Cryopreservation of human spermatozoa by vitrification versus conventional rapid freezing: Effects on motility, viability, morphology and cellular defects

The application of mean number of DNA breakpoints in sperm cryopreservation

Growing concerns over declining male semen quality and rising infertility have shifted attention to male fertility. Sperm cryopreservation emerges as a crucial tool in preserving male fertility, especially for patients who need proactive preservation, such as cancer patients before undergoing radiation or chemotherapy. Although cryopreservation does not directly address infertility, effective preservation can support future fertility. However, the process may compromise sperm DNA integrity. Despite their impairment, damaged sperm often retain vitality and may still have the potential to fertilize an egg. Nonetheless, if damaged sperm fertilize an egg, excessive DNA damage could impede embryo implantation and development, despite the egg's repair capabilities. Consequently, precise detection of sperm DNA damage is crucial and urgent. To better address the issue of sperm DNA damage detection, we have introduced a novel fluorescence biosensor technology known as the TDT/SD Probe. This technology utilizes terminal deoxynucleotidyl transferase (TdT) and strand displacement probes to accurately detect the number of sperm DNA breakage points during the cryopreservation process. Experimental results reveal that the number of sperm DNA breakpoints significantly increases after both sperm vitrification (8.17 × 105) and conventional slow freezing (10.80 × 105), compared to the DNA breakpoints of fresh semen samples (5.19 × 105). However, sperm vitrification has the least impact on sperm breakage points. This research provides innovative means for further optimizing sperm preservation techniques by offering a novel DNA damage detection method, enabling more precise assessment of sperm DNA damage during the freezing process.

Evaluation of microRNA expression profiles in human sperm frozen using permeable cryoprotectant-free droplet vitrification and conventional methods

For sperm cryopreservation, the conventional method, which requires glycerol, has been used for a long time. In addition, the permeable cryoprotectant-free vitrification method has been continuously studied. Although the differences of cryopreservation effects between the two methods have being studied, differences in microRNA (miRNA) profiles between them remain unclear. In this study, we investigated the differences in miRNA expression profiles among conventional freezing sperm, droplet vitrification freezing sperm and fresh human sperm. We also analyzed the differences between these methods in terms of differentially expressed miRNAs (DEmiRs) related to early embryonic development and paternal epigenetics. Our results showed no significant differences between the cryopreservation methods in terms of sperm motility ratio, plasma membrane integrity, DNA integrity, mitochondrial membrane potential, acrosome integrity, and ultrastructural damage. However, sperm miRNA-sequencing showed differences between the two methods in terms of the numbers of DEmiRs (28 and 19 with vitrification using a nonpermeable cryoprotectant and the conventional method, respectively) in postthaw and fresh sperm specimens. DEmiRs related to early embryonic development and paternal epigenetics mainly included common DEmiRs between the groups. Our results showed that the differences between conventional freezing and droplet vitrification were minimal in terms of miRNA expression related to embryonic development and epigenetics. Changes in sperm miRNA expression due to freezing are not always detrimental to embryonic development. This study compared differences in miRNA expression profiles before and after cryopreservation between cryopreservation by conventional and vitrification methods. It offers a new perspective to evaluate various methods of sperm cryopreservation.

Effects of Slow Freezing and Vitrification of Human Semen on Post-Thaw Semen Quality and miRNA Expression

Semen cryopreservation has played an important role in medically assisted reproduction for decades. In addition to preserving male fertility, it is sometimes used for overcoming logistical issues. Despite its proven clinical usability and safety, there is a lack of knowledge of how it affects spermatozoa at the molecular level, especially in terms of non-coding RNAs. Therefore, we conducted this study, where we compared slow freezing and vitrification of good- and poor-quality human semen samples by analyzing conventional sperm quality parameters, performing functional tests and analyzing the expression of miRNAs. The results revealed that cryopreservation of normozoospermic samples does not alter the maturity of spermatozoa (protamine staining, hyaluronan binding), although cryopreservation can increase sperm DNA fragmentation and lower motility. On a molecular level, we revealed that in both types of cryopreservation, miRNAs from spermatozoa are significantly overexpressed compared to those in the native semen of normozoospermic patients, but in oligozoospermic samples, this effect is observed only after vitrification. Moreover, we show that expression of selected miRNAs is mostly overexpressed in native oligozoospermic samples compared to normozoospermic samples. Conversely, when vitrified normozoospermic and oligozoospermic samples were compared, we determined that only miR-99b-5p was significantly overexpressed in oligozoospermic sperm samples, and when comparing slow freezing, only miR-15b-5p and miR-34b-3p were significantly under-expressed in oligozoospermic sperm samples. Therefore, our results imply that cryopreservation of normozoospermic sperm samples can modulate miRNA expression profiles in spermatozoa to become comparable to those in oligozoospermic samples.

Safety evaluation of single-sperm cryopreservation technique applied in intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) is a technique that directly injects a single sperm into the cytoplasm of mature oocytes. Here, we explored the safety of single-sperm cryopreservation applied in ICSI. This retrospective study enrolled 186 couples undergoing ICSI-assisted pregnancy. Subjects were allocated to the fresh sperm (group A)/single-sperm cryopreservation (group B) groups based on sperm type, with their clinical baseline/pathological data documented. We used ICSI-compliant sperm for subsequent in vitro fertilization and followed up on all subjects. The recovery rate/cryosurvival rate/sperm motility of both groups, the pregnancy/outcome of women receiving embryo transfer, and the delivery mode/neonatal-related information of women with successful deliveries were recorded. The clinical pregnancy rate, cumulative clinical pregnancy rate, abortion rate, ectopic pregnancy rate, premature delivery rate, live birth delivery rate, neonatal birth defect rate, and average birth weight were analyzed. The two groups showed no significant differences in age, body mass index, ovulation induction regimen, sex hormone [anti-Müllerian hormone (AMH)/follicle-stimulating hormone (FSH)/luteinizing hormone (LH)] levels, or oocyte retrieval cycles. The sperm recovery rate (51.72%-100.00%) and resuscitation rate (62.09% ± 16.67%) in group B were higher; the sperm motility in the two groups demonstrated no significant difference and met the ICSI requirements. Group B exhibited an increased fertilization rate, decreased abortion rate, and increased safety versus group A. Compared with fresh sperm, the application of single-sperm cryopreservation in ICSI sensibly improved the fertilization rate and reduced the abortion rate, showing higher safety.

Successful recovery of motile and viable boar sperm after vitrification with different methods (pearls and mini straws) using sucrose as a cryoprotectant

Vitrification of sperm by direct contact with liquid nitrogen is increasing in popularity as an alternative to conventional (slow) freezing. Although slow freezing is very challenging in boar sperm cryopreservation, this is currently the standard method used. We compared vitrification in "pearls" and in "mini straws" using the in vitro fertilization media Porcine Gamete Media with 0.3 M sucrose with the standard (slow) method used to preserve boar sperm. Both vitrification methods reduced the viability of the sperm sample more than slow freezing (42.2 ± 4.3% total motility and 71.4 ± 2.3% alive), however, both protocols allowed for the successful recovery of the sperm samples. By comparing two different methods of vitrification and two different methods of post-thaw preparation we were able to determine the optimal vitrification-thaw protocol for boar sperm. When comparing pearls and mini-straws, the smaller liquid volume associated with pearls had a positive effect on the survivability of the samples, reducing sperm DNA damage (1.2 ± 0.2% vs. 5.1 ± 0.1.7%) and preserving motility (26.15 ± 2.8% vs 9.39 ± 0.9%) after thawing. In conclusion, the pearl method was the most suitable of the vitrification techniques for use with boar sperm.

Lactobacillus plantarum secretions may exert a cryoprotective effect on human sperm motility: A prospective in vitro study

BACKGROUND

Semen cryopreservation is a widely used procedure for fertility preservation, despite some level of cryodamage that may occur in spermatozoa after thawing. However, there is some evidence that lactobacilli, one of the bacteria found in semen, might benefit sperm quality.

OBJECTIVES

This study aims to determine whether the addition of Lactobacillus plantarum secretions to sperm freezing medium has an impact on sperm motility, morphology, and DNA fragmentation.

MATERIALS AND METHODS

This is a prospective auto-controlled study. It was conducted on 30 raw semen samples from 30 infertile men attending a fertility center for semen analysis. Before freezing, all the samples were analyzed for motility, morphology, and DNA fragmentation percentages. Each sample was then divided equally into three aliquots. Cryopreservation was performed on each aliquot using one of the following three media: without Lactobacillus plantarum secretions (control group) or with 107 or 108 colony-forming units/mL Lactobacillus plantarum secretions. Sperm motility, morphology, and DNA integrity were evaluated after the cryopreservation media were added and after semen thawing.

RESULTS

The results of this study indicated that after thawing, no statistically significant decrease in progressive motility and non-progressive percentages were detected in the sperm freezing medium supplemented with 108 colony-forming units/mL Lactobacillus plantarum secretions than the fresh raw semen. Moreover, multivariate linear regression model analyses showed that the progressive motility (p = 0.02), non-progressive motility (p = 0.016), and non-motile spermatozoa (p = 0.012) percentages were significantly decreased in the freezing medium (without Lactobacillus plantarum secretions) compared to the fresh raw semen.

DISCUSSION AND CONCLUSION

To the best of our knowledge, this is the first study showing that Lactobacillus plantarum secretions had a cryoprotective effect on sperm motility when added to the sperm freezing medium. Furthermore, Lactobacillus plantarum secretions were found to protect sperm DNA integrity more effectively than the freezing medium without Lactobacillus plantarum secretions in non-normozoospermia group. Cryopreservation procedures must therefore be optimized to minimize any iatrogenically induced sperm DNA damage, given the correlation between sperm DNA damage and increased mutation loads in progeny.

Epididymal Spermatozoa Show Higher Cryoresistance to Vitrification Process Than Ejaculated Spermatozoa in Dogs

The aim of this study was to investigate differences in the sperm response to a vitrification-warming process between ejaculated and epididymal dog spermatozoa, and to evaluate the efficacy of an animal protein-free extender for vitrification of both types of sperm cells. Vitrified-warmed spermatozoa from the epididymis showed greater (p < 0.001) progressive motility and total motility values than ejaculated spermatozoa, regardless of the diluent. The vitrification procedure returned better results for viability and intact acrosome when human tubal fluid (HTF®) was used (25.10 ± 7.90 and 56.50 ± 6.7, respectively) compared with Tris-Citric acid-Glucose (TCG) (15.20 ± 4.70 and 43.70 ± 7.9, respectively) in ejaculated samples. Similarly, higher total motility (34.5 ± 4.5) was observed in HTF postwarmed samples compared with TCG-treated samples (19.52 ± 5.1). The interaction source (epididymis, ejaculated) × extender had a significant effect (p < 0.001) on the values of total motile spermatozoa after warming. HTF-based extender improved (p < 0.001) total motility values in epididymal samples, but not in ejaculated samples. In conclusion, epididymal spermatozoa show higher cryoresistance to the vitrification process than ejaculated spermatozoa in dogs. The use of HTF is adequate for both ejaculated and epididymal canine sperm vitrification.

Onco-TESE (Testicular Sperm Extraction): Insights from a Tertiary Center and Comprehensive Literature Analysis

Background and Objectives: The peak of incidence of testicular cancer (TC) occurs among individuals in their reproductive age, emphasizing the importance of fertility preservation as an integral aspect of disease management. Sperm cryopreservation performed before orchiectomy is ineffective in azoospermic men, necessitating alternative approaches such as microdissection testicular sperm extraction (mTESE) at the time of orchiectomy (onco-mTESE) to obtain viable sperm. This study presents the findings from our institution's experience with onco-mTESE and critically discusses our results in light of the existing body of literature. Materials and Methods: This is a tertiary center retrospective analysis of onco-mTESE procedures performed at a single center between December 2011 and July 2022. The included patients were post-puberal men with testicular tumors requiring orchiectomy, along with concomitant severe oligozoospermia or azoospermia. Bilateral mTESE was performed in all cases. Surgical outcomes, sperm retrieval rates, the usage of preserved viable sperm, assistive reproductive techniques' results, and post-operative serum testosterone were recorded. Results: A total of nine patients were included, with a median age of 34 (IQR 29-36) years. All patients had germ cell tumors (GCTs), with seminomatous and non-seminomatous GCTs accounting for 44.4% (n = 4) and 55.6% (n = 5) of patients, respectively. Sperm retrieval occurred in three (33%) patients: one patient in the ipsilateral testis, one in the contralateral testis, and one in both testes. No complications were reported during the procedure, and no post-operative hypogonadism was observed. Among the three patients with successful sperm retrieval, an intracytoplasmic sperm injection (ICSI) was performed in two patients, resulting in two pregnancies, leading to one healthy live birth and one miscarriage. Conclusions: In the context of TC, it is essential to conduct a thorough evaluation of testicular function, including a semen analysis and cryopreservation. Onco-mTESE has proven its safety in preserving fertility in azoospermic cases while ensuring the efficacy of oncological treatment.

Evaluation of Post-Thaw Swim-Up Selection Combined With Glutathione Addition for Improvement of Sperm Chromatin Maturity in Normozoospermic Samples

BACKGROUND

Cryopreservation of human semen alters the spermatozoal structure, resulting in a reduction in sperm function parameters. Various antioxidants may be able to slow or prevent this type of injury. Glutathione (GSH) has numerous antioxidant properties; supplementing the semen with GSH before freezing may assist in the restoration of post-thaw sperm functionality.

OBJECTIVE

 To investigate the effect of adding 5mM of glutathione before freezing on human sperm cryosurvival.

MATERIALS AND METHODS

Semen samples were collected from 30 patients (22 normozoospermic and 8 asthenozoospermic) after 3-5 days of sexual abstinence. Following liquefaction, macro- and microscopic examinations were performed. The samples were then divided into two equal aliquots: the first aliquot received 5 mM of glutathione before freezing, and the second aliquot was considered the control (without glutathione). The samples were frozen using the rapid cryopreservation method and then preserved for 7-10 days in a liquid nitrogen tank before being thawed. Thawed samples from each group were examined microscopically according to the WHO 2010 guidelines. Aniline blue was used to assess the maturity of the DNA. Then, the direct-swim-up technique was applied to thawed samples from both groups to select the best sperm quality.

RESULTS

The cryopreservation process negatively impacts all sperm characteristics in both groups. Sperm DNA integrity decreased. Glutathione addition before freezing decreased sperm chromatin immaturity (SCI) percent compared to the control (22.98 ± 0.83, 20.79 ± 0.56). The post-thaw performance of the swim-up technique resulted in a select sperm population with high progressive motility (p = 0.04) and an improvement in DNA integrity in the treated group versus the control group after thawing.

CONCLUSION

The DNA integrity in normozoospermic samples was improved by adding 5 mM glutathione before freezing. Performing the swim-up technique after thawing had no effect on sperm quality in asthenozoospermic patients.

Biomaterials for Testicular Bioengineering: How far have we come and where do we have to go?

Traditional therapeutic interventions aim to restore male fertile potential or preserve sperm viability in severe cases, such as semen cryopreservation, testicular tissue, germ cell transplantation and testicular graft. However, these techniques demonstrate several methodological, clinical, and biological limitations, that impact in their results. In this scenario, reproductive medicine has sought biotechnological alternatives applied for infertility treatment, or to improve gamete preservation and thus increase reproductive rates in vitro and in vivo. One of the main approaches employed is the biomimetic testicular tissue reconstruction, which uses tissue-engineering principles and methodologies. This strategy pursues to mimic the testicular microenvironment, simulating physiological conditions. Such approach allows male gametes maintenance in culture or produce viable grafts that can be transplanted and restore reproductive functions. In this context, the application of several biomaterials have been proposed to be used in artificial biological systems. From synthetic polymers to decellularized matrixes, each biomaterial has advantages and disadvantages regarding its application in cell culture and tissue reconstruction. Therefore, the present review aims to list the progress that has been made and the continued challenges facing testicular regenerative medicine and the preservation of male reproductive capacity, based on the development of tissue bioengineering approaches for testicular tissue microenvironment reconstruction.

Cryopreservation of Human Spermatozoa: Functional, Molecular and Clinical Aspects

Cryopreservation is an expanding strategy to allow not only fertility preservation for individuals who need such procedures because of gonadotoxic treatments, active duty in dangerous occupations or social reasons and gamete donation for couples where conception is denied, but also for animal breeding and preservation of endangered animal species. Despite the improvement in semen cryopreservation techniques and the worldwide expansion of semen banks, damage to spermatozoa and the consequent impairment of its functions still remain unsolved problems, conditioning the choice of the technique in assisted reproduction procedures. Although many studies have attempted to find solutions to limit sperm damage following cryopreservation and identify possible markers of damage susceptibility, active research in this field is still required in order to optimize the process. Here, we review the available evidence regarding structural, molecular and functional damage occurring in cryopreserved human spermatozoa and the possible strategies to prevent it and optimize the procedures. Finally, we review the results on assisted reproduction technique (ARTs) outcomes following the use of cryopreserved spermatozoa.

EVALUATION OF TWO CRYOPROTECTANTS USED IN A NEW HUMAN SPERM CRYOPRESERVATION TECHNIQUE

OBJECTIVE

The aim: To examine the efficiency of different concentrations of Dimethyl sulfoxide (DMSO) and glycerol as a cytoprotectants in protection of human sperms during cryopres¬ervation in this technique.

PATIENTS AND METHODS

Materials and methods: Thirty oligozoospermic semen samples were used in this study. Samples diagnosed according to WHO 2010 criteria. Sheep's ovarian follicles obtained from local slaughterhouse and prepared by slicing the ovaries and evacuating the follicular fluid and oocyte. Each semen sample divided into six equal parts, and diluted 1:1 with cryosolution contains 5%, 10%, 15% DMSO or glycerol and injected within the emptied follicles. After freezing and thawing, the semen mixture aspired outside the follicles and sperm concentration, progressive motility, total motility, and normal morphology were examined.

RESULTS

Results: The best recovery rate of progressive and total motility post-thawing were with the use of 5% glycerol, and the lowest recovery rate of progressive and total motility and normal morphology were with the use of 15% DMSO.

CONCLUSION

Conclusions: In this technique, glycerol was more efficient than DMSO regarding sperm motility. The best concentration of glycerol for cryopreserve human spermatozoa is 5%.

Quercetin: Putative effects on the function of cryopreserved sperms in domestic animals

Quercetin is one of the most used antioxidant flavonoids and largely exists in many fruits and vegetables because of its capability to scavenge the free reactive oxygen species (ROSs) by repressing lipid peroxy radical fusion, metal ion chelating through enzyme inhibition, and adopting the repair mechanisms. It also exhibits various biological actions, including antioxidative, anti-inflammatory and antimicrobial activities. Furthermore, it contributes well to sustaining the endogenous cellular antioxidant defence system. The process of cryopreservation is associated with increased oxidative stress, and some steps are potential sources of ROSs, including the method of semen collection, handling, cryopreservation culture media, and thawing, which result in impaired sperm function. Several antioxidants have been proposed to counteract the harmful impact of ROS during semen cryopreservation. The antioxidant capability of quercetin has been verified in different animal species for providing valuable defence to sperm during the cryopreservation process. The beneficial properties of quercetin on various parameters of fresh and post-thaw sperm in different species are clarified in this review. More in-depth investigations are required to clarify quercetin's mechanism of action in different animal species.

Extend the Survival of Human Sperm In Vitro in Non-Freezing Conditions: Damage Mechanisms, Preservation Technologies, and Clinical Applications

Preservation of human spermatozoa in vitro at normothermia or hypothermia maintaining their functions and fertility for several days plays a significant role in reproductive biology and medicine. However, it is well known that human spermatozoa left in vitro deteriorate over time irreversibly as the consequence of various stresses such as the change of osmolarity, energy deficiency, and oxidative damage, leading to substantial limitations including the need for semen examinations, fertility preservation, and assisted reproductive technology. These problems may be addressed with the aid of non-freezing storage techniques. The main and most effective preservation strategies are the partial or total replacement of seminal plasma with culture medium, named as extenders, and temperature-induced metabolic restriction. Semen extenders consist of buffers, osmolytes, and antioxidants, etc. to protect spermatozoa against the above-mentioned adverse factors. Extended preservation of human spermatozoa in vitro has a negative effect on sperm parameters, whereas its effect on ART outcomes remains inconsistent. The storage duration, temperature, and pre-treatment of semen should be determined according to the aims of preservation. Advanced techniques such as nanotechnology and omics have been introduced and show great potential in the lifespan extension of human sperm. It is certain that more patients will benefit from it in the near future. This review provided an overview of the current knowledge and prospects of prolonged non-freezing storage of human sperm in vitro.

Vapour fast freezing with low semen volumes can highly improve motility and viability or DNA quality of cryopreserved human spermatozoa

OBJECTIVES

To challenge a vapour fast freezing (VFF) cryopreservation procedure (conventional VFF) with several vitrification protocols and VFF conducted with small semen volumes (10 μl, microVFF), in order to implement a procedure for sperm banking in subjects with small sperm number.

MATERIALS AND METHODS

Conventional VFF was conducted with test yolk buffer (TYB) as freezing medium and 500 μl straws as carriers. MicroVFF was conducted with TYB and using tips or cell sleepers as carriers. Vitrification was performed with TYB or SpermFreeze as freezing medium and with microspheres and tips as carriers. The effect of different procedures on progressive and total motility, viability, oxidative stress and DNA fragmentation of spermatozoa (sDF) was determined. Fresh and thawed samples, the latter after adequate washing/centrifuging, were evaluated. In some experiments, motility and viability recovery was determined in thawed samples, omitting the washing/centrifuging step.

RESULTS

All the cryopreservation procedures blunted sperm motility and viability and induced increase of oxidative stress and sDF. However, VFF better preserved sperm motility and viability and less induced oxidative stress and sDF than vitrification, independently from the freezing medium and the carriers used in the latter. MicroVFF with cell sleepers resulted in a percentage increase of 57.58 ± 63.63%, 48.82 ± 74.96% and 24.55 ± 39.20% of, respectively, progressive and total motility and viability compared to the conventional VFF. Further, when tips were used, microVFF resulted in a percentage decrease of 15.77 ± 20.77% of sDF with respect to conventional VFF. Finally, omission of washing/centrifuging in post thawed samples, resulted in a much lower negative effect on motility and viability.

DISCUSSION AND CONCLUSION

VFF, and in particular microVFF, better prevents sperm cryodamage than vitrification. Washing/centrifuging step after sample thawing seems to be responsible for a relevant fraction of damage to sperm motility and viability. Overall, our results are promising for developing a novel strategy of sperm banking in subjects with small sperm number, where low semen volumes are mandatory.

Preoperative Cryopreservation Promotes Digital Survival after Digit Replantation

Cryopreservation has been applied in the replantation of limbs with a minimal amount of muscle tissue replanted. And small composite tissues have also been reported to be successfully replanted by preoperative cryopreservation. In this study, we aimed to study the effect of preoperative cryopreservation on digital survival after digit replantation. Accordingly, we collected and compared the demographic and clinicopathological characteristics of patients with digit injury of patients, and we observed no significant difference between the NT and CP patients of digital injury. We also investigated the records of successful digit replantation and other parameters which influenced the odds of digital survival of all recruited patients. Accordingly, we found that the number of survived digits was remarkably increased in patients in the CP group compared with that in patients in the NT group. And the number of patients requiring blood transfusion and the mean length of hospital stay were notably decreased in the CP group. And compared with other patient characteristics, the mechanism of injury (blade, crush, or avulsion) showed a remarkable difference between the two groups of digital failure. Moreover, we analyzed the correlations between patient characteristics and the odds of digit survival and found that compared with other basic characteristics of patients and their injury, the preservation temperature, especially cryopreservation, could significantly promote digital survival after replantation.

Micro-straw: An efficient cryopreservation carrier for rare human spermatozoa

BACKGROUND

Many cryopreservation carriers have been introduced to freeze rare human spermatozoa, however, these carriers relative attributes and comparative effectivenesses have not yet been systematically studied.

OBJECTIVES

Is the Micro-straw cryopreservation carrier more effective for cryopreserving rare human spermatozoa compared with the Cryoplus and LSL carriers?

MATERIALS AND METHODS

This study involves ninety-three samples from healthy sperm donors and forty samples from patients diagnosed with oligospermia, asthenospermia, oligoasthenospermia, or obstructive azoospermia. we determined the optimal freeze-thaw protocol for the Micro-straw carrier. The post-thaw survival rate, normal sperm morphology, acrosome integrity, and DNA fragmentation for Micro-straw, Cryoplus, and LSL carriers were then determined. Finally, we verified the effects of freezing using these carriers by comparing the qualities of post-thaw spermatozoa from patients.

RESULTS

The highest total motility (TM) and progressive motility (PR) survival rates were obtained by placing the Micro-straw at 1 cm above the LN₂ surface for 70 s during freezing and in a 42-°C water bath for 40 s during thawing. No differences were observed in PR survival rate, acrosome integrity, and DNA fragmentation of the post-thaw spermatozoa from the three carriers. However, the normal morphology rate of spermatozoa frozen using the Micro-straw carrier was higher than for the Cryoplus carrier (p < 0.05), and the TM survival rate of spermatozoa frozen with the Micro-straw was higher than that for the LSL carrier (p < 0.01). In verification tests, there were no significant differences in the quality of post-thaw spermatozoa cryopreserved using these carriers for both rare spermatozoa or epididymal sperm.

DISCUSSION AND CONCLUSION

Micro-straw, Cryoplus, and LSL carriers are all efficient means of freezing rare human spermatozoa. However, the Micro-straw carrier is more economical, safe, and user-friendly. This article is protected by copyright. All rights reserved.

A Simple and Efficient Method to Cryopreserve Human Ejaculated and Testicular Spermatozoa in −80°C Freezer

Human autologous sperm freezing involves ejaculated sperm, and testicular or epididymal puncture sperm freezing, and autologous sperm freezing is widely used in assisted reproductive technology. In previous studies, researchers have tried to cryopreserve sperm from mammals (rats, dogs, etc.) using a −80°C freezer and have achieved success. It is common to use liquid nitrogen vapor rapid freezing to cryopreserve human autologous sperm. However, the operation of this cooling method is complicated, and the temperature drop is unstable. In this study, we compared the quality of human ejaculation and testicular sperm after liquid nitrogen vapor rapid freezing and −80°C freezing for the first time. By analyzing sperm quality parameters of 93 ejaculated sperm and 10 testicular sperm after liquid nitrogen vapor rapid freezing and −80°C freezing, we found reactive oxygen species (ROS) of sperm of the −80°C freezer was significantly lower than liquid nitrogen vapor rapid freezing. Regression analysis showed that progressive motility, ROS, and DNA fragmentation index (DFI) in post-thaw spermatozoa were correlated with sperm progressive motility, ROS, and DFI before freezing. For the freezing method, the −80°C freezer was positively correlated with the sperm progressive motility. Among the factors of freezing time, long-term freezing was negatively correlated with sperm progressive motility and ROS. Although freezing directly at −80°C freezer had a slower temperature drop than liquid nitrogen vapor rapid freezing over the same period, the curves of the temperature drop were similar, and slight differences in the freezing point were observed. Furthermore, there were no statistically significant differences between the two methods for freezing testicular sperm. The method of direct −80°C freezing could be considered a simplified alternative to vapor freezing for short-term human sperm storage. It could be used for cryopreservation of autologous sperm (especially testicular sperm) by in vitro fertilization centers.

Clinical Trial Registration: (website), identifier (ChiCTR2100050190).

Cryopreservation of dog epididymal spermatozoa by conventional freezing or ultra-rapid freezing with nonpermeable cryoprotectant

This study was aimed to assess the effectiveness of two methods for cryopreservation of dog epididymal spermatozoa, one by conventional freezing (CF) with shortening both equilibration and cooling times, and the other by ultra-rapid freezing (URF) with nonpermeable cryoprotectant. Sixty epididymides were recovered from thirty orchiectomized adult dogs and the sperm samples were retrieved by retrograde flushing using TCG-EY (tris, citric acid, glucose + 20% egg yolk) extender and then 20 pools were conformed. Each pool was divided into 2 aliquots and then cryopreserved by CF and URF methods respectively. The CF method maintained the cooled-pool samples for 2h (1h without and 1h with 5% glycerol) and then were frozen by liquid nitrogen (LN₂) vapors for 2 min. The URF method cryopreserved the cooled-pool samples using TCG-EY+250 mM sucrose, equilibrating during 30 min (5 °C) and submerging 30-μL drops directly in LN₂. The results showed that the URF method produced a lower percentage of total and progressive motilities and acrosome integrity (P < 0.05) than the CF method. However, the kinetic variables (curvilinear and straight-line velocities, straightness, linearity, wobble, amplitude of lateral head displacement, and beat-cross frequency) and plasma membrane integrity did not differ (P > 0.05) between both cryopreservation methods. Unlike the URF method, the width, area and perimeter of sperm head were reduced after the CF method (P < 0.05). In conclusion, despite the low motility achieved after the ultra-rapid freezing method, the similar values of kinetic, viability and head morphometric dimensions to those obtained after conventional freezing, suggest that ultra-rapid freezing with sucrose may be a useful alternative for the cryopreservation of canine epididymal sperm.

A review of methods for preserving male fertility

Male infertility is responsible for 50% of men's health problems and has always been a concern for personal and social issues. A survey of global statistics suggests an increase in infertility rate as one of the critical issues documented in studies. There are different ways of maintaining fertility in men, depending on their age. In this paper, we review the preservation methods used for fertility treatment in Iran and other countries. Available data were reviewed from Google Scholar, PubMed, Scopus, Web of Science, IranMedex, MEDLIB, IranDoc and Scientific Information Database and searched for articles published up to 2018, using the medical subject heading (MeSH) terms for cryopreservation, sperm, testicular, spermatogonia stem cell, male infertility and/or Iranian and in the world, to provide evidence from evaluation of fertility preservation the methods. Based the search strategy, 274 manuscripts were found. After reviewing the titles, abstracts and manuscripts in their entirety, 119 articles were obtained and selected according to the eligibility criteria. The 85 studies mentioned above were divided into three categories (sperm, testis, and spermatogonia stem cells (SSCs)), and methods of fertility preservation were investigated. Ways to maintain male fertility were different depending on age, and included sperm, testicular, and SSC freezing. The number of studies on testicular tissue and SSCs was low for human samples, and more studies are still needed. Sperm freezing at infertility centres is the top for male fertility preservation.

Tissue and sperm handling before assisted reproductive technology (ART): A systematic review

Objective

: To explore the medical literature on techniques of tissue and sperm handling after surgical retrieval for intracytoplasmic sperm injection (ICSI).

Methods

: A search was performed in PubMed and Google Scholar databases, according to a modified Preferred Reporting Items for Systemic Reviews and Meta-Analyses (PRISMA) guideline, considering the studies investigating tissue handling and sperm selection techniques for ICSI.

Results

: Overall, 42 articles were included in this study, investigating sample handling, methods for sperm selection, and the use of chemical compounds to improve sperm motility and fertilisation rates.

Conclusion

: The ideal sperm handling method should provide a high sperm count, high vitality and appropriate sperm function, without side-effects. In this review the most common and useful techniques are described and the best combination strategies discussed in clinical scenarios.

Unraveling Subcellular and Ultrastructural Changes During Vitrification of Human Spermatozoa: Effect of a Mitochondria-Targeted Antioxidant and a Permeable Cryoprotectant

Mitochondria-targeted antioxidants have great potential to counterbalance the generated reactive oxygen species (ROS) because they cross the inner membrane of the mitochondria. Still, their use was not reported in vitrified human spermatozoa. Our laboratory has successfully vitrified spermatozoa without the use of permeable cryoprotectants, but subcellular-level evidence was missing. Therefore, this study aimed to improve spermatozoa vitrification using a mitochondria-targeted antioxidant (mitoquinone, MitoQ), reveal ultrastructural changes in the spermatozoa due to the use of a permeable cryoprotectant, and report alterations of functional proteins during the spermatozoa vitrification process. For this, each of 20 swim-up-prepared ejaculates was divided into seven aliquots and diluted with a vitrification medium supplemented with varying concentrations of MitoQ (0.02 and 0.2 μM), glycerol (1, 4, and 6%), and a combination of MitoQ and glycerol. All aliquots were vitrified by the aseptic capillary method developed in our laboratory. The spermatozoa function assays revealed that the addition of either MitoQ (0.02 μM), glycerol (1%), or a combination of MitoQ (0.02 μM) and glycerol (1%) in the vitrification medium results in better or equivalent spermatozoa quality relative to the control. Transmission electron microscopy revealed that MitoQ protects the spermatozoa from undergoing ultrastructural alterations, but glycerol induced ultrastructural alterations during the vitrification process. Next, we performed label-free quantitative proteomics and identified 1,759 proteins, of which 69, 60, 90, and 81 were altered in the basal medium, 0.02 μM MitoQ, 1% glycerol, and Mito-glycerol groups, respectively. Actin, tubulins, and outer dense fiber proteins were not affected during the vitrification process. Some of the identified ubiquitinating enzymes were affected during spermatozoa vitrification. Only a few proteins responsible for phosphorylation were altered during vitrification. Similarly, several proteins involved in spermatozoa–egg fusion and fertilization (IZUMO1 and Tektin) were not affected during the vitrification process. In conclusion, MitoQ attenuates the vitrification-induced ultrastructural changes and alterations in the key proteins involved in spermatozoa functions and fertilization.

Sperm Selection Procedures for Optimizing the Outcome of ICSI in Patients with NOA

Retrieving spermatozoa from the testicles has been a great hope for patients with non-obstructive azoospermia (NOA), but relevant methods have not yet been developed to the level necessary to provide resolutions for all cases of NOA. Although performing testicular sperm extraction under microscopic magnification has increased sperm retrieval rates, in vitro selection and processing of quality sperm plays an essential role in the success of in vitro fertilization. Moreover, sperm cryopreservation is widely used in assisted reproductive technologies, whether for therapeutic purposes or for future fertility preservation. In recent years, there have been new developments using advanced technologies to freeze and preserve even very small numbers of sperm for which conventional techniques are inadequate. The present review provides an up-to-date summary of current strategies for maximizing sperm recovery from surgically obtained testicular samples and, as an extension, optimization of in vitro sperm processing techniques in the management of NOA.

Comparative study of fertility parameters in vitrified human spermatozoa in the presence or absence of EmbryORP® : A novel antioxidant

The cryopreservation of spermatozoa has the main purpose of preserving male fertility. However, current preservation techniques have shown to produce lesions in the structure and alter sperm functions, probably due to the production of reactive oxygen species (ROS) during cryopreservation. To overcome the damage provoked by ROS, we introduced a novel antioxidant called EmbryORP^® in a vitrification protocol and compared eight fertility parameters: motility, viability, morphology, concentration, the semen pH, the oxidation-reduction potential (ORP), the spontaneous acrosomal reaction (AR) and the mitochondrial membrane potential (MMP), in the presence or absence of EmbryORP^® . We analysed 20 samples from healthy human sperm donors and observed that the antioxidant significantly decreased the semen pH as well as the MMP and the ORP affecting the balance of ROS. The antioxidant also lowered the motility and viability of the cells, but preserved the acrosome and sperm morphology in general. We concluded that EmbryORP^® lowered the ORP, but to a suboptimal level that may be harmful to spermatozoa. Despite these results, our work opens new perspectives on how to improve cryopreservation media. Therefore, we recommend exploring the EmbryORP^® potential benefit by reducing its concentration or changing the exposure time during the cryopreservation protocol.

Aseptic capillary vitrification of human spermatozoa: Cryoprotectant-free vs. cryoprotectant-included technologies

The protocol of aseptic cryoprotectant-free vitrification on human spermatozoa is well documented. However, data about the effect of permeable cryoprotectants at this procedure is limited. Presented study aimed to test the aseptic capillary vitrification technologies using permeable cryoprotectant-included or cryoprotectant-free media. Thirty-two normal samples were included and analyzed after vitrification in three different media and thawing. Three treatment groups were formed: Group 1, basic medium; Group 2, basic medium with 0.25 M sucrose; Group 3, basic medium with glycerol. Before plunging into liquid nitrogen, capillaries were filled by 10 μl of spermatozoa suspension and isolated from liquid nitrogen by location in hermetically closed 0.25 ml straws. Progressive motility, plasma membrane integrity, total motility/viability after 24, 48 and 72 h in vitro culture, apoptosis and mitochondrial membrane potential (ΔΨm) were determined after thawing at 42 °C. Progressive motility of spermatozoa in groups 1, 2, 3 was 24.9 ± 1.7%, 34.5 ± 2.8% and 34.0 ± 1.4%, respectively (P_1-2,3<0.05). The plasma membrane integrity of spermatozoa in groups 2 and 3 (48.4 ± 2.9% and 45.5 ± 3.9%, respectively) was higher than in Group 1 (33.3 ± 2.1%, P < 0.05). After 24 h, 48 h and 72 h in vitro culture, the total motility and viability of spermatozoa in Group 1 was significantly lower than Group 2 and Group 3. The apoptosis rate in Group 3 (44.5 ± 3.0%) and Group 2 (47.7 ± 4.1%) were lower than in Group 1 (52.5 ± 4.4%; P < 0.05). ΔΨm rates in Group 3 and Group 2 were higher than in Group 1 (P < 0.05) with no statistical differences between this parameter in Group 2 and Group 3 (P > 0.1). In conclusion, supplementation of medium for aseptic capillary technology for cryoprotectant-free vitrification of human spermatozoa by permeable cryoprotectant does not improve the quality of spermatozoa after warming.

Advanced paternal age: effects on sperm parameters, assisted reproduction outcomes and offspring health

Many factors, including postponement of marriage, increased life expectancy, and improved success with assisted reproductive technologies have been contributing to increased paternal age in developed nations. This increased average paternal age has led to concerns about adverse effects of advanced paternal age on sperm quality, assisted reproductive outcomes, and the health of the offspring conceived by older fathers. This review discusses the association between advanced paternal age and sperm parameters, assisted reproduction success rates, and offspring health.

Increasing of malignancy of breast cancer cells after cryopreservation: molecular detection and activation of angiogenesis after CAM-xenotransplantation

Background

Ovarian tissue cryopreservation has a wide range of cancerous indications. Avoiding relapse becomes a specific concern that clinicians frequently encounter. The data about the comparative viability of cancer cells after cryopreservation are limited. This study aimed to evaluate the effect of cryopreservation on breast cancer cells.

Methods

We used in-vitro cultured ZR-75-1 and MDA-MB-231 cell lines. Cell samples of each lineage were distributed into the non-intervened and cryopreserved groups. The cryopreservation procedures comprised programmed slow freezing followed by thawing at 100 °C, 60 s. Biological phenotypes and the related protein markers were compared between the two groups. The EVOS FL Auto 2 Cell Image System was used to monitor cell morphology. Cell proliferation, motility, and penetration were characterized by CCK-8, wound-healing, and transmembrane assay, respectively. The expression of Ki-67, P53, GATA3, E-cadherin, Vimentin, and F-Actin was captured by immunofluorescent staining and western blotting as the proxy measurements of the related properties. The chorioallantoic membrane (CAM) xenotransplantation was conducted to explore angiogenesis induced by cancer cells.

Results

After 5 days in vitro culture, the cell concentration of cryopreserved and non-intervened groups was 15.7 × 10⁴ vs. 14.4 × 10⁴cells/ml, (ZR-75-1, p > 0.05), and 25.1 × 10⁴ vs. 26.6 × 10⁴ cells/ml (MDA-MB-231, p > 0.05). Some cryopreserved ZR-75-1 cells presented spindle shape with filopodia and lamellipodia and dissociated from the cell cluster after cryopreservation. Both cell lines demonstrated increased cell migrating capability and invasion after cryopreservation. The expression of Ki-67 and P53 did not differ between the cryopreserved and non-intervened groups. E-cadherin and GATA3 expression downregulated in the cryopreserved ZR-75-1 cells. Vimentin and F-actin exhibited an upregulated level in cryopreserved ZR-75-1 and MDA-MB-231 cells. The cryopreserved MDA-MB-231 cells induced significant angiogenesis around the grafts on CAM with the vascular density 0.313 ± 0.03 and 0.342 ± 0.04, compared with that of non-intervened cells of 0.238 ± 0.05 and 0.244 ± 0.03, p < 0.0001.

Conclusions

Cryopreservation promotes breast cancer cells in terms of epithelial-mesenchymal transition and angiogenesis induction, thus increasing metastasis risk.

Studies on the basic issues relevant to sperm cryopreservation in humans

Rapid freezing and vitrification are becoming popular for sperm freezing in humans; however, basic and critical issues relevant to sperm cryopreservation remain to be resolved. The aims of the present study were to study the effects of osmolality of freezing medium, sperm concentrations, thawing methods, and sugars (sucrose and trehalose) on sperm motility and DNA integrity by rapid freezing using 0.5 ml standard straws loaded with 100 µl sperm each. The results showed that (1) the post-thaw recovery rates of total motility and progressive motility of sperm cryopreserved in freezing medium containing 0.25 M sucrose with 442 mOsm/kg osmolality were significantly higher (p < 0.05) than that of sperm cryopreserved in freezing medium containing 0.25 M sucrose with 536 mOsm/kg osmolality (36.5 ± 2.8% and 36.9 ± 1.7% versus 30.4 ± 1.9% and 30.3 ± 2.9%, respectively), (2) cryopreservation of both total and progressive motilities was not significantly affected (p > 0.05) by sperm concentrations in the range from 5 to 20 × 10⁶ sperm/ml, (3) thawing method 37°C for 2 min was better than 42°C for 15 s in terms of post-thaw recovery rates of both total and progressive motilities (p < 0.05), (4) 0.25 M trehalose was better than 0.25 M sucrose in cryopreserving both total and progressive motilities (p < 0.05), and (5) sperm nuclear DNA is relatively resistant to the changes of the above factors compared with sperm motility. It was concluded that human sperm can be best cryopreserved by rapid freezing using 0.25 M sucrose or trehalose with osmolality 442 to 457 mOsm/kg at high sperm concentration followed by thawing at 37°C. Trehalose is a stronger cryoprotectant than sucrose for sperm cryopreservation.

Individual variation in fresh and frozen semen of Bali bulls (Bos sondaicus)

AIM

This study aimed to analyze the individual factors influencing the sperm quality of Bali bulls at Baturiti Artificial Insemination (AI) center.

MATERIALS AND METHODS

Semen that was ejaculated from nine Bali bulls was collected using artificial vaginas (n=5/bull). Semen ejaculates were evaluated immediately after collection to measure the quality of the fresh semen, including semen volume, sperm concentration, progressive motility, membrane integrity (MI), and abnormal morphology. Frozen semen was evaluated for progressive sperm motility, concentration, viability, MI, abnormal morphology, and deoxyribonucleic acid (DNA) fragmentation. Other secondary data, focusing on semen quantity (semen volume and sperm concentration), were also collected from frozen the semen production data of the Baturiti AI center from 2017 to 2019. Data were analyzed statistically using a completely randomized design, and one-way analysis of variance was applied to find differences among individual bulls.

RESULTS

Significant differences (p<0.05) were found among the bulls in semen volume, sperm motility, concentration, and MI of the fresh semen. Significant differences (p<0.05) were also found among the bulls in sperm motility, viability, MI, abnormal morphology, and DNA fragmentation of the frozen semen.

CONCLUSION

Individual variation in all the tested sperm parameters of the fresh semen of Bali bulls, except sperm viability and abnormalities, was noted. Similarly, individual variation in all the tested sperm parameters in frozen semen, except sperm concentration, was noted. Therefore, individual factors can be used for selecting a superior bull in Bali cattle.

Vitrification Using Soy Lecithin and Sucrose: A New Way to Store the Sperm for the Preservation of Canine Reproductive Function

A challenge in freezing semen for short and long-term availability is avoiding damage to intact spermatozoa caused by the freezing process. Vitrification protocols provide better results through less manipulation of semen and shorter freezing time compared to slow freezing techniques. Our research was aimed at improving vitrification methods for canine semen. Semen quality was determined in 20 ejaculates after collection. Each ejaculate was divided into eight aliquots, each with a different extender. The control extender contained TRIS, citric acid, fructose, and antibiotics. Soy lecithin and sucrose were added to the control extender at different concentrations to make up the test extenders and final concentration of 50 × 10⁶ spermatozoa/mL. From each group, a 33µL (1.65 × 10⁶ spermatozoa) suspension of spermatozoa was dropped directly into liquid nitrogen and devitrified at least one week later and evaluated as before. Soy lecithin at 1% and 0.25 M sucrose added to the base vitrification media effectively preserved all sperm qualities. Our results demonstrate the effectiveness of our methods. Vitrification media containing sucrose and soy lecithin cause a minimal decline in quality of canine semen after devitrification. Furthermore, extenders used in our research did not contain egg yolk, which was replaced by soy lecithin, thus allowing for ease of shipping to other countries with strict requirements.

Optimizing the protocol for vitrification of individual spermatozoa by adjusting equilibration time

Efficient cryopreservation of small numbers of human spermatozoa is essential in cases of severe male infertility, especially those requiring surgical sperm retrieval. Although vitrifying individual spermatozoa on sperm vitrification devices (SpermVD®) provided optimal cell retrieval upon warming, motility rates tended to be lower than with bulk-freezing. Post-warming motility is directly affected by cryoprotectant exposure; however, optimal cryoprotectant equilibration time is unknown. We evaluated several timeframes exposing individual spermatozoa to cryoprotectant before freezing and different cryoprotectants. A total of 2,925 spermatozoa from 20 patients ranging from normozoospermic to moderate oligoteratoasthenozoospermic were vitrified in small groups, on 60 SpermVD®, in 1 µl droplets of 1:1 v/v cryoprotectant/washing medium mixture. Each group was vitrified after 2-60 minutes equilibration time. Motility of each group was evaluated after warming. Leftover pellets were frozen in cryotubes in a mixture of 1:1 v/v cryoprotectant/washing medium after 10 minutes equilibration at room temperature and 10 minutes on liquid nitrogen vapors. Post-thaw motility correlated negatively with cryoprotectant exposure time. The highest post-warming motility rate (32.1%) was observed with 8-minutes equilibration. After 10 minutes, motility rate of vitrified sperm was lower than that of bulk-freezing (31.7% vs. 37.0%, p < 0.0001). Different cryoprotectants did not affect the results. Therefore, for vitrifying small numbers of spermatozoa, we suggest maximum equilibration time of 8-minutes to achieve maximum motility after warming.

Human sperm vitrification: the state of the art

Sperm cryopreservation has been widely used in assisted reproductive technology (ART) and has resulted in millions of live births. Two principal approaches have been adopted: conventional (slow) freezing and vitrification. As a traditional technique, slow freezing has been successfully employed and widely used at ART clinics whereas the latter, a process to solidify liquid into an amorphous or glassy state, may become a faster alternative method of sperm cryopreservation with significant benefits in regard to simple equipment and applicability to fertility centers. Sperm vitrification has its own limitations. Firstly, small volume of load is usually plunged to liquid nitrogen to achieve high cooling rate, which makes large volume sample cryopreservation less feasible. Secondly, direct contact with liquid nitrogen increases the potential risk of contamination. Recently, new carriers have been developed to facilitate improved control over the volume and speed, and new strategies have been implemented to minimize the contamination risk. In summary, although sperm vitrification has not yet been applied in routine sperm cryopreservation, its potential as a standard procedure is growing.

Progress in translational reproductive science: testicular tissue transplantation and in vitro spermatogenesis

Since the birth of the first child conceived via in vitro fertilization 40 years ago, fertility treatments and assisted reproductive technology have allowed many couples to reach their reproductive goals. As of yet, no fertility options are available for men who cannot produce functional sperm, but many experimental therapies have demonstrated promising results in animal models. Both autologous (stem cell transplantation, de novo morphogenesis, and testicular tissue grafting) and outside-the-body (xenografting and in vitro spermatogenesis) approaches exist for restoring sperm production in infertile animals with varying degrees of success. Once safety profiles are established and an ideal patient population is chosen, some of these techniques may be ready for human experimentation in the near future, with likely clinical implementation within the next decade.

Knockout serum replacement is an efficient serum substitute for cryopreservation of human spermatozoa

The freeze-thaw procedure causes irreversible structural and functional changes in human spermatozoa. In order to decrease the detrimental effects of cryopreservation and improve the quality of post-thawed spermatozoa, the constituents of the freezing solution attracted considerable attention. In this study, for the first time, we evaluated the efficacy of knockout serum replacement (KSR) as a substitute for human serum albumin (HSA) for cryopreservation of human spermatozoa. Twenty semen samples were collected from normozoospermic men and divided them into five equal groups. One of the aliquots was diluted with glycerol-based medium as a control group (CON). The other four aliquots were diluted with the sucrose solution containing 5% HSA (H5), 10% HSA (H10), 5% KSR (K5), and 10% KSR (K10). The diluted samples were frozen and preserved in liquid nitrogen. Post thawed sperm parameters including motion characteristics, viability, membrane integrity, mitochondrial activity, acrosome integrity and DNA intactness in all of the sucrose-based groups were comparable with glycerol-based medium. The replacement of HSA by 10% KSR in the freezing medium resulted in significantly higher post-thawed viability, acrosome integrity and DNA intactness compared with other sucrose-based groups. In conclusion, the addition of 10% KSR to the sucrose-based freezing solution improves the quality of post-thawed human spermatozoa and may have potential to develop chemically defined freezing medium.

Ejaculated compared with epididymal stallion sperm vitrification

The aim of this study was to evaluate the effect of trehalose and lactose extenders on ejaculated and epididymal stallion sperm vitrification. Ejaculated semen samples were collected from seven fertile stallions, and cauda epididymis samples were collected from ten stallion carcasses after slaughter. Both the ejaculated and the epididymis samples were diluted and vitrified using INRA 96® and bovine serum albumin as well as trehalose or lactose. As a control, ejaculated and epididymal samples were collected and frozen using the conventional method. Vitrification was performed by immersing sperm suspensions directly in LN2. After thawing or devitrification, there was assessment of samples for sperm motility using computer-assisted analysis. Viability was assessed using SYBR-14 and propidium iodide (PI) and acrosome integrity by fluorescein using isothiocyanate combined with peanut agglutinin (FITC-PNA) and PI. Epididymal sperm vitrification with trehalose (EPT) or lactose (EPL) resulted in greater progressive sperm motility than sperm of the control sample (EPC). After post-thaw/devitrification of sperm in the EPT group, sperm motility was greater (P<0.001) compared to that using EPL (50.72 ± 5.09% compared with 34.21 ± 3.02%). The results from assessment of ejaculated sperm samples after undergoing the vitrification process indicated cells were less viable (P<0.001) than the control (EJC) sample. In conclusion, vitrification of epididymal stallion sperm using trehalose might be a beneficial alternative for the long-term storage of sperm samples with great economic value. Spermatozoa from vitrified ejaculates of stallions, however, had lesser motility and viability rates than samples subjected to conventional freezing.

Does conventional freezing affect sperm DNA fragmentation?

Objective

Sperm cryopreservation has been widely used in assisted reproductive technology, as it offers great potential for the treatment of some types of male infertility. However, cryopreservation may result in changes in membrane lipid composition and acrosome status, as well as reductions in sperm motility and viability. This study aimed to evaluate sperm DNA fragmentation damage caused by conventional freezing using the sperm chromatin dispersion test.

Methods

In total, 120 fresh human semen samples were frozen by conventional methods, using SpermFreeze Solution as a cryoprotectant. Routine semen analysis and a Halosperm test (using the Halosperm kit) were performed on each sample before freezing and after thawing. Semen parameters and sperm DNA fragmentation were compared between these groups.

Results

There was a significant decrease in sperm progressive motility, viability, and normal morphology after conventional freezing (32.78%, 79.58%, and 3.87% vs. 16%, 55.99%, and 2.55%, respectively). The sperm head, midpiece, and tail defect rate increased slightly after freezing. Furthermore, the DNA fragmentation index (DFI) was significantly higher after thawing than before freezing (19.21% prior to freezing vs. 22.23% after thawing). Significant increases in the DFI after cryopreservation were observed in samples with both normal and abnormal motility and morphology, as well as in those with normal viability.

Conclusion

Conventional freezing seems to damage some sperm parameters, in particular causing a reduction in sperm DNA integrity.