Defining and refining sperm selection strategies

Cells

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 micr...

Molecular Human Reproduction, 2011

Sperm motility is one of the three fundamental tenets of semen analysis providing diagnostic and prognostic information for both natural and assisted reproduction technology (ART) conception. The landmark papers of John MacLeod and Ruth Gold demonstrated clear differences between subfertile and fertile men in sperm motility (MacLeod and Gold, 1951) which have been confirmed by a plethora of subsequent studies (Barratt et al., 2011). The WHO new reference values for motility, as well as sperm concentration (Cooper et al., 2010), are remarkably similar to those proposed by MacLeod and Gold in 1951 (32% motile cells as a 5% centile of a fertile population), suggesting that these observations are robust. The primary conclusion from all these studies is that although there is no magic number or threshold for in vivo fertility, at the lower ends of the motility spectrum, there are significantly higher chances of subfertility (Fig. 1). This overwhelming body of clinical information ignited a series of studies developing new methods to obtain sperm kinematic data. Initial information was very encouraging, e.g. using the biological endpoints of penetration of cervical mucus (Mortimer et al., 1986). With the advent of computer-assisted semen analysis (CASA) machines, making kin

The swim-up technique is a clinical practice used to select highly motile sperm cells from patient ejaculates to use in assisted fertilization. The aim of this study was to investigate whether the length of different sperm-cell components is related to gamete function. Thus, we explored whether swim-up technique selects for longer sperm cells than mean sperm cells from unprocessed ejaculates. Sperm midpiece, tail endpiece, and total length were measured before and after the swimup selection by means of contrast-phase and electron microscopy. Correlations between sperm dimensions, sperm motility, and sperm concentration were also investigated. Swim-up selected cells with longer midpiece compared with the unprocessed fractions (5.8 mm (CI 5.52-6.16 mm) vs. 5.3 mm (CI 4.97-5.61 mm), p < 0.05) and shorter tail endpiece (7.8 mm (CI 7.11-8.44 mm) vs. 8.5 mm (CI 7.81-9.14 mm), p < 0.05 after meta-analysis), whereas no effect of swim-up selection was detected on the total sperm cell length. Individuals producing high sperm concentrations had longer sperm midpiece than had men producing lower sperm concentrations. It is concluded that short sperm flagellar tips with long midpieces may be used as biomarkers in infertility therapy.

Human Reproduction Update, 2015

cells since only motile cells can pass through cervical mucus and gain initial entry into the female reproductive tract. In animals, some studies indicate that the sperm selected by the reproductive tract and recovered from the uterus and the oviducts have higher fertilization rates but this is not a universal finding. Some species show less discrimination in sperm selection and abnormal sperm do arrive at the oviduct. In contrast, assisted reproductive technologies (ART) utilize a more random sperm population. In this review we contrast the journey of the spermatozoon in vivo and in vitro and discuss this in the context of developing new sperm preparation and selection techniques for ART. methods: A review of the literature examining characteristics of the spermatozoa selected in vivo is compared with recent developments in in vitro selection and preparation methods. Contrasts and similarities are presented. results and conclusions: New technologies are being developed to aid in the diagnosis, preparation and selection of spermatozoa in ART. To date progress has been frustrating and these methods have provided variable benefits in improving outcomes after ART. It is more likely that examining the mechanisms enforced by nature will provide valuable information in regard to sperm selection and preparation techniques in vitro. Identifying the properties of those spermatozoa which do reach the oviduct will also be important for the development of more effective tests of semen quality. In this review we examine the value of sperm selection to see how much guidance for ART can be gleaned from the natural selection processes in vivo.

Fertility and sterility, 2009

Objective: To understand the correlation between normalcy of the sperm, fertilization, and early embryo development, and to establish a detailed classification scoring scale for the individual spermatozoon with the highest predictive fertilizing potential in real time during intracytoplasmic sperm injection (ICSI). Design: A retrospective and analysis. Setting: Laboratory Drouot. Patient(s): 27 couples with male factor infertility referred for ICSI treatment. Intervention(s): Before ICSI, motile spermatozoa were scored after aspiration. Main Outcome Measure(s): Oocyte fertilization, embryo development and morphology, outcome of scored motile injected spermatozoa. Result(s): Our suggested formula is (Normal head score ¼ 2) þ (Lack of vacuole score ¼ 3) þ (Normal base score ¼ 1) ¼ (Total score ¼ 6) for a morphologic ''normal top'' spermatozoon, calculated with the major criteria affecting the outcome of ICSI. We take into account the normalcy of head size and shape, the base of the head, and the lack of vacuoles. Our scoring of three classes of injected spermatozoa revealed a statistically significant difference in fertilization rate: 39 out of 46 (84%), 94 out of 128 (73%), and 27 out of 44 (61%), respectively. Our examination of the contribution of maternal age in correlation to sperm score revealed a distinction between oocytes originating from women younger than 30 years and oocytes from women aged 30 years and older. Conclusion(s): Our suggested classification provides allows the best spermatozoon to be chosen for ICSI, particularly for oocytes from women aged 30 years and older.

Journal of In Vitro Fertilization and Embryo Transfer, 1990

The relationship between sperm parameters and fertilizing capacity in vitro was examined retrospectively, with the aim of finding predictive criteria for successful in vitro fertilization. Three hundred thirty semen samples were used to inseminate 1462 oocytes. Conventional parameters of sperm concentration and percentage motility in the ejaculate as well as swim-up migration were analyzed in relation to fertilization rate. It was shown that the probability of fertilizing human oocytes in vitro decreases significantly when (a) the sperm concentration is below 20 • 106 spermatozoa/ml ejaculate (P = 0.006), (b) motility is lower than 80% (P = 0.002), or (c) less than 4 • 106 motile spermatozoa/ml are concentrated in the swimup fraction (P < 0.0001). It was also demonstrated that nonfertilizing sperm could not be distinguished from fertilizing sperm by the conventional criteria but rather by the average concentration of motile spermatozoa in the swim-up fraction [12.5 +-1.5 and22.3 • 2.3 • lO6/ml for the 0 and the 100% fertilization groups, respectively (mean +-SE; P < 0.01)]. Thus, the swim-up migration technique can serve as a predictive test for the in vitro fertilizing capacity of sperm.

Fertility and Sterility, 2013

The increasing focus on developing new tools to more accurately diagnose and select individual sperm before intracytoplasmic sperm injection will allow us to counsel and treat couples with greater confidence and efficiency. Current sperm selection techniques are based on the premise that if an ejaculated spermatozoon has cleared spermatogenesis with the correct morphology and/or membrane properties then it is most likely normal. Techniques that are designed to prepare a clean ''normal'' sperm population or that assist in selecting an individual ''normal'' spermatozoon are currently being investigated. The use of techniques, including density-gradient preparation, electrophoretic separation, microfluidics, high-magnification sperm morphology selection, and hyaluronic acid binding, is discussed. The research evidence that supports the interrelated developmental and genetic integrity of the selected sperm, particularly sperm DNA damage and clinical outcome evidence are presented.

Theriogenology, 2006

Bailliere's Clinical Obstetrics and Gynaecology, 1994

Systems Biology in Reproductive Medicine, 2016

Intracytoplasmic sperm injection (ICSI) is the most frequently applied method for fertilization making the process of identifying the perfect spermatozoon fundamental. Herein we offer a critical and thorough presentation on the techniques reported regarding (i) handling and preparing semen samples, (ii) identifying and 'fishing' spermatozoa, and (iii) improving key factors, such as motility for a successful ICSI practice. These approaches are suggested to make the process easier and more effective especially in atypical and challenging circumstances. Furthermore, we present an epigrammatic opinion-where appropriate-based upon our collective experience. Techniques such as intracytoplasmic morphologically selected sperm injection, hyaluronic binding, polarized light microscopy, and annexin V agent identification for comparing sperm cells and their chromatin integrity are analyzed. Moreover, for the demanding cases of total sperm immotility the use of the hypoosmotic swelling test, methylxanthines, as well as the option of laser assisted immotile sperm selection are discussed. Finally, we refer to the employment of myoinositol as a way to bioreactively improve ICSI outcome for oligoasthenoteratozoospermic men. The diversity and the constant development of novel promising techniques to improve ICSI from the spermatozoon perspective, is certainly worth pursuing. The majority of the techniques discussed are still a long way from being established in routine practices of the standard IVF laboratory. In most cases an experienced embryologist could yield the same results. Although some of the techniques show great benefits, there is a need for large scale multicenter randomized control studies to be conducted in order to specify their importance before suggesting horizontal application. Taking into consideration the a priori invasive nature of ICSI, when clinical application becomes a possibility we need to proceed with caution and ensure that in the pursuit for innovation we are not sacrificing safety and the balance of the physiological and biological pathways of the spermatozoon's dynamic.