Early cleaving embryos result in blastocysts with increased aspartate and glucose consumption, which exhibit different metabolic gene expression that persists in placental and fetal tissues.

OBJECTIVES: Using time-lapse microscopy, previous research has shown that IVF mouse embryos that cleave earlier at the first division ('fast') develop into blastocysts with increased glucose consumption and lower likelihood of post-implantation loss as compared to slower cleaving embryos ('slow'). Further, metabolomics analysis employing LC-MS conducted on groups of 'fast' blastocysts revealed that more aspartate was consumed. With the worldwide adoption of single blastocyst transfer as the standard of care, the need for quantifiable biomarkers of viability, such as metabolism of specific nutrients, would greatly assist in embryo selection for transfer. METHODS: Here we describe the development of a targeted enzymatic assay to quantitate aspartate uptake of single blastocysts. RESULTS: Results demonstrate that the rates of aspartate and glucose consumption were significantly higher in individual 'fast' blastocysts. Blastocysts, together with placental and fetal liver tissue collected following transfer, were analysed for the expression of genes involved in aspartate and carbohydrate metabolism. In 'fast' blastocysts, expressions of B3gnt5, Slc2a1, Slc2a3, Got1 and Pkm2 were found to be significantly higher. In placental tissue derived from 'fast' blastocysts, expression of Slc2a1, Got1 and Pkm2 were significantly higher, while levels of Got1 and Pkm2 were lower in fetal liver tissue compared to tissue from 'slow' blastocysts. CONCLUSIONS: Importantly, this study shows that genes regulating aspartate and glucose metabolism were increased in blastocysts that have higher viability, with differences maintained in resultant placentae and fetuses. Consequently, the analysis of aspartate uptake in combination with glucose represents biomarkers of development and may improve embryo selection efficacy and pregnancy rates.

Deep learning as a predictive tool for fetal heart pregnancy following time-lapse incubation and blastocyst transfer.

STUDY QUESTION: Can a deep learning model predict the probability of pregnancy with fetal heart (FH) from time-lapse videos? SUMMARY ANSWER: We created a deep learning model named IVY, which was an objective and fully automated system that predicts the probability of FH pregnancy directly from raw time-lapse videos without the need for any manual morphokinetic annotation or blastocyst morphology assessment. WHAT IS KNOWN ALREADY: The contribution of time-lapse imaging in effective embryo selection is promising. Existing algorithms for the analysis of time-lapse imaging are based on morphology and morphokinetic parameters that require subjective human annotation and thus have intrinsic inter-reader and intra-reader variability. Deep learning offers promise for the automation and standardization of embryo selection. STUDY DESIGN, SIZE, DURATION: A retrospective analysis of time-lapse videos and clinical outcomes of 10 638 embryos from eight different IVF clinics, across four different countries, between January 2014 and December 2018. PARTICIPANTS/MATERIALS, SETTING, METHODS: The deep learning model was trained using time-lapse videos with known FH pregnancy outcome to perform a binary classification task of predicting the probability of pregnancy with FH given time-lapse video sequence. The predictive power of the model was measured using the average area under the curve (AUC) of the receiver operating characteristic curve over 5-fold stratified cross-validation. MAIN RESULTS AND THE ROLE OF CHANCE: The deep learning model was able to predict FH pregnancy from time-lapse videos with an AUC of 0.93 [95% CI 0.92-0.94] in 5-fold stratified cross-validation. A hold-out validation test across eight laboratories showed that the AUC was reproducible, ranging from 0.95 to 0.90 across different laboratories with different culture and laboratory processes. LIMITATIONS, REASONS FOR CAUTION: This study is a retrospective analysis demonstrating that the deep learning model has a high level of predictability of the likelihood that an embryo will implant. The clinical impacts of these findings are still uncertain. Further studies, including prospective randomized controlled trials, are required to evaluate the clinical significance of this deep learning model. The time-lapse videos collected for training and validation are Day 5 embryos; hence, additional adjustment would need to be made for the model to be used in the context of Day 3 transfer. WIDER IMPLICATIONS OF THE FINDINGS: The high predictive value for embryo implantation obtained by the deep learning model may improve the effectiveness of previous approaches used for time-lapse imaging in embryo selection. This may improve the prioritization of the most viable embryo for a single embryo transfer. The deep learning model may also prove to be useful in providing the optimal order for subsequent transfers of cryopreserved embryos. STUDY FUNDING/COMPETING INTEREST(S): D.T. is the co-owner of Harrison AI that has patented this methodology in association with Virtus Health. P.I. is a shareholder in Virtus Health. S.C., P.I. and D.G. are all either employees or contracted with Virtus Health. D.G. has received grant support from Vitrolife, the manufacturer of the Embryoscope time-lapse imaging used in this study. The equipment and time for this study have been jointly provided by Harrison AI and Virtus Health.

Antioxidants improve IVF outcome and subsequent embryo development in the mouse.

STUDY QUESTION: What is the effect of a combination of three antioxidants (Acetyl-L-Carnitine, N-Acetyl-L-Cysteine and α-Lipoic Acid), present in IVF medium during mouse oocyte and sperm collection, on fertilization and subsequent IVF embryo development? SUMMARY ANSWER: A combination of antioxidants resulted in faster developmental times from the 2-cell stage through to expanded blastocyst stage, accompanied by a significant increase in blastocyst cell number and a reduction of intracellular hydrogen peroxide (H2O2) levels. WHAT IS KNOWN ALREADY: The antioxidant combination Acetyl-L-Carnitine, N-Acetyl-L-Cysteine and α-Lipoic Acid, when present in embryo culture media, has a significant beneficial effect on in vitro fertilized mouse pronucleate oocyte development, especially under oxidative stress. STUDY DESIGN, SIZE, DURATION: IVF was conducted with combined antioxidants supplemented in IVF medium that was used for mouse oocyte collection and fertilization (oocyte IVF medium, 4 h exposure) and sperm collection and preparation (sperm IVF medium, 1 h exposure). PARTICIPANTS/MATERIALS, SETTINGS, METHODS: IVF was conducted under 20% oxygen, in the presence or absence of a combination of antioxidants (10 µM Acetyl-L-Carnitine, 10 µM N-Acetyl-L-Cysteine, 5 µM α-Lipoic Acid) and resultant embryos cultured with and without antioxidants under 20% oxygen. Subsequently, the effects of antioxidants on either oocytes or sperm was evaluated. Embryo development was analysed through time-lapse microscopy followed by differential nuclear staining to determine cell allocation in the blastocyst. Intracellular levels of H2O2 were assessed using an aryl boronate probe after 4 h of incubation with antioxidants. Controls were gametes and embryos that had no antioxidants in the medium. In a separate series of experiments, pronucleate oocytes were collected in handling medium with and without antioxidants for 20 min and subsequent cell numbers analysed. MAIN RESULTS AND THE ROLE OF CHANCE: Antioxidant treatment during both IVF and culture resulted in significantly faster development times to two cell cleavage (P < 0.01), which continued through to the expanded blastocyst stage (P < 0.05). Resultant blastocysts had a significant increase in both trophectoderm (TE) cell numbers, inner cell mass (ICM) and total cell numbers (P < 0.001). The addition of antioxidants to IVF medium or embryo culture media exclusively also resulted in a significant increase in both blastocyst TE and ICM numbers leading to an increase in total cell numbers (P < 0.001). Antioxidant supplementation of either oocyte IVF medium alone, or in both oocyte and sperm IVF medium, lead to significantly faster times to two cell cleavage, which continued through to the expanded blastocyst stage. Blastocyst cell number in both these groups had significantly higher TE cell numbers resulting in an increase in total cell numbers. In contrast, there were no differences in embryo developmental rates and blastocyst cell number when antioxidants were present only in the sperm IVF medium. Levels of H2O2 were significantly reduced in pronucleate oocytes that were cultured in the presence of antioxidants (P < 0.001) compared to control, untreated embryos. Similarly, pronucleate oocytes treated with the combined antioxidants during pronucleate oocyte collection resulted in significantly increased blastocyst ICM numbers compared with controls (P < 0.05). LIMITATIONS, REASONS FOR CAUTION: Embryo development was only examined in the mouse. WIDER IMPLICATIONS OF THE FINDINGS: These findings suggest that supplementation of antioxidants to the IVF medium, as well as to embryo culture media, may further assist in maintaining the viability of human embryos in ART, conceivably through the reduction of oxidative stress. STUDY FUNDING/COMPETING INTEREST(S): This work was funded by a research grant from Vitrolife AB (Sweden). The authors have no conflict of interest to declare.

Developmental kinetics of cleavage stage mouse embryos are related to their subsequent carbohydrate and amino acid utilization at the blastocyst stage.

STUDY QUESTION: What is the relationship between cleavage stage embryo kinetics, blastocyst metabolism and subsequent embryo viability? SUMMARY ANSWER: Embryos cleaving faster at the first cleavage division resulted in blastocysts with a larger inner cell mass (ICM), higher glucose consumption, lower glycolytic rate, higher aspartate uptake, lower global amino acid turnover and higher percentage of developing fetuses on E13.5 when compared with blastocysts that developed from slower cleaving embryos. WHAT IS KNOWN ALREADY: Previous research has shown that morphokinetics, blastocyst carbohydrate metabolism and cleavage stage amino acid metabolism of the preimplantation embryo can be used independently as markers of its developmental competence and subsequent viability. STUDY DESIGN, SIZE, DURATION: Morphokinetics of in vitro fertilized mouse zygotes were observed using a time-lapse imaging system and they were identified as 'fast' or 'slow' cleaving embryos. Spent culture media from resultant blastocysts were analysed for carbohydrate and amino acid utilization. Blastocysts either had their ICM and trophectoderm (TE) cell number determined, were cultured further in an outgrowth assay or transferred to a recipient female to assess implantation and fetal development. PARTICIPANTS/MATERIALS, SETTING, METHODS: Morphokinetics of in vitro fertilized C57BL/6xCBA (F1) zygotes individually cultured in 2 µl drops of G1/G2 media with HSA under Ovoil in 5% O2, 6% CO2 and 89% N2 were analysed using a time-lapse incubator. At 72 h post-insemination, blastocysts were separated into quartiles derived from timing of the first cleavage division. Blastocysts were cultured for a further 24 h and spent media samples, including controls containing no embryos, were frozen and subsequently analysed for amino acid utilization using liquid chromatography-mass spectrometry. These blastocysts were then analysed over a further 1.5 h period for carbohydrate utilization and subsequently stained to determine ICM and TE cells. To analyse implantation potential, fetal quality and viability, additional 'fast' and 'slow' blastocysts were cultured further in an outgrowth model or transferred to recipient females. MAIN RESULTS AND THE ROLE OF CHANCE: Embryos cleaving faster at the time of first cleavage (first quartile, designated 'fast') were on average 2.5 h ahead of slower embryos (fourth quartile, designated 'slow', 15.1 ± 0.1 versus 17.6 ± 0.1 h, P < 0.001). On Day 5 of culture, blastocysts developed from 'fast' embryos had a larger ICM number (17.4 ± 2.1 versus 7.4 ± 2.0, P < 0.01), a higher glucose consumption (21.2 ± 1.2 versus 14.3 ± 1.0 pmol/embryo/h, P < 0.001) and a lower glycolytic rate (expressed as the percentage of glucose converted to lactate) (49.6 ± 2.8 versus 59.7 ± 2.8%, P < 0.05) compared with 'slow' embryos. Further non-invasive metabolomic analysis revealed that 'fast' blastocysts consumed more aspartate (2.2 ± 0.1 versus 1.8 ± 0.1 pmol/embryo/h, P < 0.05) and produced little or no glutamate compared with 'slow' blastocysts (0.02 ± 0.07 consumed versus 0.32 ± 0.11 pmol/embryo/h produced, P < 0.05). Transfer of 'fast' blastocysts to pseudo-pregnant recipients resulted in higher fetal survival post-implantation compared with 'slow' blastocysts (69.6 versus 40.4%, P < 0.01). LIMITATIONS, REASONS FOR CAUTION: The timing of the first cleavage division was used to classify blastocysts as 'fast' or 'slow' embryos; however, a combination of several developmental kinetic markers (cleavage time of 3- to 8-cell, duration between cleavage division times) may be used to more accurately determine an embryo as 'fast' or 'slow'. Only the fastest and slowest quartiles (those embryos with the fastest and slowest first cleavage division) were analysed in this study. WIDER IMPLICATIONS OF THE FINDINGS: These findings show that kinetically different embryos develop into blastocysts with different metabolic profiles and viability. Work is now being undertaken to determine if using these viability markers in combination will increase embryo selection efficacy and further improve implantation and pregnancy rates. STUDY FUNDING/COMPETING INTERESTS: The study was funded by the University of Melbourne. The authors have no conflicts of interest to declare.

Impact of oxygen concentration on adult murine pre-antral follicle development in vitro and the corresponding metabolic profile.

Oxygen concentration during in vitro culture has a significant effect on the physiology of embryos, altering metabolic profile and developmental outcome. Although atmospheric oxygen has been used routinely for the culture of ovarian follicles, oxygen concentration may also be critical for follicle growth but the optimal concentration has not been determined. In this study, mechanically isolated primary and secondary follicles (80-140 µm diameter) from adult mouse ovaries were cultured in serum-free conditions for 8 days in either 5 or 20% oxygen to determine growth (follicular diameter), morphology and viability. For each oxygen concentration, half of the medium was replaced on Days 2, 4 and 6 or on Day 4 only. In the latter group, metabolic analysis of spent follicular culture media was performed by (1)H-NMR. The proportion of viable, growing follicles was significantly (P < 0.0001) higher in 5% than in 20% oxygen (59% versus 8%). Reducing the frequency of medium replacement during culture in 5% oxygen resulted in significantly (P < 0.001) more viable follicles (79 versus 46%). In 20% oxygen, poor follicular viability was observed irrespective of the frequency of medium replacement (8 and 10% respectively). Metabolic profiles showed marked differences in amino acid and carbohydrate utilization with respect to both oxygen concentration and between Days 4 and 8 of development. Metabolites which significantly discriminated between oxygen concentration at both time points were glucose consumption, lactate utilization, alanine, alanyl-glutamine, leucine and proline. In conclusion, the poor in vitro follicular development previously observed in minimal culture conditions may reflect the use of 20% oxygen. Frequent medium replenishment is not necessary and does not overcome the detrimental effect of high oxygen on follicle viability. Further optimization of culture conditions would benefit from metabolic analyses and the use of 5% oxygen should be tested further for impact on functional aspects of follicle culture such as steroid production which is currently unknown.

Endometrial signals improve embryo outcome: functional role of vascular endothelial growth factor isoforms on embryo development and implantation in mice.

STUDY QUESTION: Does vascular endothelial growth factor (VEGF) have important roles during early embryo development and implantation? SUMMARY ANSWER: VEGF plays key roles during mouse preimplantation embryo development, with beneficial effects on time to cavitation, blastocyst cell number and outgrowth, as well as implantation rate and fetal limb development. WHAT IS KNOWN ALREADY: Embryo implantation requires synchronized dialog between maternal cells and those of the conceptus. Following ovulation, secretions from endometrial glands increase and accumulate in the uterine lumen. These secretions contain important mediators that support the conceptus during the peri-implantation phase. Previously, we demonstrated a significant reduction of VEGFA in the uterine cavity of women with unexplained infertility. Functional studies demonstrated that VEGF significantly enhanced endometrial epithelial cell adhesive properties and embryo outgrowth. STUDY DESIGN, SIZE, DURATION: Human endometrial lavages (n = 6) were obtained from women of proven fertility. Four-week old Swiss mice were superovulated and mated with Swiss males to obtain embryos for treatment with VEGF in vitro. Preimplantation embryo development was assessed prior to embryo transfer (n = 19-30/treatment group/output). Recipient F1 female mice (8-12 weeks of age) were mated with vasectomized males to induce pseudopregnancy and embryos were transferred. On Day 14.5 of pregnancy, uterine horns were collected for analysis of implantation rates as well as placental and fetal development (n = 14-19/treatment). PARTICIPANTS/MATERIALS, SETTING, METHODS: Lavage fluid was assessed by western immunoblot analysis to determine the VEGF isoforms present. Mouse embryos were treated with either recombinant human (rh)VEGF, or VEGF isoforms 121 and 165. Preimplantation embryo development was quantified using time-lapse microscopy. Blastocysts were (i) stained for cell number, (ii) transferred to wells coated with fibronectin to examine trophoblast outgrowth or (iii) transferred to pseudo pregnant recipients to analyze implantation rates, placental and fetal development. MAIN RESULTS AND THE ROLE OF CHANCE: Western blot analysis revealed the presence of VEGF121 and 165 isoforms in human uterine fluid. Time-lapse microscopy analysis revealed that VEGF (n = 22) and VEGF121 (n = 23) treatment significantly reduced the preimplantation mouse embryo time to cavitation (P < 0.05). VEGF and VEGF165 increased both blastocyst cell number (VEGF n = 27; VEGF165 n = 24: P < 0.001) and outgrowth (n = 15/treatment: 66 h, P < 0.001; 74, 90, 98 and 114 h, P < 0.01) on fibronectin compared with control. Furthermore, rhVEGF improved implantation rates and enhanced fetal limb development (P < 0.05). LIMITATIONS, REASONS FOR CAUTION: Due to the nature of this work, embryo development and implantation was only examined in the mouse. WIDER IMPLICATIONS OF THE FINDINGS: The absence or reduction in levels of VEGF during the preimplantation period likely affects key events during embryo development, implantation and placentation. The potential for improvement of clinical IVF outcomes by the addition of VEGF to human embryo culture media needs further investigation. STUDY FUNDING/COMPETING INTERESTS: This study was supported by a University of Melbourne Early Career Researcher Grant #601040, the NHMRC (L.A.S., Program grant #494802; Fellowship #1002028; N.J.H., Fellowship # 628927; J.E.; project grant #1047756) and L.A.S., Monash IVF Research and Education Foundation. N.K.B. was supported by an Australian Postgraduate Award. Work at PHI-MIMR Institute was also supported by the Victorian Government's Operational Infrastructure Support Program. There are no conflicts of interest to declare.

A brief history of technical developments in intracytoplasmic sperm injection (ICSI). Dedicated to the memory of J.M. Cummins.

Intracytoplasmic sperm injection (ICSI) is an assisted reproductive technology for treatment of severe male infertility introduced into clinical practice in 1992. This review provides a brief history of the development of ICSI by acknowledging major developments in the field. The review addresses key developments in pre-clinical and early studies, how ICSI compares with in vitro fertilisation, long-term consequences, how the mechanistic approach to ICSI has changed in both manual and semi-automated approaches, and how sperm selection procedures are integrated into ICSI. From the beginnings using animal models in the 1960-1970s, the development of ICSI is a remarkable and transformative success story. Indeed, its broad use (70% of cycles globally) exceeds the need required for treating infertile males, and this remains a controversial issue. There remain questions around the long-term health impacts of ICSI. Furthermore, advances in automation of the ICSI procedure are occurring. An estimated 6million children have been born from the ICSI procedure. With further automation of sperm selection technologies, coupled with automation of the injection procedure, it is likely that the proportion of children born from ICSI will further increase.

Human and mouse embryonic development, metabolism and gene expression are altered by an ammonium gradient in vitro.

Ammonium is generated in culture media by the spontaneous deamination of amino acids at 37 °C and through the metabolism of amino acids by human embryos. The appearance of ammonium is a time-dependent phenomenon and can compromise embryo physiology, development and viability. In this study, the effects of a gradient of ammonium on the development, metabolism and transcriptome of human and mouse embryos were investigated. Pronucleate oocytes were cultured in the presence of an ammonium gradient that mimicked the spontaneous deamination of Eagle's amino acids together with 1 mM glutamine. All embryos were cultured in sequential media G1/G2 at 5% O2, 6% CO2 and 89% N2. Human embryo metabolism was assessed through a non-invasive fluorometric analysis of pyruvate consumption. Transcriptome analysis was performed on the resultant blastocysts from both species using a microarray technology. Embryo development prior to compaction was negatively affected by the presence of low levels of ammonium in both species. Human embryo metabolism was significantly inhibited after just 24 and 48 h of culture. Transcriptome analysis of blastocysts from both species revealed significantly altered gene expression profiles, both decreased and increased. Functional annotation of the altered genes revealed the following over represented biological processes: metabolism, cell growth and/or maintenance, transcription, cell communication, transport, development and transcription regulation. These data emphasize the enhanced sensitivity of the cleavage-stage embryo to its environment and highlight the requirement to renew culture media at frequent intervals in order to alleviate the in vitro induced effects of ammonium build-up in the environment surrounding the embryo.

Analysis of global gene expression following mouse blastocyst cryopreservation.

BACKGROUND: The aim of this study was to examine the effect of the cryopreservation procedure (slow freezing or vitrification) and cryoprotectants (1,2-propanediol or dimethylsulphoxide) on mouse blastocyst gene expression. METHODS: Cultured mouse blastocysts were cryopreserved with different protocols. Following thawing/warming, total RNA from re-expanded blastocysts was isolated, amplified and then analyzed using mouse whole-genome microarrays. RESULTS: Compared with non-cryopresevered control blastocysts, gene expression was only significantly altered by slow freezing. Slow freezing affected the expression of 115 genes (P < 0.05). Of these, 100 genes exhibited down-regulation and 15 genes were up-regulated. Gene ontology revealed that the majority of these genes are involved in protein metabolism, transcription, cell organization, signal transduction, intracellular transport, macromolecule biosynthesis and development. Neither of the vitrification treatment groups showed statistically different gene expression from the non-cryopreserved control embryos. Hierarchical cluster analysis, did however, reveal that vitrification using 1,2-propanediol could result in a gene expression profile closest to that of non-cryopreserved blastocysts. CONCLUSIONS: Investigating the effects of cryopreservation on cellular biology, such as gene expression, is fundamental to improving techniques and protocols. This study demonstrates that of the cryopreservation regimens employed, slow freezing induced the most changes in gene expression compared with controls.

Time-lapse analysis of mouse embryo development in oxygen gradients.

Atmospheric oxygen (approximately 20%) in culture significantly impairs preimplantation embryo development. However, it is not known whether all stages of preimplantation embryo development are susceptible to oxygen toxicity. This study investigated the temporal responses of preimplantation embryos to oxygen conditions in vitro. Mouse embryos were cultured in atmospheric (approximately 20%) or lower (5%) oxygen concentrations for the first 48 h, followed by culture in the same or reciprocal oxygen concentrations for another 48 h: group 1 (control, 5 and 5%); group 2 (5 and 20%); group 3 (20 and 5%); and group 4 (20 and 20%). Time-lapse microscopy was performed with imaging of individual embryos at 15-min intervals. Compared with embryos cultured in 5% oxygen, embryos cultured in 20% oxygen were delayed at the 1st cleavage by 0.45 h (P<0.05), at the 2nd cleavage by 0.84 h (P<0.01) and at the 3rd cleavage by 3.19 h (P<0.001). Switching from 20% to 5% oxygen after 48 h did not completely alleviate earlier induced perturbations. Partial or complete culture in atmospheric oxygen resulted in significantly fewer blastocyst cell numbers compared with control (P<0.05). Oxygen can influence mouse embryo development at both the cleavage and post-compaction stages.

Blastocysts from patients with polycystic ovaries exhibit altered transcriptome and secretome.

Polycystic ovaries (PCO) is a common phenotype of women presenting for infertility treatment. This study investigated whether blastocysts derived from women with PCO have an altered molecular signature which could be a causative factor contributing to reproductive failure. Morphologically similar blastocysts derived from women with PCO and donor oocyte cycles were analysed for transcription and protein secretion. Unsupervised hierarchical clustering demonstrated that the transcriptome profiles of blastocysts derived from PCO patients and control blastocysts were markedly different with complete branch separation. Statistical analysis revealed 829 genes with significantly different expression: 784 decreased (94.6%) and 45 increased (5.4%) in blastocysts derived from women with PCO compared with controls (P<0.05). Functional annotation of these genes revealed predominant gene ontology biological processes including protein metabolism (30%), transcription (22%), signal transduction (15%), biosynthesis (15%) and cell cycle (14%). Proteomic profiling identified 12 biomarkers that displayed significant decrease in expression in blastocysts derived from women with PCO compared with controls (P<0.05). These data indicate molecular alterations in human blastocysts derived from PCO patients, potentially demonstrating for the first time a link between patient aetiology/phenotype and subsequent embryo development, which in part may explain the observed reduction in reproductive capacity.

The role of proteomics in defining the human embryonic secretome.

Non-invasive gamete and embryo assessment is considered an important focus in assisted reproductive technologies (ART). Currently, the selection of embryos for transfer is based on morphological indices. Though successful, the field of ART would benefit from a non-invasive quantitative method of viability determination. Omics technologies, including transcriptomics, proteomics and metabolomics, have already begun providing evidence that viable gametes and embryos possess unique molecular profiles with potential biomarkers that can be utilized for developmental and/or viability selection. Unlike the human genome that is relatively fixed and steady throughout the human body, the human proteome, estimated at over a million proteins, is more complex, diverse and dynamic. It is the proteins themselves that contribute to the physiological homeostasis in any cell or tissue. Of particular interest in ART is the secretome, those proteins that are produced within the embryo and secreted into the surrounding environment. Defining the human embryonic secretome has the potential to expand our knowledge of embryonic cellular processes, including the complex dialogue between the developing embryo and its maternal environment, and may also assist in identifying those embryos with the highest implantation potential. Advances in proteomic technologies have allowed the non-invasive profiling of the human embryonic secretome with ongoing research focused on correlation with outcome. From a clinical perspective, embryo selection based on morphological assessment and non-invasive analysis of the human embryonic secretome may improve IVF success and lead to routine single embryo transfers.

Transcriptome analysis of in vivo and in vitro matured bovine MII oocytes.

In vitro maturation (IVM) of mammalian oocytes does not support the same rates of embryo development or pregnancy when compared to oocytes that have matured in vivo. Therefore, environment has a significant influence on the oocyte's ability to complete maturation and acquire the mRNA and proteins required for successful fertilization and normal embryonic development. The aim of this study was to analyze the MII oocyte transcriptome between in vivo and in vitro conditions. Total RNA was extracted, processed and hybridized to the Affymetrix GeneChip Bovine Genome Array. Following normalization of the microarray data, analysis revealed 10 differentially expressed genes after IVM compared to in vivo matured controls, including Aqp3, Sept7, Abhd4 and Siah2 (P<0.05). K-means cluster analysis coupled with associated gene ontology, identified several biological processes affected by IVM, including metabolism, energy pathways, cell organization and biogenesis, and cell growth and maintenance. Quantitative real-time PCR validated the microarray data and also revealed altered expression levels after IVM of specific putatively imprinted genes, Igf2r, Peg3 and Snrpn (P<0.05). Distinct IVM transcription patterns reflected the oocyte's response to its surrounding environment. Monitoring transcription levels of key oocyte maturation genes may subsequently assist in improving IVM success.

A randomized controlled study of human Day 3 embryo cryopreservation by slow freezing or vitrification: vitrification is associated with higher survival, metabolism and blastocyst formation.

BACKGROUND: The aim of this study was to compare two methods of cryopreservation for the cleavage-stage human embryo: slow freezing and vitrification. METHODS: A total of 466 Day 3 embryos, donated with consent, underwent cryopreservation by either slow freezing in straws or vitrification using the cryoloop. The vitrification procedure did not include dimethyl sulfoxide, but rather employed ethylene glycol and 1,2-propanediol as the cryoprotectants. Survival, embryonic metabolism and subsequent development to the blastocyst were used to determine the efficacy of the two procedures. RESULTS: Significantly, more embryos survived the vitrification procedure (222/234, 94.8%) than slow freezing (206/232, 88.7%; P < 0.05). Consistent with this observation, pyruvate uptake was significantly greater in the vitrification group, reflecting a higher metabolic rate. Development to the blastocyst was also higher following vitrification (134/222, 60.3%) than following freezing (106/206, 49.5%; P < 0.05). In a separate cohort of 73 patients who had their supernumerary embryos cyropreserved with vitrification, the resulting implantation rate and clinical pregnancy rate were 30 and 49%, respectively. CONCLUSIONS: Analysis of metabolism revealed that vitrification had less impact on the metabolic rate of the embryo than freezing, which was reflected in higher survival rate and subsequent development in vitro. Excellent pregnancy outcomes followed the warming and transfer of vitrified cleavage-stage embryos. These data provide further evidence that vitrification imparts less trauma to cells and is, therefore, a more effective means of cryopreserving the human embryo than conventional slow freezing. Clinicaltrials.gov identifier: NCT00608010.

Symposium: innovative techniques in human embryo viability assessment. Can proteomics help to shape the future of human assisted conception?

Proteomics describes the changes in all proteins expressed and translated from a single genome. At present little is known regarding either the genome or proteome of human gametes or the preimplantation embryo. The unravelling of this information is fundamental to understanding the complexity of reproductive physiology, including the dialogue between the developing embryo and its maternal environment. To date, a lack of sensitivity has been the main reason behind the inability to introduce proteomics technology into assisted reproduction techniques. Proteomics alone involves several sophisticated techniques including imaging, mass spectrometry and bioinformatics to identify, quantify and characterize a proteome. The recent increased sensitivity of these techniques has allowed for the development of new protocols that are capable of not only profiling the proteome of individual human oocytes and embryos, but also the proteins produced by the embryo into the surrounding medium (the secretome). Hence, the identification of proteins that are involved in oocyte maturation, embryo development and implantation could lead to further improvements in assisted reproduction techniques as well as the development of new diagnostic tests. Furthermore, proteomics may contribute in the design of a non-invasive viability assay to assist in the selection of embryos for transfer in human assisted reproduction.

Embryology in the era of proteomics.

Currently, relatively little is known regarding the protein production of mammalian embryos. Unlike the genome, the proteome itself is dynamic reflecting both internal and external environmental stimuli. Until now the lack of sensitivity has remained a stumbling block for the global introduction of proteomics into the field of mammalian embryology. However, new developments in mass spectrometry have been revolutionary, utilizing protein profiling and peptide sequencing to elucidate underlying biological processes. The sensitivity of these platforms have allowed for the development of new protocols that are capable of profiling the proteome of individual mammalian oocytes and embryos. This information is fundamental to unravelling the complexity of embryo physiology including the dialogue between the developing embryo and its maternal environment. Such proteomic approaches are also assisting in the optimization of ART techniques, including oocyte cryopreservation and in vitro maturation. Embryo selection for transfer is another area of ART that should benefit in this era of proteomics. Currently, mammalian embryos are selected for transfer based on morphological grading systems. Although of great value, analysis of morphology alone cannot determine the embryo's physiological state or chromosomal complement. Subsequently, there is a need to identify in culture those embryos with the highest implantation potential. Proteomic analysis of the embryonic secretome (proteins produced by the embryo and secreted into the surrounding medium) followed by the identification of specific proteins critical for implantation, may lead to the development of a non-invasive viability assay to assist in the selection of embryos for transfer.

Impact of the IVF laboratory environment on human preimplantation embryo phenotype.

The phenotype of the human embryo conceived through in vitro fertilization (IVF), that is its morphology, developmental kinetics, physiology and metabolism, can be affected by numerous components of the laboratory and embryo culture system (which comprise the laboratory environment). The culture media formulation is important in determining embryo phenotype, but this exists within a culture system that includes oxygen, temperature, pH and whether an embryo is cultured individually or in a group, all of which can influence embryo development. Significantly, exposure of an embryo to one suboptimal component of the culture system of laboratory typically predisposes the embryo to become more vulnerable to a second stressor, as has been well documented for atmospheric oxygen and individual culture, as well as for oxygen and ammonium. Furthermore, the inherent viability of the human embryo is derived from the quality of the gametes from which it is created. Patient age, aetiology, genetics, lifestyle (as well as ovarian stimulation in women) are all known to affect the developmental potential of gametes and hence the embryo. Thus, as well as considering the impact of the IVF laboratory environment, one needs to be aware of the status of the infertile couple, as this impacts how their gametes and embryos will respond to an in vitro environment. Although far from straight forward, analysing the interactions that exist between the human embryo and its environment will facilitate the creation of more effective and safer treatments for the infertile couple.

Effects of oxygen tension on the establishment and lactate dehydrogenase activity of murine embryonic stem cells.

The lack of a standardized culture environment for establishment of embryonic stem cell lines has hindered the orchestrated differentiation of cells and the application of this technology. Oxygen concentration has a profound effect on proliferation and differentiation of many cell types. This study tested the hypothesis that establishment dynamics, lactate dehydrogenase (LDH) isoforms, and mRNA expression patterns would be affected by the oxygen tension in the culture environment. Recovered (day 4) murine blastocysts were cultured in a gas environment of 6% CO(2) and either 20% or 5% O(2) (balance supplemented with N(2)). More (p < 0.05) blastocysts produced outgrowths in the low (79.3 +/- 0.1%) compared to the high (57.1 +/- 0.1%) O(2) groups, and more (p < 0.05) colonies in the low O(2) group (14/15; 93.3 +/- 0.1%) stained positive for alkaline phosphatase relative to the high O(2) group (9/15; 60.6 +/- 0.1%). Oxygen treatment had no effect on the activity of the oxioreductase lactate dehydrogenase. Interestingly, the stem cell lines in both treatments displayed multiple isoforms (III, IV, and V) of LDH, whereas the outgrowths displayed isoforms I and V. In contrast, two-cell embryos and blastocysts displayed only isoform I, and fibroblasts displayed isoforms IV and V. There were no treatment differences in mRNA expression of LDHalpha in the outgrowths, or established stem cells. LDH transition from the heart (I) to the muscle (V) isoform indicated an increase in glycolytic activity, consistent with the peri-hatching/implantation time period. Reduced O(2) environment had significant positive effects on the establishment and maintenance of murine stem cells, supporting the hypothesis, whereas the LDH isozyme transition was consistent among treatments.