Endometrial transcriptional profiling of a bovine fertility model by Next-Generation Sequencing.

Studying the multitude of molecular networks and pathways that are potentially involved in a complex trait such as fertility requires an equally complex and broad strategy. Here, we used Next-Generation Sequencing for the characterization of the transcriptional signature of the bovine endometrial tissue. Periovulatory endocrine environments were manipulated to generate two distinctly different fertility phenotypes. Cycling, non-lactating, multiparous Nelore cows were manipulated to ovulate larger (> 13 mm; LF group; high fertility phenotype) or smaller (< 12 mm; SF group) follicles. As a result, greater proestrus estrogen concentrations, corpora lutea and early diestrus progesterone concentrations were also observed in LF group in comparison to SF group. Endometrial cell proliferation was estimated by the protein marker MKI67 on tissues collected 4 (D4) and 7 (D7) days after induction of ovulation. Total RNA extracts from D7 were sequenced and compared according to the transcriptional profile of each experimental group (LF versus SF). Functional enrichment analysis revealed that LF and SF endometria were asynchronous in regards to their phenotype manifestation. Major findings indicated an LF endometrium that was switching phenotypes earlier than the SF one. More specifically, a proliferating SF endometrium was observed on D7, whereas the LF tissue, which expressed a proliferative phenotype earlier at D4, seemed to have already shifted towards a biosynthetically and metabolically active endometrium on D7. Data on MKI67 support the transcriptomic results. RNA-Seq-derived transcriptional profile of the endometrial tissue indicated a temporal effect of the periovulatory endocrine environment, suggesting that the moment of the endometrial exposure to the ovarian steroids, E2 and P4, regulates the timing of phenotype manifestation. Gene expression profiling revealed molecules that may be targeted to elucidate ovarian steroid-dependent mechanisms that regulate endometrial tissue receptivity. Data was deposited in the SRA database from NCBI (SRA Experiment SRP051330) and are associated with the Bio-Project (PRJNA270391). An overview of the gene expression data has been deposited in NCBI's Gene Expression Omnibus (GEO) and is accessible through GEO Series accession number GSE65450. Further assessment of the data in combination with other data sets exploring the transcriptional profile of the endometrial tissue during early diestrus may potentially identify novel molecular mechanisms and/or markers of the uterine receptivity.

The Receptive Endometrial Transcriptomic Signature Indicates an Earlier Shift from Proliferation to Metabolism at Early Diestrus in the Cow.

This study aimed to characterize the endometrial transcriptome and functional pathways overrepresented in the endometrium of cows treated to ovulate larger (≥13 mm) versus smaller (≤12 mm) follicles. Nelore cows were presynchronized prior to receiving cloprostenol (large follicle [LF] group) or not (small follicle [SF] group), along with a progesterone (P4) device on Day (D) -10. Devices were withdrawn and cloprostenol administered 42-60 h (LF) or 30-36 h (SF) before GnRH agonist treatment (D0). Tissues were collected on D4 (experiment [Exp.] 1; n = 24) or D7 (Exp. 2; n = 60). Endometrial transcriptome was obtained by RNA-Seq, whereas proliferation and apoptosis were assessed by immunohistochemistry. Overall, LF cows developed larger follicles and corpora lutea, and produced greater amounts of estradiol (D-1, Exp. 1, SF: 0.7 ± 0.2; LF: 2.4 ± 0.2 pg/ml; D-1, Exp. 2, SF: 0.5 ± 0.1; LF: 2.3 ± 0.6 pg/ml) and P4 (D4, Exp. 1, SF: 0.8 ± 0.1; LF: 1.4 ± 0.2 ng/ml; D7, Exp. 2, SF: 2.5 ± 0.4; LF: 3.7 ± 0.4 ng/ml). Functional enrichment indicated that biosynthetic and metabolic processes were enriched in LF endometrium, whereas SF endometrium transcriptome was biased toward cell proliferation. Data also suggested reorganization of the extracellular matrix toward a proliferation-permissive phenotype in SF endometrium. LF endometrium showed an earlier onset of proliferative activity, whereas SF endometrium expressed a delayed increase in glandular epithelium proliferation. In conclusion, the periovulatory endocrine milieu regulates bovine endometrial transcriptome and seems to determine the transition from a proliferation-permissive to a biosynthetic and metabolically active endometrial phenotype, which may be associated with the preparation of an optimally receptive uterine environment.

New applications for bovine IVP technology: from ‘single oocyte culture’ to toxicity screening

Bovine in vitro embryo production (IVP) has been around for about three decades. Over the years, it has gained a reputation as one of the most applicable of the high-tech bovine assisted reproduction techniques. It is well known that its ups and downs are basically driven by economic imperatives depending on the agricultural system in which it is used. In parallel, there has always been a strong in terest in the bovine embryo as an in vitro model for basic research purposes. This mini-review focuses on a few more recent applications of bovine IVP that can be useful for both cattle breeding business and research purposes, namely the development of a single oocyte culture system and, as an example, its possible use as a toxicity screening tool.

High throughput non-invasive oocyte quality assessment: the search continues

Non-invasive oocyte quality assessment remains a major challenge of routine bovine in vitro embryo production (IVP). There is a major need for techniques allowing early selection of developmentally competent oocytes on the basis of a simple, quick, economic and feasible protocol. The availability of such a technique would clearly in crease IVP efficiency since only competent oocytes would be used, maximising blastocyst yield by ameliorating culture conditions. This mini-review summarizes briefly the currently available techniques that allow high throughput non-invasive oocyte quality assessment and indicates their possibilities and limitations.

High throughput non-invasive oocyte quality assessment: the search continues

Non-invasive oocyte quality assessment remains a major challenge of routine bovine in vitro embryo production (IVP). There is a major need for techniques allowing early selection of developmentally competent oocytes on the basis of a simple, quick, economic and feasible protocol. The availability of such a technique would clearly in crease IVP efficiency since only competent oocytes would be used, maximising blastocyst yield by ameliorating culture conditions. This mini-review summarizes briefly the currently available techniques that allow high throughput non-invasive oocyte quality assessment and indicates their possibilities and limitations.(AU)

New applications for bovine IVP technology: from ‘single oocyte culture to toxicity screening

Bovine in vitro embryo production (IVP) has been around for about three decades. Over the years, it has gained a reputation as one of the most applicable of the high-tech bovine assisted reproduction techniques. It is well known that its ups and downs are basically driven by economic imperatives depending on the agricultural system in which it is used. In parallel, there has always been a strong in terest in the bovine embryo as an in vitro model for basic research purposes. This mini-review focuses on a few more recent applications of bovine IVP that can be useful for both cattle breeding business and research purposes, namely the development of a single oocyte culture system and, as an example, its possible use as a toxicity screening tool.(AU)