The motility-based swim-up technique separates bull sperm based on differences in metabolic rates and tail length

A proteomic approach to identifying spermatozoa proteins in Indonesian native Madura bulls

Proteins assist sperm mature, transit the female reproductive tract, and recognise sperm oocytes. Indigenous Indonesian bulls, Madura bulls, have not been studied for reproductive proteomics. As local Indonesian beef livestock, Madura cattle assist in achieving food security; hence, their number must be improved. Thus, the identification of molecular proteomics-based bull fertility biomarkers is needed. This study aimed to characterise the sperm fertility function of the superior Madura bull (Bos indicus × Bos Javanicus) spermatozoa proteome. Frozen semen from eight Madura superior bulls (Bos indicus × Bos javanicus) aged 4-8 years was obtained from the artificial insemination centre (AIC) in Singosari and Lembang. Madura superior bulls are those that have passed the bull breeding soundness evaluation. Frozen sperm were thawed and centrifuged at 3000 × g for 30 min. Proteins in sperm were characterised through proteomic analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The resulting gene symbols for each protein were then subjected to bioinformatics tools, including UniProt, DAVID, and STRING databases. Regarding sperm fertility, the analysis revealed that 15 proteins were identified in the sperm of Madura bulls. Amongst the identified proteins, the superior Madura bull sperm contained several motilities, energy-related proteins, and chaperone proteins. A substantial portion of characterised proteins are linked to metabolic pathways and the tricarboxylic acid (TCA) cycle, contributing to sperm energy production. In conclusion, the first in-depth proteome identification of sperm related to sperm quality and bull fertility of a unique indigenous Madura breed of Indonesia was performed using the LC-MS/MS proteomic method. These findings may serve as a reference point for further studies related to the functions of bovine sperm and biomarkers of fertility and sperm quality.

Semen quality and frozen semen production in Pasundan bulls: A molecular weight perspective on seminal plasma and spermatozoa protein

Objective

To determine the correlation between the molecular weight (MW) of proteins in seminal plasma and spermatozoa and the quality of fresh and frozen semen production in Pasundan bulls.

Materials and methods

Nine selected Pasundan bulls, aged 5-10 years, from the Regional Artificial Insemination Center at Ciamis, West Java, Indonesia, were used in the study, with fresh semen sperm motility ≥70% and <70%. We analyzed the motility, viability, integrity of the intact plasma membrane (IPM), and the morphological characteristics of spermatozoa. 1D-SDS-PAGE analysis was performed to determine the protein profile by assessing MW, depicted as bands on the gel.

Results

The motility, viability, and IPM of spermatozoa had lower values (p < 0.05) in Pasundan bulls named Bagaskara and Kertarajasa compared to the other bulls. Proteins with MW 35-50 kDa were not detected in the seminal plasma of Pasundan bulls, exhibiting low quality in fresh semen. The correlation analysis showed that the non-detected proteins with MW 35-50 kDa in seminal plasma correlated with spermatozoa motility (r = 0.421), viability (r = 0.424), and IPM (r = 0.428) so that fresh semen quality was low in both Pasundan bulls. Analysis of semen volume, spermatozoa concentration, and spermatozoa motility showed that the average frozen semen production of Pasundan bulls per ejaculate was 128.73 ± 15.35 straws.

Conclusion

Protein analysis based on MW is a predictive indicator for the quality of fresh semen and the production of frozen semen in Pasundan bulls. Evaluation parameters of fresh semen quality by MW analysis can be used to select Pasundan bulls in Indonesia.

Impact of inclusion of post-spermatic ejaculate fraction in boar seminal doses on sperm metabolism, quality, and interaction with uterine fluid

Boar ejaculate is composed of sperm cells and seminal plasma (SP) and is emitted in different fractions (pre-sperm fraction; spermatic-rich fraction; intermediate fraction; post-spermatic fraction), with different composition of SP and volume, which could influence the sperm quality during seminal doses preparation, conservation, and interaction with the female reproductive tract. In artificial insemination (AI) centers, seminal doses are usually prepared with the spermatic-rich and intermediate fractions, but the inclusion of other ejaculate fractions, although controversial, is beginning to be applied. The objective was to evaluate the synergic effect of accumulative ejaculated fractions on sperm functionality during seminal doses preparation, throughout storage and after incubation with uterine fluid (UF). For this purpose, a total of 57 ejaculates were collected, and the following experimental groups were prepared (n = 19 per group): (F1) spermatic-rich fraction; (F2) F1 plus intermediate fraction; (F3) F2 plus post-spermatic fraction. Each group was stored for 5 days at ∼16 °C, and the following parameters were evaluated: sperm metabolism of pure and diluted semen (day 1), sperm quality parameters (days 1, 3, 5), thermal-resistance test (TRT) and incubation with uterine fluid (UF) (day 5). Sperm metabolic rates between accumulative ejaculate fractions from pure and diluted semen did not show differences. Also, sperm quality parameters were not affected by the ejaculate fraction during storage. However, sperm subjected to TRT showed similar results except for progressive motility, which was better in F2 and F3 than F1. When sperm were incubated with UF, the quality decreased in each group, but sperm from F2 and F3 were less affected than those from F1. In conclusion, the post-spermatic fraction can be included in seminal doses for their use in AI-centers, with functionality of sperm of different SP origins not being impaired throughout the storage, and responding better to thermal and UF stress. However, further research in AI-centers is necessary to test the sperm behaviour under presented conditions.

Comprehensive analysis of microRNA and metabolic profiles in bovine seminal plasma of different semen quality

Background

Seminal plasma plays a pivotal role in modulating sperm viability and function. However, the underlying mechanisms have not been fully elucidated.

Method

In this study, the bull semen production records of core breeding farms and bull stations in the past 10 years were analyzed.

Results

We found that the semen of 5-year-old bulls collected for the first time is of the best quality (p &lt; 0.05). Despite the bull semen collected under the above conditions, low-quality sperm is still obtained from part of bulls due to individual differences. Interestingly, seminal plasma from normal semen is capable of improving low-quality semen motility. To identify the potential key factors in seminal plasma, the differences in miRNA and metabolite profiles between normal and low-quality seminal plasma were analyzed. We found that 59 miRNAs were differently expressed, including 38 up-regulated and 21 down-regulated miRNAs. Three hundred and ninety-one and 327 significantly different metabolites were identified from the positive and negative ion models, respectively. These multiple miRNAs and metabolites collectively contribute to the motility of sperm, subsequently, affect semen quality.

Discussion

Together, these results not only revealed the critical factors of seminal plasma improving sperm quality but also provided potential miRNA- or metabolite-based biomarkers to identify the high semen quality.

Effect of bovine viral diarrhea virus biotypes exposure on bovine gametes in early embryonic development in vitro

Bovine viral diarrhea virus (BVDV) is an important viral agent causing reproductive failure in cattle. The objectives of the current study were to investigate the interaction between two BVDV biotypes, cytopathic (CP) and Non-cytopathic (NCP) and bovine gametes during in vitro fertilization (IVF) processing, the existence of the virus within embryonic cells and early embryonic development rates. Sperm and ova were exposed separately to CP and NCP BVDV at two concentrations of 10^4.5 and 10^5.5 tissue culture infectious dose 50.00% (TCID₅₀) mL^-1 prior to IVF, respectively. After five days post-IVF, early embryonic development rates of infected groups were assessed. Several embryos of each group, normal and degenerated, were selected for a viral assay using reverse transcription polymerase chain reaction technique. The result showed that the early embryonic development rates were decreased in treatment groups. The rates in the CP groups were lower than the NCP groups. In the CP groups, the proportions were, respectively, 10.00, 6.00 and 11.00, and 6.00% in the infected sperm and oocyte groups (10^4.5 and 10^5.5 TCID₅₀ mL^-1) that were higher than 50.00% in the control group. In NCP groups, the rates were, respectively, 25.00, 18.00 and 24.00, and 21.00% in the infected groups compared to 48.00% in the control group. In the CP groups, no BVDV was detected in normal embryos, whereas, all degenerated embryos were completely virus-positive. In the NCP groups, the virus was detected in both normal and degenerated embryos. In conclusion, this study supported detrimental impacts of CP and NCP BVDV on early embryonic development and the role of sperm and the zona pellucida layer as carriers of the virus.

Effect of High Viscosity on Energy Metabolism and Kinematics of Spermatozoa from Three Mouse Species Incubated under Capacitating Conditions

In order to sustain motility and prepare for fertilization, sperm require energy. The characterization of sperm ATP production and usage in mouse species revealed substantial differences in metabolic pathways that can be differentially affected by capacitation. Moreover, spermatozoa encounter different environments with varying viscoelastic properties in the female reproductive tract. Here, we examine whether viscosity affects sperm ATP levels and kinematics during capacitation in vitro. Sperm from three mouse species (Mus musculus, M. spretus, M. spicilegus) were incubated under capacitating conditions in a modified Tyrode's medium containing bicarbonate, glucose, pyruvate, lactate, and bovine serum albumin (mT-BH) or in a bicarbonate-free medium as a non-capacitating control. Viscosity was increased with the inclusion of polyvinylpyrrolidone. ATP was measured with a bioluminescence kit, and kinematics were examined with a computer-aided sperm analysis system. In M. musculus sperm, ATP declined during capacitation, but no differences were found between non-capacitating and capacitating sperm. In contrast, in M. spretus and M. spicilegus, ATP levels decreased in capacitating sperm. Increasing viscosity in the medium did not modify the timing or proportion of cells undergoing capacitation but did result in additional time- and concentration-dependent decreases in ATP in M. spretus and M. spicilegus under capacitating conditions. Additionally, increased viscosity altered both velocity and trajectory descriptors. The limited impact of capacitation and higher viscosity on M. musculus sperm ATP and kinematics could be related to the low intensity of postcopulatory sexual selection in this species. Responses seen in the other two species could be linked to the ability of their sperm to perform better under enhanced selective pressures.

Opportunities and Limits of Conventional IVF versus ICSI: It Is Time to Come off the Fence

Conventional IVF (c-IVF) is one of the most practiced assisted reproductive technology (ART) approaches used worldwide. However, in the last years, the number of c-IVF procedures has dropped dramatically in favor of intracytoplasmic sperm injection (ICSI) in cases of non-male-related infertility. In this review, we have outlined advantages and disadvantages associated with c-IVF, highlighting the essential steps governing its success, its limitations, the methodology differences among laboratories and the technical progress. In addition, we have debated recent insights into fundamental questions, including indications regarding maternal age, decreased ovarian reserve, endometriosis, autoimmunity, single oocyte retrieval-cases as well as preimplantation genetic testing cycles. The “overuse” of ICSI procedures in several clinical situations of ART has been critically discussed. These insights will provide a framework for a better understanding of opportunities associated with human c-IVF and for best practice guidelines applicability in the reproductive medicine field.

An evidence of Humanin-like peptide and Humanin mediated cryosurvival of spermatozoa in buffalo bulls

Buffalo spermatozoa are vulnerable to cryo-injuries due to inherent deficiency of endogenous antioxidants, high polyunsaturated fatty acids (PUFA) content in plasma membrane and low cholesterol/phospholipid (C/P) ratio. Humanin is a potent cytoprotective agent that protects the cells against oxidative stress and apoptosis. The present study was designed to establish the presence of Humanin in buffalo and effect of Humanin supplementation on freezability of buffalo spermatozoa. Indirect immunofluorescence test revealed presence of Humanin in ejaculated and epididymal spermatozoa, and, elongated spermatids and interstitial space in the testicular tissue section. Humanin levels in seminal plasma were significantly and positively correlated with sperm concentration and individual progressive motility (IPM) in good (n = 22; IPM >70%) and poor (n = 10; IPM <50%) quality ejaculates. For supplementation studies, a total of 24 ejaculates (IPM ≥70%) were collected and each ejaculate was then divided into four aliquots. First aliquot was diluted with egg yolk-tris-glycerol (EYTG) extender without Humanin and served as control group (Group I). Rest three aliquots were diluted with extender containing 2 (Group II), 5 (Group III) and 10 μM Humanin (Group IV), respectively. Semen was cryopreserved using standard protocol and evaluated at pre-freeze for lipid peroxidation (LPO) and post-thaw stages for spermatozoa kinematics, LPO, mitochondrial membrane potential (MMP), capacitation, apoptotic status and DNA integrity. The treatment group that showed best results (5 μM) was compared with control group for in vitro fertility assessment by homologous zona binding assay. The LPO levels were lower (p < 0.05) in 5 and 10 μM Humanin supplemented group. The MMP and DNA integrity were higher (p < 0.05) in 5 μM group than other groups. F-pattern was higher (p < 0.05) and B-pattern was lower (p < 0.05) in 5 and 10 μM Humanin supplemented groups. Lower apoptotic and higher viable spermatozoa (p < 0.05) were observed in 5 μM Humanin group. The mean number of spermatozoa bound to zona pellucida was higher (p < 0.05) in 5 μM Humanin treated group than the control group. The study established the presence of Humanin in buffalo spermatozoa and seminal plasma for very first time and concluded that Humanin supplementation at 5 μM concentration improves the freezability and in vitro fertility of buffalo spermatozoa.

Relationships between Biomarkers of Oxidative Stress in Seminal Plasma and Sperm Motility in Bulls before and after Cryopreservation

This study aimed at evaluating the relationship between biomarkers of oxidative stress (OS) in seminal plasma and sperm motility in bulls before and after cryopreservation. Three ejaculates per bull were collected from 20 young bulls. Each ejaculate was analyzed for motility before and after cryopreservation (by CASA), and the SP concentration of Advanced Oxidation Protein Products (AOPP), thiols, and carbonyl groups (CT) were examined. Then, based on their motility, the ejaculates were grouped into: high motility fresh (HMF), low motility fresh (LMF), high motility thawed (HMT), and low motility thawed (LMT) groups. Higher AOPP and thiol concentrations on SP were related (p < 0.05) to the higher LIN and BCF and lower ALH of fresh semen. In addition, AOPP and thiols were significantly higher in HMF than LMF. As a confirmation of this, the Receiver Operating Characteristic (ROC) curve analysis showed that AOPP and thiol concentrations in SP were able to discriminate between HMF and LMF ejaculates (Area Under the Curve of 71.67% and 72.04%, respectively). These observations give an alternative perspective on the relationship between sperm motility and the OS parameters of SP, which need further investigations.

Capacitation promotes a shift in energy metabolism in murine sperm

In mammals, sperm acquire fertilization ability after a series of physiological and biochemical changes, collectively known as capacitation, that occur inside the female reproductive tract. In addition to other requirements, sperm bioenergetic metabolism has been identified as a fundamental component in the acquisition of capacitation. Mammalian sperm produce ATP through two main metabolic processes, oxidative phosphorylation (OXPHOS) and aerobic glycolysis that are localized to two different flagellar compartments, the midpiece, and the principal piece, respectively. In mouse sperm, the occurrence of many events associated with capacitation relies on the activity of these two energy-producing pathways, leading to the hypothesis that some of these events may impose changes in sperm energetic demands. In the present study, we used extracellular flux analysis to evaluate changes in glycolytic and respiratory parameters of murine sperm that occur as a consequence of capacitation. Furthermore, we examined whether these variations affect sperm ATP sustainability. Our results show that capacitation promotes a shift in the usage ratio of the two main metabolic pathways, from oxidative to glycolytic. However, this metabolic rewiring does not seem to affect the rate at which the sperm consume ATP. We conclude that the probable function of the metabolic switch is to increase the ATP supply in the distal flagellar regions, thus sustaining the energetic demands that arise from capacitation.

Effect of a Novel Hydroxybenzoic Acid Based Mitochondria Directed Antioxidant Molecule on Bovine Sperm Function and Embryo Production

Sperm cells are particularly vulnerable to reactive oxygen species (ROS), impairing their fertilizing ability. Our objective was to study the effect of a novel mitochondrial-directed antioxidant, AntiOxBEN2, on bovine sperm function. This antioxidant was added to the semen capacitation medium (CAP), during the swim-up process, and to the fertilization medium (FERT) during the co-incubation of matured oocytes and capacitated spermatozoa, in concentrations of 0 (control), 1, and 10 µM. After the swim-up, sperm motility (CASA and visual analysis), vitality (eosin-nigrosin), mitochondrial membrane potential (JC1), intracellular ROS, adenosine triphosphate (ATP) levels, and basal metabolism (Seahorse Xfe96) were evaluated. Embryo development and quality were also assessed. Higher cleavage rates were obtained when 1 µM AntiOxBEN2 were added to CAP and FERT media (compared to control, p < 0.04). A positive effect of AntiOxBEN2 on intracellular ROS reduction (p = 0.01), on the increment of mitochondrial membrane potential (p ≤ 0.003) and, consequently, on the sperm quality was identified. However, the highest dose impaired progressive motility, ATP production, and the number of produced embryos. The results demonstrate a beneficial effect of AntiOxBEN2 (1 µM) on sperm capacitation and fertilization processes, thus improving embryonic development. This may constitute a putative novel therapeutic strategy to improve the outcomes of assisted reproductive techniques (ART).

Bundle formation of sperm: Influence of environmental factors

Cooperative behaviour of sperm is one of the mechanisms that plays a role in sperm competition. It has been observed in several species that spermatozoa interact with each other to form agglomerates or bundles. In this study, we investigate the effect of physical and biochemical factors that will most likely promote bundle formation in bull sperm. These factors include fluid viscosity, swim-up process, post-thaw incubation time and media additives which promote capacitation. While viscosity does not seem to influence the degree of sperm bundling, swim-up, post-thaw migration time and suppressed capacitation increase the occurrence of sperm bundles. This leads to the conclusion that sperm bundling is a result of hydrodynamic and adhesive interactions between the cells which occurs frequently during prolonged incubation times.

Effects from disruption of mitochondrial electron transport chain function on bull sperm motility

Sperm mitochondrial function is essential for normal physiology and fertility, but the importance of mitochondrial activity to support specific sperm functions, such as motility, varies between species. It was previously believed that mitochondrial function was not necessary for bull sperm motility [1]; however, this theory is contradicted by recently reported findings that the upper fraction of bull sperm swim-up preparations had both high motility and elevated mitochondrial oxygen consumption rates [2]. The objective of this study was to investigate the relationship between mitochondrial function and motility in bull sperm. We hypothesized that sperm motility would be positively correlated with mitochondrial oxygen consumption (MITOX) but unaffected by pharmacological inhibition of electron transport chain (ETC) activity. This was accomplished by monitoring both mitochondrial oxygen consumption and motility parameters in the presence of mitochondrial effector drug treatments. Duplicate ejaculates were collected by electroejaculation from Black Angus bulls (n = 4). Oxygen consumption, as % air saturation (pO_2; oxygen partial pressure), over time was monitored in the presence of 5 drug treatments: vehicle control, FCCP, Antimycin (ANTI), Oligomycin (Oligo), and FCCP + Oligomycin (FCCP + OLIGO). Duplicate aliquots were prepared for concurrent motility assessment by computer-assisted sperm analysis (CASA) at 6 and 30 min post-treatment (t6 and t30). The impact of treatments on pO₂ (in % air saturation) over time were assessed by generalized linear mixed effects modeling (GLMM) which was also used to test for differences in average motility across treatment conditions and time points (t6 and t30). Pearson product-moment correlation was used to investigate relationships between oxygen consumption and motility parameters. Overall, pO₂ differed over time between treatment conditions (p < 0.0001). When compared to the vehicle treatment, ANTI and OLIGO significantly inhibited oxygen consumption (p < 0.05, adjusted), and FCCP stimulated a marked increase in oxygen consumption. No significant differences in motility over time were observed between treatments, so comparison of motility parameters between treatment conditions was performed with pooled timepoints. Motility parameters were only observed to differ significantly from the vehicle with ANTI Treatment, for which significant decreases in numerous parameters, including total motility (p = 0.007), progressive motility (p = 0.01), DAP (p = 0.01), VAP (p = 0.01) and VSL (p = 0.02) were identified. For the vehicle treatment, correlational analysis did not reveal any significant correlations between pO₂ and any motility parameters at t6; however, several significant correlations were identified at t30. Mean pO₂ was negatively correlated with local motility (p < 0.01) and positively correlated with DCL, DAP, and VCL (p < 0.05). Results from this study suggest that bovine sperm motility is impacted by mitochondrial functionality, with ETC inhibition by ANTI causing significant reduction in motility parameters. This study also demonstrates the use of a new technology for the assessment of bovine sperm mitochondrial function. This modality for evaluation of bull sperm mitochondrial function will inform future efforts to understand bull sperm function and fertility and aid investigations into toxicological agents.

Postcopulatory sexual selection is associated with sperm aggregate quality in Peromyscus mice

In some species, sperm form coordinated groups that are hypothesized to improve their swimming performance in competitive contexts or to navigate through the viscous fluids of the female reproductive tract. Here we investigate sperm aggregation across closely related species of Peromyscus mice that naturally vary by mating system to test the predictions that sperm aggregates 1) are faster than solitary sperm in species that females mate multiply to aid cells in sperm competition, and 2) outperform solitary sperm cells in viscous environments. We find significant variation in the size of sperm aggregates, which negatively associates with relative testis mass, a proxy for sperm competition risk, suggesting that postcopulatory sexual selection has a stabilizing effect on sperm group size. Moreover, our results show that sperm aggregates are faster than solitary sperm in some, but not all, species, and this can vary by fluid viscosity. Of the two species that produce the largest and most frequent groups, we find that sperm aggregates from the promiscuous P. maniculatus are faster than solitary sperm in every experimentally viscous environment but aggregation provides no such kinematic advantage under these same conditions for the monogamous P. polionotus. The reduced performance of P. polionotus aggregates is associated with less efficient aggregate geometry and the inclusion of immotile or morphological abnormal sperm. Our cross-species comparison yields insight into the evolution of sperm social behaviors, provides evidence of extensive variation in the Peromyscus lineage, and reveals that differences in sperm aggregate quality associate with postcopulatory sexual selection.

Genetic Association in the Maintenance of the Mitochondrial Microenvironment and Sperm Capacity

Sperm motility is one of the major determinants of male fertility. Since sperm need a great deal of energy to support their fast movement by active metabolism, they are thus extremely vulnerable to oxidative damage by the reactive oxygen species (ROS) and other free radicals generated as byproducts in the electron transport chain. The present study is aimed at understanding the impact of a mitochondrial oxidizing/reducing microenvironment in the etiopathology of male infertility. We detected the mitochondrial DNA (mtDNA) 4,977 bp deletion in human sperm. We examined the gene mutation of ATP synthase 6 (ATPase6 m.T8993G) in ATP generation, the gene polymorphisms of uncoupling protein 2 (UCP2, G-866A) in the uncoupling of oxidative phosphorylation, the role of genes such as manganese superoxide dismutase (MnSOD, C47T) and catalase (CAT, C-262T) in the scavenging system in neutralizing reactive oxygen species, and the role of human 8-oxoguanine DNA glycosylase (hOGG1, C1245G) in 8-hydroxy-2′-deoxyguanosine (8-OHdG) repair. We found that the sperm with higher motility were found to have a higher mitochondrial membrane potential and mitochondrial bioenergetics. The genotype frequencies of UCP2 G-866A, MnSOD C47T, and CAT C-262T were found to be significantly different among the fertile subjects, the infertile subjects with more than 50% motility, and the infertile subjects with less than 50% motility. A higher prevalence of the mtDNA 4,977 bp deletion was found in the subjects with impaired sperm motility and fertility. Furthermore, we found that there were significant differences between the occurrences of the mtDNA 4,977 bp deletion and MnSOD (C47T) and hOGG1 (C1245G). In conclusion, the maintenance of the mitochondrial redox microenvironment and genome integrity is an important issue in sperm motility and fertility.

Seminal fluid and sperm diluent affect sperm metabolism in an insect: Evidence from NAD(P)H and flavin adenine dinucleotide autofluorescence lifetime imaging

Sperm metabolism is fundamental to sperm motility and male fertility. Its measurement is still in its infancy, and recommendations do not exist as to whether or how to standardize laboratory procedures. Here, using the sperm of an insect, the common bedbug, Cimex lectularius, we demonstrate that standardization of sperm metabolism is required with respect to the artificial sperm storage medium and a natural medium, the seminal fluid. We used fluorescence lifetime imaging microscopy (FLIM) in combination with time-correlated single-photon counting (TCSPC) to quantify sperm metabolism based on the fluorescent properties of autofluorescent coenzymes, NAD(P)H and flavin adenine dinucleotide. Autofluorescence lifetimes (decay times) differ for the free and protein-bound state of the co-enzymes, and their relative contributions to the lifetime signal serve to characterize the metabolic state of cells. We found that artificial storage medium and seminal fluid separately, and additively, affected sperm metabolism. In a medium containing sugars and amino acids (Grace's Insect medium), sperm showed increased glycolysis compared with a commonly used storage medium, phosphate-buffered saline (PBS). Adding seminal fluid to the sperm additionally increased oxidative phosphorylation, likely reflecting increased energy production of sperm during activation. Our study provides a protocol to measure sperm metabolism independently from motility, stresses that protocol standardizations for sperm measurements should be implemented and, for the first time, demonstrates that seminal fluid alters sperm metabolism. Equivalent protocol standardizations should be imposed on metabolic investigations of human sperm samples.

Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in Peromyscus Mice

Mammals exhibit a tremendous amount of variation in sperm morphology and despite the acknowledgement of sperm structural diversity across taxa, its functional significance remains poorly understood. Of particular interest is the sperm of rodents. While most Eutherian mammal spermatozoa are relatively simple cells with round or paddle-shaped heads, rodent sperm are often more complex and, in many species, display a striking apical hook. The function of the sperm hook remains largely unknown, but it has been hypothesized to have evolved as an adaptation to inter-male sperm competition and thus has been implicated in increased swimming efficiency or in the formation of collective sperm movements. Here we empirically test these hypotheses within a single lineage of Peromyscus rodents, in which closely related species naturally vary in their mating systems, sperm head shapes, and propensity to form sperm aggregates of varying sizes. We performed sperm morphological analyses as well as in vitro analyses of sperm aggregation and motility to examine whether the sperm hook (i) morphologically varies across these species and (ii) associates with sperm competition, aggregation, or motility. We demonstrate inter-specific variation in the sperm hook and then show that hook width negatively associates with sperm aggregation and sperm swimming speed, signifying that larger hooks may be a hindrance to sperm movement within this group of mice. Finally, we confirmed that the sperm hook hinders motility within a subset of Peromyscus leucopus mice that spontaneously produced sperm with no or highly abnormal hooks. Taken together, our findings suggest that any adaptive value of the sperm hook is likely associated with a function other than inter-male sperm competition, such as interaction with ova or cumulous cells during fertilization, or migration through the complex female reproductive tract.

Bioenergetic Pathways in the Sperm of an Under-Ice Spawning Fish, Burbot (Lota lota): The Role of Mitochondrial Respiration in a Varying Thermal Environment

Regarding the sperm of cold-water fish, the contributions of different bioenergetic pathways, including mitochondrial respiration, to energy production at the spawning temperature and its adaptation at the maximum critical temperature (CTmax) are unclear. The roles of glycolysis, fatty acid oxidation, oxidative phosphorylation (OXPHOS) at 4 °C, and OXPHOS at 15 °C for energy production in burbot (Lota lota) spermatozoa were studied by motility and the oxygen consumption rate (OCR) (with and without pathway inhibitors and the OXPHOS uncoupler). At both temperatures, the effects of the inhibitors and the uncoupler on the motility duration, curvilinear velocity, and track linearity were insignificant; in addition, the OCRs in activation and non-activation media differed insignificantly and were not enhanced after uncoupler treatment. After inhibitor treatment in both media, OXPHOS was insignificantly different at the 2, 30, and 60 s time points at 4 °C but was reduced significantly at the 30 and 60 s time points after treatment with sodium azide at 15 °C. In conclusion, for burbot sperm at both the spawning temperature and the CTmax, the energy synthesized via OXPHOS during motility was insufficient. Therefore, the majority of the energy required to sustain motility was derived from pre-accumulated energy produced and stored during the quiescent state of the spermatozoa.

Mitochondria Content and Activity Are Crucial Parameters for Bull Sperm Quality Evaluation

Standard sperm evaluation parameters do not enable predicting their ability to survive cryopreservation. Mitochondria are highly prone to suffer injuries during freezing, and any abnormalities in their morphology or function are reflected by a decline of sperm quality. Our work focused on describing a link between the number and the activity of mitochondria, with an aim to validate its applicability as a biomarker of bovine sperm quality. Cryopreserved sperm collected from bulls with high (group 1) and low (group 2) semen quality was separated by swim up. The spermatozoa of group 1 overall retained more mitochondria (MitoTrackerGreen) and mtDNA copies, irrespective of the fraction. Regardless of the initial ejaculate quality, the motile sperm contained significantly more mitochondria and mtDNA copies. The same trend was observed for mitochondrial membrane potential (ΔΨm, JC-1), where motile sperm displayed high ΔΨm. These results stay in agreement with transcript-level evaluation (real-time polymerase chain reaction, PCR) of antioxidant enzymes (PRDX1, SOD1, GSS), which protect cells from the reactive oxygen species. An overall higher level of glutathione synthetase (GSS) mRNA was noted in group 1 bulls, suggesting higher ability to counteract free radicals. No differences were noted between basal oxygen consumption rate (OCR) (Seahorse XF Agilent) and ATP-linked respiration for group 1 and 2 bulls. In conclusion, mitochondrial content and activity may be used as reliable markers for bovine sperm quality evaluation.

Influence of Non-conventional Sperm Quality Parameters on Field Fertility in Ovine

The prediction of the fertilizing ability of a seminal dose continues to be a primary aim in the field of artificial insemination (AI). To achieve this goal, in this study we have included the evaluation of some non-conventional sperm quality markers. A total of 3,906 ewes from 52 different farms were inseminated with 357 refrigerated seminal doses obtained from 45 mature Rasa Aragonesa rams. The same samples were used for sperm quality analysis including membrane integrity, capacitation status, oxygen consumption and apoptotic-like markers such as phosphatidylserine translocation (PS), plasmalemma disorganization/mitochondrial membrane potential, caspase activation and DNA damage. Seminal doses from the breeding (B) season presented higher percentages of intact membrane (IM), non permeant (NP) membrane with high mitochondrial membrane potential (ΔΨm) and IM without PS translocation spermatozoa than those from the non-breeding (NB) season. Therefore, we can conclude that there were less spermatozoa showing apoptotic-like features in the seminal doses from the B than the NB season, although these differences did not affect field fertility. Only the percentage of intact membrane, non-capacitated (IM-NC) spermatozoa showed a significant correlation with in vivo fertility (P = 0.005) and fecundity (P = 0.007) values obtained after cervical AI when all data were evaluated. When the data were sorted by season and distance to the farms where AI was performed, the correlation between the percentage of IM-NC spermatozoa and reproductive parameters increased in the NB season and progressively with remoteness from the farms. Some other sperm parameters, like NP with high ΔΨm, IM sperm without active caspases and DNA-intact spermatozoa, also showed significant correlations with the reproductive parameters in the sorted data. Moreover, the increment in both the percentage of IM-NC and DNA-intact spermatozoa would increase the probability of obtaining a fertility higher than the mean (>52%), as revealed by a multiple logistic regression analysis. In conclusion, we have identified two seminal markers—the percentage of intact membrane, non-capacitated spermatozoa, and DNA intact spermatozoa—which could be used as a test to discard males in AI programs, which is highly important from an economic point of view and can contribute to achieving satisfactory fertility rates.

Sub-fertility in crossbred bulls: Identification of proteomic alterations in spermatogenic cells using high throughput comparative proteomics approach

The present study was carried out to compare the proteomic profiles of spermatogenic cells of crossbred and zebu cattle in an effort to understand the possible reasons for a higher incidence of sub-fertility in crossbred bulls. The spermatogenic cells collected from the testes of pre-pubertal (6 mo) and adult (24 mo) crossbred and zebu males through fine needle aspiration were proliferated in vitro, and proteomic profiling was done using a shotgun proteomics approach. The age- and species-specific variations in the expression level of proteins were identified in spermatogenic cells. The number of differentially expressed proteins (DEPs) identified in pre-pubertal zebu and crossbred was 546, while 579 DEPs were identified between adult zebu and crossbred bulls. Out of these, 194 DEPS were common to these groups and 40 DEPs displayed a fold change ≥2. However, only 20 proteins exhibited similar expression variation trends (upregulated or downregulated) among pre-pubertal as well as adult zebu and crossbred bulls. Out of these 20 DEPs, 13 proteins were upregulated, and 7 proteins were downregulated in spermatogenic cells of zebu compared to crossbred bulls. Among the upregulated proteins were RPLP2, PAXIP1, calumenin, prosaposin, GTF2F1, TMP2, ubiquitin conjugation factor E4A, COL1A2, vimentin, protein FAM13A, peripherin, GFPT2, and GRP78. Seven proteins that were downregulated in zebu bulls compared to crossbred included APOA1, G patch domain-containing protein 1, NAD P transhydrogenase mitochondrial, glutamyl aminopeptidase, synaptojanin 1 fragment, Arf GAP with SH3 domain ANK repeat and PH domain-containing protein 1, and protein transport protein sec16B. It was inferred that the proteins associated with sperm function and fertilization processes, such as calumenin, prosaposin, vimentin, GRP78, and APOA1 could be studied further to understand the precise cause of subfertility in crossbred bulls.

Replacement of Albumin by Preovulatory Oviductal Fluid in Swim-Up Sperm Preparation Method Modifies Boar Sperm Parameters and Improves In Vitro Penetration of Oocytes

Simple Summary

Part of the success of assisted reproductive techniques lies in gamete manipulation before the in vitro fertilization (IVF) procedure. Current chemically defined handling media lack crucial components for embryo development that exist under in vivo conditions. Recent studies of pigs have shown that the addition of reproductive fluids during in vitro fertilization and embryo culture improves embryo quality and their epigenetic profile in vitro. Porcine oviductal fluid (pOF) has been used to supplement the handling media used for sperm selection by centrifugation. However, its effect during sperm selection by the swim-up procedure is still unknown, as is the likely beneficial effect of replacing bovine serum albumin (BSA) by pOF as a protein source in sperm preparation media. In this study, four protein combinations in the swim-up medium were tested: 1 mg/mL BSA (the regular supplementation), 1% preovulatory pOF (1% pOF), 1 mg/mL BSA plus 1% pOF; and 5 mg/mL BSA. After sperm selection, various sperm parameters were assessed, and oocytes were inseminated in vitro. Results showed that the replacement of BSA by pOF improves some sperm motion parameters and increases in vitro oocyte penetration ability, whereas the combination of BSA + pOF did not show relevant effects. High concentrations of BSA had a detrimental effect, resulting in a decrease of sperm penetration.

Abstract

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.

Elucidating the processes and pathways enriched in buffalo sperm proteome in regulating semen quality

Sperm carries a reservoir of proteins regulating the molecular functions to attain functional competence. Semen samples collected from buffalo bulls were assessed for sperm functional attributes (n = 11) and proteome profiling (n = 6). Sperm proteins were extracted and profiled by employing LC-MS/MS. Overall, the buffalo sperm contained 1365 proteins, of which 458 were common between the groups. The unique proteins were 477 and 430 in good and poor quality semen, respectively. In the whole proteome of buffalo sperm, sexual reproduction with phosphatidylethanolamine-binding protein1 (PEBP1), fetuin-B (FETUB) and acrosin (ACR) was the most enriched (p = 8.44E-19) biological process, also with thermogenesis (p = 0.003), oocyte meiosis (p = 0.007) and vascular smooth muscle contraction (p = 0.009) apart from metabolic pathways. In good quality semen, mesenchyme migration (p = 1.24E-07) and morphogenesis (p = 0.001) were abundant biological processes. In good quality semen, the fluid shear stress (p = 0.01) and, in poor quality semen, valine, leucine and isoleucine degradation (p = 3.8E-05) pathways were enriched. In good quality semen, 7 proteins were significantly (p < 0.05) upregulated and 33 proteins were significantly (p < 0.05) downregulated. On validating the abundantly expressed sperm proteins, serine protease inhibitor Kazal-type 2-like (SPINK2; 2.17-fold) and neddylin (NEDD8; 1.13-fold) were upregulated and YBX2 was downregulated (0.41-fold) in good quality semen as compared with poor quality semen (1-fold). The present findings revealed the importance of sperm proteins in oocyte maturation, fertilization process and early embryonic development. The variations in the proteomic composition can be used as potential markers for the selection of breeding bulls.

IRONSperm: Sperm-templated soft magnetic microrobots

We develop biohybrid magnetic microrobots by electrostatic self-assembly of nonmotile sperm cells and magnetic nanoparticles. Incorporating a biological entity into microrobots entails many functional advantages beyond shape templating, such as the facile uptake of chemotherapeutic agents to achieve targeted drug delivery. We present a single-step electrostatic self-assembly technique to fabricate IRONSperms, soft magnetic microswimmers that emulate the motion of motile sperm cells. Our experiments and theoretical predictions show that the swimming speed of IRONSperms exceeds 0.2 body length/s (6.8 ± 4.1 µm/s) at an actuation frequency of 8 Hz and precision angle of 45°. We demonstrate that the nanoparticle coating increases the acoustic impedance of the sperm cells and enables localization of clusters of IRONSperm using ultrasound feedback. We also confirm the biocompatibility and drug loading ability of these microrobots, and their promise as biocompatible, controllable, and detectable biohybrid tools for in vivo targeted therapy.

Methodological considerations for examining the relationship between sperm morphology and motility

Sperm cells of all taxa share a common goal to reach and fertilize an ovum, yet sperm are one of the most diverse cell types in nature. While the structural diversity of these cells is well recognized, the functional significance of variation in sperm design remains elusive. An important function of spermatozoa is a need to migrate toward the ova, often over long distances in a foreign environment, which may include a complex and hostile female reproductive tract. Several comparative and experimental studies have attempted to address the link between sperm morphology and motility, yet the conclusions drawn from these studies are often inconsistent, even within the same taxa. Much of what we know about the functional significance of sperm design in internally fertilizing species has been gleaned from in vitro studies, for which experimental parameters often vary among studies. We propose that discordant results from these studies are in part due to a lack of consistency of methods, conditions that do not replicate those of the female reproductive tract, and the overuse of simple linear measures of sperm shape. Within this review, we provide a toolkit for imaging, quantifying, and analyzing sperm morphology and movement patterns for in vitro studies and discuss emerging approaches. Results from studies linking morphology to motility enhance our understanding of the evolution of adaptive sperm traits and the mechanisms that regulate fertility, thus offering new insights into methods used in assisted reproductive technologies in animal science, conservation and public health.

Sperm Cell Driven Microrobots-Emerging Opportunities and Challenges for Biologically Inspired Robotic Design

With the advent of small-scale robotics, several exciting new applications like Targeted Drug Delivery, single cell manipulation and so forth, are being discussed. However, some challenges remain to be overcome before any such technology becomes medically usable; among which propulsion and biocompatibility are the main challenges. Propulsion at micro-scale where the Reynolds number is very low is difficult. To overcome this, nature has developed flagella which have evolved over millions of years to work as a micromotor. Among the microscopic cells that exhibit this mode of propulsion, sperm cells are considered to be fast paced. Here, we give a brief review of the state-of-the-art of Spermbots - a new class of microrobots created by coupling sperm cells to mechanical loads. Spermbots utilize the flagellar movement of the sperm cells for propulsion and as such do not require any toxic fuel in their environment. They are also naturally biocompatible and show considerable speed of motion thereby giving us an option to overcome the two challenges of propulsion and biocompatibility. The coupling mechanisms of physical load to the sperm cells are discussed along with the advantages and challenges associated with the spermbot. A few most promising applications of spermbots are also discussed in detail. A brief discussion of the future outlook of this extremely promising category of microrobots is given at the end.

Assessments of sperm quality integrating morphology, swimming patterns, bioenergetics and cell signalling

Spermatozoa are diverse in form and function and these differences impact on their fertilizing capacity. Because of considerable inter-male and inter-species differences in sperm traits, assessments of sperm quality demand that we consider variations at different levels. We should thus pay attention not only to average values but also intra- and inter-sperm population variations and subpopulation structure. Sperm shape and size evolve in reponse to postcopulatory sexual selection. Assessments of morphological variation, with conventional microscopy or with computer-assisted systems, should bear this in mind. In rodents sperm head shape is asymmetric so it requires more complex tools, such as geometric morphometrics. Sperm function also evolves under postcopulatory sexual selection and this could be used as a basis to assess sperm performance. Sperm cells swim actively to overcome barriers in the female tract and develop a peculiar motility pattern in the final stages prior to and during fertilization. Both types of movement can be analyzed by computer-assisted microscopy systems. Sperm have high energetic demands for cell homeostasis, motility, and signalling. Bioenergetics can be analyzed by various means, including extracellular flux analyses to characterize glycolysis and mitochondrial respiration. Finally, cell signalling during capacitation has received much attention and can be assessed by microscopy (conventional or computer-assisted) or flow cytometry. Recent advances in image-flow cytometry affords analyses of high cell numbers with spatial localization of subcellular changes, which will have a big impact in the development of functional tests for the andrology clinic and in sperm preservation and use in artificial insemination.

Centrifugation Force and Time Alter CASA Parameters and Oxidative Status of Cryopreserved Stallion Sperm

Conventional sperm selection techniques used in ARTs rely on centrifugation steps. To date, the different studies reported on the effects of centrifugation on stallion sperm motility provided contrasting results and do not include effects on mitochondrial functionality and different oxidative parameters. The effects of different centrifugation protocols (300 ×g for 5', 300 ×g for 10', 1500 ×g for 5' and 1500 ×g for 10' vs no centrifugation) on motility and oxidative status in cryopreserved stallion sperm, were analyzed. After centrifugation, almost all motility parameters were significantly altered, as observed by computer-assisted sperm analysis. A polarographic assay of oxygen consumption showed a progressive decrease in mitochondria respiration from the gentlest to the strongest protocol. By laser scanning confocal microscopy, significant reduction of mitochondrial membrane potential, at any tested protocol, and time-dependent effects, at the same centrifugal force, were found. Increased DNA fragmentation index at any tested protocol and time-dependent effects at the same centrifugal force were found, whereas increased protein carbonylation was observed only at the strongest centrifugal force. These results provide more comprehensive understandings on centrifugation-induced effects on cryopreserved stallion sperm and suggest that, even at a weak force for a short time, centrifugation impairs different aspects of equine sperm metabolism and functionality.