Human Zona Research Articles

Novel Loss-of-function Variants of ZP3 Associated with Premature Ovarian Insufficiency.

Premature ovarian insufficiency (POI) is one of the leading causes of female infertility. To date, the genetic etiology of POI has been elucidated in approximately 20-25% of the total cases. The human zona pellucida (ZP) plays an important role in the organization and differentiation of granulosa cells, follicle formation, and sperm recognition. Mutations in ZP1, ZP2, and ZP3 have been reported to cause female infertility due to oocyte degeneration, empty follicle, or in vitro fertilization failure. In this study, we identified three novel missense mutations in ZP3 (NM_001110354.2): c.643G > A (p.Asp215Asn), c.215C > T (p.Thr72Ile), and c.152T > C (p.Leu51Pro) in three sporadic Han Chinese POI patients through whole-exome sequencing. These variants are absent from population databases and were predicted to be deleterious by multiple in silico tools. Structure prediction analysis showed that the affected amino acid altered the ZP3 protein structure. Western blot further confirmed that these ZP3 variants reduced the expression and secretion of ZP components. In summary, this study reports three novel deleterious variants in ZP3 associated with POI, thereby broadening the mutation spectrum of ZP3 in POI patients.

P-049 Identification of human spermatozoa with zona pellucida-binding ability using deep learning

Abstract Study question Can a deep learning model be used for identification of fertilization-competent human spermatozoa based on their distinctive morphological features? Summary answer Our results validated the clinical significance of image analysis of sperm morphology using deep learning to identify high-quality spermatozoa with zona pellucida (ZP)-binding ability. What is known already Sperm morphology is manually evaluated as part of the conventional semen analysis in clinical settings. However, the clinical predictive power of sperm morphology remains debatable due to its lack of association with the fertilization potential of spermatozoa. Human zona pellucida (ZP)-binding ability is a measurable, independent sperm parameter associated with in vitro fertilization (IVF) and pregnancy outcome. Supervised deep learning is an advanced branch to systematically identify the underlying relationship between the input images and designated output. A well-trained model with high generalization ability can generate plausible predictions for unseen images collected under the same condition as the training datasets. Study design, size, duration Human spermatozoa and oocytes were obtained with written consents from the donors attending our assisted reproduction program. Acrosome intact, ZP-bound spermatozoa were recovered after 30 min of gamete coincubation. Unbound spermatozoa were collected from clinical samples of spermatozoa with defective ZP-binding ability leading to fertilization failure following conventional insemination. Sperm images of infertile men (n = 165) with fertilization rates including 0-40% (low), 41-70% (intermediate) and 71-100% (high) following conventional insemination were collected for validation. Participants/materials, setting, methods Diff-Quik stained images of spermatozoa were processed by the K-means clustering algorithm to generate grey-scaled images of individual sperm heads. All sperm images of clinical samples were subjected an additional image conversion step using Cycle Generative Adversarial Network (CycleGAN) to ensure that their microenvironments are similar to those of the laboratory samples. A VGG 13 model was fine-tuned to classify a total of 1,083 images of ZP-bound and unbound spermatozoa over 50 epochs. Main results and the role of chance The newly fine-tuned VGG-13 model demonstrated excellent performance in classifying the ZP-bound and unbound spermatozoa, as reflected by the high sensitivity of 97.6%, specificity of 96.0%, and accuracy of 96.4%. It had a high discriminative power to distinguish between ZP-bound and unbound spermatozoa with an area under the receiver operating characteristic (ROC) curve (AUC) of 0.992. Saliency maps indicated that the model focused on the sperm head and mid-pieces in all images, with a primary emphasis on the anterior regions (43.0%±5.0%). The model was further validated on a vast collection of over 40,000 sperm images collected from the aforementioned fertilization groups. Our results revealed that the high fertilization rate group had a significantly higher percentage of predicted ZP-binding ability than the low fertilization rate group, as determined by the model (16.8%±7.2 vs. 3.2%±1.4; p < 0.05). By analyzing sperm images from infertile men (n = 113) in the high and low fertilization rates groups, a clinical threshold of 4.8% was identified using ROS curve (AUC:0.970) and Youden’s index, which can be used to distinguish between ZP-bound and unbound spermatozoa of clinical samples with a specificity of 93.8% and a sensitivity of 90.9%. Limitations, reasons for caution Our deep learning model is only applicable to diff-quik stained images of spermatozoa captured at high magnification. Further investigation is needed to examine its classification performance on images captured by different platforms and settings, ensuring consistent and reliable prediction accuracy regardless of varying degrees of image quality. Wider implications of the findings Our newly fine-tuned model can be used to evaluate sperm fertilizing potential, irrespective of the parameters evaluated in conventional semen analysis and to identify normospermic patients with defective ZP-binding ability who may benefit from intracytoplasmic sperm injection (ICSI) to improve their fertilization outcome. Trial registration number not applicable

Abstract PO4-06-08: ZP4 AS A NOVEL TARGET FOR CAR T CELL THERAPY IN TRIPLE NEGATIVE BREAST CANCER

Abstract Triple negative breast cancer (TNBC) has the worst prognosis of BC subtypes, largely due to lack of approved targeted therapies. Chimeric antigen receptor (CAR) T cells have demonstrated great success in certain hematological malignancies; however, in the treatment of solid cancers, CAR T cells are faced with a variety of obstacles that limit their efficacy, including on-target/off-tumor toxicity. To minimize these toxicities, the ideal CAR T cell target must be overexpressed by the tumor and absent from vital organs. Cancer/germline (CG) antigens satisfy this need, as their expression is restricted to male or female germ cells. Using a bioinformatic pipeline to identify novel CG antigens expressed in TNBC and other solid cancers, we have identified zona pellucida glycoprotein 4 (ZP4) as a candidate CG antigen target for CAR T cell therapy. This protein is a component of the human zona pellucida matrix, an extracellular structure that surrounds the oocyte and functions in folliculogenesis, species-specific fertilization, and early development. We have identified ZP4 expression in approximately 10% of TNBC cases from available RNAseq and proteomic databases and have confirmed ZP4 expression in several TNBC PDX models. The overall purpose of this study is to redirect T cells against ZP4 by engineering and validating a second generation ZP4-specific CAR. We have generated a library of monoclonal antibody (mAb) candidates against the extracellular portion of human ZP4. Antibody clones were screened, and their specificity validated via ELISA and flow cytometry, and the three strongest binders (z108, z128, and z164) were selected for further investigation. By IHC, we confirmed that the ZP4 mAb clones stained the area surrounding normal oocytes and did not show binding to any of the 23 normal tissues screened. The variable regions of the antibody heavy and light chains were sequenced using 5’RACE and used to assemble second generation CAR constructs composed of the variable heavy and light chain fragments separated by a linker, a CH2/CH3 hinge domain, a CD28 transmembrane domain, a CD28 co-stimulatory domain, and the CD3z signaling domain. Activated T cells transduced with retroviral supernatant express the ZP4 CAR constructs at high levels. While all ZP4 CAR T cells demonstrate antigen-specific cytotoxic killing of ZP4+ target tumor cells in short-term in vitro assays, z128 ZP4 CAR T cells demonstrate superior persistence and efficacy in long-term repeat tumor challenge in vitro assays and orthotopic in vivo mouse models. In summary, ZP4 is a promising target for TNBC and we have successfully engineered ZP4 specific CAR T cells. ZP4 CAR T cells effectively target and kill ZP4+ cells in in vitro cytotoxicity assays but perform differently in repeat tumor challenge assays and in vivo. Future studies will elucidate the precise differences between our three candidate CAR constructs and further test the effector function, trafficking, proliferation, and persistence of z128 ZP4 CAR T cells in vivo using ZP4+ PDX models. This work has exciting potential to bring a novel CAR T cell therapy to patients with TNBC, without concerns for on-target off-tumor toxicity. Citation Format: Lauren Somes, Jonathan Lei, Paul Shafer, Xinpei Yi, Diego Chamorro, Emily Madaras, Michael Lewis, Bing Zhang, Valentina Hoyos. ZP4 AS A NOVEL TARGET FOR CAR T CELL THERAPY IN TRIPLE NEGATIVE BREAST CANCER [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-06-08.

#338 : Insights into the Zona-Pellucida Mediated Selection of Fertilization-Competent Spermatozoa

Background and Aims: Human zona pellucida (ZP) selectively interacts with high-quality spermatozoa characterized by superior morphology and normal chromatin structure to achieve fertilization. Human ejaculate contains millions of spermatozoa with varying degrees of fertilization potential and genetic quality, of which only thousands of motile spermatozoa can bind to the ZP at the fertilization site. However, direct evidence for ZP-mediated sperm selection process is lacking. This study aims to demonstrate that spermatozoa-ZP interaction represents a crucial step in selecting fertilization-competent spermatozoa in humans. Method: Human spermatozoa and oocytes were obtained with written consents from the donors attending our assisted reproduction program. Acrosome intact, ZP-bound and unbound spermatozoa were recovered using the modified spermatozoa-ZP coincubation assays. ZP-binding protein expression on ZP-bound and unbound spermatozoa were examined by immunofluorescence staining. And the genetic integrity and epigenetic landscapes were evaluated by TUNEL assay, COMET assay, acridine orange staining, chromomycin A3, and immunofluorescence staining for 5-methylcytosine. Results: The time course data demonstrated that ZP interacted with a small proportion of motile spermatozoa. Heat shock 70 kDa protein 2 (HSPA2) and sperm acrosome associated 3 (SPACA 3) are two protein markers associated with the sperm ZP-binding ability. ZP-bound spermatozoa had a higher percentage of positive HSPA2 (85.8% vs. 45.9%, p<0.05) and SPACA3 signals (86.3% vs. 30.5%, p<0.05) than the unbound ones. The signal intensities of both markers were stronger in the ZP-bound spermatozoa than the unbound ones. ZP-bound spermatozoa had a significantly higher level of normal morphology, DNA integrity, chromatin integrity, protamination and global methylation when compared to the unbound ones. Conclusion: Our results validated the functional role of spermatozoa-ZP interaction in providing diagnostic information regarding the fertilization potential and genetic qualities of spermatozoa independent of those derived from the standard semen analysis.

Primary aldosteronism: molecular medicine meets public health.

Primary aldosteronism is the most common single cause of hypertension and is potentially curable when only one adrenal gland is the culprit. The importance of primary aldosteronism to public health derives from its high prevalence but huge under-diagnosis (estimated to be <1% of all affected individuals), despite the consequences of poor blood pressure control by conventional therapy and enhanced cardiovascular risk. This stateofaffairs is attributable to the fact that the tools used for diagnosis or treatment are still those that originated in the 1970-1990s. Conversely, molecular discoveries have transformed our understanding of adrenal physiology and pathology. Many molecules and processes associated with constant adrenocortical renewal and interzonal metamorphosis also feature in aldosterone-producing adenomas and aldosterone-producing micronodules. The adrenal gland has one of the most significant rates of non-silent somatic mutations, with frequent selection of those driving autonomous aldosterone production, and distinct clinical presentations and outcomes for most genotypes. The disappearance of aldosterone synthesis and cells from most of the adult human zona glomerulosa is the likely driver of the mutational success that causes aldosterone-producing adenomas, but insights into the pathways that lead to constitutive aldosterone production and cell survival may open up opportunities for novel therapies.

In silico identification and characterization of the SNPs in the human ASTL gene and their probable role in female infertility.

Ovastacin (ASTL), a zinc metalloprotease, is released from a fertilized egg during exocytosis of cortical granules which occurs minutes after the sperm and egg fuse. ASTL cleaves ZP2, one of the four primary glycoproteins of human zona pellucida, and this cleavage prevents polyspermy, causes zona pellucida hardening, and also protects the pre-implantation embryo. Any perturbation in the activity of ASTL can thus disturb this process and may lead to infertility without changing the gross morphology of the oocyte. A small amount of ASTL is also released by unfertilized oocytes but its catalytic activity is absent as it is bound by its inhibitor, Fetuin-B (FETUB). Pre-mature release of ASTL when FETUB is absent also causes infertility. To identify and understand the structural and functional effects of deleterious SNPs of ASTL on its interaction with ZP2 and FETUB and hence on fertility, a total of 4,748 SNPs from the dbSNP database were evaluated using a variety of in silico tools. All of the 40 shortlisted nsSNPs were present in the catalytic domain of the protein. Comparison of the wild type with mutants using MutPred2 suggests an alteration in the catalytic activity/zinc binding site in many SNPs. Docking studies show the involvement of hydrophobic interactions and H bonding between ASTL and ZP2 and also between ASTL and FETUB. Four positions in ASTL involved in the hydrophobic interactions (P105 and D200 between ASTL and ZP2; D198 and L278 between ASTL and FETUB) and 5 in H bonding (E75 and R159 between ASTL and ZP2; and K93, R159, and C281 between ASTL and FETUB) have SNP's associated with them validating their importance. Interestingly, a cluster of multiple SNPs was found in the motif 198DRD200, which is also a well-conserved region among several species. Statistical Coupling Analysis (SCA) suggested that the deleterious SNPs were present in the functionally important amino acid positions of ASTL and are evolutionarily coupled. Thus, these results attempt to identify the regions in ASTL, mutations in which can affect its binding with ZP2 or FETUB and cause female infertility.

Identification of zona pellucida defects revealed a novel loss-of-function mutation in ZP2 in humans and rats.

Human zona pellucida (ZP) plays an important role in reproductive process. Several rare mutations in the encoding genes (ZP1, ZP2, and ZP3) have been demonstrated to cause women infertility. Mutations in ZP2 have been reported to cause ZP defects or empty follicle syndrome. We aimed to identify pathogenic variants in an infertile woman with a thin zona pellucida (ZP)phenotype and investigated the effect of ZP defects on oocyte genetranscription. We performed whole-exome sequencing and Sanger sequencing of genes were performed for infertilite patients characterized by fertilization failure in routine in vitro fertilization (IVF). Immunofluorescence (IF) and intracytoplasmic sperm injection (ICSI) were used in the mutant oocytes. Single-cell RNA sequencing was used to investigate transcriptomes of the gene-edited (Zp2mut/mut) rat model. Biological function enrichment analysis, quantitative real-time PCR (qRT-PCR), and IF were performed. We identified a novel homozygous nonsense mutation of ZP2 (c.1924C> T, p.Arg642X) in a patient with non-consanguineous married parents. All oocytes showed a thin or no ZP under a light microscope and were fertilized after ICSI. The patient successfully conceived by receiving the only two embryos that developed to the blastocyst stage. The immunofluorescence staining showed an apparently abnormal form of the stopped oocytes. We further demonstrated a total of 374 differentially expressed genes (DEGs) in the transcriptome profiles of Zp2mut/mut rats oocytes and highlighted the signal communication between oocytes and granulosa cells. The pathway enrichment results of DEGs showed that they were enriched in multiple signaling pathways, especially the transforming growth factor-β (TGF-β) signaling pathway in oocyte development. qRT-PCR, IF, and phosphorylation analysis showed significantly downregulated expressions of Acvr2b, Smad2, p38MAPK, and Bcl2 and increased cleaved-caspase 3 protein expression. Our findings expanded the known mutational spectrum of ZP2 associated with thin ZP and natural fertilization failure. Disruption of the integrity of the ZP impaired the TGF-β signaling pathway between oocytes and surrounding granulosa cells, leading to increased apoptosis and decreased developmental potential of oocytes.

Functional substitution of zona pellucida with modified sodium hyaluronate gel in human embryos.

Zona pellucida-free (ZP-free) embryos often fail to achieve good developmental outcomes and are routinely discarded in assisted reproductive laboratories. Existing attempts to rescue ZP-free embryos are not widely used due to operational complexity and high technical requirements. To handle cases with missing ZP, we applied modified sodium hyaluronate gel (MSHG) to embryo culture to determine if it can function as a substitute for human zona pellucida. The developmental process and the blastocyst formation rate of embryos were analyzed in both mouse and human. The first clinical application of MSHG was reported, and the pregnancy outcome was continuously followed up. Human and mouse ZP-free embryos cultured with MSHG showed a blastocyst formation rate similar to ZP-intact embryos. MSHG improves blastocysts formation rate by maintaining blastomere spatial arrangement at early stages. Compared to ZP-free embryos, the proportion of tetrahedrally arranged blastomeres at the 4-cell stage increased significantly in embryos cultured with MSHG in humans. A ZP-free blastocyst cultured in MSHG with the highest score was successfully implanted after day 5 transplantation and developed normally. These data demonstrate that MSHG can substitute the function of zona pellucida and rescue human ZP-free embryos during assisted reproductive technology.

P-257 Nanosphere-based assessment of zona pellucida permeability in humans and mammalian models

Abstract Study question What is the maximum particle size that can traverse through human zona pellucida (ZP) and that of other mammals? Summary answer Human oocytes ZP is impermeable to 40-100 nm nanospheres. ZP of other mammals is impermeable to 100 nm particles, and permeability changes along preimplantation development. What is known already ZP is a porous structure that protects oocytes and early embryos, being permeable to nourishing and signaling substances while blocking the entrance of immune cells and viruses into the perivitelline space. Size-dependent ZP permeability is poorly known and may differ between species, as in humans and rabbits ZP it is composed by 4 proteins (ZP1-4), while bovine and murine ZPs contain only 3 proteins (ZP2-4 in bovine, ZP1-3 in mice). Understanding permeability is crucial to determine embryo susceptibility to viral infections or large biological particles such as exosomes, and to assess possible damages inferred by artificial reproductive techniques. Study design, size, duration The objective has been to determine ZP permeability in mice, bovine, rabbit (wild-type or lacking ZP4) or human oocytes and/or embryos based on particle size. The assay was performed in 3 replicates of 3 samples per stage: mouse samples (oocytes, zygotes, 2-cell embryos and blastocysts) collected in vivo, bovine samples (oocytes, zygotes, 4-8 cell embryos and blastocysts) produced in vitro, rabbit samples (zygotes) collected in vivo and immature human oocytes discarded for clinical use. Participants/materials, setting, methods Permeability test consisted of incubating oocytes and embryos in 0.005 % solutions of carboxylate-modified polystyrene nanospheres (20, 40 and 100 nm) loaded with a fluorophore emitting at a 505/515 nm for 30 min. Following incubation and washing, samples were observed under a structured illumination fluorescence microscope to determine if particles are present inside ZP (i.e., ZP is permeable to that size of particle) or fluorescence cannot be detected (i.e., particles unable to traverse ZP). Main results and the role of chance ZPs of all species and stages blocked efficiently the pass of 100 nm-sized nanospheres. 40 mm nanospheres were blocked by the ZP of oocytes and zygotes in all species with the exception of rabbit zygotes lacking ZP4. ZP permeability changed during early development, as ZP from murine and bovine cleaved embryos and blastocyst were permeable to 40 nm-sized particles. Finally, with the exception or WT rabbit zygotes, ZP from all oocytes and embryos analyzed were permeable to 20 nm nanospheres. As a fluorescence control, murine and bovine oocytes without ZP were exposed to nanospheres of all sizes, which were clearly visualized attached to the oolema or into the ooplasm. Limitations, reasons for caution Experiments on cleavage and blastocysts stages were performed on animal models, so whether human ZP permeability changes following fertilization remains unknown. Wider implications of the findings Mammalian ZP acts as a selective barrier during early embryo development. Understanding particle size-dependent permeability is crucial to determine embryo susceptibility to viral infection or to signaling mediated by large particles such as extracellular vesicles and exosomes and to assess the impact of oocyte manipulation techniques. Trial registration number Not applicable

Human Zona Pellucida Glycoproteins: Binding Characteristics With Human Spermatozoa and Induction of Acrosome Reaction.

Human zona pellucida (ZP) matrix is composed of four glycoproteins designated as ZP glycoprotein -1 (ZP1), -2 (ZP2), -3 (ZP3), and -4 (ZP4). Mutations in the genes encoding human ZP glycoproteins are one of the causative factors leading to abnormal ZP matrix and infertility in women. Relevance of the human ZP glycoproteins in ‘sperm–oocyte’ binding has been delineated by using either transgenic animal models expressing human zona proteins or purified native/recombinant human zona proteins. Studies based on the purified native/recombinant human zona proteins revealed that ZP1, ZP3, and ZP4 primarily bind to the capacitated acrosome-intact human spermatozoa whereas ZP2 binds to acrosome-reacted spermatozoa. On the contrary, human spermatozoa binds to the eggs obtained from transgenic mouse lines expressing human ZP2 but not to those expressing human ZP1, ZP3, and ZP4 suggesting that ZP2 has an important role in human ‘sperm–oocyte’ binding. Further studies using transgenic mouse lines showed that the N-terminus of human ZP2 mediate the taxon-specific human sperm–oocyte binding. Both glycans and protein-protein interactions have a role in human gamete interaction. Further studies have revealed that the purified native/recombinant human ZP1, ZP3, and ZP4 are competent to induce acrosome reaction. Human sperm binds to the mouse transgenic eggs expressing human ZP1-4 instead of mouse ZP1-3 proteins, penetrated the ZP matrix and accumulated in the perivitelline space, which were acrosome-reacted suggesting that human ZP2 in transgenic mouse model also induce acrosome reaction. In humans N-linked glycosylation of zona proteins have been shown to play an important role in induction of the acrosome reaction. Hence in humans, based on studies using transgenic mouse model as well as purified native/recombinant zona proteins, it is likely that more than one zona protein is involved in the ‘sperm–oocyte’ binding and induction of the acrosome reaction.

Direct visualization and characterization of the human zona incerta and surrounding structures.

The zona incerta (ZI) is a small gray matter region of the deep brain first identified in the 19th century, yet direct in vivo visualization and characterization has remained elusive. Noninvasive detection of the ZI and surrounding region could be critical to further our understanding of this widely connected but poorly understood deep brain region and could contribute to the development and optimization of neuromodulatory therapies. We demonstrate that high resolution (submillimetric) longitudinal (T1) relaxometry measurements at high magnetic field strength (7 T) can be used to delineate the ZI from surrounding white matter structures, specifically the fasciculus cerebellothalamicus, fields of Forel (fasciculus lenticularis, fasciculus thalamicus, and field H), and medial lemniscus. Using this approach, we successfully derived in vivo estimates of the size, shape, location, and tissue characteristics of substructures in the ZI region, confirming observations only previously possible through histological evaluation that this region is not just a space between structures but contains distinct morphological entities that should be considered separately. Our findings pave the way for increasingly detailed in vivo study and provide a structural foundation for precise functional and neuromodulatory investigation.

Heterozygous mutations in ZP1 and ZP3 cause formation disorder of ZP and female infertility in human.

The human zona pellucida (ZP) is a highly organized glycoprotein matrix that encircles oocytes and plays an essential role in successful reproduction. Previous studies have reported that mutations in human ZP1, ZP2 and ZP3 influence their functions and result in a lack of ZP or in an abnormal oocytes and empty follicle syndrome, which leads to female infertility. Here, we performed whole‐exome sequencing in two probands with primary infertility whose oocytes lacked a ZP, and we identified a heterozygous mutation in ZP1 (NM_207341:c.326G>A p.Arg109His), which is situated in the N‐terminus, and a heterozygous mutation in ZP3 (NM_001110354:c.400G>A p.Ala134Thr), which is situated in the ZP domain. The effects of the mutations were investigated through structure prediction and in vitro studies in HeLa cells. The results, which were in line with the phenotype, suggested that these mutations might impede the function of cross‐linking and secretion of ZP proteins. Our study showed that the two mutations in ZP1 and ZP3 influenced the formation of the ZP, causing female infertility. Meanwhile, these data highlight the importance of the ZP1 N‐terminus in addition to the conserved domains for ZP1 function and ZP formation. Additionally, the patient with the ZP1 mutation delivered a baby following intracytoplasmic sperm injection (ICSI); thus, we suggest the targeted genetic diagnosis of ZP genes to choose appropriate fertilization methods and improve the success rate of assisted reproductive technology (ART) treatments.

Pharmacological inhibition of arachidonate 15-lipoxygenase protects human spermatozoa against oxidative stress.

One of the leading causes of male infertility is defective sperm function, a pathology that commonly arises from oxidative stress in the germline. Lipid peroxidation events in the sperm plasma membrane result in the generation of cytotoxic aldehydes such as 4-hydroxynonenal (4HNE), which accentuate the production of reactive oxygen species (ROS) and cause cellular damage. One of the key enzymes involved in the metabolism of polyunsaturated fatty acids to 4HNE in somatic cells is arachidonate 15-lipoxygenase (ALOX15). Although ALOX15 has yet to be characterized in human spermatozoa, our previous studies have revealed a strong link between ALOX15 activity and the levels of oxidative stress and 4HNE in mouse germ cell models. In view of these data, we sought to assess the function of ALOX15 in mature human spermatozoa and determine whether the pharmacological inhibition of this enzyme could influence the level of oxidative stress experienced by these cells. By driving oxidative stress in vitro with exogenous H2O2, our data reveal that 6,11-dihydro[1]benzothiopyrano[4,3-b]indole (PD146176; a selective ALOX15 inhibitor) was able to significantly reduce several deleterious, oxidative insults in spermatozoa. Indeed, PD146176 attenuated the production of ROS, as well as membrane lipid peroxidation and 4HNE production in human spermatozoa. Accordingly, ALOX15 inhibition also protected the functional competence of these cells to acrosome react and bind homologous human zonae pellucidae. Together, these results implicate ALOX15 in the propagation of oxidative stress cascades within human spermatozoa and offer insight into potential therapeutic avenues to address male in fertility that arises from oxidative stress.

The Human Egg's Zona Pellucida.

Human zona pellucida (ZP) matrix, a delicate network of thin interconnected filaments, is primarily composed of four glycoproteins, namely, ZP1, ZP2, ZP3, and ZP4. All four zona proteins share common structural elements such as signal peptide, "ZP domain," consensus furin cleavage site, transmembrane-like domain, and short cytoplasmic tail. In addition, ZP1 and ZP4 also have "Trefoil domain." Recombinant/native human zona proteins have been used to investigate their binding characteristics to the capacitated and/or acrosome-reacted spermatozoa. These investigations revealed that ZP1, ZP3, and ZP4 primarily bind to the head region of the capacitated human spermatozoa, whereas ZP2 binds to the acrosome-reacted sperm. However, using transgenic mice, N-terminal region of human ZP2 has also been shown to play an important role in binding of sperm to the egg. ZP1, ZP3, and ZP4 lead to dose-dependent increase in acrosome reaction, suggesting that in humans more than one ZP glycoprotein is responsible for induction of acrosome reaction. Glycosylation of these proteins, in particular, N-linked glycosylation as well as sialyl-Lewisx, is essential for inducing acrosome reaction. Studies delineating downstream signaling events associated with induction of acrosome reaction reveal subtle differences between ZP3 and ZP1/ZP4 with respect to activation of Gi protein-coupled receptor and protein kinase A. The role of mutations in the zona proteins and ZP autoantibodies leading to infertility in women is suggestive and needs more rigorous experimentations for confirming their role in female infertility. The above-mentioned aspects of the human ZP glycoproteins have been discussed in this review.

Development of monoclonal antibodies against the human 3β-hydroxysteroid dehydrogenase/isomerase isozymes

The human 3β-hydroxysteroid dehydrogenase/isomerase (HSD3B) enzymes catalyze the conversion of 3β-hydroxy Δ5-6 steroids into 3-keto Δ4-5 steroids, which is required for the synthesis of the mature steroid hormones secreted by the adrenal and gonads. The human has 2 isozymes, the HSD3B1 that is traditionally located in placenta and extra-adrenal tissues and the HSD3B2 that is expressed in the adrenal and gonads. Mice with both cryptochrome 1 and 2 genes deletion were recently found to have salt-sensitive hypertension and hyperaldosteronism. These deletions were also associated with overexpression of the Hsd3b6 enzyme, the homolog of the human HSD3B1, in the zona glomerulosa which was believed to explain the hyperaldosteronism. A report using antibodies against human HSD3B1 suggested that it was expressed in the zona glomerulosa of normal human adrenals and in patients with idiopathic hyperaldosteronism and the HSD3B2 expressed in both the zona fasciculata and glomerulosa. We have developed specific monoclonal antibodies against the human HSD3B1 and HSD3B2 isozymes and found that the main enzyme expressed in the zona glomerulosa was the HSD3B2. Faint staining of the adrenal was also obtained using the anti-HSD3B1antibody only at high concentrations of antibody. This study fails to confirm that HSD3B1 expression in the human zona glomerulosa and double immunofluorescence clearly shows that the HSD3B2 is expressed in the zona glomerulosa and fasciculata and in the zona glomerulosa HSD3B2 is co-expressed with aldosterone synthase (CYP11B2).

A common 'aggregation-prone' interface possibly participates in the self-assembly of human zona pellucida proteins.

Human zona pellucida (ZP) is composed of four glycoproteins, namely ZP1, ZP2, ZP3 and ZP4. ZP proteins form heterodimers, which are incorporated into filaments through a common bipartite polymerizing component, designated as the ZP domain. The latter is composed of two individually folded subdomains, named ZP-N and ZP-C. Here, we have synthesized six 'aggregation-prone' peptides, corresponding to a common interface of human ZP2, ZP3 and ZP4. Experimental results utilizing electron microscopy, X-ray diffraction, ATR FT-IR spectroscopy and polarizing microscopy indicate that these peptides self-assemble forming fibrils with distinct amyloid-like features. Finally, by performing detailed modeling and docking, we attempt to shed some light in the self-assembly mechanism of human ZP proteins.

The impact of oxidative stress on chaperone-mediated human sperm-egg interaction.

How does oxidative stress impact upon human sperm-egg interaction and in particular the formation of zona pellucida-receptor complexes on the sperm surface? Oxidative stress during human sperm capacitation resulted in the chemical alkylation of the molecular chaperone heat shock protein A2 (HSPA2), a concomitant reduction in surface expression of the zona pellucida-receptor arylsulphatase A (ARSA) and a severe loss of zona pellucida binding ability. An inability to bind to the zona pellucida is commonly encountered in the defective spermatozoa generated by male infertility patients; however, the underlying mechanisms remain unresolved. Recent studies have revealed that zona pellucida binding is mediated by molecular chaperones, particularly HSPA2, that facilitate the formation of multimeric zona pellucida-receptor complexes on the surface of mammalian spermatozoa during capacitation. Spermatozoa were collected from healthy normozoospermic donors (n = 15). Low levels of oxidative stress were induced in populations of non-capacitated spermatozoa by a 1 h treatment with 4-hydroxynonenal (4HNE) or hydrogen peroxide (H2O2) and then these insults were removed and cells were capacitated for 3 h. Motility, membrane fluidity, protein tyrosine phosphorylation and lipid raft distribution were evaluated after sperm capacitation to determine the impact of oxidative stress on this process. The surface expression of ARSA and sperm adhesion molecule 1 (SPAM1) was observed using fluorescence microscopy, and the ability of treated cells to interact with homologous human zonae pellucidae was assessed through gamete co-incubation. Proximity ligation was used to evaluate the state of the HSPA2-laden zona pellucida-receptor complex and an immunoprecipitation approach was taken to establish the chemical alkylation of HSPA2 by the cytotoxic lipid aldehyde 4HNE. The validity of these findings was then tested through treatment of oxidatively stressed cells with the nucleophile penicillamine in order to scavenge lipid aldehydes and limit their ability to interact with HSPA2. All experiments were performed on samples pooled from two or more donors per replicate, with a minimum of three replicates. The oxidative treatments employed in this study did not influence sperm motility or capacitation-associated changes in membrane fluidity, tyrosine phosphorylation and lipid raft redistribution. However, they did significantly impair zona pellucida binding compared with the capacitated control (P < 0.01). The reduction in zona pellucida binding was associated with the impaired surface expression (P < 0.02) of a zona pellucida-receptor complex comprising HSPA2, SPAM1 and ARSA. Proximity ligation and immunoprecipitation assays demonstrated that impaired zona pellucida binding was, in turn, associated with the chemical alkylation of HSPA2 with 4HNE and the concomitant disruption of this zona pellucida-receptor complex. The use of penicillamine enabled a partial recovery of ARSA surface expression and zona pellucida adherence in H2O2-treated cells. These data suggest that the ability of low levels of oxidative stress to disrupt sperm function is mediated by the production of lipid aldehydes as a consequence of lipid peroxidation and their adduction to the molecular chaperone HSPA2 that is responsible for co-ordinating the assembly of functional zona pellucida-receptor complexes during sperm capacitation. While these results extend only to one particular zona pellucida-receptor complex, we postulate that oxidative stress may more broadly impact upon sperm surface architecture. In this light, further study is required to assess the impact of oxidative stress on additional HSPA2-laden protein complexes. These findings link low levels of oxidative stress to a severe loss of sperm function. In doing so, this work suggests a potential cause of male infertility pertaining to a loss of zona pellucida recognition ability and will contribute to the more accurate diagnosis and treatment of such conditions.

Oocyte zona pellucida dysmorphology is associated with diminished in-vitro fertilization success.

BackgroundAlthough irregularities in human zona pellucida (ZP) morphology are well described, there is scant literature on the clinical significance of ZP dysmorphology. We, therefore, designed a retrospective cohort trial of ZP dysmorphology to assess the clinical significance of ZP dysmorphology and its affect on IVF outcome. Over the same time period a random sample of 77 cycles of 77 subjects with all normal oocyte morphology were selected as controls.MethodsBetween July 2006 and December 2010, all fresh non-donor cases performed at a university hospital IVF center were assessed for ZP dysmorphology. ZP dysmorphology included extracytoplasmic abnormalities (dark ZP and large perivitelline space) and oocyte shape (oval or irregularly shaped ZP). 136 IVF cycles from 119 subjects were identified where a majority of oocytes displayed ZP dysmorphology. Over the same time period a random sample of 77 cycles of 77 subjects with all normal oocyte morphology were selected as controls. IVF prognostic and outcome parameters were compared between the patients with dysmorphic and normal oocytes.Results136/1710 (8.0%) cycles of fresh non-donor IVF displayed predominant ZP dysmorphology. Dysmorphic and normal oocytes showed no difference in the oocyte quality predictors such as FSH (6.03+/−2.5 vs. 6.8+/−2.3 IU/L), or AMH (2.5+/−2.0 vs. 2.30+/−1.5 ng/ml levels). ZP dysmorphology was associated with markedly diminished clinical pregnancy rates (44% vs. 70%; RR:0.62 [0.48, 0.80]; p = 0.0002), implantation rates (.17 vs. .36; IRR: 0.48 [0.34, 0.68]; p < 0.0001) and live birth rates as compared to non dysmorphic oocytes (29% vs. 52%; RR:0.55 [0.39, 0.79]; p = 0.001).ConclusionsZP dysmorphology is associated with markedly diminished pregnancy and implantation rates in IVF. The poorer outcome appears to be independent of the usual markers of ovarian reserve.

Hydroxypropyl cellulose as an option for supplementation of cryoprotectant solutions for embryo vitrification in human assisted reproductive technologies

Hydroxypropyl cellulose (HPC) was investigated as a replacement for serum substitute supplement (SSS) for use in cryoprotectant solutions for embryo vitrification. Mouse blastocysts from inbred (n = 1056), hybrid (n = 128) strains, and 121 vitrified blastocysts donated by infertile patients (n = 102) were used. Mouse and human blastocysts, with or without zona pellucida, were vitrified and warmed in either 1% or 5% HPC or in 5% or 20% SSS-supplemented media using the Cryotop (Kitazato BioPharma Co. Ltd, Fuji, Japan) method, and the survival and oxygen consumption rates were assessed. Viscosity of each vitrification solution was compared. Survival rates of mouse hybrid blastocysts and human zona pellucida-intact blastocysts were comparable among the groups. Mouse and human zona pellucida-free blastocysts, which normally exhibit poor cryoresistance, showed significantly higher survival rates in 5% HPC than 5% SSS (P < 0.05). The 5% HPC-supplemented vitrification solution showed a significantly higher viscosity (P < 0.05). The blastocysts were easily detached from the Cryotop strip during warming when HPC-supplemented vitrification solution was used. The oxygen consumption rates were similar between non-vitrified and 5% HPC groups. The results suggest possible use of HPC for supplementation of cryoprotectant solutions and provide useful information to improve vitrification protocols.

Role of zona pellucida glycoproteins during fertilization in humans

In the last decade, scientific investigations pertaining to the role of zona pellucida (ZP) glycoproteins during fertilization in humans have led to new insights. This has been achieved using purified native/recombinant human zona proteins and transgenic mice expressing human ZP glycoproteins. The proposed model in mice of ZP glycoprotein-3 (ZP3) acting as primary sperm receptor and ZP glycoprotein-2 (ZP2) as secondary sperm receptor has been modified for sperm–egg binding in humans. ZP glycoprotein-1 (ZP1), ZP3, and ZP glycoprotein-4 (ZP4) have been shown to bind to the capacitated human sperm. ZP2 binds to the acrosome-reacted human spermatozoa. Further, the eggs obtained from transgenic mice expressing human ZP2 alone or in conjunction with other human instead of mouse zona proteins showed binding of human sperm, suggesting that ZP2 might also play a role in sperm–egg binding. This function has been mapped to a domain corresponding to amino acid residues 51–144 of ZP2. In contrast to mice, where ZP3 is the primary agonist for inducing the acrosome reaction, in humans, the acrosome reaction can be mediated by ZP1, ZP3, and ZP4. The effect of mutations in the genes encoding zona proteins on the ZP morphology and infertility has not been established. Further, the role of autoantibodies against ZP in women with ‘unexplained infertility’ leading to poor outcome of in vitro fertilization is currently controversial and needs further investigations. Understanding the role of ZP glycoproteins during human fertilization facilitates the development of new contraceptives and strategies to overcome the problem of infertility.