Equine Breeding-Induced Endometritis: A Review

Use of equine embryo -derived mesenchymal stromal cells and their extracellular vesicles as a treatment for persistent breeding-induced endometritis in susceptible mares

Persistent breeding induced endometritis (PBIE) is a significant cause of infertility in mares. The development of a safe, universal, readily available therapeutic to manage PBIE and facilitate an optimal uterine environment for embryo development may improve pregnancy rates in susceptible mares. Mesenchymal stromal cells (MSCs) are being used increasingly as a therapeutic mediator for inflammatory conditions such as endometritis, and early gestational tissue provides a unique source of multipotent stem cells for creating MSCs. Extracellular vesicles (EVs) are mediators of cell communication produced by many different cell types. This study utilized embryo-derived mesenchymal stromal cells (EDMSCs) and their EVs as a potential therapeutic modality for PBIE in two groups: a) PBIE-susceptible mares challenged with pooled dead sperm (n=5); and b) client-owned mares diagnosed as susceptible to PBIE (n=37 mares and 40 estrous cycles). Mares pre-treated with intrauterine EDMSCs or their EVs resulted in a significant reduction in the accumulation of intrauterine fluid post-breeding. Nine of 19 (47 %) mares treated with EDMSCs prior to natural breeding and 13 of 20 (65 %) mares treated with EDMSC derived EVs were pregnant after the first cycle and 12 of 18 (67 %) mares treated with EDMSCs, and 15 of 19 (79 %) mares treated with EVs conceived by the end of the breeding season. These preliminary clinical studies are the first reports of the use of EDMSCs or their EVs as a potential intrauterine therapy for the management of PBIE susceptible mares.

Effect of Sampling Method on Detection of the Equine Uterine Microbiome during Estrus

Bacterial endometritis is among the most common causes of subfertility in mares. It has a major economic impact on the equine breeding industry. The sensitivity of detecting uterine microbes using culture-based methods, irrespective of the sample collection method, double-guarded endometrial swab, endometrial biopsy, or uterine low-volume lavage (LVL), is low. Therefore, equine bacterial endometritis often goes undiagnosed. Sixteen individual mares were enrolled, and an endometrial sample was obtained using each method from all mares. After trimming, quality control and decontamination, 3824 amplicon sequence variants were detected in the dataset. We found using 16S rRNA sequencing that the equine uterus harbors a distinct resident microbiome during estrus. All three sampling methods used yielded similar results in composition as well as relative abundance at phyla (Proteobacteria, Firmicutes, and Bacteroidota) and genus (Klebsiella, Mycoplasma, and Aeromonas) levels. A significant difference was found in alpha diversity (Chao1) between LVL and endometrial biopsy, suggesting that LVL is superior at detecting the low-abundant (rare) taxa. These new data could pave the way for innovative treatment methods for endometrial disease and subfertility in mares. This, in turn, could lead to more judicious antimicrobial use in the equine breeding industry.

Serological and Uterine Biomarkers for Detecting Endometritis in Mares

Serological analysis may provide relevant information on endometritis diagnostics. Therefore, mares scheduled for AI with refrigerated semen, at the time of heat signs, underwent blood and uterine fluid samplings using a swab, uterine lavage for culture analysis, and treatment with human chorionic gonadotropin to induce ovulation. After 24-28 h, the mares were inseminated and, if positive at the culture test, treated with antibiotics chosen based on the susceptibility test. Uterine cells obtained by swabs were used for cytological examination with both classical and fluorescence techniques. Blood serum and uterine fluid samples were analyzed for assessing parameters related to redox balance, inflammation, and protease regulator potential. In blood serum, total antioxidant capacity, measured as the ferric reducing ability of plasma (FRAP), was significantly lower in cytologically endometritis-positive than -negative mares. In the uterine fluid, total thiol levels (TTL), nitric oxide metabolites (NO_x), protease activity and total protein content varied significantly between groups. Although the cytological examination was more capable of discriminating between endometritis-positive and -negative mares in relation to the parameters examined, no statistically significant differences emerged in terms of pregnancy rate in relation to cytological and culture diagnosis as well as in mares diagnosed as positive and negative for endometritis.

Effect of prostaglandin F2α administration on uterine polymorphonuclear neutrophil counts in Japanese heavy draft horses

The objective of this study was to examine the effect of prostaglandin F2_α (dinoprost) and oxytocin administration on uterine polymorphonuclear neutrophil counts in the Japanese heavy draft mare. To compare polymorphonuclear neutrophil (PMN) counts in the endometrium, a total of 162 samples were collected from 54 estruses of 47 mares (before ovulation, day 0, and day 2) using a double-guarded cytology brush. Dinoprost (PG; 5 mg) was administered intramuscularly (i.m.) only once, on day 0, whereas oxytocin (OT; 20 U i.m.) was administered three times at 12-hr intervals starting on day 0. The plasma progesterone concentrations from days 0 to 14 were not different between the non-treatment (CON), PG treatment, and OT treatment groups. The PMN counts increased in all the groups from before administration to day 0 (CON, 0.90 to 3.55; PG, 1.20 to 8.45; and OT, 0.70 to 1.70; P=0.0014, 0.0046, and 0.0073, respectively). There was a significant decrease in PMNs from day 0 to day 2 only in the PG group (P=0.0073). The pregnancy rate was not different among the CON (12/18), PG (14/18), and OT (10/18) groups. The results of this study indicate that dinoprost can reduce uterine polymorphonuclear neutrophil counts.

Identification of genes associated with susceptibility to persistent breeding-induced endometritis by RNA-sequencing of uterine cytobrush samples

This study aimed to investigate the susceptibility to persistent breeding-induced endometritis (PBIE). Cytobrush samples were collected from 81 broodmares 1-3 days before artificial insemination (AI). Susceptibility to PBIE was evaluated by the presence of ≥ 2 cm of intrauterine fluid 24 h after AI, besides the fertility was determined by a sonographic pregnancy diagnosis 2 weeks after ovulation. RNA expressions were compared between susceptible non-pregnant (SNP) mares (n=9) and resistant pregnant (RP) mares (n=9) as well as between susceptible pregnant (SP) mares (n=9) and susceptible non-pregnant (SNP) mares. 66 differentially expressed genes (DEGs) were identified between SNP and RP mares and 60 DEGs between SP and SNP mares. In SNP compared to RP mares, transcript levels of genes regulating steroid hormone metabolism and neutrophil chemotaxis were lower, while higher for genes participating in uterine inflammation.Transcripts of genes related to extracellular matrix degradation, tissue adhesions, and fibrosis were lower in SP mares than in SNP mares, while higher for genes related to uterine cell proliferation, differentiation, and angiogenesis in SP mares than SNP mares. In conclusion, increased transcript levels of apolipoprotein E (APOE) and roundabout 2 (ROBO2), cluster domain 44 (CD44), integrin beta 3 (ITGB3), and epidermal growth factor (EGF) are possible biomarkers for susceptibility to PBIE. While higher expression of fibroblast growth factor 9 (FGF9), kinase domain receptor (KDR), and C-X-C motif chemokine ligand (CXCL) 16, collagen type V alpha 2 (COL5A2) and fibronectin (FN1) are suggested indicators of fertility in susceptible mares if they receive proper breeding management.

Enzymes Present in Neutrophil Extracellular Traps May Stimulate the Fibrogenic PGF2α Pathway in the Mare Endometrium

Simple Summary

Endometrosis is a fibrotic disease in mare endometrium whose pathological mechanisms remain obscure. Prostaglandin (PG)F_2α, despite modulating reproductive physiological processes, may also provoke local pathological collagen deposition (fibrogenesis). Neutrophil extracellular traps (NETs) released during inflammation have been linked to fibrogenesis in several tissues. We have previously shown that enzymes found in NETs increase in vitro collagen production in mare endometrium. In this study, activation of PGF_2α-pathway in equine endometrial explants challenged in vitro by enzymes found in NETs is shown. Our results indicate that both endocrine microenvironment (estrous cycle phase) and healthy or pathological conditions of endometrial tissues play an important role in PGF_2α-pathway activation. In the endometrium of the follicular phase, we have observed both high production of PGF_2α and/or PGF2α receptor gene transcription under the action of enzymes found in NETs, both conditions associated with fibrogenesis in other tissues. Nevertheless, transcription of the PGF_2α receptor gene does not appear to be hormone-dependent, albeit their levels seem to be dependent on endometrial category in the mid-luteal phase. This study suggests that enzymes existing in NETs may instigate changes on PGF_2α mediators, which may become an additional mechanism of fibrogenesis in mare endometrium.

Abstract

Endometrosis, a fibrotic disease of mare endometrium, impairs uterine function. Prostaglandins (PG), despite modulating reproductive physiological functions, may also cause local pathological collagen deposition (fibrogenesis). We have previously shown that neutrophil extracellular traps (NETs) may also favor mare endometrosis. The aim of this study was to investigate the effect of enzymes present in NETs on PGF_2α-pathway activation. Kenney and Doig’s type I/IIA and IIB/III mare endometria, from follicular phase (FLP) and mid-luteal (MLP) phase, were cultured in vitro in the presence of NETs enzymes (elastase, cathepsin-G or myeloperoxidase). Production of PGF_2α (EIA) and transcription (qPCR) of its synthases (PTGS2, AKR1C3) and receptor (PTGFR) genes were evaluated. PGF_2α and PTGFR were influenced by endometrial category and estrous cycle phase. In FLP endometrium, NETs enzymes induced both high PGF_2α production and/or PTGFR transcription. In MLP type I/IIA tissues, down-regulation of PTGFR transcripts occurred. However, in MLP type IIB/III endometrium, high levels of PTGFR transcripts were induced by NETs enzymes. As PGF2α-pathway activation facilitates fibrogenesis in other tissues, PGF2α may be involved in endometrosis pathogenesis. In the mare, the endocrine microenvironment of healthy and pathological endometrium might modulate the PGF_2α pathway, as well as fibrosis outcome on endometrium challenged by NETs enzymes.

The Usefulness of Mesenchymal Stem Cells beyond the Musculoskeletal System in Horses

Simple Summary

The main target of mesenchymal stem cell therapy in horses has long been the locomotor system, because these athletic animals commonly suffer from tendon and joint lesions. Originally, mesenchymal stem cells were thought to act by just differentiating into the cells of the injured tissue. However, these cells are also able to regulate and stimulate the body’s own repair mechanisms, opening the door to many applications in inflammatory and immune-mediated disorders in both animals and humans. In horses, beyond their traditional application in the musculoskeletal system, these cells have been studied for ophthalmologic pathologies such as corneal ulcers or immune-mediated processes, and for reproductive disorders such as endometritis/endometrosis. Their potential has been explored for equine pathologies very similar to those affecting people, such as asthma, metabolic syndrome, aberrant wound healing, or endotoxemia, as well as for equine-specific pathologies such as laminitis. Current evidence is still preliminary, and further research is needed to clarify different aspects, although research performed so far shows the promising potential of mesenchymal stem cells to treat a wide variety of equine pathologies, some of which are analogous to human disorders. Therefore, advancements in this path will be beneficial for both animals and people.

Abstract

The differentiation ability of mesenchymal stem cells (MSCs) initially raised interest for treating musculoskeletal injuries in horses, but MSC paracrine activity has widened their scope for inflammatory and immune-mediated pathologies in both equine and human medicine. Furthermore, the similar etiopathogenesis of some diseases in both species has advanced the concept of “One Medicine, One Health”. This article reviews the current knowledge on the use of MSCs for equine pathologies beyond the locomotor system, highlighting the value of the horse as translational model. Ophthalmologic and reproductive disorders are among the most studied for MSC application. Equine asthma, equine metabolic syndrome, and endotoxemia have been less explored but offer an interesting scenario for human translation. The use of MSCs in wounds also provides a potential model for humans because of the healing particularities in both species. High-burden equine-specific pathologies such as laminitis have been suggested to benefit from MSC-therapy, and MSC application in challenging disorders such as neurologic conditions has been proposed. The available data are preliminary, however, and require further development to translate results into the clinic. Nevertheless, current evidence indicates a significant potential of equine MSCs to enlarge their range of application, with particular interest in pathologies analogous to human conditions.

The contraceptive efficacy of a self-assembling intra-uterine device in domestic mares

OBJECTIVE

The primary aim of this study was to investigate the contraceptive efficacy of a self-assembling uterine device (iUPOD™) in the mare. In addition, the effects of iUPODs on oestrous cyclicity, uterine health and circulating concentrations of cortisol were evaluated.

METHODS

Domestic mares underwent oestrous monitoring and artificial insemination. After subsequent ovulation, mares underwent either placement (n = 7) or sham placement (n = 7; controls) of an iUPOD device. Devices were left in place for at least 3 months. Pregnancy diagnoses were carried out 14 days post-ovulation, with any pregnancies terminated at 28 days post-ovulation. All mares underwent weekly blood sampling with or without reproductive examinations throughout the study. Towards the end of the study, multiple serum samples collected over three consecutive days were analysed for concentrations of cortisol. Endometrial biopsies were collected before artificial insemination and during the subsequent breeding season. Endometrial cytology and bacterial cultures were performed before device removal (iUPOD mares) or at the end of the study (control mares).

RESULTS

Pregnancies were diagnosed in 0 of 7 iUPOD mares versus 7 of 7 control mares. Placement of iUPODs was associated with extended luteal phases and variable accumulations of intra-uterine fluid. Bacterial culture results suggested that the mild endometritis associated with iUPODs was sterile in six of seven mares. Short-term placement of iUPODs had no detrimental effects on endometrial architecture. Mean serum cortisol concentrations were significantly lower in iUPOD mares than control mares.

CONCLUSION

iUPODs represent a promising means of fertility control in the mare.

Intrauterine infusion of killed semen adversely affects uterine blood flow and endometrial gene expression of inflammatory cytokines in mares susceptible to persistent breeding-induced endometritis

Persistent breeding-induced endometritis (PBIE) is a leading cause of infertility in mares. The objective of the study was to assess genital perfusion and endometrial gene expression of inflammatory cytokines in mares classified as susceptible (n = 5) or resistant (n = 5) to PBIE. Ten mares were examined daily during estrus until 6 d after hCG-induced ovulation for two estrous cycles. Twenty-four hours after application of 1500 IU hCG, 4 mL of killed (by repeated freezing in liquid nitrogen and thawing at 50 °C) deep-frozen semen or sterile saline was instilled into the uterine body and examinations were carried out immediately before and 3, 6, and 12 h after intrauterine infusion. Examinations included blood sampling to determine plasma progesterone (P₄) concentrations, and transrectal ultrasonography in B- and color Doppler mode to determine follicular and luteal size and blood flow, the extent of intrauterine fluid, as well as time-averaged maximum velocity (TAMV), blood flow volume (BFV), and blood flow resistance (expressed as pulsatility index, PI) of the uterine arteries. Additionally, endometrial biopsies were obtained at 24 h before, and 2 and 7 d after infusion, and mRNA expressions of IL1B, IL6, IL8, IL10, TNF, CASP3, and COX2 were determined by qRT-PCR. Statistical analyses were performed with mixed models. Intrauterine fluid retention (diameter >20 mm for at least 3 d) was found after infusion of killed semen in five susceptible mares. There was no treatment effect (semen vs saline; P > 0.05) on genital blood flow, plasma P₄ concentration, and endometrial gene expression. In comparison to resistant mares, susceptible mares had an increased (P = 0.04) BFV of the uterine arteries at 24 h before intrauterine infusion of killed semen, and an increased (P = 0.03) PI at 2 d after infusion. The TAMV, plasma P₄ concentrations, and follicular and luteal size and blood flow did not differ (P > 0.05) between resistant and susceptible mares. Endometrial mRNA expression of IL1B increased (P = 0.05) at 2 d after the infusion of killed semen in the susceptible mares, and the expression of IL10 increased (P = 0.003) at 7 d after the infusion within the resistant mares. Interleukin 6 mRNA was increased (P = 0.05) in susceptible compared to resistant mares at 2 d after infusion. In summary, an intrauterine infusion of killed semen increases uterine blood flow resistance and alters endometrial gene expression of inflammatory cytokines for at least 7 d but does not affect ovarian blood supply and luteal function in mares susceptible to PBIE.

Changes in the Secretion of Anti-Inflammatory Cytokines and Acute-Phase Proteins in the Uterus after Artificial Insemination in the Mare

Simple Summary

Semen deposition into the uterus during mating or artificial insemination induces a rapid inflammatory response, and, in susceptible mares, persistent endometritis can develop. Cytokines are mediators involved in the regulation of the inflammatory process, and acute phase proteins are the most sensitive indicators of the inflammatory process. Therefore, the aim of this research was to determine the secretion of anti-inflammatory cytokines and acute-phase proteins in the uterus before and after artificial insemination in the mare. The obtained results indicate that the status of the mare before artificial insemination has little effect on the response measured shortly after artificial insemination. The presence of intrauterine fluid during estrus is not connected with the inflammation parameters investigated in this study at 7 h post artificial insemination. Detailed examination of the mare’s reproductive tract before and after artificial insemination guarantees high fertility.

Abstract

The objective of the study was to evaluate the concentrations of interleukin-1 receptor antagonist (IL-1RA), interleukin-10 (IL-10), serum amyloid A (SAA) and haptoglobin (Hp) in uterine lavage fluid before and after artificial insemination (AI). Based on ultrasound examination, mares were divided into: Group 1 (n = 9), no fluid was detected in the uterus during estrus and 7 h after AI; Group 2 (n = 8), no fluid was detected in the uterus during estrus but 7 h after AI fluid was detected in the uterus; Group 3 (n = 8), fluid was detected in the uterus during estrus and also 7 h after AI. In all groups of mares, a significant increase in polymorphonuclear cells (PMN) and a significant increase in IL-1RA and SAA were recorded 7 h after AI. The obtained results show that, regardless of the status of the mare before AI, the endometrial response characterized by PMN influx, and SAA, Hp, IL-1RA and IL-10 production, is similar. The presence of intrauterine fluid during estrus is not connected with PMN influx but can impact uterine IL-1RA production at this time.

Effects of Hysteroscopic and Uterine Body Insemination on the Presence of Selected Immune Cells in the Equine Endometrium

The effects of standard uterine body and hysteroscopic insemination on endometrial health were investigated. For this purpose, 33 mares were assigned to five different protocols: control (no insemination; n = 7), sham AI (sham uterine body insemination; n = 6), sham HysAI (sham hysteroscopic insemination; n = 7), standard AI (standard uterine body insemination, 300 × 10⁶ progressively motile sperms (PMS); n = 7) and HysAI (hysteroscopic insemination, 100 × 10⁶ PMS; n = 6). Sampling included uterine swabbing for microbiological examination, cytology for determination of polymorphonuclear neutrophils (PMNs) in the uterus, and endometrial biopsy collection for histology and characterization of endometrial immune cells on day 18 after ovulation (B1) as well as 8-10 hours (B2, day 20) and 72 hours after insemination (B3, day 23). Microbial contamination increased throughout the experiment in the sham insemination groups. Significant effects (P < .05) over time were detected for PMNs (cytology: sham HysAI, standard AI, and HysAI; histology: standard AI and HysAI), macrophages (immunohistochemistry: standard AI and HysAI) and T cells (immunohistochemistry: standard AI), showing an increase at B2 and a subsequent decrease toward baseline levels at B3. At B2, significant differences (P < .05) existed for PMNs (mean ± SEM) between control (1.3 ± 1.9%) and sham AI (2.2 ± 2.7%) versus standard AI (12.2 ± 4.7%) and for macrophages between control (4.1 ± 3.5%) and sham AI (2.5 ± 1.3%) versus standard AI (25.4 ± 15.8%). Thus, the cellular immune response of the endometrium depends on sperm deposition in the uterus and does not differ between hysteroscopic and standard uterine body insemination.

Randomized Comparative Trial of Acupuncture and Exercise Versus Uterine Ecbolics in the Treatment of Persistent Postbreeding Endometritis in Mares

Although exercise and acupuncture are frequently used therapies to treat persistent postbreeding endometritis, their efficacy to date is unproven. The objective of this study was to determine if exercise and acupuncture are effective methods to reduce intrauterine fluid and compare the effectiveness of these treatments to the use of uterine ecbolics. Twelve mares susceptible to postbreeding endometritis were enrolled in the study with a randomized cross-over design using both positive and negative controls. During each estrous cycle, mares were randomized into one of six treatment groups, including stall rest (SR), oxytocin, cloprostenol, exercise, electroacupuncture, and oxytocin and exercise. Each mare was challenged with an insemination dose of 500 × 10⁶ dead sperm at time 0 hours. Intrauterine fluid measurements were taken at 0, 4, 24, 48, 72, and 96 hours postbreeding. Associations between treatment efficacy and fluid clearance were investigated using a random-effects logistic regression model that controlled for positive uterine culture. Compared with the SR negative control, exercise was the most effective treatment and had 29.7 times increased odds of fluid clearance. The second most effective treatment was oxytocin alone, with 16.9 times increased odds of fluid clearance. This was followed by cloprostenol that had 10.6 greater odds of fluid clearance, and finally, the treatment that combined exercise with oxytocin had 8.4 times greater odds of fluid clearance. Results from this study confirm that exercise and exercise combined with oxytocin are effective methods to clear intrauterine fluid.

Assessment of uterine luminal pH in mares and the effect of dilute vinegar lavage on uterine luminal pH and endometrial health

Uterine luminal pH has been demonstrated to be a valid indicator of uterine health in species such as cattle and sheep. However, research regarding uterine luminal pH in equines is lacking. The objectives of this study were to assess uterine luminal pH in mares during the estrous cycle, and evaluate the effect of dilute vinegar lavage on both uterine luminal pH and endometrial health. The study was conducted using a randomized block design in which eight mares (four Thoroughbred and four Standardbred) were aged matched then randomly assigned to two groups. Endometrial biopsies were taken from each mare prior to trial commencement. The treatment group (n = 4; 1 Thoroughbred, 3 Standardbreds) received a uterine lavage of one liter dilute vinegar (20 mL of vinegar in 1 L saline) every second day during each estrus period throughout the trial. Control group mares did not receive a uterine lavage. Uterine luminal pH measurements were recorded in all mares in both groups for a period of up to 10 min immediately prior to lavage (0 h), one hour and 24 h post lavage (same time points in control group mares as if they had been treated). Diestrus uterine luminal pH measurements were recorded once between days 6-10 post-ovulation. Endometrial biopsies were repeated from all mares at trial completion. Mean uterine luminal pH ranged from pH 5.3 to 7.6 and was significantly lower during diestrus compared to estrus (P < 0.001). Regression analysis indicated that this variation in pH was best explained by estrous cycle day, with uterine luminal pH increasing by a mean of 0.03 units each day (P < 0.001) from 6 to 10 days post-ovulation through to ovulation. Uterine lavage with dilute vinegar did not significantly affect uterine luminal pH (P > 0.05). A scoring system to quantify the abundance of cell types in the endometrial biopsies showed that mares in the treatment group had a significant decrease in polymorphonuclear cell abundance between pre- and post-trial biopsies (P = 0.03). Mares in the treatment group also had a significant decrease in lymphocyte, plasma cell and eosinophil cell abundance (P = 0.05). Although dilute vinegar lavage was not associated with a significant change in uterine luminal pH, it was associated with a significant improvement in endometrial biopsy scores. Because the control group did not receive a uterine lavage, further research is required to determine if this significant improvement results from the addition of dilute vinegar, or the uterine lavage itself.

Endometritis: Managing Persistent Post-Breeding Endometritis

Endometritis was rated as the third most common medical problem encountered in adult horses in North America. It is the leading cause of subfertility in broodmares and is a major contributor to economic loss in the horse breeding industry, with pregnancy rates reported to be as low as 21% in mares with severe endometritis. Endometritis may be categorized as: endometrosis (chronic degenerative endometritis), acute, chronic, active, dormant, subclinical, clinical, and persistent post-breeding. These classifications are not mutually exclusive, and mares may change categories within breeding seasons or estrous cycles or may fit in multiple classifications. This chapter will focus on discussing etiology and management strategies for mares affected by persistent post-breeding endometritis. Overall, these mares are considered subfertile but acceptable pregnancy and foaling rates can be achieved with appropriate breeding management.

Dose-dependent inhibition of uterine contractility by nitric oxide: A potential mechanism underlying persistent breeding-induced endometritis in the mare

Nitric oxide (NO) may have a role in persistent breeding-induced endometritis in mares through an inhibitory effect on uterine contractility. The objectives of this study were to test the effect of NO on spontaneous uterine contractility in-vitro and to evaluate whether this effect varied between the longitudinal and circular muscle layers of the uterus. Reproductive tracts were collected from eight euthanized non-pregnant mares (age 4-19 years; body weight 405-530 kg). Transrectal examination of the reproductive tract was performed before euthanasia to evaluate stage of the estrous cycle and presence of any apparent abnormality. After euthanasia, one uterine tissue sample was collected for histological evaluation and four full-thickness uterine tissue strips (10-12 mm × 2 mm), two parallel to each muscle layer, were excised for in-vitro contractility evaluation. Strips were suspended in tissue chambers containing Krebs-Henseleit solution, with continuous aeration (95% O₂-5% CO₂; pH 7.4) at 37 °C. After equilibration, spontaneous contractility was recorded (pre-treatment) and strips excised in each direction were randomly allocated to each of two groups: 1) SNAP (S-nitroso-N-acetylpenicillamine, an NO donor); or 2) NAP (N-acetyl-d-penicillamine, vehicle and time-matched control). These were treated at 15 min intervals with increasing concentrations (10^-7 M to 10^-3 M) of SNAP and NAP, respectively. Contractility data was recorded throughout the experiment. An interaction effect of group-by-concentration was observed (P < 0.0001). The mean contractility after treatment with 10^-4 M and 10^-3 M SNAP were significantly lower than the pre-treatment contractility and the mean contractility after treatment with lower SNAP concentrations. In contrast, contractility did not change significantly in the NAP treated controls. The effect of treatment on uterine contractility was not influenced by age or weight of the mare, stage of estrous cycle, uterine histology grade, or muscle layer. Secondary findings included significant main effects of stage of estrous cycle (increased contractility in estrus compared to diestrus), uterine histology grade (decreased contractility in grade IIB compared to grade I) and age (decreased contractility in mares aged > 8 years compared to mares aged ≤ 8 years). In conclusion, results of this study indicate that NO has a dose-dependent inhibitory effect on spontaneous uterine contractility irrespective of the muscle layer in the mare.

KDC, Crespilho AM. SENSIBILIDADE DO LAMINOCULTIVO DERMATOBAC® PARA O DIAGNÓSTICO DA ENDOMETRITE FÚNGICA EM ÉGUAS

Resumo Dentre os diferentes fatores etiológicos, a endometrite fúngica representa uma causa frequente de infertilidade na égua. Nesse sentido, dois experimentos foram realizados para avaliar a sensibilidade do Dermatobac®, sistema originalmente desenvolvido para o isolamento de fungos de interesse em Medicina Humana. No Experimento 1, cepas padrão de Candida (n=4) e Aspergyllus (n=1) foram semeadas assepticamente e em duplicata no sistema Dermatobac®, acompanhando-se o crescimento fúngico a cada 24 horas por 7 dias. Para o Experimento 2, foram selecionadas 34 éguas, submetidas à colheita de material uterino para o plaqueamento em Dermatobac® e realização de esfregaços para pesquisa direta de fungos (Controle). No Experimento 1, foi possível a observação macroscópica de todas as cepas de Candida e Aspergyllus a partir de 24 horas do início do cultivo microbiológico. No Experimento 2, foi constatada a presença de leveduras nas lâminas citológicas de cinco animais (14,71%), resultados também confirmados na semeadura em Dermatobac® (sensibilidade de 100%). Foram observados cinco casos falso-positivos caracterizados pelo crescimento microbiológico em sistema Dermatobac® não confirmados através da citologia endometrial, resultados que determinaram a especificidade de 85%. No entanto, todos os casos falso-positivos foram atribuídos a microrganismos contaminantes que apresentaram morfologia diferenciada e tempo de crescimento superior (P<0,05) ao apresentado pelos principais agentes etiológicos das endometrites fúngicas equinas. Conclui-se que o sistema Dermatobac® é eficiente para o diagnóstico macroscópico da endometrite fúngica em equinos, gerando informações visuais a partir de 24 horas de cultivo.

Physiopathologic mechanisms involved in mare endometrosis

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.