Abnormal sperm morphology and other semen parameters related to the outcome of the hamster oocyte human sperm penetration assay

Decline of semen quality over the last 30 years in Uruguay

BACKGROUND

Over the last years, there has been an increasing concern about a global decline in men's fertility. Specifically, some evidence indicates that sperm quality has decreased over the last years. However, reports showing the changes in sperm quality with time are inconsistent. Part of the contradictions between studies is attributed to geographical differences. Surprisingly, few studies include data from South American countries, creating a bias in the conclusions. This study aims to determine how sperm quality has evolved over the past 30 years in Uruguay. For this purpose, 317 medical records from allegedly healthy sperm donor candidates, aged between 18 and 36 years old, who voluntarily requested to be considered as sperm donors between 1988 and 2019, were analyzed. The studied variables were the following sperm parameters: semen volume, sperm cell concentration, total sperm number, progressive motility, vitality, and sperm morphology. A correlative statistical analysis was performed between seminal parameter values and the year data were collected.

RESULTS

We found a statistically significant decrease in sperm concentration and normal sperm morphology during the studied period. There was no decrease in vitality, seminal volume, and total progressive motility. Semen parameters were not associated with tobacco, drugs, or alcohol consumption.

CONCLUSIONS

We conclude that the sperm quality of donor candidates in Uruguay decreased during this period. Further studies should be carried out to verify the occurrence of this phenomenon in the general population and find its possible causes.

Observation of sperm-head vacuoles and sperm morphology under light microscope

OBJECTIVE

The presence of sperm-head vacuoles has been suspected to be deleterious to the outcomes of assisted reproductive technology (ART). It is difficult to accurately distinguish morphologically abnormal sperm with vacuoles under a light microscope. This study was performed to analyze the result of the observation of sperm-head vacuoles using Papanicolaou staining under a light microscope and whether the male partner's age affects these vacuoles.

METHODS

Sperm morphology with vacuoles was evaluated using Papanicolaou staining and observed under a light microscope (400×) in 980 men. The normal morphology was divided into three categories (group A, <4% of normal morphology; group B, 4%-14% of normal morphology; and group C, >14% of normal morphology). The criteria for the sperm-head vacuoles were those given in the World Health Organization manual. For the analysis of the age factor, the participants were divided into the following groups: 26-30 years, 31-35 years, 36-40 years, 41-45 years, and 46-50 years.

RESULTS

The percentage of sperm-head vacuoles increased with normal sperm morphology (group A vs. groups B, C) (p<0.05). In the case of the age factor, a statistically significant difference was not observed across any of the age groups.

CONCLUSION

A majority of the sperm-head vacuoles showed a statistically significant difference among normal morphology groups. Therefore, we should consider the probability of the percentage of sperm-head vacuoles not increasing with age but with abnormal sperm morphology. A further study is required to clarify the effect of the sperm-head vacuoles on ART outcomes.

Hemizona assay and sperm penetration assay in the prediction of IVF outcome: a systematic review

The limited predictive value of semen analysis in achieving natural conception or in IVF outcome confirms the need for sperm function tests to determine optimal management. We reviewed HZA and SPA predictive power in IVF outcome, with statistical significance of diagnostic power of the assays. HZA was readily efficient in predicting IVF outcome, while evident inconsistency among the studies analysed framed the SPA's role in male fertility evaluation. Considerable variation was noted in the diagnostic accuracy values of SPA with wide sensitivity (52-100%), specificity (0-100%), and PPV (18-100%) and NPV (0-100%) together with fluctuation and notable differentiation in methodology and cutoff values employed by each group. HZA methodology was overall consistent with minor variation in cutoff values and oocyte source, while data analysis reported strong correlation between HZA results with IVF outcome, high sensitivity (75-100%), good specificity (57-100%), and high PPV (79-100%) and NPV (68-100%). HZA correlated well with IVF outcome and demonstrated better sensitivity/specificity and positive/negative predictive power. Males with normal or slightly abnormal semen profiles could benefit by this intervention and could be evaluated prior to referral to assisted reproduction. HZA should be used in a sequential fashion with semen analysis and potentially other bioassays in an IVF setting.

Sperm head vacuolization affects clinical outcome in ICSI cycle. A proposal of a cut-off value

OBJECTIVE

To evaluate the relationship between sperm nuclear vacuoles and sperm morphology and to investigate the influence of the rate of spermatozoa with head vacuolization (SVR) in a seminal sample on the clinical outcomes in couples undergoing intracytoplasmic sperm injection.

MATERIALS

26 patients undergoing infertility investigations were included and were divided in two groups according to an SVR ≤ 20,28 % (Group A) or > 20,28 % (Group B), and were investigated to verify the influence of SVR on the fertilization rate, embryo quality, pregnancy and implantation rates.

RESULTS

Abnormal spermatozoa with nuclear vacuoles were significantly higher (p < 0.001) than the percentage of normal spermatozoa with nuclear vacuoles. Patients in group A had a percentage of abnormal sperm with nuclear vacuole significantly lower compared to group B (p < 0,001), but there was no difference in the percentage of normal sperm with nuclear vacuoles. Fertilization rates and the number of top quality embryos did not differ between the two groups. The pregnancy and implantation rates were significantly higher in Group A compared to Group B (respectively p < 0,05 and p < 0.001).

CONCLUSIONS

For the first time, we propose a cut off value in the proportion of sperms with nuclear vacuolization on the total of sperm in seminal samples, and demonstrate a relationship between SNV and clinical outcomes after ICSI. The SNV rate could be introduced as an easy diagnostic evaluation prior to perform an ICSI cycle.

An assessment of new sperm tests for male infertility

The routine semen analysis, although used for more than 50 years, fails to accurately distinguish between fertile and infertile men. As a consequence, many tests of sperm function (TSF) have been developed. This review discusses both older and newer diagnostic TSF. It outlines the principles underlying each assay and reviews aggregate clinical data to determine its current relevance and utility. It concludes that the relevance of many older TSF is questionable, with the wide acceptance of intracytoplasmic sperm injection (ICSI). Newer TSF have the potential to deliver more clinically relevant information but require more extensive study to better understand their predictive role in the ICSI era.

Value of quantitative ultramorphological sperm analysis in infertile men

A specific cause of infertility cannot be identified in at least 25% of men referred to a specialized clinic. Diagnosis of infertile men is based mainly on standard semen analysis and the observation of sperm under light microscope. The aim of our study was to find the subcellular sperm characteristics that could explain infertility in a group of teratozoospermic infertile men. Morphological characteristics of sperm from non-teratozoospermic (control donors) and teratozoospermic infertile men were analyzed by transmission electron microscopy (TEM) and quantified. Our analysis showed that sperm cells from control donors presented a higher number of normal heads and tails than infertile men. Regarding subcellular characteristics of nucleus and tails, only the percentage of vacuolated nucleus, the absence of at least one pair of microtubules of the axoneme and the total distortion of the tail were statistically higher in infertile men than in control donors. There were no differences in the number of normal acrosomes between the groups. Although the ultrastructural sperm defects overlapped between control donors and infertile men, TEM permits the identification and differentiation of a larger amount of defects than light microscopy. Vacuolated nucleus and gross alterations of the tail are the major sperm defects that seem to have prognostic value in teratozoospermic men.

Semen parameters are unrelated to BMI but vary with SSRI use and prior urological surgery

BACKGROUND

Male infertility affects approximately 6% of reproductive-aged men. It has been suggested that overweight men or men with obese body mass index (BMI) experience prolonged time to pregnancy, though the influence of male BMI on fertility remains understudied.

AIMS

We hypothesized that BMI is inversely correlated with fertility, manifested by reduced sperm concentration, motility, and morphology.

METHODS

Males of age 18 to 50 with semen analyses and self-reported BMI were included (n = 530). Patient parameters analyzed included age, BMI, smoking, urological, and fertility history. Leutinizing hormone (LH), Follicle-stimulating hormone, testosterone, steroid hormone-binding globulin (SHBG) and free androgen index (FAI) levels (n = 55), and selective serotonin reuptake inhibitor (SSRI) use (n = 12) were also measured.

RESULTS

The men in this study had a mean BMI of 28.2 ± 4.9 kg/m(2) (range = 15-60), which is considered overweight, and a mean semen concentration of 55.4 ± 46.8 million/mL, which is in normal range, according to WHO standard. No consistent relationship was observed between increasing BMI and sperm concentration, motility, or morphology, although the testosterone levels trended downward with increasing BMI; there was a suggestion for decreased sperm concentration in current smokers. Men treated with combination SSRI and other psychotropic agent therapy (n = 12) had significantly reduced sperm motility (P = .009). Not unexpectedly, prior urological surgery (n = 77) was associated with lower sperm concentration (P = .0001) and morphology (P = .0008). When in vitro fertilization-embryo transfer (IVF-ET) was used as a treatment modality (n = 121), male BMI was not a significant predictor of clinical pregnancy (P = .06).

CONCLUSIONS

In our study, we did not observe a significant association between male BMI and sperm concentration, motility or morphology, or clinical pregnancy following IVF-ET. Significantly, SSRI use may affect sperm parameters negatively.

Capacitation status of stored boar spermatozoa is related to litter size of sows

Semen parameters can be considered useful predictors of sperm fertility. The objective of this study was to address the question of whether differences in in vivo fertility after the use of different ejaculates could be predicted using sperm kinematics, capacitation status, and sperm penetration ability under commercial pig production conditions. The percentage of capacitated sperm, as assessed by chlortetracycline (CTC) staining, was positively correlated with litter size (p<0.01). Our data suggest that litter size increases in proportion to the number of capacitated spermatozoa. When all semen parameters (kinematics, sperm capacitation status, and sperm penetration ability) and litter size were included in a multiple linear regression analysis, significant associations were found between the percentage of capacitated sperm (B-type), the sperm fertility index as assessed by a sperm penetration assay (SPA), and litter size. This relationship between capacitated sperm and litter size, however, was more predictive for smaller litter groups than larger ones. We found that the percentage of B-type sperm was significantly correlated with historic average litter size. However, there was no significant correlation between the percentage of B-type sperm and historic farrowing rates. To determine the normal range for B-type sperm, the lower limits were established as 30% for small litters (<8 piglets) and 35% for large litters. The overall accuracy of the assay was 92% and 83% for small and large litters, respectively. These results indicate that capacitation status as measured by CTC staining is a useful predictor of sperm fertility, equivalent to SPA. Moreover, original capacitation status exhibited better predictive ability for small litters than for large ones. Therefore, subfertile boars can be identified primarily by capacitation status.

The sperm penetration assay predicts the litter size in pigs

The prediction of sperm fertility is of paramount importance for breeding animals. Multiple laboratory approaches have been developed for this purpose, but they have yielded equivocal results. The objective of this study was to develop and standardize to a method for predicting fertility in vivo in boars using the in vitro penetration assay. To increase the sensitivity and reduce false-negative results of the assay, each step in the procedure was standardized and quality control was applied. Maximum penetration of hamster zona-free oocytes and immature porcine oocytes was obtained using heparin-treated sperm cells. Hamster zona-free oocytes showed a significantly higher penetration than immature porcine oocytes. To eliminate interassay variability, two frozen bull semen samples were applied. All possible variables related to the female were excluded. The SPA (sperm penetration assay using zona-free oocytes) result showed significant correlation with historic average litter size but had no significant correlation with farrowing rates. To determine the normal range for the SPA, lower limits of the sperm fertility index were established as 1.2 for the small litter sizes (<8 piglets) and 2.5 for the large litter sizes. The overall accuracy was 92 and 96% respectively, for the small and large litter sizes. Our laboratory has standardized the procedure for the SPA, resulting in greatly increased sensitivities for small and large litter sizes. The protocol increases the ability to discriminate between good and poor fertility groups and it was highly effective at ranking 24 boars by litter size into large and small litter groups.

Bone marrow transplantation or hydroxyurea for sickle cell anemia: long-term effects on semen variables and hormone profiles

Ten male subjects affected by sickle cell anemia (SCA) were studied to evaluate the long-term effects of therapies on their fertility. Their ages ranged from 18 to 34 years (median: 32 years). Four subjects were treated by hydroxyurea (HU) and 6 by hematopoietic stem cell transplantation (HSCT). The median follow-up after HU initiation and HSCT was 10.5 years (range: 8-15 years) and 15.5 years (range: 8-21 years), respectively. Three of the 6 in the HSCT group and two of the 4 in the HU group were azoospermic. One HSCT subject had normal semen and hormone variables, showing that normal fertility can occasionally be expected after transplantation in SCA. The remaining 4 patients (2 HSCT and 2 HU) were oligozoospermic. With regard to HU, semen impairment appears to be related to the duration of treatment. To draw general conclusions, further research with a large number of patients treated since childhood with HU or HSCT is warranted.

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.

Absolute polymorphic teratozoospermia in patients with oligo-asthenozoospermia is associated with an elevated sperm aneuploidy rate

Infertile patients with abnormal sperm parameters have an increased sperm aneuploidy rate, despite a normal blood karyotype. The evaluation of sperm chromosome aberrations in patients with teratozoospermia only has shown a rate similar to that found in patients exhibiting oligo-astheno-teratozoospermia, which suggests that teratozoospermia is the critical parameter associated with aneuploidy. However, it is not known which alteration of the sperm morphology is associated with chromosome aberrations. The few cases reported so far have shown an association with the presence of abnormal head morphology and particularly with enlarged heads. We report the sperm aneuploidy rate of 3 patients with oligo-asthenozoospermia who have absolute teratozoospermia (100% abnormal forms) and a different percentage of sperm head abnormalities. Fourteen healthy men with normozoospermia served as control subjects. Sperm aneuploidy and diploidy rates were calculated by using triple-color fluorescence in situ hybridization (FISH) for chromosomes 12, X, and Y, and double-color FISH was used for chromosomes 8 and 18. Patient K53, who had the highest number of spermatozoa with enlarged heads (54.3%), also had the highest aneuploidy and diploidy rates. The other 2 patients, K56 and K61, had sperm aneuploidy and diploidy rates lower than those of patient K53 but still well above the range found in normal men. Sperm chromosome abnormalities were intermediate in patient K61 and lower in patient K56, who had the lowest rate of spermatozoa with enlarged heads (18.9%). These data add further evidence that patients with teratozoospermia have an increased sperm aneuploidy rate and that this is particularly high in presence of an elevated percentage of spermatozoa with enlarged heads. For this reason, germ cells exhibiting this abnormality should not be used in in vitro fertilization programs.

Morphology and the sperm penetration assay

OBJECTIVE

To assess the ability of Kruger morphology to predict the outcome of the sperm penetration assay (SPA).

DESIGN

A retrospective review using univariate and multivariate analysis, t tests, and logistic regression was performed to examine the correlation between Kruger morphology and the optimized zona-free hamster egg sperm penetration assay (O-HESPA).

SETTING

University hospital.

PATIENT(S)

One hundred fifteen private-practice patients who underwent semen analysis, including Kruger morphology and O-HESPA, as part of an infertility evaluation between 1997-2000 were retrospectively reviewed.

INTERVENTION(S)

Retrospective analysis of the sperm penetration assay.

MAIN OUTCOME MEASURE(S)

Univariate and multivariate analysis, Student's t test, and logistic regression were performed to analyze Kruger morphology, count, and viability and their relationship to SCI result.

RESULT(S)

Univariate analysis demonstrated a statistically significant correlation between SCI and sperm count, viability, and Kruger morphology. Multivariate analysis demonstrated statistically significant correlations between SCI and count and viability. There was no correlation between Kruger morphology and SCI. Logistic regression was performed on the SCI results, using count, Kruger morphology, and viability. Sperm count was found to be the only variable that was statistically significant with respect to SCI results.

CONCLUSION

This study demonstrated that Kruger morphology assessment cannot be used to predict the results of SCI or replace it in the management of the infertile couple.

Induction of the acrosome reaction and zona-free hamster oocyte penetration by a bull with complete teratospermia versus a half brother with normal sperm

A fertile bull producing normal sperm and a sterile half brother exhibiting 100% teratospermia were available to study an induced sperm acrosome reaction and oocyte penetration. Pedigree analysis indicated that this condition was inherited. Experiments were undertaken to study the induction of the acrosome reaction using dilaurylphosphatidylcholine (PC12) liposomes, because this procedure was previously established to be highly correlated with bull fertility. The sperm from each bull were incubated with several PC12 concentrations for varying time periods. The initial percentages of sperm from the sterile bull with intact, partially intact, and lost acrosomes were 67%, 18%, and 14%, respectively, vs 82%, 13%, and 5% for the fertile bull (P < .05). After incubation for 15 minutes with 50 microM PC12 liposomes the corresponding values were, respectively, 51%, 26%, and 19%; and 60%, 28%, and 12%. Thus, the differences after induction of the acrosome reaction, although significant (P < .05), were small. The number of sperm adhered to each oocyte averaged 22 and 10, respectively, for the fertile and sterile bulls, whereas 74% of the fertile bull sperm and only 11% of the sterile bull sperm penetrated oocytes. Mixing the sperm-oocyte complex during incubation and increasing the sperm concentration during incubation to compensate for differences in sperm motility did not markedly affect oocyte penetration by teratogenic sperm, which is consistent with this bull being sterile. In other studies, microinjection of this type of sperm was demonstrated to induce fertilization, so the consequences of using sperm with hereditary defects in assisted reproductive programs to overcome human male sterility may be a concern.

Aneuploidy in spermatozoa of infertile men with teratozoospermia

Recent studies have shown that aneuploidy in spermatozoa of infertile men with poor semen quality is increased. The purpose of this study was to determine whether poor sperm morphology is associated with the incidence of spermatozoa with numerical chromosome abnormalities. Semen samples from 20 infertile teratozoospermic men were studied using multicolour fluorescence in situ hybridization (FISH). Men were divided into four groups according to the proportion of normal sperm morphology: infertile men with <10% (group A, n=7), 10-19% (group B, n=6), and 20-29% (group C, n=7) of morphologically normal spermatozoa, and controls (group D, n=5) with > or =30% normal forms. Two hybridizations were performed. All the samples were analysed using probes for chromosomes 1 and 7 and, in addition, in group A and in controls with normal semen parameters probes for chromosomes X, Y and 18 were also used. Ten thousand spermatozoa were scored per hybridization. Severely teratozoospermic men (<10% normal forms) had significantly higher frequency of disomy 7, 18, YY, XY and diploidy in their spermatozoa when compared with controls. The results suggest that poor sperm morphology is associated with numerical chromosome abnormalities of spermatozoa. Severely teratozoospermic men may be at an increased risk of producing aneuploid offspring.

The relationship between critical evaluation of sperm morphology and the TYB-optimized zona free hamster oocyte sperm penetration assay

The objective of this study was to analyse the relationship between the percentage of spermatozoa in semen with normal morphology, assessed using the Tygerberg criteria, and sperm fertilizing ability assessed using the TYB-optimized zona free hamster oocyte sperm penetration assay (TYB-optimized SPA), to evaluate the predictive value of strict morphology on outcome of the SPA. In a retrospective study, 56 samples were analysed. In addition to routine semen parameters, the percentage of spermatozoa with normal morphology (A forms) and the average number of penetrations per oocyte (Sperm Capacitation Index) was evaluated in all cases. Using a multiple linear regression analysis with all semen parameters, sperm morphology was the best predictor (p = 0.001) of the SPA score. The agreement between the percentage of A forms and the Sperm Capacitation Index beyond chance (kappa coefficient) was 0.5842. Twenty-two specimens had abnormal SPA scores, with 21 exhibiting abnormal sperm morphology (Sensitivity = 96%). The remaining 34 samples had normal Sperm Capacitation Index values; of these, 23 had normal sperm morphology in semen (Specificity = 68%). The positive predictive value was 96%, and the negative predictive value was 66%. All semen samples from control donors had normal semen parameters and Sperm Capacitation Index values. In conclusion, the percentage of spermatozoa with normal morphology assessed using Tygerberg criteria (> 14% A forms) are predictive of the results in the TYB-optimized SPA. However, sperm morphology appears to be a better predictor when it is normal than when it is abnormal.

Papanicolaou and Kruger assessment of sperm morphology: thresholds and agreement

The current World Health Organization guidelines (1992) suggest that the presence of > or = 30% normal sperm forms (i.e. PAP criteria) is consistent with normal semen quality. Critical evaluation of sperm morphology (CE; Kruger classification) has shown an excellent correlation with human in vitro fertilization. Utilizing Kruger criteria, > 14% normal sperm forms has been proposed as indicative of normal semen quality. We have performed a retrospective analysis on 261 individuals to assess the agreement between PAP and Kruger criteria for normal sperm morphology (NSM). When the threshold for NSM by PAP was set at 30%, a significant agreement was found between the percentage normal forms of both criteria (Kappa coefficient = 0.37; p < 0.001). Sixty-seven (92%) of the 73 men found to have abnormal sperm morphology by PAP had abnormal semen by Kruger classification. When the threshold for NSM by PAP was established at 50%, the Kappa coefficient was 0.48 (p < 0.001). Sixty of the 72 samples (83%) classified as normal by PAP staining were normal by Kruger criteria. Interestingly, when NSM by PAP was between 30 and 50%, the specimen was just as likely to have normal or abnormal sperm morphology by Kruger (40 vs. 60%, respectively). These results strongly suggest that a high or low percentage of NSM by PAP is in agreement with the Kruger classification. The excellent agreement of Kruger and WHO criteria at the extremes (< 30% and > 50%) may obviate the need for Kruger assessment. However, when WHO morphology is between 30 and 50%, the addition of Kruger evaluation may provide meaningful information to help better diagnose a patient and plan his treatment.

Response of routine semen analysis and critical assessment of sperm morphology by Kruger classification to therapeutic varicocelectomy

PURPOSE

We studied the effect of varicocelectomy on Kruger morphology and semen parameters.

MATERIALS AND METHODS

A total of 33 subfertile men diagnosed with varicoceles was evaluated 3 months before, and 3 to 4 and 6 to 8 months after varicocelectomy. Evaluation involved routine semen analysis and sperm morphology using Kruger classification.

RESULTS

Significant improvement in sperm concentration and count was found after varicocelectomy (sperm count preoperatively 117.1 +/- 29, 3 to 4 months postoperatively 162.5 +/- 41 and 6 to 8 months postoperatively 139.8 +/- 25 million sperm, p = 0.0095). Using Kruger classification, evaluation of sperm morphology revealed overall significant increase in percentage of normal A forms at 3 to 4 and 6 to 8 months after surgery (from 9.8 +/- 5.8% A forms, 13.6 +/- 7.7% A forms, and 14.5 +/- 7.5% A forms, respectively, p = 0.0002, normal greater than 14%). Twelve of the 26 patients (46%) with abnormal sperm morphology preoperatively and greater than 4% A forms reached normal levels 3 months postoperatively. Six months after surgery only 6 patients maintained normal values and 3 of the initial 14 nonresponders became normal (9 of 26, 36%). Three patients with severe teratozoospermia (less than 4% A forms) showed improvement in sperm morphology. Four patients with normal sperm morphology preoperatively were not affected by varicocelectomy.

CONCLUSIONS

Surgical correction of varicocele was associated with significant improvement in sperm morphology evaluated using Kruger classification. Concentration and count improved after varicocelectomy. Changes were observed as early as 3 months after surgery.

Post-thaw plasma membrane integrity of bull spermatozoa separated with a sephadex ion-exchange column

Previous experiments have established that filtration of bovine semen through a Sephadex ion-exchange column improves its quality before and after freezing. The present study was conducted to determine the post-thaw membrane integrity of bull spermatozoa separated with a Sephadex ion-exchange column and to determine the kind of protection to spermatozoa is provided by glycerol during freezing and thawing. Semen from Holstein bulls diluted in TEST-yolk extender (with and without glycerol) was filtered through a Sephadex ion-exchange column and frozen in liquid nitrogen (-196 degrees C). After thawing, there were more normal acrosomes in filtered spermatozoa than nonfiltered (P < 0.01). Post-thaw plasma membrane integrity and swelling ability in a hypoosmotic solution revealed that the filtered spermatozoa had a stronger (P < 0.005) plasma membranes than the nonfiltered. Filtered spermatozoa demonstrated higher zona-free hamster oocyte penetration than the nonfiltered (30.5 vs 11.5%; P < 0.0005). Spermatozoa extended in TEST-yolk without glycerol had the lowest (P < 0.001) normal acrosomes, intact plasma membranes and swelling ability. Plasma membrane over the post-acrosomal region of the head and post-midpiece region of the tail was more sensitive to damages caused by freezing and thawing than acrosomal and midpiece regions of spermatozoa. Glycerol in the extender provided significant (P < 0.05) protection to the sensitive regions of filtered and nonfiltered spermatozoa during freezing and thawing. Filtered plus glycerolated spermatozoa had the highest (P < 0.01) normal acrosomes, intact plasma membranes and swelling ability. In conclusion, the pre-freezing filtration of bovine semen harvested the spermatozoa possessing stronger plasma membranes which enabled them to endure freezing and thawing stresses. The addition of glycerol to the extender protected the post-acrosomal region of the head and post-midpiece region of the tail of spermatozoa from freezing and thawing shocks.

Strict criteria for the evaluation of human sperm morphology and its impact on assisted reproduction

Sperm morphology abnormalities can be identified in a large proportion of patients with failed and delayed fertilization when assessing this parameter with strict criteria. Statistical analyses of a large IVF population confirm that, in patients with severe teratozoospermia, fertilization rates can be enhanced in many cases by increasing insemination concentration. However, implantation rates are impaired, thereby affecting the ability of these patients to establish a viable pregnancy. Data from couples undergoing controlled ovarian stimulation/intrauterine insemination seem to support the use of strict morphology as a predictor of outcome in this setting, too. Although a descriptive parameter, sperm morphology assessed by strict criteria can be used as a biomarker of sperm dysfunction(s). These dysfunctions are multiple and include abnormalities of motion parameters, poorer capacity to bind to homologous zona pellucidae and penetrate zona-free eggs, and low incidence of spontaneous and induced acrosome reaction. At a cellular level, poor morphology is associated with a higher content of creatine kinase and impaired capacity to undergo appropriate changes in intracellular calcium concentration. Whether nuclear/DNA abnormalities are present still remains to be fully determined. A definitively objective evaluation of morphology based on these criteria may allow all centres specializing in assisted reproduction to analyse semen in a homogeneous fashion.

Defective calcium influx and acrosome reaction (spontaneous and progesterone-induced) in spermatozoa of infertile men with severe teratozoospermia

OBJECTIVE

To evaluate the acrosome reaction and its prerequisite, a calcium influx, in spermatozoa of infertile men with a high incidence of abnormal sperm forms.

DESIGN

Prospective, controlled study.

SETTING

Academic tertiary assisted reproduction center.

PATIENTS

Patients (n = 14) were allocated in the study after semen evaluation showed teratozoospermia (< 14% normal sperm forms) as diagnosed by strict criteria.

INTERVENTIONS

After swim-up separation of the motile fraction, acrosome reactions were evaluated using Pisum sativum agglutinin (both spontaneously and exogenously induced with P and the calcium ionophore A23187, both at 10 microM); the intracellular-free [Ca2+]i was assessed by the fluorescent fura-2 indicator (basal and after P).

RESULTS

Patients did not show the typical P-induced wave of [Ca2+]i that was observed in controls but rather a blunted response, no response at all, or abnormal basal [Ca2+]i levels. The percent of basal acrosome reaction was significantly lower for patients versus controls postswim-up, and at 1 hour and 3 hours. Furthermore, there was a significant difference in the response of acrosome reaction to P both at 1 hour and 3 hours, with patients showing almost no response at all. However, patients' acrosome reaction response to the calcium ionophore was similar to those of fertile men.

CONCLUSION

Infertile patients with a high incidence of abnormal sperm forms as diagnosed by strict criteria have a low incidence of spontaneous acrosome reaction and a diminished P-stimulated acrosome reaction, whereas the nonspecific response to a calcium ionophore is conserved. Parallel abnormalities of [Ca2+]i were observed in patients, suggesting that these sperm populations may have a defective nongenomic P sperm receptor and/or abnormalities of other membrane transduction systems.

Predictive value of morphologically normal sperm concentration in the medium for in-vitro fertilization

Morphological evaluation of spermatozoa using strict criteria (MEUSC) and conventional sperm parameters were studied with respect to in-vitro fertilization and pregnancy outcome before and after a swim-up selection procedure. Recovered oocytes were inseminated with 50,000 progressively motile spermatozoa, and this study assess the influence of the total number of spermatozoa and of the percentage with strictly normal morphology in the insemination sample on the outcome of IVF. The results showed that the percentages of spermatozoa with normal morphology using strict criteria, both in native and in post-swim-up samples, were the best predictors of IVF outcome. Their respective cut-off points were 5% and 8%. The number of morphologically normal spermatozoa inseminated also showed a good correlation with fertilization. However, it was not possible to find a proper cut-off point for this parameter. The patients were categorized on the basis of their native and post-swim-up scores. Category 1, in which both parameters were below their respective cut-off points, showed a 7% fertilization rate and a 0% pregnancy rate. Category 3, in which both parameters were above their cut-off points, showed a 70% fertilization rate and a 23% pregnancy rate. This suggests that sperm morphology can be used as a criterion for patient selection for IVF as an aid to identification of possibly subfertile males.

In vitro DNA fluorescence after in vitro fertilization (IVF) failure

PURPOSE

A pilot study was performed to test the diagnostic value of in vitro DNA fluorescence in oocytes that failed to fertilize after IVF. Ten patients with a cleavage rate less than 20% after IVF were included.

RESULTS

Uncleaved oocytes were observed by fluorescence microscopy after incubation with the DNA fluorescent dye Hoeschst 33342. Four main causes which may have contributed to the low cleavage rate were found: (1) sperm incapacity to penetrate the oocyte despite the absence of the usual criteria for male infertility, (2) oocyte immaturity, (3) delayed fertilization, and (4) oocyte abnormalities revealed by aberrations in the morphology of the female chromatin.

CONCLUSIONS

The possibility of a rapid and detailed analysis of the maturational status of unfertilized oocytes, the morphology of the female chromatin, the presence and quantity of spermatozoa tightly bound to the zona pellucida, and sperm penetration into the oocyte without subsequent pronucleus formation, using DNA fluorescence, allows us to clarify further the cause of fertilization failure and to orient infertility treatment toward the male, the female, or both partners.

Prediction of in vitro fertilization outcome by sperm penetration assay with TEST-yolk buffer preincubation

OBJECTIVE

To evaluate sperm penetration assay (SPA) value as a screening tool before in vitro fertilization (IVF).

DESIGN

Follow-up study comparing sperm variables and IVF outcome.

SETTING

Infertile couples in an academic research environment.

PATIENTS, PARTICIPANTS

Two hundred forty-one infertile couples scheduled for IVF.

INTERVENTIONS

Sperm penetrating assay with cold Tes-TRIS (TEST) Yolk buffer semen preincubation and IVF.

MAIN OUTCOME MEASURES

Percent of egg penetration recoded into poor and good category (0% to 20%, 21% to 100%) and compared with fertilization, embryo transfer, and pregnancy rate (PR) in IVF, as well as sperm count motility and morphology.

RESULTS

Sperm penetrating assay predicted fertilization with a high negative (74%) and positive (82%) predictive rate and good specificity value (0.96). One of 31 patients in the poor SPA category (3%) fertilized less than 50% of eggs; no pregnancy occurred. In the good SPA category, 87 of 210 patients (41%) fertilized greater than or equal to 50% of eggs with 34.3% PR. Sperm penetrating assay correlated better with fertilization rate than did sperm count and motility but not morphology.

CONCLUSIONS

Sperm penetrating assay is a useful screening assay before IVF together with sperm morphology.

Tests of human sperm function and fertilization in vitro

OBJECTIVE

To review recent studies on the development of new tests of human sperm function and evaluation of which sperm characteristics are most important for fertilization in vitro by logistic regression analysis.

STUDY SELECTION

Recent studies on the relationship between putative and new tests of human sperm function and fertility in vitro or in vivo are discussed in this review. Some physiological and technical aspects are included.

MAIN OUTCOME MEASURES

Fertilization rates in vitro and sperm tests including standard semen analysis, improved morphology assessment, objective assessment of sperm motility and movement characteristics, nuclear maturity, hypo-osmotic swelling, the acrosome and the acrosome reaction, acrosin activity, human sperm-hamster oocyte penetration assay, and sperm-zona pellucida (ZP) and sperm-oolemma binding.

RESULTS

The percentages of sperm with normal morphology and a normal intact acrosome, mean linearity, and the number of sperm binding to the ZP were highly significant related to fertilization rates in vitro. Other sperm tests evaluated usually provided no additional information about fertilization rates. The human ZP is highly selective for binding of morphologically normal sperm. Acrosome-reacted human sperm have little or no ability to bind to the ZP.

CONCLUSION

Results of in vitro fertilization can be used to evaluate tests of human sperm function. Logistic regression analysis is a powerful method for determining which groups of sperm characteristics are independently related to fertilization rates. Normal morphology, linearity, acrosome status, and sperm-ZP binding are the most important characteristics for fertilization in vitro.

The relationship between alterations in spermatozoal deoxyribonucleic acid, heparin binding sites, and semen quality**Presented in part at the 7th World Congress on In Vitro Fertilization and Assisted Procreations, Paris, France, June 30 to July 3, 1991

OBJECTIVE

To assess the relationship between spermatozoal deoxyribonucleic acid (DNA) and fertilizing potential.

DESIGN

Semen samples were examined from nine fertile donors and six donors without a confirmed pregnancy. All samples were in the normal range for count, morphology, and motility. Spermatozoa from these specimens were stained with acridine orange or Feulgen's reagent. The presence of heparin binding sites was determined by counting the number of spermatozoa that bound to heparin-coated agarose beads.

RESULTS

Acridine orange staining demonstrated that in the fertile group 42% +/- 2% of the spermatozoa fluoresced green indicating that the DNA was intact, whereas only 25% +/- 3% of the spermatozoa fluoresced green in the nonfertile group (P less than 0.05). Feulgen's staining revealed that more spermatozoa from infertile donors showed a heterogeneous DNA distribution (P less than 0.05). The DNA content of spermatozoa with heterogeneous distribution of DNA was reduced by 10% compared with those with homogeneous DNA (P less than 0.05). Normal spermatozoa as well as those with DNA anomalies possessed heparin binding sites.

CONCLUSIONS

These data demonstrated that in donor specimens with normal counts, morphology, and motility, a higher percentage of spermatozoa possess less and/or denatured DNA in the infertile group compared with the fertile donors. In contrast, the surface membranes of spermatozoa with altered DNA have heparin binding sites as do spermatozoa with intact DNA.

Concordance of mammalian ejaculate features

Different measures of ejaculate characteristics, such as ejaculate volume, proportion of normal sperm, proportion of motile sperm, and total number of sperm per ejaculate, are directly related to the probability of fertilization both when females copulate with a single male and particularly with multiple males. Selection will therefore favour the evolution of ejaculate characteristics which enhance the probability of fertilization, and I predict positive relations between ejaculate parameters. I used a literature survey of mammalian ejaculate parameters to test this prediction. The data set was corrected for similarity between taxa which resulted from common ancestry, and was reduced to statistically independent standardized linear contrasts. The number of sperm per ejaculate and ejaculate volume were positively related to body mass, but when the confounding effect of body mass was controlled for, all four ejaculate characteristics showed positive relations, and five out of six were statistically significant. This suggests that the different measures of ejaculate quality in mammals have been improved simultaneously, apparently by a common selective force.

Possible role of pure human follicle-stimulating hormone in the treatment of severe male-factor infertility by assisted reproduction: preliminary report

OBJECTIVE

Experimental clinical trial assessing the potential of systemic follicle-stimulating hormone (FSH) to improve sperm fertilizing ability in in vitro fertilization (IVF).

DESIGN

Retrospective clinical evaluation of severe male factor patients failing fertilization in IVF or showing severe sperm defects.

SETTING

Academic tertiary clinical care unit.

PATIENTS, PARTICIPANTS

Fourteen patients (41 cycles) who failed IVF, 22 patients (32 cycles) with severe quantitative and qualitative semen abnormalities indicating poor fertilization.

INTERVENTIONS

TREATMENT

FSH 150 U IM three times a week for 3 months.

MAIN OUTCOME MEASURE(S)

Pretreatment and post-treatment evaluation of endocrine profile, basic semen analysis, and fertilization and pregnancy rates.

HYPOTHESIS

FSH treatment may improve spermatogenesis quality by its multiple actions on the Sertoli-gamete cell compartment without interfering with testicular hormonogenic function.

RESULTS

No significant changes were observed in the endocrine profile or in semen parameters; individual cases showed improvements in sperm concentration and motility. Significant increase in fertilization rate of preovulatory oocytes was demonstrated; seven term pregnancies were achieved.

CONCLUSIONS

A multicenter randomized, double-blind trial with crossover is needed to demonstrate the benefit of systemic FSH administration and if this effect is FSH exclusive.

Recurrent failure of in vitro fertilization: role of the hemizona assay in the sequential diagnosis of specific sperm-oocyte defects

The results of predictive fertilization bioassays (hemizona assay, hamster ova-human sperm penetration assay), in vitro fertilization treatment, fertile donor cross-match tests with either sperm or oocytes, and oocyte micromanipulation for assisted fertilization were used to establish a pathophysiologic diagnosis in cases of recurrent failed fertilization in vitro. Disorders of sperm function manifested at the level of zona binding, zona penetration, oolemma fusion, and pronuclear decondensation as well as oocyte anomalies were considered to represent the specific gamete defects that led to abnormal sperm-oocyte interactions (i.e., failed fertilization). Our findings show that the sequential application of bioassays can elucidate specific sperm or oocyte defects that characterize functional abnormalities among sperm populations.

Delayed fertilization during in vitro fertilization and embryo transfer cycles: analysis of causes and impact on overall results

This study evaluated possible causes of delayed fertilization during in vitro fertilization (IVF) cycles, its repetitiveness, and its influence on IVF results in 23 patients (27 cycles) with delayed fertilization of greater than or equal to 1 preovulatory oocyte(s). In 15 cycles, reinsemination with husband's semen was performed at 18 hours. Possible causes of delayed fertilization were oocyte defects (10 cycles, 37.0%), sperm defects (4 cycles, 14.8%), oocyte and sperm defects (4 cycles, 14.8%), and no detectable gamete defects (9 cycles, 33.3%). Overall fertilization rate was 47.9%. No pregnancies were observed in 10 patients with one embryo transferred. Recurrence rate of delayed fertilization per patient was 17.3%; overall ongoing pregnancy rate/cycle was 10.3%. Although repetitiveness of delayed fertilization is low, it seems to impact negatively on IVF results.

Predictive value of sperm morphology and movement characteristics in the outcome of in vitro fertilization of human oocytes

One hundred fourteen semen samples from Chinese males were analyzed for routine semen parameters including the semen volume, sperm count, percentage motility, and percentage normal morphology. Of these 114 samples, 54 also had movement characteristics of seminal and swim-up sperm evaluated by the computer image analyzer system (Cellsoft; Cryo Resources Co., New York). All semen samples were subjected to the swim-up procedure to harvest the motile sperm before inseminations of human oocytes. Fertilization was considered to have occurred when at least one oocyte was observed with two or more pronuclei. Semen samples were classified as infertile (0% fertilization rate; N = 32) or fertile (greater than 0% fertilization rate; N = 82) before statistical analyses. There was a significant difference (P less than 0.005) in percentage normal morphology of seminal sperm between the fertile (mean +/- SE; 67.3 +/- 1.2%) and the infertile (59.3 +/- 2.2%) samples. The percentage normal morphology of seminal sperm correlated (r = 0.3049; P less than 0.002) with the fertilization rate and this parameter was selected by the multivariate stepwise discriminant analysis as the discriminator capable of predicting the fertilization rate with 57.9% accuracy. Statistical analyses of samples where sperm movement was also evaluated demonstrated that there was significant differences (P less than 0.01) between the fertile (N = 38) and the infertile (N = 16) samples in percentage normal morphology of seminal sperm (67.8 +/- 1.8% vs 56.2 +/- 2.6%) and curvilinear velocity of swim-up sperm (89.2 +/- 3.5 vs 68.2 +/- 7.2 microns/sec).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemizona assay: assessment of sperm dysfunction and prediction of in vitro fertilization outcome

The hemizona assay (HZA) was used in a prospective, blinded study to assess the relationship between tight sperm binding in the HZA and sperm fertilizing ability in in vitro fertilization (IVF). In each controlled assay, the authors compared sperm binding of proven fertile men with that of patients undergoing IVF. Human oocytes stored in a salt solution were used in the study, and binding results were correlated with the fertilization rate of preovulatory oocytes during IVF. Patients with poor fertilization rates in IVF had significantly lower binding than those cases with successful fertilization (7.3 +/- 1.4 versus 62.1 +/- 10.9, respectively; mean +/- standard error, P less than 0.02). Based on current standards, the HZA was able to predict fertilization accurately in 26 of 28 cases (sensitivity of 83%, specificity of 95%, positive predictive value of 83%). The authors conclude that the HZA is a valuable tool for evaluating dysfunctional sperm-zona pellucida binding, with good predictive value for fertilization in vitro.

Usefulness of sperm penetration assay in fertility predictions

The competence of the sperm penetration assay (SPA) to predict male fertility, as determined by normal sperm morphology and the fertilizing potential, as shown by human in vitro fertilization (IVF), was investigated. A significant correlation was obtained between normal sperm morphology and the SPA (phi = 0.623). A weaker correlation was however obtained with human IVF (phi = 0.397). Notwithstanding this weak association, a positive SPA (greater than 10%) was highly predictive (95%) of human IVF success. In contrast, a negative SPA (less than or equal to 10%) was associated with a high rate of false-negatives (65%). The SPA does however warn that a male factor may be present, as the mean fertilization rate of this group of patients was markedly reduced. The preincubation period for the spermatozoa did not play a major role in the predictive ability of a SPA outcome.