Aspects of embryo-maternal communication in establishment of pregnancy in cattle

Establishment of an In Vitro Embryo-Endometrium Model Using Alginate-Embedded Mouse Embryos and Human Embryoid Body

BACKGROUND

Embryo-endometrium cross-talk is one of the critical processes for implantation, and unsuccessful cross-talk leads to infertility. We established an endometrium-embryo (or embryoid bodies, hEBs) in vitro model in 2D and 3D conditions and assessed its potential through the fusion of embryos and the expression of specific markers.

METHODS

C57BL/6 mouse embryos and human embryoid body (hEB) derived from embryonic stem cells were prepared as embryo models. Mouse endometrium (EM) and human endometrium cell line, HEC-1-A, were prepared, and 2D or 3D EMs were generated. The viability of the 3D endometrium was analyzed, and the optimal ratio of the gelation was revealed. The invasion of the embryos or hEBs was examined by immunostaining and 3D image rendering.

RESULTS

The embryos and the alternative hEBs were effectively fused into 2D or 3D vitro EM models in both mouse and human models. The fused embryos and hEBs exhibited migration and further development. Notably, the established in vitro model expressed Oct4 and E-Cadherin, markers for early embryonic development; human CG Receptor and Progesterone Receptor, critical for implantation and pregnancy maintenance; and TSH Receptor, Epiregulin, and Prolactin, indicators of endometrial receptivity and embryo implantation.

CONCLUSION

This study marks a significant advancement in the field, as we have successfully established a novel in vitro model for studying embryo-endometrium cross-talk. This model, a crucial tool for understanding fertility and the causes of miscarriage due to failed implantation, provides a unique platform for investigating the complex processes of successful implantation and pregnancy, underscoring its potential impact on reproductive health.

Assessing the Influence of Maternal Age in Bovine Embryos and Oocytes: A Model for Human Reproductive Aging

In the first weeks after fertilization, embryo mortality in cattle is significantly higher. It is well known that the age of the dam is one of the crucial factors affecting the quality of embryos and oocytes in many mammalian species. In older cattle, there are several evidences that embryo quality decreases, due to a decrease in ovarian reserve, a decrease in mtDNA and ATP, a decrease in progesterone levels, and due to susceptibility to genetic mutations. Herein, we intend to provide an updated summary of recent research on the effects of maternal age on embryos and oocytes of domestic cattle which are a widely used model species for human oocytes and early embryonic development.

Differences in Microbial Community Composition between Uterine Horns Ipsilateral and Contralateral to the Corpus Luteum in Beef Cows on Day 15 of the Estrous Cycle

This study evaluated differences in uterine microbiota composition between uterine horns ipsilateral and contralateral to the corpus luteum of beef cows on day 15 of the estrous cycle. Cows (n = 23) were exposed to an estrus synchronization protocol to exogenously induce synchronized ovulation. Cows were then euthanized on day 15 of the estrous cycle, and individual swabs were collected from uterine horns ipsilateral and contralateral to the corpus luteum using aseptic techniques. DNA was extracted, and the entire (V1-V9 hypervariable regions) 16s rRNA gene was sequenced. Sequences were analyzed, and amplicon sequence variants (ASVs) were determined. Across all samples, 2 bacterial domains, 24 phyla, and 265 genera were identified. Butyribirio, Cutibacterium, BD7-11, Bacteroidales BS11 gut group, Ruminococcus, Bacteroidales RF16 group, and Clostridia UCG-014 differed in relative abundances between uterine horns. Rikenellaceae RC9 gut group, Bacteroidales UCG-001, Lachnospiraceae AC2044 group, Burkholderia-Caballeronia-Paraburkholderia, Psudobutyribibrio, and an unidentified genus of the family Chitinophagaceae and dgA-11 gut group differed between cows that expressed estrus and those that did not. The composition of the microbial community differed between the ipsilateral and contralateral horns and between cows that expressed estrus and cows that failed to express estrus, indicating that the uterine microbiota might play a role in cow fertility.

Review: Endometrial function in pregnancy establishment in cattle

The endometrium is fundamentally required for successful pregnancy in ruminants and species where the posthatching conceptus undergoes a protracted elongation and peri-implantation phase of pregnancy. Moreover, there are substantial waves of pregnancy loss during this pre- and peri-implantation period of pregnancy the precise source of which has not been clearly defined i.e., the maternal uterine contribution to this loss. Understanding the molecular interactions required for successful pregnancy in cattle will allow us to intervene to support pregnancy success during this vulnerable window. The endometrium contributes to most key developmental milestones of pregnancy establishment, including (1) contributing to the regulation of the oestrus cycle, (2) nourishing the preimplantation conceptus, (3) responding to the conceptus to create a more receptive microenvironment, (4) providing essential biophysical support, and (5) signalling and producing factors which affect the mother systemically. This review will summarise what we currently know about conceptus-maternal interactions as well as identify the gaps in our knowledge that could be filled with newer in vitro model approaches. These include the use of microfluidics, organ-on-a-chip devices, and bioinformatic approaches. This will help maximise food production efficiency (both meat and dairy) and decrease the environmental burden, while enhancing our understanding of the fundamental processes required for successful implantation in cattle.

Embryo-Uterine Cross-Talk: Exploration of the Immunomodulatory Mechanism in Buffalo

Understanding the molecular cross-talk between the embryo and uterine endometrium is crucial for the improvement of IVF outcomes. The present work was undertaken to investigate the effect of pre-implantation embryo on the expression profile of immune-related genes in uterine epithelial cells (UECs) and PBMCs in buffalo. UECs were isolated from slaughterhouse-derived non-gravid uteri, cultured ex vivo and characterized, and buffalo embryos were produced in vitro from slaughterhouse-derived ovaries. Embryos co-cultured with steroid-treated UECs significantly stimulated (p < 0.05) the relative mRNA abundance of PTGS2, ISG15, OAS1, MX2, IFNAR1 and IFNAR2 in UECs while they significantly suppressed the mRNA expression of NFkβIA, NFkβ2, TNFα and IL1B, with no significant change in TGFβ1 and IL10 in the co-culture of embryos with UECs. In vitro treatment of PBMCs with conditioned media (CM) derived from embryos as well as UEC−embryo co-culture upregulated the mRNA abundance of ISG15, TGFβ1, PTGS2OAS1, MX2 and STAT1 while it downregulated IL17 and TNFα expression. The expression of IFNAR1 and IFNAR2 was elevated in PBMCs cultured in embryo-derived CM, but there was no significant change in PBMCs cultured in UEC−embryo co-culture CM. Thus, it can be concluded that the developing embryo and its secretions modulate the expression of immune responses by inducing an anti-inflammatory action in uterine epithelial cells for acceptance of the semi-allogenic embryo in the uterus to sustain pregnancy in buffalo.

Role of reproductive fluids and extracellular vesicles in embryo&#x2013;maternal interaction during early pregnancy in cattle

The coordinated interaction between the developing embryo and the maternal reproductive tract is essential for the establishment and maintenance of pregnancy in mammals. An early cross-talk is established between the oviduct/uterus and the gametes and embryo. This dialogue will shape the microenvironment in which gamete transport, fertilisation, and early embryonic development occur. Due to the small size of the gametes and the early embryo relative to the volume of the oviductal and uterine lumina, collection of tissue and fluid adjacent to these cells is challenging in cattle. Thus, the combination of in vivo and in vitro models seems to be the most appropriate approach to better understand this fine dialogue. In this respect, the aim of this review is to summarise the recent findings in relation to gamete/embryo-maternal interaction during the pre-elongation 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.

Pregnancy and parturition in dromedary camels II. Incidence, timing and factors affecting early pregnancy loss (EPL) and the outcome of twin pregnancies

In this paper, we described the incidence of early pregnancy loss (EPL) both after natural mating and embryo transfer, evaluated risk factors, and summarized the outcome of twin pregnancies throughout gestation in dromedaries under reproductive care. Data were collected over seven breeding seasons at the world's largest camel dairy farm (study 1). In addition, we determined the timing of EPL and monitored serum progesterone (P4) concentration between Days 13-70 of gestation during one breeding season (study 2). In the first study, out of 2970 pregnancies, 507 cases (17.1%) of EPL were diagnosed with transrectal ultrasonography. The rate of EPL after natural mating and embryo transfer was 16.1% (n = 422 out of 2616) and 24.0% (n = 85 out of 354), respectively. Twin pregnancies were detected in 215 cases (7.2% of all gestations), and 57 of those (26.5%) underwent complete EPL. Almost half of the early losses (n = 243; 47.9%) occurred before 30 d of gestation. Another 43.2% (n = 219) of EPL was diagnosed during the next month, and 8.9% (n = 45) occurred after 60 d of gestation. Multivariable mixed effects logistic regression models revealed that the breeding season (year) and twin pregnancy were the most important exposure variables affecting the rate of EPL (P < 0.001). The effect of some male camels was also demonstrated while other factors, such as type of breeding, age category, month of mating, breed/ecotype and reproductive history did not prove to have a significant influence. In the second study, the overall rate of EPL was 24.5% (n = 34 of 139). There was no difference in the incidence of EPL between ET recipient (24.2%, n = 23 of 95) and mated (25%, n = 11 of 44) camels. Weekly rate of EPL ranged from 0.9% to 4.8% with a decreasing tendency, and approx. 41% of the animals (n = 14 of 34) had some ultrasonographic signs of impending EPL 1 week before the final diagnosis. Mean serum P4 concentration in camels with subsequent EPL was 5.3 ± 0.1 ng/ml compared to 5.6 ± 0.04 ng/ml in normal pregnant dromedaries. Day of gestation and future EPL influenced serum P4 levels (P < 0.001) with an interaction between the two fixed factors (P < 0.05). At the time of the final diagnosis of EPL, mean serum P4 concentration was 2.8 ± 0.44 ng/ml. Although twinning had an unfavorable prognosis with a total pregnancy loss of 36.7%, it was not entirely detrimental for the final outcome of gestation as two-thirds of twin pregnancies (n = 136 out of 212) resulted in the birth of a live calf.

mRNA Expressions of Candidate Genes in Gestational Day 16 Conceptus and Corresponding Endometrium in Repeat Breeder Dairy Cows with Suboptimal Uterine Environment Following Transfer of Different Quality Day 7 Embryos

Simple Summary

The mRNA expression of Interferon-τ (IFNT), IFN stimulated genes (ISG15, CTSL1, RSAD2, SLC2A1, CXCL10, and SLC27A6), Peroxisome proliferator-activated receptors (PPARA, D, and G), and Retinoid X receptors (RXRA, B, and G) genes and proteins (IFNT, ISG15, CXCL10, PPARG, RXRG, SLC2A1, and SLC27A6) were lower and MUC1 at mRNA and protein levels, was greater in gestation day (GD) 16 embryo and corresponding endometrium of subclinical endometritis cows, and in cows following transfer of poor quality embryo (Grade 3). All genes and proteins but MUC1 expression was lower in GD16 tubular conceptus and corresponding endometrium vs. GD16 filamentous conceptus and matching endometrium in cows with SCE and in cows following the transfer of Grade 3 embryo. Disrupted embryo-uterine communication by altered expression of candidate genes in SCE cows, and in cows following the transfer of poor GD7 embryo negatively programs the conceptus development and plausibly affects the conceptus survival.

Abstract

Effect of the gestational day (GD) 7 embryo quality grade (QG) and subclinical endometritis (SCE) on mRNA and protein expressions of candidate genes [Interferon-τ (IFNT), IFN stimulated genes (ISG15, CTSL1, RSAD2, SLC2A1, CXCL10, and SLC27A6), Peroxisome proliferator activated receptors (PPARA, D, and G), Retinoid X receptors (RXRA, B, and G), and Mucin-1 (MUC1)] in GD16 conceptus and corresponding endometrium were evaluated. After screening of performance records (n = 2389) and selection of repeat breeders (n = 681), cows with SCE (≥6% polymorphonuclear neutrophils—PMN; n = 180) and no-SCE (<6%PMN; n = 180) received GD7 embryos of different QGs. Based on GD16 conceptus recovery, cows with SCE (n = 30) and No- SCE (n = 30) that received GD7 embryos QG1 (good, n = 20), 2 (fair, n = 20), and 3 (poor, n = 20) were included for gene analysis. mRNA and protein expressions (IFNT, ISG15, CXCL10, PPARG, RXRG, SLC2A1, and SLC27A6) differed between SCE and embryo QG groups. All genes but MUC1 and all proteins but MUC1 expression was greater in filamentous conceptus and corresponding endometrium vs. tubular conceptus and matching endometrium in SCE and embryo QG groups. In conclusion, disrupted embryo-uterine communication by altered expression of candidate genes in SCE cows, and in cows following the transfer of poor embryo negatively programs the conceptus development and plausibly affects conceptus survival.

Local action of cytokines and immune cells in communication between the conceptus and uterus during the critical period of early embryo development, attachment and implantation - Implications for embryo survival in cattle: A review

Early embryo development, implantation and pregnancy involve a complex dialogue between the embryo and mother. In cattle this dialogue starts as early as days 3-4 when the embryo is still in the oviduct, and it continues to implantation. Immunological processes involving cytokines, mast cells and macrophages form an important part of this dialogue. Amongst the cytokines, interleukin-6 (Il-6) and leukemia inhibitory factor (LIF) are secreted by both the embryo and uterine endometrium and form part of an ongoing and reciprocating dialogue. Mast cells and macrophages populate the uterine endometrium during embryo development and are involved in achieving the correct balance between inflammatory and anti-inflammatory reactions at the uterus that are associated with embryo attachment and implantation. Embryo loss is the major cause of reproductive wastage in cattle, and livestock generally. A deeper understanding of immunological processes during early embryo development will help to achieve the next step change in the efficiency of natural and assisted breeding.

Proteomic profile of pre-implantational ovine embryos produced in vivo

The present study was conducted to decipher the proteome of in vivo-produced pre-implantation ovine embryos. Ten locally adapted Morana Nova ewes received hormonal treatment and were inseminated 12 hr after ovulation. Six days later, 54 embryos (morula and blastocyst developmental state) were recovered from eight ewes and pooled to obtain sufficient protein for proteomic analysis. Extracted embryo proteins were analysed by LC-MS/MS, followed by identification based on four database searches (PEAKS, Proteome Discoverer software, SearchGUI software, PepExplorer). Identified proteins were analysed for gene ontology terms, protein clusters and interactions. Genes associated with the ovine embryo proteome were screened for miRNA targets using data sets of TargetScan (http://www.targetscan.org) and mIRBase (http://www.mirbase.org) servers. There were 667 proteins identified in the ovine embryos. Biological processes of such proteins were mainly related to cellular process and regulation, and molecular functions, to binding and catalytic activity. Analysis of the embryo proteins revealed 49 enriched functional clusters, linked to energy metabolism (TCA cycle, pyruvate and glycolysis metabolism), zona pellucida (ZP), MAPK signalling pathway, tight junction, binding of sperm to ZP, translation, proteasome, cell cycle and calcium/phospholipid binding. Sixteen miRNAs were related to 25 pre-implantation ovine embryo genes, all conserved in human, bovine and ovine species. The interaction network generated by miRNet showed four key miRNAs (hsa-mir-106b-5p; hsa-mir-30-5p; hsa-mir-103a-5p and hsa-mir-106a-5p) with potential interactions with embryo-expressed genes. Functional analysis of the network indicated that miRNAs modulate genes related to cell cycle, regulation of stem cell and embryonic cell differentiation, among others. Retrieved miRNAs also modulate the expression of genes involved in cell signalling pathways, such as MAPK, Wnt, TGF-beta, p53 and Toll-like receptor. The current study describes the first major proteomic profile of 6-day-old ovine embryos produced in vivo, setting a comprehensive foundation for our understanding of embryo physiology in the ovine species.

Blastocyst-Bearing Sows Display a Dominant Anti-Inflammatory Cytokine Profile Compared to Cyclic Sows at Day 6 of the Cycle

Simple Summary

A proper uterine environment is basic for obtaining optimal embryo transfer outputs in domestic species, including the pig. However, scarce information is available about the uterine immune response of recipient (uninseminated) sows when receiving embryos during embryo transfer. Endometrial cytokine profile is among the main factors regulating uterine receptivity to embryos. In this study, using Luminex MAP^® technology, we found important differences in the endometrial production in most of the 16 cytokines analyzed between recipient sows and embryo-bearing (inseminated) sows six days after estrus, with a predominant cytokine anti-inflammatory environment in the embryo-bearing endometria. These observations suggest that insemination components and/or early embryos induce an endometrium immune-tolerant cytokine profile at Day 6 of the cycle. The findings could contribute importantly to design strategies to maximize the reproductive performance of recipients after embryo transfer in swine.

Abstract

In the context of porcine embryo transfer (ET) technology, understanding the tightly regulated local uterine immune environment is crucial to achieve an adequate interaction between the transferred embryos and the receiving endometrium. However, information is limited on the uterine immune status of cyclic-recipient sows when receiving embryos during ET. The present study postulated that the anti- and proinflammatory cytokine profile 6 days after the onset of estrus differs between endometria from uninseminated cyclic sows and blastocyst-bearing sows. On Day 6 of the cycle, endometrial explants were collected from sows inseminated or not inseminated during the postweaning estrus and cultured for 22 h. The culture medium was then analyzed for the contents of a total of 16 cytokines using Luminex MAP^® technology. The results showed important differences in the endometrial production of most cytokines between the sow categories, with a predominant anti-inflammatory environment displayed by the blastocyst-bearing endometria. These findings suggest that sperm, seminal plasma (SP) and/or early embryos modify the uterine environment by inducing an immune-tolerant cytokine profile already visible at Day 6. Whether the SP or some of its active components may help to develop strategies to maximize the reproductive performance of recipients after ET needs further investigation.

Challenges in studying preimplantation embryo-maternal interaction in cattle

A comprehensive understanding of the complex embryo-maternal interactions during the preimplantation period requires the analysis of the very early stages of pregnancy encompassing early embryonic development, maternal recognition and the events leading to implantation. Despite the fact that embryo development until blastocyst stage is somewhat autonomous (i.e., does not require contact with the maternal reproductive tract and can be successfully recapitulated in vitro), many studies on ruminant embryo production have focused on the fundamental question of why: (i) only 30%-40% of immature oocytes develop to the blastocyst stage and (ii) the quality of such blastocysts continually lags behind that of blastocysts produced in vivo. Clear evidence indicates that in vitro culture conditions are far from optimal with deficiencies being manifested in short- and long-term effects on the embryo. Thus, enhanced knowledge of mechanisms controlling embryo-maternal interactions would allow the design of novel strategies to improve in vitro embryo conditions and reproductive outcomes in cattle.

Recombinant bovine somatotropin in the synchronization of ovulation in crossbred dairy cows (Bos taurus indicus × Bos taurus taurus)

AIM

The aim of this study was to evaluate the effects of the administration of recombinant bovine somatotropin (rbST) at the moment of implementation of the timed artificial insemination protocol, on follicular dynamics and pregnancy rate in crossbred cows.

MATERIALS AND METHODS

A total of 346 cows were used in two experiments with a factorial 2×2 design. The cycling cows (Tcycling) and the anestrous cows (Tanestrous) were considered as factor 1 and the administration of rbST (TrbST) or not (Tcontrol) as factor 2. The experimental protocol: (1) Tcontrol - day 0 (D0), insertion of a progesterone-release intravaginal device (PRID) plus 2 mg of estradiol benzoate (EB); D8, PRID removal, plus 0.150 mg of prostaglandin F2α, and 400 IU of equine chorionic gonadotropin; D9, 1 mg of EB; and with artificial insemination at day 10; (2) TrbST - similar to Tcontrol plus 500 mg of rbST on D0. In experiment I, ultrasound examinations were performed in all treatments. In experiment II, the cows' pregnancy rate was evaluated. Data were analyzed with 5% probability.

RESULTS

There was no effect of the protocols on cows cyclicity or follicular growth rate (p>0.05). There was no interaction of the effects, administration of rbST, and the cyclicity of cows on the pregnancy rate. The total pregnancy rate observed was 49.0%. The pregnancy rate in cows receiving rbST was lower for anestrous compared with cycling cows (p<0.05).

CONCLUSION

The administration of rbST did not alter the patterns of follicular dynamics nor the ovulation rate. However, cows in anestrous that received rbST had lower pregnancy rates than cycling cows.