The first births and ongoing pregnancies associated with sperm cryopreservation within evacuated egg zonae

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.

Clinical benefit for cryopreservation of single human spermatozoa for ICSI: A systematic review and meta-analysis

BACKGROUND

Systematic reviews have focused on sperm recovery and post-thaw parameters after cryopreservation, but there no information on the associated clinical outcomes. In recent years, an increasing number of studies have reported cryopreservation of a single sperm due to the importance of fertility preservation.

OBJECTIVES

To assess whether the cryopreservation of single human spermatozoa improves clinical outcomes in patients with azoospermia or severe oligospermia.

MATERIALS AND METHODS

We conducted an extensive literature search using the following databases, CENTRAL, CNKI, Cochrane Systematic Reviews, EMBASE, MEDLINE, PUBMED, and Web of Science for relevant studies published through December 31, 2019. We calculated the pooled proportions of cryopreservation of single human spermatozoon to assess the recovery, survival, fertilization, pregnancy, miscarriage, and delivery rates. Subgroup analyses were performed for the following covariates, a) different carriers, b) year of publication, and c) source of sperm.

RESULTS

We included 25 studies, which included 13 carriers. The pooled proportion of recovery rate of spermatozoa cryopreserved was 92% (95% CI, 87%-96%), and the survival, fertilization, pregnancy, miscarriage, and delivery rate were 76% (95% CI, 69%-83%), 63% (95% CI, 58%-67%), 57% (95% CI, 39%-74%), 12% (95% CI, 0%-33%), and 40% (95% CI, 12%-71%), respectively. Based on the subgroup analysis, the recovery and survival rates of frozen spermatozoa in subgroup of different carriers were statistically significant. In the past decaade, frozen single human spermatozoon technology has improved the recovery rates of frozen-thawed spermatozoa. However, the differences in clinical outcomes of frozen spermatozoa in subgroup of different sources of sperm were not statistically significant.

DISCUSSION AND CONCLUSION

The techniques for single human spermatozoa are feasible and efficient and may benefit patients with severe oligospermia or azoospermia. This article is protected by copyright. All rights reserved.

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.

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.

Novel micro-straw for freezing small quantities of human spermatozoa

OBJECTIVE

To evaluate a novel micro-straw as an efficient, simple method for freezing a small number of human spermatozoa for intracytoplasmic sperm injection (ICSI).

DESIGN

Prospective cohort study.

SETTING

Sperm bank.

PATIENT(S)

Men with severe oligozoospermia or azoospermia undergoing a total of 143 ICSI cycles at the CITIC-Xiangya Hospital of Reproduction and Genetics from June 1, 2015, to June 31, 2019, and 20 donors at the Hunan Province Human Sperm Bank from 2001 to 2016.

INTERVENTION(S)

Analysis of sperm samples and clinical outcomes after sperm use.

MAIN OUTCOME MEASURE(S)

Clinical information, including number of motile sperm before and after freezing, freeze-thaw survival rates, two-pronuclear fertilization rates, clinical pregnancy, and early pregnancy loss rates after sperm use.

RESULT(S)

In the feasibility experiment using the micro-straw, we found a freeze-thaw survival rate of 73% ± 8.3% and no difference in normal sperm morphology, normal acrosome integrity, or DNA fragmentation index between the micro-straw and 1.8-mL cryotubes. The prospective cohort included 1,325 cases, and we collected sperm from testicular, epididymis, and ejaculation sources. We observed motile sperm in 1,294 (97.6%) of 1,325 frozen-thawed samples. Postthaw sperm were available for ICSI in 140 (97.9%) of 143 of cycles. The fertilization, cleavage, and high-quality embryo rates were 1,007 (81.7%) of 1,233; 995 (98.8%) of 1,007; and 537 (53.9%) of 995, respectively. Sixty-nine (49%) clinical pregnancies were achieved, and the miscarriage rate was 6 (8.6%) of 69.

CONCLUSION(S)

The micro-straw is suitable and clinically useful for the cryopreservation of small numbers of spermatozoa.

ART strategies in Klinefelter syndrome

PURPOSE

Patients with Klinefelter syndrome (KS) who receive assisted reproductive technology (ART) treatment often experience poor pregnancy rates due to decreased fertilization, cleavage, and implantation rates and even an increased miscarriage rate. Mounting evidence from recent studies has shown that various technological advances and approaches could facilitate the success of ART treatment for KS patients. In this review, we summarize the methods for guiding KS patients during ART and for developing optimal strategies for preserving fertility, improving pregnancy rate and live birth rate, and avoiding the birth of KS infants.

METHODS

We searched PubMed and Google Scholar publications related to KS patients on topics of controlled ovarian stimulation protocols, sperm extraction, fertility preservation, gamete artificial activation, round spermatid injection (ROSI), and non-invasive prenatal screening (PGD) methods.

RESULTS

This review outlines the different ovulation-inducing treatments for female partners according to the individual sperm status in the KS patient. We further summarize the methods of retrieving sperm, storing, and freezing rare sperm. We reviewed different methods of gamete artificial activation and discussed the feasibility of ROSI for sterile KS patients who absolutely lack sperm. The activation of eggs in the process of intracytoplasmic sperm injection and non-invasive PGD are urgently needed to prevent the birth of KS infants.

CONCLUSION

The integrated strategies will pave the way for the establishment of ART treatment approaches and improve the clinical outcome for KS patients.

Cryopreservation of single-sperm: where are we today?

BACKGROUND

Patients with severe oligospermia and nonobstructive azoospermia have very limited numbers of viable sperm in their epididymal and testicular samples. Thus, cryopreservation of their sperm is performed to avoid repeated sperm retrievals and to preserve their sperm from any side effects of any treatment regimens.

MAIN BODY

The development of intracytoplasmic sperm injection technology has extended the therapeutic capacity of assisted reproductive technology for men with azoospermia via the surgical or percutaneous isolation of sperm from the testis/epididymis. The conventional cryopreservation techniques are inadequate for preserving individually selected sperm. The technique for freezing single sperm was first developed in 1997 and has been explored from the perspective of frozen carriers, freezing programs, and cryoprotectant formulations. Among these methods, advances in frozen carriers have directly improved single-sperm freezing technology. In this review, we evaluate the different technologies for the cryopreservation of single sperm by discussing the advantages and disadvantages of different freezing methods, their clinical applications, and the outcomes for a range of frozen carriers.

CONCLUSION

Our review article describes the latest and current technologies implemented for the cryopreservation of single sperm that could potentially benefit patients with severe oligospermia and who rarely have any sperm in their ejaculate. This review provides a platform to understand the process and pitfalls of single-sperm cryopreservation to ensure further improvements in the cryopreservation technology in future studies.

Sperm cryopreservation: A review on current molecular cryobiology and advanced approaches

The cryopreservation of spermatozoa was introduced in the 1960s as a route to fertility preservation. Despite the extensive progress that has been made in this field, the biological and biochemical mechanisms involved in cryopreservation have not been thoroughly elucidated to date. Various factors during the freezing process, including sudden temperature changes, ice formation and osmotic stress, have been proposed as reasons for poor sperm quality post-thaw. Little is known regarding the new aspects of sperm cryobiology, such as epigenetic and proteomic modulation of sperm and trans-generational effects of sperm freezing. This article reviews recent reports on molecular and cellular modifications of spermatozoa during cryopreservation in order to collate the existing understanding in this field. The aim is to discuss current freezing techniques and novel strategies that have been developed for sperm protection against cryo-damage, as well as evaluating the probable effects of sperm freezing on offspring health.

Successful delivery derived from cryopreserved rare human spermatozoa with novel cryopiece

Herein, we report the clinical outcomes following intracytoplasmic sperm injection (ICSI) with cryopiece cryopreserved rare human spermatozoa from severe male factor infertility patients. We established a novel cryopiece system on the basis of previous studies. In this study, 126 spermatozoa from four patients with non-obstructiveazoospermia (NOA) or severe oligozoospermia were stored in cryopiece and then thawed on the day of the oocyte retrieval, 88 (83%) spermatozoa were recovered with a 47.5% (38 of 80) motile rate. Routine ICSI were performed in enrolled 30 MII oocytes from their spouse with their own spermatozoa, respectively. Twenty-two (73%) fertilization and 19 (86%) zygote cleavage were observed. Finally, a total of 11 embryos were achieved and each female patient received a transplantation of two fresh embryos. Four healthy babies were born at term. In conclusion, our novel cryopiece can be applied in assisted reproduction through ICSI with an effective motile spermatozoa recovery rate, high fertilization rate, and successful pregnancy result.

Cryopreservation of very low numbers of spermatozoa from male patients undergoing infertility treatment using agarose capsules

This study tried to cryopreserve low numbers of spermatozoa from men undergoing infertility treatments by inserting into agarose capsules. The capsules were transferred into a drop of cryoprotectant solution and injected 3-4 motile spermatozoa that were selected by the swim-up method by conventional intracytoplasmic sperm injection. These capsules were put on a Cryotop^® and frozen in liquid nitrogen vapor, and then submerged into liquid nitrogen and subsequently thawed and recovered. The motile spermatozoa in the capsules were counted. Eventually, we cryopreserved 2142 motile spermatozoa in 702 agarose capsules from 26 male patients and 1356 (63%) spermatozoa maintained their motility after thawing. The spermatozoa motility rates after thawing (MRAT) ranged from 20.0% (5/25) to 95.1% (58/61) among patients. The median MRAT was 68.3% (interquartile range 46.1-75.7). The total number of motile spermatozoa collected by swim-up method strongly correlated with MRAT (r = 0.746). It was possible to cryopreserve spermatozoa from male patients undergoing infertility treatment using agarose capsules. However, there were wide differences in MRAT among patients. It seems the spermatozoa from semen where there were many motile spermatozoa may have higher freezing resistance. Further studies using this method in cryptozoospermic semen, testicular and epididymal spermatozoa are required.

Cryopreservation of a small number of human sperm using enzymatically fabricated, hollow hyaluronan microcapsules handled by conventional ICSI procedures

PURPOSE

We investigated whether enzymatically fabricated hyaluronan (HA) microcapsules were feasible for use in the cryopreservation of a small number of sperm.

METHODS

HA microcapsules were fabricated using a system of water-immiscible fluid under laminar flow. Three sperm were injected into a hollow HA microcapsule using a micromanipulator. Capsules containing injected sperm were incubated in a freezing medium composed of sucrose as the cryoprotectant and then placed in a Cryotop® device and plunged into liquid nitrogen. After thawing, the capsule was degraded by hyaluronidase, and the recovery rate of sperm and their motility were investigated.

RESULTS

The HA microcapsule measuring 200 μm in diameter and with a 30-μm thick membrane was handled using a conventional intracytoplasmic sperm injection (ICSI) system, and the procedure involved the injection of sperm into the capsule. The HA microcapsules containing sperm were cryopreserved in a Cryotop® device and decomposed by the addition of hyaluronidase. The recovery rate of sperm after cryopreservation and degradation of HA microcapsules was sufficient for use in clinical practice (90 %).

CONCLUSIONS

Hollow HA microcapsules can be used for the cryopreservation of a small number of sperm without producing adverse effects on sperm quality.

Single human sperm cryopreservation method using hollow-core agarose capsules

OBJECTIVE

To develop an efficient cryopreservation method using a single sperm.

DESIGN

Experimental study.

SETTING

Laboratory of a private institute.

PATIENT(S)

A fertile donor.

INTERVENTION(S)

We produced hollow-core capsules with agarose walls. A single human sperm was injected into each capsule as per the conventional intracytoplasmic sperm injection (ICSI) method. The capsules that contained the spermatozoa were cryopreserved on polycarbonate or nylon mesh sheets using nitrogen vapor. Before their use, the capsules were thawed and recovered. The motile spermatozoa in the capsules were counted.

MAIN OUTCOME MEASURE(S)

The recovery rates of the agarose capsules and the spermatozoa in these capsules after thawing and the mortality and survival rates of the spermatozoa.

RESULT(S)

The recovery rates of the capsules were 91.5% (75/82) using polycarbonate sheets (PS) and 98.3% (59/60) using mesh sheets (MS) after thawing. The recovered capsules were not at all damaged. The recovery rates of the spermatozoa were 91.5% (75/82) using PS and 96.7% (58/60) using MS. Sperm motility rates were 85.3% (64/75) and 82.8% (48/58), whereas the survival rates of the immotile spermatozoa by the hypoosmotic swelling test were 81.8% (9/11) and 50.0% (5/10); furthermore, the total survival rates of the spermatozoa were 97.3% (73/75) and 91.4% (53/58) using PS and MS, respectively. There was no significant difference between the results obtained using PS and MS.

CONCLUSION(S)

A cryopreservation method for a single sperm using an agarose capsule has been developed. The method is expected to be useful in ICSI treatment in patients with few spermatozoa.

Successful use of the Cryolock device for cryopreservation of scarce human ejaculate and testicular spermatozoa

The existing methods for cryopreservation of very low count sperm samples are complex and sub-optimal for individual spermatozoa. Our purpose is to establish an effective simple method for cryoprotecting individual spermatozoa. Samples from patients with OTA were mixed with TYB or HEPES-buffered salt solution with glycerol + glucose and placed on a Cryolock that was plunged directly into liquid nitrogen or exposed to its vapors. Thawing was performed by direct immersion into a drop of warmed medium. The favorable method was tested on diluted samples (10-50 cells) and leftover TESE specimens from patients with azoospermia. Cryopreservation was considered successful if >30 spermatozoa, (>3 motile), or >5 spermatozoa (>1 motile) in diluted and TESE samples, were detected post-thawing. A significantly higher survival rate of seminal spermatozoa was obtained when using the Cryolock with TYB and freezing with liquid nitrogen vapor, compared to HEPES glycerol-glucose (95 vs. 35% respectively). Plunging the Cryolock into liquid nitrogen was detrimental. Cryolock combined with TYB cryoprotection and liquid nitrogen vapor freezing was highly effective for cryopreservation of individual spermatozoa in diluted and TESE samples. The Cryolock may serve for freezing very low-count sperm samples and individual spermatozoa. This method offers simplicity, efficacy, use of available materials, without requiring micromanipulation equipment or skills.

A new approach for cryoprotectant-free freezing of goat epididymal spermatozoa

A cryoprotectant-free method was successfully used for rapid freezing of goat epididymal spermatozoa. Lowering sperm volume may increase the temperature exchange rate and improve the freezing output of spermatozoa. The aim of this study was to compare two different packaging types [0.25 ml French straws (FS) and 96-well immune plate (WIP)] for rapid freezing of goat epididymal spermatozoa. Eleven pairs of the goat testes were transferred to the laboratory; cauda epididymidides were dissected and sliced in TRIS-BSA solution for 15 min and temperature 33-35 °C. Sperm concentration was adjusted to 20 × 10(6) ml(-1), and the suspension was subjected to rapid freezing within FS or WIP. The volume of spermatozoa in WIP method was set at 25 μl. Sperm motility, viability and abnormalities, and sperm DNA integrity were compared between two devices. The results showed similar effectiveness of WIP and FS on post-thaw sperm parameters. In conclusion, for cryoprotectant-free rapid freezing of goat epididymal spermatozoa, it is recommended to use WIP instead of French 0.25 ml straws.

Small-volume vitrification for human spermatozoa in the absence of cryoprotectants by using Cryotop

Cryotop is a carrier that has been used successfully in the cryopreservation of human spermatozoa. Here, we explored a novel method to vitrify human spermatozoa without cryoprotective agents (CPAs) using Cryotop. Spermatozoa from 21 Normozoospermic patients were collected and vitrified without CPAs or with sucrose in small volume using Cryotop. The sperm recovery rate, motility, viability, chromatin damage and DNA fragmentation were assessed. No significant difference was observed in the sperm recovery rate and motility rate between the spermatozoa cryopreserved without CPAs and with sucrose. The post-thawed spermatozoa cryopreserved without CPAs had a higher viability and lower damage to sperm chromatin and DNA than those cryopreserved with sucrose. These results suggest that small numbers of human spermatozoa can be successfully vitrified without CPAs using Cryotop.

Cryopreservation of testicular and epididymal sperm: techniques and clinical outcomes of assisted conception

The introduction of the technique of intracytoplasmic sperm injection to achieve fertilization, especially using surgically retrieved testicular or epididymal sperm from men with obstructive or non-obstructive azoospermia, has revolutionized the field of assisted reproduction. The techniques for the retrieval of spermatozoa vary from relatively simple percutaneous sperm aspiration to open excision (testicular biopsy) and the more invasive Micro-TESE. The probability of retrieving spermatozoa can be as high as 100% in men with obstructive azoospermia (congenital bilateral absence of the vas deferens, status post-vasectomy). However, in nonobstructive azoospermia, successful sperm retrieval has been reported in 10-100% of cases by various investigators. The surgical retrieval and cryopreservation of sperm, especially in men with non-obstructive azoospermia, to some extent ensures the availability of sperm at the time of intracytoplasmic sperm injection. In addition, this strategy can avoid unnecessary ovarian stimulation in those patients intending to undergo in vitro fertilization-intracytoplasmic sperm injection with freshly retrieved testicular sperm when an absolute absence of sperm in the testis is identified. Several different methods for the cryopreservation of testicular and epididymal sperm are available. The choice of the container or carrier may be an important consideration and should take into account the number or concentration of the sperm in the final preparation. When the number of sperm in a testicular biopsy sample is extremely low (e.g., 1-20 total sperm available), the use of an evacuated zona pellucida to store the cryopreserved sperm has been shown to be an effective approach.

Successful delivery derived from vitrified-warmed spermatozoa from a patient with nonobstructive azoospermia

OBJECTIVE

To report the clinical outcomes following intracytoplasmic sperm injection (ICSI) with vitrified sperm from patients with severe male factor infertility.

DESIGN

Retrospective case series.

SETTING

IVF unit of a medical center.

PATIENT(S)

Three patients with severe oligozoospermia or nonobstructive azoospermia (NOA).

INTERVENTION(S)

Cryopreservation of limited numbers of spermatozoa with the use of Cryotop and Cell Sleeper as nonbiologic containers.

MAIN OUTCOME MEASURE(S)

Four cycles underwent intracytoplasmic sperm injection (ICSI) with vitrified sperm.

RESULT(S)

A total of 148 spermatozoa in 18 containers (8.2 sperm per container) were vitrified and 36 of them (5 containers) were warmed. Thirty-three sperm (92%) were retrieved successfully and injected individually into 17 mature oocytes. Fertilization was observed in 12 oocytes (71%), and all zygotes (100%) cleaved. A couple with NOA achieved a singleton pregnancy and concluded with full-term delivery of a healthy boy (2,632 g).

CONCLUSION(S)

A successful delivery was achieved after transfer of a blastocyst derived from vitrified-warmed spermatozoa. A small number of vitrified sperm cells were used for ICSI to fertilize oocytes with predictable timing.

Human Sperm Cryopreservation: Update on Techniques, Effect on DNA Integrity, and Implications for ART

Cryopreservation of human spermatozoa-introduced in the 1960's-has been recognized as an efficient procedure for management of male fertility before therapy for malignant diseases, vasectomy or surgical infertility treatments, to store donor and partner spermatozoa before assisted reproduction treatments and to ensure the recovery of a small number of spermatozoa in severe male factor infertility. Despite the usefulness of it, cryopreservation may lead to deleterious changes of sperm structure and function: while the effects of cryopreservation on cells are well documented, to date there is no agreement in the literature on whether or not cryopreservation affects sperm chromatin integrity or on the use of a unique and functional protocol for the freezing-thawing procedure. Therefore, sperm cryopreservation is an important component of fertility management and much of its successful application seems to affect the reproductive outcome of assisted reproduction technologies (ART): appropriate use of cryoprotectants before and sperm selection technologies after cryopreservation seem to have the greatest impact on preventing DNA fragmentation, thus improving sperm cryosurvival rates.

Simple vitrification for small numbers of human spermatozoa

Conventional freezing procedures and containers are not appropriate for spermatozoa from the testis because of their low number and poor in-situ motility, and various types of container have been utilized to freeze small numbers of spermatozoa. This study tried to develop a vitrification method for small numbers of spermatozoa using the Cell Sleeper, which is a closed type of cell-cryopreservation container. The container with spermatozoa were cooled in liquid nitrogen vapour and then stored in a cryotank. Sperm motility parameters improved significantly (P < 0.05) by vitrification in oil-free droplets rather than in droplets covered with oil. After vitrification of five spermatozoa per container, all spermatozoa were recovered and the viable sperm rate was significantly higher when spermatozoa were vitrified in a 3.5-ll droplet rather than in 0.5 ll (72.0% versus 38.0%; P < 0.01). Recovery, motility and viability rates of vitrified–warmed spermatozoa were similar between the Cell Sleeper and the CryoTop groups. In conclusion, the Cell Sleeper is a highly effective tool for the cryopreservation of small numbers of spermatozoa and limited cells can be vitrified quickly and simply without significant loss.

Techniques for cryopreservation of individual or small numbers of human spermatozoa: a systematic review

BACKGROUND

Despite interest in cryopreservation of individual or small number of human spermatozoa, to date, little data is available as regards its effectiveness. We systematically reviewed the outcome after cryopreservation of individual or small numbers of human spermatozoa in patients with severe male factor of infertility.

METHODS

We searched the MEDLINE, EMBASE, Cochrane Systematic Reviews, CENTRAL, Web of Science, Scopus databases for relevant studies up to June of 2008. The search used terms referring to cryopreservation of small amount of sperm. Included studies were limited to human studies with no language restrictions.

RESULTS

We identified 30 reports including 9 carriers used for cryopreservation of small quantities/numbers of human spermatozoa (7 non-biological and 2 biological carriers). A wide variety of cryopreservation vehicles were reported. The recovery rate of spermatozoa cryopreserved in a known small number varied widely from 59 to 100%. Fertilization rates were in the range of 18-67%. Frozen-thawed spermatozoa, using this method, were subsequently used for intracytoplasmic sperm injection in only five studies, with few pregnancies reported so far. To date, there remains no consensus as to the ideal carrier for cryopreservation of small number of spermatozoa for clinical purposes.

CONCLUSIONS

Cryopreservation of individual or small numbers of human spermatozoa may replace the need for repeated surgical sperm retrieval. A controlled multicenter trial with sufficient follow-up would provide valid evidence of the potential benefit of this approach.

Single sperm cryopreservation on cryoloops: an alternative to hamster zona for freezing individual spermatozoa

Methodology enabling cryopreservation of individual spermatozoa in extreme cases of oligozoospermia would tremendously benefit patients. This study explores the use of a nylon loop for cryopreservation of small quantities of spermatozoa, and also describes a novel technique for freezing individual spermatozoa with this cryoloop. Experiments were conducted to compare sperm recovery and viability after cryopreservation in conventional vials versus on the cryoloops. Discarded human sperm specimens with varying parameters were utilized. The study also examines two different glycerolbased cryoprotectants, with and without test yolk buffer. For single sperm cryopreservation, 5-10 spermatozoa were selected and loaded onto cryoloops with the aid of a microscope and micromanipulation equipment. Sperm function testing was performed on both human and bovine spermatozoa frozen on cryoloops. Microquantities of spermatozoa frozen on cryoloops exhibited overall motility and viability parameters similar to control samples frozen in cryovials. Individually selected spermatozoa cryopreserved on loops were easily recovered and post-thaw motility was generally good. Sperm function testing demonstrated that both human and bovine spermatozoa cryopreserved on loops were able to undergo sperm head decondensation when injected into oocytes. Cryoloops may be an excellent alternative to hamster zonae for cryopreserving small numbers of human spermatozoa.

Cryopreservation of human sperm

Freezing of human sperm is considered a routine procedure in assisted reproductive technology (ART) laboratories. This article considers various aspects of cryopreservation of human sperm. Human sperm show a specific cryophysical behaviour and different sperm freezing protocols have been developed to avoid damage to the sperm cells. The damage can range from impaired motility and reduced viability to damage to the cellular organelles and effects at the molecular level, resulting in an impaired fertilizing potential. As testicular sperm are immature and only a small number can be retrieved, special techniques are required for successful freezing and thawing of these samples. Banking of human sperm has to be performed in a safe and controlled way and different guidelines are necessary to ensure that this is achieved.

Freezing a few testicular spermatozoa retrieved by TESA

Men with azoospermia can now be treated using testicular sperm aspiration (TESA). New aspirations, in subsequent cycles, may be avoided using cryopreservation. Conventional sperm freezing techniques are not suitable for TESA samples with a small number of spermatozoa. Testicular spermatozoa were obtained from 10 azoospermic men undergoing TESA for a diagnostic objective. Two different freezing protocols were performed according to the number of spermatozoa found in the final suspension: between 100-2000, we used TEST yolk buffer with glycerol, adding it to testicular sperm (Method I); for less than 100, we injected them into cell-free human zona pellucida before adding a freezing medium (Method II). Sperm and motility recovery rates were 1% and 32.3%, and 88.2% and 26.6% for methods I and II respectively. The fertilisation rate was 13.3% and 23% for methods I and II respectively. This study represents our preliminary experience in freezing testicular spermatozoa collected by TESA. Preliminary observations show that it is possible to freeze a few testicular spermatozoa inside evacuated zona pellucida.

Biological aspects of testicular sperm extraction

Since the first reports of successful pregnancies after treatment with intra cytoplasmic sperm injection (ICSI) in humans, intensive investigations focused on the use of testicular spermatozoa and immature sperm cells in the treatment of azoopsermic patients. Several studies explore the technical development of the preparation, isolation and cryo storage of testicular germ cells. Other studies focus on ICSI itself and try to identify the biochemical and biophysical processes involved in fertilisation after injection of a testicular sperm cell into a human oocyte. Indications for azoospermic patients to whom this first line treatment can be offered are becoming more defined. But one of the major concerns is of course the safety of the technique, especially, for the health and reproductive life of the babies born after application of ICSI with testicular germ cells. An evaluation of ICSI with testicular germ cells is presented in this manuscript.

Sperm deposition site during ICSI affects fertilization and development

OBJECTIVE

To evaluate the effects of sperm placement during ICSI relative to the M-II spindle location on fertilization and preimplantation development.

DESIGN

Retrospective analysis of oocyte fertilization and embryo development with respect to sperm deposition site during ICSI.

SETTING

A program of IVF-ET.

PATIENT(S)

Seven hundred seventy-six patients.

INTERVENTION(S)

Egg quality, sperm deposition site, and polar-body position were recorded during ICSI; fertilization was assessed on day 1; embryo development was evaluated on days 2 and 3.

MAIN OUTCOME MEASURE(S)

Fertilization, embryo development, and implantation rates.

RESULT(S)

Normal fertilization is not affected by polar-body orientation, with the exception of a significantly lower fertilization rate from a 9 o'clock polar-body orientation. Injections with the polar-body positioned at 7 or 11 o'clock result in the greatest number of high-quality embryos, significantly more than the adjacent 6 or 12 o'clock polar-body orientations and irrespective of oocyte anomaly frequency. Embryos originating from the 7 or 11 o'clock polar-body category implant at a higher rate, although the data are not significant.

CONCLUSION(S)

The placement of the sperm during ICSI relative to the presumed location of the meiotic spindle significantly impacts fertilization and high-quality embryo development. Sperm deposition in the M-II spindle area should be avoided. It appears that development, and not fertilization, is improved by decreasing the distance between the sperm cell and the spindle.