Neutrophils, monocytes and other immune components in the equine endometrium: Friends or foes?

Bacterial endometritis-induced changes in the endometrial proteome in mares: Potential uterine biomarker for bacterial endometritis

Equine endometritis is one of the main causes of subfertility in the mare. Unraveling the molecular mechanisms involved in this condition and pinpointing proteins with biomarker potential could be crucial in both diagnosing and treating this condition. This study aimed to identify the endometritis-induced changes in the endometrial proteome in mares and to elucidate potential biological processes in which these proteins may be involved. Secondly, biomarkers related to bacterial endometritis (BE) in mares were identified. Uterine lavage fluid samples were collected from 28 mares (14 healthy: negative cytology and culture, and no clinical signs and 14 mares with endometritis: positive cytology and culture, in addition to clinical signs). Proteomic analysis was performed with a UHPLC-MS/MS system and bioinformatic analysis was carried out using Qlucore Omics Explorer. Gene Ontology enrichment and pathway analysis (PANTHER and KEGG) of the uterine proteome were performed to identify active biological pathways in enriched proteins from each group. Quantitative analysis revealed 38 proteins differentially abundant in endometritis mares when compared to healthy mares (fold changes >4.25, and q-value = 0.002). The proteins upregulated in the secretome of mares with BE were involved in biological processes related to the generation of energy and REDOX regulation and to the defense response to bacterium. A total of 24 biomarkers for BE were identified using the biomarker workbench algorithm. Some of the proteins identified were related to the innate immune system such as isoforms of histones H2A and H2B involvement in neutrophil extracellular trap (NET) formation, complement C3a, or gelsolin and profilin, two actin-binding proteins which are essential for dynamic remodeling of the actin cytoskeleton during cell migration. The other group of biomarkers were three known antimicrobial peptides (lysosome, equine cathelicidin 2 and myeloperoxidase (MPO)) and two uncharacterized proteins with a high homology with cathelicidin families. Findings in this study provide the first evidence that innate immune cells in the equine endometrium undergo reprogramming of metabolic pathways similar to the Warburg effect during activation. In addition, biomarkers of BE in uterine fluid of mares including the new proteins identified, as well as other antimicrobial peptides already known, offer future lines of research for alternative treatments to antibiotics.

The disordered extracellular matrix landscape induced endometrial fibrosis of sheep: A multi-omics integrative analysis

Endometrial fibrosis leads to the destruction of endometrial function and affects reproductive performance. However, mechanisms underlying the development of endometrial fibrosis in sheep remain unclear. We use transcriptomic, proteomic, and metabolomic studies to reveal the formation mechanisms of endometrial fibrosis. The results showed that the fibrotic endometrial tissue phenotype presented fewer glands, accompanied by collagen deposition. Transcriptomic results indicated alterations in genes associated with the synthesis and degradation of extracellular matrix components, which alter metabolite homeostasis, especially in glycerophospholipid metabolism. Moreover, differentially expressed metabolites may play regulatory roles in key metabolic processes during fibrogenesis, including protein digestion and absorption, and amino acid synthesis. Affected by the aberrant genes, protein levels related to the extracellular matrix components were altered. In addition, based on Kyoto Encyclopedia of Genes and Genomes analysis of differentially expressed genes, metabolites and proteins, amino acid biosynthesis, glutathione, glycerophospholipid, arginine and proline metabolism, and cell adhesion are closely associated with fibrogenesis. Finally, we analyzed the dynamic changes in serum differential metabolites at different time points during fibrosis. Taken together, fibrosis development is related to metabolic obstacles in extracellular matrix synthesis and degradation triggered by disturbed gene and protein levels.

The Role of NF-κB in Endometrial Diseases in Humans and Animals: A Review

The expression of genes of various proinflammatory chemokines and cytokines is controlled, among others, by the signaling pathway of the nuclear factor kappaB (NF-κB) superfamily of proteins, providing an impact on immune system functioning. The present review addresses the influence and role of the NF-κB pathway in the development and progression of most vital endometrial diseases in human and animal species. Immune modulation by NF-κB in endometritis, endometrosis, endometriosis, and carcinoma results in changes in cell migration, proliferation, and inflammation intensity in both the stroma and epithelium. In endometrial cells, the NF-κB signaling pathway may be activated by multiple stimuli, such as bacterial parts, cytokines, or hormones binding to specific receptors. The dysregulation of the immune system in response to NF-κB involves aberrant production of chemokines and cytokines, which plays a role in endometritis, endometriosis, endometrosis, and endometrial carcinoma. However, estrogen and progesterone influence on the reproductive tract always plays a major role in its regulation. Thus, sex hormones cannot be overlooked in endometrial disease physiopathology. While immune system dysregulation seems to be NF-κB-dependent, the hormone-independent and hormone-dependent regulation of NF-κB signaling in the endometrium should be considered in future studies. Future goals in this research should be a step up into clinical trials with compounds affecting NF-κB as treatment for endometrial diseases.

Neutrophil Extracellular Traps Mediate Bovine Endometrial Epithelial Cell Pyroptosis in Dairy Cows with Endometritis

Neutrophils are involved in the development of endometritis, but it remains unknown how neutrophils induce inflammation and tissue damage. Neutrophil extracellular traps (NETs) clear invading pathogens during infection but induce pyroptosis, leading to inflammation and tissue damage. Thus, our objective was to investigate whether NETs participate in bovine endometrial epithelial cell (BEEC) pyroptosis during endometritis. To confirm this, NETs and caspase-1/4; apoptosis-associated speck-like protein containing a caspase-recruitment domain(ASC); nod-like receptor protein-3 (NLRP3); and gasdermin D N-terminal (GSDMD-N), TNF-a, IL-1β, IL-6, and IL-18 in endometrial tissue were detected. Pathological section and vaginal discharge smears were performed to visually determine endometritis in the uterus. BEECs were stimulated with NETs to induce pyroptosis, which was treated with DNase I against pyroptosis. Caspase-1/4, ASC, NLRP3, GSDMD-N, TNF-a, IL-1β, IL-6, and IL-18 in BEECs were analyzed in endometrial tissue. The results showed that NET formation, as well as pyroptosis-related proteins and proinflammatory, cytokines were elevated in the endometrial tissue of cows with endometritis. Pathological sections and vaginal discharge smears showed increased neutrophils and plasma cells in the uterus, as well as tissue congestion. In BEECs, NETs increased the level of pyroptosis-related proteins and proinflammatory cytokines and were diminished by DNase I. In summary NETs participate BEEC pyroptosis during endometritis in dairy cows.

Molecular Mechanism of Equine Endometrosis: The NF-κB-Dependent Pathway Underlies the Ovarian Steroid Receptors’ Dysfunction

Endometrosis is a frequently occurring disease decreasing mares’ fertility. Thus, it is an important disease of the endometrium associated with epithelial and stromal cell alterations, endometrium gland degeneration and periglandular fibrosis. Multiple degenerative changes are found in uterine mucosa, the endometrium. However, their pathogenesis is not well known. It is thought that nuclear factor-κB (NF-κB), a cell metabolism regulator, and its activation pathways take part in it. The transcription of the profibrotic pathway genes of the NF-κB in fibrotic endometria differed between the follicular (FLP) and mid-luteal (MLP) phases of the estrous cycle, as well as with fibrosis progression. This study aimed to investigate the transcription of genes of estrogen (ESR1, ESR2) and progesterone receptors (PGR) in equine endometria to find relationships between the endocrine environment, NF-κB-pathway, and fibrosis. Endometrial samples (n = 100), collected in FLP or MLP, were classified histologically, and examined using quantitative PCR. The phase of the cycle was determined through the evaluation of ovarian structures and hormone levels (estradiol, progesterone) in serum. The transcription of ESR1, ESR2, and PGR decreased with the severity of endometrial fibrosis and degeneration of the endometrium. Moreover, differences in the transcription of ESR1, ESR2, and PGR were noted between FLP and MLP in the specific categories and histopathological type of equine endometrosis. In FLP and MLP, specific moderate and strong correlations between ESR1, ESR2, PGR and genes of the NF-κB pathway were evidenced. The transcription of endometrial steroid receptors can be subjected to dysregulation with the degree of equine endometrosis, especially in both destructive types of endometrosis, and mediated by the canonical NF-κB pathway depending on the estrous cycle phase.

Evolution of the Concepts of Endometrosis, Post Breeding Endometritis, and Susceptibility of Mares

In this paper, the evolution of our understanding about post breeding endometritis (PBE), the susceptibility of mares, and events leading to endometrosis are reviewed. When sperm arrive in the uterus, pro-inflammatory cytokines and chemokines are released. They attract neutrophils and induce modulatory cytokines which control inflammation. In susceptible mares, this physiological defense can be prolonged since the pattern of cytokine release differs from that of resistant mares being delayed and weaker for anti-inflammatory cytokines. Delayed uterine clearance due to conformational defects, deficient myometrial contractions, and failure of the cervix to relax is detected by intrauterine fluid accumulation and is an important reason for susceptibility to endometritis. Multiparous aged mares are more likely to be susceptible. Untreated prolonged PBE can lead to bacterial or fungal endometritis called persistent or chronic endometritis. Exuberant or prolonged neutrophilia and cytokine release can have deleterious and permanent effects in inducing endometrosis. Interactions of neutrophils, cytokines, and prostaglandins in the formation of collagen and extracellular matrix in the pathogenesis of fibrosis are discussed. Endometritis and endometrosis are interconnected, influencing each other. It is suggested that they represent epigenetic changes induced by age and hostile uterine environment.

The NF-κB signaling pathway in mare's endometrium infiltrated with the inflammatory cells

Endometritis is an important issue decreasing mares' fertility. In the case of endometritis both, inflammatory cells infiltration and proinflammatory molecules production are regulated by various cellular and gene-regulatory mechanisms, including the nuclear factor-κB (NF-κB) dependent pathway. NF-κB signaling pathway has been recently studied in the equine endometrium in the context of endometrosis. Thus, this study aimed to determine gene transcription of NF-κB subunits (RelA; NF-κB1; NF-κB2), proinflammatory molecules (MCP-1; IL-6), and hyaluronan synthases (HAS 1; HAS 2; HAS 3) in endometritis and compare them with the intensity and type of inflammatory cell infiltration. Endometrial samples, collected post-mortem from cyclic mares in estrus or diestrus, were classified histologically and examined using quantitative PCR. Transcription NF-κB subunits genes did not differ with either inflammatory intensity or type of inflammatory cell infiltration. Transcription of MCP-1 and IL-6 genes increased with the severity of inflammation, with the involvement of HAS 3 and HAS 2 genes, as opposed to HAS 1 genes. These proinflammatory molecules and hyaluronan synthases in the equine inflamed endometrium do not seem to be regulated by the NF-κB pathway. Hence, separate signaling pathways for the development and progression of equine endometritis and endometrosis may be suggested.

Deoxynivalenol and zearalenone: Different mycotoxins with different toxic effects in donkey (Equus asinus) endometrial epithelial cells

Deoxynivalenol (DON) and zearalenone (ZEA), which are commonly found in feed products, exhibit serious negative effects on the reproductive systems of domestic animals. However, the toxicity of mycotoxins on the uterine function of donkey (Equus asinus) remains unclear. This study investigated the biological effects of DON and ZEA exposure on donkey endometrial epithelial cells (EECs). It was administered 10 μM and 30 μM DON and ZEA to cells cultured in vitro. The results showed that 10 μM DON exposure markedly changed the expression levels of pyroptosis-associated genes and that 30 μM ZEA exposure changed the expression levels of inflammation-associated genes in EECs. The mRNA expression of cancer-promoting genes was markedly upregulated in cells exposed to DON and 30 μM ZEA; in particular, 10 μM and 30 μM DON and ZEA markedly disturbed the expression of androgen and estrogen secretion-related genes. Furthermore, Q-PCR, Western blot, and immunofluorescence analyses verified the different expression patterns of related genes in DON- and ZEA-exposed EECs. Collectively, these results illustrated the impact of exposure to different toxins and concrete toxicity on the mRNA expression of EECs from donkey in vitro.

Simple Tube Centrifugation Method for Platelet-Rich Plasma (PRP) Preparation in Catalonian Donkeys as a Treatment of Endometritis-Endometrosis

Simple Summary

Platelet-rich plasma (PRP) is used to improve the regenerative capacity of damaged tissues in different species. In equine medicine, PRP is commonly used to treat joint diseases, tendinitis, ligamentous lesions, and persistent endometritis. Jenny endometrium shows a high sensitivity to endometritis. There are important differences between donkey and horse blood characteristics. Several protocols to obtain horse PRP have been reported, but no protocols have yet been reported for obtaining donkey PRP. Our study shows that single-spin tube centrifugation at 133× g for 10 min is appropriate to obtain donkey PRP with therapeutic potential in jenny endometritis-endometriosis.

Abstract

The aim of this study was to standardize a simple, manual platelet-rich plasma (PRP) protocol in Catalonian donkeys using single-spin tube centrifugation as a treatment for jenny endometritis. The objective was to obtain a blood product with a moderate concentration of platelets (2 or 3 times baseline physiologic values) and a low WBC (White Blood Cells) concentration. Blood was drawn from six Catalonian donkeys using acid citrate dextrose (ACD) as an anticoagulant, and then processed by single centrifugation at 133× g for two different centrifugation times (10 and 15 min). The PRP samples were evaluated by flow cytometry, and TGF-β1 (Transforming Growth Factor-Beta1) concentrations were determined by enzyme-linked immunosorbent assay (ELISA). The 10 min centrifugation protocol resulted in a slightly greater release of TGF-β1 (6044.79 ng/mL), a 2.06-fold increase in platelet concentration, and a 15-fold reduction in leukocyte concentration when compared to the initial values. The 15 min centrifugation time resulted in a 2.44-fold increase in baseline platelet concentration, a reduction in WBC count by a factor of 20, and slightly lower TGF levels (5206 ng/mL). We conclude that both protocols are adequate for the obtention of PRP, and both may have an acceptable therapeutic potential for use in this species, although this needs to be further validated.

Up-regulation of DNA2 results in cell proliferation and migration in endometriosis

Accumulating evidence has suggests that women with advanced endometriosis exhibit alterations in the expression of genes in the endometrium compared to healthy controls. Furthermore, replication stress is a characteristic feature of cancer cells, which results from sustained proliferative signaling induced by either the activation of oncogenes or the loss of tumor suppressors. In the present study, we propose that DNA replication ATP-dependent helicase/nuclease 2 (DNA2) might be upregulated in endometriosis. Immunohistochemical staining results confirmed the hypothesis that DNA2 is overexpressed in the eutopic/ectopic endometrium compared to that in a control endometrium from a healthy donor. Subsequently, ectopic endometrium-derived endometrial mesenchymal stem cells (EMSCs) showed the highest level of DNA2 and checkpoint kinase 1 (CHK1), as well as the strongest proliferation and migration capabilities, followed by eutopic endometrium-derived EMSCs, and then control EMSCs. To further analyze the function of DNA2, we knocked-down DNA2 expression in KLE cells. As expected, proliferation and migration declined when cells were transfected with DNA2 small interfering RNA. Taken together, our study demonstrated the overexpression of DNA2 in human endometriosis, which might be responsible for the upregulated cell proliferation and migration. This study provides insights into the mechanisms underlying human endometriosis.

The Inhibition of Cathepsin G on Endometrial Explants With Endometrosis in the Mare

Although proteases found in neutrophil extracellular traps (NETs) have antimicrobial properties, they also stimulate collagen type 1 (COL1) production by the mare endometrium, contributing for the development of endometrosis. Cathepsin G (CAT), a protease present in NETs, is inhibited by specific inhibitors, such as cathepsin G inhibitor I (INH; β-keto-phosphonic acid). Matrix metallopeptidases (MMPs) are proteases involved in the equilibrium of the extracellular matrix. The objective of this study was to investigate the effect of CAT and INH (a selective CAT inhibitor) on the expression of MMP-2 and MMP-9 and on gelatinolytic activity. In addition, the putative inhibitory effect of INH on CAT-induced COL1 production in mare endometrium was assessed. Endometrial explants retrieved from mares in follicular phase or midluteal phase were treated for 24 or 48 h with CAT, inhibitor alone, or both treatments. In explants, transcripts (quantitative polymerase chain reaction) of COL1A2, MMP2, and MMP9, as well as the relative abundance of COL1 protein (Western blot), and activity of MMP-2 and MMP-9 (zymography) were evaluated. The protease CAT induced COL1 expression in explants, at both estrous cycle phases and treatment times. The inhibitory effect of INH was observed on COL1A2 transcripts in follicular phase at 24-h treatment, and in midluteal phase at 48 h (P < 0.05), and on the relative abundance of COL protein in follicular phase and midluteal phase explants, at 48 h (P < 0.001). Our study suggests that MMP-2 might also be involved in an earlier response to CAT, and MMP-9 in a later response, mainly in the follicular phase. While the use of INH reduced CAT-induced COL1 endometrial expression, MMPs might be involved in the fibrogenic response to CAT. Therefore, in mare endometrium, the use of INH may be a future potential therapeutic means to reduce CAT-induced COL1 formation and to hamper endometrosis establishment.