Preincubation of human spermatozoa in test-yolk medium: effect on penetration of zona-free hamster oocytes and correlation with other semen characteristics

Association between freezing agent and acrosome damage of human spermatozoa from subnormal and normal semen

This experimental study compares the effects of human sperm preservation medium (HSPM) with TEST-yolk buffer (TYB) as cryoprotectants of human spermatozoa with respect to the integrity of the acrosome after the freeze-thawing procedure. Fifty-six semen samples were included in this study; 18 were subnormal (G1) and 38 were normal (G2) based on World Health Organization criteria, except for morphology, which was evaluated according to strict criteria. Each semen sample was divided into two parts: the first part was prepared for cryopreservation by the addition of HSPM (1:1) and the second by addition of TYB (1:1). Freezing was performed in liquid nitrogen vapour. Smears were made before freezing and after the thawing process for evaluation of acrosome integrity using fluorescent-lectin labelling. The mean percentage of spermatozoa with intact acrosomes in the subnormal group was 77.0 +/- 7.2% before freezing and decreased significantly (P < 0.001) after thawing: to 63.7 +/- 8.2% with the use of HSPM and 66.8 +/- 8.7% with the use of TYB. The corresponding values in the normal semen samples were 83.4 +/- 9.2%, 76.0 +/- 8.8% and 77.9 +/- 9.2%, respectively. It is obvious that the decrease in the mean percentage of spermatozoa with intact acrosome was significantly higher when using HSPM in comparison with TYB, not only for G1 (-14.9 +/- 1.9% versus -11.8 +/- 1.4%) but also for G2 samples (-13.8 +/- 1.5% versus -11.9 +/- 1.3%). In conclusion, TYB should be recommended for freeze-thawing of human spermatozoa as the first-choice cryoprotectant, for normal as well as subnormal semen samples, in order to protect the sperm acrosome from the deleterious effects of the freeze-thawing procedure.

Evaluation of sperm cryoprotective media in respect to fertilizing capacity tested in vitro

Nine different cryoprotectant buffers were tested to measure their protective ability towards main sperm seminological parameters. These were: maintained sperm motility, progressive motility and sperm viability. Out of the nine tested buffers, medium E (TES-Tris without glycerol) and H (glycerol only) showed significantly lower (P < 0.001) values than the rest of the studied buffers in respect to all tested seminological features. The other media did not differ significantly in their cryoprotective abilities to sperm. Richardson's medium (A) preserved sperm viability significantly better (P < 0.001) than the other tested buffers, reaching 63.1% of viable spermatozoa in proportion to the fresh sperm sample before freezing. Three cryoprotectants, A (with egg yolk, no TEST buffer system), D (neither egg yolk nor TEST buffer system), F (TEST-egg yolk buffer system) were further studied for their ability to preserve sperm function in sperm-cervical mucus penetration (Penetrak) and sperm penetration assay (SPA). In our hands, neither supplementation of the buffer with egg yolk nor TEST-egg yolk buffer system promoted sperm capacity in functional tests. A,D,F buffers did not significantly differ among each other in applied functional assays, however, they all diminished (P < 0.001) sperm penetration ratios when compared with fresh sperm samples. Therefore enhancement of sperm capacity to fertilize after equilibration with TEST-egg yolk buffer system should be contested.

Influence of media and thermal shock on sperm capacitation

To elucidate the influence of medium and thermal shock in inducing sperm capacitation, eight ejaculates were processed as follows. Each ejaculate was divided into three aliquots. To two of the aliquots, an equal volume of saline was added, while TEST-yolk was added to the remaining aliquot. All three samples were cooled slowly to 5 degrees C and incubated for 18-20 h. After aspirating the supernatant, 6 ml of Tyrode solution containing 0.06 g% egg yolk, warmed to 37 degrees C was added without disturbing the sperm pellet to the aliquot containing TEST-yolk and to one of the aliquots mixed with saline. To the remaining saline-processed sperm pellet, 6 ml TEST-yolk (37 degrees C) was added. All samples were washed twice (400 x g for 5 min) and processed for the sperm penetration assay (SPA). Samples, either pre-incubated in TEST-yolk (mean +/- SEM; 65.9 +/- 11.7%) or warmed (thermal shock) with TEST-yolk (62.6 +/-12.1%) yielded significantly (P < 0.05) higher SPA outcome than the samples processed and warmed with saline (17.8 +/- 12.0%). The penetration indices were not statistically different from each other. It therefore appears that the medium influences the sperm capacitation process to a greater extent and may augment the influence of thermal shock.

Intrauterine insemination with frozen sperm increases pregnancy rates in donor insemination cycles under gonadotropin stimulation

OBJECTIVE

To compare the efficacy of IUI donor and pericervical insemination donor in frozen sperm insemination cycles under gonadotropin stimulation.

DESIGN

Couples where infertility was caused by male conditions were randomized into two groups: IUI and pericervical insemination. Semen samples, gonadotropin stimulation, and ovarian monitoring were the same in both groups. One IUI was performed per cycle as against two pericervical inseminations.

SETTING

The donor insemination program at the Human Reproduction Unit at the Hospital of Cruces, Pais Vasco University.

PATIENTS

Eighty-eight women (47 IUI and 41 pericervical insemination) with at least one patent fallopian tube and < 40 years of age.

MAIN OUTCOME MEASURE

Intrauterine gestational sac observed by transvaginal ultrasound.

RESULTS

Per woman pregnancy rate (PR) was higher in IUI than in pericervical insemination (65.96% versus 41.46%, odds ratio [OR] = 2.73, confidence interval [CI] = 1.06 to 7.2). Pregnancy rates were always higher in IUI irrespective of woman and husband's status, but statistical significance was not reached in any subgroups analyzed independently. Per cycle PR was also significantly higher in IUI than in pericervical insemination: 24.03% (31/129) versus 11.89% (17/143) (OR = 2.34, CI = 1.17 to 4.71). Moreover, cumulative PR was higher in IUI (86% versus 49.5%) (OR = 6, CI = 1.98 to 18.80).

CONCLUSION

Per woman and per cycle PRs were significantly higher in IUI.

Effect of milk-yolk on the fertilizing capacity of spermatozoa

Pre-incubation of human sperm in egg yolk based medium (TEST-yolk) as well as milk have been shown to improve sperm fertilizing capacity. The purpose of this study was to compare a combination of these two media, called milk-yolk, against the two established media, in order to test for a possible synergistic effect(s) on sperm functions as measured by sperm motility, acrosome reaction and penetration assay. Statistically, no differences have been observed among the three media, except for SPA outcome in milk-yolk, being significantly lower than the corresponding values for the other two media. In conclusion the beneficial effects of egg yolk and milk appear to be eliminated once both media are combined, resulting in an antagonistic effect on the fertilizing capacity of the spermatozoa.

The effect of preincubation of human spermatozoa in milk on sperm penetration into zona-free hamster oocytes and on sperm binding to the human zona pellucida

OBJECTIVE

To determine whether preincubation of sperm in milk enhances the outcome of sperm penetration assay (SPA) and hemizona assay (HZA) when compared with preincubation in TES and Tris (TEST)-yolk.

DESIGN

Sperm penetration assay and HZA were performed on milk and TEST-yolk preincubated spermatozoa.

INTERVENTIONS

Ejaculates were washed and divided into two equal aliquots. An equal volume of heat-inactivated cow's milk (95 degrees C, 10 minutes) was added to one aliquot and an equal volume of TEST-yolk was added to the other aliquot. Both sperm mixtures were cooled slowly to 5 degrees C and incubated for 2 hours. They were then washed twice (400 x g for 8 minutes) with culture medium at 37 degrees C and processed for SPA and HZA.

MAIN OUTCOME MEASURES

Percentage of oocytes penetrated and the penetration index for the SPA. The number of sperm bound to hemizona and hemizona index for the HZA.

RESULTS

Sperm preincubated in milk yielded significantly higher SPA results and hemizona index when compared with TEST-yolk. The penetration index and the number of sperm bound were high but were not statistically significant.

CONCLUSION

Preincubation of sperm in milk enhances the SPA and HZA outcome when compared with TEST-yolk.

Effect of preincubation of human spermatozoa in milk on penetration of zona-free hamster oocytes: comparison to TEST yolk

PURPOSE

To investigate the effect of preincubation of human sperm in milk on their ability to penetrate zona-free hamster oocytes, 27 ejaculates were studied. Each ejaculate was divided into two portions and incubated in either milk or TEST yolk (TESTY) for 22-24 hr at 5 degrees C prior to processing for the sperm penetration assay.

RESULTS

Spermatozoa preincubated in milk penetrated a significantly (P < 0.05) higher percentage of oocytes (mean +/- SE; 74.4 +/- 6.3) than spermatozoa preincubated in TESTY (66.8 +/- 6.6). Statistically, no significant differences were noted for penetration index or postincubation sperm motility between the two media.

CONCLUSION

Preincubation of sperm in milk therefore appears to enhance their ability to penetrate zona-free hamster oocytes, compared to TESTY preincubation. Since milk is natural, simple, inexpensive, readily available, and can be easily processed, it should be the medium of choice for sperm preincubation.

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

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

Enhanced quality of capacitated spermatozoa from oligoasthenozoospermic men after incubation in test yolk medium

To improve artificially the quality of poor sperm samples to be used in assisted procreation procedures, Test Yolk Buffer (TYB) incubation effect was investigated. After adding the TYB procedure to the standard swim-up technique, a significant (P < 0.001) increase in spermatozoa velocity was observed, while the other seminal parameters were not affected. Three of 11 couples who had not had success after three intraperitoneal inseminations (IPI) with sperm prepared by the usual swim-up technique obtained pregnancies after IPI with TYB-incubated spermatozoa. These preliminary results suggest that TYB incubation for capacitated spermatozoa be employed in the assisted procreation strategies applied for male infertility.

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

OBJECTIVE

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

DESIGN

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

SETTING

The University of Southern California IVF Program.

PATIENTS

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

INTERVENTIONS

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

MAIN OUTCOME MEASURES

Fertilization rates in vitro.

RESULTS

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

CONCLUSIONS

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

The effect of egg yolk medium on human sperm binding in the hemizona assay

OBJECTIVE

To evaluate, using the hemizona assay (HZA), whether egg yolk treatment of human sperm enhances binding to the human zona pellucida in vitro and to determine whether such a treatment is as efficient as the standard swim-up procedure for promoting sperm binding ability.

DESIGN

Ejaculates were divided into aliquots and half incubated at 37 degrees C for 21 hours in standard culture medium or combined with buffered medium containing chicken egg yolk and stored at 4 degrees C for 21 hours. A second set of ejaculates were split and processed by a standard 1-hour rise alone or treated with egg yolk medium.

SETTING

University teaching hospital.

PARTICIPANTS

Two healthy sperm donors.

MAIN OUTCOME MEASURE

The number of sperm tightly bound to the hemizona were measured and compared between the groups.

RESULTS

A significant increase (P less than 0.0001) in hemizona binding (n = 46) for egg yolk treatment (90.1 +/- 9.8; range 7 to 258) as compared with standard culture medium (53.0 +/- 8.8; range 0 to 228) was observed. Similarly, a significant increase (P less than 0.0001) in binding (n = 37) for egg yolk treatment (74.9 +/- 8.2; range 7 to 219) as compared with samples obtained with a sperm rise (37.1 +/- 5.7; range 2 to 122).

CONCLUSIONS

Treatment of human spermatozoa with an egg yolk medium at 4 degrees C overnight significantly increases sperm binding in the HZA.