Accumulation of eosinophils in the infundibulum of the bovine oviduct just after ovulation

Ovarian sex steroid and epithelial control of immune responses in the uterus and oviduct: human and animal models†

The female reproductive tract (FRT), including the uterus and oviduct (Fallopian tube), is responsible for maintaining an optimal microenvironment for reproductive processes, such as gamete activation and transportation, sperm capacitation, fertilization, and early embryonic and fetal development. The mucosal surface of the FRT may be exposed to pathogens and sexually transmitted microorganisms due to the opening of the cervix during mating. Pathogens and endotoxins may also reach the oviduct through the peritoneal fluid. To maintain an optimum reproductive environment while recognizing and killing pathogenic bacterial and viral agents, the oviduct and uterus should be equipped with an efficient and rigorously controlled immune system. Ovarian sex steroids can affect epithelial cells and underlying stromal cells, which have been shown to mediate innate and adaptive immune responses. This, in turn, protects against potential infections while maintaining an optimal milieu for reproductive events, highlighting the homeostatic involvement of ovarian sex steroids and reproductive epithelial cells. This article will discuss how ovarian sex steroids affect the immune reactions elicited by the epithelial cells of the non-pregnant uterus and oviduct in the bovine, murine, and human species. Finally, we propose that there are regional and species-specific differences in the immune responses in FRT.

IL1B triggers inflammatory cytokine production in bovine oviduct epithelial cells and induces neutrophil accumulation via CCL2

PROBLEM

The oviduct is essential for reproduction. We previously showed that oviduct epithelial cells (OECs) isolated from aged cows expressed higher levels of inflammatory cytokines, including interleukin (IL) 1A and IL1B. In addition, aging is associated with tissue dysfunction and cellular senescence via a senescence-associated secretory phenotype (SASP) and immune cell accumulation. We investigated whether IL1A or IL1B causes SASP production, cellular senescence, and inflammatory responses in bovine OECs.

METHOD OF STUDY

The OECs were isolated from bovine oviducts from young (mean 50.3 months) and aged cows (mean 157.0 months) and cultured.

RESULTS

Treatment with IL1A or IL1B induced SASP production (IL8, IL6, TNFA, and CCL2) and mRNA expression of cell adhesion molecules in bovine OECs, but both IL1s did not induce cellular senescence in OECs and migration of polymorphonuclear neutrophils (PMNs). Cultured medium of OECs treated with IL1s, especially IL1B, dramatically induced PMN migration. Treatment with the CCL2 inhibitor, but not IL8 or its receptor CXCR2 inhibitors, significantly reduced immune cell migration in IL1B-treated OEC-cultured medium. Treatment with IL1B increased PMN adhesion to OECs, resulting in further SASP production in OECs due to a PMN-OEC interaction.

CONCLUSION

We suggest that senescence-associated IL1s cause SASP production in bovine OECs and CCL2 induced by IL1B is essential for the migration of immune cells to OECs. Specifically, IL1B regulates PMN migration and adhesion to bovine OECs, and PMNs accelerate inflammatory cytokine production from bovine OECs via a direct interaction. These phenomena may contribute to chronic oviductal inflammation, resulting in subfertility.

Multistep analysis reveals the relationship between blood indices at the time of ovum pick-up and in vitro embryo production in heifers

The inflammatory factors of complete blood count (CBC) are associated with a decrease in the in vitro embryo production (IVP) outcome in women. The relation between the blood indices and in vitro fertilization (IVF) outcomes in bovines remains to be elucidated. Using ovum pick-up (OPU), oocytes were retrieved from heifers (n = 60) and inseminated separately with sperm. The blastocyst formation was recorded on day 7 after insemination for each animal and the blood indices were evaluated at the time of OPU. Then, heifers were classified on the basis of (1) blastocyst formation, cleaved vs. failed, or (2) inflammation, low-grade inflammation (lymphocyte counts > 5.6 × 10⁹/L) vs. no inflammation (lymphocyte counts < 5.6 × 10⁹/L). Oocytes derived from heifers with higher lymphocytes, red blood cells (RBC), platelets, hematocrit, red cell distribution width (RDW-SD) and plateletcrit values and lower monocytes, eosinophils, mean corpuscular hemoglobin (MCH) and MCH concentration (MCHC) successfully developed to the blastocyst stage. Heifers with low-grade inflammation numerically had a higher percentage of blastocyst formation than normal heifers. The principle component analysis (PCA) showed that blastocyst formation had the strongest positive association with RDW-cv and RDW-SD, while having a strong negative association with mean corpuscular volume (MCV), hemoglobin, MCHC and MCH. The PCA determined that the number of grade A COCs and the percentage of COCs reached the cleavage stage had a negative association with white blood cells (WBC), lymphocytes, basophils and monocytes, and a positive correlation with platelet to lymphocyte ratio, platelet distribution width (PDW) and plateletcrit. Network mapping detected close similarities between BFR and RDW-SD, MPV, and lymphocytes. The area under the receiver operating characteristic curve (AUC) identified that, eosinophils (AUC 0.80), RDW-SD (AUC 0.76), monocytes (AUC 0.76) and lymphocytes (AUC 0.76) had a good predictive ability to detect heifers with high OPU-IVP outcome (≥60%). In conclusion, these findings suggest that CBC indices at the time of OPU were associated with the IVF outcome and may be incorporated into protocols for the identification of heifers with high potential for blastocyst formation.

S100A8, which increases with age, induces cellular senescence-like changes in bovine oviduct epithelial cells

PROBLEM

The oviduct is an essential component in reproduction and oviduct epithelial cells (OECs) secrete various types of cytokine. However, mechanisms of aging and inflammation of OECs are unknown. We previously reported the age-dependent functional changes of bovine OECs such that aged OECs expressed higher levels of inflammatory cytokines. We selected S100A8 and S100A9 as molecules expressed more highly in aged OECs, as candidates to induce age-related changes, and investigated using bovine OECs.

METHOD OF STUDY

The OECs were isolated from bovine oviductal tissues (Aged, more than 120 months; Young, between 30 and 50 months) and cultured.

RESULTS

Aged OECs exhibited higher senescence-associated (SA)-β-gal staining (a biomarker of cellular senescence) and mRNA expression of SA-inflammatory cytokines than young OECs. Cellular senescence occurred in both young and aged OECs upon passaging the cells. Treatment with S100A8, but not S100A9, resulted in the induction of cellular senescence in bovine OECs. Both S100A8 and S100A9 stimulated the secretion of the inflammatory cytokine IL-8 from bovine OECs. S100A8-induced IL-8 secretion was dependent on receptor RAGE, AP-1 activation, and reactive oxygen species production. In addition, S100A8 reduced the content of collagen while inducing the expression of matrix metalloproteinases, suggesting the induction of dysregulation of the extracellular matrix in OECs.

CONCLUSION

We suggest that bovine OECs recognize an excessive increase in age-associated DAMPs, such as S100A8 and S100A9, and that these signals may contribute to chronic oviductal inflammation, resulting in infertility associated with oviductal dysfunction.

Understanding the hidden relations between pro- and anti-inflammatory cytokine genes in bovine oviduct epithelium using a multilayer response surface method

An understanding gene-gene interaction helps users to design the next experiments efficiently and (if applicable) to make a better decision of drugs application based on the different biological conditions of the patients. This study aimed to identify changes in the hidden relationships between pro- and anti-inflammatory cytokine genes in the bovine oviduct epithelial cells (BOECs) under various experimental conditions using a multilayer response surface method. It was noted that under physiological conditions (BOECs with sperm or sex hormones, such as ovarian sex steroids and LH), the mRNA expressions of IL10, IL1B, TNFA, TLR4, and TNFA were associated with IL1B, TNFA, TLR4, IL4, and IL10, respectively. Under pathophysiological + physiological conditions (BOECs with lipopolysaccharide + hormones, alpha-1-acid glycoprotein + hormones, zearalenone + hormones, or urea + hormones), the relationship among genes was changed. For example, the expression of IL10 and TNFA was associated with (IL1B, TNFA, or IL4) and TLR4 expression, respectively. Furthermore, under physiological conditions, the co-expression of IL10 + TNFA, TLR4 + IL4, TNFA + IL4, TNFA + IL4, or IL10 + IL1B and under pathophysiological + physiological conditions, the co-expression of IL10 + IL4, IL4 + IL10, TNFA + IL10, TNFA + TLR4, or IL10 + IL1B were associated with IL1B, TNFA, TLR4, IL10, or IL4 expression, respectively. Collectively, the relationships between pro- and anti-inflammatory cytokine genes can be changed with respect to the presence/absence of toxins, sex hormones, sperm, and co-expression of other gene pairs in BOECs, suggesting that considerable cautions are needed in interpreting the results obtained from such narrowly focused in vitro studies.

Up-regulated mRNA expression of some anti-inflammatory mediators in bovine oviduct epithelial cells by urea in vitro: Cellular pathways by Reactome analysis

Increased urea concentration is a major cause of low fertility in dairy cows fed high-protein diets. A strong correlation exists between the urea concentration in the blood and oviduct fluid of dairy cows. In this study, bovine oviduct epithelial cells (BOECs) were incubated with varying concentrations of urea (0, 20, 40, and 80 mg/dL) in the absence of ovarian sex steroids (estradiol and progesterone) and luteinizing hormone. The 80 mg/dL urea reduced the cell viability, and thus was excluded in further analysis. Compared to the control (U0), the 20 mg/dL urea (U20) increased the mRNA expression of Toll-like receptor (TLR) 4, interleukin (IL) 10, IL4, and prostaglandin (PG) E synthase (mPGES) but decreased the mRNA expression of tumor necrosis factor α (TNFA). Compared to U0, the 40 mg/dL urea (U40) decreased the mRNA expression of TNFA and increased alpha-1-acid glycoprotein (AGP). U40 also increased TLR2, IL10, and IL4 mRNA expression compared to U0. In addition, compared to U20, the U40 decreased the mRNA expression of TLR4 and IL1B but increased that of AGP and TLR2. Subsequently, the mRNA expression data were then projected into the Reactome database. The Reactome analysis showed that pathways, including cytokine signaling in the immune system (i.e., TNFs bind their physiological receptors) and death receptor signaling (i.e., TNF signaling), were down-regulated in the presence of urea compared to the U0 group. These in vitro data implied that high urea level can alter the balance between pro- and anti-inflammatory responses in BOECs, thus providing a suboptimal environment for the early reproductive events or a weakened innate immune system, predisposing the oviduct to infections.

Age-associated mRNA expression changes in bovine endometrial cells in vitro

BACKGROUND

Endometrial cells secrete various cytokines and the dysfunction of endometrial cells may directly lead to infertility. Interferon tau (IFNT) secreted by trophoblast cells, a well-known pregnancy recognition signal in ruminants, acts on the uterus to prepare for pregnancy. Aging causes cellular and organ dysfunction, and advanced maternal age is associated with reduced fertility. However, few studies have investigated age-dependent changes in the uterus.

METHODS

Using next generation sequencing and real-time PCR, we examined mRNA expression in bovine endometrial cells in vitro obtained from young (mean 45.2 months) and aged (mean 173.5 months) animals and the effects of IFNT depending on the age.

RESULTS

We showed that inflammation-related (predicted molecules are IL1A, C1Qs, DDX58, NFKB, and CCL5) and interferon-signaling (predicted molecules are IRFs, IFITs, STATs, and IFNs) pathways were activated in endometrial cells obtained from aged compared to young cows. Also, the activation of "DNA damage checkpoint regulation" and the inhibition of "mitotic mechanisms" in endometrial cells obtained from aged cows were evident. Moreover, we showed lower cell viability levels in endometrial cells obtained from aged compared to young cows. Although treatment with IFNT upregulated various types of interferon stimulated genes both in endometrial cells obtained from young and aged cows, the rate of increase by IFNT stimulus was obviously lower in endometrial cells obtained from aged compared to young cows.

CONCLUSIONS

Endometrial cells obtained from aged cows exhibited higher levels of inflammatory- and IFN-signaling, and dysfunction of cell division compared with young cows. In addition, a high basal level of IFN-related genes in endometrial cells of aged cows is suggested a concept of "inflammaging".

Palmitic acid stimulates interleukin-8 via the TLR4/NF-κB/ROS pathway and induces mitochondrial dysfunction in bovine oviduct epithelial cells

PROBLEM

We investigated the effect of palmitic acid (PA), a major saturated fatty acid in NEFA, on bovine oviduct epithelial cells (OECs) during in vitro cell culture.

METHOD OF STUDY

Bovine oviductal tissues ipsilateral to the corpus luteum were collected 1-3 days after ovulation; the OECs were isolated and cultured.

RESULTS

PA increased lipid accumulation and activated caspase-3 in OECs, resulting in decreased cell proliferation. PA also stimulated the secretion of inflammatory cytokine interleukin (IL)-8 depending on TLR4, NF-κB activation, and reactive oxygen species (ROS) production. Moreover, PA induced mitochondrial dysfunction, including mitochondrial fission, ATP production, and mitochondrial ROS production. It also increased levels of LC3 and p62 proteins, suggesting autophagy induction in OECs.

CONCLUSION

We suggest that bovine OECs recognize an excessive increase in endogenous and sterile danger signals, such as PA, which may contribute to chronic oviductal inflammation, resulting in infertility associated with oviductal dysfunction.

Age-dependent changes in inflammation and extracellular matrix in bovine oviduct epithelial cells during the post-ovulatory phase

The mammalian oviduct is an essential site for sperm storage, the transport of gametes, fertilization, and embryo development-functions that are aided by cytokines secreted from oviduct epithelial cells (OECs). Aging leads to cellular and organ dysfunction, with infertility associated with advanced maternal age. Few studies have investigated age-dependent changes in the oviduct as a possible cause of infertility, so we compared OECs from young (30-50 months) versus aged (more than 120 months) cattle. Next-generation sequencing was first used to identify age-related differences in gene expression. Several proinflammatory-related genes (including IL1B, IL1A, IL17C, IL8, S100A8, S100A9, and TNFA) were activated in OECs from aged (more than 120 months) compare to young (30-50 months) individuals, whereas genes associated with extracellular matrix-related factors (COLs, POSTN, BGN, and LUM) were down-regulation in aged OECs. Indeed, IL1 B and IL8 abundance was higher in aged OECs than in young OECs. Young OECs also tended to proliferate faster, and the revolution frequency of young, ciliated OECs was higher than that of their aged counterparts. In contrast, aged OECs possessed more F-actin, an actin cytoskeleton marker associated with reduced elasticity, and contained high levels of reactive oxygen species, which are mediators of inflammation and senescence. These different functional characteristics of bovine OECs during the post-ovulatory phase support the emerging concept of "inflammaging," that is, age-dependent inflammation. Mol. Reprod. Dev. 83: 815-826, 2016 © 2016 Wiley Periodicals, Inc.