Biosensor capability of the endometrium is mediated in part, by altered miRNA cargo from conceptus-derived extracellular vesicles

We tested the hypothesis that the biosensor capability of the endometrium is mediated in part, by the effect of different cargo contained in the extracellular vesicles secreted by the conceptus during the peri-implantation period of pregnancy. We transferred Bos taurus taurus embryos of different origin, in vivo (high developmental potential (IV)), in vitro (intermediate developmental potential (IVF)), or cloned (low developmental potential (NT)), into Bos taurus indicus recipients. Extracellular vesicles (EVs) recovered from Day 16 conceptus-conditioned medium were characterized and their microRNA (miRNA) cargo sequenced alongside RNA sequencing of their respective endometria. There were substantial differences in the endometrial response to in vivo versus in vitro and in vivo versus cloned conceptuses (1153 and 334DEGs respectively) with limited differences between in vitro Vs cloned conceptuses (36 DEGs). The miRNA cargo contained in conceptus-derived EVs was similar between all three groups (426 miRNA in common). Only 8 miRNAs were different between in vivo and cloned conceptuses, while only 6 miRNAs were different between in vivo and in vitro-derived conceptuses. Treatment of endometrial epithelial cells with mimic or inhibitors for miR-128 and miR-1298 changed the proteomic content of target cells (96 and 85, respectively) of which mRNAs are altered in the endometrium in vivo (PLXDC2, COPG1, HSPA12A, MCM5, TBL1XR1, and TTF). In conclusion, we have determined that the biosensor capability of the endometrium is mediated in part, by its response to different EVs miRNA cargo produced by the conceptus during the peri-implantation period of pregnancy.

Cattle Cloning by Somatic Cell Nuclear Transfer

Cloning by somatic cell Nuclear Transfer (SCNT) is a powerful technology capable of reprograming terminally differentiated cells to totipotency for generating whole animals or pluripotent stem cells for use in cell therapy, drug screening, and other biotechnological applications. However, the broad usage of SCNT remains limited due to its high cost and low efficiency in obtaining live and healthy offspring. In this chapter, we first briefly discuss the epigenetic constraints responsible for the low efficiency of SCNT and current attempts to overcome them. We then describe our bovine SCNT protocol for delivering live cloned calves and addressing basic questions about nuclear reprogramming. Other research groups can benefit from our basic protocol and build up on it to improve SCNT in the future. Strategies to correct or mitigate epigenetic errors (e.g., correcting imprinting loci, overexpression of demethylases, chromatin-modifying drugs) can integrate the protocol described here.

Characterization of histone lysine β-hydroxybutyrylation in bovine tissues, cells, and cumulus-oocyte complexes

Besides their canonical roles as energy sources, short-chain fatty acids act as metabolic regulators of gene expression through histone posttranslational modifications. Ketone body β-hydroxybutyrate (BHB) causes a novel epigenetic modification, histone lysine β-hydroxybutyrylation (Kbhb), which is associated with genes upregulated in starvation-responsive metabolic pathways. Dairy cows increase BHB in early lactation, and the effects of this increase on cellular epigenomes are unknown. We searched for and identified that Kbhb is present in bovine tissues in vivo and confirmed that this epigenetic mark is responsive to BHB in bovine and human fibroblasts cultured in vitro in a dose-dependent manner. Maturation of cumulus-oocyte complexes with high concentrations of BHB did not affect the competence to complete meiotic maturation or to develop until the blastocyst stage. BHB treatment strongly induced H3K9bhb in cumulus cells, but faintly in oocytes. RNA-seq analysis in cumulus cells indicated that BHB treatment altered the expression of 345 genes. The downregulated genes were mainly involved in glycolysis and ribosome assembly pathways, while the upregulated genes were involved in mitochondrial metabolism and oocyte development. The genes and pathways altered by BHB will provide entry points to carry out functional experiments aiming to mitigate metabolic disorders and improve fertility in cattle.

Catalytic inhibition of H3K9me2 writers disturbs epigenetic marks during bovine nuclear reprogramming

Orchestrated events, including extensive changes in epigenetic marks, allow a somatic nucleus to become totipotent after transfer into an oocyte, a process termed nuclear reprogramming. Recently, several strategies have been applied in order to improve reprogramming efficiency, mainly focused on removing repressive epigenetic marks such as histone methylation from the somatic nucleus. Herein we used the specific and non-toxic chemical probe UNC0638 to inhibit the catalytic activity of the histone methyltransferases EHMT1 and EHMT2. Either the donor cell (before reconstruction) or the early embryo was exposed to the probe to assess its effect on developmental rates and epigenetic marks. First, we showed that the treatment of bovine fibroblasts with UNC0638 did mitigate the levels of H3K9me2. Moreover, H3K9me2 levels were decreased in cloned embryos regardless of treating either donor cells or early embryos with UNC0638. Additional epigenetic marks such as H3K9me3, 5mC, and 5hmC were also affected by the UNC0638 treatment. Therefore, the use of UNC0638 did diminish the levels of H3K9me2 and H3K9me3 in SCNT-derived blastocysts, but this was unable to improve their preimplantation development. These results indicate that the specific reduction of H3K9me2 by inhibiting EHMT1/2 during nuclear reprogramming impacts the levels of H3K9me3, 5mC, and 5hmC in preimplantation bovine embryos.

Metabolic gene expression and epigenetic effects of the ketone body β-hydroxybutyrate on H3K9ac in bovine cells, oocytes and embryos

The rapid decline in fertility that has been occurring to high-producing dairy cows in the past 50 years seems to be associated with metabolic disturbances such as ketosis, supporting the need for research to improve our understanding of the relations among the diet, metabolism and embryonic development. Recently, the ketone body β-hydroxybutyrate (BOHB) was demonstrated to be a potent inhibitor of histone deacetylases (HDACs). Herein, we performed a series of experiments aiming to investigate the epigenetic effects of BOHB on histone acetylation in somatic cells, cumulus-oocyte complexes (COCs) and somatic cell nuclear transfer (SCNT) embryos. Treatment with BOHB does not increase histone acetylation in cells but stimulates genes associated with ketolysis and master regulators of metabolism. We further demonstrated that maturing COCs with high levels of BOHB does not affect their maturation rate or histone acetylation but increases the expression of PPARA in cumulus cells. Treatment of somatic cell nuclear transfer zygotes with BOHB causes hyperacetylation, which is maintained until the blastocyst stage, causing enhanced FOXO3A expression and blastocyst production. Our data shed light on the epigenetic mechanisms caused by BOHB in bovine cells and embryos and provide a better understanding of the connection between nutrition and reproduction.

Influence of L-arginine during bovine in vitro fertilization

The objective of this work was to evaluate the effect of using L-arginine during in vitro fertilization (IVF) on in vitro embryonic development using Bos taurus and Bos indicus semen. Effect of different concentrations (0, 1, 10 and 50 mM) of L-arginine, added to the IVF medium, was evaluated on the fertilization rate at 18 h post-fertilization (hpf), NO3(-)/NO2(-) production during IVF by the Griess colorimetric method (30 hpf), cleavage and blastocyst rates (on Day 2 and Day 7 of culture, respectively) and total blastocyst cell number (Day 7 of culture). The results reveal that the addition of 50 mM L-arginine to IVF medium, with either Bos taurus or Bos indicus spermatozoa, decreased the cleavage rate and blastocyst rate compared to the control group. Other concentrations did not affect embryo production. However, 1 mM L-arginine with Bos indicus semen increased the proportion of hatched blastocysts. These results indicate that high L-arginine concentrations may exhibit toxic effects on bovine gametes during in vitro fertilization.

Development to term of cloned cattle derived from donor cells treated with valproic acid

Cloning of mammals by somatic cell nuclear transfer (SCNT) is still plagued by low efficiency. The epigenetic modifications established during cellular differentiation are a major factor determining this low efficiency as they act as epigenetic barriers restricting reprogramming of somatic nuclei. In this regard, most factors that promote chromatin decondensation, including histone deacetylase inhibitors (HDACis), have been found to increase nuclear reprogramming efficiency, making their use common to improve SCNT rates. Herein we used valproic acid (VPA) in SCNT to test whether the treatment of nuclear donor cells with this HDACi improves pre- and post-implantation development of cloned cattle. We found that the treatment of fibroblasts with VPA increased histone acetylation without affecting DNA methylation. Moreover, the treatment with VPA resulted in increased expression of IGF2R and PPARGC1A, but not of POU5F1. However, when treated cells were used as nuclear donors no difference of histone acetylation was found after oocyte reconstruction compared to the use of untreated cells. Moreover, shortly after artificial activation the histone acetylation levels were decreased in the embryos produced with VPA-treated cells. With respect to developmental rates, the use of treated cells as donors resulted in no difference during pre- and post-implantation development. In total, five clones developed to term; three produced with untreated cells and two with VPA-treated cells. Among the calves from treated group, one stillborn calf was delivered at day 270 of gestation whereas the other one was delivered at term but died shortly after birth. Among the calves from the control group, one died seven days after birth whereas the other two are still alive and healthy. Altogether, these results show that in spite of the alterations in fibroblasts resulting from the treatment with VPA, their use as donor cells in SCNT did not improve pre- and post-implantation development of cloned cattle.

Quantification, morphology and ultrastructure of preantral follicles of buffalo (Bubalus bubalis) foetuses

The objective of this study was to determine the number, morphology and ultrastructure of preantral ovarian follicles of buffalo (Bubalus bubalis) foetuses at different ages. Quantification revealed number of primordial, primary and secondary follicles of 48,857 ± 17,506, 26,000 ± 20,452, 18,428 ± 10,875 and 18,375 ± 19,690, 225 ± 349, 326 ± 288 at 12-34 cm and 35-60 cm crown rump length (CRL), respectively. Follicular diameter values were 28.9 (± 3.4), 34.7 (± 5.9) and 59.4 (± 12.6) μm; oocyte diameters were 21.7 (± 2.8), 24.3 (± 3.4) and 33.0 (± 7.7) μm, and the numbers of follicular cells in the follicle equatorial section were 7.1 (± 1.4), 12.0 (± 2.4) and 13.8 (± 2.4) for primordial, primary and secondary follicles, respectively. The primordial follicle consisted of an oocyte surrounded by a layer of flattened follicular cells with a normally eccentric oocyte nucleus. Dispersed Golgi complex, smooth endoplasmic reticulum, rounded mitochondria and several lipid vesicles were observed in the cytoplasm and cell junctions between the follicle cell membranes and the oocyte. This work describes the number, morphometry and ultrastructure of preantral follicles of buffalo foetuses, concluding that folliculogenesis is established between 8 and 34 cm CRL and that follicle number varies individually and according to age and that further studies are needed in this species.