Cryopreservation of human semen

A comprehensive review and update on human fertility cryopreservation methods and tools

The broad conceptualization of fertility preservation and restoration has become already a major concern in the modern western world since a large number of individuals often face it in the everyday life. Driven by different health conditions and/or social reasons, a variety of patients currently rely on routinely and non-routinely applied assisted reproductive technologies, and mostly on the possibility to cryopreserve gametes and/or gonadal tissues for expanding their reproductive lifespan. This review embraces the data present in human-focused literature regarding the up-to-date methodologies and tools contemporarily applied in IVF laboratories' clinical setting of the oocyte, sperm, and embryo cryopreservation and explores the latest news and issues related to the optimization of methods used in ovarian and testicular tissue cryopreservation.

Cyanidin-3-Ο-glucoside supplementation in cryopreservation medium improves human sperm quality

Currently, the cryopreservation of human spermatozoa must overcome the adverse effects of excessive oxidation. In this study, we aimed to evaluate the effect of supplementation of cryopreservation medium with cyanidin-3-Ο-glucoside (C3G) on sperm quality. Semen samples were obtained from men with normozoospermia according to WHO criteria (n = 39). The sperm parameter values were compared after cryopreservation in medium supplemented with and without C3G.Compared with the control group (without additive), low doses (50 μM and 100 μM) of C3G improved sperm viability and motility and decreased the reactive oxygen species (ROS) of spermatozoa, while high doses (200 μM) of C3G did not obviously enhance sperm quality. The amount of DNA fragmentation index (DFI) and high DNA stainability (HDS) after freezing were higher in the control group than in the C3G supplementation groups. Low-concentration C3G supplementation (50 μM) was negatively correlated with sperm ROS levels (r = -0.2, p = 0.03). Collectively, our findings suggest that C3G could be an efficient semen cryoprotectant that ameliorates oxidative stress in human sperm during cryopreservation.

Vitrification and conventional freezing methods in sperm cryopreservation: A systematic review and meta-analysis

OBJECTIVE

The objective is to systematically review and synthesize the literature on the efficacy with two different cryopreservation methods used for human spermatozoa and evaluate whether vitrification protocol and quality of sperm influence effect estimates.

DESIGN

The following electronic databases were searched up to September 2017: Pubmed, Embase and Web of Science. The search strategy used the following the relevant medical subject heading (MeSH) terms, keywords, and word variants for: sperm parameters, conventional freezing, and vitrification. Queries were limited to those involving humans. Randomized controlled trials (RCTs) that published in English languages were considered eligible. Studies and references were included if they reported total motility, progressive motility, morphology, or DNA fragmentation index (DFI) for vitrified or conventional cryopreserved human spermatozoa. Patients recruited in RCTs considering sperm vitrification as one of the experimental arms and conventional freezing (including slow freezing or vapor fast freezing) sperm control as the other. Studies that had high risks of allocation concealment were excluded when performing sensitivity analysis. We specified 2 subgroup variables, including vitrification protocol and quality of spermatozoa cryopreserved, to investigate sources of heterogeneity. A meta-analysis was performed using a random effects (I² > 50%) or fixed effects (I² < 50%) model to calculate weighted mean differences (MD) and 95% CI.

RESULT(S)

The search yielded a total of 2428 articles and 13 RCTs were included for analysis. They involved 486 vitrified and 486 conventional cryopreserved sperm samples. Four sperm parameters were reported as mean differences and based on adjusted estimates in all included studies. Meta-analysis of these studies showed significantly higher total motility [weighted mean differences (WMD) 6.98; 95% confidence interval (CI) 2.94; 11.02; P < 0.0001] and progressive motility [WMD 4.59; 95% CI 0.78; 8.39; P = 0.02] of past-thawed sperm following vitrification compared with conventional freezing methods. However, DNA fragmentation index (DFI) [WMD -1.18; 95% CI -2.81; 0.45; P = 0.16] and morphology [WMD 0.11; 95% CI -0.42; 0.63; P = 0.69] of past-thawed sperm are similar between two freezing groups. Subgroup analysis shown that the vitrification protocol and quality of spermatozoa are potential risk factors for the efficacy of vitrification. Higher past-thawed sperm parameters following the cryoprotectants-free (CPAs-free) vitrification were observed, as well as a lower past-thawed sperm parameters with the cryoprotectants-presence (CPAs-presence) vitrification, which could reflect the CPAs related cytotoxicity. Meanwhile, vitrification had higher ability in preservation of high quality of spermatozoa compared with vitrification of low quality spermatozoa.

CONCLUSION(S)

According to the results of present meta-analysis, vitrification is superior to conventional freezing methods in preservation of spermatozoa, regarding total and progressive motility. However, the efficacy of vitrification is influence by using different vitrification protocol and cryopreservation of different quality spermatozoa. It is must emphasized that the results of present meta-analysis is limited by the small number of studies of variable vitrification protocol. Further well conducted studies are required to confirm the efficacy of vitrification in cryopreservation of spermatozoa, in addition, allow the examination of the two cryopreservation methods in terms of pregnancy achievement and determination of the role of clinical variable on efficacy of vitrification.

Could cryopreserved human semen samples be stored at -80°C?

OBJECTIVE

To evaluate storage time effects in cryopreserved human semen samples, kept in the freezer at a controlled temperature of -80°C, on sperm viability after thawing.

METHODS

We used 20 semen samples. Each sample was cryopreserved in 10 fingers, which were divided into five groups: one group was kept in cryogenic canisters throughout the experiment(control), and four groups were kept in a VIP Ultra Low MDF-U76V- PE freezer, with the temperature set at -80°C, for 24, 48, 72 and 96 hours, respectively. After the exposure time, the samples were stored in cryogenic canisters after being thawed. The analyzed parameters were: motility, vitality and mitochondrial activity.

RESULTS

After thawing, we noticed decreased sperm motility, vitality and mitochondrial activity, when comparing the tested groups with the control group, as well as a progressive reduction in the analyzed parameters between the times evaluated.

CONCLUSIONS

Cryopreservation of semen samples at -80°C is potentially harmful to sperm viability, causing damage when submitted to longer exposure times.

The effects of storing and transporting cryopreserved semen samples on dry ice

Objective

This study aimed to test the effects on sperm viability of transporting cryopreserved semen samples on dry ice.

Methods

Twenty normozoospermic semen samples were cryopreserved and divided into five groups. The samples in Group 1 were immersed in liquid nitrogen throughout the experiment in cryogenic storage tanks; the cryopreserved straws in Group 2 were placed in a Styrofoam box containing dry ice and kept under these conditions for 48 hours; the samples in Group 3 were kept for 48 hours on dry ice under the same conditions as the Group 2 samples, and were then moved to a storage tank filled with liquid nitrogen; Group 4 samples were also kept for 48 hours in dry ice storage, and the Styrofoam box containing the samples was shipped by plane to assess the effects of shipping; the samples in Group 5 were shipped together with the Group 4 samples and were placed in a storage tank with liquid nitrogen after spending 48 hours stored on dry ice. After thawing, sperm parameters were analyzed for viability, vitality, and motility; spermatozoa were also tested for mitochondrial activity.

Results

Significant decreases in motility recovery rates (P=0.01) and vitality (P=0.001) were observed in all groups when compared to the control group. Mitochondrial activity was significantly decreased only in Group 5 (P=0.04), as evidenced by greater numbers of sperm cells not stained by reagent 3,3'-diaminobenzidine.

Conclusions

Transportation did not affect the quality of cryopreserved semen samples, but dry ice as a means to preserve the samples during transportation had detrimental effects upon the sperm parameters assessed in this study.

Spermatozoa and seminal plasma fatty acids as predictors of cryopreservation success

There is a lack of information about the importance of fatty acid composition of the human sperm membranes and seminal plasma in the cryopreservation procedure. Our aims were to study the possible relationships between the fatty acid composition of human spermatozoa or seminal fluid before freezing, and the sperm quality, measured in terms of viability and motility, before and after freezing-thawing. A further objective of this study was to determine whether the antioxidant capacity (TAC) of the seminal plasma is related to fatty acid (FA) composition and to success of the cryopreservation process. Polyunsaturated fatty acids (PUFA), ω3 PUFAs and docosahexaenoic acid (DHA) in spermatozoa were significantly positively correlated with sperm viability and motility parameters before and after freezing. An inverse relationship was found for monounsaturated (MUFA), ratio ω6/ω3, ratio saturated saturated fatty acids/PUFA (SFA/PUFA) with the seminal parameters. Seminal plasma fatty acid composition was not related to viability. However, motility parameters before and after freezing were related to stearic acid (C18:0) and DHA. TAC in seminal plasma was directly related to PUFA, w3 and DHA. On the other hand, SFA, C22:0, C24:0 and MUFA in seminal plasma were inversely related to the antioxidant capacity. TAC was directly correlated with motion parameters after thawing, We described a significant correlation between the fatty acid composition of the human spermatozoa or seminal plasma and the sperm parameters of the samples after thawing. PUFA, W3 and specially DHA are directly correlated with sperm motility and viability after freezing/thawing, and MUFA was inversely correlated. This means that in the future the fatty acid composition could be used as a predictor of the capacity of cryopreservation. On the other hand, we could design further procedures to modify the lipid composition or/and antioxidant capacity of ejaculate to make it more resistant to the cryopreservation process.

Effect of genistein supplementation of thawing medium on characteristics of frozen human spermatozoa

In this study, we evaluated the effects of genistein supplementation of the thawing extender on frozen-thawed human semen parameters. We analyzed the effect of supplementation on sperm motility, capacitation (membrane lipid disorder), reactive oxygen species (ROS) generation, chromatin condensation and DNA damage. Using this preliminary information, it maybe possible to improve the cryopreservation process and reduce the cellular damage. We have confirmed that the isoflavone genistein (10 micromol L(-1)) has antioxidant properties on the frozen-thawed spermatozoa. This results in a decreased ROS production that shows a slight improvement in the sperm motility, and decreases the membrane lipid disorder and DNA damage caused by cryopreservation. These results suggest an effect of genistein on sperm functionality that could be of interest for assisted reproduction treatments using frozen-thawed human spermatozoa, but further studies will be necessary to confirm our findings and to evaluate the possible clinical applications.

Normal birth after transfer of cryopreserved human embryos generated by microinjection of cryopreserved testicular spermatozoa into cryopreserved human oocytes

OBJECTIVE

To report the first birth after transfer of cryopreserved embryos generated by intracytoplasmic sperm injection of cryopreserved testicular spermatozoa into cryopreserved human oocytes.

DESIGN

Case report.

SETTING

Tertiary center for reproductive technology.

PATIENT(S)

A 36-year-old woman with primary infertility of 3 years' duration and a 37-year-old man with congenital bilateral absence of the vas deferens.

INTERVENTION(S)

Cryopreservation of human embryos after oocytes and sperm thawing.

MAIN OUTCOME MEASURE(S)

Live birth.

RESULT(S)

A healthy, normal female infant with a birth weight of 2,950 g was born by cesarean section at 38 weeks' gestation, with normal 6-month follow-up.

CONCLUSION(S)

Embryo cryopreservation can lead to successful results, even with the use of cryopreserved gametes.

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.

Effects of various cryopreservation media and freezing-thawing on the morphology of rat testicular biopsies

Currently, testicular sperm extraction is successfully combined with intracytoplasmic sperm injection into the oocyte (ICSI). Several pieces of a testicular biopsy can be frozen and thawed until the ICSI attempt. In this study, the effects of freezing-thawing on the morphology of rat testicular biopsies stored in different cryopreservation media were analysed. Each cryopreservation medium contained glycerol and/or dimethyl sulfoxide (DMSO) as cryoprotectants. In general, both glycerol and DMSO, when applied at moderate concentrations (6-25%), preserved the structure of the seminiferous epithelium. The freezing-thawing procedure had no significant effect on tubular diameter; however, it caused a 'folding' of the lamina propria and notable damage to Sertoli cells, spermatogonia and spermatocytes. Round and elongated spermatids and spermatozoa displayed occasional nuclear damage, vacuolization, and shrinkage/swelling of the cytoplasm. However, the vast majority of these cells maintained their normal structure in nearly all the applied cryomedia. It is concluded that freezing-thawing of testicular biopsies, and the cryopreservation medium, have a significant impact on the structure of the seminiferous epithelium, particularly on its basal compartment.

Comparison of protective media and freezing techniques for cryopreservation of human semen

OBJECTIVE

To evaluate the influence of cryopreservation medium and freezing-thawing techniques on human sperm motility and morphology.

STUDY DESIGN

63 semen samples were obtained from 39 donors to the artificial insemination programme. Possible effects of the sperm dilution with cryomedium on the motility were examined 10 min after exposure of 24 high initial quality semen samples to TEST-yolk ¿zwitterion-citrate-egg yolk extender containing TES [N-Tris (hydroxymethyl) methylaminoethane sulfonic acid] and Tris [(hydroxymethyl) aminomethane]¿ and human sperm preservation medium (HSPM). Post-thaw sperm motility from 24 frozen semen samples was examined comparing the cryoprotective efficacy of TEST-yolk and HSPM following different freezing techniques (vapour freezing, fast programmable freezing and slow programmable freezing). The relationship of sperm morphology to the effects of freezing was investigated on 39 semen samples following different freezing techniques. Post-thaw sperm motility from 39 frozen semen samples was compared among three groups divided according to the percentage of morphologically normal cells (<40, 40-50 and >50%) in fresh semen.

RESULTS

Exposure of spermatozoa to cryomedia for 10 min at room temperature significantly reduced motility in TEST-yolk treatment group for 9% and in HSPM treatment group for 18% (P<0.01). The recovery of motile sperms (mean+/-standard deviation) was 49+/-15.7, 43+/-15.2 and 52+/-16.8% when TEST-yolk was used and 34+/-17.8, 32+/-18.2 and 50+/-13.6% when HSPM was used as a cryopreservative following vapour freezing, and fast and slow programmable freezing, respectively. Following vapour freezing and also following fast programmable freezing, the recovery of motile sperm was significantly higher (P<0.05) after addition of TEST-yolk medium than after addition of HSPM. Post-thaw motility of the sperm cryopreserved in HSPM showed significant differences (P<0.05) after three different freezing techniques. The recovery of motile sperms was 57+/-26.4, 38+/-8.6 and 38+/-17.3% in groups with >50, 40-50 and <40% morphologically normal cells, respectively. The percentage of morphologically normal spermatozoa was reduced 8% after vapour freezing and 6 and 3% after fast and slow programmable freezing, respectively. The results were statistically analysed using SAS/STAT software.

CONCLUSIONS

Slow programmable freezing was superior to vapour freezing and fast programmable freezing as a method for sperm cryopreservation. However, none of these methods of freezing had discernible effects on sperm morphology. Motility of spermatozoa decreased due to the exposure of semen to cryomedium. TEST-yolk was a superior cryomedium to HSPM. Fresh semen with more than 50% of morphologically normal cells showed the best recovery of motile cells after freezing and thawing.

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.

Reactive oxygen species generation by seminal cells during cryopreservation

OBJECTIVES

To test the hypothesis that conventionally used procedures for semen cryopreservation may cause an increase in the production of reactive oxygen species (ROS) by sperm or by seminal leukocytes, which may contribute to poor sperm function following cryopreservation.

METHODS

Eighteen semen specimens with normal parameters from healthy male donors 22 to 40 years of age were each divided into two portions. The first portion was combined 1:1 with Test Yolk Buffer-Glycerol Freezing Medium and was frozen by gradual cooling into liquid nitrogen (-196 degrees C). The second portion was washed and the cells were resuspended in Sperm Washing Medium (SWM) and incubated at room temperature to serve as controls. After a period of treatment, frozen samples were thawed and semen cells were washed and resuspended in SWM. ROS generation by semen cells from each treatment group was measured on a luminometer. Sperm motility, sperm viability, and sperm membrane integrity were also measured in both control and freeze-thaw samples. To further assess ROS generation by semen cells during the cooling process, aliquots of washed semen cells and purified polymorphonuclear leukocytes (PMNs) were incubated separately at different temperature conditions (37 degrees C, 22 degrees C, 4 degrees C, and -20 degrees C). ROS activity in each treatment group was measured and compared with each other.

RESULTS

In both semen cells and PMNs, ROS activity increased significantly during the cooling process. The highest ROS levels were recorded in both groups when cooled to 4 degrees C. The ROS levels were extremely low in samples cooled to -20 degrees C and in freeze-thaw samples, probably due to marked loss of cell viability.

CONCLUSIONS

Gradual reduction of temperature during the process of semen cryopreservation can cause a significant ROS generation by semen cells. ROS is particularly elevated during cooling if the semen sample is contaminated by more than 0.5 x 10(6) leukocytes. Removal of leukocytes from semen samples or treatment with antioxidants prior to cryopreservation may improve sperm viability and function.

Effect of fluctuations in temperature encountered during handling and shipment of human cryopreserved semen

The effect of temperature fluctuations which cryopreserved spermatozoa may undergo during routine shipping and handling was evaluated in sperm frozen with two cryoprotectants. Sperm frozen in TEST-yolk buffer maintained motility better than those frozen in glycerol solution in all studies. Sperm motility was significantly compromised in samples stored more than one day in dry ice, regardless of the cryoprotectant, and more than two days in a liquid nitrogen shipping dewar if frozen in glycerol solution. Sperm motility was not compromised following exposure to room temperature for up to 3 min if TEST-yolk buffer was used as the cryoprotectant, but was compromised following 1 min exposure using glycerol cryoprotectant. This study describes the limits of non-ideal conditions that spermatozoa may undergo during shipping and handling, and demonstrates the effects of the cryoprotectant on those limits.

Effect of natural antioxidants tocopherol and ascorbic acids in maintenance of sperm activity during freeze-thaw process

Excessive generation of reactive oxygen species and increased peroxidation of the phospholipids in the membrane is proposed as a biochemical basis for the reduced activity of spermatozoa in cryopreserved semen. The possible role of alpha-tocopherol (VE) and ascorbic acid (VC) in improving the quality of frozen semen was investigated. Semen samples were divided into aliquots and frozen in freezing media with and without VC or VE. Sperm parameters, including motility after thawing and also at 2 h, % grade A motility (rapid and linear forward progression), and hypoosmotic swelling (HOS) scores, were measured in all samples. Vitamin C did not result in any improvement in sperm parameters studies. Vitamin E improved the post-thaw motility minimally. This improvement, although statistically significant, was actually very small. There were, however, wide variations between the samples. The motility improvement was considered in 5 of 12 samples, and HOS improved in some of the samples tested with VE. Future studies are needed to determine if these antioxidants can produce a consistent improvement in some individuals rather than help the majority of patients.