Bovine embryo culture in the presence or absence of serum: implications for blastocyst development, cryotolerance, and messenger RNA expression

New challenges in the analysis of gene transcription in bovine blastocysts

In the last years, enormous progress has been made in the analysis of gene transcription at the blastocyst stage. The study of gene expression at this early stage of development is challenging because of the very small amount of starting material, which limits the use of traditional mRNA analysis approaches such as Northern blot. Another problem is the difficulty for data normalization, particularly the identification of the best housekeeping gene with the lowest fluctuation under different developmental conditions. Moreover, the transcriptional analysis of embryo biopsies or individual embryos needs to take into consideration that the blastocyst is a transitional stage of development, which is composed of three different types of cells (trophoblast, epiblast and primitive ectoderm) with different patterns of gene expression, and that there are large differences between male and female blastocysts. In this review, we analyse the different specific and sensitive tools available to compare mRNA expression levels of specific genes at the blastocyst stage, and how the protocol and the analytical method used can influence the results dramatically. Finally, we describe future research challenges to identify candidate genes related to developmental competence of bovine blastocysts, not only in terms of pregnancy rates but also in relation to adverse long-term consequences in the adult animal.

Unravelling the needs of singly in vitro-produced bovine embryos: from cumulus cell co-culture to semi-defined, oil-free culture conditions

Producing bovine in vitro embryos individually is a challenge as it generally leads to impaired embryo development. Earlier research optimised a single embryo in vitro production (IVP) protocol using serum, cumulus cells and oil during culture. As some of these factors are undesirable in certain circumstances, the present study investigated their necessity and possible interactions, and defined their role during single-embryo culture. Although the cumulus cell monolayer produced progesterone, it appeared not to be a key factor in supporting single-embryo development. Because in vitro culture in large medium volumes was shown to impair single-embryo development, two new oil-free culture protocols were tested. Using a 30-µL droplet of medium in 96-well plates with a small surface area resulted in comparable blastocyst rates to those obtained under oil. When serum was used, co-culture with cumulus cells seems necessary, leading to consistently high blastocyst rates. Finally, a serum-free, oil-free culture system using insulin, transferrin, selenium and BSA resulted in embryos with similar total cell numbers and apoptotic cell ratios, but blastocyst rates did not equal those obtained with serum and co-culture. This research additionally stresses the fact that specific interaction mechanisms between somatic cells and a developing in vitro embryo are far from unravelled.

Effects of repetitive ionomycin treatment on in vitro development of bovine somatic cell nuclear transfer embryos

To artificially activate embryos in somatic cell nuclear transfer (SCNT), chemical treatment with ionomycin has been used to induce transient levels of Ca(2+) and initiate reprogramming of embryos. Ca(2+) oscillation occurs naturally several times after fertilization (several times with 15- to 30-min intervals). This indicates how essential additional Ca(2+) influx is for successful reprogramming of embryos. Hence, in this report, the experimental design was aimed at improving the developmental efficiency of cloned embryos by repetitive Ca(2+) transients rather than the commonly used ionomycin treatment (4 min). To determine optimal Ca(2+) inflow conditions, we performed three different repetitive ionomycin (10 µM) treatments in reconstructed embryos: Group 1 (4-min ionomycin treatment, once), Group 2 (30-sec treatment, 4 times, 15-min intervals) and Group 3 (1-min treatment, 4 times, 15-min intervals). Pronuclear formation rates were checked to assess the effects of repetitive ionomycin treatment on reprogramming of cloned embryos. Cleavage rates were investigated on day 2, and the formation rates of blastocysts (BLs) were examined on day 7 to demonstrate the positive effect of repeated ionomycin treatment. In Group 3, a significant increase in BL formation was observed [47/200 (23.50%), 44/197 (22.33%) and 69/195 (35.38%) in Groups 1, 2 and 3, respectively]. Culturing embryos with different ionomycin treatments caused no significant difference among the groups in terms of the total cell number of BLs (164.3, 158.5 and 145.1, respectively). Additionally, expression of the anti-apoptotic Bcl-2 gene and MnSOD increased significantly in Group 3, whereas the expression of the pro-apoptotic Bax decreased statistically. In conclusion, the present study demonstrated that repeated ionomycin treatment is an improved activation method that can increase the developmental competence of SCNT embryos by decreasing the incidence of apoptosis.

In vitro maturation supplements affect developmental competence of bovine cumulus-oocyte complexes and embryo quality after vitrification

Oocyte quality affects subsequent embryo development and quality. We examined the impact of bovine oocyte in vitro maturation (IVM) conditions on subsequent embryo yield, quality and cryosurvival. Cumulus-oocyte complexes (COCs) were sampled for cytological and gene expression analysis after IVM in TCM199 supplemented with 10% fetal bovine serum (FBS), 4 mg/ml of fatty-acid-free bovine serum albumin (FAFBSA), 4 mg/ml of polyvinylpyrrolidone (PVP), FAFBSA with epidermal growth factor (EGF, 100 ng/ml) and insulin-like growth factor 1 (IGF-I, 100 ng/ml) (FAFBSAGF), PVP with EGF and IGF-I (PVPGF) or PVP with single strength BME and MEM amino acids (PVPAA). The remaining COCs were fertilized. On day 7 (IVF=day 0) quality 1 blastocysts were vitrified or analyzed for glucose transporter 1 (Glut-1) expression levels. The remaining blastocysts (days 7-9) were evaluated for morphology and total cell counts. After warming, survival and hatching rates were evaluated followed by total cell counts and Glut-1 expression levels. Only PVPGF IVM resulted in embryo production rates comparable to those recorded with FBS IVM. Growth factors with FAFBSA and amino acids with PVP reduced embryo production rates whereas the effect of the growth factors with PVP was negligible. Insulin-like growth factor 2 binding protein 3 (IGF2BP3) and beta cell translocation gene 4 (BTG4) were revealed as potential candidates for oocyte developmental competence, and secreted protein, acidic and rich in cysteine (SPARC) for cumulus cell expansion. There were no differences among treatments in hatching rates of vitrified embryos after warming. However, total cell numbers and Glut-1 expression levels at 72 h were affected.

Improving post-transfer survival of bovine embryos produced in vitro: actions of insulin-like growth factor-1, colony stimulating factor-2 and hyaluronan

Technologies for in vitro embryo production have the potential to enhance the efficiency of cattle production systems. However, utilization of in vitro-produced embryos for transfer remains limited throughout much of the world. Despite improvements over the past two decades, problems associated with the production of bovine embryos in vitro still exist which limit the widespread commercial application of this technology. In particular, bovine embryos produced in vitro have a reduced capacity to establish and maintain pregnancy as compared with their in vivo-derived counterparts. Embryo competence for survival following transfer is improved by in vivo culture in the sheep oviduct, thus indicating that standard embryo culture conditions are sub-optimal. Therefore, one strategy to improve post-transfer survival is to modify embryo culture media to more closely mimic the in vivo microenvironment. The maternal environment in which the bovine embryo develops in vivo contains various growth factors, cytokines, hormones, and other regulatory molecules. In addition to affecting bovine embryo development in vitro, recent research indicates that embryo competence for survival following transfer can also be improved when such molecules are added to embryo culture medium. Among the specific molecules that can increase post-transfer embryo survival are insulin-like growth factor-1 (IGF-1), colony stimulating factor-2 (CSF-2) and hyaluronan. This paper will review the effects IGF-1, CSF-2 and hyaluronan on post-culture embryo viability and discuss the potential mechanisms through which each of these molecules improves post-transfer survival.

Dynamic analysis of Ca²+ level during bovine oocytes maturation and early embryonic development

Mammalian oocyte maturation and early embryo development processes are Ca²⁺-dependent. In this study, we used confocal microscopy to investigate the distribution pattern of Ca²⁺ and its dynamic changes in the processes of bovine oocytes maturation, in vitro fertilization (IVF), parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT) embryo development. During the germinal vesicle (GV) and GV breakdown stage, Ca²⁺ was distributed in the cortical ooplasm and throughout the oocytes from the MI to MII stage. In IVF embryos, Ca²⁺ was distributed in the cortical ooplasm before the formation of the pronucleus. In 4-8 cell embryos and morulas, Ca²⁺ was present throughout the blastomere. In PA embryos, Ca²⁺ was distributed throughout the blastomere at 48 h, similar to in the 4-cell and 8-cell phase and the morula. At 6 h after activation, there was almost no distribution of Ca²⁺ in the SCNT embryos. However, Ca²⁺ was distributed in the donor nucleus at 10 h and it was distributed throughout the blastomere in the 2-8 cell embryos. In this study, Ca²⁺ showed significant fluctuations with regularity of IVF and SCNT groups, but PA did not. Systematic investigation of the Ca²⁺ location and distribution changes during oocyte maturation and early embryo development processes should facilitate a better understanding of the mechanisms involved in oocyte maturation, reconstructed embryo activation and development, ultimately improving the reconstructed embryo development rate.

Gene expression differences in oocytes derived from adult and prepubertal Japanese Black cattle during in vitro maturation

The present study was carried out to compare the gene expression profiles in oocytes derived from adult and prepubertal Japanese Black cattle during in vitro maturation (IVM) using microarray gene chips (Bovine genome array containing 24,072 probe sets representing over 23,000 transcripts). Microarray experiments were conducted using total RNA isolated from immature [germinal vesicle (GV)] and in vitro matured [metaphase II, (MII)] oocytes derived from adult and prepubertal animals. A total of 333 (1.4%) and 549 (2.3%) genes were differentially expressed between prepubertal vs adult bovine GV and MII stages oocytes, respectively. Of these, 176 and 312 genes were up-regulated, while 157 and 237 were down-regulated in prepubertal when compared with adult GV and MII oocytes, respectively. It was also observed that 695 (2.9%) and 553 (2.3%) genes were differentially expressed between GV vs MII stage oocytes in the adult and prepubertal groups, respectively. Gene ontological classification of the differentially expressed genes revealed that up-regulated genes in adult oocytes were involved in signal transduction, transcriptional control and transport. Quantitative reverse transcription-PCR validated the expression profile of some selected transcripts and confirmed differences in the expression levels of transcripts between adult vs prepubertal groups in both GV and MII stages oocytes as identified by microarray data analysis. This study indicated for the first time that significant number of genes were differentially expressed (>2-fold, p < 0.01) between oocytes derived from adult and those from prepubertal Japanese Black cattle, and this difference increased during IVM.

Culture medium, gas atmosphere and MAPK inhibition affect regulation of RNA-binding protein targets during mouse preimplantation development

During oogenesis, mammalian oocytes accumulate maternal mRNAs that support the embryo until embryonic genome activation. RNA-binding proteins (RBP) may regulate the stability and turnover of maternal and embryonic mRNAs. We hypothesised that varying embryo culture conditions, such as culture medium, oxygen tension and MAPK inhibition, affects regulation of RBPs and their targets during preimplantation development. STAU1, ELAVL1, KHSRP and ZFP36 proteins and mRNAs were detected throughout mouse preimplantation development, whereas Elavl2 mRNA decreased after the two-cell stage. Potential target mRNAs of RBP regulation, Gclc, Slc2a1 and Slc7a1 were detected during mouse preimplantation development. Gclc mRNA was significantly elevated in embryos cultured in Whitten's medium compared with embryos cultured in KSOMaa, and Gclc mRNA was elevated under high-oxygen conditions. Inhibition of the p38 MAPK pathway reduced Slc7a1 mRNA expression while inhibition of ERK increased Slc2a1 mRNA expression. The half-lives of the potential RBP mRNA targets are not regulated in parallel; Slc2a1 mRNA displayed the longest half-life. Our results indicate that mRNAs and proteins encoding five RBPs are present during preimplantation development and more importantly, demonstrate that expression of RBP target mRNAs are regulated by culture medium, gas atmosphere and MAPK pathways.

Efficiency of SCNT buffalo (Bubalus bubalis) embryos in different culture medium and analysis of mRNA expression of insulin-like growth factors during embryogenesis

Growth factors in culture media are known to affect the embryo production rates in in vitro production cultures. To improve the efficiency of somatic cell nuclear transfer (SCNT) derived embryos in Indian buffaloes (Bubalus bubalis), embryos were cultured in three different culture mediums viz. Group-A; TCM-199 + FBS, Group-B; TCM-199 + Poly vinyl alcohol (PVA) and Group-C; CR1aa + BSA. Embryo production rate and expression level of insulin-like growth factor genes (IGF-1, IGF-1R, IGF-2 and IGF-2R) were analysed in embryo culture. Cleavage and blastocyst production rates were 62.5% and 22.3% in Group-A, 53.8% and 13.0% in Group-B and 62.0% and 19.2% in Group-C respectively, whereas in in vitro fertilization (IVF) control cultured in TCM-199 plus 10% FBS, rates were 79.1% and 29.4%. Relative gene expression of SCNT embryos was compared with that in IVF control. IGF-1 and IGF-2 mRNA expression at blastocyst stage was up-regulated (p ≤ 0.05) in all culture groups, while IGF-1R and IGF-2R expression was down regulated (p ≤ 0.05) in Group-B and Group-C. In conclusion, the higher mRNA levels at certain stages in different culture conditions affected in vitro development of SCNT embryos. These results show that the transcript level of the insulin-like growth factor genes was significantly altered by in vitro culture condition. Culture medium TCM-199 with 10% FBS produced higher number of embryos and was able to co-op with gene expression of IVF control. Differences continue to be observed between SCNT cultured and IVF embryos, and until these differences are minimized, aberrations in SCNT embryonic development will continue to arise.

Expression of apoptosis regulatory genes and incidence of apoptosis in different morphological quality groups of in vitro-produced bovine pre-implantation embryos

Apoptosis occurs during early development in both in vivo- and in vitro-produced embryos, and is considered as one of the causes of embryonic loss. The objectives of this study were, therefore, investigating stage-specific expression profiles of apoptosis regulatory genes in three quality groups of in vitro-produced bovine pre-implantation embryos; and analysing the relationship between cell number and DNA fragmentation with expressions of those genes. The relative abundance of mRNA of 9 pro- (Bax, caspase-9, Bcl-xs, P53, Caspase-3 and Fas) and anti- (Bcl-w and Mcl-1) apoptotic genes was analysed. Differential cell staining and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labelling were performed to analyse the variation in cell numbers and detect apoptotic nuclei respectively. Expression of Bax and Caspase-3 genes was significantly (p < 0.05) higher in poor quality pre-implantation embryos as compared with that of morphologically good quality embryos of the same developmental stages. Moreover, Mcl-1 expression was significantly higher in good quality immature oocytes than that in the poor quality group. Moreover, higher DNA fragmentation was evidenced in morphologically poor quality blastocysts. In conclusion, our study demonstrates that Bax, caspase-3 and Mcl-1 can be used as potential markers of embryo quality to evaluate in vitro-produced bovine embryos. Further studies are required to investigate specific molecular signatures that can be used in evaluating in vivo-derived embryos.

Effect of energy source during culture on in vitro embryo development, resistance to cryopreservation and sex ratio

The aim of this work was to evaluate whether minimizing the glucose concentration during culture or replacing the hexose with other energy substrates and/or embryotrophic compounds would affect the in vitro development, the resistance to cryopreservation and the sex ratio of bovine embryos. In vitro matured and fertilized oocytes were randomly assigned to 4 groups for in vitro culture, that differed in the energy substrates included: group A) 1.5 mM glucose, as in standard SOF; group B) 0.15 mM glucose; group C) 0.125 mM G3P, in the presence of 0.15 mM glucose and group D) 0.34 mM citrate, in combination with 2.77 mM myo-inositol. Blastocysts were evaluated on day 7, then vitrified by cryotop in 16.5% DMSO, 16.5% EG and 0.5 M sucrose and warmed in decreasing concentration of sucrose (0.25 to 0.15 M sucrose). The survival rates were assessed after 24 h in vitro culture. Finally, the blastocysts produced were sexed by PCR. An increased blastocyst rate was recorded in groups B, C and D, i.e., when glucose concentration was reduced, compared to group A (28.2, 41.0, 35.7 and 35.8, respectively in groups A, B, C and D; P < 0.01). However, the embryos cultured in group D showed the slowest developmental speed, indicated by the lowest percentage of advanced stage-embryos (expanded and hatched blastocysts) out of the total blastocysts (56.1, 45.8, 56.9 and 31.8 %, respectively in groups A, B, C and D; P < 0.01). Furthermore, survival rates after 24 h culture of vitrified-warmed blastocysts also decreased in group D (73.3, 73.1, 71.4 and 58.4%, respectively in groups A, B, C and D; P < 0.01). Interestingly, in group D a higher percentage of female embryos was obtained compared to group A, with intermediate values in groups B and C (45.6, 53.4, 50.0 and 61.5%, respectively in groups A, B, C and D; P < 0.05). In conclusion, it was demonstrated that the energy substrate during in vitro culture affects both the production and the viability of blastocysts. Furthermore, manipulating the metabolic profile of embryos during in vitro culture may have an impact on sex ratio.

Combining resources to obtain a comprehensive survey of the bovine embryo transcriptome through deep sequencing and microarrays

While most assisted reproductive technologies (ART) are considered routine for the reproduction of species of economical importance, such as the bovine, the impact of these manipulations on the developing embryo remains largely unknown. In an effort to obtain a comprehensive survey of the bovine embryo transcriptome and how it is modified by ART, resources were combined to design an embryo-specific microarray. Close to one million high-quality reads were produced from subtracted bovine embryo libraries using Roche 454 Titanium deep sequencing technology, which enabled the creation of an augmented bovine genome catalog. This catalog was enriched with bovine embryo transcripts, and included newly discovered indel type and 3'UTR variants. Using this augmented bovine genome catalog, the EmbryoGENE Bovine Microarray was designed and is composed of a total of 42,242 probes, including 21,139 known reference genes; 9,322 probes for novel transcribed regions (NTRs); 3,677 alternatively spliced exons; 3,353 3'-tiling probes; and 3,723 controls. A suite of bioinformatics tools was also developed to facilitate microrarray data analysis and database creation; it includes a quality control module, a Laboratory Information Management System (LIMS) and microarray analysis software. Results obtained during this study have already led to the identification of differentially expressed blastocyst targets, NTRs, splice variants of the indel type, and 3'UTR variants. We were able to confirm microarray results by real-time PCR, indicating that the EmbryoGENE bovine microarray has the power to detect physiologically relevant changes in gene expression.

Comprehensive cross production system assessment of the impact of in vitro microenvironment on the expression of messengers and long non-coding RNAs in the bovine blastocyst

In vitroproduction (IVP) of cattle embryos over the past two decades has revealed several negative impacts that have been attributed to the artificial microenvironment. Studies on embryos producedin vitroclearly point to aberrant gene expression levels. So far, the causal association between phenotype and measured gene expression has not led to substantial improvement of IVP systems. The aim of this study was to generate a unique dataset composed of microarray-derived relative transcript abundance values for blastocysts produced in tenin vitrosystems differing primarily in culture medium formulation. Between-group comparisons determine the level of overall similarity among systems relative toin vivoreference embryos. The use of the dataset to contrast allin vitrotreatments with thein vivoblastocysts pointed to a single common gene network. The ‘boutique’ array contained a panel of novel uncharacterized transcripts that were variably expressed depending on the medium in which the blastocysts were produced. These novel transcripts were differentially expressed in blastocysts even as carryover from conditions encountered 7 days earlier during oocyte maturation. All of the selected novel candidates thus expressed were from intergenic regions. The function of this long non-coding RNA remains unknown but clearly points to an additional level of complexity in early embryo development.

Sonic hedgehog supplementation of oocyte and embryo culture media enhances development of IVF porcine embryos

We investigated the expression of sonic hedgehog (SHH) receptor PTCH1 and its co-receptor smoothened (SMO) in fertilized porcine embryos. Effects of exogenous SHH on embryonic development and expressions of survival- and pluripotency-related genes were also determined. We found that PTCH1 and SMO are expressed from two-cell to blastocyst embryos. When oocytes or fertilized embryos were respectively cultured in the maturation or embryo culture medium supplemented with SHH (0.5 μg/ml), their blastocyst rates and total cell numbers increased (P<0.05) compared with the untreated control. When cultured simultaneously in thein vitromaturation (IVM) andin vitroculture (IVC) media supplemented with SHH, the oocytes gained increased blastocyst rates and total cell numbers in an additive manner, with reduced apoptotic indices (P<0.05). Interestingly, SHH treatment did not affect the expression of theBCL2L1(BCL-XL) gene, yet reducedBAXexpression. Blastocysts cultured with various SHH regimes had similar pluripotency-related gene (POU5F1(OCT-4) andCDX2) expression levels, but blastocysts derived from SHH treatment during IVM had higherZPF42(REX01) expression (P<0.05). The highestZPF42expression was observed in the blastocysts derived from SHH-supplemented IVC and from dual IVM and IVC treatments. The levels of acetylated histone 3 (AcH3K9/K14) increased in the two-cell and the four-cell embryos when IVM and/or IVC media were supplemented with SHH (P<0.05). Our findings indicate that SHH conferred a beneficial effect on preimplantation development of porcine embryos, particularly when both IVM and IVC media were supplemented with SHH, and the effects may be further carried over from IVM to the subsequent embryonic development.

In vitro maturation of ovine oocytes using different maturation media: effect of human menopausal serum

OBJECTIVE

To compare the effect of human menopausal serum with estrous sheep serum, estrous goat serum, ovine follicular fluid and bovine follicular fluid on in vitro maturation, in vitro fertilization and embryo development of sheep oocytes METHOD (S): Oocytes were treated in culture with different sera and follicular fluids supplemented media to examine effects on embryo development.

RESULTS

Basic culture medium supplemented with human menopausal serum, estrous sheep serum and estrous goat serum supported better rates of in vitro maturation, in vitro fertilization and embryo development. Ovine follicular fluid and bovine follicular fluid supplementations supported similar rates of In vitro maturation, In vitro fertilization and embryo development which were lower than those supported by human menopausal serum, estrous sheep serum, estrous goat serum and control medium.

CONCLUSION

Human menopausal serum, estrous sheep serum, and estrous goat serum resulted in higher maturation, fertilization and embryo development than ovine follicular fluid, bovine follicular fluid and control media.

Transcriptome changes at the initiation of elongation in the bovine conceptus

The majority of embryonic loss in cattle occurs before maternal recognition of pregnancy, at around Day 16 postconception. The origin of the embryo can have a significant impact on the dynamics of embryo mortality. The aim of this study was to examine the temporal changes in transcriptional profile as the embryo develops from a spherical blastocyst on Day 7 to an ovoid conceptus at the initiation of elongation on Day 13 and to highlight differences in these temporal gene expression dynamics between in vivo- and in vitro-derived blastocysts that may be associated with embryonic survival/mortality using the bovine Affymetrix microarray. All embryos were produced either in vitro by in vitro fertilization or in vivo by superovulation. A proportion of Day 7 blastocysts were snap frozen, and the remainder were transferred (n = 10 per recipient) to synchronized heifers, recovered on Day 13, and snap frozen individually. Three pools of Day 7 blastocysts (n = 25 per pool) and Day 13 conceptuses (n = 5 per pool) were used for microarray analysis. In Day 7 blastocysts, 50 genes were found to be differentially expressed (P < 0.05), of which 19 were up-regulated and 31 down-regulated in the in vivo compared to in vitro embryos. In Day 13 conceptuses, 288 genes were found to be differentially expressed (P < 0.05), of which 133 were up-regulated and 155 down-regulated in the in vivo compared to in vitro embryos. The comparison between Day 7 and Day 13 embryos revealed significant temporal changes in transcript profile with 1806 and 909 transcripts differentially expressed in the in vitro- and in vivo-derived embryos, respectively. Across the three array comparisons between Day 7 and Day 13 embryos, 444 genes were consistently exclusively present in the in vivo embryos, whereas 1341 were exclusively present in the in vitro embryos. Regardless of the origin of the embryo, 465 differentially expressed genes between Day 7 and 13 were common to both in vivo- and in vitro-derived embryos; these genes are likely critical for the transition between the blastocyst (Day 7) and ovoid conceptus (Day 13) stages of embryo development. In order to validate the microarray findings, differences in the expression of six genes (CYP51A1, FADS1, TDGF1, HABP2, APOA2, and SLC12A2) were confirmed by quantitative real-time PCR on in vivo- and in vitro-derived embryos on Day 7 and Day 13 using independent samples from those used for the microarray. Subsequent mapping of these differentially expressed genes into relevant functional groups and pathways identified important pathways involved in conceptus elongation in cattle. In conclusion, this analysis has identified genes and pathways crucial for the transition from a spherical blastocyst to an ovoid conceptus as well as those uniquely associated with a greater likelihood of embryonic survival (those unique to in vivo embryos) or loss (those unique to in vitro embryos).

Effects of chemically defined medium on early development of porcine embryos derived from parthenogenetic activation and cloning

The present study was to investigate if a completely chemically defined medium (PZM-4) could support the early development of porcine embryos derived from parthenogenetic activation (PA) and cloning (somatic cell nuclear transfer, SCNT), and to lay the foundation for determining the physiological roles of certain supplements in this medium. Porcine embryos derived from PA and SCNT were cultured in media: PZM-3 (a chemically semi-defined medium), PZM-4 (a fully defined medium), and PZM-5 (an undefined medium). Early embryo development was observed. We found that the three medium groups (PZM-3, PZM-4 and PZM-5) exhibited no significant differences in cleavage rates of PA embryos (p > 0.05), while the blastocyst rate in PZM-3 was significantly higher than in PZM-4 and PZM-5 (78.9% vs. 36.0% and 52.3%) (p < 0.05). Moreover, total cell number per blastocyst in PZM-3 was clearly higher than in PZM-5 but similar to that in PZM-4. As for SCNT embryos, no significant differences were observed for the cleavage rates or the blastocyst rates among the three groups (p > 0.05). However, total cell number per blastocyst in PZM-3 was notably higher than in PZM-5, but was similar to that in PZM-4. In conclusion, our results suggested that the completely chemically defined medium PZM-4 can be used to efficiently support the early development of porcine PA and SCNT embryos.

Desenvolvimento de embriões de camundongas após manutenção em diferentes soluções de manipulação

Avaliou-se a eficácia de duas soluções de manipulação (SM) de embriões de camundongas nos estádios de blastocisto inicial (Bin), mórula compacta grau I (McI) e II (McII), distribuídos aleatoriamente em três tratamentos (T), de acordo com a solução de manutenção. No T1 usou-se PBS modificado (controle); no T2, SME e no T3, SME enriquecida. Os embriões foram mantidos durante quatro horas na solução de manutenção e posteriormente classificados quanto ao estádio de desenvolvimento e à qualidade embrionária. Logo após, foram cultivados em meio TCM 199 e classificados novamente quanto ao estádio de desenvolvimento e à qualidade embrionária. A taxa de desenvolvimento dos embriões após manutenção por quatro horas em solução de manipulação foi menor (P<0,05) nos embriões do controle, comparada à de embriões do SME e SME enriquecida, diferença esta não observada (P>0,05) após o cultivo in vitro. Os embriões McII do T3 tiveram maior desenvolvimento (P<0,05) em relação aos embriões do T1 e T2, indicando o efeito benéfico do enriquecimento da solução SME. Conclui-se que as soluções de manipulação SME e SME enriquecida influenciaram beneficamente o desenvolvimento de embriões

Current progress in oocyte and embryo cryopreservation by slow freezing and vitrification

Preservation of female genetics is currently done primarily by means of oocyte and embryo cryopreservation. The field has seen much progress during its four-decade history, progress driven predominantly by research in humans, cows, and mice. Two basic cryopreservation techniques rule the field – controlled-rate freezing, the first to be developed, and vitrification, which, in recent years, has gained a foothold. While much progress has been achieved in human medicine, the cattle industry, and in laboratory animals, this is far from being the case for most other mammals and even less so for other vertebrates. The major strides and obstacles in human and other vertebrate oocyte and embryo cryopreservation will be reviewed here.

Equine bone marrow mesenchymal or amniotic epithelial stem cells as feeder in a model for the in vitro culture of bovine embryos

Various studies have shown that the in vitro culture environment is one of the key determinants of the blastocyst output. In the present study we investigated the effects of co-culturing bovine embryos with equine bone marrow mesenchymal stem cells (BM-MSCs) or equine amniotic epithelial stem cells (AE-SCs) on in vitro blastocysts development. BM specimens were obtained aseptically from sternal aspirates of horses under local anaesthesia and the isolated cells were resuspended in Dulbecco Modified Earle's Medium supplemented with 10 ng/ml of basic fibroblast growth factor (bFGF). Amniotic membranes were obtained from fresh placentas and, to release the AE cells, amniotic fragments were incubated with 0.05% trypsin for 45 min. Separated AE cells were plated in standard culture medium containing 10 ng/ml epidermal growth factor (EGF). Seven hundred and five cumulus–oocyte complexes were used and, after IVM and IVF, cumulus-free presumptive zygotes were randomly transferred into one of three co-culture systems in which they were cultured up to day 7: (1) co-culture with cumulus cells (control); (2) co-culture with BM-MSCs; and (3) co-culture with AE-SCs. Statistical analyses were performed by ANOVA. Blastocyst developmental rates were significantly different (p < 0.001) between control, AE-SCs and BM-MSCs (respectively 35.45, 41.84 and 30.09%). In conclusion, the AE-SC monolayer create a more suitable microenvironment necessary for inducing local cell activation and proliferation of the growing embryos in comparison with BM-MSCs and cumulus cells. It can be suggested that these cells secrete biologically active substances, including signalling molecules and growth factors of epithelial nature, different to those of the BM cells of mesenchymal origin.

Expression of mRNA, before and after freezing, in bovine blastocysts cultured under different conditions

Production methods and culture systems have been shown to affect blastocyst mRNA expression and cryopreservability, which may serve as sensitive indicators of embryo quality and developmental competence. In the present study, the impact of four established culture conditions for producing bovine blastocysts (in vitro production, IVP; gamete intra-fallopian transfer, GIFT; transfer of cleaved stages into the oviduct, CLVT; multiple ovulation embryo transfer, MOET) was assessed, in terms of both cryosurvival and levels of mRNA expression of several selected genes (occludin, desmocollin 2, solute carrier family 2 member 3, BAX, BCL-XL, heat shock protein 1A, aquaporin 3, DNA methyltransferase 1a) detected with RT-qPCR. At 24 hours post-thawing, blastocysts derived from in vitro production showed a significantly higher re-expansion rate compared to the other groups. At later times, this difference was no longer significant. Before freezing, embryos of the MOET group showed significantly more desmocollin 2 mRNA compared to embryos produced using other culture methods. After freezing, significant upregulation was found in transcripts of heat shock protein 1A in embryos of all groups; of solute carrier family 2 member 3, only in IVP derived embryos; of BAX, BCL-XL, occludin, desmocollin 2, only in the MOET and IVP groups. Aquaporin 3 and DNA methyltransferase 1a were neither up- nor downregulated in blastocysts of any group. In conclusion, these findings suggest that, after freezing, embryos seem to have switched on mRNA synthesis, an active metabolism, operational cell connections, and are prepared for hatching and beyond.

Efeito do estradiol e da progesterona no desenvolvimento e na qualidade de embriões bovinos produzidos in vitro

Avaliaram-se o desenvolvimento e a qualidade de embriões bovinos, cocultivados com células epiteliais do oviduto bovino (CEOBs) expostas ou não ao estradiol e à progesterona. Os ovócitos foram maturados in vitro por 24h e, então, fertilizados utilizando-se sêmen congelado, em estufa de CO2 a 5% e 38,5ºC. As CEOBs foram cultivadas em TCM-199 com ou sem estradiol (E2) (24 horas), nas mesmas condições da maturação e fertilização in vitro (MIV e FIV), e, em seguida, adicionadas aos diferentes grupos em CR2 com ou sem progesterona (P4) (G1=P4+E2); (G2=E2); (G3=P4) e (G4=controle). Após 18h da FIV, as células foram cultivadas nos diferentes sistemas. Nenhuma diferença (P>0,05) foi observada nas taxas de clivagem entre G1, G2 e G4 (53,5%; 56,3%; 51,7%) e nos padrões de blastocistos (BLs) (29,3%; 31,2%, 28,7%). Índices menores (P<0,05) foram obtidos no G3 para ambas as variáveis (34,5%; 16,4%). G1 e G2 apresentaram taxas de eclosão maiores (P<0,05) que os outros grupos (23,3%; 23,2%), sendo G4 (19,3%) diferente de G3 (16,1%). Em G1, G2 e G3, o número de células nos BLs aumentou 125,9; 128,4 e 123,6, respectivamente (P<0,05), em relação ao G4 (112,5). Conclui-se que o tratamento das CEOBs com o E2, nas primeiras 24 horas de cultivo, pode ser usado isoladamente ou em combinação com a progesterona, a fim de melhorar a qualidade de embriões bovinos produzidos in vitro

Quantificação de transcritos maternos em oócitos bovinos submetidos a diferentes condições de maturação

Comparou-se a quantidade relativa de transcritos de origem materna entre oócitos bovinos maturados in vivo e maturados em diferentes condições in vitro. Avaliou-se também o efeito dos sistemas de maturação in vitro sobre a viabilidade das células do cumulus. Para a maturação in vivo, os oócitos foram coletados 19-20h após aplicação de gonadorelina em doadoras superestimuladas com FSH e sincronizadas com implante de progesterona. Para a maturação in vitro, oócitos imaturos, obtidos de ovários coletados em matadouro, foram maturados sob diferentes tensões de oxigênio e suplementação proteica. Avaliou-se a abundância dos transcritos de Zar1, MATER e GDF9 por PCR em tempo real. A viabilidade das células do cumulus de oócitos maturados in vitro foi analisada pela coloração de Azul de Tripan. Observou-se sub-regulação (P<0,05) dos transcritos em oócitos submetidos às diferentes condições de maturação in vitro em relação aos maturados in vivo. Não houve diferença (P>0,05) na viabilidade das células do cumulus. Conclui-se que o sistema de maturação influencia a quantidade de transcritos de origem materna armazenados no citoplasma de oócitos bovinos

Cross-validation of techniques for measuring lipid content of bovine oocytes and blastocysts

The main objective was to test and validate a fluorescence approach to quantify lipid content of individual bovine oocytes and blastocysts. For Experiment 1, denuded oocytes were evaluated, as well as in vitro-produced blastocysts in a factorial design: cows versus feedlot heifers; three additives during Days 2.5-7.5 of culture (Control; 10% FCS; 0.3 μM phenazine ethosulfate (PES), an electron acceptor that oxidizes NADPH); and two blastocyst stages (early versus expanded). All blastocysts were graded subjectively for darkness (1 = clear … 4 = dark). In Experiment 2, denuded oocytes were used to measure lipid content in a factorial design of: cows versus heifers and four subjective darkness grades (1 = clear … 4 = dark). To quantify lipids, oocytes and 7.5 d blastocysts were fixed and then stained with 1 μg/mL Nile Red dye in mPBS overnight. A digital photograph of the equatorial part of the oocyte and embryo was taken at 200×, and fluorescence intensity (Arbitrary Fluorescence Units, AFU) was measured with Image Pro software. Reverse images of the same photographs were used to count numbers of cytoplasmic lipid droplets of various sizes (LC). The linear regression equation of LC with AFU in oocytes had an r(2) = 0.84, and for blastocysts r(2) = 0.91. The LC and AFU also had similar coefficients of variation from the ANOVA for blastocysts (38 vs 44%, respectively). Treatment differences were of similar magnitude with both procedures: lipid content in oocytes and blastocysts from heifers and cows was similar (P > 0.1); PES reduced lipid accumulation, and FCS increased it relative to the Control for AFU (18.6 vs 46.6 vs 36.9 units, respectively), and LC (1763 vs 4081 vs 3310, respectively; all, P < 0.01). Early blastocysts resulted in more lipid accumulation per unit area than expanded ones based on AFU (41.5 vs 26.6) and LC (3519 vs 2583; both P <0.01). There was a strong relationship (P < 0.01) between subjective oocyte and blastocyst darkness and lipid content. The less labor intensive fluorescence staining was a reliable technique for quantifying lipid droplets in oocytes and blastocysts.

Fetal calf serum enhances in vitro production of Bos taurus indicus embryos

The objective of this study was to determine the effect of fetal calf serum (FCS) on the quality of in vitro produced bovine embryos. Cumulus oocyte-complexes (COCs, n = 2 449) recovered by ovum pick-up from Bos taurus indicus donors were randomly assigned to experimental groups. Sperm selected by Percoll gradient was used for in vitro fertilization (insemination = Day 0). In Experiment 1 (n = 1 745 COCs), zygotes were cultured in vitro in Synthetic Oviduct Fluid + 4 mg/mL of bovine serum albumin (BSA), or BSA + 2% FCS (BSA+FCS). In Experiment 2 (n = 704 COCs), the COCs were cultured in SOF + BSA, BSA + 2% FCS, or BSA + 2% FCS on D4 (BSA + FCSD4). In Experiment 1, blastocyst yield (51%) and Quality I blastocysts (41%) at Day 7 were higher (P < 0.05) in the BSA + FCS treatment than in BSA (42 and 30%, respectively). In Experiment 2, blastocyst yield was higher (P < 0.05) in the BSA+FCS (47%) treatment. Quality I blastocyst yield was higher (P < 0.05) for BSA + FCS (34%) and BSA+FCSD4 (32%) compared to the BSA treatment (20%). A total of 820 embryos were transferred, with no significant differences among groups in pregnancy rates. In conclusion, in vitro culture in SOFaaci + BSA + FCS enhanced blastocyst yield and Quality I blastocysts; adding FCS to the culture medium increased the efficiency of IVP of bovine embryos.

Fibroblast growth factor 10 enhances bovine oocyte maturation and developmental competence in vitro

The ability of oocytes to resume meiosis, become fertilized, and generate viable pregnancies is controlled during folliculogenesis by several endocrine and paracrine factors. The aim of this work is to determine whether fibroblast growth factor 10 (FGF10) is an oocyte competent factor. Transcripts for each of the four FGF receptor types (FGFR) were present in cumulus and oocytes after their extraction from the follicles. FGFR1 transcripts predominated in cumulus cells whereas FGFR2 was most abundant in oocytes. Exposing the cumulus-oocyte complexes to FGF10 during in vitro maturation did not affect cleavage rates, but increases (P<0.05) in the percentage of embryos at the 8-16-cell stage on day 3 and at the blastocyst stage on day 7, which were evident in FGF10-supplemented oocytes. The progression of oocytes through meiosis and cumulus expansion was increased (P<0.05) by FGF10. The importance of the endogenous sources of FGFs was examined by adding anti-FGF10 IgG during oocyte maturation. Blocking endogenous FGF10 activity decreased (P<0.05) the percentage of oocytes developing into blastocysts and limited (P<0.05) cumulus expansion. Expression profiles of putative cumulus and oocyte competency markers were examined for their involvement in FGF10-mediated responses. FGF10 influenced the expression of CTSB and SPRY2 in cumulus cells and BMP15 in oocytes. In summary, this work provides new insight into the importance of FGFRs and locally derived FGF10 during oocyte maturation in cattle. Its subsequent impact on in vitro embryo development implicates it as a noteworthy oocyte competent factor.

Effect of cryotop vitrification on preimplantation developmental competence of murine morula and blastocyst stage embryos

Vitrification is an effective method for the cryopreservation of mammalian embryos. Nevertheless, it is unclear which embryonic developmental stage is the most suited for vitrification and would ensure maximal developmental competence upon subsequent warming. This study, therefore, compared the effects of cryotop vitrification on the developmental competence of murine morula and blastocyst stage embryos. Additionally, trophectoderm (TE) and inner cell mass (ICM) cell numbers were compared in two hatched blastocyst groups derived from vitrified morulae and blastocysts, respectively. The post-vitrification survival rates for mouse embryos at the morula and blastocyst stage were 95.4% (186/195) and 96.5% (195/202), respectively. The blastocyst formation rate was significantly lower for vitrified morulae (90.3%) compared with the non-vitrified control group (98.4%) (P < 0.05). The hatching rates were similar between the vitrified morula (79.6%) and the vitrified blastocyst (81.0%) groups. When further development to the fully hatched blastocyst stage was compared, fully hatched blastocysts derived from vitrified morulae had significantly higher cell counts for both the ICM and TE lineage, as compared with hatched blastocysts derived from vitrified blastocysts (P < 0.001). Cryotop vitrification of mouse embryos at the morula stage rather than blastocyst stage would thus ensure a higher degree of post-warming developmental competence.

Detrimental effects of antibiotics on mouse embryos in chromatin integrity, apoptosis and expression of zygotically activated genes

The effects of specific components in culture medium on embryo physiology have been extensively investigated to optimize in vitro culture systems; however, little attention has been paid to antibiotics, the reagents used most commonly in culture systems to prevent contamination. To investigate the potential effects of routine use of antibiotics on cultured embryos, mouse zygotes were cultured with or without antibiotics. In both groups, the developmental rate and cell number of blastocysts appear to be normal. The proportion of embryos with blastomere fragmentation increased slightly when embryos were cultured with antibiotics. In contrast, the presence of antibiotics in the embryo culture system significantly disturbs expression of zygotically activated genes, damages chromatin integrity and increases apoptosis of cultured embryos. These results provide evidence that, when cultured with antibiotics, embryos with normal appearance may possess intrinsic physiological and genetic abnormalities. We demonstrate that the adverse effects of antibiotics on mammalian embryos are more severe than we previously presumed and that antibiotics are not essential for sterility of embryo culture system therefore abolishing antibiotic supplementation during embryo culture.

Maturation, fertilisation and culture of bovine oocytes and embryos in an individually identifiable manner: a tool for studying oocyte developmental competence

The ability to successfully culture oocytes and embryos individually would facilitate the study of the relationship between follicle parameters and oocyte developmental competence, in order to identify markers of competent oocytes, as well as the ability to use small numbers of oocytes from an individual donor such as when ovum pick-up is carried out. Using a total of 3118 oocytes, the aim of the present study was to develop a system capable of supporting the development of immature bovine oocytes to the blastocyst stage in an individually identifiable manner. Initially, post-fertilisation embryo culture in the Well-of-the-Well (WOW) system, on the cell adhesive Cell-Tak or in polyester mesh was tested and shown to result in similar development to embryos cultured in standard group culture. The results demonstrate that it is possible to culture bovine oocytes to the blastocyst stage in an individually identifiable manner in all three culture systems with comparable success rates. This permits the localisation and identification of individual embryos throughout preimplantation development in vitro while retaining the developmental benefits of group culture. In terms of ease of preparation and use, culture in isolation within the strands of a polyester mesh is preferable.

Effect of oxygen tension and serum during IVM on developmental competence of bovine oocytes

With an aim to improve the in vitro production of bovine embryos, the present study investigated the effect of serum and oxygen tension during IVM on oocyte developmental competence. Four experimental groups were evaluated: G1, 10% oestrus cow serum (OCS) with 20% O2; G2, 0.1% polyvinyl alcohol (PVA) with 20% O2; G3, 10% OCS with 5% O2; and G4, 0.1% PVA with 5% O2. The proportion of MII oocytes, blastocyst rates and total cell number were not affected (P > 0.05) when the OCS was replaced with PVA under 5% O2, whereas a higher (P < 0.05) blastocyst rate and total cell number were found with OCS compared with PVA under 20% O2. The apoptosis index was lower in blastocysts from oocytes matured with PVA under 5% O2 (G4) compared with other groups (G1, G2 and G3), but no differences (P > 0.05) were found in maturation and blastocyst rates. Significant differences were found in the amount of specific transcripts in oocytes matured under different conditions. In conclusion maturation with PVA and 5% O2 provides an efficient in vitro culture condition for the maturation of bovine oocytes.

Effect of the association of IGF-I, IGF-II, bFGF, TGF-beta1, GM-CSF, and LIF on the development of bovine embryos produced in vitro

This study examined the influence of the following growth factors and cytokines on early embryonic development: insulin-like growth factors I and II (IGF-I, IGF-II), basic fibroblast growth factor (bFGF), transforming growth factor (TGF-beta), granulocyte-macrophage colony-stimulating factor (GM-CSF), and leukemia inhibitory factor (LIF). Synthetic oviduct fluid (SOF) was used as the culture medium. We studied the development of bovine embryos produced in vitro and cultured until Day 9 after fertilization. TGF-beta1, bFGF, GM-CSF, and LIF used on their own significantly improved the yield of hatched blastocysts. IGF-I, bFGF, TGF-beta1, GM-CSF, and LIF significantly accelerated embryonic development, especially the change from the expanded blastocyst to hatched blastocyst stages. Use of a combination of these growth factors and cytokines (GF-CYK) in SOF medium produced higher percentages of blastocysts and hatched blastocysts than did use of SOF alone (45% and 22% vs. 24% and 12%; P<0.05) on Day 8 after in vitro fertilization and similar results to use of SOF+10% fetal calf serum (38% and 16%, at the same stages, respectively). The averages of total cells, inner cell mass cells, and trophectoderm cells of exclusively in vitro Day-8 blastocysts for pooled GF-CYK treatments were higher than those for SOF and similar to those for fetal calf serum. The presence of these growth factors and cytokines in the embryo culture medium therefore has a combined stimulatory action on embryonic development; in particular through an increase in hatching rate and in the number of cells of both the inner cell mass and trophoblast. These results are the first to demonstrate that use of a combination of recombinant growth factors and cytokine, as IGF-I, IGF-II, bFGF, TGF-beta1, LIF, and GM-CSF, produces similar results to 10% fetal calf serum for the development of in vitro-produced bovine embryos. This entirely synthetic method of embryo culture has undeniable advantages for the biosecurity of embryo transfer.

In vitro production and cryotolerance of prepubertal and adult goat blastocysts obtained from oocytes collected by laparoscopic oocyte-pick-up (LOPU) after FSH treatment

This study compares the developmental capacity and cryotolerance of embryos produced from oocytes of stimulated prepubertal and adult Sarda goats. Twelve prepubertal and 13 adult goats were each given 110 and 175 IU FSH, respectively, and cumulus-oocyte complexes (COCs) were collected by laparoscopic oocyte-pick-up (LOPU). After in vitro maturation, fertilisation and culture (IVMFC), blastocysts were vitrified, warmed and blastocoel re-expansion and gene expression were evaluated. Prepubertal goats produced a higher COCs number than adults (mean +/- s.e.m., 89.67 +/- 5.74 and 26.69 +/- 3.66, respectively; P < 0.01). Lower developmental competence was demonstrated in the prepubertal oocytes as shown by a higher number of COCs discarded before IVM (21.1% and 14.7% for prepubertals and adults, respectively; P < 0.01) and IVF (23.4% v. 9.1%; P < 0.01) and by the lower cleavage (55.6% and 70.3%, respectively; P < 0.01) and blastocyst rates (24.2% and 33.9%, respectively; P < 0.05). Compared with the adult, prepubertal vitrified/warmed blastocysts showed significantly (P < 0.05) lower in vitro viability, as determined by the re-expansion rate (62.5% and 40.3%). No differences were observed in the time required for blastocoel re-expansion or in cyclin B1, E-cadherin, Na/K ATPase, HSP90beta and aquaporin 3 messenger RNA quantity. These results show that in vitro-produced embryos produced from prepubertal goat oocytes have a lower developmental rate and cryotolerance compared with their adult counterparts. However, we can assume that the quality of re-expanded embryos does not differ between the two groups.