Causes, effects and molecular mechanisms of testicular heat stress

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.

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.

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.

Temperature Elevation during Semen Delivery Deteriorates Boar Sperm Quality by Promoting Apoptosis

Semen delivery practice is crucial to the efficiency of artificial insemination using high-quality boar sperm. The present study aimed to evaluate the effect of a common semen delivery method, a Styrofoam box, under elevated temperatures on boar sperm quality and functionality and to investigate the underlying molecular responses of sperm to the temperature rise. Three pooled semen samples from 10 Duroc boars (3 ejaculates per boar) were used in this study. Each pooled semen sample was divided into two aliquots. One aliquot was stored at a constant 17 °C as the control group. Another one was packaged in a well-sealed Styrofoam box and placed in an incubator at 37 °C for 24 h to simulate semen delivery on hot summer days and subsequently transferred to a refrigerator at 17 °C for 3 days. The semen temperature was continuously monitored. The semen temperature was 17 °C at 0 h of storage and reached 20 °C at 5 h, 30 °C at 14 h, and 37 °C at 24 h. For each time point, sperm quality and functionality, apoptotic changes, expression levels of phosphorylated AMPK, and heat shock proteins HSP70 and HSP90 were determined by CASA, flow cytometry, and Western blotting. The results showed that elevated temperature during delivery significantly deteriorated boar sperm quality and functionality after 14 h of delivery. Storage back to 17 °C did not recover sperm motility. An increased temperature during delivery apparently promoted the conversion of sperm early apoptosis to late apoptosis, showing a significant increase in the expression levels of Bax and Caspase 3. The levels of phosphorylated AMPK were greatly induced by the temperature rise to 20 °C during delivery but reduced thereafter. With the temperature elevation, expression levels of HSP70 and HSP90 were notably increased. Our results indicate that a temperature increase during semen delivery greatly damages sperm quality and functionality by promoting sperm apoptosis. HSP70 and HSP90 could participate in boar sperm resistance to temperature changes by being associated with AMPK activation and anti-apoptotic processes.

Protective effects of epigallocatechin gallate in the mice induced by chronic scrotal hyperthermia

One of the most common complications of chronic scrotal hyperthermia (SHT) is a serious disorder in the male reproductive system. The most important factor in the occurrence of these disorders is oxidative stress. Currently, we investigated the effects of epigallocatechin gallate (EGCG), as a highly potent antioxidant, against cells and tissue disorders in mice affected by chronic SHT. Fifty-six male adult NMRI mice were allocated into seven equal groups. Except the non-treated (Control) group, six other groups were exposed to heat stress. Two treated groups including Preventive and Curative received oral administration of EGCG (50 mg/kg/day) starting immediately before heat exposure and fifteen consecutive days after the end of the heat exposure, respectively. For each treated group, two subgroups including positive control (Pre/Cur + PC groups) and vehicle (Pre/Cur + vehicle groups) were considered. At the end of the study, sperm characteristics, testosterone levels, stereological parameters, apoptosis, oxidant state, and molecular assessments were performed. We found that the sperm parameters, testosterone levels, the numerical density of spermatogonia, primary spermatocytes, spermatids, sertoli, leydig cells, and seminiferous tubules, biochemical factors (except MDA), and expression of c-kit gene were significantly higher in the Preventive and Curative groups, especially in Preventive ones, compared to other groups (P < 0.05). This is while expression of HSP72 and NF-κβ genes, MDA levels, as well as density of apoptotic cells considerably decreased in both EGCG-treated groups compared to other groups and it was more pronounced in Preventive ones (P < 0.05). Generally, EGCG attenuated cellular and molecular disorders induced by heat stress in the testis and it was more pronounced in Preventive status.

Male infertility

Clinical infertility is the inability of a couple to conceive after 12 months of trying. Male factors are estimated to contribute to 30-50% of cases of infertility. Infertility or reduced fertility can result from testicular dysfunction, endocrinopathies, lifestyle factors (such as tobacco and obesity), congenital anatomical factors, gonadotoxic exposures and ageing, among others. The evaluation of male infertility includes detailed history taking, focused physical examination and selective laboratory testing, including semen analysis. Treatments include lifestyle optimization, empirical or targeted medical therapy as well as surgical therapies that lead to measurable improvement in fertility. Although male infertility is recognized as a disease with effects on quality of life for both members of the infertile couple, fewer data exist on specific quantification and impact compared with other health-related conditions.

A biocompatible NIR-II light-responsive nanoknife for permanent male sterilization

Nanomaterial-mediated photothermal therapy (PTT) is a promising strategy for permanent male sterilization owing to its easy operation, rapid heating, minimal invasiveness, and high spatiotemporal controllability. However, the currently available PTT for male sterilization utilizes irradiation sources in the first near-infrared window (NIR-I), which may suffer from incomplete sterilization due to the insufficient penetration depth of NIR-I light. Herein, we developed a facile one-pot hydrothermal synthetic method of cysteine-coated copper sulfide (Cys-CuS) nanosheets for the second NIR window (NIR-II) PTT-mediated permanent male sterilization. In this method, Cys acted not only as a template but also as a sulfur resource in the formation of Cys-CuS nanosheets. The obtained Cys-CuS nanosheets possessed good photothermal properties and satisfied deep-tissue light response capacity under 1064 nm laser exposure. Given this, the permanent male sterilization in vivo was readily achieved by Cys-CuS nanosheets in a rapid manner (only 40 s). To the best of our knowledge, it is the first time that nanomaterial-mediated NIR-II PTT is applied for permanent male sterilization. We believe that the facilely prepared biocompatible Cys-CuS nanosheets can serve as a promising NIR-II light-responsive nanoknife to control the overpopulation of domestic pets and stray animals.

Effects of insulin-like growth factor-1 on the proliferation and apoptosis of stallion testicular cells under normal and heat stress culture conditions

This study investigated the effect of heat stress on stallion testicular cells (TCs) and the effect of insulin-like growth factor (IGF)-1 on TC viability, proliferation, and apoptosis, including different stages of germ cells. TCs were divided into control or treatment groups with 0.01, 0.1, 1, 10, and 100 ng/mL of recombinant human IGF-1 (rhIGF-1) for 24 h at 34 °C and 37 °C. The population and viability were measured before and after treatment. The effects of rhIGF-1 on TC viability, proliferation, and apoptosis were determined using RT-qPCR. Proliferating cell nuclear antigen (PCNA) and marker of proliferation Ki-67 (MKI-67) were used as proliferation markers. Myeloid leukemia-1 (MCL-1) was used as an antiapoptotic marker. BCL2 antagonist/killer-1 (BAK-1) was used as a proapoptotic marker. The relative abundance of mRNA transcript of undifferentiated cell transcription factor 1 (UTF-1), protein gene product 9.5 (PGP9.5), and deleted in azoospermia-like (DAZL), was measured for spermatogenesis progression. TCs treated with 1 ng/mL rhIGF-1 at 34 °C exhibited the highest viability. Significant upregulation of the relative abundance of mRNA transcript of PCNA, MKI-67, and MCL-1 was observed in treated TCs compared with untreated TCs; however, BAK-1 was significantly downregulated in treated TCs. Germ cells treated with 1 ng/mL rhIGF-1 exhibited the highest relative abundance of mRNA transcript of UTF-1 and DAZL, whereas TCs exposed to 0.1 ng/mL showed the highest PGP9.5 level. These data confirm that heat stress in stallions decreases TC viability. These findings may help identify a basal IGF-1 level for TC proliferation and apoptosis during heat stress-induced testicular degeneration in stallions.

Chronic exposure to warm temperature causes low sperm abundance and quality in Drosophila melanogaster

Temperature influences male fertility across organisms; however, how suboptimal temperatures affect adult spermatogenesis remains understudied. In a recent study on Drosophila melanogaster oogenesis, we observed a drastic reduction in the fertility of adult males exposed to warm temperature (29 °C). Here, we show that males become infertile at 29 °C because of low sperm abundance and quality. The low sperm abundance at 29 °C does not stem from reduced germline stem cell or spermatid numbers, as those numbers remain comparable between 29 °C and control 25 °C. Notably, males at cold 18 °C and 29 °C had similarly increased frequencies of spermatid elongation and individualization defects which, considering the high sperm abundance and male fertility measured at 18 °C, indicate that spermatogenesis has a high tolerance for elongation and individualization defects. Interestingly, the abundance of sperm at 29 °C decreases abruptly and with no evidence of apoptosis as they transition into the seminal vesicle near the end of spermatogenesis, pointing to sperm elimination through an unknown mechanism. Finally, sperm from males at 29 °C fertilize eggs less efficiently and do not support embryos past the first stage of embryogenesis, indicating that poor sperm quality is an additional cause of male infertility at 29 °C.

Ramifications of Heat Stress on Rabbit Production and Role of Nutraceuticals in Alleviating Its Negative Impacts: An Updated Review

Heat stress has become a widespread concern worldwide, which is a major environmental stress that causes substantial economic loss in the rabbit industry. Compared to other agricultural animals, rabbits are more sensitive to heat stress as they have fewer sweat glands and a thicker coat of fur, increasing the heat dissipation complexity. Thus, heat stress hurts rabbits' productivity, meat quality, reproductive performance, antioxidative properties, immune responsiveness, intestinal histomorphology, and microbiome. Nutraceuticals include vitamins, minerals, antioxidants, organic acids, fatty acids, probiotics, prebiotics, synbiotics, enzymes, and medicinal plants due to the possible impacts on maintaining common biological situations, strengthening immune response, and preventing illness, which ultimately led to an increase in productivity. Nutraceuticals have recently attracted a lot of attention to alleviate the adverse impacts of heat stress in rabbit farms. The objective of the current review is to provide acquaintance with the recent findings about the impact of heat stress on rabbit productivity and the advantages of dietary supplementation of nutraceuticals in mitigating it.

Heat stress and stallion fertility

The threat posed by increased surface temperatures worldwide has attracted the attention of researchers to the reaction of animals to heat stress. Spermatogenesis in animals such as stallions is a temperature-dependent process, ideally occurring at temperatures slightly below the core body temperature. Thus, proper thermoregulation is essential, especially because stallion spermatogenesis and the resulting spermatozoa are negatively affected by increased testicular temperature. Consequently, the failure of thermoregulation resulting in heat stress may diminish sperm quality and increase the likelihood of stallion infertility. In this review, we emphasize upon the impact of heat stress on spermatogenesis and the somatic and germ cells and describe the subsequent testicular alterations. In addition, we explore the functions and molecular responses of heat shock proteins, including HSP60, HSP70, HSP90, and HSP105, in heat-induced stress conditions. Finally, we discuss the use of various therapies to alleviate heat stress-induced reproductive harm by modulating distinct signaling pathways.

Expression of Protein Markers in Spermatogenic and Supporting Sertoli Cells Affected by High Abdominal Temperature in Cryptorchidism Model Mice

Cryptorchidism is a congenital abnormality resulting in increased rates of infertility and testicular cancer. We used cryptorchidism model mice that presented with the translocation of the left testis from the scrotum to the abdominal cavity. Mice underwent the surgical procedure of the left testis at day 0 and were sacrificed at days 3, 5, 7, 14, 21, and 28 post-operatively. The weight of the left cryptorchid testis decreased significantly at days 21 and 28. The morphological changes were observed after 5 days and showed detached spermatogenic cells and abnormal formation of acrosome at day 5, multinucleated giant cells at day 7, and atrophy of seminiferous tubules at days 21 and 28. The high abdominal temperature disrupted the normal expression of cell adhesion molecule-1, Nectin-2, and Nectin-3 which are essential for spermatogenesis. In addition, the pattern and alignment of acetylated tubulin in cryptorchid testes were also changed at days 5, 7, 14, 21, and 28. Ultrastructure of cryptorchid testes revealed giant cells that had been formed by spermatogonia, spermatocytes, and round and elongating spermatids. The study's findings reveal that cryptorchidism's duration is linked to abnormal changes in the testis, impacting protein marker expression in spermatogenic and Sertoli cells. These changes stem from the induction of high abdominal temperature.

Photobiomodulation therapy reverses spermatogenesis arrest in hyperthermia-induced azoospermia mouse model

Testicular heat stress leads to impairment of spermatogenesis in mammals. Involved mechanism in this vulnerability to heat-induced injury remains unclear, and research is being conducted to find an approach to reverse spermatogenesis arrest caused by hyperthermia. Recently, different studies have utilized photobiomodulation therapy (PBMT) therapy for the improvement of sperm criteria and fertility. This study aimed at evaluating the effect of PBMT on the improvement of spermatogenesis in mouse models of hyperthermia-induced azoospermia. A total of 32 male NMRI mice were equally divided into four groups consisting of control, hyperthermia, hyperthermia + Laser 0.03 J/cm2, and hyperthermia + Laser 0.2 J/cm2. To induce scrotal hyperthermia, mice were anesthetized and placed in a hot water bath at 43 °C for 20 min for 5 weeks. Then, PBMT was operated for 21 days using 0.03 J/cm2 and 0.2 J/cm2 laser energy densities in the Laser 0.03 and Laser 0.2 groups, respectively. Results revealed that PBMT with lower intensity (0.03 J/cm2) increased succinate dehydrogenase (SDH) activity and glutathione (GSH)/oxidized glutathione (GSSG) ratio in hyperthermia-induced azoospermia mice. At the same time, low-level PBMT reduced reactive oxygen species (ROS), mitochondrial membrane potential, and lipid peroxidation levels in the azoospermia model. These alterations accompanied the restoration of spermatogenesis manifested by the elevated number of testicular cells, increased volume and length of seminiferous tubules, and production of mature spermatozoa. After conducting experiments and analyzing the results, it has been revealed that the use of PBMT at a dosage of 0.03 J/cm2 has shown remarkable healing effects in the heat-induced azoospermia mouse model.

5-Aminolevulinic acid combined with ferrous iron ameliorates scrotal heat stress-induced spermatogenic damage by enhancing HO-1 expression

OBJECTIVE

To explore whether 5-Aminolevulinic acid combined with ferrous iron (5-ALA/Fe²⁺) could protect testicular tissues damage of mice subjected to heat stress (HS) and provide its underlying mechanisms.

METHODS

5-ALA/Fe²⁺ was administered intragastrically to mice for 10 days, then exposed to a scrotal heat stress at 43°C for 20 min on third day. Testes were harvested for morphologic and histopathological examination, oxidative stress, apoptosis, heme oxygenase-1 (HO-1) and inflammation detection. The mitogen-activated protein kinases (MAPK) signaling pathway in testis and CD4⁺FoxP3⁺regulatory T (Treg) cells in spleen were also investigated.

RESULTS

Compared to control group, the testis weight decreased and histological damage severed in HS group. Besides, HS also increased the oxidative stress, apoptosis and inflammation in testis. However, these indicators were ameliorated after 5-ALA/Fe²⁺ treatment but deteriorated after receiving ZnPPIX. The expression of HO-1 was increased both in HS group and 5-ALA/Fe²⁺ group. The protein expression levels of MAPK proteins were activated by HS and inhibited by 5-ALA/Fe²⁺. The CD4⁺FoxP3⁺ Treg generation was reduced by HS and increased by 5-ALA/Fe²⁺.

CONCLUSION

In this study, we have demonstrated that 5-ALA/Fe²⁺ ameliorated the spermatogenic damage induced by scrotal heat stress via up-regulating the expression of HO-1 and inhibiting MAPK mediated oxidative stress and apoptosis and inducing CD4⁺Foxp3⁺ Tregs to inhibit the inflammation induced by HS in mice.

Protective Effect of Curculigo orchioides Gaertn. Extract on Heat Stress-Induced Spermatogenesis Complications in Murine Model

Curculigo orchioides Gaertn. is a precious herb used in traditional medicine systems in Asian countries for various health benefits. This study investigated the potential protective effects of C. orchioides extract on reproductive health under heat stress conditions in male mice. Forty-eight mice were divided into eight groups, control condition (C group), C. orchioides extract at the dosages of 100, 200, and 400 mg/kg/day (C100, C200, C400 group), 40 °C heat exposure (H group), and combined 40 °C heat exposure and C. orchioides extract at the dosages of 100, 200, and 400 mg/kg/day (HC100, HC200, HC400 group). The result shows that the mice that received only C. orchioides extract without heat stress do not have a significant change in histological structure and testosterone level. The histological analysis of testicular tissue showed that heat stress conditions reduced reproductive function and inhibited the spermatogenesis of male mice. The C. orchioides rhizome extract treatment attenuated the heat stress-induced spermatogenesis complications in the murine model. Mice in the heat-stress group treated with C. orchioides extract had increased spermatogenic cells and spermatozoa compared with mice exposed to heat without C. orchioides treatment. Moreover, the aqueous extract of C. orchioides rhizome enhanced the serum total testosterone levels in heat-exposed mice. In conclusion, the study findings validate that C. orchioides is effective against heat stress-induced spermatogenesis complications in the murine model.

Testicular heat stress, a historical perspective and two postulates for why male germ cells are heat sensitive

Herein, we compare the different experimental regimes used to induce testicular heat stress and summarise their impact on sperm production and male fertility. Irrespective of the protocol used, scrotal heat stress causes loss of sperm production. This is first seen 1-2 weeks post heat stress, peaking 4-5 weeks thereafter. The higher the temperature, or the longer the duration of heat, the more pronounced germ cell loss becomes, within extreme cases this leads to azoospermia. The second, and often underappreciated impact of testicular hyperthermia is the production of poor-quality spermatozoa. Typically, those cells that survive hyperthermia develop into morphologically abnormal and poorly motile spermatozoa. While both apoptotic and non-apoptotic pathways are known to contribute to hyperthermic germ cell loss, the mechanisms leading to formation of poor-quality sperm remain unclear. Mechanistically, it is unlikely that testicular hyperthermia affects messenger RNA (mRNA) abundance, as a comparison of four different mammalian studies shows no consistent single gene changes. Using available evidence, we propose two novel models to explain how testicular hyperthermia impairs sperm formation. Our first model suggests aberrant alternative splicing, while the second model proposes a loss of RNA repression. Importantly, neither model requires consistent changes in RNA species.

Association between ambient temperature and semen quality among sperm donation volunteers in South China

BACKGROUND

Potential adverse effects of non-optimum temperatures on human semen quality have drawn much concern worldwide; however, the exposure-response relationship remains less understood.

OBJECTIVES

To quantitatively assess the association between exposure to ambient temperature and semen quality in South China, and to identify potential critical exposure windows.

METHODS

We conducted a longitudinal study to investigate 11,050 volunteers who lived in Guangdong province, China and intended to donate sperm in the Guangdong provincial human sperm bank during 2016-2021. Exposure to ambient temperature during 0-90 days before semen collection was assessed by extracting daily temperatures from a validated grid dataset at each subject's residential address. Linear mixed models and linear regression models were used to perform exposure-response analyses.

RESULTS

During the study period, the 11,050 subjects underwent 44,564 semen analyses. Each 5 °C increase of lag 0-90 day exposure to ambient temperature was approximately linearly associated with a 3.11 (95 % confidence interval [CI]: 2.08, 4.14) × 10⁶/ml, 9.31 (4.83, 13.80) × 10⁶, 1.27 % (0.91 %, 1.62 %), 8.20 (5.33, 11.08) × 10⁶, 1.37 % (1.01 %, 1.74 %), 8.29 (5.52, 11.06) × 10⁶, 0.67 % (0.28 %, 1.05 %), and 4.50 (2.20, 6.80) × 10⁶ reduction in sperm concentration, total sperm number, total motility, total motile sperm number, progressive motility, total progressive sperm number, normal forms, and total normal form sperm number, respectively (all p < 0.001), which was not significantly modified by age (all p for effect modification > 0.05). We identified a critical exposure period of 10-14 days before semen collection for sperm motility, and 70-90 days before semen collection for sperm count and morphology.

CONCLUSIONS

Our study provides consistent evidence that higher ambient temperature was significantly associated with a reduction in semen quality in South China. The findings highlight the needs to reduce high temperature exposures during 3 months before ejaculation to maintain better semen quality.

Cyanidin-3-O-glucoside and protocatechuic acid alleviate heat stress-induced testicular damage

Testicular hyperthermia induced by unhealthy living habits and pathological or occupational factors can cause spermatogenic dysfunction with an outcome of sub-fertility or even infertility. Cyanidin-3-O-glucoside (C3G) is the most typical anthocyanin in foods that has been recognized as an antioxidant with promising protection for male reproduction. However, its specific effect against testicular hyperthermia and the mechanisms involving its primary gastrointestinal metabolite protocatechuic acid (PCA) are still unexplored. In the present study, testicular hyperthermia in mice was established by employing a single hot water bath at 43 °C for 30 min. C3G and PCA were intragastrically given to investigate their prevention ability against heat stress-induced testicular damage. It was found that C3G and PCA restored the external diameter and thickness, and alleviated atrophy and vacuolation of seminiferous tubules. Simultaneously, C3G and PCA enhanced testicular heat stress tolerance through reducing superfluous eIF2α phosphorylation and stress granule formation. C3G and PCA effectively improved the testicular antioxidant system and regulated the IRE1α-XBP1 pathway, contributing to mitigatory spermatogenesis dysfunction and testicular damage. This finding revealed that anthocyanins were the novel compounds for alleviating testicular damage, and provided a reliable theoretical basis for improving male fertility disturbed by heat stress.

COVID-19 and its treatments: lights and shadows on testicular function

PURPOSE

The SARS-CoV-2 pandemic has rapidly spread worldwide and, among the others, the male gender was quickly recognized as an independent risk factor for both the disease and its consequences. Since the possibility of long-term hormonal axis changes and male gamete impairment have been hypothesized but a relatively low levels of evidence has been reached, we focused this narrative mini-review on summarizing key state-of-the-art knowledge on male reproductive effects of COVID-19 as a quick reference for reproductive health specialists.

METHODS

A comprehensive Medline/PubMed and Embase search was performed selecting all relevant, peer-reviewed papers in English published from 2020. Other relevant papers were selected from the reference lists.

RESULTS

Available evidence indicates that the likelihood of direct testicular damage from SARS-CoV-2 is somewhat low, but there are many indirect ways (fever, cytokine imbalance, and drugs) through which the pituitary-gonadal axis and spermatogenesis may be disrupted. These alterations are probably transient, but as available evidence is low quality, it cannot be excluded that previous pathologies or comorbidities might modulate the risk of their persistence. On the other hand, available evidence shows high safety regarding andrological health for available vaccines, although studies are mainly focused on mRNA vaccines.

CONCLUSION

A careful andrological evaluation of men recovering from COVID-19 is highly recommended. Since available evidence is relatively scarce, a careful andrological follow-up and counseling of these patients are mandatory.

Global warming and testis function: A challenging crosstalk in an equally challenging environmental scenario

Environmental pollution, accounting for both chemical and physical factors, is a major matter of concern due to its health consequences in both humans and animals. The release of greenhouse gases with the consequent increase in environmental temperature is acknowledged to have a major impact on the health of both animals and humans, in current and future generations. A large amount of evidence reports detrimental effects of acute heat stress on testis function, particularly on the spermatogenetic and steroidogenetic process, in both animal and human models, wich is largely related to the testis placement within the scrotal sac and outside the abdomen, warranting an overall scrotal temperature of 2°C-4°C lower than the core body temperature. This review will provide a thorough evaluation of environmental temperature's effect on testicular function. In particular, basic concepts of body thermoregulation will be discussed together with available data about the association between testis damage and heat stress exposure. In addition, the possible association between global warming and the secular decline of testis function will be critically evaluated in light of the available epidemiological studies.

Exposure to elevated temperature affects the expression of PIWI-interacting RNAs and associated transcripts in mouse testes

BACKGROUND

Exposure to heat waves could result in adverse effects on human health, especially in male testicles. PIWI-interacting RNA (piRNA) is a novel type of small non-coding RNA, which can notably impact mRNA turnover and preserve germline maintenance in germline cells. However, piRNA's expression status when adapting to testicular heat stress remains largely unclear.

OBJECTIVES

To investigate the function and mechanisms of relevant piRNAs during testicular heat stress.

MATERIALS AND METHODS

In this study, a mouse testicular heat stress model was constructed, and the testes were removed for piRNA-sequencing. Bioinformatics analysis was used to discover the differential expressed piRNAs, piRNA clusters, and enriched pathways. A cell heat stress model was constructed to validate the top five upregulated piRNAs. Proliferation and apoptosis assays were utilized to validate the function of selected piRNA. Bioinformatics prediction, western blotting, and immunohistochemistry were used to illustrate the downstream mechanisms.

RESULTS

Through the bioinformatics analysis, we identified the differential expression profile and enriched pathways of piRNAs and piRNA clusters during testicular hyperthermia. Besides, piR-020492 was proved to be upregulated in heat stress mouse testes and a germ cell model. A series of in vitro assays illustrated that an overexpression of piR-020492 could restrain the proliferation and promote the apoptosis of mouse germ cells. Kyoto Encyclopedia of Genes and Genomes analysis of piRNA-generating genes in the testicular heat stress model and piR-020492 targeting genes showed that the overlap pathways are adenosine monophosphate-activated protein kinase (AMPK) and insulin pathways. Validation experiments demonstrated that the key genes of AMPK and insulin pathway exhibit differential expression after an overexpression of piR-020492 or testicular heat stress.

DISCUSSION AND CONCLUSION

In conclusion, our findings revealed the expression profile of piRNAs in testicular heat stress and illustrated the function and mechanisms of piR-020492 in germ cells, which could provide novel insights into the mechanism of hyperthermia-induced testicular injury.

Effects of inactivated SARS-CoV-2 vaccination on male fertility: A retrospective cohort study

Numerous studies have revealed severe damage to male fertility from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, raising concerns about the potential adverse impact on reproductive function of the coronavirus disease 2019 (COVID-19) vaccine developed based on the virus. Interestingly, there are several researchers who have studied the impact of the COVID-19 mRNA vaccine since then but have come up with conflicting results. As a near-ideal candidate for mass immunization programs, inactivated SARS-CoV-2 vaccine has been widely used in many countries, particularly in less wealthy nations. However, little is known about its effect on male fertility. Here, we conducted a retrospective cohort study at a single large center for reproductive medicine in China between December 2021 and August 2022. Five hundred and nineteen fertile men with no history of laboratory-confirmed COVID-19 were included and categorized into four groups based on their vaccination status: unvaccinated group (n = 168), one-dose vaccinated group (n = 8), fully vaccinated group (n = 183), and booster group (n = 160). All of them underwent a semen analysis and most had serum sex hormone levels tested. There were no significant differences in all semen parameters and sex hormone levels between the unvaccinated group and either vaccinated group. To account for possible vaccination-to-test interval-specific changes, sub-analyses were performed for two interval groups: ≤90 and >90 days. As expected, most of the semen parameters and sex hormone levels remained unchanged between the control and vaccinated groups. However, participants in vaccinated group (≤90 days) have decreased total sperm motility and increased follicle-stimulating hormone level compared with the ones in unvaccinated group. Moreover, some trends similar to those found during COVID-19 infection and recovery were observed in our study. Fortunately, all values are within the normal range. In addition, vaccinated participants reported few adverse reactions. No special medical intervention was required, and no serious adverse reactions happened. Our study suggests that inactivated SARS-CoV-2 vaccination does not impair male fertility, possibly due to the low frequency of adverse effects. This information reassures young male population who got this vaccine worldwide, and helps guide future vaccination efforts.

Decline of Sperm Quality over the Last Two Decades in the South of Europe: A Retrospective Study in Infertile Patients

Semen quality has a direct relation to male fertility. Whether sperm variables in humans have decreased over the last years is still uncertain, with some studies showing a decline and others reporting no changes. In this regard, previous research has suggested that lifestyle and environmental conditions may contribute to this variability, calling for regional studies. The present work is a retrospective, unicentric study that includes semen samples analyzed between 1997 and 2017 at the Parc Taulí Hospital (Barcelona metropolitan area). First, a multivariate analysis including the age as a confounding factor showed a statistically significant decrease in semen volume, pH, progressive motility, morphology and total motile sperm over time. Contrarily, no significant variation in sperm count or concentration was observed. Mean reductions per year were -0.02 mL for volume, -0.57% for progressively motile sperm and -0.72% for sperm with normal morphology. Interestingly, the average annual temperature registered by the Spanish Meteorology Agency negatively correlated to sperm morphology and sperm count (Rs = -0.642; p = 0.002 and Rs = -0.435; p = 0.049, respectively). In conclusion, the present study based on infertile patients from the Barcelona area found a decline in sperm motility and morphology, without effects on sperm count. Changes in temperature appeared to be associated to this decline, but further studies are needed to address the mechanisms linked to the observed variations.