Characterization of spermatozoa surface antigens by antisperm antibodies and its influence on acrosomal exocytosis

A systematic review identifying seminal plasma biomarkers and their predictive ability on IVF and ICSI outcomes

The diverse nature and high molecule concentration of seminal plasma (SP) makes this fluid a good potential source for a potential biomarker that could predict assisted reproductive technology (ART) outcomes. Currently, semen quality parameters cannot accurately predict ART outcomes. A systematic literature search was conducted to identify human SP biomarkers with potential predictive ability for the outcomes of IVF and intracytoplasmic sperm injection. Observational cohort and case-control studies describing the association between biomarkers in human SP and the outcome of infertile men attending for ART were included. Forty-three studies were selected, reporting on 89 potential SP biomarkers (grouped as oxidative stress, proteins glycoproteins, metabolites, immune system components, metals and trace elements and nucleic acids). The present review supports 32 molecules in SP as potentially relevant biomarkers for predicting ART outcomes; 23 molecules were reported once and nine molecules were reported in more than one study; IL-18 and TGF-β1-IL-18 ratio were confirmed in distinct studies. This review presents the most comprehensive overview of relevant SP biomarkers to predict ART outcomes to date, which is of clinical interest for infertility investigations and assisted reproduction; nevertheless, its potential is under-exploited. This review could serve as starting point for designing an all-encompassing study for biomarkers in SP and their predictive ability for ART outcomes, and for developing a non-invasive diagnostic tool.

Heat stress and stallion fertility

The threat posed by increased surface temperatures worldwide has attracted the attention of researchers to the reaction of animals to heat stress. Spermatogenesis in animals such as stallions is a temperature-dependent process, ideally occurring at temperatures slightly below the core body temperature. Thus, proper thermoregulation is essential, especially because stallion spermatogenesis and the resulting spermatozoa are negatively affected by increased testicular temperature. Consequently, the failure of thermoregulation resulting in heat stress may diminish sperm quality and increase the likelihood of stallion infertility. In this review, we emphasize upon the impact of heat stress on spermatogenesis and the somatic and germ cells and describe the subsequent testicular alterations. In addition, we explore the functions and molecular responses of heat shock proteins, including HSP60, HSP70, HSP90, and HSP105, in heat-induced stress conditions. Finally, we discuss the use of various therapies to alleviate heat stress-induced reproductive harm by modulating distinct signaling pathways.

Implications of sperm heat shock protein 70-2 in bull fertility

Heat shock protein 70 (HSP70) is one of the most abundant chaperone proteins. Their function is well documented in facilitating the protein synthesis, translocation, de novo folding, and ordering of multiprotein complexes. HSP70 in bovine consists of four genes: HSP70-1, HSP70-2, HSP70-3, and HSP70-4. HSP70-2 was found to be involved in fertility. Current knowledge implicates HSP70-2 in sperm quality, sperm capacitation, sperm–egg recognition, and fertilization essential for bull reproduction. HSP70-2 is also involved in the biological processes of spermatogenesis, as it protects cells from the effects of apoptosis and oxidative stress. Fertilization success is not only determined by the amount of sperm found in the female reproductive tract but also by the functional ability of the sperm. However, subfertility is more likely to be associated with changes in sperm molecular dynamics not detectable using conventional methods. As such, molecular analyses and omics methods have been developed to monitor crucial aspects of sperm molecular morphology that are important for sperm functions, which are the objectives of this review.

Immune infertility in men

Male factors are implicated as the cause of roughly half of cases of infertility, and the presence of antisperm antibodies (ASA) may be responsible for some of these. Their presence is associated with a reduction in natural conception and live birth and impacts the success of assisted reproductive technologies. Interpretation of the data regarding ASAs and fertility is complicated by a lack of standardization in testing methodology and test thresholds and a lack of data on their prevalence in the healthy fertile population. Although their pathogenesis remains elusive, and many cases are idiopathic, a disruption in the immunologic blood-testis barrier (BTB) appears to contribute to the formation of ASA. As delineation of the specific antigen targets of ASA advances, it has been recognized that they may affect almost all aspects of sperm function, and ASA against different targets likely have specific mechanisms of impairing fertility. Intracytoplasmic sperm injection (ICSI) appears to be the most reliable method by which to overcome fertility impairment due to ASA, achieving similar outcomes to ASA-negative patients with regard to fertilization rates, embryonic development, clinical pregnancy rates, and live birth rates. The lack of consistency in testing for and reporting ASA remains a substantial barrier to achieving clarity in describing their role in infertility and the optimal management approach, and future research should use a unified approach to the detection and description of ASA. Determination of the specific antigens targeted by ASA, and their function and clinical relevance, would contribute to improving the understanding of ASA-mediated impacts on fertility and tailoring treatment appropriately to achieve the best outcomes for patients.

An Autoantigen Atlas From Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. We used DS-affinity proteomics to define the autoantigen-ome of lung fibroblasts and bioinformatics analyses to study the relationship between autoantigenic proteins and COVID-induced alterations. Using DS-affinity, we identified an autoantigen-ome of 408 proteins from human HFL1 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigen-ome have thus far been found to be altered at protein or RNA levels in SARS-CoV-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a connection between COVID infection and autoimmunity. The vast number of COVID-altered proteins with high intrinsic propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles suggests a need for long-term monitoring of autoimmunity in COVID. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic, such as "long COVID" syndrome.

Summary Sentence

An autoantigen-ome by dermatan sulfate affinity from human lung HFL1 cells may explain neurological and autoimmune manifestations of COVID-19.

A Master Autoantigen-ome Links Alternative Splicing, Female Predilection, and COVID-19 to Autoimmune Diseases

Chronic and debilitating autoimmune sequelae pose a grave concern for the post-COVID-19 pandemic era. Based on our discovery that the glycosaminoglycan dermatan sulfate (DS) displays peculiar affinity to apoptotic cells and autoantigens (autoAgs) and that DS-autoAg complexes cooperatively stimulate autoreactive B1 cell responses, we compiled a database of 751 candidate autoAgs from six human cell types. At least 657 of these have been found to be affected by SARS-CoV-2 infection based on currently available multi-omic COVID data, and at least 400 are confirmed targets of autoantibodies in a wide array of autoimmune diseases and cancer. The autoantigen-ome is significantly associated with various processes in viral infections, such as translation, protein processing, and vesicle transport. Interestingly, the coding genes of autoAgs predominantly contain multiple exons with many possible alternative splicing variants, short transcripts, and short UTR lengths. These observations and the finding that numerous autoAgs involved in RNA-splicing showed altered expression in viral infections suggest that viruses exploit alternative splicing to reprogram host cell machinery to ensure viral replication and survival. While each cell type gives rise to a unique pool of autoAgs, 39 common autoAgs associated with cell stress and apoptosis were identified from all six cell types, with several being known markers of systemic autoimmune diseases. In particular, the common autoAg UBA1 that catalyzes the first step in ubiquitination is encoded by an X-chromosome escape gene. Given its essential function in apoptotic cell clearance and that X-inactivation escape tends to increase with aging, UBA1 dysfunction can therefore predispose aging women to autoimmune disorders. In summary, we propose a model of how viral infections lead to extensive molecular alterations and host cell death, autoimmune responses facilitated by autoAg-DS complexes, and ultimately autoimmune diseases. Overall, this master autoantigen-ome provides a molecular guide for investigating the myriad of autoimmune sequalae to COVID-19 and clues to the rare but reported adverse effects of the currently available COVID vaccines.

An Autoantigen Profile from Jurkat T-Lymphoblasts Provides a Molecular Guide for Investigating Autoimmune Sequelae of COVID-19

In order to understand autoimmune phenomena contributing to the pathophysiology of COVID-19 and post-COVID syndrome, we have been profiling autoantigens (autoAgs) from various cell types. Although cells share numerous autoAgs, each cell type gives rise to unique COVID-altered autoAg candidates, which may explain the wide range of symptoms experienced by patients with autoimmune sequelae of SARS-CoV-2 infection. Based on the unifying property of affinity between autoantigens (autoAgs) and the glycosaminoglycan dermatan sulfate (DS), this paper reports 140 candidate autoAgs identified from proteome extracts of human Jurkat T-cells, of which at least 105 (75%) are known targets of autoantibodies. Comparison with currently available multi-omic COVID-19 data shows that 125 (89%) of DS-affinity proteins are altered at protein and/or RNA levels in SARS-CoV-2-infected cells or patients, with at least 94 being known autoAgs in a wide spectrum of autoimmune diseases and cancer. Protein alterations by ubiquitination and phosphorylation in the viral infection are major contributors of autoAgs. The autoAg protein network is significantly associated with cellular response to stress, apoptosis, RNA metabolism, mRNA processing and translation, protein folding and processing, chromosome organization, cell cycle, and muscle contraction. The autoAgs include clusters of histones, CCT/TriC chaperonin, DNA replication licensing factors, proteasome and ribosome proteins, heat shock proteins, serine/arginine-rich splicing factors, 14-3-3 proteins, and cytoskeletal proteins. AutoAgs such as LCP1 and NACA that are altered in the T cells of COVID patients may provide insight into T-cell responses in the viral infection and merit further study. The autoantigen-ome from this study contributes to a comprehensive molecular map for investigating acute, subacute, and chronic autoimmune disorders caused by SARS-CoV-2.

An Autoantigen-ome from HS-Sultan B-Lymphoblasts Offers a Molecular Map for Investigating Autoimmune Sequelae of COVID-19

To understand how COVID-19 may induce autoimmune diseases, we have been compiling an atlas of COVID-autoantigens (autoAgs). Using dermatan sulfate (DS) affinity enrichment of autoantigenic proteins extracted from HS-Sultan lymphoblasts, we identified 362 DS-affinity proteins, of which at least 201 (56%) are confirmed autoAgs. Comparison with available multi-omic COVID data shows that 315 (87%) of the 362 proteins are affected in SARS-CoV-2 infection via altered expression, interaction with viral components, or modification by phosphorylation or ubiquitination, at least 186 (59%) of which are known autoAgs. These proteins are associated with gene expression, mRNA processing, mRNA splicing, translation, protein folding, vesicles, and chromosome organization. Numerous nuclear autoAgs were identified, including both classical ANAs and ENAs of systemic autoimmune diseases and unique autoAgs involved in the DNA replication fork, mitotic cell cycle, or telomerase maintenance. We also identified many uncommon autoAgs involved in nucleic acid and peptide biosynthesis and nucleocytoplasmic transport, such as aminoacyl-tRNA synthetases. In addition, this study found autoAgs that potentially interact with multiple SARS-CoV-2 Nsp and Orf components, including CCT/TriC chaperonin, insulin degrading enzyme, platelet-activating factor acetylhydrolase, and the ezrin-moesin-radixin family. Furthermore, B-cell-specific IgM-associated ER complex (including MBZ1, BiP, heat shock proteins, and protein disulfide-isomerases) is enriched by DS-affinity and up-regulated in B-cells of COVID-19 patients, and a similar IgH-associated ER complex was also identified in autoreactive pre-B1 cells in our previous study, which suggests a role of autoreactive B1 cells in COVID-19 that merits further investigation. In summary, this study demonstrates that virally infected cells are characterized by alterations of proteins with propensity to become autoAgs, thereby providing a possible explanation for infection-induced autoimmunity. The COVID autoantigen-ome provides a valuable molecular resource and map for investigation of COVID-related autoimmune sequelae and considerations for vaccine design.

An Autoantigen Atlas from Human Lung HFL1 Cells Offers Clues to Neurological and Diverse Autoimmune Manifestations of COVID-19

COVID-19 is accompanied by a myriad of both transient and long-lasting autoimmune responses. Dermatan sulfate (DS), a glycosaminoglycan crucial for wound healing, has unique affinity for autoantigens (autoAgs) from apoptotic cells. DS-autoAg complexes are capable of stimulating autoreactive B cells and autoantibody production. Using DS affinity, we identified an autoantigenome of 408 proteins from human fetal lung fibroblast HFL11 cells, at least 231 of which are known autoAgs. Comparing with available COVID data, 352 proteins of the autoantigenome have thus far been found to be altered at protein or RNA levels in SARS-Cov-2 infection, 210 of which are known autoAgs. The COVID-altered proteins are significantly associated with RNA metabolism, translation, vesicles and vesicle transport, cell death, supramolecular fibrils, cytoskeleton, extracellular matrix, and interleukin signaling. They offer clues to neurological problems, fibrosis, smooth muscle dysfunction, and thrombosis. In particular, 150 altered proteins are related to the nervous system, including axon, myelin sheath, neuron projection, neuronal cell body, and olfactory bulb. An association with the melanosome is also identified. The findings from our study illustrate a strong connection between viral infection and autoimmunity. The vast number of COVID-altered proteins with propensity to become autoAgs offers an explanation for the diverse autoimmune complications in COVID patients. The variety of autoAgs related to mRNA metabolism, translation, and vesicles raises concerns about potential adverse effects of mRNA vaccines. The COVID autoantigen atlas we are establishing provides a detailed molecular map for further investigation of autoimmune sequelae of the pandemic.

Sperm selection in IVF: the long and winding road from bench to bedside

Spermatozoa wage battle to conquer fertilization but the traits needed to succeed remain elusive. The natural advantageous qualities that enable only a few selected sperm cells to reach the site of fertilization remain unknown. Although in vitro fertilization (IVF) facilitates the job of spermatozoa, a universally acceptable means of sperm selection is yet to be developed. No objective or reliable sperm quality indicators have been established and sperm selection is, to a great extent, based on subjective qualitative evaluation. The best method for sperm selection in IVF presents several challenges: intrinsic sperm qualities cannot be evaluated and the ideal endpoint for these studies is debatable. An ideal method for sperm selection in ART should be noninvasive and cost-effective, and allow the identification of high-quality spermatozoa and yield better outcomes in terms of pregnancy and live birth rates. This narrative review included 85 papers and focused on the new available methods and technologies that might shed some light on sperm selection in IVF. It discusses the available data on microfluidic devices, omics profiling, micronuclei studies, sperm plasma membrane markers, and other techniques, such as Magnetic Activated Cell Sorting (MACS), Raman micro-spectroscopy, and artificial intelligence systems. The new techniques herein reviewed offer fresh approaches to an old problem, for which a definite solution has yet to cross the bridge from bench to IVF clinics around the world, since clinical usefulness and application remain unproven.

HSPA1L and HSPA1B gene polymorphisms and haplotypes are associated with idiopathic male infertility in Iranian population

OBJECTIVE

Male infertility is a multifactorial disease resulting from the interaction between the genetic and environmental factors. Spermatogenic failure accounts for more than half of male infertility cases. Heat shock proteins (HSPs) are the molecular chaperones that are involved in different developmental stages of spermatogenesis. The current study was planned to investigate the role of HSPA1L rs2227956 and HSPA1B rs1061581 gene polymorphisms in idiopathic male infertility.

STUDY DESIGN

This case-control study was conducted on 516 subjects consisted of 308 patients with idiopathic male infertility and 208 age matched-(±5) control subjects. HSPA1L rs2227956 and HSPA1B rs1061581 polymorphisms were genotyped by PCR-RFLP method.

RESULTS

A significant association with male infertility was found for HSPA1L rs2227956 in genotypes (TT vs CT: OR = 2.049, 95% CI = 1.337-3.139, P = 0.001; TT vs CC: OR = 3.028, 95% CI = 1.100-8.332, P = 0.032). In the dominant genetic model, rs2227956C allele increased the risk of male infertility (OR = 2.049, 95% CI = 1.337-3.139, P = 0.001). Also, the results showed a significant association between the HSPA1B rs1061581GG genotype and male infertility (OR = 2.638, 95% CI: 1.001-4.486, P = 0.001). The rs1061581 G allele was a risk factor for male infertility (OR = 1.657, 95% CI = 1.278-2.148, P < 0.001). Haplotype analysis showed CG and TA (rs2227956/ rs1061581) haplotype affect the risk of male infertility (P < 0.001).

CONCLUSION

HSPA1L rs2227956 and HSPA1B rs1061581 gene polymorphisms are associated with susceptibility to idiopathic male infertility in Iranian population. Further studies in different ethnicity are necessary to confirm these results.

Human MOSPD2: A bacterial Lmb mimicked auto-antigen is involved in immune infertility

Autoantibody production is one of the leading factors of immune infertility, an autoimmune disease of the male reproductive system. The potential involvement of MHC-class II derived self-peptides against bacterial proteins in the antisperm antibody (ASA) production has been reported previously. Apparently, Streptococcus agalactiae has been considered as an important pathogen to impart infection-induced infertility in a bacteriospermia associated leukocytospermia (LCS/BS) state. Hence, the present study attempts to confirm S. agalactiae specific Laminin binding protein (Lmb) derived self-peptide ('KDSYTKKAKAFKKEA') namely human Motile Sperm domain-containing protein 2 (MOSPD2) as an auto-antigen in LCS/BS condition. Semen samples were collected from infertile men with LCS/BS (n ​= ​17) and their fertile counterparts (n ​= ​10). Gram-positive bacteria were predominantly identified in the entire 17 LCS samples using culture method followed by 16S rDNA sequencing technique. TLRs 2 and 4 expression used as markers of immune response in spermatozoa and sperm dysfunction were elevated in the LCS/BS spermatozoa as compared to their fertile counterparts. A significant increase in oxidative stress indices i.e., protein carbonylation, lipid peroxidation and acridine orange test (AOT), was also observed in the LCS/BS spermatozoa. Spermatozoa lysate (both auto and heterologous), bacterial lysate (control) and synthesized MOSPD2 self-peptide were used to test their antigenicity against the autoantibodies by rocket immunoelectrophoresis (RIEP) assay. Seminal plasma from LCS/BS patients with S. agalactiae was used as the source of autoantibodies. Spermatozoa and bacteria lysate; and MOSPD2 self-peptide were able to bind autoantibodies in the seminal plasma. Besides, the self-peptide showed a dose dependent increase in the precipitation of antibody. T-cell epitope mapping of 48 Enterococcus faecalis and 91Staphylococcus aureus surface proteins confirmed MOSPD2 as a global auto-antigen. Thus, augmentation of TLR expression in LCS/BS spermatozoa inferred MOSPD2 to be a putative immunogen. Altogether, these findings will delineate the significance of MOSPD2 auto-antigen in a bacteria derived immune infertility condition.

Antigenic mimicry of ubiquitin by the gut bacterium Bacteroides fragilis: a potential link with autoimmune disease

Ubiquitin is highly conserved across eukaryotes and is essential for normal eukaryotic cell function. The bacterium Bacteroides fragilis is a member of the normal human gut microbiota, and the only bacterium known to encode a homologue of eukaryotic ubiquitin. The B. fragilis gene sequence indicates a past horizontal gene transfer event from a eukaryotic source. It encodes a protein (BfUbb) with 63% identity to human ubiquitin which is exported from the bacterial cell. The aim of this study was (i) to determine if there was antigenic cross‐reactivity between B. fragilis ubiquitin and human ubiquitin and (ii) to determine if humans produced antibodies to BfUbb. Molecular model comparisons of BfUbb and human ubiquitin predicted a high level (99·8% confidence) of structural similarity. Linear epitope mapping identified epitopes in BfUbb and human ubiquitin that cross‐react. BfUbb also has epitope(s) that do not cross‐react with human ubiquitin. The reaction of human serum (n = 474) to BfUbb and human ubiquitin from the following four groups of subjects was compared by enzyme‐linked immunosorbent assay (ELISA): (1) newly autoantibody‐positive patients, (2) allergen‐specific immunoglobulin (Ig)E‐negative patients, (3) ulcerative colitis patients and (4) healthy volunteers. We show that the immune system of some individuals has been exposed to BfUbb which has resulted in the generation of IgG antibodies. Serum from patients referred for first‐time testing to an immunology laboratory for autoimmune disease are more likely to have a high level of antibodies to BfUbb than healthy volunteers. Molecular mimicry of human ubiquitin by BfUbb could be a trigger for autoimmune disease.

Improvement in pregnancy outcomes in couples with immunologically male infertility undergoing prednisolone treatment and conventional in vitro fertilization preceded by sperm penetration assay: a randomized controlled trial

PURPOSE

Anti-sperm antibodies (ASA) in men impair not only sperm motility but also fertilization and conception. However, utilization of corticosteroids to suppress ASA has shown variable pregnancy outcomes. This controversy is also extended to include the usefulness of conventional in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in treatments of men with ASA. This study was therefore designed to define factors contributing to these inconsistent results.

METHODS

Infertile men having ASA (n = 241) were randomly assigned for treatment with or without prednisolone for three cycles each of 21 days of their partner's menstrual cycles. Control and treated men underwent then human sperm penetration assay (SPA), of hamster oocytes, to diagnose men with impaired sperm fusogenic capacity. Men with positive or negative SPA results were admitted to conventional IVF or ICSI programs, respectively.

RESULTS

Treated patients had improved sperm motility and progressive motility when compared to control patients (P < 0.001). Fertilization (P = 0.04), embryo cleavage (P = 0.01), and chemical (P = 0.02) and clinical (P = 0.04) pregnancy rates were higher in treated patients than in control patients undergoing conventional IVF but not ICSI cycles.

CONCLUSIONS

Men with ASA may also have compromised sperm fusogenic capacity, which can mask the clinical significance of corticosteroids. Corticosteroid administration in men with ASA, but without compromised sperm fusogenic capacity, improves conventional IVF but not ICSI outcomes; the reason being that ICSI bypasses issues of compromised fusogenic capacity. Inclusion of SPA in infertility clinics that offer both conventional IVF and ICSI services may be useful to identify which patients with ASA benefit from corticosteroid treatments.

Male factors in ART outcome prediction

Paternal influences on reproduction are significant causing about half of the infertile couples to turn to assisted reproductive techniques. Due to the increasing proportion of infertile couples adopting to conceive by in vitro fertilisation (IVF), predicting outcomes is of ever increasing importance. Since pregnancy rates following IVF are still quite low, prognostic information is very helpful in clinical decisions. Although significant research has been done on the maternal influence, male factor infertility is relatively understudied. To date, potential predictors include: method of fertilisation, age, reactive oxygen species, sperm quality parameters and DNA fragmentation. Predictors under investigation which show promising signs, even though there is no clear cut consensus on the predictive value to date include: folate and homocysteine, anti müllerian hormone measurement, environmental factors, body mass index, smoking, male age, stress, some subsets of antisperm antibodies and epigenetic features.

Immunodominant semen proteins I: New patterns of sperm proteins related to female immune infertility

Infertility affects approximately 10% of couples at reproductive age. Semen constituents may be potential immunogenic structures for women. The aim of our work is to detect and identify sperm proteins interacting with serum IgG antibodies from women with fertility disorders. The biochemical characterization of sperm antigens was performed using one and two dimensional gel electrophoresis, both of which were followed by immunoblotting. The IgG-binding proteins of interest were identified using mass spectrometry. From the serum pool of 30 infertile women, we detected sperm antigens within a relative molecular mass range between 30–80 kDa with an isoelectric point of 4–7. No antigens were detected using the serum pool from 10 fertile women (control group). Heat shock proteins (HSP 70) were identified as major sperm antigens associated with female immune infertility. Additionally, we report for the first time that alpha-enolase is a significant sperm antigen from the serum pool of infertile women. We suggest that the IgG-binding proteins identified in our study are related to immune infertility in the case of certain women with abnormally high levels of IgG antibodies linked to sperm proteins. Our results might be useful in the diagnoses of female immune infertility and may provide potential targets for further therapeutic treatment.

The effect of pulsed 900-MHz GSM mobile phone radiation on the acrosome reaction, head morphometry and zona binding of human spermatozoa

Several recent studies have indicated that radiofrequency electromagnetic fields (RF-EMF) have an adverse effect on human sperm quality, which could translate into an effect on fertilization potential. This study evaluated the effect of RF-EMF on sperm-specific characteristics to assess the fertilizing competence of sperm. Highly motile human spermatozoa were exposed for 1 h to 900-MHz mobile phone radiation at a specific absorption rate of 2.0 W/kg and examined at various times after exposure. The acrosome reaction was evaluated using flow cytometry. The radiation did not affect sperm propensity for the acrosome reaction. Morphometric parameters were assessed using computer-assisted sperm analysis. Significant reduction in sperm head area (9.2 ± 0.7 μm² vs. 18.8 ± 1.4 μm²) and acrosome percentage of the head area (21.5 ± 4% vs. 35.5 ± 11.4%) was reported among exposed sperm compared with unexposed controls. Sperm-zona binding was assessed directly after exposure using the hemizona assay. The mean number of zona-bound sperm of the test hemizona and controls was 22.8 ± 12.4 and 31.8 ± 12.8 (p < 0.05), respectively. This study concludes that although RF-EMF exposure did not adversely affect the acrosome reaction, it had a significant effect on sperm morphometry. In addition, a significant decrease in sperm binding to the hemizona was observed. These results could indicate a significant effect of RF-EMF on sperm fertilization potential.

Sperm proteasome and fertilization

The omnipresent ubiquitin–proteasome system (UPS) is an ATP-dependent enzymatic machinery that targets substrate proteins for degradation by the 26S proteasome by tagging them with an isopeptide chain composed of covalently linked molecules of ubiquitin, a small chaperone protein. The current knowledge of UPS involvement in the process of sperm penetration through vitelline coat (VC) during human and animal fertilization is reviewed in this study, with attention also being given to sperm capacitation and acrosome reaction/exocytosis. In ascidians, spermatozoa release ubiquitin-activating and conjugating enzymes, proteasomes, and unconjugated ubiquitin to first ubiquitinate and then degrade the sperm receptor on the VC; in echinoderms and mammals, the VC (zona pellucida/ZP in mammals) is ubiquitinated during oogenesis and the sperm receptor degraded during fertilization. Various proteasomal subunits and associated enzymes have been detected in spermatozoa and localized to sperm acrosome and other sperm structures. By using specific fluorometric substrates, proteasome-specific proteolytic and deubiquitinating activities can be measured in live, intact spermatozoa and in sperm protein extracts. The requirement of proteasomal proteolysis during fertilization has been documented by the application of various proteasome-specific inhibitors and antibodies. A similar effect was achieved by depletion of sperm-surface ATP. Degradation of VC/ZP-associated sperm receptor proteins by sperm-borne proteasomes has been demonstrated in ascidians and sea urchins. On the applied side, polyspermy has been ameliorated by modulating sperm-associated deubiquitinating enzymes. Diagnostic and therapeutic applications could emerge in human reproductive medicine. Altogether, the studies on sperm proteasome indicate that animal fertilization is controlled in part by a unique, gamete associated, extracellular UPS.

Sertoli cell-specific deletion of the androgen receptor compromises testicular immune privilege in mice

In the mammalian testis, meiotic and postmeiotic germ cell antigens are granted immune privilege. Both local immune suppression and specialized intercellular junctions between somatic Sertoli cells have been proposed to contribute to a highly restricted and effective blood-testis barrier (BTB) that helps maintain tolerance to germ cell antigens. Several studies have suggested that androgens play a role in immune suppression, although direct evidence for this is lacking. We previously reported that Sertoli cell-specific ablation of the androgen receptor (Ar) decreases expression of Cldn3, an androgen-regulated gene and component of Sertoli cell tight junctions, and increases the permeability of the BTB to biotin, a small-molecular-weight tracer. The physiological consequences of Sertoli cell-specific Ar (S-Ar) ablation on immune privilege are unknown. Here we show that in the testes of S-Ar mutant mice, the ultrastructure of Sertoli cell tight junctions is defective and testicular IgG levels are elevated. The interstitium of S-Ar mutant testes becomes populated with macrophages, neutrophils, plasma cells, and eosinophils, and serum samples of mutant mice contain antibodies against germ cell antigens. Together, these results suggest that Sertoli cell-specific deletion of the androgen receptor results in loss of testicular immune privilege. Suppressed levels of androgen signaling may be a contributing factor in idiopathic male infertility.

Sperm proteasomes degrade sperm receptor on the egg zona pellucida during mammalian fertilization

Despite decades of research, the mechanism by which the fertilizing spermatozoon penetrates the mammalian vitelline membrane, the zona pellucida (ZP) remains one of the unexplained fundamental events of human/mammalian development. Evidence has been accumulating in support of the 26S proteasome as a candidate for echinoderm, ascidian and mammalian egg coat lysin. Monitoring ZP protein degradation by sperm during fertilization is nearly impossible because those few spermatozoa that penetrate the ZP leave behind a virtually untraceable residue of degraded proteins. We have overcome this hurdle by designing an experimentally consistent in vitro system in which live boar spermatozoa are co-incubated with ZP-proteins (ZPP) solubilized from porcine oocytes. Using this assay, mimicking sperm-egg interactions, we demonstrate that the sperm-borne proteasomes can degrade the sperm receptor protein ZPC. Upon coincubation with motile spermatozoa, the solubilized ZPP, which appear to be ubiquitinated, adhered to sperm acrosomal caps and induced acrosomal exocytosis/formation of the acrosomal shroud. The degradation of the sperm receptor protein ZPC was assessed by Western blotting band-densitometry and proteomics. A nearly identical pattern of sperm receptor degradation, evident already within the first 5 min of coincubation, was observed when the spermatozoa were replaced with the isolated, enzymatically active, sperm-derived proteasomes. ZPC degradation was blocked by proteasomal inhibitors and accelerated by ubiquitin-aldehyde(UBAL), a modified ubiquitin protein that stimulates proteasomal proteolysis. Such a degradation pattern of ZPC is consistent with in vitro fertilization studies, in which proteasomal inhibitors completely blocked fertilization, and UBAL increased fertilization and polyspermy rates. Preincubation of intact zona-enclosed ova with isolated active sperm proteasomes caused digestion, abrasions and loosening of the exposed zonae, and significantly reduced the fertilization/polyspermy rates after IVF, accompanied by en-mass detachment of zona bound sperm. Thus, the sperm borne 26S proteasome is a candidate zona lysin in mammals. This new paradigm has implications for contraception and assisted reproductive technologies in humans, as well as animals.

Testicular postgenomics: targeting the regulation of spermatogenesis

Sperm are, arguably, the most differentiated cells produced within the body of any given species. This is owing to the fact that spermatogenesis is an intricate and highly specialized process evolved to suit the individual particularities of each sexual species. Despite a vast diversity in method, the aim of spermatogenesis is always the same, the idealized transmission of genetic patrimony. Towards this goal certain requirements must always be met, such as a relative twofold reduction in ploidy, repackaging of the chromatin for transport and specialized enhancements for cell motility, recognition and fusion. In the past 20 years, the study of molecular networks coordinating male germ cell development, particularly in mammals, has become more and more facilitated thanks to large-scale analyses of genome expression. Such postgenomic endeavors have generated landscapes of data for both fundamental and clinical reproductive biology. Continuous, large-scale integration analyses of these datasets are undertaken which provide access to very precise information on a myriad of biomolecules. This review presents commonly used transcriptomic and proteomic workflows applied to various testicular germ cell studies. We will also provide a general overview of the technical possibilities available to reproductive genomic biologists, noting the advantages and drawbacks of each technique.

Antisperm immunity and infertility

Immunoinfertility is one of several causes of infertility in humans. Although progress on antisperm immunity and infertility has advanced during the past three decades, the nature of a real antisperm antibody (ASA) is still poorly understood. Dozens of sperm antigens have been isolated and characterized in association with infertility. However, it is difficult to identify a single predominant target antigen that could interact with all the ASAs. There are some protective mechanisms preventing ASA production in males and females. As chronic infection, vasectomy and vasovasostomy, heavy metals, and testicular cancer and torsion may induce the production of ASAs, they may be responsible for decreased motility and sperm penetration of cervical mucus, and the blockage of the acrosome reaction and the sperm-egg interaction. Many ASA assay methods have been developed, each with advantages and disadvantages. Efforts for the treatment of ASA-mediated infertility have been attempted. However, current therapy for ASA-associated infertility is almost empiric and largely unproven.

Identification of calcium-binding proteins associated with the human sperm plasma membrane

BACKGROUND

The precise composition of the human sperm plasma membrane, the molecular interactions that define domain specific functions, and the regulation of membrane associated proteins during the capacitation process, still remain to be fully understood. Here, we investigated the repertoire of calcium-regulated proteins associated with the human sperm plasma membrane.

METHODS

Surface specific radioiodination was combined with two-dimensional gel electrophoresis, a 45Ca-overlay assay, computer assisted image analysis and mass spectrometry to identify calcium-binding proteins exposed on the human sperm surface.

RESULTS

Nine acidic 45Ca-binding sperm proteins were excised from stained preparative 2D gels and identified by mass spectrometry. Five of the calcium binding proteins; HSPA2 (HSP70-1), HSPA5 (Bip), HYOU1 (ORP150), serum amyloid P-component (SAP) and protein kinase C substrate 80K-H (80K-H) were found to be accessible to Iodo-Bead catalyzed 125I-labelling on the surface of intact human sperm. Agglutination and immunofluorescence analysis confirmed that SAP is situated on the plasma membrane of intact, motile sperm as well as permeabilized cells. Western blot analysis showed increased phosphorylation of human sperm 80K-H protein following in vitro capacitation. This is the first demonstration of the 80K-H protein in a mammalian sperm.

CONCLUSION

The presence of SAP on the surface of mature sperm implies that SAP has a physiological role in reproduction, which is thought to be in the removal of spermatozoa from the female genital tract via phagocytosis. Since 80K-H is a Ca2+-sensor recently implicated in the regulation of both inositol 1,4,5-trisphosphate receptor and transient receptor potential (TRP) cation channel activities, its detection in sperm represents the first direct signaling link between PKC and store-operated calcium channels identified in human sperm.

Expression of IL-6, IL-8, TNF-alpha, IL-10, HSP-60, anti-HSP-60 antibodies, and anti-sperm antibodies, in semen of men with leukocytes and/or bacteria

PROBLEM

Different cellular and biochemical markers have been proposed as indicators of infection-inflammation of male genital tract.

METHOD OF STUDY

Semen samples from 80 men attending an andrologic clinic were evaluated to determine the presence of leukocyte, bacteria, antibodies against Chlamydia trachomatis, levels of IL-6, IL-8, IL-10, and TNF-alpha, HSP-60, anti-HSP-60 antibodies, and anti-sperm antibodies.

RESULTS

Leukocytes in semen significantly correlated with an increase in IL-6, IL-8, and TNF-alpha. The simultaneous presence of pathogens and leukocytes was associated with high levels of IL-8 and TNF-alpha, whereas IL-6 was more associated with the presence of leukocytes. Anti-HSP-60 antibodies positively correlated with IL-6 and IL-8. The presence of anti-sperm antibodies highly associated with an increase in anti-HSP-60 antibodies.

CONCLUSIONS

The type of cytokines present in the semen will depend on the single or simultaneous presence of leukocytes and/or pathogens. Chronic male genital tract infections could be associated with the development of anti-HSP-60 antibodies and anti-sperm antibodies.

Heat shock proteins on the human sperm surface

The sperm plasma membrane is known to be critical to fertilization and to be highly regionalized into domains of head, mid- and principal pieces. However, the molecular composition of the sperm plasma membrane and its alterations during genital tract passage, capacitation and the acrosome reaction remains to be fully dissected. A two-dimensional gel-based proteomic study previously identified 98 human sperm proteins which were accessible for surface labelling with both biotin and radioiodine. In this report twelve dually labelled protein spots were excised from stained gels or PDVF membranes and analysed by mass spectrometry (MS) and Edman degradation. Seven members from four different heat shock protein (HSP) families were identified including HYOU1 (ORP150), HSPC1 (HSP86), HSPA5 (Bip), HSPD1 (HSP60), and several isoforms of the two testis-specific HSP70 chaperones HSPA2 and HSPA1L. An antiserum raised against the testis-specific HSPA2 chaperone reacted with three 65kDa HSPA2 isoforms and three high molecular weight surface proteins (78-79kDa, 84kDa and 90-93kDa). These proteins, together with seven 65kDa HSP70 forms, reacted with human anti-sperm IgG antibodies that blocked in vitro fertilization in humans. Three of these surface biotinylated human sperm antigens were immunoprecipitated with a rabbit antiserum raised against a linear peptide epitope in Chlamydia trachomatis HSP70. The results indicate diverse HSP chaperones are accessible for surface labelling on human sperm. Some of these share epitopes with C. trachomatis HSP70, suggesting an association between genital tract infection, immunity to HSP70 and reproductive failure.

RNA polymerase II interacts with the Hspa1b promoter in mouse epididymal spermatozoa

The Hspa1b (Hsp70.1) gene is one of the first genes expressed after fertilization, with expression occurring during the minor zygotic genome activation (ZGA) in the absence of stress. This expression can take place in the male pronucleus as early as the one-cell stage of embryogenesis. The importance of HSPA1B for embryonic viability during times of stress is supported by studies showing that depletion of this protein results in a significant reduction in embryos developing to the blastocyte stage. Recently, we have begun addressing the mechanism responsible for allowing expression of Hspa1b during the minor ZGA and found that heat shock transcription factor (HSF) 1 and 2 bind the Hspa1b promoter during late spermatogenesis. In this report, we have extended those studies using western blots and chromatin immunoprecipitation assays and found that RNA polymerase II (Pol II) is present in epididymal spermatozoa and bound to the Hspa1b promoter. These present results, in addition to our previous results, support a model in which the binding of HSF1, HSF2, SP1, and Pol II to the promoter of Hspa1b would allow the rapid formation of a transcription-competent state during the minor ZGA, thereby allowing Hspa1b expression.

Deficiency of co-chaperone immunophilin FKBP52 compromises sperm fertilizing capacity

FKBP52 is a member of the FK506-binding family of immunophilins and serves as a co-chaperone for steroid hormone nuclear receptors to govern appropriate hormone action in target tissues. Male mice missing Fkbp52 are infertile, and this infertility has been ascribed to compromised sensitivity of the anterior prostate, external genitalia, and other accessory sex organs to androgen. Here, we show additional defects contributing to infertility. We found that epididymal Fkbp52(-/-) sperm are sparse often with aberrant morphology, and they have reduced fertilizing capacity. This phenotype, initially observed in null males on a C57BL/6/129 background, is also maintained on a CD1 background. Expression studies show that while FKBP52 and androgen receptor are co-expressed in similar cell types in the epididymis, FKBP52 is also present in epididymal sperm flagella. Collectively, our results suggest that reduced number and abnormal morphology contribute to compromised fertilizing capacity of Fkbp52(-/-) sperm. This study is clinically relevant because unraveling the role of immunophilin signaling in male fertility will help identify new targets for male contraceptives and/or alleviate male infertility.

Immunolocalization of heat shock protein 70 (Hsp 70) in boar spermatozoa and its role during fertilization

The presence and cellular distribution of heat protein 70 (Hsp70) in ejaculated, capacitated, and acrosome-reacted boar spermatozoa was evaluated by immunofluorescence and Western blot; the role of Hsp70 during fertilization was also studied. In freshly ejaculated spermatozoa, Hsp70 immunoreactivity is present in a well-defined triangular-shaped area in the equatorial segment that seems to correspond to the equatorial sub-segment. The distribution of the fluorescent signal changes in capacitated sperm, that exhibit different patterns probably in relation to the stage of capacitation of individual cells; after acrosome reaction Hsp70 immunoreactivity is localized on both a thick sub-equatorial band and a triangle in the equatorial segment. In reacted spermatozoa, Hsp70 seems to be not only relocalized but also translocated from the inner to the outer leaflet of the sperm plasma membrane, as a significant (P < 0.05) increase in the proportion of unfixed cells showing the fluorescent signal has been recorded. No differences in Hsp70 amount between fresh, capacitated, and reacted semen were observed by Western blot. The presence of anti-Hsp70 antibody in the fertilization medium significantly reduced, in a concentration-dependent manner, the fertilization rate of both zona-intact and zona-free oocytes. The overall data demonstrate that Hsp70 is present on boar sperm with a dynamic redistribution as the sperm undergoes capacitation and acrosome reaction and suggest an important role of this protein during porcine gamete interaction.

The role of molecular chaperones in mouse sperm-egg interactions

Fertilization is a unique and exquisitely choreographed cellular interaction between the male and female gamete that results in the creation of a genetically unique individual. Despite the fundamental importance of fertilization, there remains a dearth of information about the basic biochemical mechanisms that underpin this process. One of the key issues that remain unresolved is the molecular basis of sperm-egg recognition. From the female perspective, it is well established that the sperm recognition sites reside in the zona pellucida (ZP), an acellular coat that surrounds the oocyte. In contrast, numerous studies into the cognate zona receptors residing on the sperm surface have failed to shed significant light on the biochemical identity of these molecules. Such difficulties may, in part, have arisen because investigations have traditionally been based on the precept that the zona receptor represents a single molecular entity that is constitutively expressed on the sperm surface. While such a view holds obvious appeal, it fails to account for growing evidence that gamete interaction is not mediated by a simple lock-and-key mechanism. In this review, we present a novel hypothesis in which the zona recognition site is portrayed as a multimeric molecular structure that is assembled into a functional complex during a maturation process known as 'capacitation'. Furthermore, we consider the possibility that this previously cryptic complex is assembled and delivered to the outer surface of the sperm plasma membrane through the concerted action of several members of the molecular chaperone family of proteins.

Antisperm Antibodies in Semen, Sera and Follicular Fluids of Infertile Patients: Relation to Reproductive Outcome afterIn VitroFertilization

PROBLEM

Data given in the literature, regarding the influence of antisperm antibodies (ASA) in the semen and/or sera on in vitro fertilization (IVF) procedure outcome are controversial. The aim of this study was to compare the prevalence of ASA in semen, peripheral blood and follicular fluid as well as to determine total immunoglobulin concentration in the serum and follicular fluid. Selected parameters were analyzed with regard to IVF outcome.

METHOD OF STUDY

The study enrolled 52 married couples. ASA in the semen was determined by direct immunobead mixed antiglobulin reaction (MAR Screen test), while in the peripheral blood and follicular fluid was determined by indirect immunobead MAR Screen test. Immunoglobulin (IgG, IgM and IgA) concentration in the follicular fluid and serum was determined by a liquid-phase immunoprecipitation assay with nephelometric end-point detection and analyzed with regard to IVF outcome.

RESULTS

Semen MAR test IgG was < 20% in 38 couples, and > 20% in 14 couples. Fertilization (73.2% versus 71.5%) and pregnancy rates (28.9% versus 28.57%) in both groups of patients were not significantly different. The results of direct and indirect MAR test were not associated with fertilization and pregnancy rates. Total serum IgG, IgM and IgA in infertile women were within normal ranges. Follicular fluid IgG was within normal values for serum samples, while IgA and IgM were decreased.

CONCLUSION

The presence of ASA on sperm or in the serum and follicular fluid was not associated with IVF outcome in the couples with good quality semen characteristic.