New permeable cryoprotectant-free vitrification method for native human sperm

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.

The effect of the mitochondria-targeted antioxidant Mito-tempo during sperm ultra-rapid freezing

During the freeze-thaw process, human spermatozoa are susceptible to oxidative stress, which may cause cryodamage and reduce sperm quality. As a novel mitochondria-targeted antioxidant, Mito-tempo has been used for sperm cryopreservation. However, it is currently unknown what role it will play in the process of sperm ultra-rapid freezing. The purpose of this study was to investigate whether Mito-tempo can improve sperm quality during ultra-rapid freezing. In this study, samples with the addition of Mito-tempo (0, 5, 10, 20, and 40 μM) to sperm freezing medium were selected to evaluate the changes in sperm quality, antioxidant capacity and ultrastructure after ultra-rapid freezing. After ultra-rapid freezing, the quality and antioxidant function of the spermatozoa were significantly reduced and the spermatozoa ultrastructure was destroyed. The addition of 10 μM Mito-tempo significantly increased post thaw sperm motility, viability, plasma membrane integrity and mitochondrial membrane potential (P < 0.05). Moreover, the DNA fragmentation index (DFI), ROS levels and MDA content were reduced, and the antioxidant enzyme (CAT and SOD) activities were enhanced in the 10 μM Mito-tempo group (P < 0.05). Moreover, Mito-tempo protected sperm ultrastructure from damage. In conclusion, Mito-tempo improved the quality and antioxidant function of sperm after ultra-rapid freezing while reducing freezing-induced ultrastructural damage.

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.

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.

Sperm cryopreservation does not affect live birth rate in normozoospermic men: analysis of 7969 oocyte donation cycles

STUDY QUESTION

Does sperm cryopreservation influence the reproductive outcomes of normozoospermic patients in oocyte donation cycles?

SUMMARY ANSWER

After controlling for confounders, the use of cryopreserved semen from normozoospermic patients does not affect pregnancy and live birth rates after elective ICSI.

WHAT IS KNOWN ALREADY

Sperm cryopreservation by slow freezing is a common practice in ART. While frozen-thawed semen typically presents reduced motility and vitality, its use for ICSI is generally considered adequate in terms of reproductive outcomes. Nevertheless, most studies comparing reproductive outcomes between fresh and cryopreserved sperm include patients with severe male factor (testicular sperm, oligo-, and/or asthenozoospermia) or women of advanced maternal age, where the altered quality of the gametes can partially mask the full effect of freezing/thawing.

STUDY DESIGN, SIZE, DURATION

The study included a retrospective cohort of 7969 couples undergoing their first oocyte donation cycle between January 2013 and December 2019 in one large clinic, using normozoospermic semen from the male partner. All cycles involved elective ICSI, fresh oocytes, and a fresh embryo transfer, either at cleavage or blastocyst stage. Two study groups were established based on the sperm status: fresh (n = 2865) and cryopreserved (n = 5104).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A slow freezing protocol was used for all sperm cryopreservation. Sperm washing, capacitation, and selection prior to ICSI were performed identically for fresh and frozen-thawed samples, using pellet swim-up. Fertilization rate (FR), pregnancy (biochemical and ongoing), and live birth rates were compared between study groups using univariate and multivariate regression analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

Male and female age, sperm concentration and motility after ejaculation, and number of oocytes inseminated were similar between cycles using fresh or cryopreserved sperm. Analysis by Student's t-test did not indicate a significant difference in FR between fresh and cryopreserved sperm (P = 0.0591); however, after adjusting for confounders, this difference reached statistical significance: 74.65% FR for fresh (CI 95%: 73.92-75.38) versus 73.66% for cryopreserved sperm (CI 95%: 73.11-74.20), P = 0.0334. The adjusted regression analysis revealed higher odds of biochemical pregnancy when using fresh sperm (odds ratio (OR): 1.143, P = 0.0175), but no significant effects of sperm cryopreservation were observed for ongoing pregnancy (OR: 1.101, P = 0.0983) and live birth (OR: 1.082, P = 0.1805).

LIMITATIONS, REASONS FOR CAUTION

Caution should be exerted when extrapolating these results to different protocols for sperm cryopreservation and selection, or to IVM, advanced maternal age and classical IVF cycles, which were excluded from analysis. Owing to the retrospective nature of the study, some uncontrolled for variables may affect the results.

WIDER IMPLICATIONS OF THE FINDINGS

Sperm cryopreservation does not affect pregnancy and live birth rates in normozoospermic patients, and although it may lower FR s slightly, this would not be clinically relevant. In line with previous studies that included patients with an apparent male or female factor, sperm cryopreservation is a safe and convenient technique.

STUDY FUNDING/COMPETING INTEREST(S)

The study received no external funding and all authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

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.

Effect of MnTBAP on sperm ultra-rapid freezing and its proteomics study

MnTBAP is a new synthetic antioxidant that has been used for the cryopreservation of sperm. However, the exact mechanism of its cryoprotection at the molecular level is largely unknown. Therefore, in this study, normal human semen samples were selected and MnTBAP (0, 5, 10, 20, 40 μM) was added to sperm freezing medium to assess changes in kinetics parameters, apoptosis, reactive oxygen species (ROS), and DNA fragmentation index (DFI) after sperm ultra-rapid freezing. The tandem masstagging (TMT) proteomics technique was used to further investigate the changes in proteins after sperm ultra-rapid freezing. The kinetic parameters of sperm after ultra-rapid freezing and thawing were significantly reduced and apoptosis, ROS production and DFI were significantly increased. The addition of 40 μM MnTBAP improved the kinetic parameters, while it reduced apoptosis, ROS production, and DFI of sperm after ultra-rapid freezing and thawing (P < 0.05). Compared with the fresh semen, 1978 differential proteins were identified in the frozen-thawed sperm without MnTBAP and 1888 differential proteins were identified in the frozen-thawed sperm with MnTBAP (40 μM) added. The proteins affected during ultra-rapid freezing were mainly related to sperm metabolism, flagellar structure motility, apoptosis, intracellular signaling, capacitation and fertilization, while the addition of MnTBAP reduced the alterations of these proteins.

Advantages of vitrification preservation in assisted reproduction and potential influences on imprinted genes

Cryopreservation has important application in assisted reproductive technology (ART). The vitrification technique has been widely used in the cryopreservation of oocytes and embryos, as a large number of clinical results and experimental studies have shown that vitrification can achieve a higher cell survival rate and preimplantation development rate and better pregnancy outcomes. Ovarian tissue vitrification is an alternative method to slow freezing that causes comparatively less damage to the original follicular DNA. At present, sperm preservation mainly adopts slow freezing or rapid freezing (LN2 vapor method), although the vitrification method can achieve higher sperm motility after warming. However, due to the use of high-concentration cryoprotectants and ultra-rapid cooling, vitrification may cause strong stress to gametes, embryos and tissue cells, resulting in potentially adverse effects. Imprinted genes are regulated by epigenetic modifications, including DNA methylation, and show single allele expression. Their accurate regulation and correct expression are very important for the placenta, fetal development and offspring health. Considering that genome imprinting is very sensitive to changes in the external environment, we comprehensively summarized the effect of cryopreservation—especially the vitrification method in ART—on imprinted genes. Animal studies have found that the vitrification of oocytes and embryos can have a significant impact on some imprinted genes and DNA methylation, but the few studies in humans have reported almost no influence, which need to be further explored. This review provides useful information for the safety assessment and further optimization of the current cryopreservation techniques in ART.

Advances in sperm cryopreservation in farm animals: Cattle, horse, pig and sheep

Sperm cryopreservation is one of the most important procedures in the development of biotechnologies for assisted reproduction. In some farm animals, the use of cryopreserved sperm has so many benefits for which relevance has become more evident in recent decades. Values for post-thaw sperm quality, however, are variable among species and within individuals of the same species. There is no standardized methodology for each of the stages of the cryopreservation procedure (andrological examination, semen collection, dilution, centrifugation, resuspension of the pellet with the freezing medium, packaging, freezing and post-thaw sperm evaluation), which also contributes to differences among studies. Cryotolerance markers of sperm and seminal plasma (SP) have been evaluated for prediction of ejaculate freezability. In addition, in previous research, there has been a focus on supplementing cryopreservation media with different substances, such as enzymatic and non-enzymatic antioxidants. In most studies, inclusion of these substances have led to improved post-thaw sperm quality and fertilizing capacity as a result of minimizing the adverse effects on sperm structure and function. Another approach is the use of different cryoprotectants. The aim with this review article is to provide an update on sperm cryopreservation in farm animals. The main detrimental effects of cryopreservation are described, including the negative repercussion on reproductive performance. Furthermore, the potential use of molecular biomarkers to predict sperm cryotolerance is discussed, as well as the addition of substances that can mitigate the harmful impact of freezing and thawing on sperm.

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.

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.

Cryopreservation of Gametes and Embryos and Their Molecular Changes

The process of freezing cells or tissues and depositing them in liquid nitrogen at -196 °C is called cryopreservation. Sub-zero temperature is not a physiological condition for cells and water ice crystals represent the main problem since they induce cell death, principally in large cells like oocytes, which have a meiotic spindle that degenerates during this process. Significantly, cryopreservation represents an option for fertility preservation in patients who develop gonadal failure for any condition and those who want to freeze their germ cells for later use. The possibility of freezing sperm, oocytes, and embryos has been available for a long time, and in 1983 the first birth with thawed oocytes was achieved. From the mid-2000s forward, the use of egg vitrification through intracytoplasmic sperm injection has improved pregnancy rates. Births using assisted reproductive technologies (ART) have some adverse conditions and events. These risks could be associated with ART procedures or related to infertility. Cryopreservation generates changes in the epigenome of gametes and embryos, given that ART occurs when the epigenome is most vulnerable. Furthermore, cryoprotective agents induce alterations in the integrity of germ cells and embryos. Notably, cryopreservation extensively affects cell viability, generates proteomic profile changes, compromises crucial cellular functions, and alters sperm motility. This technique has been widely employed since the 1980s and there is a lack of knowledge about molecular changes. The emerging view is that molecular changes are associated with cryopreservation, affecting metabolism, cytoarchitecture, calcium homeostasis, epigenetic state, and cell survival, which compromise the fertilization in ART.

Ultrastructural analysis of Lyophilized Human Spermatozoa

Objective:

Lyophilization is potentially more practical and cost-effective alternative for sperm preservation. However, there are no studies that evaluate the ultrastructure of human spermatozoa after lyophilization. Therefore, the aim of our study was to evaluate the ultrasctructure of lyophilized spermatozoa using Transmission Electron Microscopy.

Methods:

From a total of 21 donated seminal samples, 30 aliquots were originated and divided into two aliquots so that one could have been submitted to cryopreservation/thaw and the other for lyophilization/rehydration. The liquefied aliquots were homogenized at room temperature. Samples assigned for cryopreservation were placed in straws and samples assigned for lyophilization were placed in the appropriate vials. Cryopreservation samples were placed at -30oC for 30 minutes subsequently for 30 minutes at vapour phase and then plunged into liquid nitrogen. Lately, were warmed in water bath at 37oC for 10 minutes followed by 10 minutes centrifugation. The pellet was resuspended and analysed in a Makler chamber. The semen vials assigned for lyophilization were loaded into a pre-fixed freeze-drying chamber. Following lyophilization, vials were removed from the freeze-drying chamber and kept at 4oC until rehydration. TEM was performed after rehydration and thawing. Sperm samples were fixed, rinsed in buffer, post fixed and dehydration was carried out in escalating concentrations of alcohol solution, acetone and then, embedding in Epon resin. Ultrathin sections were stained and examined in a Transmission Electron Microscope.

Results:

Analysis of sperm after freezing/thawing using Transmission Electron Microscopy showed lesions to the midpiece, with some mitochondria degeneration and random rupture of plasma membrane. In the head, we identified intact plasma membrane, nucleus and acrosome, as in the flagellum all main structures remained intact including the plasma membrane, the longitudinal columns of dense fibers and the semicircular fibers. Analysis by Transmission Electron Microscopy showed that spermatozoa heads had ruptured plasma membranes, absence of acrosomes, nuclei with heterogeneous and decompressed chromatin. Mitochondria were deteriorated in the midpiece. Longitudinal columns of dense fibers were absent in the flagellum. Axonemes, in cross-sections, were disrupted with disorganized structures.

Conclusions:

To our knowledge, our study demonstrated, for the first time, the structure of the human spermatozoa after lyophilization using Transmission Electron Microscopy. The use of a fixed lyophilization protocol with media containing cryoprotectants might explain the damage to the structures. More studies are necessary to improve the results of sperm lyophilization. In the future, the use of lyophilization of spermatozoa might reduce the costs of fertility preservation, since there will be no need for storage space and transportation is simpler.

Cryo-banking of human spermatozoa by aseptic cryoprotectants-free vitrification in liquid air: Positive effect of elevated warming temperature

Cryoprotectant-free vitrification is a common method for spermatozoa cryopreservation by direct plunging into liquid nitrogen. However, the commercial liquid nitrogen could be potentially contaminated by microorganisms. Warming temperature plays an essential role for quality of human spermatozoa after vitrification. This study aimed to evaluate comparatively a quality spermatozoa after vitrification in liquid nitrogen and clean liquid air as well as with two warming rates: at 42 °C and 45 °C. After performing of routine swim-up of normozoospermia samples, spermatozoa from the same ejaculate were divided into two groups: vitrified in liquid nitrogen (LN) and sterile liquid air (LA). Spermatozoa of LN group were warmed at 42 °C, and spermatozoa of LA groups were divided and warmed at 42 °C (LA42) and 45 °C (LA45). Then spermatozoa motility, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), reactive nitrogen species (RNS), and viability were assessed. It was no found significant differences in quality of spermatozoa from LN and LA groups in the motility, ROS, MMP, RNS rates after warming at 42 °C. A tendency to obtain better spermatozoa quality was found with using of warming by 42 °C in comparison with 45 °C. It was concluded that cryoprotectant-free vitrification by direct dropping of human spermatozoa into clean liquid air can be used as an alternative to cooling in liquid nitrogen. Warming of spermatozoa at 42 °C allows to preserve the spermatozoa physiological parameters.

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.

Improving native human sperm freezing protection by using a modified vitrification method

Slow freezing is the most commonly used technique for the cryopreservation of spermatozoa in clinical practice. However, it has been shown to have a negative impact on sperm function and structure. Vitrification as a successful alternative method has been proved to have better protective effects on human embryos, but vitrification of spermatozoa is still subject to low recovery rates. In this study, a modified vitrification method for native spermatozoa was developed. A total of 28 semen samples were included; each sample was divided into three equal parts and assigned to fresh, slow freezing, and vitrification groups. Sperm vitality, motility, morphology, DNA integrity, and acrosome reaction were assessed for each of the groups. The results showed that vitrification achieves better results for several sperm protection parameters than slow freezing; vitrification achieves a higher recovery rate (P < 0.05), motility (P < 0.05), morphology (P < 0.05), and curve line velocity (P < 0.05) than slow freezing. Furthermore, DNA fragmentation was decreased (P < 0.05) and better acrosome protection (P < 0.05) was exhibited in the spermatozoa after vitrification. Principal component analysis of all sperm parameters revealed that the vitrification cluster was closer to the fresh cluster, indicating that spermatozoa are better preserved through vitrification. In conclusion, while both slow freezing and vitrification have negative effects on sperm function and structure, the vitrification protocol described here had a relatively better recovery rate (65.8%) and showed improved preservation of several sperm quality parameters compared with slow freezing.

Fertilizing capacity of vitrified stallion sperm assessed utilizing heterologous IVF after different semen warming procedures

The aim of this study was to evaluate the fertilizing capacity of frozen or vitrified stallion sperm after assessing different warming procedures. In Experiment 1, different warming procedures were compared after sperm vitrification: immersion in extender at 43 °C (C), or in a water bath at 37 °C/30 s (W37), 43 °C/10 s (W43) or 60 °C/5 s (W60). With the W60 treatment, there were greater values (P < 0.05) for VCL (83.93 ± 3.6 μm/s) and ALH (3.00 ± 0.2 μm) than freezing and with the C group, and greater values (P < 0.001) for PM (35.33 ± 2.5 %) than with the W43 treatment. In Experiment 2, the fertilizing capacity of vitrified and frozen sperm was assessed utilizing heterologous IVF procedures, using cattle oocytes. Vitrification resulted in greater values (P < 0.05) than freezing for the number of bound sperm (1.36 ± 0.3 and 0.69 ± 0.2, respectively). There were no differences between frozen or vitrified sperm in pronuclear formation (26 hours post-insemination - hpi; 14.08 ± 4.2 % and 22.78 ± 4.8 %, respectively) or cleavage rate (32.77 ± 4.3 % and 39.66 ± 4.6 %, respectively). In conclusion, vitrified stallion sperm warmed in a water bath at 60 ºC had the capacity to penetrate cattle oocytes, leading to pronuclear formation and hybrid embryo cleavage after heterologous IVF.

Comparison of rapid freezing versus vitrification for human sperm cryopreservation using sucrose in closed straw systems

Rapid freezing and vitrification using sucrose are two simple and cost-effective sperm cryopreservation methods. However, it is still unclear which method is better and what the optimal concentration of sucrose is. This study aimed to determine the optimal sucrose concentration for human sperm cryopreservation and compare the cryoprotective effects of rapid freezing versus vitrification using different closed straw systems in terms of sperm motility and DNA integrity. Our data showed that: (1) The optimal sucrose concentration for vitrification was 0.25 mol/l among the tested 0, 0.125, 0.25 and 0.5 mol/l concentrations; (2) Sperm total motility and progressive motility were cryopreserved significantly better by rapid freezing than vitrification in standard 0.5 ml cryostraws (P < 0.05); and (3) Sperm total motility and progressive motility were cryopreserved significantly better by vitrification in the straw-in-straw system than rapid freezing in the standard 0.5 cryostraw (P < 0.05), but no difference was found in sperm nuclear DNA fragmentation level between the two cryopreservation methods (P > 0.05). It was concluded that sucrose at 0.25 mol/l concentration is suitable for human sperm rapid freezing and vitrification, and sperm cryopreservation can be achieved by rapid freezing using closed standard 0.5 ml straws or by vitrification using the novel straw-in-straw system made of standard 0.25 and 0.5 ml straws.

Laboratory and clinical management of leukocytospermia and hematospermia: a review

Leukocytospermia and hematospermia are defined as the presence of abnormally high white blood cell and red blood cell concentration in the semen, respectively. Numerous etiologies and various implications on fertility have been identified. In a small proportion of men, the presence of white blood cells or red blood cells can adversely affect sperm quality by the production of reactive oxygen species. Several methods have been used to assess the presence of white blood cells and red blood cells in samples, such as identification of round cells, immunohistochemical staining using monoclonal antibodies, the Endtz test, the peroxidase test, and flow cytometry or microscopy. In addition, techniques have been identified to separate sperm samples from white blood cells and red blood cells for cryopreservation to improve outcomes in assisted reproductive technology. In this review, laboratory and clinical management of leukocytospermia and hematospermia are discussed. Currently available diagnostic methods and treatment options are outlined, and available optimal cryopreservation techniques for samples with white blood cells or red blood cells are summarized.

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.

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.

Adverse effects of in vitro manipulation of spermatozoa

Development of in vitro reproduction techniques has not only offered some infertile couples the possibility to have a child, it also revolutionized animal reproduction. Although in vitro reproduction techniques for humans or domestic and non-domestic animals have been designed to mimic in vivo conditions, modifications due to environmental effects or in vitro manipulation of gametes and embryos are unavoidable. For male gametes, in vitro manipulations include techniques to select spermatozoa, cryopreservation and other incubation procedures, during which spermatozoa may be exposed to oxidative stress and other insults that may damage their functions and DNA. The aim of this review is to provide an overview of key studies reporting sperm damage during in vitro manipulation, with particular focus on effects on DNA integrity, a fundamental factor for fertilization and transmission of paternal genetic information to offspring.

In vitro application of Ceratonia siliqua improved sperm parameters and chromatin quality after vitrifacation in normozoospermic aged men

Background

Vitrification is the main technique in the assisted reproductive technique (ART) labs. Sperm vitrification exposes sperm to damage. The aim of the present study was to evaluate the in vitro effect of Ceratonia siliqua (C. siliqua) application on sperm parameters and chromatin quality in normozoospermic aged men. Semen samples (n = 40) were collected from normozoospermic men over 45 years old. Each specimen was divided into four aliquots to form the subsequent groups: fresh (group I), vitrification without treatment (group II), vitrification with the medium supplemented by 20 μg/ml C. siliqua (group III), and vitrification with the thawing medium supplemented by 20 μg/ml C. siliqua (group IV). Sperm progressive motility, normal morphology and viability were assessed. Also, sperm chromatin quality was evaluated by aniline blue (AB), toluidine blue (TB), and sperm chromatin dispersion (SCD) staining.

Results

Vitrification caused a significant decrease in sperm progressive motility, normal morphology and viability as well as chromatin quality compared to fresh samples (p < 0.05). Supplementation of vitrification/thawing medium with C. siliqua significantly improved sperm progressive motility, normal morphology, viability, and chromatin quality compared to vitrification without any supplementation (p < 0.05).

Conclusions

The study showed that C. siliqua can improve the detrimental effect of vitrification on sperm parameters and chromatin quality of normozoospermic aged men.

Vitrification of stallion sperm using 0.25 ml straws: Effect of volume, concentration and carbohydrates (sucrose/trehalose/raffinose)

Sperm vitrification is a rapid freezing method in which carbohydrates are used as cryoprotectants. The aim of this study was to determine the optimal volume, concentration and type of carbohydrates for stallion sperm vitrification using 0.25 ml straws in comparison to conventional freezing. Ejaculates (n = 54) were collected from six stallions. For vitrification, straws were filled with different volumes (30, 70, 100 μl), sperm concentrations (50, 100, 200 × 10⁶ sperm/ml) and extenders containing sucrose (20, 100, 200 mM), trehalose (50, 100, 200 mM) and raffinose (50, 100, 200 mM) and plunged into LN₂. Conventional freezing was performed in 0.5 ml straws frozen in LN₂ vapors. Sperm motility, plasma and acrosome membrane integrities and DNA fragmentation were compared among treatments. The use of straws filled with 100 μl at 100 × 10⁶ sperm/ml with the extender containing 100 mM trehalose resulted in greater values for sperm quality than the other concentrations, volumes and carbohydrates. With vitrification, there were greater values (mean ± SEM; P < 0.05) than freezing for progressive motility (48.2 ± 2.3 compared with 37.3 ± 2.2%), plasma membrane integrity (82.8 ± 1.5 compared with 74.1 ± 1.9%), and intact acrosomes (50.2 ±  1.2 compared with 43.1 ± 1.4%); and less DNA fragmentation (6.4 ± 0.7 compared with 8.2 ± 0.3%). In conclusion, stallion sperm can be vitrified in 0.25 ml straws filled with 100 μl of sperm at 100 x 10⁶ sperm/ml using an extender with 100 mM of trehalose, obtaining better sperm quality after warming than conventional freezing.

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

OBJECTIVES

Sperm cryopreservation has great potential for male infertility treatment as used in assisted reproduction technology (ART). There are a variety of cryopreservation methods in order to preserve sperm in a long term. Although conventional freezing and vitrification now are used widely, they have damage on sperm parameters as well as sperm DNA integrity. It is necessary to answer which method is better and appropriate for sperm cryopreservation. The aim of this study was to compare the effect of conventional freezing and vitrification regarding to motility, vitality and morphology of sperm found in washed and unwashed samples.

STUDY DESIGN

One hundred and five human fresh semen samples were divided into washed and unwashed halves using density-gradient centrifugation. Each group then was split into two aliquots: one cryopreserved by conventional freezing and the other by vitrification, using SpermFreeze Solution™ (Vitrolife, Västra Frölunda, Sweden) containing glycerol as a cryoprotectant. The sperm parameters were analyzed and compared between six groups: washed fresh (FW), unwashed fresh (FU), washed conventional freezing (CfW), unwashed conventional freezing (CfU), washed vitrification (VitW) and unwashed vitrification (VitU) samples.

RESULTS

Sperm progressive motility, vitality and normal morphology significantly decreased, together with an appreciable increase in sperm head, midpiece and tail defects when comparing to the fresh sperm parameters after thawing in all groups. In conventional freezing method groups, progressive motility and vitality were substantially higher than that in vitrification method groups. However, vitrification gave better results in normal morphology rates. Additionally, sperm head, midpiece and tail defects were significant lower in two vitrification groups in comparison with conventional freezing groups. Interestingly, washed groups had better sperm parameters than unwashed groups so that washing process before frozen seemed to improve sperm parameters.

CONCLUSION

Conventional freezing method resulted in better motility, viability in both washed/unwashed groups. On the contrary, spermatozoa undergoing vitrification were healthier regarding morphology with less defects than conventional freezing. Sperm washing before frozen was a beneficial preparation to sperm cryopreservation.

Vitrification of Large Volumes of Stallion Sperm in Comparison With Spheres and Conventional Freezing: Effect of Warming Procedures and Sperm Selection

Stallion sperm was vitrified using straws in comparison with spheres and conventional freezing. Vitrification was performed plunging 30 μL of sperm (spheres) or 0.5 mL straws into liquid nitrogen (LN₂) and conventional freezing using 0.5 mL straws frozen in LN₂ vapors. Sperm vitrified in straws were submitted to different warming procedures (42°C/20 seconds; 60°C/15 seconds) and single-layer centrifugation (SLC). Total (TM, %) and progressive sperm motility (PM, %), plasma membrane (IMS, %) and acrosome integrity (AIS, %) were statistically compared between treatments (mean ± SEM). Significant higher values (P < .001) were obtained after vitrification using spheres in comparison with conventional freezing and vitrification in straws for TM (54.46 ± 3.2 vs. 36.47 ± 3.2 vs. 2.50 ± 1.2, %), PM (38.63 ± 3.4 vs. 15.11 ± 2.0 vs. 1.9 ± 0.9, %), IMS (65.40 ± 2.8 vs. 50.50 ± 2.8 vs. 21.63 ± 2.1, %), and AIS (48.89 ± 2.8 vs. 15.46 ± 1.7 vs. 4.69 ± 0.9, %). No differences were found between warming procedures. Single-layer centrifugation after warming at 42°C/20 seconds obtained higher values (P < .05) than unselected samples for TM (32.52 ± 5.8%), PM (14.22 ± 2.8%), IMS (60.01 ± 3.2%), and AIS (44.5 ± 2.2%), whereas selection after 60°C/15 seconds increased TM (23.11 ± 4.3%) and IMS (67.11 ± 3.9%). In conclusion, vitrification in spheres obtained better sperm quality than conventional freezing and vitrification in straws. Warming procedures did not affect the sperm quality but SLC could be a strategy to enhance the quality of the samples after sperm vitrification using 0.5 mL straws.

Comparison of Conventional Slow Freeze versus Permeable Cryoprotectant-Free Vitrification of Abnormal Semen Sample: A Randomized Controlled Trial

Background:

The cryopreservation of semen samples by slow freezing remains as standard protocol. Recently, vitrification of spermatozoa was successfully reported with superior outcome. Till date, there is no randomized trial comparing the two different protocols.

Aim:

The aim of the present study is to evaluate the slow freezing with vitrification of the subfertile men spermatozoa to evaluate the progressive motility, vitality, and chromatin integrity.

Setting:

The study was conducted at University teaching hospital.

Design:

Study design involves randomized control trial.

Materials and Methods:

Twenty subfertile men with semen characteristics of severe oligoasthenozoospermia (SOA) and very SOA (VSOA) randomized to undergo slow freezing and vitrification protocol and cryopreserved at 1-month and 6-month storage interval, postthawed or warmed, samples were assessed for progressive motility, vitality, and hyaluronan binding. SPSS version 14 software was used for statistical analysis.

Results:

The SOA samples at 1 month revealed significantly higher motility (42% [22%–74%] vs. 7% [1%–13%]; P = 0.015) and vitality (57% [45%–78%] vs. 34.5% [27–42]; P < 0.001) following vitrification compared to slow-freeze method. For Very severe oligoasthenozoospermia (VSOA), the motility was significantly higher following vitrification (14.5% [2%–32%] vs. 2.5% [0%–4%]; P = 0.007). At 6 months, no statistically significant difference in motility was found between the two groups for Severe Oligoasthenozoospermia (SOA) samples (27% [13%–62%] vs. 8% [0%–11%]; P = 0.066), but motility was significantly higher following vitrification for VSOA samples (12.5% [3%–32%] vs. 2% [1%–5%]; P = 0.019). The hyaluronan-binding assay was comparable in both the groups at 6 months.

Conclusions:

The current study found the vitrification method involving the use of only nonpermeable cryoprotectants for cryopreservation of abnormal semen sample to be an effective alternative to the conventional slow-freeze technique.

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.