Pleiotropy and Redundancy of STAT Proteins in Early Pregnancy

Enrichment of Cis-Acting Regulatory Elements in Differentially Methylated Regions Following Lipopolysaccharide Treatment of Bovine Endometrial Epithelial Cells

Endometritis is an inflammatory disease that negatively influences fertility and is common in milk-producing cows. An in vitro model for bovine endometrial inflammation was used to identify enrichment of cis-acting regulatory elements in differentially methylated regions (DMRs) in the genome of in vitro-cultured primary bovine endometrial epithelial cells (bEECs) before and after treatment with lipopolysaccharide (LPS) from E. coli, a key player in the development of endometritis. The enriched regulatory elements contain binding sites for transcription factors with established roles in inflammation and hypoxia including NFKB and Hif-1α. We further showed co-localization of certain enriched cis-acting regulatory motifs including ARNT, Hif-1α, and NRF1. Our results show an intriguing interplay between increased mRNA levels in LPS-treated bEECs of the mRNAs encoding the key transcription factors such as AHR, EGR2, and STAT1, whose binding sites were enriched in the DMRs. Our results demonstrate an extraordinary cis-regulatory complexity in these DMRs having binding sites for both inflammatory and hypoxia-dependent transcription factors. Obtained data using this in vitro model for bacterial-induced endometrial inflammation have provided valuable information regarding key transcription factors relevant for clinical endometritis in both cattle and humans.

USP7 promotes decidualization of ESCs by STAT3/PR axis during early pregnancy

Decidualization is an essential process for embryo implantation during early pregnancy. Defective decidualization is a critical leading cause of early pregnancy loss (EPL). Ubiquitin-specific protease 7 (USP7) is a deubiquitinating enzyme that is involved in uterine function. This study aimed to explore the underlying mechanism by which USP7 regulates decidualization in EPL. We found that USP7 was downregulated in the decidual tissue of EPL patients. Upregulation of USP7 enhanced decidualization in endometrial stromal cells (ESCs), with increased decidualized biomarkers IGFBP1 and PRL and progesterone receptor A/B (PR-A/B) expression. Moreover, we found that signal transducer and activator of transcription 3 (STAT3) is a direct target of USP7 in ESCs. USP7 bound to STAT3 by deubiquitination and increased STAT3 levels in ESCs. Suppression of STAT3 impeded the USP7-promoted cell viability, decidualization, and PR-A/B expression of ESCs. USP7 promoted the decidualization of ESCs through the STAT3/PR signaling pathway during early pregnancy, which provides new insight into the pathological mechanism of EPL and may contribute to the clinical treatment of EPL.

Research progress on the STAT signaling pathway in pregnancy and pregnancy-associated disorders

Signal transducer and activator of transcription (STAT) proteins, pivotal regulators of signaling cascades, undergo activation in response to the stimulation of cytokines and growth factors, and participate in biological processes, including inflammation, immune responses, cell proliferation, and differentiation. During the process of pregnancy, STAT signaling is involved in regulating embryonic implantation, endometrial decidualization, and establishing and maintaining maternal-fetal immune tolerance. Increasing evidence suggests that aberrant STAT signaling contributes to the occurrence and development of pregnancy disorders, including repeated implantation failure (RIF), preeclampsia (PE), recurrent spontaneous abortion (RSA), preterm birth (PTB) and gestational diabetes mellitus (GDM). Elucidating the molecular mechanisms of the STAT signaling pathway holds promise for further understanding the establishment and maintenance of normal pregnancy, and thereby providing potent targets and strategic avenues for the prevention and management of ailments associated with pregnancy. In this review, we summarized the roles of the STAT signaling pathway and its related regulatory function in embryonic implantation, endometrial decidualization, and maternal-fetal immune tolerance. In conclusion, in-depth research on the mechanism of the STAT signaling pathway not only enhances our understanding of normal pregnancy processes but also offers STAT-based therapeutic approaches to protect women from the burden of pregnancy-related disorders.

Effect of the aflatoxins B1 and M1 on bovine oocyte developmental competence and embryo morphokinetics

Aflatoxins are considered as reproductive toxins for mammalian species. Here, we studied the effect of aflatoxin B1 (AFB1) and its metabolite aflatoxin M1 (AFM1) on the development and morphokinetics of bovine embryos. Cumulus oocyte complexes (COCs) were matured with AFB1 (0.032, 0.32, 3.2, 32 µM) or AFM1 (0.015, 0.15, 1.5, 15, 60 nM), then fertilized and the putative zygotes were cultured in an incubator equipped with a time-lapse system. Exposing COCs to 32 µM AFB1 or 60 nM AFM1 reduced the cleavage rate, whereas exposing them to 3.2 or 32 µM AFB1 further reduced the blastocyst formation. A delay was recorded for the first and second cleavages in a dose-dependent manner for both AFB1- and AFM1-treated oocytes. A delay was recorded in the third cleavage in the AFM1-treated group. To explore potential mechanisms, subgroups of COCs were examined for nuclear and cytoplasmic maturation (n = 225; DAPI and FITC-PNA, respectively), and mitochondrial function was examined in a stage-dependent manner. COCs were examined for their oxygen consumption rates (n = 875; Seahorse XFp analyzer) at the end of maturation, MII-stage oocytes were examined for their mitochondrial membrane potential (n = 407; JC1), and putative zygotes were examined using a fluorescent time-lapse system (n = 279; IncuCyte). Exposing COCs to AFB1 (3.2 or 32 µM) impaired oocyte nuclear and cytoplasmic maturation and increased mitochondrial membrane potential in the putative zygotes. These alterations were associated with changes in the expression of mt-ND2 (32 µM AFB1) and STAT3 (all AFM1 concentrations) genes in the blastocyst stage, suggesting a carryover effect from the oocyte to the developing embryos.

Genomic Regions Associated with Milk Composition and Fertility Traits in Spring-Calved Dairy Cows in New Zealand

The objective of this study was to identify genomic regions and genes that are associated with the milk composition and fertility traits of spring-calved dairy cows in New Zealand. Phenotypic data from the 2014–2015 and 2021–2022 calving seasons in two Massey University dairy herds were used. We identified 73 SNPs that were significantly associated with 58 potential candidate genes for milk composition and fertility traits. Four SNPs on chromosome 14 were highly significant for both fat and protein percentages, and the associated genes were DGAT1, SLC52A2, CPSF1, and MROH1. For fertility traits, significant associations were detected for intervals from the start of mating to first service, the start of mating to conception, first service to conception, calving to first service, and 6-wk submission, 6-wk in-calf, conception to first service in the first 3 weeks of the breeding season, and not in calf and 6-wk calving rates. Gene Ontology revealed 10 candidate genes (KCNH5, HS6ST3, GLS, ENSBTAG00000051479, STAT1, STAT4, GPD2, SH3PXD2A, EVA1C, and ARMH3) that were significantly associated with fertility traits. The biological functions of these genes are related to reducing the metabolic stress of cows and increasing insulin secretion during the mating period, early embryonic development, foetal growth, and maternal lipid metabolism during the pregnancy period.

NR3C1 and glucocorticoid-regulatory genes mRNA and protein expression in the endometrium and ampulla during the bovine estrous cycle

The bovine reproductive tract exhibits changes during the estrous cycle modulated by the interplay of steroid hormones. Glucocorticoids can be detrimental when stress-induced but are relevant at baseline levels for appropriate reproductive function. Here, an analysis of quantitative real-time PCR was performed to study the bovine glucocorticoid-related baseline gene transcription in endometrial and ampullar tissue samples derived from three time points of the estrous cycle, stage I (Days 1-4), stage III (Days 11-17) and stage IV (Days 18-20). Our results revealed expression differences during stages, as expression observed in the ampulla was higher during the post-ovulatory phase (stage I), including the glucocorticoid receptor NR3C1, and some of its regulators, involved in glucocorticoid availability (HSD11B1 and HSD11B2) and transcriptional actions (FKBP4 and FKBP5). In contrast, in the endometrium, higher expression of the steroid receptors was observed during the late luteal phase (stage III), including ESR1, ESR2, PGRMC1 and PGRMC2, and HSD11B1 expression decreased, while HSD11B2 increased. Moreover, at protein level, FKBP4 was higher expressed during the late luteal phase, and NR3C1 during the pre-ovulatory phase (stage IV). These results suggest that tight regulation of the glucocorticoid activity is promoted in the ampulla, when reproductive events are taking place, including oocyte maturation. Moreover, most expression changes in the endometrium were observed during the late luteal phase, and may be related to the embryonic maternal recognition. In conclusion, the glucocorticoid regulation changes across the estrous cycle and may be playing a role on the reproductive events occurring in the bovine ampulla and endometrium.

Identification of novel candidate genes for age at first calving in Nellore cows using a SNP chip specifically developed for Bos taurus indicus cattle

The age at first calving has a great economic impact on the beef cattle system and calving at 24 months is an objective of selection for a more efficient herd. However, an age at first calving around 36 months has been observed for Nellore cattle in Brazil. Thus, a genome-wide association study (GWAS) was carried out with 8376 records of age at first calving and 3239 animals genotyped with the GGP-Indicus 35K, which has been developed specifically for Bos taurus indicus. The weighted single-step genomic best linear unbiased prediction method was used, with adjacent SNPs (single nucleotide polymorphisms) in genomic windows of 1.0 Mb. After quality control, 3239 (2161 males and 1078 females) animals genotyped for 30,519 SNPs were used in GWAS analysis. The average and standard deviation of age at first calving were 1041.7 and 140.6 days, respectively. The heritability estimate was 0.10 ± 0.02. The GWAS analysis found seven genomic regions in BTA1, 2, 5, 12, 18, 21, and 24, which explained a total of 11.24% of the additive genetic variance of age at first calving. In these regions were found 62 protein coding genes, and the genes HSD17B2, SERPINA14, SERPINA1, SERPINA5, STAT1, NFATC1, ATP9B, CTDP1, THPO, ECE2, PSMD2, EIF4G1, EIF2B2, DVL3, POLR2H, TMTC2, and GPC6 are possible candidates for age at first birth due their function. Moreover, two molecular functions ("serine-type endopeptidase inhibitor activity" and "negative regulation of endopeptidase activity") were significant, which depend on several serpin genes. The use of a SNP chip developed especially for Bos taurus indicus allowed to find genomic regions for age at first calving, which are close to QTLs previously reported for other reproduction-related traits. Future studies can reveal the causal variants and their effects on reproductive precocity of Nellore cows.

Maternal recognition of pregnancy in the mare: does it exist and why do we care?

Maternal recognition of pregnancy (MRP) is a process by which an early conceptus signals its presence to the maternal system and prevents the lysis of the corpus luteum, thus ensuring a maternal milieu supportive of pregnancy continuation. It is a fundamental aspect of reproductive biology, yet in the horse, the mechanism underlying MRP remains unknown. This review seeks to address some of the controversies surrounding the evidence and theories of MRP in the equine species, such as the idea that the horse does not conform to the MRP paradigm established in other species or that equine MRP involves a mechanical, rather than chemical, signal. The review examines the challenges of studying this particularly clandestine phenomenon along with the new tools in scientific research that will drive this quest forward in coming years, and discusses the value of knowledge gleaned along this path in the context of clinical applications for improving breeding outcomes in the horse industry.

Natural Mating Differentially Triggers Expression of Glucocorticoid Receptor (NR3C1)-Related Genes in the Preovulatory Porcine Female Reproductive Tract

Mating initiates dynamic modifications of gene transcription in the female reproductive tract, preparing the female for fertilization and pregnancy. Glucocorticoid signaling is essential for the homeostasis of mammalian physiological functions. This complex glucocorticoid regulation is mediated through the glucocorticoid receptor, also known as nuclear receptor subfamily 3 group C member 1 (NR3C1/GR) and related genes, like 11β-hydroxysteroid dehydrogenases (HSD11Bs) and the FK506-binding immunophilins, FKBP5 and FKBP4. This study tested the transcriptome changes in NR3C1/GR regulation in response to natural mating and/or cervical deposition of the sperm-peak ejaculate fraction collected using the gloved-hand method (semen or only its seminal plasma), in the preovulatory pig reproductive tract (cervix to infundibulum, 24 h after mating/insemination/infusion treatments). Porcine cDNA microarrays revealed 22 NR3C1-related transcripts, and changes in gene expression were triggered by all treatments, with natural mating showing the largest differences, including NR3C1, FKBP5, FKBP4, hydroxysteroid 11-beta dehydrogenase 1 and 2 (HSD11B1, HSD11B2), and the signal transducer and activator of transcription 5A (STAT5A). Our data suggest that natural mating induces expression changes that might promote a reduction of the cortisol action in the oviductal sperm reservoir. Together with the STAT-mediated downregulation of cytokine immune actions, this reduction may prevent harmful effects by promoting tolerance towards the spermatozoa stored in the oviduct and perhaps elicit spermatozoa activation and detachment after ovulation.

The Interaction of lncRNA XLOC-2222497, AKR1C1, and Progesterone in Porcine Endometrium and Pregnancy

The endometrium is an important tissue for pregnancy and plays an important role in reproduction. In this study, high-throughput transcriptome sequencing was performed in endometrium samples of Meishan and Yorkshire pigs on days 18 and 32 of pregnancy. Aldo-keto reductase family 1 member C1 (AKR1C1) was found to be a differentially expressed gene, and was identified by quantitative real-time PCR (qRT-PCR) and Western blot. Immunohistochemistry results revealed the cellular localization of the AKR1C1 protein in the endometrium. Luciferase activity assay demonstrated that the AKR1C1 core promoter region was located in the region from -706 to -564, containing two nuclear factor erythroid 2-related factor 2 (NRF2) binding sites (antioxidant response elements, AREs). XLOC-2222497 was identified as a nuclear long non-coding RNA (lncRNA) highly expressed in the endometrium. XLOC-2222497 overexpression and knockdown have an effect on the expression of AKR1C1. Endocrinologic measurement showed the difference in progesterone levels between Meishan and Yorkshire pigs. Progesterone treatment upregulated AKR1C1 and XLOC-2222497 expression in porcine endometrial epithelial cells. In conclusion, transcriptome analysis revealed differentially expressed transcripts during the early pregnancy process. Further experiments demonstrated the interaction of XLOC-2222497/AKR1C1/progesterone in the endometrium and provided new potential targets for pregnancy maintenance and its control.

Differential gene expression in bovine endometrial epithelial cells after challenge with LPS; specific implications for genes involved in embryo maternal interactions

Lipopolysaccharide (LPS) expressed on the surface of Gram-negative bacteria activates pro-inflammatory pathways, dys-regulates the function of endometrial cells and is a key player in the mechanisms involved in endometritis. This study aimed to investigate the effects of LPS on bovine endometrial epithelial cells (bEEC) from whole transcriptome with a special focus on genes involved in embryo-maternal interactions. Following in vitro culture, bEEC from three cows were exposed to 0, 2, and 8 μg/mL LPS for 24h. RNA samples extracted at 0 and 24 hours were analyzed by RNA sequencing (RNA-seq). At 24h, 2035 differentially expressed genes (DEGs) were identified between controls and samples treated with 2 μg/mL LPS. Gene ontology analysis showed that over-expressed DEGs were associated to immune response, response to stress and external stimuli, catalytic activity, and cell cycle. Genes associated with cell membrane and cell adhesion pathways were under-expressed. LPS induced changes in expression of specific genes related to embryo-maternal interactions including under-expression of eight members of the cadherin superfamily, over-expression of six members of the mucin family, and differential expression of a large set of genes binding the above molecules and of more than 20 transcripts coding for cytokines and their receptors. Type I interferon-τ dependent genes were also over-expressed. From a sub-set of 19 genes, (biological replicates of bEEC from cows taken at time 6 (n = 3), 24 (n = 6) and 48 hours (n = 3), and 2 technical replicates per sample) differential gene expression was confirmed by RT²-qPCR (r² between fold changes at 24 hours by RT²-qPCR and RNA-seq = 0.97). These results indicate that LPS affects the function of bEEC in many ways by differential transcription, glycolytic metabolism and oxidative stress. Many transcriptomic signatures related to implantation and embryo maternal interactions were strongly affected by LPS. These results pave the way for further studies to investigate the duration of these changes and their possible impact on endometrial function and fertility.

Different co-culture systems have the same impact on bovine embryo transcriptome

During the last few years, several co-culture systems using either BOEC or VERO feeder cells have been developed to improve bovine embryo development and these systems give better results at high oxygen concentration (20%). In parallel, the SOF medium, used at 5% O2, has been developed to mimic the oviduct fluid. Since 2010s, the SOF medium has become popular in improving bovine embryo development and authors have started to associate this medium to co-culture systems. Nevertheless, little is known about the putative benefit of this association on early development. To address this question, we have compared embryo transcriptomes in four different culture conditions: SOF with BOEC or VERO at 20% O2, and SOF without feeders at 5% or 20% O2. Embryos have been analyzed at 16-cell and blastocyst stages. Co-culture systems did not improve the developmental rate when compared to 5% O2. Direct comparison of the two co-culture systems failed to highlight major differences in embryo transcriptome at both developmental stages. Both feeder cell types appear to regulate the same cytokines and growth factors pathways, and thus to influence embryo physiology in the same way. In blastocysts, when compared to culture in SOF at 5% O2, BOEC or VERO seems to reduce cell survival and differentiation by, at least, negatively regulating STAT3 and STAT5 pathways. Collectively, in SOF medium both blastocysts rate and embryo transcriptome suggest no influence of feeder origin on bovine early development and no beneficial impact of co-culture systems when compared to 5% O2.

Diverse endometrial mRNA signatures during the window of implantation in patients with repeated implantation failure

High endometrial receptivity in the window of implantation (WOI) is essential for successful implantation. However, a diagnostic tool with high specificity for impaired endometrial receptivity remains to be developed. We collected endometrium specimens during the WOI from patients with RIF and women who conceived after one IVF/ICSI attempt. We conducted mRNA microarray on the samples followed by relevant comparative and functional analysis. Microarray analysis revealed 357 dysregulated mRNAs between the two groups. The majority of these mRNAs were found to encode membrane proteins by Gene Ontology (GO) analysis. The major functional biological pathways associated with the down-regulated mRNAs were cytokine-cytokine receptor interaction, the p53 signalling pathway and the complement and coagulation cascades. Up-regulated mRNAs were found mainly to participate in pathways such as PPAR signalling, hematopoietic cell lineage, phosphatidylinositol signalling system, ECM-receptor interaction and notch signalling. AQP3, DPP4 and TIMP3 whose expression patterns were down-regulated in RIF patients both by microarray and real-time PCR had a high correspondence with previous studies demonstrating that these genes may contribute to the defects in endometrial receptivity in RIF patients. Overall, these RIF-associated mRNAs may help devise new diagnostic tools for endometrial receptivity.

Analysis of STAT1 expression and biological activity reveals interferon-tau-dependent STAT1-regulated SOCS genes in the bovine endometrium

Signal transducer and activator of transcription (STAT) proteins are critical for the regulation of numerous biological processes. In cattle, microarray analyses identified STAT1 as a differentially expressed gene in the endometrium during the peri-implantation period. To gain new insights about STAT1 during the oestrous cycle and early pregnancy, we investigated STAT1 transcript and protein expression, as well as its biological activity in bovine tissue and cells of endometrial origin. Pregnancy increased STAT1 expression on Day 16, and protein and phosphorylation levels on Day 20. In cyclic and pregnant females, STAT1 was located in endometrial cells but not in the luminal epithelium at Day 20 of pregnancy. The expression of STAT1 during the oestrous cycle was not affected by progesterone supplementation. In vivo and in vitro, interferon-tau (IFNT) stimulated STAT1 mRNA expression, protein tyrosine phosphorylation and nuclear translocation. Using chromatin immunoprecipitation in IFNT-stimulated endometrial cells, we demonstrated an increase of STAT1 binding on interferon regulatory factor 1 (IRF1), cytokine-inducible SH2-containing protein (CISH), suppressor of cytokine signaling 1 and 3 (SOCS1, SOCS3) gene promoters consistent with the induction of their transcripts. Our data provide novel molecular insights into the biological functions of STAT1 in the various cells composing the endometrium during maternal pregnancy recognition and implantation.

Transcriptomic analysis of the myometrium during peri-implantation period and luteolysis--the study on the pig model

In pigs, implantation begins with the attachment of embryos to the endometrium. As the process is regulated by the expression of numerous genes, endometrial transcriptomic profiles have been extensively studied in early gravid pigs. However, the myometrium, a secretory tissue, should not be neglected, as it can also participate in the regulation of implantation in early pregnant pigs. To clarify this issue, the transcriptomic profile of the porcine myometrium during the peri-implantation period (i.e. on days 15 to 16 of pregnancy) was compared with the profile observed during luteolysis (i.e. on days 15 to 16 of the oestrous cycle) with an Agilent’s Porcine (V2) Two-Colour Gene Expression Microarray 4 × 44 (Agilent, USA). Analysis of the microarray data revealed that of 526 unique, accurately annotated genes, the expression of 271 unique genes was upregulated, while the expression of 255 genes was downregulated in pregnant versus cyclic myometrium. The in-depth data analysis revealed differential expression of genes encoding for factors involved in immunomodulation, tissue growth and differentiation, and prostaglandin and steroid biosynthesis and action. Moreover, the comparison of the obtained data on the myometrial transcriptome with our previously published results on the endometrial transcriptome allowed us to determine substantial differences in the regulatory function of both tissues. The new insights into the function of the myometrium of early pregnant pigs obtained here are in agreement with our previous results that suggest that this tissue plays an important role in providing optimal conditions for developing embryos. Therefore, the importance of the myometrium as an active embryo signal-responsive tissue during early pregnancy cannot be underestimated.

SOCS genes expression during physiological and perturbed implantation in bovine endometrium

In mammals, suppressor of cytokine signalling (CISH, SOCS1 to SOCS7) factors control signalling pathways involved in the regulation of numerous physiological processes including pregnancy. In order to gain new insights into the biological functions of SOCS in the endometrium, a comprehensive analysis of SOCS gene expression was carried out in bovine caruncular (CAR) and intercaruncular (ICAR) tissues collected i) during the oestrous cycle, ii) at the time of maternal recognition of pregnancy and at implantation in inseminated females, iii) following uterine interferon-tau (IFNT) infusion at day 14 post-oestrus, iv) following a period of controlled intravaginal progesterone release and v) following transfer of embryos by somatic-cell nuclear transfer (SCNT). The regulatory effects of IFNT on in vitro cultured epithelial and stromal cells were also examined. Altogether, our data showed that CISH, SOCS4, SOCS5 and SOCS7 mRNA levels were poorly affected during luteolysis and pregnancy. In contrast, SOCS1, SOCS2, SOCS3 and SOCS6 mRNA levels were strongly up-regulated at implantation (day 20 of pregnancy). Experimental in vitro and in vivo models demonstrated that only CISH, SOCS1, SOCS2 and SOCS3 were IFNT-induced genes. Immunohistochemistry showed an intense SOCS3 and SOCS6 staining in the nucleus of luminal and glandular epithelium and of stromal cells of pregnant endometrium. Finally, SOCS3 expression was significantly increased in SCNT pregnancies in keeping with the altered immune function previously reported in this model of compromised implantation. Collectively, our data suggest that spatio-temporal changes in endometrial SOCS gene expression reflect the acquisition of receptivity, maternal recognition of pregnancy and implantation.

Intranuclear crosstalk between extracellular regulated kinase1/2 and signal transducer and activator of transcription 3 regulates JEG-3 choriocarcinoma cell invasion and proliferation

Invasiveness of trophoblast and choriocarcinoma cells is in part mediated via leukemia inhibitory factor- (LIF-) induced activation of signal transducer and activator of transcription 3 (STAT3). The regulation of STAT3 phosphorylation at its ser727 binding site, possible crosstalk with intracellular MAPK signaling, and their functional implications are the object of the present investigation. JEG-3 choriocarcinoma cells were cultured in presence/absence of LIF and the specific ERK1/2 inhibitor (U0126). Phosphorylation of signaling molecules (p-STAT3 (ser727 and tyr705) and p-ERK1/2 (thr 202/tyr 204)) was assessed per Western blot. Immunocytochemistry confirmed results, but also pinpointed the location of phosphorylated signaling molecules. STAT3 DNA-binding capacity was studied with a colorimetric ELISA-based assay. Cell viability and invasion capability were assessed by MTS and Matrigel assays. Our results demonstrate that LIF-induced phosphorylation of STAT3 (tyr705 and ser727) is significantly increased after blocking ERK1/2. STAT3 DNA-binding capacity and cell invasiveness are enhanced after LIF stimulation and ERK1/2 blockage. In contrast, proliferation is enhanced by LIF but reduced after ERK1/2 inhibition. The findings herein show that blocking ERK1/2 increases LIF-induced STAT3 phosphorylation and STAT3 DNA-binding capacity by an intranuclear crosstalk, which leads to enhanced invasiveness and reduced proliferation.

Understanding the link between the IL-6 cytokine family and pregnancy: implications for future therapeutics

Cytokines are involved in almost all processes during the menstrual cycle, the fertilization period and pregnancy. They are expressed in numerous reproduction-related body fluids and tissues. Disorders of cytokine expression patterns may cause pregnancy pathologies. Therefore, cytokines have the potential as new biomarkers in different body compartments for a variety of such pathologies. Furthermore, cytokines may also serve to treat fertility and pregnancy disorders. The IL-6-like family of cytokines is an intensively investigated group of cytokines with well-accepted functions in fertility and pregnancy. This article summarizes current knowledge on IL-6-like cytokines in regard of their role in reproduction and their potential for new strategies in the treatment of reproductive pathologies.

Effects of signal transducer and activator of transcription (STAT) genes STAT1 and STAT3 genotypic combinations on fertilization and embryonic survival rates in Holstein cattle

Infertility is a major cause of dairy cow culling and economic loss. Signal transducer and activator of transcription (STAT) proteins are transcription factors that play an important role in fertility and early embryonic development, among many other functions. Previous studies have reported the association of several genes from the JAK/STAT signaling pathway with fertility traits in cattle. The STAT1 and STAT3 genes are members of this pathway and are known to interact with each other by forming a heterodimer complex that enters the nucleus and controls expression of specific genes. Thus, the objective of this study was to investigate the effects of the interactions between polymorphisms in these genes on fertilization and early embryonic survival rates using an in vitro fertilization system. A total of 7,519 oocytes, collected from 445 ovaries, were exposed to sperm and a total of 5,075 embryos were produced. Fertilization rate was calculated as the number of cleaved embryos at 48 h post-fertilization out of the total number of oocytes exposed to sperm. Early embryonic survival rate of embryos was calculated as the number of blastocysts on d 7 of development out of the total number of embryos cultured. Effects of ovary genotypes on fertilization and early embryonic survival rates were evaluated. Single-SNP analysis revealed a statistically significant association between SNP25402 in STAT3 and fertilization rate. Oocytes produced from ovaries with AA genotype showed a 0.701 fertilization rate versus 0.666 and 0.663 for oocytes produced from AC and CC ovaries, respectively. The interaction between STAT3 SNP (SNP19069/SNP25402) was highly significant for survival rate but not for fertilization rate. Also, the interaction between STAT1 SNP and SNP19069 was highly significant for survival rate. Genotype combinations found to promote fertilization and embryonic survival could be incorporated into breeding programs aimed at improving fertility performance in dairy cattle.