Temperature sensitivity of DNA double-strand break repair underpins heat-induced meiotic failure in mouse spermatogenesis

In vivo ovarian temperature promotes the in vitro growth and developmental competence of oocytes derived from bovine early antral follicles

In cattle, the culture temperature used for the in vitro growth (IVG) of immature oocytes is generally 38.5 or 39.0 °C, which is close to the normal temperature in the vagina or rectum. However, the temperature in the in vivo ovarian tissue is approximately 1 °C lower (37.5 °C) than that in the vagina or rectum. Therefore, the generally accepted culture temperature may not be optimal for the IVG of bovine oocytes. Herein, we investigated the effects of culture temperature on the IVG of oocyte-cumulus granulosa complexes (OCGCs) derived from early antral follicles (0.5-1 mm in diameter). OCGCs were subjected to 12 days of IVG at temperatures of 37.5, 38.5, and 39.0 °C. OCGC viability and antrum formation were evaluated every 4 days. Estradiol-17β (E2) and progesterone (P4) production from OCGCs during the 1st, 2nd, and 3rd 4-day periods was evaluated by enzyme immunoassay. Viable OCGCs after IVG were subjected to in vitro maturation (IVM), in vitro fertilization, and embryo culture. Then, the nuclear status and diameter of oocytes after IVM, rates of cleavage and blastocysts, and cell number in blastocysts were evaluated. In addition, the mRNA expression of heat shock proteins (HSPs) in the granulosa cells and reduced glutathione (GSH) levels in oocytes after IVG were measured. The viability of OCGCs did not differ among the groups, whereas the rate of antrum formation on day 12 of IVG culture was highest in the 37.5 °C group (P < 0.05). P4 production did not differ among the groups; however, E2 production during days 8-12 tended to be higher in the 37.5 °C group than in the other two groups combined (P < 0.1). The mRNA expression of HSP70 and 90, and the GSH levels of oocytes, did not differ among the groups. The oocyte diameter after culture was larger in the 37.5 °C group than in the 39.0 °C group (P < 0.05), and that in the 38.5 °C group was intermediate between the other two groups. The rates of nuclear maturation and cleavage did not differ among the groups. However, the blastocyst rate was higher in the 37.5 and 38.5 °C groups than in the 39.0 °C group (P < 0.05). The cell number in the blastocysts in the 38.5 °C group was smaller than the in vivo-grown oocytes, while that in the 37.5 °C group and the in vivo-grown oocytes did not differ. In summary, OCGCs in the 37.5 °C group showed healthy morphology and steroidogenesis, as well as better growth and developmental competence of oocytes. Therefore, culture conditions close to the in vivo ovarian tissue temperature would be optimal for the IVG of immature bovine oocytes.

The involvement of TRPV1 in the apoptosis of spermatogenic cells in the testis of mice with cryptorchidism

Cryptorchidism is associated with an increased risk of male infertility and testicular cancer. Persistent exposure to high temperature in cryptorchidism can lead to the apoptosis of spermatogenic cells. Transient receptor potential vanilloid 1 (TRPV1), a thermosensitive cation channel, has been found to have differential effects on various apoptosis processes. However, whether TRPV1 is involved in spermatogenic cell apoptosis induced by cryptorchidism remains unclear. Herein, we first observed the expression pattern of TRPV1 in the testes of mice with experimental cryptorchidism, and then investigated the role and mechanism of TRPV1 in spermatogenic cell apoptosis by using Trpv1-/- mice. The results showed that TRPV1 was highly expressed on the membrane of spermatocytes in mouse testis, and the expression increased significantly in the testis of mice with experimental cryptorchidism. After the operation, Trpv1-/- mice exhibited less reproductive damage and fewer spermatogenic cell apoptosis compared to the wild-type (WT) mice. Transcriptome sequencing revealed that the expression of apoptosis-related genes (Capn1, Capn2, Bax, Aifm1, Caspase 3, Map3k5, Itpr1 and Fas) was down-regulated in spermatocytes of cryptorchid Trpv1-/- mice. Our results suggest that TRPV1 promotes the apoptosis of spermatocytes in cryptorchid mice by regulating the expression of apoptosis-related genes.

Can nutraceuticals counteract the detrimental effects of the environment on male fertility? A parallel systematic review and expert opinion

INTRODUCTION

Male fertility relies on a complex physiology that may be negatively influenced by lifestyle, diet, and environment. The beneficial effect of nutraceuticals on male fertility is a debated claim. The aim of this study was to assess if the positive effect of nutraceuticals can counteract the negative effects of the environment on male fertility.

EVIDENCE ACQUISITION

PubMed®/MEDLINE®, Embase and Cochrane Database were searched (September-October 2023), along with crosschecking of references and search for ongoing studies of the effects of the environment and nutraceuticals on male fertility, in accordance with the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

EVIDENCE SYNTHESIS

Several environmental factors such as microplastic and other endocrine-disrupting chemicals and climate changes may affect the sperm quality in terms of reduction of sperm count number, mobility and altered morphology and thereby reduce male fertility. On the other hand, new evidence demonstrates that a balanced diet rich in antioxidants and essential nutrients, together with minimized exposure to environmental toxins, may improve male fertility and reproductive health. Several nutraceutical compounds proved a protective role against negative environmental effects on male fertility.

CONCLUSIONS

Available evidence confirms that the environment may negatively impact male fertility, and this impact is estimated to rise in the forthcoming years. On the other hand, new data indicate that nutraceuticals may have a protective role against the negative impact of environmental factors on male fertility. The need for future studies to monitor and explore these aspects of men's health cannot be underestimated.

Mechanisms underlining Kelp (Saccharina japonica) adaptation to relative high seawater temperature

Saccharina japonica has been cultivated in China for almost a century. From Dalian to Fujian, the lowest and the highest seawater temperatures in the period of cultivation increased by 14℃ and 8℃, respectively. Its adaptation to elevated seawater temperature is an example of securing the natural habitats of a species. To decipher the mechanisms underlining S. japonica adaptation to relative high seawater temperature, we assembled ~ 516.3 Mb female gametophyte genome and ~ 540.3 Mb of the male, respectively. The gametophytes isolated from southern China kelp cultivars acclimated to the relative high seawater temperature by transforming amino acids, glycosylating protein, maintaining osmotic pressure, intensifying the innate immune system, and exhausting energy and reduction power through the PEP-pyruvate-oxaloacetate node and the iodine cycle. They adapted to the relative high seawater temperature by transforming amino acids, changing sugar metabolism and intensifying innate immune system. The sex of S. japonica was determined by HMG-sex, and around this male gametophyte determiner the stress tolerant genes become linked to or associated with.

Abnormal H3K27me3 underlies degenerative spermatogonial stem cells in cryptorchid testis

Cryptorchidism is the most frequent congenital defect in newborn males characterized by the absence of the testis from the scrotum. Approximately 90% of individuals with untreated bilateral cryptorchidism exhibit azoospermia due to defective spermatogenesis in the affected testis. Although abnormal spermatogonial stem cell maintenance or differentiation is suggested to cause germ cell degeneration in the cryptorchid testis, the underlying molecular mechanisms remain unclear. Here, we profiled spermatogonial epigenetic landscapes using surgically induced cryptorchid testis in the mouse. We show that cryptorchidism leads to alterations in local, but not global, H3K27me3 and H3K9me3 in undifferentiated spermatogonia. Of these, the loss of H3K27me3 was correlated with activation of developmental and proapoptotic pathway genes that are repressed by the polycomb machinery in germ cells. Cryptorchid spermatogonia exhibit an increase of the H3K27me3 demethylases KDM6A and KMD6B. Furthermore, we reveal that an increased temperature leads to Kdm6a/b upregulation in germline stem cells cultured in vitro. Thus, our study suggests that temperature-dependent histone demethylation may induce mRNA dysregulation due to the partial loss of H3K27me3 in spermatogonia.

Temperature regulates negative supercoils to modulate meiotic crossovers and chromosome organization

Crossover recombination is a hallmark of meiosis that holds the paternal and maternal chromosomes (homologs) together for their faithful segregation, while promoting genetic diversity of the progeny. The pattern of crossover is mainly controlled by the architecture of the meiotic chromosomes. Environmental factors, especially temperature, also play an important role in modulating crossovers. However, it is unclear how temperature affects crossovers. Here, we examined the distribution of budding yeast axis components (Red1, Hop1, and Rec8) and the crossover-associated Zip3 foci in detail at different temperatures, and found that both increased and decreased temperatures result in shorter meiotic chromosome axes and more crossovers. Further investigations showed that temperature changes coordinately enhanced the hyperabundant accumulation of Hop1 and Red1 on chromosomes and the number of Zip3 foci. Most importantly, temperature-induced changes in the distribution of axis proteins and Zip3 foci depend on changes in DNA negative supercoils. These results suggest that yeast meiosis senses temperature changes by increasing the level of negative supercoils to increase crossovers and modulate chromosome organization. These findings provide a new perspective on understanding the effect and mechanism of temperature on meiotic recombination and chromosome organization, with important implications for evolution and breeding.

Simulated climate change and atrazine contamination can synergistically impair zebrafish testicular function

Elements that interfere with reproductive processes can have profound impacts on population and the equilibrium of ecosystems. Global warming represents the major environmental challenge of the 21st century, as it will affect all forms of life in the coming decades. Another coexisting concern is the persistent pollution by pesticides, particularly the herbicide Atrazine (ATZ), which is responsible for a significant number of contamination incidents in surface waters worldwide. While it is hypothesized that climate changes will significantly enhance the toxic effects of pesticides, the actual impact of these phenomena remain largely unexplored. Here, we conducted a climate-controlled room experiment to assess the interactive effects of the projected 2100 climate scenario and environmentally realistic ATZ exposures on the reproductive function of male zebrafish. The gonadosomatic index significantly decreased in fish kept in the extreme scenario. Cellular alterations across spermatogenesis phases led to synergic decreased sperm production and increased germ cell sloughing and death. ATZ exposure alone or combined with climate change effects, disrupted the transcription levels of key genes involved in steroidogenesis, hormone signaling and spermatogenesis regulation. An additive modulation with decreased 11-KT production and increased E2 levels was also evidenced, intensifying the effects of androgen/estrogen imbalance. Moreover, climate change and ATZ independently induced oxidative stress, upregulation of proapoptotic gene and DNA damage in post-meiotic germ cell, but the negative effects of ATZ were greater at extreme scenario. Ultimately, exposure to simulated climate changes severely impaired fertilization capacity, due to a drastic reduction in sperm motility and/or viability. These findings indicate that the future climate conditions have the potential to considerably enhance the toxicity of ATZ at low concentrations, leading to significant deleterious consequences for fish reproductive function and fertility. These may provide relevant information to supporting healthcare and environmental managers in decision-making related to climate changes and herbicide regulation.

Protocol for in vivo CRISPR screening targeting murine testicular cells

In vivo genome-wide screening elucidates tissue-specific molecular events. Here, we present a protocol for an in vivo genome-wide CRISPR-Cas9 single-guide RNA (sgRNA) library screening technique optimized for mouse testicular cells to investigate spermatogenesis. We describe steps for virus injection, sperm sorting, and primase-based whole-genome amplification. We then detail procedures for library reconstruction using a "revival screening" technique. Our approach reveals intricate spermatogenesis processes and is adaptable for diverse tissue-specific studies. For complete details on the use and execution of this protocol, please refer to Noguchi et al.1.

Evaluation of the scrotal thermal environment and the testicular sizes in prepubertal hemiscrotal agenesis without cryptorchidism

Introduction

Hemiscrotal agenesis is a rare scrotal developmental disorder. Orchiopexy on the opposite side of the scrotum with rugae or scrotoplasty combined with orchiopexy is usually performed as a surgical treatment for hemiscrotal agenesis with cryptorchidism. Till date, there are only eight published case studies of hemiscrotal agenesis.

Case presentation

A 6-year-old boy, who had been previously treated for infantile hemangiomas, was referred by a pediatrician to our hospital for the follow-up of hemiscrotal agenesis without cryptorchidism. Thermography demonstrated that the temperature of the right scrotal skin with no rugae was higher than that of the left scrotal skin with rugae. The patient's parent declined scrotoplasty because the hemiscrotal agenesis was to be followed up without scrotoplasty and scrotal ultrasonography revealed no abnormal findings in both testes.

Conclusion

High-temperature environment may not impair the testicular growth in prepubertal hemiscrotal agenesis without cryptorchidism.

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.

A novel alternative method for long-term evaluation of male reproductive toxicity and its recovery using a pre-pubertal mouse testis organ culture system

Successful treatment of pediatric cancers often results in long-term health complications, including potential effects on fertility. Therefore, assessing the male reproductive toxicity of anti-cancer drug treatments and the potential for recovery is of paramount importance. However, in vivo evaluations are time-intensive and require large numbers of animals. To overcome these constraints, we utilized an innovative organ culture system that supports long-term spermatogenesis by placing the testis tissue between a base agarose gel and a polydimethylsiloxane ceiling, effectively mirroring the in vivo testicular environment. The present study aimed to determine the efficacy of this organ culture system for accurately assessing testicular toxicity induced by cisplatin, using acrosin-green fluorescent protein (GFP) transgenic neonatal mouse testes. The testis fragments were treated with different concentrations of cisplatin-containing medium for 24 h and incubated in fresh medium for up to 70 days. The changes in tissue volume and GFP fluorescence over time were evaluated to monitor the progression of spermatogenesis, in addition to the corresponding histopathology. Cisplatin treatment caused tissue volume shrinkage and reduced GFP fluorescence in a concentration-dependent manner. Recovery from testicular toxicity was also dependent on the concentration of cisplatin received. The results demonstrated that this novel in vitro system can be a faithful replacement for animal experiments to assess the testicular toxicity of anti-cancer drugs and their reversibility, providing a useful method for drug development.

Atypical heat shock transcription factor HSF5 is critical for male meiotic prophase under non-stress conditions

Meiotic prophase progression is differently regulated in males and females. In males, pachytene transition during meiotic prophase is accompanied by robust alteration in gene expression. However, how gene expression is regulated differently to ensure meiotic prophase completion in males remains elusive. Herein, we identify HSF5 as a male germ cell-specific heat shock transcription factor (HSF) for meiotic prophase progression. Genetic analyzes and single-cell RNA-sequencing demonstrate that HSF5 is essential for progression beyond the pachytene stage under non-stress conditions rather than heat stress. Chromatin binding analysis in vivo and DNA-binding assays in vitro suggest that HSF5 binds to promoters in a subset of genes associated with chromatin organization. HSF5 recognizes a DNA motif different from typical heat shock elements recognized by other canonical HSFs. This study suggests that HSF5 is an atypical HSF that is required for the gene expression program for pachytene transition during meiotic prophase in males.

A point mutation in the meiotic crossover formation gene HEI10/TFS2 leads to thermosensitive genic sterility in rice

Thermosensitive genic female sterility (TGFS) is a promising property to be utilized for hybrid breeding. Here, we identified a rice TGFS line, tfs2, through an ethyl methyl sulfone (EMS) mutagenesis strategy. This line showed sterility under high temperature and became fertile under low temperature. Few seeds were produced when the tfs2 stigma was pollinated, indicating that tfs2 is female sterile. Gene cloning and genetic complementation showed that a point mutation from leucine to phenylalanine in HEI10 (HEI10tfs2), a crossover formation protein, caused the TGFS trait of tfs2. Under high temperature, abnormal univalents were formed, and the chromosomes were unequally segregated during meiosis, similar to the reported meiotic defects in oshei10. Under low temperature, the number of univalents was largely reduced, and the chromosomes segregated equally, suggesting that crossover formation was restored in tfs2. Yeast two-hybrid assays showed that HEI10 interacted with two putative protein degradation-related proteins, RPT4 and SRFP1. Through transient expression in tobacco leaves, HEI10 were found to spontaneously aggregate into dot-like foci in the nucleus under high temperature, but HEI10tfs2 failed to aggregate. In contrast, low temperature promoted HEI10tfs2 aggregation. This result suggests that protein aggregation at the crossover position contributes to the fertility restoration of tfs2 under low temperature. In addition, RPT4 and SRFP1 also aggregated into dot-like foci, and these aggregations depend on the presence of HEI10. These findings reveal a novel mechanism of fertility restoration and facilitate further understanding of HEI10 in meiotic crossover formation.

Heatwaves are detrimental to fertility in the viviparous tsetse fly

Heatwaves are increasing in frequency and intensity due to climate change, pushing animals beyond physiological limits. While most studies focus on survival limits, sublethal effects on fertility tend to occur below lethal thresholds, and consequently can be as important for population viability. Typically, male fertility is more heat-sensitive than female fertility, yet direct comparisons are limited. Here, we measured the effect of experimental heatwaves on tsetse flies, Glossina pallidipes, disease vectors and unusual live-bearing insects of sub-Saharan Africa. We exposed males or females to a 3-day heatwave peaking at 36, 38 or 40°C for 2 h, and a 25°C control, monitoring mortality and reproduction over six weeks. For a heatwave peaking at 40°C, mortality was 100%, while a 38°C peak resulted in only 8% acute mortality. Females exposed to the 38°C heatwave experienced a one-week delay in producing offspring, whereas no such delay occurred in males. Over six weeks, heatwaves resulted in equivalent fertility loss in both sexes. Combined with mortality, this lead to a 10% population decline over six weeks compared to the control. Furthermore, parental heatwave exposure gave rise to a female-biased offspring sex ratio. Ultimately, thermal limits of both survival and fertility should be considered when assessing climate change vulnerability.

In vivo CRISPR screening directly targeting testicular cells

CRISPR-Cas9 short guide RNA (sgRNA) library screening is a powerful approach to understand the molecular mechanisms of biological phenomena. However, its in vivo application is currently limited. Here, we developed our previously established in vitro revival screening method into an in vivo one to identify factors involved in spermatogenesis integrity by utilizing sperm capacitation as an indicator. By introducing an sgRNA library into testicular cells, we successfully pinpointed the retinal degeneration 3 (Rd3) gene as a significant factor in spermatogenesis. Single-cell RNA sequencing (scRNA-seq) analysis highlighted the high expression of Rd3 in round spermatids, and proteomics analysis indicated that Rd3 interacts with mitochondria. To search for cell-type-specific signaling pathways based on scRNA-seq and proteomics analyses, we developed a computational tool, Hub-Explorer. Through this, we discovered that Rd3 modulates oxidative stress by regulating mitochondrial distribution upon ciliogenesis induction. Collectively, our screening system provides a valuable in vivo approach to decipher molecular mechanisms in biological processes.

Improvements in in vitro spermatogenesis: oxygen concentration, antioxidants, tissue-form design, and space control

Incorporation of bovine serum-derived albumin formulation (AlbuMAX) into a basic culture medium, MEMα, enables the completion of in vitro spermatogenesis through testicular tissue culture in mice. However, this medium was not effective in other animals. Therefore, we sought an alternative approach for in vitro spermatogenesis using a synthetic medium without AlbuMAX and aimed to identify its essential components. In addition to factors known to be important for spermatogenesis, such as retinoic acid and reproductive hormones, we found that antioxidants (vitamin E, vitamin C, and glutathione) and lysophospholipids are vital for in vitro spermatogenesis. Moreover, based on our experience with microfluidic devices (MFD), we developed an alternative approach, the PDMS-ceiling method (PC method), which involves simply covering the tissue with a flat chip made of PDMS, a silicone resin material used in MFD. The PC method, while straightforward, integrates the advantages of MFD, enabling improved and uniform oxygen and nutrient supply via tissue flattening. Furthermore, our studies underscored the significance of lowering the oxygen concentration to 10-15%. Using an integrated cultivation method based on these findings, we successfully achieved in vitro spermatogenesis in rats, which has been a long-standing challenge. Further improvements in culture conditions would pave the way for spermatogenesis completion in diverse animal species.

Effect of Temperature on the Development of Stages of Spermatogenesis and the Functionality of Sertoli Cells In Vitro

Spermatogenesis is the process of proliferation and differentiation of spermatogonial cells to meiotic and post-meiotic stages and sperm generation. Normal spermatogenesis occurs in vivo at 34 °C to 35 °C, and high temperatures are known to cause male infertility. The aim of the present study was to examine the effect of temperature (35 °C compared to 37 °C) on the viability/apoptosis of developed cells, on the development of different stages of spermatogenesis in 3D in vitro culture conditions, and the functionality of Sertoli cells under these conditions. We used isolated cells from seminiferous tubules of sexually immature mice. The cells were cultured in methylcellulose (as a three-dimensional (3D) in vitro culture system) and incubated in a CO2 incubator at 35 °C or 37 °C. After two to six weeks, the developed cells and organoids were collected and examined for cell viability and apoptosis markers. The development of different stages of spermatogenesis was evaluated by immunofluorescence staining or qPCR analysis using specific antibodies or primers, respectively, for cells at each stage. Factors that indicate the functionality of Sertoli cells were assessed by qPCR analysis. The developed organoids were examined by a confocal microscope. Our results show that the percentages and/or the expression levels of the developed pre-meiotic, meiotic, and post-meiotic cells were significantly higher at 35 °C compared to those at 37 °C, including the expression levels of the androgen receptor, the FSH receptor, transferrin, the androgen-binding protein (ABP), and the glial-derived nerve growth factor (GDNF) which were similarly significantly higher at 35 °C than at 37 °C. The percentages of apoptotic cells (according to acridine orange staining) and the expression levels of BAX, FAS, and CASPAS 3 were significantly higher in cultures incubated at 37 °C compared to those incubated at 35 °C. These findings support the in vivo results regarding the negative effect of high temperatures on the process of spermatogenesis and suggest a possible effect of high temperatures on the viability/apoptosis of spermatogenic cells. In addition, increasing the temperature in vitro also impaired the functionality of Sertoli cells. These findings may deepen our understanding of the mechanisms behind optimal conditions for normal spermatogenesis in vivo and in vitro.

Trpv4-mediated apoptosis of Leydig cells induced by high temperature regulates sperm development and motility in zebrafish

Exposure of testes to high-temperature environment results in defective spermatogenesis. Zebrafish exposed to high temperature exhibited apoptosis not only in germ cells but also in Leydig cells, as expected from studies using mice or salmon. However, the role of testicular somatic cells in spermatogenesis defects remains unclear. We found that in Leydig cells the Trpv4 gene encoding the temperature sensitive ion channel was specifically upregulated in high temperature. High temperature also reduced hormone synthesis in Leydig cells and led to a prompt downregulation of sperm motility. In the Trpv4 null mutant, neither Leydig cell-specific apoptosis nor decreased sperm motility was observed under high temperature. These results indicate that Leydig cell specific-apoptosis is induced via Trpv4 by high temperature. Notably this Trpv4-dependent mechanism was specific to Leydig cells and did not operate in germ cells. Because sperm exposed to high temperature exhibited compromised genome stability, we propose that temperature sensing leading to apoptosis in Leydig cells evolved to actively suppress generation of offspring with unstable genome.

Uncoupling elephant TP53 and cancer

Elephant testicles do not descend, with implications for sperm production being hot enough to compromise germline DNA replication/repair. Uniquely, elephants also possess 20 copies of a gene encoding for the p53 protein. Did elephants evolve multiplication of the TP53 gene complex to protect their germline rather than to fight cancer?

Potential Function of Testicular MicroRNAs in Heat-Stress-Induced Spermatogenesis Disorders

Spermatogenesis is temperature-dependent, and the increase in testicular temperature seriously affects mammalian spermatogenesis and semen quality. In this study, the testicular heat stress model of mice was made with a 43 °C water bath for 25 min, and the effects of heat stress on semen quality and spermatogenesis-related regulators were analyzed. On the 7th day after heat stress, testis weight shrank to 68.45% and sperm density dropped to 33.20%. High-throughput sequencing analysis showed that 98 microRNAs (miRNAs) and 369 mRNAs were down-regulated, while 77 miRNAs and 1424 mRNAs were up-regulated after heat stress. Through gene ontology (GO) analysis of differentially expressed genes and miRNA-mRNA co-expression networks, it was found that heat stress may be involved in the regulation of testicular atrophy and spermatogenesis disorders by affecting cell meiosis process and cell cycle. In addition, through functional enrichment analysis, co-expression regulatory network, correlation analysis and in vitro experiment, it was found that miR-143-3p may be a representative potential key regulatory factor affecting spermatogenesis under heat stress. In summary, our results enrich the understanding of miRNAs in testicular heat stress and provide a reference for the prevention and treatment of heat-stress-induced spermatogenesis disorders.

Results of lifestyle modification promotion and reproductive/general health check for male partners of couples seeking conception

Purpose

Male infertility is partially caused by an inappropriate lifestyle and comorbidities. In this study, we analyzed the prevalence of these factors and the effects of lifestyle modifications as part of male preconception care.

Methods

Four hundred and two male partners of couples seeking conception with abnormal parameters upon the first semen analysis were enrolled. They were advised to modify their inappropriate lifestyle as male preconception care. Afterward, their general and male reproductive health was examined. Semen quality was compared before and after the promotion.

Results

Smoking, chronic alcohol use, and genital heat stress were found in 22.6%, 47.0%, and 75.1% of patients, respectively. Palpable varicoceles, hypogonadism, obesity (body mass index ≧30 kg/m²), hypertension, zinc deficiency, hyperlipidemia, liver dysfunction, and diabetes mellitus were found in 25.9%, 17.0%, 7.0%, 14.9%, 16.2%, 37.0%, 26.9% and 3.4% of the participants, respectively; 98.8% of the patients had at least one factor. After the promotion, semen parameters and sperm DNA fragmentation were improved significantly. Improvement was found in those with palpable varicocele or hypogonadism but not in those with night work shift, abstinence (>3 days), erectile dysfunction, hypertension, obesity, zinc deficiency, or diabetes mellitus.

Conclusions

Comorbidities and inappropriate lifestyle choices were common among men with infertility. The promotion of lifestyle modifications as part of male preconception care could improve semen quality without urologic intervention.

Where are all the egg genes?

Complementary forward and reverse genetic approaches in several model systems have resulted in a recent burst of fertilization gene discovery. The number of genetically validated gamete surface molecules have more than doubled in the last few years. All the genetically validated sperm fertilization genes encode transmembrane or secreted molecules. Curiously, the discovery of genes that encode oocyte molecules have fallen behind that of sperm genes. This review discusses potential experimental biases and inherent biological reasons that could slow egg fertilization gene discovery. Finally, we shed light on current strategies to identify genes that may result in further identification of egg fertilization genes.

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.

Cryptorchidism: The dog as a study model

Cryptorchidism (CO) or undescended testicle is an abnormality of male gonadal development that can generate long-term repercussions in men, such as infertility and germ cell neoplasia in situ (GCNIS). The origin of these alterations in humans is not completely clear, due to the absence of an animal model with similar testicular development as in humans with CO. This work intends to describe the testicular histological development of dogs with congenital CO, and determine whether the species could adequately serve as a study model for this pathology in humans. The study was carried out with 36 dogs, equally distributed in two groups: healthy control (CTRL) and CO groups. The contralateral testis to the undescended one in CO group of the animals was considered and analyzed. Each group was subdivided in three stages of development: (1) peripubertal stage (6–8 months), (2) young adult (9–48 months) and (3) senile (49–130 months). Histological development, the presence of cells with gonocyte morphology, cell proliferation, testicular lipoperoxidation and hormonal concentrations of testosterone, estradiol, FSH and LH were evaluated and described. In the cryptorchid testes, the first histological alterations appeared from the first stage of development and were maintained until the senile stage. A pronounced testicular lipoperoxidation occurred only in the second stage of development. The histological alterations due to CO were markedly evident in the young adult stage. Testosterone concentrations witnessed a decrease starting from in the second stage and kept on until the last stage. The contralateral testes of the CO animals showed alterations that positioned them between the control and CO testes. Testicular development of dogs with CO is similar to that of humans. The results of the study suggest that this species could serve as a suitable model for the study of CO in humans.