In vivo oocyte developmental competence is reduced in lean but not in obese superovulated dairy cows after intraovarian administration of IGF1

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

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

Single-cell transcriptomic profiling to evaluate the effects of Di(2-ethylhexyl)phthalate exposure on early meiosis of female mouse germ cells

Di(2-ethylhexyl)phthalate (DEHP) has proven characteristics of an endocrine-disrupting compound (EDC), which can threaten the reproductive health of humans and other animals. In mammals, a series of chromosomal events occur during the meiotic stage of oocytes. External toxins may enter the body and cause infertility and other related diseases. Therefore, it is crucial to explore the influence of DEHP exposure on the molecular mechanism of germ cell meiosis. We used single-cell RNA sequencing (scRNA-seq) to analyse the ovaries of foetal mice at embryonic day 12.5 (E12.5) and E14.5 after maternal DEHP exposure. DEHP exposure further activated the pathways related to DNA repair in germ cells, increased the expression of genes related to DNA damage and changed the developmental trajectory of germ cells. DEHP exposure may affect the proliferation of pregranulosa (PG) cells. Moreover, DEHP exposure altered the signal transduction between PG cells and germ cells. We showed that DEHP affects meiosis by causing DNA damage in oocytes and disrupting the signal transduction between PG cells and germ cells. These results provide a strong theoretical basis for the prevention and treatment of DEHP-mediated female reproductive health problems.

Effect of insulin or insulin-like growth factor-I administration at mid-luteal phase of the estrous cycle during superovulation on hormonal profile of Sahiwal cows

Aim:

The present study was designed to study the effect of insulin and insulin-like growth factor-1 (IGF-I) administration during luteal phase of the estrous cycle on the hormonal profile of Sahiwal embryo donor cows during superovulation.

Materials and Methods:

Cows (n=18) were selected and divided into three groups; control (n=6, untreated), T-I (n=6, insulin-treated), and T-II (n=6, IGF-I treated). Insulin and IGF-I were given S/C on 5^th, 6^th, 7^th, and 8^th days of estrous cycle. Superovulatory treatment was started on day 9^th of the estrous cycle. With the sixth dose of follicle-stimulating hormone, prostaglandin was injected to induce superovulatory heat. The superovulated cows were bred, and superovulatory response of each animal was recorded. The embryos were collected non-surgically on the 7^th day of superovulatory estrus. About 15 ml blood without anticoagulant was collected on days 5, 7, 9, 11, 13, 15, 17, 19, and 21 or day of embryo recovery where day 0 of estrous cycle was taken as day of estrus. Serum was separated, centrifuged, and transferred into sterilized serum vials. All samples were stored at −20°C till analysis. Progesterone, insulin, and IGF-I were estimated in blood serum by radioimmunoassay using radioimmunoassay kits.

Results and Discussion:

The mean concentration of progesterone on days 7 and 11, insulin on days 7 and 9, and IGF-I on days 5, 7, 9, 11, and 15 was significantly higher in insulin-treated T-I groups as compared to untreated control.

Conclusion:

It may be concluded that exogenous insulin administration during mid-luteal phase may be helpful in follicular and embryonic development through modulation of progesterone, insulin, and IGF-I in indigenous (Bos indicus) Sahiwal embryo donor cows.

Exposure to maternal obesity alters gene expression in the preimplantation ovine conceptus

Background

Embryonic and fetal exposure to maternal obesity causes several maladaptive morphological and epigenetic changes in exposed offspring. The timing of these events is unclear, but changes can be observed even after a short exposure to maternal obesity around the time of conception. The hypothesis of this work is that maternal obesity influences the ovine preimplantation conceptus early in pregnancy, and this exposure will affect gene expression in embryonic and extraembryonic tissues.

Results

Obese and lean ewe groups were established by overfeeding or normal feeding, respectively. Ewes were then bred to genetically similar rams. Conceptuses were collected at day 14 of gestation. Morphological assessments were made, conceptuses were sexed by genomic PCR analysis, and samples underwent RNA-sequencing analysis. While no obvious morphological differences existed between conceptuses, differentially expressed genes (≥ 2-fold; ≥ 0.2 RPKM; ≤ 0.05 FDR) were detected based on maternal obesity exposure (n = 21). Also, differential effects of maternal obesity were noted on each conceptus sex (n = 347). A large portion of differentially expressed genes were associated with embryogenesis and placental development.

Conclusions

Findings reveal that the preimplantation ovine conceptus genome responds to maternal obesity in a sex-dependent manner. The sexual dimorphism in response to the maternal environment coupled with changes in placental gene expression may explain aberrations in phenotype observed in offspring derived from obese females.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5120-0) contains supplementary material, which is available to authorized users.

Overweight negatively affects outcome of superovulation treatment in female mice

Superovulatory response is characterized by a high degree of variability and unpredictability. The aim of the present experimental study was to examine whether the amount of maternal body fat can influence the efficiency of ovarian stimulation with gonadotropins. Female mice of two body condition types, normal and obese, produced in a standardized two-generation model, were subjected to ovarian stimulation using eCG and hCG followed by natural mating. Produced ova and embryos were recovered on day 1 and day 4 of pregnancy respectively, and several quantitative, qualitative and developmental parameters were evaluated in them. The overall response of mouse females with normal and elevated amounts of body fat to superovulation was similar: They produced almost the same numbers of ova and embryos on average. Conversely, a higher number of immature oocytes, non-fertilized mature oocytes and lower-stage zygotes were collected from fat females. In both groups, the majority of fertilized oocytes was able to cleave and reach the higher stages of development. However, in the group of fat mice, a lower number of blastocysts was collected, and these blastocysts showed increased incidence of apoptotic cell death. In conclusion, although the response of normal and fat mice to superovulatory treatment was similar, the quality and developmental capacities of produced ova were lower in the group of fat donors.

Cell signalling during blastocyst morphogenesis

Blastocyst morphogenesis is prepared for even before fertilisation. Information stored within parental gametes can influence both maternal and embryonic gene expression programmes after egg activation at fertilisation. A complex network of intrinsic, cell-cell mediated and extrinsic, embryo-environment signalling mechanisms operates throughout cleavage, compaction and cavitation. These signalling events not only ensure developmental progression, cell differentiation and lineage allocation to inner cell mass (embryo proper) and trophectoderm (future extraembryonic lineages) but also provide a degree of developmental plasticity ensuring survival in prevailing conditions by adaptive responses. Indeed, many cellular functions including differentiation, metabolism, gene expression and gene expression regulation are subject to plasticity with short- or long-term consequences even into adult life. The interplay between intrinsic and extrinsic signals impacting on blastocyst morphogenesis is becoming clearer. This has been best studied in the mouse which will be the focus of this chapter but translational significance to human and domestic animal embryology will be a focus in future years.

Impact of maternal malnutrition during the periconceptional period on mammalian preimplantation embryo development

During episodes of undernutrition and overnutrition the mammalian preimplantation embryo undergoes molecular and metabolic adaptations to cope with nutrient deficits or excesses. Maternal adaptations also take place to keep a nutritional microenvironment favorable for oocyte development and embryo formation. This maternal-embryo communication takes place via several nutritional mediators. Although adaptive responses to malnutrition by both the mother and the embryo may ensure blastocyst formation, the resultant quality of the embryo can be compromised, leading to early pregnancy failure. Still, studies have shown that, although early embryonic mortality can be induced during malnutrition, the preimplantation embryo possesses an enormous plasticity that allows it to implant and achieve a full-term pregnancy under nutritional stress, even in extreme cases of malnutrition. This developmental strategy, however, may come with a price, as shown by the adverse developmental programming induced by even subtle nutritional challenges exerted exclusively during folliculogenesis and the preimplantation period, resulting in offspring with a higher risk of developing deleterious phenotypes in adulthood. Overall, current evidence indicates that malnutrition during the periconceptional period can induce cellular and molecular alterations in preimplantation embryos with repercussions for fertility and postnatal health.

[Impact of maternal overnutrition on the periconceptional period]

Overnutrition may lead to obesity. Maternal obesity may affect fertility not only via anovulation, but also through direct effects on oocytes and preimplantation embryos, indicating that the periconceptional period is sensitive to conditions of overnutrition. The periconceptional period includes from folliculogenesis to implantation. Animal model studies suggest that oocytes derived from obese females usually have a small size and mitochondrial abnormalities. These disruptions are probably induced by changes in the components of the ovarian follicular fluid. Experimental evidence also suggests that obesity may affect the microenvironment in oviducts and uterus, resulting in development of preimplantation embryos with reduced cell numbers and up-regulation of proinflammatory genes. However, further research is needed for in-depth characterization of the effects of maternal obesity during the periconceptional period.

Molecular effects of supraphysiological doses of doping agents on health

Supraphysiological doses of doping agents, such as T/DHT and GH/IGF-1, affect cellular pathways associated with apoptosis and inflammation.

Biomedical applications of ovarian transvaginal ultrasonography in cattle

Ovarian transvaginal ultrasonography (OTU) has been used world-wide for commercial ovum pick-up programs for in vitro embryo production in elite herds, providing an excellent model for the elucidation of factors controlling bovine oocyte developmental competence. Noninvasive sampling and treatment of ovarian structures is easily accomplished with bovine OTU techniques providing a promising system for in vivo delivery of transgenes directly into the ovary. The current review summarizes existing bovine OTU models and provides prospective applications of bovine OTU to undertake research in reproductive topics of biomedical relevance, with special emphasis on the development of in vivo gene transfer strategies.

IGF-I slightly improves nuclear maturation and cleavage rate of bovine oocytes exposed to acute heat shock in vitro

An in vitro model of embryo production was used to examine the effects of insulin-like growth factor (IGF)-I on maturation and developmental competence of oocytes exposed to heat shock. Cumulus–oocyte complexes were matured at 38.5°C or exposed to acute heat shock (HS; 41.5°C), with or without 100 ng/ml IGF-I, for 22 h through in vitro maturation. The experimental groups were control (C), C + IGF-I, HS, and HS + IGF-I. Oocytes were fertilized at the end of maturation, and the proportion of cleaved embryos was recorded 44 h later. HS during maturation increased the proportion of TUNEL-positive oocytes (P < 0.05). HS did not have any effect on cortical granule translocation but impaired resumption of meiosis, expressed as a decreased proportion of oocytes with nuclei in metaphase I (P < 0.05) and metaphase II (MII; P < 0.05). HS decreased the proportion of oocytes that cleaved (P < 0.05), in particular those oocytes that further developed to 4-cell-stage embryos (P < 0.05). IGF-I alleviated, to some extent, the deleterious effects of HS on the oocytes as reflected by a reduced proportion of TUNEL-positive oocytes (P < 0.03). While not significant, IGF-I tended to increase the proportion of MII-stage oocytes (P < 0.08) and 4-cell-stage cleaved embryos (P < 0.06). Further examination is required to explore whether IGF-I also affects the developmental competence of oocytes exposed to HS.

Global endometrial transcriptomic profiling: transient immune activation precedes tissue proliferation and repair in healthy beef cows

BACKGROUND

All cows experience bacterial contamination and tissue injury in the uterus postpartum, instigating a local inflammatory immune response. However mechanisms that control inflammation and achieve a physiologically functioning endometrium, while avoiding disease in the postpartum cow are not succinctly defined. This study aimed to identify novel candidate genes indicative of inflammation resolution during involution in healthy beef cows. Previous histological analysis of the endometrium revealed elevated inflammation 15 days postpartum (DPP) which was significantly decreased by 30 DPP. The current study generated a genome-wide transcriptomic profile of endometrial biopsies from these cows at both time points using mRNA-Seq. The pathway analysis tool GoSeq identified KEGG pathways enriched by significantly differentially expressed genes at both time points. Novel candidate genes associated with inflammatory resolution were subsequently validated in additional postpartum animals using quantitative real-time PCR (qRT-PCR).

RESULTS

mRNA-Seq revealed 1,107 significantly differentially expressed genes, 73 of which were increased 15 DPP and 1,034 were increased 30 DPP. Early postpartum, enriched immune pathways (adjusted P < 0.1) included the T cell receptor signalling pathway, graft-versus-host disease and cytokine-cytokine receptor interaction pathways. However 30 DPP, where the majority of genes were differentially expressed, the enrichment (adjusted P < 0.1) of tissue repair and proliferative activity pathways was observed. Nineteen candidate genes selected from mRNA-Seq results, were independently assessed by qRT-PCR in additional postpartum cows (5 animals) at both time points. SAA1/2, GATA2, IGF1, SHC2, and SERPINA14 genes were significantly elevated 30 DPP and are functionally associated with tissue repair and the restoration of uterine homeostasis postpartum.

CONCLUSIONS

The results of this study reveal an early activation of the immune response which undergoes a temporal functional change toward tissue proliferation and regeneration during endometrial involution in healthy postpartum cows. These molecular changes mirror the activation and resolution of endometrial inflammation during involution previously classified by the degree of neutrophil infiltration. SAA1/2, GATA2, IGF1, SHC2, and SERPINA14 genes may become potential markers for resolution of endometrial inflammation in the postpartum cow.

In vivo oocyte IGF-1 priming increases inner cell mass proliferation of in vitro-formed bovine blastocysts

Studies addressing the effects of supraphysiological levels of IGF-1 on oocyte developmental competence are relevant for unravelling conditions resulting in high bioavailability of IGF-1, such as the polycystic ovary syndrome (PCOS). This study investigated the effects of supraphysiological levels of IGF-1 during in vivo folliculogenesis on the morula-blastocyst transition in bovine embryos. Compacted morulae were non-surgically collected and frozen for subsequent mRNA expression analysis (IGF1R, IGBP3, TP53, AKT1, SLC2A1, SLC2A3, and SLC2A8), or underwent confocal microscopy analysis for protein localization (IGF1R and TP53), or were cultured in vitro for 24 h. In vitro-formed blastocysts were subjected to differential cell staining. The mRNA expression of SLC2A8 was higher in morulae collected from cows treated with IGF-1. Both IGF1R and TP53 protein were present in the plasma membrane and cytoplasm. IGF-1 treatment did not affect protein localization of both IGF1R and TP53. In vitro-formed blastocysts derived from morulae recovered from IGF-1-treated cows displayed a higher number of cells in the inner cell mass (ICM). Total cell number (TCN) of in vitro-formed blastocysts was not affected. A higher mean ICM/TCN proportion was observed in in vitro-formed blastocysts derived from morulae collected from cows treated with IGF-1. The percentage of in vitro-formed blastocysts displaying a low ICM/TCN proportion was decreased by IGF-1 treatment. In vitro-formed blastocysts with a high ICM/TCN proportion were only detected in IGF-1 treated cows. Results show that even a short in vivo exposure of oocytes to a supraphysiological IGF-1 microenvironment can increase ICM cell proliferation in vitro during the morula to blastocyst transition.