Sperm processing for advanced reproductive technologies: Where are we today?

A simplified fixed-time insemination protocol using frozen-thawed stallion spermatozoa stored at 17°C for up to 24 h before insemination

BACKGROUND

Insemination of mares with frozen-thawed spermatozoa requires intensive management and results in 40%-60% per cycle pregnancy rates.

OBJECTIVES

To determine if satisfactory fertility is possible for frozen-thawed semen after processing it through a microfluidic device, followed by storage at 17°C for up to 24 h before fixed-time insemination.

STUDY DESIGN

Uncontrolled field trials.

METHODS

A pilot study evaluated the motility of frozen-thawed spermatozoa after centrifugation and storage (17°C) in two different media for up to 48 h. Subsequently, the motility of frozen-thawed semen processed through a microfluidic device, resuspended in two different media during storage (17°C) for up to 24 h was evaluated. The fertility of frozen-thawed spermatozoa, after microfluidic sorting and storage at 17°C for up to 24 h, was evaluated after fixed-time insemination in a commercial embryo programme. Experiment 1: Frozen-thawed spermatozoa (N = 5 stallions) were centrifuged and resuspended in Botusemen Gold™ or SpermSafe™ and stored (17°C) for up to 48 h. Sperm motility was evaluated by CASA at 0, 6, 24 and 48 h. Experiment 2: Frozen-thawed spermatozoa (N = 4 stallions) underwent microfluidic sorting and storage (17°C) for up to 24 h in both media. Sperm concentration and motility were evaluated at 0, 16 and 24 h. Experiment 3: Fertility of frozen-thawed spermatozoa (N = 3 stallions) was evaluated after insemination of 42 mare cycles at 6, 16 and 24 h after thawing, microfluidic sorting and storage before fixed-time insemination.

RESULTS

The stallion significantly influenced sperm motility, but there was no effect of media on motility parameters. Storage time significantly affected sperm motility after centrifugation but not after microfluidic sorting. Storage time had no effect on the overall embryo recovery rate (52%, n = 42).

MAIN LIMITATIONS

Field trial with small mare numbers and no control at time = 0 h.

CONCLUSIONS

Fixed-time insemination of frozen-thawed spermatozoa after microfluidic sorting and storage at 17°C for up to 24 h produced satisfactory embryo recovery rates.

Advances in microfluidic technology for sperm screening and in vitro fertilization

About 18% of reproductive-age adults worldwide are affected by infertility. In vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are widely used assisted reproductive technologies (ARTs) aimed at improving clinical outcomes. Efficient and noninvasive selection and isolation of highly motile sperm with intact DNA are essential for the success of IVF and ICSI and can potentially impact the therapeutic efficacy and the health of the offspring. Compared to traditional methods, microfluidic technology offers significant advantages such as low sample consumption, high efficiency, minimal damage, high integration, similar microenvironment, and high automation, providing a new platform for ARTs. Here, we review the current situation of microfluidic technology in the field of sperm motility screening and evaluation and IVF research. First, we focus on the working principle, structural design, and screening results of sperm selection microfluidic platforms. We then highlight how the multiple steps of the IVF process can be facilitated and integrated into a microfluidic chip, including oocyte capture, sperm collection and isolation, sperm sorting, fertilization, and embryo culture. Ultimately, we summarize how microfluidics can complement and optimize current sperm sorting and IVF protocols, and challenges and possible solutions are discussed.

Can Microfluidics Improve Sperm Quality? A Prospective Functional Study

The same sperm selection techniques in assisted reproduction clinics have remained largely unchanged despite their weaknesses. Recently, microfluidic devices have emerged as a novel methodology that facilitates the sperm selection process with promising results. A prospective case-control study was conducted in two phases: 100 samples were used to compare the microfluidic device with Density Gradient, and another 100 samples were used to compare the device with the Swim-up. In the initial phase, a significant enhancement in progressive motility, total progressive motile sperm count, vitality, morphology, and sperm DNA fragmentation were obtained for the microfluidic group compared to Density Gradient. Nevertheless, no statistically significant differences were observed in sperm concentration and chromatin structure stability. In the subsequent phase, the microfluidic group exhibited significant increases in sperm concentration, total progressive motile sperm count, and vitality compared to Swim-up. However, non-significant differences were seen for progressive motility, morphology, DNA structure stability, and DNA fragmentation. Similar trends were observed when results were stratified into quartiles. In conclusion, in a comparison of microfluidics with standard techniques, an improvement in sperm quality parameters was observed for the microfluidic group. However, this improvement was not significant for all parameters.

Leukocytospermia and/or Bacteriospermia: Impact on Male Infertility

Infertility is a globally underestimated public health concern affecting almost 190 million people, i.e., about 17.5% of people during their lifetime, while the prevalence of male factor infertility is about 7%. Among numerous other causes, the prevalence of male genital tract infections reportedly ranges between 10% and 35%. Leukocytospermia is found in 30% of infertile men and up to 20% in fertile men. Bacterial infections cause an inflammatory response attracting leukocytes, which produce reactive oxygen species (ROS) and release cytokines, both of which can cause damage to sperm, rendering them dysfunctional. Although leukocytospermia and bacteriospermia are both clinical conditions that can negatively affect male fertility, there is still debate about their impact on assisted reproduction outcomes and management. According to World Health Organization (WHO) guidelines, leukocytes should be determined by means of the Endtz test or with monoclonal antibodies against CD15, CD68 or CD22. The cut-off value proposed by the WHO is 1 × 106 peroxidase-positive cells/mL. For bacteria, Gram staining and semen culture are regarded as the "gold standard", while modern techniques such as PCR and next-generation sequencing (NGS) are allowing clinicians to detect a wider range of pathogens. Whereas the WHO manual does not specify a specific value as a cut-off for bacterial contamination, several studies consider semen samples with more than 103 colony-forming units (cfu)/mL as bacteriospermic. The pathogenic mechanisms leading to sperm dysfunction include direct interaction of bacteria with the male germ cells, bacterial release of spermatotoxic substances, induction of pro-inflammatory cytokines and ROS, all of which lead to oxidative stress. Clinically, bacterial infections, including "silent" infections, are treatable, with antibiotics being the treatment of choice. Yet, non-steroidal antiphlogistics or antioxidants should also be considered to alleviate inflammatory lesions and improve semen quality. In an assisted reproduction set up, sperm separation techniques significantly reduce the bacterial load in the semen. Nonetheless, contamination of the semen sample with skin commensals should be prevented by applying relevant hygiene techniques. In patients where leukocytospermia is detected, the causes (e.g. infection, inflammation, varicocele, smoking, etc.) of the leukocyte infiltration have to be identified and addressed with antibiotics, anti-inflammatories or antioxidants in cases where high oxidative stress levels are detected. However, no specific strategy is available for the management of leukocytospermia. Therefore, the relationship between bacteriospermia and leukocytospermia as well as their specific impact on functional sperm parameters and reproductive outcome variables such as fertilization or clinical pregnancy must be further investigated. The aim of this narrative review is to provide an update on the current knowledge on leukocytospermia and bacteriospermia and their impact on male fertility.

Artificial Intelligence in Andrology: From Semen Analysis to Image Diagnostics

Artificial intelligence (AI) in medicine has gained a lot of momentum in the last decades and has been applied to various fields of medicine. Advances in computer science, medical informatics, robotics, and the need for personalized medicine have facilitated the role of AI in modern healthcare. Similarly, as in other fields, AI applications, such as machine learning, artificial neural networks, and deep learning, have shown great potential in andrology and reproductive medicine. AI-based tools are poised to become valuable assets with abilities to support and aid in diagnosing and treating male infertility, and in improving the accuracy of patient care. These automated, AI-based predictions may offer consistency and efficiency in terms of time and cost in infertility research and clinical management. In andrology and reproductive medicine, AI has been used for objective sperm, oocyte, and embryo selection, prediction of surgical outcomes, cost-effective assessment, development of robotic surgery, and clinical decision-making systems. In the future, better integration and implementation of AI into medicine will undoubtedly lead to pioneering evidence-based breakthroughs and the reshaping of andrology and reproductive medicine.

Nuclear sperm integrity and ICSI prognosis in Tunisian patients with MMAF syndrome (multiple morphological abnormalities of the sperm flagella)

Multiple Morphological Abnormalities of the Sperm Flagella (MMAF) is a severe form of teratozoospermia associated with several sperm flagellar abnormalities. The study included 52 patients with MMAF syndrome and a control group of 25 fertile men. The impact of nuclear sperm quality on intracytoplasmic sperm injection (ICSI) results was studied in 20 couples. TUNEL assay was used to assess sperm DNA fragmentation and aniline-blue staining was used to assess chromatin condensation. To investigate chromosomal meiotic segregation, we used fluorescence in situ hybridization (FISH). Semen morphology analysis revealed a mosaic of multiple flagella morphological abnormalities, including 46.73% short flagella, 16.22% bent flagella, 22.07% coiled flagella, and 10.90% absent flagella, all of which were associated with a high percentage of sperm head abnormalities. The mean DNA fragmentation index was substantially higher in patients compared to controls (p = 0.001), whereas the rate of aniline blue-reacted spermatozoa was not significantly different. There was a significant difference in aneuploidy frequencies between the two groups (p < 0.05). Infertile males with MMAF syndrome had lower sperm nuclear quality, which affected ICSI results. As a result, better sperm selection procedures are being employed to increase the success rate of assisted reproductive technologies (ART).

Surgically retrieved spermatozoa for ICSI cycles in non-azoospermic males with high sperm DNA fragmentation in semen

Intracytoplasmic sperm injection (ICSI) using surgically retrieved spermatozoa outside the classic context of azoospermia has been increasingly used to overcome infertility. The primary indications include high levels of sperm DNA damage in ejaculated spermatozoa and severe oligozoospermia or cryptozoospermia, particularly in couples with ICSI failure for no apparent reason. Current evidence suggests that surgically retrieved spermatozoa for ICSI in the above context improves  outcomes, mainly concerning pregnancy and miscarriage rates. The reasons are not fully understood but may be related to the lower levels of DNA damage in spermatozoa retrieved from the testis compared with ejaculated counterparts. These findings are consistent with the notion that excessive sperm DNA damage  can be a limiting factor responsible for the failure to conceive. Using testicular in preference of low-quality ejaculated spermatozoa bypasses post-testicular sperm DNA damage caused primarily by oxidative stress, thus increasing the likelihood of oocyte fertilization by genomically intact spermatozoa. Despite the overall favorable results, data remain limited, and mainly concern males with confirmed sperm DNA damage in the ejaculate. Additionally, information regarding the health of ICSI offspring resulting from the use of surgically retrieved spermatoa of non-azoospermic males is still lacking. Efforts should be made to improve the male partner's reproductive health for safer ICSI utilization. A comprehensive andrological evaluation aiming to identify and treat the underlying male infertility factor contributing to sperm DNA damage is essential for achieving this goal.

Lab-on-chip (LoC) application for quality sperm selection: An undelivered promise?

Quality sperm selection is essential to ensure the effectiveness of assisted reproductive techniques (ART). However, the methods employed for sperm selection in ART often yield suboptimal outcomes, contributing to lower success rates. In recent years, microfluidic devices have emerged as a promising avenue for investigating the natural swimming behavior of spermatozoa and developing innovative approaches for quality sperm selection. Despite their potential, the commercial translation of microfluidic-based technologies has remained limited. This comprehensive review aims to critically evaluate the inherent potential of lab-on-chip technology in unraveling sophisticated mechanisms encompassing rheotaxis, thermotaxis, and chemotaxis. By reviewing the current state-of-the-art associated with microfluidic engineering and the swimming of spermatozoa, the goal is to shed light on the multifaceted factors that have impeded the broader commercialization of these cutting-edge technologies and recommend a commercial that can surmount the prevailing constraints. Furthermore, this scholarly exploration seeks to enlighten and actively engage reproductive clinicians in the profound potential and implications of microfluidic methodologies within the context of human infertility.

Equine Spermatozoa Selection by Magnetic Activation for Use in Assisted Reproduction

This study aimed to select high-quality spermatozoa by sperm separation by magnetic activation of the fresh equine semen, compared to density gradient centrifugation and evaluating cell quality after selection. The semen of 10 stallions was collected by the artificial vagina technique. The samples analyzed were: (1) fresh semen; (2) density gradient centrifugation (DGC); (3) separation by magnetic activation (MASS) (nonapoptotic portion NAP); (4) separation by MASS (apoptotic portion-APT). Was analyzed: motility (light microscopy), concentration (Neubauer chamber), semen morphology (humid chamber in phase contrast), and supravital test (eosin/nigrosine). In DGC, 20 × 10⁶ spermatozoa were used in the gradient of Percoll at 90% and 45% (400 μL each), centrifugation at 900 G/5 min, the pellet was diluted in HEPES. In MASS, 10 × 10⁶ spermatozoa were diluted in 1.5 mL of HEPES, centrifugation at 300 G/10 min, pellet was resuspended in 150 μL of HEPES with 20 μL of nanoparticles bound to annexin V, incubation for 15 minutes and filtered in the magnetic separation column. The nonapoptotic fraction was collected directly and the apoptotic fraction after removal the column from the magnet and adding 300 μL of HEPES. The total abnormalities were 43.2% ± 2.78%, with the DGC and MASS being effective in reducing sperm abnormality by 15.6% ± 2.10% and 24.30% ± 1.63%, respectively, like the observed for the number of cells with intact membranes (50% lower in the APT portion). This nanotechnological method is efficient in producing high-quality semen samples for assisted reproduction procedures.

Sperm quality metrics were improved by a biomimetic microfluidic selection platform compared to swim-up methods

Sperm selection is an essential component of all assisted reproductive treatments (ARTs) and is by far the most neglected step in the ART workflow in regard to technological innovation. Conventional sperm selection methodologies typically produce a higher total number of sperm with variable motilities, morphologies, and levels of DNA integrity. Gold-standard techniques, including density gradient centrifugation (DGC) and swim-up (SU), have been shown to induce DNA fragmentation through introducing reactive oxygen species (ROS) during centrifugation. Here, we demonstrate a 3D printed, biologically inspired microfluidic sperm selection device (MSSP) that utilizes multiple methods to simulate a sperms journey toward selection. Sperm are first selected based on their motility and boundary-following behavior and then on their expression of apoptotic markers, yielding over 68% more motile sperm than that of previously reported methods with a lower incidence of DNA fragmentation and apoptosis. Sperm from the MSSP also demonstrated higher motile sperm recovery after cryopreservation than that of SU or neat semen. Experiments were conducted side-by-side against conventional SU methods using human semen (n = 33) and showed over an 85% improvement in DNA integrity with an average 90% reduction in sperm apoptosis. These results that the platform is easy-to-use for sperm selection and mimics the biological function of the female reproductive tract during conception.

A review of the use of antioxidants in bovine sperm preparation protocols

Reactive oxygen species (ROS) and oxidative stress (OS), the imbalance between the production of free radicals and the cellular antioxidant defenses, are discussed in relation to their role in bovine sperm physiology. Oxidative stress has been associated to male infertility and low fertility rates in Assisted Reproductive Techniques (ART). Antioxidant supplementation is an interesting approach to overcome OS-related infertility and assisted reproduction drawbacks. Several studies have been conducted to identify the potential sources of ROS in a typical ART setting and the impact of antioxidant supplementation on semen quality and pregnancy outcome. Procedures such as freezing and thawing, centrifugation and incubation are thought to produce significant amounts of ROS with a negative impact on sperm quality parameters and reproductive competence. Given the important role of ROS in sperm function, the addition of antioxidants in sperm media to prevent OS and to improve the reproductive outcome requires attention. Currently, there is limited evidence to support the ameliorative effect of antioxidant supplementation on fertilization and embryo development in farm animals. This review summarizes the different types and concentrations of antioxidants used in sperm preparation media of bovine species and their effectiveness in neutralizing excessive ROS production while preserving physiological sperm function.

A microfluidic method for passive trapping of sperms in microstructures

Sperm motility is a prerequisite for male fertility. Enhancing the concentration of motile sperms in assisted reproductive technologies - for human and animal reproduction - is typically achieved through aggressive methods such as centrifugation. Here, we propose a passive technique for the amplification of motile sperm concentration, with no externally imposed forces or flows. The technique is based on the disparity between probability rates, for motile cells, of entering and escaping from complex structures. The effectiveness of the technique is demonstrated in microfluidic experiments with microstructured devices, comparing the trapping power in different geometries. In these micro-traps, we observe an enhancement of cells' concentration close to 10, with a contrast between motile and non-motile cells increased by a similar factor. Simulations of suitable interacting model sperms in realistic geometries reproduce quantitatively the experimental results, extend the range of observations and highlight the components that are key to the optimal trap design.

Escaping Behavior of Sperms on the Biomimetic Oviductal Surface

Before fertilization, sperms adhere to oviductal epithelium cells, and only a restrictive number of winner sperms can escape to reach the egg. To study the sperm escape behavior from the oviductal surface, we developed a microfluidic chip to fabricate an adhesive surface and to create a gradient of progesterone (P₄) for mimicking the oviduct microenvironment in vivo. We identified three sperm motion patterns in such a microenvironment─anchored spin, run-and-spin, and escaped mode. By using kinetic analysis, we verified the hypothesis that the responsive rotation energy anchored with the adhered sperm head determines whether the sperm is trapped or detaching, which is defined as the hammer flying strategy of successful escape after accumulating energy in the process of rotating. Intriguingly, this hammer-throw escaping is able to be triggered by the P₄ biochemical stimulation. Our results revealed the tangled process of sperm escape before fertilization in the ingenious microfluidic system.

Effects of photobiomodulation therapy on human sperm function

INTRODUCTION

Sperm motility is a crucial factor in male infertility and it depends on mitochondrial tail movements. Photobiomodulation light therapy allows the cells to produce their energy through activation of the mitochondria. The aim of the present study was to examine the impact of photobiomodulation on sperm motility in astenozoospermic individuals.

MATERIALS AND METHODS

Following semen analyses of 20 astenozoospermic individuals, collected semen samples were centrifuged. Pellet was obtained and homogenized through mixing with culture media in 1:1 ratio. Each semen samples were divided into 3 groups. In the first group, control samples were not exposed to laser irradiation. The Group 2 and Group 3 were exposed to 650nm wavelength of photobiomodulation from 10cm distance in dark environment via a 36cm² aperture sizer with 200mW output power for 30 and 60min duration, respectively. Sperm motilities were evaluated and chromatin condensation of sperms was determined.

RESULTS

Sperm motilities were significantly increased in photobiomodulation groups compared with the controls. Sperm motilities tended to be different between the 30 and 60min red light exposure groups; however, it was not statistically significant. When the motility grades were compared, no significant difference was observed in non-progressive motility sperms. While immotile sperms decreased significantly in the photobiomodulation groups compared to the control group, progressive sperms increased.

CONCLUSIONS

The results of the present study demonstrated that the photobiomodulation is an efficient method to increase the sperm motility of astenozoospermic individuals independent of the duration of exposure.

Sperm selection with Annexin-V coated polystrene bead technique (APB-Tech): A novel and reliable method for the microscopic selection of viable and non-apoptotic sperm to be used for intracytoplasmic sperm injection

Infertility is a growing health problem that affects 20% of couples who want to conceive. 'Intracytoplasmic sperm injection' (ICSI) is a commonly used assisted reproduction treatment technique that offers the couples to overcome a wide variety of infertility reasons, including female, male and unexplained infertility. A crucial step in ICSI is choosing the correct sperm with the highest potential to form a healthy embryo and thus a healthy offspring. The sperm selection strategies aim to obtain a sperm population with better motility and morphology, which are insufficient to predict a sperm's reproductive potential. The elimination of apoptotic sperms, which is shown to be higher in infertile males and which is shown to affect embryo development and reproductive cohort significantly should also be included in the selection strategies. Among all sperm selection methods, there are only a few which can eliminate apoptotic sperm, but because they need extra types of equipments, a long training period, and high costs, they couldn't find place in the most commonly used techniques in an IVF lab. Selecting the non-apoptotic sperm cells will help us choose a sperm that is more likely to be chosen by the natural selection mechanisms and thus will help to mimic the natural conception more. The study aimed to develop a novel, easy and a harmless individual sperm selection technique to enable choosing non-apoptotic viable sperm cells via light microscopy without any need for extra equipment, education and cost to be used for ''ICSI'. The technique is based on the binding ability of Annexin-V covered polystrene beads to the externalized phosphatidylserine at the outer leaflet of an apoptotic sperm's plasma membrane. After Annexin-V covered polystyrene beads were prepared, beads obtained were attached to BALB-c mice sperm, and the technique is optimized to obtain the most efficient attachment conditions. The results are then compared with the results of four well-known reliable apoptosis detection techniques to test the validity and sperm survival test to test the toxicity of the technique. The method is proven to be '''reliable' by comparing it with the results of well-known techniques, including TUNEL and SCSA (sperm chromatin structure assay), and '''safe' by showing its non-toxicity via sperm survival test (SST). In addition, the method enables the selection of sperm cells more closer to naturally-chosen ones from a pool of sperm that should not be allowed to be randomly chosen during microinjection. To date, it was impossible to distinguish a non-apoptotic sperm without harming it or without needing additional equipment other than a routine IVF lab and extra training other than routine andrology work. The technique is named as 'Annexin-V coated polystyrene bead technique (APB-Tech)'. Based on our results, further studies on APB-Tech should be focused on the possible improvement of ICSI outcomes and, thus, success rates.

Microfluidic devices employing chemo- and thermotaxis for sperm selection can improve sperm parameters and function in patients with high DNA fragmentation

Conventional sperm processing uses centrifugation has a negative effect on sperm parameters and DNA integrity. We designed and fabricated a novel microfluid device based on chemotaxis and thermotaxis, and compared it with the swim-up method. Twenty normal samples with high DNA fragmentation were included. Each sample was divided into four groups: Group 1, control, Group 2: sperm selection by thermotaxis, Group 3: sperm selection by chemotaxis, and Group 4: sperm selection with thermotaxis and chemotaxis. We used cumulus cells in a microfluid device to create chemotaxis, and, two warm stages to form a temperature gradient for thermotaxis. The spermatozoa were assessed based on the concentration, motility, and fine morphology using Motile Sperm Organelle Morphology Examination, mitochondrial membrane potential (MMP), acrosome reaction (AR), and sperm DNA fragmentation. Concentration (22.40 ± 5.39 vs. 66.50 ± 19.21; p < 0.001) and DNA fragmentation (12.30 ± 3.96% vs. 17.95 ± 2.89%; p < 0.001) after selection in the chemotaxis and thermotaxis microfluid device were significantly lower than control group. The progressive motility (93.75 ± 4.39% vs. 75.55 ± 5.86%, p < 0.001), normal morphology (15.45 ± 2.50% vs. 10.35 ± 3.36, p < 0.001), MMP (97.65 ± 1.81% vs. 94 ± 3.89%, p = 0.02), and AR status (79.20 ± 5.28% vs. 31.20 ± 5.24%, p < 0.001) in the chemotaxis and thermotaxis microfluid device were significantly increased compared to control group. According to these findings, spermatozoa that have penetrated the cumulus oophorus have better morphology and motility, as well as acrosome reactivity and DNA integrity.

Action of swim-up and caffeine on equine frozen sperm

Cryopreservation of equine semen is crucial to semen commercialization. However, it reduces sperm motility and longevity. Thus, sperm selection methods and addition of motility-activating substances to sperm, such as caffeine, may improve sperm quality of equine frozen semen. The objective of the current work was to evaluate the effects of caffeine on recovery and quality parameters of frozen-thawed sperm subjected to swim-up selection to be used in intracytoplasmic sperm injection (ICSI) in assisted reproductive techniques. Stallion semen were frozen and after thawing different caffeine concentrations were added to the samples performing four treatments control (no caffeine), 3, 5, and 7.5 mM caffeine. Sperm kinematic and motility were assessed by computer-assisted sperm analysis (CASA). Then, the four treated samples were submitted to the swim-up sperm selection, and the number of recovered sperm and morphology were evaluated at four times 20, 40, 60, and 80 min. The swim-up increased the recovery proportion of normal morphology sperm without (80.1±1%) or with caffeine addition (3mM: 81.2±1%, 5mM: 79.9±1% and 7.5 mM 78.9±1%) compared to the thawed semen (70±2%). However, the addition of 5 mM caffeine induced an increase in sperm motility (38.9±2.8 vs. 32.6±3.4%, P<0.05), and sperm recovery after swim-up (7.9x10⁶ vs. 3.4x10⁶ sperm/ml, P<0.05) compared to the control. The addition of 5 mM caffeine to frozen-thawed equine semen before swim-up selection improved sperm motility and increased the sperm recovery rate while not decreasing the percentage of morphologically normal sperm. Thus, caffeine addition to frozen-thawed equine semen before swim-up selection has potential clinical application in improving sperm quality for use in ICSI.

Opportunities and Limits of Conventional IVF versus ICSI: It Is Time to Come off the Fence

Conventional IVF (c-IVF) is one of the most practiced assisted reproductive technology (ART) approaches used worldwide. However, in the last years, the number of c-IVF procedures has dropped dramatically in favor of intracytoplasmic sperm injection (ICSI) in cases of non-male-related infertility. In this review, we have outlined advantages and disadvantages associated with c-IVF, highlighting the essential steps governing its success, its limitations, the methodology differences among laboratories and the technical progress. In addition, we have debated recent insights into fundamental questions, including indications regarding maternal age, decreased ovarian reserve, endometriosis, autoimmunity, single oocyte retrieval-cases as well as preimplantation genetic testing cycles. The “overuse” of ICSI procedures in several clinical situations of ART has been critically discussed. These insights will provide a framework for a better understanding of opportunities associated with human c-IVF and for best practice guidelines applicability in the reproductive medicine field.

Efficacy of density gradient centrifugation technique (DGC) in enhancing sperm cell DNA quality for assisted reproductive technique

Objective

Density gradient centrifugation (DGC) is commonly used for sperm preparation before assisted reproductive technology (ART) procedures. This technique separates superior motile spermatozoa with normal morphology from the total sperm population. However, there is still controversy as to the effects of this sperm separation technique on sperm cell DNA integrity which is a determining element in the process of fertilization and embryonic development.

The objective of this study was to determine the effects of DGC on sperm cell DNA integrity as assessed by a novel association between two cytogenetic tests.

Study designs

Semen samples were collected from 30 fertile donors and 40 patients being candidates for ART treatment. Each sample was divided into two parts: the first portion was subjected to selection by two layers of DGC (45% and 90%) and the second fraction was rinsed with phosphate-buffered saline solution and centrifuged without density gradient.

Abnormal sperm chromatin structure as evaluated by a sperm chromatin dispersion (SCD) test and DNA denaturation as assessed by an acridine orange (AO) test were monitored in the initially washed sample and in the different layers of the density gradient centrifugation.

Results

DGC significantly improved the proportion of sperm progressive motility, total motility, and sperm morphology. Moreover, following density gradient centrifugation, the proportion of spermatozoa with denaturated DNA significantly decreased when compared with whole semen (p < 0.001). In addition, we found that spermatozoa isolated in the 90% layer possessed a significantly lower percentage of sperm chromatin decondensation when compared with those remaining in the 45% layer and unprocessed semen (p < 0.001).

Conclusions

Using double cytogenetic tests, our study shows that semen processing by density gradient centrifugation is useful in selecting sperm with higher double-strand DNA integrity and recommended to be used in sperm preparation for assisted reproduction.

Effect of Sperm Selection by Magnetic-Activated Cell Sorting in D-IUI: A Randomized Control Trial

Clinical outcome in assisted reproduction techniques (ARTs) is mainly influenced by the quality of gametes used. It is known that a high percentage of sperm DNA fragmentation (DNAf) decreases the success of ART clinical results. Therefore, techniques such as magnetic-activated cell sorting (MACS) help to improve results in cases of patients with a high percentage of DNAf. Cryopreservation of sperm in donor intrauterine insemination (D-IUI) treatments increases sperm DNAf, so patients using these sperm samples can benefit from using this technique. This prospective randomized national multicenter study analyzed clinical outcomes of 181 D-IUI treatments. MACS was performed after density gradient centrifugation (DGC) in 90 thawed semen donor samples (MACSG), whereas only DGC was performed in 91 thawed semen donor samples (CG). To our knowledge, this is the first study analyzing the effect of MACS on D-IUI cycles. Our results show no significant differences in gestation, live birth, or miscarriage rates between the two groups. We believe that further studies with a larger sample size are needed to evaluate the application of MACS in combination with standard IUI donor sperm preparations in fertility clinics.

Electrically-driven handling of gametes and embryos: taking a step towards the future of ARTs

Electrical stimulation of gametes and embryos and on-chip manipulation of microdroplets of culture medium serve as promising tools for assisted reproductive technologies (ARTs). Thus far, dielectrophoresis (DEP), electrorotation (ER) and electrowetting on dielectric (EWOD) proved compatible with most laboratory procedures offered by ARTs. Positioning, entrapment and selection of reproductive cells can be achieved with DEP and ER, while EWOD provides the dynamic microenvironment of a developing embryo to better mimic the functions of the oviduct. Furthermore, these techniques are applicable for the assessment of the developmental competence of a mammalian embryo in vitro. Such research paves the way towards the amelioration and full automation of the assisted reproduction methods. This article aims to provide a summary on the recent developments regarding electrically stimulated lab-on-chip devices and their application for the manipulation of gametes and embryos in vitro.

Separation of motile human sperms in a T-shaped sealed microchannel

Microfluidic methods act as an effective motile sperm separation technique used in infertility treatments. This work presents a standalone microfluidic device to separate motile sperm cells from non-motile sperm cells and debris. The separation mechanism is based on the centrifugal force acting on sperms and the ability of progressive motile sperms to swim upstream. The separation of motile sperm is carried out using a simple T-shaped microchannel which constitutes three reservoirs: one inlet and two outlets. Herein, one of the outlets is kept sealed. The sealed channel leads to a high-velocity gradient and a rheotaxis zone at the T junction resulting in the separation of motile sperms. Separated sperms are isolated in a sealed channel with a low Reynolds number flow so that sperms cannot have a net displacement, which ensures that the sperms do not re-enter the fluid flow. CFD simulation is conducted to study the flow fields inside the channel and experimental investigation is carried to observe the separation behaviour of sperms. The reported device provides 100% sperm separation efficiency and ensures the entrapment of sperm cells for a longer period. A modified colorimetric nitroblue tetrazolium test conducted on separated sperm cells shows that there is only a marginal increase in superoxide (O₂ ^-) production, proving normal sperm integrity. This device offers an effective and safe alternative to conventional sperm sorting methods.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13534-022-00229-9.

Isolating motile sperm cell sorting using biocompatible electrospun membranes

Motility is an indicator of sperm cell viability due to higher probability in swimming through the female reproductive tract and undergo fertilization with the egg cell. Centrifugation method is a technique to process high volume semen and isolate motile sperm cells but decreases the biochemical integrity of spermatozoa due to the contact with reactive oxygen species (ROS) from dead cells released during centrifugation. This study uses solution electrospun poly(ε-caprolactone) membranes as an alternative in isolating motile spermatozoa by utilizing a rationally designed 3D printed module set up, providing the same benefits as commercially available techniques with minimal processing time, and bypassing the centrifugation step to provide higher quality sperm cells. The membranes, with nominal pore size distributions ranging from 5 to 6 µm are highly porous structures suitable for establishing baseline data for sperm cell sorting by motility. The proposed method allows for isolation of motile sperm cells with 74% purity, while decreasing the processing time by 98% when compared to centrifugation techniques. This novel approach provides a facile method for isolating motile spermatozoa directly from frozen semen samples without any pretreatments and is easily scalable for small and medium scale farms as well as larger industries.

Selection of healthy sperm based on positive rheotaxis using a microfluidic device

For conception, sperm cells travel towards the oocyte. This journey is accomplished by only a few sperm cells, following various guidance mechanisms. Of these mechanisms, rheotaxis plays a significant role in guiding the sperm over a long distance. By taking advantage of this natural rheotaxis behavior of sperm, we have developed a microfluidic chip that isolates healthy sperm cells. The developed chip consists of different chambers separated by microchannels that facilitate separation of motile sperm cells from unprocessed semen samples with the help of fluid flow. The sperm cells are subjected to different velocities in different parts of the chip that direct functional sperm towards the collection chamber utilizing positive rheotaxis. The results from the developed microfluidic chip (with 0.5 μL min^-1 flow rate) have shown almost 100% motility, a significantly higher percentage of morphologically normal sperm cells with lesser sperm DNA fragmentation than the control (no-flow) and raw semen sample. This chip satisfies the need of a clinical setting as it is low-cost, easy to operate and uses a small semen volume for sperm sorting.

Antibody-Conjugated Magnetic Beads for Sperm Sexing Using a Multi-Wall Carbon Nanotube Microfluidic Device

This study proposes a microfluidic device used for X-/Y-sperm separation based on monoclonal antibody-conjugated magnetic beads, which become positively charged in the flow system. Y-sperms were selectively captured via a monoclonal antibody and transferred onto the microfluidic device and were discarded, so that X-sperms can be isolated and commercially exploited for fertilization demands of female cattle in dairy industry. Therefore, the research team used monoclonal antibody-conjugated magnetic beads to increase the force that causes the Y-sperm to be pulled out of the system, leaving only the X-sperm for further use. The experimental design was divided into the following: Model 1, the microfluid system for sorting positive magnetic beads, which yielded 100% separation; Model 2, the sorting of monoclonal antibody-conjugated magnetic beads in the fluid system, yielding 98.84% microcirculation; Model 3, the sorting of monoclonal antibody-conjugated magnetic beads with sperm in the microfluid system, yielding 80.12% microcirculation. Moreover, the fabrication microfluidic system had thin film electrodes created via UV lithography and MWCNTs electrode structure capable of erecting an electrode wall 1500 µm above the floor with a flow channel width of only 100 µm. The system was tested using a constant flow rate of 2 µL/min and X-/Y-sperm were separated using carbon nanotube electrodes at 2.5 V. The structure created with the use of vertical electrodes and monoclonal antibody-conjugated magnetic beads technique produced a higher effective rejection effect and was able to remove a large number of unwanted sperm from the system with 80.12% efficiency.

Prospective randomized controlled study of a microfluidic chip technology for sperm selection in male infertility patients

The purpose of this study is to evaluate the impact of a microfluidic approach for spermatozoon selection in male infertility patients undergoing intracytoplasmic sperm injection (ICSI). This research enrolled 128 individuals who had ICSI for male-factor infertility. The patients were separated into two groups according to the method used to pick the spermatozoa: group I (n = 64), which used traditional swim-up procedures, and group II (n = 64), which used the Fertile Chip for spermatozoon selection during ICSI therapy. Fertilization rates and embryo quality were the major outcomes. The rates of pregnancy, clinical pregnancy and live birth were used as secondary outcomes. As a result, there was no statistically significant difference between the two groups in terms of fertilization rate, total grade 1 and 2 embryos. Implantation rate was significantly higher in the Fertile Chip group than in the control group (50% vs. 31%, p = 0.02). The Fertile Chip group had considerably greater pregnancy rates, clinical pregnancy rates (CPR) and live birth rates than the control group (62.5% vs. 45.3%, p = 0.038; 59.4% vs. 35.9%, p = 0.006 and 46.8% vs. 25%, p = 0.009). Fertile Chip had no effect on fertilization rates or embryo quality in male-factor infertility couples. However, the Fertile Chip group had a statistically higher pregnancy rate, CPR and live birth rate.

The influence of the female reproductive tract and sperm features on the design of microfluidic sperm-sorting devices

Although medical advancements have successfully helped a lot of couples with their infertility by assisted reproductive technologies (ART), sperm selection, a crucial stage in ART, has remained challenging. Therefore, we aimed to investigate novel sperm separation methods, specifically microfluidic systems, as they do sperm selection based on sperm and/or the female reproductive tract (FRT) features without inflicting any damage to the selected sperm during the process. In this review, after an exhaustive studying of FRT features, which can implement by microfluidics devices, the focus was centered on sperm selection and investigation devices. During this study, we tried not to only point to the deficiencies of these systems, but to put forth suggestions for their improvement as well.

Sperm Selection for ICSI: Do We Have a Winner?

In assisted reproductive technology (ART), the aim of sperm cells’ preparation is to select competent spermatozoa with the highest fertilization potential and in this context, the intracytoplasmic sperm injection (ICSI) represents the most applied technique for fertilization. This makes the process of identifying the perfect spermatozoa extremely important. A number of methods have now been developed to mimic some of the natural selection processes that exist in the female reproductive tract. Although many studies have been conducted to identify the election technique, many doubts and disagreements still remain. In this review, we will discuss all the sperm cell selection techniques currently available for ICSI, starting from the most basic methodologies and continuing with those techniques suitable for sperm cells with reduced motility. Furthermore, different techniques that exploit some sperm membrane characteristics and the most advanced strategy for sperm selection based on microfluidics, will be examined. Finally, a new sperm selection method based on a micro swim-up directly on the ICSI dish will be analyzed. Eventually, advantages and disadvantages of each technique will be debated, trying to draw reasonable conclusions on their efficacy in order to establish the gold standard method.

Does Microfluidic Sperm Sorting Affect Embryo Euploidy Rates in Couples with High Sperm DNA Fragmentation?

Male infertility contributes as the main factor in 30-50% of infertility cases. Conventional methods for sperm preparation have induced questioning of sperm recovery rates. The microfluidic sperm sorting (MSS) technique selects highly motile sperm with lower levels of SDF (sperm DNA fragmentation) compared to conventional sperm sorting techniques. This study aimed to determine whether utilizing this technique will reveal better embryo quality and euploidy rates in couples with repeated implantation failure (RIF) and high SDF in a new PGT-A (preimplantation genetic testing for aneuploidies) cycle. This retrospective study included couples referred to PGT-A for previous repeated ART (assisted reproductive techniques) cycle failures and with high SDF. In their new cycles, couples who accepted the technique were assigned to the MSS group, and the rest were managed with DGC (density-gradient centrifugation). Two groups were compared in terms of fertilization and euploidy rates, clinical miscarriage and live birth rates, the total number of blastocysts, and top quality blastocysts. There was no difference between the groups regarding fertilization rates, euploidy rates, clinical miscarriage, and live birth rates. The total number of blastocysts and top quality blastocysts were significantly higher in the MSS group. The MSS technique provides a higher number of top-quality blastocysts than DGC; however, neither euploidy nor live birth rates improved. Studies focusing on confounding factors to embryonic genomic status in the presence of high SDF are needed.

Rheotaxis-based microfluidic device for selecting sperm from samples infected with a virus

OBJECTIVE

To investigate whether the presented rheotaxis-based microfluidic device could be used to separate spermatozoa from viruses (i.e., Zika) in the infected semen sample during the selection and washing process.

DESIGN

Quantitative and experimental study of the sperm washing/selection process through the microfluidic platform exploiting the positive rheotaxis of sperm.

SETTING

None.

PATIENT(S)

None.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Human sperm were purchased from a sperm bank. The raw semen sample was mixed with viruses and loaded into a microfluidic device. Experiments were performed with 2 different flow rates (0 and 25 μL/minute) to investigate the washing efficiency of the device in the sperm selection process. The sperm sample was collected after 45 minutes and analyzed to check whether the collected sample is free of any infections (viruses) after isolation.

RESULT(S)

Fluorescent microscopy and quantitative polymerase chain reaction-based analysis showed that the sperm selected with the presented rheotaxis-based microfluidic device at the optimal flow rate (25 μL/minute) was free of any viruses.

CONCLUSION(S)

We have developed a simple, cost-effective microfluidic device that mimics the conditions of the female genital tract while washing out the raw semen efficiently during the selection process for assisted reproductive technology.

Machine learning for sperm selection

Infertility rates and the number of couples seeking fertility care have increased worldwide over the past few decades. Over 2.5 million cycles of assisted reproductive technologies are being performed globally every year, but the success rate has remained at ~33%. Machine learning, an automated method of data analysis based on patterns and inference, is increasingly being deployed within the health-care sector to improve diagnostics and therapeutics. This technique is already aiding embryo selection in some fertility clinics, and has also been applied in research laboratories to improve sperm analysis and selection. Tremendous opportunities exist for machine learning to advance male fertility treatments. The fundamental challenge of sperm selection - selecting the most promising candidate from 10⁸ gametes - presents a challenge that is uniquely well-suited to the high-throughput capabilities of machine learning algorithms paired with modern data processing capabilities.

Sperm Oxidative Stress during In Vitro Manipulation and Its Effects on Sperm Function and Embryo Development

Reactive oxygen species (ROS) generated at low levels during mitochondrial respiration have key roles in several signaling pathways. Oxidative stress (OS) arises when the generation of ROS exceeds the cell's antioxidant scavenging ability and leads to cell damage. Physiological ROS production in spermatozoa regulates essential functional characteristics such as motility, capacitation, acrosome reaction, hyperactivation, and sperm-oocyte fusion. OS can have detrimental effects on sperm function through lipid peroxidation, protein damage, and DNA strand breakage, which can eventually affect the fertility of an individual. Substantial evidence in the literature indicates that spermatozoa experiencing OS during in vitro manipulation procedures in human- and animal-assisted reproduction are increasingly associated with iatrogenic ROS production and eventual impairment of sperm function. Although a direct association between sperm OS and human assisted reproductive techniques (ART) outcomes after in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI) is still a matter of debate, studies in animal models provide enough evidence on the adverse effects of sperm OS in vitro and defective fertilization and embryo development. This review summarized the literature on sperm OS in vitro, its effects on functional ability and embryo development, and the approaches that have been proposed to reduce iatrogenic sperm damage and altered embryonic development.

Curvature in the reproductive tract alters sperm-surface interactions

The fallopian tube is lined with a highly complex folded epithelium surrounding a lumen that progressively narrows. To study the influence of this labyrinthine complexity on sperm behavior, we use droplet microfluidics to create soft curved interfaces over a range of curvatures corresponding to the in vivo environment. We reveal a dynamic response mechanism in sperm, switching from a progressive surface-aligned motility mode at low curvatures (larger droplets), to an aggressive surface-attacking mode at high curvatures (smaller droplets of <50 µm-radius). We show that sperm in the attacking mode swim ~33% slower, spend 1.66-fold longer at the interface and have a 66% lower beating amplitude than in the progressive mode. These findings demonstrate that surface curvature within the fallopian tube alters sperm motion from a faster surface aligned locomotion in distal regions to a prolonged physical contact with the epithelium near the site of fertilization, the latter being known to promote capacitation and fertilization competence.

The influence of processed total non-forward and non-motile sperm count on the outcome of artificial insemination with the husband's semen

Background

Artificial insemination with the husband’s semen (AIH) is an economical and noninvasive method of infertility treatment. However, AIH’s pregnancy rate is much lower than in vitro fertilization (IVF) as its multiple and complex uncertainty factors. Semen quality has been one of the main factors which affect the pregnancy outcome of AIH.

Methods

The relevant parameters of 1,142 AIH cycles were retrospectively studied, including the general parameters and the semen quality parameters among clinical pregnancy, biochemical pregnancy, non-pregnancy group, age, infertility duration, infertility type, body mass index (BMI), cycle count, morphology in previously semen examination, and semen quality parameters on the day of AIH.

Results

The statistically significant difference was only found on processed total non-forward and non-motile sperm count (N-TFMSC). The mean processed N-TFMSC in the biochemical pregnancy group was 6.37±4.27 million, significantly higher than the other two groups (vs. 4.40±3.15 million or vs. 4.48±3.60 million, P<0.05). The study was then divided into two groups according to processed N-TFMSC, Group 1 ≤5.0 million, and Group 2 >5.0 million. A statistical increase in biochemical pregnancy rate was observed when the processed N-TFMSC was >5.0 million (2.72% vs. 0.90%).

Conclusions

Processed N-TFMSC may be one of the independent factors on AIH’s outcome; it should be given equal attention the same as processed total forward motile sperm count (TFMSC).

Microfluidic sperm selection yields higher sperm quality compared to conventional method in ICSI program: A pilot study

An appropriate preparation technique, should be capable of isolating highquality spermatozoa for intracytoplasmic sperm injection (ICSI). The aim was to assess sperm quality parameters, DNA integrity, embryo development, and clinical outcomes using a practical and accessible Microfluidic Sperm Sorting (MSS) technique. A total of 95 ICSI cases performed using sperm samples were prepared with our MSS (group 1) or by Direct Swim Up (DSU; control) method (group 2). Both sperm quality parameters and sperm DNA fragmentation (SDF) were compared between the groups. DNA fragmentation was assessed using Sperm Chromatin Dispersion (SCD) test and fine morphology was assessed using Motile Sperm Organelle Morphology Examination (MSOME). Embryo development and clinical outcomes were compared between the groups. In the MSS group, progressive motility and the fraction of Class I sperm morphology sperm were significantly higher compared to DSU group (P < 0.01 and P < 0.001, respectively). Moreover, the rates of DNA fragmentation and immotile spermatozoa were significantly lower in MSS when compared to DSU group (P < 0.001). Also, higher rates of high-quality embryo formation (P < 0.001), implantation (P = 0.04) and pregnancy (P = 0.05) were achieved in the MSS compared to DSU groups. The MSS technique proved to be a noninvasive, disposable, easy to use, and inexpensive method for separation of high-quality spermatozoa. Both laboratory parameters and clinical outcomes were improved with application of MSS for neat sperm collection in ICSI.AbbreviationsICSI: Intracytoplasmic Sperm Injection; MSS: Microfluidic Sperm Sorting; Sperm DNA Fragmentation (SDF); SCD: Sperm Chromatin Dispersion; MSOME: Motile Sperm Organelle Morphology Examination; DGC: Density Gradient Centrifugation; DSU: Direct Swim Up; ROS: Reactive Oxygen Species; ART: Assisted Reproducetive Technology.

Sperm-oocyte interplay: an overview of spermatozoon's role in oocyte activation and current perspectives in diagnosis and fertility treatment

The fertilizing spermatozoon is a highly specialized cell that selects from millions along the female tract until the oocyte. The paternal components influence the oocyte activation during fertilization and are fundamental for normal embryo development; however, the sperm-oocyte interplay is in a continuous debate. This review aims to analyze the available scientific information related to the role of the male gamete in the oocyte activation during fertilization, the process of the interaction of sperm factors with oocyte machinery, and the implications of any alterations in this interplay, as well as the advances and limitations of the reproductive techniques and diagnostic tests. At present, both PLCζ and PAWP are the main candidates as oocyte activated factors during fertilization. While PLCζ mechanism is via IP₃, how PAWP activates the oocyte still no clear, and these findings are important to study and treat fertilization failure due to oocyte activation, especially when one of the causes is the deficiency of PLCζ in the sperm. However, no diagnostic test has been developed to establish the amount of PLCζ, the protocol to treat this type of pathologies is broad, including treatment with ionophores, sperm selection improvement, and microinjection with PLCζ protein or RNA.

Effects of In Vitro Interactions of Oviduct Epithelial Cells with Frozen-Thawed Stallion Spermatozoa on Their Motility, Viability and Capacitation Status

Simple Summary

The use of assisted reproductive techniques, which involve the manipulation of sperm and oocytes in the laboratory, support owner production of valuable animals’ offspring. However, several limitations remain underlining the need to further optimize existing protocols as well as to develop new strategies. For example, the required conditions to make equine spermatozoa competent to fertilize an oocyte in vitro (IVF) have not been established. Therefore, our initial goal was to optimize different conditions associated with frozen equine sperm manipulations in order to improve their quality. We observed that simple factors such as sample concentration, incubation period and centrifugation time affect the sperm motility. Since in vivo fertilization involves the interaction between spermatozoa and epithelial cells in the mare’s oviductal tract, our next goal was to mimic this environment by establishing primary cultures of oviductal cells. Using this in vitro system, we were able to select a sperm population capable of fertilization. In short, this study provides a novel protocol that improves the yield of fertilization-capable sperm obtained from equine frozen spermatozoa.

Abstract

Cryopreservation by negatively affecting sperm quality decreases the efficiency of assisted reproduction techniques (ARTs). Thus, we first evaluated sperm motility at different conditions for the manipulation of equine cryopreserved spermatozoa. Higher motility was observed when spermatozoa were incubated for 30 min at 30 × 10⁶/mL compared to lower concentrations (p < 0.05) and when a short centrifugation at 200× g was performed (p < 0.05). Moreover, because sperm suitable for oocyte fertilization is released from oviduct epithelial cells (OECs), in response to the capacitation process, we established an in vitro OEC culture model to select a sperm population with potential fertilizing capacity in this species. We demonstrated E-cadherin and cytokeratin expression in cultures of OECs obtained. When sperm–OEC cocultures were performed, the attached spermatozoa were motile and presented an intact acrosome, suggesting a selection by the oviductal model. When co-cultures were incubated in capacitating conditions a greater number of alive (p < 0.05), capacitated (p < 0.05), with progressive motility (p < 0.05) and with the intact acrosome sperm population was observed (p < 0.05) suggesting that the sperm population released from OECs in vitro presents potential fertilizing capacity. Improvements in handling and selection of cryopreserved sperm would improve efficiencies in ARTs allowing the use of a population of higher-quality sperm.

Chemotactic selection of frozen-thawed stallion sperm improves sperm quality and heterologous binding to oocytes

The successful use of assisted reproduction techniques (ART) depends in part on the sperm physiological status. Several sperm selection procedures have been applied to improve quality of sperm population when using the ART. There has previously been development of a Sperm Selection Assay (SSA) for humans which is based on the attraction of capacitated sperm by chemotaxis towards progesterone (P), resulting in an enriched sperm population with an optimal physiological status similar to capacitated spermatozoa, with these cells having very little DNA fragmentation and optimal concentrations of reactive oxygen species (ROS). In the present study, the aim was to adapt the SSA for frozen-thawed stallion semen samples and evaluate the functional status of those sperm selected using the SSA procedure, and to determine whether this enriched sperm population has a greater capacity to bind to the zona pellucida of cattle oocytes. There were experimental conditions developed to conduct the SSA with stallion sperm. Using these conditions, the indexes of induced acrosome reaction, protein tyrosine phosphorylation, mitochondrial membrane potential, mitochondrial and cytoplasmic reactive oxygen species, and number of sperm bound to the zona pellucida of cattle were greater when the sperm population was selected using the SSA. Consistently, the DNA fragmentation and phospholipase C zeta indexes were less for the selected sperm. In conclusion, stallion sperm selected using chemotaxis utilizing the SSA provides a sperm population of greater quality, which when used may improve the outcomes with use of the ART.

Sperm selection in IVF: the long and winding road from bench to bedside

Spermatozoa wage battle to conquer fertilization but the traits needed to succeed remain elusive. The natural advantageous qualities that enable only a few selected sperm cells to reach the site of fertilization remain unknown. Although in vitro fertilization (IVF) facilitates the job of spermatozoa, a universally acceptable means of sperm selection is yet to be developed. No objective or reliable sperm quality indicators have been established and sperm selection is, to a great extent, based on subjective qualitative evaluation. The best method for sperm selection in IVF presents several challenges: intrinsic sperm qualities cannot be evaluated and the ideal endpoint for these studies is debatable. An ideal method for sperm selection in ART should be noninvasive and cost-effective, and allow the identification of high-quality spermatozoa and yield better outcomes in terms of pregnancy and live birth rates. This narrative review included 85 papers and focused on the new available methods and technologies that might shed some light on sperm selection in IVF. It discusses the available data on microfluidic devices, omics profiling, micronuclei studies, sperm plasma membrane markers, and other techniques, such as Magnetic Activated Cell Sorting (MACS), Raman micro-spectroscopy, and artificial intelligence systems. The new techniques herein reviewed offer fresh approaches to an old problem, for which a definite solution has yet to cross the bridge from bench to IVF clinics around the world, since clinical usefulness and application remain unproven.

Sperm selection strategies and their impact on assisted reproductive technology outcomes

The application of assisted reproductive technologies (ART) has revolutionised the treatment of human infertility, giving hope to the patients previously considered incapable of establishing pregnancy. While semen analysis is performed to access whether a sample has an adequate number of viable, motile and morphologically normal sperm cells able to achieve fertilisation, sperm selection techniques for ART aim to isolate the most competent spermatozoon which is characterised by the highest fertilising potential. Based on the semen analysis results, the correct sperm selection technique must be chosen and applied. In this review, different sperm selection strategies for retrieving spermatozoa with the highest fertilising potential and their impact on ART outcomes are discussed. In addition, advantages and disadvantages of each method and the best suited techniques for each clinical scenario are described.

Comparison of Sperm Telomere Length between Two Sperm Selection Procedures: Density Gradient Centrifugation and Zeta Potential

Background

Telomeres are particular sequences of DNA located at the end of the eukaryotic chromosomes that are essential for genome integrity. Telomere length in spermatozoa differs among males, as well as spermatozoa. Also, decreased telomere length in spermatozoa of infertile men is associated with the reduction of fertility potential and embryo quality. Density gradient centrifugation (DGC) and swim-up are useful techniques for separation of spermatozoa with longer telomeres. Also, the selection of sperm based on surface negative electric charge or "Zeta potential", can separate high percentage of spermatozoa with intact chromatin compared to DGC alone, and also the combination of DGC-Zeta can improve clinical outcomes of infertile men candidate for intracytoplasmic sperm injection (ICSI). Therefore, we compared sperm telomere length and DNA fragmentation between two sperm preparation procedures, namely DGC and zeta potential.

Materials and Methods

In this experimental study, we assessed sperm telomere length and DNA fragmentation by quantitative real-time polymerase chain reaction (PCR) and TUNEL assay methods, respectively. The spermatozoa were obtained from infertile men with normozoospermia between September 2017 and December 2017 and prepared either by DGC or zeta potential methods. Sperm telomere length was expressed as relative and absolute units.

Results

Compared with washed semen samples or control, no significant (P>0.05) difference was observed in the mean relative or absolute sperm telomere length when the two methods DGC or zeta potential were compared. However, the mean percentage of DNA fragmentation was significantly (P<0.05) lower in spermatozoa prepared by DGC or zeta potential methods than spermatozoa obtained from control samples.

Conclusion

This is the first study that compared the effect of DGC and zeta potential as the sperm preparation methods on sperm telomere length. It seems that both methods can select sperm population with high DNA integrity and the same sperm telomeres length.

Towards a better testicular sperm extraction: novel sperm sorting technologies for non-motile sperm extracted by microdissection TESE

Non-obstructive azoospermia (NOA) is the most severe form of male factor infertility. It is characterized by a lack of spermatogenesis in the seminiferous tubules. Microdissection testicular sperm extraction (microTESE) has significantly improved testicular sperm retrieval rates compared to conventional techniques for NOA. Following testicular biopsy, the sperm is usually non-motile and contained within seminiferous tubules requiring extensive laboratory processing to find individual sperm sufficient for artificial reproductive technologies (ART). Current techniques include mechanical and enzymatic processing which is time-consuming and often damaging to sperm. We review novel techniques that may help improve sperm retrieval rates after microTESE including microfluidics (dielectrophoretic cell sorting, spiral channel sorting, and pinched flow fractionation), fluorescence-activated cell sorting (FACS), and magnetic-activated cell sorting (MACS).

DGC/Zeta as A New Strategy to Improve Clinical Outcome in Male Factor Infertility Patients following Intracytoplasmic Sperm Injection: A Randomized, Single-Blind, Clinical Trial

Objective

The aim of this blind randomised clinical trial study was to assess the clinical efficiency of combined density gradient centrifugation/Zeta (DGC/Zeta) sperm selection procedure compared to conventional DGC in infertile men candidates for intracytoplasmic sperm injection (ICSI). The literature shows that DGC/Zeta is more effective compared to DGC alone in selection of sperms with normal chromatin and improves the clinical outcome of the ICSI procedure. Therefore, this study re-evaluates the efficiency of DGC/Zeta in improving the clinical outcomes of ICSI in an independent clinical setting.

Materials and Methods

In this randomized, single-blind, clinical trial, a total of 240 couples with male factor infertility and at least one abnormal sperm parameter were informed regarding the study and 220 participated. Based on inclusion and exclusion criteria, 103 and 102 couples were randomly allocated into the DGC/Zeta and DGC groups, respectively. ICSI outcomes were followed and compared between the two groups.

Results

Although there was no significant difference in fertilization rate (P=0.67) between the DGC/Zeta and DGC groups, mean percentage of good embryo quality (P=0.04), good blastocysts quality (P=0.049), expanded blastocysts (P=0.007), chemical pregnancies (P=0.005) and clinical pregnancies (P=0.007) were significantly higher in the DGC/ Zeta group compared to DGC. In addition, implantation rate was insignificantly higher in DGC/Zeta compared to DGC (P=0.17).

Conclusion

This is the second independent study showing combined DGC/Zeta procedure improves ICSI outcomes, especially the pregnancy rate, compared to the classical DGC procedure and this is likely related to the improved quality of sperm selected by the DGC/Zeta procedure (Registration number: IRCT20180628040270N1).

High quality human sperm selection for IVF: A study on sperm chromatin condensation

The study consisted of semen samples of 20 male individuals who applied to Abant Izzet Baysal University Faculty of Medicine and participated in a spermiogram. The aim of this study was to determine how to obtain the healthiest spermatozoa by employing a variety of swim-up methods over differing time periods and without the use of centrifuge. Ejaculate samples were taken from the 20 patients and each patient's homogenized semen sample was divided into 4 groups without centrifugation. Group 1 was taken as the sample of untreated semen. For the other 3 groups, 250 μl of medium was added in the semen samples. Afterwards, the samples were kept at 37 °C for different time periods, 30 min for Group 2, 60 min for Group 3 and 90 min for Group 4 in order for the spermatozoa to swim to the media in the upper layer. At the end of the periods, 10 μl of propagation preparations were prepared from the swim-up fluid. Using Aniline Blue for chromatin condensation analysis, two hundred cells were immunostained by Caspase 3 for apoptotic analysis. Subsequently, the result of the four groups were compared for each test. The spermatozoa obtained at the end of the 30 min. of swim-up was compared to the spermatozoa obtained from the swim-up of 60 min., the swim-up of 90 min. It was found that the control group had statistically significant lower rates of apoptosis and was healthier in terms of chromatin integrity. The swim-up method without centrifugation is the best suited sperm preparation, based on sperm DNA integrity and sperm chromatin condensation.

Intracytoplasmic sperm injection for male infertility and consequences for offspring

Intracytoplasmic sperm injection (ICSI) has become the most commonly used method of fertilization in assisted reproductive technology. The primary reasons for its popularity stem from its effectiveness, the standardization of the procedure, which means that it can easily be incorporated into the routine practice of fertility centres worldwide, and the fact that it can be used to treat virtually all forms of infertility. ICSI is the clear method of choice for overcoming untreatable severe male factor infertility, but its (over)use in other male and non-male factor infertility scenarios is not evidence-based. Despite all efforts to increase ICSI efficacy and safety through the application of advanced sperm retrieval and cryopreservation techniques, as well as methods for selecting sperm with better chromatin integrity, the overall pregnancy rates from infertile men remain suboptimal. Treating the underlying male infertility factor before ICSI seems to be a promising way to improve ICSI outcomes, but data remain limited. Information regarding the health of ICSI offspring has accumulated over the past 25 years, and there are reasons for concern as risks of congenital malformations, epigenetic disorders, chromosomal abnormalities, subfertility, cancer, delayed psychological and neurological development, and impaired cardiometabolic profile have been observed to be greater in infants born as a result of ICSI than in naturally conceived children. However, as subfertility probably influences the risk estimates, it remains to be determined to what extent the observed adverse outcomes are related to parental factors or associated with ICSI.