Comparison of in vitro fertilization outcomes in ICSI cycles after human sperm preparation by density gradient centrifugation and direct micro swim-up without centrifugation

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.

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.

Management of male factor infertility: position statement from the Italian Society of Andrology and Sexual Medicine (SIAMS) : Endorsing Organization: Italian Society of Embryology, Reproduction, and Research (SIERR)

PURPOSE

Infertility affects 15-20% of couples and male factors are present in about half of the cases. For many aspects related to the diagnostic and therapeutic approach of male factor infertility, there is no general consensus, and the clinical approach is not uniform.

METHODS

In the present document by the Italian Society of Andrology and Sexual Medicine (SIAMS), endorsed by the Italian Society of Embryology, Reproduction, and Research (SIERR), we propose evidence-based recommendations for the diagnosis, treatment, and management of male factor infertility to improve patient and couple care.

RESULTS

Components of the initial evaluation should include at minimum medical history, physical examination, and semen analysis. Semen microbiological examination, endocrine assessment, and imaging are suggested in most men and recommended when specific risk factors for infertility exist or first-step analyses showed abnormalities. Full examination including genetic tests, testicular cytology/histology, or additional tests on sperm is clinically oriented and based on the results of previous investigations. For treatment purposes, the identification of the specific cause and the pathogenetic mechanism is advisable. At least, distinguishing pre-testicular, testicular, and post-testicular forms is essential. Treatment should be couple-oriented, including lifestyle modifications, etiologic therapies, empirical treatments, and ART on the basis of best evidence and with a gradual approach.

CONCLUSION

These Guidelines are based on two principal aspects: they are couple-oriented and place high value in assessing, preventing, and treating risk factors for infertility. These Guidelines also highlighted that male infertility and in particular testicular function might be a mirror of general health of a man.

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.

A fast and safe technique for sperm preparation in ICSI treatments within a randomized controlled trial (RCT)

Recently a novel method based on horizontal sperm migration in injection dishes has been introduced as an additional tool for preparation of semen sample in assisted reproductive technology (ART) procedures. In the present study, we evaluated both timing and reproductive outcomes in a randomized controlled study including 1034 intra-cytoplasmic sperm injection (ICSI) procedures followed by fresh embryo transfer. Couples enrolled were divided into two sub-groups, namely conventional swim-up method (Group A), and horizontal sperm migration in injection dishes (Group B).No significant differences were found between groups with respect to fertilization rate, implantation success, clinical pregnancy outcomes and ongoing pregnancies. On the contrary, both cleavage and blastocyst rates were statistically higher in Group B, suggesting superior efficiency and safety of this innovative technique also including time-saving and cheaper costs as compared to the classical swim-up sperm preparation.Our data support the interpretation of the horizontal sperm migration as a promising procedure for semen preparation in ART cycles.

Novel Techniques of Sperm Selection for Improving IVF and ICSI Outcomes

Almost 50% of the infertility cases are due to male factors. Assisted reproductive technologies (ARTs) allow to overcome the incapacity of these patients' spermatozoa to fertilize the oocyte and produce a viable and healthy offspring, but the efficiency of the different techniques has still the potential to improve. According to the latest reports of the European Society of Human Reproduction and Embryology (ESHRE) and the Centers for Disease Control and Prevention of the United States (CDC), the percentages of deliveries per ART cycle in 2014 and 2016 were 21 and 22%, respectively. Among the reasons for this relatively low efficiency, the quality of the spermatozoa has been pointed out as critical, and the presence of high percentages of DNA-damaged spermatozoa in patients' ejaculates is possibly one of the main factors reducing the ARTs outcomes. Thus, one of the main challenges in reproductive medicine is to ensure the highest quality of the spermatozoa used in ARTs, and specifically, in terms of genetic integrity. The latest techniques for the preparation and selection of human spermatozoa are herein discussed focusing on those proven to improve one or several of the following parameters: sperm genetic integrity, fertilization capacity, embryo production, and in vitro survival, as well as pregnancy and delivery rates following in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). In addition, we discuss the potential of techniques developed in non-human mammals that could be further transferred to the clinic.

Sperm selection with density gradient centrifugation and swim up: effect on DNA fragmentation in viable spermatozoa

Subjects increasing sperm DNA fragmentation (sDF) during Density Gradient Centrifugation (DGC), a common sperm selection procedure in Assisted Reproduction Techniques (ARTs), experience a 50% lower probability of pregnancy. Hence, identification of these subjects is of clinical importance. Here, we investigated whether such subjects are identified with higher accuracy detecting DNA fragmentation in viable (viable sDF) instead of total spermatozoa (total sDF) and whether swim up, an alternative procedure to DGC, does not increase sDF. With DGC, we identified 10/20 subjects increasing total sDF, and 2 more subjects using viable sDF. With swim up, we identified 8/40 subjects increasing total sDF, and 8 more subjects using viable sDF. In addition, viable sDF reveals more accurately the increase of the damage when it occurs. Finally, a multivariate analysis demonstrated that the proportional increase of sDF was higher after DGC respect to swim up. In conclusion, viable sDF is a more accurate parameter to reveal the increase of the damage by selection both with swim up and DGC. Swim up increases sDF in some samples, although at a lesser extent than DGC, suggesting that it should be used to select spermatozoa for ARTs when possible.