The nature of human sperm head vacuoles: a systematic literature review

Different Nuclear Architecture in Human Sperm According to Their Morphology

Human sperm parameters serve as a first step in diagnosing male infertility, but not in determining the potential for successful pregnancy during assisted reproductive technologies (ARTs) procedures. Here, we investigated the relationship between sperm head morphology at high magnification, based on strict morphologic criteria, and the nuclear architecture analyzed by fluorescence in situ hybridization (FISH). We included five men. Two of them had an elevated high-magnification morphology score of 6 points (Score 6) indicating high fertility potential, whereas three had a low score of 0 points (Score 0), indicating low fertility potential. We used FISH to study the inter-telomeric distance and the chromosomal territory area of chromosome 1 (Chr. 1). We then compared these two parameters between subjects with high and low scores. FISH data analysis showed that the inter-telomeric distance (ITD) and chromosomal territory area (CTA) of Chr. 1 were significantly higher in subjects with low scores (score 0) than high scores (score 6). Our results suggest that (i) there is a link between nuclear architecture and sperm head abnormalities, particularly vacuoles; and (ii) it is possible to select spermatozoa with normal nuclear architecture, which might indirectly explain the positive ART outcomes observed with this technique.

Fast Noninvasive Morphometric Characterization of Free Human Sperms Using Deep Learning

The selection of high-quality sperms is critical to intracytoplasmic sperm injection, which accounts for 70–80% of in vitro fertilization (IVF) treatments. So far, sperm screening is usually performed manually by clinicians. However, the performance of manual screening is limited in its objectivity, consistency, and efficiency. To overcome these limitations, we have developed a fast and noninvasive three-stage method to characterize morphology of freely swimming human sperms in bright-field microscopy images using deep learning models. Specifically, we use an object detection model to identify sperm heads, a classification model to select in-focus images, and a segmentation model to extract geometry of sperm heads and vacuoles. The models achieve an F1-score of 0.951 in sperm head detection, a z-position estimation error within ±1.5 μm in in-focus image selection, and a Dice score of 0.948 in sperm head segmentation, respectively. Customized lightweight architectures are used for the models to achieve real-time analysis of 200 frames per second. Comprehensive morphological parameters are calculated from sperm head geometry extracted by image segmentation. Overall, our method provides a reliable and efficient tool to assist clinicians in selecting high-quality sperms for successful IVF. It also demonstrates the effectiveness of deep learning in real-time analysis of live bright-field microscopy images.

Human Sperm Morphology as a Marker of Its Nuclear Quality and Epigenetic Pattern

Background: Human sperm chromatin condensation is a sum of epigenetic events that allows for the near-complete replacement of histones with protamines. Under high-magnification microscopy, nuclear vacuoles have been described as thumbprints with poor chromatin condensation. The objective of this study is to examine whether vacuolated spermatozoa carry specific epigenetic marks, which may influence embryo development. Methods: The presence and three-dimensional distribution of ten epigenetic marks (protamine-P2, histone-H3, H3K4me1/me2/me3, H3K9me1/me2/me3, H3K27me3, H4k20me2) were evaluated and compared in morphometrically normal spermatozoa according to the presence or absence of a large vacuole occupying more than 15% of the head surface (n = 4193). Results: Vacuolated spermatozoa were significantly more frequently labelled with H3 and H3K4me3 than normal spermatozoa (88.1% ± 2.7 and 78.5% ± 5.2 vs. 74.8% ± 4.8 and 49.1% ± 7.4, respectively; p = 0.009 and p < 0.001) and significantly less marked by P2 and H3K27me3 (50.2% ± 6.2 and 63.9% ± 6.3 vs. 82.1% ± 4.4 and 73.6% ± 5.1, respectively; p < 0.001 and p = 0.028). In three dimensions, vacuoles are nuclear concavities filled with DNA carrying the H3K4me3 marker. Conclusion: High-magnification microscopy is a simple tool to estimate in real time the sperm epigenetic profile. The selection of normal spermatozoa without vacuoles and the deselection of spermatozoa with vacuoles appear to be epigenetically favorable to embryo development and safe offspring.

Viscous Cervical Environment-on-a-Chip for Selecting High-Quality Sperm from Human Semen

When ejaculated sperm travels through the vagina to the uterus, mucus secreted by the cervical canal generally filters out sperm having low motility and poor morphology. To investigate this selection principle in vivo, we developed a microfluidic sperm-sorting chip with a viscous medium (polyvinylpyrrolidone: PVP) to imitate the biophysical environment mimic system of the human cervical canal. The material property of the PVP solution was tuned to the range of viscosities of cervical mucus using micro-viscometry. The selection of high-quality human sperm was experimentally evaluated in vitro and theoretically analyzed by the convection-diffusion mechanism. The convection flow is shown to be dominant at low viscosity of the medium used in the sperm-sorting chip when seeded with raw semen; hence, the raw semen containing sperm and debris convectively flow together with suppressed relative dispersions. Also, it was observed that the sperm selected via the chip not only had high motilities but also normal morphologies and high DNA integrity. Therefore, the biomimetic sperm-sorting chip with PVP medium is expected to improve male fertility by enabling the selection of high-quality sperm as well as uncovering pathways and regulatory mechanisms involved in sperm transport through the female reproductive tract for egg fertilization.

Molecular Profiling of Spermatozoa Reveals Correlations between Morphology and Gene Expression: A Novel Biomarker Panel for Male Infertility

Choosing spermatozoa with an optimum fertilizing potential is one of the major challenges in assisted reproductive technologies (ART). This selection is mainly based on semen parameters, but the addition of molecular approaches could allow a more functional evaluation. To this aim, we used sixteen fresh sperm samples from patients undergoing ART for male infertility and classified them in the high- and poor-quality groups, on the basis of their morphology at high magnification. Then, using a DNA sequencing method, we analyzed the spermatozoa methylome to identify genes that were differentially methylated. By Gene Ontology and protein-protein interaction network analyses, we defined candidate genes mainly implicated in cell motility, calcium reabsorption, and signaling pathways as well as transmembrane transport. RT-qPCR of high- and poor-quality sperm samples allowed showing that the expression of some genes, such as AURKA, HDAC4, CFAP46, SPATA18, CACNA1C, CACNA1H, CARHSP1, CCDC60, DNAH2, and CDC88B, have different expression levels according to sperm morphology. In conclusion, the present study shows a strong correlation between morphology and gene expression in the spermatozoa and provides a biomarker panel for sperm analysis during ART and a new tool to explore male infertility.

Association between early embryo morphokinetics plus transcript levels of sperm apoptotic genes and clinical outcomes in IMSI and ICSI cycles of male factor patients

PURPOSE

The aim was to assess the correlation of sperm apoptotic transcript levels with cleavage stage embryokinetic and pregnancy outcomes of intracytoplasmic morphologically selected sperm injection (IMSI) and ICSI methods in patients with male factor infertility.

MATERIAL AND METHODS

Eighty male factor cases were divided into ICSI and IMSI groups. ICSI was done routinely, and for IMSI, sperm was selected at high magnification and injected. On day 3, time-lapse parameters were evaluated, and the best embryos were transferred and followed to delivery. In addition, sperm DNA fragmentation and apoptotic transcript levels were quantified using reverse transcription Q-PCR between the groups.

RESULTS

IMSI selected spermatozoa had lower DNA fragmentation and apoptotic transcript levels compared with ICSI (p < 0.0001). Moreover, all cytokinetic variables and cleavage abnormalities were noticeably different between groups (p < 0.0001); the rates of clinical outcomes were higher in the IMSI group. The transcript levels of Caspase 3 showed a moderate negative correlation with s2 and s3 (rs = - 0.57, P = 0.008 and rs = - 0.51, p = 0.021, respectively) in the IMSI group. However, there was no relationship between sperm apoptotic transcript levels and clinical outcomes in two groups.

CONCLUSIONS

Sperms selected at high magnification showed lower DNA fragmentation and apoptosis genes transcript. Also, better embryo kinetics and clinical outcomes were confirmed in IMSI than ICSI groups. Some time-lapse parameters may be associated with transcript levels of apoptosis genes. Therefore, these noninvasive techniques may be unique in assisting couples with male factor infertility.

TRIAL REGISTRATION

This trial retrospectively registered on 4 July 2020 (IRCT20180130038561N1).

SPANX-A/D protein subfamily plays a key role in nuclear organisation, metabolism and flagellar motility of human spermatozoa

Human sperm protein associated with the nucleus on the X chromosome (SPANX) genes encode a protein family (SPANX-A, -B, -C and -D), whose expression is limited to the testis and spermatozoa in normal tissues and to a wide variety of tumour cells. Present only in hominids, SPANX-A/D is exclusively expressed in post-meiotic spermatids and mature spermatozoa. However, the biological role of the protein family in human spermatozoa is largely unknown. Combining proteomics and molecular approaches, the present work describes the presence of all isoforms of SPANX-A/D in human spermatozoa and novel phosphorylation sites of this protein family. In addition, we identify 307 potential SPANX-A/D interactors related to nuclear envelop, chromatin organisation, metabolism and cilia movement. Specifically, SPANX-A/D interacts with fumarate hydratase and colocalises with both fumarate hydratase and Tektin 1 proteins, involved in meeting energy demands for sperm motility, and with nuclear pore complex nucleoporins. We provide insights into the molecular features of sperm physiology describing for the first time a multifunctional role of SPANX-A/D protein family in nuclear envelope, sperm movement and metabolism, considered key functions for human spermatozoa. SPANX-A/D family members, therefore, might be promising targets for sperm fertility management.

In vitro study of effects of ELF-EMF on testicular tissues of roe deer (Capreolus capreolus) - FTIR and FT-Raman spectroscopic investigation

Electromagnetic fields (EMF) are classified as an environmental factor affecting living organisms. The aim of the study was to evaluate the effect of EMF at different frequencies (50 and 120 Hz), durations of treatment (2 and 4 h) and with the magnetic induction of 8 m T on testicular tissues of roe deer (Capreolus capreolus) in vitro by comparison with the control samples. Fourier Transform Raman Spectroscopy (FT-Raman) and Fourier Transform Infrared Spectroscopy (FTIR) were utilized in this study to identify the chemical changes in the testicular tissues. The FTIR and FT-Raman spectroscopy methods were used to evaluate differences in spectra of the treated tissues compared to the control group. The results from the analysis of the spectra indicated there were characteristic differences in the testicular tissue compared with the control samples. There was identification of peaks attributed to different biochemical components. Comparing the spectra for different frequencies and treatment times, there was a greater intensity of peaks originating from most of the functional groups in the tissues evaluated. With the FTIR spectra, there were five of 15 peaks, while with the FT-Raman spectra, there were six of ten peaks that were shifted. For FTIR and FT-Raman analyzed spectral ranges, results from the PCA analysis indicate there was no similarity between control groups (2 and 4 h) and samples treated with EMF at a frequency of 120 Hz for 2 and 4 h. In conclusion, therefore, EMF is an environmental factor affecting the testis of roe deer.

Automated Non-Invasive Measurement of Single Sperm's Motility and Morphology

Measuring cell motility and morphology is important for revealing their functional characteristics. This paper presents automation techniques that enable automated, non-invasive measurement of motility and morphology parameters of single sperm. Compared to the status quo of qualitative estimation of single sperm's motility and morphology manually, the automation techniques provide quantitative data for embryologists to select a single sperm for intracytoplasmic sperm injection. An adapted joint probabilistic data association filter was used for multi-sperm tracking and tackled challenges of identifying sperms that intersect or have small spatial distances. Since the standard differential interference contrast (DIC) imaging method has side illumination effect which causes inherent inhomogeneous image intensity and poses difficulties for accurate sperm morphology measurement, we integrated total variation norm into the quadratic cost function method, which together effectively removed inhomogeneous image intensity and retained sperm's subcellular structures after DIC image reconstruction. In order to relocate the same sperm of interest identified under low magnification after switching to high magnification, coordinate transformation was conducted to handle the changes in the field of view caused by magnification switch. The sperm's position after magnification switch was accurately predicted by accounting for the sperm's swimming motion during magnification switch. Experimental results demonstrated an accuracy of 95.6% in sperm motility measurement and an error <10% in morphology measurement.

TUNEL labeling with BrdUTP/anti-BrdUTP greatly underestimates the level of sperm DNA fragmentation in semen evaluation

Many studies have now confirmed that sperm DNA fragmentation (SDF) is associated with a poorer outcome of some forms of assisted reproduction technology. For this reason, SDF is an important parameter to evaluate in male fertility assessment. TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) assay coupled to flow cytometry is one of the most promising methods for SDF quantification. Several kits for the detection of DNA fragmentation are currently available on the market and all are recommended as equally appropriate to quantify SDF. In this work we compared for the first time the efficacy of two different types of TUNEL kits for SDF quantification: one using an indirect antibody-based labeling system (BrdUTP/fluorescein-anti-BrdUTP) and another using a direct labeling system (fluorescein-dUTP). We demonstrated that TUNEL indirect labeling system largely underestimates SDF when compared with the direct labeling, the differences ranging from 19.2% to 85.3% (p<0.05, n = 22). We observed that these differences were most pronounced among dead spermatozoa where indirect labeling stained 40.1% [23.6%, 58.2%] and the direct system 65.7% [36.5%, 90.9%] (n = 10, p<0.05). Interestingly, we found that both systems stained the living spermatozoa with the same efficiency. We showed that the differences are due to the steric hindrance of the antibody during its binding to the BrdUTP. Indeed, after sperm DNA decondensation, the percentages of TUNEL positivity increased significantly from 46.3% [31.8%, 61.7%] to 97.5% [96.1%, 98.8%] (p<0.05, n = 5). Our results are important for future use of TUNEL in clinical practice. Laboratories relying on the use of an antibody-based system heavily underestimate SDF, most particularly in infertile patients with reduced sperm motility. As a consequence, the kit using BrdUTP/fluorescein-anti-BrdUTP should not be recommended as a method to assay DNA damage in semen. This study represents one further step in the standardization of TUNEL among laboratories.

The IMSI Procedure Improves Laboratory and Clinical Outcomes Without Compromising the Aneuploidy Rate When Compared to the Classical ICSI Procedure

PURPOSE

The intracytoplasmic morphologically selected sperm injection (IMSI) procedure has been associated with better laboratory and clinical outcomes in assisted reproduction technologies. Less information is available regarding the relationship between embryo aneuploidy rate and the IMSI procedure. The aim of this study is to compare the clinical outcomes and chromosomal status of IMSI-derived embryos with those obtained from intracytoplasmic sperm injection (ICSI) in order to establish a clearer view of the benefits of IMSI in infertile patients.

METHODS

We retrospectively analyzed a total of 11 cycles of IMSI and 20 cycles of ICSI with preimplantation genetic diagnosis. The fertilization rate, cleavage rate, embryo quality, blastocyst development, aneuploidy rate, pregnancy rate, implantation rate, and miscarriage rate were compared between the groups.

RESULTS

Similar rates of fertilization (70% and 73%), cleavage (98% and 100%), and aneuploidy (76.9% and 70.9%) were observed in the IMSI and ICSI groups, respectively. The IMSI group had significantly more good quality embryos at day 3 (95% vs 73%), higher blastocyst development rates (33% vs 19%), and greater number of hatching blastocysts (43% vs 28%), cycles with at least one blastocyst at day 5 (55% vs 35%), and blastocysts with good trophoectoderm morphology (21% vs 6%) compared with the ICSI group (P < 0.001). Significantly higher implantation rates were observed in the IMSI group compared with the ICSI group (57% vs 27%; P < 0.05). Pregnancy and miscarriage rates were similar in both groups (80% vs 50% and 0% vs 33%, respectively).

CONCLUSION

The IMSI procedure significantly improves the embryo quality/development by increasing the implantation rates without affecting the chromosomal status of embryos. There is a tendency for the IMSI procedure to enhance the pregnancy rates and lower the miscarriage rates when compared with ICSI.