Defining the valid hemizona assay: accounting for binding variability within zonae pellucidae and within semen samples from fertile males**Supported in part by the Contraceptive Research and Development Program (CONRAD), Eastern Virginia Medical School, under a Cooperative Agreement (DPE-2044-A-00-6063-00) with the United States Agency for International Development (A.I.D.) Rosslyn, Virginia, and by the South African Medical Research Council, Republic of South Africa. The views expressed by the author do not necessarily reflect the views of A.I.D

Sperm-egg interaction and functional assessment of springbok, impala and blesbok cauda epididymal spermatozoa using a domestic cattle in vitro fertilization system

The study assesses the possibility to estimate the potential fertility of post-thawed antelope (Antidorcas marsupialis), impala (Aepyceros melampus) and blesbok (Damaliscus dorcus phillipsi) epididymal sperm using homologous and heterologous IVF and the functioning of cattle IVF system to produce antelope embryos. Cauda epididymal sperm were collected from the antelope and cryopreserved under field conditions. In vitro matured domestic cow, blesbok and springbok oocytes were co-incubated in modified-Tyrode Lactate (m-TL) IVF media with springbok, impala and blesbok sperm for heterologous IVF and springbok and blesbok sperm for homologous IVF. A group of presumptive zygotes from each treatment were examined for sperm penetration and male pronuclear formation after 18h and the remainder were cultured and evaluated for embryo cleavage 22h later. The study shows that Modified Tyrode Lactate in vitro fertilization media supports survivability, capacitation and hyperactivation of springbok, impala and blesbok sperm. Springbok, impala and blesbok post-thawed epididymal spermatozoa are capable of fertilizing domestic cow oocytes under conditions that support domestic cattle IVF. Penetration, male pronuclear formation and embryo cleavage did not differ (p>0.05) between cow oocytes inseminated with sperm from springbok, impala or blesbok however these parameters were higher (p<0.05) for oocytes inseminated with bull sperm. Modified Tyrode Lactate IVF media supported homologous fertilization and embryo development in springbok and blesbok however did not support blastocyst development. These findings suggest that cattle provide a useful model for evaluating springbok, impala and blesbok post-thawed cauda epididymal sperm functionality. Domestic cattle embryo culture conditions need to be modified to promote blastosyst development in these antelope species. Such research provides an important tool in assisted reproductive technology development when high biological value material is utilized for wild species recovery plans.

The hemizona assay for assessment of sperm function

The hemizona assay (HZA) has been developed as a diagnostic test for the tight binding of human spermatozoa to the human zona pellucida to predict fertilization potential. In this homologous bioassay, the two matching hemizona halves are functionally equal surfaces allowing controlled comparison of binding from a fertile control versus a test sample, with reproducible measurements of sperm binding obtained from a single oocyte. Oocytes from different sources (surplus from IVF treatment or recovered from ovarian tissue) are salt-stored and used after microbisection. Extensive clinical data have demonstrated excellent predictive power of the HZA for the outcomes of intrauterine insemination and IVF, and therefore the assay has relevance in the clinical diagnostic setting in infertility.

Diagnostic significance of sperm-zona pellucida interaction

Spermatozoa binding to the zona pellucida is an early, critical event leading to fertilization and early pre-embryo development. Fertilization involves a complex and orderly sequence of events that is completed at syngamy, which is defined as the union of the two sets of haploid chromosomes to form a new diploid fertilized ovum (zygote). In order to be able to fertilize an oocyte, spermatozoa need to undergo a process called ‘capacitation’, which is usually defined as a series of changes that renders the sperm cells capable of undergoing the acrosome reaction. This process that naturally occurs within the female genital tract is possible under in vitro conditions. However, capacitation is not the only process spermatozoa must undergo to fertilize the oocytes successfully. To fertilize an oocyte, spermatozoa must also be at least highly motile, as well as being capable of undergoing the acrosome reaction timely, penetrating through the oocyte investments and fusing with the oocyte plasma membrane properly.

Predictive value of the hemizona assay for pregnancy outcome in patients undergoing controlled ovarian hyperstimulation with intrauterine insemination

OBJECTIVE

The hemizona assay (HZA) is an established functional test that examines in vitro sperm-zona pellucida binding capacity with high predictive power for fertilization outcome in IVF. The objective of this study was to evaluate the value of the HZA as a predictor of pregnancy in patients undergoing controlled ovarian hyperstimulation (COH) and intrauterine insemination (IUI).

DESIGN

Prospective clinical study.

SETTING

Academic center.

PATIENT(S)

Eighty-two couples with unexplained or male factor infertility that underwent 313 IUI cycles.

INTERVENTION(S)

Basic semen analysis and HZA were performed within three months of starting COH/IUI therapy.

MAIN OUTCOME MEASURE(S)

Hemizona index (HZI) and clinical pregnancy.

RESULT(S)

Overall, patients with an HZI of <30 had a significantly lower pregnancy rate compared to patients with an HZI of > or =30 (11.1% vs. 40.6%, respectively; P<.05; relative risk for failure to conceive: 1.5 (confidence interval 1.2-1.9)). In all patients combined, and in the range of HZI 0-60, the duration of infertility (P=.000) and the HZI (P=.004) were significant determinants of conception (receiver operating characteristics (ROC) analysis). In couples with male infertility, the average path velocity and HZI were significant predictors of conception (P=.001 and P=.005, respectively, ROC analysis). The negative and positive predictive values of the HZA for pregnancy were 93% and 69%, respectively. Logistic regression analysis provided models of HZI (P=.021) and duration of infertility (P=.037) with highest predictability of conception in male factor and unexplained infertility groups, respectively.

CONCLUSION(S)

The HZA predicted pregnancy in the IUI setting with high sensitivity and negative predictive value in couples with male infertility. Results of this sperm function test are useful in counseling couples before allocating them into COH/IUI therapy.

Relationship between zona pellucida-induced acrosome reaction, sperm morphology, sperm-zona pellucida binding, and in vitro fertilization

OBJECTIVE

To evaluate the possible relationships between sperm morphology, acrosome responsiveness to solubilized human zona pellucida, and sperm-zona binding potential among [1] consecutive andrology referrals and [2] randomly selected in vitro fertilization (IVF) cases.

DESIGN

Prospective analytical study.

SETTING

Academic training hospital.Randomly selected couples consulting for infertility.

INTERVENTION(S)

Acrosome reaction response to solubilized human zona pellucida was recorded.

MAIN OUTCOME MEASURE(S)

We determined the difference in the percentage of sperm that acrosome reacted after exposure to solubilized zona pellucida and spontaneous acrosome reaction. The results were expressed as percentage zona induced acrosome reaction (ZIAR).

RESULT(S)

Data were analyzed using correlation coefficients (r) and receiver operator characteristics (ROC curve analyses). The ROC curve analyses indicated ZIAR to be a sensitive indicator for fertilization failure during IVF therapy, with sensitivity and specificity of 81% and 75%, respectively. For andrology referrals, a positive and statistically significant correlation existed between ZIAR data and sperm morphology (r = 0.65) and sperm-zona binding (r = 0.57).

CONCLUSION(S)

ZIAR results provide further information regarding dysfunctional sperm and can be used as an additional diagnostic test. Our results predicted fertilization failure during IVF treatment.

Use of microbeads for the detection of binding sites on the human zona pellucida: a scanning electron microscopy (SEM) assay

One prerequisite for fertilization is the specific binding of spermatozoa to the zona pellucida. However, the factors and mechanisms involved in this gamete contact are not well understood. Gamete recognition and binding are species-specific and are controlled by oligosaccharides of the zona and their corresponding carbohydrates on the spermatozoon. By using a specific lectin we developed a technique to detect those oligosaccharides on the human zona pellucida that might be involved in the binding process. Microbeads (Ø = 2.8 microm), used as artificial spermatozoa, were coated with lectin Con A and cultured together with 75 unfertilized oocytes (group A) remaining after intracytoplasmic sperm injection. Con A binds specifically to alpha-d-mannose and alpha-d-glucose. As a control, 75 unfertilized oocytes after intracytoplasmic sperm injection (group B) were also cultured together with Con A-covered microbeads, but in a medium containing a binding inhibiting sugar (alpha-methyl-mannopyrasosid). The number and distribution of the microbeads on human oocytes of both groups were analysed on scanning electron microscopy images. Beads on oocytes of group A had binding patterns similar to those of spermatozoa. They were distributed in an extremely heterogeneous way with various numbers of bound beads both on individual and different oocytes. Most of the group A oocytes (85%) had more than 50 beads bound to the zona, in contrast to the control oocytes of group B, where 68% had less than 10 bound beads. The use of an inhibiting sugar abolished the binding capacity of the microbeads nearly completely. This technique is a powerful tool for the detection of binding sites on the zona pellucida, i.e. those sugars that are responsible for contact between spermatozoa and the zona pellucida.

In vitro tests for essential sperm functions using the phyto-oestrogen genistein as a test substance

Sperm motility, binding of spermatozoa to the zona pellucida and induction of the acrosome reaction are prerequisites for successful oocyte fertilization. Examination of the physiological and nonphysiological effects of particular compounds on sperm functions requires high-quality in vitro test systems. In this short methodological overview, a reliable combined in vitro test system with bovine gametes is described. The purpose of the study was to evaluate whether aliquots of pooled post-thaw spermatozoa are suitable for examination of environmental substances that affect essential sperm functions. The combined test system includes a number of known methods for the assessment of sperm vitality and motion parameters, acrosomal status, inducibility of acrosome reaction and sperm zona pellucida binding. First observations indicate that genistein inhibits the induction of acrosomal exocytosis and binding of spermatozoa to the zona pellucida. Motility parameters and the viability of bovine spermatozoa were not affected by this substance. It is concluded that genistein, a phyto-oestrogen which is abundant in several plants, can be used as a test substance for the evaluation of effects upon essential bovine sperm functions in vitro.

Evidence for the participation of beta-hexosaminidase in human sperm-zona pellucida interaction in vitro

Mammalian sperm-zona pellucida (ZP) interaction is mediated by sperm lectin-like proteins and ZP glycoproteins. We have previously reported the participation of binding sites for N-acetylglucosamine (GlcNAc) residues in human sperm function, including sperm interaction with the ZP. Additionally, previous results from our laboratory suggested that some of these events may be mediated by the glycosidase N-acetylglucosaminidase (beta-hexosaminidase, Hex, in mammals). In this study, we report the possible participation of Hex in human sperm-ZP interaction. Human recombinant Hex (hrHex) was obtained by expression in a stable transfected CHO cell line. When the recombinant enzyme was present during hemizona (HZ) assays, the number of sperm bound per HZ was significantly reduced. The same result was obtained when HZ were preincubated with hrHex. Additionally, the presence of a Hex-specific substrate during the HZ assay produced the same inhibitory effect. These results suggest the participation of a sperm Hex in the interaction with human ZP in vitro.

New aspects of sperm-zona pellucida binding

Sperm-zona pellucida binding tests have become a widely used diagnostic application for clinicians to obtain guidance in so far as the therapeutic approach of the subfertile couple is concerned. Expanding the oocyte sources is imperative to ensure the consistent use of sperm-zona binding assays. Sources include oocytes derived from post-mortem ovaries, inseminated non-fertilized IVF oocytes and recycled hemizonae. Identification of specific gamete dysfunction is one of the most formidable tasks and fertilization disorders due to defective sperm-zona pellucida interaction are relatively common in the clinical practice, thereby emphasizing the importance of sperm-zona binding tests as diagnostic/predictive tests. Independent publications from Norfolk (USA), Melbourne (Australia), Tygerberg (South Africa) and Israel of highly comparable results confirm that sperm-zona binding tests are good predictors of fertilization. Studies using solubilized human pellucida recently evaluated the influence of solubilized human pellucida on spermatozoa during the capacitational process and subsequent sperm-zona binding. Involvement of G protein and carbohydrate moieties in sperm-zona pellucida binding emphasized the biological and biochemical properties of lectin and have afforded much weight to their employment as membrane probes to evaluate cell surface components. Attention has been focused on the alterations of sperm surface receptors (oligosaccharides) during the differential pathway, epididymal transit and capacitation.

Preliminary results of hemizona assay (HZA) as a fertility test for canine spermatozoa

The Hemizona assay (HZA) is considered to be an effective test for predicting the fertilizing potential of spermatozoa. It is a functional test that distinguishes the zona-binding capacity of spermatozoa from fertile and infertile males. The objective of this study was to validate the HZA for canine spermatozoa, as a test for diagnosing canine male fertility status. Various parameters that affect binding capacity were examined: the presence of an adequate number of capacitated and motile spermatozoa for an HZA, the influence of fertility status, sperm-binding variability within fertile dogs over 60 d, variability in sperm-binding capacity of different oocytes, the lower limit number of spermatozoa binding to a zona from the fertile control, and evaluation of HZI to determine the fertilizing capacity of spermatozoa. Hemizonae were obtained from frozen oocytes of spayed bitches. The oocytes were manually cut into nearly equal halves. Spermatozoa were capacitated by swim-up and 1 h incubation at 37 degrees C in modified Ham's F10 medium. Spermatozoa and hemizonae were co-incubated in 100-microL drops at 37 degrees C for 1 h. Spermatozoa from 7 fertile and 3 infertile dogs were used for this study. The optimal sperm concentration for hemizona insemination was 1 x 10(6)/mL capacitated and motile spermatozoa. A significant difference (P < 0.001) was found the number of tightly zonabound spermatozoa between fertile and infertile dogs. Although there was a small difference in zona binding capacity between ejaculates of the same fertile dog (44 +/- 18.24), the main cause for the difference mentioned above was that of poor zona pellucida-binding capacity of spermatozoa from infertile dogs. We found a maximum of 14.28% bad oocytes when we compared sperm samples from 3 fertile and 3 infertile dogs in 56 HZA replicates. To avoid the effect of bad zona on sperm binding we calculated 37 (95% CI) bound spermatozoa from infertile dogs in 56 replicates. Thus, an HZA experiment in which a control dog had < 37 zona bound spermatozoa was repeated. Based on a minimum of 37 bound spermatozoa for fertile males (controls), a differential zona-binding capacity and hemizona index (HZI) between fertile and infertile dogs and between 2 fertile dogs was determined. The binding differential between fertile and infertile dogs was 64.92 +/- 24.29, while between 2 fertile dogs it was 22.38 +/- 10.02 (P < 0.001). According to the HZI values, a value equal to or less than 41.11 indicated an infertile test dog, while an HZI value equal to or greater than 57.95 indicated a fertile test dog. Any value between these two could indicate either fertility or infertility. The evaluation of fertilizing potential of spermatozoa can be improved using the HZA protocols described above.

Zona pellucida mediated acrosome reaction and sperm morphology

Sperm samples from 29 men randomly selected from the andrology laboratory, were used to evaluate acrosome reaction response to solubilized human zona pellucida. Capacitated sperm samples were exposed to a solution containing 2 zona pellucidae (ZP) per microl for 60 min, after which acrosomal status were recorded using a PSA-FITC technique. Controls included samples supplied by fertile sperm donors. After completion of acrosome reaction studies, patient samples were divided according to the percentage of morphologically normal spermatozoa. Three basic groups were identified, namely, fertile donors, teratozoospermic (normal sperm morphology 5-14%; n = 25) and severely teratozoospermic (normal sperm morphology < 4%; n = 4) groups. The mean percent normal sperm were 15.8 +/- 0.9, 10.4 +/- 0.7 and 2.7 +/- 0.7, respectively, for normozoospermic donors, teratozoospermic and severely teratozoospermic men. The mean percentage (+/-SE) ZP mediated acrosome reacted sperm among teratozoospermic and severely teratozoospermic cases was 25.8% +/- 0.9 and 19.0% +/- 0.9 (P = 0.001), compared to 36.8% +/- 0.9 for the donor controls. Results were analysed and expressed as correlations between sperm morphology and acrosomal response to human solubilized zona pellucida, spontaneous and calcium ionophore induced acrosome reaction. Predictive values for acrosome responsiveness were depicted with ROC curve analyses. Sperm morphology evaluated by strict criteria correlated positively and highly significantly with the responsiveness of the acrosome reaction (r = 0.91, P = 0.0001). At a morphology cut-off value of 4%, the ROC curve analysis showed sperm morphology to be highly predictive of zona pellucida induced acrosome responsiveness with a sensitivity of 100% and negative predictive value of 100%. Spontaneous and calcium ionophore induced acrosome reactions revealed no correlation with sperm morphology. It was concluded that (i) morphological features of human spermatozoa are indicative of specific functional characteristics; (ii) zona pellucida induction of the acrosome reaction is superior, as a predictor of sperm morphology, compared to calcium ionophore induced and spontaneous acrosome reactions.

Isolation and characterization of a protein with homology to angiotensin converting enzyme from the periacrosomal plasma membrane of equine spermatozoa

The periacrosomal plasma membrane of spermatozoa is involved in sperm binding to oviductal epithelial cells and to the zona pellucida. A protein of 68-70 kD molecular mass was purified biochemically from the isolated periacrosomal plasma membrane of equine spermatozoa as a possible receptor for adhesion of spermatozoa to oviductal epithelial cells. A polyclonal antibody raised in rabbits against the purified equine sperm membrane protein recognized the 70 kD and an antigenically related to 32 kD protein in preparations of isolated periacrosomal sperm plasma membrane and in detergent extracted ejaculated and epididymal spermatozoa. A larger protein (approximately 110 kD) was detected in equine testis. Two antigenically related proteins (64 and 45 kD) were recognized on the plasma membrane of cynomolgus macaque spermatozoa. In vitro sperm-binding assays were performed in the presence of antigen-binding fragments or IgG purified from the polyclonal antiserum to investigate a possible function to the isolated protein in binding of equine spermatozoa to homologous oviductal epithelial cells or zona pellucida. Incubation with antigen-binding fragments or IgG purified from the antiserum did not inhibit binding of equine spermatozoa either to oviductal epithelial cells or the zona pellucida. On ultrastructural examination, the antibody bound exclusively to the cytoplasmic side of the periacrosomal plasma membrane of equine and macaque spermatozoa. Microsequence analysis of 13 residues of sequence showed strong homology with a number of angiotensin converting enzymes: An 84% identity was identified with testis specific and somatic forms of human and mouse angiotensin-converting enzyme. Immunocytochemistry and immunoblot analysis established that the protein is specific for the periacrosomal membrane of ejaculated, epididymal, and testicular stallion spermatozoa.

Hemizona assay: evaluation of fertility potential in patients with vasectomy reversal

Approximately 40 to 60% of men who undergo a successful vasovasostomy have "functional failure" or failure to conceive even though active sperm are present. Factors of this functional failure include sperm abnormalities (oligoasthenoteratospermia) and antisperm antibodies. Nine male patients 32 to 43 years of age who underwent vasovasostomy were included in the study group. These patients demonstrated ductal patency 3 to 6 months after surgery. After attempts at fertility with their spouses failed, the couples underwent urological and gynecological evaluation. Semen parameters were recorded and further evaluation was performed using immobilizing and agglutination antibodies as well as direct immunobead test and the hemizona assay (HZA). Semen parameters presented varying levels of sperm concentration, percent motility, and morphology (strict). Antisperm antibodies were present in 4 of the 9 patients. Three of 4 patients with antibodies and 4 of 5 patients without antibodies benefitted from hemizona assay results in that it either supported a desired therapy or gave objective data that would dictate more aggressive therapy. Six men had a hemizona index of > 35%, predictive of adequate zona bind capability. Using these individual situations combined with gynecologic findings, recommendations are made as to identifying realistic options and therapeutic recommendations.

Aging, hyaluronidase removal of the cumulus, and microinjection do not affect the sperm binding potential of human oocytes

PURPOSE

We studied the influence of aging, hyaluronidase removal of the cumulus, and microinjection on the sperm binding potential of human oocytes under intact zona assay conditions to determine the safe use of unstored aged unfertilized ICSI oocytes on zona binding tests. Results were also compared with those for aged IVF oocytes under the same conditions.

METHODS

To avoid the large variation in sperm binding scores, we compared the ratios of the number of sperm bound to nontreated versus to treated oocytes. Treated oocytes were those whose zonae were exposed to hyaluronidase, an agent that decreases sperm binding. Experimental groups were fresh oocytes, experimentally aged fresh oocytes, fresh oocytes whose cumulus was removed either mechanically or with hyaluronidase, aged ICSI oocytes, and aged IVF oocytes.

RESULTS

Statistical analysis within and between groups showed that aging, previous insemination, cumulus removal by hyaluronidase, and microinjection did not affect the sperm binding potential of human oocytes.

CONCLUSIONS

As the zona binding ability of fresh and unfertilized aged ICSI oocytes is similar, they can be used safely in zona assays.

Influence of batches of bovine oocytes on the outcome of an intact zona pellucida binding assay and in vitro fertilization

A series of experiments was performed in vitro to determine the variation between batches of abattoir-derived bovine oocytes to bind and to be fertilized by frozen-thawed spermatozoa provided by a single ejaculate from a bull with high field fertility after artificial insemination. Fourteen batches of oocytes, collected over a 90-day period, were divided randomly into two equal groups at each sampling period. One group of oocytes was subjected to in-vitro maturation and subsequently in-vitro fertilization (IVF) while the other group was used as intact oocytes in a zona binding assay (ZBA). Fertilized oocytes were evaluated for penetration and pronuclear formation and, in the ZBA, the number of spermatozoa bound to each oocyte was registered. Neither the results of the ZBA nor the IVF results varied significantly (p = 0.45) between batches. Furthermore, when a sperm concentration of 0.5 x 10(6)/ml was used, the number of spermatozoa bound to the zona pellucida correlated significantly with the frequency of oocytes penetrated after IVF (r = 0.76). The results suggest that variation between the batches of oocytes has no detrimental significance for the application of intact zona pellucida binding or IVF for assaying frozen-thawed bull semen, provided that a large number of oocytes/batch (> 15) are assayed.

Sperm binding capacity of human zona pellucida derived from oocytes obtained from different sources

The important contributions of sperm-oocyte interaction to infertility diagnostics is well established. Scientists are urged to search for methods to improve the assessment of gamete interaction. Sperm binding and penetration assays have frequented the literature, reporting on various aspects of sperm-oocyte interaction using either microbisected or whole human oocytes during the assay procedure. The objective of the study was to evaluate additional zona pellucida sources which can be used during zona binding studies. Hemizonae were obtained from the following oocytes: 1) experiment 1, prophase I oocytes from post-mortem ovarian tissue from different age groups namely, 7 months, 5 years, 7 years, 12 years and 30 years; 2) experiment 2 used donated immature Prophase I oocytes from the IVF treatment program and 3) experiment 3 evaluated zona binding for hemizonae which were previously used in hemizona assays. Results indicated that, in experiment 1, ovarian age does not have any influence on the zona pellucida's capacity to bind spermatozoa. The mean number of bound sperm among the different age groups did not differ significantly, namely 38.9 +/- 17 (7 months), 31.0 +/- 27 (5 years), 49.3 +/- 21 (7 years), 32.8 +/- 18 (12 years) and 39.5 +/- 17 (30 years). The pooled mean +/- SD binding for all the age groups in experiment 1 was 37.7 +/- 7. Likewise, the mean number of sperm bound (experiment 2) to zonae collected from oocytes using different ovulation induction regimes were 31.1 +/- 20 (unstimulated), 54.4 +/- 12 (HMG/HCG) and 15.3 +/- 9 (HMG alone).(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between morphology, motility and zona pellucida binding potential of human spermatozoa

Prediction of the fertilizing potential of human gametes under in vitro conditions has been a major field of interest of assisted reproductive programmes. However, sperm morphology has been regarded as a predictor of human in vitro fertilization rate. This paper prospectively evaluates the relationships among normal sperm morphology and (1) motion characteristics viz. curvilinear velocity (VCL), straight line velocity (VSL), and linearity (LIN) (n = 37) and (2) sperm-zona pellucida binding capacity under HZA conditions (n = 144) of two separate groups of infertile couples. Semen was evaluated for sperm concentration, percentage motility, forward progression, and percentage normal morphology (strict criteria). The motility characteristics were measured using a computerized Sperm Motility Quantifier (SMQ). The zona binding potential of sperm was evaluated using the hemizona assay. Firstly, the VCL significantly differed between the P-pattern and both the G (72.9 +/- 7 vs. 86.3 +/- 16 microns s-1; P = 0.04) and N patterns (72.9 +/- 7 vs. 91.0 +/- 15 microns s-1; P = 0.002). The VSL differed only between the P and N patterns, being 19.7 +/- 7 vs. 32.6 +/- 15 microns s-1 (P = 0.02), respectively. No significant differences in LIN were noted between any of the three patterns. The sperm concentration differed significantly between the P and both the G (37.9 +/- 35 vs. 80.8 +/- 9 x 10(6) ml-1; P = 0.03) and the N patterns (37.9 +/- 35 vs. 89.7 +/- 72 x 10(6) ml-1; P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Moderate heat treatment increases the penetrability of zonae pellucidae of salt-stored mammalian oocytes by spermatozoa

The zona pellucida of mammalian oocytes stored in highly concentrated solutions of neutral salts is known to retain its biological and biochemical properties. However, the zona may become resistant to sperm penetration as the storage period is increased. In cattle and hamsters, the penetrability of zonae of salt-stored oocytes was restored or increased by treating the oocytes with moderate heat without altering the gross morphology of the zona. Although this technique did not work for salt-stored human ova, this may have been due to the use of so-called inseminated-unfertilised ova which (1) may have been fertilised but failed to activate, or (2) were not fertilised because of functionally defective zonae.

Validation of the hemizona assay (HZA) in a monkey model. II. Kinetics of binding and influence of cryopreserved-thawed spermatozoa

We compared fresh and frozen-thawed cynomolgus monkey spermatozoa tight binding to the zona pellucida under hemizona assay (HZA) conditions. Monkey oocytes were recovered after superovulation and stored in salt solution. Matching hemizonae were obtained by micromanipulation. Semen, obtained by electroejaculation, was used fresh or was cyropreserved, thawed, and washed by swim-up separation. At the standard initial dilution of 500,000 motile sperm/ml (or 5 x 10(4) motile sperm/hemizona), binding was significantly higher for fresh sperm (P = 0.00004). For frozen-thawed samples, there was a linear increase in the number of tightly bound sperm with increasing sperm concentration (r = 0.95). At 1.5 x 10(6) motile sperm/hemizona, binding of frozen-thawed spermatozoa was similar to that of fresh at a standard concentration. Kinetic studies showed peak binding at 1 hr of gametes coincubation. We conclude that, in this monkey model, the HZA is a valuable bioassay for evaluation of sperm binding to the zona pellucida, the initial requisite for fertilization and embryo development.

The specificity of human spermatozoa/zona pellucida interaction under hemizona assay conditions

The objective of this prospective study was to evaluate the specificity of human sperm/zona pellucida interaction under hemizona assay (HZA) conditions in experiments with gametes from the same and different species. Human, cynomolgus monkey and hamster oocytes were used after salt-storage. Oocytes were bisected into matching hemizonae by micromanipulation and used in the HZA. Semen was obtained from healthy men (donors) and male cynomolgus monkeys and prepared by wash and swim-up. Sperm binding to matching hemizonae was assessed (tight binding) after 4-h coincubation in the HZA in homologous and interspecies experiments. Acrosome reaction was evaluated in the sperm droplets using FITC-PSA and on the hemizonae using the T-6 monoclonal antibody. On human hemizonae, the number of tightly bound sperm for human and monkey were 93.2 +/- 15.8 and 3.9 +/- 1.3, respectively (P < 0.001). On monkey hemizonae, the number of tightly bound sperm for monkey and human were 126.0 +/- 34.8 and 2.8 +/- 1.6, (P = 0.02) respectively. On hamster hemizonae, there was negligible binding of human and monkey sperm. There was a significantly higher incidence of acrosome reacted sperm on the zona pellucida in homologous compared to heterologous experiments. These results demonstrate a high species-specificity of human gamete functions under HZA conditions, providing further support for the use of this bioassay in infertility and contraception testing.

The hemizona assay: its role in identifying male factor infertility in assisted reproduction

OBJECTIVES

To identify male factor infertility among a group of patients in an assisted reproductive program (phase 1) and to evaluate the hemizona assay (HZA) in the diagnosis and prognosis of such a program (phase 2).

DESIGN

The IVF performance of normal gametes in the Tygerberg program were critically evaluated. Female patients were classified as pure tubal factor infertility, having a normal FSH:LH ratio on day 3 of the menstrual cycle. All participating women produced three or more preovulatory oocytes at retrieval and were inseminated with sperm considered normal by all present diagnostic criteria. The total and normal fertilization rate thresholds were defined in that group. Using those thresholds, couples tested for sperm binding in the HZA (n = 48) were used and divided into two groups according to their fertilization rates, namely group 1, low fertilization (< 55%) and group 2, normal fertilization (> 55%).

SETTING

University-based tertiary care center.

PATIENTS

Ninety-nine couples (589 oocytes) with pure tubal factor infertility and normal male factor were used in phase 1. Forty-eight couples with normal and abnormal male factors that had both HZA performed and IVF treatment were included in phase 2.

RESULTS

Investigation of the performance of normal gametes in 99 couples (589 oocytes) revealed the total fertilization rate (total number of oocytes fertilized/total number of oocytes inseminated) was (mean +/- SD) 88.6% +/- 16.8% and the normal fertilization rate (total number of oocytes with normal fertilization/total number of oocytes inseminated) was 81.3% +/- 22%. The minimum total fertilization rate that can be considered normal in the Tygerberg program using mean--2 SD is therefore 55% and for normal fertilization rate is 37%. The group with low fertilization rate (< 55%) showed a mean hemizona index (HZI) significantly lower; nevertheless, the distribution overlapping indicates a low discriminating power of the HZA. A sensitivity of 75% and a specificity of 75% were found; the positive and negative predictive values were 81% and 68%, respectively.

CONCLUSIONS

The results indicated the HZA and HZI contribute important information and can serve in conjunction with other semen characteristics as useful tools during the diagnosis of the male factor in assisted reproduction.

Use of human zonae from cryopreserved oocytes in a test to assess the binding capacity of human spermatozoa

Aged unfertilized oocytes from an assisted conception programme were cryopreserved and then utilized after thawing in a zona-binding assay. Oocytes frozen using dimethyl sulphoxide (DMSO) showed poor survival post-thaw (2/40, 5%) compared to those frozen with propanediol (PROH) (63/134, 47%). When the zonae were exposed to spermatozoa from fertile donors, those frozen with DMSO showed a significantly higher number of bound spermatozoa than did those frozen with PROH (P < 0.002). In both groups, oocytes which failed to survive the freeze-thaw processes had greater numbers of bound spermatozoa than did those which survived (P < 0.05). Oocytes from cases of failed fertilization showed no difference in their rate of sperm binding compared with oocytes from cases in which some fertilization had occurred. Zonae frozen in PROH but which were from oocytes which were not viable after thawing were used to assess the binding of spermatozoa from men who had failed previously to fertilize their partner's oocytes in vitro and spermatozoa from men with poor quality semen and who had elected for treatment by micro-injection sperm transfer. The number of spermatozoa bound to zonae was reduced significantly in both groups compared to a fertile donor.

Prediction of fertilization in vitro with human gametes: is there a litmus test?

OBJECTIVES

The objectives of this study were as follows: (1) to evaluate the relationships between sperm concentration, morphologic pattern, motion parameters, and sperm-zona pellucida binding capacity and (2) to assess their ability to predict fertilization outcome under in vitro fertilization conditions.

STUDY DESIGN

Semen samples from 44 infertile men were prospectively evaluated for density, morphologic pattern (strict criteria), computerized motion parameters (motility, velocity, and linearity), and hemizona assay (outcome expressed as hemizona assay index), and results were correlated with fertilization outcomes of preovulatory oocytes during in vitro fertilization.

RESULTS

Of all sperm parameters, morphologic pattern was the best predictor of the ability of the sperm to bind to the zona pellucida. Hemizona assay index was the best predictor of fertilization rate. Stepwise regression analysis provided a model of hemizona assay index plus motility with highest predictability (R2 = 53.4%).

CONCLUSIONS

(1) The influence of sperm morphologic pattern as a prognosticator of fertilization outcome is established in major part as a determinant of sperm binding ability to the zona pellucida; (2) the hemizona assay provides a robust index that is highly predictive of the potential of human gametes to achieve fertilization and highlights its use in infertility and contraception testing.

Hemizona assay and its impact on the identification and treatment of human sperm dysfunctions

The HZA, a functional test for human gamete interaction, has become a useful and valuable experimental tool for physiological and cellular analysis of the early events leading to fertilization. The analysis of the conventional semen parameters with emphasis on sperm morphology (as judged by strict criteria) and motion characteristics (evaluated by computer assisted analysis) constitutes the first obligatory step for a critical evaluation of male-factor patients. Patients in whom fertilization disorders are suspected should be evaluated through bioassays of sperm function of established accuracy. The HZA, a bioassay of sperm-zona binding capacity is here proven to be highly predictive of IVF outcome. Ultimately, our increasing knowledge of sperm biology and dysfunction will provide a basis for a better diagnosis (membrane receptor defects and metabolic/biochemical abnormalities?) as well as better therapeutic interventions in patients with sperm disorders. It seems likely that the HZA may be eventually replaced by a standardized test kit in which recombinant human DNA-derived zona receptors mimic the natural function of the hemizonae currently used. This ZP3 reagent may also be a useful antigen for contraceptive development. The HZA therefore constitutes a useful adjuvant in the armentarium for the diagnosis and therapy of male-factor patients.