Scientific landscape of oxidative stress in male reproductive research: A scientometric study

Global status of research on fertility preservation in male patients with cancer: A bibliometric and visual analysis

Background

Recently, male fertility preservation before cancer treatment has become more prevalent. The research in this field has progressed over time, with some studies having a major impact and providing guidance for further research. However, the trends and hotspots of research on fertility preservation in male cancer patients may have changed; exploring them is essential for relevant research progress.

Design

We extracted relevant studies from the Web of Science Core Collection database, capturing information on the countries of study, affiliations, authors, keywords, as well as co-citations of references and journals. To identify publication trends, research strengths, key subjects, prominent topics, and emerging areas, we conducted a bibliometric analysis using CiteSpace.

Results

We included 3201 articles on fertility preservation in male cancer patients published over January 1999 to December 2023 were included. Although the relevant research growth rate was slow initially, the number of publications increased annually. Of all study countries, the United States, Germany, and Japan reported the earliest studies; the United States published the highest number of relevant studies. The US institutions remained at the forefront for all 25 years, and the US researcher Ashok Agarwal published the most articles. Literature co-citation analyses indicated a transformation in the study participants; they comprised a younger demographic (i.e., a large number of adolescent male patients underwent fertility preservation); moreover, fertility preservation techniques evolved from sperm cryopreservation to testicular tissue cryopreservation. Research on reproductive outcomes of sperm cryopreservation was the recent hotspot in male fertility preservation research, and the impact of immunotherapy and checkpoint inhibitors on male fertility requires further research.

Conclusions

Male fertility preservation will be a major future research focus, with closer connections and collaborations between countries and organizations. Our results present the historical data on the development of research on male fertility preservation in cancer patients, providing relevant insights for future research and development in this study area.

Effects of microplastics on reproductive characteristics and mechanisms of the marine rotifer Brachionus plicatilis

Microplastic pollution, especially secondary microplastics (MPs), poses a significant threat to marine ecosystems. Despite its prevalence, the impact of natural-aged MPs on marine organisms, hindered by collection challenges, remains poorly understood. This study focused on 1-3 μm natural-aged MPs collected from Japan's coastal sea, investigating their effects on the rotifer Brachionus plicatilis sensu stricto and its reproductive mechanisms. Rotifers exposed to varying MP concentrations (0, 20, and 200 particles/mL) over 14-day batch cultures exhibited reduced population growth and fertilization rates. Down-regulation of reproductive genes and up-regulation of oxidative stress-related genes were observed, indicating MP-induced disruptions. Enhanced activities of superoxide dismutase and acetylcholinesterase and elevated malondialdehyde levels further emphasized oxidative stress. These findings underscore the detrimental impact of MPs on rotifer reproductivity, shedding light on the underlying mechanisms.

Effects and possible mechanisms of combined exposure to noise and carbon monoxide on male reproductive system in rats

Environmental hazards are an increasing concern due to the rapid pace of industrialization. Among these hazards, noise and carbon monoxide (CO) are common risk factors and have been shown to cause serious health problems. However, existing studies focused on the individual effects of noise and CO exposure and the combined effects of these two factors remain poorly understood. Our study aimed to examine the combined effects of noise and CO exposure on testicular function by constructing individual and combined exposure models. Our findings indicated that combined exposure to noise and CO was associated with a higher risk of testicular damage and male reproductive damage when compared to exposure alone. This was evidenced by poorer semen quality and more severe pathological damage to the testis. This combined exposure led to higher levels of oxidative stress and apoptosis in the testes, with bioinformatics analyses suggesting the signaling pathways involved in these responses. Specifically, activation of the P53 signaling pathway was found to contribute to the testicular damage caused by the combined exposure. Encouragingly, pterostilbene (PTE), a novel phytochemical, alleviated combined exposure-induced testicular damage by reducing oxidative stress and germ cell apoptosis. Overall, we identified joint reproductive toxicity resulting from the exposure to noise and CO, and found that PTE is a promising potential treatment for injuries caused by these factors. The cover image is based on the Research Article Effects and possible mechanisms of combined exposure to noise and carbon monoxide on male reproductive system in rats by Yingqing Li et al., https://doi.org/10.1002/tox.23927.

From animal to cell model: Pyroptosis targeted-fibrosis is a novel mechanism of lead-induced testicular toxicity

Lead (Pb) exists widely in soil and seriously threatens agricultural soil and food crops. Pb can cause serious damage to organs. In this study, the animal model of Pb-induced rat testicular injury and the cell model of Pb-induced TM4 Sertoli cell injury were established to verify whether the testicular toxicity of Pb was related to pyroptosis-mediated fibrosis. The results of experiment in vivo showed that Pb could cause oxidative stress and up-regulated the expression levels of inflammation, pyroptosis, and fibrosis-related proteins in the testis of rats. The results of experiments in vitro showed that Pb induced the cell damage, enhanced the reactive oxygen species level in the TM4 Sertoli cells. After using nuclear factor-kappa B inhibitors and Caspase-1 inhibitors, the elevation of TM4 Sertoli cell inflammation, pyroptosis, and fibrosis-related proteins induced by Pb exposure was significantly decreased. Taken together, Pb can cause pyroptosis-targeted fibrosis and ultimately issues in testicular damage.

A microplate-based DCFH-DA assay for the evaluation of oxidative stress in whole semen

Aims

The well-documented relationship between sperm oxidation and male infertility strongly encourages the development of assays for reactive oxygen species detection in semen samples. The present study aims to apply the microplate-based 2’,7’-dichlorofluorescein diacetate assay to the evaluation of oxidative stress in unprocessed whole semen, thus avoiding sample centrifugations and other manipulations that may cause significant reactive oxygen species increments.

Main methods

The fluorescence assay consisted in the quantification of both intracellular and extracellular reactive oxygen species levels in unwashed semen specimens by using the probe 2’,7’-dichlorofluorescein diacetate into a 96-well plate. The method was useful for the preliminary assessment of the oxidation levels of whole semen samples from men undergoing standard sperm analysis as well as to evaluate the effect of some pro-glutathione molecules on semen oxidative status.

Key findings

The 2’,7’-dichlorofluorescein diacetate assay was successfully adapted to the evaluation of oxidative stress in whole semen, effectively revealing the perturbation of the redox homeostasis of the sample. Accordingly, specimens with abnormal sperm parameters (n = 10) presented oxidation indexes significantly higher than those with normospermia (n = 10) [7729 (range 3407–12769) vs. 1356 (range 470–2711), p < 0.001]; in addition, semen oxidation indexes negatively correlated to sperm motility and morphology. Noteworthy, whole semen exposure to pro-glutathione compounds led to reduced semen oxidation levels and sperm protection against oxidative damage.

Significance

Based on our pilot experimental data, the microplate-based 2’,7’-dichlorofluorescein diacetate assay appears to be a convenient method for the detection of reactive oxygen species levels in whole semen samples, avoiding artifacts due to semen centrifugation steps. At the same time, the test could be a helpful tool for the basic and quick screening of antioxidant molecules able to preserve semen quality.

Association between Seminal Oxidation-Reduction Potential and Sperm DNA Fragmentation-A Meta-Analysis

Seminal oxidative stress and sperm DNA damage are potential etiologies of male factor infertility. The present study aims to evaluate the relationship between oxidation-reduction potential (ORP), a measure of oxidative stress, and sperm DNA fragmentation (SDF) by conducting a systematic review and meta-analysis of relevant clinical data. A literature search was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The COVIDENCE tool was used to screen and identify studies evaluating seminal ORP and SDF. Studies (n = 7) that measured seminal ORP and SDF of 3491 semen samples were included in the analysis. The fixed-effects model revealed a significant pooled correlation coefficient (r = 0.24; p < 0.001) between seminal ORP and SDF. Furthermore, subgroup analyses indicated that the pooled correlation coefficient between ORP and sperm chromatin dispersion (SCD) assay was less than other SDF assays (0.23 vs. 0.29). There was a moderate level of heterogeneity (I2 = 42.27%) among the studies, indicating a lack of publication bias. This is the first meta-analysis to reveal a positive correlation between seminal ORP and SDF. Furthermore, this study indicates the role of oxidative stress in the development of sperm DNA damage and thus warrants prospectively exploring the clinical value of these sperm function tests.

Comprehensive Analysis of Global Research on Human Varicocele: A Scientometric Approach

Purpose

This study provides a comprehensive analysis of research trends on the etiology, mechanisms, potential risk factors, diagnosis, prognosis, surgical and non-surgical treatment of varicocele, and clinical outcomes before and after varicocele repair.

Materials and Methods

Varicocele studies published between 1988 and 2020 were retrieved from the Scopus database on April 5, 2021. Original studies on human varicocele were included, irrespective of language. Retrieved articles were manually screened for inclusion in various sub-categories. Bibliometric data was subjected to scientometric analysis using descriptive statistics. Network, heat and geographic mapping were generated using relevant software.

Results

In total, 1,943 original human studies on varicocele were published. These were predominantly from the northern hemisphere and developed countries, and published in journals from the United States and Germany. Network map analysis for countries showed several interconnected nodal points, with the USA being the largest, and Agarwal A. from Cleveland Clinic, USA, being a center point of worldwide varicocele research collaborations. Studies of adolescents were underrepresented compared with studies of adults. Studies on diagnostic and prognostic aspects of varicocele were more numerous than studies on varicocele prevalence, mechanistic studies and studies focusing on etiological and risk factors. Varicocele surgery was more investigated than non-surgical approaches. To evaluate the impact of varicocele and its treatment, researchers mainly analyzed basic semen parameters, although markers of seminal oxidative stress are being increasingly investigated in the last decade, while reproductive outcomes such as live birth rate were under-reported in the literature.

Conclusions

This study analyzes the publication trends in original research on human varicocele spanning over the last three decades. Our analysis emphasizes areas for further exploration to better understand varicocele’s impact on men’s health and male fertility.

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

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

Species-specific effects of iron on temperate and tropical marine rotifers in reproduction, lipid and ROS metabolisms

Two euryhaline rotifers, the temperate species Brachionus plicatilis and tropical species Brachionus rotundiformis, were used to investigate the effects of iron (FeSO₄·7H₂O), an essential trace metal, on reproductive patterns and lifetables, including the metabolism of lipid and reactive oxygen species (ROS). B. plicatilis was more sensitive to iron with regard to sexual reproduction. While iron had no significant effect on the population growth at 0-48 μg/mL, it caused a decrease in the resting egg production. B. plicatilis exposed to 6 and 12 μg/mL of iron showed an increase in the intracellular ROS levels and a decrease in the neutral lipid content in sexual organs, accompanied by downregulation of antioxidant components CuZnSOD and two cytochromes (CYP clan 2&3). These patterns suggested that iron-induced oxidative stress was not neutralized by its antioxidant defense system, thus negatively affecting the fecundity of fertilized mictic females. However, B. rotundiformis showed a dose-dependent increase in population growth with extended lifespan and positive sexual reproduction in response to 0-24 μg/mL iron. Furthermore, compared to Fe-exposed B. plicatilis, B. rotundiformis showed better antioxidant mechanism, whereas genes involved in lipid synthesis (citrate lyase, mitochondrial CYP) and reproduction (vasa, sirtuin-2) were significantly upregulated compared to the control, implying that B. rotundiformis was likely to have higher resilience in response to iron-induced oxidative stress. These findings suggest that iron is likely to cause interspecific interactions in the B. plicatilis species complex, whereas the tropical species B. rotundiformis may have evolved an effective defense mechanism against iron-induced stress.

Synbiotic (FamiLact) administration in idiopathic male infertility enhances sperm quality, DNA integrity, and chromatin status: A triple-blinded randomized clinical trial

BACKGROUND

Idiopathic male infertility is often treated empirically. A recent body of evidence has indicated the association between pro ± prebiotics administration and improvement in semen parameters.

OBJECTIVE

To assess the effect of FamiLact (probiotic + prebiotic) administration on male subjects with idiopathic infertility.

MATERIALS AND METHODS

Fifty-six men with idiopathic male infertility were randomly/equally divided into two groups. Men in the case and control groups received 500 mg of FamiLact and an identical placebo for 80 days, respectively. A semen sample was obtained from each of the participants before initiation and after the termination of the treatment course. Samples underwent regular semen analysis and were further analyzed to assess the level of DNA damage (sperm chromatin structure assay), oxidative stress (BODIPY C11 staining), and protamine deficiency (chromomycin-A3 staining) in spermatozoa.

RESULTS

No significant difference was observed between the baseline values of both groups. After intervention, mean sperm concentration, motility, and normal morphology were significantly higher in the FamiLact group compared to the placebo group (p < 0.05). In the FamiLact receivers, we detected improvement regarding the following parameters: concentration, motility, abnormal morphology, sperm lipid peroxidation, and DNA fragmentation (p ≤ 0.02). Likewise, in the placebo group, we noticed a decrease in the post-medication mean value of DNA fragmentation (p = 0.03) while observing no significant difference regarding other parameters.

CONCLUSION

FamiLact administration improves sperm concentration, motility, and abnormal morphology and decrease sperm DNA damage, possibly through alleviating oxidative stress in the seminal fluid.