Effects of single layer centrifugation (SLC) on bull spermatozoa prior to freezing on post-thaw semen characteristics

Selection of spermatozoa with high motility and quality from bovine frozen-thawed semen using the centrifuge-free device

This study aimed to assess the potential of the centrifuge-free commercial device (MIGLIS®) in selecting functional frozen-thawed bovine sperm by migration-sedimentation, its effect on embryo development, and compare the potential with that of centrifugation-based techniques, including washing and Percoll density gradient centrifugation (DGC). In experiment 1, different dilutions (1.5×, 2×, and 3×) of frozen-thawed spermatozoa were assessed to identify the adequate one for the MIGLIS method. In experiment 2, the recovery rates, quality, and reactive oxygen species (ROS) concentrations of the spermatozoa selected using MIGLIS, washing, and Percoll DGC were compared. In experiment 3, the resultant in vitro fertilised embryos from spermatozoa selected using the three methods were evaluated for blastocyst formation rates and intracellular ROS concentrations at the 2-4 cell stage. The intracellular ROS concentrations were investigated using 2', 7'-dichlorodihydrofluorescein diacetate staining. Using the MIGLIS device, significantly more spermatozoa were recovered at 2× dilution compared with the other dilution ratio, but the motility was not affected by the dilution ratio. On the selection of spermatozoa using the three methods, employing MIGLIS decreased the recovery rates. However, the MIGLIS method increased motility, viability, and acrosome integrity rates compared to those in spermatozoa from the other methods. The ROS concentration of spermatozoa in the MIGLIS method was significantly lower than that in the washing method. Nevertheless, blastocyst formation rates were similar among the three methods, but the ROS concentration of early-stage embryos produced using MIGLIS was significantly lower than those produced using Percoll DGC. In conclusion, the MIGLIS method has the potential to select functional, high-quality frozen-thawed bovine spermatozoa.

Pre-freezing selection of Holstein bull semen with the BoviPure colloid as double- or single-layer centrifugation improves the post-thawing quality

Artificial insemination (AI) is critical for breeding in the dairy industry. High-merit bulls can present low freezability, hampering genetic dissemination. Thawed semen can be improved using density gradient centrifugation (DGC) with colloids, but little information deals with the pre-freezing application. Thus, the BoviPure colloid (optimized for bull spermatozoa) was tested for pre-freezing application as the usual double-layer (DLC) versus single-layer (SLC, quick and economical). Semen from twelve Holstein-Friesian bulls was extended with OPTIXcell extender, frozen (Control), or processed by SLC or DLC and frozen. Sperm were assessed pre-freezing for motility and viability and post-thawing (directly and after 4 h 38 °C) for apoptosis, capacitation status, acrosomal damage, mitochondrial activity, cytoplasmic and mitochondrial reactive oxygen species (ROS), and chromatin status (SCSA for DNA fragmentation and chromatin compaction and monobromobimane, mBBr, for disulfide bridges evaluation). The DGC improved parameters post-thawing (e.g., 57.5%±10.1 motility vs. control 53.3% ± 11.2) at the cost of sperm loss (sperm recovery of DGC 14.4% ± 2.5 and SLC 17.4% ± 2.5). DNA fragmentation (%DFI) decreased (0.21% ± 0.53 vs. control 1.30% ± 0.10), and SLC reduced chromatin compaction. A clustering procedure separated lesser (LF) and greater freezability (GF) bulls. LF samples were especially benefited by DGC, with SLC providing better post-thawing results for this group. In conclusion, pre-freezing DGC improved sperm parameters post-thawing, potentially improving the cryopreservation of low-freezability semen from high-merit bulls. SLC, quicker and economical, would be preferable since it showed similar or higher performance than DLC.

Optimization of the Equine-Sperm Freeze Test in Purebred Spanish Horses by Incorporating Colloidal Centrifugation

The Purebred Spanish Horse, according to our clinical experience, is characterized by having a high number of stallions that do not meet the international commercial recommendations for equine-sperm cryopreservation. This means that artificial insemination with frozen semen from these stallions is less widespread than in other breeds. In this study, we investigated if the incorporation of single-layer colloidal centrifugation prior to cryopreservation in clinical conditions could increase the number of ejaculates of Purebred Spanish stallions suitable for this processing, observing the influence of centrifugation and freezing extender protocol on post-thawed sperm motility. Using colloidal centrifugation, the percentage of ejaculates available to be frozen was increased from 35% (6/17) to 71% (12/17), doubling the number of samples that could have been subjected to cryopreservation. We only found significant differences in linearity (LIN) and lateral head displacement (ALH) after 5 min of incubation at 37 °C between colloidal and simple centrifugation processing techniques. No significant differences were found between the two different colloidal protocols in any of the variables considered. Colloidal centrifugation allowed us to obtain, from worse fresh-quality ejaculates, thawed sperm doses with similar quality to that of good-quality ejaculates. BotuCrio^® produced, in general, higher motility parameters and its characteristics than the other extenders analyzed, with significant differences found in comparison to Inra-Freeze^® and Lac-Edta in both total (MOT) and progressive motility (PMOT) when using colloidal centrifugation and only in PMOT when applying simple centrifugation. Colloidal centrifugation optimized the efficiency of cryopreservation, as it allowed us to increase the number of ejaculates of Purebred Spanish Horses suitable to be frozen. Including these semen processing techniques in the freeze test could help to optimize equine-sperm cryopreservation protocols, especially when dealing with individuals or breeds for which initially low sperm quality prevents or limits their inclusion in sperm cryopreservation programs.

Sperm Quality in Young Bull Semen Can Be Improved by Single Layer Centrifugation

Simple Summary

Genomic selection enables bulls with desirable genes to be identified early in life. Livestock producers need to use the semen from young bulls as early as possible for efficient milk and meat production with fewer greenhouse gas emissions. However, semen from young bulls is often of lower quality than needed for freezing for commercial artificial insemination. Colloid centrifugation selects spermatozoa with the desirable characteristics needed for fertilization from the rest of the ejaculate. In this study, split ejaculates from young bulls were prepared with or without colloid centrifugation. Using this technique, sperm doses of acceptable quality for artificial insemination could be produced from ejaculates that would otherwise be discarded. Thus, the semen from young bulls would be usable for artificial insemination sooner than is currently the case.

Abstract

Interest in using semen from young bulls is increasing due to identifying promising animals by genomic selection. However, sperm quality in these ejaculates may not reach currently accepted standards for the cattle breeding industry. The purpose of this study was to determine if centrifugation of semen from young bulls through the Bovicoll colloid could improve sperm quality sufficiently for the frozen semen to be acceptable for artificial insemination. Ejaculates from 19 young bulls were split and either processed by Single-Layer Centrifugation (SLC) or not (CON) before freezing. After thawing, sperm quality was evaluated by determination of membrane integrity, mitochondrial membrane potential, DNA integrity, production of reactive oxygen species, sperm morphology and motility. Approximately half of the CON samples reached acceptable post-thaw quality (membrane integrity ≥ 40%) despite being below the breeding company´s desired sperm concentration threshold pre-freezing. In the remaining samples, sperm quality was improved by SLC such that 45% of them reached acceptable quality post-thaw. Almost 75% of the young bull sperm samples could have produced usable frozen semen doses by adjusting the breeding company´s current processing protocols. Since lowering the generation interval has a direct effect on the genetic gain per year, SLC could aid genetic progress in cattle breeding.

Influence of Single Layer Centrifugation with Canicoll on Semen Freezability in Dogs

Simple Summary

Freezing dog semen is not always possible due to low quality sperm or poor survival during freezing. In order to make this assisted reproductive technique available to a larger number of dogs, this study investigated the benefit of selecting the best spermatozoa before freezing using single layer centrifugation (SLC). The results indicated that this technique was effective in separating spermatozoa according to their quality, although this resulted in losing some good quality spermatozoa. After thawing, spermatozoa centrifuged by SLC were of better quality than after standard centrifugation. However, spermatozoa from suboptimal quality semen did not survive freezing as well as spermatozoa from semen of optimal quality, even after SLC. Single layer centrifugation, therefore, makes it possible to obtain better quality spermatozoa after thawing but is not sufficient on its own to improve the inferior freezing ability of spermatozoa from suboptimal quality semen. So far, eighteen pups were born after insemination with SLC-selected frozen-thawed semen, proving that these selected spermatozoa remain fertile.

Abstract

This study evaluated how semen selection by single layer centrifugation (SLC) with Canicoll affects semen freezability in dogs. A total of eighteen ejaculates, collected from dogs with optimal and suboptimal semen quality (optimal: normal morphology (NM) ≥ 80%, n = 9; suboptimal: NM between 60 and 79%, n = 9), were divided into two aliquots and subjected to standard centrifugation or SLC before cryopreservation. Motility, NM, membrane integrity, mitochondrial membrane potential (MMP), and DNA integrity were improved in fresh samples after SLC, regardless of semen quality, but at the expense of some good quality spermatozoa. After thawing, NM and membrane integrity were improved in SLC-selected semen in both semen qualities. Interestingly, MMP was also higher but only in optimal quality semen. Still, spermatozoa from suboptimal quality semen did not survive freezing to the same extent as spermatozoa from optimal quality semen, even after selecting superior spermatozoa. Semen selection with Canicoll is, therefore, an effective technique to isolate a subpopulation of high-quality spermatozoa and obtain sperm samples of better quality after thawing, but is not sufficient to improve the intrinsic inferior freezability of suboptimal quality semen. So far, eighteen pups were born after insemination with SLC-selected frozen-thawed semen, proving that these selected spermatozoa remain fertile.

Implications of cryopreservation on structural and functional attributes of bovine spermatozoa: An overview

Sperm cryopreservation is an important adjunct to assisted reproduction techniques (ART) for improving the reproductive efficiency of dairy cattle and buffaloes. Improved understanding of mechanisms and challenges of bovine semen cryopreservation is vital for artificial insemination on a commercial basis. Although cryopreservation of bovine spermatozoa is widely practiced and advanced beyond that of other species, there are still major gaps in the knowledge and technology. Upon cryopreservation, disruption of spermatozoal plasma membrane configuration due to alterations in metabolic pathways, enzymes and antioxidants activity add to lower efficiency with loss of sperm longevity and fertilising ability. Therefore, the effective amalgamation of cryo-variables like ambient temperature, cooling and thawing rates, nucleation temperature, type and concentration of the cryoprotectant, seminal plasma composition, free radicals and antioxidant status are required to optimise cryopreservation. Novel strategies like supplementation of cholesterol-loaded cyclodextrins (CLC), nanovesicles, osteopontin, antioxidants, etc., in an extender and recent techniques like nano-purification and modified packaging have to be optimised to ameliorate the cryodamage. This article is intended to describe the basic facts about the sperm cryopreservation process in bovine and the associated biochemical, biophysical, ultra-structural, molecular and functional alterations.

Lipid peroxidation in bull semen influences sperm traits and oxidative potential of Percoll®-selected sperm

Although bovine embryo in vitro production (IVP) is a common assisted reproductive technology, critical points warrant further study, including sperm traits and oxidative status of sperm for in vitro fertilization (IVF). Our aim was to evaluate whether the lipid peroxidation index of commercial bull semen is influenced by sperm traits and oxidative status of sperm populations selected using Percoll® gradient. Semen straws from 48 batches from 14 Nelore bulls were thawed individually, analyzed for motility and subjected to Percoll selection. After Percoll, the lipid peroxidation index of the extender was evaluated, whereas selected sperm were analyzed for motility, acrosome and membrane integrity, mitochondrial membrane potential, chromatin resistance and oxidative potential under IVF conditions. Batches were divided retrospectively in four groups according to lipid peroxidation index. Sperm from Group 4 with the lowest index of lipid peroxidation had, after Percoll selection, greater plasma membrane integrity (81.3%; P = 0.004), higher mitochondrial potential (81.1%; P = 0.009) and lower oxidative potential (135.3 ng thiobarbituric acid reactive substances (TBARS)/ml; P = 0.026) compared with Group 1 with highest lipid peroxidation index (74.3%, 73% and 213.1 ng TBARS/ml, respectively). Furthermore, we observed negative correlations for the lipid peroxidation index with motility, membrane integrity and mitochondrial potential, and positive correlations with oxidative potential. In conclusion, oxidative stress in semen straws, as determined using lipid peroxidation in the extender, is associated with sperm traits and their oxidative potential under IVF conditions. These results provided further insights regarding the importance of preventing oxidative stress during semen handling and cryopreservation, as this could affect sperm selected for IVF. Finally, Percoll selection did not completely remove sperm with oxidative markers.

Influence of seminal plasma during different stages of bovine sperm cryopreservation

This study aimed to evaluate the effect of seminal plasma on bovine sperm cryopreservation and to assess the integrity of plasma and acrosomal membranes, mitochondrial potential, remodelling of F-actin cytoskeleton and sperm chromatin fragmentation during the cooling, equilibrium and freezing/thawing stages. Six ejaculates collected from seven Nelore bulls (n = 42) were used in this study. Each ejaculate was divided into two aliquots (with seminal plasma = SP group; without seminal plasma = NSP group) and packed to a final concentration of 50 × 10⁶ sperm per straw. Statistical analyses were performed using SAS software (version 9.3), and p ≤ .05 was considered significant. A time effect was observed for all sperm characteristics (p < .05), except for chromatin fragmentation (p > .05). The presence of seminal plasma better preserved the acrosomal integrity (SP = 75.2% and NSP = 71.7%; p < .05) and also provided lower F-actin remodelling during cryopreservation process (SP = 29.9% and NSP = 32.4%; p < .05). Regarding to the cryopreservation stages, it was observed that cooling step induced higher remodelling of F-actin than the equilibrium and freezing/thawing stages (56.3%, 32.2% and 23.9%, respectively; p < .05). The equilibrium step had minor influence on overall sperm characteristics while the freezing/thawing stage was responsible for the highest percentage of damage in plasma membrane (-65.2%), acrosomal membrane (-34.0%) and mitochondrial potential (-48.1%). On the other hand, none of the cryopreservation stages affected chromatin integrity. It was concluded that the presence of seminal plasma provides increased acrosomal integrity and reduced remodelling of F-actin cytoskeleton. Higher F-actin remodelling is observed after the cooling step while the freezing/thawing step is most damaging to sperm membranes and mitochondrial potential during bovine sperm cryopreservation.

Purification of cryopreserved camel spermatozoa following protease-based semen liquefaction by lectin-functionalized DNA-defrag magnetic nanoparticles

Although incorporating proteases into sperm medium is considered the most effective procedure to eliminate camel semen viscosity, it drastically affects viability, morpho-functional properties and, hence, fertilization potential of spermatozoa. The present work aimed at evaluating adequacy of employing magnetic nanoparticles-based sperm purification technique for eluting impaired and apoptotic camel spermatozoa from cryopreserved semen doses following protease-based semen liquefaction. Thirty cryopreserved semen doses (50 x 10⁶ sperm/straw) representing the following liquefaction treatments: control (untreated), 0.1 mg/ml papain or 5 U/ml bromelain were used (n = 10 straws per treatment). Immediately after thawing (38°C for 40 s), sperm concentration of each straw within treatment was readjusted to 15 x 10⁶ sperm/mL by dilution in PBS (37°C). Sperm physical and cytological properties were then assessed (non-purified semen). Thereafter, each specimen was subjected to lectin-functionalized DNA-defrag magnetic nanoparticles sperm purification, and the same sperm traits were re-evaluated after undergoing purification (purified semen). Sperm DNA fragmentation level within each group, prior to and after magnetic nano-purification, was also determined by fluorescent imaging. The results showed a dramatic improvement (p < .05) in post-thaw motility (%), viability (%), normal sperm (%), intact acrosome (%) and HOST-reacted (%) spermatozoa in protease-liquefied semen following sperm magnetic nano-purification. Additionally, the highest (p < .05) DNA fragmentation level was recorded in all cryopreserved semen groups prior to purification, whereas the lowest (p < .05) was observed in the protease-treated specimens after magnetic nano-purification. These results indicate that protease-based semen liquefaction prior to cryopreservation in conjunction with magnetic nano-purification post-thawing holds potential for reducing the proportion of damaged and dead spermatozoa, hence improving camel sperm fertilization competence.

Differences in sperm functionality and intracellular metabolites in Norwegian Red bulls of contrasting fertility

In the dairy breeding industry, prediction of bull fertility in artificial insemination (AI) is important for efficient and economically sustainable production. However, it is challenging to identify bulls with superior fertility applying conventional in vitro sperm assays. In the present study, sperm functionality was investigated to identify a multivariate model that could predict fertility. Two groups of young Norwegian Red bulls were selected, one with inferior fertility (18 bulls) and one with superior fertility (19 bulls) based on non-return rate after 56 days (NR56). Frozen-thawed semen doses were analysed for sperm chromatin integrity, viability, acrosome integrity, motility, and ATP content. A targeted approach was used to study intracellular concentrations of amino acids and trace elements in viable sperm cells. Significant differences between the two groups of bulls were observed, both for sperm functional attributes and intracellular concentrations of metabolites. Pearson correlation analyses indicated a negative relationship between NR56 and chromatin integrity parameters, DNA fragmentation index (DFI) and high DNA stainability (HDS). Several motility parameters correlated positively with NR56. The concentrations of cysteine and glutamic acid in sperm cells correlated negatively with NR56, while the concentrations of aspartic acid, leucine and serine showed a positive NR56-correlation. The sperm intracellular concentrations of the trace elements Fe, Al and Zn, correlated negatively with NR56. Correlations were observed between several sperm parameters and metabolites. Stepwise multiple regression analysis indicated that the best predictor of NR56 was a model containing %DFI, together with the intracellular sperm concentration of aspartic acid, Fe and Zn. This model explained 59% of the variability in NR56.

Bull seminal plasma stimulates in vitro production of TGF-β, IL-6 and IL-8 from bovine endometrial epithelial cells, depending on dose and bull fertility

Seminal plasma (SP) regulates immune responses in the female reproductive tract through specific cytokines. It is not known whether SP from high fertility bulls (H) differs from SP from low fertility bulls (L). In this study, the cytokine response of bovine endometrial epithelial cells (bEEC) in culture was investigated after challenge with SP from two bulls of below average (L) or three bulls of above average fertility (H). The bEECs were challenged with 1% or 4% SP from l- or H-fertility bulls (L1, L4, H1, H4, respectively) or 1% or 4% PBS as control (C1, C4) for 72 h. The culture media were analysed for concentrations (pg/million cells) of transforming growth factor beta (TGF-β1, TGF-β2 and TGF-β3) by Luminex, and Interleukin 6 and 8 (IL-6, IL-8) by ELISA. Challenge significantly affected production of TGF-ß1, TGF-ß2 and IL-8 compared to controls and was affected by bull fertility (p < 0.0001), SP concentration (p < 0.0001) and their interaction (p < 0.0001). A higher production of TGF-β1, TGF-β2 and IL-8 (p < 0.0001), and also IL-6 (p < 0.01), resulted from challenge with high doses of SP, being higher for L than H (p < 0.05). For TGF-β3, fertility of bull (p < 0.05). For TGF-B3, fertility of bull (p < 0.05) and the interaction between fertility and concentration of SP were significant (p < 0.01). In conclusion, 4% SP from L bulls stimulated more TGF-β1, TGF-β2, TGF-β3, IL-6 and IL-8 production than SP from H bulls, indicating that stimulation of the endometrium is relevant for fertility. Seminal plasma from high fertility bulls seems to affect cytokine production in utero positively in inseminated cows.

Colloid centrifugation reduces bacterial load in chilled dog semen

Conventional semen extenders contain antibiotics to prevent bacterial growth. Finding alternatives would be beneficial to minimize the development of bacterial resistance mechanisms. The aim of this study was to determine the effect of Single Layer Centrifugation (SLC) with Canicoll of dog semen on microbial load and sperm quality during cooled storage. Twenty-four ejaculates were obtained from healthy dogs by digital manipulation. Samples were diluted in Tris-citrate-fructose extender without antibiotics and divided into two treatment groups: SLC-selected samples and unselected samples. Sperm motility (CASA), viability and acrosome integrity (PI/FITC-PNA) as well as bacterial load of each microorganism species (colony-forming units/mL) were assessed at 0 and 48 h of storage at 4 °C. Results indicate SLC-selected dog spermatozoa have greater percentages of motility, viability and acrosome integrity (P < 0.05). Bacterial growth in SLC sperm samples was less (P < 0.05) than unselected samples. Removal of individual bacterial species varied from 91 % to 98 % for Escherichia coli (91.62 %), Streptococcus spp. (98.18 %), Staphylococcus spp.(95.33 %) and Pseudomonas spp. (92.50 %). In conclusion, the use of SLC with Canicoll has the potential to decrease bacterial load in chilled dog semen.

State-of-the-Art and Prospective of Nanotechnologies for Smart Reproductive Management of Farm Animals

Many biotechnological assisted reproductive techniques (ART) are currently used to control the reproductive processes of farm animals. Nowadays, smart ART that considers technique efficiency, animal welfare, cost efficiency and environmental health are developed. Recently, the nanotechnology revolution has pervaded all scientific fields including the reproduction of farm animals, facilitating certain improvements in this field. Nanotechnology could be used to improve and overcome many technical obstacles that face different ART. For example, semen purification and semen preservation processes have been developed using different nanomaterials and techniques, to obtain semen doses with high sperm quality. Additionally, nanodrugs delivery could be applied to fabricate several sex hormones (steroids or gonadotrophins) used in the manipulation of the reproductive cycle. Nanofabricated hormones have new specific biological properties, increasing their bioavailability. Applying nanodrugs delivery techniques allow a reduction in hormone dose and improves hormone kinetics in animal body, because of protection from natural biological barriers (e.g., enzymatic degradation). Additionally, biodegradable nanomaterials could be used to fabricate hormone-loaded devices that are made from non-degradable materials, such as silicon and polyvinyl chloride-based matrixes, which negatively impact environmental health. This review discusses the role of nanotechnology in developing some ART outcomes applied in the livestock sector, meeting the concept of smart production.

Effects of season and single layer centrifugation on bull sperm quality in Thailand

Objective

The aim of study was to investigate the effects of season and single layer centrifugation (SLC) before cryopreservation on post-thaw bull sperm quality in Thailand.

Methods

Semen was collected from 6 bulls (Bos indicus) in summer, rainy season and winter 2014 through 2016. Semen characteristics, sperm morphology, sperm kinematics, viability, chromatin structure and mitochondrial membrane were evaluated. Meteorological data were available from the local meteorological station;

Results

Season had an effect on semen characteristics in the raw ejaculate, with higher proportions of normal spermatozoa and lower abnormalities in winter than in the other two seasons. Sperm kinematics, viability, DNA fragmentation index, and mitochondrial membrane potential were not different between seasons. Sperm samples selected by SLC had greater normal morphology and a lower proportion with bent tails than controls and higher values of progressive motility (PRO), beat cross frequency, linearity, straightness, wobble (WOB), and lower values of slow motility, velocity average path (VAP), velocity curved line, and amplitude of lateral head displacement than controls. In addition, SLC-selection had a favorable effect on PRO, VAP, and WOB that differed among seasons.

Conclusion

Our results suggested that these bulls were well adapted to their location, with season having an effect on sperm morphology. Moreover, SLC could be used prior to cryopreservation, regardless of season, to enhance normal morphology and kinematics of bull sperm samples without adversely affecting other parameters of sperm quality. However, there was considerable variation among bulls in DNA fragmentation index, mitochondrial membrane potential and sperm viability. In addition, SLC had a positive effect on sperm morphology and sperm kinematics, which could be expected to influence fertility.

Effect of colloid centrifugation on boar sperm quality during storage and function in in vitro fertilization

Ejaculates contain a heterogeneous population of spermatozoa with differing ability to fertilize. It may be possible to reduce the numbers of spermatozoa required for artificial insemination or in vitro fertilization by selecting the sperm sub-population that possesses certain desired characteristics. This review describes what is meant by sperm quality, mentions different methods of sperm selection and then describes the effect of sperm selection by colloid centrifugation on boar sperm quality, both quality during storage and functionality in in vitro fertilization. Several versions of the technique known as Single Layer Centrifugation are available depending on the volume of ejaculate to be processed. Semen can be processed in volumes ranging from 0.25 to 150 mL, in suitably sized tubes. Processing small volumes of semen (0.25 mL on 1 mL colloid) is best done in a 15 mL tube, since the area of the interface between the semen and colloid is greater than in a 1.5 mL microcentrifuge tube. Potential uses of this processing technique are described, such as conservation breeding of rare breeds and removal of pathogens. Reducing the bacterial load in semen by single layer centrifugation though a low density colloid could provide an alternative to the use of antibiotics in semen extenders, and is an interesting development.

Perspectives of nanotechnology in male fertility and sperm function

Recent advances in nanotechnology have tremendously expanded its possible applications in biomedicine. Although, the effects of nanoparticles (NPs) at cellular and tissue levels have not been fully understood, some of these biological effects might be employed in assisted reproduction to improve male fertility particularly by enhancing sperm cell quality either in vivo or in vitro. This review summarises the available literature regarding the potential applications of nanomaterials in farm animal reproduction, with a specific focus on the male gamete and on different strategies to improve breeding performances, transgenesis and targeted delivery of substances to a sperm cell. Antioxidant, antimicrobial properties and special surface binding ligand functionalization and their applications for sperm processing and cryopreservation have been reviewed. In addition, nanotoxicity and detrimental effects of NPs on sperm cells are also discussed due to the increasing concerns regarding the environmental impact of the expanding use of nanotechnologies on reproduction.

Colloid centrifugation of fresh semen improves post-thaw quality of cryopreserved dromedary camel spermatozoa

Colloids have been successfully used in a number of species to improve sperm populations for IVF and for cryopreservation The usefulness of Single Layer Centrifugation (SLC) for freezing dromedary camel spermatozoa in two different extenders was evaluated by examining the motility, viability, acrosome status, DNA integrity, and ability of cryopreserved sperm to penetrate oocytes in vitro in a heterologus IVF system. Two ejaculates from each of five males were divided into four aliquots: two were processed by SLC (selected) while two were centrifuged without colloid (control). Pellets were cryopreserved in Green Buffer or INRA-96® containing 3% glycerol and evaluated at 0 and 1 h post thawed. The SLC improved post-thaw total and progressive motility at 0 (both P < 0.0001) and 1 (P < 0.001; P < 0.01, respectively) h, and STR (both P < 0.05) and BCF (both P < 0.001) at 0 h. Sperm viability and acrosome integrity (both P < 0.001) were improved at both time points. Sperm frozen in Green Buffer had greater total and progressive motilities at 0 (both P < 0.001) and 1 (both P < 0.001) h than INRA-96® samples. Spermatozoa in Green Buffer also had a greater VAP, VCL and VSL at 0 h and improved viability and acrosome integrity at 0 h (P < 0.05; P = 0.001, respectively) and 1 h (P < 0.05; P < 0.001, respectively). Viability of SLC spermatozoa was improved in Green Buffer at 1 h (P < 0.05). Oocyte penetration (P < 0.05) and pronuclear formation (P < 0.01) were greater with SLC-selected spermatozoa than non-selected spermatozoa, regardless of extender. No difference was observed between treatments or extenders in the mean number of spermatozoa per oocyte penetrated. The SLC spermatozoa had less (P < 0.01) DNA fragmentation compared to controls. The DNA fragmentation was moderately and negatively correlated with penetration (r = -0.4162; P = 0.02) and pronuclear formation (r = -0.3390; P < 0.01). In conclusion, colloid centrifugation of spermatozoa and cryopreservation in Green Buffer improves post thaw motility variables and IVF performance of dromedary camel spermatozoa.

Effect of different mini-volume colloid centrifugation configurations on flow cytometrically sorted sperm recovery efficiency and quality using a computer-assisted semen analyzer

Straws of sex-sorted sperm are usually packaged at a low concentration (e.g., ~2.1 × 10⁶  sperm/ml) and cost significantly more than unsorted conventional semen from the same sire. In order to maximize the efficiency of using sex-sorted sperm under in vitro fertilization conditions, the selection of an appropriate sperm separation technique is essential. In this study, the effect of using different silane-coated silica colloid dilutions and layering configurations during centrifugation of sex-sorted sperm was examined over an extended period of incubation time. Sperm recovery and viability after centrifugation using the colloid separation technique were measured along with several sperm motility parameters using CASA. For this purpose, frozen and thawed sex-sorted sperm samples were centrifuged using mini-volume single-layer (40%, 60% and 80%) and mini-volume two-layer (45%/90%, 40%/80% and 30%/60%) separation configurations using PureSperm^® . A single layer of 40% PureSperm^® recovered significantly more sex-sorted sperm (78.07% ± 2.28%) followed by a single layer of 80% PureSperm^® (68.43% ± 2.33%). The lowest sperm recovery was obtained using a two-layer PureSperm^® dilution of 45%/90% (47.57% ± 2.33%). Single-layer centrifugation recovered more sorted sperm (68.67% ± 1.74%) than two layer (53.74% ± 1.74%) (p < .0001). A single layer of 80% PureSperm^® exhibited the highest sorted sperm viability (72.01% ± 2.90%) after centrifugation (p < .05). The mini-volume single layer of 80% PureSperm^® was determined to be an effective alternative to a two-layer centrifugation configuration for sex-sorted sperm selection. In addition, single-layer colloid dilution of 80% performed either as well as or significantly outperformed the other treatments, as well as the control, with regard to motility (MOT) for all time periods of analysis.