Gene expression and developmental competence of bovine embryos produced in vitro under varying embryo density conditions

Protocol for the electroporation of CRISPR-Cas for DNA and RNA targeting in Bos taurus zygotes

The use of CRISPR-Cas9 ribonucleoproteins has revolutionized manipulation of genomes. Here, we present a protocol for the electroporation of CRISPR-Cas for DNA and RNA targeting in Bos taurus zygotes. First, we describe steps for production and preparation of presumptive zygotes for electroporation. The first electroporation introduces ribonucleoproteins formed by Cas9D10A with two guide RNAs to target DNA, and the second introduces the same ribonucleoprotein complex to target DNA plus Cas13a with one guide RNA to target RNAs. For complete details on the use and execution of this protocol, please refer to Nix et al.1.

Multiphase flow in microfluidics: From droplets and bubbles to the encapsulated structures

Microfluidic technologies have a unique ability to control more precisely and effectively on two-phase flow systems in comparison with macro systems. Controlling the size of the droplets and bubbles has led to an ever-increasing expansion of this technology in two-phase systems. Liquid-liquid and gas-liquid two-phase flows because of their numerous applications in different branches such as reactions, synthesis, emulsions, cosmetic, food, drug delivery, etc. have been the most critical two-phase flows in microfluidic systems. This review highlights recent progress in two-phase flows in microfluidic devices. The fundamentals of two-phase flows, including some essential dimensionless numbers, governing equations, and some most well-known numerical methods are firstly introduced, followed by a review of standard methods for producing segmented flows such as emulsions in microfluidic systems. Then various encapsulated structures, a common two-phase flow structure in microfluidic devices, and different methods of their production are reviewed. Finally, applications of two-phase microfluidic flows in drug-delivery, biotechnology, mixing, and microreactors are briefly discussed.

In vitro versus In vivo: Development-, Apoptosis-, and Implantation- Related Gene Expression in Mouse Blastocyst

Background

While mammalian embryos can adapt to their environments, their sensitivity overshadows their adaptability in suboptimal in vitro conditions. Therefore, the environment in which the gametes are fertilized or to which the embryo is exposed can greatly affect the quality of the embryo and consequently its implantation potential.

Objectives

Since providing an optimal culture condition needs a deep understanding of the environmental effects, and regarding the fact that normal morphology fails to be a reliable indicator of natural embryo development, the current study aimed at comparing in vivo- and in vitro-derived blastocysts at the molecular level.

Materials and Methods

In vivo and in vitro mouse blastocysts were obtained by flushing the uterine horns and in vitro fertilization/culture, respectively. Normal blastocysts of both groups were evaluated in terms of hatching rate and expression of three lineage-differentiation-, apoptosis-, and implantation-related genes.

Results

The hatching rate was lower in In vitro fertilization (IVF)-produced blastocysts in comparison with that of the in vivo counterparts. More importantly, the study results indicated significant changes in the expression levels of eight out of ten selected genes, especially Mmp-9 (about -10.7-fold). The expression of Mmp-9 in trophoblast cells is required for successful implantation and trophoblast invasion.

Conclusions

The current study, in addition to confirming that the altered gene expression pattern of in vitro-produced embryos resulted in normal morphology, provided a possible reason for lower implantation rate of in vitro-produced blastocysts regarding the Mmp-9 expression.

Oral propylene glycol modifies follicular fluid and gene expression profiles in cumulus-oocyte complexes and embryos in feed-restricted heifers

Dietary supplementation with propylene glycol (PG) increases in vitro production of high-quality embryos in feed-restricted heifers. The aim of the present study was to evaluate the effects of PG in feed-restricted heifers on follicular fluid insulin and insulin-like growth factor (IGF) 1 concentrations, expression of IGF system genes in oocytes and cumulus cells and the expression of selected genes in blastocysts. Feed-restricted (R) heifers were drenched with water or PG during induced oestrous cycles (400mL of PG or water/drench, daily drenching at 1600 hours for the first 9 days of the oestrous cycle). Ovum pick-up (OPU) was performed after superovulation to produce in vitro embryos and without superovulation to recover oocytes, cumulus cells and follicular fluid. OPU was also performed in a control group (not feed restricted and no drenching). Follicular fluid IGF1 concentrations were reduced by R, and PG restored IGF1 concentrations to those seen in the control group. In cumulus cells, expression of IGF1, IGF1 receptor (IGF1R) and IGF binding protein 4 (IGFBP4) was decreased in the R group, and fully (IGF1 and IGF1R) or partially (IGFBP4) restored to control levels by PG. Blastocyst perilipin 2 (PLIN2; also known as adipophilin), Bcl-2-associated X protein (BAX), SCL2A1 (facilitated glucose/fructose transporter GLUT1), aquaporin 3 (AQP3), DNA (cytosine-5)-methyltransferase 3A (DNMT3A) and heat shock 70-kDa protein 9 (HSPA9B) expression were decreased in R heifers; PG restored the expression of the last four genes to control levels. In conclusion, these results suggest that, during follicular growth, PG exerts epigenetic regulatory effects on gene expression in blastocyst stage embryos.

Epidermal growth factor improves developmental competence and embryonic quality of singly cultured domestic cat embryos

This study examined the influence of EGF on the expression of EGF receptors (EGFR) and developmental competence of embryos cultured individually versus those cultured in groups. Cat oocytes were in vitro matured and fertilized (IVM/IVF), and cleaved embryos were randomly assigned to one of seven culture conditions: one group each in which embryos were subjected to group culture supplemented with or without 5 ng/ml EGF and five groups in which embryos were subjected to single-embryo culture supplemented with EGF (0, 5, 25, 50 or 100 ng/ml). Morulae, blastocysts and hatching blastocysts were assessed at days 5 and 7; post IVF, respectively, and total blastocyst cell numbers were assessed at day 7. Relative mRNA expressions of EGFR of 2–4-cell embryos, 8–16-cell embryos, morulae and blastocysts cultured in groups or singly with or without EGF supplementation were examined. OCT3/4 and Ki67 in blastocysts derived from the group or single-embryo culture systems with or without EGF supplementation were localized. A higher rate of embryos cultured in groups developed to blastocysts than individually incubated cohorts. Although EGF increased blastocyst formation in the single-embryo culture system, EGF did not affect embryo development in group culture. Expression levels of EGFR decreased in morulae and blastocysts cultured with EGF. An increased ratio of Ki67-positive cells to the total number of cells in the blastocyst was observed in singly cultured embryos in the presence of EGF. However, EGF did not affect the expression of OCT3/4. These findings indicate that EGF enhanced developmental competence of cat embryos cultured singly by stimulating cell proliferation and modulating the EGFR expression at various developmental stages.

Developmental competence and expression pattern of bubaline (Bubalus bubalis) oocytes subjected to elevated temperatures during meiotic maturation in vitro

OBJECTIVE

To determine the direct effect of physiologically relevant high temperatures (40.5 and 41.5 °C) for two time periods (12 and 24 h) on bubaline oocytes during in vitro maturation.

METHOD

The control group oocytes were cultured at 38.5 °C for 24 h. The treatment 1 (T1) and 3 (T3) group oocytes were cultured at 40.5 and 41.5 °C respectively, for the first 12 h and at 38.5 °C for rest of the 12 h. However, treatment 2 (T2) and 4 (T4) group oocytes were cultured at 40.5 and 41.5 °C for complete 24 h.

RESULTS

Development of oocytes to blastocyst was severely compromised (p < 0.001) when matured at 40.5 and 41.5 °C for both exposure periods (12 h and 24 h). It was found that the cleavage rates, blastocyst yield and mean cell number decreased remarkably (p < 0.001) in the treatment groups compared to control. The relative mRNA expression of heat shock protein (Hsp 70.1, 70.2, 70.8, 60, 10 and HSF1), pro-apoptotic (caspases-3, -7, -8, Bid and Bax) and oxidative stress (iNOS) related genes was significantly higher (p < 0.05) in all the treatment groups compared to control. However, mRNA abundance of anti-apoptotic (Bcl-2, Mcl-1, Bcl-xl), glucose transport (Glut1, Glut3 and IGF1R), developmental competence (ZAR1 and BMP15) and oxidative stress (MnSOD) related genes was significantly decreased (p < 0.05) in the treatment groups compared to control.

CONCLUSION

The present study clearly establishes that physiologically relevant elevated temperatures during in vitro meiotic maturation reduce developmental competence of bubaline oocytes.

Effect of elevated temperatures on bovine corpus luteum function: expression of heat-shock protein 70, cell viability and production of progesterone and prostaglandins by cultured luteal cells

Summer heat stress lowers fertility in cattle in hot environments by influencing oocyte quality, follicular activity and progesterone (P4) level in blood plasma. However, the mechanisms by which elevated temperature influences corpus luteum function remain unclear. Elevated temperature has generally been known to upregulate the gene expression of heat-shock protein (HSP) 70 in a variety of cell types. To clarify the direct effects of elevated temperature on bovine corpus luteum function, we examined the expressions of HSP70, cell viability and the production of P4 and prostaglandins (PGs) in luteal cells cultured at 37.5°C (normal temperature in our culture system), 39.0°C (moderately elevated temperature) or 41.0°C (severely elevated temperature) for 12 or 24 h. HSP70 mRNA expression was increased by incubation at 39.0°C for 12 h and at 41.0°C for 12 and 24 h, whereas HSP70 protein expression was not significantly affected. The viability of luteal cells cultured for 24 h, measured by flow cytometry with propidium iodide staining, was not significantly affected by temperature. Interestingly, the production of P4 by cultured luteal cells was higher at 39.0°C than at 37.5°C after 12 and 24 h of incubation. The production of PGF2α was higher at 39.0°C and 41.0°C than at 37.5°C after 12 and 24 h of incubation. The production of PGE2 was higher at 41.0°C than at 37.5°C after 24 h of incubation. The overall results suggested that elevated temperature does not negatively affect luteal function, and that the low fertility observed during summer is not due to a direct effect of elevated temperature on luteal cells.

Morphology, sex ratio and gene expression of day 14 in vivo and in vitro bovine embryos

The present study was designed to compare Day 14 bovine embryos that were produced entirely in vitro using the post-hatching development (PHD) system with in vivo-derived embryos without or with transient PHD culture from Day 7 to Day 14. Embryos on Day 14 were used for sex determination and gene expression analysis of PLAC8, KRT8, CD9, SLC2A1, SLC2A3, PGK1, HSF1, MNSOD, HSP70 and IFNT using real-time quantitative (q) polymerase chain reaction (PCR). First, Day 7 in vivo- and in vitro-produced embryos were subjected to the PHD system. A higher rate of survival was observed for in vitro embryos on Day 14. Comparing Day 14 embryos produced completely in vivo or completely in vitro revealed that the mean size of the former group was greater than that of the latter (10.29±1.83 vs 2.68±0.33mm, respectively). Expression of the HSP70 and SLC2A1 genes was down- and upregulated, respectively, in the in vitro embryos. The present study shows that in vitro embryos cultured in the PHD system are smaller than in vivo embryos and that of the 10 genes analysed, only two were differentially expressed between the two groups. These findings indicate that, owing to the poor survival rate, the PHD system is not reliable for evaluation of in vitro embryo quality.

Post-hatching development of in vitro bovine embryos from day 7 to 14 in vivo versus in vitro

This study evaluates the post-hatching development of in vitro-produced (IVP) embryos until Day 14. On Day 7, IVP embryos were either transferred to recipient uteruses or placed in a post-hatching development (PHD) system. As a control group, in vivo-produced (IVV), Day-7 embryos were also transferred to recipient uteruses. All groups were collected on Day 14 and were morphologically evaluated. Day-7 and Day-14 IVV and IVP embryos were used for quantification of eight genes (PLAC8, CD9, SLC2A1, SLC2A3, KRT8, SOD2, HSP1A1, and IFNT2) by reverse transcriptase qPCR. Day-14 embryos from the PHD system were smaller (2.92 ± 0.45 mm) and had a lower embryonic disk diameter (0.14 ± 0.00 mm) than those produced by IVV (24.18 ± 3.71; 0.29 ± 0.03 mm, respectively) or IVP (19.06 ± 2.43; 0.28 ± 0.01 mm) culture and transferred to the uterus (P > 0.05). Day-7 IVP embryos had a higher expression of the HSP1A1, SCL2A1, and SCL2A3 genes than IVV embryos. When these embryos were cultured in the uterus, no differences in gene expression were observed on Day 14. Conversely, Day-14 IVP embryos cultured in the PHD system showed a higher expression of PLAC8, SOD2, and SLC2A3 genes. It is concluded that Day-7 IVP embryos are different from IVV embryos in regards to gene expression, although exposure to the uterine environment during the elongation period allowed the IVP embryos to overcome this difference. In contrast, IVP embryos cultured in the PHD system were morphologically and molecularly different, being of poorer quality than those cultured in the uterus.

In vitro culture of feline embryos increases stress-induced heat shock protein 70 and apoptotic related genes

Developmental competence and quality of in vitro produced embryos has been demonstrated to be lower than in vivo derived embryos. This study aimed specifically to determine the effects of in vitro culture of feline embryos using various culture densities on developmental competence and expression of stress- and apoptotic-related genes in terms of heat shock protein 70 (HSP70) and apoptotic-related (BAX and BCL-2) gene expressions. In experiment 1, we characterized the inducible form of a feline-specific HSP70 mRNA sequence, as it has not been previously reported. The primers for feline HSP70 mRNA were synthesized and tested on heat-treated cat fibroblasts. In experiment 2, feline embryos were cultured at different culture densities (embryo:culture volume; 1:1.25, 1:5 and 1:20). The developmental competence was determined along with HSP70, BAX and BCL-2 transcript abundances using quantitative RT-PCR. In vivo derived embryos were used as a control group. A partial cat HSP70 mRNA sequence (190 bp) was characterized and exhibited high nucleotide identity (93 to 96%) with other species. Cleaved embryos cultured at high density (1:1.25) developed to blastocysts at a lower rate than those generated from lower densities. Irrespective of the culture densities used, in vitro cultured blastocysts showed increased levels of HSP70 and BAX transcripts compared with in vivo counterparts. Blastocysts derived from the highest culture density (1:1.25) showed higher levels of upregulation of HSP70 and BAX transcripts than those cultured at lower culture densities (1:5 and 1:20). In conclusion, increased levels of pro-apoptotic (BAX) and stress-response (HSP70) transcripts correlated with developmental incompetence of embryos cultured at high embryonic density, indicating that stress accumulated during in vitro embryo culture affected the fate for embryo development and quality.

Effect of embryo density on in vitro development and gene expression in bovine in vitro-fertilized embryos cultured in a microwell system

To identify embryos individually during in vitro development, we previously developed the well-of-the-well (WOW) dish, which contains 25 microwells. Here we investigated the effect of embryo density (the number of embryos per volume of medium) on in vitro development and gene expression of bovine in vitro-fertilized embryos cultured in WOW dishes. Using both conventional droplet and WOW culture formats, 5, 15, and 25 bovine embryos were cultured in 125 µl medium for 168 h. The blastocysts at Day 7 were analyzed for number of cells and expression of ten genes (CDX2, IFN-tau, PLAC8, NANOG, OCT4, SOX2, AKR1B1, ATP5A1, GLUT1 and IGF2R). In droplet culture, the rates of formation of >4-cell cleavage embryos and blastocysts were significantly lower in embryos cultured at 5 embryos per droplet than in those cultured at 15 or 25 embryos per droplet, but not in WOW culture. In both droplet and WOW culture, developmental kinetics and blastocyst cell numbers did not differ among any groups. IFN-tau expression in embryos cultured at 25 embryos per droplet was significantly higher than in those cultured at 15 embryos per droplet and in artificial insemination (AI)-derived blastocysts. Moreover, IGF2R expression was significantly lower in the 25-embryo group than in the 5-embryo group and in AI-derived blastocysts. In WOW culture, these expressions were not affected by embryo density and were similar to those in AI-derived blastocysts. These results suggest that, as compared with conventional droplet culture, in vitro development and expression of IFN-tau and IGF2R in the microwell system may be insensitive to embryo density.

Expression and characterization of constitutive heat shock protein 70.1 (HSPA-1A) gene in in vitro produced and in vivo-derived buffalo (Bubalus bubalis) embryos

Cells are blessed with a group of stress protector molecules known as heat shock proteins (HSPs), amongst them HSP70, encoded by HSPA-1A gene, is most abundant and highly conserved protein. Variety of stresses hampers the developmental competence of embryos under in vivo and in vitro conditions. Present work was designed to study the quantitative expression of HSPA-1A mRNA in immature oocytes (IMO), matured oocytes (MO), in vitro produced (IVP) and in vivo-derived (IVD) buffalo embryos to assess the level of stress to which embryos are exposed under in vivo and in vitro culture conditions. Further, HSPA-1A gene sequence was analysed to determine its homology with other mammalian sequences. The mRNA expression analysis was carried out on 72 oocytes (40 IMO; 32 MO), 76 IVP and 55 IVD buffalo embryos. Expression of HSPA-1A was found in oocytes and throughout the developmental stages of embryos examined irrespective of the embryo source; however, higher (p < 0.05) expression was observed in 8-16 cell, morula and blastocyst stages of IVP embryos as compared to IVD embryos. Phylogenetic analysis of bubaline HSPA-1A revealed that it shares 91-98% identity with other mammalian sequences. It can be concluded that higher level of HSPA-1A mRNA in IVP embryos in comparison with in vivo-derived embryos is an indicator of cellular stress in IVP system. This study suggests need for further optimization of in vitro culture system in which HSPA-1A gene could be used as a stress biomarker during pre-implantation development.

Effect of culture medium volume and embryo density on early mouse embryonic development: tracking the development of the individual embryo

PURPOSE

To determine the optimal volume or density of embryos for the well-of-the-well (WOW) system in order to track the development of individual embryos and to determine whether the WOW system can reverse the negative impact of culturing embryos singly.

METHODS

(1) Mouse embryos (groups of nine at the 2-cell stage) were cultured in 6.25 μl, 12.50 μl, 25.00 μl and 50.00 μl of droplets of culture medium under paraffin oil; (2) Groups of three, six, nine and twelve embryos at the 2-cell stage were cultured in 50 μl of droplet of culture medium under paraffin oil; (3) Groups of nine embryos at the 2-cell stage were cultured in 50 μl of droplet under paraffin oil with or without nine micro-wells made on the bottom of the Petri dish into each of which were placed one of the nine embryos (WOW system). Also single 2-cell stage embryos was cultured individually in 5.5 μl of droplet of culture medium under paraffin oil with or without a single micro-well made on the bottom of the Petri dish (WOW system for single culture). At the end of culture, the percentages of blastocyst development, hatching and hatched blastocysts were compared in each group. The blastocysts were fixed for differential staining.

RESULTS

The blastocyst development was significantly higher (P < 0.05) when nine embryos were cultured in 50 μl of droplet of culture medium compared with other volumes. The blastocyst development was significantly reduced (P < 0.05) in single embryo culture compared to group embryo culture with or without the WOW system. The blastocyst development was not improved when single embryo cultured individually in a micro-well was compared to single embryo cultured individually without micro-well. The total cell numbers of blastocysts were significantly higher in group embryo culture than single embryo culture regardless of whether the WOW system was used. In addition, the total cell numbers of blastocysts were significantly higher (P < 0.05) in single embryo culture with the WOW system than without.

CONCLUSIONS

Group embryo culture is superior to single embryo culture for blastocyst development. The WOW system with 50 μl of droplet of culture medium can be used to track the individual development of embryo cultured in groups while preserving good embryonic development. The reduced embryonic development with single embryo culture cannot be ameliorated by the WOW system.

Culture systems: embryo density

Embryo density is defined as the embryo-to-volume ratio achieved during in vitro culture; in other words, it is the number of embryos in a defined volume of culture medium. The same density can be achieved by manipulating either the number of embryos in a given volume of medium, or manipulating the volume of the medium for a given number of embryos: for example, a microdrop with five embryos in a 50 μl volume under oil has the same embryo-to-volume ratio (1:10 μl) as a microdrop with one embryo in a 10 μl volume under oil (1:10 μl). Increased embryo density can improve mammalian embryo development in vitro; however, the mechanism(s) responsible for this effect may be different with respect to which method is used to increase embryo density.Standard, flat sterile plastic petri dishes are the most common, traditional platform for embryo culture. Microdrops under a mineral oil overlay can be prepared to control embryo density, but it is critical that dish preparation is consistent, where appropriate techniques are applied to prevent microdrop dehydration during preparation, and results of any data collection are reliable, and repeatable. There are newer dishes available from several manufacturers that are specifically designed for embryo culture; most are readily available for use with human embryos. The concept behind these newer dishes relies on fabrication of conical and smaller volume wells into the dish design, so that embryos rest at the lowest point in the wells, and where putative embryotrophic factors may concentrate.Embryo density is not usually considered by the embryologist as a technique in and of itself; rather, the decision to culture embryos in groups or individually is protocol-driven, and is based more on convenience or the need to collect data on individual embryos. Embryo density can be controlled, and as such, it can be utilized as a simple, yet effective tool to improve in vitro development of human embryos.

Post-hatching development of bovine embryos in vitro: the effects of tunnel preparation and gender

The objective of this study was to compare morphological characteristics, kinetics of development, and gene expression of male and female IVP embryos that were cultured until day (D)15 (fertilization = D0), using either phosphate-buffered saline (PBS) or Milli-Q water (MQW) to dilute the agarose gel used for tunnel construction. On D11, embryos (n = 286) were placed in agarose gel tunnels diluted in PBS and MQW. Embryos were evaluated for morphology, and embryo size was recorded on D11, D12.5, D14 and D15. Then, embryos were sexed and used for gene expression analyses (G6PD, GLUT1, GLUT3, PGK1, PLAC8, KRT8, HSF1 and IFNT). The percentage of elongated embryos at D15 was higher (p < 0.05) in the PBS (54%) than in the MQW (42%) gel. However, embryos produced in MQW were bigger (p < 0.05) and had a lower expression of GLUT1 (p = 0.08) than those cultured in PBS. There was a higher proportion of male than female embryos at D15 in both treatments, MQW (65% vs. 35%; p < 0.05) and PBS (67% vs. 33%; p < 0.05); however, embryo size was not significantly different between genders. Moreover, D15 female embryos had greater expression of G6PD (p = 0.05) and KRT8 (p = 0.03) than male embryos. In conclusion, the diluent used for tunnel construction affected embryo development in the post-hatching development (PHD) system, and the use of MQW was the most indicative measure for the evaluation of embryo quality. Male and female embryos cultured from D11 to D15, either in an MQW or PBS agarose gel, demonstrated similar development but different gene expression.

Quality Management Issues in the Assisted Reproduction Laboratory

In the United States, the Clinical Laboratory Improvement Act (CLIA) of 1988 describes requirements and guidelines for implementing a quality control/quality assurance (QC/QA) program for moderate and high complexity laboratories. These requirements and guidelines apply to Assisted Reproductive Technology (ART) laboratories as well. The general topic of QC and QA as it pertains to in vitro fertilization (IVF) and embryo transfer (ET) is extensively reviewed. This review summarizes many of the QC and QA events that contribute to the advancement of knowledge in this biotechnological field. These events include control of the culture environment inside and outside of the incubator, as well as factors that affect culture media. This review also discusses, in considerable detail, the QC and the QA that pertain to equipment used within the laboratory and how to control for potential contaminants, which reside within the laboratory. This review provides evidence to indicate the need for laboratory personnel to monitor quality improvement issues on a continuous basis. Personnel must be willing to change as improvements in technology occur in order to meet the ever-evolving demands of a more difficult patient population. Suggestions for meeting these demands are offered.

Effect of timing of development on total cell number and expression profile of HSP-70.1 and GLUT-1 in buffalo (Bubalus bubalis) oocytes and preimplantation embryos produced in vitro

The present study was designed to compare the expression profile of two developmentally important genes (HSP-70.1 and GLUT-1) and TCN (total cell number) count in fast (group A) and slow (group B) cleaved buffalo embryos to access their in vitro developmental competence. Buffalo COCs (cumulus oocyte complexes) were collected from local abattoir ovaries and subjected to in vitro maturation in: TCM-199 supplemented with 10% FBS (fetal bovine serum), BSA (3 mg/ml), sodium pyruvate (0.25 mM) and 20 ng/ml EGF (epidermal growth factor) at 38.5 degrees C under 5% CO2. In vitro derived embryos were collected at 4-8, 8-16 cell, morula and blastocyst stages at specific time points for gene expression analysis and total cell count. A semiquantitative RT-PCR (reverse transcriptase-PCR) assay was used to determine the HSP-70.1 and GLUT-1 transcripts. Results showed that developmental competence and TCN count in fast (group A)-cleaving embryos was significantly (P<0.05) higher than in the slow group (group B). The gene transcript of HSP-70.1 and GLUT-1 was expressed in oocytes (immature and mature) and throughout the embryonic developmental stages in the fast group (group A), while in the slow (group B) cleaving embryos, the expression of HSP-70.1 was absent in all the embryonic developmental stages, and expression of GLUT-1 was absent after 8-16 cell stage. In conclusion, TCN count and expression profile of HSP-70.1 and GLUT-1 genes in buffalo embryos are different taking into account the cleavage rate. Quality of such embryos for research purposes, TCN and expression profiling of developmentally important genes should be employed to optimize the in vitro culture system to produce superior quality of embryos.

Expression pattern of oxygen and stress-responsive gene transcripts at various developmental stages of in vitro and in vivo preimplantation bovine embryos

The present study examined the expression pattern of oxygen (O(2)) and stress-responsive gene transcripts at various preimplantation developmental stages of in vitro produced (IVP) and in vivo derived (IVD) bovine embryos. Embryos were produced in vitro from oocytes matured, fertilized and cultured in synthetic oviductal fluid (SOF) medium under low (5%) and high (20%) O(2) concentrations. In vivo embryos were derived from 18 superovulated and artificially inseminated cows. In IVP and IVD groups, embryos were collected at 2-, 4-, 8-, 16-cell morula and blastocyst stages at specific time points for gene expression analysis. The cleavage rates (69.8+/-4.8%) did not differ significantly, but blastocyst rates were significantly higher (28.5+/-3.7%) in low O(2) than those in high O(2) group (18.7+/-3.9%). Mean cell number in low O(2) (145+/-12) and high O(2) (121+/-73) IVP blastocyst were lower (P<0.05) than those of IVD blastocyst (223+/-25). The ICM ratio of IVD blastocyst (26+/-4) was lower (P<0.05) than that of IVP embryos under 5% O(2) (33+/-5) and 20% O(2) (34+/-4) concentrations, respectively. Using real time PCR, for the set of target transcripts (Glut1, Glut5, Sox, G6PD, MnSOD, PRDX5, NADH and Hsp 70.1) analyzed, there were differences in the mRNA expression pattern at 2-, 4-, 8-, 16-cell morula and Day 7 blastocyst stages between the two embryo sources. It can be concluded that, although in vitro bovine embryo culture in SOF medium under low (5%) O(2) concentration provided a more conducive environment in terms of blastocyst formation; differences in the total cell number and gene expression pattern between the IVP and IVD embryos reflected the effect of O(2) concentration.