Comparison of various methods of processing human cryopreserved-thawed semen samples

Phosphatidylcholine and L-acetyl-carnitine-based freezing medium can replace egg yolk and preserves human sperm function

Background

Conventional cryopreservation methods induce chemical and mechanical damage to the sperm membranes. The cryoprotectant potential of phospholipids of vegetal origin as soybean lecithin has been investigated as a substitute for egg yolk in diluents used for the cryopreservation of human spermatozoa. Therefore, the objective of this study was comparing the efficacy of a synthetic cryoprotectant supplemented with L-α-phosphatidylcholine (PC) and L-acetyl-carnitine (ANTIOX-PC) and the standard egg-based TEST-yolk buffer (TYB) in preserving sperm motility and chromatin quality in cryopreserved semen samples.

Methods

Prospective experimental study in which semen samples from 63 men with normal sperm motility and 58 men with low sperm motility were included and analyzed both before and after cryopreservation using ANTIOX-PC or TYB freezing media. Sperm quality was evaluated by routine semen analysis and DNA fragmentation index using the Terminal deoxynucleotidyl transferase dUTP nick end labeling assay.

Results

Differences in the post-thaw progressive motility and DNA fragmentation index were not detected between TYB and ANTIOX-PC cryoprotectants in both normal and low sperm motility groups (P>0.05). However, ANTIOX-PC medium retained higher non-progressive motility and lower percentage of immotile sperm when compared to TYB medium, resulting in a greater total motile sperm count (P<0.05), regardless baseline values of motility characteristic of the normospermic or asthenozoospermic samples.

Conclusions

ANTIOX-PC medium was effective to protect human sperm during a freeze-thaw cycle compared to the TYB medium. A clinically relevant advantage in better preserving kinetic parameters as higher total motility and lower immotile post-thawed sperm from ANTIOX-PC, in normal and low motility semen samples, demonstrated the positive impact of phospholipid and antioxidant treatment on sperm cryotolerance with high potential for egg yolk lipids replacement and biosafety.

Strategies for Fertility Preservation in Female and Male Cancer Survivors

Improved survival rates and quality of life following modern cancer treatment have resulted in a growing number of patients requesting maintenance of reproductive capacity, both before and after completion of treatment. Several established options are currently available. In men, sperm banking should be offered as soon as the diagnosis of any malignant disease is established, irrespective of the expected cryosurvival rate. In such cases, conception can be achieved with frozen-thawed spermatozoa following either intrauterine insemination (IUI) or intracytoplasmic sperm injection (ICSI). In women, depending on the type of cancer, the presence of an adequate ovarian reserve, and time to delay cancer treatment, in vitro fertilization (IVF) with embryo cryopreservation constitutes a valid alternative. On the other hand, cryopreservation of mature oocytes following IVF/ICSI offers some advantages, but it is still limited by its low success rate. Emerging and exciting techniques of germ cell/gonadal tissue cryopreservation (banking) followed by autotransplantation have been clinically explored, particularly in women. Novel cryotechnologies of ovarian and testicular tissue have proven efficacious and new transplantation strategies promise improved results. However, only one live birth following autotransplanted frozen-thawed ovarian tissue has been established and there are still no pregnancies reported from autotransplanted cryopreserved testicular tissue in the human. Efficiency and safety of these techniques needs to be demonstrated. Methods for gamete in vitro maturation also need further development. Gonadal tissue cryopreservation and transplantation should be considered experimental in humans for the present time until greater evidence regarding efficacy and safety is accrued.

Evaluation of the Efficiency of Two Different Freezing Media and Two Different Protocols to Preserve Human Spermatozoa from Cryoinjury

It is universally recognized that cryopreservation impairs sperm quality. In order to improve postthawing sperm survival and motility, media of different composition and different protocols have been proposed. However, no clear evidence is available to understand which are the most efficient protocol and medium for sperm cryopreservation. The present study evaluates the efficiency of two different cryopreservation protocols and two common freezing media (FM) containing different cryoprotectants (CPs), TEST Yolk Buffer (TYB) and Sperm Freeze (SF), to preserve human sperm quality. Our data suggest that TYB is better than SF both in terms of postthaw viability and in terms of progressive motility, while the direct addition of FM to the sperm sample resulted in the most efficient protocol in terms of postthaw viability but not in terms of progressive motility.

Percoll gradient separation of cryopreserved common carp spermatozoa to obtain a fraction with higher motility, velocity and membrane integrity

We attempted to select a fraction of common carp, Cyprinus carpio spermatozoa that best survived a conventional freeze/thaw procedure, by centrifugation of frozen/thawed sperm through a Percoll gradient (45% and 90%). The proportion of motile spermatozoa (65.81 ± 5.19%), their velocity (77.58 ± 31.07 μm/sec), and membrane integrity (83.66 ± 4.38% intact) were significantly higher in separated sperm than in whole samples (motility 23.36 ± 2.98%, velocity 55.55 ± 19.03 μm/sec, and membrane integrity 57.92 ± 4.65%). Our results demonstrated that Percoll gradient centrifugation shows promise as a technique for selecting high quality cryopreserved fish spermatozoa, which could be useful for cryobiological research. Further studies are needed to evaluate the potentially higher fertilizing ability of the separated spermatozoa.

Effect of thawing temperature on the motility recovery of cryopreserved human spermatozoa

OBJECTIVE

To investigate the effects of thawing temperature on sperm function after cryopreservation. The technical aspects of sperm cryopreservation have significantly improved over the last few decades. However, a standard protocol designed to optimize sperm motility recovery after thawing has not yet been established.

DESIGN

Prospective study.

SETTING

Private infertility institute and university-based research laboratory.

PATIENT(S)

Eighty consenting normozoospermic patients consulting for infertility.

INTERVENTION(S)

Spermatozoa from donor semen samples were thawed at different temperatures.

MAIN OUTCOME MEASURE(S)

Sperm motility, viability, adenosine-5'-triphosphate (ATP) content, acrosomal status, and DNA integrity were evaluated as a function of thawing temperature in cryopreserved human sperm samples.

RESULT(S)

Thawing at 40 degrees C resulted in a statistically significant increase in sperm motility recovery compared with thawing at temperatures between 20 degrees C and 37 degrees C. There were no statistically significant differences in sperm viability, acrosomal status, ATP content, and DNA integrity after thawing at 40 degrees C compared with thawing at temperatures between 20 degrees C and 37 degrees C.

CONCLUSION(S)

Sperm thawing at 40 degrees C could be safely used to improve motility recovery after sperm cryopreservation.

The DNA integrity of cryopreserved spermatozoa separated for use in assisted reproductive technology is unaffected by the type of cryoprotectant used but is related to the DNA integrity of the fresh separated preparation

OBJECTIVE

To investigate and compare seven different commercially available cryoprotectant media in terms of the DNA integrity of spermatozoa recovered after cryopreservation and separation using density gradient centrifugation (DGC).

DESIGN

A prospective clinical study.

SETTING

Tertiary care fertility clinic.

PATIENT(S)

Three hundred twenty men presenting for infertility investigations.

INTERVENTION(S)

Each sample was randomly assigned to one of seven commercially available cryoprotectants or to no cryoprotectant.

MAIN OUTCOME MEASURE(S)

Percentage sperm DNA fragmentation after cryopreservation and preparation using DGC.

RESULT(S)

The mean percentage fragmentation was significantly higher post-thaw and post-DGC; however, some patients (26.3%) demonstrated a lower percentage fragmentation post-thaw. No single cryoprotectant was identified as the best at preserving DNA integrity. The difference in fragmentation after thawing and DGC was found to be highly dependent on the prefreeze fragmentation. Motility was also significantly correlated with the difference in fragmentation post-thaw (r = -0.161).

CONCLUSION(S)

Neither the presence nor type of cryoprotectant affects the DNA integrity of spermatozoa after cryopreservation and DGC. Individuals with lower prefreeze fragmentation in DGC-prepared spermatozoa have larger increases in fragmentation and are less likely to exhibit lower levels of fragmentation post-thaw. The reverse effect observed in those with higher prefreeze fragmentation gives rise to a possible novel method of reducing fragmentation in sperm used for assisted reproductive technology treatment cycles without the need for testicular sperm retrievals.

Molecular glass wool filtration as a new tool for sperm preparation

BACKGROUND

Magnetic-activated cell sorting (MACS) using annexin V-conjugated microbeads in a liquid phase eliminates apoptotic spermatozoa based on the externalization of phosphatidylserine (EPS) residues. The procedure allows the enrichment of a sperm population free of apoptosis markers, giving higher fertilization potential. Our aim was to determine if the annexin V binding principle can be transferred onto a glass wool filter system in order to produce a solid phase filter.

METHODS

Semen samples (n = 42) were subjected to a molecular glass wool filter system using glass surfaces coated with annexin V and compared with aliquots separated by conventional glass wool, as well as with annexin V-MACS. The extent of apoptosis was assessed by measuring levels of activated caspase 3 using fluorescein-labelled inhibitors of caspase, alterations in mitochondrial membrane potential (MMP) using a lipophilic cationic dye, and EPS using a fluorescein isothiocyanate-coupled monoclonal antibody.

RESULTS

Annexin V-negative sperm filtered out by the newly developed molecular glass wool filtration (GWF) system displayed superior quality in terms of high MMP integrity, as well as, to a small extent, caspase 3 activation and EPS.

CONCLUSIONS

The effect of traditional GWF can be further improved by combination with annexin V binding. This newly developed solid phase molecular filter system has been proven to enrich spermatozoa free of apoptosis markers to the same extent as the annexin V magnetic separation technique. The selection of spermatozoa free of apoptosis markers by molecular glass wool filters may enhance the results of IVF.

Comparison of the effects of Percoll and PureSpermR on the common marmoset (Callithrix jacchus) semen

Density gradient centrifugation is a widely used technique for the separation of motile from non-motile sperm, for the removal of contaminating agents such as bacteria and viruses, and for the removal of seminal plasma or cryoprotectant. In the choice of a density gradient medium for a new species, it is important to perform toxicity tests. The present study was carried out to evaluate the potential toxic effects of two silica-based density gradient products (Percoll and PureSperm), on the sperm of the common marmoset. We assessed two different batches of Percoll (polyvinylpyrrolidone (PVP)-coated colloidal silica particles) and one of PureSperm (saline-coated colloidal silica suspension) by means of a computer-aided sperm analysis on semen collected by vibrostimulation. The results showed that although some of the sperm patterns of movement and viability changed significantly over time, and provide a first description of marmoset sperm motility changes under capacitating conditions, there was no significant difference in the sperm treated with Percoll or PureSperm in comparison with the control. We conclude that simple exposure to either of these products does not have a negative effect on viability or motility of marmoset sperm.

Advantage of combining magnetic cell separation with sperm preparation techniques

The selection of vital, non-apoptotic spermatozoa is a prerequisite for achieving optimal conception rates in assisted reproductive techniques. Magnetic cell sorting using annexin-V microbeads can effectively separate apoptotic and non-apoptotic spermatozoa. The objective of the present study was to optimize the integration of magnetic cell sorting in standard sperm preparations and to correlate the effect of different sperm preparation procedures on apoptotic markers. Semen specimens collected from 15 healthy donors were prepared by either density gradient centrifugation or by one-step sperm wash technique separately and in combination with magnetic cell sorting. The preparation methods were evaluated by assessment of semen parameters (motility, viability and morphology) as well as markers of apoptosis (levels of active caspase-3, integrity of membrane mitochondrial potential and externalization of phosphatidylserine). The apoptotic markers were measured using fluorochrome dyes coupled with flow cytometry. The results showed that the combination of density gradient centrifugation and annexin-V magnetic cell sorting was superior to all other sperm preparation methods in terms of providing motile, viable and non-apoptotic spermatozoa. This study clearly shows the advantage of integrating magnetic cell sorting as a part of sperm preparation, which in turn may positively affect the success rates of assisted reproductive techniques.

Semen preparation techniques for intrauterine insemination

BACKGROUND

Semen preparation techniques for assisted reproduction, including intrauterine insemination (IUI), were developed to separate the motile morphological normal spermatozoa. Leucocytes, bacteria and dead spermatozoa produce oxygen radicals that negatively influence the ability to fertilize the egg. The yield of as many motile, morphologically normal spermatozoa might influence treatment choices and therefore outcomes.

OBJECTIVES

To compare the effectiveness of gradient, swim-up, or wash and centrifugation in subfertile couples undergoing intrauterine insemination (IUI) on clinical outcome as well as on semen parameters.

SEARCH STRATEGY

We searched the Menstrual Disorders and Subfertility Group's trials register (30 June 2003), MEDLINE (1966 to July 2003), EMBASE (1980 to July 2003), Science Direct Database (1966 to July 2003), Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2003), National Research Register (2000 to Issue 2, 2003), Biological Abstracts (2000 to June 2003), CINAHL (1982 to July 2003) and reference lists of relevant articles. We also contacted experts and authors in the field.

SELECTION CRITERIA

Parallel randomised controlled trials (RCTs), comparing the efficacy of semen preparation techniques used for subfertile couples undergoing IUI, were included. RCTs or split sample studies examining semen parameters after different semen preparation techniques were also included.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data. Study authors were contacted for additional information.

MAIN RESULTS

Two randomised controlled trials comparing clinical outcomes, including 81 participants in total, were included in the meta-analysis (Dodson 1998-I/ II; Xu 2000-I/ II). Both studies compared swim-up technique versus gradient technique in 65 subfertile couples undergoing IUI. One study compared the effectiveness of both techniques with wash technique. No trials reported the primary outcome of live birth. There was no statistically significant difference between pregnancy rates (PR) for swim-up versus gradient / wash centrifuge (Peto OR 0.55, 95% CI 0.17 to 1.76; Peto OR 1.74, 95% CI 0.2 to 14.9; PR/ couple swim-up 20%, gradient 40%, wash 12.5%) or gradient versus wash centrifuge (Peto OR 4.01, 95% CI 0.82 to 19.56; PR/ couple swim-up 15%, gradient 20%). There was no significant difference in the miscarriage rate (MR) per couple between either of the three treatment groups in the one trial reporting this outcome (MR/ couple swim-up 0%, gradient 10.3%, wash 0%. MR/ pregnancy gradient 30.3%). There was no statistically significant difference in the multiple pregnancy rate (MPR) per couple between either of the three treatment groups in Dodson 1998-I/ II (MPR/ couple swim -up 0%, gradient 0%, wash 6.3%). One triplet pregnancy was recorded. Fifteen studies comparing semen parameters after processing were included. Two studies were included in the meta-analysis, we were not able to pool results.

REVIEWERS' CONCLUSIONS

There is insufficient evidence to recommend any specific preparation technique. Large high quality randomised controlled trials, comparing the effectiveness of a gradient and/ or a swim-up and/ or wash and centrifugation technique on clinical outcome are lacking. Further randomised trials are warranted. Results from studies comparing semen parameters may suggest a preference for gradient technique, but firm conclusions cannot be drawn and the limitations should be taken into consideration.

Cryopreservation of fractionated, highly motile human spermatozoa: effect on membrane phosphatidylserine externalization and lipid peroxidation

INTRODUCTION

This study investigated lipid peroxidation (LPO) and membrane integrity following cryopreservation-thawing.

METHODS

Infertile men (study group) and donors (control group) were examined. Purified populations of highly motile spermatozoa were cryopreserved using TEST-yolk buffer and glycerol (TYB-G) followed by quick thaw. LPO was measured by a spectrophotometric assay, with and without a ferrous ion promoter. Annexin V binding was used to assess membrane translocation of phosphatidylserine (PS).

RESULTS

Pre-freeze LPO was significantly higher in the study than in the control group (P = 0.03). In both groups, LPO measurements after thawing were significantly higher than the pre-freeze samples not exposed to TYB-G (P = 0.002 and P = 0.001 respectively). However, when the pre-freeze samples with TYB-G were compared with the post-thaw samples (all exposed to TYB-G), these differences were not significant. There was a significant increase in PS externalization following cryopreservation in both groups (P = 0.02 and P = 0.003 respectively). In donors, pre-freeze LPO concentrations had a significant positive correlation with thawed spermatozoa depicting PS externalization (r = 0.77, P = 0.04).

CONCLUSION

Although patients had higher basal LPO than donors, LPO did not differ between fresh and cryopreserved-thawed fractionated motile spermatozoa. Freezing-thawing was associated with translocation of PS to the external membrane leaflet.

Cysteine, glutathione, and Percoll treatments improve porcine oocyte maturation and fertilization in vitro

Several factors have been examined to improve in vitro fertilization and development of porcine oocytes. Cysteine is known to be beneficial for oocyte maturation and male pronuclear formation in pigs and glutathione is known to help prevent membrane disruption of sperm in other species, including human. It has also been reported that the presence of cumulus cells influences the outcome of in vitro fertilization in cattle. The objectives of the present study were to investigate the effects of several factors involved in porcine in vitro maturation (IVM) and fertilization (IVF) procedures on oocyte embryogenic competence. The following factors were examined: the effects of different concentrations (0, 0.285, 0.57, 1.14, 2.28 microM) and exposure duration (22 and 44 hr) of cysteine during IVM, glutathione inclusion and of cumulus presence during IVF, and the use of gradient Percoll (45%/90%) during sperm preparation. The presence of cysteine in maturation medium improved blastocyst development significantly regardless of the duration of exposure when compared to the control (11--16% vs. 4%, P < 0.01). However, no dose-responsive effect was observed at the concentrations tested. The use of gradient Percoll during sperm preparation significantly improved cleavage (85% vs. 57%, P < 0.01) and blastocyst development (24% vs. 6%, P < 0.01) over conventional sperm preparation. Significant improvement was also achieved by the addition of glutathione to Percoll gradient (30% vs. 20%, P < 0.05). In conclusion, cysteine and glutathione as well as Percoll and cumulus were beneficial to embryogenic competence of porcine oocytes in this study. Mol. Reprod. Dev. 59:330-335, 2001.

Cryopreservation-thawing of fractionated human spermatozoa and plasma membrane translocation of phosphatidylserine

OBJECTIVE(S)

[1] To evaluate sperm membrane damage during cryopreservation-thawing by the assessment of phosphatidylserine (PS) translocation and [2] to examine the relationship between reactive oxygen species (ROS) and cryopreservation-related alterations.

DESIGN

Prospective cohort study.

SETTING

University-based center.

PATIENT(S)

Men consulting for infertility and fertile donors (controls).

INTERVENTION(S)

Semen processing was performed by density gradient separation followed by cryopreservation and thawing.

MAIN OUTCOME MEASURE(S)

Membrane PS translocation was evaluated with annexin V binding, generation of ROS was detected by chemiluminescence, and motion parameters were assessed by computer analysis.

RESULT(S)

Annexin V binding was detected in the prefreeze fractions with high and low sperm motility. In the patient group, there were significantly higher postthaw levels of annexin V binding in both fractions when compared with prefreezing values. However, such induction of PS translocation was significantly higher in the fractions with high sperm motility. Significantly higher ROS levels were detected in prefreeze samples of the fractions with low sperm motility.

CONCLUSION(S)

In the population of men studied, [1] cryopreservation-thawing was associated with induction of membrane PS translocation; [2] postthaw ROS levels were lower than before freezing; and [3] neither annexin V binding results nor the generation of ROS were able to accurately predict sperm cryosurvival rates.

Assessment of sperm cryodamage and strategies to improve outcome

Sperm cryopreservation still represents a valuable clinical aid in the management of infertility. Its current principal indications include (1) donor sperm insemination; (2) freezing before cancer therapy to maintain reproductive capacity; (3) patient's convenience; and (4) because of the outstanding success with ICSI, even patients with different degrees of oligo-asthenoteratozoospermia can now be offered the use of frozen/thawed sperm for oocyte micromanipulation. Although sperm cryopreservation/thawing and results of insemination and IVF have been consistently good using donor semen, results of infertile men (with or without various degrees of oligoasthenoteratozoospermia) have yielded remarkably lower rates of survival and pregnancy. Freezing/thawing techniques have not been subjected to major changes in the last years, Furthermore, the exact nature of sperm cryodamage still remains to be elucidated. Various aspects of sperm freezing are revisited here (1) development of new technical approaches for cryopreservation; (2) analysis of the stimulatory effect of putative cryoprotectant additives; (3) the use of intrauterine insemination-ready processed samples; and (4) selection and optimization of end-points for analysis of cryodamage. It is expected that advances in such areas will improve significantly the cryopreservation/thawing outcome particularly as related to semen samples of subfertile men.

Influence of seminal plasma on cryopreservation of human spermatozoa in a biological material-free medium: study of normal and low-quality semen

The objective was to evaluate the efficiency of a biological material-free medium and the role of seminal plasma (SP) in the cryopreservation of human spermatozoa. Normal semen samples and low-quality semen samples were used for this study. After centrifugation of 300 microL fractions of whole semen, pellets were resuspended either in autologous SP or in a chemically defined medium (BM) supplemented or not with 3% bovine serum albumin (BSA); after 15 min at 37 degrees C, the samples were diluted (V/V) with cryoprotective medium (30 mM NaCl; 22 mM sodium citrate, 19.4 mM fructose; 80 mM glutamine; 14%, V/V, glycerol) and maintained for 15 min at room temperature before freezing. Assessment of viability and motility was performed using fresh semen (T0), after centrifugation and resuspension prior to adding the cryoprotectant (T15), after adding the cryoprotectant (T30) and after freezing and thawing (Tpost). In all three resuspending media used, sperm viability and motility (forward and total) decreased (p < 0.05) during both the equilibration period especially before addition of the cryoprotective medium (between T0 and T15) and during the freeze-thaw process comparison between T30 and Tpost. The recovery of viable and motile spermatozoa (post-thaw values/values of fresh samples) was higher (p < 0.05) in normal semen than in low-quality semen. In both groups, the recovery was slightly, but significantly, higher with SP than with BM and the presence of BSA has no beneficial effect. To conclude, these data suggest that SP may reduce the deleterious effects of cryopreservation. Nevertheless cryopreservation of spermatozoa in a medium containing neither SP nor biological substances could offer an acceptable cryoprotection of spermatozoa to be used in assisted fertilization procedures, especially for intracytoplasmic sperm injection.