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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.

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BACKGROUND: Carriers of reciprocal translocations often have more unbalanced spermatozoa and higher DNA fragmentation rates, elevating reproductive risk. The simple swim-up method (SSUM) can decrease the amount of spermatozoa with abnormal chromatin structure and fragmented DNA, however, it has limited efficacy in eliminating chromosomally unbalanced sperm. METHODS: The spermatozoa of eight Robertsonian translocation (Rob) carriers were split into three groups: original raw semen group (control group); SSUM and swimming trapper method group (STM) processed semen samples. After different semen preparation procedures, semen qualities, sperm chromosomal aneuploidy, and sperm fragmented DNA were evaluated. RESULTS: Although spermatozoa with higher motility was obtained by both SSUM and STM, the population of faster forward moving sperm was greater with STM as compared to SSUM. While the rates of DNA fragmentation were statistically much lower in both groups than ejaculated semen sample, our data showed better effect on the decrease of DNA fragmentation index (DFI) after selection by STM for patients who have high DFI (>20%) in neat semen. For all patients, significant decrease in the frequency of chromosomally unbalanced spermatozoa was observed after selection using STM. Although similar trends can be seen in the SSUM group, a significant difference was identified in one patient only. CONCLUSIONS: Use of swimming trapper (STM) is superior for enriching high-motile and genetically competent sperm in comparison with SSUM.

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Purpose: This study aimed to evaluate the effects of swim-up and density gradient centrifugation methods on sperm DNA fragmentation. Methods: Nineteen normozoospermic patient samples with ≥100 × 106 motile sperms were included in this study. Sperm DNA fragmentation, progressive motility, and progressive motile sperm number were measured before and after the swim-up method or density gradient centrifugation. Results: Sperm DNA fragmentation was not statistically different between swim-up-(14.4 ± 2.1%, p = 0.32) and density gradient centrifugation-processed (25.0 ± 3.0%, p = 0.20) and unprocessed semen samples (19.2 ± 1.9%). Sperm DNA fragmentation was significantly lower in swim-up-than in density gradient centrifugation-processed samples (p < 0.05). Sperm progressive motility was significantly higher (p < 0.05) in swim-up-(92.9 ± 1.0%) and density gradient centrifugation-processed (81.3 ± 2.0%) samples, with the former being higher, than in unprocessed semen samples (53.1 ± 3.7%). The recovery rate of progressive motile sperms was significantly lower in swim-up-(9.7 ± 1.4%) than in density gradient centrifugation-processed samples (17.2 ± 1.8%, p < 0.05). Conclusions: The swim-up method is superior to density gradient centrifugation, evidenced by less sperm DNA fragmentation and higher sperm progressive motility. The recovery rate of progressive motile sperms was better after density gradient centrifugation than after swim-up.

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Many factors associated with assisted reproductive technologies significantly influence the success of pregnancy after in vitro fertilization (IVF) either directly or indirectly. These factors include sperm processing techniques, egg retrieval, intrauterine artificial insemination, intracytoplasmic sperm injection, and embryo transfer. Among these technologies, sperm quality is one of the most critical factors for a successful IVF pregnancy. The method used for sperm processing plays a crucial role in determining the quality of sperm. Several widely used sorting techniques, such as conventional swim-up, density gradient centrifugation, magnetic activated cell sorting, and hyaluronic acid, have been extensively compared in various studies. Previous studies have shown that each sperm processing method causes varying degrees of sperm damage, particularly in sperm motility, concentration, morphological features, viability, and DNA integrity. However, sperm processing techniques have been developed slowly, and the impact of these methods on pregnancy rates is still unclear. Further exploration is needed. In this review, we aim to compare the results of different sperm processing techniques concerning sperm quality and IVF pregnancy rates. We will also discuss possible clinical approaches, such as microfluidics and integrated approaches, for testing and improving sperm quality.

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Methods for seminal plasma (SP) removal and the selection of collared peccary sperm for fertilization were compared. The experiments evaluated the following: the (I) impact of centrifugation for SP removal before swim-up for sperm selection and (II) a comparison of different Percoll® gradient densities (PG 45-90% and PG 35-70%). Non-selected sperm served as the control. Sperm quality was assessed based on motility patterns, morphology, membrane functional integrity, viability, reactive oxygen species (ROS), glutathione (GSH), and DNA integrity. Subsequently, the most successful group in the previous experiment and washing by centrifugation (WC) were compared for motility patterns and fertilization using pig oocytes. Swim-up decreased motility and enhanced ROS compared to the control. Centrifugation before swim-up harmed integrity and viability compared to the control. PG 45-90% (96.8 vs. 69.7 vs. 40.7 µm/s) allowed for a better velocity average pathway (VAP), a better velocity straight line, and better linearity (LIN) than those of the control and PG 35-70% (88.4 vs. 56.0 vs. 27.3 µm/s). Thus, PG 45-90% was used for fertilization. PG 45-90% obtained a higher VAP, a higher amplitude of the lateral head, straightness, and higher LIN than those of the control and WC. Cleavage (25.2-26.3%) and morula (8.1-10.5%) rates did not differ between the groups. Therefore, PG 45-90% and WC were efficient in isolating collared peccary sperm capable of fertilizing pig oocytes.

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Determination of factors affecting sex ratio is important while considering application of sex ratio enrichment approach. Present study aimed to design a SYBR Green qPCR-based method for measurement of primary sex ratio and to evaluate different factors (genetic group, sire, spermiogenic cycle and processing layer) affecting boar sperm sex ratio. The qPCR was based on relative copy number analysis of sex chromosome-specific single copy gene fragments with an autosomal gene as reference and was evaluated using DNA dilution series from pigs with numerically normal karyotype. The sex ratio was estimated from genomic DNA samples isolated from boar semen collected from different genetic groups at different time points and different processing layers. The X chromosome frequencies of semen samples revealed significant effect of genetic group. However, significant variation was observed neither within same genetic group nor between ejaculates of different spermatogenic cycles. Among the processing techniques studied, swim-up technique produced a significant X sperm enrichment in comparison to control whereas, Percoll density gradient failed to show any significant difference among layers. The lower layer in swim-up technique was found to contain higher proportion of X sperms. The designed qPCR is found to be an easy, less time-consuming method and does not require high end laboratory facilities or the specialized expertise. The lower layer of swim-up processing has a scope for X sperm enrichment in boar semen with proper validation.

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OBJECTIVE: To compare the degree of efficiency between density gradient centrifugation (DGC) method and an extended horizontal swim-up (SU) method. METHODS: A total of 97 couples undergoing in vitro fertilization were enrolled in the study. Semen samples were divided into three aliquots and treated using DGC, extended horizontal SU, and combined methods. DNA fragmentation and chromatin decondensation were detected in native semen samples and their three corresponding aliquots. The corresponding mature oocytes of each semen sample were divided into two sibling cultures. The first sibling culture was microinjected with semen pellets from DGC, and the second sibling culture was microinjected with semen pellets from the combination of both methods. Fertilization rate and embryonic development were assessed at day 3. RESULTS: DNA fragmentation and chromatin decondensation was significantly low in DGC and extended horizontal SU samples; however, the rates of DNA fragmentation and chromatin decondensation were significantly lower in extended horizontal SU samples than in DGC samples. The lowest rates of DNA fragmentation and chromatin decondensation corresponded to the samples treated with both methods. The highest rates of DNA fragmentation and chromatin decondensation corresponded to the samples treated with DGC. No significant difference was found in the fertilization rate or day 3 embryos between sibling cultures. CONCLUSION: The combination of DGC and the extended horizontal SU techniques is best for giving the lowest rates of sperm DNA fragmentation and chromatin decondensation.

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Abstract: Sperm cryopreservation is a valuable tool for the long-term preservation of male fertility. Thus, determining the optimal technique for isolating spermatozoa post-thaw is vital to ensure recovery of the highest quality spermatozoa with minimal iatrogenic damage. This not only enhances the chances of successful conception but also reduces the risk of genetic damage in the embryo. To address this issue, human semen samples were cryopreserved using a slow freezing protocol and Quinn's Advantage™ Sperm Freeze medium. The samples were subsequently thawed and subjected to three types of sperm isolation procedures: direct swim-up, density gradient centrifugation, and electrophoretic separation using the Felix™ device. Cryopreservation led to the anticipated loss of sperm motility and vitality in association with increases in lipid peroxidation and DNA damage. Following sperm selection, all three isolation techniques resulted in an increase in sperm motility which was particularly evident with the swim-up and Felix™ procedures. The latter also significantly improved sperm vitality. There were no differences between sperm separation techniques with respect to morphology, and mitochondrial reactive oxygen species generation remained essentially unchanged when cell vitality was taken into account. By contrast, major differences were observed in DNA integrity and lipid aldehyde formation, where Felix™ isolated cells exhibiting significantly less DNA damage than the other isolation procedures as well as lower levels of 4-hydroxynonenal formation. Electrophoretic sperm isolation, therefore, offers significant advantages over alternative separation strategies, in terms of the quality of the gametes isolated and the time taken to achieve the isolation. Lay Summary: Long-term storage of sperm is vital to assisted reproductive technology because it permits the preservation of fertility that might be compromised as a result of factors such as chemotherapy or vasectomy. This goal can be achieved via cryopreservation - the freezing of cells to -196°C. When the sperm are subsequently required for conception, they must be carefully separated from the cryopreservation medium in a manner that maximizes the chances of successful conception and minimizes the risk of genetic defects in the offspring. In this paper, three isolation techniques were compared for their ability to separate ideal sperm from semen and media following cryopreservation. It was found that cryopreservation led to lower levels of motility and vitality and created higher levels of DNA and cell membrane damage. Of the three techniques compared, only cells separated on the basis of their size and electric charge (electrophoretic isolation) exhibited significantly lower levels of DNA fragmentation.

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Objective To compare the difference between sperm floating plate and density gradient centrifugation combined with swim-up in human sperm preparation.Methods The semen samples were obtained from 50 infertile men in the clinic of Reproductive Medi-cine of Northwest Women's and Children's Hospital excluding azoospermia,severe oligoasthenozoospermia and semen volume less than 2 mL.After semen liquefaction,the differences of sperm concentration,total progressively motile sperm count(TMSC),percentages of progressively motile sperm and normal morphology sperm,recovery rate and DNA fragmentation index(DFI)were measured by both the methods of sperm floating plate and density gradient centrifugation combined with swim-up,and the results were compared.Results Compared with the pre-sorting samples,sperm concentrations[(16.08±13.39)x 106/mL,(8.88±8.06)x 106/mL vs(60.05± 27.21)×106/mL],TMSC[(7.41±6.14)×106,(3.98±3.57)×106vs(22.24±13.74)×106]and DFI[(2.20±3.44)％,(5.20± 10.79)％vs(26.38±13.92)％]in the sorting groups by sperm floating plate and density gradient centrifugation combined with swim-up were decreased significantly,and the percentages of progressive motile sperm[(91.67±4.75)％,(87.86±7.90)％vs(40.21± 16.83)％]and normal morphology sperm[(9.58±5.08)％,(7.72±4.01)％vs(3.58±2.06)％]were increased significantly.Com-pared with the density gradient centrifugation combined with swim-up,the results of sperm floating plate were higher in sperm concen-tration,percentages of progressively motile sperm and normal morphology sperm,TMSC and sperm recovery rate[(30.74±13.70)％vs(17.09±9.20)％],but DFI was lower,time-consuming was shorter[(32.38±1.01)min vs(60.08±2.06)min],and the difference between the two groups was statistically significant(P＜0.05).Conclusion The sperm floating plate may have certain clinical applica-tion prospects in the future due to better parameters of sperm preparation than those of density gradient centrifugation combined with swim-up in simple operation and shorter time-consuming.

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The integrity of chromatin in the spermatozoon is essential for reproductive outcome. The aim of this study was to evaluate the most effective and cost-effective method to reduce the percentage of spermatozoa with defects in chromatin decondensation for use in assisted reproductive technologies (ART) procedures. Sperm samples from 15 sub-fertile males were examined at CFA Naples to determine the sperm decondensation index (SDI), using the aniline blue test, before and after preparation, comparing density gradients with two different swim-up approaches. All three techniques led to a reduction in decondensed spermatozoa with no statistical difference (P > 0.05) between the control and the treated sperm. In contrast, we found a highly significant decrease in SDI (P < 0.01) after the two swim-up methods in all the samples, confirming the efficacy of these methods in lowering the percentage of chromatin compaction damage. There was no statistical difference between the two swim-up methods, however swim-up from the pellet led to improved count, motility and the percentage of normal condensed spermatozoa. We suggest that swim-up from the pellet be used in ART on sub-fertile males, both to reduce cell stress by multiple centrifugation and improve the recovery rate of mature spermatozoa.

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BoviPure® is a salt solution containing colloidal silica particles coated with silane used to select sperm (e.g., ruminants) by density-gradient centrifugation (DGC). This research assessed the suitability of the BoviPure-DGC and swim-up methods for selecting dog epididymal sperm in fresh, chilled and frozen-thawed samples on post-treatment sperm quality. Sperm samples (n = 60 epididymides) were recovered by retrograde flushing from thirty orchiectomized adult dogs. Thereafter, 20 sperm pools, containing sperm aliquots of three randomly selected animals, were used for chilling (at 5 ºC for 24 h) and freezing (in liquid nitrogen vapors). Sperm selection by BoviPure-DCG and swim-up was performed in both individual and pooled samples, including non-selected samples as controls. Overall, after BoviPure-DGC selection a higher sperm retrieval rate was obtained than the swim-up selection in both individual (P < 0.05) and pooled (P < 0.01) samples. BoviPure-DGC improved (P < 0.05) the total (TM) and progressive (PSM) sperm motilities, curvilinear (VCL) and straight-line (VSL) velocities, linearity (LIN), wobble (WOB), beat-cross frequency (BCF), and integrity of plasmatic (IPM) and acrosomal (IAM) membranes of individual samples in comparison with non-selected samples. In pooled samples, however, the BoviPure-DGC improved (P < 0.05) the PSM, VCL, WOB, and IPM of chilled and frozen-thawed samples. The swim-up method improved (P < 0.05) only some kinematic variables of the individual (VCL, WOB and BCF) and cryopreserved pooled samples (VCL and ALH) in comparison with non-selected samples. In conclusion, BoviPure-DGC was more effective for recovering and selecting both fresh and cryopreserved dog epididymal sperm than the swim-up procedure improving the kinematic variables, and membranes intactness.

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OBJECTIVE: To report on the pregnancy outcomes of timed intercourse (TI) with controlled ovarian hyperstimulation (COH) as the first-line treatment of unexplained subfertility, and provide some evidence on the factors involved. METHODS: The records of couples treated between January 2016 and March 2019 were retrospectively analyzed. Couples were selected for TI based on standard infertility evaluation. Semen analysis by swim-up was conducted and the total motile sperm count (TMSC) obtained. The main outcome measured was the clinical pregnancy rates. Data were analyzed with t test, Pearson's Chi-squared test, and the Wald test for logistic regression with p≤0.05. RESULTS: The records of 275 couples (449 cycles) were included in the analysis. Patients underwent TI up to six attempts. Patient- and cycle-based pregnancy rates were 18.55% and 13.14%, respectively. Eight patients got pregnant twice, resulting in a cumulative pregnancy rate of 21.4%. Women that did not get pregnant demonstrated a statistically higher mean age value than women who did (p=0.0186). Logistic regression indicated that for every year added to the woman's age, the chances of pregnancy reduced by 6.45%, and for cycles with TMSC ≥ 5 million, the chances of pregnancy were 1.91 times higher when compared to TMSC < 5 million. CONCLUSIONS: TI with COH should be considered as the first-line treatment for selected couples with unexplained subfertility before more traumatic and costly IVF treatments were considered. The findings can assist doctors to conduct a more educated counselling concerning the chances patients have to get pregnant with TI.

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OBJECTIVE: This study was performed to determine the effect of swim-up (SU) and density gradient centrifugation (DGC) on sperm survival and DNA fragmentation. METHODS: Individual semen samples were analyzed before each was divided into two aliquots (half for SU and half for DGC) for calculation of sperm survival and the DNA fragmentation index (DFI). Sperm DNA fragmentation was determined using the sperm chromatin dispersion test. RESULTS: The DFI of the 63 semen samples processed using both procedures was lower than that of the fresh semen samples. The DFI was significantly lower for samples processed using the SU than DGC method. In the sperm survival test, the SU technique was associated with increased sperm motility and vitality following preparation. After 24 hours, however, the concentration and percentage of surviving sperm were significantly lower in the SU than DGC group. CONCLUSIONS: Both semen preparation techniques help to minimize sperm DNA fragmentation; however, when the DFI is <30%, the SU technique is more appropriate than DGC. While DGC may be superior for intrauterine insemination, the SU method may be preferable for in vitro fertilization or maturation.

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BACKGROUND: Density gradient centrifugation (DGC) and swim-up (SU) are the two most widely used sperm preparation methods for in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). However, existing comparisons of IVF/ICSI outcomes following these sperm preparation methods are insufficient and controversial. METHODS: This retrospective study included all first autologous IVF and ICSI cycles performed between March 1, 2016, and December 31, 2020 in a single university-based center. A total of 3608 cycles were matched between DGC and SU using propensity score (PS) matching for potential confounding factors at a ratio of 1:1. The primary outcome was the cumulative live birth rate (cLBR) per aspiration. RESULTS: PS matching provided 719 cycles after DGC and 719 cycles after SU. After adjusting for confounders, the recovery rate, progressive motility rate after sperm preparation, fertilization rate, good-quality embryo rate, and blastocyst formation rate were similar between the DGC and SU groups. The cLBR (odds ratio [OR] = 1.143, 95% confidence interval [CI]: 0.893-1.461) and LBR per transfer (OR = 1.082, 95% CI: 0.896-1.307) were also not significantly different between the groups. Furthermore, no significant differences were found in all of the laboratory and clinical outcomes following conventional IVF or ICSI cycles between the two groups. However, a significantly higher fertilization rate (ß = 0.074, 95% CI: 0.008-0.140) was observed when using poor-quality sperm in the DGC group than in the SU group. CONCLUSIONS: Sperm preparation using DGC and SU separately resulted in similar IVF/ICSI outcomes. Further studies are warranted to compare the effects of these methods on IVF/ICSI outcomes when using sperm from subgroups of different quality.

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Present study aimed to evaluate field fertility rate and calf sex ratio of Nili Ravi buffalo semen sexed through modified swim-up method (Animal Reproduction Science, 182, 2017, 69). For this purpose, five mature Nili-Ravi buffalo bulls kept at semen production unit, Qadirabad, Pakistan, were selected. Two consecutive ejaculates per week were collected with artificial vagina for 3 weeks. Qualified semen ejaculates were pooled and divided into two aliquots. The first aliquot was processed by routine procedure (control), whereas the second was processed by modified swim-up technique. After separation, semen was diluted in tris-citric acid extender and cryopreserved using standard techniques. Sexed semen was evaluated for fertility trials during peak breeding season. Artificially inseminated animals were examined for pregnancy rate through rectal palpation at least 3 months after insemination under field conditions. Calving ratio of female and male calves were recoded after Parturition. The fertility rate was higher (p < .05) in X-sorted sperm (70%) as compared with control (47%). The female calf ratio was higher (p < .05) in X-sorted sperm (78.58%) compared with control (53.3%). In Conclusion, conception rate and production of female calf were significantly higher with sexed semen separated through modified swim-up method compared with unsexed control.

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In sperm processing for IVF/ICSI incubation times differ considerably both between and within assisted reproduction facilities. There is no established consensus on the optimal sperm incubation timings to maximize pregnancy rates, and the few studies addressing this association rely on manual and operator-dependent methods for time recording. The present retrospective cohort study includes 1169 ICSI cycles using fresh semen processed by swim-up. An operator-independent, radiofrequency-based system was used to record sperm incubation times: from sample collection to swim-up (T1, 0.35 ± 0.26); from swim-up to ICSI (T2, 3.30 ± 2.2); and total time from sample collection to ICSI (T, 3.66 ± 2.26). In oocyte donation cycles, we observed a significant negative effect of T1 on fertilization rate (FR; generalized linear modelling regression, coeff. -0.20, p = 0.001); however, after analysing all times by deciles and by adjusted logistic regression, none of the time intervals had a significant effect on pregnancy (biochemical, clinical, and ongoing) and live birth (LB) rates (p > 0.05 for all outcomes). In cycles using the patient's oocytes, we observed a negative effect of T2 (ordinal regression, coeff. -0.25, p = 0.011) and T (-0.33, p = 0.005) on the mean morphological score of the embryo cohort. In these cycles, a trend associating longer values of T with higher LB rates was identified (OR = 1.47, p = 0.050), although this difference is likely not clinically significant. In conclusion, while longer sperm incubation in vitro may impact slightly both FRs and embryo morphology after ICSI, no adverse effects were detected on the reproductive outcomes.

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OBJECTIVE: Our study aims to retrospectively examine the relationship between two different sperm preparation methods used in IUI among eight years in terms of pregnancy and live birth rates. METHODS: We evaluated the data of semen samples between December 2012 and March 2020. Three hundred eighty-four samples prepared with Conventional Swim-up (CSW) and 361 samples prepared with Density Gradient-Swim up (DGC-SW) obtained from men applying for IUI were analyzed. Spermiogram results of the semen samples given by men applying for IUI were examined. Data about sperm preparation method, post washed sperm parameters, pregnancy, and live birth rate were collected. Statistical analysis was performed. RESULTS: Basal progressive sperm count was significantly higher in pregnant couples in both CSW and DGC-SW groups (p = 0,032, p = 0,035, respectively). In each group, the post washed total progressive motile sperm count obtained by CSW and DGC-SW methods were significantly higher in pregnant patients (p < 0.05). There was no significant difference between CSW and DGC-SW methods in pregnancy achievement (p = 0,399, χ2 = 0,712). Live birth and miscarriage rates were not different between the groups (p = 0,243, χ2 = 2.827). CONCLUSION: In conclusion, there is no significant difference between CSW and DGC-SW for pregnancy and live birth rates. Our results suggest that both sperm preparation techniques used in IUI are not superior to each other. In other words, the choice of sperm preparation method does not affect the pregnancy rate in couples undergoing IUI.

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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.

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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.

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More suitable and efficient methods to protect gametes from external harmful effects during in vitro handling can be achieved by adding preovulatory porcine oviductal fluid (pOF) to in vitro culture media. The objective of this study was to assess the swim-up procedure's suitability as a sperm selection method using a medium supplemented with 1mg/mL BSA, 1% preovulatory pOF (v/v), 1% v/v pOF plus 1mg/mL BSA, and 5mg/mL BSA. After selection, various sperm parameters were studied, such as sperm recovery rate, sperm morphology, motility (by CASA), vitality, acrosome status and intracellular calcium (by flow cytometry) and ability to penetrate oocytes in vitro. Around 2% of sperm were recovered after swim-up, and the replacement of BSA by pOF showed a beneficial reduction of motility parameters calcium concentration, resulting in an increased penetration rate. The combination of albumin and oviductal fluid in the medium did not improve the sperm parameters results, whereas a high concentration of BSA increased sperm morphological abnormalities, motility, and acrosome damage, with a reduction of calcium concentration and penetration rate. In conclusion, the replacement of albumin by preovulatory oviductal fluid in the swim-up sperm preparation method modifies boar sperm parameters and improves the in vitro penetration of oocytes.