Consequences of transfer of an in vitro-produced embryo for the dam and resultant calf

A large population study to assess the magnitude of prenatal programming in dairy cattle

The performance of an adult dairy cow may be influenced by events that occur before her birth. The present study investigated potential effects of 2 prenatal groups of factors, Assisted Reproductive Techniques (ART) and maternal characteristics (e.g., dam parity), on offspring performance during their first lactation, in populations of 2 dairy cow breeds: French Holstein and Montbéliarde. The different ART studied included the type of semen (conventional or X-sorted) used for Artificial Insemination (AI) and the technology of conception used (AI, embryo transfer, or in vitro fertilization). Three maternal characteristics were considered: (1) the dam age at first calving, (2) dam parity number, and (3) indicators of dam udder health during gestation (somatic cell score and events of clinical mastitis). First, we investigated whether heifer survival from 3d to 18 mo old was associated with any of the prenatal factors considered. We then estimated the associations of these prenatal factors with 8 traits of commercial interest: (1) stature, (2-4) milk, fat, and protein yields, (5) somatic cell score, (6) clinical mastitis, and (7-8) heifer and cow conception rate, all measured on genotyped cows. Linear models were used for this study with the prenatal factors as covariates in the model, and for the 8 traits, phenotypes were adjusted for their corresponding genomic estimated breeding value. The results indicated that the survival rate of heifers born from embryo transfer was significantly higher than that of heifers born from AI (probably due to preferential management practices), while the other prenatal factors did not explain differences in heifer survival. Among the Montbéliarde cows born from AI, those born from X-sorted semen showed a lightly but significantly lower milk yield than those born without X-sorting of the semen (-52 kg of milk in the first lactation). Among the Holstein cows, those born from embryo transfer presented significantly lower milk performance than cows born from AI. Regarding the maternal characteristics, none or very weak associations were found between the dam age at first calving and the offspring performance in both breeds. Dam parity, on the other hand, was associated with offspring performance for milk, fat, and protein yield in both breeds, however not in the same direction. In the Holstein breed, an increase in dam parity was favorable for offspring performance for milk, fat, and protein yield, whereas in the Montbéliarde breed, an increase in dam parity was associated with lower milk and protein yield and no association was found for fat yield. The udder health of the dam during gestation was not or only weakly associated with the traits studied in the offspring. Although some significant associations were identified due to the large sample size, the effects were modest, typically less than 1% of the phenotypic mean, and were not consistently observed across the 2 breeds.

Production of light-coloured, low heat-absorbing Holstein Friesian cattle by precise embryo-mediated genome editing

CONTEXT

Genome editing enables the introduction of beneficial sequence variants into the genomes of animals with high genetic merit in a single generation. This can be achieved by introducing variants into primary cells followed by producing a live animal from these cells by somatic cell nuclear transfer cloning. The latter step is associated with low efficiencies and developmental problems due to incorrect reprogramming of the donor cells, causing animal welfare concerns. Direct editing of fertilised one-cell embryos could circumvent this issue and might better integrate with genetic improvement strategies implemented by the industry.

METHODS

In vitro fertilised zygotes were injected with TALEN editors and repair template to introduce a known coat colour dilution mutation in the PMEL gene. Embryo biopsies of injected embryos were screened by polymerase chain reaction and sequencing for intended biallelic edits before transferring verified embryos into recipients for development to term. Calves were genotyped and their coats scanned with visible and hyperspectral cameras to assess thermal energy absorption.

KEY RESULTS

Multiple non-mosaic calves with precision edited genotypes were produced, including calves from high genetic merit parents. Compared to controls, the edited calves showed a strong coat colour dilution which was associated with lower thermal energy absorbance.

CONCLUSIONS

Although biopsy screening was not absolutely accurate, non-mosaic, precisely edited calves can be readily produced by embryo-mediated editing. The lighter coat colouring caused by the PMEL mutation can lower radiative heat gain which might help to reduce heat stress.

IMPLICATIONS

The study validates putative causative sequence variants to rapidly adapt grazing cattle to changing environmental conditions.

Health assessment of Holstein calves born after in vitro fertilization, biopsy-based genotyping at the blastocyst stage and subsequent embryo transfer

Establishing methods for evaluating genomic estimated breeding values of bovine embryos can potentially increase the efficiency of breeding programs by transferring only embryos with a high genomic estimated breeding value. This may be achieved by analyzing DNA from trophectoderm biopsies. However, manipulation of bovine embryos is associated with a risk of impaired conceptus health. More knowledge on the health implications of embryonic handling procedures is required. In this study, we followed pregnancies after transfer of in vitro-produced (IVP) embryos and assessed the health of the offspring during the first 2 weeks of life. Three groups of calves were studied: i) freshly transferred non-biopsied embryos (39 transfers, 17 calves; Group B-/C-); ii) biopsied and freshly transferred IVP embryos (42 transfers, 21 calves; Group B+/C-); iii) biopsied and cryopreserved IVP embryos (17 transfers, 6 calves; Group B+/C+). Blood biochemical and hematologic values were compared between groups and to a control group of 13 calves produced by conventional artificial insemination. The pregnancy rate on day 50 and the calving rate did not differ among the groups, but the average gestation length of the B+/C+ group was significantly shorter and with wider variation than the two other groups. There was a tendency toward a higher average body weight at birth in group B+/C+ (45.1 kg) and the standard deviation in body weight was larger (11.7 kg) compared to the B-/C- (39.5 kg; 3.2 kg) and B+/C- (41.8 kg; 6 kg) groups. Body weight on day 14 was higher in the B+/C+ calves compared to the other groups. There was no difference in the biochemical and hematological values at birth between the groups and these were within the normal range. However, when compared to a group of calves produced by standard artificial insemination, significantly higher concentrations were found for the hepatic-related enzymes ALAT, ASAT, ALP, and GGT in group B-/C-and B+/C-, while only higher ALP concentrations were found in B+/C+ calves. The biochemical findings indicate higher heterogeneity in IVP calves compared to calves produced by artificial insemination. The more manipulated IVP embryos also showed increased heterogeneity in body weight at birth, with a shift toward heavier calves, which calls for closer attendance at parturition to handle dystocia in a timely manner and minimize fetal losses.

The mammalian preimplantation embryo: Its role in the environmental programming of postnatal health and performance

During formation of the preimplantation embryo several cellular and molecular milestones take place, making the few cells forming the early embryo vulnerable to environmental stressors than can impair epigenetic reprogramming and controls of gene expression. Although these molecular alterations can result in embryonic death, a significant developmental plasticity is present in the preimplantation embryo that promotes full-term pregnancy. Prenatal epigenetic modifications are inherited during mitosis and can perpetuate specific phenotypes during early postnatal development and adulthood. As such, the preimplantation phase is a developmental window where developmental programming can take place in response to the embryonic microenvironment present in vivo or in vitro. In this review, the relevance of the preimplantation embryo as a developmental stage where offspring health and performance can be programmed is discussed, with emphasis on malnutrition and assisted reproductive technologies; two major environmental insults with important implications for livestock production and human reproductive medicine.

Developmental Hurdles That Can Compromise Pregnancy during the First Month of Gestation in Cattle

Several key developmental events are associated with early embryonic pregnancy losses in beef and dairy cows. These developmental problems are observed at a greater frequency in pregnancies generated from in-vitro-produced bovine embryos. This review describes critical problems that arise during oocyte maturation, fertilization, early embryonic development, compaction and blastulation, embryonic cell lineage specification, elongation, gastrulation, and placentation. Additionally, discussed are potential remediation strategies, but unfortunately, corrective actions are not available for several of the problems being discussed. Further research is needed to produce bovine embryos that have a greater likelihood of surviving to term.

Comparison of cattle derived from in vitro fertilization, multiple ovulation embryo transfer, and artificial insemination for milk production and fertility traits

The use of assisted-reproduction technologies such as in vitro fertilization (IVF) is increasing, particularly in dairy cattle. The question of consequences in later life has not yet been directly addressed by studies on large animal populations. Studies on rodents and early data from humans and cattle suggest that in vitro manipulation of gametes and embryos could result in long-term alteration of metabolism, growth, and fertility. Our goal was to better describe these presumed consequences in the population of dairy cows produced by IVF in Québec (Canada) and to compare them to animals conceived by artificial insemination (AI) or multiple ovulation embryo transfer (MOET). To do so, we leveraged a large phenotypic database (2.5 million animals and 4.5 million lactations) from milk records in Québec aggregated by Lactanet (Sainte-Anne-de-Bellevue, QC, Canada) and spanning 2012 to 2019. We identified 304,163, 12,993, and 732 cows conceived by AI, MOET, and IVF, respectively, for a total of 317,888 Holstein animals from which we retrieved information for 576,448, 24,192, and 1,299 lactations (total = 601,939), respectively. Genetic energy-corrected milk yield (GECM) and Lifetime Performance Index (LPI) of the parents of cows were used to normalize for genetic potential across animals. When compared with the general Holstein population, MOET and IVF cows outperformed AI cows. However, when comparing those same MOET and IVF cows with only herdmates and accounting for their higher GECM in the models, we found no statistical difference between the conception methods for milk production across the first 3 lactations. We also found that the rate of Lifetime Performance Index improvement of the IVF population during the 2012 to 2019 period was less than the rate observed in the AI population. Fertility analysis revealed that MOET and IVF cows also scored 1 point lower than their parents on the daughter fertility index and had a longer interval from first service to conception, with an average of 35.52 d compared with 32.45 for MOET and 31.87 for AI animals. These results highlight the challenges of elite genetic improvement while attesting to the progress the industry has made in minimizing epigenetic disturbance during embryo production. Nonetheless, additional work is required to ensure that IVF animals can maintain their performance and fertility potential.

Gestational and health outcomes of dairy cows conceived by assisted reproductive technologies compared to artificial insemination

Herd gestation and health management are key aspects of effective dairy farm operations and animal welfare improvement. Unfortunately, very little is known about the developmental divergences induced by assisted reproduction technologies (ART) and their consequences once the animal is mature. Indeed, the gestational and health outcomes of this subset of the Holstein population is yet to be characterized. In this study, the intergenerational impacts of ART conception were assessed by looking at the gestation and health outcomes of a large cohort of cows (n = 284,813) for which the conception methods were known. Our results showed that cows conceived by multiple ovulation embryo transfer (MOET) and in vitro fertilisation (IVF) displayed longer gestations: +0.37 ± 0.079 and +0.65 ± 0.21 day compared to cows conceived by artificial insemination (AI). Surprisingly, animals conceived by all methods experienced a similar 1-day decline in average gestation length from 2012 to 2019. Cows conceived by IVF were not more likely to experience stillbirths but were affected by common diseases such as ovarian cysts, mastitis, and uterine diseases in different proportions compared to cows conceived by other methods. This study provides new and unique information on ART animals regarding perinatal mortality and general health outcomes.

Offspring physiology following the use of IVM, IVF and ICSI: a systematic review and meta-analysis of animal studies

BACKGROUND

Since the birth of the first baby using IVF technology in 1978, over 10 million children have been conceived via ART. Although most aspects of ARTs were developed in animal models, the introduction of these technologies into clinical practice was performed without comprehensive assessment of their long-term safety. The monitoring of these technologies over time has revealed differences in the physiology of babies produced using ARTs, yet due to the pathology of those presenting for treatment, it is challenging to separate the cause of infertility from the effect of treatments offered. The use of systematic review and meta-analysis to investigate the impacts of the predominant ART interventions used clinically in human populations on animals produced in healthy fertile populations offers an alternative approach to understanding the long-term safety of reproductive technologies.

OBJECTIVE AND RATIONALE

This systematic review and meta-analysis aimed to examine the evidence available from animal studies on physiological outcomes in the offspring conceived after IVF, IVM or ICSI, compared to in vivo fertilization, and to provide an overview on the landscape of research in this area.

SEARCH METHODS

PubMed, Embase and Commonwealth Agricultural Bureaux (CAB) Abstracts were searched for relevant studies published until 27 August 2021. Search terms relating to assisted reproductive technology, postnatal outcomes and mammalian animal models were used. Studies that compared postnatal outcomes between in vitro-conceived (IVF, ICSI or IVM) and in vivo-conceived mammalian animal models were included. In vivo conception included mating, artificial insemination, or either of these followed by embryo transfer to a recipient animal with or without in vitro culture. Outcomes included birth weight, gestation length, cardiovascular, metabolic and behavioural characteristics and lifespan.

OUTCOMES

A total of 61 studies in five different species (bovine, equine, murine, ovine and non-human primate) met the inclusion criteria. The bovine model was the most frequently used in IVM studies (32/40), while the murine model was mostly used in IVF (17/20) and ICSI (6/8) investigations. Despite considerable heterogeneity, these studies suggest that the use of IVF or maturation results in offspring with higher birthweights and a longer length of gestation, with most of this evidence coming from studies in cattle. These techniques may also impair glucose and lipid metabolism in male mice. The findings on cardiovascular outcomes and behaviour outcomes were inconsistent across studies.

WIDER IMPLICATIONS

Conception via in vitro or in vivo means appears to have an influence on measurable outcomes of offspring physiology, manifesting differently across the species studied. Importantly, it can be noted that these measurable differences are noticeable in healthy, fertile animal populations. Thus, common ART interventions may have long-term consequences for those conceived through these techniques, regardless of the pathology underpinning diagnosed infertility. However, due to heterogeneous methods, results and measured outcomes, highlighted in this review, it is difficult to draw firm conclusions. Optimizing animal and human studies that investigate the safety of new reproductive technologies will provide insight into safeguarding the introduction of novel interventions into the clinical setting. Cautiously prescribing the use of ARTs clinically may also be considered to reduce the chance of promoting adverse outcomes in children conceived before long-term safety is confidently documented.

Fitness of calves born from in vitro-produced fresh and cryopreserved embryos

In cattle, vitrified/warmed (V/W) and frozen/thawed (F/T), in vitro-produced (IVP) embryos, differ in their physiology and survival from fresh embryos. In this study, we analyzed the effects of embryo cryopreservation techniques on the offspring. IVP embryos cultured with albumin and with or without 0.1% serum until Day 6, and thereafter in single culture without protein, were transferred to recipients on Day 7 as F/T, V/W, or fresh, resulting in N = 24, 14, and 13 calves, respectively. Calves were clinically examined at birth, and blood was analyzed before and after colostrum intake (Day 0), and subsequently on Day 15 and Day 30. On Day 0, calves from V/W and F/T embryos showed increased creatinine and capillary refill time (CRT) and reduced heartbeats. Calves from F/T embryos showed lower PCO₂, hemoglobin, and packed cell volume than calves from V/W embryos while V/W embryos led to calves with increased Na⁺ levels. Colostrum effects did not differ between calves from fresh and cryopreserved embryos, indicating similar adaptive ability among calves. However, PCO₂ did not decrease in calves from V/W embryos after colostrum intake. Serum in culture led to calves with affected (P < 0.05) temperature, CRT, HCO 3 - , base excess (BE), TCO₂, creatinine, urea, and anion gap. On Day 15, the effects of embryo cryopreservation disappeared among calves. In contrast, Day 30 values were influenced by diarrhea appearance, mainly in calves from V/W embryos (i.e., lower values of TCO₂, HCO 3 - , and BE; and increased glucose, anion gap, and lactate), although with no more clinical compromise than calves from fresh and F/T embryos. Diarrhea affected PCO₂ and Na⁺ in all groups. Embryo cryopreservation, and/or culture, yield metabolically different calves, including effects on protein and acid-base metabolism.

Developmental Programming of Fertility in Cattle-Is It a Cause for Concern?

Cattle fertility remains sub-optimal despite recent improvements in genetic selection. The extent to which an individual heifer fulfils her genetic potential can be influenced by fetal programming during pregnancy. This paper reviews the evidence that a dam's age, milk yield, health, nutrition and environment during pregnancy may programme permanent structural and physiological modifications in the fetus. These can alter the morphology and body composition of the calf, postnatal growth rates, organ structure, metabolic function, endocrine function and immunity. Potentially important organs which can be affected include the ovaries, liver, pancreas, lungs, spleen and thymus. Insulin/glucose homeostasis, the somatotropic axis and the hypothalamo-pituitary-adrenal axis can all be permanently reprogrammed by the pre-natal environment. These changes may act directly at the level of the ovary to influence fertility, but most actions are indirect. For example, calf health, the timing of puberty, the age and body structure at first calving, and the ability to balance milk production with metabolic health and fertility after calving can all have an impact on reproductive potential. Definitive experiments to quantify the extent to which any of these effects do alter fertility are particularly challenging in cattle, as individual animals and their management are both very variable and lifetime fertility takes many years to assess. Nevertheless, the evidence is compelling that the fertility of some animals is compromised by events happening before they are born. Calf phenotype at birth and their conception data as a nulliparous heifer should therefore both be assessed to avoid such animals being used as herd replacements.

Bioactive supplements influencing bovine in vitro embryo development

Ovum pickup and in vitro production (IVP) of bovine embryos are replacing traditional multiple ovulation embryo transfer (MOET) as the primary means for generating transferable embryos from genetically elite sires and dams. However, inefficiencies in the IVP process limit the opportunities to produce large numbers of transferable embryos. Also, the post-transfer competency of IVP embryos is inferior to embryos produced by artificial insemination or MOET. Numerous maternal, paternal, embryonic, and culture-related factors can have adverse effects on IVP success. This review will explore the various efforts made on describing how IVP embryo development and post-transfer competency may be improved by supplementing hormones, growth factors, cytokines, steroids and other bioactive factors found in the oviduct and uterus during early pregnancy. More than 40 of these factors, collectively termed as embryokines, are reviewed here. Several embryokines contain abilities to promote embryo development, including improving embryo survivability, improving blastomere cell numbers, and altering the distribution of blastomere cell types in blastocysts. A select few embryokines also can benefit pregnancy retention after IVP embryo transfer and improve neonatal calf health and performance, although very few embryokine-supplemented embryo transfer studies have been completed. Also, supplementing several embryokines at the same time holds promise for improving IVP embryo development and competency. However, more work is needed to explore the post-transfer consequences of adding these putative embryokines for any adverse outcomes, such as large offspring syndrome and poor postnatal health, and to specify the specific embryokine combinations that will best represent the ideal conditions found in the oviduct and uterus.

In vitro and in vivo-produced male dairy calves show molecular differences in the hepatic and muscular energy regulation

In cattle, the in vitro production (IVP) of embryos is becoming more relevant than embryos produced in vivo, i.e. after multiple ovulation and embryo transfer (MOET). However, the effects of IVP on the developmental programming of specific organs in the postnatal calves are yet unknown. Previously, we reported an epigenomic and transcriptomic profile of the hypothalamus–pituitary–testicular axis compatible with its earlier activation in IVP calves compared to MOET animals. Here, we studied the hepatic and muscular epigenome and transcriptome of those same male dairy calves (n = 4 per group). Tissue samples from liver and semitendinosus muscle were obtained at 3 months of age, and the extracted gDNA and RNA were sequenced through whole-genome bisulfite sequencing and RNA-sequencing, respectively. Next, bioinformatic analyses determined differentially methylated cytosines or differentially expressed genes [false discovery rate (FDR) < 0.05] for each Omic dataset; and nonparametrically combined genes (NPCG) for both integrated omics (P < 0.05). KEGG pathways enrichment analysis showed that NPCG upregulated in the liver and the muscle of the IVP calves were involved in oxidative phosphorylation and the tricarboxylic acid cycle. In contrast, ribosome and translation were upregulated in the liver but downregulated in the muscle of the IVP calves compared to the MOET calves (FDR < 0.05). A model considering the effect of the methylation levels and the group on the expression of all the genes involved in these pathways confirmed these findings. In conclusion, the multiomics data integration approach indicated an altered hepatic and muscular energy regulation in phenotypically normal IVP calves compared to MOET calves.

Identification of large offspring syndrome during pregnancy through ultrasonography and maternal blood transcriptome analyses

In vitro production (IVP) of embryos in cattle can result in large/abnormal offspring syndrome (LOS/AOS) which is characterized by macrosomia. LOS can cause dystocia and lead to the death of dam and calf. Currently, no test exists to identify LOS pregnancies. We hypothesized that fetal ultrasonography and/or maternal blood markers are useful to identify LOS. Bovine fetuses were generated by artificial insemination (control) or IVP. Fetal ultrasonographies were taken on gestation D55 (D55) and fetal collections performed on D56 or D105 (gestation in cattle ≈ D280). IVP fetuses weighing ≥ 97 percentile of the control weight were considered LOS. Ultrasonography results show that the product of six D55 measurements can be used to identify extreme cases of LOS. To determine whether maternal blood can be used to identify LOS, leukocyte mRNA from 23 females was sequenced. Unsupervised hierarchical clustering grouped the transcriptomes of the two females carrying the two largest LOS fetuses. Comparison of the leukocyte transcriptomes of these two females to the transcriptome of all other females identified several misregulated transcripts on gestation D55 and D105 with LOC783838 and PCDH1 being misregulated at both time-points. Together our data suggest that LOS is identifiable during pregnancy in cattle.

Present state and future outlook for the application of in vitro oocyte maturation (IVM) in human infertility treatment

In vitro oocyte maturation (IVM) is an assisted reproductive technology in which a meiotically immature oocyte (prophase I or germinal vesicle stage) is recovered from an antral follicle and matured in vitro prior to fertilization. This technology, although in widespread use in domestic livestock, is not typically implemented during human IVF cycles. This review examines how IVM is currently used in the clinical setting, including the various ways IVM is defined in practice. The role of IVM in patient care, and the major challenges for implementation are described. Efficiency and safety are critically explored. The role of IVM in oncofertility will also be discussed. Finally, the outlook for the future of clinical IVM is considered.

Year-Long Phenotypical Study of Calves Derived From Different Assisted-Reproduction Technologies

Assisted reproductive technologies play a major role in the cattle industry. An increase in the use of in vitro-derived embryos is currently being seen around the globe. But the efficiency and quality of the in vitro-derived embryos are substandard when compared to the in vivo production. Different protocols have been designed to overcome this issue, one of those being the use of reproductive fluids as supplementation to embryo culture media. In this study, in vitro-derived calves produced with reproductive fluids added to their embryo production protocol were followed for the first year of life pairwise with their in vivo control, produced by artificial insemination (AI), and their in vitro control, produced with standard supplementation in embryo production. The objective was to assess if any differences could be found in terms of growth and development as well as hematological and biochemical analytes between the different systems. All the analysed variables (physical, hematological, and biochemical) were within physiological range and very similar between calves throughout the entire experiment. However, differences were more evident between calves derived from standard in vitro production and AI. We concluded that the use of reproductive fluids as a supplementation to the embryo culture media results in calves with closer growth and development patterns to those born by AI than the use of bovine serum albumin as supplementation.

How the environment affects early embryonic development

In the field of animal reproduction, the environment associated with gametes and embryos refers to the parents' condition as well as conditions surrounding gametes and embryos in vivo or in vitro . This environment is now known to influence not only the functionality of the early embryo but potentially the future phenotype of the offspring. Using transcriptomic and epigenetic molecular analysis, and the bovine model, recent research has shown that both the female and the male metabolic status, for example age, can affect gene expression and gene programming in the embryo. Evidence demonstrates that milking cows, which are losing weight at the time of conception, generates compromised embryos and offspring with a unique metabolic signature. A similar phenomenon has been associated with different culture conditions and the IVF procedure. The general common consequence of these situations is an embryo behaving on 'economy' mode where translation, cell division and ATP production is reduced, potentially to adapt to the perceived future environment. Few epidemiological studies have been done in bovines to assess if these changes result in a different phenotype and more studies are required to associate specific molecular changes in embryos with visible consequences later in life.

Epigenomic and transcriptomic analyses reveal early activation of the HPG axis in in vitro-produced male dairy calves

In cattle, several calves born after IVP ("in vitro" embryo production) present similar birthweight to those generated after MOET (multiple ovulation and embryo transfer). However, the underlying molecular patterns in organs involved in the developmental process are unknown and could indicate physiological programming. The objectives of this study were: (1) to compare epigenomic and transcriptomic modifications in the hypothalamus, pituitary, gonadal and adrenal organs between 3 months old ovum pick-up-IVP and MOET male calves (n = 4 per group) and (2) to use blood epigenomic data to proxy methylation of the inner organs. Extracted gDNA and RNA were sequenced through whole-genome bisulfite sequencing and RNA sequencing, respectively. Next, bioinformatic analyses determined differentially methylated cytosines (DMC) and differentially expressed genes (DEG) (FDR < 0.05) in IVP versus MOET samples and the KEGG pathways that were overrepresented by genes associated with DMC or DEG (FDR < 0.1). Pathways related to hypothalamus, pituitary, gonadal (HPG) axis activation (GnRH secretion in the hypothalamus, GnRH signaling in the pituitary, and steroidogenesis in the testicle) were enriched in IVP calves. Modeling the effect of the methylation levels and the group on the expression of all the genes involved in these pathways confirmed their upregulation in HPG organs in IVP calves. The application of the DIABLO method allowed the identification of 15 epigenetic and five transcriptomic biomarkers, which were able to predict the embryo origin using the epigenomic data from the blood. In conclusion, the use of an integrated epigenomic-transcriptomic approach suggested an early activation of the HPG axis in male IVP calves compared to MOET counterparts, and the identification of potential biomarkers allowed the use of blood samples to proxy methylation levels of the relevant internal organs.

Cytokines That Serve as Embryokines in Cattle

Simple Summary

This review will explore how some cytokines also influence early embryonic development. We term these types of molecules as embryokines. Understanding how cytokines serve as embryokines could offer new opportunities to improve embryo development and the overall health of the embryo so that pregnancies will be retained after embryo transfer and so that viable offspring are produced. At least two cytokines may offer these benefits to bovine embryos produced in vitro. Additional cytokines also are identified in this review that may contain beneficial activities on bovine embryos.

Abstract

The term “embryokine” has been used to denote molecules produced by the endometrium, oviduct, or by embryo itself that will influence embryo development. Several cytokines have been identified as embryokines in cattle and other mammals. This review will describe how these cytokines function as embryokines, with special emphasis being placed on their actions on in vitro produced (IVP) bovine embryos. Embryokines are being explored for their ability to overcome the poor development rates of IVP embryos and to limit post-transfer pregnancy retention efficiencies that exist in IVP embryos. This review will focus on describing two of the best-characterized cytokines, colony-stimulating factor 2 and interleukin 6, for their ability to modify bovine embryo quality and confirmation, promote normal fetal development, and generate healthy calves. Additional cytokines will also be discussed for their potential to serve as embryokines.

The global gene expression outline of the bovine blastocyst: reflector of environmental conditions and predictor of developmental capacity

Background

Morphological evaluation of embryos has been used to screen embryos for transfer. However, the repeatability and accuracy of this method remains low. Thus, evaluation of an embryo’s gene expression signature with respect to its developmental capacity could provide new opportunities for embryo selection. Since the gene expression outline of an embryo is considered as an aggregate of its intrinsic characteristics and culture conditions, we have compared transcriptome profiles of in vivo and in vitro derived blastocysts in relation to pregnancy outcome to unravel the discrete effects of developmental competence and environmental conditions on bovine embryo gene expression outlines. To understand whether the gene expression patterns could be associated with blastocyst developmental competency, the global transcriptome profile of in vivo (CVO) and in vitro (CVT) derived competent blastocysts that resulted in pregnancy was investigated relative to that of in vivo (NVO) and in vitro (NVT) derived blastocysts which did not establish initial pregnancy, respectively while to unravel the effects of culture condition on the transcriptome profile of embryos, the transcriptional activity of the CVO group was compared to the CVT group and the NVO group was compared to the NVT ones.

Results

A total of 700 differentially expressed genes (DEGs) were identified between CVO and NVO blastocysts. These gene transcripts represent constitutive regions, indel variants, 3′-UTR sequence variants and novel transcript regions. The majority (82%) of these DEGs, including gene clusters like ATP synthases, eukaryotic translation initiation factors, ribosomal proteins, mitochondrial ribosomal proteins, NADH dehydrogenase and cytochrome c oxidase subunits were enriched in the CVO group. These DEGs were involved in pathways associated with glycolysis/glycogenesis, citrate acid cycle, pyruvate metabolism and oxidative phosphorylation. Similarly, a total of 218 genes were differentially expressed between CVT and NVT groups. Of these, 89%, including TPT1, PDIA6, HSP90AA1 and CALM, were downregulated in the CVT group and those DEGs were overrepresented in pathways related to protein processing, endoplasmic reticulum, spliceasome, ubiquitone mediated proteolysis and steroid biosynthesis. On the other hand, although both the CVT and CVO blastocyst groups resulted in pregnancy, a total of 937 genes were differential expressed between the two groups. Compared to CVO embryos, the CVT ones exhibited downregulation of gene clusters including ribosomal proteins, mitochondrial ribosomal protein, eukaryotic translation initiation factors, ATP synthases, NADH dehydrogenase and cytochrome c oxidases. Nonetheless, downregulation of these genes could be associated with pre and postnatal abnormalities observed after transfer of in vitro embryos.

Conclusion

The present study provides a detailed inventory of differentially expressed gene signatures and pathways specifically reflective of the developmental environment and future developmental capacities of bovine embryos suggesting that transcriptome activity observed in blastocysts could be indicative of further pregnancy success but also adaptation to culture environment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07693-0.

Consequences of assisted reproductive technologies for offspring function in cattle

Abnormal fetuses, neonates and adult offspring derived by assisted reproductive technologies (ART) have been reported in humans, rodents and domestic animals. The use of ART has also been associated with an increased likelihood of certain adult diseases. These abnormalities may arise as a result of an excess of or missing maternally derived molecules during invitro culture, because the invitro environment is artificial and suboptimal for embryo development. Nonetheless, the success of ART in overcoming infertility or improving livestock genetics is undeniable. Limitations of invitro embryo production (IVEP) in cattle include lower rates of the establishment and maintenance of pregnancy and an increased incidence of neonatal morbidity and mortality. Moreover, recent studies demonstrated long-term effects of IVEP in cattle, including increased postnatal mortality, altered growth and a slight reduction in the performance of adult dairy cows. This review addresses the effects of an altered preimplantation environment on embryo and fetal programming and offspring development. We discuss cellular and molecular responses of the embryo to the maternal environment, how ART may disturb programming, the possible role of epigenetic effects as a mechanism for altered phenotypes and long-term effects of ART that manifest in postnatal life.

A review of simulation analyses of economics and genetics for the use of in-vitro produced embryos and artificial insemination in dairy herds

The use of in-vitro produced (IVP) embryo transfer (ET) in dairy herds is growing fast. Much of this growth is on dairy farms where the focus is on milk production and not on selling breeding stock. The value of implementing IVP-ET in a dairy herd arises from a higher genetic merit of the IVP-embryo, but the cost to produce a pregnancy with an IVP embryo is greater than the cost of artificial insemination (AI). The first objective of this study was to review estimates of the net benefit of using IVP-ET over AI in dairy herds using existing literature. Another objective was to show how much IVP-ET use in a herd is optimal. Most of the literature is based on simulation modeling, including our own work that focuses on the dairy industry in the USA. We found that the most profitable use of AI and IVP-ET is often a combination of the two. More IVP-ET should be used when the value of surplus calves is greater and the cost of IVP-ET is lower, among many other factors. In the future, use of IVP-ET will be further improved by more accurately identifying superior donors and recipients, reducing the generation interval, and achieving greater efficiency in embryo production.

Reproductive Outcomes and Endocrine Profile in Artificially Inseminated versus Embryo Transferred Cows

Simple Summary

Bovine embryos are nowadays produced in laboratories, frozen and transferred to other cows. However, the percentage of pregnancies obtained after these transfers as well as difficulties found during labor, especially due to increased size of calves, are a matter of great concern. One of the possible explanations for these problems relies on the embryo being produced in in vitro conditions (laboratory settings), more specifically the culture medium (liquid) used to develop these embryos. In an attempt to better mimic what happens naturally, female reproductive liquids (from oviducts and uterus) were used as a supplement to the culture of the embryos. As controls, embryos produced using the standard protocol in the laboratory were produced, as well as embryos derived from artificial insemination of cows (in vivo). An evaluation on the pregnancy rates, how the hormonal profile of the recipients changed during pregnancy, difficulties during parturitions, and phenotype of calves were recorded. Results showed that all the groups were very similar, but many differences were noted on the hormonal profiles during pregnancy. In conclusion, all systems provided safe production of calves, but long-term analysis of these calves is necessary to understand the future impact of the laboratory protocols.

Abstract

The increasing use of in vitro embryo production (IVP) followed by embryo transfer (ET), alongside with cryopreservation of embryos, has risen concerns regarding the possible altered pregnancy rates, calving or even neonatal mortality. One of the hypotheses for these alterations is the current culture conditions of the IVP. In an attempt to better mimic the physiological milieu, embryos were produced with female reproductive fluids (RF) as supplements to culture medium, and another group of embryos were supplemented with bovine serum albumin (BSA) as in vitro control. Embryos were cryopreserved and transferred while, in parallel, an in vivo control (artificial insemination, AI) with the same bull used for IVP was included. An overview on pregnancy rates, recipients’ hormonal levels, parturition, and resulting calves were recorded. Results show much similarity between groups in terms of pregnancy rates, gestation length and calves’ weight. Nonetheless, several differences on hormonal levels were noted between recipients carrying AI embryos especially when compared to BSA. Some calving issues and neonatal mortality were observed in both IVP groups. In conclusion, most of the parameters studied were similar between both types of IVP derived embryos and the in vivo-derived embryos, suggesting that the IVP technology used was efficient enough for the safe production of calves.

Implications of Assisted Reproductive Technologies for Pregnancy Outcomes in Mammals

Development of assisted reproductive technologies has been driven by the goals of reducing the incidence of infertility, increasing the number of offspring from genetically elite animals, facilitating genetic manipulation, aiding preservation and long-distance movement of germplasm, and generating research material. Superovulation is associated with reduced fertilization rate and alterations in endometrial function. In vitro production of embryos can have a variety of consequences. Most embryos produced in vitro are capable of establishing pregnancy and developing into healthy neonatal animals. However, in vitro production is associated with reduced ability to develop to the blastocyst stage, increased incidence of failure to establish pregnancy, placental dysfunction, and altered fetal development. Changes in the developmental program mean that some consequences of being produced in vitro can extend into adult life. Reduced competence of the embryo produced in vitro to develop to the blastocyst stage is caused largely by disruption of events during oocyte maturation and fertilization. Conditions during embryo culture can affect embryo freezability and competence to establish pregnancy after transfer. Culture conditions, including actions of embryokines, can also affect the postnatal phenotype of the resultant progeny.

Characteristics of offspring derived from conventional and X-sorted bovine sperm

The objective of this retrospective study was to compare survival during the first year of life and adult performance of offspring derived from artificial insemination (AI) with X-sorted or conventional sperm processed from the same ejaculates. We analyzed a data set that included AI of dairy heifers and lactating cows with fresh conventional sperm (3 × 10⁶ sperm per straw), fresh X-sorted sperm (1 or 2 × 10⁶ sperm per straw), or frozen X-sorted sperm (2 × 10⁶ sperm per straw). The data set contained records of 5,179 offspring born on 396 farms. Offspring were classified as born from conventional sperm (CONV) if they were the product of an insemination with fresh conventional sperm, or born from X-sorted sperm (SS) if they were product of any of the 3 X-sorted sperm treatments. Generalized linear mixed models were used to evaluate the effect of sperm treatment on (1) survival during the first year of life; (2) reproductive performance, lactation performance, and survival of female offspring; and (3) slaughter characteristics of male offspring. Stillbirth rates and mortality rates during the first 2 mo of life were greater for male calves (2.8 and 5.0%, respectively) than for female calves (1.6 and 2.0%, respectively). No differences between offspring derived from SS and CONV were detected for incidences of stillbirth or mortality during the first 12 mo of life within sex of calf. Reproductive performance, milk volume, milk fat, milk protein yields during first; second; and third lactations, and survival to third lactation did not differ between female offspring derived from CONV and SS. Across all age groups, CONV steers had heavier carcasses than SS steers (325.3 vs. 318.3 kg), but there were no differences in weight between CONV and SS steers within any of the age groups (≤24, 25-27, 28-30, and >30 mo of age). The distribution of slaughter age did not differ between CONV and SS steers when the analysis was restricted to herds that reared steers derived from both types of sperm. Carcass conformation and fat scores of steers were not affected by sperm treatment. There was no difference in carcass weight between young bulls (≤2 yr) derived from CONV or SS. In conclusion, the results provide no evidence of differences in survival during the first year of life between offspring derived from CONV or SS, or for any of the reproductive and lactation performance characteristics studied between female offspring derived from CONV or SS. Modest differences in carcass weight between CONV and SS steers were detected, but this may reflect differences in management and husbandry in the rearing herds rather than the sex-sorting process. A controlled study using steers derived from conventional or X-sorted sperm from split ejaculates and reared under the same husbandry conditions is needed to clarify whether there is a true difference in body weight gain due to the sex-sorting process.

Review: Environmental impact on early embryonic development in the bovine species

Assisted reproduction techniques (ARTs) provide access to early stage embryos whose analysis and assessment deliver valuable information. The handling of embryos, including the in vitro production of bovine embryos, is a rapidly evolving area which nonetheless exposes the embryos to unnatural conditions for a period of time. The Fallopian tube provides innumerable quantitative and qualitative factors, all of which guarantee the successful development of the embryo. It is well known that the Fallopian tube can be bypassed, using embryo transfer, resulting in successful implantation in the target recipient animal and the birth of calves. However, the question arises as to whether such circumvention has a negative impact on the embryo during this sensitive development period. First crosstalk between the embryo and its environment confirms mutual recognition activities and indicate bilateral effects. Nowadays, in vitro production of bovine embryos is a well-established technology. However, it is still evident that in vitro generated embryos are not qualitatively comparable to embryos obtained ex vivo. To counteract these differences, comparative studies between in vitro and ex vivo embryos are advantageous, as embryos grown in their physiological environment can provide a blueprint or gold standard against which to compare embryos produced in vitro. Attempts to harness the bovine oviduct were sometimes very invasive and did not result in wide acceptance and routine use. Long-term development and refinement of transvaginal endoscopy for accessing the bovine oviduct has meanwhile been routinely applied for research as well as in practice. Comparative studies combining in vitro development with development in the cattle oviduct revealed that the environmental conditions to which the embryo is exposed before activation of the embryonic genome can have detrimental and lasting effects on its further development. These effects are manifested as deviations in gene expression profiles and methylation signatures as well as frequency of whole chromosomal or segmental aberrations. Furthermore, it was shown that hormonal superstimulation (multiple ovulation and embryo transfer), varying progesterone concentrations as well as metabolic disorders caused by high milk production, markedly affected embryo development in the postpartum period. Assisted reproductive techniques that allow the production and handling of extra numbers of generated embryos promise to have a very high impact on scientific and practical application. Any influence on the early embryonic life, both in animals and in vitro, is accompanied by a sensitive change in embryonic activity and should be assessed in vivo on the basis of physiological conditions before being used for ART.

L-carnitine supplementation in culture media improves the pregnancy rate of in vitro produced embryos with sexed semen from Bos taurus indicus cows

The in vitro embryo production industry in the actual world presents some difficulties related to low embryonic production rates, a problem that could be associated with in vitro culture conditions that differed from the in vivo (oviductal) conditions, mainly related to cytoplasmic lipid accumulation. L-carnitine is known as a modulator of β-oxidation in the developing embryo, as it has been demonstrated that it improves embryo quality without affecting the in vitro embryo production rate. The aim of the present work was to evaluate the effect of L-carnitine supplemented during the in vitro maturation and culture processes on the implantation rate of in vitro produced embryos. Supplementation with 3.8 mM of L-carnitine was used during in vitro maturation, and later, during late in vitro culture, it was added at 1.5 mM. A control group contained no L-carnitine supplementation. Bovine oocytes obtained by ultrasound-guided follicle aspiration from healthy Bos taurus indicus cows were matured, fertilized and cultured in vitro. Multiparous F1 (Bos taurus taurus × Bos taurus indicus) cows were used as recipients. Overall, 460 oocytes were processed in three independent replicates from in vitro maturation until day 8 of the in vitro culture. No significant difference was found between treatments of in vitro embryo production. However, pregnancy rate at days 45 and 72 was significantly higher in blastocysts derived from L-carnitine treatment (31.55 ± 9.78%) compared to the control group (18.68 ± 6.31%). In conclusion, addition of L-carnitine at 3.8 mM and 1.5 mM in the maturation, and culture medium after day 3 of in vitro production process, significantly improved pregnancy rate after embryo transfer.

Efficient one-step direct transfer to recipients of thawed bovine embryos cultured in vitro and frozen in chemically defined medium

Direct transfer (DT) of cryopreserved embryos to recipients facilitates on-farm application. We analyzed a new freezing/thawing (F/T) procedure for in vitro produced (IVP) embryos, integrating: 1) an ethylene-glycol based system; 2) a culture step without protein; and 3) a synthetic protein substitute (CRYO3) in cryopreservation medium. IVP embryos from abattoir ovaries were cultured in groups in BSA-containing synthetic oviduct fluid with or without 0.1% fetal calf serum (FCS) until Day-6. Morulae and early blastocysts were subsequently cultured without protein from Day-6 onwards. Day 7 and Day 8 expanded blastocysts (EXB) were subjected to F/T or vitrification/warming (V/W). Thawed and warmed EXB were cultured in vitro, and development rates, cell counts and dead cells were analyzed in surviving embryos. V/W improved survival over F/T (live and hatching rates at 2 h, 24 h and 48 h) (P < 0.0001), and FCS before Day 6 did not affect in vitro survival. After F/T, embryos had lower cell counts in the ICM, TE and total cells than after V/W. Day-7 embryos after F/T showed % apoptotic, % pycnotic and % total dead cells higher (p < 0.05) than their Day-8 counterparts, probably because F/T reduced the numbers of ICM cells within Day-8 embryos. Thereafter, Day-7 blastocysts were transferred to heifers in an experimental herd. There were no differences in birth rates with frozen (-FCS [n = 40]: 45%; +FCS [n = 14]: 28%), vitrified (-FCS [n = 47]: 53%; +FCS [n = 11]: 36%) and fresh (-FCS [n = 30]: 47%; +FCS [n = 17]: 53%) embryos. However, frozen embryos produced with FCS showed 5/9 miscarriages after Day-40. Calves born from frozen (n = 22), vitrified (n = 29) and fresh (n = 22) transfers did not differ in birth weight, gestation length and daily gain weight (P > 0.10). Subsequently, transfer of frozen embryos (n = 29) derived from oocytes collected from live, hormonally stimulated cows in experimental herd, led to pregnancy rates of 57% (heifers) and 40% (dry cows). with EXB on Day-62 Finally, embryos produced with BSA were transferred to cows in an on-field trial (frozen [n = 80]; fresh [n = 58]), with no differences in pregnancy rates (days 30-40). Pregnancy and birth rates could not be predicted from in vitro approaches. The new F/T system yields pregnancy and birth rates comparable to vitrified and fresh embryos without birth overweight. The absence of products of animal origin, defined chemical composition, and direct transfer entail sanitary, manufacturing and application advantages.

IMD/ADM21-47, a factor that improves embryo quality

Starting in vitro fertilization process with competent oocytes that may endure first cellular divisions is a critical step for obtaining an embryo. To obtain in vitro competent oocytes, culture conditions should emulate the in vivo microenvironment as close as possible. With the aim of improving the in vitro culture medium, the present study evaluated the IMD/ADM2_1-47 peptide as a factor that promotes oocyte competence and improves embryo quality in bovine systems. The culture supplemented with 153 μg/mL of IMD/ADM2_1-47 was correlated with the production of healthy oocytes in metaphase II (MII) stage in compacted cumulus-oocyte complexes (COC) with a decrease of BAX/BCL-2 to mRNA ratio and a reduction of late apoptosis by TUNEL in MII oocytes. In addition to this, treatment with IMD/ADM2_1-47 caused cAMPi level to be constant over time, and the cAMPi level kept increasing until 6 h. COC supplementation with 153 μg/mL of IMD/ADM2_1-47 increased the blastocyst production rate two-fold in comparison with control conditions. Only embryos from COC treatment with this peptide were capable of developing blastocysts in stage-6 grade I; compared with the control culture, it was the treatment with the greater number of blastocysts stage-5; these are characteristics of good quality blastocysts.

Conditions of embryo culture from days 5 to 7 of development alter the DNA methylome of the bovine fetus at day 86 of gestation

PURPOSE

We tested whether in vitro production (IVP) causes changes in DNA methylation in fetal liver and skeletal muscle and if exposure of cultured embryos to colony-stimulating factor 2 (CSF2) alters DNA methylation.

METHODS

Female fetuses were produced by artificial insemination or transfer of an IVP embryo. Embryos were treated from days 5 to 7 after fertilization with CSF2 or vehicle. DNA methylation in fetal liver and skeletal muscle was determined by post-bisulfite adaptor tagging-based sequencing. The degree of DNA methylation for CpG sites in 50-bp windows of the promoter region 500 bp upstream of the transcriptional start site was compared between treatments.

RESULTS

For liver, there were 12 genes (6% of those analyzed) in which DNA methylation was affected by treatment, with one 50-bp window per gene affected by treatment. For muscle, the degree of DNA methylation was affected by treatment for 32 windows (19% of the total windows analyzed) representing 28 distinct genes (23% of analyzed genes). For 19 of the 28 genes in muscle, the greatest deviation in DNA methylation was for the CSF2 group.

CONCLUSION

Results are consistent with alterations in the methylome being one of the mechanisms by which IVP can result in altered fetal development and postnatal function in the resultant offspring. In addition, results indicate that maternally derived cell-signaling molecules can regulate the pattern of DNA methylation.

BOARD INVITED REVIEW: Post-transfer consequences of in vitro-produced embryos in cattle

In vitro embryo production (IVP) in cattle has gained worldwide interest in recent years, but the efficiency of using IVP embryos for calf production is far from optimal. This review will examine the pregnancy retention rates of IVP embryos and explore causes for pregnancy failures. Based on work completed over the past 25 yr, only 27% of cattle receiving IVP embryos will produce a live calf. Approximately 60% of these pregnancies fail during the first 6 wk of gestation. When compared with embryos generated by superovulation, pregnancy rates are 10% to 40% lower for cattle carrying IVP embryos, exemplifying that IVP embryos are consistently less competent than in vivo-generated embryos. Several abnormalities have been observed in the morphology of IVP conceptuses. After transfer, IVP embryos are less likely to undergo conceptus elongation, have reduced embryonic disk diameter, and have compromised yolk sac development. Marginal binucleate cell development, cotyledon development, and placental vascularization have also been documented, and these abnormalities are associated with altered fetal growth trajectories. Additionally, in vitro culture conditions increase the risk of large offspring syndrome. Further work is needed to decipher how the embryo culture environment alters post-transfer embryo development and survival. The risk of these neonatal disorders has been reduced by the use of serum-free synthetic oviductal fluid media formations and culture in low oxygen tension. However, alterations are still evident in IVP oocyte and embryo transcript abundances, timing of embryonic cleavage events and blastulation, incidence of aneuploidy, and embryonic methylation status. The inclusion of oviductal and uterine-derived embryokines in culture media is being examined as one way to improve the competency of IVP embryos. To conclude, the evidence presented herein clearly shows that bovine IVP systems still must be refined to make it an economical technology in cattle production systems. However, the current shortcomings do not negate its current value for certain embryo production needs and for investigating early embryonic development in cattle.

Post-transfer outcomes in cultured bovine embryos supplemented with epidermal growth factor, fibroblast growth factor 2, and insulin-like growth factor 1

This work examined the downstream fetal and placental outcomes of introducing a cocktail of uterine-derived growth factors during bovine embryo culture. Abattoir-derived bovine oocytes were matured and fertilized in vitro. On day 4 post-fertilization, ≥ 8-cell embryos were harvested, pooled and exposed to an embryokine mix, termed EFI, which contained recombinant human epidermal growth factor (10 ng/ml), bovine fibroblast growth factor-2 (10 ng/ml) and human insulin-like growth factor 1 (50 ng/ml) or to a carrier-only control treatment (CON). On day 7, individual, transfer-quality embryos were transferred to recipients. Timed ovulation was completed in mature, non-suckled commercial beef cows. Cows either were artificial inseminated (AI) or received an embryo (ET) on day 7 post-estrus (n = 23-31 cows/treatment over 4 replicate studies). The percentage of grade 1 and 2 morulae and blastocysts was greater (P < 0.05) for EFI-treated embryos than CON. The percentage of pregnant cows diagnosed by transrectal ultrasonography did not differ among the AI and ET groups on days 28, 42 and 56 post-estrus. There also were no differences in the ratio of male to female fetuses determined on day 60 post-estrus by transrectal ultrasonography. On day 21 post-estrus, the relative abundance of three interferon-stimulated gene (ISG) transcripts in peripheral leukocytes were not different based on AI/ET group or the sex of the conceptus. Circulating pregnancy-associated glycoprotein (PAG) concentrations differed (P < 0.05) among days. Also, a difference in PAG concentrations (P < 0.05) were detected between male and female pregnancies in the CON-ET group but not in the AI or EFI-ET groups. Crown-rump length was not affected by AI/ET group on day 42 but were less (P < 0.05) in the CON and EFI-ET groups than the AI group on day 56. These findings implicate EFI supplementation as a means for improving transferable embryo production in a bovine IVP system, but it is not clear if this treatment improves embryo competency after ET.

Protein in culture and endogenous lipid interact with embryonic stages in vitro to alter calf birthweight after embryo vitrification and warming

Short-term protein removal in vitro improves long-term blastocyst competence to survive vitrification. We investigated the mechanisms and effects underlying protein removal. Day-6 morulae and early blastocysts were cultured individually with and without protein for 24h. Development and lipid content were analysed in expanded blastocysts derived from morulae (M-XB) and from early blastocysts (EB-XB). Expression of genes involved in lipid metabolism, stress responses and apoptosis was analysed in fresh and vitrified-warmed M-XB produced with and without protein. Pregnancy rates, birth rates and birthweight (BW) were recorded after transfer of embryos. Day-7 EB-XB production rates (with, 66.9±6.2 and without, 68.8±6.0 protein) were higher than M-XB rates (with, 21.4±4.6 and without, 9.4±4.6 protein; P<0.005). EB-XB showed fewer lipids than M-XB (P=0.03). In fresh M-XB, expression of sterol regulatory element binding protein (SREBP1) was lower with (4.1±2.2) than without (13.6±2.2) protein, contrary to results obtained for Patatin-like phospholipase domain containing 2, Hormone-sensitive lipase and Bcl-2-associated X protein (P<0.05). Protein did not affect pregnancy rates and birth phenotypes (P>0.05). However, BW was higher (P<0.01) in calves born from vitrified M-XB (48.6±3.4kg) than from EB-XB (39.8±2.9kg). Such effects were more pronounced in females (P<0.001). Calves from fresh embryos did not show BW differences. These results indicate that embryonic kinetics and vitrification impact birth phenotypes, at least in females. Alterations might involve exogenous protein and mobilisation of lipid stocks.

PreImplantation factor (PIF) protects cultured embryos against oxidative stress: relevance for recurrent pregnancy loss (RPL) therapy

Recurrent pregnancy loss (RPL) affects 2-3% of couples. Despite a detailed work-up, the etiology is frequently undefined, leading to non-targeted therapy. Viable embryos and placentae express PreImplantation Factor (PIF). Maternal circulating PIF regulates systemic immunity and reduces circulating natural killer cells cytotoxicity in RPL patients. PIF promotes singly cultured embryos' development while anti-PIF antibody abrogates it. RPL serum induced embryo toxicity is negated by PIF. We report that PIF rescues delayed embryo development caused by <3 kDa RPL serum fraction likely by reducing reactive oxygen species (ROS). We reveal that protein disulfide isomerase/thioredoxin (PDI/TRX) is a prime PIF target in the embryo, rendering it an important ROS scavenger. The 16F16-PDI/TRX inhibitor drastically reduced blastocyst development while exogenous PIF increased >2 fold the number of embryos reaching the blastocyst stage. Mechanistically, PDI-inhibitor preferentially binds covalently to oxidized PDI over its reduced form where PIF avidly binds. PIF by targeting PDI/TRX at a distinct site limits the inhibitor's pro-oxidative effects. The >3kDa RPL serum increased embryo demise by three-fold, an effect negated by PIF. However, embryo toxicity was not associated with the presence of putative anti-PIF antibodies. Collectively, PIF protects cultured embryos both against ROS, and higher molecular weight toxins. Using PIF for optimizing in vitro fertilization embryos development and reducing RPL is warranted.

Colony-stimulating factor 2 acts from days 5 to 7 of development to modify programming of the bovine conceptus at day 86 of gestation†

Colony-stimulating factor 2 (CSF2) is an embryokine that improves competence of the embryo to establish pregnancy and which may participate in developmental programming. We tested whether culture of bovine embryos with CSF2 alters fetal development and alleviates abnormalities associated with in vitro production (IVP) of embryos. Pregnancies were established by artificial insemination (AI), transfer of an IVP embryo (IVP), or transfer of an IVP embryo treated with 10 ng/ml CSF2 from day 5 to 7 of development (CSF2). Pregnancies were produced using X-sorted semen. Female singleton conceptuses were collected on day 86 of gestation. There were few morphological differences between groups, although IVP and CSF2 fetuses were heavier than AI fetuses. Bicarbonate concentration in allantoic fluid was lower for IVP than for AI or CSF2. Expression of 92 genes in liver, placenta, and muscle was determined. The general pattern for liver and placenta was for IVP to alter expression and for CSF2 to sometimes reverse this effect. For muscle, CSF2 affected gene expression but did not generally reverse effects of IVP. Levels of methylation for each of the three tissues at 12 loci in the promoter of insulin-like growth factor 2 (IGF2) and five in the promoter of growth factor receptor bound protein 10 were unaffected by treatment except for CSF2 effects on two CpG for IGF2 in placenta and muscle. In conclusion, CSF2 can act as a developmental programming agent but alone is not able to abolish the adverse effects of IVP on fetal characteristics.

Economic and genetic performance of various combinations of in vitro-produced embryo transfers and artificial insemination in a dairy herd

The objective of this study was to find the optimal proportions of pregnancies from an in vitro-produced embryo transfer (IVP-ET) system and artificial insemination (AI) so that profitability is maximized over a range of prices for embryos and surplus dairy heifer calves. An existing stochastic, dynamic dairy model with genetic merits of 12 traits was adapted for scenarios where 0 to 100% of the eligible females in the herd were impregnated, in increments of 10%, using IVP-ET (ET0 to ET100, 11 scenarios). Oocytes were collected from the top donors selected for the trait lifetime net merit (NM$) and fertilized with sexed semen to produce IVP embryos. Due to their greater conception rates, first ranked were eligible heifer recipients based on lowest number of unsuccessful inseminations or embryo transfers, and then on age. Next, eligible cow recipients were ranked based on the greatest average estimated breeding values (EBV) of the traits cow conception rate and daughter pregnancy rate. Animals that were not recipients of IVP embryos received conventional semen through AI, except that the top 50% of heifers ranked for EBV of NM$ were inseminated with sexed semen for the first 2 AI. The economically optimal proportions of IVP-ET were determined using sensitivity analysis performed for 24 price sets involving 6 different selling prices of surplus dairy heifer calves at approximately 105 d of age and 4 different prices of IVP embryos. The model was run for 15 yr after the start of the IVP-ET program for each scenario. The mean ± standard error of true breeding values of NM$ of all cows in the herd in yr 15 was greater by $603 ± 2 per cow per year for ET100 when compared with ET0. The optimal proportion of IVP-ET ranged from ET100 (for surplus dairy heifer calves sold for ≥$300 along with an additional premium based on their EBV of NM$ and a ≤$100 embryo price) to as low as ET0 (surplus dairy heifer calves sold at $300 with a $200 embryo price). For the default assumptions, the profit/cow in yr 15 was greater by $337, $215, $116, and $69 compared with ET0 when embryo prices were $50, $100, $150, and $200. The optimal use of IVP-ET was 100, 100, 62, and 36% of all breedings for these embryo prices, respectively. At the input price of $165 for an IVP embryo, the difference in the net present value of yr 15 profit between ET40 (optimal scenario) and ET0 was $33 per cow. In conclusion, some use of IVP-ET was profitable for a wide range of IVP-ET prices and values of surplus dairy heifer calves.

Low serum concentration in bovine embryo culture enhances early blastocyst rates on Day-6 with quality traits in the expanded blastocyst stage similar to BSA-cultured embryos

In bovine, single in vitro embryo culture in protein-free medium from Day-6 to Day-7 leads to expanded blastocyst (XB) with improved pregnancy and birth rates after cryopreservation. Under these conditions, early blastocysts (EB) progress to the XB stage at higher rates than morulae (M). However, embryo production with BSA in culture prior to Day-6 leads to low EB rates. We investigated whether a very low FCS concentration (0.1%) in culture from Day-1 to Day-6 would improve EB rates and, subsequently, increase XB rates on Day-7 after single culture in protein-free medium. The quality of embryos produced was evaluated in terms of survival to cryopreservation, apoptosis percentage, lipid accumulation and transfer to recipients. On Day-6, EB rates from embryos cultured with FCS were higher than with BSA (P=0.022). On Day-7, XB rates were higher in embryos from Day-6 EB than from Day-6M, both with and without FCS (P<0.005). After vitrification/warming of Day-7 XB, 100% embryos survived at 24h in all treatments, and total cell number and apoptosis percentage were not affected by the presence of FCS or embryonic stage on Day-6. Cryopreserved and fresh embryos produced with FCS until Day-6, and then deprived of protein and cultured individually, led to pregnancies after ET. In conclusion, minute FCS concentration improves EB rates on Day-6 leading, after one-day single culture without protein, to more XBs. The quality of XB produced with FCS compares well with XB produced with BSA in terms of apoptosis, lipid accumulation and pregnancy.

Epigenetics and developmental programming of welfare and production traits in farm animals

The concept that postnatal health and development can be influenced by events that occur in utero originated from epidemiological studies in humans supported by numerous mechanistic (including epigenetic) studies in a variety of model species. Referred to as the 'developmental origins of health and disease' or 'DOHaD' hypothesis, the primary focus of large-animal studies until quite recently had been biomedical. Attention has since turned towards traits of commercial importance in farm animals. Herein we review the evidence that prenatal risk factors, including suboptimal parental nutrition, gestational stress, exposure to environmental chemicals and advanced breeding technologies, can determine traits such as postnatal growth, feed efficiency, milk yield, carcass composition, animal welfare and reproductive potential. We consider the role of epigenetic and cytoplasmic mechanisms of inheritance, and discuss implications for livestock production and future research endeavours. We conclude that although the concept is proven for several traits, issues relating to effect size, and hence commercial importance, remain. Studies have also invariably been conducted under controlled experimental conditions, frequently assessing single risk factors, thereby limiting their translational value for livestock production. We propose concerted international research efforts that consider multiple, concurrent stressors to better represent effects of contemporary animal production systems.