Endometrial receptivity in cattle: the mutual reprogramming paradigm.

Prior to implantation in cattle, the mucous medium contained in the uterine lumen serves as a working interface for molecular exchange and signaling between the lining endometrium and the embryo. The composition of this luminal fluid changes temporally according to the secretory and reabsorptive activities of the uterus and the embryo, which are under complex regulation. Via this interface, both the embryo and the endometrium reprogram each other's functions to support pregnancy continuation beyond the pre-implantation period. More specifically, the embryo receives elongation signals and the uterus receives anti-luteolytic stimuli. Here, characteristics of the luminal compartment as well as the regulation of its composition to determine the pregnancy outcome will be discussed.

Endometrial receptivity in cattle: the mutual reprogramming paradigm

Prior to implantation in cattle, the mucous medium contained in the uterine lumen serves as a working interface for molecular exchange and signaling between the lining endometrium and the embryo. The composition of this luminal fluid changes temporally according to the secretory and reabsorptive activities of the uterus and the embryo, which are under complex regulation. Via this interface, both the embryo and the endometrium reprogram each other's functions to support pregnancy continuation beyond the pre-implantation period. More specifically, the embryo receives elongation signals and the uterus receives anti-luteolytic stimuli. Here, characteristics of the luminal compartment as well as the regulation of its composition to determine the pregnancy outcome will be discussed.(AU)

Silvopastoral system is an alternative to improve animal welfare and productive performance in meat production systems.

Climate change is a reality and global surface temperature is projected to rise substantially in the next 80 years. Agriculture practices will have to adapt to climate change, and also help to mitigate this effect using, among other strategies, forest conservation and management. Silvopastoral systems have been adopted in tropical climate livestock areas but their benefits on thermal comfort and reproductive performance of beef cows are not completely known. Therefore, our aims were to compare the microclimate of silvopastoral and intensive rotational unshaded grazing systems in different months and to evaluate physiological variables (Exp. 1 and 2), metabolism, and in vitro embryo production (Exp. 2) in crossbred beef females. Our hypothesis is that the silvopastoral system can improve the thermal comfort of beef heifers and cows and, consequently, also improve dry matter intake, body weight gain, and in vitro embryo production when compared to the unshaded rotational grazing system. In Exp 1, the silvopastoral system decreased body temperature and increased welfare and performance of heifers. In Exp. 2, the silvopastoral system enhanced the body weight but did not affect metabolism and the general reproductive performance, but increased the recovery rate of oocytes in primiparous cows.

The pre-hatching bovine embryo transforms the uterine luminal metabolite composition in vivo.

In cattle, conceptus development after elongation relies on well-characterized, paracrine interactions with the hosting maternal reproductive tract. However, it was unrecognized previously that the pre-hatching, pre-implantation bovine embryo also engages in biochemical signalling with the maternal uterus. Our recent work showed that the embryo modified the endometrial transcriptome in vivo. Here, we hypothesized that the embryo modulates the biochemical composition of the uterine luminal fluid (ULF) in the most cranial portion of the uterine horn ipsilateral to the corpus luteum. Endometrial samples and ULF were collected post-mortem from sham-inseminated cows and from cows inseminated and detected pregnant 7 days after oestrus. We used quantitative mass spectrometry to demonstrate that the pre-hatching embryo changes ULF composition in vivo. Embryo-induced modulation included an increase in concentrations of lipoxygenase-derived metabolites [12(S)-HETE, 15(S)-HETE] and a decrease in the concentrations of amino acids (glycine), biogenic amines (sarcosine), acylcarnitines and phospholipids. The changed composition of the ULF could be due to secretion or depletion of specific molecules, executed by either the embryo or the endometrium, but initiated by signals coming from the embryo. This study provides the basis for further understanding embryo-initiated modulation of the uterine milieu. Early embryonic signalling may be necessary to guarantee optimal development and successful establishment of pregnancy in cattle.

Oviductal transcriptional profiling of a bovine fertility model by next-generation sequencing.

In cattle, the oviduct plays a fundamental role in the reproductive process. Oviductal functions are controlled by the ovarian sex steroids: estradiol and progesterone. Here, we tested the hypothesis that the exposure to contrasting sex steroid milieus differentially impacts the oviductal transcriptional profile. We manipulated growth of the pre-ovulatory follicle to obtain cows that ovulated a larger (LF group) or a smaller (SF group) follicle. The LF group presented greater proestrus/estrus concentrations of estradiol and metaestrus concentrations of progesterone (Gonella-Diaza et al. 2015 [1], Mesquita et al. 2014 [2]). Also, the LF group was associated with greater fertility in timed-artificial insemination programs (Pugliesi et al. 2016 [3]). Cows were slaughtered on day 4 of the estrous cycle and total RNA was extracted from ampulla and isthmus fragments and analyzed by RNAseq. The resulting reads were mapped to the bovine genome (Bos taurus UMD 3.1, NCBI). The differential expression analyses revealed that 325 and 367 genes in ampulla and 274 and 316 genes in the isthmus were up-regulated and down-regulated in LF samples, respectively. To validate the RNAseq results, transcript abundance of 23 genes was assessed by qPCR and expression patterns were consistent between the two techniques. A functional enrichment analysis was performed using Database for Annotation, Visualization and Integrated Discovery (DAVID) software. Processes enriched in the LF group included tissue morphology changes (extracellular matrix remodeling), cellular changes (proliferation), and secretion changes (growth factors, ions and metal transporters). An overview of the gene expression data was deposited in the NCBI's Gene Expression Omnibus (GEO) and is accessible through the accession number GSE65681. In conclusion, differences in the peri-ovulatory sex steroid milieu modify the oviductal gene expression profiles. Such differences may be associated with the greater fertility of the LF cows. This dataset is useful for further investigations of the oviductal biology and the impact of sex-steroid on the female reproductive tract.

Pre-hatching embryo-dependent and -independent programming of endometrial function in cattle.

The bovine pre-implantation embryo secretes bioactive molecules from early development stages, but effects on endometrial function are reported to start only after elongation. Here, we interrogated spatially defined regions of the endometrium transcriptome for responses to a day 7 embryo in vivo. We hypothesize that exposure to an embryo changes the abundance of specific transcripts in the cranial region of the pregnant uterine horn. Endometrium was collected from the uterotubal junction (UTJ), anterior (IA), medial (IM) and posterior (IP) regions of the uterine horn ipsilateral to the CL 7 days after estrus from sham-inseminated (Con) or artificially inseminated, confirmed pregnant (Preg) cows. Abundance of 86 transcripts was evaluated by qPCR using a microfluidic platform. Abundance of 12 transcripts was modulated in the Preg endometrium, including classical interferon-stimulated genes (ISG15, MX1, MX2 and OAS1Y), prostaglandin biosynthesis genes (PTGES, HPGD and AKR1C4), water channel (AQP4) and a solute transporter (SLC1A4) and this was in the UTJ and IA mainly. Additionally, for 71 transcripts, abundance varied according to region of the reproductive tract. Regulation included downregulation of genes associated with proliferation (IGF1, IGF2, IGF1R and IGF2R) and extracellular matrix remodeling (MMP14, MMP19 and MMP2) and upregulation of anti-adhesive genes (MUC1) in the cranial regions of uterine horn. Physical proximity to the embryo provides paracrine regulation of endometrial function. Embryo-independent regulation of the endometrial transcriptome may support subsequent stages of embryo development, such as elongation and implantation. We speculate that successful early embryo-dependent and -independent programming fine-tune endometrial functions that are important for maintenance of pregnancy in cattle.

Programação da receptividade uterina e fertilidade em vacas de corte / Uterine receptivity and fertility programming in beef cows

Em bovinos de corte, ocorre significativa mortalidade embrionária durante as três primeiras semanas degestação. Durante esse período, o desenvolvimento de zigoto a concepto depende exclusivamente das secreçõesovidutais e uterinas. O processo de secreção, bem como a qualidade dessas secreções são programados pelaexposição sequencial do trato reprodutivo ao estradiol (E2) durante o proestro/estro e à progesterona (P4)durante o diestro inicial. Estratégias visando a otimização da qualidade dos ambientes ovidutal e uterino para odesenvolvimento embrionário serão discutidas e incluem o gerenciamento do crescimento do folículo pré-ovulatório, a suplementação de E2 no proestro, a suplementação de P4 no diestro inicial e combinações entreelas. Ao final, discute-se a intrigante possibilidade do embrião bovino programar o funcionamento doendométrio já na primeira semana de gestação.

In beef cattle, there is significant embryonic mortality during the three initial weeks of pregnancy.During this period, the development from zygote to conceptus depends exclusively on secretions from the oviductand uterus. The process of secretion as well as the quality of such secretions are programmed by the sequentialexposure of the reproductive tract to estradiol (E2), during proestrus and estrus, and to progesterone (P4),during early diestrus. Strategies that aim to optimize the quality of the oviductal and the uterine environmentstowards embryo development are discussed. Strategies include managing growth of the pre-ovulatory follicle,E2 supplementation at proestrus, P4 supplementation during early diestrus and combinations. Last but not least,we discuss the intriguing possibility of bovine embryo programming endometrial function as early as the firstweek of gestation.

Programação da receptividade uterina e fertilidade em vacas de corte / Uterine receptivity and fertility programming in beef cows

Em bovinos de corte, ocorre significativa mortalidade embrionária durante as três primeiras semanas degestação. Durante esse período, o desenvolvimento de zigoto a concepto depende exclusivamente das secreçõesovidutais e uterinas. O processo de secreção, bem como a qualidade dessas secreções são programados pelaexposição sequencial do trato reprodutivo ao estradiol (E2) durante o proestro/estro e à progesterona (P4)durante o diestro inicial. Estratégias visando a otimização da qualidade dos ambientes ovidutal e uterino para odesenvolvimento embrionário serão discutidas e incluem o gerenciamento do crescimento do folículo pré-ovulatório, a suplementação de E2 no proestro, a suplementação de P4 no diestro inicial e combinações entreelas. Ao final, discute-se a intrigante possibilidade do embrião bovino programar o funcionamento doendométrio já na primeira semana de gestação.(AU)

In beef cattle, there is significant embryonic mortality during the three initial weeks of pregnancy.During this period, the development from zygote to conceptus depends exclusively on secretions from the oviductand uterus. The process of secretion as well as the quality of such secretions are programmed by the sequentialexposure of the reproductive tract to estradiol (E2), during proestrus and estrus, and to progesterone (P4),during early diestrus. Strategies that aim to optimize the quality of the oviductal and the uterine environmentstowards embryo development are discussed. Strategies include managing growth of the pre-ovulatory follicle,E2 supplementation at proestrus, P4 supplementation during early diestrus and combinations. Last but not least,we discuss the intriguing possibility of bovine embryo programming endometrial function as early as the firstweek of gestation.(AU)

Size of the Ovulatory Follicle Dictates Spatial Differences in the Oviductal Transcriptome in Cattle.

In cattle, molecular control of oviduct receptivity to the embryo is poorly understood. Here, we used a bovine model for receptivity based on size of the pre-ovulatory follicle to compare oviductal global and candidate gene transcript abundance on day 4 of the estrous cycle. Growth of the pre-ovulatory follicle (POF) of Nelore (Bos indicus) cows was manipulated to produce two groups: large POF large corpus luteum (CL) group (LF-LCL; greater receptivity) and small POF-small CL group (SF-SCL). Oviductal samples were collected four days after GnRH-induced ovulation. Ampulla and isthmus transcriptome was obtained by RNA-seq, regional gene expression was assessed by qPCR, and PGR and ERa protein distribution was evaluated by immunohistochemistry. There was a greater abundance of PGR and ERa in the oviduct of LF-LCL animals thus indicating a greater availability of receptors and possibly sex steroids stimulated signaling in both regions. Transcriptomic profiles indicated a series of genes associated with functional characteristics of the oviduct that are regulated by the periovulatory sex steroid milieu and that potentially affect oviductal receptivity and early embryo development. They include tissue morphology changes (extra cellular matrix remodeling), cellular changes (proliferation), and secretion changes (growth factors, ions and metal transporters), and were enriched for the genes with increased expression in the LF-LCL group. In conclusion, differences in the periovulatory sex steroid milieu lead to different oviductal gene expression profiles that could modify the oviductal environment to affect embryo survival and development.