Cryopreservation of single-sperm: where are we today?

Pentoxifylline treatment as a safe method for selecting viable testicular spermatozoa before cryopreservation of a small numbers of spermatozoa in azoospermia individuals

BACKGROUND

Single sperm cryopreservation (SSC) is a specific technique especially used in individuals with small numbers of sperm who suffered from non-obstructive azoospermia (NOA). Testicular specimens possess poor motility and low population of viable spermatozoa. Therefore, sperm selection methods such as applying pentoxifylline (PTX) may improve motility in these cases. The main aim of this study was to evaluate the protective effects of PTX on testicular spermatozoa before and after performing SSC.

METHODS

Thirty testicular samples were obtained from men with azoospermia. This study was conducted in two phases. Phase 1 evaluated the effect of PTX for sperm selection before SSC. Twenty testicular samples were divided to two experimental groups: SSC without (I) and with PTX treatment (II). For PTX treatment spermatozoa were incubated with PTX at 37°C for 30 min and only motile spermatozoa were selected for SSC. In phase 2, ten testicular samples were cryopreserved with SSC and warming procedure was carried out in droplet with and without PTX. Motility and viability rates, morphology by motile sperm organelle morphology examination (MSOME), DNA fragmentation by sperm chromatin dispersion test (SCD) and mitochondrial membrane potential (MMP) were evaluated.

RESULTS

In phase 1, post warm motility rate was higher in PTX exposed group compared to the unexposed group (25.6 ± 8.13 vs. 0.85 ± 2.1) (p > 0.00). Recovery rate, viability and morphology were not significantly different between groups. DNA integrity and MMP were also similar between both groups. In phase 2 although motility increased in PTX group compared to without PTX group (29.30 ± 12.73 vs. 1.90 ± 2.64) (p > 0.00), the viability rate was not different (70.40 ± 12.12 vs. 65.30 ± 11.87). All above mentioned parameters were similar between the two SSC groups.

CONCLUSIONS

Supplementation of testicular spermatozoa with PTX before cryopreservation increases motility and did not have adverse effects on viability, morphology, DNA integrity and MMP. PTX could be used as sperm selection method before single sperm cryopreservation, but PTX could not maintain motile the most of viable testicular sperms.

A Pilot Analysis of Whole Transcriptome of Human Cryopreserved Sperm

Sperm cryopreservation is a procedure widely used to store gametes for later use, to preserve fertility in patients prior to gonadotoxic treatments or surgery, and for sperm donation programs. The purpose of the study was to assess the impact of cryopreservation on human sperm transcriptome. Semen samples were collected from 13 normospermic men. Each sample was divided into two aliquots. The total RNA was immediately extracted from one aliquot. The second aliquot was frozen and total RNA was extracted after a week of storage in liquid nitrogen. The RNA samples were randomized in four pools, each of six donors, and analyzed by microarrays. The paired Significance Analysis of Microarray was performed. We found 219 lower abundant transcripts and 28 higher abundant transcripts in cryopreserved sperm than fresh sperm. The gene ontology analysis disclosed that cryopreservation alters transcripts of pathways important for fertility (i.e., spermatogenesis, sperm motility, mitochondria function, fertilization, calcium homeostasis, cell differentiation, and early embryo development), although the increase of some transcripts involved in immune response can compensate for the harmful effects of freezing.

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.

Technology for Biobanking of Epididymal Spermatozoa from Patient with Obstructive Azoospermia: Case Report about Baby Born after Conventional Freezing Only with a Nonpermeable Cryoprotectant 360 kDa Polyvinylpyrrolidone

This publication reports, for the first time, the birth of a healthy child after intracytoplasmic sperm injection (ICSI) of motile spermatozoa after conventional ("slow") freezing of epididymal spermatozoa using 5% polyvinylpyrrolidone (PVP) of high molecular weight (360 kDa). Cryopreservation solution with 10% PVP was added to 30 µL of spermatozoa suspension in a 1:1 ratio, with a final PVP concentration of 5%. Then, polycarbonate capillaries for oocyte denudation with a diameter of 170 µm were filled with 60 µL of the resulting sperm suspension. After that, the capillaries were placed for 10 minutes at a height of 15 cm above liquid nitrogen and immersed into liquid nitrogen. To warm the spermatozoa, the capillaries were immersed in a water bath at a temperature of 40°C for 30 seconds. Oocyte fertilization was performed by ICSI. Zygotes were cultured in vitro for 5 days to the blastocyst stage. More than 100 spermatozoa were obtained after percutaneous epidydimal sperm aspiration, of which 80% were motile. After cryopreservation, storage for 3 months in liquid nitrogen, and thawing, 72% of the total sperm cells remained motile. Ten oocyte-cumulus complexes were found after follicle puncture, and eight metaphase II stage oocytes were fertilized using ICSI. After 18 hours, two pronuclei were found in seven (88%) of the oocytes. An analysis of the morphological characteristics of 5-day-old embryos showed that four (57%) of them reached the blastocyst stage. One embryo was transferred, and the remaining embryos were cryopreserved (vitrified). The onset of pregnancy was detected on the 14th day after embryo transfer, and one healthy girl (3300 g) was born at term.

Cryopreservation of Limited Sperm Using A Combination of Sucrose and Taurine, Loaded on Two Different Devices, and Thawed at Two Different Temperatures

BACKGROUND

Cryopreservation of sperm is essential for patients with low sperm counts and couples undergoing infertility treatment. The aim of this study was to compare the effects of Taurine (T) and Sucrose (S) in individual sperm cryopreservation utilizing cryotop and petri dish and thawing at 37 and 42°C.

MATERIALS AND METHODS

In this experimental study, 17 normospermic semen samples were processed using the "Swim-up" procedure and progressively motile sperm were then isolated from these samples using an inverted microscope. Sperm were added to droplets of "sucrose medium" with 25 mM Taurine antioxidant (S+T) and the commercial cryoprotectant "Sperm Freeze" (CPA), loaded on a petri dish and cryotop. After rapid freezing of the samples, they were thawed at two different temperatures (37°C and 42°C), and the sperm classical parameters, viability, and DNA fragmentation were assessed.

RESULTS

Statistical analysis displayed a significant increase in total and progressive motility in individual sperm freezing on cryotop with CPA and thawing at 42°C (P<0.05). Other parameters did not show any differences between the CPA and S+T groups and two thawing temperatures in either of the cryopreservation methods.

CONCLUSION

Although, both cryoprotectants (CPA and S+T) may preserve individual sperm effectively using cryotop, the CPA and thawing at 42°C showed a better effect on the motility percentage of the small number of sperm.

Bridging the Gap: Animal Models in Next-Generation Reproductive Technologies for Male Fertility Preservation

This review aims to explore advanced reproductive technologies for male fertility preservation, underscoring the essential role that animal models have played in shaping these techniques through historical contexts and into modern applications. Rising infertility concerns have become more prevalent in human populations recently. The surge in male fertility issues has prompted advanced reproductive technologies, with animal models playing a pivotal role in their evolution. Historically, animal models have aided our understanding in the field, from early reproductive basic research to developing techniques like artificial insemination, multiple ovulation, and in vitro fertilization. The contemporary landscape of male fertility preservation encompasses techniques such as sperm cryopreservation, testicular sperm extraction, and intracytoplasmic sperm injection, among others. The relevance of animal models will undoubtedly bridge the gap between traditional methods and revolutionary next-generation reproductive techniques, fortifying our collective efforts in enhancing male fertility preservation strategies. While we possess extensive knowledge about spermatogenesis and its regulation, largely thanks to insights from animal models that paved the way for human infertility treatments, a pressing need remains to further understand specific infertility issues unique to humans. The primary aim of this review is to provide a comprehensive analysis of how animal models have influenced the development and refinement of advanced reproductive technologies for male fertility preservation, and to assess their future potential in bridging the gap between current practices and cutting-edge fertility techniques, particularly in addressing unique human male factor infertility.

Early Pharmacologic Approaches to Avert Anabolic Steroid-induced Male Infertility: A Narrative Review

PURPOSE

To review the impact of testosterone and other androgenic-anabolic steroids (AASs) on male fertility, exploring potential drugs that can be used to preserve or restore male fertility upon AAS use or prior contact.

METHODS

A review was performed to provide a unifying clinical link between drugs used to preserve or restore male fertility (ie, clomiphene citrate, human chorionic gonadotropin, selective estrogen receptor modulators, recombinant luteinizing and follicle-stimulating hormones, and human menopausal gonadotrophin) in the context of AAS-induced infertility and related aspects.

FINDINGS

Human chorionic gonadotropin (125-500 IU every other day), clomiphene citrate (12.5-50 mg/d), recombinant luteinizing hormone (125-500 IU every other day), recombinant follicle-stimulating hormone (75-150 IU 1-3×/wk), and human menopausal gonadotrophin (75-150 IU 1-3×/wk) are promising early pharmacologic approaches to avert AAS-induced male infertility. Additionally, a full partner assessment is crucial to the success of a couple planning to have children. The partner's age and gynecopathies must be considered. Egg or sperm cryopreservation can also be alternatives for future fertility. Reinforcing AAS cessation is imperative to achieving better success in misusers.

IMPLICATIONS

The exponential increase in AAS misuse raises concerns about the impact on male fertility. This review suggests that gonadotropin analogs and selective androgen receptor modulators (clomiphene citrate) are viable approaches to early preserve or restore fertility in men on AAS use or with previous contact. However, proper standardization of doses and combinations is required and hence physicians should also be aware of patients' and partners' fertility.

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.

A new cryotop vial device system provides an aseptic cryoprotectant-free and centrifuge-free cryopreservation of human spermatozoa (a closed system)

Single sperm cryopreservation is a new method to preserve small numbers of spermatozoa in small droplets. So far, several devices have been introduced for this technique, but more studies are needed for its optimization. The aim of this study was optimizing the previous device for low number of spermatozoa and low volume semen, which led to design of Cryotop Vial device. Normal semen samples from 25 patients were prepared by swim-up method and divided into four groups: Fresh (F), Rapid freezing (R) and ultra-rapid freezing with Cryotop Device (CD) and Cryotop Vial Device (CVD). In R group, the diluted sperm suspension with sperm freezing medium was cooled in the vapor phase and then immersed in liquid nitrogen. Ultra rapid freezing was performed with sucrose in small volume using the Cryotop Device (CD) or Cryotop Vial Device (CVD). Sperm viability, motility, fine morphology, mitochondrial activity and DNA fragmentation were assessed in all samples. All sperm parameters decreased significantly in all the cryo groups compared to the fresh group. The comparison between the cryo groups showed that progressive motility (69.28 ± 6.82 vs. 55.68 ± 9.04, and 54.76 ± 5.34, p < 0.001) and viability (77.36 ± 5.48 vs.68.84 ± 8.51, p < 0.001, and 70.04 ± 7.44, P = 0.002) were significantly higher in the CVD compared to the CD and R groups respectively. DNA fragmentation was also significantly lower in both ultra-rapid freezing groups (CD and CVD) compared to the R group. Fine morphology and mitochondrial activity were not different between the cryo groups. The CVD as a cryoprotectant and centrifuge-free technique preserved sperm motility, viability and DNA integrity after cryopreservation better than other groups.

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.

Micro-TESE strategy in patients with NOA caused by AZFc deletion: synchronous or asynchronous?

In the treatment of infertile patients with non-obstructive azoospermia (NOA) caused by the deletion of the azoospermia factor c region (AZFc) on the Y chromosome, synchronous and asynchronous surgical strategies are discussed. Clinical data from NOA patients with the AZFc deletion who underwent micro-TESE were analyzed retrospectively. The sperm retrieval rate (SRR) and sperm utilization rate of synchronous and asynchronous operation groups were followed up and compared. The fertilization rate, high-quality embryo rate, clinical pregnancy rate, abortion rate, and cumulative live birth rate of ICSI in patients with successful sperm retrieval were compared between the two groups. The two groups had sperm utilization rates of 98.9% (93/94) and 50.0% (14/28), respectively. The asynchronous group's sperm consumption rates were much lower than those of the synchronous operation group. Fertilization rate, high-quality embryo rate, clinical pregnancy rate of fresh transfer cycle, abortion rate, and cumulative live birth rate of patients in the synchronous operation group with fresh sperm, and the asynchronous operation group with thawed sperm, respectively, were 30.6% vs 33.8%, 33.8% vs 40.7%, 40.0% vs 12.5%, 30.4% vs 7.1%. Between the two groups, there was no significant difference. This suggests that individuals with NOA caused by the AZFc deletion have a high possibility of successfully acquiring sperm using micro-TESE and ICSI to conceive their own offspring. Synchronous micro-TESE is recommended to improve sperm utilization rate and the cumulative live birth rate.

Treatment progress of cryptozoospermia with Western Medicine and traditional Chinese medicine: A literature review

Background and Aims

Cryptozoospermia is an extreme oligozoospermia with an unsatisfactory treatment effect, with an incidence rate of approximately 8.73% in male infertility, whose effective solution has become the call of the times. Western Medicine has achieved certain effects through drugs, surgery, and assisted reproductive therapy, but this is still not ideal. Traditional Chinese medicine (TCM) has made many achievements in other disciplines; however, there is still a lack of evidence-based medical evidence to improve sperm production.

Methods

The relevant literatures from the China National Knowledge Internet (CNKI) and PubMed in the past 10 years were collected in this article, of which the mechanisms, advantages, or current controversies of various treatment methods of Western Medicine and TCM were analyzed, to find new treatment methods and research directions.

Results

With the development of modern science and technology, medical treatments for cryptozoospermia have become increasingly abundant; however, there is still no universally recognized unified and effective guiding plan. Although TCM has not been fully verified by evidence-based medicine, most TCM combined with Western Medicine can achieve unexpected results.

Conclusion

The combination of TCM and Western Medicine may become a bane for cryptozoospermia and bring good news to infertile men worldwide.

Sperm cryopreservation for impaired spermatogenesis

Sperm cryopreservation for men with severely impaired spermatogenesis is one of the commonest reasons for short-term sperm storage, usually in advance of fertility treatment. Cryopreservation is generally very effective, although not all spermatozoa survive the process of freezing and thawing. This review considers various aspects of freezing sperm, including an overview of methods, appropriate use of cryoprotectants and practical considerations, as well as oxidative stress and mechanisms of cell cryodamage.

Clinical and neonatal outcomes of individually vitrified human sperm with Cryotop and Cell Sleeper

Technique for preserving limited number of human spermatozoa is important for successful treatment of patients with azoospermia and cryptozoospermia. This study determined whether the non-biological devices (Cryotop and Cell Sleeper) efficiently vitrify small numbers of human spermatozoa. From December 2011 to December 2018, 10 males with very low sperm numbers managed with a single sperm vitrification method. Post-warmed sperm recovery was similar with both devices. Post-warmed sperm motility and fertilization after intracytoplasmic sperm injection were significantly higher in Cryotop group than in Cell Sleeper group (40.0% vs. 22.0%, P < 0.01 and 50.7% vs. 21.7%, P < 0.01, respectively). The pregnancy rate was 15.4% and 2 healthy babies were born in the Cryotop, while 14.3% and 1 baby in the Cell Sleeper, which did not differ between the groups. Both devices have clinical advantages in terms of easy use and safety, and would be performed more efficiently by using devices with different properties.

Ultra-Rapid Freezing Preserves Morphofunctional Integrity and Fertilizing Ability of Epididymal Cat Spermatozoa

Vitrification and ultra-rapid freezing, which are more commonly used for oocytes and embryos, have recently been applied to spermatozoa in an attempt to make semen cryopreservation in field conditions easier compared to conventional freezing. It is well-known that in case of unexpected death of rare and wild animals, preserving epididymal spermatozoa from isolated testicles represents a great chance of salvaging male germplasm for future use in assisted reproductive technologies. The aim of this study was to evaluate the morphofunctional integrity of cat epididymal spermatozoa ultra-rapid frozen in pellets or straws with two different extenders [E1 (Tris buffer with 20% egg yolk and 0.25 M sucrose) or E2 (Ham's F10 with 1% bovine serum albumin and 0.4 M sucrose)] and to test whether spermatozoa preserved by the best combination were able to fertilize oocytes and produce embryos in vitro by intracytoplasmic sperm injection (ICSI) of in vitro matured cat oocytes. The results showed that E1 and E2 in straw or pellet were comparable (at warming, about 30% normal morphology, 45% intact membranes, and 20% intact acrosomes), except for post-warming motility that was better maintained along time by E1 pellet (21.7 ± 7.4% at warming and 3.6 ± 2.9% after 6 h). Such spermatozoa could fertilize conspecific oocytes and support embryonic development (cleavage 35.5%) as well as frozen control spermatozoa (cleavage 54.29%, p = 0.22). In conclusion, cat epididymal spermatozoa better maintained their morphofunctional features after ultra-rapid freezing with E1 and could successfully produce embryos in vitro after ICSI. This underscores their usefulness as cryobanked material for fertility and biodiversity preservation purposes.

Cryopreservation of human spermatozoa by freezing testicular seminiferous tubule with novel cryopiece

This study was carried out to evaluate the effectiveness of cryopreservation of human spermatozoa by freezing testicular seminiferous tubule with a new cryocarrier named ‘novel cryopiece’. Testicular tissue (TT) was collected from patients who underwent diagnostic testicular biopsy. Overall, 35 TT samples were obtained. Each TT sample was equally divided into four groups named (e.g. G1, G2, G3 and Gc). G1 was frozen as testicular seminiferous tubule using novel cryopiece, G2 was frozen as testicular cell suspensions using novel cryopiece, G3 was frozen as testicular cell suspensions using 0.25 ml straw, and Gc was not frozen. The samples in G1 and G2 experimental groups were cryopreserved in five separate aliquots and stored in the same cryovial. The freeze–thaw sperm DNA fragmentation index (DFI) of G2 was lower than that of G3 (20.27 ± 5.40 vs 23.55 ± 6.02; p = 0.004). After thawing, spermatozoa could be found in all 35 testicular seminiferous tubule specimens in G1; however, it could not be found in 2 of 35 (5.7%) and 1 of 35 (2.9%) testicular cell suspensions samples in G2 and G3 respectively. This study indicates that novel cryopiece presented for the cryopreservation of testicular seminiferous tubules and testicular cell suspension is simple and effective.

Single sperm vitrification with permeable cryoprotectant-free medium is more effective in patients with severe oligozoospermia and azoospermia

Testicular sperm extraction (TESE) is an invasive surgery for achieving the spermatozoa in cases with azoospermia. In these patients, the number of retrieved spermatozoa is limited and the optimal cryo-storage is very critical for their fertility preservation. Therefore, single sperm vitrification has been introduced for preservation of low number of spermatozoa. The goal was to assess the efficacy of sperm freezing medium (SFM) and sucrose medium as cryoprotectants for single sperm vitrification in cases with severe oligozoospermia and azoospermia. A total of 20 ejaculates from severe oligozoospermia and 20 testicular samples from azoospermia were processed. Twenty-five sperm cells were collected using ICSI injection pipette and transferred to a cryoprotectant droplet placed on the Cryotech, then vitrified by plunging in liquid nitrogen. Sperm motility, viability, fine-morphology, mitochondrial activity and DNA fragmentation index (DFI) were assessed before and after vitrification. Sperm motility, viability and the percentage of cells with mitochondrial activity were significantly decreased after vitrification in both severe oligozoospermic and testicular samples in either cryoprotectants. However, the rates of post-warm sperm motility and the cells with mitochondrial activity increased significantly in sucrose medium in both severe oligozoospermic and testicular samples compared to SFM. In testicular samples, the DFI of spermatozoa vitrified in SFM was significantly higher than those vitrified with sucrose medium. Sperm motility, viability, mitochondrial activity, and DNA integrity were better preserved in sucrose medium than SFM after single cell vitrification. The presented method may be a useful candidate for successful freezing of individual sperm cells in clinical setting.

Rapid cryopreservation of small quantities of human spermatozoa by a self-prepared cryoprotectant without animal component

Cryopreservation of small quantities of human spermatozoa whilst maintaining adequate post‐thawing motility has been found an essential challenge for male fertility preservation. Therefore, the study used an effective, and convenient rapid‐freezing method to freeze small amounts of human spermatozoa by adding self‐prepared cryoprotectant (SPC) without animal component. In the feasibility experiment, no significant differences in progressive motility, normal sperm morphology, vitality or DNA fragmentation index between the conventional slow freezing and rapid freezing were realised. The present study prospectively analysed the effects of sperm freezing and resuscitation in 175 patients with severe oligozoospermia (sperm concentration <1 × 10⁶/ml). We observed the 120 severe oligozoospermia specimens had a mean recovery rate of 60.19% ± 10.43% and a mean cryosurvival rate of 68.0% ± 9.17%. In addition, 55 cryptozoospermia specimens were analysed. The small‐volume cryopreservation showed advantages. The total sperm recovery, motility recovery and sperm loss rates were 98.48%, 50.17% and 1.52% respectively. In short, the SPC is safe and effective, and can be used to rapidly freeze severe oligozoospermia specimens. That is useful for successful sperm freezing whilst avoiding the risk of azoospermia in the later stages and promoting comprehensive fertility preservation.

Fresh vs frozen testicular sperm for assisted reproductive technology in patients with non-obstructive azoospermia: A systematic review

Objective

: To review the debate about the routine use of cryopreserved testicular sperm for intracytoplasmic sperm injection (ICSI) from patients with non-obstructive azoospermia (NOA), as some authors suggest repeating sperm retrieval in such cases due to poorer ICSI results when frozen–thawed testicular sperm is used compared with fresh sperm.

Methods

: A systematic literature review was performed in August 2020 using the Medical Literature Analysis and Retrieval System Online (MEDLINE), Web of Science databases and the Excerpta Medica dataBASE (EMBASE), and we included 26 studies that were considered eligible for this systematic review.

Results

: In all, 1189 publications were screened and 26 articles were included in the systematic review. Three meta-analysis reviews were included and they all concluded that the use of fresh and frozen sperms for ICSI from patients with NOA showed comparable fertilisation and pregnancy rates.

Conclusion

: The use of frozen testicular sperm from men with NOA results in fertilisation and clinical pregnancy rates similar to those of fresh sperm. This may encourage fertility centres to use frozen testicular sperm samples, as this policy has certain advantages that would help with organising their workflow.

Abbreviations: CPR: clinical pregnancy rate; 2PN%: two pronuclei % fertilisation rate; ICSI: intracytoplasmic sperm injection; NOA: non-obstructive azoospermia; OA, obstructive azoospermia; SCO: Sertoli cell-only syndrome; (micro-)TESE: (microsurgical) testicular sperm extraction

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.

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 agarose-gel microcapsules and Cryotop in cryopreservation of extremely small numbers of human spermatozoa

We investigated the feasibility of agarose-gel microcapsules to cryopreserve extremely small numbers of sperm for assisted reproductive technology. Semen samples were collected from 16 patients attending the center for reproductive medicine male infertility clinic at a university hospital. We used agarose microcapsules to cryopreserve extremely small numbers of sperm from 16 patients with male infertility (10 with sperm concentration ≥1 million/mL; 6 with sperm concentration <1 million/mL). Six spermatozoa were injected into agarose-gel microcapsules and cryopreserved in a liquid nitrogen tank for 7 days. The Crytop method was used for cryopreservation as a control. After thawing, spermatozoa were recovered. Sperm recovery rates, motility and viability, and recovery time were compared.The post-thawing recovery rate, motility rate, and viability rate were higher whereas the recovery time was shorter in samples preserved using the agarose-gel microcapsule method compared to samples preserved using the Cryotop method in both the group with sperm concentrations of 1 million/mL or above and the group with sperm concentrations of less than 1 million/mL. This study demonstrated that using the agarose-gel microcapsule method increased post-thawing sperm recovery rate, sperm motility rate, and sperm viability rate, and reduced sperm recovery time compared with the conventional Cryotop method when cryopreserving samples with low sperm count. Although requiring further study, the agarose-gel microcapsule method shows much promise as a new option for freezing sperm.

Intra-Cytosplamic sperm injection outcomes with fresh and cryopreserved human epidydimal sperm from patients with obstructive azoospermia

Techniques for the cryopreservation of epididymal sperm was are widely used in clinical practice. However, given the unique characteristics of sperm from patients with obstructive azoospermia, epididymal sperm cryopreservation is more difficult because of low count and weak motility; therefore, conventional methods of sperm cryopreservation may not result in the best outcomes. We used the micro-straw method to store small quantities of sperm obtained from patients with severe oligozoospermia or azoospermia and achieved successful deliveries in the previous study. This retrospective study of ICSI cycles included the first ICSI cycles of fresh or frozen/thawed epididymal sperm that were performed in patients suffering from obstructive azoospermia who were admitted to the CITIC-Xiangya Hospital of Reproduction and Genetics of China from June 1, 2015 to June 31, 2019. A total of 2441 patients with obstructive azoospermia were divided according to the use of fresh (n = 2342) or frozen/thawed (n = 99) epididymal sperm. The results showed that the fertilisation rate was higher with fresh epididymal sperm than that with frozen/thawed epididymal sperm (85.14% vs. 79.26%, respectively; p = 0.000). However, the rates of embryo cleavage, high-quality embryos, clinical pregnancy, miscarriage, singletons and birth defect were similar between fresh and frozen/thawed epididymal sperm (98.28% vs. 99.13%, 60.34% vs. 57.29%, 67.90% vs. 70.51%, 8.12% vs. 10.91%, 57.76% vs. 49.09%, 1.59% vs. 1.45%respectively; p = 0.088, 0.109, 0.628, 0.462,0.203 and 0.686). In addition, the short-term cryostorage of small quantities of epididymal sperm did not affect clinical outcomes. The results indicated that in cases of obstructive azoospermia, cryostorage of small quantities epididymal sperm is a reliable option.

A decellularized oocyte-derived scaffold provides a "sperm safe" to preserve mammalian spermatozoa

BACKGROUND

Although only one spermatozoon is needed to create a zygote, a significant challenge is the storage and recovery of germ cells when sperm counts are extremely low.

OBJECTIVES

We engineered an oocyte-derived biomaterial-the zona pellucida (ZP)-as a "sperm safe" for storing spermatozoon. The ZP is a glycoprotein matrix that surrounds the mammalian oocyte.

MATERIALS AND METHODS

We made a hole in the ZPs using a Piezo drill and mechanically separated them from the oocyte cytoplasm. A subset of ZPs were further purified through decellularization. Using a modified ICSI approach, we injected sperm heads into purified ZPs and tested the efficacy of cryopreservation and recovery of spermatozoon as well as function.

RESULTS

Between 1-6 sperm heads were injected into purified ZPs (average 2.7 ± 1.7 sperm heads/ZP), which were then cryopreserved. Upon thawing, an average of 2.5 ± 1.4 sperm heads/ZP were observed, and in 11 of 12 thawed "sperm safes," we recovered all spermatozoa. Decellularized "sperm safes" maintained their three-dimensional structure and had a denser matrix relative to untreated controls as assessed by scanning and transmitted electron microscopy. The efficacy of "sperm safe" derived spermatozoon was evaluated by ICSI. Spermatozoon stored in either untreated or decellularized "sperm safes" elicited egg activation-associated calcium transients and zinc sparks when injected into eggs. Of the resulting zygotes, >80% of them formed pronuclei irrespective of the sperm source. 26.8 ± 4.6% and 18.1 ± 7.0% of the pre-implantation embryos generated from spermatozoon recovered from untreated or decellularized "sperm safes" developed to the blastocyst stage, respectively. Although this development was lower than that using fresh spermatozoon (59.3 ± 19.3%) or conventionally frozen-thawed spermatozoon (28.4 ± 1.7%), these differences were not significant.

DISCUSSION AND CONCLUSION

Purified ZPs represent a natural biomaterial for the efficient preservation and recovery of small sperm numbers.

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.