Beta-defensins as marker for male fertility: a comprehensive review†

Bovine male fertility in animals has a direct impact on the productivity of dairy herds. The epididymal sperm maturations involve extensive sperm surface modifications to gain the fertilizing ability, especially by absorptions of the plethora of biomolecules, including glycoprotein beta-defensins (BDs), enzymes, organic ions, protein, and phospholipids. Defensins are broad-range nonspecific antimicrobial peptides that exhibit strong relations with innate and adaptive immunity, but their roles in male fertility are relatively recently identified. In the course of evolution, BD genes give rise to different clusters with specific functions, especially reproductive functions, by undergoing duplications and nonsynonymous mutations. BD polymorphisms have been reported with milk compositions, disease resistance, and antimicrobial activities. However, in recent decades, the link of BD polymorphisms with fertility has emerged as an appealing improvement of reproductive performance such as sperm motility, membrane integrity, cervical mucus penetration, evading of uterus immunosurveillance, oviduct cell attachment, and egg recognition. The reproductive-specific glycosylated BD class-A BDs (CA-BDs) have shown age- and sex-specific expressions in male reproductive organs, signifying their physiological pleiotropism, especially in the sperm maturation and sperm transport in the female reproductive tract. By considering adult male reproductive organ-specific BD expressions, importance in sperm functionalities, and bioinformatic analysis, we have selected two bovine BBD126 and BBD129 genes as novel potential biomarkers of bovine male fertility. Despite the importance of BDs, however, genomic characterization of most BD genes across most livestock and nonmodel organisms remains predictive/incomplete. The current review discusses our understanding of BD pleiotropic functions, polymorphism, and genomic structural attributes concerning the fertilizability of the male gamete in dairy animals.

Analysis of amplification and association polymorphisms in the bovine beta-defensin 129 (BBD129) gene revealed its function in bull fertility

β-defensins are adsorbable on the sperm surface in the male reproductive tract (MRT) and enhance sperm functional characteristics. The beta-defensin 129 (DEFB129) antimicrobial peptide is involved in sperm maturation, motility, and fertilization. However, its role in bovine fertility has not been well investigated. This study examines the relationship between the bovine BBD129 gene and Bos indicus x Bos taurus bull fertility. The complete coding sequence of BBD129 mRNA was identified by RNA Ligase Mediated-Rapid Amplification of cDNA End (RLM-RACE) and Sanger sequencing methodologies. It consisted of 582 nucleotides (nts) including 5' untranslated region (UTR) (46nts) and 3'UTR (23nts). It conserves all beta-defensin-like features. The expression level of BBD129 was checked by RT-qPCR and maximal expression was detected in the corpus-epididymis region compared to other parts of MRT. Polymorphism in BBD129 was also confirmed by Sanger sequencing of 254 clones from 5 high fertile (HF) and 6 low fertile (LF) bulls at two positions, 169 T > G and 329A > G, which change the S57A and N110S in the protein sequence respectively. These two mutations give rise to four types of BBD129 haplotypes. The non-mutated TA-BBD129 (169 T/329A) haplotype was substantially more prevalent among high-fertile bulls (P < 0.005), while the double-site mutated GG-BBD129 (169 T > G/329A > G) haplotype was significantly more prevalent among low-fertile bulls (P < 0.005). The in silico analysis confirmed that the polymorphism in BBD129 results in changes in mRNA secondary structure, protein conformations, protein stability, extracellular-surface availability, post-translational modifications (O-glycosylation and phosphorylation), and affects antibacterial and immunomodulatory capabilities. In conclusion, the mRNA expression of BBD129 in the MRT indicates its region-specific dynamics in sperm maturation. BBD129 polymorphisms were identified as the deciding elements accountable for the changed proteins with impaired functionality, contributing to cross-bred bulls' poor fertility.

C-Type Natriuretic Peptide (CNP) Could Improve Sperm Motility and Reproductive Function of Asthenozoospermia

This study is to analyze the effect of C-type natriuretic peptide (CNP) on sperm motility of asthenozoospermia and explore the influence mechanism of CNP on the reproductive system and sperm motility. Our results showed that the concentration of CNP in asthenospermia patients’ semen was lower than in normal people’s. The motility of sperm could be improved markedly by CNP and 8-Br-cGMP, while the effect of CNP was inhibited by NPR-B antagonist and KT5823. In the asthenozoospermia mouse model induced by CTX, CNP injection could improve sperm motility in the epididymis, alleviate tissue damage in the testes and epididymis, and increase testosterone levels. The asthenospermia mouse model showed high activity of MDA and proinflammatory factors (TNF-α, IL-6), as well as low expression of antioxidants (SOD, GSH-Px, CAT) in the testis and epididymis, but this situation could be significantly ameliorated after being treated with CNP. Those studies indicated that the concentration of CNP in the semen of asthenospermia patients is lower than in normal people and could significantly promote sperm motility through the NPR-B/cGMP pathway. In the asthenospermia mouse model induced by CTX, CNP can alleviate the damage of cyclophosphamide to the reproductive system and sperm motility. The mechanism may involve increasing testosterone and reducing ROS and proinflammatory factors to damage the tissue and sperm.

Antimicrobial peptides in domestic animals and their applications in veterinary medicine

Antimicrobial peptides (AMPs) are molecules with a broad-spectrum activity against bacteria, fungi, protozoa, and viruses. These peptides are widely distributed in insects, amphibians and mammals. Indeed, they are key molecules of the innate immune system with remarkable antimicrobial and immunomodulatory activity. Besides, these peptides have also shown regulatory activity for gut microbiota and have been considered inductors of growth performance. The current review describes the updated findings of antimicrobial peptides in domestic animals, such as bovines, goats, sheep, pigs, horses, canines and felines, analyzing the most relevant aspects of their use as potential therapeutics and their applications in Veterinary medicine.

Molecular Identification and Antibacterial Activity Analysis of Blue Fox (Vulpes lagopus) β-Defensins 108 and 122

Simple Summary

The blue fox (Vulpes lagopus) is an important fur animal in China; its reproductive performance is directly related to the economic benefits of breeding. β-Defensins can protect the male reproductive system from bacterial invasion, maintain the stability of reproductive tract microenvironment and improve semen quality in mammals. Few studies have proposed to investigate the antibacterial effect of Vulpes lagopus beta-defensin (vBDs). In this study, we analyzed the antibacterial activity of recombinant vBD108 and vBD122 protein in vitro by an antibacterial activity analysis experiment. Our preliminary results demonstrate that the two vBDs have good antibacterial activity. The blue fox β-defensins may be used as an extender component of the semen diluent to protect semen from bacterial infection.

Abstract

The blue fox (Vulpes lagopus), a fur-bearing animal, is an important component of the breeding industry in China. Semen quality is a key factor for the reproductive process and the breeding effectiveness of the farmed blue fox. However, bacterial contamination in semen samples utilized in artificial fertilization is very common. The β-defensins, a class of important antimicrobial peptides in mammals, could protect the reproductive system of male animals from bacterial invasion, maintain the stability of the genital tract microenvironment and improve semen quality. In this study, molecular cloning and bioinformatics analysis were conducted to analyze the protein structure and function of blue fox β-defensin 108 (Vulpes lagopus beta-defensin 108, vBD108) and 122 (Vulpes lagopus beta-defensin 122, vBD122). To evaluate the bacteriostatic effect of recombinant vBDs (Vulpes lagopus beta-defensins) protein, varying concentrations (0, 25, 50, 100, 200 µg/mL) were taken to evaluate the effects on Escherichia coli and Staphylococcus aureus at different times (0, 2, 4, 6, 8, 12 h). The results showed that vBD108 and vBD122 existed in different forms in protein structure and had antibacterial activity. Both proteins, at 50 µg/mL, had efficacious bacteriostatic activity. This study shows that recombinant vBD108 and vBD122 proteins have good antibacterial activity in vitro. This implies a potential role in improving semen quality and hygienic measures in the process of artificial insemination as an extender of semen dilution with antibacterial activity.

Sperm modulate uterine immune parameters relevant to embryo implantation and reproductive success in mice

Seminal fluid factors modulate the female immune response at conception to facilitate embryo implantation and reproductive success. Whether sperm affect this response has not been clear. We evaluated global gene expression by microarray in the mouse uterus after mating with intact or vasectomized males. Intact males induced greater changes in gene transcription, prominently affecting pro-inflammatory cytokine and immune regulatory genes, with TLR4 signaling identified as a top-ranked upstream driver. Recruitment of neutrophils and expansion of peripheral regulatory T cells were elevated by seminal fluid of intact males. In vitro, epididymal sperm induced IL6, CXCL2, and CSF3 in uterine epithelial cells of wild-type, but not Tlr4 null females. Collectively these experiments show that sperm assist in promoting female immune tolerance by eliciting uterine cytokine expression through TLR4-dependent signaling. The findings indicate a biological role for sperm beyond oocyte fertilization, in modulating immune mechanisms involved in female control of reproductive investment.

The truncated human beta-defensin 118 can modulate lipopolysaccharide mediated inflammatory response in RAW264.7 macrophages

The family of human β-defensins consists of small cysteine-rich peptides, which are receiving significant attention due to their antimicrobial activity. The N-terminal cysteine motif of β-defensin is considered to contribute to its biological activity. Human β-defensin 118 (DEFB 118) is a particular anion β-defensin expressed predominantly in the male reproductive tract, but its physiological activity has not yet been revealed. In order to verify the potential role of the N-terminal domain of DEFB118 peptide in the regulation of infection, the truncated β-defensin core region of DEFB118 peptide was expressed with IMPACT-pTWIN1 system in Escherichia coli. Herein, the purified homogeneous DEFB118 peptide was identified by mass spectrometry and circular dichroism spectroscopy. The in vitro experiments revealed that DEFB118 peptide exhibited prominent LPS-binding potency (K_D: 2.94 nM). Moreover, the DEFB118 core peptide significantly inhibited the mRNA level of LPS-induced inflammatory cytokines including IL-α, IL-1β, IL-6 and TNF-α in RAW264.7 cells, and correspondingly decreased secretion of IL-6 and TNF-α. We concluded that strong binding of DEFB118 to LPS might prevent LPS from binding to its receptor, and hence inhibited cytokines secretion. The results of this study may be a benefit to elucidate the immune protection of DEFB118 in the male reproductive tract.

Five subfamilies of β-defensin genes are present in salmonids: Evolutionary insights and expression analysis in Atlantic salmon Salmo salar

β-defensins (BD) are the largest family of vertebrate defensins with potent antimicrobial, chemotactic and immune-regulatory activities. Four BD genes (BD1-4) have been cloned previously in rainbow trout but none have been reported in other salmonids. In this study seven BD genes (BD1a-b, 2-4, 5a-b) are characterised in Atlantic salmon and additional BD genes (BD1b and BD5) in rainbow trout. Bioinformatic analysis revealed up to seven BD genes in the genomes of other salmonids that belong to five subfamilies (BD1-5) due to whole genome duplications. BD1-2 and BD4-5 are also present in basal teleosts but only BD1 and/or BD5 are present in advanced teleosts due to loss of one chromosomal locus. BD3 is salmonid specific. Fish BD have a unique three-coding exon structure. Fish BD are highly divergent between subfamilies but conserved within each subfamily. Atlantic salmon BD genes are differentially expressed in tissues, often with low level expression in systemic immune organs (head kidney and spleen) yet with at least one BD gene highly expressed in mucosal tissues, heart, blood and liver. This suggests an important role of these BD genes in innate immunity in mucosa, liver and blood in Atlantic salmon.

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.

Unusual interplay of contrasting selective pressures on β-defensin genes implicated in male fertility of the Buffalo (Bubalus bubalis)

BACKGROUND

The buffalo, despite its superior milk-producing ability, suffers from reproductive limitations that constrain its lifetime productivity. Male sub-fertility, manifested as low conception rates (CRs), is a major concern in buffaloes. The epididymal sperm surface-binding proteins which participate in the sperm surface remodelling (SSR) events affect the survival and performance of the spermatozoa in the female reproductive tract (FRT). A mutation in an epididymal secreted protein, beta-defensin 126 (DEFB-126/BD-126), a class-A beta-defensin (CA-BD), resulted in decreased CRs in human cohorts across the globe. To better understand the role of CA-BDs in buffalo reproduction, this study aimed to identify the BD genes for characterization of the selection pressure(s) acting on them, and to identify the most abundant CA-BD transcript in the buffalo male reproductive tract (MRT) for predicting its reproductive functional significance.

RESULTS

Despite the low protein sequence homology with their orthologs, the CA-BDs have maintained the molecular framework and the structural core vital to their biological functions. Their coding-sequences in ruminants revealed evidence of pervasive purifying and episodic diversifying selection pressures. The buffalo CA-BD genes were expressed in the major reproductive and non-reproductive tissues exhibiting spatial variations. The Buffalo BD-129 (BuBD-129) was the most abundant and the longest CA-BD in the distal-MRT segments and was predicted to be heavily O-glycosylated.

CONCLUSIONS

The maintenance of the structural core, despite the sequence divergence, indicated the conservation of the molecular functions of the CA-BDs. The expression of the buffalo CA-BDs in both the distal-MRT segments and non-reproductive tissues indicate the retention the primordial microbicidal activity, which was also predicted by in silico sequence analyses. However, the observed spatial variations in their expression across the MRT hint at their region-specific roles. Their comparison across mammalian species revealed a pattern in which the various CA-BDs appeared to follow dissimilar evolutionary paths. This pattern appears to maintain only the highly efficacious CA-BD alleles and diversify their functional repertoire in the ruminants. Our preliminary results and analyses indicated that BuBD-129 could be the functional ortholog of the primate DEFB-126. Further studies are warranted to assess its molecular functions to elucidate its role in immunity, reproduction and fertility.

Characterization of the β-defensin genes in giant panda

β-Defensins are small antimicrobial proteins expressed in various organisms and have great potential for improving animal health and selective breeding programs. Giant pandas have a distinctive lineage in Carnivora, and it is unclear whether β-defensin genes have experienced different selective pressures during giant panda evolution. We therefore characterized the giant panda (Ailuropoda melanoleuca) β-defensin gene family through gap filling, TBLASTN, and HMM searches. Among 36 β-defensins identified, gastrointestinal disease may induce the expression of the DEFB1 and DEFB139 genes in the digestive system. Moreover, for DEFB139, a significant positive selection different from that of its homologs was revealed through branch model comparisons. A Pro-to-Arg mutation in the giant panda DEFB139 mature peptide may have enhanced the peptide’s antimicrobial potency by increasing its stability, isoelectric point, surface charge and surface hydrophobicity, and by stabilizing its second β-sheet. Broth microdilution tests showed that the increase in net charge caused by the Pro-to-Arg mutation has enhanced the peptide’s potency against Staphylococcus aureus, although the increase was minor. We expect that additional gene function and expression studies of the giant panda DEFB139 gene could improve the existing conservation strategies for the giant panda.

A dual targeted β-defensin and exome sequencing approach to identify, validate and functionally characterise genes associated with bull fertility

Bovine fertility remains a critical issue underpinning the sustainability of the agricultural sector. Phenotypic records collected on >7,000 bulls used in artificial insemination (AI) were used to identify 160 reliable and divergently fertile bulls for a dual strategy of targeted sequencing (TS) of fertility-related β-defensin genes and whole exome sequencing (WES). A haplotype spanning multiple β-defensin genes and containing 94 SNPs was significantly associated with fertility and functional analysis confirmed that sperm from bulls possessing the haplotype showed significantly enhanced binding to oviductal epithelium. WES of all exons in the genome in 24 bulls of high and low fertility identified 484 additional SNPs significantly associated with fertility. After validation, the most significantly associated SNP was located in the FOXJ3 gene, a transcription factor which regulates sperm function in mice. This study represents the first comprehensive characterisation of genetic variation in bovine β-defensin genes and functional analysis supports a role for β-defensins in regulating bull sperm function. This first application of WES in AI bulls with divergent fertility phenotypes has identified a novel role for the transcription factor FOXJ3 in the regulation of bull fertility. Validated genetic variants associated with bull fertility could prove useful for improving reproductive outcomes in cattle.

Fertilization Mechanisms in Flowering Plants

Compared with the animal kingdom, fertilization is particularly complex in flowering plants (angiosperms). Sperm cells of angiosperms have lost their motility and require transportation as a passive cargo by the pollen tube cell to the egg apparatus (egg cell and accessory synergid cells). Sperm cell release from the pollen tube occurs after intensive communication between the pollen tube cell and the receptive synergid, culminating in the lysis of both interaction partners. Following release of the two sperm cells, they interact and fuse with two dimorphic female gametes (the egg and the central cell) forming the major seed components embryo and endosperm, respectively. This process is known as double fertilization. Here, we review the current understanding of the processes of sperm cell reception, gamete interaction, their pre-fertilization activation and fusion, as well as the mechanisms plants use to prevent the fusion of egg cells with multiple sperm cells. The role of Ca(2+) is highlighted in these various processes and comparisons are drawn between fertilization mechanisms in flowering plants and other eukaryotes, including mammals.

Seminal fluid of honeybees contains multiple mechanisms to combat infections of the sexually transmitted pathogen Nosema apis

The societies of ants, bees and wasps are genetically closed systems where queens only mate during a brief mating episode prior to their eusocial life and males therefore provide queens with a lifetime supply of high-quality sperm. These ejaculates also contain a number of defence proteins that have been detected in the seminal fluid but their function and efficiency have never been investigated in great detail. Here, we used the honeybee Apis mellifera and quantified whether seminal fluid is able to combat infections of the fungal pathogen Nosema apis, a widespread honeybee parasite that is also sexually transmitted. We provide the first empirical evidence that seminal fluid has a remarkable antimicrobial activity against N. apis spores and that antimicrobial seminal fluid components kill spores in multiple ways. The protein fraction of seminal fluid induces extracellular spore germination, which disrupts the life cycle of N. apis, whereas the non-protein fraction of seminal fluid induces a direct viability loss of intact spores. We conclude that males provide their ejaculates with efficient antimicrobial molecules that are able to kill N. apis spores and thereby reduce the risk of disease transmission during mating. Our findings could be of broader significance to master honeybee diseases in managed honeybee stock in the future.

Sperm-Coating Beta-Defensin 126 Is a Dissociation-Resistant Dimer Produced by Epididymal Epithelium in the Bovine Reproductive Tract

Beta-defensins are innate immune molecules, often described as antimicrobial peptides because of their bactericidal activity and are now known to have diverse additional functions, including cell signaling, chemoattraction, immunoregulation, and reproduction. In humans and primates, beta-defensin 126 has been shown to regulate the ability of sperm to swim through cervical mucus and to protect sperm from attack by the female immune system during transit toward the oviduct. Bovine beta-defensin 126 (BBD126) is the ortholog of human defensin 126, and computational analysis here revealed significant conservation between BBD126 and other mammalian orthologs at the N-terminus, although extensive sequence differences were detected at the C-terminus, implying possible species-specific roles for this beta-defensin in reproduction. We had previously demonstrated preferential expression of this and related beta-defensin genes in the bovine male reproductive tract, but no studies of bovine beta-defensin proteins have been performed to date. Here, we analyzed BBD126 protein using a monoclonal antibody (a-BBD126) generated against a 14 amino acid peptide sequence from the secreted fragment of BBD126. The specificity of a-BBD126 was validated by testing against the native form of the peptide recovered from bovine caudal epididymal fluid and recombinant BBD126 generated using a prokaryotic expression system. Western blot analysis of the native and recombinant forms showed that BBD126 exists as a dimer that was highly resistant to standard methods of dissociation. Immunohistochemical staining using a-BBD126 demonstrated BBD126 protein expression by epithelial cells of the caudal epididymis and vas deferens from both mature and immature bulls. BBD126 could also be seen (by confocal microscopy) to coat caudal sperm, with staining concentrated on the tail of the sperm cells. This study is the first to demonstrate beta-defensin 126 protein expression in the bovine reproductive tract and on bull sperm. Its dissociation-resistant dimeric structure is likely to have important functional implications for the role of BBD126 in bovine reproduction.

Identification of New Epididymal Luminal Fluid Proteins Involved in Sperm Maturation in Infertile Rats Treated by Dutasteride Using iTRAQ

Background: Spermatozoa become mature and acquire fertilizing capacity during their passage through the epididymal lumen. In this study, we identified new epididymal luminal fluid proteins involved in sperm maturation in infertile rats by dutasteride, a dual 5α-reductase inhibitor, in order to provide potential epididymal targets for new contraceptives and infertility treatment. Methods: Male rats were treated with dutasteride for 28 consecutive days. We observed the protein expression profiles in the epididymal luminal fluids in infertile and normal rats using isobaric tags for relative and absolute quantitation (iTRAQ) technique. The confidence of proteome data was validated by enzyme-linked immunosorbent assays. Results: 1045 proteins were tested, and 23 of them presented different expression profiling in the infertile and normal rats. The seven proteins were down-regulated, and 16 proteins were up-regulated. Among the seven proteins which were significantly down-regulated by dutasteride in the epididymal luminal fluids, there were three β-defensins (Defb2, Defb18 and Defb39), which maybe the key proteins involved in epididymal sperm maturation and male fertility. Conclusions: We report for the first time that dutasteride influences the protein expression profiling in the epididymal luminal fluids of rats, and this result provides some new epididymal targets for male contraception and infertility therapy.

TLR4 Signaling Is a Major Mediator of the Female Tract Response to Seminal Fluid in Mice

Seminal fluid interacts with epithelial cells lining the female reproductive tract to induce expression of proinflammatory cytokines and chemokines, initiating immune tolerance mechanisms to facilitate pregnancy. TGFB cytokines are key signaling agents in seminal plasma but do not fully account for the female response to seminal fluid. We hypothesized that additional molecular pathways are utilized in seminal fluid signaling. Affymetrix microarray was employed to compare gene expression in the endometrium of mice 8 h after mating with either intact males or seminal fluid deficient (SVX/VAS) males. Bioinformatics analysis revealed TLR4 signaling as a strongly predicted upstream regulator activated by the differentially expressed genes and implicated TGFB signaling as a second key pathway. Quantitative PCR and microbead data confirmed that seminal fluid induces endometrial synthesis of several TLR4-regulated cytokines and chemokines, including CSF3, CXCL1, CXCL2, IL1A, IL6, LIF, and TNF. In primary uterine epithelial cells, CSF3, CXCL1, and CXCL2 were strongly induced by the TLR4 ligand LPS but suppressed by TGFB, while IL1A, TNF, and CSF2 were induced by both ligands. TLR4 was confirmed as essential for the full endometrial cytokine response using mice with a null mutation in Tlr4, where seminal fluid failed to induce endometrial Csf3, Cxcl2, Il6, and Tnf expression. This study provides evidence that TLR4 contributes to seminal fluid modulation of the periconception immune environment. Activation of TLR4 signaling by microbial or endogenous components of seminal fluid is thus implicated as a key element of the female tract response to seminal fluid at the outset of pregnancy in mice.

Comparative genomic identification and expression profiling of a novel ?-defensin gene cluster in the equine reproductive tract

?-defensins are small cationic proteins with potent immunoregulatory and antimicrobial activity. The number of genes encoding these peptides varies significantly between and within species but they have not been extensively characterised in the horse. Here, we describe a systematic search of the Equus caballus genome that identified a cluster of novel ?-defensin genes on Chromosome 22, which is homologous to a cluster on bovine Chromosome 13. Close genomic matches were found for orthologs of 13 of the bovine genes, which were named equine ?-defensins (eBD) 115, eBD116, eBD117, eBD119, eBD120, eBD122a, eBD123, eBD124, eBD125, eBD126, eBD127, eBD129 and eBD132. As expression of the homologous cluster in cattle was limited to the reproductive tract, tissue sections were obtained from the testis, caput, corpus and cauda epididymis and the vas deferens of three stallions and from the ovary, oviduct, uterine horn, uterus, cervix and vagina of three mares. Using a quantitative real-time polymerase chain reaction approach, each of the novel ?-defensin genes showed distinct region-specific patterns of expression. Preferential expression in the caput epididymis of these novel defensins in the stallion and in the oviduct in the mare suggests a possible role in immunoprotection of the equine reproductive tract or in fertility.

Seminal Fluid Signalling in the Female Reproductive Tract: Implications for Reproductive Success and Offspring Health

Carriage of sperm is not the only function of seminal fluid in mammals. Studies in mice show that at conception, seminal fluid interacts with the female reproductive tract to induce responses which influence whether or not pregnancy will occur, and to set in train effects that help shape subsequent fetal development. In particular, seminal fluid initiates female immune adaptation processes required to tolerate male transplantation antigens present in seminal fluid and inherited by the conceptus. A tolerogenic immune environment to facilitate pregnancy depends on regulatory T cells (Treg cells), which recognise male antigens and function to suppress inflammation and immune rejection responses. The female response to seminal fluid stimulates the generation of Treg cells that protect the conceptus from inflammatory damage, to support implantation and placental development. Seminal fluid also elicits molecular and cellular changes in the oviduct and endometrium that directly promote embryo development and implantation competence. The plasma fraction of seminal fluid plays a key role in this process with soluble factors, including TGFB, prostaglandin-E, and TLR4 ligands, demonstrated to contribute to the peri-conception immune environment. Recent studies show that conception in the absence of seminal plasma in mice impairs embryo development and alters fetal development to impact the phenotype of offspring, with adverse effects on adult metabolic function particularly in males. This review summarises our current understanding of the molecular responses to seminal fluid and how this contributes to the establishment of pregnancy, generation of an immune-regulatory environment and programming long-term offspring health.