Functional Tests of Spermatozoa

Male Infertility in Humans: An Update on Non-obstructive Azoospermia (NOA) and Obstructive Azoospermia (OA)

Non-obstructive azoospermia (NOA) and obstructive azoospermia (OA) are two common causes of infertility that affect a considerable number of men. However, few studies were performed to understand the molecular etiology of these disorders. Studies based on bioinformatics and genetic analyses in recent years, however, have yielded insightful information and have identified a number of genes that are involved in these disorders. In this review, we briefly summarize and evaluate these findings. We also discuss findings based on epigenetic modifications of sperm DNAs that affect a number of genes pertinent to NOA and OA. The information summarized in this Chapter should be helpful to investigators in future functional studies of NOA and OA.

The use of genomics, proteomics, and metabolomics in identifying biomarkers of male infertility

Although male factors account for approximately 50% of all infertility, the mechanisms underlying their origin are unknown. Currently, clinicians rely primarily on semen analyses to predict male reproductive potential and chart treatment success. Even when invasive procedures are performed, the causes of male factor infertility frequently remain elusive. Recently, the advent of new technologies has spurred the search for novel male infertility biomarkers, and the detection of genes, proteins, or metabolites unique to the infertile male holds much promise. The concept that a cost-effective, noninvasive, and accurate set of biomarkers can be identified to diagnose male factor infertility is tantalizing. This review focuses on the various methodologies used in the discovery of novel biomarkers along with their findings. Specific attention is paid to recent advances in the fields of genetics, proteomics, and metabolomics.

Semen analysis in 21st century medicine: the need for sperm function testing

Sperm function testing, once commonly performed for the infertile couple before employing assisted reproductive technology (ART), has fallen out of favour in many reproductive medicine centers throughout the world. Indeed, the most recent addition of the 'World Health Organisation (WHO) Laboratory Manual for the Examination and Processing of Human Semen' now groups many of these procedures into a section termed Research Procedures. In large part, this reflects the current clinical practice of bypassing the in-depth evaluation of the male partner, while assuming that if a spermatozoon can be found for intracytoplasmic sperm injection (ICSI), it must be a healthy cell capable of achieving fertilization. Nevertheless, sperm function testing can provide valuable clinical insights into defects causing male infertility. Admittedly, in some cases, functional sperm deficiencies can be overcome using an ART. In other cases, couples will be empowered by the knowledge of the cause of their infertility, and for some couples, perhaps even the likelihood of ICSI success (relative to the spermatozoa). The knowledge allows them to make truly informed reproductive decisions, including (perhaps) the decision to seek donor insemination, to adopt or to remain childless. Knowledge of the cause of their infertility may provide closure for couples and a sense of confidence regarding their choice of reproductive treatment.

Human sperm microinjection into hamster oocytes: a new tool for training and evaluation of the technical proficiency of intracytoplasmic sperm injection

OBJECTIVE

To design a system for teaching intracytoplasmic sperm injection (ICSI) and to provide a standardized method to assess technical competency.

SETTING

University andrology laboratory.

DESIGN

Prospective study of method for training ICSI and prediction of ICSI outcome.

PATIENT(S)

Male infertility candidates for ICSI and fertile donors.

INTERVENTION(S)

Sperm from 14 fertile donors and 21 oligospermic patients were microinjected into hamster ova. Sperm head decondensation rates (SHD) and oocyte damage rates were measured. Hamster ICSI (HICSI) was used to train technicians, to assess competency, for quality control, and to predict ICSI fertilization. Sperm fertilization potential measured by HICSI was compared with the outcome of ICSI.

MAIN OUTCOME MEASURE(S)

Sperm head decondensation or fertilization.

RESULT(S)

Sperm head decondensation was observed in 425 of 773 hamster oocytes with a mean (+/- SD) rate of 60.9 +/- 15.5. Consistency was shown by repetitive testing of the same donor, comparing fresh and frozen semen, and testing of the multiple frozen aliquots of the same ejaculate. Technicians have been trained with this protocol. Excellent initial ICSI success rates for new technicians were demonstrated. Oligospermic semen samples (21 men, 251 hamster ova) tested in the HICSI test exhibited SHD rates from 12% to 100%. The poor outcome of ICSI in clinical cases was predicted by HICSI.

CONCLUSION(S)

The HICSI provides a method for determining the competency for the ICSI technician and interlaboratory comparison, for the prediction of success of sperm for ICSI.

A quality control system for the optimized sperm penetration assay

OBJECTIVE

To develop a quality control system for the optimized sperm penetration assay (SPA) and to use this system to monitor interassay variability and stability over time.

DESIGN

Four semen donors were tested consecutively for a period of weeks (7 to 139 weeks) with the SPA. Their average semen analyses and SPA scores were evaluated to monitor natural biologic variation. Intra-assay variation was obtained by dividing 11 semen samples into three aliquots and testing each separately in the SPA. A single ejaculate from seven individuals was aliquoted and frozen to be used as a control. They were tested on different assay days in 1986 and subsequently in 1991 to evaluate the assay stability over time.

MAIN OUTCOME MEASURES

Results were expressed as a sperm capacitation index (mean number of sperm penetrations per ovum).

RESULTS

Consecutive weekly semen analyses and SPAs on donors exhibited coefficients of variation ranging from 20% to > 40%. In contrast, these variations were much greater than intra-assay variability. Analysis of frozen semen specimens tested in several SPAs also displayed a low coefficient of variation. When aliquots of these frozen samples were tested in the SPA 5 years later, there were no differences in the observed values, showing the remarkable stability of this assay over time. The lower limit of the normal fertile range did not change over a period of 2 years.

CONCLUSIONS

Results show that using fresh semen samples as a positive control in the SPA is inadequate. This deficiency has been overcome with the use of frozen semen controls. With frozen semen for quality control, the optimized SPA developed in this laboratory is a highly reproducible assay that meets the strict criteria required for clinical laboratory certification.

Analysis of TEST (TES and Tris) yolk buffer effects on human sperm

OBJECTIVE

To assess different parameters of TEST (TES and Tris) yolk buffer (TYB) treatment of human sperm that may contribute to the biologic effects of TYB on sperm function.

DESIGN

The influence of TYB treatment on occurrence of acrosome reactions was studied, as was the influence of the concentration of acrosome-reacted sperm reacted by TYB or Biggers-Whitten-Whittingham medium (BWW) incubation on penetration levels in the sperm penetration assay (SPA). The necessity for the TYB to achieve enhanced SPA performance as well as the effect of heat shock on sperm also were studied.

SETTING

Andrology laboratory of a university hospital.

PATIENTS

Sperm donors.

MAIN OUTCOME MEASURES

Sperm penetration levels in the SPA and acrosomal loss as evaluated by a fluorescent lectin staining technique.

RESULTS

Sperm incubated in TYB for 42 to 46 hours at 4 degrees C demonstrated a higher rate of acrosomal loss than did sperm capacitated in BWW media for 20 to 22 hours. The difference was not significant. When insemination concentrations were normalized to identical concentrations of acrosome-reacted sperm, TYB treated specimens demonstrated much higher penetration levels compared with BWW specimens. Samples incubated in BWW versus TYB for 42 to 46 hours at 4 degrees C before heat shock had identical penetration levels. Samples washed with 37 degrees C BWW (positive heat shock) had significantly higher penetration levels than did samples washed with 4 degrees C BWW (negative heat shock).

CONCLUSION

Although TYB treatment does increase the occurrence of acrosome reactions, this alone does not account for the dramatic increase in penetration levels in SPA seen with these samples. TEST yolk buffer is not required for enhancement of penetration, and the heat shock step of the procedure seems to be most important for enhancement of sperm fusion ability in the SPA.

Sperm recovery and survival: two tests that predict in vitro fertilization outcome

OBJECTIVES

To determine if human sperm recovery during swim-up and sperm survival after 24 hours, as obtained from a screening semen specimen, are predictive of subsequent IVF and clinical pregnancy rates (PRs) and to determine if these techniques can identify men with normal semen analysis parameters and poor IVF success.

DESIGN

Historical prospective study.

SETTING

All semen evaluations and IVF cycles were performed at the University of Pittsburgh, Magee-Womens Hospital, Pittsburgh, Pennsylvania.

PATIENTS, PARTICIPANTS

Couples undergoing IVF at Magee-Womens Hospital from August 1988 through June 1993.

INTERVENTIONS

A screening semen analysis and swim-up procedure were performed on all couples undergoing IVF. The number of spermatozoa recovered after swim-up and the percentage of motile spermatozoa present after a 24-hour incubation were recorded.

MAIN OUTCOME MEASURES

Fertilization and PRs were compared according to the parameters obtained from routine semen analysis, the number of spermatozoa obtained with swim-up, and the percentage of motile spermatozoa at 24 hours.

RESULTS

Using chi2 or Fisher's exact test, fertilization rates were significantly different according to the number of spermatozoa recovered after swim-up (< or = 2.0 and > 2.0 x 10(6) spermatozoa recovered, 48.3% versus 71.4%) as were PRs (16.9% versus 29.8%). Similarly, the percentage of motile spermatozoa present at 24 hours (< or = 20% and > 20%) discriminated between fertilization rates (45.9% versus 65.8%) and PRs (16.4% versus 36.5%). Among a subset of men with normal semen analyses and total motile sperm counts > or = 40 x 10(6), the results from swim-up and survival discriminated between men with high and low fertilization and PRs. Receiver operating characteristic analysis revealed that swim-up results better discriminated between pregnant and nonpregnant IVF patients than sperm motility, but that the percentage of motile spermatozoa present at 24 hours was no better in this regard than sperm motility.

CONCLUSIONS

The number of spermatozoa recovered after swim-up and the percentage of spermatozoa that maintain their motility after 24 hours were both helpful in assessing IVF and PRs and may be helpful in altering physicians to a subset of men having normal semen analysis parameters yet poor IVF success.

Effect of human sperm capacitation treatments on the penetration of freshly obtained and zona-free frozen hamster oocytes

A study was conducted to evaluate the effect of sperm capacitation treatments on hamster egg penetration test (HEPT) values when using freshly obtained and zona-free frozen hamster oocytes. Semen was collected from 12 healthy donors with proven fertility and each sample processed by a sperm swim-up method, incubation in human follicular fluid (hFF), Percoll centrifugation, and refrigeration in test-yolk buffer (TYB). Capacitated sperm were then incubated with fresh and frozen-thawed eggs and the percent penetration scores and indices were calculated. Motility values of pre- and postprocessed sperm were also determined. A significant overall reduction in percent penetration scores but not penetration indices was observed when using frozen oocytes. However, within sperm treatments, differences between fresh and frozen oocytes were observed for the sperm swim-up, hFF incubation, and Percoll centrifugation groups, but not for TYB. Differences in sperm movement parameters according to sperm treatment did not appear to reflect specific penetration scores. In conclusion, despite the practical advantage of using frozen oocytes over freshly obtained oocytes for the HEPT, the specific sperm capacitation treatment must be considered a factor when the decision to use fresh or frozen oocytes is made. Furthermore, these findings reinforce the need to carefully reevaluate the predictive value of the HEPT any time modifications to the test are introduced.

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.

A prospective controlled evaluation of TEST-yolk buffer in the preparation of sperm for human in vitro fertilization in suspected cases of male infertility

OBJECTIVE

To evaluate sperm preincubation in tes and tris (TEST)-yolk buffer as a potential enhancing agent of fertilizing capacity of sperm during human in vitro fertilization (IVF).

DESIGN

Oocytes obtained during IVF were divided into two groups: one group fertilized with TEST-yolk buffer-treated sperm and the other group with standard-prepared sperm.

SETTING

The University of Southern California IVF Program.

PATIENTS

Thirty-nine couples with suspected male factor infertility undergoing IVF.

INTERVENTIONS

Preinsemination incubation of sperm in TEST-yolk buffer for 24 hours.

MAIN OUTCOME MEASURES

Fertilization rates in vitro.

RESULTS

TEST-yolk buffer-treated sperm fertilized 140 of 241 oocytes (58%), whereas control sperm fertilized 108 of 251 oocytes (43%). Of four couples who had previously failed to fertilize during IVF, one fertilized with both specimens and three fertilized with TEST-yolk buffer-treated sperm only.

CONCLUSIONS

TEST-yolk buffer pretreatment of sperm for 24 hours results in higher fertilization rates during IVF among suspected male factor patients.

Influence of sperm processing on the fertilizing capacity and recovery of motile sperm from thawed human semen

Artificial insemination programs now rely almost exclusively on frozen semen preparations as their source of sperm. Unfortunately, several reports indicate that conception rates using frozen-thawed semen are inferior to freshly ejaculated specimens. The present study was designed to investigate the fertilizing capacity of sperm and the recovery of motile sperm from thawed semen following different sperm processing methods. Washed resuspended pellets contained sperm with at least the same fertilizing potential as sperm from swim-up techniques. However, the recovery of motile sperm from the pellets was more than 3 times greater than from the swim-up techniques. Percentage motility, progressive velocity, and amplitude of lateral head displacement were generally higher in the sperm from swim-up techniques than in the sperm from the pellets, despite equivalent fertilizing potentials. It can be argued from these results that washed resuspended sperm preparations provide a significantly greater number of motile sperm without a loss in fertility when compared to sperm from swim-up techniques. Accordingly, this study raises questions about the use of the sperm swim-up as a procedure for processing thawed semen for use in intrauterine insemination in which maximal numbers of motile sperm are required. It also demonstrates the need to identify new methods for processing frozen-thawed specimens for assisted reproductive procedures.

Prediction of human sperm penetrating ability using computerized motion parameters

The sperm penetration assay (SPA) is used to assess male fertilizing potential but it is tedious and costly. Computer analysis could replace the need for the SPA in some cases, if computerized sperm motility parameters are highly predictive of SPA performance. The objective of this study was to determine whether computerized motility parameters from fresh semen samples could be used to predict SPA performance. Computer automated semen analysis (CASA; CellSoft, Cryo Resources) was used to quantitate sperm concentration (CONC), percent motility (MOT), curvilinear velocity (VEL), linearity of swimming trajectory (LIN), mean amplitude of lateral head displacement (ALH), and beat/cross frequency (B/CF). The SPA was performed using either Biggers, Whitten, and Whittingham's medium (BWW) or TEST-yolk buffer (TYB). Patients were divided into three groups depending on SPA performance: group 1, BWW-treated, 0% versus greater than 0% penetration; group 2, TYB-treated, 0% versus greater than 0% penetration; and group 3, TYB-treated, less than 20% versus less than or equal to 20% penetration. SPA performance was highly correlated with CONC, MOT, VEL, and B/CF. CONC, MOT, VEL, and B/CF were significantly higher for patients who penetrated in the SPA than for those who failed to penetrate. Discriminant function analysis (DFA) successfully classified 76% of all patients treated with TYB (group 2) who penetrated and 86% of nonpenetrators based on their computerized motility parameters. For group 2 DFA predicted that 93 men would penetrate in the SPA with TYB. Of these, 90 (97%) successfully penetrated at least one egg.(ABSTRACT TRUNCATED AT 250 WORDS)

Establishment of TEST-yolk buffer enhanced sperm penetration assay limits for fertile males

TEST-yolk buffer has been shown to enhance sperm penetration of zona-free hamster eggs. Review of sperm penetration assay (SPA) data from a fertile population was undertaken to determine a normal range for SPA with TEST-yolk buffer enhancement. Thirty-eight intrauterine insemination patients and 4 artificial insemination donors who had successfully initiated a pregnancy within 18 months of SPA analysis were examined. All 42 enhanced SPAs demonstrated penetration of greater than 10%, and 37 of these (88%) yielded SPA values of greater than or equal to 20%. Thirty-three percent (14/42) of these individuals achieved 0% penetration in the SPA without TEST-yolk buffer. The SPA performed with the TEST-yolk modification has fewer false negatives than the assay done with the original methodology.

The value of semen analysis and sperm function assays in predicting pregnancy among infertile couples

Over a 2-year period, 227 couples were evaluated by an extended assessment of the male partner's ejaculate. This extended assessment comprised sperm penetration of denuded hamster oocytes, ability of sperm to penetrate synthetic mucus, and the adenosine triphosphate (ATP) content of whole semen. In proportional hazards analysis adjusting for the contribution of clinical and other seminal variables, the sperm penetration assay (SPA) test was a predictor of pregnancy in the subgroup with normal conventional seminal variables (greater than 40 million motile sperm per ejaculate). When the SPA result was 20% or more the probability of pregnancy was 3.7 times higher; the performance of the SPA as a diagnostic test was better in the couples with treated tubal disease than in other diagnostic categories.

Factors affecting penetration of zona-free hamster ova

The sperm penetration assay is an expensive, time-consuming test to assess male fertility in vitro. Although some investigators are enthusiastic in its application, others feel that it is not sensitive or specific enough to be used as part of the routine infertility evaluation. Indeed, this bioassay is not a faithful reproduction of in vivo conditions. However, if the SPA is abnormal, it is unlikely that sperm will fertilize a human ovum in vivo. Conversely, a normal SPA does not guarantee successful in vivo fertilization. No bioassay can be absolute in its predictive value, but false-negative results must be kept to a minimum for this bioassay to be of any clinical significance. Each laboratory performing the SPA should optimize the assay for sensitivity, reproducibility, and minimization of false-negative results and then establish normal and abnormal ranges of its own. If the limitations of the SPA are kept in mind, and if we employ it very selectively, it may still be useful.