Separation efficiency of a microfluidic sperm sorter to minimize sperm DNA damage

Revolutionizing sexed sorting sperm using scFv antibodies combined with microbeads for porcine sexed semen

This study aimed to evaluate porcine sperm sex selection using scFv antibodies combined with magnetic-activated cell sorting (MACS) to optimize X/Y sperm separation while maintaining essential sperm quality parameters, including viability, motility, membrane integrity, and apoptosis, with the goal of developing a novel method for swine sexing technology. The H4L4 scFv antibody, at a concentration of 1 mg/mL, effectively bound to PLA microbeads (HL-beads), achieving separation efficiencies of 75.4 ± 2.30 % for X-sperm and 78.6 ± 1.94 % for Y-sperm. FTIR confirmed the binding of H4L4 scFv to microbead carboxylic acid groups, and SEM verified sperm binding. In quality assessments, the X-enriched fraction (XF) presented a sperm quality comparable to that of conventional semen (CONV) and the negative control (NC). However, the Y-enriched fraction (YF) was lower in quality than the other groups were on Day 3 of storage. Apoptosis analysis revealed no significant difference in the number of necrotic cells among the XF, CONV, and NC groups. The XF group achieved a 76.1 % enriched X-sperm ratio, whereas the YF group achieved a 78.4 % enriched Y-sperm ratio. This method enhances the X-sperm proportion in the XF group with an acceptable quality for farm applications. These results demonstrate the potential of HL-beads for porcine sperm sexing, offering a promising approach for improving sex ratios in swine production.

A Narrative Review on the Sperm Selection Methods in Assisted Reproductive Technology: Out with the New, the Old Is Better?

Background: Male infertility, accounting for nearly half of infertility cases worldwide, has spurred significant research into its causes, diagnosis, and treatment strategies. Genetic abnormalities, social causes, environmental exposures, lifestyle, and further health conditions are key contributors. Methods: Essential to improving the outcomes of ART is, among other things, the selection of high-quality sperm, which requires methods that assess sperm motility, morphology, DNA integrity, and oxidative stress levels. Results: Traditional techniques such as semen analysis, swim-up, and density gradient centrifugation (DGC) are still widely used, but there is ongoing discussion regarding the limitations in detecting DNA damage and oxidative stress. Advanced methods like magnetic-activated cell sorting (MACS) and microfluidic sorting have emerged as more precise tools for selecting sperm with better genetic integrity, although they face challenges in terms of their standardization, cost, and clinical adoption. Emerging technologies such as artificial intelligence (AI) and Raman spectroscopy offer the potential for more automated, accurate sperm selection, minimizing human error and variability. However, the integration of these methods into clinical practice requires further validation through large-scale studies, including assessments of their long-term safety and cost-effectiveness. Conclusions: Future research should focus on refining sperm selection techniques, tailoring them to personalized infertility approaches, and addressing the gaps in the evidence to improve ART outcomes and patient care.

A novel microfluidic device for human sperm separation based on rheotaxis

This study explores the efficacy of a novel microfluidic device in isolating rheotactic sperm and assesses their advantages compared with other motile sperm. Two microfluidic devices were used in this study: the microfluidic device we designed to separate sperm based on rheotaxis and a simple passive microfluidic device. We compared the results with the density gradient centrifugation technique. Sperm attributes including concentration, morphology, viability and motility were assessed using related procedures. Statistical analyses were conducted using one-way analysis of variance. Results showed differences in sperm concentration, motility, morphology and vitality using different sperm separation techniques. The sperms separated using our microfluidic device demonstrated the highest motilities, normal morphology percentages and higher sperm vitality but significantly lower sperm concentrations. These findings suggest the potential of our microfluidic design in enhancing sperm quality. Our findings are in agreement with previous research, emphasizing the capability of microfluidics in enhancing sperm quality. Specifically, our designed microfluidic device exhibited exceptional efficacy in isolating highly motile sperm, a critical factor for successful fertilization.

Preliminary steps for fabrication of microfluidic systems for swine sperm sorting: Materials, perfusing systems and flow

The success rate of assisted reproductive techniques in the livestock production can be optimized by improving the quality of the semen sample by selecting only the good quality sperm from the ejaculate. Microfluidic technology has been studied for sperm sorting mainly in human ejaculates but has not been studied for boar sperm. Spermatozoa have been proven to be highly sensitive to different microplastics, but the potential toxic effects of the materials used to set up microfluidic systems have not been studied. The main goal of this study was to assess the possible toxic effect on boar sperm of materials commonly used for a microfluidic system and to evaluate the effect of different flow control systems (peristaltic pump, syringe pump and a microfluidic flow controller) at different flow rates (10 μl*min-1, 100 μl*min-1 and 1 ml*min-1) on sperm quality, as preliminary information for the development of a swine sperm sorting microfluidic system. Results showed no negative effect of the different materials at different concentrations. The control reached the highest curvilinear velocity compared to the peristaltic pump and the pressure-based flow control system. In the flow rates, 10 μm*min-1 showed the poorest results and no significant differences were observed between control and 1 mlmin-1 flow in any of the parameters. In conclusion, all materials that were studied for microfluidic fabrications were suitable for sperm sorting, any of the pumps would be suitable for sperm selection and 1 ml*min-1 flow rate would be the flow rate of choice for sperm pumping.

A biomimetic sperm selection device for routine sperm selection

RESEARCH QUESTION

Can a biomimetic microfluidic sperm sorter isolate motile sperm while minimizing DNA damage in comparison with density gradient centrifugation (DGC)?

DESIGN

This was a two-phase study of 61 men, consisting of a proof-of-concept study with 21 donated semen samples in a university research laboratory, followed by a diagnostic andrology study with 40 consenting patients who presented at a fertility clinic for semen diagnostics. Each sample was split to perform DGC and microfluidic sperm selection (one-step sperm selection with 15 min of incubation) side-by-side. Outcomes evaluated included concentration, progressive motility, and DNA fragmentation index (DFI) of raw semen, and sperm isolated using DGC and the microfluidic device. Results were analysed using Friedman's test for non-parametric data (significant when P < 0.05). DFI values were assessed by sperm chromatin dispersion assay.

RESULTS

Sperm isolated using DGC and the microfluidic device showed improved DFI values and motility compared with the raw semen sample in both cohorts. However, the microfluidic device was significantly better than DGC at reducing DFI values in both the proof-of-concept study (P = 0.012) and the diagnostic andrology study (P < 0.001). Progressive motility was significantly higher for sperm isolated using the microfluidic device in the proof-of-concept study (P = 0.0061) but not the diagnostic andrology study. Sperm concentration was significantly lower for samples isolated using the microfluidic device compared with DGC for both cohorts (P < 0.001).

CONCLUSIONS

Channel-based biomimetic sperm selection can passively select motile sperm with low DNA fragmentation. When compared with DGC, this method isolates fewer sperm but with a higher proportion of progressively motile cells and greater DNA integrity.

New approaches in bovine spermatozoa evaluation and their relationship with male fertility

Male fertility potential depends on physical, endocrine, and genetic factors responsible for producing functional male gametes. Although the main function of the male gamete, the spermatozoon, is to deliver its genetic material to the oocyte, this premise has been modified over the past few years. It is believed that the spermatozoon provides essential factors for fertilization and pre-implantation embryo development. A viable/healthy spermatozoon has functional subcellular compartments (nucleus, acrosome, midpiece, and flagellum) due to the actions of proteins, transcripts, and epigenetic marks in the organelles present in them that have important roles in reproductive biology. Male fertility potential reflects viable spermatozoa with proper function. Therefore, new approaches to functional sperm analysis are essential. Additionally, intrinsic factors and sperm molecules constitute potential biomarkers of viable spermatozoa and male fertility. Among these factors are proteins, the genome, and coding and non-coding RNAs, such as microRNAs, that act during fertilization and early embryo development. Research has been seeking increasingly efficient tools to predict fertility and functional studies of these molecules through gene and protein expression. Thus, analytical tools are essential to identify and classify viable and functional spermatozoa, to evaluate assisted reproductive male potential.

Embryology outcomes of a device-based sperm separation technique compared to density gradient centrifugation using thawed spermatozoa-a sibling donor oocyte study

OBJECTIVE

To evaluate whether the ZyMōt™ Multi 850 μl sperm separation device (SSD) effectively recovers motile spermatozoa from cryopreserved ejaculates and compare its effect on key embryology outcomes including fertilization, cleavage stage, and total and top-quality blastocyst formation rates to the traditional Density Gradient Centrifugation (DGC) method.

METHODS

In this prospective, single-center, controlled study, we used fresh sibling donor oocytes and non-donor cryopreserved ejaculates. In total, 150 couples participated in this study. At least eight MII donor oocytes were allocated to each couple split into two arms. One arm underwent ICSI with the control DGC-processed sample, and the other arm processed with SSD.

RESULTS

No significant difference on fertilization and cleavage stage embryo rates was observed between the two techniques. We observed a significant increase in the percentage of total (SSD: 74.03 ± 23.47% vs. DGC: 67.86 ± 23.92%; p = 0.016) and top-quality (SSD: 66.38 ± 24.94% vs. DGC: 60.98 ± 24.40%; p = 0.035) blastocysts formed post-SSD processing. Sub-analysis showed that this increase remained significant for the WHO-normal group (n = 118), but not for the WHO-abnormal group (n = 32).

CONCLUSION

The SSD was successfully applied in all 150 cases, providing adequate numbers of spermatozoa to undergo ICSI. Additionally, SSD significantly improved blastocyst development rates; however, this was of limited clinical impact considering the minor improvement on the average number of top-quality blastocysts. It can be hypothesized that this positive contribution may be stronger and clinically significant when a larger number of oocytes is used or in homologous oocyte ICSI cycles, where the repair mechanisms of the oocytes may insufficient for promoting healthy embryo development.

Sperm DNA Fragmentation and Fertility

Elevated levels of sperm deoxyribonucleic acid (DNA) fragmentation (SDF) have been associated with several adverse reproductive outcomes, including: lower natural and assisted reproductive technology (ART) pregnancy rates, abnormal embryo development, and recurrent pregnancy loss. However, due to conflicting study results, limited high-level evidence, multiple clinically available assays, and variable standard reference ranges, precisely how SDF testing should be applied to the evaluation and treatment of infertile men remains controversial. To better understand SDF and its role in clinical practice, this chapter aims to: (1) review the literature that has made SDF such a controversial topic, (2) discuss newly published evidence contributing to this complex discussion, and (3) outline the most recent practice guidelines currently available.

Equine ICSI: an update on semen perspective

Intracytoplasmic Sperm Injection (ICSI) has increased usage in cases of stallion fertility issues, particularly for older stallions, those with reduced sperm numbers or quality, or stallions that have passed away, and only a limited amount of frozen semen is available. By manipulating the frozen semen through thawing, diluting, and refreezing or by cutting the straw under liquid nitrogen, the supply of semen for ICSI can be extended. While ICSI requires a minimal number of spermatozoa per procedure, it is important to consider sperm quality as a crucial factor affecting fertilization and embryo development. Although it is possible to produce healthy embryos and offspring from low quality sperm samples, it is preferable to process and select morphologically and functionally superior sperm to maximize the chances of successful fertilization and embryo development. Several techniques are available for selecting the spermatozoa for ICSI, such as swim-up, washing, density gradient centrifugation, microfluidic sorting, and some combinations. In this review, we will focus on semen type, handling, recent breakthroughs, stallion effects on ICSI efficiency and the prospects of this technology within the equine industry.

Microfluidics-A novel technique for high-quality sperm selection for greater ART outcomes

Microfluidics represent a quality sperm selection technique. Human couples fail to conceive and this is so in a significant population of animals worldwide. Defects in male counterpart lead to failure of conception so are outcomes of assisted reproduction affected by quality of sperm. Microfluidics, deals with minute volumes (μL) of liquids run in small-scale microchannel networks in the form of laminar flow streamlines. Microfluidic sperm selection designs have been developed in chip formats, mimicking in vivo situations. Here sperms are selected and analyzed based on motility and sperm behavioral properties. Compared to conventional sperm selection methods, this selection method enables to produce high-quality motile sperm cells possessing non-damaged or least damaged DNA, achieve greater success of insemination in bovines, and achieve enhanced pregnancy rates and live births in assisted reproduction-in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Besides, the concentration of sperm available to oocyte can be controlled by regulating the flow rate in microfluidic chips. The challenges in this technology are commercialization of chips, development of fully functional species-specific microfluidic tools, limited number of studies available in literature, and need of thorough understanding in reproductive physiology of domestic animals. In conclusion, incorporation of microfluidic system in assisted reproduction for sperm selection may promise a great success in IVF and ICSI outcomes. Future prospectives are to make this technology more superior and need to modify chip designs which is cost effective and species specific and ready for commercialization. Comprehensive studies in animal species are needed to be carried out for wider application of microfluidic sperm selection in in vitro procedures.

Microfluidics: The future of sperm selection in assisted reproduction

BACKGROUND

Obtaining functional sperm cells is the first step to treat infertility. With the ever-increasing trend in male infertility, clinicians require access to effective solutions that are able to single out the most viable spermatozoa, which would max out the chance for a successful pregnancy. The new generation techniques for sperm selection involve microfluidics, which offers laminar flow and low Reynolds number within the platforms can provide unprecedented opportunities for sperm selection. Previous studies showed that microfluidic platforms can provide a novel approach to this challenge and since then researchers across the globe have attacked this problem from multiple angles.

OBJECTIVE

In this review, we seek to provide a much-needed bridge between the technical and medical aspects of microfluidic sperm selection. Here, we provide an up-to-date list on microfluidic sperm selection procedures and its application in assisted reproductive technology laboratories.

SEARCH METHOD

A literature search was performed in Web of Science, PubMed, and Scopus to select papers reporting microfluidic sperm selection using the keywords: microfluidic sperm selection, self-motility, non-motile sperm selection, boundary following, rheotaxis, chemotaxis, and thermotaxis. Papers published before March 31, 2023 were selected.

OUTCOMES

Our results show that most studies have used motility-based properties for sperm selection. However, microfluidic platforms are ripe for making use of other properties such as chemotaxis and especially rheotaxis. We have identified that low throughput is one of the major hurdles to current microfluidic sperm selection chips, which can be solved via parallelization.

CONCLUSION

Future work needs to be performed on numerical simulation of the microfluidics chip prior to fabrication as well as relevant clinical assessment after the selection procedure. This would require a close collaboration and understanding among engineers, biologists, and medical professionals. It is interesting that in spite of two decades of microfluidics sperm selection, numerical simulation and clinical studies are lagging behind. It is expected that microfluidic sperm selection platforms will play a major role in the development of fully integrated start-to-finish assisted reproductive technology systems.

Development of a thermotaxis and rheotaxis microfluidic device for motile spermatozoa sorting

Male infertility is a pervasive global reproductive challenge, primarily attributed to a decline in semen quality. Addressing this concern, there has been a growing focus on spermatozoa sorting in assisted reproductive technology. This study introduces a groundbreaking development in the form of a thermotaxis and rheotaxis microfluidic (TRMC) device designed for efficient motile spermatozoa sorting within a short 15-min timeframe. The TRMC device mimics the natural sperm sorting mechanism of the oviduct, selecting spermatozoa with superior motility and DNA integrity. The experimental outcomes demonstrate a remarkable enhancement in the percentage of progressive spermatozoa following sorting, soaring from 3.90% to an impressive 96.11% when subjected to a temperature decrease from 38 °C to 35 °C. Notably, sperm motility exhibited a substantial 69% improvement. The TRMC device exhibited a commendable recovery rate of 60.93%, surpassing current clinical requirements. Furthermore, the sorted spermatozoa displayed a notable reduction in the DNA fragmentation index to 6.94%, signifying a substantial 90% enhancement in DNA integrity. This remarkable advancement positions the TRMC device as highly suitable for applications in in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), offering a promising solution to male infertility challenges.

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.

Microfluidic sperm sorting selects a subpopulation of high-quality sperm with a higher potential for fertilization

STUDY QUESTION

Is a microfluidic sperm sorter (MSS) able to select higher quality sperm compared to conventional methods?

SUMMARY ANSWER

The MSS selects sperm with improved parameters, lower DNA fragmentation, and higher fertilizing potential.

WHAT IS KNOWN ALREADY

To date, the few studies that have compared microfluidics sperm selection with conventional methods have used heterogeneous study population and have lacked molecular investigations.

STUDY DESIGN, SIZE, DURATION

The efficiency of a newly designed MSS in isolating high-quality sperm was compared to the density-gradient centrifugation (DGC) and swim-up (SU) methods, using 100 semen samples in two groups, during 2023-2024.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Semen specimens from 50 normozoospermic and 50 non-normozoospermic men were sorted using MSS, DGC, and SU methods to compare parameters related to the quality and fertilizing potential of sperm. The fertilizing potential of sperm was determined by measurement of phospholipase C zeta (PLCζ) and post-acrosomal sheath WW domain-binding protein (PAWP) expression using flow cytometry, and the chromatin dispersion test was used to assess sperm DNA damage.

MAIN RESULTS AND THE ROLE OF CHANCE

In both normozoospermic and non-normozoospermic groups, the MSS-selected sperm with the highest progressive motility, PLCζ positive expression and PLCζ and PAWP fluorescence intensity the lowest non-progressive motility, and minimal DNA fragmentation, compared to sperm selected by DGC and SU methods (P < 0.05).

LIMITATION, REASONS FOR CAUTION

The major limitations of our study were the low yield of sperm in the MSS chips and intentional exclusion of severe male factor infertility to yield a sufficient sperm count for molecular experiments; thus testing with severe oligozoospermic semen and samples with low count and motility is still required. In addition, due to ethical considerations, at present, it was impossible to use the sperm achieved from MSS in the clinic to assess the fertilization rate and further outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

Our research presents new evidence that microfluidic sperm sorting may result in the selection of high-quality sperm from raw semen. This novel technology might be a key to improving clinical outcomes of assisted reproduction in infertile patients.

STUDY FUNDING/COMPETING INTEREST(S)

The study is funded by the Iran University of Medical Sciences and no competing interest exists.

TRIAL REGISTRATION NUMBER

N/A.

A compact, high-throughput semi-automated embryo vitrification system based on hydrogel

RESEARCH QUESTION

What is the efficiency and efficacy of the novel Biorocks semi-automated vitrification system, which is based on a hydrogel?

DESIGN

This comparative experimental laboratory study used mouse model and human day 6 blastocysts. Mouse oocytes and embryos were quality assessed post-vitrification.

RESULTS

The Biorocks system successfully automated the solution exchanges during the vitrification process, achieving a significantly improved throughput of up to 36 embryos/oocytes per hour. Using hydrogel for cryoprotective agent delivery, 12 vessels could be processed simultaneously, fitting comfortably within an assisted reproductive technology (ART) workstation. In tests involving the cryopreservation of oocytes and embryos, the system yielded outcomes equivalent to the manual Cryotop method. For example, the survival rate for mouse oocytes was 98% with the Biorocks vitrification system (n = 46) and 95% for the manual Cryotop method (n = 39), of which 46% and 41%, respectively, progressed to blastocysts on day 5 after IVF. CC-grade day 6 human blastocysts processed with the Biorocks system (n = 39) were associated with a 92% 2 h re-expansion rate, equivalent to the 90% with Cryotop (n = 30). The cooling/warming rates achieved by the Biorocks system were 31,900°C/minute and 24,700°C/minute, respectively. Oocyte quality was comparable or better post-vitrification for Biorocks than Cryotop.

CONCLUSIONS

The Biorocks semi-automated vitrification system offers enhanced throughput without compromising the survival and developmental potential of oocytes and embryos. This innovative system may help to increase the efficiency and standardization of vitrification in ART clinics. Further investigations are needed to confirm its efficacy in a broader clinical context.

Microfluidics as an emerging paradigm for assisted reproductive technology: A sperm separation perspective

Millions of people are subject to infertility worldwide and one in every six people, regardless of gender, experiences infertility at some period in their life, according to the World Health Organization. Assisted reproductive technologies are defined as a set of procedures that can address the infertility issue among couples, culminating in the alleviation of the condition. However, the costly conventional procedures of assisted reproduction and the inherent vagaries of the processes involved represent a setback for its successful implementation. Microfluidics, an emerging tool for processing low-volume samples, have recently started to play a role in infertility diagnosis and treatment. Given its host of benefits, including manipulating cells at the microscale, repeatability, automation, and superior biocompatibility, microfluidics have been adopted for various procedures in assisted reproduction, ranging from sperm sorting and analysis to more advanced processes such as IVF-on-a-chip. In this review, we try to adopt a more holistic approach and cover different uses of microfluidics for a variety of applications, specifically aimed at sperm separation and analysis. We present various sperm separation microfluidic techniques, categorized as natural and non-natural methods. A few of the recent developments in on-chip fertilization are also discussed.

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.

Strategies for Bacterial Eradication from Human and Animal Semen Samples: Current Options and Future Alternatives

The primary role of semen processing and preservation is to maintain a high proportion of structurally and functionally competent and mature spermatozoa, that may be used for the purposes of artificial reproduction when needed, whilst minimizing any potential causes of sperm deterioration during ex vivo semen handling. Out of a multitude of variables determining the success of sperm preservation, bacterial contamination has been acknowledged with an increased interest because of its often unpredictable and complex effects on semen quality. Whilst antibiotics are usually the most straight-forward option to prevent the bacterial contamination of semen, antimicrobial resistance has become a serious threat requiring widespread attention. As such, besides discussing the consequences of bacteriospermia on the sperm vitality and the risks of antibiotic overuse in andrology, this paper summarizes the currently available evidence on alternative strategies to prevent bacterial contamination of semen prior to, during, and following sperm processing, selection, and preservation. Alternative antibacterial supplements are reviewed, and emphasis is given to modern methods of sperm selection that may be combined by the physical removal of bacteria prior to sperm preservation or by use in assisted reproductive technologies.

Performing a sperm DNA fragmentation test in addition to semen examination based on the WHO criteria can be a more accurate diagnosis of IVF outcomes

BACKGROUND

We analyzed the sperm DNA fragmentation index (DFI) and general semen test based on the World Health Organization (WHO) criteria and compared the two tests using semen factors. In addition, we examined whether DFI is a reliable parameter associated with in vitro fertilization (IVF) outcomes.

METHODS

Sperm chromatin dispersion (SCD) and general semen tests were conducted in accordance with the WHO 2010 guidelines, and correlations between the two tests were investigated. The WHO criteria were set as the cutoff values for each of the following factors: semen volume, concentration, total sperm count, motility, and normal morphology, and compared with the DFI results.

RESULTS

The subjects had a mean sperm DFI of 15.3% ± 12.6%, and the DFI increased with age. In contrast, motility and normal morphology decreased as the DFI increased. Patients who satisfied the WHO criteria in terms of concentration, total sperm count, and motility had a significantly lower DFI than those who did not satisfy the criteria. Therefore, evaluation with a general semen test based on the WHO criteria should be regarded as a qualitative evaluation of all factors other than semen volume and normal morphology.

CONCLUSIONS

High DFI (≥ 30%) caused a low blastocyst development rate following intracytoplasmic sperm injection. Male infertility due to DFI should be suspected when IVF results are poor despite normal semen findings based on the WHO criteria. The results of this study suggest that the SCD test may more accurately evaluate the correlation between IVF clinical outcomes and male infertility. Therefore, it is important to focus on DFI measurements.

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.

Temporal trends in sperm count: a systematic review and meta-regression analysis of samples collected globally in the 20th and 21st centuries

BACKGROUND

Numerous studies have reported declines in semen quality and other markers of male reproductive health. Our previous meta-analysis reported a significant decrease in sperm concentration (SC) and total sperm count (TSC) among men from North America-Europe-Australia (NEA) based on studies published during 1981-2013. At that time, there were too few studies with data from South/Central America-Asia-Africa (SAA) to reliably estimate trends among men from these continents.

OBJECTIVE AND RATIONALE

The aim of this study was to examine trends in sperm count among men from all continents. The broader implications of a global decline in sperm count, the knowledge gaps left unfilled by our prior analysis and the controversies surrounding this issue warranted an up-to-date meta-analysis.

SEARCH METHODS

We searched PubMed/MEDLINE and EMBASE to identify studies of human SC and TSC published during 2014-2019. After review of 2936 abstracts and 868 full articles, 44 estimates of SC and TSC from 38 studies met the protocol criteria. Data were extracted on semen parameters (SC, TSC, semen volume), collection year and covariates. Combining these new data with data from our previous meta-analysis, the current meta-analysis includes results from 223 studies, yielding 288 estimates based on semen samples collected 1973-2018. Slopes of SC and TSC were estimated as functions of sample collection year using simple linear regression as well as weighted meta-regression. The latter models were adjusted for predetermined covariates and examined for modification by fertility status (unselected by fertility versus fertile), and by two groups of continents: NEA and SAA. These analyses were repeated for data collected post-2000. Multiple sensitivity analyses were conducted to examine assumptions, including linearity.

OUTCOMES

Overall, SC declined appreciably between 1973 and 2018 (slope in the simple linear model: -0.87 million/ml/year, 95% CI: -0.89 to -0.86; P < 0.001). In an adjusted meta-regression model, which included two interaction terms [time × fertility group (P = 0.012) and time × continents (P = 0.058)], declines were seen among unselected men from NEA (-1.27; -1.78 to -0.77; P < 0.001) and unselected men from SAA (-0.65; -1.29 to -0.01; P = 0.045) and fertile men from NEA (-0.50; -1.00 to -0.01; P = 0.046). Among unselected men from all continents, the mean SC declined by 51.6% between 1973 and 2018 (-1.17: -1.66 to -0.68; P < 0.001). The slope for SC among unselected men was steeper in a model restricted to post-2000 data (-1.73: -3.23 to -0.24; P = 0.024) and the percent decline per year doubled, increasing from 1.16% post-1972 to 2.64% post-2000. Results were similar for TSC, with a 62.3% overall decline among unselected men (-4.70 million/year; -6.56 to -2.83; P < 0.001) in the adjusted meta-regression model. All results changed only minimally in multiple sensitivity analyses.

WIDER IMPLICATIONS

This analysis is the first to report a decline in sperm count among unselected men from South/Central America-Asia-Africa, in contrast to our previous meta-analysis that was underpowered to examine those continents. Furthermore, data suggest that this world-wide decline is continuing in the 21st century at an accelerated pace. Research on the causes of this continuing decline and actions to prevent further disruption of male reproductive health are urgently needed.

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.

Rheotaxis of sperm in fertile and infertile men

Sperm rheotaxis refers to the ability of sperm cells to align their swimming direction with or against fluid flow. Positive rheotaxis (PR) is the tendency of sperm cells to swim against the flow. Herein, we describe sperm rheotaxis in fertile and infertile males, using a microfluidic platform and focus on rheotaxis as a potential marker of male fertility. A previously reported computer-assisted sperm analysis (CASA) plugin for Image-J was used to detect and analyze the motion of human sperm cells in microfluidic environments. The fabricated microchannels mimic the female reproductive tracts and use an image-processing program to monitor sperm swimming behavior in semen samples from fertile and infertile men. We have constructed an image-processing pipeline. The image-processing pipeline incorporated strengthens object detection and particle tracking to adapt to sperm that are out of focus while swimming on the same track. PR% was defined as the number of PR sperm cells over the number of motile sperm cells. The results showed that the percentage of PR correlates with fertility, wherein the fertile male specimens showed a higher PR% than the other groups (P < 0.05). There is no difference in progressive motility between the control group (fertile men with normal sperm analysis) and group 1 (G1; infertile men with normal sperm analysis). However, PR% was lower (P < 0.05) in the G1 group (13.5 ± 0.4%) compared to the control group (40.3 ± 3.3%) and group 2 (G2; infertile with reduced sperm motility) (15.3 ± 4.6%). Thus, PR% may be used as a novel parameter to explain infertility even in situations where basic sperm analysis following the World Health Organization (WHO) guidelines is unable to do so. We propose to use PR% as a novel parameter for sperm analysis and as a method of sperm selection in assisted reproductive technology.

Sperm DNA Damage and Its Relevance in Fertility Treatment: A Review of Recent Literature and Current Practice Guidelines

Sperm deoxyribonucleic acid (DNA) damage has recently emerged as one of the most controversial topics in male reproductive medicine. While level I evidence indicates that abnormal sperm DNA damage has substantial adverse effects on reproductive outcomes (including chance of pregnancy and risk of miscarriage), there is limited consensus on how sperm DNA fragmentation (SDF) testing should be performed and/or interpreted in clinical practice. In this article, we review: (1) how SDF is assessed, (2) cumulative evidence regarding its impact on reproductive outcomes, (3) methods for mitigating high SDF, and (4) the most recent practice guidelines available for clinicians regarding the use and interpretation of SDF testing.

The role of spermatozoa-zona pellucida interaction in selecting fertilization-competent spermatozoa in humans

Human fertilization begins when a capacitated spermatozoon binds to the zona pellucida (ZP) surrounding a mature oocyte. Defective spermatozoa-ZP interaction contributes to male infertility and is a leading cause of reduced fertilization rates in assisted reproduction treatments (ARTs). Human ejaculate contains millions of spermatozoa with varying degrees of fertilization potential and genetic quality, of which only thousands of motile spermatozoa can bind to the ZP at the fertilization site. This observation suggests that human ZP selectively interacts with competitively superior spermatozoa characterized by high fertilizing capability and genetic integrity. However, direct evidence for ZP-mediated sperm selection process is lacking. This study aims to demonstrate that spermatozoa-ZP interaction represents a crucial step in selecting fertilization-competent spermatozoa in humans. ZP-bound and unbound spermatozoa were respectively collected by a spermatozoa-ZP coincubation assay. The time-course data demonstrated that ZP interacted with a small proportion of motile spermatozoa. Heat shock 70 kDa protein 2 (HSPA2) and sperm acrosome associated 3 (SPACA 3) are two protein markers associated with the sperm ZP-binding ability. Immunofluorescent staining indicated that the ZP-bound spermatozoa had significantly higher expression levels of HSPA2 and SPACA3 than the unbound spermatozoa. ZP-bound spermatozoa had a significantly higher level of normal morphology, DNA integrity, chromatin integrity, protamination and global methylation when compared to the unbound spermatozoa. The results validated the possibility of applying spermatozoa-ZP interaction to select fertilization-competent spermatozoa in ART. This highly selective interaction might also provide diagnostic information regarding the fertilization potential and genetic qualities of spermatozoa independent of those derived from the standard semen analysis.

Sperm selection techniques in cattle: Microfilter device versus conventional methods

Microfluidics and microfilter devices have been developed to mimic the characteristics of the female reproductive tract, minimizing the risk of sperm damage. This study aimed to compare the use of a microfilter device versus conventional methods for sperm selection used in in vitro fertilization (IVF). For selecting spermatozoa, the pooled samples were processed in a microfilter device, swim-up and mini-Percoll gradient. Kinematic and morphometric parameters, vitality and DNA damage were analysed before and after sperm selection. After selection, 10,000 motile spermatozoa per oocyte were used in IVF drops. Embryos were assessed at three (cleavage rate) and seven (blastocyst rate) days post-IVF. Results of sperm kinematic parameters including average path velocity, velocity straight line, curvilinear velocity, linearity, lateral head displacement with the microfilter device were superior to density gradient (p < 0.05), but similar to swim-up method. Likewise, sperm DNA damage was significantly reduced using the microfilter device and swim-up method. Regarding the total sperm recovery rate post selection, results with the microfilter device (17.64%) and mini-Percoll gradient (18.27%) were higher than with swim-up method (6.52%). However, the cleavage and blastocyst rates were the lowest using the microfilter device. In conclusion, sperm selection using the microfilter device and swim-up method can improve kinematic parameters, although the mini Percoll gradient was the most efficient method for embryo production.

A Review of the Impact of Microfluidics Technology on Sperm Selection Technique

Sperm sorting procedures depend on centrifugation processes. These processes produce oxidative stress and cell damage that are undesirable for in-vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcomes because they affect fertilization and implantation chances. The microfluidic sperm selection technique has shown promise in this area. It can create a platform for isolating and manipulating good-quality sperm cells using diverse triggers such as mechanical factors, chemical agents, and temperature gradients. Furthermore, microfluidic platforms can direct sperm cells for IVF or sperm sorting by utilizing an approach that is passive or active. In this review, we explain the use of microfluidics technologies for sorting and arranging sperm cells for different purposes. We also discuss the use of microfluidics technology in selecting and assessing sperm parameters and how it affects male infertility.

Does Choosing Microfluidics for Sperm Sorting Offer an Advantage to Improve Clinical Pregnancies in Donor Egg Recipients?

Background:

Microfluidics (MF), an advanced sperm sorting technology results in the extraction of spermatozoa with higher DNA integrity and lower DNA damage compared to existing conventional sperm sorting methods.

Aims:

The aim of the present study is to assess the efficiency of MF and to isolate the best spermatozoa for intracytoplasmic sperm injection (ICSI) over the density gradient (DG) technique.

Study Setting and Design:

We recruited couples who choose the oocyte donation programme for this study to eliminate confounding factors associated with oocyte quality.

Materials and Methods:

Sperm was processed by MF (n = 180) and DG (n = 151). ICSI was performed and positive pregnancy, miscarriage and clinical pregnancy rates were compared.

Statistical Analysis:

All variables were analysed using Graph Pad Prism 5. The unpaired two-tailed t-test was used to assess the significance. A value of P < 0.05 was considered statistically significant.

Results:

There was no significant difference in pregnancy rates between the groups. However, a clear demarcation is seen in terms of clinical pregnancy rates, where the DG group achieved higher clinical pregnancies (91.7%) compared to the MF group (80.7%). Further, we compared miscarriage rates and biochemical pregnancies, and found a significantly higher miscarriage and biochemical pregnancy rate in the MF group (14.5% and 4%, respectively) compared to the DG group (6% and 1%, respectively).

Conclusions:

Based on the available literature, we anticipated a higher clinical pregnancy rate with MF compared with conventional processing. Our results show MF does not have any add-on positive effect on clinical pregnancy rate.

Multi-dimensional-double-spiral (MDDS) inertial microfluidic platform for sperm isolation directly from the raw semen sample

Here, we propose a fully-automated platform using a spiral inertial microfluidic device for standardized semen preparation that can process patient-derived semen samples with diverse fluidic conditions without any pre-washing steps. We utilized the multi-dimensional double spiral (MDDS) device to effectively isolate sperm cells from other non-sperm seminal cells (e.g., leukocytes) in the semen sample. The recirculation platform was employed to minimize sample dependency and achieve highly purified and concentrated (up to tenfold) sperm cells in a rapid and fully-automated manner (~ 10 min processing time for 50 mL of diluted semen sample). The clinical (raw) semen samples obtained from healthy donors were directly used without any pre-washing step to evaluate the developed separation platform, which showed excellent performance with ~ 80% of sperm cell recovery, and > 99.95% and > 98% removal of 10-μm beads (a surrogate for leukocytes) from low-viscosity and high-viscosity semen samples, respectively. We expect that the novel platform will be an efficient and automated tool to achieve purified sperm cells directly from raw semen samples for assisted reproductive technologies (ARTs) as an alternative to density centrifugation or swim-up methods, which often suffer from the low recovery of sperm cells and labor-intensive steps.

The Future of IVF: The New Normal in Human Reproduction

Increased demand for in vitro fertilization (IVF) due to socio-demographic trends, and supply facilitated by new technologies, converged to transform the way a substantial proportion of humans reproduce. The purpose of this article is to describe the societal and demographic trends driving increased worldwide demand for IVF, as well as to provide an overview of emerging technologies that promise to greatly expand IVF utilization and lower its cost.

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.

Cross flow coupled with inertial focusing for separation of human sperm cells from semen and simulated TESE samples

A triplet spiral channel coupled with cross-flow filtration has been designed and fabricated in an effort to separate sperm cells from either semen or simulated testicular sperm extraction (TESE) samples. This device separates a fraction of cells from the sample by taking advantage of inertial focusing combined with hydrodynamic filtration in multiple micro-slits. Compared to the conventional swim-up technique, the proposed microfluidic device is capable of efficiently separating sperm cells without any tedious semen sample processing and centrifugation steps with a lower level of reactive oxygen species and DNA fragmentation. The device processing capability on the simulated TESE samples confirmed its proficiency in retrieving sperm cells from the samples with an approximate yield of 76%. Conclusively, the introduced microfluidic device can pave the path to proficiently separate sperm cells in assisted reproductive treatment cycles.

Use of some cost-effective technologies for a routine clinical pathology laboratory

Classically, the need for highly sophisticated instruments with important economic costs has been a major limiting factor for clinical pathology laboratories, especially in developing countries. With the aim of making clinical pathology more accessible, a wide variety of free or economical technologies have been developed worldwide in the last few years. 3D printing and Arduino approaches can provide up to 94% economical savings in hardware and instrumentation in comparison to commercial alternatives. The vast selection of point-of-care-tests (POCT) currently available also limits the need for specific instruments or personnel, as they can be used almost anywhere and by anyone. Lastly, there are dozens of free and libre digital tools available in health informatics. This review provides an overview of the state-of-the-art on cost-effective alternatives with applications in routine clinical pathology laboratories. In this context, a variety of technologies including 3D printing and Arduino, lateral flow assays, plasmonic biosensors, and microfluidics, as well as laboratory information systems, are discussed. This review aims to serve as an introduction to different technologies that can make clinical pathology more accessible and, therefore, contribute to achieve universal health coverage.

Simulating nature in sperm selection for assisted reproduction

Sperm selection in the female reproductive tract (FRT) is sophisticated. Only about 1,000 sperm out of millions in an ejaculate reach the fallopian tube and thus have a chance of fertilizing an oocyte. In assisted reproduction techniques, sperm are usually selected using their density or motility, characteristics that do not reflect their fertilization competence and, therefore, might result in failure to fertilize the oocyte. Although sperm processing in in vitro fertilization (IVF) and intrauterine insemination (IUI) bypasses many of the selection processes in the FRT, selection by the cumulus mass and the zona pellucida remain intact. By contrast, the direct injection of a sperm into an oocyte in intracytoplasmic sperm injection (ICSI) bypasses all natural selection barriers and, therefore, increases the risk of transferring paternal defects such as fragmented DNA and genomic abnormalities in sperm to the resulting child. Research into surrogate markers of fertilization potential and into simulating the natural sperm selection processes has progressed. However, methods of sperm isolation - such as hyaluronic acid-based selection and microfluidic isolation based on sperm tactic responses - use only one or two parameters and are not comparable with the multistep sperm selection processes naturally occurring within the FRT. Fertilization-competent sperm require a panel of molecules, including zona pellucida-binding proteins and ion channel proteins, that enable them to progress through the FRT to achieve fertilization. The optimal artificial sperm selection method will, therefore, probably need to use a multiparameter tool that incorporates the molecular signature of sperm with high fertilization potential, and their responses to external cues, within a microfluidic system that can replicate the physiological processes of the FRT in vitro.

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.

Sperm Selection and Embryo Development: A Comparison of the Density Gradient Centrifugation and Microfluidic Chip Sperm Preparation Methods in Patients with Astheno-Teratozoospermia

In recent years, microfluidic chip-based sperm sorting has emerged as an alternative tool to centrifugation-based conventional techniques for in vitro fertilization. This prospective study aims to compare the effects of density gradient centrifugation and microfluidic chip sperm preparation methods on embryo development in patient populations with astheno-teratozoospermia. In the study, the semen samples of the patients were divided into two groups for preparation with either the microfluidic or density gradient methods. Selected spermatozoa were then used to fertilize mature sibling oocytes and the semen parameters and embryo development on days 3 and 5 were assessed. While the density gradient group was associated with a higher sperm concentration, motility (progressive and total) was significantly higher in the microfluidic chip group. No significant differences were observed in the fertilization rates or grade 1 (G1) and grade 2 (G2) proportions of the third-day embryos. Furthermore, while the proportions of the poor, fair and good blastocysts on day 5 did not differ significantly, excellent blastocysts (indicating high-quality embryos) were observed in a significantly higher proportion of the microfluidic chip group. When compared to the classical density gradient method, the microfluidic chip sperm preparation yielded sperm with higher motility and higher quality blastocysts at day 5; in patients with astheno-teratozoospermia.

Microfluidic Systems for Isolation of Spermatozoa from Testicular Specimens of Non-Obstructive Azoospermic Men: Does/Can It Improve Sperm Yield?

Intracytoplasmic sperm injection (ICSI) has allowed reproduction options through assisted reproductive technologies (ARTs) for men with no spermatozoa within the ejaculate (azoospermia). In men with non-obstructive azoospermia (NOA), the options for spermatozoa retrieval are testicular sperm extraction (TESE), testicular sperm aspiration (TESA), or micro-surgical sperm extraction (microTESE). At the initial time of spermatozoa removal from the testis, spermatozoa are immobile. Independent of the means of spermatozoa retrieval, the subsequent steps of removing spermatozoa from seminiferous tubules, determining spermatozoa viability, identifying enough spermatozoa for oocyte injections, and isolating viable spermatozoa for injection are currently performed manually by laboratory microscopic dissection and collection. These laboratory techniques are highly labor-intensive, with yield unknown, have an unpredictable efficiency and/or success rate, and are subject to inter-laboratory personnel and intra-laboratory variability. Here, we consider the potential utility, benefits, and shortcomings of developing technologies such as motility induction/stimulants, microfluidics, dielectrophoresis, and cell sorting as andrological laboratory add-ons to reduce the technical burdens and variabilities in viable spermatozoa isolation from testicular samples in men with NOA.

The Effect of Male Sexual Abstinence Periods on the Clinical Outcomes of Fresh Embryo Transfer Cycles Following Assisted Reproductive Technology: A Meta-Analysis

A sexual abstinence period (SAP) lasting for 2–7 days is recommended before undertaking semen analyses. However, there is no consensus regarding the length of the SAP for couples using assisted reproductive technology (ART). Therefore, a meta-analysis was performed to compare the effect of short SAPs (less than 4 days) and long SAPs (4–7 days) on the clinical outcomes of fresh embryo transfer cycles after ART. A total of four studies were included in the meta-analysis. Although the fertilization rate in short SAP couples was higher than that in long SAP couples, a pooled analysis demonstrated that it was not statistically significant (p = .09). The implantation rate was, however, significantly higher in short SAP couples (p = .0001). The pooled analysis revealed that the pregnancy rate was significantly higher in short SAP couples than that in long SAP couples. The overall odds ratio (OR) for the pregnancy rate was 1.44 (p = .0006). No significant difference in miscarriage rates between the short and long SAP couples was found (p = .88). The meta-analysis indicates that a shorter abstinence period could result in higher implantation and pregnancy rates for patients undertaking ART treatments.

A microfluidic sperm-sorting device reduces the proportion of sperm with double-stranded DNA fragmentation

Sperm DNA fragmentation can be produced in one (ssSDF) or both (dsSDF) DNA strands, linked to difficulties in naturally achieving a pregnancy and recurrent miscarriages, respectively. The techniques more frequently used to select sperm require centrifugation, which may induce sperm DNA fragmentation (SDF). The objective of this study was to assess whether the microfluidic-based device FertileChip® (now ZyMot®ICSI) can diminish the proportion of sperm with dsSDF. First, in a blinded split pilot study, the semen of nine patients diagnosed with ≥60% dsSDF, was divided into three aliquots: not processed, processed with FertileChip®, and processed with swim up. The three aliquots were all analyzed using neutral COMET for the detection of dsSDF, resulting in a reduction of 46% (P < 0.001) with FertileChip® (dsSDF: 34.9%) compared with the ejaculate and the swim up (dsSDF: 65%). Thereafter, the FertileChip® was introduced into clinical practice and a cohort of 163 consecutive ICSI cycles of patients diagnosed with ≥60% dsSDF was analyzed. Fertilization rate was 75.41%. Pregnancy rates after the first embryo transfer were 53.2% (biochemical), 37.8% (clinical), 34% (ongoing) and the live birth rate was 28.8%. Cumulative pregnancy rates after one (65.4% of patients), two (27.6% of patients) or three (6.4% of patients) transfers were 66% (biochemical), 56.4% (clinical), 53.4% (ongoing) and the live birth rate was 42%. The selection of spermatozoa using Fertile Chip® significantly diminishes the percentage of dsSDF, compared with either the fresh ejaculate or after swim up. Its applicability in ICSI cycles of patients with high dsSDF resulted in good laboratory and clinical outcomes.

Effect of Microfluidic Sperm Separation vs. Standard Sperm Washing Processes on Laboratory Outcomes and Clinical Pregnancy Rates in an Unselected Patient Population

A prospective, multicenter, randomized, sibling oocyte study was conducted with 86 couples to evaluate if a microfluidic sperm separation device improved ICSI sperm selection and subsequent cycle outcomes of fertilization, blastocyst utilization, ploidy, and clinical pregnancy rate when applied to a general patient population. Patients with at least 10 metaphase II oocytes were enrolled in the study and sibling oocyte groups were split in half. One half of the oocytes underwent ICSI with the control processed sperm and the other half were injected with sperm sorted by the ZyMōt microfluidic sperm separation device. Fertilization rate was recorded and resulting blastocysts were biopsied and evaluated for ploidy status with NGS. Euploid, non-mosaic embryos were randomly selected for single embryo transfer. A total of 787 oocytes were evaluated in the ZyMōt group and 777 in the control group. No statistical differences were observed between ZyMōt and control processing methods in any of the study outcomes evaluated. It is possible that the selection of normal, progressive sperm for ICSI, and the repair capacity of oocytes are sufficient to promote normal embryonic development in the general infertility population.

Progressive bovine sperm separation using parallelized microchamber-based microfluidics

Motility is one of the most important factors in sperm migration toward an egg. Therefore, sperm separation based on motility might enhance sperm selection for infertility treatments. Conventional centrifugation-based methods increase the risk of damage to sperm cells. Microfluidic systems, on the other hand, can sort sperm in a less intrusive way, but their efficiency and throughput still needs improvement, especially in low-concentration samples (oligozoospermia). Here, a microchamber-based microfluidic platform is demonstrated that can separate progressively motile sperm from non-viable sperm and debris, and trap nonprogressive sperm in microchambers. This platform can be operated in a short period of time (<10 min) with an excellent degree of controllability with no sample preparation. Sperm were screened in a 384-microchamber platform. The mean average-path velocity of the motile sperm in the collected sample increased significantly, from 57 ± 10 μm s^-1 in the raw semen sample to 81 ± 13 μm s^-1. The DNA Integrity of the separated sperm showed 20% improvement over the raw sample which indicated that separated sperm were of higher quality. We began with a 22.5 μL raw bovine sperm sample which had a concentration of 8.5 million sperm per milliliter (M mL^-1) with 38% motility. After separation, the concentration of the collected sperm was 2.1 M mL^-1 with a motility rate of 90%. This corresponds to a 75% retrieval efficiency and the selection of approximately 5.2 × 10⁴ progressively motile spermatozoa. Our results show that the microchamber depth does not affect the residence time of motile sperm; therefore, it is possible to inspect higher sample volumes within the same time frame. This microfluidic platform may provide an easy-to-implement solution for high-throughput, robust, and efficient, collection of progressive sperm with the DNA integrity needed for assisted reproductive technologies (ARTs). However, further studies are necessary to show the implications of this method in human cases.

A Review on Microfluidics: An Aid to Assisted Reproductive Technology

Infertility is a state of the male or female reproductive system that is defined as the failure to achieve pregnancy even after 12 or more months of regular unprotected sexual intercourse. Assisted reproductive technology (ART) plays a crucial role in addressing infertility. Various ART are now available for infertile couples. Fertilization in vitro (IVF), intracytoplasmic sperm injection (ICSI) and intrauterine insemination (IUI) are the most common techniques in this regard. Various microfluidic technologies can incorporate various ART procedures such as embryo and gamete (sperm and oocyte) analysis, sorting, manipulation, culture and monitoring. Hence, this review intends to summarize the current knowledge about the application of this approach towards cell biology to enhance ART.

Recent Microfluidic Innovations for Sperm Sorting

Sperm selection is a clinical need for guided fertilization in men with low-quality semen. In this regard, microfluidics can provide an enabling platform for the precise manipulation and separation of high-quality sperm cells through applying various stimuli, including chemical agents, mechanical forces, and thermal gradients. In addition, microfluidic platforms can help to guide sperms and oocytes for controlled in vitro fertilization or sperm sorting using both passive and active methods. Herein, we present a detailed review of the use of various microfluidic methods for sorting and categorizing sperms for different applications. The advantages and disadvantages of each method are further discussed and future perspectives in the field are given.

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.

A novel microfluidic chip-based sperm-sorting device constructed using design of experiment method

Microfluidics is proposed as a technique for efficient sperm sorting, to achieve the ultimate goal of resolving infertility problems in livestock industry. Our study aimed to design a microfluidic sperm-sorting device (SSD) through a high-efficacy and cost- and time-effective fabrication process, by using COMSOL Multiphysics simulation and modeling software, and the design of experiment (DOE) method. The eight factors affecting SSD performance were established. The simulation was then run, and statistically significant factors were analyzed. Minitab16 was used to optimize the design modulus factor. By setting the statistical significance at p < 0.05, the factors affecting experimental structure were analyzed. At a desirability of 97.99, the optimal parameters for the microfluidic chip were: angle between sperm and medium inlet chambers (A = 43°), sperm inlet flow rate (B = 0.24 µL min^-1), medium inlet flow rate (C = 0.34 µL min^-1), and inlet and outlet chamber lengths (D = 5000 µm). These optima were then applied to microfluidics device construction. The device was produced using soft lithographic microfabrication techniques and tested on Holstein-Friesian bull sperm. The highest bull sperm-sorting performance for this microfluidic device prototype was 96%. The error between the simulation and the actual microfluidic device was 2.72%. Fluid viscosity ranges analysis-based simulations revealed acceptable fluid viscosity tolerances for the SSD. The simulation results revealed that the acceptable tolerance range for fluid viscosity was 0.00001-0.003 kg m^-1 s^-1. This optimally designed microfluidic chip-based SSD may be integrated into sperm x/y separation micro devices.