Effect of sperm pooling with seminal plasma collected in breeding or nonbreeding season on Saanen goat sperm cryosurvival

The aim of this study was to determine the effects of both the removal of seminal plasma (SP) and the pre-freezing addition of seminal plasma collected during the breeding or nonbreeding season on goat sperm survival after thawing. Semen samples were pooled. One aliquot of pooled semen was used as a control group. Four aliquots were then centrifuged, and the SP was removed in Group I, pipetted but not removed in Group II, removed and then pooled for animals collected in the breeding season in Group III and removed and pooled for animals collected in the nonbreeding season in Group IV. Group samples were frozen and then were assessed for rates of sperm motility, plasma membrane functional integrity hypo-osmotic swelling test (HOST), defective acrosomes (FITC-PSA), DNA fragmentation (TUNEL) and mitochondrial membrane damage (Rhodamine 123). The results showed that pre-freezing addition of SP collected in breeding season maintained post-thaw sperm characteristics at 0 hr better than SP removal group, but removing seminal plasma showed positive effects on spermatozoa, as incubation time increased to 5 hr. In conclusion, the pre-freezing addition of seminal plasma did not maintain post-thaw goat sperm characteristics as successfully as in the groups with seminal plasma removed after an incubation period.

22 SEMEN AND REPRODUCTIVE PROFILES OF CLONED ANATOLIAN GREY CATTLE

Anatolian grey cattle (endangered native Anatolian cattle) as 1 male (clone 1) and 4 females (clones 2–5) were produced from cells of 1 male and 1 female cattle by somatic cell nuclear transfer (SCNT) in a previous study. In this study, we examined the reproductive potential of these cloned animals, which are now 4 and 5 years old. The parameters evaluated by phase contrast microscopy for motility, TUNEL for DNA fragmentation, eosin staining for viability, Hoechst 33258 staining and hypo-osmotic swelling test (HOST) for membrane integrity, and fluorescein isothiocyanate-Pisum sativum agglutinin (FITC-PSA) for acrosome integrity of frozen-thawed spermatozoa, as well as birth and survival of calves following insemination with frozen-thawed semen of cloned and nuclear donor bull and normal bull. Six ejaculates and 3 samples per ejaculate from each bull were tested, and the Mann-Whitney U test was used to analyse the data. The spermatological parameters of cloned bull semen – volume, concentration, and motility of fresh – were within accepted limits for artificial insemination (4.60 ± 0.47 mL, 1.55 ± 0.21 × 109 spermatozoa mL–1, 80.00 ± 1.07%, respectively). Frozen-thawed sperm motility and viability rate were higher in the cloned bull (56.6%, 56.7%) than in its nuclear donor (47%, 43%; P < 0.05). Intact membrane and DNA fragmentation rate of cloned bull and its nuclear donor bull sperm were similar (P > 0.05) but the intact acrosome rate of cloned bull was higher than that of its nuclear donor (P < 0.05). Low rates in frozen-thawed sperm of nuclear donor can be related to storage time of sperm which were frozen 5 years before. One (clone 4) of the cloned grey heifers was artificially inseminated with frozen semen from nuclear donor bull and the other (clone 5) was naturally mated with a Holstein bull. Two healthy calves were delivered naturally. When same cloned cows (clones 4–5) and 2 other cloned heifers (clones 2–3) were artificially inseminated with frozen semen of the cloned grey bull, clones 2 and 4 gave birth to 2 healthy female calves. One cloned cow (clone 3) aborted in the third month of gestation and other one (clone 5) is currently 8 months pregnant. Two calves of clone 4 and 5 are 17 months old and 2 other calves of clone 2 and 4 are now 6 and 1 months old. Except for clone 3, our results show that cloned Anatolian grey bull and cows produced from frozen cells in gene bank have normal fertility.

150 IN VITRO AND IN VIVO DEVELOPMENT OF EMBRYO FOLLOWING BIOPSY WITH DIFFERENT TECHNIQUES IN MOUSE EMBRYOS

In vitro development ratios, quality evaluation, in vivo implantation, and fetal development ratios were investigated following aspiration biopsy in 8-cell mouse embryos and trophectoderm biopsy in blastocyst developed from 8-cell stage embryos in vitro. Superovulated CB6F1 hybrid female mice (5–6 weeks) were sacrificed 68 to 72 hours after hCG administration. Eight-cell embryos were flushed from oviducts of the sacrificed mouse with HTF medium supplemented with HEPES and 3 mg mL–1 BSA. Embryos were randomly divided into two groups. In the first group, embryos at 8-cell stage were used for a single cell blastomer aspiration; in the second group, embryos were cultured in vitro until blastocyst stage. Trophectoderm cells (15% of trophoblastic cells) were biopsied from developing blastocysts. There were also control groups for both groups. Biopsy procedures for both groups were applied in 50 µL drops of Ca2+/Mg2+ free HTF medium containing HEPES+3 mg mL–1 BSA+5 µg mL–1 cytochalasine B. After biopsy, embryos were cultured in Quinn’s blastocyst medium supplemented with 4 mg mL–1 BSA and incubated in 5% CO2 and 5% O2 incubator at 37°C for 48 and 24 hours for blastomer aspiration and trophectoderm biopsy groups, respectively. While some developing blastocysts were used for determining total cell number, some of them were transferred to the recipients. Results were evaluated by independent t-test and ANOVA of SPSS 17.0 statistic program (SPSS Inc., Chicago, IL, USA). In blastomere biopsy and control groups, development rates were determined as 81.02% (121/152) and 96.37% (62/63), while the total cell numbers were determined as 50 and 50, respectively. There was no significant difference between groups in terms of development ratios and total cells. In blastomer biopsy and control groups, the implantation sites and fetal development rates were found as 25% (9/36) and 26% (8/30), and 19.44% (7/36) and 20% (6/30), respectively. No significant difference was observed between groups in terms of implantation sites and fetal development rates. In trophectoderm biopsy and control groups, while the development rates were found as 86.96% (69/79) and 93.33% (23/28), the total cell numbers were 26.66 and 55.33, respectively. Although there was not any significant difference between groups in terms of development rates, there was a significant difference between groups in terms of total cell numbers (P < 0.05). In trophectoderm biopsy and control groups, the implantation sites and fetal development rates were determined as 21.88% (7/32) and 59.09% (13/22), and 0% (0/32) and 18.18% (4/22), respectively. Although there was not any significant difference between groups in terms of implantation sites, there was a significant difference between groups in terms of fetal development rates (P < 0.05). Therefore, it was concluded that biopsy applied at early stage of embryonic development does not affect embryo development negatively and biopsy procedures applied at early developmental stages have more advantages especially in embryos developing faster with low total cell numbers such as mouse species. Supported by TUBITAK KAMAG-107G027).

177 GENE EXPRESSION PROFILES OF IN VITRO- AND IN VIVO-DERIVED BOVINE EMBRYOS

Microarray technology is one of the most powerful tools for gene expression profiling in animal sciences. The objectives of this study were to determine the effect of vitrification on gene expression in in vitro- and in vivo-derived bovine embryos, and to identify differential mRNA expression patterns between embryos produced by in vivo v. in vitro conditions. Three pools of in vivo- and in vitro-derived blastocyst-stage embryos were used for microarray analysis. Total RNA was isolated using the PicoPure RNA Isolation Kit (Arcturus Bioscience, Mountain View, CA). Bovine ovarian tissue total RNA was used as the reference. Total RNA samples were amplified using an Ovation® Pico WTA System (NuGEN Technologies, San Carlos, CA). The bovine 16 846-member microarrays spotted with 70-mer oligonucleotides were purchased from the Bovine Genomics Laboratory, University of Missouri. Amplified cDNA samples were labeled with Alexa Fluor 647 and 546 dyes (Molecular Probes, Eugene, OR), respectively. Combined, labeled samples were dried and resuspended in hybridization buffer containing 50% formamide (vol/vol), 5× SSC, and 0.1% sodium dodecyl sulfate (wt/vol). After denaturation and cooling, cDNA was applied onto a microarray slide. Microarrays were hybridized overnight at 42°C. Following hybridization, the slides were washed with different stringency buffers and water. After drying by centrifugation, the arrays were scanned on a GenePix 4000B scanner (Axon Instruments, Union City, CA). GenePix Pro4.1 software was used for griding and analysis of spot intensities. Good-quality spots were analyzed using the GeneSpring 7.3 software (Agilent Technologies, Inc., CA, Santa Clara, CA). The data were normalized per spot and per array by Lowess normalization. When comparing two treatments, the Welch t-test with Benjamini and Hochberg multiple testing correction was performed to determine the differentially expressed genes between embryo groups. Microarray experiments were performed in 3 biological and 2 technical replicates for all embryo samples. Differentially expressed genes between all embryo groups were identified. The DAVID Functional Annotation Tool was used to analyze the genes that were differentially expressed. The DAVID Functional Annotation Tool determined the co-occurrence probability and provided gene-GO term enrichment analysis to highlight the most relevant GO terms associated with a given gene list. Differentially expressed Kyoto Encyclopedia of Genes and Genomes pathways are as follows: Ribosome, oxidative phosphorylation, spliceosome, and oocyte meiosis were significantly upregulated in the fresh embryos, whereas sphingolipid and purine metabolism was the upregulated in the vitrified in vitro-derived embryos. Gene expression was very similar between fresh and vitrified in vivo-derived, as opposed to in vitro-derived, embryos. This study was funded by the TUBITAK (Project no. KAMAG107G027) and startup funds to Yuksel Agca at the University of Missouri.

21 CLONING OF ANATOLIAN GREY BULL

One of the application fields of nuclear transfer (NT) is to increase the population of endangered mammals. In the present study, cloning of native Anatolian Grey Cattle living semi-wildly especially in the Marmara Region was aimed. Bovine oocytes isolated from slaughterhouse ovaries were matured in TCM-199 supplemented with 10% fetal bovine serum (FBS), 50 μg mL–1 of sodium pyruvate, 1% v/v penicillin-streptomycin (10.000 U mL–1 of penicillin G, 10 000 mg mL–1 of streptomycin), 50 ng mL–1 of epidermal growth factor, 0.5 μg mL–1 of FSH, 5 μg mL–1 of LH (Arat et al. 2004 Reprod. Fertil. Dev. 16, 135). After removing the cumulus cells of matured oocytes (MII), meiotic spindles and first polar bodies were removed. As nuclear material source, cartilage and fibroblast cells obtained from the ear tissue of 3-year-old Anatolian Grey Bull were used. This animal is kept under the National Conservation Program of the Turkish Government. Prior to NT, all somatic cells were allowed to grow to confluency (G1/G0) in DMEM-F12 supplemented with 10% FBS (Arat et al. 2002 Biol. Reprod. 66, 1768–1774). After transfer of single cells to enucleated oocytes, oocyte-cell couples were fused by a DC pulse of 2.66 kV cm–1 for 30 μs in the Zimmerman medium. After fusion, fused NT units were activated using a combination of calcium ionophore (5 μm for 5 min), cytochalasin D (2.5 μg mL–1) and cycloheximide (CHX, 10 μg mL–1) for 1 h and CHX alone for 4 h. In the first experiment, after activation, NT units were cultured in Sage cleavage medium (Cooke et al. 2002 Fertil. Steril. 78, 1254–1260; Tang et al. 2006 Hum. Reprod. 21, 1179–1183) supplemented with 8 mg mL–1 of BSA for 72 h and then developing embryos were divided into 4 groups. After 72 h of culture, all cleaved embryos from cartilage cells in groups I, II, III, and IV were respectively cultured in Sage blastocyst media supplemented with 8 mg mL–1 of BSA, 8 mg mL–1 of BSA + 5% FCS, 4 mg mL–1 of BSA + 5% FCS, and 4 mg mL–1 of BSA + 100 ng mL–1 of insulin-like growth factor for additional 4 days. Differences among groups were analyzed by one-way ANOVA after arcsin square transformation (P = 0.05). In group III, development rate to blastocyst (27.3%) was significantly higher than the other groups (18.2, 21.2, and 15.0% for groups I, II, and IV, respectively). In the second experiment, development rates of embryos from cartilage or fibroblast cells, cultured in the group III medium treatment above, were compared. Development rate to blastocyst of 1-cell embryos from cartilage cells (30.8%) was significantly higher than the rate of embryos from fibroblast cells (20.8%). Forty-two good quality embryos from cartilage cells and 11 embryos from fibroblast cells were transferred into 23 Holstein dairy recipient cows (2–5 blastocysts/cow). Day 35 pregnancies were diagnosed in 10 cows from cartilage cells (53% 10/19; one of them was over to 100 days) and in 1 cow from fibroblast cells (50% 1/2). Two recipient cows carrying embryos from fibroblast cells were not yet examined for pregnancy. This cloning study is the first on the Anatolian Grey Cow and is still going on. This study was supported by grants from TUBITAK, Turkey (TOVAG-104O360 and KAMAG-106G005).

Bovine germinal vesicle oocyte and cumulus cell proteomics

Germinal vesicle (GV) breakdown is fundamental for maturation of fully grown, developmentally competent, mammalian oocytes. Bidirectional communication between oocytes and surrounding cumulus cells (CC) is essential for maturation of a competent oocyte. However, neither the factors involved in this communication nor the mechanisms of their actions are well defined. Here, we define the proteomes of GV oocytes and their surrounding CC, including membrane proteins, using proteomics in a bovine model. We found that 4395 proteins were expressed in the CC and 1092 proteins were expressed in oocytes. Further, 858 proteins were common to both the CC and the oocytes. This first comprehensive proteome analysis of bovine oocytes and CC not only provides a foundation for signaling and cell physiology at the GV stage of oocyte development, but are also valuable for comparative studies of other stages of oocyte development at the molecular level. Furthermore, some of these proteins may represent molecular biomarkers for developmental potential of oocytes.

Dynamics of global transcriptome in bovine matured oocytes and preimplantation embryos

Global activation of the embryonic genome is the most critical event in early mammalian development. After fertilization, a rich supply of maternal proteins and RNAs support development whereas a number of zygotic and embryonic genes are expressed in a stage-specific manner leading to embryonic genome activation (EGA). However, the identities of embryonic genes expressed and the mechanism(s) of EGA are poorly defined in the bovine. Using the Affymetrix bovine-specific DNA microarray as the biggest available array at present, we analyzed gene expression at two key stages of bovine development, matured oocytes (MII) and 8-cell-stage embryos, constituting the ultimate reservoir for life and a stage during which EGA takes place, respectively. Key genes in regulation of transcription, chromatin-structure cell adhesion, and signal transduction were up-regulated at the 8-cell stage as compared with 8-cell embryos treated with alpha-amanitin and MII. Genes controlling DNA methylation and metabolism were up-regulated in MII. These changes in gene expression, related to transcriptional machinery, chromatin structure, and the other cellular functions occurring during several cleavage stages, are expected to result in a unique chromatin structure capable of maintaining totipotency during embryogenesis and leading to differentiation during postimplantation development. Dramatic reprogramming of gene expression at the onset of development also has implications for cell plasticity in somatic cell nuclear transfer, genomic imprinting, and cancer.

265 DEVELOPMENT AND DYNAMICS OF GENE EXPRESSION OF BOVINE EMBRYOS CULTURED IN VITRO IN THREE DIFFERENT MEDIA

Dramatic reprogramming of gene expression occurs during embryonic genome activation (EGA), an essential event initiating as early as the 1-cell zygotic stage in the bovine and increasing gradually as embryonic development advances. It is this reprogramming of gene expression that sets the stage for later development. Expression of embryonic genes is altered in different culture conditions and this may influence developmental potential both during pre-implantation and during fetal development. The objective of this study was to define some most commonly used embryo culture media (KSOMaa, CR1aa, and SOFaa) based on their ability to support embryonic development to the blastocyst stage, mean cell number, percentages of apoptotic cells, and the expression patterns of a panel of developmentally important genes. Oocytes with several layers of cumulus cells obtained from an abattoir were matured in TCM 199 (supplemented with 0.25 mM pyruvate, 0.5 μg/mL FSH, 5 μg/mL LH, 100 U/mL penicillin, 100 μg/mL streptomycin, and 10% FCS) for 24 h and in vitro-fertilized (Day 0) using frozen bull semen. Presumptive zygotes were transferred into three different media (KSOMaa, CR1aa, and SOFaa) 16–18 h post-insemination, supplemented with 10% FCS on Day 4, and cultured until Day 8 at which time they were fixed or frozen for further analysis. Mean cell numbers and percentages of apoptotic cells in blastocysts were determined using terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL). Real-time quantitative PCR was performed to assess gene transcripts of glucose transporter-1 (Glut-1), heat shock protein 70.1 (Hsp70), interferon-tau (IF-tau), insulin-like growth factor II receptor (Igf-2r), desmosomal glycoprotein desmocollin III (DcIII), and DNA methyltransferase 3a (Dnmt3a). Gene expression data were analyzed relative to transcripts of housekeeping gene glyceraldehyde 3-phosphate dehydrogenase (Gapdh). In three separate trials, a total of 538, 518, and 503 oocytes were used for KSOMaa, CR1aa, and SOFaa groups, respectively. Cleavage rates were 79.2%, 77.5%, and 80.2%; and rates of development to the blastocyst stage were 22.2%, 23.4%, and 32.9% for KSOMaa, CR1aa, and SOFaa groups, respectively. The blastocyst rate of the SOFaa group was significantly higher than those of the KSOMaa and CR1aa groups (P < 0.05). Mean cell numbers were 109.3, 101.0, and 114.0; and the percentages of apoptotic cell numbers per blastocyst were 1.25, 1.91, and 1.87 for KSOMaa, CR1aa, and SOFaa groups, respectively. There was no difference among groups in terms of mean cell numbers and percentages of apoptotic cells per blastocyst. The expressions of Glut-1 and DcIII genes did not differ among the groups. However, expressions of Hsp70, IF-tau, and Dnmt3a genes were all significantly up-regulated in the CR1aa group as compared to the SOFaa and KSOMaa groups (P < 0.05). In conclusion, SOFaa supports higher development to the blastocyst stage than KSOMaa and CR1aa, and culture conditions influence gene expression.

166 EFFECTS OF LEPTIN AND IGF-1 ON PRE-IMPLANTATION DEVELOPMENT, DNA FRAGMENTATION, AND GENE EXPRESSION OF BOVINE EMBRYOS CULTURED IN VITRO

Adequate regulatory proteins, growth factors, and hormones in in vitro embryo culture systems are important for improving the quality of embryos to a level similar to that in vivo conditions. The objective of this study was to define the effects of leptin, insulin-like growth factor-1 (IGF-1), and their combination on embryonic development, apoptosis, and expression profiles of a panel of developmentally important genes. Presumptive zygotes (16–18 h post-insemination) were randomly assigned and cultured in control (no supplementation), 5 ng/mL leptin (Group I), 100 ng/mL IGF-1 (Group II), and 5 ng/mL leptin and 100 ng/mL IGF-1 (Group III), all supplemented with 10% FCS on Day 4. On Day 8, the embryos reaching blastocyst stage were randomly either fixed for determination of DNA-fragmented nuclei by using terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling (TUNEL) or frozen for real-time relative quantitative RT-PCR analysis. The RT-PCR was performed to assess gene transcripts of glucose transporter-1 (Glut-1), heat shock protein 70.1 (Hsp70.1), interferon tau (IF-tau), insulin-like growth factor II receptor (IGF-IIr), desmosomal glycoprotein desmocollin III (DcIII), and DNA methyltransferase 3a (Dnmt3a). A total of 349, 322, 347, and 360 zygotes were used for the control group and Groups I, II, and III, respectively. Data were analyzed with a randomized complete block design and arcsine square root transformation of the dependent variables consisting of four treatments and six replicates. Cleavage rates were 79.5, 84.2, 87.3, and 82.4% for the control group and Groups I, II, and III, respectively, and only Group II was different from the control (P < 0.05). The percentages of embryos developed beyond the 8–16 cell stage were 44.2, 48.2, 49.0, and 50.7 for the control group and Groups I, II, and III, respectively, and Group III was different from the control (P < 0.05). Percentages of blastocyst development were 26.7, 29.6, 31.5, and 29.8, and the mean blastocyst cell numbers were 96.6, 98.6, 104.4, and 104.1 for the control group and Groups I, II, and III, respectively. The percentage of nuclei with fragmented DNA were 4.2, 3.3, 2.5, and 1.9 for the control group and Groups I, II, and III, respectively. Addition of IGF-1 and/or combination with leptin (Groups II and III) decreased the number of nuclei with fragmented DNA (P < 0.01) as compared to the control group. Although the expression of Glut1, DcIII, and Igf2r did not change among the groups, IF-tau and Dnmt3a were down-regulated in Group II. Hsp70 and IF-tau were up regulated in Group III. Results indicate that addition of IGF-I in culture media improved the cleavage rate; combination with leptin also improved the development rates to 8–16-cell-stage embryos, decreased the TUNEL-positive nuclei, and altered expression of some of the developmentally important genes.

25COLD STORAGE OF TISSUES AS SOURCE FOR DONOR CELLS DOES NOT REDUCE THE IN VITRO DEVELOPMENT OF BOVINE EMBRYOS FOLLOWING NUCLEAR TRANSFER

So far, most calves have been cloned from live adult cows or fresh fetal samples. There are few reports on using cells from a dead mammal for nuclear transfer (NT). This study was conducted to investigate whether different kind of viable cells could be obtained from tissues stored in cold for different duration and whether these cells could be used for NT. Bovine oocytes isolated from slaughterhouse ovaries were matured in TCM199 supplemented with 10% fetal calf serum (FCS), 50μgmL−1 sodium pyruvate, 1% v:v penicillin-streptomycin (10.000UmL−1 penicillin G, 10.000μgmL−1 streptomycin), 10ngmL−1 EGF, 0.5μgmL−1 FSH, and 5μgmL−1LH. First cell line (CC) was established from articular cartilage of the leg of a slaughtered cow stored at 0°C in a cold storage room for 48h. Second cell line (MC) was established from leg muscle of a cow carcass stored at 0°C for 24h. Tissues from articular cartilage and muscle were cut into small pieces. Tissue explants were cultured in DMEM-F12 supplemented with 10% FBS at 37°C in 5% CO2 in air. Bovine granulosa cells (GC) were isolated from ovarian follicles and used for NT as control cells. Prior to NT, all somatic cells were allowed to grow to confluency (G1/G0) in DMEM-F12 supplemented with 10% FBS. Cumulus cells were removed by vortexing with hyaluronidase at 18h after the start of maturation. Matured oocytes labeled with DNA fluorochrome Hoechst 33342 were enucleated under UV to ensure full removal of the chromatin. A single cell was inserted into the perivitelline space of the enucleated oocyte. Oocyte-cell couples were fused by a DC pulse of 133V/500μm for 25μs. After fusion, NT units were activated using a combination of calcium ionophore (5μM), cytochalasin D (2.5μgmL−1), and cycloheximide (10μgmL−1), and cultured for 7 days. Differences among groups were analyzed by one-way ANOVA after arcsin square transformation. The results are summarized in Table 1. The results suggest that viable cells can be obtained from articular cartilage and muscle of a cow carcass stored at cold temperature for 24 and 48h and these cells have ability to generate NT blastocysts at rates similar to that of the controls. This study was supported by a grant from TUBITAK, Turkey (VHAG-1908-102V048). F Ergin is a volunteer young researcher. Table 1 In vitro development of NT embroys from different cell lines

118VITRIFICATION OF PRONUCLEAR-STAGE MOUSE EMBRYOS ON ALUMINUM FOIL FLOATING ON LIQUID NITROGEN

The cryopreservation of pronuclear-stage embryos has a special importance in transgenic technology, cloning, and human-assisted reproductive technology. The objective of this study was to investigate the efficiency of a vitrification method modified in our lab for pronuclear-stage embryos. In experiment I, groups of 10 pronuclear-stage mouse embryos were cultured in 20μL drops of three different culture media (G1.3/G2.3, CZB and M16) covered with mineral oil (Sigma M-8410, St. Louis, MO, USA). Twenty-four hours later, embryos cultured in G1.3 were transferred into G2.3 medium. In experiment II, 25–30 pronuclear-stage embryos were transferred into a 50-μL drop of equilibration medium containing 4% ethylene glycol (EG, Sigma E-9129) in TCM-199 (Sigma M-2520) supplemented with 10% FCS at 37°C for 12–15min; then they were rinsed three times in 30-μL drops of vitrification medium containing 35% EG, 5% polyvinylpyrrolidone (PVP, Sigma P-0930) and 0.4M trehalose (Sigma T-0167) in TCM-199 supplemented with 10% FCS at 37°C for 20–30s. Embryos rinsed in vitrification solution were aspirated into a micropipette as a 1–2-μL drop containing 25–30 embryos and dropped onto aluminum foil floating on liquid nitrogen (LN2). Vitrified droplets were stored in cryovials in LN2. Warming was performed by moving the vitrified droplets into 0.3M trehalose in TCM-199 supplemented with 10% FCS at 37°C. Embryos having normal morphological appearance under stereomicroscope examination were cultured in G1.3/G2.3 medium. Differences in the two experiments were analyzed by one-way ANOVA. In experiment I, development rates to the blastocyst stage were 26%, 10% and 4% for G1.3/G2.3, CZB and M16 media, respectively. The highest development rate in experiment I was obtained in G1.3/G2.3 culture media (P&lt;0.05). Therefore, G1.3/G2.3 media were used for culturing of vitrified-warmed and control embryos. In experiment II, the rate of embryos having normal morphology was 98.5%. There were no significant differences between the development rates of vitrified (13.1%) and control (18.7%) embryos to the blastocyst stage (P&gt;0.05). Although the vitrification method resulted in a high survival rate based on the morphological appearance, developmental rates of vitrified and control embryos were found to be lower than expected and reported previously by other researchers. We believe that the low developmental rates in this study were due to our culture conditions but not our vitrification method. Therefore, it could be concluded that this vitrification method is an efficient one for pronuclear-stage embryo cryopreservation and better development rates could be obtained by improving the culture conditions. This study was supported by a grant from TUBITAK, Turkey (VHAG-1908-102V048). F. Ergin is a young volunteer researcher.

Vitrification of pronuclear-stage mouse embryos on solid surface (SSV) versus in cryotube: Comparison of the effect of equilibration time and different sugars in the vitrification solution

The cryopreservation of pronuclear-stage embryos has particular importance in transgenic technology and human assisted reproductive technology (ART). The objective of this study was to improve the efficiency of cryopreservation of pronuclear-stage mouse embryos. Two vitrification methods (solid surface vitrification (SSV) vs. vitrification in cryotube) have been compared with special emphasis on the effect of the exposure of the embryos to the solutions for various times and the sugar content (trehalose, sucrose, or raffinose) of the vitrification solutions. Pronuclear-stage embryos were either exposed to 1 M dimethyl sulfoxide (DMSO) + 1 M propylene-glycol (PG) solution for 2, 5, 10, or 15 min or not exposed to this "equilibration" solution. The vitrification solutions consisted of 2.75 M DMSO and 2.75 M PG in M2 medium supplemented with 1 M trehalose (DPT), 1 M sucrose (DPS), or 1 M raffinose (DPR). In the cryotube method, groups of 15-25 embryos were transferred into a 1.8 ml cryotube containing 30 microl of DPT, DPS, or DPR. After 30 sec, the cryotubes were directly plunged into liquid nitrogen (LN(2)) and stored for 1 day to 1 month. Vitrified samples were warmed by immersing the cryotubes in a 40 degrees C water bath and then immediately diluted with 300 microl of 0.3 M trehalose, sucrose, or raffinose in M2. In the SSV method, after equilibration 15-20 embryos were exposed to DPT, DPS, or DPR solutions for around 20 sec before being dropped in 2-microl drops onto a pre-cooled (-150 to -180 degrees C) metal surface. Vitrified droplets were stored in cryovials in LN(2). Warming was performed by transferring the vitrified droplets into 0.3 M solutions of trehalose, sucrose, or raffinose at 37 degrees C, respectively. Results showed that both SSV and cryotube vitrification methods can result in high rates of in vitro blastocyst development (up to 58.3 and 68.5% with DPR, respectively), not statistically different from that of the controls (58.3 and 64.4%). Even without the equilibration step prior to vitrification, relatively high-survival rates have been achieved, except for the DPS solution. In conclusion, vitrification of pronuclear-stage mouse embryos can result in high rates of in vitro development to blastocyst, and the use of raffinose in the vitrification solution is advantageous to improve cryosurvival.

Production of transgenic mice from vitrified pronuclear-stage embryos

Cryopreservation of pronuclear-stage embryos would be useful for transgenic technology and genome preservation purposes. We compared a novel vitrification technique (solid surface vitrification, SSV) with another vitrification method in straws for cryosurvival and to generate transgenic progeny from cryopreserved mouse zygotes following microinjection. The SSV solution consisted of 35% ethylene glycol (EG), 5% polyvinyl-pyrrolidone (PVP), and 0.4 M trehalose in M2 supplemented with 4 mg/ml BSA; the in straw vitrification solution was 7 M EG in M2 plus BSA. In experiment I, we compared the effect of the vitrification solutions alone, without cooling. No reduction was detected in survival and cleavage rates. In experiment II, SSV yielded a significantly higher percentage of morphologically normal zygotes (96%) that also cleaved at significantly higher rates (80%) when compared to that following "in straw" vitrification (68 and 66%, respectively). Cleavage rate in the non-vitrified control group (93%) was significantly higher than that of both vitrified groups. Following embryo transfer, there was no difference in the rate of pups obtained from the SSV, "in straw" vitrified, and control groups (97/457, 21%; 15/75, 20% and 56/209, 27%, respectively). In experiment III, SSV vitrified and fresh embryos were used for pronuclear DNA injection. Survival rate of vitrified embryos after microinjection was reduced compared to nonvitrified ones (64 vs. 72%, respectively; P < 0.05); however, development to two-cell stage was not different (76 vs. 72%, respectively). Following embryo transfer of vitrified vs. fresh microinjected embryos, in both cases 10% live pups were generated, including transgenic pups. The results demonstrated that the efficiency of generating transgenic pups from SSV vitrified pronuclear zygotes is comparable to that from fresh embryos.