Cryopreservation increases DNA fragmentation in spermatozoa of smokers

Evaluation of microRNA expression profiles in human sperm frozen using permeable cryoprotectant-free droplet vitrification and conventional methods

For sperm cryopreservation, the conventional method, which requires glycerol, has been used for a long time. In addition, the permeable cryoprotectant-free vitrification method has been continuously studied. Although the differences of cryopreservation effects between the two methods have being studied, differences in microRNA (miRNA) profiles between them remain unclear. In this study, we investigated the differences in miRNA expression profiles among conventional freezing sperm, droplet vitrification freezing sperm and fresh human sperm. We also analyzed the differences between these methods in terms of differentially expressed miRNAs (DEmiRs) related to early embryonic development and paternal epigenetics. Our results showed no significant differences between the cryopreservation methods in terms of sperm motility ratio, plasma membrane integrity, DNA integrity, mitochondrial membrane potential, acrosome integrity, and ultrastructural damage. However, sperm miRNA-sequencing showed differences between the two methods in terms of the numbers of DEmiRs (28 and 19 with vitrification using a nonpermeable cryoprotectant and the conventional method, respectively) in postthaw and fresh sperm specimens. DEmiRs related to early embryonic development and paternal epigenetics mainly included common DEmiRs between the groups. Our results showed that the differences between conventional freezing and droplet vitrification were minimal in terms of miRNA expression related to embryonic development and epigenetics. Changes in sperm miRNA expression due to freezing are not always detrimental to embryonic development. This study compared differences in miRNA expression profiles before and after cryopreservation between cryopreservation by conventional and vitrification methods. It offers a new perspective to evaluate various methods of sperm cryopreservation.

High sperm DNA fragmentation: do we have robust evidence to support antioxidants and testicular sperm extraction to improve fertility outcomes? a narrative review

To date, infertility affects 10% to 15% of couples worldwide. A male factor is estimated to account for up to 50% of cases. Oral supplementation with antioxidants could be helpful to improve sperm quality by reducing oxidative damage. At the same time, there is a growing interest in the literature on the use of testicular sperm in patients with high DNA fragmentation index (DFI). This narrative review aims to evaluate the effectiveness of supplementation of oral antioxidants in infertile men with high DFI compared to testicular sperm retrieval. The current evidence is non-conclusive because of serious risk of bias due to small sample sizes and statistical methods. Further large well-designed randomised placebo-controlled trials are still required to clarify the exact role of these to different therapeutic approaches.

Impact of heavy alcohol consumption and cigarette smoking on sperm DNA integrity

The purposes of the presents study were to investigate the impact of alcohol consumption and cigarette smoking on semen parameters and sperm DNA quality, as well as to determine whether tobacco smoking, or alcohol consumption causes more deterioration of sperm quality. Two hundred and eleven semen samples of men were included in this study. Four groups were studied: heavy smokers (N = 48), heavy drinkers (N = 52), non-smokers (n = 70), and non-drinkers (n = 41). Semen parameters were determined according to WHO guidelines, protamine deficiency assessed by chromomycin (CMA3) staining, and sperm DNA fragmentation (sDF) evaluated by TUNEL assay. Sperm parameters were significantly higher in non-smokers versus smokers and in non-drinkers versus drinkers (p < 0.005). However, protamine deficiency and sDF were significantly lower in non-smokers versus smokers and in non-drinkers versus drinkers (p < 0.0001). No significant difference in the semen analysis parameters was observed between heavy smokers and heavy drinkers (semen volume: 3.20 ± 1.43 vs. 2.81 ± 1.56 ml, semen count: 65.75 ± 31.32 vs. 53.51 ± 32.67 mill/ml, total motility: 24.27 ± 8.18 vs. 23.75 ± 1.75%, sperm vitality: 36.15 ± 18.57 vs. 34.62 ± 16.65%, functional integrity: 41.56 ± 18.57 vs. 45.96 ± 17.98% and the morphologically normal spermatozoa: 28.77 ± 11.82 vs. 27.06 ± 13.13%, respectively). However, protamine deficiency was significantly higher among drinkers than smokers (37.03 ± 9.75 vs. 33.27 ± 8.56%, p = 0.020). The sDF was also significantly higher among drinkers than smokers (22.37 ± 7.60 vs. 15.55 ± 3.33%, p < 0.0001). Thus, cigarette smoking, and heavy alcohol intake can deteriorate sperm quality. However, alcohol consumption deteriorates sperm maturity and damages DNA integrity at significantly higher rates than cigarette smoking.

Cyanidin-3-Ο-glucoside supplementation in cryopreservation medium improves human sperm quality

Currently, the cryopreservation of human spermatozoa must overcome the adverse effects of excessive oxidation. In this study, we aimed to evaluate the effect of supplementation of cryopreservation medium with cyanidin-3-Ο-glucoside (C3G) on sperm quality. Semen samples were obtained from men with normozoospermia according to WHO criteria (n = 39). The sperm parameter values were compared after cryopreservation in medium supplemented with and without C3G.Compared with the control group (without additive), low doses (50 μM and 100 μM) of C3G improved sperm viability and motility and decreased the reactive oxygen species (ROS) of spermatozoa, while high doses (200 μM) of C3G did not obviously enhance sperm quality. The amount of DNA fragmentation index (DFI) and high DNA stainability (HDS) after freezing were higher in the control group than in the C3G supplementation groups. Low-concentration C3G supplementation (50 μM) was negatively correlated with sperm ROS levels (r = -0.2, p = 0.03). Collectively, our findings suggest that C3G could be an efficient semen cryoprotectant that ameliorates oxidative stress in human sperm during cryopreservation.

Short/long-term cryopreservation prior to comet assay of whole-blood leukocytes and in vitro-cultured lung fibroblasts

Single-cell gel electrophoresis (comet assay) is a valuable test that can be used in ecotoxicological, epidemiological, and biomonitoring contexts. We assessed the effects of short- (without cryopreservation) and long-term (with cryopreservation) storage of DMEM-cultivated human peripheral blood leukocytes (HPBLs) and a human lung fibroblast cell line (FLECH-104) on comet assay results. Samples were stored for 6 or 24 h at room temperature (23°С) or 4 °C and frozen at -80 °C or -196 °C for 1, 2, or 4 weeks. Short-term storage led to significant increases in the comet tail intensity (TI) and Olive tail moment (OTM) in HPBL and FLECH-104 samples. Freezing FLECH-104 samples at -80°С and -196°С resulted in TI mean increases, with no differences in OTM. All frozen HPBL samples did not exhibit significant increases in TI or OTM, and instead exhibited a slight decrease in TI versus the control at both -80 °C and -196 °C. Increased frequency of highly damaged cells was observed in FLECH-104 and HPBL cultures during both short-term storage and after freezing, which may indicate a significant destructive effect. Therefore, freezing of cell cultures and whole blood according to our protocol is not recommended.

Green tea extract as a cryoprotectant additive to preserve the motility and DNA integrity of human spermatozoa

Cryopreservation impairs sperm quality and functions, including motility and DNA integrity. Antioxidant additives in sperm freezing media have previously brought improvements in postthawed sperm quality. Green tea extract (GTE) is widely considered as an excellent antioxidant, and its beneficial role has been proven in other human cells. This study aims to evaluate the GTE as a potential additive in cryopreservation media of human spermatozoa. In part one, the semen of 20 normozoospermic men was used to optimize the concentration of GTE that maintains sperm motility and DNA integrity against oxidative stress, induced by hydrogen peroxide (H2O2). Spermatozoa were treated with GTE at different concentrations before incubation with H2O2. In part two, the semen of 45 patients was cryopreserved with or without 1.0 ng ml-1 GTE. After 2 weeks, the semen was thawed, and the effect on sperm motility and DNA fragmentation was observed. Our data showed that GTE significantly protected sperm motility and DNA integrity against oxidative stress induced by H2O2when added at a final concentration of 1.0 ng ml-1. We found that the addition of 1.0 ng ml-1 GTE to cryopreservation media significantly increased sperm motility and DNA integrity (both P < 0.05). More interestingly, patients with high sperm DNA damage benefited similarly from the GTE supplementation. However, there was no significant change in the reactive oxygen species (ROS) level. In conclusion, supplementing sperm freezing media with GTE has a significant protective effect on human sperm motility and DNA integrity, which may be of clinical interest.

Tobacco smoking and its impact on the expression level of sperm nuclear protein genes: H2BFWT, TNP1, TNP2, PRM1 and PRM2

The aim of this current study was to investigate the influence of tobacco smoke on sperm quality determined by standard parameters, on sperm DNA maturity tested by chromomycin A3 (CMA3) staining, on sperm DNA fragmentation tested by TUNEL assay and on the transcript level of sperm nuclear proteins H2BFWT, PRM1, PRM2, TNP1 and TNP2 genes quantified by RT-PCR. One hundred forty-one (141) sperm samples (43 nonsmokers (G.1) and 98 heavy smokers (G.2)) of couples undergoing ICSI were enrolled in this study. In G2, a significant decrease in standard semen parameters in comparison with nonsmokers was shown (p < .01). In contrast, protamine deficiency (CMA3 positivity) and sperm DNA fragmentation (sDF) were significantly higher in G2 than in G1 (p < .01). Furthermore, the studied genes were differentially expressed (p < .01), down-regulated in the spermatozoa of G.2 compared to that of G.1 (fold change <0.5) and were significantly correlated between each other (p < .01). Moreover, in comparison with G1, the protamine mRNA ratio in G2 was significantly higher (p < .01). It can therefore be concluded that smoking alters mRNA expression levels of H2BFWT, TNP1, TNP2, PRM1 and PRM2 genes and the protamine mRNA ratio and consequently alters normal sperm function.

Application of the comet assay in human biomonitoring: An hCOMET perspective

The comet assay is a well-accepted biomonitoring tool to examine the effect of dietary, lifestyle, environmental and occupational exposure on levels of DNA damage in human cells. With such a wide range of determinants for DNA damage levels, it becomes challenging to deal with confounding and certain factors are inter-related (e.g. poor nutritional intake may correlate with smoking status). This review describes the effect of intrinsic (i.e. sex, age, tobacco smoking, occupational exposure and obesity) and extrinsic (season, environmental exposures, diet, physical activity and alcohol consumption) factors on the level of DNA damage measured by the standard or enzyme-modified comet assay. Although each factor influences at least one comet assay endpoint, the collective evidence does not indicate single factors have a large impact. Thus, controlling for confounding may be necessary in a biomonitoring study, but none of the factors is strong enough to be regarded a priori as a confounder. Controlling for confounding in the comet assay requires a case-by-case approach. Inter-laboratory variation in levels of DNA damage and to some extent also reproducibility in biomonitoring studies are issues that have haunted the users of the comet assay for years. Procedures to collect specimens, and their storage, are not standardized. Likewise, statistical issues related to both sample-size calculation (before sampling of specimens) and statistical analysis of the results vary between studies. This review gives guidance to statistical analysis of the typically complex exposure, co-variate, and effect relationships in human biomonitoring studies.

Leptin in sperm analysis can be a new indicator

Purpose Radiotherapy, chemotherapy, various tumors and invasive surgery can result in ejaculatory dysfunction and testicular insufficiency. Sperm cryopreservation is the only method which can provide a baby for couples. Cryopreservation freezes tissues and cells, allowing them to be stored for future use by stopping all biological activities. Cryopreservation can cause some harmful changes in the structure and function of the sperm. Leptin molecule plays many roles in most biological processes including the satiety and cell renewal, proliferation, angiogenesis, modulation of energy expenditure and regulation of the neuroendocrine system. Leptin was also reported to be associated with spermatogenesis in several studies. Methods This study aims to use leptin molecule as a parameter for sperm motility and DNA fragmentation before and after the cryopreservation. In this study, semen samples were taken from 30 normospermic male volunteers. Each semen sample was examined for the same parameters before and after the cryopreservation. Samples were analyzed before and after cryopreservation in terms of sperm motility by morphological sperm analysis with spermac stain dye, DNA fragmentation by TUNEL assay, ultrastructural analysis with transmission electron microscopy (TEM), seminal leptin levels by ELISA method and reactive oxygen species (ROS) levels by colorimetric method. Results Decreased sperm motility, distribution of sperm morphology and increased DNA fragmentation were determined after cryopreservation. Similarly, seminal ROS and leptin levels were also increased significantly. There was a negative correlation between seminal leptin and sperm motility. Additionally, there was a positive correlation between seminal leptin and DNA fragmentation. Conclusion According to these results, leptin molecule can be used as a marker for sperm motility and DNA fragmentation before and after cryopreservation. We think that the results of this study can contribute to further studies in the clinical aspect.

From sperm to offspring: Assessing the heritable genetic consequences of paternal smoking and potential public health impacts

Individuals who smoke generally do so with the knowledge of potential consequences to their own health. What is rarely considered are the effects of smoking on their future children. The objective of this work was to review the scientific literature on the effects of paternal smoking on sperm and assess the consequences to offspring. A literature search identified over 200 studies with relevant data in humans and animal models. The available data were reviewed to assess the weight of evidence that tobacco smoke is a human germ cell mutagen and estimate effect sizes. These results were used to model the potential increase in genetic disease burden in offspring caused by paternal smoking, with specific focus on aneuploid syndromes and intellectual disability, and the socioeconomic impacts of such an effect. The review revealed strong evidence that tobacco smoking is associated with impaired male fertility, and increases in DNA damage, aneuploidies, and mutations in sperm. Studies support that these effects are heritable and adversely impact the offspring. Our model estimates that, with even a modest 25% increase in sperm mutation frequency caused by smoke-exposure, for each generation across the global population there will be millions of smoking-induced de novo mutations transmitted from fathers to offspring. Furthermore, paternal smoking is estimated to contribute to 1.3 million extra cases of aneuploid pregnancies per generation. Thus, the available evidence makes a compelling case that tobacco smoke is a human germ cell mutagen with serious public health and socio-economic implications. Increased public education should be encouraged to promote abstinence from smoking, well in advance of reproduction, to minimize the transmission of harmful mutations to the next-generation.

The effect of two cryopreservation methods on human sperm DNA damage

Several methods are currently available for selection when conducting sperm cryopreservation, however, these methods might cause different degrees of damage on sperm DNA. The aim of the this study is to compare the effects of storage at -80 °C (in ultra-low temperature refrigerator) and at -196 °C (in liquid nitrogen) on sperm DNA damage, thus to provide a reference for choosing the right method according to different aims. We randomly collected 28 semen samples from college students of Chongqing city. The samples stored at -80 °C were neat semen samples and the samples stored at -196 °C were mixed with additional cryoprotectants. Each sample was subjected to two freezing-thawing cycles, and the sperm DNA damage levels of fresh and thawed samples were measured by single cell gel electrophoresis (SCGE) and sperm chromatin structure assay (SCSA). Both SCGE and SCSA assays showed cryopreservation induced significant damage to sperm DNA. However, storage at -196 °C lead to more severe damage to sperm DNA than storage at -80 °C measured by SCSA. Sperm DNA damage increased simultaneously with the higher frequency of freezing-thawing cycles. We concluded that storage of neat semen samples at -80 °C had milder damage to sperm DNA than storage at -196 °C mixed with cryoprotectants. To avoid additional sperm DNA damage, repeated freezing and thawing should be prevented.