Temporally differential protein expression of glycolytic and glycogenic enzymes during in vitro preimplantation bovine embryo development

Cell specification and functional interactions in the pig blastocyst inferred from single-cell transcriptomics and uterine fluids proteomics

The embryonic development of the pig comprises a long in utero pre- and peri-implantation development, which dramatically differs from mice and humans. During this peri-implantation period, a complex series of paracrine signals establishes an intimate dialogue between the embryo and the uterus. To better understand the biology of the pig blastocyst during this period, we generated a large dataset of single-cell RNAseq from early and hatched blastocysts, spheroid and ovoid conceptus and proteomic datasets from corresponding uterine fluids. Our results confirm the molecular specificity and functionality of the three main cell populations. We also discovered two previously unknown subpopulations of the trophectoderm, one characterised by the expression of LRP2, which could represent progenitor cells, and the other, expressing pro-apoptotic markers, which could correspond to the Rauber's layer. Our work provides new insights into the biology of these populations, their reciprocal functional interactions, and the molecular dialogue with the maternal uterine environment.

Factors Influencing the Maturation and Developmental Competence of Yak (Bos grunniens) Oocytes In Vitro

The yak (Bos grunniens) is a unique breed living on the Qinghai-Tibet Plateau and its surrounding areas, providing locals with a variety of vital means of living and production. However, the yak has poor sexual maturity and low fertility. High-quality mature oocytes are the basis of animal breeding technology. Recently, in vitro culturing of oocytes and embryo engineering technology have been applied to yak breeding. However, compared to those observed in vivo, the maturation rate and developmental capacity of in vitro oocytes are still low, which severely limits the application of in vitro fertilization and embryo production in yaks. This review summarizes the endogenous and exogenous factors affecting the in vitro maturation (IVM) and developmental ability of yak oocytes reported in recent years and provides a theoretical basis for obtaining high-quality oocytes for in vitro fertilization and embryo production in yaks.

Maternal Undernutrition Induces Cell Signalling and Metabolic Dysfunction in Undifferentiated Mouse Embryonic Stem Cells

Peri-conceptional environment can induce permanent changes in embryo phenotype which alter development and associate with later disease susceptibility. Thus, mouse maternal low protein diet (LPD) fed exclusively during preimplantation is sufficient to lead to cardiovascular, metabolic and neurological dysfunction in adult offspring. Embryonic stem cell (ESC) lines were generated from LPD and control NPD C57BL/6 blastocysts and characterised by transcriptomics, metabolomics, bioinformatics and molecular/cellular studies to assess early potential mechanisms in dietary environmental programming. Previously, we showed these lines retain cellular and epigenetic characteristics of LPD and NPD embryos after several passages. Here, three main changes were identified in LPD ESC lines. First, their derivation capacity was reduced but pluripotency marker expression was similar to controls. Second, LPD lines had impaired Mitogen-activated protein kinase (MAPK) pathway with altered gene expression of several regulators (e.g., Maff, Rassf1, JunD), reduced ERK1/2 signalling capacity and poorer cell survival characteristics which may contribute to reduced derivation. Third, LPD lines had impaired glucose metabolism comprising reduced upstream enzyme expression (e.g., Gpi, Mpi) and accumulation of metabolites (e.g., glucose-6-P, fructose-6-P) above the phosphofructokinase (PFK) gateway with PFK enzyme activity reduced. ESC lines may therefore permit investigation of peri-conceptional programming mechanisms with reduced need for animal experimentation.

Graphical Abstract

Novel Synthetic oviductal fluid for Conventional Freezing 1 (SCF1) culture medium improves development and cryotolerance of in vitro produced Holstein embryos

In vitro produced (IVP) embryos hold great promise in the cattle industry; however, suboptimal in vitro culture conditions induce metabolic dysfunction, resulting in poor development and low cryotolerance of IVP embryos. This limits the use of IVP embryos in the cattle industry for embryo transfer and commercial scale-up. Previous studies have reported the use of individual metabolic regulators in culture media to improve blastocyst development rates and cryopreservation. In this study, we hypothesized that using a combination of select regulators, chosen for their unique synergistic potential, would alleviate metabolic dysfunction and improve the development of in vitro produced embryos to make them more closely resemble in vivo derived embryos. To test this, we first compared lipid content between Holstein and Jersey embryos produced in vivo and in vitro, and then systematically determined the combination of metabolic regulators that led to the greatest improvements in embryonic development, lipid content, mitochondrial polarity, and cryotolerance. We also tested different slow freezing techniques to further improve cryotolerance and finally validated our results via a clinical trial. Overall, we found that the use of multiple metabolic regulators in one culture media, which we refer to as Synthetic oviductal fluid for Conventional Freezing 1 (SCF1), and an optimized slow freezing technique resulted in improved pregnancy rates for frozen IVP embryos compared to embryos cultured in a synthetic oviductal fluid media. Additionally, there was no difference in pregnancy rate between frozen and fresh IVP embryos cultured in SCF1. This suggests that optimizing culture conditions and slow freezing technique can produce cryotolerance IVP and should allow further dissemination of this assisted reproductive technology.

Proteomic reveals the influences of smoke-water and karrikinolide on the biosynthesis of salvianolic acids and lignins in Salvia miltiorrhiza hairy roots

The proteins related to the biosynthesis of salvianolic acids and lignins were regulated by smoke-water and karrikinolide in Salvia miltiorrhiza hairy roots. The effects of smoke-water (SW) and karrikinolide (KAR₁) on the biosynthesis of salvianolic acids and lignins in Salvia miltiorrhiza hairy roots have been studied using proteomic technology. The results showed that a total of 1290 and 1678 differentially expressed proteins were respectively obtained in SW and KAR₁ comparing to the control. Bioinformatics analysis indicated the differentially expressed proteins responding to SW and KAR₁ treatments mainly involved in macromolecule metabolic process, cell part, binding, etc., and most of the proteins were located at the cytoplasm and cell membrane, followed by nuclear. In addition, the proteins involved in salvianolic acids biosynthesis were up-regulated, including 4-coumarate-CoA ligase (EC 6.2.1.12) and shikimate O-hydroxycinnamoyl-transferase (EC 2.3.1.133). Enzymes involved in lignins biosynthesis were also identified, e.g. cinnamyl-alcohol dehydrogenase (EC 1.1.1.195) and peroxidase (EC 1.11.1.7). The results indicated that proteins related to the biosynthesis of salvianolic acids and lignins were regulated by SW and KAR₁ in S. miltiorrhiza hairy roots. This study will enhance our understanding of the mechanism by which SW and KAR₁ on the biosynthesis of salvianolic acids and lignins in S. miltiorrhiza hairy roots.

Lipid Metabolism in Bovine Oocytes and Early Embryos under In Vivo, In Vitro, and Stress Conditions

Lipids are a potential reservoir of energy for initial embryonic development before activation of the embryonic genome and are involved in plasma membrane biosynthesis. Excessive lipid droplet formation is detrimental to cryotolerance and is related to alterations in mitochondrial function, which likely affects lipid metabolism. Increased lipid accumulation in in vitro produced embryos is a consequence of the stress during in vitro embryonic development process. There are several open questions concerning embryo lipid metabolism and developmental potential. Oocyte maturation and embryo development in vivo and in vitro may vary if the donors are subjected to any type of stress before follicle puncture because crucial changes in oocyte/embryonic metabolism occur in response to stress. However, little is known about lipid metabolism under additional stress (such as heat stress). Therefore, in this review, we aimed to update the information regarding the energy metabolism of oocytes and early bovine embryos exhibiting developmental competence, focusing on lipid metabolic pathways observed under in vivo, in vitro, and stress conditions.

Metabolites Secreted by Bovine Embryos In Vitro Predict Pregnancies That the Recipient Plasma Metabolome Cannot, and Vice Versa

This work describes the use of mass spectrometry-based metabolomics as a non-invasive approach to accurately predict birth prior to embryo transfer (ET) starting from embryo culture media and plasma recipient. Metabolomics was used here as a predictive platform. Day-6 in vitro produced embryos developed singly in modified synthetic oviduct fluid culture medium (CM) drops for 24 h were vitrified as Day-7 blastocysts and transferred to recipients. Day-0 and Day-7 recipient plasma (N = 36 × 2) and CM (N = 36) were analyzed by gas chromatography coupled to the quadrupole time of flight mass spectrometry (GC-qTOF). Metabolites quantified in CM and plasma were analyzed as a function to predict pregnancy at Day-40, Day-62, and birth (univariate and multivariate statistics). Subsequently, a Boolean matrix (F1 score) was constructed with metabolite pairs (one from the embryo, and one from the recipient) to combine the predictive power of embryos and recipients. Validation was performed in independent cohorts of ETs analyzed. Embryos that did not reach birth released more stearic acid, capric acid, palmitic acid, and glyceryl monostearate in CM (i.e., (p < 0.05, FDR < 0.05, Receiver Operator Characteristic—area under curve (ROC-AUC) > 0.669)). Within Holstein recipients, hydrocinnamic acid, alanine, and lysine predicted birth (ROC-AUC > 0.778). Asturiana de los Valles recipients that reached birth showed lower concentrations of 6-methyl-5-hepten-2-one, stearic acid, palmitic acid, and hippuric acid (ROC-AUC > 0.832). Embryonal capric acid and glyceryl-monostearate formed F1 scores generally >0.900, with metabolites found both to differ (e.g., hippuric acid, hydrocinnamic acid) or not (e.g., heptadecanoic acid, citric acid) with pregnancy in plasmas, as hypothesized. Efficient lipid metabolism in the embryo and the recipient can allow pregnancy to proceed. Changes in phenolics from plasma suggest that microbiota and liver metabolism influence the pregnancy establishment in cattle.

The proteome of human Fallopian tube lavages during the phase of embryo transit reveals candidate proteins for the optimization of preimplantation embryo culture

STUDY QUESTION

Are there phase-specific changes in the early secretory (ES) phase human tubal lavage proteome that can inform and potentially optimize IVF culture media?

SUMMARY ANSWER

The human tubal lavage proteome during the ES phase relative to the menstrual phase reveals substantial differential protein abundance in pathways such as glycolysis, redox homeostasis and activation of 14-3-3 zeta-mediated signaling.

WHAT IS KNOWN ALREADY

The Fallopian tube is uniquely suited to the development of the preimplantation embryo as it transits the tube during the ES phase of the menstrual cycle. Euploid cleavage-stage embryo arrest may reflect incomplete recapitulation of in-vivo conditions by current media formulations.

STUDY DESIGN, SIZE, DURATION

Proteome-wide analysis of distal tubal lavage specimens collected from 26 healthy women undergoing open microtubal anastomosis surgery from January 2013 to January 2018 was performed. Specimens were grouped by menstrual cycle phase in order to analyze phase-specific differences in protein abundance. For the murine embryo assay, single-cell embryos (N = 482) were collected from superovulated wild type C57BL/6 female mice and cultured in microdrops over 5 days for the assessment of blastocyst development.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human tubal lavage specimens were processed for label-free mass spectrometry. Reported menstrual cycle day was confirmed by measuring serum hormones. Key protein targets in the ES phase were validated via immunoblot. The ES phase-specific increase in 14-3-3 zeta protein was confirmed via ELISA of conditioned media obtained from primary human Fallopian tube epithelial cell culture. A murine embryo assay was performed to investigate the impact of graduated concentrations of 14-3-3 zeta on the blastocyst development rate.

MAIN RESULTS AND THE ROLE OF CHANCE

Comparison of the ES and menstrual phase human tubal lavage proteomes revealed 74 differentially expressed proteins with enrichment of pathways and biological processes involved in the regulation of carbohydrate metabolism, oxidative stress and cell survival. The adapter-regulator protein 14-3-3 zeta was among the most significantly increased in the ES phase. Supplementation of embryo culture media with 14-3-3 zeta at concentrations tested did not significantly improve the murine blastocyst development.

LIMITATIONS, REASONS FOR CAUTION

Although select associations were recapitulated in the conditioned media from sex steroid exposed primary human tubal epithelial cells, cell culture represents an in-vitro approximation. Changes to embryo culture media, such as protein supplementation, must undergo rigorous preclinical safety testing prior to adoption for human use.

WIDER IMPLICATIONS OF THE FINDINGS

This study represents the first description of the human Fallopian tube lavage proteome across the menstrual cycle, revealing a unique proteomic signature during the ES phase. Although supplementation of culture media with 14-3-3 zeta at appropriate concentrations showed no significant impact on the murine blastocyst development rate, other biologically plausible candidate proteins for individual or high throughput testing strategies are identified.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded in part by an Army Medical Department Advanced Medical Technology Initiative grant from the United States Army Medical Research and Materiel Command's Telemedicine and Advanced Technology Research Center. There are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Treatment of Buffalo (Bubalus bubalis) Somatic Cell Nuclear Transfer Embryos with MicroRNA-29b Mimic Improves Their Quality, Reduces DNA Methylation, and Changes Gene Expression Without Affecting Their Developmental Competence

microRNA-29b (miR-29b) plays an important role in controlling DNA methylation in cells. We investigated its role during early embryonic development in buffalo embryos produced by somatic cell nuclear transfer (SCNT) and in vitro fertilization (IVF). miR-29b expression was highest at the 2-cell stage, decreased (p < 0.001) at the 4-cell stage, and remained low thereafter at the 8-cell, morula, and blastocyst stages, showing a similar pattern in cloned and IVF embryos. Treatment of reconstructed embryos with miR-29b mimic for 1 hour after 1 hour of electrofusion increased (p < 0.05) the total cell number and decreased (p < 0.05) the levels of apoptosis and DNA methylation compared with controls. It also increased (p < 0.05) the ratio of inner cell mass:trophectoderm cell numbers of blastocysts compared with controls to the levels observed in IVF blastocysts. However, the blastocyst rate was not affected by treatment with miR-29b mimic (29.0% ± 2.0% vs. 27.0% ± 2.0% for controls). The treatment decreased (p < 0.001) the expression of epigenetic-related genes, DNMT3A and DNMT3B, but not DNMT1, and increased (p < 0.05) that of pluripotency- (NANOG, OCT4, and SOX2) and development-related genes (FGF4 and GLUT1) in blastocysts compared with controls. Our results suggest that miR-29b mimic treatment of reconstructed embryos improves the quality, reduces the level of apoptosis and DNA methylation, and changes gene expression in SCNT blastocysts without affecting the blastocyst rate.