Sperm DNA fragmentation induced by cryopreservation: new insights and effect of a natural extract from Opuntia ficus-indica

Carboxylated Poly-L-lysine Potentially Reduces Human Sperm DNA Fragmentation after Freeze-Thawing, and Its Function Is Enhanced by Low-Dose Resveratrol

Sperm DNA fragmentation (SDF) that occurs during the freezing-thawing of sperm may negatively impact the treatment outcomes of assisted reproductive technologies (ART). In a previous study, we developed a human sperm cryopreservation reagent containing carboxylated poly-L-lysine (CPLL) that reduced SDF after freeze-thawing compared with clinically popular cryopreservation reagents containing human serum albumin. However, it is unclear whether CPLL reduces SDF, as it differed from the constituents of the commercial cryopreservation reagents used for comparison. Therefore, here, we examined whether CPLL reduces the SDF of human sperm and evaluated reactive oxygen species (ROS) levels and lipid peroxidation (LPO), which are the causes of SDF; mitochondrial injury, ROS production; and impaired sperm motility. Furthermore, optimal antioxidants and their concentrations that could further enhance the reduction in SDF were determined for future clinical application in ART and underwent the same functional evaluations. CPLL can reduce SDF via inhibition of intracytoplasmic ROS and LPO. Furthermore, the addition of 0.1 mM resveratrol avoided the enhancement of SDF, which potentially affects mitochondrial and cytoplasmic ROS and LPO. This novel human sperm cryopreservation reagent containing CPLL and resveratrol has the potential to improve treatment outcomes in ART using frozen sperm.

Human Sperm as an In Vitro Model to Assess the Efficacy of Antioxidant Supplements during Sperm Handling: A Narrative Review

Spermatozoa are highly differentiated cells that produce reactive oxygen species (ROS) due to aerobic metabolism. Below a certain threshold, ROS are important in signal transduction pathways and cellular physiological processes, whereas ROS overproduction damages spermatozoa. Sperm manipulation and preparation protocols during assisted reproductive procedures-for example, cryopreservation-can result in excessive ROS production, exposing these cells to oxidative damage. Thus, antioxidants are a relevant topic in sperm quality. This narrative review focuses on human spermatozoa as an in vitro model to study which antioxidants can be used to supplement media. The review comprises a brief presentation of the human sperm structure, a general overview of the main items of reduction-oxidation homeostasis and the ambivalent relationship between spermatozoa and ROS. The main body of the paper deals with studies in which human sperm have been used as an in vitro model to test antioxidant compounds, including natural extracts. The presence and the synergic effects of different antioxidant molecules could potentially lead to more effective products in vitro and, in the future, in vivo.

The Addition of Opuntia ficus-indica Ethanolic Extract to a Skimmed Milk-Based Extender Impacts Ram Sperm Quality

Recently, researchers have focused on the use of natural antioxidants to improve semen quality as a key element for successful artificial insemination. In this context, the first aim of this study was to determine the antioxidant activity and composition (minerals, vitamins, and sugars) of Opuntia ficus-indica cladode ethanolic extract (ETHEX). A further purpose of the study was to investigate the effect of ETHEX supplementation on the quality of liquid ram semen extended with skim milk (SM) at 5°C. The antioxidant activity of ETHEX was studied using free radical 1, 1-diphenyl-2-picrylhydrazyl (DPPH•) assay. The mineral composition and the sugar and vitamin contents of ETHEX were determined using an inductively coupled plasma optical emission spectrometry (ICP-OES) and HPLC-DAD-RID analytical instruments. As a second part, semen was collected from five Boujaâd rams with an artificial vagina. The ejaculates with more than 70% motility were pooled, extended with skim milk (SM) extender without (control) or supplemented with 1-8% of ETHEX (37°C; 0.8 × 109 sperm/mL). Sperm quality parameters were assessed at 8, 24, 48, and 72 h. The results showed that ETHEX had a higher antioxidant activity compared to those of ascorbic acid and butylated hydroxytoluene (BHT). Furthermore, ETHEX contains a considerable amount of minerals, vitamins, and sugars. The inclusion of 1 or 2% ETHEX in SM increased the sperm motility, viability, and membrane integrity and decreased the abnormality of spontaneous and catalyzed lipids peroxidation (p < 0.05) up to 72 h. In addition, semen diluted with 1 and 2% ETHEX decreased the level of DNA fragmentation compared to the control group (p < 0.05). In conclusion, the ETHEX could be recommended to improve the quality of liquid ram spermatozoa. However, its effects on artificial insemination should be further studied.

Impact of quercetin, carnosine, and ozone in the cryopreservation on Nellore (Bos indicus) semen

The objective of this study was to reduce the effects of cryoinjury caused in bovine semen by cryopreservation. Ejaculates were collected from Nellore bulls and subjected to freezing in C (control), ozone (15, 30, and 60 µg mL^-1 of ozone), quercetin (25, 50, and 100 µg mL^-1 of quercetin), and carnosine groups (100, 200, and 300 ng mL^-1 of carnosine). Samples were evaluated post-thaw (M0) and post-rapid thermoresistance test (M30) for sperm kinetics (total motility, progressive motility, curvilinear speed, linearity and amplitude of lateral head displacement) and cell structure viability (plasma membrane integrity, acrosomal integrity, mitochondrial potential, membrane fluidity, and lipid peroxidation). There were no differences (P > 0.05) between the control, quercetin, and carnosine-treated groups for the parameters evaluated at M0 and M30. In turn, supplementation with ozone resulted in lower values for sperm kinetics (P < 0.05) and lower mitochondrial potential at M30 (P < 0.05). Quercetin and carnosine at the concentrations used did not promote significant gains in frozen semen, nor did they demonstrate cytotoxicity. We expected to obtain positive results with the use of ozone. Nonetheless, the addition was harmful to the parameters of sperm kinetics, and its effect was not observed as a possible pro-antioxidant. We believe that the fact that the gas did not harm the sperm structure opens avenues for tests with lower dosages, since, by reducing its concentration, we could minimize the damage to sperm kinetics.

The use of frozen embryos and frozen sperm have complementary IVF outcomes: a retrospective analysis in couples experiencing IVF/Donor and IVF/Husband

Background

The cryopreservation of sperm or embryos has been an important strategy in the treatment of infertility. Recently studies have revealed the outcomes after IVF (in vitro fertilization) treatment for single-factor exposure either to frozen sperm or embryos.

Methods

This retrospective study was to uncover the exposure to both frozen sperm and embryo effects using IVF/H (in vitro fertilization using husbands’ fresh sperm) or IVF/D (in vitro fertilization using donors’ frozen sperm) treatment.

Results

The results showed the clinical pregnancy rate (CPR), live birth rate (LBR) and low birth weight rate (LBW) increased to 63.2% (or 68.1%), 61.1% (or 66.4%) and 15.8% (or 16.2%) after using frozen embryo transfer within Group IVF/H (or Group IVF/D). After using frozen sperm, the high-quality embryo rate (HER) increased to 52% and baby with birth defect rate (BDR) reduced to 0% in subgroup D/ET comparing to subgroup H/ET. While the fertilization rate (FER), cleavage rate (CLR), HER and multiple pregnancy rate (MUR) reduced to 75%, 71%, 45% and 9.2% in subgroup D/FET comparing to subgroup H/FET. Finally, our study found accumulative frozen gamete effects, including both sperm and embryos, led to the significantly increasing in the HER (p < 0.05), CPR (p < 0.001), LBR (p < 0.001) and LBW (p < 0.05) in subgroup D/FET comparing to subgroup H/ET.

Conclusion

The use of frozen embryos and frozen sperm have complementary IVF outcomes. Our findings highlighted the parent’s distinguished frozen effect not only for clinical studies but also for basic research on the mechanism of cellular response adaptations to cryopreservation.

Use of Purslane (Portulaca oleracea) Extracts and Cysteine in Diluents to Improve the Cryopreserved Quality of Goat Sperm

Highlights Using cysteine and purslane extracts in extenders improved significantly the post-thaw sperm characteristics. Sperm viability, DNA integrity, and mitochondrial activity demonstrate an improvement in post-thaw sperm. Malondialdehyde production was decreased based on the positive effects of treated extenders. The obtained results demonstrate that supplementation of 50 μg/mL of purslane methanolic extract with cysteine to freezing extenders was significantly superior compared with other treatments.

Opuntia genus in Human Health: A Comprehensive Summary on Its Pharmacological, Therapeutic and Preventive Properties. Part 1

Opuntia spp. is a diverse and widely distributed genus in Africa, Asia, Australia, and America. Mexico has the largest number of wild species; mainly O. streptacantha, O. hyptiacantha, O. albicarpa, O. megacantha and O. ficus-indica. The latter being the most cultivated and domesticated species. Throughout history, plants and their phytochemicals have played an important role in health care and Opuntia spp. has shown a high nutritional, medicinal, pharmaceutical, and economic impacts. Its main bioactive compounds include pigments (carotenoids, betalains and betacyanins), vitamins, flavonoids (isorhamnetin, kaempferol, quercetin) and phenolic compounds. Together, they favor the different plant parts and are considered phytochemically important and associated with control, progression and prevention of some chronic and infectious diseases. This first review (Part 1), compiles information from published research (in vitro, in vivo, and clinical studies) on its preventive effects against atherosclerotic cardiovascular diseases, diabetes and obesity, hepatoprotection, effects on human infertility and chemopreventive and/or antigenotoxic capacity. The aim is to provide scientific evidences of its beneficial properties and to encourage health professionals and researchers to expand studies on the pharmacological and therapeutic effects of Opuntia spp.

Normal seminal plasma could preserve human spermatozoa against cryopreservation damages in Oligozoospermic patients

BACKGROUND

Cryopreservation of human spermatozoa has been identified as an efficient procedure to preserve fertility in men before any cancer therapy or surgical infertility treatment. Despite the benefits of the procedure, the deleterious effects of cryopreservation have been proven on sperm structure and function. This study aimed to evaluate seminal plasma effects on human sperm characteristics after cryopreservation, and compare the addition of normozoospermic and oligozoospermic seminal plasma in the prepared oligozoospermic samples. Semen samples were collected from fifty-five oligozoospermic men and the twenty fertile individuals who referred to the infertility center. At first, a semen analysis was carried out on each neat ejaculate, and then some were cryopreserved. The remainder of the semen was divided into two, one for seminal plasma removal and the other for sperm preparation. Then, the prepared spermatozoa were cryopreserved in three groups: one with, and another without the addition of oligozoospermic seminal plasma, and still another with the addition of normal seminal plasma. After thawing, sperm DNA integrity, viability, motility, and morphology were determined.

RESULTS

The percentages of all parameters were significantly lower after cryopreservation in all groups compared to the fresh sample. However, this reduction was lower in the oligozoospermic samples cryopreserved with normal seminal plasma.

CONCLUSION

The results indicated that seminal plasma in oligozoospermic patients could not support sperm against cryo-injuries, an indication likely due to insufficient antioxidants and other protective components in oligozoospermic patients. However, normal seminal plasma could slightly preserve sperm characteristics after cryopreservation in oligozoospermic patients.

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.

Carboxylated Poly-l-Lysine as a Macromolecular Cryoprotective Agent Enables the Development of Defined and Xeno-Free Human Sperm Cryopreservation Reagents

In human sperm cryopreservation, test yolk buffer and human serum albumin have been used as permeating macromolecular-weight cryoprotectants. In clinical reproductive medicine, human serum albumin is frequently used because of low risks of zoonoses and allergic reactions. However, the risk of allogeneic infectious diseases exists, and the supply may be unstable because human serum albumin is derived from human blood. Therefore, the development of xeno-free human sperm cryopreservative reagents that could overcome the aforementioned problems is warranted. We succeeded in developing a new xeno-free and defined sperm cryopreservation reagent containing glycerol, carboxylated poly-l-lysine, and raffinose. The cryopreservation reagent was not significantly different in terms of sperm motility, viability, and DNA fragmentation and was comparable in performance to a commercial cryopreservation reagent containing human serum albumin. Moreover, the addition of saccharides was essential for its long-term storage. These results may help elucidate the unknown function of macromolecular-weight permeating cryoprotective agents.

The Role of Resveratrol in Human Male Fertility

Resveratrol (RSV) (3,4′,5 trihydroxystilbene) is a natural non-flavonoid polyphenol widely present in the Mediterranean diet. In particular, RSV is found in grapes, peanuts, berries, and red wine. Many beneficial effects of this molecule on human health have been reported. In fact, it improves some clinical aspects of various diseases, such as obesity, tumors, hypertension, Alzheimer’s disease, stroke, cardiovascular diseases, and diabetes mellitus. However, little is known about the relationship between this compound and male fertility and the few available results are often controversial. Therefore, this review evaluated the effects of RSV on human male fertility and the mechanisms through which this polyphenol could act on human spermatozoa.

Protective Effects of Curcumin on the Outcome of Cryopreservation in Human Sperm

Cryopreservation causes decreased sperm fertility potential due to reactive oxygen species (ROS) production and physical-chemical damage, resulting in reduced sperm viability and motility. The addition of antioxidants to freezing media could protect sperm from cryo-damage, counteracting the harmful effects of ROS. The aim of this study was to assess the effects of curcumin supplementation in freezing medium on preventing cryo-damage in human semen. Semen samples collected from fertile men were cryopreserved in freezing medium supplemented with different concentrations of curcumin (2.5, 5, 10, and 20 μM). After freezing-thawing, sperm parameters, DNA fragmentation, intracellular ROS, and glutathione peroxidase 4 (GPX4) gene expression were evaluated. Supplementation with 20 μM curcumin in freezing medium caused increases in progressive and nonprogressive motility and significant reductions in intracellular ROS and DNA fragmentation in frozen-thawed sperm cells. Following cryopreservation, GPX4 mRNA expression was significantly upregulated in thawed semen supplemented with 20 μM curcumin compared to the control. The results showed that curcumin supplementation in freezing medium was protective against human sperm parameters and sperm DNA, counteracting oxidative damage induced by the freeze-thaw process.

Does resveratrol affect prepared sperm parameters and chromatin quality in normozoospermic and asthenozoospermic patients before and after freezing? A lab trial study

Background

Previous studies have examined the effect of resveratrol as a potent antioxidant for free radicals in semen. While, the prepared spermatozoa are more affected by ROS factors due to centrifugation and incubation.

Objective

To evaluate the RSV's effects on the prepared sperm parameters and chromatin quality in both normozoospermic and asthenozoospermic cases before and after freezing.

Materials and Methods

The sample of 10 normozoospermic and asthenozoospermic men was prepared through the swim-up method. The groups were then divided into two samples of control and experimental (exposure to 30 µmol/l of RSV) to evaluate and compare the sperm parameters and chromatin quality before and after freezing.

Results

The motility and viability of spermatozoa were seen to be significantly different before and after freezing separately in the control and treatment samples of the groups (p ≤ 0.001 and p = 0.001, respectively). However, the stated difference between the control and treatment samples of normozoospermic and asthenozoospermic patients were not significant (p > 0.05). In addition, the sperm morphology and chromatin quality were not significantly different between the two samples of each group; nonetheless, chromatin quality of the treated sample was better than that of the control before and after freezing.

Conclusion

Despite the protective effects of RSV on the semen samples, RSV cannot affect significantly the prepared sperms parameters and chromatin quality in normozoospermic and asthenozoospermic patients.

The Effects of Calligonum Extract and Low-Intensity Ultrasound on Motility, Viability, and DNA Fragmentation of Human Frozen-Thawed Semen Samples

Background

The study aimed to evaluate the impact of Calligonum extract and US radiation on sperm parameters of cryopreserved human semen samples.

Materials and Methods

In this experimental study, twenty-five semen specimens were obtained from healthy semen donors and incubated in human tubal fluid (HTF) medium supplemented with 10% human serum albumin (HSA) for 45 minutes. Samples were treated with Calligonum extract (10 μg/ml) alone (CGM group) and US radiation (LIPUSexposed group) alone or a combination of both treatments (CGM+LIPUS). The US group received US stimulation (in both continuous and pulsed wave modes) at a frequency of 1 MHZ and intensity of 200 mW/cm2 for 200 seconds. Sperm morphology was assessed by Diff-Quik staining. The DNA fragmentation was evaluated the Halo sperm kit. Sperm parameters was analyzed by a computer-assisted semen analysis system. Reactive oxygen species (ROS) was assessed by flow cytometry.

Results

The results showed that the treatment with Calligonum extract significantly (P<0.05) increased the progressive motility of spermatozoa in the CGM group as compared with the control group. The application of low-intensity US significantly (P<0.05) decreased the motility and viability of spermatozoa in the US group when compared with the control group. Our findings also indicated that the use of both low-intensity US in continuous mode and Calligonum extract slightly increased progressive motility; however, such an increase was not statistically significant. The rate of DNA fragmentation was considerably higher (P<0.05) in control and LIPUS-exposed groups than the other groups.

Conclusion

Treatment of spermatozoa with Calligonum extract slightly improved the sperm parameters due to its antioxidant activity, on the other hand, according to our results, US radiation did not improve sperm parameters which may be due to interference with the motility of sperm, as well as its physical effects on spermatozoa.

Is there a role for phosphodiesterase inhibitors in the treatment of male subfertility?

Intracytoplasmic sperm injection (ICSI) is frequently used to overcome severe deficits in semen quality. Concerns, however, are arising over its increasing use for non-male factor infertility. Moreover, increased risk of cardiovascular disease, congenital abnormalities, aneuploidies and childhood cancers have all been reported in the literature in relation to ICSI and it is possible that the quality of sperm chosen for injection may be an important factor in these unwanted outcomes. Given the wider adoption of ICSI to treat beyond the requirements of male infertility alone, research focussed on alternative methods to diagnose and treat the infertile couple is gaining increasing attention. This review focuses on the information available to date on the use of non-selective phosphodiesterase inhibitors (PDEI), specifically pentoxifylline (PF), caffeine (CF) and theophylline (TP) to stimulate sperm motility, thereby potentially reducing the need for ICSI in certain patient groups who may benefit from either expectant management or from a less stressful, minimally invasive and inexpensive treatment such as intrauterine insemination (IUI). The review focuses firstly on the mechanism of action of PDEI followed by treatment effects on sperm parameters such as motility and hyperactivated motility and sperm DNA integrity. Specific clinical implications are discussed that outline the potential role of PDEI in clinical practice and highlights areas in need of further research.

Adverse effects of in vitro manipulation of spermatozoa

Development of in vitro reproduction techniques has not only offered some infertile couples the possibility to have a child, it also revolutionized animal reproduction. Although in vitro reproduction techniques for humans or domestic and non-domestic animals have been designed to mimic in vivo conditions, modifications due to environmental effects or in vitro manipulation of gametes and embryos are unavoidable. For male gametes, in vitro manipulations include techniques to select spermatozoa, cryopreservation and other incubation procedures, during which spermatozoa may be exposed to oxidative stress and other insults that may damage their functions and DNA. The aim of this review is to provide an overview of key studies reporting sperm damage during in vitro manipulation, with particular focus on effects on DNA integrity, a fundamental factor for fertilization and transmission of paternal genetic information to offspring.

The efficacy of antioxidants in sperm parameters and production of reactive oxygen species levels during the freeze-thaw process: A systematic review and meta-analysis

To investigate the impact of antioxidants in sperm parameters and reduction in reactive oxygen species production during the freeze-thaw process. PubMed, Scopus, Web of Science, Embase and Cochrane central library were systematically searched. Of the 1583 articles, 23 studies were selected for data extraction. Our results show that antioxidants improved sperm progressive motility (standardised mean difference (SMD) = 1; 95% CI: 0.62, 1.38; p < .001) and viability (SMD = 1.20; 95% CI: 0.50, 1.91; p = .001) and reduced sperm DNA fragmentation (SDF) and hydrogen peroxide (H₂ O₂ ) production, but there was no significant improvement in total sperm motility after thawing. Acetyl-l-carnitine/l-carnitine, melatonin and catalase had a significant positive impact on progressive motility. The role of tempol and melatonin in improving viability was significant compared to other antioxidants. Moreover, a significant reduction in SDF was observed after addition of butylated hydroxytoluene, tempol and vitamin E. However, the prevention of H₂ O₂ production was significant only after the addition of tempol. Our overall results displayed the positive impact of antioxidants on progressive sperm motility, viability and reduction in SDF and H₂ O₂ production, but no significant impact of antioxidants on total sperm motility was seen during the freeze-thaw process.

Does myoinositol supplement improve sperm parameters and DNA integrity in patients with oligoasthenoteratozoospermia after the freezing-thawing process?

Sperm cryopreservation is a routine method in andrology and IVF laboratory. However, the sperm quality and its fertilizing capacity have been decreased during this process. The purpose of this experiment was to determine the role of myoinositol as a supplement in amelioration of total and progressive sperm motility, DNA fragmentation, total antioxidant capacity (TAC), reactive oxygen species (ROS), and lipid peroxidation after the freezing-thawing process on patients with oligoasthenoteratozoospermia (OAT) syndrome. Semen samples obtained from 40 patients were divided into two aliquots and freezed with simple and 2 mg/mL myoinositol (MYO) supplemented freezing media. All samples were thawed and assessed after one month. Semen parameters were analyzed in terms of the motility by CASA, the level of total ROS by fluorimetry, TAC and MDA by colorimetric assay and finally DNA fragmentation by TUNEL assay. Our results clearly showed that MYO could improve total (37.46 vs. 12.91, p < 0.001) and progressive motility (21.92 vs. 6.49, p < 0.001) in experimental group compared to control group. A higher TAC level was observed in the MYO treated group in comparison to control group (1.11 vs. 0.91, p = 0.05). While MYO supplementation could not be effective on ROS level, it reduced DNA fragmentation of sperm after freeze-thaw process (p = 0.01). Therefore, MYO could be a good supplement for sperm freezing to reduce the detrimental effects of freezing process especially on DNA integrity, which is an important factor in the success of ART, in OAT suffered patients.

In vitro application of Ceratonia siliqua improved sperm parameters and chromatin quality after vitrifacation in normozoospermic aged men

Background

Vitrification is the main technique in the assisted reproductive technique (ART) labs. Sperm vitrification exposes sperm to damage. The aim of the present study was to evaluate the in vitro effect of Ceratonia siliqua (C. siliqua) application on sperm parameters and chromatin quality in normozoospermic aged men. Semen samples (n = 40) were collected from normozoospermic men over 45 years old. Each specimen was divided into four aliquots to form the subsequent groups: fresh (group I), vitrification without treatment (group II), vitrification with the medium supplemented by 20 μg/ml C. siliqua (group III), and vitrification with the thawing medium supplemented by 20 μg/ml C. siliqua (group IV). Sperm progressive motility, normal morphology and viability were assessed. Also, sperm chromatin quality was evaluated by aniline blue (AB), toluidine blue (TB), and sperm chromatin dispersion (SCD) staining.

Results

Vitrification caused a significant decrease in sperm progressive motility, normal morphology and viability as well as chromatin quality compared to fresh samples (p < 0.05). Supplementation of vitrification/thawing medium with C. siliqua significantly improved sperm progressive motility, normal morphology, viability, and chromatin quality compared to vitrification without any supplementation (p < 0.05).

Conclusions

The study showed that C. siliqua can improve the detrimental effect of vitrification on sperm parameters and chromatin quality of normozoospermic aged men.

Cryopreservation of Sperm: Effects on Chromatin and Strategies to Prevent Them

Cryopreservation is a technique that can keep sperm alive indefinitely, enabling the conservation of male fertility. It involves the cooling of semen samples and their storage at -196 °C in liquid nitrogen. At this temperature all metabolic processes are arrested. Sperm cryopreservation is of fundamental importance for patients undergoing medical or surgical treatments that could induce sterility, such as cancer patients about to undergo genotoxic chemotherapy or radiotherapy, as it offers these patients not only the hope of future fertility but also psychological support in dealing with the various stages of the treatment protocols.Despite its importance for assisted reproduction technology (ART) and its success in terms of babies born, this procedure can cause cell damage and impaired sperm function. Various studies have evaluated the impact of cryopreservation on chromatin structure, albeit with contradictory results. Some, but not all, authors found significant sperm DNA damage after cryopreservation. However, studies attempting to explain the mechanisms involved in the aetiology of cryopreservation-induced DNA damage are still limited. Some reported an increase in sperm with activated caspases after cryopreservation, while others found an increase in the percentage of oxidative DNA damage. There is still little and contradictory information on the mechanism of the generation of DNA fragmentation after cryopreservation. A number of defensive strategies against cryoinjuries have been proposed in the last decade. Most studies focused on supplementing cryoprotectant medium with various antioxidant molecules, all aimed at minimising oxidative damage and thus improving sperm recovery. Despite the promising results, identification of the ideal antioxidant treatment method is still hampered by the heterogeneity of the studies, which describe the use of different antioxidant regimens at different concentrations or in different combinations. For this reason, additional studies are needed to further investigate the use of antioxidants, individually and in combination, in the cryopreservation of human sperm, to determine the most beneficial conditions for optimal sperm recovery and preservation of fertility.

Interventions to Prevent Sperm DNA Damage Effects on Reproduction

Excessive oxidation and antioxidant imbalance resulting from several conditions may cause sperm DNA damage, which, in turn, affect male fertility, both natural and assisted. Sperm DNA damage transferred to the embryo might also affect the health of offspring. Several conditions associated with excessive oxidative stress are modifiable by the use of specific treatments, lifestyle changes, and averting exposure to environmental/occupational toxicants. Here, we discuss the strategies to reduce sperm DNA damage with a focus on clinical and surgical interventions.

Does supplementation of sperm freezing/thawing media with Ceratonia siliqua improve detrimental effect of cryopreservation on sperm parameters and chromatin quality in normozoospermic specimens?

Human sperm banking is an important procedure in the assisted reproductive technique centers. It entails sperm damage. The aim of this study was to investigate beneficial effect of Ceratonia siliqua (C. siliqua) supplement in freezing/thawing media on post thaw sperm parameters and sperm chromatin quality in normozoospermic samples. Forty normozoospermic specimens were included in this prospective study. Each sample was divided into ten groups. In groups one to five, 0 (as control group) 5, 10, 20 and 30 µg/ml C. siliqua were added to freezing medium and in groups six to ten, similar concentration of C. siliqua were added to thawing medium for 30 min incubation. Sperm concentration, progressive motility, normal morphology, viability, aniline blue (AB), toluidine blue (TB) and sperm chromatin dispersion (SCD) staining tests were evaluated before vitrification and after thawing. The results showed that 10 and 20 µg/ml supplementation of C. siliqua in freezing/thawing media significantly increased progressive motility, normal morphology and viability of sperm (p < 0.05) as well as decreased AB, TB and SCD (p < 0.05). Also, 20 µg/ml had significantly higher improvement compared to 10 µg/ml C. siliqua (p < 0.05). The present study showed that C. siliqua supplemented freezing/thawing media can improve sperm quality of normozoospermic samples after freezing/thawing.

Environment and Male Fertility: Effects of Benzo-α-Pyrene and Resveratrol on Human Sperm Function In Vitro

Lifestyle, cigarette smoking and environmental pollution have a negative impact on male fertility. Therefore, the aim of this study was to evaluate the in-vitro effects of benzo-α-pyrene (BaP) and aryl hydrocarbon receptor (AHR) agonists on motility and bio-functional sperm parameters. We further assessed whether resveratrol (RES), an AHR antagonist and antioxidant molecule, had any protective effect. To accomplish this, 30 normozoospermic, healthy, non-smoker men not exposed to BaP were enrolled. Spermatozoa of 15 men were incubated with increasing concentrations of BaP to evaluate its effect and to establish its dose response. Then, spermatozoa of the 15 other men were incubated with BaP (15 µM/mL), chosen according to the dose-response and/or RES to evaluate its antagonistic effects. The effects of both substances were evaluated after 3 h of incubation on total and progressive sperm motility and on the following bio-functional sperm parameters evaluated by flow cytometry: Degree of chromatin compactness, viability, phosphatidylserine externalization (PS), late apoptosis, mitochondrial membrane potential (MMP), DNA fragmentation, degree of lipoperoxidation (LP), and concentrations of mitochondrial superoxide anion. Benzo-α-pyrene decreased total and progressive sperm motility, impaired chromatin compactness, and increased sperm lipoperoxidation and mitochondrial superoxide anion levels. All these effects were statistically significant at the lowest concentration tested (15 µM/mL) and they were confirmed at the concentration of 45 µM/mL. In turn, RES was able to counteract the detrimental effects of BaP on sperm motility, abnormal chromatin compactness, lipid peroxidation, and mitochondrial superoxide. This study showed that BaP alters sperm motility and bio-functional sperm parameters and that RES exerts a protective effect on BaP-induced sperm damage.

Acetyl-L-carnitine: An effective antioxidant against cryo-damage on human spermatozoa with asthenospermia

A variety of natural and artificial cryoprotectant extenders have been explored to enhance sperm recovery following cryopreservation-thawing process. The current investigation is aimed at evaluating the effect of acetyl-L-carnitine on human spermatozoa and reactive species oxygen (ROS) level after freezing-thawing process. The spermatozoa were collected from 35 male patients diagnosed as having asthenospermia. The cryopreservation of human spermatozoa treated with acetyl-L-carnitine at different concentrations (group B: 2.5 mmol/L, group C: 7.5 mmol/L, group D: 15 mmol/L) was compared with control (group A: no acetyl-L-carnitine given). For the frozen-thawed spermatozoa, the viability, motility and DNA integrity were measured by comet assay, acrosome integrity by FITC-PNA staining and ROS level was determined in each group. The results showed that there were no significant differences in motility and viability between group A and group B, while the motility and viability of spermatozoa in group C and group D were significantly increased as compared with those in group A. As compared with group A, the values for DNA integrity parameters including comet rate (CR), tail DNA percentage (TD), tail length (TL) and Oliver tail moment (OTM) were significantly reduced in group C and group D. Group C and group D also displayed a higher proportion of intact acrosome than group A. No significant difference in ROS level was found between group A and group B, while with the increase in acetyl-L-carnitine concentration, the ROS level in groups C and D was significantly reduced as compared with that in group A. In conclusion, acetyl-L-carnitine at a concentration of 7.5 mmol/L is an effective antioxidant against cryo-damage on post-thawed human spermatozoa.

Chelating agents in combination with rosmarinic acid for boar sperm freeze-drying

The presence of DNA protective agents in the medium is necessary to maintain sperm functionality after freeze-drying procedure. The objective of this study was to investigate the effect of chelating agents, ethylene diaminetetraacetic acid (EDTA) and ethylene glycoltetraacetic acid (EGTA), in combination with rosmarinic acid (RA) on DNA integrity of freeze-dried boar sperm. We also examined the effect of these agents on the in vitro developmental ability of porcine oocytes following sperm injection (ICSI). Heterospermic mix, obtained from ejaculated sperm of three boars, was freeze-dried in two different chelating agents' media: 50mM EDTA or 50mM EGTA, and in these media supplemented with 105μM of rosmarinic acid. Frozen-thawed sperm was used as control. After rehydration, samples were subjected to DNA damage detection using Sperm Chromatin Dispersion test. ICSI was performed to verify the ability of freeze-dried sperm to participate in embryonic development. Five replicated trials were carried out for each group. In the presence of rosmarinic acid, the percentage of spermatozoa with DNA damage decreased significantly (p=0.010), without differences between the two chelating agents combination. EDTA solution preserves more efficiently DNA integrity of boar sperm than EGTA solution (p=0.002). There were no significant differences among the studied groups related to the blastocyst formation rate. Results suggested that the addition of rosmarinic acid to the medium improves sperm DNA integrity after freeze-drying, but does not promote fertilization and blastocyst development. We also observed a similar percentage of embryos production with freeze-dried and with frozen-thawed sperm.

Antioxidant effect of hydroxytyrosol on human sperm quality during in vitro incubation

The aim of the study was to evaluate the antioxidant potential of hydroxytyrosol (HT) on human sperm quality during incubation in vitro. Semen samples collected from men attending the Laboratory of Histology-Embryology of Sfax Faculty of Medicine (Tunisia) for infertility investigations were evaluated for initial sperm parameters. Only normal selected ejaculates (n = 15) were centrifuged and incubated further with or without HT (200ug ml^-1 ) at room temperature for 45 min. After incubation, sperm motility and viability, DNA oxidation and reactive oxygen species (ROS) production were assessed. The results showed that centrifugation significantly influenced sperm motility and viability. The supplementation of HT in incubating media improved (P = 0.01) significantly sperm viability and decreased sperm DNA oxidation (P < 0.001) and ROS levels (P = 0.03) following centrifugation. It can be concluded that supplementation of HT might be helpful to maintain the human spermatozoon after centrifugation.

Sperm cryopreservation update: Cryodamage, markers, and factors affecting the sperm freezability in pigs

Cryopreservation is the most efficient method for long-term preservation of mammalian sperm. However, freeze-thawing procedures may strongly impair the sperm function and survival and thus decrease the reproductive performance. In addition, the sperm resilience to withstand cryopreservation, also known as freezability, presents a high individual variability. The present work summarizes the principles of cryoinjury and the relevance of permeating and nonpermeating cryoprotective agents. Descriptions about sperm cryodamage are mainly focused on boar sperm, but reference to other mammalian species is also made when relevant. Main cryoinjuries not only regard to sperm motility and membrane integrity, but also to the degradation effect exerted by freeze-thawing on other important components for sperm fertilizing ability, such as mRNAs. After delving into the main differences between good and poor freezability boar ejaculates, those protein markers predicting the sperm ability to sustain cryopreservation are also mentioned. Moreover, factors that may influence sperm freezability, such as season, diet, breed, or ejaculate fractions are discussed, together with the effects of different additives, like seminal plasma and antioxidants. After briefly referring to the effects of long-term sperm preservation in frozen state and the reproductive performance of frozen-thawed boar sperm, this work speculates with new research horizons on the preservation of boar sperm, such as vitrification and freeze-drying.

Protective effects of l-carnitine on astheno- and normozoospermic human semen samples during cryopreservation

This study was conducted to determine the effects of l-carnitine (LC), as an antioxidant, in preventing spermatozoa damage during the freezing–thawing process in both astheno- and normozoospermic human semen samples. Seventy semen samples (37 asthenozoospermic and 33 normozoospermic) were involved in this study. Cryopreservation medium supplemented with 1.0 g/l LC was mixed with semen at a ratio of 1:1 (v/v). Controls were cryopreserved with freezing medium only. Assessment of motility, viability (VIA), mitochondrial membrane potential (MMP) and DNA fragmentation index (DFI) were performed on aliquots of fresh semen, frozen–thawed control and frozen–thawed LC treated samples. Supplementation of the cryopreservation medium with LC induced a significant improvement in post-thaw sperm parameters in both the asthenozoospermic and normozoospermic semen samples, compared with those of the control, regarding sperm fast forward motility, forward motility, total motility and VIA. LC showed better protective effects towards asthenozoospermia for DFI (F = 115.85, P < 0.01) and VIA (F = 67.14, P < 0.01) than did normozoospermic semen samples. We conclude that supplementation with LC prior to the cryopreservation process reduced spermatozoa cryodamage in both asthenozoospermic and normozoospermic semen samples. LC had better protective effects for asthenozoospermic human semen samples. Future research should focus on the molecular mechanism for and the different protective effects of LC between asthenozoospermic and normozoospermic semen samples during cryopreservation.

Antioxidant effect of rosemary (Rosmarinus officinalis L.) extract in soybean lecithin-based semen extender following freeze-thawing process of ram sperm

The aim of current study was to evaluate effect of rosemary aqueous extract on post-thawed ram sperm quality in a soybean lecithin-based (SL) extender. Ram semen samples were obtained, extended with SL extender and supplemented with 0% (SL-R0), 2% (SL-R2), 4% (SL-R4), 6% (SL-R6), and 8% (SL-R8) rosemary aqueous extract. Following equilibration, the straws were frozen, and then plunged into the liquid nitrogen. After thawing, sperm motility and velocity parameters, plasma membrane functionality, viability, acrosomal and capacitation status were evaluated. Membrane lipid peroxidation was also analyzed through the malondialdehyde (MDA) concentration. Our results showed that SL-R4 and SL-R6 groups resulted in higher (p < 0.05) percentages of total motility, progressive motility, and plasma membrane functionality, as compared with other groups. Highest (p < 0.05) viable and lowest (p < 0.05) dead spermatozoa were observed in SL-R6 group compared to the other groups. The acrosomal and capacitation status were not affected (p > 0.05) by different levels of rosemary aqueous extract. Lower (p < 0.05) MDA concentration has been observed in SL-R4 and SL-R6 groups. The results of this study demonstrate that supplementation of SL extender with rosemary aqueous extract influences post-thawed ram sperm quality in a dose dependent manner.

SUMO1 in human sperm: new targets, role in motility and morphology and relationship with DNA damage

In studies carried out previously, we demonstrated that small ubiquitin-like modifier 1 (SUMO1) is associated with poor sperm motility when evaluated with a protocol that reveals mostly SUMO1-ylated live sperm. Recently, with another protocol, it has been demonstrated that SUMO is expressed in most sperm and is related to poor morphology and motility, suggesting that sumoylation may have multiple roles depending on its localisation and targets. We show herein, by confocal microscopy and co-immunoprecipitation, that dynamin-related protein 1 (DRP1), Ran GTPase-activating protein 1 (RanGAP1) and Topoisomerase IIα, SUMO1 targets in somatic and/or germ cells, are SUMO1-ylated in mature human spermatozoa. DRP1 co-localises with SUMO1 in the mid-piece, whereas RanGAP1 and Topoisomerase IIα in the post-acrosomal region of the head. Both SUMO1 expression and co-localisation with the three proteins were significantly higher in morphologically abnormal sperm, suggesting that sumoylation represents a marker of defective sperm. DRP1 sumoylation at the mid-piece level was higher in the sperm of asthenospermic men. As in somatic cells, DRP1 sumoylation is associated with mitochondrial alterations, this protein may represent the link between SUMO and poor motility. As SUMO pathways are involved in responses to DNA damage, another aim of our study was to investigate the relationship between sumoylation and sperm DNA fragmentation (SDF). By flow cytometry, we demonstrated that SUMO1-ylation and SDF are correlated (r=0.4, P<0.02, n=37) and most sumoylated sperm shows DNA damage in co-localisation analysis. When SDF was induced by stressful conditions (freezing and thawing and oxidative stress), SUMO1-ylation increased. Following freezing and thawing, SUMO1-Topoisomerase IIα co-localisation and co-immunoprecipitation increased, suggesting an involvement in the formation/repair of DNA breakage.

Assessment of the reproductive toxicity of inhalation exposure to ethyl tertiary butyl ether in male mice with normal, low active and inactive ALDH2

No data are available regarding aldehyde dehydrogenase 2 (ALDH2) polymorphisms related to the reproductive toxicity possibly caused by ethyl tertiary butyl ether (ETBE). In this study, two inhalation experiments were performed in Aldh2 knockout (KO), heterogeneous (HT) and wild type (WT) C57BL/6 male mice exposed to ETBE, and the data about general toxicity, testicular histopathology, sperm head numbers, sperm motility and sperm DNA damage were collected. The results showed that the 13-week exposure to 0, 500, 1,750 and 5,000 ppm ETBE significantly decreased sperm motility and increased levels of sperm DNA strand breaks and 8-hydroxy-deoxyguanosine in both WT and KO mice, the effects were found in 1,750 and 5,000 ppm groups of WT mice, and all of the three exposed groups of KO mice compared to the corresponding control; furthermore, ETBE also caused decrease in the relative weights of testes and epididymides, the slight atrophy of seminiferous tubules of testis and reduction in sperm numbers of KO mice exposed to ≥500 ppm. In the experiment of exposure to lower concentrations of ETBE (0, 50, 200 and 500 ppm) for 9 weeks, the remarkable effects of ETBE on sperm head numbers, sperm motility and sperm DNA damage were further observed in KO and HT mice exposed to 200 ppm ETBE, but not in WT mice. Our findings suggested that only exposure to high concentrations of ETBE might result in reproductive toxicity in mice with normal active ALDH2, while low active and inactive ALDH2 enzyme significantly enhanced the ETBE-induced reproductive toxicity in mice, even exposed to low concentrations of ETBE, mainly due to the accumulation of acetaldehyde as a primary metabolite of ETBE.

Development of a specific method to evaluate 8-hydroxy,2-deoxyguanosine in sperm nuclei: relationship with semen quality in a cohort of 94 subjects

Oxidative stress (OS) is involved in many disoders including male infertility. Human spermatozoa are very sensitive targets of reactive oxygen species (ROS) and most sperm functions are impaired in the case of OS. In addition unbalanced production of ROS is considered one of the most important causes of sperm DNA fragmentation, a semen trait of infertile men. The relationship between oxidative damage and semen quality is partially controversial, probably due to the different methods and/or targets used to reveal the OS. In this study, by fluorescence microscopy and flow cytometry, we compared two methods to reveal 8-hydroxy,2-deoxyguanosine (8-OHdG), the hallmark of oxidative DNA damage: an immunofluorescence method and the commercial OxyDNA kit. We found that although both methods localized the labelling in sperm nuclei they yielded different measures, and only with the immunofluorescence method was the labelling specific for sperm 8-OHdG. The immunofluorescence method, coupled to flow cytometry, was thus selected to analyse the 8-OHdG content in semen samples from 94 subfertile patients and to investigate the relationship with semen quality. We found that the percentages of spermatozoa with 8-OHdG (mean±s.d., 11.4±6.9%) were related to sperm count (Pearson's correlation coefficient (r)=−0.27, P=0.04 (ANOVA and student's t-test)), motility (progressive: r=−0.22, P=0.04; non-progressive: r=0.25, P=0.01), and normal morphology (r=−0.27, P=0.01). In conclusion, we demonstrate that immunofluorescence/flow cytometry is a reliable and specific method to detect 8-OHdG at single-cell level and show that oxidative damage only partially overlaps poor semen quality, suggesting that it could provide additional information on male fertility with respect to routine semen analysis.