Complimentary Diagnostic Tools for Endometrosis in Biopsies of Mares with Clinical Subfertility

Background: Endometrosis is a multifactorial disease and one of the main causes of infertility in mares, its etiology and pathogenesis are not completely understood. It is defined as peri glandular and/or stromal endometrial fibrosis with glandular alterations. Due to the few clinical symptoms, besides anamnesis and fertility data, endometrosis requires histological confirmation. The histo-morphology and immune histochemical characteristics of the endometrium vary among individuals according to the disease progression. The aim of this research was to combine histology with new immune and histochemical tools for a more precise detection of fibrotic changes of mares with endometrosis.Materials, Methods & Results: The endometrium of forty thoroughbred mares aged 5-18 years, that did not become pregnant during the last two breeding seasons in a Chilean commercial equine breeding center were biopsied. Samples were subjected to conventional histopathology with hematoxylin-eosin as well as to specific histological staining using specific techniques such  as Alcian blue and Masson Fontana, aimed to ascertain what types of mucopolysaccharides were present in those samples. In order to have a deeper picture of the progression of the pathology, immune histochemical methods for the detection of vimentin, cytokeratin, progesterone receptor and lymphocyte marker CD3  were used. Finally in order to detect fibrillar collagen we used second harmonic generation (SHG) technique with detects fibrillar collagen without staining, due to intrinsic hyperpolarization ability of this type of collagen, which can be detected by atomic force microscopy. As a result of our research samples were categorized according to the scale of Keeney and Doig into categories I, IIa, IIb and III (45, 42, 7.5 and 5% respectively). These samples also were characterized by the methods listed earlier and a result we found specific staining in 15 samples coming from higher endometrial damage using Masson-Fontana, while acid staining indicative of acid mucopolysaccharides were detected in 97% of the samples. At immunostaining, we found cytokeratin and vimentin differentially expressed as a function of the degree of the lesions. Cytokeratin was detected in glands from healthy mares, but it was almost absent as the injury was increased. Vimentin in turn, was detected in 26 samples with different degree of intensity. In nine animals, vimentin expression was anomalous, and the marker was detected in fibrotic foci concentrically surrounding glands in biopsies of grade I and IIA only. Although  progesterone receptor was detected, there was no correlation with endometrosis. Finally, the lymphocyte T specific CD3 marker was positive in 100% of cases analyzed in which  moderate lymphocytic infiltration was found by hematoxylin-eosin; however no staining could be detected in mares with more advanced endometrosis.  By combining immunofluorescence with the detection of second harmonic it was possible to detect in the same sample two proteins and collagen deposition at the same time, this had not been reported earlier for endometrosis and mares.Discussion: Our results suggest that the combination of the different methods mentioned is useful for validation and further characterization of the routine hematoxylin-eosin, and can be used as a complementary tool for the diagnosis. Of value, it was possible to combine immunofluorescence with SHG in a single sample in situ

Endometrial Stem Cells in Farm Animals: Potential Role in Uterine Physiology and Pathology

The endometrium is an accessible source of mesenchymal stem cells. Most investigations of endometrial mesenchymal stem cells (eMSCs) have been conducted in humans. In animals, particularly in livestock, eMSC research is scarce. Such cells have been described in the bovine, ovine, caprine, porcine, and equine endometrium. Here we provide the state of the art of eMSCs in farm animals with a focus on the bovine species. In bovines, eMSCs have been identified during the phases of the estrous cycle, during which their functionality and the presence of eMSC-specific markers has been shown to change. Moreover, postpartum inflammation related to endometritis affects the presence and functionality of eMSCs, and prostaglandin E2 (PGE2) may be the mediator of such changes. We demonstrated that exposure to PGE2 in vitro modifies the transcriptomic profile of eMSCs, showing its potential role in the fate of stem cell activation, migration, and homing during pathological uterine inflammation in endometritis and in healthy puerperal endometrium. Farm animal research on eMSCs can be of great value in translational research for certain uterine pathologies and for immunomodulation of local responses to pathogens, hormones, and other substances. Further research is necessary in areas such as in vivo location of the niches and their immunomodulatory and anti-infective properties

Extracellular Vesicles Secreted by Pre-Hatching Bovine Embryos Produced In Vitro and In Vivo Alter the Expression of IFNtau-Stimulated Genes in Bovine Endometrial Cells

The embryo-maternal interaction occurs during the early stages of embryo development and is essential for the implantation and full-term development of the embryo. In bovines, the secretion of interferon Tau (IFNT) during elongation is the main signal for pregnancy recognition, but its expression starts around the blastocyst stage. Embryos release extracellular vesicles (EVs) as an alternative mechanism of embryo-maternal communication. The aim of the study was to determine whether EVs secreted by bovine embryos during blastulation (D5-D7) could induce transcriptomic modifications, activating IFNT signaling in endometrial cells. Additionally, it aims to assess whether the EVs secreted by embryos produced in vivo (EVs-IVV) or in vitro (EVs-IVP) have different effects on the transcriptomic profiles of the endometrial cells. In vitro- and in vivo-produced bovine morulae were selected and individually cultured for 48 h to collect embryonic EVs (E-EVs) secreted during blastulation. E-EVs stained with PKH67 were added to in vitro-cultured bovine endometrial cells to assess EV internalization. The effect of EVs on the transcriptomic profile of endometrial cells was determined by RNA sequencing. EVs from both types of embryos induced several classical and non-classical IFNT-stimulated genes (ISGs) and other pathways related to endometrial function in epithelial endometrial cells. Higher numbers of differentially expressed genes (3552) were induced by EVs released by IVP embryos compared to EVs from IVV (1838). Gene ontology analysis showed that EVs-IVP/IVV induced the upregulation of the extracellular exosome pathway, the cellular response to stimulus, and the protein modification processes. This work provides evidence regarding the effect of embryo origin (in vivo or in vitro) on the early embryo-maternal interaction mediated by extracellular vesicles

Table_1_Mare stromal endometrial cells differentially modulate inflammation depending on oestrus cycle status: an in vitro study.docx

The modulation of inflammation is pivotal for uterine homeostasis. Here we evaluated the effect of the oestrus cycle on the expression of pro-inflammatory and anti-inflammatory markers in a cellular model of induced fibrosis. Mare endometrial stromal cells isolated from follicular or mid-luteal phase were primed with 10 ng/mL of TGFβ alone or in combination with either IL1β, IL6, or TNFα (10 ng/mL each) or all together for 24 h. Control cells were not primed. Messenger and miRNA expression were analyzed using real-time quantitative PCR (RT-qPCR). Cells in the follicular phase primed with pro-inflammatory cytokines showed higher expression of collagen-related genes (CTGF, COL1A1, COL3A1, and TIMP1) and mesenchymal marker (SLUG, VIM, CDH2, and CDH11) genes; p < 0.05. Cells primed during the mid-luteal overexpressed genes associated with extracellular matrix, processing, and prostaglandin E synthase (MMP2, MMP9, PGR, TIMP2, and PTGES; p < 0.05). There was a notable upregulation of pro-fibrotic miRNAs (miR17, miR21, and miR433) in the follicular phase when the cells were exposed to TGFβ + IL1β, TGFβ + IL6 or TGFβ + IL1β + IL6 + TNFα. Conversely, in cells from the mid-luteal phase, the treatments either did not or diminished the expression of the same miRNAs. On the contrary, the anti-fibrotic miRNAs (miR26a, miR29b, miR29c, miR145, miR378, and mir488) were not upregulated with treatments in the follicular phase. Rather, they were overexpressed in cells from the mid-luteal phase, with the highest regulation observed in TGFβ + IL1β + IL6 + TNFα treatment groups. These miRNAs were also analyzed in the extracellular vesicles secreted by the cells. A similar trend as seen with cellular miRNAs was noted, where anti-fibrotic miRNAs were downregulated in the follicular phase, while notably elevated pro-fibrotic miRNAs were observed in extracellular vesicles originating from the follicular phase. Pro-inflammatory cytokines may amplify the TGFβ signal in the follicular phase resulting in significant upregulation of extracellular matrix-related genes, an imbalance in the metalloproteinases, downregulation of estrogen receptors, and upregulation of pro-fibrotic factors. Conversely, in the luteal phase, there is a protective role mediated primarily through an increase in anti-fibrotic miRNAs, a decrease in SMAD2 phosphorylation, and reduced expression of fibrosis-related genes.</p