Effect of the addition of beta-mercaptoethanol to a thawing solution supplemented with caffeine on the function of frozen-thawed boar sperm and on the fertility of sows after artificial insemination

Role of exogenous antioxidants on the performance and function of pig sperm after preservation in liquid and frozen states: A systematic review

In situations where an excessive generation of reactive oxygen species overwhelms antioxidant capacity, a harmful effect on sperm function is exerted. Antioxidants are molecules capable of minimizing this detrimental effect, which is important in pig sperm due to the high content of polyunsaturated fatty acids in their plasma membrane. The present systematic review aims at evaluating whether supplementing semen extenders (for liquid storage at 17 °C) or freezing and/or thawing media (for cryopreservation) with antioxidants influences sperm quality and functionality parameters, and in vitro/in vivo fertility outcomes. We defined inclusion and exclusion criteria in a PICOS table according to PRISMA guidelines, and conducted a literature search through MEDLINE-PubMed in November 2020. After systematic selection, 75 studies were included: 47 focused on cryopreservation and 28 on liquid storage at 17 °C. More than 70% of the studies included in this review showed that adding semen extenders for liquid storage and/or freezing/thawing media for cryopreservation with antioxidants enhances sperm quality and functionality parameters. In addition, this supplementation improves in vivo/in vitro fertility outcomes, supporting the hypothesis that the beneficial effect observed upon sperm quality has a positive impact on reproduction outcomes.

Relationship between Fertility Traits and Kinematics in Clusters of Boar Ejaculates

Simple Summary

Swine reproduction efficiency is determined by the fertility potential of the sow and sperm quality. The objective of this study is to compare boar sperm motility and kinematic features to evaluate their relationships with reproductive success after artificial insemination (AI). In this study, the movement patterns of boar ejaculates were analyzed by a computer-assisted semen analysis (CASA)-Mot system, and the kinematic values of ejaculate clusters were assessed. The semen of the Pietrain boars showed more linear trajectory of the spermatozoa, while curvilinear velocity and oscillatory movement characterized the semen of the Duroc × Pietrain boars. The offspring of sows inseminated with Pietrain boars showed significantly lower number of stillbirths. In addition, ejaculate grouping into clusters did not have a predictive capacity on litter size variables. Nevertheless, the kinematic variables of the ejaculate may have a predictive, albeit reduced, capacity regarding litter size variables. The results of this study therefore open up possibilities for future assessments of fertility.

Abstract

The aim was to determine the relationship between kinematic parameters of boar spermatozoa and fertility rates of sow, as well as to assess the effect of sperm clusters on the fertility capacity of the ejaculate. Semen samples were collected from 11 sexually mature boars. Samples were analyzed by an ISAS^®v1 CASA-Mot system for eight kinematic parameters. Ejaculate clusters were characterized using multivariate procedures, such as principal factors (PFs) analysis and clustering methods (the k-means model). Four different ejaculate clusters were identified from two kinematic PFs which involved linear trajectory and velocity. There were differences (p < 0.05) between the sperm kinematic variables by sire line. There was no statistical difference (p > 0.05) between dam lines and ejaculate clusters in fertility variables. The discriminant ability of the different kinematics of sperm variables to predict litter size fertility was analyzed using receiver operating characteristics (ROC) curve analysis. Curvilinear velocity (VCL), average path velocity (VAP), amplitude of lateral head displacement (ALH), and beat-cross frequency (BCF) showed significant, albeit limited, predictive capacity for litter size fertility variables (range: 0.55–0.58 area under curve, AUC). The kinematic analysis of the ejaculates in clusters did not have a predictive capacity for litter size variables.

Notoginsenoside R1 protects boar sperm during liquid storage at 17°C

Reactive oxygen species (ROS) damage mammalian sperm during liquid storage. Notoginsenoside R1 (NR1) is a compound isolated from the roots of Panax notoginseng; it has powerful ROS-scavenging activities. This work hypothesized that the antioxidant capacity of NR1 could improve boar sperm quality and fertility during liquid storage. During liquid storage at 17°C, the supplementation of semen extender with NR1 (50 μM) significantly improved sperm motility, membrane integrity and acrosome integrity after 5 days of preservation. NR1 treatment also reduced ROS and lipid peroxidation (LPO) levels at day 5 (p <0.05). Higher glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) levels and sperm-zona pellucida binding capacity were observed in the 50 μM NR1 group than those in the control group at day 7 (p <0.05). Importantly, statistical analysis of the fertility of 200 sows indicated that addition of NR1 to the extender improved the fertility parameters of boar spermatozoa during liquid storage at 17°C (p <0.05). These results demonstrate the practical feasibility of using 50 μM NR1 as an antioxidant in boar extender during liquid storage at 17°C, which is beneficial to both spermatozoa quality and fertility.

Melatonin and Caffeine Supplementation Used, Respectively, as Protective and Stimulating Agents in the Cryopreservation of Human Sperm Improves Survival, Viability, and Motility after Thawing compared to Traditional TEST-Yolk Buffer

Cryopreservation processes can damage spermatozoa and impair structural and functional cell characteristics. Plasma, nuclear membranes, and cellular organelles can suffer from the freeze and thaw process. This study evaluates the protective and stimulant effect of melatonin and caffeine supplementation on the functional characteristics of human spermatozoa before and after freezing. Thirty seminal samples from normozoospermic men aged 19–45 years old collected between October 2012 and May 2017 were included. Semen samples were supplemented with either 2 mM melatonin (MEL) prior to cryopreservation, 2 mM caffeine (CAF) in postthaw, or CAF and MEL (CM) in precryopreservation and postthaw, respectively. Kinetics and seminal parameters, mitochondrial activity, DNA fragmentation, and reactive oxygen species (ROS) levels were analyzed before and after cryopreservation. A significant reduction in sperm concentration, total and progressive motility, sperm kinetics, and mitochondrial activity, as well as a significant increase in DNA fragmentation and ROS production in postthaw samples compared to fresh samples, was identified. After administration of a caffeine and/or melatonin supplement, there was a significant increase in progressive motility in the CAF (p = 0.005) and CM (p = 0.048) groups, as well as mitochondrial activity in the CM group (p < 0.05). Cryopreservation has negative effects on overall sperm quality and increases ROS production. A combination of caffeine and melatonin in prefreeze and postthaw sperm samples has proven to be a very effective and simple way to improve semen quality. This will be particularly useful for initial low-quality semen samples, those which suffer the most from the freezing/thawing process.

Antioxidants and Male Fertility: from Molecular Studies to Clinical Evidence

Spermatozoa are physiologically exposed to reactive oxygen species (ROS) that play a pivotal role on several sperm functions through activation of different intracellular mechanisms involved in physiological functions such as sperm capacitation associated-events. However, ROS overproduction depletes sperm antioxidant system, which leads to a condition of oxidative stress (OS). Subfertile and infertile men are known to present higher amount of ROS in the reproductive tract which causes sperm DNA damage and results in lower fertility and pregnancy rates. Thus, there is a growing number of couples seeking fertility treatment and assisted reproductive technologies (ART) due to OS-related problems in the male partner. Interestingly, although ART can be successfully used, it is also related with an increase in ROS production. This has led to a debate if antioxidants should be proposed as part of a fertility treatment in an attempt to decrease non-physiological elevated levels of ROS. However, the rationale behind oral antioxidants intake and positive effects on male reproduction outcome is only supported by few studies. In addition, it is unclear whether negative effects may arise from oral antioxidants intake. Although there are some contrasting reports, oral consumption of compounds with antioxidant activity appears to improve sperm parameters, such as motility and concentration, and decrease DNA damage, but there is not sufficient evidence that fertility rates and live birth really improve after antioxidants intake. Moreover, it depends on the type of antioxidants, treatment duration, and even the diagnostics of the man’s fertility, among other factors. Literature also suggests that the main advantage of antioxidant therapy is to extend sperm preservation to be used during ART. Herein, we discuss ROS production and its relevance in male fertility and antioxidant therapy with focus on molecular mechanisms and clinical evidence.

Addition of chlorogenic acid and caffeine during the processing of cooled boar semen

ABSTRACT A study was conducted to evaluate the effect of chlorogenic acid (ChA) added pre-cooling and its combination with caffeine added during warming on cooled-stored boar semen parameters. Ten ejaculates were diluted in commercial extender with or without 4.5mg/ml ChA and stored at 15°C. After 0, 24 and 72 hours of storage, aliquots of these doses were taken and incubated at 37°C in the presence or absence of 8.0mM caffeine. Semen quality was evaluated after 10 and 120 minutes of incubation. The ChA increased (P <0.01) the sperm motility, viability, acrosomal integrity and the percentage of spermatozoa with high mitochondrial activity (PMHA), however, decreased (P <0.01) the malondialdehyde (MDA) concentration. Caffeine increased (P<0.05) the sperm motility, viability, PMHA and the MDA concentration and reduced (P <0.05) the acrosome integrity. When associated (ChA+caffeine), there was an increase (P <0.05) in sperm motility and viability, PMHA and acrosome integrity. The addition of ChA to the dilution medium improves the quality of the swine inseminating doses. The addition of caffeine during re-warming is only recommended when the semen is stored for prolonged periods (72h), and the inseminating dose should be used immediately after its addition.

Post-cervical artificial insemination in porcine: The technique that came to stay

The porcine industry is of great importance worldwide, and so any technological innovation in one or more of the associated production areas is of interest for meat production. Among such innovations in the reproduction area, post-cervical or intrauterine artificial insemination (PCAI) has emerged as a new approach in artificial insemination (AI). PCAI is gradually replacing traditional cervical insemination (CAI), particularly in countries with intensive pig production industries. This type of insemination, which deposits the semen in the body of the uterus (as opposed to traditional cervical deposition), is increasingly used in the field due to its simplicity and the numerous advantages that it provides at production level (e.g. reduced number of sperm, less time required to perform insemination and faster genetic improvement) and, consequently, from an economic point of view. In addition, since its inception, PCAI has been combined with other reproductive biotechnologies, such as the use of frozen-thawed sperm, fixed-time AI or sperm-mediated gene transfer. However, despite its wide acceptance and application, new approaches for increasing the efficiency of PCAI are constantly being sought, such as the adjustment and standardization in sperm numbers, the conservation of the PCAI semen dose, its association with other biotechnologies (sex-sorted sperm) or its efficacy in young (nulliparous and primiparous) females.

T. Effect of β-mercaptoetanol and cysteine on post-thawing quality and oxidative activity of ram sperm and on the viability of vitrified sheep embryos

ABSTRACT The effects of β-mercaptoethanol (BME) and cysteine on the viability and oxidative activity of ram sperm after thawing and on development in vitro and viability of vitrified sheep embryos were evaluated. Ejaculates from four rams were pooled and extended, composing six treatments: no antioxidants; 2mM BME; 5mM BME; 2mM BME and 5mM cysteine; 5mM BME and 5mM cysteine; and 5mM cysteine. Sperm motility, membrane and acrosome integrity, mitochondrial functionality, production of reactive oxygen species and total antioxidant capacity were similar across treatments (P>0.05). A medium with no antioxidant presented cleavage and blastocyst development rates (60.3% and 33.6%, respectively) similar (P>0.05) to those of a medium with 50μM BME and 600μM cysteine (64.3% and 36.6%, respectively). Post-thawing viability of vitrified embryos was similar between media (P>0.05). Cysteine and BME had no influence on the post-thawing viability and oxidative activity of ram sperm and on the viability of vitrified sheep embryos.

Recent Advances in Boar Sperm Cryopreservation: State of the Art and Current Perspectives

While sperm cryopreservation is the best technology to store boar semen for long-term periods, only 1% of all artificial inseminations (AI) conducted worldwide are made using frozen-thawed boar sperm. With the emergence of long-term extenders for liquid storage, the use of cryopreserved sperm in routine AI is less required. However, banks of boar semen contain cryopreserved sperm and planning inseminations in AI centres may benefit from the use of frozen-thawed semen. Therefore, there is an interest in the use of this technology to preserve boar sperm. In this regard, although the first attempts to cryopreserve boar semen date back to the seventies and this technology is still considered as optimal, some relevant improvements have been made in the last decade. After giving a general picture about boar sperm cryodamage, the present review seeks to shed light on these recent cryopreservation advances. These contributions regard to protein markers for predicting ejaculate freezability, sperm selection prior to start cryopreservation procedures, additives to freezing and thawing extenders, relevance of the AI-technique and insemination-to-ovulation interval. In conclusion, most of these progresses have allowed counteracting better boar sperm cryodamage and are thus considered as forward steps for this storage method. It is also worth noting that, despite being lower than fresh/extended semen, reproductive performance outcomes following AI with frozen-thawed boar sperm are currently acceptable.

Methods for Improving In Vitro and In Vivo Boar Sperm Fertility

Fertility of boar spermatozoa is changed after ejaculation in vivo and in vitro. During processing for in vitro fertilization (IVF), although spermatozoa are induced capacitation, resulting in a high penetration rate, persistent obstacle of polyspermic penetration is still observed with a high incidence. For artificial insemination (AI), we still need a large number of spermatozoa and lose a majority of those in the female reproductive tract. Fertility of cryopreserved boar spermatozoa is still injured through freezing and thawing process. In the present brief review, factors affecting fertility of boar sperm during IVF, AI and cryopreservation are discussed in the context of discovering methodologies to improve it.

Fertilisation rate obtained with frozen-thawed boar semen supplemented with rosmarinic acid using a single insemination timed according to vulvar skin temperature changes

Artificial insemination (AI) of sows with frozen-thawed semen usually results in lower pregnancy rates and litter sizes than the use of liquid preserved semen. The present study evaluated the effectiveness of vulvar skin temperature changes as a predictor of ovulation in sows and determined the fertility rates obtained after AI with frozen-thawed semen supplemented with rosmarinic acid (RA). Semen was collected from mature boars and cryopreserved in experimental extenders supplemented with or without 105 μM of RA. Multiparous sows were inseminated with a single dose of semen when vulvar skin temperature decreased to a value below 35 °C. Intrauterine insemination was performed using 1.5 × 109 spermatozoa. The sows were slaughtered 48 h after AI and the embryos and oocytes were recovered from the oviducts. Total and progressive motility, viability and acrosome integrity were significantly (P < 0.05) higher in RA-supplemented semen samples compared with the control. Fertilisation occurred in all sows inseminated in the study, although there were no significant differences between the experimental groups. Sows inseminated with RA-supplemented semen showed a slight increase in the number of embryos recovered as compared to sows inseminated with control semen. In conclusion, insemination according to vulvar skin temperature changes resulted in successful fertilisation in all sows, although supplementation of the freezing media with RA did not improve the fertilising ability of frozen-thawed boar sperm.

A review: alteration of in vitro reproduction processes by thiols -emphasis on 2-mercaptoethanol

Descriptions of organosulfurs altering biologically relevant cellular functions began some 40 years ago when murine in vitro cell mediated and humoral immune responses were shown to be dramatically enhanced by any of four xenobiotic, sulfhydryl compounds-2-mercaptoethanol (2ME), dithiothreitol (DTT), glutathione, and L-cysteine; the most effective were 2ME and DTT. These findings triggered a plethora of reports defining 2ME benefits for a multitude of immunological processes. This in turn led to investigations on 2ME alterations of (a) immune functions in other species, (b) activities of other cell-types, and (c) in vivo diseases. In addition, these early findings preceded the identification of previously undefined anticarcinogenic chemicals in specific foods as organosulfurs. Taken all together, there is little doubt that organosulfur compounds have enormous benefits for cellular functions and for a multitude of diseases. Issues of importance still to be resolved are (a) clarification of mechanisms that underlie alteration of in vitro and in vivo processes and perhaps more importantly, (b) which if any in vitro alterations are relevant for (i) alteration of in vivo diseases and (ii) identification of other diseases that might therapeutically benefit from organosulfurs. As one means to address these questions, reviews of different processes impacted by thiols could be informative. Therefore, the present review on alterations of in vitro fertilization processes by thiols (mainly 2ME, since cysteamine alterations have been reviewed) was undertaken. Alterations found to occur in medium supplemented with 2ME were enhancement, no effect, or inhibition. Parameters associated with which are discussed as they relate to postulated thiol mechanisms.

Current and future assisted reproductive technologies for mammalian farm animals

Reproduction in domestic animals is under control by man and the technologies developed to facilitate that control have a major impact on the efficiency of food production. Reproduction is an energy-intensive process. In beef cattle, for example, over 50 % of the total feed consumption required to produce a unit of meat protein is consumed by the dam of the meat animal (Anim Prod 27:367-379, 1978). Sows are responsible for about 20 % of the total feed needed to produce animals for slaughter (Adv Pork Prod 19:223-237, 2008). Accordingly, energy input to produce food from animal sources is reduced by increasing number of offspring per unit time a breeding female is in the herd. Using beef cattle as an example again, life-cycle efficiency for production of weaned calves is positively related to early age at puberty and short calving intervals (J Anim Sci 57:852-866, 1983). Reproductive technologies also dictate the strategies that can be used to select animals genetically for traits that improve production. Of critical importance has been artificial insemination (AI) (Anim Reprod Sci 62:143-172, 2000; Stud Hist Philos Biol Biomed Sci 38:411-441, 2007; Reprod Domest Anim 43:379-385, 2008; J Dairy Sci 92:5814-5833, 2009) and, as will be outlined in this chapter, emerging technologies offer additional opportunities for improvements in genetic selection. Given the central role of reproduction as a determinant of production efficiency and in genetic selection, improvements in reproductive technologies will be crucial to meeting the challenges created by the anticipated increases in world population (from seven billion people in 2011 to an anticipated nine billion by 2050; World population prospects: the 2010 revision, highlights and advance tables. Working Paper No. ESA/P/WP.220, New York) and by difficulties in livestock production wrought by climate change (SAT eJournal 4:1-23, 2007).The purpose of this chapter will be to highlight current and emerging reproductive technologies that have the potential to improve efficiency of livestock production. The focus will be on technologies that manipulate male and female gametes as well as the stem cells from which they are derived and the preimplantation embryo. While technology is crucial to other interventions in the reproductive process like control of seasonal breeding, hormonal regulation of ovulation, estrous cyclicity and pregnancy establishment, feeding to optimize reproduction, minimizing environmental stress, and selection of genes controlling reproduction, these will not be considered here. Rather the reader is directed to other chapters in this volume as well as some reviews on other aspects of artificial manipulation of reproduction (Reprod Fertil Dev 24:258-266, 2011; Reprod Domest Anim 43:40-47, 2008; Reprod Domest Anim 43:122-128, 2008; Soc Reprod Fertil Suppl 66:87-102, 2009; Comprehensive biotechnology, Amsterdam, pp 477-485; Dairy production medicine, Chichester, pp 153-163; Theriogenology 76:1619-1631, 2011; Theriogenology 76:1568-1582, 2011; Theriogenology 77:1-11, 2012). Given the large number of mammalian species used for production of products useful for man and the diversity in their biology and management, the review will not be comprehensive but instead will use results from species that are most illustrative of the opportunities generated by assisted reproductive technologies.