Abnormal offspring following in vitro production of bovine preimplantation embryos: a field study

The counterpart congenital overgrowth syndromes Beckwith-Wiedemann Syndrome in human and large offspring syndrome in bovine involve alterations in DNA methylation, transcription, and chromatin configuration

Beckwith-Wiedemann Syndrome (BWS, OMIM #130650) is a congenital epigenetic disorder in humans which affects approximately 1 in 10,340 children. The incidence is likely an underestimation as the condition is usually recognized based on observable phenotypes at birth. BWS children have up to a 28% risk of developing tumors and currently, only 80% of patients can be corroborated molecularly (epimutations/variants). It is unknown how the subtypes of this condition are molecularly similar/dissimilar globally, therefore there is a need to deeply characterize the syndrome at the molecular level. Here we characterize the methylome, transcriptome and chromatin configuration of 18 BWS individuals together with the animal model of the condition, the bovine large offspring syndrome (LOS). Sex specific comparisons are performed for a subset of the BWS patients and LOS. Given that this epigenetic overgrowth syndrome has been characterized as a loss-of-imprinting condition, parental allele-specific comparisons were performed using the bovine animal model. In general, the differentially methylated regions (DMRs) detected in BWS and LOS showed significant enrichment for CTCF binding sites. Altered chromosome compartments in BWS and LOS were positively correlated with gene expression changes, and the promoters of differentially expressed genes showed significant enrichment for DMRs, differential topologically associating domains, and differential A/B compartments in some comparisons of BWS subtypes and LOS. We show shared regions of dysregulation between BWS and LOS, including several HOX gene clusters, and also demonstrate that altered DNA methylation differs between the clinically epigenetically identified BWS patients and those identified as having DNA variants (i.e. CDKN1C microdeletion). Lastly, we highlight additional genes and genomic regions that have the potential to serve as targets for biomarker development to improve current molecular methodologies. In summary, our results suggest that genome-wide alternation of chromosome architecture, which is partially caused by DNA methylation changes, also contribute to the development of BWS and LOS.

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.

Maternal contributions to pregnancy success: from gamete quality to uterine environment

The establishment and maintenance of a pregnancy that goes to term is sine qua non for the long-term sustainability of dairy and beef cattle operations. The oocyte plays a critical role in providing the factors necessary for preimplantation embryonic development. Furthermore, the female, or maternal, environment where oocytes and embryos develop is crucial for the establishment and maintenance of a pregnancy to term. During folliculogenesis, the oocyte must sequentially acquire meiotic and developmental competence, which are the results of a series of molecular events preparing the highly specialized gamete to return to totipotency after fertilization. Given that folliculogenesis is a lengthy process in the cow, the occurrence of disease, metabolic imbalances, heat stress, or other adverse events can make it challenging to maintain oocyte quality. Following fertilization, the newly formed embryo must execute a tightly planned program that includes global DNA remodeling, activation of the embryonic genome, and cell fate decisions to form a blastocyst within a few days and cell divisions. The increasing use of assisted reproductive technologies creates an additional layer of complexity to ensure the highest oocyte and embryo quality given that in vitro systems do not faithfully recreate the physiological maternal environment. In this review, we discuss cellular and molecular factors and events known to be crucial for proper oocyte development and maturation, as well as adverse events that may negatively affect the oocyte; and the importance of the uterine environment, including signaling proteins in the maternal-embryonic interactions that ensure proper embryo development. We also discuss the impact of assisted reproductive technologies in oocyte and embryo quality and developmental potential, and considerations when looking into the prospects for developing systems that allow for in vitro gametogenesis as a tool for assisted reproduction in cattle.

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.

Blastulation time measured with time-lapse system can predict in vitro viability of bovine blastocysts

The objective of this study was to evaluate the time of blastulation monitored by time-lapse technology to predict in vitro viability of bovine blastocysts. This technology can be a powerful tool for bovine embryos selection with higher implantation capacity and competence. Also, in humans an early blastulation is associated with higher quality and pregnancy rate. Cumulus oocyte complexes (COCs) were matured for 20 to 22 h and then fertilized by co-incubation of COCs and spermatozoa (10,000 sperm per oocyte) for 18 h. Presumptive zygotes were placed individually in microwells, in droplets of commercial culture medium. The Primo Vision TL system (EVO+; Vitrolife) captured digital images of developing embryos every 15 minutes. The time frame from IVF to the start of blastulation (tSB) and to blastocyst development (tB) was recorded. After day 7.5, the blastocysts were in vitro culture for 48 h until day 9.5 after IVF to evaluate post hatching development. In vitro viability was evaluated at day 9.5: those with a diameter greater than 200 μm and a total cell count greater than 180 were classified as viable (value 1), while the rest were classified as non in vitro viable (value 0). The area under the ROC curve (AUC) was estimated to determine the predictive power of in vitro viability through blastulation time. In addition, binary logistic regression analysis was used to generate a mathematical model with morphokinetic variables that allow the best prediction of in vitro viability. In 13 sessions, the blastocyst production rate was 46.2% (96/208). The cut-off time to discriminate early or late blastulation was 149.8 h. The post-hatching development of the embryos with early blastulation was 63.3% (31/49), being statistically superior (p = 0.001) than the late blastulation group 14.9% (7/47). Likewise, the time of blastulation showed an accuracy of 90.8% (p < 0.001) in predicting in vitro viability of bovine blastocysts. In conclusion, the selection of blastocysts based on blastulation time (< 155 h) and blastocyst diameter measured on day 7.5 after IVF (> 180 μm) maximizes the in vitro viability.

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.

Review: Large offspring syndrome in ruminants: current status and prediction during pregnancy

Large/abnormal Offspring Syndrome (LOS/AOS) is a congenital overgrowth condition of cattle and sheep, characterized by macrosomia, abdominal wall defects, organomegaly, difficulty to stand and suckle at parturition. The condition was first described as an exclusive consequence of assisted reproductive technologies, such as in vitro production and somatic cell nuclear transfer (cloning). However, we recently reported the spontaneous occurrence of this syndrome in cattle. The etiology of LOS is unclear, although the syndrome is an epigenetic condition characterized by multi-locus loss-of-imprinting, global dysregulation of small and long RNAs, changes in DNA methylation, and altered chromosomal architecture. These molecular and epigenetic changes affect biological pathways implicated in organ size, cell proliferation, cell survival, resulting in the phenotypes which characterize LOS. The lack of accurate tools for the prediction and diagnosis of LOS and the prevention of dystocia resulting from fetal overgrowth is a major concern for the dairy and beef industries. Furthermore, death of the calf and/or dam during calving adds animal welfare issues and affects the net income of the industry. An early diagnosis of LOS/AOS during gestation is critical to facilitate the decision-making process on whether to allow the pregnancy to continue or not in order to prevent harm to the dam as well as to provide producers with the timely necessary information to prepare for a difficult birth. The present review summarizes the definition, traits, incidence, and molecular characteristics of LOS to provide information and serve as a guide for future investigations regarding the early identification of LOS during pregnancy in cattle.

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.

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.

Spontaneous and ART-induced large offspring syndrome: similarities and differences in DNA methylome

Large/abnormal offspring syndrome (LOS/AOS) is a congenital overgrowth syndrome reported in ruminants produced by assisted reproduction (ART-LOS) which exhibit global disruption of the epigenome and transcriptome. LOS/AOS shares phenotypes and epigenotypes with the human congenital overgrowth condition Beckwith-Wiedemann syndrome. We have reported that LOS occurs spontaneously (SLOS); however, to date, no study has been conducted to determine if SLOS has the same methylome epimutations as ART-LOS. In this study, we performed whole-genome bisulphite sequencing to examine global DNA methylation in bovine SLOS and ART-LOS tissues. We observed unique patterns of global distribution of differentially methylated regions (DMRs) over different genomic contexts, such as promoters, CpG Islands, shores and shelves, as well as at repetitive sequences. In addition, we included data from two previous LOS studies to identify shared vulnerable genomic loci in LOS. Overall, we identified 320 genomic loci in LOS that have alterations in DNA methylation when compared to controls. Specifically, there are 25 highly vulnerable loci that could potentially serve as molecular markers for the diagnosis of LOS, including at the promoters of DMRT2 and TBX18, at the imprinted gene bodies of IGF2R, PRDM8, and BLCAP/NNAT, and at multiple CpG Islands. We also observed tissue-specific DNA methylation patterns between muscle and blood, and conservation of ART-induced DNA methylation changes between muscle and blood. We conclude that as ART-LOS, SLOS is an epigenetic condition. In addition, SLOS and ART-LOS share similarities in methylome epimutations.

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.

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.

Sex-specific epigenetic profile of inner cell mass of mice conceived in vivo or by IVF

The preimplantation stage of development is exquisitely sensitive to environmental stresses, and changes occurring during this developmental phase may have long-term health effects. Animal studies indicate that IVF offspring display metabolic alterations, including hypertension, glucose intolerance and cardiac hypertrophy, often in a sexual dimorphic fashion. The detailed nature of epigenetic changes following in-vitro culture is, however, unknown. This study was performed to evaluate the epigenetic (using whole-genome bisulfite sequencing (WGBS) and assay for transposase-accessible chromatin using sequencing (ATAC-seq)) and transcriptomic changes (using RNA-seq) occurring in the inner cell mass (ICM) of male or female mouse embryos generated in vivo or by IVF. We found that the ICM of IVF embryos, compared to the in-vivo ICM, differed in 3% of differentially methylated regions (DMRs), of which 0.1% were located on CpG islands. ATAC-seq revealed that 293 regions were more accessible and 101 were less accessible in IVF embryos, while RNA-seq revealed that 21 genes were differentially regulated in IVF embryos. Functional enrichment analysis revealed that stress signalling (STAT and NF-kB signalling), developmental processes and cardiac hypertrophy signalling showed consistent changes in WGBS and ATAC-seq platforms. In contrast, male and female embryos showed minimal changes. Male ICM had an increased number of significantly hyper-methylated DMRs, while only 27 regions showed different chromatin accessibility and only one gene was differentially expressed. In summary, this study provides the first comprehensive analysis of DNA methylation, chromatin accessibility and RNA expression changes induced by IVF in male and female ICMs. This dataset can be of value to all researchers interested in the developmental origin of health and disease (DOHaD) hypothesis and might lead to a better understanding of how early embryonic manipulation may affect adult health.

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.

Consequences of assisted reproductive techniques on the embryonic epigenome in cattle

Procedures used in assisted reproduction have been under constant scrutiny since their inception with the goal of improving the number and quality of embryos produced. However, invitro production of embryos is not without complications because many fertilised oocytes fail to become blastocysts, and even those that do often differ in the genetic output compared with their invivo counterparts. Thus only a portion of those transferred complete normal fetal development. An unwanted consequence of bovine assisted reproductive technology (ART) is the induction of a syndrome characterised by fetal overgrowth and placental abnormalities, namely large offspring syndrome; a condition associated with inappropriate control of the epigenome. Epigenetics is the study of chromatin and its effects on genetic output. Establishment and maintenance of epigenetic marks during gametogenesis and embryogenesis is imperative for the maintenance of cell identity and function. ARTs are implemented during times of vast epigenetic reprogramming; as a result, many studies have identified ART-induced deviations in epigenetic regulation in mammalian gametes and embryos. This review describes the various layers of epigenetic regulation and discusses findings pertaining to the effects of ART on the epigenome of bovine gametes and the preimplantation embryo.

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.

In vitro fertilisation in domestic mammals-a brief overview

Many factors influence the final oocyte maturation, fertilisation, and early embryo development, and there are both similarities and differences between species. When comparing the advancement of assisted reproductive technologies (ARTs), the development in the bovine species is not far behind the medical front, with around one million in vitro-produced bovine embryos each year. This rate of progress is not seen in the other domestic species. This review aims to give an overview of the development and specific difficulties of in vitro embryo production in various domestic animal species, with the main focus on cows, pigs, and cats. In production animals, the aim of ARTs is commonly to increase the genetic progress, not to treat reproductive failure. The ARTs are also used for preservation of genetic diversity for the future. However, specifically for oocyte maturation, fertilisation, and early embryonic development, domestic mammals such as the cow and pig can be used as models for humans. This is particularly attractive from an animal welfare point of view since bovine and porcine oocytes are available in large numbers from discarded slaughterhouse material, thereby decreasing the need for research animals. Both for researchers on the animal and human medical fronts, we aim for the development of in vitro production systems that will produce embryos and offspring that are no different from those conceived and developed in vivo. Species-comparative research and development can provide us with crucial knowledge to achieve this aim and hopefully help us avoid unnecessary problems in the future.

Recent progress in bovine in vitro-derived embryo cryotolerance: Impact of in vitro culture systems, advances in cryopreservation and future considerations

Cryopreservation of in vitro-derived bovine embryos is a crucial step for the widespread reproduction and conservation of valuable high-merit animals. Given the current popularity of bovine in vitro embryo production (IVP), there is a demand for a highly efficient ultra-low temperature storage method in order to maximize donor ovum pickup (OPU) turn-over, recipient availability/utilization and domestic/overseas commercial trading opportunities. However, IVP bovine embryos are still very sensitive to chilling and cryopreservation, and despite recent progress, a convenient (simple and robust) protocol has not yet been developed. At the moment, there are two methods for bovine IVP embryo cryopreservation: slow programmable freezing and vitrification. Both of the aforementioned techniques have pros and cons. While controlled-rate slow cooling can easily be adapted for direct transfer (DT), ice crystal formation remains an issue. On the other hand, vitrification solved this problem but the possibility of successful DT commercial incorporation remains to be determined. Moreover, simplification of the vitrification protocol (including warming) through the use of an in-straw dilution without the use of a microscope is a prerequisite for its use under farm conditions. This review summarizes the bovine IVP embryo cryopreservation achievements, strengths and limitations of both freezing systems and prospective improvements to enhance cryosurvival, as well as perspectives on future directions of this assisted reproductive technology.

Equine hydrallantois is associated with impaired angiogenesis in the placenta

INTRODUCTION

Hydrallantois is the excessive accumulation of fluid in the allantoic cavities during the last trimester of pregnancy, leading to abdominal wall hernias, cardiovascular shock, abortion, and dystocia. It has been postulated that hydrallantois is associated with structural and/or functional changes in the chorioallantoic membrane. In the present study, we hypothesized that angiogenesis is impaired in the hydrallantoic placenta.

METHOD

Capillary density in the hydrallantoic placenta was evaluated in the chorioallantois via immunohistochemistry for Von Willebrand Factor. Moreover, the expression of angiogenic genes was compared between equine hydrallantois and age-matched, normal placentas.

RESULTS

In the hydrallantoic samples, edema was the main pathological finding. The capillary density was significantly lower in the hydrallantoic samples than in normal placentas. The reduction in the number of vessels was associated with abnormal expression of a subset of angiogenic and hypoxia-associated genes including VEGF, VEGFR1, VEGFR2, ANGPT1, eNOS and HIF1A. We believe that the capillary density and the abnormal expression of angiogenic genes leads to tissue hypoxia (high expression of HIF1A) and edema. Finally, we identified a lower expression of genes associated with steroidogenic enzyme (CYP19A1) and estrogen receptor signaling (ESR2) in the hydrallantoic placenta.

DISCUSSION

Based on the presented data, we believe that formation of edema is due to disrupted vascular development (low number of capillaries) and hypoxia in the hydrallantoic placenta. The edema leads to further hypoxia and consequently, causes an increase in vessel permeability which leads to a gradual increase in interstitial fluid accumulation, resulting in an insufficient transplacental exchange rate and accumulation of fluid in the allantoic cavity.

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.

Overgrowth Syndrome

Large offspring syndrome (LOS) is a fetal overgrowth condition in bovines most often observed in offspring conceived with the use of assisted reproductive technologies (ART). Phenotypes observed in LOS include, overgrowth, enlarged tongues, umbilical hernias, muscle and skeleton malformations, abnormal organ growth and placental development. Although LOS cases have only been reported to be associated with ART, fetal overgrowth can occur spontaneously in cattle (S-LOS). S-LOS refers to oversized calves that are born at normal gestation lengths. ART-induced LOS has been characterized as an epigenetic syndrome, more specifically, a loss-of-imprinting condition. We propose that S-LOS is also a loss-of-imprinting condition.

Regulation and safety considerations of somatic cell nuclear transfer-cloned farm animals and their offspring used for food production

This document discusses recent developments in cloning of husbandry animals through somatic cell nuclear transfer, particularly with a view on improvements in their efficacy. Commercial developments in North and South America, Australia-New Zealand, and China are noted. The regulations and safety aspects surrounding the use of clones and their offspring for the purpose of food production are discussed. It is generally considered that foods from offspring of clones are no different than similar foods from conventional animals, yet besides safety, also ethical and animal welfare considerations come into play at the policy level. The related topic of detection and traceability of clones is discussed, which covers both molecular and documentary methods.

Ultrasonographic measurements in first trimester concepti identify predictors of birth weight and postnatal development in cattle

The placenta is a major driver of prenatal growth and involved in programming of postnatal performance. We therefore determined placental and embryo-fetal ultrasonographic parameters in early pregnancy and their relationships with birth weight and postnatal weights in a Bos indicus-Bos taurus composite beef cattle population. Pregnancies were generated in 2-yr-old Droughtmaster heifers by artificial insemination after estrus synchronization in 2 consecutive years (2009, n = 36 and 2010, n = 57), with a subset of 2010 heifers used again as lactating 3-yr-old cows in 2011 (n = 24). Each cohort was managed as 1 contemporary group for measurements of Corpus luteum diameter, amnion length and width, placentome width and thickness, and embryo-fetal crown-rump length, at 7 and 8 wk of gestation. This was followed by recordings of birth weight, branding weight at 5 to 6 mo of age and weaning weight 2 mo later. At a significance threshold of P < 0.05, placentome thickness at week 7 was negatively correlated with weights at birth (r = -0.23), branding (r = -0.25), and weaning (r = -0.35), whereas placentome width at week 7 (r = 0.24) and thickness at week 8 (r = 0.29) were positively correlated with birth weight. Thicker placentomes in males at week 7 (7%) difference mirrored sex differences in weights at birth (7%), branding (10%), and weaning (6%). The sex difference trend for birth weight was not consistent across sire-year combinations, ranging from -3.2 to +4.7 kg (birth weight of males - females per sire). These results support the hypothesis that placental parameters at the transition from embryo to fetal stage are major predictors of fetal and postnatal growth, albeit with significant environmentally induced plasticity, in stabilized B. indicus-B. taurus composite populations, and suggest that elements of B. indicus-B. taurus reciprocal differences in birth weight persist in composite populations.

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.

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.

Mechanisms of epigenetic remodelling during preimplantation development

Epigenetics involves mechanisms independent of modifications in the DNA sequence that result in changes in gene expression and are maintained through cell divisions. Because all cells in the organism contain the same genetic blueprint, epigenetics allows for cells to assume different phenotypes and maintain them upon cell replication. As such, during the life cycle, there are moments in which the epigenetic information needs to be reset for the initiation of a new organism. In mammals, the resetting of epigenetic marks occurs at two different moments, which both happen to be during gestation, and include primordial germ cells (PGCs) and early preimplantation embryos. Because epigenetic information is reversible and sensitive to environmental changes, it is probably no coincidence that both these extensive periods of epigenetic remodelling happen in the female reproductive tract, under a finely controlled maternal environment. It is becoming evident that perturbations during the extensive epigenetic remodelling in PGCs and embryos can lead to permanent and inheritable changes to the epigenome that can result in long-term changes to the offspring derived from them, as indicated by the Developmental Origins of Health and Disease (DOHaD) hypothesis and recent demonstration of inter- and trans-generational epigenetic alterations. In this context, an understanding of the mechanisms of epigenetic remodelling during early embryo development is important to assess the potential for gametic epigenetic mutations to contribute to the offspring and for new epimutations to be established during embryo manipulations that could affect a large number of cells in the offspring. It is of particular interest to understand whether and how epigenetic information can be passed on from the gametes to the embryo or offspring, and whether abnormalities in this process could lead to transgenerationally inheritable phenotypes. The aim of this review is to highlight recent progress made in understanding the nature and mechanisms of epigenetic remodelling that ensue after fertilisation.

Morphometric developmental pattern of bovine handmade cloned concepti in late pregnancy

Cloning procedures often interfere with conceptus growth and life ex utero, in a set of symptoms known as abnormal offspring syndrome (AOS). The aim of the present study was to compare the developmental pattern of in vivo-derived (IVD), IVF-derived and handmade cloning-derived (NT-HMC) Day 225 bovine concepti using established procedures. Pregnancy diagnosis was performed on Day 30 following blastocyst transfer on Day 7. Conceptus morphometry was assessed by ultrasonography on Day 51, and on Day 225 pregnant cows were killed for morphological examination of concepti. Pregnancy outcome was similar between groups, with greater pregnancy losses in the first trimester (70.6%) and smaller fetuses on Day 51 in the NT-HMC group than in the IVD (14.3%) and IVF (20.0%) groups. However, NT-HMC-derived concepti were twofold larger on Day 225 of gestation than controls. A higher frequency (63.5%) of placentomes larger than the largest in the IVD group was observed in the NT-HMC group, which may be relevant to placental function. Conceptus traits in the IVF group were similar to the IVD controls, with only slight changes in placentome types. Morphological changes in cloned concepti likely affected placental function and metabolism, disrupting the placental constraining mechanism on fetal growth in mid- to late pregnancy.

A missense mutation in solute carrier family 12, member 1 (SLC12A1) causes hydrallantois in Japanese Black cattle

BACKGROUND

Hydrallantois is the excessive accumulation of fluid within the allantoic cavity in pregnant animals and is associated with fetal mortality. Although the incidence of hydrallantois is very low in artificial insemination breeding programs in cattle, recently 38 cows with the phenotypic appearance of hydrallantois were reported in a local subpopulation of Japanese Black cattle. Of these, 33 were traced back to the same sire; however, both their parents were reported healthy, suggesting that hydrallantois is a recessive inherited disorder. To identify autozygous chromosome segments shared by individuals with hydrallantois and the causative mutation in Japanese Black cattle, we performed autozygosity mapping using single-nucleotide polymorphism (SNP) array and exome sequencing.

RESULTS

Shared haplotypes of the affected fetuses spanned 3.52 Mb on bovine chromosome 10. Exome sequencing identified a SNP (g.62382825G > A, p.Pro372Leu) in exon 10 of solute carrier family 12, member 1 (SLC12A1), the genotype of which was compatible with recessive inheritance. SLC12A1 serves as a reabsorption molecule of Na(+)-K(+)-2Cl(-) in the apical membrane of the thick ascending limb of the loop of Henle in the kidney. We observed that the concentration of Na(+)-Cl(-) increased in allantoic fluid of homozygous SLC12A1 (g.62382825G > A) in a hydrallantois individual. In addition, SLC12A1-positive signals were localized at the apical membrane in the kidneys of unaffected fetuses, whereas they were absent from the apical membrane in the kidneys of affected fetuses. These results suggested that p.Pro372Leu affects the membrane localization of SLC12A1, and in turn, may impair its transporter activity. Surveillance of the risk-allele frequency revealed that the carriers were restricted to the local subpopulation of Japanese Black cattle. Moreover, we identified a founder individual that carried the mutation (g.62382825G > A).

CONCLUSIONS

In this study, we mapped the shared haplotypes of affected fetuses using autozygosity mapping and identified a de novo mutation in the SLC12A1 gene that was associated with hydrallantois in Japanese Black cattle. In kidneys of hydrallantois-affected fetuses, the mutation in SLC12A1 impaired the apical membrane localization of SLC12A1 and reabsorption of Na(+)-K(+)-2Cl(-) in the thick ascending limb of the loop of Henle, leading to a defect in the concentration of urine via the countercurrent mechanism. Consequently, the affected fetuses exhibited polyuria that accumulated in the allantoic cavity. Surveillance of the risk-allele frequency indicated that carriers were not widespread throughout the Japanese Black cattle population. Moreover, we identified the founder individual, and thus could effectively manage the disorder in the population.

Forty years of embryo transfer in cattle: a review focusing on the journal Theriogenology, the growth of the industry in North America, and personal reminisces

After the first successful transfer of mammalian embryos in 1890, it was approximately 60 years before significant progress was reported in the basic technology of embryo transfer (ET) in cattle. Starting in the early 1970s, technology had progressed sufficiently to support the founding of commercial ET programs in several countries. Today, well-established and reliable techniques involving superovulation, embryo recovery and transfer, cryopreservation, and IVF are utilized worldwide in hundreds, if not thousands, of commercial businesses located in many countries. The mean number of embryos produced via superovulation has changed little in 40 years, but there have been improvements in synchrony and hormonal protocols. Cryopreservation of in vivo-derived embryos is a reliable procedure, but improvements are needed for biopsied and in vitro-derived embryos. High pregnancy rates are achieved when good quality embryos are transferred into suitable recipients and low pregnancy rates are often owing to problems in recipient management and not technology per se. In the future, unanticipated disease outbreaks and the ever-changing economics of cattle and milk prices will continue to influence the ET industry. The issue of abnormal pregnancies involving in vitro embryos has not been satisfactorily resolved and the involvement of abnormal epigenetics associate with this technology merits continued research. Last, genomic testing of bovine embryos is likely to be available in the foreseeable future. This may markedly decrease the number of embryos that are actually transferred and stimulate the evolution of more sophisticated ET businesses.

Embryo development, fetal growth and postnatal phenotype of eGFP lambs generated by lentiviral transgenesis

Lentiviral technology has been recently proposed to generate transgenic farm animals more efficiently and easier than traditional techniques. The objective was to evaluate several parameters of lambs obtained by lentiviral transgenesis in comparison with non-transgenic counterparts. In vitro produced embryos were microinjected (TG group) at two-cell stage with a lentiviral construct containing enhanced green fluorescent protein (eGFP) gene, while embryos produced by in vitro fertilization (IVF group) or intrauterine insemination (IUI group) were not microinjected. Microinjection technique efficiently generated eight-cell transgenic embryos (97.4%; 114/117). Development rate on day 5 after fertilization was similar for TG (39.3%, 46/117) and IVF embryos (39.6%, 44/111). Pregnancy rate was detected in 50.0% (6/12) of recipient ewes with TG embryos, in 46.7% (7/15) with IVF embryos, and in 65.0% (13/20) of IUI ewes (P = NS). Nine lambs were born in TG group, six lambs in IVF group, and 16 lambs in IUI group. All TG lambs (9/9) were GFP positive to real-time PCR and eight (88.9%) showed a strong and evident GFP expression in mucosae, eyes and keratin tissues. Fetal growth monitored every 15 day by ultrasonography did not show significant differences. Transgenic lambs neither differ in morphometric variables in comparison with non transgenic IVF lambs within 3 months after birth. Transmission of the transgene to the progeny was observed in green fluorescent embryos produced by IVF using semen from the TG founder lambs. In conclusion, this study demonstrates the high efficiency of lentiviral technology to produce transgenic sheep, with no clinic differences in comparison with non transgenic lambs.

Incidence of abnormal offspring from cloning and other assisted reproductive technologies

In animals produced by assisted reproductive technologies, two abnormal phenotypes have been characterized. Large offspring syndrome (LOS) occurs in offspring derived from in vitro cultured embryos, and the abnormal clone phenotype includes placental and fetal changes. LOS is readily apparent in ruminants, where a large calf or lamb derived from in vitro embryo production or cloning may weigh up to twice the expected body weight. The incidence of LOS varies widely between species. When similar embryo culture conditions are applied to nonruminant species, LOS either is not as dramatic or may even be unapparent. Coculture with serum and somatic cells was identified in the 1990s as a risk factor for abnormal development of ruminant pregnancies. Animals cloned from somatic cells may display a combination of fetal and placental abnormalities that are manifested at different stages of pregnancy and postnatally. In highly interventional technologies, such as nuclear transfer (cloning), the incidence of abnormal offspring continues to be a limiting factor to broader application of the technique. This review details the breadth of phenotypes found in nonviable pregnancies, together with the phenotypes of animals that survive the transition to extrauterine life. The focus is on animals produced using in vitro embryo culture and nuclear transfer in comparison to naturally occurring phenotypes.

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

No reports exist on consequences of in vitro production (IVP) of embryos for the postnatal development of the calf or on postparturient function of the dam of the calf. Three hypotheses were evaluated: calves born as a result of transfer of an IVP embryo have reduced neonatal survival and altered postnatal growth, fertility, and milk yield compared with artificial insemination (AI) calves; cows giving birth to IVP calves have lower milk yield and fertility and higher incidence of postparturient disease than cows giving birth to AI calves; and the medium used for IVP affects the incidence of developmental abnormalities. In the first experiment, calves were produced by AI using conventional semen or by embryo transfer (ET) using a fresh or vitrified embryo produced in vitro with X-sorted semen. Gestation length was longer for cows receiving a vitrified embryo than for cows receiving a fresh embryo or AI. The percentage of dams experiencing calving difficulty was higher for ET than AI. We observed a tendency for incidence of retained placenta to be higher for ET than AI but found no significant effect of treatment on incidence of prolapse or metritis, pregnancy rate at first service, services per conception, or any measured characteristic of milk production in the subsequent lactation. Among Holstein heifers produced by AI or ET, treatment had no effect on birth weight but the variance tended to be greater in the ET groups. More Holstein heifer calves tended to be born dead, died, or were euthanized within the first 20d of life for the ET groups than for AI. Similarly, the proportion of Holstein heifer calves that either died or were culled for poor health after 20d of age was greater for the ET groups than for AI. We observed no effect of ET compared with AI on age at first service or on the percentage of heifers pregnant at first service, calf growth, or milk yield or composition in the first 120d in milk of the first lactation. In a second experiment, embryos were produced using 1 of 2 culture media: synthetic oviductal fluid-bovine embryo 1 (SOF-BE1) or Block-Bonilla-Hansen 7 (BBH7). We detected no difference between cows receiving an SOF-BE1 or BBH7 embryo in gestation length, the percentage of cows in which parturition was induced, or the percentage of cows that experienced calving difficulty, retained placenta, prolapse, or metritis. Among Holstein heifers, birth weight was higher for BBH7 calves than for SOF-BE1 calves. Treatment had no significant effect on calf death. Results indicate that calves born as a result of IVP-ET are more likely to experience alterations in birth weight and increased death in early life but that there were few consequences to the dam of carrying a fetus derived by IVP-ET.

Health of Human and Livestock Conceived by Assisted Reproduction

Assisted reproduction is used to resolve infertility problems in human and in breeding programs to generate livestock. Except for gestation length and birth weight, perinatal outcome of children conceived by In Vitro Fertilization is similar to that of spontaneously conceived children. However, large offspring syndrome observed after In Vitro Production in livestock is quite alarming. The distinct parts of assisted reproduction (oocyte maturation, fertilization and culture) have been found to contribute to abnormal fetal growth and development. Genomic imprinting is suggested to be involved in the induction of the aberrant phenotypes observed after assisted reproduction. Furthermore, current knowledge on postnatal health of offspring conceived by assisted reproduction and speculations on potential longterm effects of In Vitro Fertilization will be described.

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

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

Embryo culture: can we perform better than nature?

Culture of preimplantation-stage embryos has always been a key element of laboratory embryology and has contributed substantially to the success of many assisted reproduction procedures. During the past decade, its importance has increased as extended in-vitro embryo culture and single blastocyst transfer have become indispensable parts of the approach to decreasing the chance of multiple pregnancy while preserving the overall efficiency of the treatment. However, in spite of the scientific and commercial challenge stimulating research worldwide to optimize embryo culture conditions, a consensus is missing even in the basic principles, including composition and exchange of media, the required physical and biological environment and even the temperature of incubation. This review attempts to summarize the controversies, demonstrate the fragility of some widely accepted dogmas and generate an open-minded debate towards rapid and efficient optimization. New approaches expanding the traditional frames of mammalian embryo culture are also discussed. Although some researchers suppose that the efficiency of the presently applied in-vitro culture systems have already approached the biological limits, authors are confident that substantial improvement may be achieved that may expand considerably the possibilities of future assisted reproduction in humans.