Egg-penetration ability and structural properties of human sperm prepared by Percoll-gradient centrifugation

17BIPHE2, an engineered cathelicidin antimicrobial peptide with low susceptibility to proteases, is an effective spermicide and microbicide against Neisseria gonorrhoeae

STUDY QUESTION

Is 17BIPHE2, an engineered cathelicidin antimicrobial peptide with low susceptibility to proteases, a better spermicide in cervicovaginal fluid (CVF) than its parental peptides, LL-37 and GF-17?

SUMMARY ANSWER

At the same mass concentration, 17BIPHE2 exhibited the highest spermicidal activity on human sperm resuspended in CVF-containing medium.

WHAT IS KNOWN ALREADY

LL-37 and its truncated peptide GF-17 exert both spermicidal and microbicidal activities, although they are prone to proteolytic degradation in body fluids.

STUDY DESIGN, SIZE, DURATION

Spermicidal activities of 17BIPHE2 were evaluated in vitro in mouse and human sperm, both resuspended in medium, and then on human sperm incubated in CVF-containing medium; in the latter condition, the spermicidal activity and peptide stability in CVF of 17BIPHE2 were compared with that of LL-37 and GF-17. The in vivo contraceptive effects of 17BIPHE2 and the reversibility thereof were then assessed in mice. Finally, in vitro microbicidal effects of 17BIPHE2 on Neisseria gonorrhoeae were determined.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Sperm motility and plasma membrane integrity were assessed by videomicroscopy and exclusion of Sytox Green, a membrane-impermeable fluorescent dye, respectively. Successful in vitro fertilization (IVF) was determined by the presence of two pronuclei in oocytes following their coincubation with capacitated untreated or 17BIPHE2-treated sperm. Sperm alone or with 17BIPHE2 were transcervically injected into female mice and successful in vivo fertilization was indicated by the formation of two-cell embryos 42-h postinjection, and by pregnancy through pup delivery 21-25 days afterwards. Peptide intactness was assessed by immunoblotting and HPLC. Reversibility of the contraceptive effects of 17BIPHE2 was evaluated by resumption of pregnancy of the female mice, pretranscervically injected with 17BIPHE2, following natural mating with fertile males. Minimum inhibitory/bactericidal concentrations of 17BIPHE2 on N. gonorrhoeae were obtained through microdilution broth assay.

MAIN RESULTS AND THE ROLE OF CHANCE

At the same mass concentration, 17BIPHE2 was a more effective spermicide than LL-37 or GF-17 on human sperm resuspended in CVF-containing medium, with the spermicidal concentration of 32.4 µM. This was mainly due to lower susceptibility of 17BIPHE2 to CVF proteases. Importantly, the reproductive tract of mouse females treated three times with 32.4 µM 17BIPHE2 remained normal and their fecundity resumed after stopping 17BIPHE2 treatment.

LIMITATIONS, REASONS FOR CAUTION

For ethical reasons, the inhibitory effects of 17BIPHE2 on fertilization and pregnancy cannot presently be performed in women. Also, while our study has proven the effectiveness of 17BIPHE2 as a spermicide for mouse and human sperm in vitro, dosage formulation (e.g. in hydrogel) of 17BIPHE2 still needs to be developed to allow 17BIPHE2 to remain in the vagina/uterine cavity with controlled release for its spermicidal action.

WIDER IMPLICATIONS OF THE FINDINGS

Since 17BIPHE2 also exerted bactericidal activity against N. gonorrhoeae at its spermicidal concentration, it is a promising candidate to be developed into a vaginal multipurpose prevention technology agent, thus empowering women against unplanned pregnancies and sexually transmitted infections.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Canadian Institutes of Health Research (PJT 173268 to N.T.). There are no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Sperm can act as vectors for HIV-1 transmission into vaginal and cervical epithelial cells

PROBLEM

Sperm are the major cells in semen. Human sperm possess a number of HIV-1 gp120 binding ligands including sulfogalactosylglycerolipid (SGG). However, the mechanisms of how sperm capture HIV-1 onto their surface are unclear. Furthermore, the ability of sperm to deliver HIV-1 to vaginal/cervical epithelial cells lining the lower female reproductive tract, as a first step in HIV-1 transmission, needs to be determined.

METHOD OF STUDY

Sperm from healthy donors were incubated with dual-tropic HIV-1_CS204 (clinical isolate), and virus capture was determined by p24 antigen ELISA. The involvement of SGG in HIV-1 capture was assessed by determining K_d values of HIV-1 gp120-SGG binding as well as computational docking of SGG to the gp120 V3 loop. The ability of sperm-associated HIV-1 to infect peripheral blood mononuclear cells (PBMCs) and TZM-bl indicator cells was determined. Lastly, infection of vaginal (Vk2/E6E7), ectocervical (Ect1/E6E7), and endocervical (End1/E6E7) epithelial cells mediated by HIV-1-associated sperm was evaluated.

RESULTS

Sperm were able to capture HIV-1 in a dose-dependent manner, and the capture reached a maximum within 5 minutes. Captured HIV-1, however, could be removed from sperm by Percoll-gradient centrifugation. Affinity of gp120 for SGG was substantial, implicating sperm SGG in HIV-1 capture. Sperm-associated HIV-1 could productively infect PBMCs and TZM-bl cells, and was capable of being transmitted into vaginal/cervical epithelial cells.

CONCLUSION

Sperm are able to capture HIV-1, which remains infectious and is able to be transmitted into vaginal/cervical epithelial cells, a result indicating the importance of sperm in HIV transmission.

Potential Use of Antimicrobial Peptides as Vaginal Spermicides/Microbicides

The concurrent increases in global population and sexually transmitted infection (STI) demand a search for agents with dual spermicidal and microbicidal properties for topical vaginal application. Previous attempts to develop the surfactant spermicide, nonoxynol-9 (N-9), into a vaginal microbicide were unsuccessful largely due to its inefficiency to kill microbes. Furthermore, N-9 causes damage to the vaginal epithelium, thus accelerating microbes to enter the women's body. For this reason, antimicrobial peptides (AMPs), naturally secreted by all forms of life as part of innate immunity, deserve evaluation for their potential spermicidal effects. To date, twelve spermicidal AMPs have been described including LL-37, magainin 2 and nisin A. Human cathelicidin LL-37 is the most promising spermicidal AMP to be further developed for vaginal use for the following reasons. First, it is a human AMP naturally produced in the vagina after intercourse. Second, LL-37 exerts microbicidal effects to numerous microbes including those that cause STI. Third, its cytotoxicity is selective to sperm and not to the female reproductive tract. Furthermore, the spermicidal effects of LL-37 have been demonstrated in vivo in mice. Therefore, the availability of LL-37 as a vaginal spermicide/microbicide will empower women for self-protection against unwanted pregnancies and STI.

Centrifugation stress reduces the responsiveness of spermatozoa to a capacitation stimulus in in vitro-aged semen

Density gradient centrifugation of semen is commonly used in many assisted reproduction techniques. Although gradients have the potential to isolate and enrich motile and viable spermatozoa, the centrifugation force presents a stress factor to cell organelles and membranes. The objective of the study was to evaluate the impact of density gradient centrifugation stress on sperm capacitation dynamics, cell stability and the ability of spermatozoa to specifically respond to bicarbonate in extended semen undergoing in vitro ageing. Extended boar semen (n = 7) was stored for 12, 24, 72 and 120 h respectively at 17 °C before centrifugation and incubation in variations of an in vitro capacitation medium. The number of viable, acrosome intact sperm and motility parameters as assessed by computer-assisted semen analysis did not change during storage. Kinetic changes in viability (plasma membrane integrity) and intracellular calcium levels (calcium influx) during in vitro capacitation were assessed after preparation of semen samples with both, a Percoll and a sucrose gradient centrifugation, either only Percoll, only sucrose centrifugation or no centrifugation. Changes in the viable sperm population that could be specifically attributed as a response to either bicarbonate or calcium were determined. In in vitro-aged (>12 h stored) spermatozoa, centrifugation reduced the proportion of spermatozoa which specifically responded to the capacitating stimulus bicarbonate. Concomitantly, centrifugation increased the proportion of spermatozoa responding to calcium in absence of bicarbonate, thus indicating an increased sensitivity to incubation per se. Absence of centrifugation steps during semen preparation, revealed a highly conserved ability of in vitro-aged spermatozoa to specifically respond to bicarbonate. In conclusion, density gradient centrifugation alters the physiological property of spermatozoa for controlled capacitation, which may influence the success rates of centrifuged semen in assisted reproductive technologies and confound interpretation of capacitation assays.

Effects of various physical stress factors on mitochondrial function and reactive oxygen species in rat spermatozoa

The aim of the present study was to evaluate the effects of various physical interventions on the function of epididymal rat spermatozoa and determine whether there are correlations among these functional parameters. Epididymal rat spermatozoa were subjected to various mechanical (pipetting, centrifugation and Percoll gradient separation) and anisotonic conditions, and sperm motility, plasma membrane integrity (PMI), mitochondrial membrane potential (MMP) and intracellular reactive oxygen species (ROS) were evaluated. Repeated pipetting caused a loss in motility, PMI and MMP (P<0.05). Minimal centrifugation force (200 g) had no effect on motility, PMI and MMP, whereas an increase in the centrifugation force to 400 g or 600 g decreased sperm function (P<0.005). Percoll gradient separation increased total motility, PMI and MMP (P<0.05). However, the spermatozoa that were subjected to mechanical interventions showed high susceptibility to a ROS stimulant (P<0.005). Anisotonic conditions decreased motility, PMI and MMP, and hypotonic conditions in particular increased basal ROS (P<0.05). In correlation tests, there were strong positive correlations among total motility, PMI and MMP, whereas ROS showed no or negatively weak correlations with the other parameters. In conclusion, the physical interventions may act as important variables, affecting functional parameters of epididymal rat spermatozoa. Therefore, careful consideration and proper protocols for handling of rat spermatozoa and osmotic conditions are required to achieve reliable results and minimise damage.

Antimicrobial host defence peptide, LL-37, as a potential vaginal contraceptive

STUDY QUESTION

Does antimicrobial peptide, LL-37, inhibit sperm fertilizing ability?

SUMMARY ANSWER

Our results indicate that LL-37 inhibits mouse and human sperm fertilizing ability.

WHAT IS KNOWN ALREADY

LL-37, a cationic antimicrobial peptide, exerts its microbicidal effects through the disruption of microbial cytoplasmic membranes following its interaction with microbial surface anionic phospholipids. ALL-38 (an LL-37 close analogue: LL-37 + Ala at the N-terminus) is produced in the vagina 2-6 h post-intercourse from its precursor hCAP-18, a seminal plasma component. At this time, motile sperm have already swum into the uterine cavity, thus unexposed to ALL-38. Since sperm contain a substantial amount of acidic sulfogalactosylglycerolipid (SGG) on their surface, treatment of sperm with LL-37 may cause their membrane disruption in an analogous manner to that occurring on microbial membranes.

STUDY DESIGN, SIZE AND DURATION

Mouse/human sperm treated (2-30 min) with LL-37 in a physiological concentration range (up to 10.8 µM) were assessed for SGG-dependent LL-37 binding, and parameters relevant to fertilizing ability, namely motility and intactness of the sperm acrosome and plasma membrane. Ability of mouse sperm to fertilize eggs in vitro was also evaluated. Each study was performed with greater than or equal to three different sperm samples. The efficacy of LL-37 to inhibit sperm fertilizing ability in vivo was determined in female mice (n = 26 each for LL-37 treatment and no treatment), using sperm retrieved from 26 males.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human sperm samples were donated by fertile men. LL-37 was chemically synthesized and was biotinylated for sperm binding studies. Sperm motility was assessed by videomicroscopy and the acrosomal status by Coomassie blue staining of acrosome-intact mouse sperm or the exposure of CD46, an inner acrosomal membrane protein, of acrosome reacted human sperm. Sperm membrane permeabilization/disruption was assessed by the loss of hypo-osmotic swelling response, an incorporation of Sytox Green (a membrane impermeable fluorescent DNA dye), and electron microscopy. Mouse IVF was scored by the presence of two pronuclei in eggs 6 h post-insemination. Ability of mouse sperm to fertilize eggs in vivo was determined by the pregnancy outcome of female mice injected transcervically with sperm with or without LL-37.

MAIN RESULTS AND THE ROLE OF CHANCE

Biotinylated LL-37 bound to both mouse and human sperm and the binding was partially dependent on sperm surface SGG. Mouse and human sperm became immotile and underwent a premature acrosome reaction upon treatment with LL-37 at 3.6 and 10.8 µM, respectively. The initial action of LL-37 on both mouse and human sperm appeared to be through permeabilization/disruption of sperm surface membranes evidenced by the loss of hypo-osmotic swelling response, Sytox Green staining and electron microscopy revealing ultrastructural damage. Mouse sperm treated with 3.6 µM LL-37 lost the ability to fertilize eggs both in vitro and in vivo. All 26 female mice inseminated with sperm and LL-37 did not become pregnant. No apparent damage to the reproductive tract was observed as revealed by histological characterization in LL-37-inseminated mice and these females resumed fecundity following mating with fertile males.

LIMITATIONS, REASONS FOR CAUTION

Direct demonstration that LL-37 treated human sperm fail to fertilize eggs was limited by legal restrictions on obtaining human eggs for such use.

WIDER IMPLICATIONS OF THE FINDINGS

Our results reveal selective inhibitory effects of LL-37 on sperm fertilizing ability in mice without apparent impairment to the female reproductive tract. LL-37 is therefore a promising candidate to be developed into a vaginal contraceptive with microbicidal activity.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Grand Challenges Explorations grant from the Bill & Melinda Gates Foundation (OPP1024509), Canadian Institutes of Health Research (MOP119438 & CCI82413) and International Collaboration and Exchanges NSFC of China (No.30611120525). There are no competing interests to declare.

[Is there an association between sperm normal morphology and their kinetic displacement?]

OBJECTIVE

To evaluate if there exist an association between the % of normal forms and the kinetic characteristics in human spermatozoa

MATERIAL AND METHODS

A retrospective study was performed to analyze semen samples of 203 patients by Computer Assisted Semen Analysis. Sperm morphology was evaluated by the aid of a micrometric objective according to strict criteria. Only the patients presenting >20 x 106 sperm/ml and > 50% of progressive motility were included. Data from 168 patients were divided according to the % of normal forms in three groups a) <4% (n=22), b) between 4-13% (n=89) and c) >14% (n=57). Data collected among groups were compared. In order to select a motile sperm population 35 samples were treated by a discontinuous gradient and the % of normal forms as well as motility parameters evaluated before and after selection.

RESULTS

The kinetic analysis showed that sperm concentration, the % of motile and rapid spermatozoa (>25 microm/s) as well as the average path velocity (VAP) and the lateral head displacement (LHD) were increased in association with the % of normal spermatozoa presenting the lowest values in the group <4% with respect to the > or = 14% group, (p<0.05). Linearity (LIN) remained constant among groups. Kinetic parameters and sperm morphology were significantly increased (p<0.0001) in the selected samples Results showed that the use of gradients even in teratozoospermic samples improves significantly the % of normal forms respect to baseline values (p<0.0002).

CONCLUSIONS

Our results would support the hypothesis that morphologically better spermatozoa would be associated with those with better movement parameters measured in an objective way. In this manner we could suggest that in vivo the best spermatozoa would comprise one "elite" in the journey through the fertilization site.

Integrated morphophysiological assessment of two methods for sperm selection in bovine embryo production in vitro

Extensive work was done regarding the ability of Swim up and Percoll gradient to select functional sperm for in vitro embryo production (IVP) systems. The aim of this work was to compare Swim up and Percoll as methods of sperm selection by ultrastructural, biochemical and functional studies. Frozen-thawed semen from two bulls (Experiments 1 and 2, respectively) were treated using Swim up or Percoll discontinuous gradients. Motility, sperm membrane ultrastructure, sperm proteins, in vitro embryo production (insemination doses, cleavage, embryo yield and quality) and embryo sex ratio were scored and compared. Electron transmission microscopy of outer sperm membranes showed higher (P<0.05) percentage of sperm with lost acrosomes in Percoll treated samples compared to Swim up. A differential protein pattern was also detected. When in vitro embryo production was performed, Percoll gradient produced higher (P<0.05) number of fertilizing doses (7.6 versus 5.9, Bull 1; 13.5 versus 7.8, Bull 2) and higher sperm motility (90% versus 76.6%, Bull 1; 81.7% versus 68.3%, Bull 2) than Swim up. The percentage of cleavage (Day 3) was similar in both treatment groups, whereas embryo production rate (Day 7) was higher (39.4% versus 30.2%, Bull 1; 38% versus 32.4%, Bull 2; P<0.05) when Percoll gradient was used. The percentage of hatched embryos (Day 11) and sex ratio did not differ. Total cell counting and embryo differential staining (inner cell mass and trophoblast cells) of Day 7 embryos showed that Percoll treated sperm produced better quality embryos compared to Swim up. We concluded that Percoll had a better performance selecting sperm and an enhanced capacity for embryo production when compared with the Swim up procedure; this could be attributed to a better acrosome exocytosis, associated to the absence of certain membrane proteins.

Glycodelin-S in Human Seminal Plasma Reduces Cholesterol Efflux andInhibits Capacitation ofSpermatozoa

Tight control of sperm capacitation is important for successful fertilization. Glycodelin-S is one of the most abundant glycoproteins in the human seminal plasma. However, its function is unclear. We investigated the role of glycodelin-S on capacitation of human spermatozoa. Binding kinetics experiments demonstrated the presence of two saturable and reversible binding sites of glycodelin-S on human spermatozoa. Differently glycosylated other isoforms of glycodelin, glycodelin-A and -F, did not compete with glycodelin-S for these binding sites, suggesting that the glycodelin-S binding sites are different from those of the other isoforms. Indirect immunofluorescent staining revealed specific binding of glycodelin-S around the sperm head. This immunoreactivity was greatly reduced in spermatozoa that had migrated through the cervical mucus surrogates. Glycodelin-S at physiological concentrations significantly reduced the bovine serum albumin and cyclodextrin-induced cholesterol efflux and down-regulated the adenylyl cyclase/protein kinase A/tyrosine kinase signaling pathway, resulting in suppression of capacitation. Deglycosylation abolished glycodelin-S binding and the effect of glycodelin-S on bovine serum albumin-induced capacitation. This indicates that the carbohydrate moiety of glycodelin-S is critical for the function of the molecule. It is concluded that glycodelin-S in seminal plasma maintains the uncapacitated state of human spermatozoa.

Percoll Gradient-Centrifuged Capacitated Mouse Sperm Have Increased Fertilizing Ability and Higher Contents of Sulfogalactosylglycerolipid and Docosahexaenoic Acid-Containing Phosphatidylcholine Compared to Washed Capacitated Mouse Sperm1

Although Percoll gradient centrifugation has been used routinely to prepare motile human sperm, its use in preparing motile mouse sperm has been limited. Here, we showed that Percoll gradient-centrifuged (PGC) capacitated mouse sperm had markedly higher fertilizing ability (sperm-zona pellucida [ZP] binding and in vitro fertilization) than washed capacitated mouse sperm. We also showed that the lipid profiles of PGC capacitated sperm and washed capacitated sperm differed significantly. The PGC sperm had much lower contents of cholesterol and phospholipids. This resulted in relative enrichment of male germ cell-specific sulfogalactosylglycerolipid (SGG), a ZP-binding ligand, in PGC capacitated sperm, and this would explain, in part, their increased ZP-binding ability compared with that of washed capacitated sperm. Analyses of phospholipid fatty acyl chains revealed that PGC capacitated sperm were enriched in phosphatidylcholine (PC) molecular species containing highly unsaturated fatty acids (HUFAs), with docosahexaenoic acid (DHA; C22: 6n-3) being the predominant HUFA (42% of total hydrocarbon chains of PC). In contrast, the level of PC-HUFAs comprising arachidonic acid (20:4n-6), docosapentaenoic acid (C22:5n-6), and DHA in washed capacitated sperm was only 27%. Having the highest unsaturation degree among all HUFAs in PC, DHA would enhance membrane fluidity to the uppermost. Therefore, membranes of PGC capacitated sperm would undergo fertilization-related fusion events at higher rates than washed capacitated sperm. These results suggested that PGC mouse sperm should be used in fertilization experiments and that SGG and DHA should be considered to be important biomarkers for sperm fertilizing ability.

Sperm preparation for ART

The onset of clinical assisted reproduction, a quarter of a century ago, required the isolation of motile spermatozoa. As the indication of assisted reproduction shifted from mere gynaecological indications to andrological indications during the years, this urged andrological research to understand the physiology of male germ cell better and develop more sophisticated techniques to separate functional spermatozoa from those that are immotile, have poor morphology or are not capable to fertilize oocytes. Initially, starting from simple washing of spermatozoa, separation techniques, based on different principles like migration, filtration or density gradient centrifugation evolved. The most simple and cheapest is the conventional swim-up procedure. A more sophisticated and most gentle migration method is migration-sedimentation. However, its yield is relatively small and the technique is therefore normally only limited to ejaculates with a high number of motile spermatozoa. Recently, however, the method was also successfully used to isolate spermatozoa for intracytoplasmic sperm injection (ICSI). Sperm separation methods that yield a higher number of motile spermatozoa are glass wool filtration or density gradient centrifugation with different media. Since Percoll as a density medium was removed from the market in 1996 for clinical use in the human because of its risk of contamination with endotoxins, other media like IxaPrep, Nycodenz, SilSelect, PureSperm or Isolate were developed in order to replace Percoll. Today, an array of different methods is available and the selection depends on the quality of the ejaculates, which also includes production of reactive oxygen species (ROS) by spermatozoa and leukocytes. Ejaculates with ROS production should not be separated by means of conventional swim-up, as this can severely damage the spermatozoa. In order to protect the male germ cells from the influence of ROS and to stimulate their motility to increase the yield, a number of substances can be added to the ejaculate or the separation medium. Caffeine, pentoxifylline and 2-deoxyadenosine are substances that were used to stimulate motility. Recent approaches to stimulate spermatozoa include bicarbonate, metal chelators or platelet-activating factor (PAF). While the use of PAF already resulted in pregnancies in intrauterine insemination, the suitability of the other substances for the clinical use still needs to be tested. Finally, the isolation of functional spermatozoa from highly viscous ejaculates is a special challenge and can be performed enzymatically to liquefy the ejaculate. The older method, by which the ejaculate is forcefully aspirated through a narrow-gauge needle, should be abandoned as it can severely damage spermatozoa, thus resulting in immotile sperm.

Functional changes and motility characteristics of Japanese Black bull spermatozoa separated by Percoll

Spermatozoa from two Japanese Black bulls (Bull-ATF and Bull-KTG) were separated by centrifugation at 700 x g for 15min in modified TALP with or without 45-90% Percoll. Control washed spermatozoa and those collected from the bottom of 45 and 90% Percoll fractions were examined for viability and membrane integrity (using Hoechst bis-benzimide 33258 or propidium iodide and 6-carboxyfluorescein diacetate (PI-CFDA)), acrosomal status (using fluorescence isothiocyanate (FITC) conjugated Pisum Sativum agglutinin (PSA) and Peanut agglutinin (PNA), Naphthol Yellow S and Erythrosin B (NE) or triple staining (TS)), capacitation status (using chlortetracycline (CTC)), motility characteristics (using a computer-assisted sperm motion analysis system (CASA)) and for in vitro fertility. Percoll-separated spermatozoa showed greater viability and membrane integrity than controls, as determined by supravital staining. Differences were observed in the results regarding viability and acrosomal status of spermatozoa among sperm staining methods. Bull-ATF, which showed significantly greater in vitro fertility than Bull-KTG (P<0.05), showed a significantly higher rate of CTC-B-pattern (capacitated) spermatozoa (P<0.01) than Bull-KTG. The motility characteristics of control washed spermatozoa and those separated by 45-90% Percoll were analyzed by CASA. More motile and progressively motile spermatozoa were observed in the fraction at the bottom of the 90% Percoll solution than in the 45% Percoll fraction or in controls (P<0.01). Moreover, the spermatozoa of Bull-KTG, which showed lower in vitro fertility than Bull-ATF, did not show significant differences in motility from those of Bull-ATF. These results provided basic information about Japanese Black bull spermatozoa, and suggested that spermatozoa with greater motility and viability can be obtained by Percoll separation than without separation. However, Percoll separation did not enhance their in vitro fertility.

Towards a more precise assay of sperm function in egg binding

Historically, the treatment of severe male factor infertility has relied on donor sperm insemination. A decade ago the option of treating severe male factor infertility with partner sperm became a viable alternative. With the introduction of intracytoplasmic sperm injection (ICSI) in conjunction with in vitro fertilization (IVF), only men who produce no sperm are denied the option of fathering their own children. The use of ICSI has been extended to couples with mild male factors. Despite the known genetic risks (both inherent and de novo) of ICSI to offspring, couples with male factors as part of their infertility problem often prefer ICSI to standard IVF, due to apprehension that their sperm might not otherwise succeed in fertilization. This apprehension would be alleviated if an assay for the egg binding capability of human sperm were available. We examine here the possibility that recombinant human zona pellucida 3 (rec hZP3), the primary sperm receptor sulfoglycoprotein of the egg zona pellucida (ZP), be used as a human ZP surrogate for assessing sperm ability to bind to the ZP. Unlike human eggs, which cannot be obtained for this purpose, rec hZP3 can be produced in quantity. An efficient assay can be established by incubating sperm with rec hZP3 coated to a microwell plate. Infertile men with sperm having ability to bind to rec hZP3 can be advised to select standard IVF or intrauterine insemination, which have fewer genetic and medical risks.

Use of atomic force microscopy for morphological and morphometric analyses of acrosome intact and acrosome-reacted human sperm

The objective of this study was to use atomic force microscopy (AFM), with submicron resolution, for morphophologic and morphometric analyses of acrosome intact and acrosome-reacted human sperm heads. A mixed population of acrosome intact and reacted sperm was produced by treating capacitated sperm with A23187, which induced the acrosome reaction in approximately 50% of total sperm population. This A23187-treated sperm suspension was then plated onto a coverslip and acrosome reacted sperm were preidentified by their specific staining with rhodamine-conjugated Concanavalin A. The sperm coverslip was then air-dried and scanned by a Nanoscope IIIa atomic force microscope, using the contact mode. Top and side view images processed through the illuminate mode revealed three dimensional sperm head contour, with the highest point situated in the head posterior in both acrosome intact and acrosome reacted sperm. Maximum height, length, and width measured in 50 acrosome intact and 50 acrosome-reacted sperm were the same in both populations. However, head length at half maximum height was significantly decreased in acrosome reacted sperm (2.99 +/- 0.24 microm vs. 3.56 +/- 0.32 microm of acrosome intact sperm), due to the sudden change of the height contour from the maximum peak to the anterior tip of acrosome-reacted sperm. Our results described here can therefore be used to differentiate acrosome intact and reacted sperm from each other. This would allow future studies on subcellular changes, related to the acrosome reaction, at the submicron resolution level under more physiological conditions, since AFM does not require fixing or staining of the samples.

Sulfogalactosylglycerolipid is involved in human gamete interaction

Recent results from our laboratory have revealed the role of sulfogalactosylglycerolipid (SGG) in mouse sperm-zona pellucida (ZP) binding. In this report, we demonstrated the presence of SGG in Percoll-gradient centrifuged (PGC) human sperm by high performance thin layer chromatography with orcinol and Azure A staining, specific for glycolipids and sulfolipids, respectively. SGG in human PGC sperm was quantified by its affinity to Azure A to be 12-15 mol% of sperm lipids. Indirect immunofluorescence revealed that SGG existed on both live and aldehyde fixed human sperm in the head region. Pretreatment of human PGC sperm with affinity purified antiSGG Fab markedly inhibited sperm binding to the ZP in a concentration dependent manner, without any changes in the spontaneous acrosome rate or sperm motility parameters. Fluorescently labeled SGG liposomes also bound uniformly to isolated human ZP, while fluorescently labeled galactosylglycerolipid (GG, SGG's parental lipid) or phosphatidylserine (PS, negatively charged like SGG) liposomes did not. All of these results suggested the role of human sperm SGG in ZP binding.

Comparison of sperm preparation methods: effect on chromatin and morphology recovery rates and their consequences on the clinical outcome after in vitro fertilization embryo transfer

The aim of this study was to evaluate the efficacy of swim-up, PureSperm gradient centrifugation and glass-wool filtration methods for semen preparation and to assess the possible enhancement of the quality of the subpopulation of spermatozoa in terms of sperm concentration, morphology and chromatin condensation. Moreover, to determine the effect of this semen processing technique on the clinical outcome after in vitro fertilization embryo transfer (IVF-ET). A total of 180 semen samples of patients' husbands who were undergoing IVF therapy were prepared by swim-up (G1, n = 60), PureSperm gradient centrifugation (G2, n=60) or glass-wool (G3, n=60) methods. Chromatin condensation was assessed by Chromomycin (CMA3), whereas sperm morphology was evaluated according to strict criteria. In all three semen processing methods, the percentage of chromatin condensed and morphologically normal spermatozoa was higher after semen processing in comparison with native semen samples. The proportion of normal chromatin condensed spermatozoa prepared in glass-wool filtration was significantly higher than that in swim-up (G.I, p=0.02) or PureSperm (G.II, p=0.001). In addition semen processing with PureSperm yields significantly a higher percentage of morphologically normal spermatozoa than swim-up (p < 0.001) or glass-wool method (p < 0.002). However, the fertilization, implantation and pregnancy rates, in turn were similar in all semen preparation methods. In conclusion, PureSperm gradient centrifugation yields a higher percentage of morphologically normal spermatozoa than shown in traditional swim-up or glass-wool filtration. However, the percentage of chromatin condensed spermatozoa was significantly higher after semen processing via glass-wool in comparison with the other two methods. Nevertheless, there were no significant difference in the fertilization, implantation and pregnancy rates of sperm prepared by means of swim-up, PureSperm or glass-wool filtration. Therefore, glass-wool filtration should be recommended as the first choice for semen preparation for Intracytoplasmic sperm injection (ICSI) technique as the natural selection is bypassed. Whereas, swim-up and PureSperm should be used for semen processing in IVF programme.

Comparisons of oocyte maturation times and of three methods of sperm preparation for their effects on the production of goat embryos in vitro

Various times of in vitro maturation of oocytes, and three methods of separating spermatozoa from frozen-thawed semen (Percoll density-gradient centrifugation, swim-up, and glass-wool filtration), were compared for their effects on goat embryo production in vitro. Cumulus-oocyte-complexes (COCs) from abattoir ovaries were matured in M199 supplemented with 10% fetal calf serum and hormones. In Experiment 1, COCs were fixed at 4 h intervals from 0 to 27 h of culture to assess oocyte nuclear maturation. A higher proportion cultured for 27 h than for 24 h were in Metaphase II (27/37, 73% vs. 18/33, 55%, P < 0.05). In Experiment 2, the effects of separation methods on total numbers and numbers of membrane-intact spermatozoa, and the acrosome reaction were compared. Total numbers after Percoll density-gradient centrifugation were approximately 4 times higher than after swim-up and approximately 2 times higher than after glass-wool filtration (P < 0.001). Progression of the acrosome reaction was not affected differentially. In Experiments 3 and 4, after 27 h of culture the COCs were inseminated with sperm isolated by the three methods. In Experiment 3, presumptive zygotes were examined for pronucleus (PN) formation at 6, 12, 18 and 24 h post-insemination. At 12 h, male PN formation rate from Percoll-treated spermatozoa was higher than from sperm subjected to swim-up and glass-wool treatments (20/37, 54% vs. 6/37, 16% and 6/38, 16%, respectively; P < 0.001). In Experiment 4, embryos were compared for cleavage at 48 h and development into blastocysts, hatching rates and cell number at 192 h. The rates of cleavage and blastocyst formation in the Percoll-treated group were higher (P < 0.05) than in the swim-up and glass-wool groups (62% and 18% vs. 50% and 11%, and 45% and 8%, respectively). Similarly, the mean cell number in the Percoll group was higher (P < 0.05) than in the swim-up and glass-wool groups (167 +/- 5 vs. 149 +/- 4 and 126 +/- 4, respectively). We conclude that Percoll density-gradient centrifugation is superior to the other two methods for separating goat spermatozoa from frozen-thawed semen in preparation for IVF.

Anti-SLIP1-reactive proteins exist on human spermatozoa and are involved in zona pellucida binding

Sulpholipid immobilizing protein 1 (SLIP1) is an evolutionarily conserved 68 kDa plasma membrane protein, present selectively in germ cells. We have previously shown that mouse sperm SLIP1 is involved in sperm-zona pellucida (ZP) binding. In this report, we extended our study to the human system. Immunoblotting demonstrated that anti-SLIP1-reactive proteins (mol. wt 68 and 48 kDa) could be extracted from human spermatozoa by an ATP-containing solution, a result that is consistent with observations in other species. Direct immunofluorescence, using Cy3-conjugated anti-SLIP1 IgG, revealed SLIP1 staining over the acrosomal region, with higher intensity at the posterior area. Using the human sperm-ZP binding assay, we demonstrated that pretreatment of human spermatozoa from three donors with anti-SLIP1 IgG revealed lower numbers of zona-bound spermatozoa, as compared to the corresponding control spermatozoa treated with normal rabbit serum IgG. This decrease in zona pellucida binding was not from an antibody-induced decline in sperm motility or an increase in the premature acrosome reaction. The results strongly suggest that anti-SLIP-reactive proteins on human spermatozoa play an important role in ZP binding.

Role of egg sulfolipidimmobilizing protein 1 on mouse sperm-egg plasma membrane binding

We have shown that sperm sulfolipidimmobilizing protein 1 (SLIP1, molecular mass of 68 kDa), a sulfogalactosylglycerolipid (SGG)-binding protein, is significant in sperm-zona pellucida (ZP) interaction. The objective of this study was to localize SLIP1 on the egg and determine its role in gamete interaction. Immunofluorescence and immunoprotein A gold electron microscopy localized SLIP1 to the egg plasma membrane. In vitro gamete binding, using zona-free eggs preincubated with antiSLIP1 Fab before coincubation with sperm, showed a significant, dose-dependent decrease in sperm-egg plasma membrane binding. Similar results were obtained when affinity-purified antiSLIP1 IgG was used for egg pretreatment. The significance of egg SLIP1 in sperm-egg plasma membrane binding was further demonstrated by a decrease (36-52%) in in vitro fertilization when zona-intact eggs were pretreated with antiSLIP1 IgG. Since SLIP1 has been shown to bind SGG in vitro, we investigated the possibility that sperm SGG may participate in sperm-egg plasma membrane binding through egg SLIP1. Pretreatment of sperm with antiSGG Fab prior to coincubation with zona-free eggs resulted in a dose-dependent decrease in sperm-egg plasma membrane binding. Collectively, these findings strongly suggest a role for egg SLIP1 in sperm-egg plasma membrane interaction, which may be through its binding to sperm SGG.

Sperm separation in patients with urogenital infections

A total of 196 patients attending the Center of Dermatology and Andrology, Giessen, Germany, were examined for fertility problems. Polymorphonuclear elastase, reactive oxygen species (ROS) and the number of round and peroxidase-positive cells were investigated in addition to routine semen analysis. The ejaculates were also analysed before and after sperm separation by means of swim-up or glass wool filtration. In 20 cases of leukocytospermia, sperm concentration, motility, viability, production of reactive oxygen species, and the number of peroxidase-positive cells were evaluated before and after glass wool filtration. The results show that ROS production by viable spermatozoa is highly correlated with the concentration of PMN elastase and the number of both peroxidase-positive and round cells. Multiple regression analysis with motility as dependent parameter showed the number of round cells (n = 91; r = -0.332; P = 0.0030) to be the most important parameter affecting motility, while ROS mainly affects the viability of spermatozoa (n = 69; r = 0.250; P = 0.0107). In the case of leukocytospermia, glass wool filtration significantly reduced the number of peroxidase-positive cells and ROS production (P = 0.0098 and P = 0.0005, respectively). Receiver operating characteristic (ROC) curve analysis for ROS production in the ejaculate using a concentration of 1.000 ng ml-1 PMN elastase as decisive parameter resulted in a cut-off value of 49,489.9 counts 10(-7) viable spermatozoa. The statistical parameters were: Sensitivity: 63.2%, specificity: 100%, positive predictive value: 100%, negative predictive value: 36.1%.

Preparation by differential gradient centrifugation is better than swim-up in selecting sperm with normal morphology (strict criteria)

OBJECTIVE

To evaluate two commonly used methods of sperm preparation with respect to their effects on sperm morphology (strict criteria).

DESIGN

Auto-controlled, split sample study performed on the semen of 74 male partners of couples enrolled for IVF.

SETTING

In vitro fertilization and andrology laboratories at a tertiary care, major teaching hospital.

PATIENT(S)

Seventy-four male partners of couples who were scheduled to undergo IVF.

INTERVENTION(S)

Equal halves of the same semen sample were evaluated for strict criteria sperm morphology before and after preparation by differential gradient centrifugation using Percoll (Pacific Andrology, Montrose, CA) and by the standard swim-up method.

MAIN OUTCOME MEASURE(S)

The percentage of morphologically normal sperm was assessed using strict criteria before and after the two methods of sperm preparation. Specific parameters studied were individual abnormalities of the head, midpiece, and tail.

RESULT(S)

Sperm preparation using differential gradient centrifugation with Percoll produced a significantly greater number of specimens with normal sperm morphology and also showed higher absolute quantitative improvement over the swim-up method. The two methods were comparable in regard to their effects on specific sperm abnormalities (i.e., head, midpiece, and tail defects).

CONCLUSION(S)

The differential gradient sperm separation method using Percoll is superior to the swim-up method for selecting sperm with normal morphology as assessed by strict criteria. Because sperm morphology as assessed by strict criteria is a good predictor of oocyte fertilization, this method can be recommended as the method of choice for assisted reproductive technology laboratories. Use of this method may help improve outcome by increasing fertilization rates.

Differentiation of ejaculates showing reactive oxygen species production by spermatozoa or leukocytes

Differences between subgroups and correlations between reactive oxygen species (ROS), sperm motility, concentration of leukocytes and viability in semen samples from 143 men were investigated. Patients with azoospermia or leukocytospermia were excluded from the study. Spermatozoa were separated by means of glass wool filtration. Reactive oxygen species were determined by means of luminol chemiluminescence before and after sperm separation; thereafter, normozoospermic and oligozoospermic patients were divided into three subgroups using the mean of all patients investigated (17462 count 10(-7) viable spermatozoa) as cut-off value as follows: G1--high reactive oxygen species production in native semen and after glass wool filtration; G2--high production of reactive oxygen species only in native semen; G3--low levels of reactive oxygen species before and after glass wool filtration. In general, reactive oxygen species were significantly higher in oligozoospermic samples than in normozoospermic samples. In men with normal sperm count, ROS production correlated significantly with the number of leukocytes in the ejaculate before glass wool filtration, but not thereafter. Glass wool filtration is useful to distinguish between sperm samples in which reactive oxygen species are generated by leukocytes and those in which reactive oxygen species are excessively generated by the spermatozoa themselves.

Improved motile sperm recovery by a hyperosmotic Percoll gradient

PURPOSE

Our purpose was to investigate whether a new, relatively hyperosmotic Percoll gradient, Enhance-S, can improve total motile sperm recovery rates compared with the commonly used Percoll gradient Perception.

METHODS

Semen specimens from each of 17 donors were divided into two equal aliquots. One part was washed using Percoll Perception, while the other was prepared using Percoll Enhance-S.

RESULTS

Compared to the unwashed specimen, sperm motion characteristics (motility and velocity) improved significantly after Percoll separation using either the Perception or the Enhance-S gradient. There was no difference in motility or velocity in spermatozoa recovered after wash with either of the two preparations. However, the total motile sperm recovery was significantly higher using the Percoll Enhance-S gradient than with the Percoll Perception gradient (P < 0.0024).

CONCLUSION

The new Percoll Enhance-S gradient provides significantly more total motile sperm than the Percoll Perception gradient.

Influence of artificial stimulation on unprocessed and Percoll-washed cryopreserved sperm

The ability of pentoxifylline and 2-deoxyadenosine to stimulate sperm motility and motion characteristics was assessed in unprocessed and processed (Percoll-separated) cryopreserved specimens. Specimens from 12 healthy volunteers were obtained, and the motion characteristics were analyzed; half the sample was immediately cryopreserved and the other was washed using the Percoll gradient technique. To study stimulation, samples were thawed and divided into four aliquots: One was used as a control, and the others were incubated with 2.5 mM 2-deoxyadenosine, 2.5 mM pentoxifylline, or 5.0 mM pentoxifylline for 60 min. Sperm characteristics were analyzed on a sperm motion analyzer at 0 and 60 min incubation. In both unprocessed and processed samples, percentage motility improved significantly after stimulation with 2-deoxyadenosine or pentoxifylline (p = .003 or p = .0002, respectively); other characteristics improved to varying extent after 2-deoxyadenosine or pentoxifylline stimulation. Comparison after stimulation revealed that sperm motion characteristics in the unprocessed specimen were similar to sperm motion characteristics in the processed group.

Preparation and recovery of frozen-thawed bovine spermatozoa via various sperm selection techniques employed in assisted reproductive technologies

A number of semen manipulative techniques are currently available to remove the undesirable spermatozoa, debris and other factors and to increase sperm quality. The use of motility stimulants such as caffeine or others could optimize the recovery and quality of frozen-thawed spermatozoa processed by a variety of sperm selection techniques. Frozen-thawed specimens from 5 bulls were slowly diluted and washed with Ham's F-10 medium containing 3% BSA (w/v) and 0 or 2 mM caffeine. Aliquots containing approximately 50 x 10(6) total sperm cells were used for conventional sperm wash, swim-up, Percoll density gradient centrifugation (80, 70, 55 and 40% Percoll gradients) and Sephadex (SpermPrep I) filtration. Quantitative and qualitative characteristics of selected spermatozoa included: total sperm (x 10(6)), percentage and grade (0 to 4) of motility, percentage of spermatozoa with coiled tails and response to the hypoosmotic swelling (HOS) test (percentage of swollen spermatozoa). When compared to washed specimens, fewer spermatozoa were recovered via the swim-up, Percoll and SpermPrep I filtration methods. Quantitative and qualitative characteristics of these spermatozoa improved further after processing with Ham's F-10 containing 2 mM caffeine, followed by selection via the various techniques. Enhancement of sperm motility, in conjunction with the most appropriate sperm selection technique, represents an efficient method for the recovery of spermatozoa with improved qualitative characteristics.

Cholesterol and phospholipid levels of washed and percoll gradient centrifuged mouse sperm: presence of lipids possessing inhibitory effects on sperm motility

Levels of DNA, cholesterol, and phospholipids of mouse caudal epididymal and vas deferens sperm that were processed through simple washing and Percoll gradient centrifugation were measured. The DNA and cholesterol contents of washed sperm and Percoll gradient centrifuged (PGC) sperm (DNA = 3.6 +/- 0.3 pg/sperm and 3.4 +/- 0.3 pg/sperm, respectively; cholesterol = 0.219 +/- 0.057 nmole/microgram DNA and 0.224 +/- 0.030 nmole/microgram DNA, respectively, for washed and PGC sperm) were not significantly different from each other; however, the phospholipid level of PGC sperm was only one half of that of washed sperm (0.315 +/- 0.071 nmole/microgram DNA versus 0.720 +/- 0.075 nmole/microgram DNA, respectively). The presence of 0.3% bovine serum albumin (BSA) in the culture medium used in sperm washing did not change the cholesterol and phospholipid contents of washed sperm. Similarly, the cholesterol and phospholipid levels of washed sperm and PGC sperm that were further incubated in BSA-containing medium for 30 min remained the same. Interestingly, substantial amounts of lipids, as determined by the cholesterol and phospholipid levels, were released into the supernatants of the sperm washes, and sperm needed to be washed at least twice to ensure their stable levels of cholesterol and phospholipids. The lipid mixture in the first sperm wash supernatant was shown to have inhibitory effects on PGC sperm motility.

Improvements and short-term viability of mouse epididymal spermatozoa recovered through the Spermprep™ filtration method

This study was designed to determine the effects of Sephadex filtration (SpermprepI method) on the separation of motile, morphologically normal, mouse epididymal spermatozoa and to study the viability of the recovered spermatozoa over a 3-h incubation period. Spermatozoa were harvested from the caudae epididymie (5 animals per run or replication; n=10) following bilateral testicular excision, after which they were incubated in 2-ml of Test-Yolk buffer (TYB) at 37 degrees C for 15-min. The specimens were then split into 2 1-ml aliquots, with Aliquot 1 as the control and Aliquot 2 as the filtered sample. The SpermprepI column was employed according to the manufacturer's specifications using TYB. During filtration (10-min), 2 different fractions were obtained: first 5-min (Sample 1) and second 5-min (Sample 2). The 2 fractions were evaluated and incubated at 37 degrees C and assessed for percentage of motility and grade of motility (0 to 4) every 30-min for 3-h. Filtration resulted in a significant improvement in the percentage and grade of motility (91.5% and 3.0 vs 76.5% and 2.5, respectively). The results indicate that filtration with the SpermprepI method improved the percentage and grade of motility (P<0.05) but not the percentage of normal morphology of the spermatozoa. In addition, the SpermprepI method enabled the recovery of 45% (8.3x10(6) spermatozoa recovered) of the total number of spermatozoa processed in the control aliquot (18.4x10(6) spermatozoa), which is consistent with previous observations. Most importantly, filtered spermatozoa incubated for 3-h showed a greater percentage and grade of motility than the control spermatozoa (63% and 1.66 vs 39% and 0.82, respectively. The SpermprepI filtration method selected a higher proportion of quality spermatozoa, which also displayed significant long-term motility (longevity) during in vitro incubation.

Identification of two human sperm populations using flow and image cytometry

Flow cytometric studies of human sperm from fertile men display a constant and characteristic bimodal nonartifactual DNA pattern confirming the existence of two distinct populations. The main population is represented by a peak followed by a shoulder ("marginal population"). The appearance of this marginal population fluctuates with either freezing and thawing or with Percoll gradient centrifugation. We have analyzed both the main and marginal sperm populations by flow cytometry after cell sorting, laser scanning cytometry, light microscopic evaluation, and their sensitivity to DNase digestion. We have observed that the marginal population detected in fertile men represents a sperm group altered in the nuclear condensation, yielding unstable chromatin which appears more stainable with propidium iodide.

Sperm function and its manipulation for microassisted fertilization

Comprehension of the intricate complexities of sperm function is clearly crucial to the success of attempts to manipulate it for the purposes of assisted conception. This is particularly important when considering various procedures for microassisted fertilization since these bypass critical physiological events that are mandatory for normal fertilization, to varying degrees. Methylxanthine derivatives such as pentoxifylline are useful agents for the management of oligoasthenozoospermic patients. This is particularly so for procedures such as SUZI where adequate motility of spermatozoa injected into the perivitelline space is crucial for fusion with the vitelline membrane to achieve fertilization. The generation of minute concentrations of reactive oxygen species in vitro may prove to be a valuable technique in this respect, in the light of recent evidence for their involvement in capacitation and hyperactivation. Induction of the acrosome reaction by non-invasive, non-toxic agents should markedly improve success rates for microassisted fertilization. Acrosin appears to play a central role in this and, therefore, it would seem prudent to monitor levels of acrosin activity in samples of spermatozoa used in assisted conception procedures. With respect to microassisted fertilization, the potential to select recently acrosome-reacted spermatozoa coated by activated acrosin promises to be a major improvement. Current methods employed for determination of the fertilization potential of spermatozoa are clearly inadequate (Polansky and Lamb, 1988; Aitken, 1990). In fact, the prevailing evidence suggests that no single parameter of sperm function reflects this potential (Zaneveld and Jeyendran, 1988). Therefore, we have both a scientific and a moral responsibility to investigate these processes further. Subsequently, we should be in a position to identify individual gametes with the potential for fertilization and so utilize procedures that result in maximal fertilization rates with minimal risk of polyploidy or abnormality.

Clinical pregnancy rate after the double method wash and intrauterine insemination

The protocol for intrauterine insemination (IUI) involves sperm processing using different methods that have produced varying results. These sperm wash methods do not take into consideration the problems of the exact timing of ovulation and the requirements of sperm cells at different stages of capacitation. The objectives of this study were 1) to use the double method wash previously reported to produce a mixture of different populations of sperm cells and determine the pregnancy outcome after IUI and 2) to compare the sperm kinematic parameters after the double method wash with those after the centrifuge (or whole-population) wash method. Patients were divided into either the double method group (n = 119) or the centrifuge method group (n = 76). The Hamilton-Thorn HTM-C automated sperm motility analyzer (Hamilton-Thorn Research, Danvers, MA) was used to analyze sperm motility parameters. Pregnancy outcomes were evaluated after controlled ovarian stimulation and IUI. An almost 2-fold increase was seen in the pregnancy rate with the double method wash compared with the centrifuge method wash. Sperm motility and velocity were also enhanced in the double method wash groups. The results support the usefulness of the double method wash for the preparation of sperm for IUI.

Improved preservation of rat epididymal sperm for high-resolution low-voltage scanning electron microscopy (HR-LVSEM)

Various fixation protocols were used in an attempt to improve preservation of rat epididymal sperm for high-resolution low-voltage scanning electron microscopy (HR-LVSEM). Wash solutions and fixatives of different composition and osmolarity were tested. Paraformaldehyde and glutaraldehyde concentrations were varied between 0.5% and 3%. Ruthenium red was tested as an additive in both primary fixation and postfixation, or in postfixation alone. HR-LVSEM revealed various degrees of ruffing, folding, blebbing, and peeling off of the plasma membrane, as well as holes of different sizes. The plasma membrane overlying the acrosome and the connecting piece proved to be particularly sensitive to varying fixation conditions. Consistent topographical differences were revealed among the different domains over the sperm head. Most of the differences were considered to be artifacts. Their consistency, however, suggests that structural and biochemical differences exist either within the membrane or in the structures subjacent to the membrane. Primary fixation turned out to be less critical than postfixation. Preservation of a smooth plasma membrane without holes could only be achieved when primary fixation in low aldehyde concentrations, with or without ruthenium red, was followed by postfixation with OSO4 and 1,000 ppm ruthenium red. Examination of thin sections of the same material confirmed that even a considerable number of small holes are difficult to detect in transmission electron microscopy. These results show that with the recent increase in resolution of LVSEM there is need for further effort to improve sample processing.

Intrauterine insemination after ovarian stimulation as a treatment for subfertility because of subnormal semen: a prospective randomized controlled trial

OBJECTIVE

To determine whether intrauterine insemination (IUI) after ovarian stimulation with human menopausal gonadotropin (hMG) gives a better pregnancy rate (PR) than natural intercourse in couples with subfertility because of subnormal semen.

DESIGN

Prospective randomized controlled trial.

SETTING

University based subfertility clinic.

PATIENTS

Couples with subnormal semen as the only identifiable cause of subfertility.

INTERVENTIONS

In control cycles, the couples had natural intercourse. In IUI cycles, IUI was performed after ovarian stimulation with hMG and human chorionic gonadotropin.

MAIN OUTCOME MEASURE

The clinical PRs and complications of IUI cycles and control cycles were compared.

RESULTS

There were six clinical pregnancies in the 42 IUI cycles, whereas there was no clinical pregnancy in the 42 control cycles. The clinical PR in IUI cycles (14.3% per cycle) was significantly higher than that in control cycles (0%). Six patients (14.3%) developed moderate degree of ovarian hyperstimulation syndrome in IUI cycles.

CONCLUSION

Intrauterine insemination after ovarian stimulation with hMG is useful in treatment of subfertile couples with subnormal semen.

Residual sperm function in oligozoospermia induced by testosterone enanthate administered as a potential steroid male contraceptive

To investigate the fertility of men who remain oligozoospermic despite sex steroid suppression, the in-vitro fertilizing capacity of residual spermatozoa was assessed in 30 men receiving intramuscular testosterone enanthate (TE). Spermatozoa were prepared by either Percoll or repetitive centrifugation/washing. Although the mean (+/- SEM) pretreatment zona-free hamster oocyte penetration (HOP) rates were similar (59.4 +/- 10.1 and 63.8 +/- 10.8%), following the induction of oligozoospermia the Percoll-prepared spermatozoa exhibited a penetration rate (26.9 +/- 10.2%) which was markedly greater than that obtained for sperm prepared by repetitive washing (0 +/- 0%). In addition, the partners of two men exhibiting a HOP test with Percoll-prepared spermatozoa, conceived despite a sperm concentration of 3 x 10(6) ml-1 and a negative HOP test with spermatozoa prepared by repetitive washing. These results suggest that Percoll preparation optimizes the assessment of in-vitro sperm function and that the fertility of men with TE-induced severe oligozoospermia is suppressed but not abolished.

Selected sperm differ from nonselected cells in their electrophoretic mobility (EPM) after demembranation

Human semen samples were first treated by swim-up migration or by Percoll density gradient centrifugation for selection of spermatozoa. The net surface charges of spermatozoa in the resulting compartments were indirectly evaluated by the electrophoretic mobility (EPM) during spermatozoal microelectrophoresis. Significantly different electrophoretic mobilities were measured between the compartments after demembranation with 0.1% (v/v) Triton X-100. However, without intermediate treatment by the detergent no significant differences were detected between the spermatozoal EPM. In addition, spermatozoa were divided into migrated and nonmigrated spermatozoal populations by the swim-up technique, and then treated with urea to remove spermatozoal coats. No significant differences in EPM were detected between these two groups. This investigation demonstrates that selected spermatozoa from semen exhibit an additional dimension of superiority, in EPM, to nonselected spermatozoa, which may better equip them for the process of fertilization. Measurements of EPM, therefore, may provide yet another, perhaps valid, means of developing a clinical tool for evaluating the potential fertilizing capacity of a semen sample in infertility studies.

A double method sperm wash for artificial insemination

Recently, there have been concerns regarding the presence of reactive oxygen species (ROS) produced during sperm processing for insemination. However, the sperm wash methods that yielded low ROS levels also had low sperm recovery after processing. The objective of this study was to compare sperm recovery after swim-up from pellet, overlay, and 2-layer Percoll wash methods with the recovery after the double method wash. The latter method consisted of a combination of 2 sperm wash methods, namely, the overlay and the Percoll method. Motile sperm were first collected through the overlay method. The leftover semen was then processed through the 2-layer Percoll method to scavenge motile sperm and the resultant pellet combined with the pellet from the overlay method. In this manner, the level of ROS was kept to a minimal, sperm recovery was improved, and a mixture of sperm with different surface properties was produced as a result of using different processing methods. The results indicated an improvement in sperm recovery and in total sperm motility in noncryopreserved sperm after using the double method wash when compared with the other wash methods. The study suggests that the double method wash is a feasible method for processing sperm for insemination.

Preparation of human frozen-thawed seminal specimens using the SpermPrep filtration method: improvements over the conventional swim-up method

OBJECTIVE

To examine the qualitative and quantitative characteristics of frozen-thawed spermatozoa recovered through the SpermPrep (ZBL, Inc., Lexington, KY) filtration method or the swim-up technique for the purpose of intrauterine insemination (IUI) or other techniques for assisted reproduction.

DESIGN, SETTING, PATIENTS

Thirty pairs of frozen specimens purchased from three commercial semen suppliers were used in this study. Each pair consisted of two aliquots from the same semen specimen.

MAIN OUTCOME MEASURES

Spermatozoa recovered via the SpermPrep filtration and swim-up processes were evaluated for sperm numbers recovered, sperm motility, grade of sperm motility, percentage of morphologically normal spermatozoa, the response of spermatozoa to a hypo-osmotic environment (hypo-osmotic swelling test), and the amount of debris present.

RESULTS

Application of the SpermPrep filtration method resulted in recovery of significantly greater numbers of spermatozoa (P less than 0.01) than were recovered with the swim-up method (31.1 +/- 3.2 x 10(6) versus 10.2 +/- 1.8 x 10(6) spermatozoa, respectively). This represents a mean recovery of approximately one half (49%) of all spermatozoa applied to the filter, whereas for the swim-up method, it was only 15%. The overall quality of recovered spermatozoa was virtually identical between the two methods (P greater than 0.05). The percent motile sperm improved by a mean of 18% to 20%, the grade of motility improved by a mean of 0.4 points (scale 0 to 4), the percent of morphologically normal spermatozoa increased by a mean of approximately 10%, the percent of spermatozoa reactive to a hypo-osmotic medium test increased by a mean of approximately 9%, and the debris score decreased by a mean of 0.2 to 0.3 points (scale 0 to 4). Most importantly, the mean total number of motile, morphologically normal spermatozoa after filtration through the SpermPrep column was 20.2 +/- 1.1 x 10(6), representing a mean recovery of 73% of the normal spermatozoa originally applied to the column. This was 316% greater than the yield obtained with the swim-up method (6.4 +/- 0.8 x 10(6)), which was significantly greater (P less than 0.01) than that recovered via the swim-up method. Also, the time required to harvest sperm through SpermPrep filtration was 20 to 25 minutes versus 80 minutes required for the swim-up method (P less than 0.05).

CONCLUSION

Considering that the effectiveness of frozen-thawed semen is already limited when compared with fresh semen, SpermPrep filtration is the method of choice over the swim-up technique of sperm selection because the former provides significantly greater numbers of high quality sperm. It should be considered as an adjunct in semen preparation for IUI or other forms of assisted reproduction.

Role of a germ cell-specific sulfolipid-immobilizing protein (SLIP1) in mouse in vivo fertilization

Sulfolipid-immobilizing protein 1 (SLIP1) is a germ cell plasma membrane protein that binds specifically to sulfogalactosylglycerolipid, a sulfoglycolipid found preferentially in mammalian male germ cells (Lingwood, Can. J. Biochem. Cell. Biol. 63:1077-1085, 1985b). SLIP1 in mouse and rat sperm exists on the periacrosomal membrane, where sperm initially bind to eggs. Using the in vitro mouse sperm-egg binding assay with in vitro-capacitated sperm, we obtained results previously suggesting that sperm SLIP1 is involved in mouse sperm-zona pellucida interaction. In this study, using the in vitro sperm-egg binding assay, we showed that SLIP1 in uterine sperm was similarly engaged in this process. Involvement of mouse sperm SLIP1 was also shown to be important in the in vivo fertilization process. Superovulated females inseminated with caudal epidididymal and vas deferens sperm preexposed to anti-SLIP1 IgG yielded only 20% fertilized zygotes, while 80% fertilization was observed in females inseminated with sperm preincubated with preimmune serum IgG. The lower fertilization rate was not due to changes in the sperm capacitation rate as assessed by chlortetracycline staining.

Steroid metabolism by germ cells and spermatozoa in men after vasoepididymostomy

The ability of germ cells (spermatocytes and spermatids) and spermatozoa present in human ejaculate to metabolize steroids was studied in men with obstructive infertility who had undergone vasoepididymostomy as corrective surgery. Steroid metabolism by spermatozoa in men who had undergone vasovasostomy was also investigated. Germ cells converted testosterone mainly to androstenedione. In addition to androstenedione, dihydrotestosterone and androstanediols were also formed in incubations using spermatids. Both types of germ cells converted estradiol to estrone. Spermatozoa from subjects who had undergone vasoepididymostomy or vasovasostomy converted testosterone to androstenedione as in normal men, while spermatozoa from infertile subjects converted testosterone mainly to dihydrotestosterone. Seminal fluid, free of germ cells, did not show steroid-metabolizing capability.

Quantitative assessment of the serum-induced stimulation of human sperm motility

In previous studies, sperm populations with high motility and fertilizing potential have been isolated using Percoll gradients and/or addition of serum or caffeine, but no objective measurements of the motility parameters affected have been presented. In addition, the types of sperm populations and the incidence of positive or negative responses to these treatments have never been documented. In this paper, the proportion of samples responding positively or negatively to these treatments and the type of motility stimulation observed was measured using the CellSoft computer-assisted digital image analysis system. Semen, obtained from the Infertility Clinic, was washed on discontinuous Percoll gradients. Sperm motility parameters were measured in the original semen and after washing through a Percoll gradient in the presence or absence of serum or caffeine. Percoll washing permitted a good recovery of essentially pure sperm. The Percoll treatment had little effect on the percentage of motile sperm but caused a decrease in the linearity-related parameters. A high proportion of the washed sperm samples supplemented with serum showed an increase in at least one of the motility parameters when compared to sperm populations in the original semen (68% of cases) or after Percoll washing (96% of cases). These effects were maintained for several hours. The stimulation of motility was concentration-dependent, with an optimum around 25-30% serum. Caffeine (4 mM) increased linear velocity but lowered linearity. In contrast to caffeine, which stimulated sperm motility for less than 1 h, the effects of human serum lasted for more than 16 h.

Immunodetectable galactosyltransferase is associated only with human spermatozoa of high buoyant density

Human ejaculated spermatozoa are heterogeneous and can be separated into two distinct populations according to their respective buoyant densities. In order to investigate the functional differences between these two types of spermatozoa, we have searched for the presence of galactosyltransferase. A Western blot of sperm proteins following their electrophoresis was probed with an anti-galactosyltransferase serum revealing that this enzyme is present in human spermatozoa. Furthermore, galactosyltransferase is detectable only in those proteins isolated from the head of high density spermatozoa. These results suggest that ejaculated spermatozoa consist of two populations that are functionally different.

Inhibitory effects of gossypol analogs on human sperm motility

Aqueous-soluble gossypol Schiff's bases, SP562: bis-8,8'-[(N-(2-(dimethylamino)ethyl]-iminomethylene]- [1,1',6,6',7,7'-hexahydroxy-5,5'-diisopropyl-3,3'-dimethyl-2,2- binaphthalene dihydrochloride; SP563: bis-8,8'-[(N-(2-(diethylamino)ethyl]-iminomethylene]-1,1',6,6',7,7 '- hexahydroxy-5,5'-diisopropyl-3,3'-dimethyl-2,2'-binaphthalene++ + dihydrochloride; and SP564: bis-8,8'-[(N-(2-(diethylamino)propyl]-iminomethylene]- 1,1',6,6',7,7'-hexahydroxy-5,5'-diisopropyl-3,3'-dimethyl-2,2'- binaphthalene dihydrochloride, were investigated for their effects on human sperm motility. SP564, which has the longest alkyl substituent of the Schiff's base, appeared to exert the greatest inhibitory effects on human sperm motility. These inhibitory effects were even greater than those caused by (+/-)gossypol acetic acid at the same concentration.

Semen manipulation: improved sperm recovery and function with a two-layer Percoll gradient

The authors compared a simple, two-layer Percoll density gradient technique with the swim-up technique for semen preparation in 128 men. In samples from normospermic (n = 55), oligospermic (n = 26), and asthenospermic (n = 29) men, the Percoll technique significantly improved yield, percent motility, and absolute number of motile sperm recovered, but in samples from oligoasthenospermic men (n = 18), only percent motility was improved. The Percoll density gradient also selected sperm with markedly improved function as assessed by both the sperm penetration assay and the fertility index. In 37 samples negative on the sperm penetration assay when processed with the swim-up technique, 19 (51%) became positive when processed with the Percoll technique. The Percoll density gradient is an improved method for semen manipulation as it allows greater recovery of sperm with higher motility and improved sperm function.