, 2%) was significantly lower (P&lt;0.05) than that for the other three treatments: G1.3/2.3/BSA/FBS (9/49, 18%), DMEM/F-12/BSA (9/50, 18%), or DMEM/F-12/BSA/FBS (10/50, 20%). There was no significant difference in blastocyst development among the latter three treatments. These findings indicate that G1.3/2.3 media with BSA only do not adequately support growth of equine embryos. Development of up to 20% of injected oocytes to the blastocyst stage in G media supplemented with FBS, in DMEM/F-12/BSA or in DMEM/F-12/BSA/FBS represents the highest in vitro equine blastocyst rate in medium alone (i.e. without co-culture) yet reported. The success of DMEM/F-12 as an embryo culture medium may provide a relatively simple basis for equine in vitro culture programs. To determine whether this medium was able to support further developmental competence, we cultured equine embryos resulting from nuclear transfer of in vitro-matured oocytes in DMEM/F-12+10% FBS (without BSA). We transferred 4 resulting blastocysts to recipient mares by transcervical transfer; one pregnancy is ongoing at 230d gestation at the time of this writing. This work was supported by the Link Equine Research Endowment Fund, Texas A&amp;M University.


Reproduction ◽  
2017 ◽  
Vol 153 (3) ◽  
pp. 327-340 ◽  
Author(s):  
A R Highet ◽  
T Bianco-Miotto ◽  
K G Pringle ◽  
A Peura ◽  
S Bent ◽  
...  

The preimplantation embryoinvivois exposed to numerous growth factors in the female reproductive tract, which are not recapitulated in embryo culture mediain vitro. The IGF2 and plasminogen activator systems facilitate blastocyst development. We hypothesized that the addition of IGF2 in combination with urokinase plasminogen activator (uPA) and plasminogen could improve rates of blastocyst hatching and implantation in mice. B6BcF1 and CBAB6F2 mouse embryos were divided into one of four supplemented culture media treatment groups: (1) control (media only); (2) 12.5 nM IGF2; (3) 10 µg/mL uPA and 5 µg/mL plasminogen; or (4) a combination of IGF2, uPA and plasminogen treatments. Embryo development to blastocyst stage and hatching were assessed before transfer to pseudopregnant recipient females and implantation, pregnancy rates and postnatal growth were assessed. After 90.5 h of culture, IGF2 + U + P treatment increased the percentage of B6BcF1 embryos that were hatching/hatched and percentage developing to blastocyst stage compared with controls (P < 0.02). Following B6BcF1 embryo transfer, IGF2 + U + P treatment increased implantation sites at day 8 of pregnancy compared with controls (P < 0.05). Replication in the CBAB6F2 mouse strain showed significant improvements in pregnancy rates at days 8 and 18 but not in blastocyst development. No adverse effects were seen on gestational age, litter size or birthweight, or the reproductive capacity of offspring of IGF2 + U + P treated embryos. For embryos susceptible to detrimental effects ofin vitroculture, IGF2, uPA and plasminogen supplementation of culture media can improve pregnancy success, but the effect of treatment is dependent on the mouse strain.


2004 ◽  
Vol 16 (2) ◽  
pp. 202 ◽  
Author(s):  
W.F. Swanson ◽  
A.L. Manharth ◽  
J.B. Bond ◽  
H.L. Bateman ◽  
R.L. Krisher ◽  
...  

Domestic cat embryos typically are cultured in media formulated for somatic cells or embryos from rodents or livestock species. Under these conditions, blastocyst development has been inconsistent and delayed relative to embryos grown in vivo, and embryo viability following transfer has been low. Our goal is to systematically define the culture requirements of the feline embryo to improve embryo development and viability. The objective of this study was to determine the ionic (NaCl, KCl, KH2PO4, and CaCl2:MgSO4) preferences of domestic cat IVF embryos. Anestral female cats were injected (i.m.) with 150IU eCG followed 84h later by 100IUhCG. Oocytes were recovered via laparoscopic follicular aspiration approximately 24h post-hCG injection (Day 0). Semen was collected from one of two males by means of an artificial vagina and washed once in HEPES-buffered IVF medium. Mature cumulus-oocyte complexes were co-incubated with 2.5–5×105 motile sperm mL−1 in IVF medium (100mM NaCl, 4.0mM KCl, 1.0mM KH2 PO4, 2.0mM CaCl2, 1.0mM MgSO4-7H2O, 25.0mM NaHCO3, 3.0mM glucose, 0.1mM pyruvate, 6.0mM L-lactate, 1.0mM glutamine, 0.1mM taurine, 1×MEM nonessential amino acids, 50μgmL−1 gentamicin, and 4.0mgmL−1 BSA) for 19 to 22h in 6% CO2 in air (38.7°C). Cumulus cells were removed and embryos cultured (8–11 embryos/50μL drop; 6% CO2, 5% O2, 89% N2, 38.7°C) in media containing 100.0 or 120.0mM NaCl, 4.0 or 8.0mM KCl, 0.25 or 1.0mM KH2PO4, and 1.0mM:2.0mM or 2.0mM:1.0mM CaCl2:MgSO4 (2×2×2×2 factorial design). The remaining components of the culture medium were identical to the IVF medium (but w/o gentamicin). Development to the blastocyst stage by Day 6, metabolism (glycolysis and pyruvate) of each blastocyst, and final cell number (Hoechst 33342 staining) of all embryos were evaluated. Final cell number of cleaved embryos and development to the blastocyst stage were analyzed using analysis of variance in the GLIMMIX macro of SAS. A total of 236 oocytes were inseminated, yielding 128 cleaved embryos (54%), including 6 blastocysts (4.7% of cleaved embryos). Cell number was not (P&gt;0.05) affected by NaCl, KCl, or KH2PO4 concentrations, but tended (P=0.057) to be higher after culture in 2.0mM:1.0mM CaCl2:MgSO4. Treatments did not significantly affect (P&gt;0.05) development to the blastocyst stage, but numerically more blastocysts were produced in 100.0mM NaCl (4/6), 8.0mM KCl (5/6), or 1.0mM KH2PO4 (5/6). Both CaCl2:MgSO4 ratios resulted in 3 blastocysts. Blastocysts contained 61.08±5.1 (mean±SEM, n=6) cells and actively metabolized glucose (glycolysis, 3.7±0.8pmol/embryo/3h or 0.06±0.01pmol/cell/3h) and pyruvate (0.75±0.27pmol/embryo/3h or 0.013±0.005pmol/cell/3h). These results suggest that the ionic composition of culture media influences the in vitro development of cat IVF embryos. (Supported by NIH grant RR15388.)


2021 ◽  
pp. 3164-3169
Author(s):  
Mohamed M. M. El-Sokary ◽  
Al-Shimaa Al-H. H. El-Naby ◽  
Amal R. Abd El Hameed ◽  
Karima Gh. M. Mahmoud ◽  
T. H. Scholkamy

Background and Aim: Despite many trials, buffalo embryos have poor cryosurvivability because of their high lipid content. L-carnitine was found to be a lipid-reducing agent when added to oocyte and embryo culture media. The study aimed to determine the most effective concentration of L-carnitine to improve the oocyte developmental competence and cryotolerance of buffalo embryos. Materials and Methods: In vitro maturation and embryo culture media were supplemented with four concentrations of L-carnitine: 0 (control), 0.25, 0.5, and 1 mM. Good-quality embryos on 7 days were vitrified using mixtures of dimethyl sulfoxide and ethylene glycol at two concentrations (3.5 and 7 M). Results: The result showed that the cleavage and morula rates were significantly (p<0.05) higher in the 0.5 mM group. Blastocyst rates were significantly (p<0.05) higher at both 0.5 and 1 mM. The rates of viable embryos directly after thawing were significantly (p<0.05) increased in the 0.5 mM group. No significant difference was found in embryos cultured for 24 h after warming among all the groups. Conclusion: The addition of L-carnitine at a concentration of 0.5 mM to the culture media improves the oocyte developmental competence and cryotolerance of buffalo embryos directly after warming but not after 24 h of culture. Nevertheless, further studies must identify how L-carnitine exerts its beneficial micromechanisms.


2014 ◽  
Vol 26 (1) ◽  
pp. 154 ◽  
Author(s):  
D. Moreno ◽  
A. Neira ◽  
L. Dubreil ◽  
L. Liegeois ◽  
S. Destrumelle ◽  
...  

In the majority of media for embryo culture, 2 of typical components used are FCS or BSA; however, the presence of FCS in the culture medium has been shown to have a negative effect on embryo quality and the use of animal-derived proteins in culture media increases the risks of disease transmission through in vitro embryo production. The aim of this study was to develop an in vitro embryo culture medium free from FCS and BSA, but with the addition of various growth factors and cytokines (GF-CYK: IGF-I, IGF-II, bFGF, LIF, GM-CSF) 50 ng mL–1 and (TGF-β1) 100 ng mL–1 supplemented with hyaluronan (HA) and recombinant albumin (RA). Bovine oocytes (n = 1043, 6 replicates) from abattoir ovaries were matured in TCM-199 medium with 60 μg mL–1 penicillin, 60 μg mL–1 streptomycin, and 10 ng mL–1 EGF for 24 h at 39°C and 5% CO2 in humidified air. Afterward, the oocytes were fertilized in IVF-TALP medium with 6 mg mL–1 fatty acid-free BSA and 1.7 IU mL–1 heparin for 18 h under the same conditions. After fertilization, presumptive zygotes were divided into two groups and cultured in 30 μL droplets of SOF supplemented with (1) 0.4% BSA + 5 μg mL–1 insulin, 5 μg mL–1 transferrin, and 5 ng mL–1 selenium (ITS) as a control; or (2) GF-CYK + 0.5 mg mL–1 HA + 0.15% RA (M1). Droplets were preserved under mineral oil in a humidified atmosphere of 5% CO2, 5% O2, and 90% N2 at 39°C. Blastocyst development and blastocyst diameter was observed at 7 and 8 days post-fertilization (dpf). Developmental and diameter data were analysed using the Wilcoxon test by using R software. The blastocyst rates were not significantly different between the control and M1 medium: at 7 dpf (22.9% ± 4.8 and 30.2% ± 3.0), and at 8 dpf (29.6% ± 5.1 and 37.4% ± 2.0 respectively; P > 0.05). The blastocyst diameter obtained with the M1 medium was significantly greater (P < 0.05) than that of the control at 7 dpf (173.3 μm ± 4.9 and 157.2 μm ± 4.1, respectively); however, no significant differences were observed at 8 dpf (190.3 μm ± 5.2 and 179.7 μm ± 5.3, respectively). In conclusion, the FCS- and BSA-free medium with GF-CYK, HA, and RA (M1) showed a comparable development rate to the control medium at 7 and 8 dpf. These growth factors and cytokines in association with hyaluronan and recombinant albumin have a synergistic action by promoting an increase in the blastocyst diameter at 7 dpf. This is fully synthetic method of embryo culture; it presents a valuable tool to reduce the risks of disease transmission via embryo transfer.


2016 ◽  
Vol 28 (2) ◽  
pp. 131
Author(s):  
M. D. Snyder ◽  
J. H. Pryor ◽  
M. D. Peoples ◽  
G. L. Williamson ◽  
M. C. Golding ◽  
...  

Epigenetic patterns established during early bovine embryogenesis via DNA methylation and histone modification patterns are essential for proper gene expression and embryonic development. We have previously discovered that suppression of absent, small, or homeotic-like (ASH2L) with small interfering RNA (siRNA) had no significant effect during in vitro embryo development when compared with its respective control (31.3 ± 2.0% standard error of the mean, n = 466 v. 34.8 ± 1.9%, n = 418). Analysing DNA methylation and histone modifications via immunocytochemistry will further explain the role of ASH2L during embryonic development, specifically at the blastocyst stage. In this experiment, we obtained mature bovine oocytes from a commercial supplier (De Soto Biosciences, Seymour, TN) and preformed IVF following standard laboratory protocol. Eighteen hours after IVF, presumptive zygotes were divided into 3 treatments: noninjected controls, nontargeting siRNA injected controls (siNULL), and injection with siRNA targeting ASH2L (siASH2L). Each embryo was injected with ~100 pL of 20 nM siRNA previously verified to suppress expression of ASH2L by ~79%. Embryos were cultured in Bovine Evolve (Zenith Biotech, Guilford, CT) supplemented with 4 mg mL–1 of BSA (Probumin, Millipore) for 7 days. Blastocysts from each treatment (N = 601) were fixed and prepared for immunocytochemistry following standard laboratory protocol. The following primary antibodies were used to target specific DNA and histone methylation marks: 5mc mAb (Epigentek, Farmingdale, NY), 5hmc pAb, H3K4me3 pAb (Active Motif, Carlsbad, CA), H3K4me2 pAb, H3K9me2–3 mAb, and H3K27me3 mAb (Abcam, Cambridge, MA). Embryos were fluorescently labelled with the following secondary antibodies: Alexa Flour 488 Goat Anti-Rabbit, Alexa 488 Donkey Anti-Goat, and Alexa Flour 594 Goat Anti-Mouse (Invitrogen, Carlsbad, CA). The DNA was stained with Hoechst 33342 (Invitrogen). Fluorescent images were captured using the Zeiss Stallion digital imaging work station. Ratio averages (targeting mark/DNA) were calculated and statistical analysis performed using one-way ANOVA and Tukey’s honestly significant difference to assess treatment effects. The ratio of DNA methylation to total DNA increased in siASH2L as compared with control and siNULL embryos (0.35 ± 0.01, 0.26 ± 0.02, and 0.30 ± 0.01, respectively; P < 0.01). The 5hmC was inversely related to 5mC levels and decreased in siASH2L embryos (0.75 ± 0.01, 0.93 ± 0.02, 0.87 ± 0.02, respectively; P < 0.0001). The H3K4me3 and H3K27me3 are also inversely related with decreased H3K4me3 in siASH2L versus control and siNULL embryos (0.48 ± 0.02, 0.57 ± 0.02, 0.58 ± 0.02, respectively; P < 0.001) and increased H3K27me3 (0.62 ± 0.02, 0.053 ± 0.01, 0.54 ± 0.02, respectively; P < 0.001). No differences were observed in H3K9me2–3 or H3K4me2 labelling across treatments. These results indicate that ASH2L may play a role in DNA methylation by decreasing 5mc and 5hmc conversion, which is a key event during early embryonic development. Suppression of ASH2L also alters global levels of H3H4me3 and H3K27me3, which may lead to transcription aberrations. Further analysis of siASH2L embryos via RNA-seq will help define its role during early embryonic development.


2018 ◽  
Vol 36 (03/04) ◽  
pp. 211-220 ◽  
Author(s):  
Sneha Mani ◽  
Monica Mainigi

AbstractAssisted reproductive technologies (ARTs) lead to an increased risk for pregnancy complications, congenital abnormalities, and specific imprinting disorders. Epigenetic dysfunction is thought to be one common mechanism which may be affecting these outcomes. The timing of multiple ART interventions overlaps with developmental time periods that are particularly vulnerable to epigenetic change. In vitro embryo culture is known to impact blastocyst development, in vitro fertilization (IVF) success rates, as well as neonatal outcomes. Embryo culture, in contrast to other procedures involved in ART, is obligatory, and has the highest potential for causing alterations in epigenetic reprograming. In this review, we summarize progress that has been made in exploring the effects of embryo culture, culture media, and oxygen tension on epigenetic regulation in the developing embryo. In humans, it is difficult to isolate the role of embryo culture on epigenetic perturbations. Therefore, additional well-controlled animal studies isolating individual exposures are necessary to minimize the epigenetic effects of modifiable factors utilized during ART. Findings from these studies will likely not only improve IVF success rates but also reduce the risk of adverse perinatal outcomes.


Zygote ◽  
2012 ◽  
Vol 21 (2) ◽  
pp. 203-213 ◽  
Author(s):  
S. Eswari ◽  
G. Sai Kumar ◽  
G. Taru Sharma

SummaryThe objective of this study was to evaluate the effect of supplementation of recombinant leukaemia inhibitory factor (LIF) in culture media on blastocyst development, total cell number and blastocyst hatching rates and the reverse transcription-polymerase chain reaction analysis of preimplantation buffalo embryos to determine whether they contain the LIF-encoding mRNA and its beta receptor (LIFRβ) genes in different stages of preimplantation buffalo embryos. Cumulus–oocyte complexes retrieved from slaughterhouse buffalo ovaries were matured in vitro and fertilized using frozen buffalo semen. After 18 h of co-incubation with sperm, the presumptive zygotes were cultured in modified synthetic oviductal fluid without (control) or with rhLIF (100 ng/ml). There was no significant difference in the overall cleavage rate up to morula stage however the development of blastocysts, hatching rate and total cell numbers were significantly higher in the LIF-treated group than control. Transcripts for LIFRβ were detected from immature, in vitro-matured oocytes and in the embryos up to blastocyst stage, while transcripts for the LIF were detected from 8–16-cell stage up to blastocyst, which indicated that embryo-derived LIF can act in an autocrine manner on differentiation process and blastocyst formation. This study indicated that the addition of LIF to the embryo culture medium improved development of blastocysts, functional (hatching) and morphological (number of cells) quality of the blastocysts produced in vitro. The stage-specific expression pattern of LIF and LIFRβ mRNA transcripts in buffalo embryos indicated that LIF might play an important role in the preimplantation development and subsequent implantation of buffalo embryos.


2020 ◽  
Vol 1 (1) ◽  
pp. 1-14
Author(s):  
Mitchel C. Schiewe ◽  
Shane Zozula ◽  
Nancy L. Nugent ◽  
John B. Whitney ◽  
Ilene Hatch ◽  
...  

Objective: To develop and validate a reliable in vitro culture system for human embryos. Design: Retrospective analyses of a series of four studies were conducted between 2006 and 2010 to assess the effect of incubator type (CO2 box versus Tri-gas minibox), media type, oil type, and hyaluronate supplementation. Optimization of in vitro blastocyst development was verified by assessing our National CDC/ART Surveillance reports between 2010 and 2016. Material and Methods: All patients experienced controlled ovarian hyperstimulation, followed by egg retrieval 35 h post-hCG. Cumulus-oocyte complexes were temporarily cultured in P1 or LG Fert medium plus HSA. Eggs were moved to a more complex media (G-medium or Global®-LG medium) containing a synthetic protein and embryo adhesion supplement (SPS and EAS, respectively; mLG) post-ICSI insemination. Zygotes were assigned to group culture in 25 µl droplets under oil (light mineral oil or paraffin oil; 37 °C) and embryo development was evaluated on Days 3, 5, and 6 and transferred on Day 3 to 5 depending on the number/quality of embryos available and the IVF history of the patient. Transfers were performed under ultrasound guidance, primarily using a Sureview-Wallace catheter, and enriched ET medium containing 500 µg/mL EAS. Results: Pilot study results (Expt. 1) showed that a mLG single-step medium could be effectively used in combination with Sanyo MCO-5 tri-gas (TG) incubators. Once adapted to SCIRS Lab in 2007 (Expt. 2), the latter culture system yielded improved blastocyst production and pregnancy outcomes compared to CO2 in air sequential incubation in P1/Multi-blast medium. In Expt. 3, the mLG/TG system yielded high levels of ≥2BB quality blastocysts (51 to 66%) across all age groups, and greater (p < 0.05) pregnancy success/live birth rates using fewer embryos transferred on Day 5 versus Day 3. After validating its clinical effectiveness, mLG was then prospectively compared to a new generation G-media (1.5 & 2.5; Expt. 4) and determined that the crossover treatment using paraffin oil (Ovoil™) allowed the mLG system to be optimized. Subsequently, a compilation of our Annual CDC/ART reported data over six years verified the overall viability of in vitro cultured and vitrified blastocysts produced in the mLG/TG system. Conclusion: By systematically evaluating and implementing various components of an embryo culture system we were able to optimize blastocyst development over the last decade. Our mLG/TG culture system modified an exceptionally well designed KSOMAA LG medium using endotoxin-free EAS and SPS additives to support cellular membrane wellness under stressful in vitro conditions (e.g., culture, cell biopsy, vitrification). Our use of the mLG/TG culture system has proven to be effective, creating reliably high blastocyst production, implantation, and healthy live births.


2015 ◽  
Vol 27 (1) ◽  
pp. 124 ◽  
Author(s):  
T. Somfai ◽  
N. T. Men ◽  
H. Kaneko ◽  
J. Noguchi ◽  
S. Haraguchi ◽  
...  

Cryotop and solid surface vitrification are frequently used methods for the cryopreservation of porcine oocytes. These methods differ not only in the vitrification carrier but also in the cryoprotectant (CPA) treatment including the type of sugar, permeable CPA (pCPA) combinations, and the equilibration regimen. This study compared the distinct points of CPA treatment of these 2 methods to determine the optimum CPA treatment for the solid surface vitrification of immature porcine oocytes. We vitrified and warmed follicular cumulus-oocyte complexes by our method (Somfai et al. 2014 PLoS One 9, e97731). In each experiment, the vitrification solution consisted of 50 mg mL–1 polyvinyl pyrrolidone, 0.3 M of the actual sugar, and 35% [v/v] in total of the actual pCPA combination (depending on the experiment). After warming, the cumulus-oocyte complexes were subjected to in vitro maturation, IVF, and embryo culture (Kikuchi et al. 2002 Biol. Reprod. 66, 1033–1041). Oocyte survival was assessed after IVF by morphological evaluation, and live oocytes were subjected to in vitro embryo culture. Cleavage and blastocyst rates were calculated from cultured oocytes on Day 2 (Day 0 = IVF) and Day 6, respectively. Each experiment was replicated at least 3 times. Results were analysed by ANOVA. In Experiment 1, we compared trehalose (n = 416) and sucrose (n = 440) as supplementations during vitrification and warming (0.3 M and 0.4 M of each, respectively). There was no significant difference between oocytes vitrified with trehalose or sucrose in terms of survival, cleavage, and blastocyst development (83.2% v. 80.3%, 39.7% v. 42.4%, and 3.6% v. 5.9%, respectively). Thus, vitrification and warming media were supplemented with sucrose thereafter. In Experiment 2, we compared 1 : 1 combinations of ethylene glycol with propylene glycol (EG+PG group, n = 452) and ethylene glycol with dimethyl sulfoxide (EG+DMSO group, n = 465) used as pCPA for equilibration (4% [v/v] pCPA in total for 15 min) and vitrification (35% [v/v] pCPA in total for 30 s). Oocyte survival rate was higher (P < 0.05) in the EG+PG group compared with the EG+DMSO group (73.8% v. 51.1%, respectively); however, cleavage and blastocyst development rates of surviving oocytes were not significantly different between the 2 groups (30.5% v. 44.5% and 4.1% v. 6.3%, respectively). In Experiment 3, we compared an equilibration treatment in 4% [v/v] of EG+PG for 13 to 15 min (regimen A, n = 368) with an equilibration in 15% [v/v] of EG+PG for 5 to 7 min (regimen B, n = 363) for oocyte vitrification. Survival, cleavage, and blastocyst development rates were higher (P < 0.01) for oocytes vitrified using regimen A compared with those vitrified using regimen B (82.5% v. 22.7%, 24.0% v. 7.7%, and 3.2% v. 0%, respectively). In conclusion, trehalose and sucrose are equally effective during vitrification and warming, the combination of EG+PG as pCPA is superior to EG+DMSO, and equilibration in 4% pCPA for 13 to 15 min is superior to that in 15% pCPA for 5 to 7 min for the vitrification of immature porcine oocytes.This work was partly supported by JSPS KAKENHI Grant Number 26870839.


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