Sperm transport and survival in the mare

Endometrial expression of antimicrobial peptides as markers of subclinical endometritis in mares

BACKGROUND

Endometritis is a major cause of subfertility in mares. Multiparous old mares are more susceptible to developing endometritis given that ageing is associated with an altered immune response and with inadequate physiological uterine clearance after breeding, which can lead to degenerative changes in the endometrium. Molecules such as antimicrobial peptides (AMPs) have been proposed as endometritis markers in the equine species.

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To investigate the endometrial expression of defensin-beta 4B (DEFB4B), lysozyme (LYZ) and secretory leukocyte peptidase inhibitor (SLPI) genes in mares either affected or not by subclinical endometritis, due to the role of these AMPs in the immune response to bacteria and inflammatory reactions.

METHODS

Endometrial biopsy for histopathological and gene expression examinations was performed on 26 mares. The inclusion criteria for the normal mare group (NM, N = 7) were 2-4 years of age, maiden status, no clinical signs of endometritis and a uterine biopsy score of I, while for mares affected by subclinical endometritis (EM, N = 19) the inclusion criteria were 10-22 years of age, barren status for 1-3 years, no clinical signs of endometritis and a uterine biopsy score between IIA and III.

RESULTS

A significantly higher expression of LYZ (NM: 0.76 [1.84-0.37] vs. EM: 2.78 [5.53-1.44], p = 0.0255) and DEFB4B (NM: 0.06 [0.11-0.01] vs. EM: 0.15 [0.99-0.08], p = 0.0457) genes was found in endometritis mares versus normal mares. Statistically significant moderate positive correlations were found between the level of expression of LYZ gene and both the age (r = 0.4071, p = 0.039) and the biopsy grade (r = 0.4831, p = 0.0124) of the mares.

MAIN LIMITATIONS

The study investigated a limited number of genes and mares, and the presence/location of the proteins coded by these genes was not confirmed within the endometrium by IHC.

CONCLUSIONS

If the results of this study are confirmed, LYZ and DEFB4B genes can be used as markers to identify mares that are affected by subclinical endometritis.

The role of equine seminal plasma derived cysteine rich secretory protein 3 (CRISP3) in the interaction between polymorphonuclear neutrophils (PMNs) and populations of viable or dead spermatozoa, and bacteria

Breeding-induced endometritis is a physiological reaction to clear the uterus from excess spermatozoa and bacteria after breeding. Cysteine rich secretory protein 3 in seminal plasma (spCRISP3) protects spermatozoa from binding and destruction by uterine PMNs, but it is not clear if this involves all sperm and bacteria, or if it is selective to a sub-population of live sperm. The objective of this report was to determine if spCRISP3 (1) is selective in its suppression of PMN-binding to sperm based on viability of spermatozoa, (2) protects bacteria from binding to PMNs, and (3) to determine the localization pattern of spCRISP3 on viable and dead sperm. Semen was collected from five stallions and each ejaculate was divided into (1) live and (2) snap frozen (dead) sperm. Two distinct sperm populations were confirmed by DNA fragmentation and membrane integrity assays. CRISP3 was purified from pooled seminal plasma, and binding of PMNs (isolated from peripheral blood) to the two sperm populations and E. coli was evaluated with flow cytometry in the presence of spCRISP3. In addition, localization of spCRISP3 on live and dead spermatozoa was determined by immunocytochemistry. Comparisons between treatments were analyzed using a one-way-ANOVA and Bonferroni's comparison test, or Kruskal-Wallis ANOVA if not normally distributed. spCRISP3 significantly suppressed binding of PMNs to live spermatozoa (p < 0.0001) but had no effect on dead sperm or bacteria (p > 0.05). Immunocytochemistry confirmed binding of spCRISP3 to live, but not dead spermatozoa. It was concluded that a selective interaction between spCRISP3 and live spermatozoa may be part of a biological mechanism that allows safe transport of viable spermatozoa to the oviducts, while enabling dead spermatozoa and bacteria to be eliminated in a timely fashion after breeding.

Sperm exposure to accessory gland secretions alters the transcriptomic response of the endometrium in cattle

In cattle, mating to intact, but not vasectomised, bulls has been shown to modify the endometrial transcriptome, suggesting an important role of sperm in the modulation of the uterine environment in this species. However, it is not clear whether these changes are driven by intrinsic sperm factors, or by factors of accessory gland (AG) origin that bind to sperm at ejaculation. Therefore, the aim of the present study was to determine whether ejaculated sperm, which are suspended in the secretions of the AGs, elicit a different endometrial transcriptomic response than epididymal sperm, which have never been exposed to AG factors. To this end, bovine endometrial explants collected from heifers in oestrus were (co-)incubated for 6 h alone (control), or with epididymal sperm or ejaculated sperm, following which transcriptomic changes in the endometrium were evaluated. Epididymal sperm elicited a more dramatic endometrial response than ejaculated sperm, in terms of the number of differentially expressed genes (DEGs). Indeed, RNA-sequencing data analysis revealed 1912 DEGs in endometrial explants exposed to epididymal sperm compared with control explants, whereas 115 DEGs were detected between endometrial explants exposed to ejaculated sperm in comparison to control explants. The top pathways associated with genes upregulated by epididymal sperm included T cell regulation and TNF, NF-KB and IL17 signalling. Interestingly, ejaculated sperm induced downregulation of genes associated with T cell immunity and Th17 differentiation, and upregulation of genes involved in NF-KB signalling, in comparison to epididymal sperm. These data indicate that factors of AG origin modulate the interaction between sperm and the endometrium in cattle.

Comparison of the metabolite profile of donkey and horse seminal plasma and its relationship with sperm viability and motility

Previous research revealed that several seminal plasma (SP) metabolites are related to sperm functionality, fertility, and preservation. While it is understood that variations between species exist, whether the SP metabolome differs between donkeys and horses has not been previously investigated. The aim of this work, therefore, was to characterize and compare donkey and horse SP metabolites using nuclear magnetic resonance (NMR) spectroscopy, and relate them to sperm viability and motility. For this purpose, ejaculates from 18 different donkeys and 18 different horses were collected and separated into two aliquots: one for harvesting the SP by centrifugation and obtaining the metabolic profile through NMR, and the other for evaluating sperm viability and motility. Based on total motility and sperm viability, samples were classified as with good (GQ) or poor (PQ) quality. The metabolomic profile of donkey and horse SP revealed the presence of 28 metabolites, which coincided in the two species. Yet, differences between horses and donkeys were observed in the concentration of 18 of these 28 metabolites, as well as between ejaculates classified as GQ or PQ and in the relationship of metabolites with sperm motility and viability. These findings suggest that sperm from donkeys and horses differ in their metabolism and energetic requirements, and that the concentration of specific SP metabolites may be related to sperm functionality. Further research should shed light on the metabolic needs of donkey and horse sperm, and evaluate how the knowledge collected from the contribution of these metabolites can help improve semen preservation in the two species.

Immune Regulation of Seminal Plasma on the Endometrial Microenvironment: Physiological and Pathological Conditions

Seminal plasma (SP) accounts for more than 90% of semen volume. It induces inflammation, regulates immune tolerance, and facilitates embryonic development and implantation in the female reproductive tract. In the physiological state, SP promotes endometrial decidualization and causes changes in immune cells such as macrophages, natural killer cells, regulatory T cells, and dendritic cells. This leads to the secretion of cytokines and chemokines and also results in the alteration of miRNA profiles and the expression of genes related to endometrial tolerance and angiogenesis. Together, these changes modulate the endometrial immune microenvironment and contribute to implantation and pregnancy. However, in pathological situations, abnormal alterations in SP due to advanced age or poor diet in men can interfere with a woman's immune adaptation to pregnancy, negatively affecting embryo implantation and even the health of the offspring. Uterine pathologies such as endometriosis and endometritis can cause the endometrium to respond negatively to SP, which can further contribute to pathological progress and interfere with conception. The research on the mechanism of SP in the endometrium is conducive to the development of new targets for intervention to improve reproductive outcomes and may also provide new ideas for semen-assisted treatment of clinical infertility.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Oxidative stress and the long-term storage of horse spermatozoa

In brief

The growing understanding of the mechanisms regulating redox homeostasis in the stallion spermatozoa, together with its interactions with energetic metabolism, is providing new clues applicable to the improvement of sperm conservation in horses. Based on this knowledge, new extenders, adapted to the biology of the stallion spermatozoa, are expected to be developed in the near future.

Abstract

The preservation of semen either by refrigeration or cryopreservation is a principal component of most animal breeding industries. Although this procedure has been successful in many species, in others, substantial limitations persist. In the last decade, mechanistic studies have shed light on the molecular changes behind the damage that spermatozoa experience during preservation. Most of this damage is oxidative, and thus in this review, we aim to provide an updated overview of recent discoveries about how stallion spermatozoa maintain redox homeostasis, and how the current procedures of sperm preservation disrupt redox regulation and cause sperm damage which affects viability, functionality, fertility and potentially the health of the offspring. We are optimistic that this review will promote new ideas for further research to improve sperm preservation technologies, promoting translational research with a wide scope for applicability not only in horses but also in other animal species and humans.

A stallion spermatozoon's journey through the mare's genital tract: In vivo and in vitro aspects of sperm capacitation

Conventional in vitro fertilization is not efficacious when working with equine gametes. Although stallion spermatozoa bind to the zona pellucida in vitro, these gametes fail to initiate the acrosome reaction in the vicinity of the oocyte and cannot, therefore, penetrate into the perivitelline space. Failure of sperm penetration most likely relates to the absence of optimized in vitro fertilization media containing molecules essential to support stallion sperm capacitation. In vivo, the female reproductive tract, especially the oviductal lumen, provides an environmental milieu that appropriately regulates interactions between the gametes and promotes fertilization. Identifying these 'fertilization supporting factors' would be a great contribution for development of equine in vitro fertilization media. In this review, a description of the current understanding of the interactions stallion spermatozoa undergo during passage through the female genital tract, and related specific molecular changes that occur at the sperm plasma membrane is provided. Understanding these molecular changes may hold essential clues to achieving successful in vitro fertilization with equine gametes.

Uterine Inflammatory Response After Prostaglandin E1 (Misoprostol) Infusion Prebreeding or Immediately After Embryo Flushing in Commercial Donor Mares

Misoprostol, a synthetic PGE1, is becoming a common therapy for mares with suspected uterine tube obstruction. Recently, there have been concerns that uterine administration of misoprostol induces exacerbated uterine inflammation; however, this has not been critically evaluated. This study aimed to assess the inflammatory response and potential systemic reactions after uterine administration of misoprostol, either during prebreeding or immediately after postembryo flushing. Privately owned embryo donor mares (n = 11) were randomly assigned in a crossover design to receive misoprostol (3 mL +200 µg) or sham (3 mL of lactate Ringer's solution) infusions, bilaterally deposited via deep-horn, at least 72 hours prebreeding (experiment 1) or immediately after embryo flushing (experiment 2). Each mare had one cycle for misoprostol and sham in both experiments and a breeding cycle (no sham or misoprostol) between experiments. Uterine edema, fluid accumulation, and the number of uterine PMN were assessed before each infusion and then daily for 72 hours. Uterine lavage was performed the day after each infusion across groups and experiments. Ovulation was hastened with a GnRH agonist and confirmed at 24 hour-intervals. Mares were bred with semen from one of six stallions per owner's choice. Embryo flushing was performed 8 to 9 days postovulation. In either experiment, misoprostol did not affect uterine edema or fluid accumulation (P > .05). However, both the sham and misoprostol infusions increased the number of PMN up to 48 hours postinfusion in both experiments. Embryo recoveries were similar between sham (45%, 5/11) and misoprostol cycles in experiments 1 (45%, 5/11; P > .05) and 2 (sham, 68%, 7/11; misoprostol, 45%, 5/11; P > .05). In conclusion, misoprostol did not induce exacerbated uterine inflammation in mares or systemic adverse reactions when infused prebreeding or immediately after embryo flushing.

Comparative study utilizing different post-breeding treatment regimens in cyclic Arabian mares

BACKGROUND AND AIM

Post-breeding treatment is the most common practice in the reproductive management of mares. Oxytocin, uterine lavage, and intrauterine (I/U) antibiotic are usually used as prophylactic therapy. This study aimed to determine the most efficient prophylactic treatment regimen among six treatment protocols applied during natural breeding of cyclic Arabian mares.

MATERIALS AND METHODS

The current study was conducted on cyclic Arabian mares that were subdivided into three age categories (n=968): Category I (5-10 years, n=380), Category II (11-15 years, n=361), and Category III (≥16 years, n=227). Six prophylactic treatments were applied after 4 h of breeding. According to the treatment regimen, treated mares (n=483) were divided into six treatment groups: A (n=80), treated with I/U antibiotic (1 g gentamicin); B (n=81), I/U lavage (normal saline 500 mL); C (n=83), intramuscular (I/M) oxytocin (10 IU); D (n=82), I/U antibiotic and I/M oxytocin; E (n=78), I/U lavage and I/M oxytocin; and F (n=79), I/U lavage with I/U antibiotic and I/M oxytocin. Non-treated mares were classified as controls (n=485). Ultrasonography was performed to monitor pregnant mares 30 and 60 days after mating, and mares were followed until foaling.

RESULTS

Pregnancy and foaling results reveals that in age Category I, treatment with oxytocin alone or oxytocin with I/U lavage showed the highest pregnancy and foaling rates (p<0.01). In age Category II, the highest pregnancy and foaling rates were observed in lavage treatment (p<0.01), whereas, in age Category III, the good pregnancy and foaling rates were monitored in treatment with oxytocin and I/U lavage (p<0.01).

CONCLUSION

Treatment with systemic I/M oxytocin is ideal in early age group mares (5-10 years of age). However, irrespective of the age categories, all mares exhibited high pregnancy and foaling rates after treatment with systemic I/M oxytocin and I/U lavage with normal saline (0.9%) 4 h post-breeding.

Oxidative profile and protease regulator potential to predict sperm functionality in donkey (Equus asinus)

Seminal plasma (SP) of donkey stallions was evaluated using various oxidative stress parameters as well as protease and protease inhibitor activities. SP was obtained by nine donkey stallions. In addition, one donkey stallion with non-obstructive azoospermia was enrolled in this study. Free radical scavenging activity (FRSA), the ferric reducing ability of plasma (FRAP), total antioxidant capacity (TAC), and total thiol level (TTL) were highly correlated with each other and with the protease inhibitor activity. However, only FRAP, TAC, and the nitrate/nitrite concentration (NOx) were significantly correlated with sperm concentration, production, and kinetics. Protease inhibitor activity was highly correlated with sperm concentration and production; however, it did not correlate with sperm kinetics. The azoospermic stallion produced a lower amount of semen than the normospermic stallions and its SP showed a lower antioxidant activity when evaluated with FRAP, TAC, and TTL as well as a higher NOx and a lower protease inhibitor activity. In conclusion, the evaluation of SP oxidative profile by FRAP, TAC, and NOx may provide reliable information on donkey sperm quality whereas protease inhibitor activity may play a role as a marker of the sperm concentration in this species.

Intrauterine Blood Plasma Platelet-Therapy Mitigates Persistent Breeding-Induced Endometritis, Reduces Uterine Infections, and Improves Embryo Recovery in Mares

Microorganisms, including pathogenic or opportunistic bacteria and fungi, may gain access to the uterus during breeding, and infectious endometritis plays a major role in equine subfertility. This study aimed to assess the post-breeding inflammatory response, endometrial culture, and embryo recovery of mares susceptible to persistent breeding-induced endometritis (PBIE) treated with plasma-rich (PRP) or -poor (PPP) plasma. Mares (n = 12) susceptible to PBIE had three cycles randomly assigned to receive intrauterine infusions of lactate ringer solution (LRS, control), or autologous PRP or PPP pre- (−48 and −24 h) and post-breeding (6 and 24 h). Mares were bred with fresh semen from one stallion. Intrauterine fluid accumulation (IUF) and endometrial neutrophils were assessed every 24 h up to 96 h post-breeding. Uterine cytokines (Ilβ, IL6, CXCL8, and IL10) were evaluated before (0 h), 6, and 24 h post-breeding, and endometrial culture three and nine days after breed. Embryo flushing was performed 8 days post-ovulation. Data were analyzed with mixed model, Tukey’s post-hoc test, and multivariate regression. PRP treatment reduced endometrial neutrophils, post-breeding IUF, and pro-inflammatory cytokines when compared to control-assigned cycles, but not significantly different than PPP. Controls had a significantly higher percentage of positive bacterial cultures (33%) in comparison to PRP-assigned cycles (0%), whereas cycles treated with PPP were not significantly different from the other groups (25%). The PRP-assigned cycles had significantly greater embryo recovery rates (83%) than the control (33%), though not significantly different than PPP (60%). Plasma infusion reduced the duration and intensity of the post-breeding inflammatory response and improved embryo recovery in mares susceptible to PBIE. Platelets incrementally downregulate PBIE and appear to have a dose-dependent antimicrobial property.

Peptidoglycan Switches Off the TLR2-Mediated Sperm Recognition and Triggers Sperm Localization in the Bovine Endometrium

In mammals, the uterine mucosal immune system simultaneously recognizes and reacts to most bacteria as well as allogenic sperm mainly through the Toll-like receptors (TLR)2/4 signaling pathway. Here, we characterized the impact of pathogen-derived TLR2/4 ligands (peptidoglycan (PGN)/lipopolysaccharide (LPS)) on the immune crosstalk of sperm with the bovine endometrial epithelium. The real-time PCR analysis showed that the presence of low levels of PGN, but not LPS, blocked the sperm-induced inflammatory responses in bovine endometrial epithelial cells (BEECs) in vitro. Immunoblotting analysis revealed that PGN prevented the sperm-induced phosphorylation of JNK in BEECs. Activation or blockade of the TLR2 system in the endometrial epithelium verified that TLR2 signaling acts as a commonly-shared pathway for PGN and sperm recognition. The impairment of endometrial sperm recognition, induced by PGN, subsequently inhibited sperm phagocytosis by polymorphonuclear neutrophils (PMNs). Moreover, using an ex vivo endometrial explant that more closely resembles those in vivo conditions, showed that sperm provoked a mild and reversible endometrial tissue injury and triggered PMN recruitment into uterine glands, while PGN inhibited these events. Of note, PGN markedly increased the sperm attachment to uterine glands, and relatively so in the surface epithelium. However, addition of the anti-CD44 antibody into a PGN-sperm-explant co-culture completely blocked sperm attachment into glands and surface epithelia, indicating that the CD44 adhesion molecule is involved in the PGN-triggered sperm attachment to the endometrial epithelium. Together, these findings demonstrate that, the presence of PGN residues disrupts sperm immune recognition and prevents the physiological inflammation induced by sperm in the endometrial epithelium via the MyD88-dependent pathway of TLR2 signaling, possibly leading to impairment of uterine clearance and subsequent embryo receptivity.

Effect of Mycobacterium cell wall fraction on endometrial histomorphometry of mares resistant and susceptible to persistent breeding-induced endometritis

Mycobacterium cell wall fraction (MCWF) is a biological component made up of molecules with immunostimulant properties, which is therapeutically used to modulate persistent breeding-induced endometritis (PBIE). The aim of this study was to analyze the effect of this immunomodulator on the endometrial histological structure during the diestrus of PBIE-resistant and -susceptible mares that either received treatment with MCWF or not. The experiment was conducted with 10 resistant mares (RM) and 9 susceptible mares (SM). In the first estrous cycle of the trial, all mares were inseminated with dead semen as an inflammatory stimulus (Group A); at the next cycle, all mares were inseminated with dead semen and treated with a MCWF commercial immunomodulator (Group B). In both groups, endometrial biopsies were taken on day 7 post-ovulation (diestrus). Endometrial biopsies of untreated-RM (UTRM, n = 6), untreated-SM (UTSM, n = 7) MCWF-treated-RM (TRM, n = 6) and MCWF-treated-SM (TSM, n = 6) were evaluated. They were randomly chosen as representative mares of Group A and B, respectively. The height of lining and glandular epithelia, glandular diameter, glandular density and glandular area were evaluated. The histological structure revealed lymphocytic infiltration and dilated, tortuous glands with some glandular nests, particularly in UTSM. The histomorphometrical results showed no differences (ρ > 0.05) between the analyzed groups. This would indicate that post-service treatment with the MCWF immunomodulator does not modify the endometrial histoarchitecture but, apparently, its action would be mainly based on the stimulation of the cellular and humoral immune responses.

Persistent Breeding-Induced Endometritis in Mares - a Multifaceted Challenge: From Clinical Aspects to Immunopathogenesis and Pathobiology

Post-breeding endometritis (i.e., inflammation/infection of the endometrium), is a physiological reaction taking place in the endometrium of mares within 48 hours post-breeding, aimed to clear seminal plasma, excess sperm, microorganisms, and debris from the uterine lumen in preparation for the arrival of an embryo. Mares are classified as susceptible or resistant to persistent breeding-induced endometritis (PBIE) based on their ability to clear this inflammation/infection by 48 hours post-breeding. Mares susceptible to PBIE, or those with difficulty clearing infection/inflammation, have a deficient immune response and compromised physical mechanisms of defense against infection. Molecular pathways of the innate immune response known to be involved in PBIE are discussed herein. The role of the adaptive uterine immune response on PBIE remains to be elucidated in horses. Advances in the pathobiology of microbes involved in PBIE are also revised here. Traditional and non-traditional therapeutic modalities for endometritis are contrasted and described in the context of clinical and molecular aspects. In recent years, the lack of efficacy of traditional therapeutic modalities, alongside the ever-increasing incidence of antibiotic-resistant microorganisms, has enforced the development of non-traditional therapies. Novel biological products capable of modulating the endometrial inflammatory response are also discussed here as part of the non-traditional therapies for endometritis.

Effects of pentoxifylline supplementation to semen extender on post-breeding inflammation response assessed by endometrial cytology and vascular perfusion in mares

The aim was to evaluate effects of addition of pentoxifylline to skimmed milk semen extender on uterine inflammatory response. Thirty-six estrous cycles of 15 mares were randomly divided into five groups for artificial insemination (AI): Control: mimicking the AI procedure (n = 7); Extender: deposition of skimmed milk based extender (n = 7); Extender + PTX: skimmed milk based extender plus pentoxifylline (7.18 mM; n = 8); Semen: semen diluted with extender without pentoxifylline (n = 7), and Semen + PTX: semen diluted with extender containing pentoxifylline (n = 7). Mares in estrus were examined by trans-rectal palpation and using ultrasonography, and ovulation was induced. Uterine hemodynamics were assessed immediately before ovulation induction (T-30), immediately before AI (T0), 2 (T2), 6 (T6), 12 (T12), 24 (T24) and 48 (T48) h after AI. Endometrial samples were collected 6 h after AI, and slides were stained and examined to determine percentage of PMN. Pentoxifylline had no additional effect on vascular perfusion. There was a major inflammatory response with pentoxifylline treatment that was greater than that of the control group. In the group treated with Extender + PTX, there were more PMN (57.98 ± 9.42%) than in the group treated with Extender (20.20 ± 6.63%) and in the Semen + PTX group more PMN (82.84 ± 5.71%) than in the Semen-treated group (47.83 ± 10.61%). These findings indicate the addition of pentoxifylline does not stimulate blood flow; however, it induces a greater immune defense response because more neutrophils migrate to the uterine lumen.

Influences of intrauterine semen administration on regulatory T lymphocytes in the oestrous mare (Equus caballus)

In the mare, early pregnancy loss is common, but involvement of the maternal immune system in the pathogenesis of this condition has not been investigated in detail so far. In the present study, we assessed effects of exposure of the endometrium to semen or seminal plasma in oestrous mares on the response of regulatory T lymphocytes (Tregs) in the peripheral circulation as well as in the endometrium. Raw semen, seminal plasma or PBS (control) were introduced into the uterus of oestrous mares (n = 12). Blood was collected immediately before insemination or PBS infusion (time 0), and 12, 24 and 48 h thereafter. Endometrial biopsies were collected at 24 h. In peripheral blood, Treg (CD4⁺Foxp3⁺) cells were determined by flow cytometry. In endometrial biopsies, Tregs were assessed as cells staining positive for Foxp3 by immunohistochemistry. The percentage of Tregs in blood decreased (p < 0.05) at 12 h after exposure to seminal plasma, tended to decrease in response to raw semen (p = 0.095) but not to PBS. Leukocyte and PMN counts were not affected. In the endometrium, numbers of Foxp3 positive cells at 24 h after insemination or PBS infusion were not changed by treatment. Results of the present study provide only little evidence that maternal tolerance of pregnancy in the horse is modulated already by exposure of the oestrous endometrium to seminal plasma at mating.

Expression of indoleamine 2,3-dioxygenase 1 as transcript and protein in the healthy and diseased equine endometrium

The enzyme indoleamine 2,3-dioxygenase 1 (IDO1) acts immunomodulatory and restricts bacterial growth. In the uterus of women and mice, it likely contributes to tissue homeostasis and disease pathogenesis. Pregnancy failure in mares is often caused by endometritis and endometrosis. The pathogenesis of nonsuppurative endometritis and endometrosis is still uncertain. To the authors' knowledge, no information on IDO1 expression in the equine endometrium is published. Aim of this study was to examine the presence of IDO1 as transcripts and proteins in the healthy and diseased endometrium of 25 mares and to determine its cellular expression. By PCR, IDO1 transcripts were detected in healthy (3 mares) and diseased endometria (22 mares). Western blot on 15 samples showed the concurrent presence of IDO1 proteins. Immunohistochemistry revealed its expression in macrophages and epithelial cells. Endometria of 21 mares showed an intense staining of glandular epithelia, whereas glands of the remaining 4 mares were negative or contained only few positive cells. Tissue samples of all mares showed a minimal to mild IDO1 expression in the surface epithelium and glandular ducts. Quantification of immunohistochemistry on biopsies of 6 mares collected at different stages of the same endometrial cycle indicated that the IDO1 expression is not influenced by the endometrial cycle. This study confirmed IDO1 expression also in the equine endometrium and suggests an immunomodulatory role of uterine macrophages and epithelial cells. A markedly reduced glandular IDO1 expression as detected in 4 mares may be associated with alterations of uterine immune defenses.

Uterine clinical findings, fertility rate, leucocyte migration, and COX-2 protein levels in the endometrial tissue of susceptible mares treated with platelet-rich plasma before and after AI

Persistent mating-induced endometritis (PMIE) results in decreased fertility in horses, thereby causing a significant impact in the horse market. Platelet-rich plasma (PRP), a modulator of the inflammatory response, has been largely used in veterinary medicine. Here, we investigated the effects of PRP on uterine inflammation, conception rate, endometrial polymorphonuclear neutrophil (PMN) migration, and COX-2 protein levels in the endometrial tissue. Thirteen PMIE-susceptible mares were used for artificial insemination (AI). The mares were inseminated with fresh semen in three consecutive cycles in a cross-over study design. The following cycle classifications were used: control cycle, no pharmacological interference; pre-AI, 20 mL of PRP was infused 24 h before AI; and post-AI, 20 mL of PRP was infused four h after AI. Follicular dynamics were monitored daily by transrectal ultrasound. When a follicle larger than 35 mm was detected, ovulation was induced with deslorelin acetate (1 mg, im). AI was performed 24 h after ovulation induction. Intrauterine fluid (FLU) was evaluated by ultrasonography before and 24 h after AI. PMNs in uterine cytology (CYT) and biopsy (HIS) were also observed before and 24 h after AI. Pregnancy was determined within 14 days after ovulation. Number of COX-2 positive cells was evaluated by immunohistochemistry. Both PRP treatments resulted in a decrease of PMNs in the CYT after breeding when compared to controls. FLU did not differ between cycles; however, the conception rates were significantly higher in the PRP mares. Mares positive for endometritis decreased in both treatment groups, and a more intense positive COX-2 labeling was observed in the control group when compared to the two treatment groups. In conclusion, PRP beneficially reduces inflammatory response in PMIE mares independent of when treatments were administered, thus increasing chances of successful pregnancy.

The contribution of the maternal immune system to the establishment of pregnancy in cattle

Immune cells play an integral role in affecting successful reproductive function. Indeed, disturbed or aberrant immune function has been identified as primary mechanisms behind infertility. In contrast to the extensive body of literature that exists for human and mouse, studies detailing the immunological interaction between the embryo and the maternal endometrium are quite few in cattle. Nevertheless, by reviewing the existing studies and extrapolating from sheep, pig, mouse, and human data, we can draw a reasonably comprehensive picture. Key contributions of immune cell populations include granulocyte involvement in follicle differentiation and gamete transfer, monocyte invasion of the peri-ovulatory follicle and their subsequent role in corpus luteum formation and the pivotal roles of maternal macrophage and dendritic cells in key steps of the establishment of pregnancy, particularly, the maternal immune response to the embryo. These contributions are reviewed in detail below and key findings are discussed.

Polymorphonuclear neutrophil profile in genital discharge vis-à-vis pregnancy outcome in crossbred cows: effect of varying cow fertility and insemination from different bulls

The study investigated the relationship between count and/or viability percentage of polymorphonuclear neutrophil(s) (PMN) in genital discharge and pregnancy outcome during 180 estrous periods in 163 normal and repeat breeder. The relationship was also evaluated as a response to AI by three of the most frequently used bulls. The estrous periods leading to pregnancy in the normal cows were considered fertile (FE; n=66), whereas others with pregnancy failure were considered non-fertile in the remaining normal (NFE; n=86) and the entire group of repeat breeder cows (RB; n=28) cows. Another set of reproductively healthy cows, not inseminated, were also studied (C; n=10). The PMN characteristics were investigated in 3μl fraction of cervical discharge, aspirated initially at mid-estrus in C/pre-AI in the inseminated cows and subsequently 18 to 24h later. The first sample did not reveal PMN in all the cows. However, there was a variable PMN response in the second sample. The PMN count of 9.3±1.9 in the C group was least and significantly less than the FE and NFE groups. A count of 90.9±8.4 in the FE group was greater (P<0.01) than 60.9±5.1 in the NFE and 36.7±5.2 in the RB group. The PMN viability percentage among the four groups was similar (range: 61.3±6.5% to 70.1±6.4%). The average PMN count in response to AI with all the three bulls, JY-426 (47 inseminations), JY-450 (23 inseminations) and HF-5 (33 inseminations), was less in the NFE than the FE group, the differences being marked in NFE compared with FE for JY-450 (51.8±12.4 compared with 88.0±17.4; P=0.10) and HF-5 (38.5±10.1 compared with 92.9±26.5; P<0.05). It is concluded that a greater PMN count post-AI could favor pregnancy outcome. Further, PMN migration is likely to be controlled by maternal factors rather than semen characteristics.

Effect of Cholesterol and Equex-STM Addition to an Egg Yolk Extender on Pure Spanish Stallion Cryopreserved Sperm

Cholesterol and Equex-STM are frequently added to different commercial and experimental extenders improving postthawing sperm quality. Doses of 125-150 mM of cholesterol from pig liver and 0.5-0.7% of Equex-STM were evaluated in a standard eggyolk extender (Martin et al., 1979). Six ejaculates per stallion from six pure Spanish stallions (6-8 years old) were collected in Martin's extender (B) and different mixtures of 125 mM-0.5% (I), 125 mM-0.7% (II), 150 mM-0.5% (III), and 150 mM-0.7% (IV) were added to original Martin's extender. Samples were frozen in 0.5 mL straws (100 × 10(6) spermatozoa) and thawed (21 s., 37°C water bath). After thawing the following parameters were evaluated: viability (V), motility (computer assisted sperm analysis, CASA; % nonprogressive NP; % progressive MP), hipoosmotic swelling test (HOST), acrosome integrity (A), fluorescence test (FL), and resistance test (RT). Sperm quality was significantly affected by stallion (in the parameters V, VI, NP, MP, HOST, A, FL, and RT), extraction (VI, NP, MP, HOST, A, and FL), and the different combinations of Equex-STM-cholesterol (FL). We concluded that 0.5% of Equex-STM mixed with 125 mM of cholesterol has obtained better sperm quality results than those of original Martin's extender, showing a simple and economic improvement of this home-made practical seminal extender.

Female postmating immune responses, immune system evolution and immunogenic males

Females in many taxa experience postmating activation of their immune system, independently of any genital trauma or pathogenic attack arising from male-female genital contact. This response has always been interpreted as a product of natural selection as it either prepares the female immune system for antigens arising from an implanted embryo (in the case of placental mammals), or is a "pre-emptive strike" against infection or injury acquired during mating. While the first hypothesis has empirical support, the second is not entirely satisfactory. Recently, studies that have experimentally dissected the postmating responses of Drosophila melanogaster females point to a different explanation: male reproductive peptides/proteins that have evolved in response to postmating male-male competition are directly responsible for activating particular elements of the female immune system. Thus, in a broad sense, males may be said to be immunogenic to females. Here, we discuss a possible direct role of sexual selection/sexual conflict in immune system evolution, in contrast to indirect trade-offs with other life-history traits, presenting the available evidence from a range of taxa and proposing ways in which the competing hypotheses could be tested. The major implication of this review is that immune system evolution is not only a product of natural selection but also that sexual selection and potentially sexual conflict enforces a direct selective pressure. This is a significant shift, and will compel researchers studying immune system evolution and ecological immunity to look beyond the forces generated by parasites and pathogens to those generated by the male ejaculate.

Treatment of persistent mating-induced endometritis in mares with the non-steroid anti-inflammatory drug vedaprofen

Recently, successful treatment of mares with a history of persistent mating-induced endometritis (PMIE) with dexamethasone has been reported. As systemic treatment of horses with glucocorticoids should be handled with caution, we tested the hypothesis that treatment with the non-steroid anti-inflammatory drug (NSAID) vedaprofen, an inhibitor of cyclooxygenase-2, may have comparative, positive effects on fertility. Barren mares with a history of repeated PMIE were treated with vedaprofen (n = 8; initially 2 mg/kg bodyweight followed by 1 mg/kg orally twice daily) from 1 day before the first insemination to 1 day after ovulation or left untreated (n = 9). All mares received oxytocin (20 I.E. s.c.) thrice daily. Uterine swabs were collected for bacteriology and cytology. The day after ovulation, fluid accumulation was detected in three control mares and four treated mares (n.s.). The percentage of neutrophils in uterine cytology was significantly increased in comparison to the day before ovulation irrespective of treatment. Pregnancy was confirmed in two of nine mares in the control group and seven of eight mares in the treatment group (p < 0.05). NSAIDs may positively affect fertility in mares with a history of PMIE.

Deep intra-uterine artificial inseminations using cryopreserved spermatozoa in beluga (Delphinapterus leucas)

Artificial insemination (AI) with liquid-stored spermatozoa and sperm cryopreservation using directional freezing (DF) have been successful in the beluga. This study built on this foundation to develop a deep intra-uterine AI technique with frozen-thawed semen in beluga. Forty-two ejaculates from one male were cryopreserved using DF technology and subsequently used for 10 insemination attempts with seven females. Percentage pre- and post-thaw progressive motility and viability were (mean +/- SD) 73.0 +/- 12.2, 38.4 +/- 8.8, 88.0 +/- 0.1, and 59.3 +/- 15.7%, respectively. A series of GnRH injections (3 x 250 microg, IV, 1.5 to 2 h apart) were used to induce ovulation, once a growing follicle >2.5 cm in diameter was visualized via trans-abdominal ultrasonography. Artificial insemination was performed at 30.1 +/- 3.8 h post-initial GnRH injection with semen deposited in the uterine horn, 92.6 +/- 16.2 cm beyond the genital opening using a flexible endoscope. The external cervical os (cEOS) was located beyond a series of 5 to 10 vaginal rings, 44.8 +/- 9.3 cm from the external genital opening. The internal bifurcation of the uterus was 27 +/- 6.8 cm beyond the cEOS. Ovulation occurred at 8.5 +/- 7.6 h post-AI. Two of 10 inseminations (20%) resulted in pregnancy. The first pregnancy resulted in twins; both calves were born 442 d after AI, with one surviving. The second pregnancy is ongoing. These findings represent the first successful application of AI using frozen-thawed semen in beluga, and are important examples of how assisted reproductive technologies can provide tools for the global management of threatened species.

Effect of sperm numbers and concentration on sperm transport and uterine inflammatory response in the mare

Our objective was to determine whether the concentration of cooled sperm inseminated influenced sperm transport and intensity of the uterine inflammatory reaction 2, 4 and 24h after insemination. Experimental subjects were 189 estrous mares with a dominant follicle > or =35 mm in diameter and no bacterial growth or neutrophils detected in uterine smears. Each mare was randomly assigned to receive one of the following intrauterine treatments (volume, 20 mL): insemination with 5x10(6) mL(-1) or 25x10(6) mL(-1) or 50x10(6) mL(-1) sperm diluted in 3 mL seminal plasma (SP) and 17 mL skim milk; seminal plasma or skim milk extender. Mares in a control group received no intrauterine treatment. Mares were slaughtered 2, 4 or 24h after insemination or infusion. Oviducts were separated from the uterus, and uterus and oviducts were then flushed with phosphate-buffered saline (PBS). After flushing, an endometrial sample was collected for further histopathological examination. The grade of uterine fibrosis and the amount of neutrophils in the stratum compactum were evaluated. A sample of each tubal flushing was examined for sperm count, and a sample of each uterine flushing was examined for PMN count. It was concluded that compounds in the insemination dose provoked a uterine inflammatory response, which was more rapid and intense as sperm concentration increased. In contrast, sperm transport through 4h after insemination was not influenced by sperm concentration.

Effect of boar exposure at time of insemination on factors influencing fertility in gilts

The effect of boar exposure during artificial insemination (AI) on semen backflow, fertilization, and embryo quality was evaluated. Gilts (approximately 170 d) were induced into estrus with PG600, and ovulation was synchronized using hCG 72 h later. Estrus detection was initiated after PG600 and continued at 12-h intervals. At estrus, gilts were allotted to receive boar exposure (BE, n = 20) or no boar exposure (NBE, n = 20) during AI. Gilts receiving NBE were identified to be in estrus prior to AI and the boar was then removed for 1 h, whereas gilts in the BE group received 15 min of exposure during AI. Insemination occurred in crates at 12 and 24 h after onset of estrus with 3 x 10(9) sperm/80 mL. Backflow was collected continuously with samples taken at time 0, (during AI), and at 0.25, 0.5, 0.75, 1, 2, 4, and 8 h after first and second AI. The effect of treatment was evaluated for time of insemination (min), backflow (mL), and sperm in backflow samples. Oviducts were flushed 2 d after first AI to evaluate the effect oftreatment on fertilization rate, accessory sperm numbers on embryos (scored 1 to 5), and embryo quality. There was no effect of first or second AI; therefore, data were pooled. Average duration of AI was 3.7 +/- 0.2 min and was not influenced by BE (P < 0.10). However, during the initial stage of AI, BE reduced the volume of semen (18.6 vs 32.4 +/- 3 mL) and the number of sperm lost (0.8 vs 1.3 +/- 0.15 x 10(9) sperm) compared to NBE (P < 0.05). There was a treatment x time effect (P < 0.05) for volume of backflow. By 45 min, the BE gilts lost more volume (9.0 vs 3.6 mL) compared to the NBE group, but sperm loss did not differ. Between 1 and 8 h after AI, neither volume nor sperm loss was influenced by treatment. By 8 h, total leakage (65 vs 63 mL) and total sperm loss (1.6 x 10(9) vs 1.8 x 10(9) sperm) were not influenced by BE (P > 0.10). However, more accessory sperm (P < 0.01) were found on embryos for the NBE (> or = 11 sperm/embryo) compared to BE embryos (< or = 10 sperm/embryo). Despite this observation, percentages of fertilized embryos (99.5 +/- 0.5 %) and number of embryos (11.5 +/- 0.1) were not different (P > 0.10). In conclusion, AI in the presence of a mature boar did not affect total semen leakage, sperm loss, fertilized embryos, or embryo quality. The importance of boar exposure during insemination was evident from less leakage during insemination, but had no effect on fertility; this suggests that the elimination of boar exposure during AI may not be deleterious to reproductive performance.

In vitro fertilization of in vitro-matured equine oocytes: effect of maturation medium, duration of maturation, and sperm calcium ionophore treatment, and comparison with rates of fertilization in vivo after oviductal transfer

Three experiments were conducted to evaluate the effect of oocyte and sperm treatments on rates of in vitro fertilization (IVF) in the horse and to determine the capacity of in vitro-matured horse oocytes to be fertilized in vivo. There was no effect of duration of oocyte maturation (24 vs. 42 h) or calcium ionophore concentration during sperm capacitation (3 microM vs. 7.14 microM) on in vitro fertilization rates. Oocytes matured in 100% follicular fluid had significantly higher fertilization (13% to 24%) than did oocytes matured in maturation medium or in 20% follicular fluid (0% to 12%; P < 0.05). There was no significant difference in fertilization rate among 3 sperm treatments utilizing 7.14 microM calcium ionophore (12% to 21%). Of in vitro-matured oocytes recovered 40-44 h after transfer to the oviducts of inseminated mares, 77% showed normal fertilization (2 pronuclei to normal cleavage). Cleavage to 2 or more cells was seen in 22% of oocytes matured in follicular fluid and 63% of oocytes matured in maturation medium; this difference was significant (P < 0.05). We conclude that in vitro-matured horse oocytes are capable of being fertilized at high rates in the appropriate environment and that in vitro maturation of oocytes in follicular fluid increases fertilization rate in vitro but reduces embryo development after fertilization in vivo. Further work is needed to determine the optimum environment for sperm capacitation and IVF in the horse.