Low acrosin activity in a subgroup of men with idiopathic infertility dose not correlate with sperm density, percent motility, curvilinear velocity, or linearity

Sperm acrosin activity may be a useful factor in choosing between ICSI and IVF for infertile male patients

The clinical applications of acrosin activity are limited. We analyzed 61 578 male partners in infertile couples who visited the outpatient department of the Reproductive and Genetic Hospital of CITIC-Xiangya (Changsha, China) between August 2014 and December 2019 to determine the reference ranges and thresholds for acrosin activity in infertile Chinese men; to determine whether correlations exist between acrosin activity and age, sperm concentration, sperm morphology, or sperm motility; and to evaluate whether acrosin activity could serve as an effective prognostic indicator for choosing between in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in the clinic. The cut-off value for the normal reference range of acrosin activity for male partners in infertile couples was 24.78 µIU per 10 6 sperm. There was no significant association between acrosin activity and age, sperm concentration, semen volume, total sperm count, progressive motility, or total motile spermatozoa. A weak positive correlation was found between acrosin activity and normal sperm morphology. There was a statistically significant difference in abnormal acrosome morphology between the group with high acrosin activity (>24.78 µIU per 10 6 sperm) and the group with low acrosin activity (<24.78 µIU per 10 6 sperm). The group with a low IVF fertilization rate had a high index of abnormal acrosomal morphology at 21.2%, while the group with a high IVF fertilization rate had a low index of 0.2%. At an acrosin activity of <24.78 µIU per 10 6 sperm, in one cycle of the same patient, the fertilization rate, normal fertilization rate, and good-quality embryo rate for ICSI were significantly higher than those for IVF. Therefore, the most promising application of acrosin activity could be in the selection of ICSI over IVF for infertile male patients with complete fertilization failure or a low fertilization rate.

The diagnostic significance of the induced acrosome reaction

In trying to discern potential causes of male infertility, little investigation has been done to determine if there is predictive value in assessing acrosome reaction inducibility of human spermatozoa for clinical interpretation and application. The purpose of this review is to outline what is currently known in terms of the diagnostic significance of the induced acrosome reaction and to discuss what might be anticipated for the future. In constructing this review, every effort has been made to provide a comprehensive literature review for the reader and a number of review articles have been cited to serve as sources for additional related material. Regarding the aforementioned, it is essential to qualify that, with the exception of the Section entitled: ‘General characteristics of capacitation and the acrosome reaction’, only characteristics, properties and areas relevant to human spermatozoa will be addressed. Thus, in total, this review will: (1) provide a general description of capacitation and the acrosome reaction; (2) briefly characterize the acrosome and its properties; (3) address the signalling mechanism(s) by which the acrosome reaction occurs; (4) outline various methods for detecting the acrosome reaction; (5) definein vitroculture conditions that facilitate the acrosome reaction; (6) define agents, i.e., biological and chemical, that induce the reaction; (7) discuss the association of the acrosome reaction with fertilization; (8) discuss the clinical implications of the induced acrosome reaction; (9) discuss the relevance of sperm function assays in general; and lastly, (10) discuss future application of acrosome reaction assessment for the clinical diagnosis of male infertility.

Acrosin activity in spermatozoa of infertile Nigerian males

The objective of this study was to evaluate acrosin activity in spermatozoa of infertile Nigerian men and to compare with those of the fertile men. The acrosin activity was evaluated using the Acroscreen reagent kit. The acrosin activity of the fertile men was 40.7±5.2 mIU/10(6) sperm (range 30.1-51.3) and those of the infertile men was 22.4±8.33 mIU/10(6) sperm (range 5.7-39.1). The difference in the mean was statistically significant (P<0.001). There was a subpopulation of the infertile men who had their acrosin activity within normal range of the fertile men, 32.9±1.57 mIU/10(6) sperm. But the difference in the mean was statistically significant (P<0.001). Acrosin activity decreased with increased morphological changes in the spermatozoa. It is concluded that acrosin activity in the infertile Nigerian men is significantly lower than that in the fertile men. Acrosin activity may also be affected by morphological changes in the spermatozoa.

Acrosome reaction: methods for detection and clinical significance

The present article reviews the methods for detection and the clinical significance of the acrosome reaction. The best method for the detection of the acrosome reaction is electron microscopy, but it is expensive and labour-intensive and therefore cannot be used routinely. The most widely used methods utilize optical microscopy where spermatozoa are stained for the visualization of their acrosomal status. Different dyes are used for this purpose as well as lectins and antibodies labelled with fluorescence. The acrosome reaction following ionophore challenge (ARIC) can separate spermatozoa that undergo spontaneous acrosome reaction from those that are induced, making the result of the inducible acrosome reaction more meaningful. Many different stimuli have been used for the induction of the acrosome reaction with different results. The ARIC test can provide information on the fertilizing capability of a sample. The ARIC test was also used to evaluate patients undergoing in vitro fertilization since a low percentage of induced acrosome reaction was found to be associated with lower rates of fertilization. The cut-off value that could be used to identify infertile patients is under debate. Therapeutic decisions can also be made on the basis of the value of the ARIC test.

Relationship of acrosin activity to sperm function tests

Acrosin activity of spermatozoa from infertile patients and fertile volunteers was measured. Acrosin activity of spermatozoa from asthenozoospermic patients and patients with unexplained infertility was lower than that from fertile volunteers. We utilize the zona-free hamster egg-sperm penetration test to select candidates for conventional in vitro fertilization among unexplained infertile patients. The zona-free hamster egg sperm penetration test, however, requires several hours and special equipment which are not used in the clinical setting. It is preferable that other sperm function tests or a combination of them can replace this test. Thus three distinct tests of sperm function, namely, acrosin activity, Penetrak test, hypo-osmotic swelling test, were compared with the hamster test, using spermatozoa from patients with unexplained infertility. A combination of the Penetrak test and measurement of acrosin activity could predict the results of the zona-free hamster egg sperm penetration test with 88.2% accuracy. Thus, the hamster test should be done when either Penetrak test or measurement of acrosin activity showed abnormal values.

Acrosin activity in pelleted frozen sperm does not correlate with in vitro fertilization of oocytes

Spermatozoa pelleted after swim-up were frozen and then analysed in batches for acrosin activity, using a spectrophotometric method, and expressed as microIU micrograms DNA-1. A total of 259 sperm samples were analysed and the acrosin activity compared with fertilization in vitro. Of these, 224 samples fertilized at least one oocyte and 35 samples failed to fertilize any oocyte. Analysis by Student's t-test indicated that there was a statistically significant difference (P = 0.02) in acrosin activity between the two groups. However, when samples that failed to fertilize were matched for concentration, motility and normal morphology with samples that fertilized, this significance was lost (P = 0.77). It is concluded that total acrosin in pelleted sperm frozen after regular swim-up, does not correlate with fertilizing ability of spermatozoa used for insemination.

Impaired hamster egg penetration by human sperm from ejaculates with low acrosin activity but otherwise normal

OBJECTIVE

To determine if a low acrosin activity in otherwise normal ejaculate from infertile patients is associated with an impairment of sperm functions involved in the hamster egg penetration.

SETTING

A tertiary care center, the Andrology Clinic, Department of Internal Medicine, University of L'Aquila.

PATIENTS

Nine infertile patients with low acrosin activity in otherwise normal ejaculate (including normal immunoreactivity for acrosin) were studied; nine fertile men served as a control group. The two groups were homogeneous for seminal parameters.

INTERVENTIONS

The hamster egg penetration assay and the acrosome reaction rate assessment were performed on capacitated sperm suspensions in basal conditions and after ionophore challenge.

MAIN OUTCOME MEASURES

The penetration rate, the penetration index, and the acrosome reaction rate were measured and compared between the groups.

RESULTS

No penetration was achieved in seven patients and a low penetration was achieved in two cases. The difference with the control group was significant. The ionophore challenge was associated to penetration of hamster eggs in seven of nine patients, but the penetration index was significantly lower than the controls. Acrosin activity was correlated to hamster egg penetration. Both spontaneous and induced acrosome reaction rate were similar in the two groups.

CONCLUSIONS

A low sperm acrosin activity in otherwise normal ejaculate is associated with an impaired hamster egg penetration. This impairment does not seem to be due to altered dynamics of acrosome reaction.

Improvement in membrane integrity and acrosin levels of human sperm by use of L4 membrane

Previous results have demonstrated the advantage of using an L4 filter as a method for sperm preparation is assisted reproductive techniques. The present study examined the effect of two sperm processing methods (L4 filter and swim-up) on sperm acrosin levels and the integrity of the sperm membrane as measured by the hypoosmotic swelling (HOS) test. Semen specimens from 35 men (19 suspected subfertile men and 16 normal volunteers) were used to measure acrosin activity; 30 specimens (14 patients and 16 normal men) were used to assess the integrity of sperm membrane by the HOS test. The acrosin activity of L4-filtered spermatozoa (mean 110 +/- 85 microIU acrosin/10(6) sperm) in patients and donors was significantly higher (p < .002) than in either the swim-up specimens (76 +/- 58 microIU) or original unprocessed ejaculate (46 +/- 27 microIU). Similarly, the percentage of tail swelling measured by HOS test was significantly higher (p < .01) in the L4-filtered sperm (mean 71 +/- 13%) than in either swim-up specimens (59 +/- 18%) or original ejaculate (61 +/- 10%). These results clearly demonstrate improvement in two important functional parameters of sperm fertilizing ability in sperm processed by the L4-filter technique, thereby providing new evidence in support of the use of L4 filters for sperm processing.

Relation of human sperm acrosin activity and fertilization in vitro

The aim of the study described here was to determine the possible contribution of the acrosin activity test to routine semen analysis in enhancing the precision of the prognosis of IVF success in a group of patients in which the contribution of the egg factor to infertility was ruled out (20 cases) compared to a control IVF group (39 cases). Semen analysis, acrosin activity and acrosome ultrastructure were determined for all semen samples. The group with high fertilization rates was comprised of normozoospermic patients while the group with low fertilization rates was comprised of astheno-teratozoospermic patients. The mean acrosin level of the positive IVF group was significantly higher than that of the negative group (51.7 +/- 33.2 and 28.6 +/- 13.7, respectively). Two parameters: per cent motile spermatozoa and acrosin level, were found to have a significant positive correlation with subsequent successful IVF (r = 0.36, P < 0.006; r = 0.37, P < 0.004, respectively); and agenesis of the acrosome was found to have a significant negative correlation (r = -0.33, P < 0.01). The ability of these parameters to correctly predict fertilization success was 59%, with 5% false positive, among which 15.4% was predicted solely by the acrosin level (above 54 microIU 10(6) cells-1) and 23% solely by per cent motile spermatozoa (above 50%). Abnormalities of the acrosome ultrastructure did not contribute further to the correct classification. The apparent clinical benefit of the acrosin level test is discussed.

Acrosin activity of human sperm did not correlate with IVF

To evaluate the predicting value of sperm acrosin activity in human, the acrosin activity index (AAI) was measured in 95 semen samples from patients participating in an IVF program. All patients had at least two mature oocytes. Of 95 patients, 84 had successful fertilization and 11 failed to fertilize all oocytes in vitro. The numbers of mature oocytes were similar between fertilization and nonfertilization groups. The mean AAI, measured using a commercially available (Accu-Sperm) acrosin activity assay, was greater in the fertilization group than in the nonfertilization group, but the difference was not significant. There was no correlation between AAI and the in vitro fertilization rate of mature oocytes. The relation between AAI and semen parameters also showed no significant difference. It would appear that measurement of AAI inaccurately reflects in vitro fertilizability of human sperm.

Association between human in vitro fertilization rate and pregnancy outcome: a possible involvement of spermatozoal quality in subsequent embryonic viability

A conventional view of mammalian fertilization is that the active component of the process: the spermatozoon, by virtue of its progressive motility and acrosomal enzymes, penetrates an otherwise passive oocyte. This concept has placed bias on spermatozoal normality as largely determining the outcome of fertilization; once this has been achieved then the contribution of the spermatozoon is often forgotten, and attention switches to the maternally derived "blue-print" for early embryonic development. Paternal genomic contribution is known to start at the eight-cell stage in the human, but this is usually after the time when early cleavage stage (2 to 8-cell stage) embryos are replaced in human assisted reproductive technologies (ART) procedures such as in vitro fertilization and embryo transfer (IVF-ET). Hence, fundamental abnormal contributions to embryogenesis derived from the fertilizing spermatozoon have often been ignored. Human IVF-ET has permitted far greater powers of analysis of the fertilization event, and fertilization success appears to be determined in such a system by three main factors: spermatozoal quality, oocyte quality, and quality of in vitro culture conditions (the gamete environment). If the second two factors are more carefully controlled than the first, as is the usual emphasis in routine human IVF practice, then any large variation in fertilization rates that are also significantly related to embryonic viability and ultimately pregnancy outcome, may be thought to be more directly associated with original quality of the fertilizing spermatozoon. An analysis of results of 758 IVF cases provides preliminary evidence to show that there is a close association between human in vitro fertilization rate and subsequent embryo viability following replacement. In accepting this hypothesis as a possibility, we should drastically change our attitude from one of the spermatozoon as a robust, simple initiator of embryonic development, and embrace the idea of the vulnerability of such germ cells both during and after their production, and how detrimental influences on this might profoundly affect embryogenesis after successful fertilization.

Is spermatozoan acrosin a predictor of fertilization and embryo quality in the human?

OBJECTIVE

To investigate whether acrosin is a more reliable criterion than conventional parameters for assessing semen samples.

DESIGN

Total acrosin was estimated biochemically in semen samples obtained for routine screening for infertility and for IVF-ET procedures.

SETTING

Assisted Conception Unit, St. James's University Hospital, Leeds, United Kingdom.

PATIENTS

Four hundred sixty-three couples being investigated for causes of infertility, and 132 couples undergoing IVF-ET for any indication except antisperm antibodies between 1990 and 1991 were included in the study.

INTERVENTIONS

Semen samples were collected as part of routine investigation. Samples from men with consistently high viscosity were collected in alpha-chymotrypsin.

MAIN OUTCOME MEASURES

Total spermatozoan acrosin in motile spermatozoa and motile spermatozoan density in couples being assessed for IVF-ET and fertilization and embryo quality in those receiving treatment are considered.

RESULTS

Total acrosin levels were less variable (within subject) than either total or motile spermatozoan concentration at ejaculation. Although severely oligozoospermic ejaculates had the lowest levels of total acrosin, overall, there was no significant correlation of spermatozoan concentration between total acrosin levels and percentage fertilization.

CONCLUSIONS

Total spermatozoan acrosin activity correlates positively with fertilization rates but not with spermatozoan count. Motile spermatozoan density for insemination may be adjusted to achieve > 7.5 microIU acrosin per oocyte, without compromising fertilization or further embryo development to blastocysts in vitro.

Human sperm acrosin activity with relation to semen parameters and acrosomal ultrastructure

It was suggested that although not related to the standard semen parameters the level of the acrosin enzyme system is related to the fertility potential in men. Recently a simple clinical assay for total acrosin level was recommended for routine semen analysis. The improved clinical assay was analysed on the freshly liquified semen of 198 Asthenoteratozoospermic men and compared with the routine semen parameters including biochemical data and the ultrastructure of the acrosome. Only the sum of the per cent of live, motile, and normal-shaped spermatozoa had positive significant and reasonably high correlation with the acrosin level (r = 0.382, P < 0.0001). Each characteristic exhibits significant but low (< 0.35) correlation. Similarly negative significant and reasonably high correlation was obtained between the acrosin level and the sum of the principle acrosomal malformations observed by TEM (r = 0.396, P < 0.0001) while lower negative correlation was found only with agenesis or loss of the acrosome. Acrosin levels below 8.1 microIU 10(-6) cells were obtained in 4 specimens with above 80% round-form associated with more than 95% of agenesis of the acrosome. The possible significance of the low correlation obtained between the acrosin levels and seminal plasma zinc levels, malformations in the acrosomal equatorial region, and the presence of white blood cells is also discussed. We concluded that the acrosin activity reflects an aspect of male fertility which is not diagnosed by the routine semen analysis or by the ultrastructure of the acrosome, and is therefore a useful diagnostic sperm parameter.

Effect of abstinence on sperm acrosin, hypoosmotic swelling, and other semen variables

OBJECTIVE

To compare the variability of sperm acrosin and hypoosmotic swelling to the more standard semen variables in relationship to controlled periods of sexual abstinence using a defined group of men.

DESIGN

Ten men abstained sequentially for 1, 2, 3, 4, 5, and 10 days and produced an ejaculate after each time period. The ejaculate variables measured at each time point were sperm acrosin, hypoosmotic swelling, volume, sperm number, sperm concentration, sperm motility, sperm morphology, pH, and white blood cells (WBCs). Comparisons were performed between the values obtained at each abstinence period.

RESULTS

The percentage of hypoosmotically reactive spermatozoa did not vary significantly with the abstinence period. Sperm acrosin remained similar up to 5 days of abstinence but decreased almost twofold after 10 days of abstinence. The sperm volume and concentration increased gradually with the length of abstinence, being approximately twofold higher after 10 days of abstinence than after 1 day of abstinence. The total sperm number increased about fourfold from 1 day of abstinence to 10 days of abstinence. The percent normal sperm forms tended to increase until 5 days of abstinence but decreased after 10 days of abstinence. The WBC count showed only a small increase with longer abstinence periods. The pH remained essentially the same.

CONCLUSIONS

The length of abstinence affects the various semen variables differently. An abstinence period of up to 10 days does not alter the hypoosmotic swelling test results. However, the sperm acrosin values decrease after prolonged abstinence so that the abstinence period needs to be taken into consideration when performing this assay.

Sperm acrosin activity and fluorescence microscopic assessment of proacrosin/acrosin in ejaculates of infertile and fertile men

OBJECTIVE

To compare biochemically active with immunoreactive sperm acrosin in fertile and infertile men.

SETTING

This study was conducted in a tertiary care center, the Andrology Clinic, Department of Internal Medicine, University of L'Aquila.

PATIENTS

We evaluated the males in 40 infertile couples with no recognized cause of female infertility and 20 fertile men.

INTERVENTIONS

Ejaculates were collected under standardized conditions of abstinence.

MAIN OUTCOME MEASURES

Total sperm acrosin activity was measured on a spectrophotometer in washed sperm stored at -80 degrees C for 1 to 6 days. The percent of spermatozoa immunostained by an antiserum against proacrosin/acrosin by indirect immunofluorescence (IFL) was determined on methanol fixed sperm smears.

RESULTS

Biochemically active acrosin was correlated to immunoreactive acrosin (P = 0.0028), and both were inversely correlated to the percent of spermatozoa with an abnormal head (P = 0.00024 for acrosin activity and P = 0.0013 for IFL). Biochemically active and immunoreactive acrosin were lower in infertile compared with fertile men (P = 0.0012 and P = 0.0009, respectively). Sixty-eight percent of ejaculates with an acrosin activity lower than the limit value observed in fertile men showed a normal sperm morphology and a normal immunoreactivity for acrosin.

CONCLUSIONS

A low sperm acrosin activity in teratospermic ejaculates is because of a lack or a defect of the immunogenic and functional domains of the protein. A low sperm acrosin in infertile men with normal semen parameters results from a possible functional defect of the enzyme that is immunohistochemically detected in spermatozoa.

Fertilization failure and dysfunctions as possible causes for human idiopathic infertility

Consideration of the most common currently practiced laboratory assays for human spermatozoal fertility are discussed, with reference to the relevance of such assays to success or failure in human in vitro fertilization (IVF). Such IVF therapy should be the definitive challenge for human spermatozoal fertilization ability. However, when fertilization fails, is polyspermic, or is suboptimal, then questions concerning the step or steps in the process of fertilization which are dysfunctional remain unanswered. Quite possibly new assays need to be devised to address these problems, while in the meantime our present laboratory assay systems need to be improved to discern those defects in fertilization which operate in many cases of human idiopathic infertility.

Acrosin activity in patients with idiopathic infertility

Acrosin is a sperm acrosomal enzyme that is involved in the acrosome reaction, the binding of spermatozoa to the zona pellucida, and fertilization. This study was designed to determine whether sperm acrosin measurements can identify subpopulations of infertile or subfertile patients that are not recognized by routine semen analyses. We measured the total acrosin activity of ejaculates in a group of 19 men (15 suspected subfertile patients and 4 fertile donors). The acrosin activity was measured in liquefied semen specimens using the methodology described by Kennedy et al. [1989) J Urol 10:221-231). Ten patients in the suspected subfertile group had a mean acrosin value of 7.8 microIU acrosin/million sperm, which is clearly in the abnormal range (less than 14 microIU/10(6) sperm). Three patients had a mean acrosin value of 20.1 microIU/10(6) sperm, which is in the indeterminate range. Two other patients and four proven fertile donors had acrosin values in the normal range (greater than 25 microIU/10(6) sperm) (Agarwal A, Loughlin KR (1990): 2d International Meeting of Andrology, Como, Italy; Abstr 22). The normal fertile controls had a mean acrosin value of 32.5 microIU/10(6) sperm.