Seminal DNase frees spermatozoa entangled in neutrophil extracellular traps

Effects of seminal plasma on uterine polymorphonuclear dynamics and fertility of jennies inseminated with glycerol-free, frozen-thawed donkey semen

BACKGROUND

Insemination of jennies with frozen-thawed donkey semen usually causes an intense uterine inflammation and results in low fertility.

OBJECTIVES

To evaluate the effects of seminal plasma on the time course of endometrial inflammation after insemination of jennies with donkey semen that was frozen using formamides as cryoprotective agents.

METHODS

Jennies were inseminated with fresh semen (FS, n = 14), frozen-thawed semen (FTS, n = 12) or frozen-thawed semen plus seminal plasma (FTS-SP, n = 13), and uterine cytology was evaluated at 8, 24 and 48 h post-insemination.

RESULTS

At 8 h post-insemination the percentage of polymorphonuclear cells (%PMN) was higher (P < 0.05) in the FTS group (90.7 ± 4.6) than in the FS group (68.9 ± 4.3), while jennies in the FTS-SP had intermediate levels (82.7 ± 4.5). At 24 h the %PMN was higher (P < 0.05) in jennies in the FTS-SP group (84.8 ± 4.5) than in the other groups. However, a faster decline in %PMN from 24 h to 48 h post-insemination in the FTS-SP group resulted in no difference between groups at 48 h. All groups still had mean %PMNs above 50 % at 48 h post-insemination, but the females that became pregnant had faster clearance rates from 24 h to 48 h post-insemination, resulting in lower %PMNs (44.4 ± 3.8) than those in the non-pregnant jennies (64.8 ± 3.6) at 48 h post-insemination (P<0.05).

CONCLUSION

Seminal plasma induced faster uterine polymorphonuclear clearance after 24 h post-insemination in jennies inseminated with frozen-thawed donkey semen, and this effect could be related to improved fertility.

Surface N- or O-linked glycans on bovine spermatozoa play minimal role in evading macrophage mediated phagocytosis

Bull spermatozoa possess glycocalyx made of carbohydrate moieties attached to proteins and lipids on their membranes that is involved in fertility associated functions including immune evasion in the female reproductive tract. The current study aimed to establish whether the differences in the glycocalyx of spermatozoa provide selective advantage in evading phagocytosis mediated by female macrophages. Based on removal of either N- or O-linked surface glycans from the spermatozoa, their susceptibility to phagocytosis by macrophages was assessed in vitro in bovines (Bos indicus) through flow cytometry. We found no significant difference (p > 0.05) in the phagocytosis of spermatozoa without N-glycans or O-glycans compared to those with intact glycocalyx. Out of nearly 2,000 events analysed, the mean number of macrophages phagocytosing the spermatozoa were found to be 416, 423 and 345, respectively for spermatozoa with an intact glycocalyx, with N-glycans removed and with O-glycans removed. The difference in the mean values of the individual sample geometric mean fluorescence intensities (n = 3) of the phagocytosed spermatozoa among all the treatment groups were also statistically insignificant (p > 0.05) indicating that the macrophages are not involved in the selection of spermatozoa based on their surface glycan profiles. Therefore, it is plausible to conclude that macrophages may be exploiting other signature molecules if at all they are involved in the cryptic female choice, or they might be phagocytosing spermatozoa with less stringency that may not be dependent on O- or-N-glycans on sperm surface. However, further studies are required to gain deeper insights into this phenomenon.

Genomic and transcriptomic evaluations of infertile or subfertile Arunachali yak sperm

Sperm infertility or subfertility is detrimental to the precious highland germplasm like yak whose population has been gradually declining in India. Understanding the 'omic' landscape of infertile or subfertile yak sperm can reveal some interesting insights. In an attempt to do the same, this study considered the semen of infertile or subfertile yak bulls for whole-genome and transcriptome evaluations. DNA sequencing revealed that the yak sperm genome contains the necessary genes to carry out all the important biological processes related to the growth, development, survival and multiplication of an organism. Interestingly, RNA Seq results highlighted that genes like VAMP7, MYLK, ARAP2 and MARCH6 showed increased expression, while biological processes related to immune response (GO:0043308, GO:0002447, GO:0002278, GO:0043307, GO:0043312, GO:0002283, GO:0043299 and GO:0002446) were significantly overrepresented. These findings hint at a possible role played by immune system in regulating infertility or subfertility in yaks. Further, in-depth studies can validate these findings and help in improving our biological understanding in this area.

Neutrophil extracellular traps in homeostasis and disease

Neutrophil extracellular traps (NETs), crucial in immune defense mechanisms, are renowned for their propensity to expel decondensed chromatin embedded with inflammatory proteins. Our comprehension of NETs in pathogen clearance, immune regulation and disease pathogenesis, has grown significantly in recent years. NETs are not only pivotal in the context of infections but also exhibit significant involvement in sterile inflammation. Evidence suggests that excessive accumulation of NETs can result in vessel occlusion, tissue damage, and prolonged inflammatory responses, thereby contributing to the progression and exacerbation of various pathological states. Nevertheless, NETs exhibit dual functionalities in certain pathological contexts. While NETs may act as autoantigens, aggregated NET complexes can function as inflammatory mediators by degrading proinflammatory cytokines and chemokines. The delineation of molecules and signaling pathways governing NET formation aids in refining our appreciation of NETs' role in immune homeostasis, inflammation, autoimmune diseases, metabolic dysregulation, and cancer. In this comprehensive review, we delve into the multifaceted roles of NETs in both homeostasis and disease, whilst discussing their potential as therapeutic targets. Our aim is to enhance the understanding of the intricate functions of NETs across the spectrum from physiology to pathology.

Contribution of the seminal microbiome to paternal programming

The field of Developmental Origins of Health and Disease has primarily focused on maternal programming of offspring health. However, emerging evidence suggests that paternal factors, including the seminal microbiome, could potentially play important roles in shaping the developmental trajectory and long-term offspring health outcomes. Historically, the microbes present in the semen were regarded as inherently pathogenic agents. However, this dogma has recently been challenged by the discovery of a diverse commensal microbial community within the semen of healthy males. In addition, recent studies suggest that the transmission of semen-associated microbes into the female reproductive tract during mating has potentials to not only influence female fertility and embryo development but could also contribute to paternal programming in the offspring. In this review, we summarize the current knowledge on the seminal microbiota in both humans and animals followed by discussing their potential involvement in paternal programming of offspring health. We also propose and discuss potential mechanisms through which paternal influences are transmitted to offspring via the seminal microbiome. Overall, this review provides insights into the seminal microbiome-based paternal programing, which will expand our understanding of the potential paternal programming mechanisms which are currently focused primarily on the epigenetic modifications, oxidative stresses, and cytokines.

Extrusion of Neutrophil Extracellular Traps (NETs) Negatively Impacts Canine Sperm Functions: Implications in Reproductive Failure

Reproductive failure in dogs is often due to unknown causes, and correct diagnosis and treatment are not always achieved. This condition is associated with various congenital and acquired etiologies that develop inflammatory processes, causing an increase in the number of leukocytes within the female reproductive tract (FRT). An encounter between polymorphonuclear neutrophils (PMNs) and infectious agents or inflammation in the FRT could trigger neutrophil extracellular traps (NETs), which are associated with significantly decreased motility and damage to sperm functional parameters in other species, including humans. This study describes the interaction between canine PMNs and spermatozoa and characterizes the release of NETs, in addition to evaluating the consequences of these structures on canine sperm function. To identify and visualize NETs, May-Grünwald Giemsa staining and immunofluorescence for neutrophil elastase (NE) were performed on canine semen samples and sperm/PMN co-cultures. Sperm viability was assessed using SYBR/PI and acrosome integrity was assessed using PNA-FITC/PI by flow cytometry. The results demonstrate NETs release in native semen samples and PMN/sperm co-cultures. In addition, NETs negatively affect canine sperm function parameters. This is the first report on the ability of NETs to efficiently entrap canine spermatozoa, and to provide additional data on the adverse effects of NETs on male gametes. Therefore, NETs formation should be considered in future studies of canine reproductive failure, as these extracellular fibers and NET-derived pro-inflammatory capacities will impede proper oocyte fertilization and embryo implantation. These data will serve as a basis to explain certain reproductive failures of dogs and provide new information about triggers and molecules involved in adverse effects of NETosis for domestic pet animals.

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.

DNase I rescues goat sperm entrapped by neutrophil extracellular traps

Artificial insemination has been a predominant technique employed in goat husbandry for breeding purposes. Subsequent to artificial insemination, sperm can elicit inflammation in the reproductive tract, resulting in substantial the accumulation of neutrophils. Recognized as foreign entities, sperm may become entrapped within neutrophil extracellular traps (NETs) released by neutrophils, thereby exploiting their properties of pathogen elimination. Deoxyribonuclease I (DNase I), which is known for disintegrating NETs and causing loss of function, has been utilized to ameliorate liver and brain damage resulting from NETs, as well as to enhance sperm quality. This study investigated the mechanism of sperm-induced NETs and further explored the impact of DNase I on NETs. Sperm quality was evaluated using optical microscopy, while the structure of NETs was observed through immunofluorescence staining. The formation mechanism of NETs was examined using inhibitors and PicoGreen. The findings revealed that sperm induced the formation of NETs, a process regulated by glycolysis, NADPH oxidase, ERK1/2, and p38 signaling pathways. The composition of NETs encompassed DNA, citrullinated histone H3 (citH3), and elastase (NE). DNase I protects sperm by degrading NETs, thereby concurrently preserving the integrity of plasma membrane and motility of sperm. In summary, the release of sperm-induced NETs leads to its damage, but this detrimental effect is counteracted by DNase I through degradation of NETs. These observations provide novel insights into reproductive immunity in goats.

Morphology of the immune cells in the wall of the human uterine tube and their possible impact on reproduction-uterine tube as a possible immune privileged organ

The uterine tube, as well as other parts of the upper female reproductive system, is immunologically unique in its requirements for tolerance to allogenic sperm and semi-allogenic embryos, yet responds to an array of sexually transmitted pathogens. To understand this dichotomy, there is a need to understand the functional morphology of immune cells in the wall of the uterine tube. Thus, we reviewed scientific literature regarding immune cells and the human uterine tube by using the scientific databases. The human uterine tube has a diverse population of immunocompetent cells representing both the innate and adaptive immune systems. We describe in detail the possible roles of cells of the mononuclear phagocyte system (macrophages and dendritic cells), T and B lymphocytes, natural killer cells, neutrophils and mast cells in association with the reproductive functions of uterine tubes. We are also discussing about the possible "immune privilege" of the uterine tube, as another mechanism to tolerate sperm and embryo without eliciting an inflammatory immune response. In uterine tube is not present an anatomical blood-tissue barrier between antigens and circulation. However, the immune cells of the uterine tube probably represent a type of "immunological barrier," which probably includes the uterine tube among the immunologically privileged organs. Understanding how immune cells in the female reproductive tract play roles in reproduction is essential to understand not only the mechanisms of gamete transport and fertilization as well as embryo transport through the uterine tube, but also in improving results from assisted reproduction.

Effect of different sperm populations on neutrophils extracellular traps (NETs) formation in cattle

In cattle, clinical and subclinical inflammation in the bovine female reproductive tract (FRT) significantly reduces fertility. PMN participate in this FRT-associated inflammation by eliminating pathogens by eliciting various defense mechanisms, with the release of neutrophil extracellular traps NETs) being the latest process discovered. Consistently, human-, bovine- and porcine-derived spermatozoa induce release of NETs in exposed PMN of the same species origin, and thereby decreasing sperm motility through NETs-mediated entrapment. The release of NETs in the presence of different sperm sub-populations is evaluated in this work. Cryopreserved bovine sperm were selected and different sperm populations were used: viable sperm, sperm with oxidative stress, capacitated sperm, and sperm with loss of viability. Isolated PMN of dairy cows were co-incubated with these sperm populations for 4 h. Neutrophil elastase (NE) and DNA were detected by fluorescence microscopy analysis. It was noted that exposed bovine PMN released NETs in the presence of sperm. Moreover, sperm-triggered NETosis resulted different phenotypes of NETs, i. e. spread NETs (sprNETs), diffused NETs (diffNETs) and aggregated NETs (aggNETs). Viable/motile spermatozoa induced a higher proportion of NETotic cells at 15, 60 and 120 min in comparison to controls. In conclusion, all bovine sperm populations in co-culture with PMN generated NETs extrusion while viable sperm activated NETotic cells to a greater extent. With this being an early event in the activation of bovine PMN.

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.

Suspension of hostility: Positive interactions between spermatozoa and female reproductive tracts

Interactions between spermatozoa and the female reproductive tract (FRT) are complex, in many cases poorly understood, and likely to contribute to the mechanistic basis of idiopathic infertility. As such, it is not surprising that the FRT was often viewed historically as a "hostile" environment for spermatozoa. The FRT has also been touted as a selective environment to ensure that only the highest quality spermatozoa progress to the oocyte for the opportunity to participate in fertilization. Recent advances, however, are giving rise to a far more nuanced view in which supportive spermatozoa × FRT interactions-in both directions-contribute to beneficial, even essential, effects on fertility. In this perspective article, we discuss several examples of positive spermatozoa × FRT interactions. We believe that these examples, arising in part from studies of taxonomically diverse nonmammalian systems, are useful to efforts to study mammalian spermatozoa × FRT interactions and their relevance to fertility and the advancement of assisted reproductive technologies.

Interaction of sperm cells with the female reproductive tract in cattle: Focus on neutrophil extracellular trap formation

After insemination of cows, either naturally or artificially, the deposition of semen into the vagina or uterus results in an immune reaction which is based on polymorphonuclear neutrophil activity. Sperm must be resistant to immune system actions of the female for an adequate time to allow fertilization to occur. Neutrophils, however, either directly phagocytize sperm through cell-cell attachment or entrap sperm cells in neutrophil extracellular traps (NETs), structures consisting of neutrophil nuclear DNA and associated proteins. In this review article, the interaction of neutrophils and sperm cells in t cattle will be described, with a special focus on the formation of neutrophil extracellular traps (NETs).

Diversity of sialic acids and sialoglycoproteins in gametes and at fertilization

Sialic acids are a family of 9-carbon monosaccharides with particular physicochemical properties. They modulate the biological functions of the molecules that carry them and are involved in several steps of the reproductive process. Sialoglycoproteins participate in the balance between species recognition and specificity, and the mechanisms of these aspects remain an issue in gametes formation and binding in metazoan reproduction. Sialoglycoproteins form a specific coat at the gametes surface and specific polysialylated chains are present on marine species oocytes. Spermatozoa are submitted to critical sialic acid changes in the female reproductive tract facilitating their migration, their survival through the modulation of the female innate immune response, and the final oocyte-binding event. To decipher the role of sialic acids in gametes and at fertilization, the dynamical changes of enzymes involved in their synthesis and removal have to be further considered.

Composition and effects of seminal plasma in the female reproductive tracts on implantation of human embryos

The function of seminal plasma involves acting as a transport medium for sperm and as a means of communication between the reproductive tissues of the male and female. It is also a vital factor to prime the reproductive tracts of the female for optimal pregnancy. When the reproductive tract of the female is exposed to seminal plasma, serious alterations take place, enhancing pathogen and debris clearance observed in the uterus throughout mating. It is also capable of supporting embryo growth, promoting the receptivity of the uterus, and establishing tolerance to the semi-allogenic embryo. Moreover, seminal plasma is capable of regulating the functions of several female reproductive organs and providing an ideal condition for effective embryo implantation and pregnancy. It is believed that the health state of the offspring is affected by exposure to seminal plasma. For the treatment of infertility, assisted reproductive technologies have been extensively employed. The application of seminal plasma as a therapeutic approach to enhance the development of embryo competency and rate of implantation, receptivity of endometrium, and establishment of maternal immune tolerance in cycles of ART appears possible. Herein, current knowledge on the composition of seminal plasma and the physiological roles it possesses on various parts of the female reproductive tract are summarized. Moreover, the role of seminal plasma in the development of embryos, implantation, and the following fetal growth and survival have been reviewed in this article.

Adverse Effects of Single Neutrophil Extracellular Trap-Derived Components on Bovine Sperm Function

Neutrophil extracellular traps (NETs) play a key role in fertilisation by eliminating microorganisms and entrapping spermatozoa in the female reproductive tract (FRT). The deleterious effects of NETs on spermatozoa have been previously described; however, individual exposure to NET-derived components in bull spermatozoa has not been explored. The aim of this study was to evaluate the effects of the main NET-derived proteins, histone 2A (H2A), neutrophil elastase (ELA), myeloperoxidase (MPO), pentraxin 3 (PTX), cathepsin G (Cat-G), and cathelicidin LL37 (LL-37), at concentrations of 1, 10, and 30 μg/mL, on sperm parameters. Sperm were selected and incubated with different NET-derived proteins for 4 h. Membrane and acrosome integrity, lipoperoxidation, and membrane phospholipid disorders were also evaluated. Bovine polymorphonuclear neutrophil (PMN)/sperm co-cultures were evaluated by scanning electron microscopy and immunofluorescence. All NET-derived proteins/enzymes resulted in a reduction in membrane integrity, acrosome integrity, and lipoperoxidation at a concentration of 30 μg/mL. Bovine PMN/sperm co-cultures showed marked NET formation in the second hour. In conclusion, all NET-derived proteins/enzymes exerted cytotoxic effects on bull sperm, and this effect should be considered in future investigations on the uterine microenvironment and the advancement of spermatozoa in the FRT.

The Expanding Role of Extracellular Traps in Inflammation and Autoimmunity: The New Players in Casting Dark Webs

The first description of a new form of neutrophil cell death distinct from that of apoptosis or necrosis was discovered in 2004 and coined neutrophil extracellular traps "(NETs)" or "NETosis". Different stimuli for NET formation, and pathways that drive neutrophils to commit to NETosis have been elucidated in the years that followed. Critical enzymes required for NET formation have been discovered and targeted therapeutically. NET formation is no longer restricted to neutrophils but has been discovered in other innate cells: macrophages/monocytes, mast Cells, basophils, dendritic cells, and eosinophils. Furthermore, extracellular DNA can also be extruded from both B and T cells. It has become clear that although this mechanism is thought to enhance host defense by ensnaring bacteria within large webs of DNA to increase bactericidal killing capacity, it is also injurious to innocent bystander tissue. Proteases and enzymes released from extracellular traps (ETs), injure epithelial and endothelial cells perpetuating inflammation. In the context of autoimmunity, ETs release over 70 well-known autoantigens. ETs are associated with pathology in multiple diseases: lung diseases, vasculitis, autoimmune kidney diseases, atherosclerosis, rheumatoid arthritis, cancer, and psoriasis. Defining these pathways that drive ET release will provide insight into mechanisms of pathological insult and provide potential therapeutic targets.

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

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

Transcriptomic analysis of the seminal vesicle response to the reproductive toxicant acrylamide

BACKGROUND

The seminal vesicles synthesise bioactive factors that support gamete function, modulate the female reproductive tract to promote implantation, and influence developmental programming of offspring phenotype. Despite the significance of the seminal vesicles in reproduction, their biology remains poorly defined. Here, to advance understanding of seminal vesicle biology, we analyse the mouse seminal vesicle transcriptome under normal physiological conditions and in response to acute exposure to the reproductive toxicant acrylamide. Mice were administered acrylamide (25 mg/kg bw/day) or vehicle control daily for five consecutive days prior to collecting seminal vesicle tissue 72 h following the final injection.

RESULTS

A total of 15,304 genes were identified in the seminal vesicles with those encoding secreted proteins amongst the most abundant. In addition to reproductive hormone pathways, functional annotation of the seminal vesicle transcriptome identified cell proliferation, protein synthesis, and cellular death and survival pathways as prominent biological processes. Administration of acrylamide elicited 70 differentially regulated (fold-change ≥1.5 or ≤ 0.67) genes, several of which were orthogonally validated using quantitative PCR. Pathways that initiate gene and protein synthesis to promote cellular survival were prominent amongst the dysregulated pathways. Inflammation was also a key transcriptomic response to acrylamide, with the cytokine, Colony stimulating factor 2 (Csf2) identified as a top-ranked upstream driver and inflammatory mediator associated with recovery of homeostasis. Early growth response (Egr1), C-C motif chemokine ligand 8 (Ccl8), and Collagen, type V, alpha 1 (Col5a1) were also identified amongst the dysregulated genes. Additionally, acrylamide treatment led to subtle changes in the expression of genes that encode proteins secreted by the seminal vesicle, including the complement regulator, Complement factor b (Cfb).

CONCLUSIONS

These data add to emerging evidence demonstrating that the seminal vesicles, like other male reproductive tract tissues, are sensitive to environmental insults, and respond in a manner with potential to exert impact on fetal development and later offspring health.

Comparison of the uterine inflammatory response to frozen-thawed sperm from high and low fertility bulls

Some bulls with apparently normal semen quality yield unacceptably low pregnancy rates. We hypothesised that a differential uterine immunological response to sperm from high and low fertility bulls may contribute to these differences. The experimental model used was heifer follicular phase uterine explants incubated with frozen-thawed sperm from high and low fertility bulls (3-5 replicates per experiment). Inflammatory gene expression of IL1A, IL1B, IL6, TNFA and CXCL8 were assessed by qPCR and IL1-β and IL-8 were quantified in explant supernatants by ELISA. Neutrophil binding affinity to sperm from high and low fertility bulls was also assessed. There was a significant up-regulation of IL1A, IL1B and TNFA from frozen-thawed sperm, irrespective of fertility status, compared to the unstimulated control. This response was confirmed at the protein level, with an increase of IL-1β and IL-8 protein concentrations by 5 and 2.7 fold, respectively (P < 0.05). Although no significant differences in the inflammatory response at the gene or protein level were evident between high and low fertility bulls, more sperm from low compared to high fertility bulls bound to neutrophils (P < 0.05). Using bulls of unknown fertility, cauda epididymal sperm (CES) plus seminal plasma (SP) upregulated IL6 (P < 0.05) but there was no upregulation of any inflammatory gene expression for CES alone. Overall, this ex vivo study demonstrated an upregulation of inflammatory gene expression in the uterus in response to frozen-thawed bull sperm. While there was no difference between sperm from high and low fertility bulls, there was a greater binding affinity of low fertility sperm by neutrophils.

DNase activity in human seminal plasma and follicular fluid and its inhibition by follicular fluid chelating agents

RESEARCH QUESTION

What is the mechanism by which human follicular fluid inhibits seminal plasma DNase activity?

DESIGN

Human genomic DNA was incubated with human follicular fluid and seminal plasma (reaction mixture) under different experimental conditions; increasing volumes of human follicular fluid; proteinase K digested or heat inactivated human follicular fluid; and the addition of Ca²⁺ or Mg²⁺ to the reaction mixture.

RESULTS

Increasing volume of human follicular fluid resulted in a dose-dependent inhibition of seminal plasma DNase activity. Inhibition was not caused by proteins in the human follicular fluid as digestion with proteinase K or heat inactivation of human follicular fluid failed to abolish its inhibitory effect. Addition of divalent cations resulted in a reversion of the inhibitory effect, providing evidence that human follicular fluid inhibition of seminal plasma DNase activity seems to be mediated by a compound with chelating activity. Furthermore, incubation of genomic DNA with human follicular fluid in the presence of divalent cations served to elicit the existence of DNase activity.

CONCLUSIONS

Human follicular fluid seems to contain a molecule or molecules with chelating capacity that inhibits DNase activity of both follicular fluid and seminal plasma. Our findings provide new insight to understanding sperm preservation and the physiology of fertilization biology.

Extracellular Reactive Oxygen Species (ROS) Production in Fresh Donkey Sperm Exposed to Reductive Stress, Oxidative Stress and NETosis

Jenny shows a large endometrial reaction after semen influx to the uterus with a large amount of polymorphonuclear neutrophils (PMN) migrating into the uterine lumen. PMN act as a sperm selection mechanism through phagocytosis and NETosis (DNA extrudes and, together with proteins, trap spermatozoa). While a reduced percentage of spermatozoa are phagocytosed by PMN, most are found to be attached to neutrophil extracellular traps (NETs). This selection process together with sperm metabolism produces a large amount of reactive oxygen species (ROS) that influence the reproductive success. The present study aimed to determine the extracellular ROS production in both sperm and PMN. With this purpose, (1) donkey sperm were exposed to reductive and oxidative stresses, through adding different concentrations of reduced glutathione (GSH) and hydrogen peroxide (H₂O₂), respectively; and (2) PMN were subjected to NETosis in the presence of the whole semen, sperm, seminal plasma (SP) or other activators such as formyl-methionyl-leucyl-phenylalanine (FMLP). Extracellular ROS production (measured as H₂O₂ levels) was determined with the Amplex^® Red Hydrogen Peroxide/Peroxidase Assay Kit. Donkey sperm showed more resilience to oxidative stress than to the reductive one, and GSH treatments led to greater H₂O₂ extracellular production. Moreover, not only did SP appear to be the main inducer of NETosis in PMN, but it was also able to maintain the extracellular H₂O₂ levels produced by sperm and NETosis.

Swine spermatozoa trigger aggregated neutrophil extracellular traps leading to adverse effects on sperm function

In pigs, the number of PMN in uterus lumen increases within few hours after natural or artificial AI resulting in early PMN-derived innate immune reactions. Sperm-NETs formation was recently reported to occur in various mammalian species. Aim of this study was to investigate direct interactions of boar spermatozoa with swine PMN, the release of sperm-mediated NETs, and to assess NET-derived effects on sperm functionality. Sperm-triggered NETs were visualized by SEM- and immunofluorescence analyses. Sperm-mediated NETosis was confirmed by presence of extruded DNA with global histones and NE. Largest sizes of sperm-mediated aggNETs were detected after 5 h thereby resulting in effective massive sperm entrapment. The number of aggNETs increased from 3 h onwards. Kinetic studies of swine sperm-mediated NETosis showed to be a time-dependent cellular process. In addition, number of NETs-entrapped spermatozoa increased at 3 h of exposure whilst few free spermatozoa were detected after 3 h. Anchored NETs also increased from 3 h onwards. The cytotoxicity of NETs was confirmed by diminution of the total motility and the progressive motility. Spermatozoa membrane integrity and function loss exposed to NETs was confirmed from 3 h. Experiments revealed NETs-derived damaging effects on swine spermatozoa in membrane integrity, motility and functionality. We hypothesize that swine sperm-triggered aggNETs might play a critical role in reduced fertility potential in swine reproductive technique. Thus, aggNETs formation needs to be considered in future studies about uterine environment as well as advance of sperm in the porcine female reproductive tract.

Specific Seminal Plasma Fractions Are Responsible for the Modulation of Sperm-PMN Binding in the Donkey

While artificial insemination (AI) with frozen-thawed sperm results in low fertility rates in donkeys, the addition of seminal plasma, removed during cryopreservation, partially counteracts that reduction. Related to this, an apparent inflammatory reaction in jennies is induced following AI with frozen-thawed sperm, as a high amount of polymorphonuclear neutrophils (PMN) are observed within the donkey uterus six hours after AI. While PMN appear to select the sperm that ultimately reach the oviduct, two mechanisms, phagocytosis and NETosis, have been purported to be involved in that clearance. Remarkably, sperm interacts with PMN, but the presence of seminal plasma reduces that binding. As seminal plasma is a complex fluid made up of different molecules, including proteins, this study aimed to evaluate how different seminal plasma fractions, separated by molecular weight (<3, 3-10, 10-30, 30-50, 50-100, and >100 kDa), affect sperm-PMN binding. Sperm motility, viability, and sperm-PMN binding were evaluated after 0 h, 1 h, 2 h, 3 h, and 4 h of co-incubation at 38 °C. Two seminal plasma fractions, including 30-50 kDa or 50-100 kDa proteins, showed the highest sperm motility and viability. As viability of sperm not bound to PMN after 3 h of incubation was the highest in the presence of 30-50 and 50-100 kDa proteins, we suggest that both fractions are involved in the control of the jenny's post-breeding inflammatory response. In conclusion, this study has shown for the first time that specific fractions rather than the entire seminal plasma modulate sperm-PMN binding within the donkey uterus. As several proteins suggested to be involved in the control of post-AI endometritis have a molecular weight between 30 and 100 kDa, further studies aimed at determining the identity of these molecules and evaluating their potential effect in vivo are much warranted.

Seminal plasma, and not sperm, induces time and concentration-dependent neutrophil extracellular trap release in donkeys

BACKGROUND

In several mammalian species, acute endometritis driven by the recruitment of polymorphonuclear cells (PMN) occurs in response to semen. These PMNs release DNA to form neutrophil extracellular traps (NETs) in cattle, horse and human, leading to sperm entrapment. While there is no evidence of this phenomenon occurring in donkeys, artificial insemination (AI) with frozen-thawed semen, which results in very poor pregnancy rates, leads to a large PMN recruitment to the uterus.

OBJECTIVES

To investigate whether donkey semen can trigger NET release (NETosis) and if excessive NETosis occurs in response to frozen-thawed semen.

STUDY DESIGN

In vitro experiments.

METHODS

Jenny PMNs were exposed to jackass fresh or frozen-thawed semen, isolated sperm or seminal plasma (SP), over the course of three experiments. NET formation in response to different treatments was assessed through manual quantification of stained slides. A one-way analysis of variance (ANOVA), followed by a post hoc Sidak test, was carried out to determine statistical significance.

RESULTS

NET release occurred in a semen concentration- and incubation-time-dependent manner. Surprisingly, frozen-thawed donkey sperm did not increase NETosis rate in comparison with the control (23 ± 2.5% vs. 31 ± 3.7%; P > .05), whereas fresh semen exposure did (78 ± 5.7% vs. 26 ± 3.2%, P < .01). NETosis increased in the presence of SP, regardless of the presence or absence of sperm, in comparison with the control in both fresh (84 ± 5.2% and 77 ± 5.0% vs. 12 ± 2.7%, respectively; P < .01) and frozen (95 ± 2.2% and 94 ± 2.9% vs. 14 ± 3.8%, respectively; P < .01) samples. Moreover, exposure of PMN to viable and motile sperm, in the absence of SP, did not increase NETosis rates (P > .05).

CONCLUSIONS

Donkey SP, and not sperm-intrinsic factors, is able to trigger NETosis in both time- and semen concentration-dependent manner. The physiological relevance of such response against semen in the donkey remains to be elucidated.

Myeloperoxidase Inhibition Decreases the Expression of Collagen and Metallopeptidase in Mare Endometria under In Vitro Conditions

Neutrophils can originate neutrophil extracellular traps (NETs). Myeloperoxidase (MPO) is a peroxidase found in NETs associated to equine endometrosis and can be inhibited by 4-aminobenzoic acid hydrazide (ABAH). Metallopeptidases (MMPs) participate in extracellular matrix stability and fibrosis development. The objectives of this in vitro work were to investigate, in explants of mare's endometrium, (i) the ABAH capacity to inhibit MPO-induced collagen type I (COL1) expression; and (ii) the action of MPO and ABAH on the expression and gelatinolytic activity of MMP-2/-9. Explants retrieved from the endometrium of mares in follicular or mid-luteal phases were treated with MPO, ABAH, or their combination, for 24 or 48 h. The qPCR analysis measured the transcription of COL1A2, MMP2, and MMP9. Western blot and zymography were performed to evaluate COL1 protein relative abundance and gelatinolytic activity of MMP-2/-9, respectively. Myeloperoxidase elevated COL1 relative protein abundance at both treatment times in follicular phase (p < 0.05). The capacity of ABAH to inhibit MPO-induced COL1 was detected in follicular phase at 48 h (p < 0.05). The gelatinolytic activity of activated MMP-2 augmented in mid-luteal phase at 24 h after MPO treatment, but it was reduced with MPO+ABAH treatment. The activity of MMP-9 active form augmented in MPO-treated explants. However, this effect was inhibited by ABAH in the follicular phase at 48 h (p < 0.05). By inhibiting the pro-fibrotic effects of MPO, it might be possible to reduce the development of endometrosis. Metallopeptidase-2 might be involved in an acute response to MPO in the mid-luteal phase, while MMP-9 might be implicated in a prolonged exposition to MPO in the follicular phase.

Seasonal differences in seminal plasma proteins from two bovine breeds adapted to a subtropical climate

This study was designed to evaluate the seasonal expression of seminal plasma proteins from two bovine breeds adapted to a subtropical climate and their associations with post-thawing sperm and environmental characteristics. Semen samples were obtained three times in summer and three times in winter from four Crioulo Lageano and four Angus bulls. Seminal plasma was obtained by centrifugation, and the other portion of the semen was cryopreserved. Seminal plasma proteins were identified by 2D-nanoUPLC-MS^E. Post-thawing assessments of sperm kinetics, morphology and membrane integrity were performed. Environmental data such as air temperature, air humidity and black globe temperature (BGT) were recorded, and the temperature-humidity index (THI) was calculated in summer and winter. Results showed that the climate varied significantly between seasons. Although no statistical differences were observed in semen quality between breeds, the protein profiles varied within and between seasons. We suggest that the most critical proteins in summer affecting sperm characteristics were TIMP-2, DNase, Clusterin, CFAH and GPx6. TIMP-2 and DNase showed a higher abundance in Crioulo Lageano in comparison with Angus, while Clusterin, CFAH and GPx6 presented a lower abundance. To the best of our knowledge, this is the first report of a recently evolved type of glutathione peroxidase, GPx6, in seminal plasma of bovines. In winter, five proteins were considered to be more critical: BSP1, BSP3, CCL2, Sulfhydryl oxidase and TIMP-2. BSP1 and TIMP-2 showed a lower abundance while BSP3, CCL2 and Sulfhydryl oxidase presented a higher abundance in this season in Crioulo Lageano in comparison with Angus.

Single Layer Centrifugation Improves the Quality of Fresh Donkey Semen and Modifies the Sperm Ability to Interact with Polymorphonuclear Neutrophils

Simple Summary

Donkey Artificial Insemination (AI) with frozen/thawed semen results in poor fertility outcomes. Jennies show a significant post-AI endometrial reaction, with a large amount of defense cells—polymorphonuclear neutrophils (PMN)—migrating to the uterine lumen. Seminal plasma (SP) has a detrimental effect on sperm conservation and its removal is a necessary step in the semen freezing protocol. However, several SP proteins seem to control sperm-PMN binding. Single layer centrifugation (SLC) with colloids, which has been used to select spermatozoa and improve reproductive performance in different species, is known to remove SP proteins attached to the sperm membrane. In this study, two experiments were performed. The first one compared the quality of SLC-selected and non-selected fresh donkey spermatozoa. In the second experiment, PMN obtained from the peripheral blood were co-incubated with selected and unselected spermatozoa, and the interaction between PMN and spermatozoa was analyzed. In conclusion, SLC of fresh donkey semen increases the proportion of functionally intact spermatozoa and appears to remove the SP proteins that inhibit sperm-PMN binding, thus increasing sperm phagocytosis by PMN.

Abstract

This study sought to determine whether single layer centrifugation (SLC) of fresh donkey semen with Equicoll has any impact on sperm quality parameters and on the modulation of endometrial reaction following semen deposition using an in vitro model. Seventeen ejaculates from five jackasses were obtained using an artificial vagina and diluted in a skim-milk extender. Samples were either selected through SLC (Equicoll) or non-treated (control). Two experiments were performed. The first one consisted of incubating selected or non-selected spermatozoa at 38 °C for 180 min. Integrity and lipid disorder of sperm plasma membrane, mitochondrial membrane potential, and intracellular levels of calcium and reactive oxygen species were evaluated at 0, 60, 120, and 180 min. In the second experiment, polymorphonuclear neutrophils (PMN) isolated from jennies blood were mixed with selected and unselected spermatozoa. Interaction between spermatozoa and PMN was evaluated after 0, 60, 120, and 180 min of co-incubation at 38 °C. SLC-selection increased the proportions of spermatozoa with an intact plasma membrane and low lipid disorder, of spermatozoa with high mitochondrial membrane potential and with high calcium levels, and of progressively motile spermatozoa. In addition, selection through SLC augmented the proportion of phagocytosed spermatozoa, which supported the modulating role of seminal plasma proteins on sperm-PMN interaction. In conclusion, SLC of fresh donkey semen increases the proportions of functionally intact and motile spermatozoa, and appears to remove the seminal plasma proteins that inhibit sperm-PMN binding.

Semen extender and seminal plasma alter the extent of neutrophil extracellular traps (NET) formation in cattle

During artificial insemination in bovine, the deposition of semen into the uterus results in an immune reaction which is based on polymorphonuclear neutrophils activity, including the formation of neutrophil extracellular traps. The formation of neutrophil extracellular traps as a reaction of neutrophils to spermatozoa was recently described. However, it is not completely clear which components of the semen are responsible for this reaction. The objective of this study was to quantify and compare the formation of neutrophil extracellular traps following in vitro incubation of bovine polymorphonuclear neutrophils with semen and extenders of different origins and conditions. We investigated the interactions between bovine polymorphonuclear neutrophils and different semen extenders, various seminal plasma concentrations from young and old bulls as well as sexed and non-sexed semen and their corresponding extenders. Three different semen extenders from two companies in fresh and frozen-thawed conditions were compared. Fresh semen extenders showed higher neutrophil extracellular traps induction than did frozen-thawed ones. The formation of neutrophil extracellular traps were also dependent on the presence of seminal plasma. We could show that seminal plasma alone, without any sperm cells, induced the reaction and that the addition of at least 1% seminal plasma already resulted in the formation of neutrophil extracellular traps. Furthermore, seminal plasma from young bulls led to significant higher neutrophil extracellular traps induction. No difference between non-sex-sorted and sex-sorted sperm and its extenders was observed. Taken together, different semen extenders as well as the amount and origin of seminal plasma influence neutrophil extracellular traps formation, whereas sex-sorted sperm did not affect the reaction.

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

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

Sperm interactions with the female reproductive tract: A key for successful fertilization in mammals

Sperm migration through the female genital tract is not a quiet journey. Uterine contractions quickly operate a drastic selection, leading to a very restrictive number of sperm reaching the top of uterine horns and finally, provided the presence of key molecules on sperm, the oviduct, where fertilization takes place. During hours and sometimes days before fertilization, subpopulations of spermatozoa interact with dynamic and region-specific maternal components, including soluble proteins, extracellular vesicles and epithelial cells lining the lumen of the female tract. Interactions with uterine and oviductal cells play important roles for sperm survival as they modulate the maternal immune response and allow a transient storage before ovulation. The body of work reported here highlights the importance of sperm interactions with proteins originated from both the uterine and oviductal fluids, as well as hormonal signals around the time of ovulation for sperm acquisition of fertilizing competence.

A Higher Abundance of O-Linked Glycans Confers a Selective Advantage to High Fertile Buffalo Spermatozoa for Immune-Evasion From Neutrophils

The glycans on the plasma membrane of cells manifest as the glycocalyx, which serves as an information-rich frontier that is directly in contact with its immediate milieu. The glycoconjugates (GCs) that adorn most of the mammalian cells are also abundant in gametes, especially the spermatozoa where they perform unique reproduction-specific functions e.g., inter-cellular recognition and communication. This study aimed to implicate the sperm glycosylation pattern as one of the factors responsible for low conception rates observed in buffalo bulls. We hypothesized that a differential abundance of glycans exists on the spermatozoa from bulls of contrasting fertilizing abilities endowing them with differential immune evasion abilities. Therefore, we investigated the role of glycan abundance in the phagocytosis and NETosis rates exhibited by female neutrophils (PMNs) upon exposure to such spermatozoa. Our results indicated that the spermatozoa from high fertile (HF) bulls possessed a higher abundance of O-linked glycans e.g., galactosyl (β-1,3)N-acetylgalactosamine and N-linked glycans like [GlcNAc]1-3, N-acetylglucosamine than the low fertile (LF) bull spermatozoa. This differential glycomic endowment appeared to affect the spermiophagy and NETosis rates exhibited by the female neutrophil cells (PMNs). The mean percentage of phagocytizing PMNs was significantly different (P < 0.0001) for HF and LF bulls, 28.44 and 59.59%, respectively. Furthermore, any introduced perturbations in the inherent sperm glycan arrangements promoted phagocytosis by PMNs. For example, after in vitro capacitation the mean phagocytosis rate (MPR) rate in spermatozoa from HF bulls significantly increased to 66.49% (P < 0.01). Likewise, the MPR increased to 70.63% (p < 0.01) after O-glycosidase & α2-3,6,8,9 Neuraminidase A treatment of spermatozoa from HF bulls. Moreover, the percentage of PMNs forming neutrophil extracellular traps (NETs) was significantly higher, 41.47% when exposed to spermatozoa from LF bulls vis-à-vis the spermatozoa from HF bulls, 15.46% (P < 0.0001). This is a pioneer report specifically demonstrating the role of O-linked glycans in the immune responses mounted against spermatozoa. Nevertheless, further studies are warranted to provide the measures to diagnose the sub-fertile phenotype thus preventing the losses incurred by incorrect selection of morphologically normal sperm in the AI/IVF reproduction techniques.

Increase of leucocyte-derived extracellular traps (ETs) in semen samples from human acute epididymitis patients-a pilot study

PURPOSE

To study the effector mechanism against pathogens of polymorphonuclear neutrophils (PMN) and macrophages, called ETosis, involving the release of extracellular traps (ETs) in patients with acute epididymitis. To assess the different ET phenotypes present in semen samples and to identify correlations between ETosis and clinical parameters.

MATERIALS AND METHODS

Samples from patients diagnosed with acute epididymitis were examined and compared with samples from uninfected controls. Biochemical analyses of seminal fluid included determination of peroxidase, α-glucosidase, fructose, and elastase levels. ETosis in semen was determined through presence of citrullinated histones, global histones, and extracellular DNA. Different ETosis phenotypes such as spread ETs, aggregated ETs, and diffuse ETs were identified by co-localisation of extruded DNA with myeloperoxidase and global histones. Anti-CD15⁺ and anti-CD68⁺ antibodies were used to identify different cell lines.

RESULTS

Revealed a high number of ETs compared with the control group. The mean number of CD15⁺PMN and CD68⁺ macrophages was higher in the acute epididymitis group. ETosis increase in ejaculates correlated with clinical parameters such as enhancement of elastase concentrations and diminution of fructose in the semen.

CONCLUSIONS

This work shows for the first time the presence of ETs and their components in semen from patients with acute epididymitis. The presence of infections is an important factor for induction of ETs in semen. Furthermore, the presence of ETosis in ejaculates is suggestive of developing infectious processes and might possibly have a diagnostic value.

Assessment of the anti-inflammatory and engraftment potential of horse endometrial and adipose mesenchymal stem cells in an in vivo model of post breeding induced endometritis

Horse mesenchymal stem cells (MSC) are potential anti-inflammatory tools for post-breeding induced endometritis (PBIE). In this research MSCs isolated from the endometrium or subcutaneous fat of the same donors were infused iu into mares with PBIE for assessment of their anti-inflammatory action and engraftment. PBIE was induced in nine gynecologically healthy mares by iu infusion of 500 million dead sperm in saline. Inflammatory markers were analyzed in uterine lavages and biopsies immediately before (phase I) and 3 h after infusion of sperm (phase II). Measurements: polymorph nuclear cells (PMN), proteins IL-6 and TNFα (ELISA in the lavages) and immunostaining in biopsies, transcripts of IL-1α, 6, 8, 10, TNFα and COX2 (qPCR of pelleted lavages). At 24 h after sperm deposition (phase III), mares were instilled iu with 20 ml of saline containing 2 × 10⁷ adipose MSCs (n = 3, group 1) or endometrial MSCs (n = 3, group 2). Cells were labeled previously with carboxyfluorescein diacetate succinimidyl ester (CFDA SE). A third group (n = 3) received 20 mL of sterile saline alone. After 48 h another biopsy/lavage were done and the same parameters analyzed. For engraftment, additional biopsies were taken at days 10 and 30 of sperm infusion and analyzed by confocal microscopy. Dead sperm in saline markedly increased PMNs counts, IL-6 and TNFα expression in the ELISA (p < 0.05) and immunostaining. In phase III a significant reduction (p < 0.0001) of PMN was found in all samples, including control mares. A decrease (p < 0.05) of IL-6 and TNF-α was detected by ELISA, in the groups that received MSC, but not in control group. In the aMSC-treated group, a significant decrease was found in the expression of (IL1α, p = 0.0003; IL-6 p 0.04; IL-8, p = 0.006, TNFα p = 0.004). Expression of IL-10 and COX2 remained unchanged (p = 0.08). In the mares that received eMSC, IL-6 and 8 decreased significantly (p = 0.01), IL-10 increased (p = 0.009), while TNFα, COX2 and IL1α did not significantly change their expression. In the engraftment experiment CFDA label was found sparingly in all the samples analyzed until day 30, mainly at the stromal compartment of the endometrium. No differences in the engraftment pattern was found among cell origins. We conclude that inoculation of MSCs significantly reduced inflammation independently of the origin of the cells and that cells perform limited engraftment detectable after one month of infusion. These findings can be of help for the design of new anti-inflammatory therapies of uterine diseases in mares.

The In Vitro Inhibitory Effect of Sivelestat on Elastase Induced Collagen and Metallopeptidase Expression in Equine Endometrium

Neutrophil extracellular traps (NETs) fight endometritis, and elastase (ELA), a protease found in NETs, might induce collagen type I (COL1) accumulation in equine endometrium. Metallopeptidases (MMPs) are involved in extracellular matrix balance. The aim was to evaluate the effects of ELA and sivelestat (selective elastase inhibitor) on MMP-2 and MMP-9 expression and gelatinolytic activity, as well as the potential inhibitory effect of sivelestat on ELA-induced COL1 in equine endometrium. Endometrial explants from follicular (FP) and mid-luteal (MLP) phases were treated for 24 or 48 h with ELA, sivelestat, and their combination. Transcripts of COL1A2, MMP2, and MMP9 were evaluated by qPCR; COL1 protein relative abundance by Western blot, and MMP-2 and MMP-9 gelatinolytic activity by zymography. In response to ELA treatment, there was an increase in MMP2 mRNA transcription (24 h) in active MMP-2 (48 h), both in FP, and in MMP9 transcripts in FP (48 h) and MLP (24 h) (p < 0.05). Sivelestat inhibited ELA-induced COL1A2 transcripts in FP (24 h) and MLP (24 h, 48 h) (p < 0.05). The sivelestat inhibitory effect was detected in MMP9 transcripts in FP at 48 h (p < 0.05), but proteases activity was unchanged. Thus, MMP-2 and MMP-9 might be implicated in endometrium fibrotic response to ELA. In mare endometrium, sivelestat may decrease ELA-induced COL1 deposition and hinder endometrosis development.

Seminal Plasma, Sperm Concentration, and Sperm-PMN Interaction in the Donkey: An In Vitro Model to Study Endometrial Inflammation at Post-Insemination

In the donkey, artificial insemination (AI) with frozen-thawed semen is associated with low fertility rates, which could be partially augmented through adding seminal plasma (SP) and increasing sperm concentration. On the other hand, post-AI endometrial inflammation in the jenny is significantly higher than in the mare. While previous studies analyzed this response through recovering Polymorphonuclear Neutrophils (PMN) from uterine washings, successive lavages can detrimentally impact the endometrium, leading to fertility issues. For this reason, the first set of experiments in this work intended to set an in vitro model through harvesting PMN from the peripheral blood of jennies. Thereafter, how PMN, which require a triggering agent like formyl-methionyl-leucyl-phenylalanine (FMLP) to be activated, are affected by donkey semen was interrogated. Finally, we tested how four concentrations of spermatozoa (100 × 10⁶, 200 × 10⁶, 500 × 10⁶ and 1000 × 10⁶ spermatozoa/mL) affected their interaction with PMN. We observed that semen, which consists of sperm and SP, is able to activate PMN. Whereas there was a reduced percentage of spermatozoa phagocytosed by PMN, most remained attached on the PMN surface or into a surrounding halo. Spermatozoa not attached to PMN were viable, and most of those bound to PMN were also viable and showed high tail beating. Finally, only sperm concentrations higher than 500 × 10⁶ spermatozoa/mL showed free sperm cells after 3 h of incubation, and percentages of spermatozoa not attached to PMN were higher at 3 h than at 1 h, exhibiting high motility. We can thus conclude that semen activates PMN in the donkey, and that the percentage of spermatozoa phagocytosed by PMN is low. Furthermore, because percentages of spermatozoa not attached to PMN were higher after 3 h than after 1 h of incubation, we suggest that PMN-sperm interaction plays an instrumental role in the reproductive strategy of the donkey.

Endometrial Cancer Immune Escape Mechanisms: Let Us Learn From the Fetal-Maternal Interface

The immune escape mechanisms at the base of tumor progression in endometrial cancer mimic immune tolerance mechanisms occurring at the maternal-fetal interface. The biological and immunological processes behind the maternal-fetal interface are finely tuned in time and space during embryo implantation and subsequent pregnancy stages; conversely, those behind cancer progression are often aberrant. The environment composition at the maternal-fetal interface parallels the pro-tumor microenvironment identified in many cancers, pointing to the possibility for the use of the maternal-fetal interface as a model to depict immune therapeutic targets in cancer. The framework of cancer environment signatures involved in immune adaptations, precisely timed in cancer progression, could reveal a specific "immune clock" in endometrial cancer, which might guide clinicians in patient risk class assessment, diagnostic workup, management, surgical and therapeutic approach, and surveillance strategies. Here, we review studies approaching this hypothesis, focusing on what is known so far about oncofetal similarities in immunity with the idea to individualize personalized immunotherapy targets, through the downregulation of the immune escape stage or the reactivation of the pro-inflammatory processes suppressed by the tumor.

Extracellular Traps: An Ancient Weapon of Multiple Kingdoms

The discovery, in 2004, of extracellular traps released by neutrophils has extended our understanding of the mode of action of various innate immune cells. This fascinating discovery demonstrated the extracellular trapping and killing of various pathogens by neutrophils. During the last decade, evidence has accumulated showing that extracellular traps play a crucial role in the defence mechanisms of various cell types present in vertebrates, invertebrates, and plants. The aim of this review is to summarise the relevant literature on the evolutionary history of extracellular traps used as a weapon in various kingdoms of life.

Sperm surface changes and their consequences for sperm transit through the female reproductive tract

Spermatozoa are faced with considerable challenges during their passage through the female reproductive tract. Following deposition, they must deal with several physical and biochemical barriers as well as an aggressive immune defence system before they reach the site of fertilisation. While many factors are at play, the surface characteristics of spermatozoa are central to communication with the female and successful transit. The surface proteome of spermatozoa has been extensively studied and shown to vary considerably between species that deposit semen in the vagina (ram and bull) and uterus (boar and stallion), likely due to major differences in accessory sex gland anatomy. Comparing the surface characteristics of spermatozoa from these domestic species and how individual components may equip spermatozoa to interact with different features of the female tract could help understand how spermatozoa navigate from vagina or uterus to oviduct ampulla. Furthermore, we can begin to explain why use of high quality preserved spermatozoa in artificial insemination programs may still result in reduced fertility due to altered interaction with the female. In this review, we describe the sperm surface characteristics of the ram, bull, boar and stallion and compare changes as a result of mixture with seminal plasma and/or in vitro processing. The role of these seminal components in facilitating sperm survival and transit within the female reproductive tract is summarised, drawing attention to potential implications for applied reproductive technologies.

The incidence and etiology of sperm DNA fragmentation in the ejaculates of males with spinal cord injuries

STUDY DESIGN

Retrospective descriptive study.

OBJECTIVES

To determine the incidence and probable etiology of sperm DNA fragmentation (SDF) in a sample of males with spinal cord injury (SCI).

SETTING

Hospital in Toledo, Spain; University-based Genetics laboratory in Madrid, Spain.

METHODS

Semen collected by vibro-stimulation from 27 males with various levels of spinal cord injury. Classical semen parameters, SDF, leukocytospermia and pro-oxidant capacity were assessed and compared with a cohort of normozoospermic fertile donors (n = 10).

RESULTS

Males with SCI presented with lower semen quality compared with normozoospermic donors with respect to progressive motility (p = 0.0002), SDF (p < 0.00005), pro-oxidant capacity (p = 0.0191) and leukocytospermia (p < 0.00005). Although there was no significant correlation between semen quality and time since the lesion occurred, the period of abstinence appeared to be positively correlated with SDF (r = 0.486; p = 0.041). When the semen parameters of males with SCI were categorized based on those with cervical and thoracic lesions, sperm concentration was higher for those with cervical damage (p = 0.0257). Males with complete lesions (AIS A) had ejaculates that were lower in progressive motility (p = 0.0040) than those with incomplete injuries (AIS B-D).

CONCLUSIONS

Ejaculates of males with SCI have excessively elevated SDF when compared with normozoospermic donors, which is likely to be associated with coincident high levels of leucocytospermia and pro-oxidant capacity. We propose that these phenomena are caused by the accumulation and degeneration of spermatozoa in the cauda epididymidis.

The Female Response to Seminal Fluid

Seminal fluid is often assumed to have just one function in mammalian reproduction, delivering sperm to fertilize oocytes. But seminal fluid also transmits signaling agents that interact with female reproductive tissues to facilitate conception and .pregnancy. Upon seminal fluid contact, female tissues initiate a controlled inflammatory response that affects several aspects of reproductive function to ultimately maximize the chances of a male producing healthy offspring. This effect is best characterized in mice, where the female response involves several steps. Initially, seminal fluid factors cause leukocytes to infiltrate the female reproductive tract, and to selectively target and eliminate excess sperm. Other signals stimulate ovulation, induce an altered transcriptional program in female tract tissues that modulates embryo developmental programming, and initiate immune adaptations to promote receptivity to implantation and placental development. A key result is expansion of the pool of regulatory T cells that assist implantation by suppressing inflammation, mediating tolerance to male transplantation antigens, and promoting uterine vascular adaptation and placental development. Principal signaling agents in seminal fluid include prostaglandins and transforming growth factor-β. The balance of male signals affects the nature of the female response, providing a mechanism of ‟cryptic female choiceˮ that influences female reproductive investment. Male-female seminal fluid signaling is evident in all mammalian species investigated including human, and effects of seminal fluid in invertebrates indicate evolutionarily conserved mechanisms. Understanding the female response to seminal fluid will shed new light on infertility and pregnancy disorders and is critical to defining how events at conception influence offspring health.

Potential roles of neutrophils in maintaining the health and productivity of dairy cows during various physiological and physiopathological conditions: a review

Neutrophils represent the first line of innate immunity and are the most prominent line of cellular defence against invading microorganisms. On stimulation, they can quickly move through the walls of veins and into the tissues of the body to immediately attack or monitor the foreign antigens. Neutrophils are highly versatile and sophisticated cells which are endowed with highly sensitive receptor-based perception systems. They were traditionally classified as short-lived phagocytes actively involved during infection and inflammation, but recently, it has been seen that neutrophils are capable of detecting the presence of sperms during insemination as well as an implanting embryo in the female reproductive tract. These specialised phagocytes play a major role in tissue remodelling and wound healing, and maintain homeostasis during parturition, expulsion of placenta, folliculogenesis, corpus luteum formation and luteolysis. Here, we review the role played by neutrophils in maintaining homeostasis during normal and inflammatory conditions of dairy cattle. We have summarised the alteration in the expression of some cell adhesion molecules and cytokines on bovine neutrophils during different physiological and physiopathological conditions. Some emerging issues in the field of neutrophil biology and the possible strategies to strengthen their activity during the period of immunosuppression have also been discussed.

Sialylated Cervical Mucins Inhibit the Activation of Neutrophils to Form Neutrophil Extracellular Traps in Bovine in vitro Model

In order to combat invading pathogens neutrophils can release neutrophil extracellular traps (NETs). However, since NETs can also damage endogenous cells, several control mechanisms for the formation of NETs must work effectively. For instance, neutrophil activation is silenced within blood circulation by the binding of sialylated glycoconjugates to sialic acid binding immunoglobulin-like lectins (Siglecs) on neutrophils. As neutrophils are recruited within the female reproductive tract, after mating, a comparable mechanism may also take place within the bovine cervix to prevent an exaggerated NET formation and thus, infertility. We examined, if the highly glycosylated mucins, which are the major functional fraction of biomolecules in mucus, represent a potential regulator of NET formation. The qPCR data revealed that in polymorphonuclear neutrophils (PMNs) inhibitory Siglecs are the most frequently expressed Siglecs and might be a potential target of sialylated glycans to modulate the activation of PMNs. Remarkably, the addition of bovine cervical mucins significantly inhibited the formation of NET, which had been induced in response to lipopolysaccharides (LPS) or a combination of phorbol myristate acetate (PMA) and ionomycin. The inhibitory effects were independent of the stage of estrous cycle (estrus, luteal, and follicular mucins). PMNs retained their segmented nuclei and membrane perforation was prevented. However, the inhibitory effects were diminished, when sialic acids were released under acidic conditions. Comparable results were achieved, when sialic acids were targeted by neuraminidase digestion, indicating a sialic acid dependent inhibition of NET release. Thus, bovine cervical mucins have an anti-inflammatory capability to modulate NET formation and might be further immunomodulatory biomolecules that support fertility.

Bovine oviduct epithelial cells suppress the phagocytic activity of neutrophils towards sperm but not for bacteria in vitro: Immunofluorescence and electron microscopic observations

Previously, we reported that polymorphonuclear neutrophils (PMNs) are constantly existent in the bovine oviduct fluid during the pre-ovulatory stage under physiological conditions. Moreover, incubation of PMNs with bovine oviduct epithelial cells-conditioned medium (BOEC-CM) resulted in suppression of their phagocytic activity for sperm. During pathophysiological conditions, cows may be inseminated by infected semen which exposes oviductal PMNs to allogenic sperm simultaneously with pathogens. This study aimed to visually investigate the role of oviduct epithelium in regulating the phagocytic behavior of PMNs toward sperm as a physiological stimulus, with Escherichia coli (E. coli) as a pathological stimulus. In our experiment, PMNs were incubated for 2 h in BOEC-CM. Phagocytosis was then assayed by co-incubation of these PMNs either with sperm, E. coli, or latex beads. BOEC-CM significantly suppressed the direct phagocytosis of PMNs for sperm, but did not affect their phagocytic activity for E. coli or latex beads. Additionally, an investigation with scanning electron microscopy revealed that BOEC-CM suppressed the formation of DNA-based neutrophil extracellular traps (NETs) for sperm entanglement. BOEC-CM did not alter NETs formation towards E. coli. A quantification of NETs formation using an immunofluorescence microscopy showed that the areas of NETs formation for E. coli were significantly larger than those formed for sperm. Our data clearly show that the bovine oviduct, through secretions, protects sperm from phagocytosis by PMNs and eliminates bacterial dissemination through maintaining the phagocytic activity of PMNs towards bacteria.

Combined addition of superoxide dismutase, catalase and glutathione peroxidase improves quality of cooled stored stallion semen

During cold storage stallion spermatozoa experience undergo oxidative stress, which can impair sperm function and fertilizing capacity. Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) are the main endogenous enzymatic antioxidants in stallion seminal plasma, and counteract reactive oxygen species. Semen dilution reduces the endogenous antioxidant concentrations. The aim of this study was to investigate whether addition of 15 IU/mL each of SOD, CAT, and GPX to diluted stallion semen would ameliorate a reactive oxygen-mediated decrease in semen quality during 72 h of storage at 5 °C. Ejaculates (n = 7) were divided in two aliquots and diluted in INRA 96 without (control) or with addition of antioxidants. Semen analysis was performed at the time of dilution and every 24 h during chilled storage. Antioxidant supplementation completely inhibited the storage-dependent increase in activated caspase 3 (P < 0.05). Concomitantly, the antioxidant-supplemented samples had a greater percentage of viable, motile and rapidly moving sperm than control samples after 72 h storage (P < 0.05). The DNA damage, as evaluated by TUNEL assay and SCSA, increased with storage time (P < 0.05). Antioxidant supplementation did not prevent, but did significantly reduce the increase in DNA strand breakage. The results indicate part of the intrinsic apoptotic pathway leading to effector caspase activation was inhibited, although an activation of molecules with endonuclease activity still occurred. In conclusion, adding equal concentrations of SOD, CAT and GPX to a semen extender suppressed caspase-3 activation and improved preservation of stallion sperm motility and viability during 72 h of storage at 5 °C.

"In sickness and in health" - how neutrophil extracellular trap (NET) works in infections, selected diseases and pregnancy

The discovery of the NET network (neutrophil extracellular trap) has revolutionized the perception of defense mechanisms used by neutrophils in infections and non-infectious states, as this mechanism proves the complexity of the ways in which neutrophils can act in the organism. The paper describes the NET network and its participation in bacterial, viral, fungal and parasitic infections, both in a positive and a negative aspect. In addition, attention was paid to the participation of NETs in the course of autoimmune diseases, cancer, as well as its impact on pregnancy and fertility in mammals.

Sperm success and immunity

The moment of the fertilization of an egg by a spermatozoon-the point of "sperm success"-is a key milestone in the biology of sexually reproducing species and is a fundamental requirement for offspring production. Fertilization also represents the culmination of a suite of sexually selected processes in both sexes and is commonly used as a landmark to measure reproductive success. Sperm success is heavily dependent upon interactions with other key aspects of male and female biology, with the immune system among the most important. The immune system is vital to maintaining health in both sexes; however, immune reactions can also have antagonistic effects on sperm success. The effects of immunity on sperm success are diverse, and may include trade-offs in the male between investment in the production or protection of sperm, as well as more direct, hostile, immune responses to sperm within the female, and potentially the male, reproductive tract. Here, we review current understanding of where the biology of immunity and sperm meet, and identify the gaps in our knowledge.

Ovulatory follicular fluid induces sperm phagocytosis by neutrophils, but oviductal fluid around oestrus suppresses its inflammatory effect in the buffalo oviduct in vitro

We have recently shown that the conditioned media from bovine oviductal epithelial cell culture suppress sperm phagocytosis by neutrophils, suggesting that the oviduct around oestrus supplies the anti-inflammatory microenvironment. To investigate the immune response of neutrophils toward the sperm at ovulation in the buffalo oviduct, we examined (a) a detailed distribution of neutrophils in the oviduct in buffaloes, (b) the effect of ovulatory follicular fluid (FF) and oviductal fluid (OF) on sperm phagocytosis by neutrophils, and (c) the interaction of the ovulatory FF with OF on sperm phagocytosis by neutrophils in vitro. Buffalo oviducts were collected from healthy reproductive tracts at a local slaughterhouse. A detailed observation by histological examination and transmission electron microscopy revealed that neutrophils exist in the oviduct epithelium and lumen throughout the oestrous cycle in buffaloes. The number of neutrophils at the oestrus stage was higher in ampulla compared with those in isthmus, whereas they remained relatively constant at the dioestrus stage. Two hours of preincubation of neutrophils with FF enhanced sperm phagocytosis through the formation of neutrophil extracellular traps (NETs) together with H₂ O₂ production, whereas OF around oestrus (eOF) suppressed sperm phagocytosis, NETs formation, and H₂ O₂ production and relieved the above FF-induced inflammatory response. Our findings show that neutrophils exist in the healthy cyclic oviduct across bovine species, and the OF supplies a strong anti-inflammatory environment that could minimize the inflammatory effect of the FF that flows into the oviduct lumen after ovulation and supports the occurrence of fertilization.

The role of neutrophil activation in determining the outcome of pregnancy and modulation by hormones and/or cytokines

Neutrophils are often exclusively considered as a first-line innate immune defence, able to rapidly kill or trap pathogens and causing in case of over-activation tissue damage. In the female reproductive tract, however, the presence and activity of neutrophils seems to be tightly regulated. Major players in orchestrating this regulation are cyclical steroid sex hormones present during the menstrual cycle and pregnancy. This review describes the role of sex hormones in regulating directly or indirectly the functionality of neutrophils, the role of neutrophils during fertilization and pregnancy and in controlling viral, fungal and bacterial infection. This review also discusses the consequence of overt neutrophil activation in pregnancy pathologies.