Contents Endometrosis is a degenerative chronic process, characterized by paramount fibrosis development in mare endometrium. This condition is one of the major causes of subfertility/infertility in mares. As in other organs, fibrosis might be a pathologic sequel of many chronic inflammatory diseases. However, aetiology and physiopathologic mechanisms involved in endometrial fibrosis are still controversial. This review presents new hypotheses based on our newest data. As the first line of innate immune defence, systemic neutrophils arrive in the uterus at mating or in the presence of pathogens. A novel paradigm is that neutrophils cast out their DNA in response to infectious stimuli and form neutrophil extracellular traps (NETs). We have shown that bacterial strains of Streptococcus zooepidemicus, Escherichia coli or Staphylococcus capitis, known to cause endometritis in mares were able to induce NETs release in vitro by equine PMN to different extents. An intriguing dilemma is the dual action of NETs. While NETs play a desirable role fighting micro‐organisms in mare uterus, they may also contribute to endometrial fibrosis. A long‐term in vitro exposure of mare endometrium explants to NETs components (myeloperoxidase, elastase and cathepsin G) up‐regulated fibrosis markers TGFβ and Tissue inhibitor of metalloproteinase (TIMP‐1). Also, pro‐fibrotic cytokines regulated collagen deposition and fibrosis. Changes in expression of connective tissue growth factor (CTGF), interleukins (IL)1‐α, IL‐1β, IL‐6 and receptors in endometrium with different degrees of fibrosis and/or inflammation were observed. A putative role of CTGF, IL and NETs components in endometrosis development should be considered. Additionally, we speculate that in sustained endometritis in mares, prostaglandins may not only cause early luteolysis or early pregnancy loss, but may also be related to endometrial fibrosis pathogenesis by stimulating collagen deposition.

BackgroundUntil recently, the corpus luteum (CL) was considered to be the main source of progesterone (P4) during pregnancy in the domestic cat (Felis catus). However, other possible sources of P4 have not been ruled out. Although feline placental homogenates were found to be capable of synthesizing P4, expression of the respective steroidogenic enzymes has not been investigated at the molecular level. Therefore, in the present study, expression of the two major factors involved in the synthesis of P4 - 3beta-hydroxysteroid dehydrogenase (3betaHSD) and steroidogenic acute regulatory protein (StAR) - was investigated in the feline CL and placenta during the course of pseudopregnancy and pregnancy.MethodsThe mRNA levels of StAR and 3betaHSD were determined using Real Time PCR and their localizations were determined by immunohistochemistry. Placental P4 concentrations, after ethyl extraction, were measured by EIA.ResultsLuteal 3betaHSD and StAR mRNA levels were strongly time-dependent, peaking during mid-pregnancy. The placental 3betaHSD mRNA level was significantly upregulated towards the end of pregnancy. In the CL, 3betaHSD and StAR protein were localized in the luteal cells whereas in the placenta they were localized to the maternal decidual cells. Placental P4 concentrations were low in early pregnant queens, but increased along with gestational age.ConclusionsThese results confirm that the placenta is an additional source of P4 in pregnant queens and can thereby be considered as an important endocrine organ supporting feline pregnancy.

The human endometrium is a fertility-determining tissue and a target of steroid hormones' action. Endocrine disruptors (EDs) can exert adverse effects on the physiological function of the decidua at the maternal-fetal interface. We examined the potential effects of an ED, bisphenol A (BPA), on endometrial maturation/decidualization, receptivity, and secretion of decidual factors (biomarkers). In vitro decidualized, endometrial stromal cells from six hysterectomy specimens were treated with 1 pM-1 mM of BPA, for 24 h and assessed for cell viability and proliferation. Three non-toxic concentrations of BPA (1 mM, 1 nM, and 1 pM) were selected to study its influence on secretion of cell decidualization biomarkers (IGF-binding protein and decidual prolactin (dPRL)), macrophage migration inhibitory factor (MIF) secretion, and hormone receptors' expression (estrogen receptors (ERa and ERb); progesterone receptors (PRA and PRB); and human chorionic gonadotropin (hCG)/LH receptor (LH-R)). The results showed a decrease in cell viability (P!0.001) in response to BPA at the level of 1 mM. At the non-toxic concentrations used, BPA perturbed the expression of ERa, ERb, PRA, PRB, and hCG/LH-R (P!0.05). Furthermore, 1 mM of BPA reduced the mRNA transcription of dPRL (P!0.05). Secretion of MIF was stimulated by all BPA treatments, the lowest concentration (1 pM) being the most effective (P!0.001). The multi-targeted disruption of BPA on decidual cells, at concentrations commonly detected in the human population, raises great concern about the possible consequences of exposure to BPA on the function of decidua and thus its potential deleterious effect on pregnancy.Reproduction (2015) 150 115-125

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The aim of the study was to characterize endometrial mRNA transcription, immunolocalization, and protein expression of interleukin (IL) 1alpha, IL1beta, IL6, and IL1RI, IL1RII, and IL6Ralpha/beta in the course of endometrosis during the estrous cycle. Additionally, the influence of IL1alpha, IL1beta, and IL6 on prostaglandin (PG) secretion and PG synthase mRNA transcription in endometrial tissue during endometrosis was investigated. The endometrial samples were obtained at the early (n = 12), mid- (n = 12), and late (n = 12) luteal phases and at the follicular (n = 12) phase of the estrous cycle. Within each of these phases, there were four samples within each category I, II, and III of endometrium, according to the Kenney classification. In experiment 1, transcription of IL1alpha, IL1beta, IL6, and their receptor's (IL1RI, IL1RII, and IL6Ralpha/beta) mRNAs and their immunolocalization and protein expression were determined using real-time PCR and immunohistochemistry, respectively. In Experiment 2, endometrial samples (n = 5 samples within categories I, II, and III) were obtained for tissue culture in the midluteal phase of the estrous cycle. The endometrial tissues were stimulated with IL1alpha (10 ng/ml), IL1beta (10 ng/ml), IL6 (10 ng/ml), and oxytocin (positive control; 10⁻⁷ M) for 24 h. The PG concentration was determined using ELISA. In addition, transcription of PTGS-2, PGES, and PGFS mRNAs was determined using real-time PCR. ILs were found to regulate PG secretion via modulation of PG synthases in equine endometrium. The alterations in IL and the expression of their receptors, and in endometrial secretory functions, were observed during the course of endometrosis, and suggest serious changes in the endometrial microenvironment. The described disturbances may be closely related to impaired endometrial processes responsible for the subfertility or the infertility in endometrosis.

A proper fetomaternal immune-endocrine cross-talk in pregnancy is fundamental for reproductive success. This might be unbalanced by exposure to environmental chemicals, such as bisphenol A (BPA). As fetoplacental contamination with BPA originates from the maternal compartment, this study investigated the role of the endometrium in BPA effects on the placenta. To this end, in vitro decidualized stromal cells were exposed to BPA 1 nM, and their conditioned medium (diluted 1 : 2) was used on chorionic villous explants from human placenta. Parallel cultures of placental explants were directly exposed to 0.5 nM BPA while, control cultures were exposed to the vehicle (EtOH 0.1%). After 24–48 h, culture medium from BPA-treated and control cultures was assayed for concentration of hormone human Chorionic Gonadotropin (β-hCG) and cytokine Macrophage Migration Inhibitory Factor (MIF). The results showed that direct exposure to BPA stimulated the release of both MIF and β-hCG. These effects were abolished/diminished in placental cultures exposed to endometrial cell-conditioned medium. GM-MS analysis revealed that endometrial cells retain BPA, thus reducing the availability of this chemical for the placenta. The data obtained highlight the importance of in vitro models including the maternal component in reproducing the effects of environmental chemicals on human fetus/placenta.

Regulation of immune-endocrine interactions in the equine endometrium is not fully understood. The aims of the present study were to: (1) investigate the presence of tumour necrosis factor alpha (TNF), interferon gamma (IFNG), Fas ligand (FASLG) and their receptors in the mare endometrium throughout the oestrous cycle; and (2) assess endometrial secretory function (prostaglandins), angiogenic activity and cell viability in response to TNF, oestradiol (E2), progesterone (P4) and oxytocin (OXT). Transcription of TNF and FASLG mRNA increased during the early and late luteal phase (LP), whereas IFNG mRNA increased in late LP. Transcription of the mRNA of both TNF receptors was highest in the mid-LP. All cytokines and receptors were expressed in surface and glandular epithelium, as well as in the stroma. Expression of TNF and its receptor TNFRSF1A increased during the follicular phase (FP) and mid-LP. IFNG was expressed in the mid-LP, whereas its receptor IFNR1 was expressed in the in mid- and late LP. The highest expression of FASLG and FAS occurred during the late LP. OXT increased the secretion of prostaglandin (PG) E2 and PGF2α in the FP and mid-LP. In the mid-LP, E2 and P4+E2 stimulated PGF2α secretion, whereas TNF and P4 increased cell viability. All treatments, with the exception of P4, increased nitric oxide and angiogenic activity in both phases. The coordinated action of cytokines and ovarian hormones may regulate secretory, angiogenic and proliferative functions in the equine endometrium.

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