Hyperactivated Motility Research Articles

P-053 Comparative analysis between microfluidic sperm sorting and Swim-up technique to select spermatozoa with better characteristics in hyper viscous samples

Abstract Study question What is the best technique to select spermatozoa in hyper viscous semen samples? Summary answer Microfluidics is the best technique that allows to select spermatozoa with better seminal characteristics and hyperactivated motility, and less sperm DNA fragmentation. What is known already Density gradient centrifugation and Swim-up (SU) are the two traditional selection methods used during assisted reproduction techniques (ART) to collect the highly motile sperm fraction. Many studies reported that centrifugation increase sperm DNA fragmentation and oxidative status which could affect reproductive outcomes. To overcome the limitations of centrifugation, an alternative approach by using microfluidic-based devices was recently designed. In microfluidic protocol, sample is applied to the device’s inlet port, connected to a lower chamber. This chamber consists of a microporous filter, where the most motile spermatozoa migrate upward through the filter. Study design, size, duration An observational study was conducted on 29 semen samples from patients undergoing routine semen analysis for couple infertility in the Andrology Laboratory of Careggi University Hospital of Florence from January 2023 to January 2024. In these samples we compare two different methods for sperm selection: indirect SU technique and microfluidic devices (MSS). Participants/materials, setting, methods We evaluated seminal parameters (sperm progressive and total motility, viability, and concentration), sperm kinematic parameters by Computer-Assisted Sperm Analysis (C.A.S.A. system), sperm DNA fragmentation by TUNEL/PI assay and sperm oxidative status by CellROX® Orange (which we have recently shown to identify a fraction of viable oxidized spermatozoa with better characteristics (Traini G., et al. 2022)) in 29 normozoospermic and 18 hyper viscous semen samples selected by SU and MSS. Main results and the role of chance In normozoospermic samples, sperm selection with both indirect SU technique and microfluidic devices, ameliorated sperm characteristics compared to not selected samples. Spermatozoa selected by MSS showed statistically significant higher progressive and total motility, viability and concentration compared to those selected by indirect SU. Moreover, an increase in most of kinematic semen parameters (like VAP, VCL and VSL) and hyperactivated motility was observed in MSS selected samples. Also, sperm DNA fragmentation was significantly reduced after MSS selection compared to indirect SU. We evaluated the percentage of viable oxidized spermatozoa by using CellROX® Orange. A significant increase of the percentage of CellROX® Orange positive spermatozoa was observed in most of MSS selected samples. In all 18 hyper viscous samples, the results obtained in normozoospermic samples were confirmed. Indeed, an overall improvement of sperm progressive and total motility, viability and concentration together with an increase in most of kinematic semen parameters and in hyperactivated motility were evidenced in MSS selected spermatozoa respect to those selected by indirect SU. Again, a significant decrease of sperm DNA fragmentation and an increase of the percentage of CellROX® Orange positive spermatozoa, were observed after MSS selection. Limitations, reasons for caution The number of semen samples included in the study is not very elevated. Results obtained in hyper viscous semen samples should be confirmed in a greater number of samples. Wider implications of the findings Our data indicate that MSS selects the sperm fraction with better characteristics and less DNA fragmentation. These results suggest that MSS could improve ART outcomes, particularly for specific categories of patients, including hyper viscous semen samples, for which the selection by SU does not always guarantee good yields. Trial registration number not applicable

P-058 The role of sperm selection in improving embryo euploidy rate: a comparison between Swim-up and Microfluidic Sperm Selection

Abstract Study question Does Microfluidic Sperm Selection (MSS) improve the blastocysts’ development rate and the euploidy rate compared to Swim-up sperm selection? Summary answer MSS doesn’t improve the rate of blastocyst development and euploidy compared to Swim-up. Furthermore, in women age ≥ 37 years D6 aneuploid blastocyst rate increases What is known already Sperm defects have been shown to have a negative impact on embryo quality and development. MSS was introduced as an alternative to traditional centrifugation-based sperm preparation techniques to efficiently isolate highly motile and healthy spermatozoa. Centrifugation has been suggested to compromise membrane integrity, motility, mitochondrial energy production, and DNA structure. Less DNA fragmentation and ROS formation was observed in spermatozoa isolated with MSS compared to standard techniques. Our study aims to analyze whether MSS also improves biological outcomes. Study design, size, duration In a prospective study of 51 ICSI/PGT-A cycles performed between September 2022 and November 2023, freshly ejaculated semen sample was divided into two aliquots and processed by Swim-up and MSS. Split sperm sample was used to inject siblings’ mature oocytes (249 vs 274 oocytes in Swim-up vs MSS groups). Inclusion criteria: retrieved MII oocytes ≥8, oligoteratozoospermic and normozoospermic semen. Results were analyzed according to women’s age <37 years (21 cycles) and ≥37 years (30 cycles). Participants/materials, setting, methods Spermatozoa were selected using either conventional Swim-up or a microfluidics device (ZyMōtTM). Post treatment sperm parameters (sperm count; total sperm motility; progressive motility and hyperactivated motility) were examined for both. Embryo culture was performed in Irvine Continuous Culture-NX media until day5 or day6 and biopsy was performed at the blastocyst stage by next generation sequencing. Primary endpoint was fertilization rate, blastocyst development and usable blastocysts rate. Chi-square analysis was performed and p < 0.05 was considered significant Main results and the role of chance There is no significant differences overall between Swim-up and MSS in fertilization rate (73% vs 75%), blastocyst development rate (47% vs 54%) and ploidy rate: aneuploid (47% vs 50%), usable blastocyst (i.e. euploid+mosaics) (53% vs 50%). When considering female age, no significant difference is observed in the primary endpoints in the <37 years group. However, in women aged ≥37 years, the rate of blastocyst development is similar in the two sperm preparation groups, but a significant difference is observed in the timing of blastocyst development: The percentage of blastocysts formed on day 6 in the MSS group is significantly higher than in the Swim-up group (43% vs. 19% p < 0.05). In addition, the aneuploidy rate of blastocysts on day 6 is also significantly higher than in the Swim-up group (79% vs. 50% respectively, p < 0.05). The concentration of sperm recovered post-treatment was similar in Swim-up vs MSS (23 x106 vs 19 x106); total motility and progressive motility were similar in Swim-up compared to MSS (92.7% vs. 95.3% and 85% vs. 87% respectively). Only hyperactivated motility assessed with the SCASCOPE CASA System (Microptic) was significantly higher in MSS vs Swim-up 41% vs 4% respectively (p < 0.0005). Limitations, reasons for caution Our study included couples with different infertility diagnosis and semen parameters. Further studies with an increased number of patients may provide more comprehensive data to better evaluate biological and clinical outcomes to eventually suggest the use of MSS in laboratory routines Wider implications of the findings Recently, some studies reported that microfluidic-sorted sperm showed significantly less ROS formation and DNA fragmentation compared to those treated with conventional Swim-up method. Nevertheless, our data does not currently show the expected increase in embryo euploidy rate to justify the routine use of these expensive devices in male infertility treatment Trial registration number non applicabile

O-197 Correlation of intracellular pH of non-normozoospermic men with fertilization rates in assisted reproduction procedures (Pilot study)

Abstract Study question Does measuring qualitative changes in the sperm pHi could predict the fertilizing potential of a non-normozoospermic patients under fertility treatment? Summary answer The increase of pHi correlates with fertilization rates. What is known already The intracellular pHi (pHi) is of great importance for a wide variety of sperm physiological processes, including its motility. The pHi regulates several key sperm proteins, such as the Ca2+ channel, CatSper (sperm cation channel) which is involved in sperm hyperactivation and the K+ channel SLO3.The latter participates in the regulation of membrane potential during capacitation. Interestingly, human sperm pHi has been found to positively correlate with both hyperactivated motility and in vitro fertilization (IVF) success in normozoospermic patients. Study design, size, duration This prospective study employed unidentified semen samples from 62 non-normozoospermic men (patients, age 38 ± 4 years old) undergoing fertility treatment from January to November 2023 at CITMER Reproductive Medicine, Mexico City. Frozen semen samples and procedures with less than 4 oocytes were excluded. The pHi of sperm samples was evaluated by time-lapse flow cytometry. For comparison, the pHi of 13 normozoospermic men (donors, age 28 + 6 years old) were also analyzed. Participants/materials, setting, methods Sperm were separated by density gradient and incubated in capacitating HTF media to be used for conventional IVF or ICSI. Cells were stained with vitality (propidium iodide) and pHi (BCECF-AM) sensitive fluorescent dyes. Fluorescence changes were evaluated using an AccuriC6 flow cytometer. For each pHi recording, 10 mM NH4Cl were used as an alkalinization positive control and for data normalization. Basal levels of sperm pHi and its correlation with fertilization rates, were performed using R. Main results and the role of chance The changes in pHi were recorded as changes in the BCECF fluorescence. The increase in fluorescence is proportional to an increase in pHi and vice versa. Interestingly, we observed that the increase in pHi in sperm used for ICSI but not for IVF procedures, which were paired with oocytes from female donors, are positively and significantly correlated with higher fertilization rates (R = 0.68; *p=0.02). This seems to be the same for ICSI treatment pairing sperm with oocyte from the female partner, although the correlation is not yet statistically significant (R = 0.44; p = 0.12). We did not find significant differences in the basal pHi values between sperm from donors and patients; however, we observed that sperm from patients, had higher pHi values (0.57 + 0.15 a.u.f) compared to sperm from donors (0.48 + 0.24 a.u.f). Our results suggest that sperm pHi may be an important regulator for the process of fusion and not only for fertilization. Qualitative sperm pHi values can contribute to predicting fertilization success in patients undergoing ICSI treatment. Limitations, reasons for caution The preliminary nature of the results implies a necessity to increase the number of analyzed semen samples. Physiological responses may vary even among the same patient or cell’s donor. Our population-based analysis could be underestimating such single cell variations. Wider implications of the findings Current protocols for sperm analysis fail to successfully predict the fertilizing capacity of semen samplest.Measuring pHi in capacitated sperm, could be a promising tool to help clinicians choose the best fertilization technique for each couple. This protocol is easy to perform in a laboratory that has a flow cytometer. Trial registration number Not applicable

P-065 HyperSperm, a new sperm preparation method for IVF/ICSI improves sperm capacitation while maintaining a high safety profile

Abstract Study question Does HyperSperm improve sperm capacitation without affecting sperm quality? Summary answer HyperSperm enhances sperm hyperactivated motility, a hallmark of capacitation, without compromising sperm viability, acrosome integrity, or DNA fragmentation. What is known already HyperSperm is a novel semen preparation method for IVF/ICSI based on mimicking effective capacitation that occurs in the female tract. HyperSperm, which consists of 3 media used sequentially to treat sperm before insemination, gave rise to more high-quality blastocysts compared to current standard of care in a pilot split oocyte study in 10 couples. Study design, size, duration This prospective in vitro study was conducted between July 2023 and January 2024 in an academic department. A consecutive cohort of 15 normozoospermic individuals were recruited and included. Each participant provided a semen sample by masturbation after written informed consent was obtained on the day of the collection. Participants/materials, setting, methods Semen samples from normozoospermic individuals (n = 15) were divided into two halves. After density gradient centrifugation, Control half was incubated in modified HTF (Human Tubal Fluid) for 2-4 hours, while the other half underwent HyperSperm treatment. The following parameters were assessed: sperm viability (eosin exclusion); motility and kinematic parameters (CASA); acrosome integrity (fluorescein-labeled Pisum sativum lectin staining); and DNA fragmentation by TUNEL. Differences between groups were evaluated by paired T-test. Significant differences were considered when p < 0.05. Main results and the role of chance Following treatments, sperm viability (90±3% Control vs. 91±3% HyperSperm) and motility (87±2% Control vs. 89±3% HyperSperm) were similar between groups (p > 0.05). Notably, HyperSperm induced a significant hyperactivation increase (9±2% Control vs. 22±3% HyperSperm), along with associated kinematic parameters (i.e., curvilinear velocity and lateral head displacement) (p < 0.05). Furthermore, HyperSperm treatment did not promote motility decrease over time. Finally, there were no differences in the percentage of sperm with intact acrosome (91±2% Control vs. 90±2% HyperSperm) and DNA fragmentation (3±1% Control vs. 3±1% HyperSperm) between groups (p > 0.05). Altogether, HyperSperm has shown to significantly improve sperm capacitation parameters while maintaining a high safety profile in the treated sample. Limitations, reasons for caution The study is limited to normozoospermic samples, and further research should validate these findings across broader male populations undergoing IVF/ICSI. Wider implications of the findings HyperSperm has demonstrated an increase in the production of high-quality blastocysts via IVF, that would reduce barriers to treatment access through higher cumulative success rates and lower treatment repetitions. The observed increase in hyperactivation combined with the safety profile of HyperSperm supports its potential for future adoption in reproductive clinics. Trial registration number not applicable

P-035 Catecholamine neuroreceptors are differentially located in functional regions of the human sperm

Abstract Study question How are the expression and distribution of Adrenergic and Dopamine receptors in human sperm cells? Summary answer Using ultra-high-resolution microscopy techniques, we identified that each type of catecholamine receptor is expressed in a different functional region of the human sperm. What is known already Human sperm present complex cell signalling complexes with several neuroreceptors in their membrane. The spermatozoa is a terminal differentiated cell showing specialized regions optimized for physiological processes like motility, acrosome reaction and membrane fusion during fertilization. Although indirect methods have determined the presence of catecholamine receptors in human sperm, there is no direct evidence nor description of the exact localisation of these receptors. Catecholamine receptors are the direct target of medications used to treat very frequent health problems like hypertension (beta blockers), asthma (bronchodilators) and mental health disorders (antipsychotics and antidepressants). Study design, size, duration We design the study by developing new techniques that allow us to use high-resolution microscopes (i.e. Laser Scanning Confocal Microscopy LSCM and Field Emission Scanning Electron Microscopy or FE-SEM) to identify the localisation and distribution of catecholamine receptors. We determined sperm functional regions and quantified the relative amount of the different receptors on each one of those regions to perform a statistical analysis. Participants/materials, setting, methods After informed consent and ethical approval, sperm from young, healthy donors (n = 20) were included in the study. We used the neuroblastoma cell line SH-SY5Y as a positive control. Immunolabelling techniques used specific primary antibodies for each receptor, followed by the gold-conjugated secondary antibodies for FE-SEM. Negative controls were performed by omitting the primary antibody. In FE-SEM images, we quantify the number of gold nanoparticles in the sperm cells and the background. Main results and the role of chance We confirm the differential localisation of the different receptors studied. Dopamine D2 receptors are mainly expressed on the equatorial band of the acrosome, while beta-adrenergic receptors are restricted to the terminal piece of the flagellum. In both cases, the mean number of gold particles showed statistical differences (p < 0,001) between the region of expression and the rest of the regions and the background. Limitations, reasons for caution The present study only shows the presence of the receptors on the sperm plasma membrane. The activity of those receptors should be investigated by developing bioassays based on the use of agonists and/or antagonists. A more reliable genetic overexpression or knockout approach was impossible in human sperm. Wider implications of the findings The presence of receptors on restricted regions of the sperm suggests their participation in critical physiological events, like regulation of sperm motility hyperactivation or acrosome reaction. It may also suggest a possible side effect of beta-blockers or bronchodilators with the male fertility potential that needs to be investigated. Trial registration number not applicable

O-120 The role of CatSper in male infertility - from bench to bedsite and back

Abstract Infertility is on the rise, but the underlying causes still remain mostly unknown. In fact, for about one third of infertile men, semen parameters are within reference limits. This so called ‘unexplained male infertility’ seems to rest on elusive functional defects of the sperm undetectable by semen analysis, precluding early diagnosis of the infertility and evidence-based treatment by medically assisted reproduction (MAR). As a result, affected couples often experience failed MAR attempts, subjecting the ‘healthy’ female to recurring medical risks. We set out to gain insight into the pathomechanisms underlying unexplained male infertility. To this end, we systematically assessed the function of the sperm-specific multisubunit CatSper-channel complex in sperm of 2,300 men undergoing a fertility workup at our center, using a simple motility-based ‘CatSper-Test’ combined with [Ca2+]i fluorimetric and electrophysiological recordings. Thereby, we identified a group of men with normal semen parameters, but defective CatSper function. These men or couples failed to conceive naturally and upon MAR via intrauterine insemination and in vitro fertilization. Intracytoplasmic sperm injection (ICSI) was, ultimately, required to conceive a child. We revealed that the defective CatSper function was caused by variations in CATSPER genes. Moreover, we unveiled that CatSper-deficient human sperm were unable to undergo hyperactive motility and, therefore, failed to penetrate the egg coat. Thus, we provide the experimental evidence that sperm hyperactivation is required for human fertilization, explaining the infertility of CatSper-deficient men and need of ICSI for medically assisted reproduction. Finally, our study also revealed that defective CatSper function and ensuing failure to hyperactivate represents the most common cause of unexplained male infertility known thus far and that this sperm channelopathy can readily be diagnosed, enabling future evidence-based treatment of affected couples.

Hamster spermatozoa incorporate hypotaurine via TauT for self-protection.

Mammalian spermatozoa actively generate reactive oxygen species (ROS) during capacitation, a maturational process necessary for fertilization in vivo. This study shows that hypotaurine, a precursor of taurine present in the oviduct, is incorporated and concentrated in hamster sperm cells via the taurine transporter, TauT, for cytoprotection against self-produced ROS. To achieve fertilization competence, mammalian spermatozoa undergo capacitation, during which they actively generate reactive oxygen species (ROS). Therefore, mammalian spermatozoa must protect themselves from these self-generated ROS. The mammalian oviductal fluid is rich in hypotaurine, a taurine precursor, which reportedly protects mammalian spermatozoa, including those of hamsters, from ROS; however, its precise mechanism remains unknown. This study aimed to elucidate the mechanism underlying hypotaurine-mediated protection of spermatozoa from ROS using hamsters, particularly focusing on the taurine/hypotaurine transporter TauT. The effect of hypotaurine on sperm motility and ROS levels was tested using sperm motility analysis and the CellROX dye and luminol assays. RNA sequencing analysis was performed to verify TauT expression. We found that hypotaurine was necessary for maintaining sperm motility and hyperactivated motility. Hypotaurine did not scavenge extracellular ROS but lowered intracellular ROS levels and was incorporated and concentrated in hamster spermatozoa. TauT was detected at both mRNA and protein levels. β-Alanine blocked hypotaurine transport, increased intracellular ROS levels, and inhibited hyperactivation. Elimination of Na+ or Cl- ions inhibited hypotaurine transport and increased intracellular ROS levels. Thus, these results indicated that hamster spermatozoa incorporated and concentrated hypotaurine in sperm cells via TauT to protect themselves from self-generated ROS.

Membrane potential hyperpolarization: a critical factor in acrosomal exocytosis and fertilization in sperm within the female reproductive tract.

Hyperpolarization of the membrane potential (Em), a phenomenon regulated by SLO3 channels, stands as a central feature in sperm capacitation-a crucial process conferring upon sperm the ability to fertilize the oocyte. In vitro studies demonstrated that Em hyperpolarization plays a pivotal role in facilitating the mechanisms necessary for the development of hyperactivated motility (HA) and acrosomal exocytosis (AE) occurrence. Nevertheless, the physiological significance of sperm Em within the female reproductive tract remains unexplored. As an approach to this question, we studied sperm migration and AE incidence within the oviduct in the absence of Em hyperpolarization using a novel mouse model established by crossbreeding of SLO3 knock-out (KO) mice with EGFP/DsRed2 mice. Sperm from this model displays impaired HA and AE in vitro. Interestingly, examination of the female reproductive tract shows that SLO3 KO sperm can reach the ampulla, mirroring the quantity of sperm observed in wild-type (WT) counterparts, supporting that the HA needed to reach the fertilization site is not affected. However, a noteworthy distinction emerges-unlike WT sperm, the majority of SLO3 KO sperm arrive at the ampulla with their acrosomes still intact. Of the few SLO3 KO sperm that do manage to reach the oocytes within this location, fertilization does not occur, as indicated by the absence of sperm pronuclei in the MII-oocytes recovered post-mating. In vitro, SLO3 KO sperm fail to penetrate the ZP and fuse with the oocytes. Collectively, these results underscore the vital role of Em hyperpolarization in AE and fertilization within their physiological context, while also revealing that Em is not a prerequisite for the development of the HA motility, essential for sperm migration through the female tract to the ampulla.

Feature-based 3D+t descriptors of hyperactivated human sperm beat patterns

The flagellar movement of the mammalian sperm plays a crucial role in fertilization. In the female reproductive tract, human spermatozoa undergo a process called capacitation which promotes changes in their motility. Only capacitated spermatozoa may be hyperactivated and only those that transition to hyperactivated motility are capable of fertilizing the egg. Hyperactivated motility is characterized by asymmetric flagellar bends of greater amplitude and lower frequency. Historically, clinical fertilization studies have used two-dimensional analysis to classify sperm motility, despite the inherently three-dimensional (3D) nature of sperm motion. Recent research has described several 3D beating features of sperm flagella. However, the 3D motility pattern of hyperactivated spermatozoa has not yet been characterized. One of the main challenges in classifying these patterns in 3D is the lack of a ground-truth reference, as it can be difficult to visually assess differences in flagellar beat patterns. Additionally, it is worth noting that only a relatively small proportion, approximately 10-20% of sperm incubated under capacitating conditions exhibit hyperactivated motility. In this work, we used a multifocal image acquisition system that can acquire, segment, and track sperm flagella in 3D+t. We developed a feature-based vector that describes the spatio-temporal flagellar sperm motility patterns by an envelope of ellipses. The classification results obtained using our 3D feature-based descriptors can serve as potential label for future work involving deep neural networks. By using the classification results as labels, it will be possible to train a deep neural network to automatically classify spermatozoa based on their 3D flagellar beating patterns. We demonstrated the effectiveness of the descriptors by applying them to a dataset of human sperm cells and showing that they can accurately differentiate between non-hyperactivated and hyperactivated 3D motility patterns of the sperm cells. This work contributes to the understanding of 3D flagellar hyperactive motility patterns and provides a framework for research in the fields of human and animal fertility.

Both protein and non-protein components in extracellular vesicles of human seminal plasma improve human sperm function via CatSper-mediated calcium signaling.

What is the significance and mechanism of human seminal plasma extracellular vesicles (EVs) in regulating human sperm functions? EV increases the intracellular Ca2+ concentrations [Ca2+]i via extracellular Ca2+ influx by activating CatSper channels, and subsequently modulate human sperm motility, especially hyperactivated motility, which is attributed to both protein and non-protein components in EV. EVs are functional regulators of human sperm function, and EV cargoes from normal and asthenozoospermic seminal plasma are different. Pre-fusion of EV with sperm in the acidic and non-physiological sucrose buffer solution could elevate [Ca2+]i in human sperm. CatSper, a principle Ca2+ channel in human sperm, is responsible for the [Ca2+]i regulation when sperm respond to diverse extracellular stimuli. However, the role of CatSper in EV-evoked calcium signaling and its potential physiological significance remain unclear. EV isolated from the seminal plasma of normal and asthenozoospermic semen were utilized to investigate the mechanism by which EV regulates calcium signal in human sperm, including the involvement of CatSper and the responsible cargoes in EV. In addition, the clinical application potential of EV and EV protein-derived peptides were also evaluated. This is a laboratory study that went on for more than 5 years and involved more than 200 separate experiments. Semen donors were recruited in accordance with the Institutional Ethics Committee on human subjects of the Affiliated Hospital of Nantong University and Jiangxi Maternal and Child Health Hospital. The Flow NanoAnalyzer, western blotting, and transmission electron microscope were used to systematically characterize seminal plasma EV. Sperm [Ca2+]i responses were examined by fluorimetric measurement. The whole-cell patch-clamp technique was performed to record CatSper currents. Sperm motility parameters were assessed by computer-assisted sperm analysis. Sperm hyperactivation was also evaluated by examining their penetration ability in viscous methylcellulose media. Protein and non-protein components in EV were analyzed by liquid chromatography-mass spectrum. The levels of prostaglandins, reactive oxygen species, malonaldehyde, and DNA integrity were detected by commercial kits. EV increased [Ca2+]i via an extracellular Ca2+ influx, which could be suppressed by a CatSper inhibitor. Also, EV potentiated CatSper currents in human sperm. Furthermore, the EV-in [Ca2+]i increase and CatSper currents were absent in a CatSper-deficient sperm, confirming the crucial role of CatSper in EV induced Ca2+ signaling in human sperm. Both proteins and non-protein components of EV contributed to the increase of [Ca2+]i, which were important for the effects of EV on human sperm. Consequently, EV and its cargos promoted sperm hyperactivated motility. In addition, seminal plasma EV protein-derived peptides, such as NAT1-derived peptide (N-P) and THBS-1-derived peptide (T-P), could activate the sperm calcium signal and enhance sperm function. Interestingly, EV derived from asthenozoospermic semen caused a lower increase of [Ca2+]i than that isolated from normal seminal plasma (N-EV), and N-EV significantly improved sperm motility and function in both asthenozoospermic samples and frozen-thawed sperm. N/A. This was an in vitro study and caution must be taken when extrapolating the physiological relevance to in vivo regulation of sperm. Our findings demonstrate that the CatSper-mediated-Ca2+ signaling is involved in EV-modulated sperm function under near physiological conditions, and EV and their derivates are a novel CatSper and sperm function regulators with potential for clinical application. They may be developed to improve sperm motility resulting from low [Ca2+]i response and/or freezing and thawing. This research was supported by the National Natural Science Foundation of China (32271167), the Social Development Project of Jiangsu Province (BE2022765), the Nantong Social and People's Livelihood Science and Technology Plan (MS22022087), the Basic Science Research Program of Nantong (JC22022086), and the Jiangsu Innovation and Entrepreneurship Talent Plan (JSSCRC2021543). The authors declare no conflict of interest.

Analysis of Ca2+-mediated sperm motility to evaluate the functional normality of the sperm-specific Ca2+ channel, CatSper.

Ca2+ is a key secondary messenger that modulates sperm motility by tuning flagellar movement in various species. The sperm-specific Ca2+ channel, CatSper, is a primary Ca2+ gate that is essential for male fertility in mammals. CatSper-mediated Ca2+ signaling enables sperm to develop hyperactivated motility and fertilize the eggs in the female tract. Therefore, altered CatSper function compromises the entry of Ca2+ into the sperm, followed by impairing hyperactivation and male fertility. However, methods to evaluate the function of the CatSper channel are limited to patch clamping and functional imaging using Ca2+ dye. Previous studies have revealed that various parameters for sperm motility are highly correlated with intracellular Ca2+ levels in mouse. Here, I cover a step-by-step protocol to analyze the change in Ca2+-mediated sperm motility by using computer-assisted semen analysis (CASA) to evaluate the functional normality of the CatSper channel in sperm. This approach analyzes sperm motility parameters during intracellular Ca2+ chelation followed by in vitro capacitation to recover intracellular Ca2+ via the activated CatSper channel. Thus, this Ca2+-handling method is handy and could be broadly applied in reproductive biology labs and clinics that have CASA equipment to examine the functional normality of the CatSper channel.

The influence of lifestyle and biological factors on semen variability

PurposeSemen parameters are subjected to within-individual variability over time. The driving factors for this variability are likely multi-factorial, with healthier lifestyle associated with better semen quality. The extent in which variations in individual’s lifestyle contributes to within-individual semen variability is unknown.MethodsA total of 116 repeat semen samples from 29 men aged 19–37 over 6 months were collected. Basic semen analysis as per 5th WHO manual and extended semen parameters (sperm DNA fragmentation, redox potential and lipid peroxidation, sperm binding to hyaluronan and hyperactive motility) were assessed. An additional 39 lifestyle/biological factors (weight, blood pressure, etc.) were collected at each sample including validated health questionnaires SF36 Health Status, Australian Recommend Food Score, and International Physical Activity Questionnaire.ResultsOnly 10 out of the 39 lifestyle factors varied within men across samples including age (P = 0.0024), systolic blood pressure (P = 0.0080), social functioning (P = 0.0340), energy (P = 0.0069), non-alcoholic caffeinated beverages (P = 0.0010), and nutrition (P < 0.0001). The only semen parameter that varied between collections was sperm morphology (coefficient of variation 23.8 (6.1–72.0), P < 0.05). We only observed weak (r < 0.3) to moderate (r > 0.3– < 0.6) correlations between lifestyle factors, including body mass index, waist circumference, nutrition, exercise, blood pressure and semen parameters including sperm count, progressive motility, and sperm DNA fragmentation (P < 0.05).ConclusionIn healthy men from the general population, semen quality and associated lifestyle factors do not significantly vary over 6 months, indicating that one semen sample is likely sufficient for determining male fertility in this population.

Human fertilization in vivo and in vitro requires the CatSper channel to initiate sperm hyperactivation.

The infertility of many couples rests on an enigmatic dysfunction of the man's sperm. To gain insight into the underlying pathomechanisms, we assessed the function of the sperm-specific multisubunit CatSper-channel complex in the sperm of almost 2,300 men undergoing a fertility workup, using a simple motility-based test. We identified a group of men with normal semen parameters but defective CatSper function. These men or couples failed to conceive naturally and upon medically assisted reproduction via intrauterine insemination and in vitro fertilization. Intracytoplasmic sperm injection (ICSI) was, ultimately, required to conceive a child. We revealed that the defective CatSper function was caused by variations in CATSPER genes. Moreover, we unveiled that CatSper-deficient human sperm were unable to undergo hyperactive motility and, therefore, failed to penetrate the egg coat. Thus, our study provides the experimental evidence that sperm hyperactivation is required for human fertilization, explaining the infertility of CatSper-deficient men and the need of ICSI for medically assisted reproduction. Finally, our study also revealed that defective CatSper function and ensuing failure to hyperactivate represents the most common cause of unexplained male infertility known thus far and that this sperm channelopathy can readily be diagnosed, enabling future evidence-based treatment of affected couples.

Pyruvate modulation of redox potential controls mouse sperm motility

Sperm gain fertilization competence in the female reproductive tract through a series of biochemical changes and a requisite switch from linear progressive to hyperactive motility. Despite being essential for fertilization, regulation of sperm energy transduction is poorly understood. This knowledge gap confounds interpretation of interspecies variation and limits progress in optimizing sperm selection for assisted reproduction. Here, we developed a model of mouse sperm bioenergetics using metabolic phenotyping data, quantitative microscopy, and spectral flow cytometry. The results define a mechanism of motility regulation by microenvironmental pyruvate. Rather than being consumed as a mitochondrial fuel source, pyruvate stimulates hyperactivation by repressing lactate oxidation and activating glycolysis in the flagellum through provision of nicotinamide adenine dinucleotide (NAD)+. These findings provide evidence that the transitions in motility requisite for sperm competence are governed by changes in the metabolic microenvironment, highlighting the unexplored potential of using catabolite combination to optimize sperm selection for fertilization.

Sperm Capacitation and Kinematics in Phodopus Hamsters.

This study was designed to analyze changes in the spermatozoa of three species of Phodopus hamsters incubated under different conditions. Cauda epididymal sperm were incubated for 4 h in modified Tyrode's medium containing albumin, lactate, pyruvate, and Hepes (mTALP-H), in the same medium with the addition of bicarbonate (mTALP-BH), or with bicarbonate and 20 ng/mL of progesterone (mTALP-BH+P4). Media with bicarbonate are believed to promote capacitation in rodent species. Sperm motility, viability, capacitation patterns, and kinematics were assessed at different times. Capacitation in live cells was quantified after staining with Hoechst 33258 and chlortetracycline. Patterns believed to correspond to non-capacitated cells (F pattern), capacitated, acrosome-intact cells (B pattern), and acrosome-reacted cells (AR pattern) were recognized. Kinematics were examined via computer-assisted sperm analysis (CASA). The results showed a decrease in total motility in all three species in different media, with a sharp decrease in progressive motility in bicarbonate-containing media (without or with progesterone), suggesting hyperactivated motion. However, none of the other signs of hyperactivation described in rodents (i.e., decrease in STR or LIN, together with an increase in ALH) were observed. F pattern cells diminished with time in all media and were generally lower in P. roborovskii and higher in P. campbelli. B pattern cells increased in mTALP-BH media in all species. Progesterone did not enhance the percentage of B pattern cells. Finally, AR pattern cells increased in all species incubated in different media, showing the highest percentage in P. roborovskii and the lowest in P. campbelli. Comparisons between media revealed that there were higher percentages of F pattern cells and lower percentages of B pattern cells over time in medium without bicarbonate (mTALP-H) in comparison to media containing bicarbonate (mTALP-BH; mTALP-BH+P4). Overall, changes consistent with the acquisition of capacitation and development of hyperactivated motility were found; however, further studies are required to better characterize media necessary to support the pathways involved in these processes in Phodopus species.

Bacterial production of recombinant contraceptive vaccine antigen from CatSper displayed on a human papilloma virus-like particle

CatSper is a voltage dependent calcium ion channel present in the principal piece of sperm tail. It plays a crucial role in sperm hyperactivated motility and so in fertilization. Extracellular loops of mouse sperm CatSper were used to develop a vaccine to achieve protection from pregnancy. These loops were inserted at one of the three hypervariable regions of Human Papilloma Virus (HPV) capsid protein (L1). Recombinant vaccines were expressed in E.coli as inclusion body (IB), purified, refolded and assembled into virus-like particles (VLP) in vitro, and adsorbed on alum. Four vaccine candidates were tested in Balb/C mice. All the constructs proved immunogenic, one showed contraceptive efficacy. This recombinant contraceptive vaccine is a non-hormonal intervention and is expected to give long-acting protection from undesired pregnancies.

Effects of Benzo[a]pyrene on Human Sperm Functions: An In Vitro Study.

Benzo(a)pyrene (BaP) is considered one of the most dangerous air pollutants for adverse health effects, including reproductive toxicity. It is found both in male and female reproductive fluids likely affecting spermatozoa after the selection process through cervical mucus, a process mimicked in vitro with the swim-up procedure. In vitro effects of BaP (1, 5, 10 µM) were evaluated both in unselected and swim-up selected spermatozoa after 3 and 24 h of incubation. BaP reduced total, progressive and hyperactivated motility and migration in a viscous medium both in swim-up selected and unselected spermatozoa. Viability was not significantly affected in swim-up selected but was reduced in unselected spermatozoa. In swim-up selected spermatozoa, increases in the percentage of spontaneous acrosome reaction and DNA fragmentation were observed after 24 h of incubation, whereas no differences between the control and BaP-treated samples were observed in caspase-3 and -7 activity, indicating no effects on apoptotic pathways. ROS species, evaluated by staining with CellROX® Orange and Dihydroethidium, did not differ in viable spermatozoa after BaP treatment. Conversely, the percentage of unviable ROS-positive spermatozoa increased. Our study suggests that BaP present in male and female genital fluids may heavily affect reproductive functions of human spermatozoa.

A CUG-initiated CATSPERθ functions in the CatSper channel assembly and serves as a checkpoint for flagellar trafficking

Calcium signaling is critical for successful fertilization. In spermatozoa, calcium influx into the sperm flagella mediated by the sperm-specific CatSper calcium channel is necessary for hyperactivated motility and male fertility. CatSper is a macromolecular complex and is repeatedly arranged in zigzag rows within four linear nanodomains along the sperm flagella. Here, we report that the Tmem249-encoded transmembrane (TM) domain-containing protein, CATSPERθ is essential for the CatSper channel assembly during sperm tail formation. CATSPERθ facilitates the channel assembly by serving as a scaffold for a pore-forming subunit CATSPER4. CATSPERθ is specifically localized at the interface of a CatSper dimer and can self-interact, suggesting its potential role in CatSper dimer formation. Male mice lacking CATSPERθ are infertile because the sperm lack the entire CatSper channel from sperm flagella, rendering sperm unable to hyperactivate, regardless of their normal expression in the testis. In contrast, genetic abrogation of any of the other CatSper TM subunits results in loss of CATSPERθ protein in the spermatid cells during spermatogenesis. CATSPERθ might act as a checkpoint for the properly assembled CatSper channel complex to traffic to sperm flagella. This study provides insights into the CatSper channel assembly and elucidates the physiological role of CATSPERθ in sperm motility and male fertility.

Ameliorative effect of chitosan nanoparticles in capacitation media on post-thawing in vitro fertilizing ability of bovine spermatozoa.

This study aimed to investigate the effect of supplementation of chitosan nanoparticles (CSNPs) on the capacitation of bovine spermatozoa during the in vitro fertilization process. Hyperactivated motility (HAM) and acrosome reaction (AR) of sperm cells as well as in vitro fertilization and cleavage rates are the main parameters used to estimate the effect of CSNPs on bovine spermatozoa's fertilizing ability. In this study, three different concentrations of CSNPs (10, 20 and 100 μg/mL) were prepared and characterized. Motile spermatozoa were separated from frozen-thawed semen by a swim-up technique and capacitated in Sperm-TALP medium supplemented with heparin only without CSNPs treatment (positive control), heparin + 10 μg/mL CSNPs, heparin + 20 μg/mL CSNPs, heparin + 100 μg/mL CSNPs and the last one served as a negative control tube which supplemented with 10 μg/mL CSNPs without adding heparin. Sperm cells were incubated for 90 min at 39°C in a 5% CO2 incubator and evaluated every 30 min at intervals. Cumulus oophorus complex (COCs) were matured in a 5% CO2 incubator at 39°C and inseminated in vitro with frozen-thawed bull sperm of the above concentrations. The inseminated oocytes were incubated at 39°C in a 5% CO2 incubator for 24 h and then examined for evidence of fertilization. The results of this investigation showed that HAM and AR were best affected by CSNPs at a concentration of 20 μg/mL during an incubation time of 60 min. As time went on, the overall proportion of spermatozoa with progressive motility (PM) decreased across all groups, and a substantially lower value was found at the dose mentioned above. Additionally, the impact of sperm treated with CSNPs on fertilization rate was assessed. The outcomes demonstrated that in comparison to the other concentrations (10 and 100 μg/mL), the positive control and the negative control, the proportion of fertilized oocytes was significantly higher in the CSNPs concentration (20 μg/mL). In conclusion, it could be inferred from this investigation that CSNPs support sperm functions during IVF and can be used for biomedical interventions in bovine spermatozoa. Additionally, a high IVF rate was achieved by using sperm treated with CSNPs as CSNPs enhance sperm capacitation and acrosome reaction.

P-056 Oxidative stress and human semen quality: new results for diagnostic process of male infertility

Abstract Study question Is oxidative stress (OS) evaluated in human spermatozoa a predictive marker of better semen quality? Summary answer CellROX®Orange is a new fluorescent probe able to detect Reactive Oxygen Species (ROS) identifying a viable oxidized sperm fraction related to a better sperm performance. What is known already OS, defined as an unbalance between ROS production and antioxidant defences, is considered one of the causes of male infertility. OS evaluation in spermatozoa represents an important goal of research in this field because this parameter could be helpful to predict sperm fertilization ability to improve Assisted Reproductive Technology outcomes. By using different probes and methods for OS evaluation in spermatozoa or in semen, several studies were performed demonstrating a negative role of ROS on sperm functions. Such studies were not conclusive for the small number of included subjects, the high variability in the cohorts and the lack of validation. Study design, size, duration An observational study was conducted on 121 semen samples from patients undergoing routine semen analysis for couple infertility in the Andrology Laboratory of Careggi University Hospital of Florence from September 2021 to March 2022. Washed and Swim-up selected spermatozoa were incubated with two fluorescent probes, CellROX® Orange and Dihydroethidium (DHE), and revealed by flow cytometry. Participants/materials, setting, methods After routine semen analysis, the percentage of oxidized spermatozoa was evaluated with CellROX® Orange and DHE, and then correlated with standard semen parameters and sperm DNA fragmentation (sDF, evaluated by TUNEL/PI). Sperm kinematic parameters and hyperactivated motility were also assessed by C.A.S.A. system. Furthermore, CellROX® Orange positivity and phosphatidylserine membrane exposure (determined by Annexin V staining) or Caspase 3 and 7 activities (measured by FLICA™) were concomitantly evaluated. Main results and the role of chance We demonstrated that CellROX® Orange is able to detect hydrogen peroxide only in viable spermatozoa and the percentage of CellROX® Orange positive spermatozoa were positively associated with semen quality and negatively with sDF. To confirm these results, we performed the same experiments by using DHE, another probe which reveals hydrogen peroxide and superoxide anion in both viable and unviable cells. Similarly to CellROX® Orange, a positive correlation with semen quality and a negative one with sDF were found in viable spermatozoa. Conversely, in unviable spermatozoa, opposite associations were observed. These results indicate that oxidative status revealed by the two probes is related to a better sperm quality. To further investigate this possibility, we double labelled spermatozoa with CellROX® Orange and Annexin V (a marker of early signs of apoptosis) as well as with CellROX® Orange and FLICA™ (that detects caspase activity, a late sign of apoptosis). We found that CellROX® Orange mostly identifies spermatozoa without apoptotic features. Furthermore, we evaluated CellROX® Orange positivity in Swim-up selected spermatozoa, finding significantly higher levels in these samples respect to unselected samples, demonstrating once again that this probe identifies spermatozoa with better quality. Limitations, reasons for caution Our results indicate that within the viable oxidized spermatozoa there are cells with physiological and non-physiological intracellular ROS levels, however, they do not explain at what levels ROS cease to be functional and become deleterious for spermatozoa. Wider implications of the findings ROS evaluation in viable spermatozoa with the commercially available probes CellROX® Orange and DHE, allows the identification of the oxidized sperm fraction related to a sperm better performance. Therefore, the two probes may be useful to determine such fraction, likely improving the diagnostic process of male infertility. Trial registration number not applicable