Causes, effects and molecular mechanisms of testicular heat stress

The Spontaneous Abortion of Females is Influenced by Their Male Partner's Heat Wave Exposure During Adolescence: A Nationwide Observational Study in China

OBJECTIVE

Heat wave exposure significantly impacts human health. Nevertheless, studies on the long-term effects of heat wave exposure during adolescence on adverse pregnancy outcomes (APOs) are rare. This study aimed to investigate the relationship between the long-term effects of heat wave exposure during adolescence and APOs.

METHODS

We analyzed data from 3,376 female and 3,013 male participants across 31 provinces in China. All adolescents (10-19 years old), early adolescents (10-14), and late adolescents (15-19) were chosen as exposure windows. Heat waves were defined as periods lasting 2‒4 consecutive days with the daily temperature exceeding the 75th, 90th, and 92.5th percentiles. We employed multivariate logistic regression models to assess the associations between exposure to heat waves during adolescence and APOs.

RESULTS

The results revealed significant associations between male exposure to heat wave events during late adolescence and spontaneous abortion (P < 0.05), which was more pronounced in South China. In contrast, no statistically significant associations were detected between males' exposure to heat wave events during adolescence and their partners' preterm birth (P > 0.05 for all comparisons). The exposure of females to heat waves during adolescence was not significantly associated with subsequent spontaneous abortion or preterm birth (P > 0.05 for all comparisons).

CONCLUSIONS

This study demonstrates that spontaneous abortion in females is associated with heat wave exposure in their male partner during adolescence.

A novel paradigm in the prediction of the performance of breeding buffalo bulls: role of hair cortisol and testosterone

Despite having strong pedigree records, passing breeding soundness evaluations, and receiving appropriate management and nutrition, some breeding bulls consistently underperform in similar environmental conditions where other bulls thrive. These underperforming bulls are economically unsuitable for semen stations that produce semen doses. Our study aims to predict the performance of breeding bulls based on hair cortisol and testosterone concentrations. We also measured these hormones in buffalo calves. Furthermore, we assessed seminal plasma cortisol and testosterone concentrations in poor-quality and good-quality ejaculates. To evaluate bull performance, we categorized the bulls into two groups based on ejaculate discard rates: consistent (n = 9) and inconsistent semen quality bulls (n = 6). The breeding bulls' hair cortisol and testosterone levels were evaluated at two-month intervals for one year. We analyzed the semen from both groups for motility and kinematic parameters using a computer-assisted semen analyzer and acrosome integrity, mitochondrial membrane potential, and superoxide production through flow cytometry. The bulls that exhibited consistent semen quality had higher (P < 0.05) hair testosterone concentrations than those with inconsistent quality; however, there was no difference (P > 0.05) in hair cortisol levels between the two groups. Additionally, the ejaculates from bulls with inconsistent semen quality met minimum standards, showing no differences (P > 0.05) in sperm motility. However, mitochondrial membrane potential and superoxide production were compromised at the subcellular level. Acrosome integrity was also lower (P < 0.05) in bulls with inconsistent semen quality than those with consistent quality. In poor-quality ejaculates, regardless of the bull group, cortisol and testosterone concentrations were higher (P < 0.05) than in good-quality ejaculates intended for cryopreservation. Additionally, hair testosterone concentration increased with age in male calves, while hair cortisol levels were higher during July-August and lower from March to April. In conclusion, bulls that exhibited consistent semen quality appear stress-tolerant, while those with inconsistent quality are more stress-susceptible. Our findings suggest that hair testosterone is a better indicator of stress in breeding bulls than hair cortisol.

The Effect of Scrotal PRP Injection on Testes Function and Spermatogenesis Resumed in Azoospermia Mice Model Caused by Chronic Hyperthermia

Infertility is an important health concern that affects around 15% of couples, 40-50% of infertile cases are because of malefactors. Azoospermia is known as one of the important causes of male infertility. PRP is an autologous source of growth factors used in various therapeutic strategies. In the present study, PRP was injected into mice scrotum, after induced azoospermia caused by scrotal hyperthermia, and then therapeutic effects were evaluated. 24 adult male mice were divided into 4 groups: Control, Azoospermia (model induced by scrotal hyperthermia every other day after anesthesia for 35 days), and ketamine/xylazine (Ket/Xi) (to assess the probable effect of anesthesia), PRP (injected 10ul of PRP in the scrotum of azoospermia mice) after 16 days animals were anesthetized and sacrificed. Plasma testosterone, seminiferous diameter, oxidative stress, and sperm parameters were evaluated. Plasma testosterone level in the Azoospermia group significantly decreased and PRP treatment improved it. Also, the testicular tissue showed impairment, and oxidative stress levels increased in the testes in the Azoospermia group and PRP treatment ameliorated them. Spermatogenesis completely arrested after scrotal hyperthermia that after treatment with PRP, resumed. PRP injection in the scrotum resumed spermatogenesis and increased the production of testosterone, reduced the oxidative stress level in the testicular tissue, and resumed sperm production. PRP shows promise in promoting testicular recovery following hyperthermia-induced damage.

The effects of radiofrequency radiation on male reproductive health and potential mechanisms

Recent studies have demonstrated that radiofrequency (RF) radiation emanating from devices such as mobile phones and Wi-Fi may have adverse effects on male reproductive health. This radiation can elevate testicular temperature, potentially compromising sperm quality and DNA integrity, and influence the specific absorption rate (SAR) across different body regions, leading to detrimental reproductive outcomes. Furthermore, exposure to RF radiation has been linked to conditions that could affect male reproductive function, such as oxidative stress, alterations in ion transitions across cell membranes, and inflammation. The article reviews research conducted on both humans and animal models regarding the effects of electromagnetic radiation on sperm quality, DNA damage, oxidative stress, hormone levels, and testicular function, suggesting that exposure to electromagnetic radiation could have harmful implications for male reproductive health. However, further research is necessary to fully understand the mechanisms and implications of non-ionizing electromagnetic radiation on male infertility.

Semen Quality, Testicular Cell Apoptosis, and Transcriptome Analysis Following Mild Scrotal Heat Stress in Wugu-Hu Crossbred and Hu Rams

Hu and Wugu × Hu rams underwent scrotal insulation to simulate mild heat stress, resulting in a 3.0 ± 0.1 °C increase in scrotal surface temperature. Semen samples were collected every five days from day 11 to 56, and testis samples immediately after insulation. Both breeds experienced similar semen quality reductions and recovery trends, including reduced motility, concentration and the percentage of morphologically normal, but on days 41 and 46, Wugu-Hu rams exhibited significantly lower sperm motility than Hu rams (p < 0.05). Wugu-Hu rams demonstrate more transcriptomic changes. Further GO analysis revealed enrichment in spermatogenesis-related processes, while KEGG analysis identified Oocyte meiosis and cell cycle pathways, with a downregulation of key genes (CDK1, CDK2, CDC20, and PLK1) indicating impaired meiosis in Wugu-Hu rams. In contrast, Hu rams showed minimal transcriptional changes, contrary to the transcriptomic results. The significantly increased apoptosis rate of Wugu-Hu sheep testicular cells (p < 0.05) suggests compensatory or post-transcriptional mechanisms mitigating functional impacts caused by transcriptomic changes. The conclusion is that mild scrotal heat stress affects sperm quality and testicular gene expression. Wugu-Hu rams demonstrate greater transcriptomic sensitivity, but this does not show significant differences in semen quality recovery due to the compensatory mechanism of cell apoptosis.

Paternal Effects in Mammalian Reproduction: Functional, Environmental, and Clinical Relevance of Sperm Components in Early Embryos and Beyond

In addition to widely recognized contributions of the paternal genome, centriole, and oocyte-activation factors, sperm deliver a wide range of macromolecules to the fertilized embryo. The impacts of these factors on the embryo, progeny, and even subsequent generations have become increasingly apparent, along with an understanding of an extensive potential for male health and environmental exposures to exert both immediate and long-term impacts on mammalian reproduction. Available data reveal that sperm factors interact with and regulate the actions of oocyte factors as well as exerting additional direct effects on the early embryo. This review provides a summary of the nature and mechanisms of paternal effects in early mammalian embryos, long-term effects in progeny, susceptibility of sperm components to diverse environmental factors, and potential approaches to mitigate adverse effects of such exposures.

The consequences of climate change and male reproductive health: A review of the possible impact and mechanisms

A global decline in male fertility has been reported, and climate change is considered a major cause of this. Climate change refers to long-term shifts in temperatures and weather patterns, and results from greenhouse gas emissions like carbon dioxide and methane that act as a blanket wrapped around the earth, trapping heat and elevating temperatures. Sad to say, the consequences of climatic variation are beyond the dramatic elevated temperature, they include cold stress, increased malnutrition, air pollution, cardiovascular diseases respiratory tract infections, cancer, sexually transmitted infections, mental stress, and heat waves. These negative effects of climate change impair male reproductive function through multiple pathways, like ROS-sensitive signaling, suppression of steroidogenic markers, and direct damage to testicular cells. The present study aimed to describe the impact of the consequences of climate change on male reproductive health with details of the various mechanisms involved. This will provide an in-depth understanding of the pathophysiological and molecular basis of the possible climatic variation-induced decline in male fertility, which will aid in the development of preventive measures to abate the negative effects of climate change on male reproductive function.

Mitochondrial content and mtDNA copy number in spermatozoa and penetrability into oocytes

The current narrative review aims to summarize the relation of mitochondrial content (MC) and mitochondrial DNA copy number (MDCN) in spermatozoa with sperm penetrability, and to discuss the various determining factors during the process of spermatogenesis in mammals. There are many potential factors associated with the quantitative alteration of MC and MDCN in male gametes from spermatogenesis to ejaculation. Particularly, spermatogenesis may be the first step to jointly contribute to an incomplete reduction of MC and MDCN in spermatozoon. It appears to be now quite clear that some abnormalities during spermatogenesis and oxidative stress are the main factors highly associated with the quantitative change of MC and MDCN in spermatozoa, consequently affecting sperm quality and their penetrability into oocytes. Currently, a series of proteins contributing to form sperm midpiece during spermatogenesis and cytoplasmic elimination during spermiation have been currently identified. The present review provides insight into how these factors interact with sperm MC and MDCN, and handholds to gain a better understanding of their roles. This review also highlights the uniqueness of normal fertile spermatozoa which have relatively lower MC and MDCN, but have mitochondria that function completely in multiple pivotal physiological pathways.

Heat stress regulates the migration and proliferation of lens epithelial cells through ferroptosis and NCOA4-FTH1 interaction

Posterior capsule opacification (PCO) due to the proliferation and migration of lens epithelial cells (LECs) is the main complication after surgery. Heat stress has demonstrated impressive results in halting cell proliferation and migration, while also facilitating cell death. This study aimed to investigate the role and mechanism of ferroptosis in the proliferation and migration of LECs under heat stress. CCK-8 assays, scratch assays, and transcriptome analysis were used to evaluate the impact of temperature on human lens epithelial cells (HLECs) and explore the potential mechanisms. The role of ferroptosis in the proliferation of HLECs induced by heat was investigated using the ferroptosis inhibitor Fer-1 and siRNA-mediated NCOA4 protein interference. Fluorescence staining and Western blot experiments were used to detect the expression of Fe2+, reactive oxygen species (ROS), and ferroptosis-related proteins NCOA4, FTH1, and SLC3A2. The results of CCK-8 assays, scratch assays, and transcriptome analysis demonstrated significant thermal effects on HLEC behavior. After heat treatment, there were significant changes in the fluorescence expression of Fe2+ and ROS in the HLECs and lens explant. In addition, the expression of NCOA4, FTH1, and SLC3A2 also changed significantly. Using Fer-1 or NCOA4 siRNA-mediated interference restored cell viability decreased by thermal stress. Furthermore, interference with NCOA4 protein effectively restored the expression of Fe2+, ROS, and FTH1. In conclusion, heat stress has a significant effect on LECs by regulating ferroptosis and the interaction between NCOA4 and FTH1 proteins play an important role.

Investigating male factors and their relationships with reproductive health outcomes: a case-control study protocol for Towards Optimal Fertility, Fathering, and Fatherhood studY (TOFFFY) in Singapore

INTRODUCTION

Despite the global prevalence of low fertility rates, male contributions to fertility and reproductive health outcomes have been understudied. This study aims to investigate the male contribution to fertility and explore the underlying biological mechanisms. Specifically, we aim to (1) identify male factors associated with successful pregnancy, (2) develop a fertility index incorporating modifiable factors for both males and females to predict pregnancy rate and (3) explore the relationship of male modifiable factors with semen parameters and molecular characteristics.

METHODS AND ANALYSIS

We will conduct an unmatched case-control study involving 240 couples with impaired male fertility (cases) and 240 couples with normal male fertility (controls). Between July 2024 and June 2026, we will recruit 480 eligible couples from KK Women's and Children's Hospital, Singapore. Male and female participants will complete questionnaires on sociodemographics, general health and lifestyle factors, and their anthropometry and body fat composition will be measured. Blood and semen samples from the male participants will be collected for biochemical, molecular and semen analyses. Predictive male factors will be identified using the least absolute shrinkage and selection operator method, accounting for female factors. We will construct a logistic regression model incorporating both male and female factors to derive a fertility index, which will be evaluated using cross-validation on subsets of the study population. Multivariable linear regression will be used to explore relationships between male modifiable exposures and semen parameters.

ETHICS AND DISSEMINATION

The study protocol has received approval from the Centralised Institutional Review Board of SingHealth (2024/2120), Singapore. Participants will provide written informed consent. Study results will be disseminated through conferences and peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

NCT06293235.

Resveratrol mitigates heat stress-induced testicular injury in rats: enhancing male fertility via antioxidant, antiapoptotic, pro-proliferative, and anti-inflammatory mechanisms

This study investigates the protective effects of resveratrol (RSV) against heat stress (HS)-induced testicular injury in rats. Climate change has exacerbated heat stress, particularly affecting male fertility by impairing testicular function and sexual behavior. A total of 32 rats were allocated into four experimental groups: control, RSV control, HS control, and RSV + HS. The HS groups were subjected to a 43 °C water bath for 20 min to induce testicular hyperthermia, while the RSV + HS group received 20 mg/kg of RSV starting just before HS and continuing for eight weeks. Our findings reveal that HS significantly impairs male sexual behavior, evidenced by reduced mount and intromission numbers, and increased latencies. It also negatively affects the reproductive system, decreasing the weights of testes (Cohen's d = 1.8), epididymis, and accessory sex glands, and deteriorating sperm profile parameters such as motility (Cohen's d = 2.1), viability, and morphology. Furthermore, HS notably decreases reproductive performance in female rats, reducing litter size, live births, and conception rates. Biochemically, HS decreases activities of key antioxidant enzymes in the testes-glutathione peroxidase, superoxide dismutase, and catalase-while increasing lipid peroxidation, nitrite levels, and proinflammatory cytokines (IL-1β and TNF-α). It also reduces serum levels of reproductive hormones like testosterone (Cohen's d = 2.0) and 17β-estradiol. These results were affirmed with the histopathological evaluation and the immunohistochemistry staining (Ki-67, PCNA, Bax 5, and caspase-3 protein expression). Remarkably, RSV treatment mitigated these adverse effects, restoring both physiological and biochemical parameters toward normal levels (e.g., testicular weight Cohen's d = 1.6, sperm motility Cohen's d = 1.9, and testosterone levels Cohen's d = 1.7). This suggests that RSV's antioxidative, anti-inflammatory, antiapoptotic, and androgenic properties could effectively counteract the degenerative impacts of testicular hyperthermia. This highlights the potential of RSV as a therapeutic agent against climate change-induced fertility issues in males.

Hyperthermia suppresses the biological characteristics and migration of chicken primordial germ cells

Primordial germ cells (PGCs) play a crucial role in transmitting genetic information to the next-generation. In chickens, genetically edited PGCs can be propagated in vitro and subsequently transplanted into recipient embryos to produce offspring with desired genetic traits. However, during early embryogenesis, the effects of external conditions on PGC migration through the vascular system to the gonads have yet to be explored, which may affect the efficiency of preparing gene-edited chickens. In this study, we investigated the effects of hyperthermia on the biological characteristics and migration of chicken PGCs. A gonad-derived PGC line of White Leghorn (WLH) chicken was established and verified through PAS staining and immunofluorescence of PGC-specific proteins. To visually observe PGC migration in vivo, GFP-positive PGCs were prepared and locations of chimeras were validated. Cell viability, glycogen granule contents, and mRNA expression levels of pluripotency markers (NANOG and POUV), germ cell-specific markers (DAZL and CVH), and telomerase reverse transcriptase (TERT) were reduced in PGCs cultured under high temperatures (43°C for 12, 24, and 48 h). After the heat treatment of donor PGCs (43°C) or recipient embryos (39.5°C), GFP-positive PGCs in gonads were rarely observed. Taken together, our results underscore the negative effects of hyperthermia on the biological characteristics and migration of chicken PGCs, which provides valuable insights for the implementation of PGC-based gene editing techniques in chickens.

The Influence of an Intense Training Regime in Professional and Non-Professional Athletes on Semen Parameters: A Systematic Review

Background/Objectives: Male infertility is influenced by physiological factors like age, as well as lifestyle factors, including physical activity. However, the specific impact of sport activity on semen parameters, and thus on male fertility, remains unclear. Specifically, the aim of this systematic review is to evaluate how an intense regime of training may affect sperm parameters in professional and non-profession athletes. Methods: Studies reporting sperm parameters associated with high training load were included. In April 2024, three electronic databases and literature sources (PubMed, Scopus, and Web of Science) were searched. Quality appraisal was performed independently by three authors using the National Heart, Lung, and Blood Institute Quality Assessment Tools (NHLBI-QAT). Results: Four studies met the inclusion criteria, reporting a total of 156 participants. Sixteen weeks of intensive cycling training produced a significant decrease in seminal volume, sperm concentration, sperm motility, and morphology, with a return to their initial levels, except for sperm morphology and sperm concentration, after at least one week of rest. In addition, in athletes with varicocele, a 6-month stop from sports activity went a long way toward improving sperm concentration and sperm motility. However, DNA fragmentation, a greater presence of round cells, and high numbers of active macrophages were described. At least 30 days improve semen parameters in professional and non-professional athletes. Conclusions: Intensive training could worsen seminal parameters and, consequently, male fertility. However, certainty of evidence is very low, and the results should be interpreted with caution.

Spinal muscular atrophy is also a disorder of spermatogenesis

BACKGROUND

Spinal muscular atrophy (SMA) patients benefit from pre-mRNA splicing modifiers targeting the SMN2 gene, which aims to increase functional SMN production. The animal toxicity affecting spermatogenesis associated with one such treatment raised questions about male SMA patients' spermatogenesis.

METHODS

This descriptive, cross-sectional study was conducted from June 2022 to July 2023. The study involved adult male patients with genetically confirmed SMA type 2 (SMA2) or SMA3 from 13 French neuromuscular centers. The patients' general data, motor severity, urological history, exposure to certain factors, parenthood, and spermogram results were obtained. All patients were enrolled prior to exposure to risdiplam.

FINDINGS

Sixty-eight patients were enrolled ( 36 SMA2 and 32 SMA3 patients). Forty-one patients had fertility data (parenthood history and spermogram analyses) and underwent 33 spermograms. Fertility disorders were identified in 27 of the 41 patients (65·9%, 95%CI 51·3-80·4%) in particular SMA2 patients: 19 cases (90.5%, CI 77·9-100%) (SMA3: 8 cases (40%, CI 18·5-61·5%). Among the patients with available spermograms, 81% (27/33) had abnormal sperm concentration; 30% presented azoospermia. These abnormalities were significantly associated with SMA type (more prevalent in SMA2 patients, p < 0·001), disease motor severity, which included age at the loss of walking ability and wheelchair use duration (p < 0·001). The Motor Function Measure (MFM) determined that the sperm counts were also correlated with disease severity (p < 0·01).

INTERPRETATION

The fertility disorders were correlated with SMA severity and were particularly evident in SMA2 patients. In the latter, sperm concentration positively correlated with MFM. This study is the first one to link fertility disorders with spermogram abnormalities in SMA males. Understanding spermatogenesis in SMA is crucial, especially with new therapies such as risdiplam. Consequently, conducting systematic spermogram studies prior to SMA treatment is recommended.

Transcriptome Analysis Reveals Sertoli Cells Adapting Through Redox and Metabolic Pathways Under Heat Stress in Goats

BACKGROUND/OBJECTIVES

Climate change-induced temperature elevations pose significant challenges to livestock reproduction, particularly affecting testicular function in small ruminants. This study investigates the acute heat-stress response in goat Sertoli cells (SCs), aiming to elucidate the molecular mechanisms underlying heat-induced damage to male reproductive tissues.

METHODS

SCs were isolated from testes of 4-month-old black goats and exposed to heat stress (44 °C for 2.5 h). We employed transcriptome sequencing, CCK-8 assay, electron microscopy, ROS measurement, autophagy detection, Western blot analysis, and lactate concentration measurement. Bioinformatics analyses including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, and protein-protein interaction network analyses were performed on the transcriptome data.

RESULTS

Heat stress significantly reduced SC viability, induced oxidative stress and autophagy, and altered gene expression profiles. We identified 1231 significantly differentially expressed genes, with significant enrichment in membrane-related processes and metabolic pathways. Metabolism-related genes, including PKLR, ACOT11, and LPCT12, were significantly downregulated. Protein-protein interaction network analysis revealed ten hub genes potentially crucial in the heat-stress response: HSP90AA1, HSPA5, BAG3, IGF1, HSPH1, IL1A, CCL2, CXCL10, ALB, and CALML4.

CONCLUSIONS

This study provides comprehensive insights into the molecular mechanisms underlying goat SC response to heat stress. The identified genes and pathways, particularly those related to metabolism and stress response, offer potential targets for developing strategies to mitigate heat-stress effects on livestock reproduction. These findings contribute to our understanding of climate change impacts on animal husbandry and may inform the development of heat-stress resistant livestock lines.

The sitting men: A systematic review of spare and working time exposure to sedentariness in relation to semen parameters

BACKGROUND

Over the past few decades, several studies have found that semen quality parameters have steadily declined over time. Many hypotheses have been made to explain this finding, among which a sedentary lifestyle has been investigated. To synthesize the current evidence, we performed a systematic review of published papers reporting on the relationship between sedentary habits and semen parameters.

METHODS

Embase and PubMed were systematically searched for papers published in English up to May 2023. We included all full-text observational papers that reported the relationship between sedentariness and semen parameters. Article selection adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines.

RESULTS

Sixteen observational studies were ultimately included, six in healthy men and ten in men from Fertility Clinics. They encompassed a total of 13,509 men, with 9877 being healthy men and 3632 presenting at Fertility Clinics for initial assessment. In terms of semen volume, no association emerged in the six studies involving healthy men: however, results in men referring to fertility clinics mainly showed no association, with one indicating a decline and one higher volume. Twelve studies did not report differences in sperm concentration, while one study in men from Fertility Clinics and two in healthy men observed a decline in this parameter with increasing time spent on TV watching or sedentary posture in spare time. Total sperm count was found to be similar across groups of inactivity, except for one study that showed a significant decrease when men from Fertility Clinics spent more time watching TV. No significant differences were reported in sperm motility across all studies, with only one study, among those addressing sperm morphology, indicating a lower percentage of normal forms in men watching TV more than 3 h per day. Finally, three studies conducted in men referring to Fertility Clinics analyzed the sperm DNA fragmentation index. Two of these studies found a higher DNA fragmentation index in men spending more time per day in a sitting posture.

CONCLUSIONS

This review suggests a weak association between time spent sitting during spare time and sperm concentration, but the findings are inconsistent, highlighting the need for further research.

The effects of vitamin C and vitamin B12 on improving spermatogenesis in mice subjected to long-term scrotal heat stress

OBJECTIVE

Scrotal hyperthermia poses a significant threat to spermatogenesis and fertility in mammalian species. This study investigated the effects of vitamin B12 and vitamin C on spermatogenesis in adult male mice subjected to long-term scrotal hyperthermia. The rationale is based on the sensitivity of germ cells and epididymal sperm to increased scrotal temperatures. While various factors, both internal and external, can raise the testicular temperature, this study focused on the potential therapeutic roles of vitamins B12 and C.

METHODS

After inducing scrotal hyperthermia in mice, vitamin B12 and vitamin C were administered for 35 days. We assessed sperm parameters, serum testosterone levels, stereological parameters, the percentage of apoptotic cells, reactive oxygen species (ROS) levels, and glutathione (GSH) levels. Additionally, real-time polymerase chain reaction was used to analyze the expression of the c-kit, stimulated by retinoic acid gene 8 (Stra8), and proliferating cell nuclear antigen (Pcna) genes.

RESULTS

Vitamin C was more effective than vitamin B12 in improving sperm parameters and enhancing stereological parameters. The study showed a significant decrease in apoptotic cells and a beneficial modulation of ROS and GSH levels following vitamin administration. Moreover, both vitamins positively affected the expression levels of the c-kit, Stra8, and Pcna genes.

CONCLUSION

This research deepens our understanding of the combined impact of vitamins B12 and C in mitigating the effects of scrotal hyperthermia, providing insights into potential therapeutic strategies for heat stress-related infertility. The findings highlight the importance of considering vitamin supplementation as a practical approach to counter the detrimental effects of elevated scrotal temperatures on male reproductive health.

Subchronic elevation in ambient temperature drives alterations to the sperm epigenome and accelerates early embryonic development in mice

Forecasted increases in the prevalence and severity of extreme weather events accompanying changes in climatic behavior pose potential risk to the reproductive capacity of humans and animals of ecological and agricultural significance. While several studies have revealed that heat stress induced by challenges such as testicular insulation can elicit a marked negative effect on the male reproductive system, and particularly the production of spermatozoa, less is known about the immediate impact on male reproductive function following subchronic whole-body exposure to elevated ambient temperature. To address this knowledge gap, we exposed unrestrained male mice to heat stress conditions that emulate a heat wave (daily cycle of 8 h at 35 °C followed by 16 h at 25 °C) for a period of 7 d. Neither the testes or epididymides of heat-exposed male mice exhibited evidence of gross histological change, and similarly, spermatozoa of exposed males retained their functionality and ability to support embryonic development. However, the embryos generated from heat-exposed spermatozoa experienced pronounced changes in gene expression linked to acceleration of early embryo development, aberrant blastocyst hatching, and increased fetal:placental weight ratio. Such changes were causally associated with an altered sperm small noncoding RNA (sncRNA) profile, such that these developmental phenotypes were recapitulated by microinjection of wild-type embryos sired by control spermatozoa with RNAs extracted from heat-exposed spermatozoa. Such data highlight that even relatively modest excursions in ambient temperature can affect male reproductive function and identify the sperm sncRNA profile as a particular point of vulnerability to this imposed environmental stress.

The association between ambient temperature and semen quality in a Northern Peninsular Province, China

BACKGROUND

Extreme ambient temperature has been linked to decline in males' semen quality. Although the temperature-semen quality association has been examined in certain cities of South China, how the effect size of the extreme temperature may lag over critical windows in spermatogenesis and whether the strength of association may vary in North China have yet been adequately explored.

OBJECTIVES

To quantify the association between air temperature and semen quality, and identify critical exposure windows in a Northern Peninsular Province, China.

MATERIALS AND METHODS

Data on semen quality in 2014-2019 were collected from the Human Sperm Bank of Institute of Women, Children and Reproductive Health, Shandong University, China. Daily meteorological data (0.01°×0.01°) were assigned to each subject's residential address. The linear mixed-effect model combined with the distributed lag nonlinear model was used to estimate the effect of ambient temperature over critical spermatogenesis windows.

RESULTS

The temperature-semen quality association was inverted V-shaped, with the maximum lag being 0-45 days before ejaculation and the threshold being 9.2°C. Progressively and total motile sperm number, and total sperm number declined more substantially than other semen quality parameters. Semen quality was more sensitive to cold exposure during the epididymal storage period than the sperm motility development period. By contrast, semen quality was insensitive to heat exposure during both critical spermatogenesis windows. Impairment of certain semen quality parameters was more obvious for males with higher educational attainment and those aged over 35 years.

DISCUSSION AND CONCLUSION

Exposure to non-optimal temperature is associated with decreased semen quality in North China, with the epididymal storage and sperm motility development periods more sensitive to cold exposure than heat. Older males and those with higher educations may need particular awareness.

Bovine testicular heat stress: From climate change to effects on microRNA profile

Heat stress is caused by exposure of animals to high temperatures and humidity, outside their thermal comfort zone. This can have negative outcomes, including adversely affecting general well-being and reducing productive and reproductive performance. In males, heat stress can disrupt testicular thermoregulation, with deleterious effects on spermatogenesis and consequently, decreases in sperm quality and fertility potential. Thus, high environmental temperature is considered one of the most important factors that predisposes bulls to subfertility and has already been the subject of many studies, particularly in tropical or subtropical countries. It is essential to study effects of testicular heat stress in bulls, know the chronology of clinical and sperm findings, and understand the underlying pathophysiology. In addition, elucidating molecular mechanisms involved in heat stress and testicular function could provide the basis for effective, evidence-based strategies for selecting more thermotolerant animals. Excessive heat affects expression of messenger RNA (mRNA) and microRNA (miRNA) in sperm, which have important roles in regulating male fertility. Based on current trends in climate change, the incidence of chronically high temperatures that cause heat stress is expected to increase, posing increasing risks to health and survival of many species. The study of mRNAs and miRNAs can provide valuable insights to select animals that are more resilient to climate change. In addition to the search for more thermotolerant animals, other strategies to mitigate effects of heat stress include reproductive biotechniques and promotion of a better environment.

MTHFR C677T、MTHFR A1298C、MTRR A66G and MTR A2756G polymorphisms and male infertility risk: a systematic review and meta-analysis

BACKGROUND

Epidemiological studies have reported that polymorphisms of folate-metabolizing genes have a significant impact on male infertility. However, the results of published studies have come to different conclusions.

OBJECTIVE

To determine an association between folate-metabolizing gene polymorphisms and the risk of male infertility.

METHODS

The meta-analysis was conducted according to the PRISMA 2020 statement. The protocol was registered with PROSPERO (CRD42023412251). Studies were searched from PubMed, Google Scholar, Embase, Scopus, and the Cochrane Library up to 24st October2023. Articles that satisfied the inclusion criteria were evaluated for their quality using the Newcastle-Ottawa Scale. Data were extracted from the eligible studies and were analyzed for pooled up odds ratio (OR) with 95% confidence interval (CI). Meta-analysis was conducted using STATA 12.

RESULTS

Forty-six case-control studies were included in the meta-analysis which comprised 20,639 participants. The pooled analysis revealed that the MTHFR C677T polymorphism was significantly associated with male infertility and abnormospermia.Three-fifths of the model showed there was a significant association between the MTR A2756G polymorphism and male infertility. Both MTHFR A1298C and MTRR A66G polymorphisms were not significantly associated with male fertility. Furthermore, subgroup analysis revealed a significant association between the MTHFR C677T polymorphism and male fertility in Asian countries.

CONCLUSION

This meta-analysis suggests that the MTHFR C677T and MTR A2756G polymorphisms may be a potential risk factor for male infertility.

Adaptive divergence in reproductive seasonality and underlying physiological features fit Rattus norvegicus to live as opportunistic breeders

How organisms respond to complex environments is one of the unsolved problems in ecology. Life history patterns of a species provide essential information on how different populations may respond and adapt to environmental changes. Compared to typical seasonal breeders, which have limited distributions, the worldwide distribution of brown rats (Rattus norvegicus) across highly complex and divergent habitats suggests they exhibit exceptional adaptiveness. However, the difference in physiological mechanisms by which brown rats respond and adapt to markedly different environments is seldom investigated. Here, we reveal a significant divergence in reproductive seasonality and environmental responses between two brown rat subspecies: one subspecies, R. n. caraco, lives in the temperate zone, and another subspecies, R. n. norvegicus, lives in the subtropical region. Although R. n. caraco displayed a significantly higher reproductive seasonality than R. n. norvegicus, both subspecies adapted to sub-optimal breeding conditions mainly by regulating the seminal vesicle rather than testis development. Especially in responding to severe winter conditions in high-latitude regions, bodyweight-dependent recovery of testicular development in adults enables R. n. caraco to initiate reproduction more rapidly when conditions are suited. These findings elucidate a regulatory process of how brown rats live as opportunistic breeders by benefiting from enhanced semen production.

Protective impact of Betanin against noise and scrotal hyperthermia on testicular toxicity in Wistar rat: Role of apoptosis, oxidative stress and inflammation

The heat exposure and white noise can induce damage on reproductive organs. The main objective of this study is to observe, if betanin administration could ameliorate oxidative stress, apoptosis and inflammation in testis of rodents following noise and scrotal hyperthermia exposure. Wistar rats were divided into 6 groups; control, betanin, noise, hyperthermia and two treatment groups. Scrotal hyperthermia model was performed by heat exposure of rat testicular (43 °C) for 15 min and 3 times per weeks for 14 days. Noise induction model was done following exposure of rats with 100-dB noise level for 14 days and 8 h daily similar to real exposure condition in human. Betanin was administrated at the sub-effective dose (15 mg/kg) by gavage route for 4 weeks (5 times a week) to male rats. The animals were euthanized and testis were dissected and stored at -80 °C. Then, the oxidative stress biomarkers (MDA and GSH), apoptosis (cytochrome c & Annexin V), and inflammatory cytokines (TNF-α & IL-6) were measured by the real time polymerase chain reaction (RT-PCR) of testis collected samples. The data output demonstrates the impact of noise and hyperthermia in testicular toxicity induction by mitigating oxidative damage, apoptosis and inflammatory mediators. Following treatment with 15 mg/kg per day of betanin, lipid peroxidation and GSH content have been modulated, and TNF-α and IL-6 gene expression has been declined. Our results revealed that in Wistar rats, betanin displays protective effects against noise and scrotal hyperthermia-induced acute testicular toxicity through the inhibition of oxidative stress, apoptosis, and inflammation.

Oxidative Stress-induced Hormonal Disruption in Male Reproduction

Research into the impacts of oxidative stress (OS), and hormonal balance on reproductive potential has increased over the last 40 years possibly due to rising male infertility. Decreased antioxidant levels and increased OS in tissues result from hormonal imbalance, which in turn leads to male infertility. Increased reactive oxygen species (ROS) generation in seminal plasma has been linked to many lifestyle factors such as alcohol and tobacco use, toxicant exposure, obesity, varicocele, stress, and aging. This article provides an overview of the crosslink between OS and gonadal hormone disruption, as well as a potential mode of action in male infertility. Disrupting the equilibrium between ROS generation and the antioxidant defense mechanism in the male reproductive system may affect key hormonal regulators of male reproductive activities. Unchecked ROS production may cause direct injury on reproductive tissues or could disrupt normal regulatory mechanisms of the hypothalamic-pituitary-gonadal (HPG) axis and its interaction with other endocrine axes, both of which have negative effects on male reproductive health and can lead to male infertility.

The effects of climate change and environmental pollution on human reproduction: A scientific review commissioned by the European Board and College of Obstetrics and Gynaecology (EBCOG)

The European Board and College of Obstetrics and Gynaecology (EBCOG) and the European Network of Trainees in Obstetrics and Gynaecology (ENTOG) express their concerns on the effect of climate change and environmental pollution. This paper reviews the impact on reproductive health and the contribution to climate change by the field of obstetrics and gynaecology. It concludes that its contributors and the effects of climate change cause definite adverse consequences to fertility and adverse obstetric outcomes. Mankind, and obstetrics and gynaecology personnel as well, must be aware and responsible of its contribution to climate change and consider the impact of their actions and interventions.

Impact of heat waves on semen quality: A retrospective study in Argentina between 2005 and 2023

Heat waves, defined as periods with daily temperatures surpassing the historical average for a specific region, have become more frequent worldwide in recent years. Previous studies have reported a negative association between temperature and semen quality, but the focus has mainly been on Asian and European populations. The study included 54,926 men (18-60 years) undergoing routine semen analysis between 2005 and 2023 at CEUSA-LAEH andrology unit, in Buenos Aires, Argentina. Hourly temperature readings were provided by the Servicio Meteorológico Nacional. R programming (R Studio v2022.07.2) was used to define heat waves, calculate key characteristics, visualize results, and perform statistical tests at the IBYME laboratory. During the period studied, a total of 124 days had heat waves (defined after at least 3 consecutive days with 32.3 °C and 22 °C). Men exposed to heat waves during spermatogenesis exhibited lower sperm number (concentration and count; P < 0.0001) and decreased normal morphology (percentage of normal sperm and normal motile count; P < 0.05) compared to those not exposed. These differences were most pronounced between semen samples from years with several heat waves (2013, 2023) and none (2005, 2007, 2016), displaying 4-5 times higher fold changes (P < 0.05). Further analysis employing multiple regression revealed a significantly negative association between semen quality and heat wave length, suggesting that a prolonged exposure may be more detrimental than an acute exposure. Subsequent analysis focusing on prolonged exposure (≥6-days heat wave) during spermatogenesis revealed a negative (P < 0.05) association between early exposure (spermatocytogenesis: 64-90 days prior semen collection) and semen quality. This study underscores the negative association between early exposure to heat waves during sperm development and semen quality, raising concerns about its possible association with the worldwide declining male fertility. A comprehensive collaborative approach is crucial, involving global governmental policies, sustainable practices, and coordinated efforts across scientific, healthcare, and policy domains.

Hydrogen sulfide and its potential as a possible therapeutic agent in male reproduction

Hydrogen sulfide (H2S) is an endogenously produced signaling molecule that belongs to the group of gasotransmitters along with nitric oxide (NO) and carbon monoxide (CO). H2S plays a pivotal role in male reproductive processes. It is produced in various tissues and cells of the male reproductive system, including testicular tissue, Leydig and Sertoli cells, epididymis, seminal plasma, prostate, penile tissues, and sperm cells. This review aims to summarize the knowledge about the presence and effects of H2S in male reproductive tissues and outline possible therapeutic strategies in pathological conditions related to male fertility, e. g. spermatogenetic disorders and erectile dysfunction (ED). For instance, H2S supports spermatogenesis by maintaining the integrity of the blood-testicular barrier (BTB), stimulating testosterone production, and providing cytoprotective effects. In spermatozoa, H2S modulates sperm motility, promotes sperm maturation, capacitation, and acrosome reaction, and has significant cytoprotective effects. Given its vasorelaxant effects, it supports the erection of penile tissue. These findings suggest the importance and therapeutic potential of H2S in male reproduction, paving the way for further research and potential clinical applications.

From pathophysiology to practice: addressing oxidative stress and sperm DNA fragmentation in Varicocele-affected subfertile men

Varicocele can reduce male fertility potential through various oxidative stress mechanisms. Excessive production of reactive oxygen species may overwhelm the sperm's defenses against oxidative stress, damaging the sperm chromatin. Sperm DNA fragmentation, in the form of DNA strand breaks, is recognized as a consequence of the oxidative stress cascade and is commonly found in the ejaculates of men with varicocele and fertility issues. This paper reviews the current knowledge regarding the association between varicocele, oxidative stress, sperm DNA fragmentation, and male infertility, and examines the role of varicocele repair in alleviating oxidative-sperm DNA fragmentation in these patients. Additionally, we highlight areas for further research to address knowledge gaps relevant to clinical practice.

Synergistic protective effects of 3,4-dihydroxyphenylglycol and hydroxytyrosol in male rats against induced heat stress-induced reproduction damage

Testicular heat stress disrupts spermiogenesis and damages testicular tissue. The study aims to assess 3,4-dihydroxyphenylglycol (DHPG) and hydroxytyrosol (HT) from olive oil as antioxidants to reduce heat-induced testicular damage. Seven groups of 35 male rats were used. Group I got normal saline. Group 2 had HS (43 °C for 20 min/day) and normal saline for 60 days. Groups 3-7 had HS and DHPG/HT doses (0.5 mg/kg DHPG, 1 mg/kg DHPG, 5 mg/kg HT, 0.5 mg/kg DHPG + 5 mg/kg HT, and 1 mg/kg DHPG + 5 mg/kg HT). The evaluation included tests on testicular tissue, sperm quality, oxidative status, gene activity, and fertility after 60 days. After DHPG and HT treatment, sperm motility, viability, and plasma membrane functionality, as well as levels of total antioxidant capacity (TAC), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), and Bcl-2 gene expression, and in vivo fertility indexes increased. Meanwhile, abnormal morphology and DNA damage decreased, along with levels of glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA), and Bax, caspase-3, and caspase-9 gene expression, compared to the HS group. The study found that DHPG and HT have a more substantial synergistic effect when used together, improving reproductive health.

Morinda citrifolia protective effects on paclitaxel-induced testis parenchyma toxicity: An experimental study

The current study aimed to investigate the sensitivity of male testis parenchyma cells to chemotherapy agents and the protective effects and mechanisms of Morinda citrifolia (Noni) administration against structural and functional changes before and after chemotherapy (Paclitaxel (PTX)). For this purpose, rats were randomly assigned into four groups (Control = G1, PTX 5 mg/kg = G2; PTX + Noni 10 mg/kg = G3, PTX + Noni 20 mg/kg = G4). PTX was injected intraperitoneally for 4 consecutive weeks, at a dose of 5 mg/kg to all groups except the control group. Then noni was administrated in 10 (G3) and 20 (G4) mg/kg groups orally (gavage) for 14 days. Biochemical analyses, Real-Time Polymerase Chain Reaction (PCR), and immunohistochemical analyses were performed. According to our results, Total Oxidative Stress (TOS) and Malondialdehyde (MDA) were significantly increased in the PTX group (P < 0.01). Superoxide Dismutase (SOD) enzyme activity and Total Antioxidant Capacity (TAC) levels were decreased (P < 0.01). The changes in the rats treated with PTX + Noni 20 mg/kg were noteworthy. The increased levels of IL1-β (Interleukin 1 beta) and TNFα (tumor necrosis factor-alpha) with PTX were down-regulated after treatment with PTX + Noni 20 mg/kg (P < 0.01) (9 % and 5 % respectively). In addition, Noni restored the testicular histopathological structure by reducing caspase-3 expression and significantly (61 %) suppressed oxidative DNA damage and apoptosis (by regulating the Bax (bcl-2-like protein 4)/Bcl-2 (B-cell lymphoma gene-2) ratio). In conclusion, Noni reduced cellular apoptosis and drastically changed Caspase 8 and Bax/Bcl-2 levels. Furthermore, it considerably decreases oxidative damage and can be used in testicular degeneration.

The use of time-dynamic patterns of temperature and flexible generalized models to clarify the relations between temperature and semen quality

BACKGROUND

Sperm quality has decreased over the last decades worldwide. It is affected, among others, by season and heat. This study aimed to address the association between ambient temperature and sperm quality by assessing its shape using flexible multivariate models and identifying distinct time-dynamic patterns of temperature change based on unsupervised analysis.

MATERIAL AND METHODS

A retrospective population-based study has been conducted, including all samples of males attending the Fertility and In-Vitro-Fertilization unit at a single medical center during 2016-2022. Flexible generalized models were fitted to characterize the relations between sperm quality and temperature while accounting for patients characteristics, and to identify temperature levels that correspond with the optimal sperm quality. This information was then used to estimate adjusted slope coefficients at specified time-windows.

RESULTS

In total, 4555 sperm samples were provided by 3229 individuals. Sperm concentration, motility and progressive motility were higher by 8 %, 11 % and 16 %, respectively, during the spring versus the fall season. Furthermore, their quality during early spermatogenesis improved with temperature, until a certain optimum around 23 °C-24 °C. Increasing temperature at later developmental stages was associated with lower sperm concentration and higher motility. Sperm concentration and motility were highest following a period of moderate gradual warming. Motility was higher and sperm concentration was lower, following a period with heatwaves or summer.

CONCLUSIONS

This study assessed temperature role in sperm production quality by considering both average and time-dynamic temperatures. It identified several temperature change patterns over time and stratified the analysis by them. The differences in the relations across stages of spermatogenesis were addressed. Several mechanisms may explain the associations found, including heat-induced apoptosis of the sperm cells, and destruction of sperm cells DNA integrity by over-production of reactive oxygen species. The gradual global warming necessitates exploration of individual response to outdoor temperature in relations to genetic predisposition, lifestyle, and other health characteristics.

Sestrin2 and Sestrin3 protect spermatogenesis against heat-induced meiotic defects†

Heat stress induces testicular oxidative stress, impairs spermatogenesis, and increases the risk of male infertility. Recent studies have highlighted the antioxidative properties of the Sestrins family in reducing cellular oxidative damage. However, the role of Sestrins (Sestrin1, 2, and 3) in the testicular response to heat stress remains unclear. Here, we found that Sestrin2 and 3 were highly expressed in the testis relative to Sestrin1. Then, the Sestrin2-/- and Sestrin3-/- mice were generated by CRISPR/Cas9 to investigate the role of them on spermatogenesis after heat stress. Our data showed that Sestrin2-/- and Sestrin3-/- mice testes exhibited more severe damage manifested by exacerbated loss of germ cells and higher levels of oxidative stress as compared to wild-type counterparts after heat stress. Notably, Sestrin2-/- and Sestrin3-/- mice underwent a remarkable increase in heat-induced spermatocyte apoptosis than that of controls. Furthermore, the transcriptome landscape of spermatocytes and chromosome spreading showed that loss of Sestrin2 and Sestrin3 exacerbated meiotic failure by compromising DNA double-strand breaks repair after heat stress. Taken together, our work demonstrated a critical protective function of Sestrin2 and Sestrin3 in mitigating the impairments of spermatogenesis against heat stress.

Protective effects of L-theanine and dihydromyricetin on reproductive function in male mice under heat stress

Heat stress can impair the male reproductive function. L-Theanine and dihydromyricetin have biological activities against heat stress; however, their effects on reproductive function in heat-stressed males are unclear. In this study, male mice were given L-theanine, dihydromyricetin, or a combination of both for 28 days, followed by 2 h of heat stress daily for 7 days. All interventions alleviated heat stress-induced testicular damage, improving the testicular organ index, sperm density, acrosome integrity, sperm deformity rate, and hormone levels. Treatment increased the antioxidant enzyme activity and decreased the markers of oxidative and inflammatory stress in the testes. A combination dose of 200 + 200 mg kg-1 d-1 showed the best protective effect. The potential mechanism involves the regulation of HSP27 and HSP70, which regulate the levels of reproductive hormones through the StAR/Cyp11a1/Hsd3b1/Cyp17a1/Hsd17b3 pathway, alleviate inflammation and oxidative stress through the P38/NF-κB/Nrf2/HO-1 pathway, and regulate the Bcl-2/Fas/Caspase3 apoptotic pathway. Overall, L-theanine and dihydromyricetin may play a protective role against heat stress-induced reproductive dysfunction, suggesting their potential use in heat stress-resistant foods.

Advances in Male Contraception: When Will the Novel Male Contraception be Available?

Many contraceptive methods have been developed over the years due to high demand. However, female contraceptive pills and devices do not work for all females due to health conditions and side effects. Also, the number of males who want to actively participate in family planning is gradually increasing. However, the only contraceptive options currently available to males are condoms and vasectomy. Therefore, many male contraceptive methods, including medication (hormonal and non-hormonal therapy) and mechanical methods, are under development. Reversibility, safety, persistence, degree of invasion, promptness, and the suppression of anti-sperm antibody formation are essential factors in the development of male contraceptive methods. In this paper, male contraceptive methods under development are reviewed according to those essential factors. Furthermore, the timeline for the availability of a new male contraception is discussed.

The Effect of Endurance Exercise on Semen Quality in Male Athletes: A Systematic Review

BACKGROUND

Endurance exercise has the potential to affect reproductive function, with amenorrhea in female athletes. However, most studies focus on women. Evidence on the association between endurance exercise and male fertility is limited.

OBJECTIVE

To synthesise existing literature on exercise-induced alterations in semen parameters and to assess the clinical impact on male fertility.

METHODS

Studies reporting on the association between semen parameters and endurance exercise in healthy men were eligible. Men attending fertility clinics were excluded. We searched MEDLINE (PubMed), Embase, SPORTDiscus, Cochrane Central Register of Controlled Trials (CENTRAL), ClinicalTrials.gov and International Clinical Trials Registry Platform (ICTRP) from their inception to May 28th 2022. JBI Critical Appraisal Tool was used to assess the potential risk of bias.

RESULTS

Thirteen studies met inclusion criteria, reporting on 280 subjects. Eight articles reported on endurance runners, three on cyclists and four on triathletes. Four studies did not find any statistically significant sperm alterations. Five reported significant changes in semen parameters, but these were not clinically relevant, as semen parameters remained well above World Health Organisation (WHO) thresholds. Four articles reported a decrease in semen quality with potential clinical consequences as they found a reduced number of sperm cells exhibiting normal morphology in cyclists and triathletes and a greater amount of DNA fragmentation in triathletes.

CONCLUSION

Endurance exercise can have a negative effect on semen quality, although rarely with a clinically relevant impact on male fertility. Evidence is however limited, with poor quality of the included studies.

REGISTRATION

PROSPERO International prospective register of systematic reviews (CRD42022336753).

Comparative expression and localization of visfatin, chemerin, and chemerin receptor proteins in a heat-stressed mouse testis

The adipokines, visfatin, chemerin, and its receptor are expressed in the testis. It has also been shown that heat-stress alters the secretion and expression of other adipokines. Testicular heat-stress is now well known to cause the impairment in the testis. It has also been documented that heat-stress changes the expression of genes and proteins in the testis. To the best of our knowledge, the expression and localization of visfatin chemerin and its receptor have not been investigated in the heat-stressed testis. Therefore, the present study has investigated the expression and localization of these proteins in the heat-stressed testis. The expression of visfatin and chemerin and receptor exhibits a differential repossess against the heat stress. Visfatin expression was up-regulated while chemerin and chemerin receptor was down-regulated in the heat-stressed testis as shown by western blot analysis. The immunolocalization of visfatin and chemerin showed increased abundance in the seminiferous tubules of heat-stressed mice testis. Furthermore, abundance of visfatin, chemerin, and its receptor showed a decrease in abundance in the Leydig cells of heat-stressed testis. The decreased abundance of these proteins in the Leydig cells coincides with decreased 3β-HSD immunostaining along with decreased testosterone levels. These results suggest that heat-stress might decrease testosterone secretion by modulating visfatin and chemerin in the Leydig cells. The increased abundance of visfatin and chemerin in the primary spermatocytes, round spermatid, and multinucleated germ cells also coincides with increased immunostaining of active caspase-3. Moreover, expression of Bcl-2 was down-regulated, and expression of active caspase-3 and HSP70 were up-regulated along with increased oxidative stress in the heat-stressed testis, suggesting stimulated apoptosis. In conclusion, our results showed that visfatin, chemerin, and its receptor are differentially expressed in the testis under heat-stress and within the testis also it might differentially regulate testosterone biosynthesis in the Leydig cells and apoptosis in the seminiferous tubules.

Heat stress-induced dysbiosis of the gut microbiota impairs spermatogenesis by regulating secondary bile acid metabolism in the gut

Heat stress (HS) poses a substantial challenge to livestock. Studies have demonstrated that HS reduces fertility and leads to gut microbiota dysbiosis in bulls. However, the impact of the gut microbiota on fertility in bulls during HS is still unclear. Our research revealed that HS exposure decreased semen quality in bulls, and fecal microbiota transplantation (FMT) from heat-stressed bulls to recipient mice resulted in a significant decrease in number of testicular germ cells and epididymal sperm. Untargeted metabolomics methodology and 16S rDNA sequencing conjoint analysis revealed that Akkermansia muciniphila (A. muciniphila) seemed to be a key bacterial regulator of spermatogenesis after HS exposure. Moreover, the research indicated that A. muciniphila regulated secondary bile acid metabolism by promoting the colonization of bile salt hydrolase (BSH)-metabolizing bacteria, leading to increase of retinol absorption in the host gut and subsequently elevation of testicular retinoic acid level, thereby improving spermatogenesis. This study sheds light on the relationship between HS-induced microbiota dysbiosis and spermatogenesis, offering a potential therapeutic approach for addressing bull spermatogenic dysfunction triggered by HS exposure.

Role of nuclear factor erythroid 2-related factor 2 (Nrf2) in female and male fertility

Oxidative stress refers to a condition where there is an imbalance between the production of reactive oxygen species and their removal by antioxidants. While the function of reactive oxygen species as specific second messengers under physiological conditions is necessary, their overproduction can lead to numerous instances of cell and tissue damage. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of many cytoprotective genes that respond to redox stresses. Nrf2 is regularly degraded by kelch-like ECH-associated protein 1 through the ubiquitin-proteasome pathway. The kelch-like ECH-associated protein 1 and Nrf2 complex have attracted attention in both basic and clinical infertility research fields. Oxidative stress is implicated in the pathogenesis of female infertility, including primary ovarian insufficiency, polycystic ovarian syndrome, and endometriosis, as well as male infertility, namely varicocele, cryptorchidism, spermatic cord torsion, and orchitis. Most scientists believe that Nrf2 is a potential therapeutic method in female and male infertility disorders due to its antioxidant effect. Here, the potential roles of oxidative stress and Nrf2 in female and male infertility disorders are reviewed. Moreover, the key role of Nrf2 in the inhibition or induction of these diseases is discussed.

Ameliorative effects of omega-3 and omega-6 on spermatogenesis, testicular antioxidant status and in vivo fertility index in heat-stressed rats

The current study aimed to investigate the use of omega-6 (ω6) or omega-3 (ω3) in reducing heat-induced damage to the testicles. This is due to the known detrimental effects of heat and the potential protective properties of ω6 and ω3. In the study, 48 male rats were divided into eight groups, each containing 6 rats. Group I (control) received normal saline. Group 2 was exposed to high temperatures (43 °C for 20 min/day) and also received normal saline for 60 days. Groups 3-7 underwent identical HS conditions and received varying doses of ω6 or ω3 (0.5 mg/kg DHPG, 1 mg/kg DHPG, 5 mg/kg HT, 0.5 mg/kg DHPG + 5 mg/kg HT, and 1 mg/kg DHPG + 5 mg/kg HT), respectively. After 60 days, various tests were conducted on the testicular tissue, sperm quality, oxidative status, gene activity, and in vivo fertility indexes to evaluate the effects of the treatments. Treatment with ω6 and ω3 could reduce abnormal morphology and DNA damage while increasing total and progressive motility, characteristics motility, viability, and plasma membrane functional impairment compared with HS-exposed groups. Antioxidant status levels in testicular tissue were improved after administration of ω6 and ω3. Furthermore, after receiving ω6 and ω3, there were significantly lower expression levels of P53 and Caspase-3 and significantly higher expression levels of Bcl-2 compared to the HS-exposed group. Furthermore, the results showed that administration of ω6 and ω3 to rats exposed to HS could increase their in vivo fertility indexes compared to the group not exposed to HS. According to our data, all doses of ω6 and ω3 (particularly doses of ω6-1.25 and ω3-300) can improve the testicular damage, testicular antioxidant defense mechanism, regulate germ cell apoptosis, and increase in vivo fertility indexes.

Sperm traits and seminal plasma proteome of locally adapted hairy rams subjected to intermittent scrotal insulation

The present study evaluated the effects of heat stress on reproductive parameters of hairy rams. Six animals were subjected to scrotal insulation during four consecutive nights (6 PM - 6 AM). Day (D) 0 was the first day of insulation. Scrotal circumference increased from 30.5 ± 0.3 cm (at pre-insulation) to 31.8 ± 0.4 cm on D4, decreased 3.9 cm on D28, returning to 30.6 ± 0.6 cm on D57. Sperm concentration decreased from 3.7 ± 0.12 ×109 sperm/mL before insulation to 2.6 ± 0.1 ×109 on D23, returning to normal on D57. Sperm motility averaged 75 ± 2.9% before insulation, was undetectable on D23, and became normal on D77. Sperm with normal morphology reached 5.9 ± 2.6% on D35 but recovered (86.8 ± 2.1%) on D91. Sperm DNA integrity decreased from 86.5 ± 4.7% before insulation to 11.1 ± 3.7% on D63, returning to pre-insulation values on D120. Sperm BSP immunostaining was reduced after scrotal insulation. Variations in seminal protein abundances coincided with changes in sperm parameters. Seminal plasma superoxide dismutase, carboxypeptidase Q-precursor and NPC intracellular cholesterol transporter 2 decreased on D18, returning to normal after D28. Albumin, inhibitor of carbonic anhydrase precursor, EGF-like repeat and discoid I-like domain-containing protein 3 and polymeric immunoglobulin receptor increased after insulation. In summary, intermittent scrotal insulation drastically altered ram sperm attributes and seminal proteins, especially those associated with oxidative stress. Knowledge of animal´s response to thermal stress is vital in the scenario of climate changes.

Relationship of environmental exposure temperature and temperature extremes on sperm DNA fragmentation index in men with different BMI values and the indirect effect of DNA fragmentation index on semen parameters

Prior studies have established a significant correlation between the DNA fragmentation index (DFI) and infertility. Additionally, certain investigations suggest that environmental exposure may serve as an etiological factor impacting semen quality. This study aimed to explore the impact of season, ambient temperature, and weather extremes on the DFI of sperm, along with other relevant parameters. Furthermore, it sought to assess how ambient temperature affects the DFI of sperm and other semen parameters in populations with varying BMI values. Additionally, the study analyzed the transient indirect effect of DFI on sperm parameters. This retrospective study analyzed semen samples from 11,877 men, selected based on female factor considerations, spanning from January 2016 to December 2021. Participants were grouped according to the season of semen collection. The results showed that samples collected in summer had a lower semen volume and sperm motility, while those collected in autumn had a lower DFI. We analyzed the exposure-response ratio between environmental exposure temperature and semen parameters using a generalized additive model. Results showed that the curve of the exposure-response relationship was U-shaped or inverted U-shaped; when the air temperature exposure was below the threshold, for each degree of temperature increase, the total sperm motility, sperm concentration, and progressive motility increased by 0.16 %, 0.29 × 10 (Levine, 1999)/ml and 0.14 %, respectively, while the DFI and inactivity rate decreased by 0.078 % and 0.15 %, respectively. When the air temperature exposure exceeded the threshold, for each degree of temperature increase, the sperm concentration, total sperm motility, semen volume and progressive motility decreased by 0.42 × 10 (Levine, 1999)/ml, 0.11 %, 0.0078 ml and 0.15 %, respectively, while the DFI and inactivity rate increased by 0.13 % and 0.12 %, respectively. Extremely cold weather during spermatogenesis was positively correlated with DFI, and extremely hot weather was negatively correlated with sperm motility. Subgroup analysis revealed that individuals classified as overweight / obese exhibited more pronounced changes in sperm parameters and the DFI in response to variations in environmental exposure temperature compared to those with a normal BMI. In the analysis of the relationship between DFI and sperm parameters, the results showed an inverted U-shape relationship between DFI and semen volume, and a negative correlation between DFI and sperm concentration and sperm motility. And we found that ambient temperature affects sperm parameters through DFI at low as well as average temperatures, whereas at high temperatures this indirect effect is no longer present.

What is the maximal timeframe between sperm acquisition to sperm cryopreservation, in different "culture" conditions?

OBJECTIVE

Most of the literature about postmortem sperm retrieval (PMSR) deals with the controversies surrounding ethical and legal aspects, while the optimal time interval between the death and viable sperm acquisition is indefinite. In an attempt to aid fertility specialists, while counseling whether to pursue and adopt PMSR, we aim to explore the maximal time frame from ejaculated sperm acquisition to sperm cryopreservation in different "culture" conditions, observations that might be extrapolated to PMSR requests.

PATIENTS AND METHODS

Five healthy men with normal semen analysis were enrolled. The sperm specimen from each man was diluted to 6.5 mL. After extracting 0.5 mL for cryopreservation, the remaining 6 mL were divided into three tubes: one was maintained in room temperature (23-25 °C), the second in an incubator (37 °C), and the third in a refrigerator (4 °C). Thereafter, every day, a 0.5 mL of each sample was extracted, examined, and cryopreserved. A week later, all the cryopreserved samples were thawed and tested for sperm motility and viability.

RESULTS

While at room temperature, frozen/thawed sperm were still motile (6.5%) and viable (9.9%) up to 96 h; those maintained in the refrigerator, following freezing/thawing were immotile already at 48 h in culture, but still viable (6.0%) up to 72 h in culture. Those maintained in the incubator demonstrated the worse results with negligible motility (1.5%) and viability (3.7%) following freezing/thawing, already after 48 h in culture.

CONCLUSIONS

The timeframe cut-off between ejaculated sperm acquisition and cryopreservation should be 72 h, unless sperm was maintained at room temperature, where it might be longer. It would be prudent to check for sperm vitality prior to freezing in cases where only immotile sperms are present.

Morin hydrate ameliorates heat-induced testicular impairment in a mouse model

BACKGROUND

Heat stress is known to adversely affect testicular activity and manifest the pathogenesis of spermatogenesis. Morin hydrate is a plant-derived compound, which contains a wide range of biological activities. Thus, it is hypothesized that morin hydrate might have an ameliorative effect on heat-induced testicular impairment. There has not been any research on the impact of morin hydrate on heat-induced testicular damage.

METHODS

The experimental mice were divided into four groups, groups1 as the normal control group (CN), and the second which underwent heat stress (HS) by immersing the lower body for 15 min in a thermostatically controlled water bath kept at 43 °C (HS), and third and fourth heat-stressed followed by two different dosages of morin hydrate 10 mg/kg (HSM10) and 100 mg/kg (HSM100) for 14 days.

RESULTS

Morin hydrate treatment at 10 mg/kg improved, circulating testosterone levels (increases 3βHSD), and oxidative stress along with improvement in the testis and caput and corpus epididymis histoarchitecture, however, both doses of morin hydrate improved sperm parameters. Morin hydrate treatment significantly increases germ cell proliferation, (GCNA, BrdU staining), expression of Bcl2 and decreases expression of active caspase 3. Heat stress also decreased the expression of AR, ER- α, and ER-β, and Morin hydrate treatment increased the expression of these markers in the 10 mg/kg treatment group.

CONCLUSION

Morin hydrate ameliorates heat-induced testicular impairment modulating testosterone synthesis, germ cell proliferation, and oxidative stress. These effects could be manifested by regulating androgen and estrogen receptors. However, the two doses showed differential effects of some parameters, which requires further investigations.

Potential molecular mechanisms of myrtenal against colon cancer: A systematic review

Colon cancer is a serious health problem across the globe with various dietary lifestyle modifications. It arises as an inflammation mediated crypts in the colon epithelial cells and undergoes uncontrolled cell division and proliferation. Bacterial enzymes contribute to a major outbreak in colon cancer development upon the release of toxic metabolites from the gut microflora. Pathogen associated molecular patterns and damage associated molecular patterns triggers the NLPR3 inflammasome pathways that releases pro-inflammatory cytokines to induce cancer of the colon. Contributing to this, specific chemokines and receptor complexes attribute to cellular proliferation and metastasis. Bacterial enzymes synergistically attack the colon mucosa and degenerate the cellular integrity causing lysosomal discharge. These factors further instigate the Tol like receptors (TLRs) and Nod like receptors (NLRs) to promote angiogenesis and supply nutrients for the cancer cells. Myrtenal, a monoterpene, is gaining more importance in recent times and it is being widely utilized against many diseases such as cancers, neurodegenerative diseases and diabetes. Based on the research data's, the reviews focus on the anticancer property of myrtenal by emphasizing its therapeutic properties which downregulate the inflammasome pathways and other signalling pathways. Combination therapy is gaining more importance as they can target every variant in the cellular stress condition. Clinical studies with compounds like myrtenal of the monoterpenes family is provided with positive results which might open an effective anticancer drug therapy. This review highlights myrtenal and its biological potency as a cost effective drug for prevention and treatment of colon cancer.

Heat stress and ram semen production and preservation: Exploring impacts and effective strategies

As global warming persists, heat stress (HS) continues to affect animals, particularly those raised in extensive systems such as sheep. As a result, there is a growing body of research investigating the physiological and biological consequences of HS on these animals. Recent studies have specifically examined the effects of climate change, global warming, and HS on gametes. Heat stress has been shown to affect ram semen production, resulting in decreased sperm quality and volume in both fresh and stored samples. This is attributed to the effect of heat on hormone production in the testicles, which is critical for successful spermatogenesis. Such effects can have significant consequences on the fertility of female sheep, which could affect the farmers' revenue. Therefore, farmers and researchers are utilizing various strategies and laboratory techniques to mitigate these negative effects. This review aims to comprehensively evaluate the impact of HS on ram semen production and conservation and analyze the different mitigation strategies at various levels, including management and nutritional interventions. The findings of this review will serve as a critical foundation for the development of targeted interventions and sustainable practices in sheep farming, ensuring resilient and profitable operations in the face of ongoing global climate challenges.

Exploring edible bird nest's potential in mitigating Wi-Fi's impact on male reproductive health

Purpose

This study aimed to evaluate the protective effects of edible bird nest (EBN) against the detrimental impact of Wi-Fi on male reproductive health. Specifically, it examines whether EBN can mitigate Wi-Fi-induced changes in male reproductive hormones, estrogen receptors (ER), spermatogenesis, and sperm parameters.

Methods

Thirty-six adult male rats were divided into six groups (n = 6): Control, Control EBN, Control E2, Wi-Fi, Wi-Fi+EBN, and Wi-Fi+E2. Control EBN and Wi-Fi+EBN groups received 250 mg/kg/day EBN, while Control E2 and Wi-Fi+E2 groups received 12 μg/kg/day E2 for 10 days. Wi-Fi exposure and EBN supplementation lasted eight weeks. Assessments included organ weight, hormone levels (FSH, LH, testosterone, and E2), ERα/ERβ mRNA and protein expression, spermatogenic markers (c-KIT and SCF), and sperm quality.

Results

Wi-Fi exposure led to decreased FSH, testosterone, ERα mRNA, and sperm quality (concentration, motility, and viability). EBN supplementation restored serum FSH and testosterone levels, increased serum LH levels, and the testosterone/E2 ratio, and normalized mRNA ERα expression. Additionally, EBN increased sperm concentration in Wi-Fi-exposed rats without affecting motility or viability.

Conclusions

EBN plays a crucial role in regulating male reproductive hormones and spermatogenesis, leading to improved sperm concentration. This could notably benefit men experiencing oligospermia due to excessive Wi-Fi exposure.

Heat Stress Impairs Male Reproductive System with Potential Disruption of Retinol Metabolism and Microbial Balance in the Testis of Mice

BACKGROUND

Heat stress (HS) has a harmful impact on the male reproductive system, primarily by reducing the sperm quality. The testicular microenvironment plays an important role in sperm quality.

OBJECTIVES

This study aimed to explore the underlying mechanism by which HS impairs the male reproductive system through the testicular microenvironment.

METHODS

Ten-week-old male mice (n = 8 mice/group) were maintained at a normal temperature (25°C, control) or subjected to HS (38°C for 2 h each day, HS) for 2 wk. The epididymides and testes were collected at week 2 to determine sperm quality, histopathology, retinol concentration, the expression of retinol metabolism-related genes, and the testicular microbiome. The testicular microbiome profiles were analyzed using biostatistics and bioinformatics; other data were analyzed using a 2-sided Student's t test.

RESULTS

Compared with the control, HS reduced (P < 0.05) sperm count (42.4%) and motility (97.7%) and disrupted the integrity of the blood-testis barrier. Testicular microbial profiling analysis revealed that HS increased the abundance of the genera Asticcacaulis, Enhydrobacter, and Stenotrophomonas (P < 0.05) and decreased the abundance of the genera Enterococcus and Pleomorphomonas (P < 0.05). Notably, the abundance of Asticcacaulis spp. showed a significant negative correlation with sperm count (P < 0.001) and sperm motility (P < 0.001). Moreover, Asticcacaulis spp. correlated significantly with most blood differential metabolites, particularly retinol (P < 0.05). Compared with the control, HS increased serum retinol concentrations (25.3%) but decreased the testis retinol concentration by 23.7%. Meanwhile, HS downregulated (P < 0.05) the expression of 2 genes (STRA6 and RDH10) and a protein (RDH10) involved in retinol metabolism by 27.3%-36.6% in the testis compared with the control.

CONCLUSIONS

HS reduced sperm quality, mainly because of an imbalance in the testicular microenvironment potentially caused by an increase in Asticcacaulis spp. and disturbed retinol metabolism. These findings may offer new strategies for improving male reproductive capacity under HS.

The role of miR-199a-3p in inhibiting the proliferation of spermatogonial stem cells under heat stress

MicroRNAs (miRNAs) play a crucial role in regulating various physiological processes, including cell differentiation, proliferation, and apoptosis. However, their specific functions in response to heat stress are not fully understood. This study aimed to investigate the regulatory effects of miR-199a-3p on the proliferation of heat stress-treated spermatogonial stem cells (SSCs). SSCs were isolated from mouse testes and cultured in vitro to identify marker molecules. Lentiviruses carrying miR-199a-3p-over, miR-199a-3p-inhibit, and ID4-over constructs were generated for stable transfection. Luciferase assay was employed to confirm the targeting relationship between miR-199a-3p and ID4. An in vitro SSCs heat stress model was established, and the miR-199a-3p-inhibit and ID4-over groups were included. Cellular proliferation was assessed using CCK-8, EdU, and cell cycle analysis methods after heat stress. Expression levels of miR-199a-3p and ID4 were evaluated by western blotting and qRT-PCR. The results demonstrated that miR-199a-3p-over inhibited SSCs proliferation, while ID4-over promoted an increase in SSCs number. Luciferase assay confirmed the regulatory effect of miR-199a-3p on ID4 expression. Moreover, after heat stress treatment, miR-199a-3p-inhibit and ID4-over enhanced SSCs proliferation compared to the control group. These findings suggest that miR-199a-3p modulates SSCs proliferation by targeting ID4, especially under heat stress conditions.

Heat wave exposure and semen quality in sperm donation volunteers: A retrospective longitudinal study in south China

BACKGROUND

Previous studies have suggested an association between non-optimum ambient temperature and decreased semen quality. However, the effect of exposure to heat waves on semen quality remains unclear.

METHODS

Volunteers who intended to donate sperm in Guangdong provincial human sperm bank enrolled. Heat waves were defined by temperature threshold and duration, with a total of 9 definitions were employed, specifying daily mean temperature exceeding the 85th, 90th, or 95th percentile for at least 2, 3, or 4 consecutive days. Residential exposure to heat waves during 0-90 days before ejaculation was evaluated using a validated gridded dataset on ambient temperature. Association and potential windows of susceptibility were evaluated and identified using linear mixed models and distributed lag non-linear models.

RESULTS

A total of 2183 sperm donation volunteers underwent 8632 semen analyses from 2018 to 2019. Exposure to heat wave defined as daily mean temperature exceeding the 95th percentile for at least 4 consecutive days (P95-D4) was significantly associated with a 0.11 (95% confidence interval [CI]: 0.03, 0.18) ml, 3.36 (1.35, 5.38) × 106/ml, 16.93 (7.95, 25.91) × 106, and 2.11% (1.4%, 2.83%) reduction in semen volume, sperm concentration, total sperm number, and normal forms, respectively; whereas exposure to heat wave defined as P90-D4 was significantly associated with a 1.98% (1.47%, 2.48%) and 2.08% (1.57%, 2.58%) reduction in total motility and progressive motility, respectively. Sperm count and morphology were susceptible to heat wave exposure during the early stage of spermatogenesis, while sperm motility was susceptible to exposure during the late stage.

CONCLUSION

Heat wave exposure was significantly associated with a reduction in semen quality. The windows of susceptibility during 0-90 days before ejaculation varied across sperm count, motility, and morphology. Our findings suggest that reducing heat wave exposure before ejaculation may benefit sperm donation volunteers and those attempting to conceive.

Reactive X (where X = O, N, S, C, Cl, Br, and I) species nanomedicine

Reactive oxygen, nitrogen, sulfur, carbonyl, chlorine, bromine, and iodine species (RXS, where X = O, N, S, C, Cl, Br, and I) have important roles in various normal physiological processes and act as essential regulators of cell metabolism; their inherent biological activities govern cell signaling, immune balance, and tissue homeostasis. However, an imbalance between RXS production and consumption will induce the occurrence and development of various diseases. Due to the considerable progress of nanomedicine, a variety of nanosystems that can regulate RXS has been rationally designed and engineered for restoring RXS balance to halt the pathological processes of different diseases. The invention of radical-regulating nanomaterials creates the possibility of intriguing projects for disease treatment and promotes advances in nanomedicine. In this comprehensive review, we summarize, discuss, and highlight very-recent advances in RXS-based nanomedicine for versatile disease treatments. This review particularly focuses on the types and pathological effects of these reactive species and explores the biological effects of RXS-based nanomaterials, accompanied by a discussion and the outlook of the challenges faced and future clinical translations of RXS nanomedicines.