Colony-stimulating factor 2 (CSF-2) improves development and posttransfer survival of bovine embryos produced in vitro

Interleukin-6 supplementation improves bovine conceptus elongation and transcriptomic indicators of developmental competence†

A high incidence of pregnancy failures occurs in cattle during the second week of pregnancy as blastocysts transition into an elongated conceptus. This work explored whether interleukin-6 supplementation during in vitro embryo production would improve subsequent conceptus development. Bovine embryos were treated with 0 or 100 ng/mL recombinant bovine interleukin-6 beginning on day 5 post-fertilization. At day 7.5 post-fertilization, blastocysts were transferred into estrus synchronized beef cows (n = 5 recipients/treatment, 10 embryos/recipient). Seven days after transfer (day 14.5), cows were euthanized to harvest reproductive tracts and collect conceptuses. Individual conceptus lengths and stages were recorded before processing for RNA sequencing. Increases in conceptus recovery, length, and the proportion of tubular and filamentous conceptuses were detected in conceptuses derived from interleukin-6-treated embryos. The interleukin-6 treatment generated 591 differentially expressed genes in conceptuses (n = 9-10/treatment). Gene ontology enrichment analyses revealed changes in transcriptional regulation, DNA-binding, and antiviral actions. Only a few differentially expressed genes were associated with extraembryonic development, but several differentially expressed genes were associated with embryonic regulation of transcription, mesoderm and ectoderm development, organogenesis, limb formation, and somatogenesis. To conclude, this work provides evidence that interleukin-6 treatment before embryo transfer promotes pre-implantation conceptus development and gene expression in ways that resemble the generation of a robust conceptus containing favorable abilities to survive this critical period of pregnancy.

Addition of GM-CSF during in vitro oocyte maturation improves embryo development and implantation and birth rate in mice

The present study determined whether adding granulocyte macrophage colony stimulating factor (GM-CSF) during in vitro oocyte maturation (IVM) could improve oocyte developmental competence by examining embryo development and implantation and birth rates following embryo transfer in mice. In an initial dose response experiment, we demonstrated that the addition of 2 and 10 ng/mL of GM-CSF during IVM increased cumulus expansion (P<0.05) but did not affect fertilisation rate compared with the control group. The addition of 10 ng/mL increased blastocyst rate (17.0%; P<0.05) and tended to increase the number of good quality blastocysts present at 96 h of culture (+19.4%; P=0.06) and increased blastocyst inner cell mass (+25.2%; P<0.001), trophectoderm (+29.9%; P<0.01), and total cell numbers (+28.6%; P<0.05). GM-CSF also reduced the incidence of DNA damage in blastocysts in the 10 ng/mL group (-16.2%) compared with the control group. These improvements translated into increases in implantation rate (+21.0%; P<0.05) and birth rate (+17.0%; P<0.05) following the transfer of vitrified blastocysts.GM-CSF treatment did not alter any fetal and placental parameters. Together these results suggest that the addition of GM-CSF during IVM may improve livestock in vitro embryo production and human IVM.

Weighted single-step genome-wide association study for direct and maternal genetic effects associated with birth and weaning weights in sheep

Body weight is an important economic trait for sheep meat production, and its genetic improvement is considered one of the main goals in the sheep breeding program. Identifying genomic regions that are associated with growth-related traits accelerates the process of animal breeding through marker-assisted selection, which leads to increased response to selection. In this study, we conducted a weighted single-step genome-wide association study (WssGWAS) to identify potential candidate genes for direct and maternal genetic effects associated with birth weight (BW) and weaning weight (WW) in Baluchi sheep. The data used in this research included 13,408 birth and 13,170 weaning records collected at Abbas-Abad Baluchi Sheep Breeding Station, Mashhad-Iran. Genotypic data of 94 lambs genotyped by Illumina 50K SNP BeadChip for 54,241 markers were used. The proportion of variance explained by genomic windows was calculated by summing the variance of SNPs within 1 megabase (Mb). The top 10 window genomic regions explaining the highest percentages of additive and maternal genetic variances were selected as candidate window genomic regions associated with body weights. Our findings showed that for BW, the top-ranked genomic regions (1 Mb windows) explained 4.30 and 4.92% of the direct additive and maternal genetic variances, respectively. The direct additive genetic variance explained by the genomic window regions varied from 0.31 on chromosome 1 to 0.59 on chromosome 8. The highest (0.84%) and lowest (0.32%) maternal genetic variances were explained by genomic windows on chromosome 10 and 17, respectively. For WW, the top 10 genomic regions explained 6.38 and 5.76% of the direct additive and maternal genetic variances, respectively. The highest and lowest contribution of direct additive genetic variances were 1.37% and 0.42%, respectively, both explained by genomic regions on chromosome 2. For maternal effects on WW, the highest (1.38%) and lowest (0.41%) genetic variances were explained by genomic windows on chromosome 2. Further investigation of these regions identified several possible candidate genes associated with body weight. Gene ontology analysis using the DAVID database identified several functional terms, such as translation repressor activity, nucleic acid binding, dehydroascorbic acid transporter activity, growth factor activity and SH2 domain binding.

Meta-analysis to determine efficacy of colony-stimulating factor 2 for improving pregnancy success after embryo transfer in cattle

Results have been inconsistent as to whether addition of colony stimulating factor 2 (CSF2) to culture medium improves embryo competence for establishment of pregnancy in cattle and humans. The purpose of the current study was to use all available experiments in cattle concerning effects of CSF2 on pregnancy success after transfer into recipient cattle. The approach was to perform a meta-analysis of all published data sets as well as data from an unpublished experiment described for the first time here. Meta-analysis failed to support the hypothesis that addition of CSF2 to embryo culture medium improves competence of bovine blastocysts to increase pregnancy or calving rates after transfer into recipient females. Thus, its general use as a culture medium additive to increase pregnancy success after embryo transfer is not recommended.

Effects of mycobacterium cell wall fraction on embryo development following in vitro embryo production and pregnancy rates following embryo transfer in virgin dairy heifers

An experiment was conducted to determine whether administration of mycobacterium cell wall fraction (MCWF; Amplimune, NovaVive) could enhance embryo developmental competence following in vitro embryo production (IVP) and pregnancy establishment after embryo transfer (ET). Nulliparous, Holstein heifers (n = 40; age 8-15 months) were submitted to two rounds of ovum pick-up (OPU) and IVP in a crossover design. Thirty-six h after follicle wave synchronization, treatments (saline or MCWF, 5 mL, im) were administered in conjunction with a single dose of follicle stimulating hormone (175 IU) and OPU was performed 48-52 h later. Recovered cumulus-oocyte complexes were used for IVP to assess embryo development. For ET, nulliparous, Holstein heifers (n = 225; age 12-18 months) were used as recipients. At 12-24 h after detection of spontaneous estrus, recipients were randomly treated with either saline or MCWF (5 mL, im). The effect of MCWF on pregnancy per ET (P/ET) was assessed in a 2 × 2 factorial design with recipients treated with or without MCWF receiving a fresh IVP embryo from a donor treated with or without MCWF at day 7 or 8 after detected estrus. Blood samples were collected from a subset of donors (n = 8) and recipients (n = 26 to 33 per treatment) prior to treatment and at 6 and 24 h post-treatment to determine serum concentration of interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and interferon-γ. Blood samples were also collected from a group of recipients (n = 31 to 39 per treatment) to assess serum concentration of progesterone at days 4, 7, and 16 post-treatment. Pregnancy status was determined at days 40 and 100 of gestation. Donor treatment with MCWF tended (P < 0.07) to increase the proportion of oocytes that developed into transferable embryos, but there was no effect of MCWF on other parameters of embryo development. The P/ET at days 40 and 100 of gestation and pregnancy loss were not affected by donor treatment or recipient treatment with MCWF and there was no interaction. Serum concentration of proinflammatory cytokines among donors and recipients and serum concentration of progesterone among recipients were not increased by treatment with MCWF. Results of the present study indicate that treatment of donors with MCWF has minimal impact on subsequent embryo development following IVP. Moreover, regardless of whether donors or recipients were treated with MCWF, there was no effect on P/ET following transfer of IVP embryos.

Insulin-like growth factor (IGF) performance in ovarian function and applications in reproductive biotechnologies

The role of the insulin-like growth factor (IGF) system has attracted close attention. The activity of IGF binding proteins (IGFBPs) within the ovary has not been fully elucidated to date. These proteins bind to IGF with an equal, or greater, affinity than to the IGF1 receptor, thus being in the main position to regulate IGF signalling, in addition to extending the half-life of IGFs within the bloodstream and promoting IGF storage in specific tissue niches. IGF1 has an important part in cell proliferation, differentiation and apoptosis. Considering the importance of IGFs in oocyte maturation, this review sought to elucidate aspects including: IGF production mechanisms; constituent members of their family and their respective functions; the role that these factors play during folliculogenesis, together with their functions during oocyte maturation and apoptosis, and their performance during luteal development. This review also explores the role of IGFs in biotechnological applications, focusing specifically on animal genetic gain.

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.

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: Some challenges and unrealized opportunities toward widespread use of the in vitro-produced embryo in cattle production

The embryo produced by in vitro oocyte maturation, fertilization, and embryonic development is an important resource for genetic improvement and has the potential to improve female fertility and to be programmed to produce offspring with superior ability for health and production. The cultured embryo is also an important component of several realized and potential technologies such as gene editing, somatic cell nuclear cloning, stem cell technologies and gamete generation in vitro. Full realization of the opportunities afforded by the in vitro-produced embryo will require overcoming some technical obstacles to cost-effective implementation of an embryo transfer program. Among the research goals for improving the penetration of embryo transfer in the cattle industry are development of methods to increase the supply of oocytes from genetically elite females, enhance the proportion of oocytes that become transferrable embryos, improve the fraction of embryos that establish pregnancy after transfer, reduce pregnancy wastage after pregnancy diagnosis, and identify culture conditions to optimize postnatal phenotype.

Disruption of CSF2RA in the bovine preimplantation embryo reduces development and affects embryonic gene expression in utero

The hypothesis that CSF2 plays a role in the preimplantation development of the bovine embryo was tested by evaluating consequences of inactivation of CSF2RA (the functional receptor in the embryo) for development of embryos in utero. CRISPR/Cas9 was used to alter sequences on exon 5 and intron 5 of CSF2RA, Control embryos were injected with Cas9 mRNA only. Embryos > 16 cells at day 5 after insemination were transferred to synchronized recipient females in groups of 7 to 24. Embryos were flushed from the uterus two days later. The proportion of recovered embryos that developed to the blastocyst stage was lower for knockout embryos (39%) than for control embryos (63%). RNA sequencing of individual morulae and blastocysts indicated a total of 27 (morula) or 15 (blastocyst) differentially-expressed genes (false discovery rate <0.05). Gene set enrichment analysis indicated that the knockout affected genes playing roles in several functions including cell signaling and glycosylation. It was concluded that signaling through CSF2RA is not obligatory for development of the bovine preimplantation embryo to the blastocyst stage but that CSF2 signaling does enhance the likelihood that the embryo can become a blastocyst and result in specific changes in gene expression.

Effects of Heat Stress on Bovine Oocytes and Early Embryonic Development-An Update

Heat stress is a major threat to cattle reproduction today. It has been shown that the effect of high temperature not only has a negative effect on the hormonal balance, but also directly affects the quality of oocytes, disrupting the function of mitochondria, fragmenting their DNA and changing their maternal transcription. Studies suggest that the induction of HSP70 may reduce the apoptosis of granular layer cells caused by heat stress. It has been shown that the changes at the transcriptome level caused by heat stress are consistent with 46.4% of blastocyst development disorders. Cows from calves exposed to thermal stress in utero have a lower milk yield in their lifetime, exhibit immunological disorders, have a lower birth weight and display a shorter lifespan related to the expedited aging. In order to protect cow reproduction, the effects of heat stress at the intracellular and molecular levels should be tracked step by step, and the impacts of the dysregulation of thermal homeostasis (i.e., hyperthermy) should be taken into account.

Composition and effects of seminal plasma in the female reproductive tracts on implantation of human embryos

The function of seminal plasma involves acting as a transport medium for sperm and as a means of communication between the reproductive tissues of the male and female. It is also a vital factor to prime the reproductive tracts of the female for optimal pregnancy. When the reproductive tract of the female is exposed to seminal plasma, serious alterations take place, enhancing pathogen and debris clearance observed in the uterus throughout mating. It is also capable of supporting embryo growth, promoting the receptivity of the uterus, and establishing tolerance to the semi-allogenic embryo. Moreover, seminal plasma is capable of regulating the functions of several female reproductive organs and providing an ideal condition for effective embryo implantation and pregnancy. It is believed that the health state of the offspring is affected by exposure to seminal plasma. For the treatment of infertility, assisted reproductive technologies have been extensively employed. The application of seminal plasma as a therapeutic approach to enhance the development of embryo competency and rate of implantation, receptivity of endometrium, and establishment of maternal immune tolerance in cycles of ART appears possible. Herein, current knowledge on the composition of seminal plasma and the physiological roles it possesses on various parts of the female reproductive tract are summarized. Moreover, the role of seminal plasma in the development of embryos, implantation, and the following fetal growth and survival have been reviewed in this article.

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.

Actions of CSF2 and DKK1 on bovine embryo development and pregnancy outcomes are affected by composition of embryo culture medium

Procedures for in vitro embryo production in cattle have not been optimized. In the current experiment, we utilized a 3 × 3 factorial design to test whether the proportion of embryos becoming blastocysts in culture and the pregnancy rate after embryo transfer are affected by type of serum in the medium [no serum; 3% (v/v) KnockOut Serum Replacement (SR); 3% (v/v) fetal bovine serum (FBS)] and addition of specific embryokines [vehicle; 10 ng/mL colony stimulating factor 2 (CSF2); 100 ng/mL dickkopf related protein 1 (DKK1)] at day 5 of culture. Embryos were produced using abattoir-derived ovaries and Y-sorted semen from two Angus sires. The percent of putative zygotes and cleaved embryos becoming blastocysts was improved by SR and FBS. Pregnancy rate at day 30 was determined for 1426 Nelore recipients and calving rate for 266 recipients. In the absence of CSF2 or DKK1, pregnancy rates were lower for embryos cultured with SR or FBS. CSF2 and DKK1 reduced pregnancy rate for embryos cultured without serum but had no detrimental effect in the SR or FBS groups. Indeed, CSF2 blocked the negative effect of FBS on pregnancy rate. Data on birth weights were available for 67 bull calves. There were no effects of treatment. The sire used to produce embryos had significant and large effects on development to the blastocyst stage, pregnancy rate at day 30, calving rate and pregnancy loss between day 30 and calving. Results indicate that (1) SR and FBS can improve embryonic development in vitro while also compromising competence of embryos to survive after transfer, (2) actions of CSF2 and DKK1 depend upon other characteristics of the embryo production system, and (3) sire can have a large effect on embryonic development before and after transfer.

Increased expression of pro-inflammatory cytokines at the fetal-maternal interface in bovine pregnancies produced by cloning

PROBLEM

A significant rate of spontaneous abortion is observed in cattle pregnancies produced by somatic cell nuclear transfer (SCNT). Major histocompatibility complex class I (MHC-I) proteins are abnormally expressed on the surface of trophoblast cells from SCNT conceptuses.

METHOD OF STUDY

MHC-I homozygous compatible (n = 9), homozygous incompatible (n = 8), and heterozygous incompatible (n = 5) pregnancies were established by SCNT. Eight control pregnancies were established by artificial insemination. Uterine and trophoblast samples were collected on day 35 ±1 of pregnancy, the expression of immune-related genes was examined by qPCR, and the expression of trophoblast microRNAs was assessed by sequencing.

RESULTS

Compared to the control group, trophoblast from MHC-I heterozygous incompatible pregnancies expressed increased levels of CD28, CTLA4, CXCL8, IFNG, IL1A, IL2, IL10, IL12B, TBX21, and TNF, while GNLY expression was downregulated. The MHC-I homozygous incompatible treatment group expressed increased levels of IFNG, IL1A, and IL2 while the MHC-I homozygous compatible group did not differentially express any genes compared to the control group. In the endometrium, relative to the control group, MHC-I heterozygous incompatible pregnancies expressed increased levels of CD28, CTLA4, CXCL8, IFNG, IL10, IL12B, and TNF, while GATA3 expression was downregulated. The MHC-I homozygous incompatible group expressed decreased amounts of CSF2 transcripts compared with the control group but did not have abnormal expression of any other immune-related genes. MHC-I incompatible pregnancies had 40 deregulated miRNAs compared to control pregnancies and 62 deregulated microRNAs compared to MHC-I compatible pregnancies.

CONCLUSIONS

MHC-I compatibility between the dam and fetus prevented an exacerbated maternal immune response from being mounted against fetal antigens.

GM-CSF perturbs cell identity in mouse pre-implantation embryos

Growth factors became attractive candidates for medium supplementation to further improve the quality of embryo culture and to mimic in vivo nutrition. Granulocyte macrophage colony-stimulating factor (GM-CSF) is a cytokine influencing the maternal-fetal interface and supporting placental development in mouse and human. It is expressed in epithelial cells of the endometrium under the regulation of estrogens. The factor is already in clinical use and a large clinical trial showed that, if supplemented to an embryo culture medium, it leads to increased survival of embryos, especially in women with previous miscarriages. Animal and cell culture studies on isolated trophectoderm cells support an effect mainly on cellular expansion. Aim of this study was to investigate, if the supplementation of GM-CSF either in a human ART medium or in a mouse optimized medium, leads to a change in cell number and cell lineages in the early pre-implantation mouse embryo. Our data shows that mouse GM-CSF increased total cell numbers with increasing concentrations. This increase of cell number has not been found in embryos cultured in ART media with or without human GM-CSF (hGM-CSF) or in a mouse medium supplemented with different concentrations of hGM-CSF. The changes were caused by a marked difference in TE and primitive endoderm cell numbers but not due to a change in epiblast cell numbers. Additionally, results show an ectopic expression of NANOG among trophectoderm cells in both, human ART media (with and without GM-CSF) and at increasing concentrations in the mouse and the human GM-CSF supplemented media. In conclusion, we could show that GM-CSF has an effect on cell identity in mice, which might probably also occur in the human. Therefore, we would like to rare awareness that the use of supplements without proper research could bare risks for the embryo itself and probably also in the post-implantation phase.

Progesterone differentially affects the transcriptomic profiles of cow endometrial cell types

Background

The endometrium is a heterogeneous tissue composed of luminal epithelial (LE), glandular epithelial (GE), and stromal cells (ST), experiencing progesterone regulated dynamic changes during the estrous cycle. In the cow, this regulation at the transcriptomic level was only evaluated in the whole tissue. This study describes specific gene expression in the three types of cells isolated from endometrial biopsies following laser capture microdissection and the transcriptome changes induced by progesterone in GE and ST cells.

Results

Endometrial LE, GE, and ST cells show specific transcriptomic profiles. Most of the differentially expressed genes (DEGs) in response to progesterone are cell type-specific (96%). Genes involved in cell cycle and nuclear division are under-expressed in the presence of progesterone in GE, highlighting the anti-proliferative action of progesterone in epithelial cells. Elevated progesterone concentrations are also associated with the under-expression of estrogen receptor 1 (ESR1) in GE and oxytocin receptor (OXTR) in GE and ST cells. In ST cells, transcription factors such as SOX17 and FOXA2, known to regulate uterine epithelial-stromal cross-talk conveying to endometrial receptivity, are over-expressed under progesterone influence.

Conclusions

The results from this study show that progesterone regulates endometrial function in a cell type-specific way, which is independent of the expression of its main receptor PGR. These novel insights into uterine physiology present the cell compartment as the physiological unit rather than the whole tissue.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08323-z.

Human Immune System Diseasome Networks and Female Oviductal Microenvironment: New Horizons to be Discovered

Human hypofertility and infertility are two worldwide conditions experiencing nowadays an alarming increase due to a complex ensemble of events. The immune system has been suggested as one of the responsible for some of the etiopathogenic mechanisms involved in these conditions. To shed some light into the strong correlation between the reproductive and immune system, as can be inferred by the several and valuable manuscripts published to date, here we built a network using a useful bioinformatic tool (DisGeNET), in which the key genes involved in the sperm-oviduct interaction were linked. This constitutes an important event related with Human fertility since this interaction, and specially the spermatozoa, represents a not-self entity immunotolerated by the female. As a result, we discovered that some proteins involved in the sperm-oviduct interaction are implicated in several immune system diseases while, at the same time, some immune system diseases could interfere by using different pathways with the reproduction process. The data presented here could be of great importance to understand the involvement of the immune system in fertility reduction in Humans, setting the basis for potential immune therapeutic tools in the near future.

Effects of heat stress on the endometrial epidermal growth factor profile and fertility in dairy cows

The endometrial epidermal growth factor (EGF) profile is an indicator of uterine function and fertility in cattle. The present study aimed to investigate the effects of heat stress on the endometrial EGF profile and fertility in lactating Holstein cows. The endometrial EGF profiles of 365 cows in the Hokkaido and Kyushu regions were examined between June and September (heat stress period, n = 211) and between October and January (control period, n = 154). EGF profiles were investigated using uterine endometrial tissues obtained by biopsy 3 days after estrus (Day 3). The proportion of cows with an altered EGF profile was higher between June and September than between October and January (41.2 vs. 16.2%, P < 0.05). The effects of rectal temperature on Days 0 and 3 on the endometrial EGF profile were also assessed in cows (n = 79) between June and September in the Kyushu region. A single embryo was transferred to cow on Day 7 to evaluate fertility (n = 67). Regardless of the rectal temperature on Day 3, the proportion of cows with an altered EGF profile was higher (64.1 vs. 30.0%, P < 0.05) and the pregnancy rate after embryo transfer (ET) was lower (26.7 vs. 51.4%, P < 0.05) in cows with a rectal temperature ≥ 39.5°C on Day 0 than in cows with a rectal temperature < 39.5°C on Day 0. The present results indicate that alterations in the endometrial EGF profile induced by an elevated body temperature on Day 0 contributed to reductions in fertility in lactating dairy cows during the heat stress period.

Atlas of receptor genes expressed by the bovine morula and corresponding ligand-related genes expressed by uterine endometrium

Regulation of the mammalian embryo involves cell‐signaling molecules produced by the maternal oviduct and endometrium. Here, datasets on the transcriptome of the gestational Days 5 and 6 bovine morula and Day 5 maternal endometrium were examined to identify receptor genes expressed by the morula and expression of the corresponding ligand‐related genes in the endometrium. A total of 175 receptor genes were identified in the morula, including 48 encoding for growth factors or WNT signaling molecules, 25 for cytokines and chemokines, 35 involved in juxtacrine and matricellular signaling and 25 encoding for receptors for small molecules. Some of the highly‐expressed pairs of endometrial ligand and embryo receptor genes included MDK and its receptors ITGB1, SDC4 and LRP2, WNT5A (RYK), VEGFA (ITGB1), GPI (AMFR), and the hedgehog proteins IHH and DHH (HHIP). The most highly expressed receptors for small molecules were GPRC5C (retinoic acid receptor), PGRMC1 (progesterone), and CHRNB2 (acetylcholine). There were also 84 genes encoding for cell signaling ligands expressed by the morula, with the most highly expressed being GPI, AIMP1, TIMP1, IK, and CCN2. The atlas of receptor and ligand genes should prove useful for understanding details of the communication between the embryo and mother that underlies optimal embryonic development.

Programming of postnatal phenotype caused by exposure of cultured embryos from Brahman cattle to colony-stimulating factor 2 and serum

Alterations in the environment of the preimplantation embryo can affect competence to establish pregnancy and phenotype of resultant calves. In this study, the bovine embryo produced in vitro was used to evaluate postnatal programming actions of the embryokine colony-stimulating factor 2 (CSF2) and serum, which is a common additive of culture media. Oocytes were collected by ovum pick up from Brahman donors and fertilized with semen from Brahman bulls. Embryos were randomly assigned to one of the three treatments: vehicle, CSF2 10 ng/mL, or 1% (v/v) serum. Treatments were added to the culture medium from day 5 to 7 after fertilization. Blastocysts were harvested on day 7 and transferred into crossbred recipients. Postnatal body growth and Longissimus dorsi muscle characteristics of the resultant calves were measured. The percent of cleaved embryos becoming blastocysts was increased by serum and, to a lesser extent, CSF2. Treatment did not affect survival after embryo transfer but gestation length was shortest for pregnancies established with serum-treated embryos. Treatment did not significantly affect postnatal body weight or growth. At 3 mo of age, CSF2 calves had lower fat content in the Longissimus dorsi muscle and less subcutaneous fat over the muscle than vehicle calves. There was a tendency for cross-sectional area of the muscle to be smaller for serum calves than vehicle calves. Results confirm the importance of the preimplantation period as a window to modulate postnatal phenotype of resultant calves. In particular, CSF2 exerted actions during the preimplantation period to program characteristics of accumulation of intramuscular and subcutaneous fat of resultant calves. The use of a low serum concentration in culture medium from day 5 to 7 of development can increase the yield of transferrable embryos without causing serious negative consequences for the offspring.

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.

Molecular fingerprint of female bovine embryos produced in vitro with high competence to establish and maintain pregnancy†

The objective was to identify the transcriptomic profile of in vitro-derived embryos with high competence to establish and maintain gestation. Embryos produced with X-sorted sperm were cultured from day 5 to day 7 in serum-free medium containing 10 ng/ml recombinant bovine colony-stimulating factor 2 (CSF2) or vehicle. The CSF2 was administered because this molecule can increase blastocyst competence for survival after embryo transfer. Blastocysts were harvested on day 7 of culture and manually bisected. One demi-embryo from a single blastocyst was transferred into a synchronized recipient and the other half was used for RNA-seq analysis. Using P < 0.01 and a fold change >2-fold or <0.5 fold as cutoffs, there were 617 differentially expressed genes (DEG) between embryos that survived to day 30 of gestation vs those that did not, 470 DEG between embryos that survived to day 60 and those that did not, 432 DEG between embryos that maintained pregnancy from day 30 to day 60 vs those where pregnancy failed after day 30, and 635 DEG regulated by CSF2. Pathways and ontologies in which DEG were overrepresented included many related to cellular responses to stress and cell survival. It was concluded that gene expression in the blastocyst is different between embryos that are competent to establish and maintain pregnancy vs those that are not. The relationship between expression of genes related to cell stress and subsequent embryonic survival probably reflects cellular perturbations caused by embryonic development taking place in the artificial environment associated with cell culture.

Culture Medium and Sex Drive Epigenetic Reprogramming in Preimplantation Bovine Embryos

Assisted reproductive technologies impact transcriptome and epigenome of embryos and can result in long-term phenotypic consequences. Whole-genome DNA methylation profiles from individual bovine blastocysts in vivo- and in vitro-derived (using three sources of protein: reproductive fluids, blood serum and bovine serum albumin) were generated. The impact of in vitro culture on DNA methylation was analyzed, and sex-specific methylation differences at blastocyst stage were uncovered. In vivo embryos showed the highest levels of methylation (29.5%), close to those produced in vitro with serum, whilst embryos produced in vitro with reproductive fluids or albumin showed less global methylation (25-25.4%). During repetitive element analysis, the serum group was the most affected. DNA methylation differences between in vivo and in vitro groups were more frequent in the first intron than in CpGi in promoters. Moreover, hierarchical cluster analysis showed that sex produced a stronger bias in the results than embryo origin. For each group, distance between male and female embryos varied, with in vivo blastocyst showing a lesser distance. Between the sexually dimorphic methylated tiles, which were biased to X-chromosome, critical factors for reproduction, developmental process, cell proliferation and DNA methylation machinery were included. These results support the idea that blastocysts show sexually-dimorphic DNA methylation patterns, and the known picture about the blastocyst methylome should be reconsidered.

Interleukin-6 supplementation improves post-transfer embryonic and fetal development of in vitro-produced bovine embryos

The use of in vitro produced embryos in dairy and beef cattle has increased in recent years, but compromised post-transfer pregnancy success prevents producers from capturing all the benefits this technology can provide. This study explored whether supplementing interleukin-6 (IL6) during in vitro embryo development influences post-transfer development of the embryo-proper, fetus and placenta during early gestation in cattle. Slaughterhouse-derived cumulus oocyte complexes underwent IVM (day -1) and IVF (day 0). On day 5 post-fertilization, embryos were treated with either 0 (CONT) or 100 ng/mL recombinant bovine IL6. No difference in blastocyst formation was detected on day 7.5 post-fertilization, but an increase (P < 0.05) in inner cell mass cell numbers and tendency for increased (P = 0.08) trophectoderm cell numbers were detected in IL6-treated blastocysts. A subset of the blastocysts was loaded individually into transfer straws, and embryo transfer (ET) was completed using estrous cycle stage-matched, nonlactating commercial beef and dairy cows. A subset of cows from each group underwent timed artificial insemination (TAI). Pregnancy rates were similar among all three treatment groups at day 28 and 70. No differences in crown-rump length (CRL), crown nose length (CNL), abdominal diameter (AD), or placental fluid volume (PFV) were detected between TAI and ET-IL6 groups. Reductions (P < 0.05) in CRL and AD were detected at day 56 and a tendency for a reduction (P = 0.08) in PFV was detected on day 35 when comparing the ET-CONT group with the TAI group. Reductions (P < 0.05) in CRL and PFV on day 28 and CNL and AD on day 56 as well as a tendency for a reduction (P = 0.08) in PFV on day 35 were detected when contrasting ET-CONT with ET-IL6. Circulating plasma pregnancy-associated glycoprotein concentrations were similar among all treatment groups. In summary, IL6 treatment to IVP embryos before ET produced pregnancies that more closely resembled TAI-generated pregnancies than pregnancies generated using conventionally cultured embryos. These findings failed to find any adverse effects of IL6 supplementation on early development of the embryo-proper and fetus or on placental activity. Rather, these observations suggest that IL6 treatment may normalize the developmental trajectory of the embryo-proper and fetus for in vitro produced embryos.

A Shorter Equilibration Period Improves Post-Warming Outcomes after Vitrification and in Straw Dilution of In Vitro-Produced Bovine Embryos

This study was designed to the optimize vitrification and in-straw warming protocol of in vitro-produced bovine embryos by comparing two different equilibration periods, short equilibrium (SE: 3 min) and long equilibrium (LE: 12 min). Outcomes recorded in vitrified day seven (D7) and day eight (D8) expanded blastocysts were survival and hatching rates, cell counts, apoptosis rate, and gene expression. While survival rates at 3 and 24 h post-warming were reduced (p < 0.05) after vitrification, the hatching rates of D7 embryos vitrified after SE were similar to the rates recorded in fresh non-vitrified blastocysts. The hatching rates of vitrified D8 blastocysts were lower (p < 0.05) than of fresh controls regardless of treatment. Total cell count, and inner cell mass and trophectoderm cell counts were similar in hatched D7 blastocysts vitrified after SE and fresh blastocysts, while vitrified D8 blastocysts yielded lower values regardless of treatment. The apoptosis rate was significantly higher in both treatment groups compared to fresh controls, although rates were lower for SE than LE. No differences emerged in BAX, AQP3, CX43, and IFNτ gene expression between the treatments, whereas a significantly greater abundance of BCL2L1 and SOD1 transcripts was observed in blastocysts vitrified after SE. A shorter equilibration vitrification protocol was found to improve post-warming outcomes and time efficiency after in-straw warming/dilution.

Regulation of gene expression in the bovine blastocyst by colony-stimulating factor 2 is disrupted by CRISPR/Cas9-mediated deletion of CSF2RA

Colony-stimulating factor 2 (CSF2) functions in the reproductive tract to modulate the function of the preimplantation embryo. The β subunit of the CSF2 receptor (CSF2RB) is not expressed in the embryo, and signal transduction is therefore different than for myeloid cells where the receptor is composed of α (CSF2RA) and β subunits. Here, we produced embryos in which exons 5 and 6 of CSF2RA were disrupted using the CRISPR/Cas 9 system to test whether CSF2RA signaling was essential for actions of CSF2 in the bovine embryo. Wild-type and CSF2RA knockout embryos were treated with 10 ng/mL CSF2 or vehicle at day 5 of development. Blastocysts were harvested at day 8 to determine transcript abundance of 90 genes by real-time polymerase chain reaction (PCR). Responses in female blastocysts were examined separately from male blastocysts because actions of CSF2 are sex-dependent. For wild-type embryos, CSF2 altered expression of 10 genes in females and 20 in males. Only three genes were affected by CSF2 in a similar manner for both sexes. Disruption of CSF2RA prevented the effect of CSF2 on expression for 9 of 10 CSF2-regulated genes in females and 19 of 20 genes in males. The results confirm the importance of CSF2RA for regulation of gene expression by CSF2 in the blastocyst.

Innate Immune Interference Attenuates Inflammation In Bacillus Endophthalmitis

Purpose

To explore the consequences of innate interference on intraocular inflammatory responses during Bacillus endophthalmitis.

Methods

Bacillus endophthalmitis was induced in mice. Innate immune pathway activation was interfered by injecting S layer protein-deficient (∆slpA) B. thuringiensis or by treating wild-type (WT)-infected mice with a TLR2/4 inhibitor (WT+OxPAPC). At 10 hours postinfection, eyes were harvested and RNA was purified. A NanoString murine inflammation panel was used to compare gene expression in WT-infected, WT+OxPAPC, ∆slpA-infected, and uninfected eyes.

Results

In WT-infected eyes, 56% of genes were significantly upregulated compared to uninfected controls. Compared to WT-infected eyes, the expression of 27% and 50% of genes were significantly reduced in WT+OxPAPC and ∆slpA-infected eyes, respectively. Expression of 61 genes that were upregulated in WT-infected eyes was decreased in WT+OxPAPC and ∆slpA-infected eyes. Innate interference resulted in blunted expression of complement factors (C3, Cfb, and C6) and several innate pathway genes (TLRs 2, 4, 6, and 8, MyD88, Nod2, Nlrp3, NF-κB, STAT3, RelA, RelB, and Ptgs2). Innate interference also reduced the expression of several inflammatory cytokines (CSF2, CSF3, IL-6, IL-1β, IL-1α, TNFα, IL-23α, TGFβ1, and IL-12β) and chemokines (CCL2, CCL3, and CXCLs 1, 2, 3, 5, 9, and 10). All of the aforementioned genes were significantly upregulated in WT-infected eyes.

Conclusions

These results suggest that interfering with innate activation significantly reduced the intraocular inflammatory response in Bacillus endophthalmitis. This positive clinical outcome could be a strategy for anti-inflammatory therapy of an infection typically refractory to corticosteroid treatment.

The incompletely fulfilled promise of embryo transfer in cattle-why aren't pregnancy rates greater and what can we do about it?

Typically, bovine embryos are transferred into recipient females about day 7 after estrus or anticipated ovulation, when the embryo has reached the blastocyst stage of development. All the biological and technical causes for failure of a female to produce a blastocyst 7 d after natural or artificial insemination (AI) are avoided when a blastocyst-stage embryo is transferred into the female. It is reasonable to expect, therefore, that pregnancy success would be higher for embryo transfer (ET) recipients than for inseminated females. This expectation is not usually met unless the recipient is exposed to heat stress or is classified as a repeat-breeder female. Rather, pregnancy success is generally similar for ET and AI. The implication is that either one or more of the technical aspects of ET have not yet been optimized or that underlying female fertility that causes an embryo to die before day 7 also causes it to die later in pregnancy. Improvements in pregnancy success after ET will depend upon making a better embryo, improving uterine receptivity, and forging new tools for production and transfer of embryos. Key to accelerating progress in improving pregnancy rates will be the identification of phenotypes or phenomes that allow the prediction of embryo competence for survival and maternal capacity to support embryonic development.

In vitro maturation in the presence of Leukemia Inhibitory Factor modulates gene and miRNA expression in bovine oocytes and embryos

Members of the interleukin-6 (IL-6) family of cytokines are important for reproductive function that are mediated through changes in gene and miRNA expression. Herein, we characterized the expression of miR-21, miR-155, miR-34c and miR-146a in bovine oocytes and cumulus cells during in vitro maturation (IVM) with leukemia inhibitory factor (LIF), IL-6 and IL-11 or unsupplemented controls. LIF-exposed COCs showed higher expression of miR-21 and miR-155 in oocytes, whereas miR-146a expression was increased in oocytes matured with IL-6 and IL-11. In cumulus cells, miR-155 expression was elevated by all treatments while only LIF increased miR-21 expression. Based on these results, we next examined how LIF exposure during IVM affected oocyte competence, through IVF and the expression of specific genes in GV- and MII-oocytes, in 2- and 8-cell embryos, and in Day 8-blastocysts. LIF supplementation did not affect cleavage rate, blastocyst yield or several other developmental parameters, but did increase hatching rate. LIF suppressed DPPA3, ZAR1 and NPM2 expression in 2 cell- and/or 8-cell embryos. LIF increased the expression of KAT2A and HSPA1A in MII-oocytes, and that of HDAC1, KAT2A and HSP90AA1 and the BAX:BCL2L1 ratio in 2-cell embryos. In contrast, HDAC1, KAT2A and HSP90AA1 expression and BAX:BCL2L1 ratio was lower in 8-cell embryos derived from LIF oocytes. IVM with LIF also increased the expression of DNMT3A, HSPA1A and HSP90AA1 in blastocysts. In conclusion, supplementation with LIF during IVM was consistently associated with changes in the relative abundance of transcripts in mature bovine oocytes and in specific embryo developmental stages.

Actions of putative embryokines on development of the preimplantation bovine embryo to the blastocyst stage

Once it enters the uterus at d 4 to 5 after ovulation, the preimplantation bovine embryo is controlled in its development by regulatory signaling molecules from the mother called embryokines. Here, several cell-signaling molecules whose genes are expressed in the endometrium during d 5 to 7 after estrus were tested for the ability to affect the competence of the embryo for further development and the characteristics of the resultant blastocysts. Molecules tested were C-natriuretic peptide (CNP), IL-8, bovine morphogenetic protein 4 (BMP-4), IL-6, and leukemia inhibitory factor (LIF). None of the cell-signaling molecules tested improved the competence of the embryo to become a blastocyst; in fact, BMP-4 decreased development. All molecules modified attributes of the blastocyst formed in culture. In particular, CNP increased the number of cells in the ICM, whereas IL-8 decreased inner cell mass cell numbers and tended to increase the proportion of blastocysts that were hatching or hatched. In addition, BMP-4 decreased the proportion of blastocysts that were hatching. Interleukin-6 and, to a lesser extent, LIF activated the Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) signaling pathway in the inner cell mass, and LIF increased the percent of cells in the blastocyst that were positive for both NANOG and phosphorylated (activated) STAT3. In conclusion, our results indicate that CNP, IL-8, IL-6, LIF, and BMP-4 can modify embryonic development of the cow in a manner that affects characteristics of the resultant blastocyst. Further research is required to understand how these changes in characteristics of the blastocyst would affect competence of the embryo to establish and maintain pregnancy.

In Vitro Maturation with Leukemia Inhibitory Factor Prior to the Vitrification of Bovine Oocytes Improves Their Embryo Developmental Potential and Gene Expression in Oocytes and Embryos

Oocyte cryopreservation has a significant impact on subsequent embryonic development. Herein, we investigated whether supplementing in vitro maturation medium with Leukemia Inhibitory Factor (LIF) prior to vitrification affects embryo development and gene expression at different embryo developmental stages. A panel of genes including maternal effect, epigenetics, apoptosis and heat stress was relatively quantified. The results show reduced cleavage rates after vitrification, regardless of the LIF treatment. Although not statistically different from control-vitrified oocytes, oocyte apoptosis and the blastocyst yield of LIF-vitrified oocytes were similar to their non-vitrified counterparts. Vitrification increased oocyte ZAR1, NPM2 and DPPA3 gene expression while its expression decreased in LIF-vitrified oocytes to similar or close levels to those of non-vitrified oocytes. With a few gene-specific exceptions, vitrification significantly increased the expression of DNMT3A, HDAC1, KAT2A, BAX and BCL2L1 in oocytes and most stages of embryo development, while comparable expression patterns for these genes were observed between LIF-vitrified and non-vitrified groups. Vitrification increased HSPA1A expression in oocytes and HSP90AA1 in 2-cell embryos. Our data suggest that vitrification triggers stage-specific changes in gene expression throughout embryonic development. However, the inclusion of LIF in the IVM medium prior to vitrification stimulates blastocyst development and several other developmental parameters and induces oocytes and embryos to demonstrate gene expression patterns similar to those derived from non-vitrified oocytes.

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.

Effect of Dickkopf-1 and colony stimulating factor-2 on the developmental competence, quality, gene expression and live birth rate of buffalo (Bubalus bubalis) embryos produced by hand-made cloning

A functional canonical WNT signaling pathway exists in preimplantation embryos and inhibits embryonic development. Recent studies suggest that this pathway is over-expressed in nuclear transferred (NT), compared to IVF embryos. The present study investigated the effects of Dickkopf-1 (DKK1), an inhibitor of canonical WNT signaling pathway and colony stimulating factor-2 (CSF2), an embryokine, on the developmental competence, quality, gene expression and live birth rate of NT buffalo embryos produced by Hand-made cloning (HMC). Following supplementation of the in vitro culture medium on day 5 with DKK1 (100 ng/mL), CSF2 (10 ng/mL), DKK1+CSF2 or no supplementation (control), the blastocyst rate was higher (P < 0.05) with DKK1 and DKK1+CSF2 (42.6 ± 1.4% and 46.6 ± 0.9%, respectively) than with CSF2 or controls (40.6 ± 1.3% and 39.0 ± 1.3%, respectively). The apoptotic index of the blastocysts was lower (P < 0.05) for DKK1, CSF2 and DKK1+CSF2 groups (3.44 ± 0.14, 3.39 ± 0.11 and 3.11 ± 0.22, respectively) compared to controls (6.64 ± 0.25), and was similar to that of the IVF blastocysts (3.67 ± 0.18). Although the total cell number was similar for the DKK1, CSF2, DKK1+CSF2 and control groups (200.4 ± 3.05, 196.4 ± 3.73, 204.7 ± 3.71 and 205 ± 4.03, respectively), the inner cell mass:trophectoderm cell number ratio of DKK1, CSF2 and DKK1+CSF2 groups (0.21 ± 0.01, 0.17 ± 0.01 and 0.22 ± 0.02, respectively) was higher (P < 0.05) than controls (0.13 ± 0.01) and was similar to that of IVF blastocysts (0.19 ± 0.01). Treatment with DKK1 or CSF2 or both increased (P < 0.05) the expression level of OCT4, NANOG,SOX2, GATA6, BCL2, PTEN, P53, FGF4, GLUT1 and IFN-τ, and decreased that of C-MYC, CDX2, CASPASE, DNMT3a, TCF7 and LEF1 in blastocysts, compared to controls. Transfer of DKK1-treated embryos to 13 recipients resulted in 4 pregnancies (30.8%; 2 live births, one abortion and one currently at 9 months of pregnancy) whereas, transfer of DKK1+CSF2-treated embryos to 16 recipients, resulted in 4 pregnancies (25.0%), all of which resulted in live births. No pregnancy was obtained after transfer of control and CSF-treated embryos to 12 and 16 recipients, respectively. These results suggest that DKK1 treatment of NT embryos increases the blastocyst, conception and live birth rate, and improves their quality whereas, CSF2 treatment, does not affect the blastocyst, conception and live birth rate despite improvement in embryo quality.

Growth Factors, and Cytokines; Understanding the Role of Tyrosine Phosphatase SHP2 in Gametogenesis and Early Embryo Development

Growth factors and cytokines have vital roles in germ cell development, gamete maturation, and early embryo development. Cell surface receptors are present for growth factors and cytokines to integrate with and trigger protein signaling in the germ and embryo intracellular milieu. Src-homology-2-containing phosphotyrosine phosphatase (SHP2) is a ubiquitously expressed, multifunctional protein that plays a central role in the signaling pathways involved in growth factor receptors, cytokine receptors, integrins, and G protein-coupled receptors. Over recent decades, researchers have recapitulated the protein signaling networks that influence gamete progenitor specification as well as gamete differentiation and maturation. SHP2 plays an indispensable role in cellular growth, survival, proliferation, differentiation, and migration, as well as the basic events in gametogenesis and early embryo development. SHP2, a classic cytosolic protein and a key regulator of signal transduction, displays unconventional nuclear expression in the genital organs. Several observations provided shreds of evidence that this behavior is essential for fertility. The growth factor and cytokine-dependent roles of SHP2 and its nuclear/cytoplasmic presence during gamete maturation, early embryonic development and embryo implantation are fascinating and complex subjects. This review is intended to summarize the previous and recent knowledge about the SHP2 functions in gametogenesis and early embryo development.

Genes associated with survival of female bovine blastocysts produced in vivo

The objective was to characterize the transcriptome profile of in vivo-derived female embryos competent to establish and maintain gestation. Blastocysts from superovulated heifers were bisected to generate two demi-embryos. One demi-embryo was transferred into a synchronized recipient and the other part was used for RNA-seq analysis. Data on transcript abundance was analyzed for 4 demi-embryos that established and maintained pregnancy to day 60 (designated as PP) and 3 that did not result in a pregnancy at day 30 (designated as NP). Using a false discovery rate of P < 0.10 as cutoff, a total of 155 genes were differentially expressed between PP and NP embryos, of which 73 genes were upregulated and 82 genes were downregulated in the PP group. The functional cluster with the greatest enrichment score for embryos that survived, representing 28 genes (48% of the annotated genes), was related to membrane proteins, particularly those related to olfaction and neural development and function. The functional cluster with the greatest enrichment score for downregulated genes in embryos that survived included terms related to oxidative phosphorylation, mitochondrial function, and transmembrane proteins. In conclusion, competence of in vivo-derived female bovine embryos to survive after transfer is associated with increased expression of genes encoding transmembrane proteins, perhaps indicative of differentiation of the inner cell mass to epiblast, and decreased expression of genes involved in oxidative phosphorylation, perhaps indicative of reduced metabolic activity.

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.

GM-CSF does not rescue poor-quality embryos: secondary analysis of a randomized controlled trial

Purpose

To evaluate implantation potential of cleavage-stage embryos cultured in medium containing 2 ng/ml granulocyte–macrophage colony-stimulating factor (GM-CSF) versus control medium, according to embryo morphological quality and then transferred on day 3.

Methods

Explorative secondary data analysis of a multicenter, randomized, placebo-controlled, double-blinded prospective study of 1149 couples with embryo transfer after IVF/ICSI. This analysis includes a subgroup of 422 subjects with either single-embryo transfer (SET, N = 286) or double-embryo transfer of two embryos with equivalent morphological quality (DET, N = 136). Implantation rate and live birth rate were assessed according to category of morphological embryo quality on day 3.

Results

Culture with GM-CSF did not increase the implantation rate for embryos classified as poor quality. A trend towards greater benefit of GM-CSF on implantation and survival until live birth for top-quality embryos (TQEs) compared with poor-quality embryos was observed, although not statistically significant. For TQEs, the percentage of transferred embryos resulting in a live born baby was: 40.9 ± 5.3% (GM-CSF) versus 30.5 ± 4.6% (control) (P = 0.24; odds ratio [OR] 1.43, 95% confidence interval [CI] 0.79–2.59), and for embryos with less than 6 cells at day 3 this same rate was: 7.4 ± 3.3% (GM-CSF) versus 12.0 ± 4.0% (control) (P = 0.26; OR 0.53, 95% CI 0.17–1.61).

Conclusion

This exploratory analysis is consistent with GM-CSF protecting morphologically normal embryos from culture-induced stress and does not support an effect of GM-CSF in rescuing poor-quality embryos.

ClinicalTrials.gov identifier: NCT00565747.

The Female Response to Seminal Fluid

Seminal fluid is often assumed to have just one function in mammalian reproduction, delivering sperm to fertilize oocytes. But seminal fluid also transmits signaling agents that interact with female reproductive tissues to facilitate conception and .pregnancy. Upon seminal fluid contact, female tissues initiate a controlled inflammatory response that affects several aspects of reproductive function to ultimately maximize the chances of a male producing healthy offspring. This effect is best characterized in mice, where the female response involves several steps. Initially, seminal fluid factors cause leukocytes to infiltrate the female reproductive tract, and to selectively target and eliminate excess sperm. Other signals stimulate ovulation, induce an altered transcriptional program in female tract tissues that modulates embryo developmental programming, and initiate immune adaptations to promote receptivity to implantation and placental development. A key result is expansion of the pool of regulatory T cells that assist implantation by suppressing inflammation, mediating tolerance to male transplantation antigens, and promoting uterine vascular adaptation and placental development. Principal signaling agents in seminal fluid include prostaglandins and transforming growth factor-β. The balance of male signals affects the nature of the female response, providing a mechanism of ‟cryptic female choiceˮ that influences female reproductive investment. Male-female seminal fluid signaling is evident in all mammalian species investigated including human, and effects of seminal fluid in invertebrates indicate evolutionarily conserved mechanisms. Understanding the female response to seminal fluid will shed new light on infertility and pregnancy disorders and is critical to defining how events at conception influence offspring health.

Determinants of survival of the bovine blastocyst to cryopreservation stress: treatment with colony stimulating factor 2 during the morula-to-blastocyst transition and embryo sex

BACKGROUND

Colony-stimulating factor 2 (CSF2) is an important maternal regulator of embryonic development. Earlier research indicates that CSF2 can regulate genes involved in cellular stress responses and block apoptosis. Here, we tested whether addition of 10 ng/mL CSF2 at day 5 of development would increase the survival of blastocysts harvested at day 7 and subjected to vitrification. Additional objectives were to determine whether embryo sex affected survival or whether effects of CSF2 interacted with sex.

RESULTS

Survival after vitrification was measured as the percent of warmed blastocysts that re-established a blastocoele after culture and that underwent hatching from the zona pellucida. In the first experiment, blastocysts were vitrified, warmed, cultured for 24 h, and DNA embryo sexing performed by PCR. There was no effect of CSF2, sex, or the interaction on the percent of blastocysts that re-expanded or that were hatching or hatched. In the second experiment, vitrified blastocysts were warmed and cultured for 24, 48, and 72 h. Treatment with CSF2 increased (P = 0.021) the percent of blastocysts that re-expanded as compared to the vehicle group (overall, 77.8 ± 4.7% vs 73.3 ± 4.7%). Percent re-expansion was highest at 24 h and declined slightly thereafter (P = 0.024). Although the interaction was not significant, the effect of CSF2 was greater at 48 and 72 h than at 24 h because CSF2 reduced the incidence of embryos collapsing after re-expansion. Furthermore, the proportion of re-expanded blastocysts at 24 h that experienced blastocoel collapse by 72 h was lower (P = 0.053) for CSF2 (3.6%; 7/195) than for vehicle (8.2%; 16/195). The percent of warmed blastocysts that were hatching or hatched increased with time (P < 0.0001) but there was no effect of CSF2 or the interaction with time on hatching.

CONCLUSION

Treatment with CSF2 from day 5 to 7 of development did not cause a significant effect on the percent of blastocysts that re-established the blastocoele after 24 h of culture but CSF2 reduced the collapse of the blastocoele that occurred for a portion of the embryos that had experienced re-expansion at 24 h. Thus, CSF2 can provide protection to a proportion of blastocysts from cryodamage caused by vitrification. Further work is needed to evaluate whether CSF2 increases survival of vitrified blastocysts after embryo transfer.

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.

Reproductive physiology of the heat-stressed dairy cow: implications for fertility and assisted reproduction

Heat stress causes a large decline in pregnancy success per insemination during warm times of the year. Improvements in fertility are possible by exploiting knowledge about how heat stress affects the reproductive process. The oocyte can be damaged by heat stress at the earliest stages of folliculogenesis and remains sensitive to heat stress in the peri-ovulatory period. Changes in oocyte quality due to heat stress are the result of altered patterns of folliculogenesis and, possibly, direct effects of elevated body temperature on the oocyte. While adverse effects of elevated temperature on the oocyte have been observed in vitro, local cooling of the ovary and protective effects of follicular fluid may limit these actions in vivo. Heat stress can also compromise fertilization rate. The first seven days of embryonic development are very susceptible to disruption by heat stress. During these seven days, the embryo undergoes a rapid change in sensitivity to heat stress from being very sensitive (2- to 4-cell stage) to largely resistant (by the morulae stage). Direct actions of elevated temperature on the embryo are likely to be an important mechanism for reduction in embryonic survival caused by heat stress. An effective way to avoid effects of heat stress on the oocyte, fertilization, and early embryo is to bypass the effects through embryo transfer because embryos are typically transferred into females after acquisition of thermal resistance. There may be some opportunity to mitigate effects of heat stress by feeding antioxidants or regulating the endocrine environment of the cow but neither approach has been reduced to practice. The best long-term solution to the problem of heat stress may be to increase genetic resistance of cows to heat stress. Thermotolerance genes exist within dairy breeds and additional genes can be introgressed from other breeds by traditional means or gene editing.

Interferon-gamma inhibits seminal plasma induction of colony-stimulating factor 2 in mouse and human reproductive tract epithelial cells

Seminal fluid interacts with the female reproductive tract to initiate a permissive immune response that facilitates embryo implantation and pregnancy success. The immune-regulatory cytokine interferon-γ (IFNG), which can be elevated in seminal plasma, is associated with reduced fertility. Here, we investigated how IFNG influences the female immune response to seminal fluid. In human Ect1 cervical epithelial cells, IFNG added at physiologically relevant concentrations substantially impaired seminal plasma-induced synthesis of key cytokines colony-stimulating factor 2 (CSF2) and interleukin-6 (IL6). Seminal fluid-induced CSF2 synthesis was also suppressed in the uterus of mice in vivo, when IFNG was delivered transcervically 12 h after mating. Transforming growth factor B1 (TGFB1) is the major seminal fluid signaling factor which elicits CSF2 induction, and IFNG exhibited potent dose-dependent suppression of CSF2 synthesis induced by TGFB1 in murine uterine epithelial cells in vitro. Similarly, IFNG suppressed TGFB1-mediated CSF2 induction in Ect1 cells and human primary cervical epithelial cells; however, IL6 regulation by IFNG was independent of TGFB1. Quantitative PCR confirmed that CSF2 regulation by IFNG in Ect1 cells occurs at the gene transcription level, secondary to IFNG suppression of TGFBR2 encoding TGFB receptor 2. Conversely, TGFB1 suppressed IFNG receptor 1 and 2 genes IFNGR1 and IFNGR2. These data identify IFNG as a potent inhibitor of the TGFB-mediated seminal fluid interaction with relevant reproductive tract epithelia in mice and human. These findings raise the prospect that IFNG in the male partner's seminal fluid impairs immune adaptation for pregnancy following coitus in women.

Bovine oviductal and uterine fluid support in vitro embryo development

In order to mimic the maternal oviductal environment, we evaluated the effect of oviductal fluid (OF) and/or uterine fluid (UF) supplementation on in vitro embryo development and quality. In vitro-produced zygotes were cultured with 1.25% OF from Day 1 to Day 4 after insemination (OF group), 1.25% OF from Day 1 to Day 4 followed by 1.25% UF from Day 4 to Day 9 (OF+UF group) or 1.25% UF only from Day 4 to Day 9 (UF group). Control groups were cultured in the presence of synthetic oviduct fluid (SOF) supplemented with 3mgmL-1 bovine serum albumin (BSA) or 5% fetal calf serum (FCS). Supplementation of the culture medium with OF and/or UF (both at 1.25%) supported embryo development (Day 9 blastocyst rate 28.2-30.6%). At 72h after vitrification-warming, the survival of blastocysts from the OF and OF+UF groups was similar to that of blastocysts in the SOF+BSA group (61.0±5.7% and 62.8±6.4% vs 64.8±6.4% respectively), but significantly higher than that of blastocysts from the SOF+FCS group (31.6±4.9%; P<0.001). Blastocysts from the OF group exhibited upregulation of epigenetic genes (i.e. DNA methyltransferase 3α (DNMT3A) and insulin-like growth factor 2 receptor (IGF2R)), compared with expression in the SOF+FCS group (P<0.05). Whereas those from OF+UF and UF groups exhibited downregulation of oxidative stress genes compared to SOF+BSA and OF groups for glutathione peroxidase (GPX1) and to SOF+FCS, SOF+BSA and OF groups for chloride intracellular channel 1 (CLIC1) (P<0.05). In addition, accumulation of reactive oxygen species was lower in blastocysts from the OF, OF+UF and UF groups. In conclusion, the use of low concentrations of OF and UF in in vitro serum-free culture supports embryo development, with OF providing a better control of embryo methylation, whereas UF may have antioxidant activity.

Regulation of present and future development by maternal regulatory signals acting on the embryo during the morula to blastocyst transition - insights from the cow

The preimplantation embryo has a remarkable ability to execute its developmental program using regulatory information inherent within itself. Nonetheless, the uterine environment is rich in cell signaling molecules termed embryokines that act on the embryo during the morula-to-blastocyst transition, promoting blastocyst formation and programming the embryo for subsequent developmental events. Programming can not only affect developmental processes important for continuance of development in utero but also affect characteristics of the offspring during postnatal life. Given the importance of embryokines for regulation of embryonic development, it is likely that some causes of infertility involve aberrant secretion of embryokines by the uterus. Embryokines found to regulate development of the bovine embryo include insulin-like growth factor 1, colony stimulating factor 2 (CSF2), and dickkopf WNT signaling pathway inhibitor 1. Embryo responses to CSF2 exhibit sexual dimorphism, suggesting that sex-specific programming of postnatal function is caused by maternal signals acting on the embryo during the preimplantation period that regulate male embryos differently than female embryos.

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.

Embryo and cow factors affecting pregnancy per embryo transfer for multiple-service, lactating Holstein recipients

The objective was to determine whether pregnancy success after embryo transfer (ET) during heat stress in multi-service Holstein cows depends upon characteristics of the embryo or recipient. Female embryos produced in vitro were cultured with either 0.0 (control) or 1.8 mM choline chloride and transferred fresh. Fresh embryos of undetermined breed and frozen Holstein embryos were used when experimental embryos were insufficient. Embryos were transferred 8 d after the last GnRH injection of an ovulation synchronization program. Embryo type [frozen vs. fresh, choline vs. control, unknown breed vs. (control + choline)] and characteristics of recipients (average of 190 d in milk at transfer) were evaluated. Pregnancy per ET was lower for cows receiving frozen embryos (7.0%; 3/43) than for cows receiving fresh embryos (26.7%; 32/120) but there were no differences between various types of fresh embryo. Pregnancy per ET was lower for cows diagnosed with metritis in the early postpartum period (7.1%; 2/28) than for cows without metritis (24.4%; 33/135). In conclusion, the use of frozen/thawed embryos produced in vitro and recipients which had metritis in the early postpartum period reduced the success of ET in multiple-service Holstein cows.

Revolutionize livestock breeding in the future: an animal embryo-stem cell breeding system in a dish

Meat and milk production needs to increase ~ 70–80% relative to its current levels for satisfying the human needs in 2050. However, it is impossible to achieve such genetic gain by conventional animal breeding systems. Based on recent advances with regard to in vitro induction of germ cell from pluripotent stem cells, herein we propose a novel embryo-stem cell breeding system. Distinct from the conventional breeding system in farm animals that involves selecting and mating individuals, the novel breeding system completes breeding cycles from parental to offspring embryos directly by selecting and mating embryos in a dish. In comparison to the conventional dairy breeding scheme, this system can rapidly achieve 30–40 times more genetic gain by significantly shortening generation interval and enhancing selection intensity. However, several major obstacles must be overcome before we can fully use this system in livestock breeding, which include derivation and mantaince of pluripotent stem cells in domestic animals, as well as in vitro induction of primordial germ cells, and subsequent haploid gametes. Thus, we also discuss the potential efforts needed in solving the obstacles for application this novel system, and elaborate on their groundbreaking potential in livestock breeding. This novel system would provide a revolutionary animal breeding system by offering an unprecedented opportunity for meeting the fast-growing meat and milk demand of humans.