The Mammalian Blood-Testis Barrier: Its Biology and Regulation

Icariin alleviates the injury of Sertoli cell junction function by upregulating PKR pathway via ERα/c-fos signaling in aged mice

ETHNOPHARMACOLOGICAL RELEVENACE

Sertoli cells are vital to maintain spermatogenesis and their function decline during aging. Epimedium has the effects of tonifying kidney-yang, strengthening bones and muscles, and expelling wind and dampness, and is commonly used in the treatment of kidney-yang deficiency, impotence and spermatorrhea. Icariin is the main active ingredients from Epimedium exhibiting delaying aging effects and improving male reproductive dysfunction. Whereas, it remains poorly understood how icariin alleviates age-associated decline in testicular function by protecting against the damage of junction function of Sertoli cells.

AIM OF THE STUDY

This study aimed to evaluate the improvement effect of icariin on Sertoli cell junction function damage and explore the underlying mechanisms.

MATERIALS AND METHODS

Male C57BL/6 mice and mouse Sertoli cell line TM4 cells were utilized to assess the improvement effect of icariin on aging-associated Sertoli cell junction function injury. H&E staining, transmission electron microscopy, qPCR, Western blot, molecular docking, siRNA transfection, and immunofluorescence were performed in this study.

RESULTS

Dietary administration of icariin remarkly attenuated age-associated deterioration in spermatogenic function as evidenced by elevated testicular weight and index, sperm concentration and sperm viability. In addition, icariin protected Sertoli cell junction function from age-associated damage as proven by increased Sertoli cell numbers, improved tight junction ultrastructure, and upregulated junction-related proteins (ZO-1, Occludin and β-Catenin). Moreover, icariin significantly upregulated ERα/c-fos signaling and PKR pathway in testicular Sertoli cells. Similarly, in vitro studies revealed that deletion of ERα, c-fos or PKR abolished the improvement effects of icariin on Sertoli cell junction function damage.

CONCLUSIONS

Icariin effectively mitigates age-associated decline in testicular function by diminished Sertoli cell junction function damage through upregulating PKR pathway via ERα/c-fos signaling. Therefore, attenuating Sertoli cell junction function injury by the upregulation of PKR pathway via ERα/c-fos signaling probably indicates an effective target for the prevention and treatment of testicular spermatogenic function with aging.

Nanoparticles in drinking water: Assessing health risks and regulatory challenges

Nanoparticles (NPs) pose a significant concern in drinking water due to their potential health risks and environmental impact. This review provides a comprehensive analysis of the current understanding of NP sources and contamination in drinking water, focusing on health concerns, mitigation strategies, regulatory frameworks, and future perspectives. This review highlights the importance of nano-specific pathways, fate processes, health risks & toxicity, and the need for realistic toxicity assessments. Different NPs like titanium dioxide, silver, nanoplastics, nanoscale liquid crystal monomers, copper oxide, and others pose potential health risks through ingestion, inhalation, or dermal exposure, impacting organs and potentially leading to oxidative stress, inflammatory responses, DNA damage, cytotoxicity, disrupt intracellular energetic mechanisms, reactive oxygen species generation, respiratory and immune toxicity, and genotoxicity in humans. Utilizing case studies and literature reviews, we investigate the health risks associated with NPs in freshwater environments, emphasizing their relevance to drinking water quality. Various mitigation and treatment strategies, including filtration systems (e.g., reverse osmosis, and ultra/nano-filtration), adsorption processes, coagulation/flocculation, electrocoagulation, advanced oxidation processes, membrane distillation, and ultraviolet treatment, all of which demonstrate high removal efficiencies for NPs from drinking water. Regulatory frameworks and challenges for the production, applications, and disposal of NPs at both national and international levels are discussed, emphasizing the need for tailored regulations to address NP contamination and standardize safety testing and risk assessment practices. Looking ahead, this review underscores the necessity of advancing detection methods and nanomaterial-based treatment technologies while stressing the pivotal role of public awareness and tailored regulatory guidelines in upholding drinking water quality standards. This review emphasizes the urgency of addressing NP contamination in drinking water and provides insights into potential solutions and future research directions. Lastly, this review worth concluded with future recommendations on advanced analytical techniques and sensitive sensors for NP detection for safeguarding public health and policy implementations.

The protective effect of glucose selenol on cadmium-induced testicular toxicity in male rat

This study aimed to investigate the protective effects of glucose selenol on cadmium (Cd)-induced testicular toxicity. Twenty-four male Sprague-Dawley (SD) rats were randomly divided into four groups. Cd was administered orally at a dose of 40 mg/L or in combination with orally administered glucose selenol at doses of 0.15 mg/L and 0.4 mg/L for 30 days. The results showed that sperm quality decreased and testicular tissue was damaged in the Cd group; Glucose selenol significantly attenuated the negative effects by improving sperm quality and reducing testicular damage. Transcriptome sequencing analysis showed that Cd stress affected spermatogenesis, sperm motility, oxidative stress, blood-testis barrier and protein metabolism. Four clusters were obtained using the R Mfuzz package, which clustered highly expressed genes under different administrations, and 36 items were enriched. Notably, protein phosphorylation was enriched in the Cd group and is considered to play a key role in the response to Cd stress. We identified fifty-six target selenium (Se) and Cd co-conversion differentially expressed genes (DEGs), including three genes relating to spermatogenesis (Dnah8, Spata31d1b, Spata31d1c). In addition, the obtained DEGs were used to construct a protein-protein interaction network, co-processed with Se and Cd, and 5 modules were constructed. Overall, the analyses of rat testicular physiology and gene expression levels offer new insights into the reproductive toxicity of Cd in rats, and provide potential application prospects for glucose selenol in alleviating the impact of Cd-induced testicular damage.

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.

LncRNA SNHG5/IGF2BP1/Occludin axis regulates Nd2O3 induced blood-testis barrier disruption

Neodymium oxide (Nd2O3) is a rare earth element that can lead to various type of tissue and organ damage with prolonged exposure. The long noncoding RNA small nucleolar ribonucleic acid host gene 5 (lncRNA SNHG5) plays a role in disease progressiong. However, its connection with Nd2O3 induced reproductive harm in males has not been thoroughly investigated. Our research discovered that exposure to Nd2O3 increases the expression of SNHG5 in the testes of mice, which in turn binds directly to and reduces in the protein levels of insulin like growth factor 2 mRNA-binding protein 1 (IGF2BP1) both in vivo and in vitro. This process disrupts the cytoskeleton of blood-testis barrier(BTB) by impacting the stability of the tight junction protein Occludin (Ocln) mRNA structure and the permeability of the BTB. In summary, our study elucidates the regulatory mechanism of SNHG5/IGF2BP1/Occludin axis in Nd2O3-induced BTB injury, providing valuable insights for the treatment of male infertility.

L-Cysteine Upregulates Testosterone Biosynthesis and Blood-Testis Barrier Genes in Cultured Human Leydig Cells and THP-1 Monocytes and Increases Testosterone Secretion in Human Leydig Cells

Leydig cells are the primary source of testosterone or androgen production in male mammals. The blood-testis barrier (BTB) maintains structural integrity and safeguards germ cells from harmful substances by blocking their entry into the seminiferous tubules. L-cysteine is essential to the production of glutathione, a powerful antioxidant crucial to protecting against oxidative stress-induced damage. Animal studies have demonstrated the protective effect of L-cysteine in preventing testicular damage caused by chemicals or radiation. This study examines whether L-cysteine enhances the expression of testosterone biosynthesis and the BTB genes in human Leydig cells and THP-1 monocytes. The Leydig cells and THP-1 monocytes were treated with L-cysteine for 24 h. RNA was extracted following treatment, and the gene expression was analyzed using quantitative RT-PCR. Testosterone levels in the cell supernatant were measured using an ELISA kit. L-cysteine treatment in Leydig cells significantly upregulated the expression of CYP11A1 (p = 0.03) and the BTB genes CLDN1 (p = 0.03), CLDN11 (p = 0.02), and TJP1 (p = 0.02). Similarly, L-cysteine significantly upregulated the expression of CYP11A1 (p = 0.03) and CYP19A1 (p < 0.01), and the BTB genes CLDN1 (p = 0.04), CLDN2 (p < 0.01), CLDN4 (p < 0.01), CLDN11 (p < 0.01), and TJP1 (p = 0.03) in THP-1 monocytes. Further, L-cysteine supplementation increased the testosterone secretion levels in human Leydig cells. The findings suggest that L-cysteine supplementation could be used as an adjuvant therapy to promote the integrity of the BTB genes, testosterone biosynthesis and secretion, and the maintenance of testicular functions, which in turn mitigates the risk of male infertility.

The Protective Role of L-Cysteine in the Regulation of Blood-Testis Barrier Functions-A Brief Review

Blood-testis barrier (BTB) genes are crucial for the cellular mechanisms of spermatogenesis as they protect against detrimental cytotoxic agents, chemicals, and pathogens, thereby maintaining a sterile environment necessary for sperm development. BTB proteins predominantly consist of extensive tight and gap junctions formed between Sertoli cells. These junctions form a crucial immunological barrier restricting the intercellular movement of substances and molecules within the adluminal compartment. Epithelial tight junctions are complex membrane structures composed of various integral membrane proteins, including claudins, zonula occludens-1, and occludin. Inter-testicular cell junction proteins undergo a constant process of degradation and renewal. In addition, the downregulation of genes crucial to the development and preservation of cell junctions could disrupt the functionality of the BTB, potentially leading to male infertility. Oxidative stress and inflammation may contribute to disrupted spermatogenesis, resulting in male infertility. L-cysteine is a precursor to glutathione, a crucial antioxidant that helps mitigate damage and inflammation resulting from oxidative stress. Preclinical research indicates that L-cysteine may offer protective benefits against testicular injury and promote the expression of BTB genes. This review emphasizes various BTB genes essential for preserving its structural integrity and facilitating spermatogenesis and male fertility. Furthermore, it consolidates various research findings suggesting that L-cysteine may promote the expression of BTB-associated genes, thereby aiding in the maintenance of testicular functions.

Expression of GLOD4 in the Testis of the Qianbei Ma Goat and Its Effect on Leydig Cells

The expression pattern of GLOD4 in the testis and its regulatory effect on testicular cells was explored in goats to enhance our understanding of spermatogenesis and improve reproduction in breeding rams. In this study, we demonstrated the localization of GLOD4 in testicular cells using immunohistochemistry and subcellular localization analyses. Subsequently, we analyzed the GLOD4 expression pattern in four age-based groups (0, 6, 12, and 18 months old) using real-time quantitative polymerase chain reaction (qRT-PCR) and protein blotting. Finally, we performed GLOD4 silencing and overexpression studies in Leydig cells (LCs) and explored the effects on cell proliferation, the cell cycle, steroid hormone secretion and the expression of candidate testosterone hormone-regulated genes. GLOD4 was mainly expressed in Leydig cells, and the subcellular localization results showed that the GLOD4 protein was mainly localized in the cytoplasm and nucleus. Silencing of GLOD4 significantly suppressed the mRNA expression levels of the testosterone secretion-related genes CYP11A1, 3β-HSD, and CYP17A1 and the mRNA expression levels of cell cycle-related genes CDK6, PCNA, and Cyclin E. Moreover, the cell cycle was blocked at the G2/M phase after GLOD4 silencing, which significantly suppressed testosterone secretion. In contrast, GLOD4 overexpression significantly increased the mRNA expression levels of the testosterone secretion-related genes CYP11A1, 3β-HSD, and CYP17A1 and increased the expression of the cell cycle-related genes CDK6, PCNA, and Cyclin E. Moreover, GLOD4 overexpression promoted the cell cycle from G0/G1 phases to enter the S phase and G2/M phases, promoted the secretion of testosterone. Taken together, our experimental results indicate that GLOD4 may affect the development of cells in Qianbei Ma goats of different ages by influencing the cell cycle, cell proliferation, and testosterone hormone synthesis. These findings enhance our understanding of the functions of GLOD4 in goats.

Vangl2 regulates intercellular junctions by remodeling actin-based cytoskeleton through the Rock signaling pathway during spermatogenesis in Eriocheir sinensis

As a key planar cell polarity protein, Van Gogh-like 2 (Vangl2) is essential for mammalian spermatogenesis. As a decapod crustacean, Eriocheir sinensis exhibits distinct spermatogenic processes due to its unique seminiferous tubule morphology and hemolymph-testis barrier (HTB). To determine whether Vangl2 performs analogous functions in E. sinensis, we identified the Es-Vangl2. Es-Vangl2 exhibited high expression and wide distribution in the testes, indicating its crucial involvement in spermatogenesis. Following targeted knockdown of Es-Vangl2in vivo, the structure of seminiferous tubules was disrupted, characterized by vacuolization of the germinal zone and obstruction of spermatozoon release. Concurrently, the integrity of the HTB was compromised, accompanied by reduced expression and aberrant localization of junction proteins. More importantly, the regulatory influence of Es-Vangl2 was manifested through modulating the organization of microfilaments, a process mediated by epidermal growth factor receptor pathway substrate 8 (Eps8). Further studies demonstrated that these phenotypes resulting from Es-Vangl2 knockdown were attributed to the inhibition of Rock signaling pathway activity, which was verified by the Es-Rock interference and Y27632 inhibition assays. In summary, the findings highlight the pivotal role of Es-Vangl2 in stabilizing HTB integrity by regulating Eps8-mediated actin remodeling through the Rock signaling pathway in the spermatogenesis of E. sinensis.

Chlorogenic acid can improve spermatogenic dysfunction in rats with varicocele by regulating mitochondrial homeostasis and inhibiting the activation of NLRP3 inflammasomes by oxidative mitochondrial DNA and cGAS/STING pathway

In recent years, Varicocele (VC) has been recognized as a common cause of male infertility that can be treated by surgery or drugs. How to reduce the damage of VC to testicular spermatogenic function has attracted extensive attention in recent years. Among them, overexpressed ROS and high levels of inflammation may play a key role in VC-induced testicular damage. As the key mediated innate immune pathways, cGAS-STING shaft under pathological conditions, such as in cell and tissue damage stress can be cytoplasmic DNA activation, induce the activation of NLRP3 inflammatory corpuscle, triggering downstream of the inflammatory cascade reaction. Chlorogenic acid (CGA), as a natural compound from a wide range of sources, has strong anti-inflammatory and antioxidant activities, and is a potential effective drug for the treatment of varicocele infertility. The aim of this study is to investigate the role of CGA in the spermatogenic dysfunction of the rat testis induced by VC and the potential mechanisms. The results of this study have shown that CGA gavage treatment ameliorated the pathological damage of seminiferous tubules, increased the number of sperm in the lumen, and increased the expression levels of Occludin and ZO-1, which indicated the therapeutic effect of CGA on spermatogenic dysfunction in the testis of VC rats. Meanwhile, the damage of mitochondrial structure was alleviated and the expression levels of ROS, NLRP3 and pro-inflammatory cytokines (IL-1β, IL-6, IL-18) were significantly reduced in the testicular tissues of model rats after CGA treatment. In addition, we demonstrated for the first time the high expression status of cGAS and STING in testicular tissues of VC model rats, and this was ameliorated to varying degrees after CGA treatment. In conclusion, this study suggests that CGA can improve the spermatogenic function of the testis by reducing mitochondrial damage and inhibiting the activation of the cGAS-STING axis, inhibiting the activation of the NLRP3 inflammasome, and improving the inflammatory damage of the testis, highlighting the potential of CGA as a therapeutic agent for varicocele infertility.

Organophosphate pesticide chlorpyrifos and its metabolite 3,5,6-trichloropyridinol downregulate the expression of genes essential for spermatogenesis in caprine testes

Organophosphate pesticides have potent endocrine disrupting effects, hence banned in many countries. However, many organophosphates like chlorpyrifos, malathion et cetera continue to be used in some countries (Wołejko et al., 2022; Wołejko et al., 2022)including India. Fodder mediated ingestion of these substances may be harmful for livestock fertility. We have investigated the effect of the widely used organophosphate pesticide chlorpyrifos (CPF) and its metabolite, 3,5,6-trichloropyridinol (TCPy) on the expression of genes essential for spermatogenesis in goat testicular tissue. The testicular Sertoli cells (Sc) regulate germ cell division and differentiation under the influence of follicle stimulating hormone (FSH) and testosterone (T). Impaired FSH and T mediated signalling in Sc can compromise spermatogenesis leading to sub-fertility/infertility. As Sc express receptors (R) for FSH and T, they are highly susceptible to the endocrine disrupting effects of pesticides affecting fertility by dysregulating the functioning of Sc. Our results indicated that exposure to different concentrations of CPF and TCPy can compromise Sc function by downregulating the expression of FSHR and AR which was associated with a concomitant decline in the expression of genes essential for germ cell division and differentiation, like KITLG, INHBB, CLDN11 and GJA1. CPF also induced a significant reduction in the activity of acetylcholinesterase in the testes and increased the total testicular antioxidant capacity. Our results suggested that CPF and its metabolite TCPy may induce reproductive toxicity by dysregulating the expression of Sc specific genes essential for spermatogenesis.

AZIN2 is associated with apoptosis of germ cells in undescended testis

Undescended testis (UDT), known as cryptorchidism (CRY), is a common congenital disorder in which one or both testicles do not descend normally into the scrotum. A unilateral UDT model was established by inducing UDT in mice through surgery. The results showed that the testis in the UDT model group was abnormal; the lumen of the seminiferous tubule was atrophic; apoptosis, necrosis and shedding were observed in many of the germ cells; the level of sex hormones was abnormal; and mature sperm was reduced. Subsequently, transcriptome sequencing was conducted on the testicular tissue of UDT model mice. Through analysis and verification of differential genes, AZIN2 was identified as playing a key role in the decline in male fertility caused by cryptorchidism. AZIN2 expression and spermine content was down-regulated in the testis of the UDT group. We then used a combination of hypoxanthine and xanthine to create a GC-1 cell damage model. In this model, AZIN2 expression and spermine content was down-regulated. When si-Azin2 transfected GC-1 cells, cell viability and proliferation were decreased. However, in the GC-1 cell damage model transfected with Azin2 over-expressed plasmid, AZIN2 expression and spermine content was up-regulated, reversing the cell damage caused by hypoxanthine and xanthine, and restoring the proliferation ability of GC-1 cells. These results indicate that in UDT, down-regulated AZIN2 expression is a factor in testicular damage. This discussion of the connection between AZIN2 and germ cells has important clinical significance as it provides an important reference for the diagnosis and treatment of cryptorchidism.

Biophysics of claudin proteins in tight junction architecture: Three decades of progress

Tight junctions are cell-cell adhesion complexes that act as gatekeepers of the paracellular space. Formed by several transmembrane proteins, the claudin family performs the primary gate-keeping function. The claudin proteins form charge and size-selective diffusion barriers to maintain homeostasis across endothelial and epithelial tissue. Of the 27 known claudins in mammals, some are known to seal the paracellular space, while others provide selective permeability. The differences in permeability arise due to the varying expression levels of claudins in each tissue. The tight junctions are observed as strands in freeze-fracture electron monographs; however, at the molecular level, tight junction strands form when multiple claudin proteins assemble laterally (cis assembly) within a cell and head-on (trans assembly) with claudins of the adjacent cell in a zipper-like architecture, closing the gap between the neighboring cells. The disruption of tight junctions caused by changing claudin expression levels or mutations can lead to diseases. Therefore, knowledge of the molecular architecture of the tight junctions and how that is tied to tissue-specific function is critical for fighting diseases. Here, we review the current understanding of the tight junctions accrued over the last three decades from experimental and computational biophysics perspectives.

Different expression patterns of DNA methyltransferases during horse testis development

DNA methyltransferases (DNMTs) are important epigenetic modification during spermatogenesis. To further evaluate the pattern of DNMTs in horse testes during development, we investigated the expression and localization of DNMT1, DNMT3a and DNMT3b at different time points. The qRT-PCR results showed that DNMT1 expression was maintained in testes tissue from 6-month-old (0.5y) to 2-year-old (2y) of age and decreased after 3-year-old (3y) (P < 0.01). The expression levels of DNMT3a and DNMT3b peaked in testes tissue at 3y (P < 0.01). At 4-year-old (4y), the expression of DNMT3a and DNMT3b was decreased and became similar to that at 0.5y. Immunofluorescence of DNMT1, DNMT3a and DNMT3b on testis samples confirmed the differential expression and localization of these three DNA methylation transferases during horse development. Further molecular biological studies are needed to understand the implications of the expression patterns of these DNMTs in horse testes.

Aging and physiological barriers: mechanisms of barrier integrity changes and implications for age-related diseases

The phenomenon of compartmentalization is one of the key traits of life. Biological membranes and histohematic barriers protect the internal environment of the cell and organism from endogenous and exogenous impacts. It is known that the integrity of these barriers decreases with age due to the loss of homeostasis, including age-related gene expression profile changes and the abnormal folding/assembly, crosslinking, and cleavage of barrier-forming macromolecules in addition to morphological changes in cells and tissues. The critical molecular and cellular mechanisms involved in physiological barrier integrity maintenance and aging-associated changes in their functioning are reviewed on different levels: molecular, organelle, cellular, tissue (histohematic, epithelial, and endothelial barriers), and organ one (skin). Biogerontology, which studies physiological barriers in the aspect of age, is still in its infancy; data are being accumulated, but there is no talk of the synthesis of complex theories yet. This paper mainly presents the mechanisms that will become targets of anti-aging therapy only in the future, possibly: pharmacological, cellular, and gene therapies, including potential geroprotectors, hormetins, senomorphic drugs, and senolytics.

Expression of SARS-CoV-2 entry molecules ACE2, NRP1, TMPRSS2, and FURIN in the reproductive tissues of male macaques

Coronavirus disease 2019 (COVID-19) reportedly affects male reproductive function by causing spermatogenesis dysfunction and suppressing testosterone secretion. However, the relationship between COVID-19 and impaired reproductive function, such as whether these effects on reproductive function are a direct effect of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection in male reproductive organs or an indirect effect of high fever, is not known. Here, we examined whether the cell entry molecules of SARS-CoV-2, namely, ACE2, NRP1, TMPRSS2, and FURIN, are expressed in the male reproductive organs using the testes and accessory gonads of macaques during the breeding season. RT-PCR expression analysis showed that the testes alone expressed all four molecules. Immunohistochemical staining of testis tissue sections revealed that ACE2 is expressed in Leydig cells and the apical region of Sertoli cells, whereas NRP1 is expressed in the cell bodies surrounding the Leydig and Sertoli cell nuclei. FURIN is mainly expressed in Leydig cells, secondary spermatocytes, and spermatids. However, TMPRSS2 immunopositive cells were not observed. Therefore, it was not possible to observe cells expressing all four molecules in the gonads and accessory gonads of male primates. These results suggest that SARS-CoV-2 is unlikely to directly affect spermatogenesis in primates or proliferate in cells of the seminiferous tubules and undergo release into the semen through the previously known ACE2-mediated infection route. However, the expression of three molecules, including ACE2, was observed in Leydig cells, suggesting that testosterone synthesis and secretion may be affected when primates, including humans, are infected with SARS-CoV-2.

The Protective Effect of Quercetin against the Cytotoxicity Induced by Fumonisin B1 in Sertoli Cells

Fumonisin B1 (FB1), a mycotoxin produced by Fusarium species, is prevalent in crops and animal feed, posing significant health risks to livestock and humans. FB1 induces oxidative stress in Sertoli cells, destroys testicular structure, and affects spermatogenesis. However, methods to mitigate the reproductive toxicity of FB1 in testes remain unknown. Quercetin, a natural flavonoid antioxidant, may offer protective benefits. This study investigated the protective effects and mechanisms of quercetin against FB1-induced reproductive toxicity in TM4 cells (a Sertoli cell line). The results indicated that 40 μM quercetin improved cell viability, reduced apoptosis, and preserved cell functions. Quercetin also decreased reactive oxygen species (ROS) levels in TM4 cells exposed to FB1, enhanced the expression of antioxidant genes, and improved mitochondrial membrane potential. Compared with FB1 alone, the combination of quercetin and FB1 increased ATP levels, as well as pyruvate and lactic acid, the key glycolysis products. Furthermore, this combination elevated the mRNA and protein expression of glycolysis-related genes, including glucose-6-phosphate isomerase 1 (Gpi1), hexokinase 2 (Hk2), aldolase (Aldoa), pyruvate kinase, muscle (Pkm), lactate dehydrogenase A (Ldha) and phosphofructokinase, liver, B-type (Pfkl). Quercetin also boosted the activity of PKM and LDHA, two crucial glycolytic enzymes. In summary, quercetin mitigates FB1-induced toxicity in TM4 cells by reducing ROS levels and enhancing glycolysis. This study offers new insights into preventing and treating FB1-induced toxic damage to the male reproductive system and highlights the potential application of quercetin.

Protective effect of Cordycepin on blood-testis barrier against pre-puberty polystyrene nanoplastics exposure in male rats

Plastic pollution is an emerging environmental issue, with microplastics and nanoplastics raising health concerns due to bioaccumulation. This work explored the impact of polystyrene nanoparticle (PS-NPs) exposure during prepuberty on male reproductive function post maturation in rats. Rats were gavaged with PS-NPs (80 nm) at 0, 3, 6, 12 mg/kg/day from postnatal day 21 to 95. PS-NPs accumulated in the testes and reduced sperm quality, serum reproductive hormones, and testicular coefficients. HE staining showed impaired spermatogenesis. PS-NPs disrupted the blood-testis barrier (BTB) by decreasing junction proteins, inducing inflammation and apoptosis. Transcriptomics identified differentially expressed genes related to metabolism, lysosome, apoptosis, and TLR4 signaling. Molecular docking revealed Cordycepin could compete with polystyrene for binding to TLR4. Cordycepin alleviated oxidative stress and improved barrier function in PS-NPs treated Sertoli cells. In conclusion, prepubertal PS-NPs exposure induces long-term reproductive toxicity in male rats, likely by disrupting spermatogenesis through oxidative stress and BTB damage. Cordycepin could potentially antagonize this effect by targeting TLR4 and warrants further study as a protective agent. This study elucidates the mechanisms underlying reproductive toxicity of PS-NPs and explores therapeutic strategies.

Recent Progress of Induced Spermatogenesis In Vitro

Sperm, a crucial gamete for reproduction in sexual reproduction, is generated through the proliferation, differentiation, and morphological transformations of spermatogonial stem cells within the specialized microenvironment of the testes. Replicating this environment artificially presents challenges. However, interdisciplinary advancements in physics, materials science, and cell engineering have facilitated the utilization of innovative materials, technologies, and structures for inducing in vitro sperm production. This article offers a comprehensive overview of research progress on inducing in vitro sperm production by categorizing techniques into two major systems based on matrix-based and non-matrix-based approaches, respectively. Detailed discussions are provided for both types of technology systems through comparisons of their similarities and differences, as well as research advancements. The aim is to provide researchers in this field with a comprehensive panoramic view while presenting our own perspectives and prospects.

Efficacy of propolis and royal jelly in attenuating cadmium-induced spermatogenesis and steroidogenesis dysregulation, causing infertility in rats

Bee-derived pharmaceutical products, including propolis (PRO) and royal jelly (ROJ), possess outstanding pharmacological properties. However, their efficiency in counteracting the deleterious influences of cadmium (Cd) in testes and the relevant mechanisms entail further investigations. Therefore, this study sheds light on the therapeutic efficacy of PRO and ROJ against testicular dysfunction and infertility induced by Cd. Toward this end, 30 mature male Wistar albino rats were randomly divided into six groups (5 animals/group), including (I) control, (II) Cd, (III) PRO, (IV) ROJ, (V) PRO + Cd, and (VI) ROJ + Cd groups. Furthermore, antioxidant factors, semen quality, hormonal levels, steroidogenic enzymes, and genotoxicity were assessed. Moreover, histopathological and ultrastructural attributes and offspring rates were investigated. The Cd-treated group revealed marked reductions in reduced glutathione (GSH), total antioxidant capacity (TAC), and superoxide dismutase (SOD) with an amplification of lipid peroxidation in testes, indicating disruption of the antioxidant defense system. Furthermore, myeloperoxidase (MPO) activity and DNA damage were significantly heightened, implying inflammation and genotoxicity, respectively. Moreover, steroidogenic enzymes, including 17β-Hydroxy Steroid Dehydrogenase 3 (HSD17b3), 3β-Hydroxy Steroid Dehydrogenase 2 (HSD3b2), 17α-hydroxylase/17,20-lyase (CYP17A1), and steroid 5α-reductase 2 (SRD5A2) were markedly diminished accompanied with disorders in luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone. Besides, spermatozoa quality was reduced, associated with a diminution in the diameter of seminiferous tubules. By contrast, PRO or ROJ significantly protected and/or counteracted the Cd-induced pathophysiological consequences, ameliorating antioxidant and inflammatory biomarkers, steroidogenic enzymes, hormonal levels, and sperm properties, along with lessening DNA impairments. Critically, histological and ultrastructural analyses manifested several anomalies in the testicular tissues of the Cd-administered group, including the Leydig and Sertoli cells and spermatozoa. Conversely, PRO or ROJ sustained testicular tissues' structure, enhancing spermatozoa integrity and productivity. Interestingly, treatment with PRO or ROJ improved fertility indices through offspring rates compared to the Cd-animal group. Our data suggest that PRO is a more effective countermeasure than ROJ against Cd toxicity for securing the delicate testicular microenvironment for spermatogenesis and steroidogenesis.

Advances in immunology of male reproductive toxicity induced by common environmental pollutants

Humans are exposed to an ever-increasing number of environmental toxicants, some of which have gradually been identified as major risk factors for male reproductive health, even associated with male infertility. Male infertility is usually due to the reproductive system damage, which may be influenced by the exposure to contaminants such as heavy metals, plasticizers, along with genetics and lifestyle. Testicular immune microenvironment (TIM) is important in maintaining normal physiological functions of the testis, whether disturbed TIM after exposure to environmental toxicants could induce reproductive toxicity remains to be explored. Therefore, the current review aims to contribute to the further understanding of exposure and male infertility by characterizing environmental exposures and the effect on TIM. We first summarized the male reproductive toxicity phenotypes induced by common environmental pollutants. Contaminants including heavy metals and plastic additives and fine particulate matter (PM2.5), have been repetitively associated with male infertility, whereas emerging contaminants such as perfluoroalkyl substances and micro(nano)plastics have also been found to disrupt TIM and lead to male reproductive toxicity. We further reviewed the importance of TIM and its homeostasis in maintaining the normal physiological functions of the testis. Most importantly, we discussed the advances in immunology of male reproductive toxicity induced by metals and metalloids, plastic additives, persistent organic pollutants (POPs), micro(nano)plastic and PM2.5 to suggest the importance of reproductive immunotoxicology in the future study of environmental toxicants, but also contribute to the development of effective prevention and treatment strategies for mitigating adverse effects of environmental pollutants on human health.

Signatures of metabolic diseases on spermatogenesis and testicular metabolism

Diets leading to caloric overload are linked to metabolic disorders and reproductive function impairment. Metabolic and hormonal abnormalities stand out as defining features of metabolic disorders, and substantially affect the functionality of the testis. Metabolic disorders induce testicular metabolic dysfunction, chronic inflammation and oxidative stress. The disruption of gastrointestinal, pancreatic, adipose tissue and testicular hormonal regulation induced by metabolic disorders can also contribute to a state of compromised fertility. In this Review, we will delve into the effects of high-fat diets and metabolic disorders on testicular metabolism and spermatogenesis, which are crucial elements for male reproductive function. Moreover, metabolic disorders have been shown to influence the epigenome of male gametes and might have a potential role in transmitting phenotype traits across generations. However, the existing evidence strongly underscores the unmet need to understand the mechanisms responsible for transgenerational paternal inheritance of male reproductive function impairment related to metabolic disorders. This knowledge could be useful for developing targeted interventions to prevent, counteract, and most of all break the perpetuation chain of male reproductive dysfunction associated with metabolic disorders across generations.

Mechanistic screening of reproductive toxicity in a novel 3D testicular co-culture model shows significant impairments following exposure to low-dibutyl phthalate concentrations

To improve the mechanistic screening of reproductive toxicants in  chemical-risk assessment and drug development, we have developed a three-dimensional (3D) heterogenous testicular co-culture model from neonatal mice. Di-n-butyl phthalate (DBP), an environmental contaminant that can affect reproductive health negatively, was used as a model compound to illustrate the utility of the in vitro model. The cells were treated with DBP (1 nM to 100 µM) for 7 days. Automated high-content imaging confirmed the presence of cell-specific markers of Leydig cells (CYP11A1 +), Sertoli cells (SOX9 +), and germ cells (DAZL +). Steroidogenic activity of Leydig cells was demonstrated by analyzing testosterone levels in the culture medium. DBP induced a concentration-dependent reduction in testosterone levels and decreased the number of Leydig cells compared to vehicle control. The levels of steroidogenic regulator StAR and the steroidogenic enzyme CYP11A1 were decreased already at the lowest DBP concentration (1 nM), demonstrating upstream effects in the testosterone biosynthesis pathway. Furthermore, exposure to 10 nM DBP decreased the levels of the germ cell-specific RNA binding protein DAZL, central for the spermatogenesis. The 3D model also captured the development of the Sertoli cell junction proteins, N-cadherin and Zonula occludens protein 1 (ZO-1), critical for the blood-testis barrier. However, DBP exposure did not significantly alter the cadherin and ZO-1 levels. Altogether, this 3D in vitro system models testicular cellular signaling and function, making it a powerful tool for mechanistic screening of developmental testicular toxicity. This can open a new avenue for high throughput screening of chemically-induced reproductive toxicity during sensitive developmental phases.

AXDND1 is required to balance spermatogonial commitment and for sperm tail formation in mice and humans

Dynein complexes are large, multi-unit assemblies involved in many biological processes via their critical roles in protein transport and axoneme motility. Using next-generation sequencing of infertile men presenting with low or no sperm in their ejaculates, we identified damaging variants in the dynein-related gene AXDND1. We thus hypothesised that AXDND1 is a critical regulator of male fertility. To test this hypothesis, we produced a knockout mouse model. Axdnd1-/- males were sterile at all ages but presented with an evolving testis phenotype wherein they could undergo one round of histologically replete spermatogenesis followed by a rapid depletion of the seminiferous epithelium. Marker experiments identified a role for AXDND1 in maintaining the balance between differentiation-committed and self-renewing spermatogonial populations, resulting in disproportionate production of differentiating cells in the absence of AXDND1 and increased sperm production during initial spermatogenic waves. Moreover, long-term spermatogonial maintenance in the Axdnd1 knockout was compromised, ultimately leading to catastrophic germ cell loss, destruction of blood-testis barrier integrity and immune cell infiltration. In addition, sperm produced during the first wave of spermatogenesis were immotile due to abnormal axoneme structure, including the presence of ectopic vesicles and abnormalities in outer dense fibres and microtubule doublet structures. Sperm output was additionally compromised by a severe spermiation defect and abnormal sperm individualisation. Collectively these data identify AXDND1 as an atypical dynein complex-related protein with a role in protein/vesicle transport of relevance to spermatogonial function and sperm tail formation in mice and humans. This study underscores the importance of studying the consequences of gene loss-of-function on both the establishment and maintenance of male fertility.

Male animal sterilization: history, current practices, and potential methods for replacing castration

Sterilization and castration have been synonyms for thousands of years. Making an animal sterile meant to render them incapable of producing offspring. Castration or the physical removal of the testes was discovered to be the most simple but reliable method for managing reproduction and sexual behavior in the male. Today, there continues to be global utilization of castration in domestic animals. More than six hundred million pigs are castrated every year, and surgical removal of testes in dogs and cats is a routine practice in veterinary medicine. However, modern biological research has extended the meaning of sterilization to include methods that spare testis removal and involve a variety of options, from chemical castration and immunocastration to various methods of vasectomy. This review begins with the history of sterilization, showing a direct link between its practice in man and animals. Then, it traces the evolution of concepts for inducing sterility, where research has overlapped with basic studies of reproductive hormones and the discovery of testicular toxicants, some of which serve as sterilizing agents in rodent pests. Finally, the most recent efforts to use the immune system and gene editing to block hormonal stimulation of testis function are discussed. As we respond to the crisis of animal overpopulation and strive for better animal welfare, these novel methods provide optimism for replacing surgical castration in some species.

Triptolide exposure triggers testicular vacuolization injury by disrupting the Sertoli cell junction and cytoskeletal organization via the AKT/mTOR signaling pathway

BACKGROUND

Despite the known reproductive toxicity induced by triptolide (TP) exposure, the regulatory mechanism underlying testicular vacuolization injury caused by TP remains largely obscure.

METHODS

Male mice were subjected to TP at doses of 15, 30, and 60 μg/kg for 35 consecutive days. Primary Sertoli cells were isolated from 20-day-old rat testes and exposed to TP at concentrations of 0, 40, 80, 160, 320, and 640 nM. A Biotin tracer assay was conducted to assess the integrity of the blood-testis barrier (BTB). Transepithelial electrical resistance (TER) assays were employed to investigate BTB function in primary Sertoli cells. Histological structures of the testes and epididymides were stained with hematoxylin and eosin (H&E). The expression and localization of relevant proteins or pathways were assessed through Western blotting or immunofluorescence staining.

RESULTS

TP exposure led to dose-dependent testicular injuries, characterized by a decreased organ coefficient, reduced sperm concentration, and the formation of vacuolization damage. Furthermore, TP exposure disrupted BTB integrity by reducing the expression levels of tight junction (TJ) proteins in the testes without affecting basal ectoplasmic specialization (basal ES) proteins. Through the TER assay, we identified that a TP concentration of 160 nM was optimal for elucidating BTB function in primary Sertoli cells, correlating with reductions in TJ protein expression. Moreover, TP exposure induced changes in the distribution of the BTB and cytoskeleton-associated proteins in primary Sertoli cells. By activating the AKT/mTOR signaling pathway, TP exposure disturbed the balance between mTORC1 and mTORC2, ultimately compromising BTB integrity in Sertoli cells.

CONCLUSION

This investigation sheds light on the impacts of TP exposure on testes, elucidating the mechanism by which TP exposure leads to testicular vacuolization injury and offering valuable insights into comprehending the toxic effects of TP exposure on testes.

The blood-testis barrier disruption is a prerequisite for toxicant-induced peritubular macrophage increases in the testis of peripubertal rats

Peritubular macrophages (PTMφ) are predominantly localized near spermatogonial stem cells in the testis. We previously revealed that exposure of peripubertal male Fischer rats to mono-(2-ethylhexyl) phthalate (MEHP) leads to increased PTMφs in the testis. The mechanisms that trigger increases in PTMφs in the testis are poorly understood. However, MEHP exposure is known to both induce spermatocyte apoptosis and to perturb the blood-testis barrier (BTB). This study aims to elucidate the association between the disruption of BTB and the increases of PTMφs in the testis by comparing the effects observed with MEHP to 2 other testicular toxicants with variable effects on the BTB and subtype of germ cell undergoing apoptosis. Methoxyacetic acid (MAA) acts directly on spermatocytes and does not affect BTB function, whereas cadmium chloride (CdCl2) induces profound injury to BTB. The results indicated that MAA exposure significantly increased spermatocyte apoptosis, whereas no significant changes in the numbers of PTMφs in the testis occurred. In contrast, CdCl2 exposure disrupted BTB function and increased the abundance of PTMφs in the testis. To further investigate whether MEHP-induced changes in BTB integrity accounted for the increase in PTMφs, a plasmid for LG3/4/5, the functional component of laminin-alpha 2, was overexpressed in the testis to stabilize BTB integrity before MEHP exposure. The results showed that LG3/4/5 overexpression substantially reduced the ability of MEHP to compromise BTB integrity and prevented the increase in PTMφ numbers after MEHP exposure. These results indicate that BTB disruption is necessary to increase PTMφs in the testis induced by toxicants.

Differential gene expression and gut microbiota composition in low-altitude and high-altitude goats

Previous studies have presented evidence suggesting that altitude exerts detrimental effects on reproductive processes, yet the underlying mechanism remains elusive. Our study employed two distinct goat breeds inhabiting low and high altitudes, and conducted a comparative analysis of mRNA profiles in testis tissues and the composition of gut microbiota. The results revealed a reduced testis size in high-altitude goats. RNA-seq analysis identified the presence of 214 differentially expressed genes (DEGs) in the testis. These DEGs resulted in a weakened immunosuppressive effect, ultimately impairing spermatogenesis in high-altitude goats. Additionally, 16S rDNA amplicon sequencing recognized statistically significant variations in the abundance of the genera Treponema, unidentified_Oscillospiraceae, Desulfovibrio, Butyricicoccus, Dorea, Parabacteroides between the two groups. The collective evidence demonstrated the gut and testis played a synergistic role in causing decreased fertility at high altitudes. Our research provides a theoretical basis for future investigations into the reproductive fitness of male goats.

PTBP1 mediates Sertoli cell actin cytoskeleton organization by regulating alternative splicing of actin regulators

Spermatogenesis is a biological process within the testis that produces haploid spermatozoa for the continuity of species. Sertoli cells are somatic cells in the seminiferous epithelium that orchestrate spermatogenesis. Cyclic reorganization of Sertoli cell actin cytoskeleton is vital for spermatogenesis, but the underlying mechanism remains largely unclear. Here, we report that RNA-binding protein PTBP1 controls Sertoli cell actin cytoskeleton reorganization by programming alternative splicing of actin cytoskeleton regulators. This splicing control enables ectoplasmic specializations, the actin-based adhesion junctions, to maintain the blood-testis barrier and support spermatid transport and transformation. Particularly, we show that PTBP1 promotes actin bundle formation by repressing the inclusion of exon 14 of Tnik, a kinase present at the ectoplasmic specialization. Our results thus reveal a novel mechanism wherein Sertoli cell actin cytoskeleton dynamics is controlled post-transcriptionally by utilizing functionally distinct isoforms of actin regulatory proteins, and PTBP1 is a critical regulatory factor in generating such isoforms.

Octanoic acid mitigates busulfan-induced blood-testis barrier damage by alleviating oxidative stress and autophagy

BACKGROUND

The management of male infertility continues to encounter an array of challenges and constraints, necessitating an in-depth exploration of novel therapeutic targets to enhance its efficacy. As an eight-carbon medium-chain fatty acid, octanoic acid (OCA) shows promise for improving health, yet its impact on spermatogenesis remains inadequately researched.

METHODS

Mass spectrometry was performed to determine the fatty acid content and screen for a pivotal lipid component in the serum of patients with severe spermatogenesis disorders. The sperm quality was examined, and histopathological analysis and biotin tracer tests were performed to assess spermatogenesis function and the integrity of the blood-testis barrier (BTB) in vivo. Cell-based in vitro experiments were carried out to investigate the effects of OCA administration on Sertoli cell dysfunction. This research aimed to elucidate the mechanism by which OCA may influence the function of Sertoli cells.

RESULTS

A pronounced reduction in OCA content was observed in the serum of patients with severe spermatogenesis disorders, indicating that OCA deficiency is related to spermatogenic disorders. The protective effect of OCA on reproduction was tested in a mouse model of spermatogenic disorder induced by busulfan at a dose 30 mg/kg body weight (BW). The mice in the study were separated into distinct groups and administered varying amounts of OCA, specifically at doses of 32, 64, 128, and 256 mg/kg BW. After evaluating sperm parameters, the most effective dose was determined to be 32 mg/kg BW. In vivo experiments showed that treatment with OCA significantly improved sperm quality, testicular histopathology and BTB integrity, which were damaged by busulfan. Moreover, OCA intervention reduced busulfan-induced oxidative stress and autophagy in mouse testes. In vitro, OCA pretreatment (100 µM) significantly ameliorated Sertoli cell dysfunction by alleviating busulfan (800 µM)-induced oxidative stress and autophagy. Moreover, rapamycin (5 µM)-induced autophagy led to Sertoli cell barrier dysfunction, while OCA administration exerted a protective effect by alleviating autophagy.

CONCLUSIONS

This study demonstrated that OCA administration suppressed oxidative stress and autophagy to alleviate busulfan-induced BTB damage. These findings provide a deeper understanding of the toxicology of busulfan and a promising avenue for the development of novel OCA-based therapies for male infertility.

Adverse effects and potential mechanisms of polystyrene microplastics (PS-MPs) on the blood-testis barrier

Microplastics (MPs) are defined as plastic particles or fragments with a diameter of less than 5 mm. These particles have been identified as causing male reproductive toxicity, although the precise mechanism behind this association is yet to be fully understood. Recent research has found that exposure to polystyrene microplastics (PS-MPs) can disrupt spermatogenesis by impacting the integrity of the blood-testis barrier (BTB), a formidable barrier within mammalian blood tissues. The BTB safeguards germ cells from harmful substances and infiltration by immune cells. However, the disruption of the BTB leads to the entry of environmental pollutants and immune cells into the seminiferous tubules, resulting in adverse reproductive effects. Additionally, PS-MPs induce reproductive damage by generating oxidative stress, inflammation, autophagy, and alterations in the composition of intestinal flora. Despite these findings, the precise mechanism by which PS-MPs disrupt the BTB remains inconclusive, necessitating further investigation into the underlying processes. This review aims to enhance our understanding of the pernicious effects of PS-MP exposure on the BTB and explore potential mechanisms to offer novel perspectives on BTB damage caused by PS-MPs.

Protective effect of selenomethionine on rabbit testicular injury induced by Aflatoxin B1

The aim of this study was to investigate the alleviating effect of selenomethionine (SeMet) on aflatoxin B1 (AFB1)-induced testicular injury in rabbits. Twenty-five 90-d-old rabbits were randomly divided into 5 groups (the control group, the AFB1 group, the 0.2 mg/kg SeMet + AFB1 group, the 0.4 mg/kg SeMet + AFB1 group and the 0.6 mg/kg SeMet + AFB1 group). After 1 d of the experiment, the SeMet-treated groups were fed 0.2 mg/kg SeMet, 0.4 mg/kg SeMet, or 0.6 mg/kg SeMet daily, and the remaining two groups were fed a normal diet for 30 d. On Day 31, all rabbits in the model group and the three treatment groups were fed 0.5 mg/kg AFB1 for 21 d. The levels of testosterone (T), luteinizing hormone (LH) and follicle stimulating hormone (FSH) in rabbit plasma were detected. Rabbit semen was collected, and its quality was evaluated. Pathological changes in rabbit testes were observed by hematoxylin-eosin (HE) staining. The expression of related proteins in testicular tissue was detected by immunohistochemistry, immunofluorescence and western blot (WB) analysis. Enzyme-linked immunosorbent assays (ELISAs) were used to detect oxidative stress-related indices and inflammatory factors in testicular tissue. The results showed that AFB1 can induce oxidative stress and inflammation to activate the p38/MSK/NF-κB signalling pathway, mediate apoptosis, inhibit the proliferation and differentiation of testicular cells, destroy the integrity of the blood-testis barrier (BTB) and the normal structure of the testis, and reduce the content of sex hormones and semen quality. SeMet pretreatment significantly alleviated testicular injury oxidative stress, and the inflammatory response in rabbits. Thus, we demonstrated that SeMet restores AFB1-induced testicular toxicity by inhibiting the p38/MSK/NF-κB signalling pathway. In addition, in this study, 0.4 mg/kg SeMet had the most impactful effect.

The limitations of testicular organoids: are they truly as promising as we believe?

Organoid systems have revolutionised various facets of biological research by offering a three-dimensional (3D), physiologically relevant in vitro model to study complex organ systems. Over recent years, testicular organoids have been publicised as promising platforms for reproductive studies, disease modelling, drug screening, and fertility preservation. However, the full potential of these systems has yet to be realised due to inherent limitations. This paper offers a comprehensive analysis of the current challenges associated with testicular organoid models. Firstly, we address the inability of current organoid systems to fully replicate the intricate spatial organisation and cellular diversity of the in vivo testis. Secondly, we scrutinise the fidelity of germ cell maturation within the organoids, highlighting incomplete spermatogenesis and epigenetic inconsistencies. Thirdly, we consider the technical challenges faced during organoid culture, including nutrient diffusion limits, lack of vasculature, and the need for specialised growth factors. Finally, we discuss the ethical considerations surrounding the use of organoids for human reproduction research. Addressing these limitations in combination with integrating complementary approaches, will be essential if we are to advance our understanding of testicular biology and develop novel strategies for addressing reproductive health issues in males.

Bubbling beyond the barrier: exosomal RNA as a vehicle for soma-germline communication

'Weismann's barrier' has restricted theories of heredity to the transmission of genomic variation for the better part of a century. However, the discovery and elucidation of epigenetic mechanisms of gene regulation such as DNA methylation and histone modifications has renewed interest in studies on the inheritance of acquired traits and given them mechanistic plausibility. Although it is now clear that these mechanisms allow many environmentally acquired traits to be transmitted to the offspring, how phenotypic information is communicated from the body to its gametes has remained a mystery. Here, we discuss recent evidence that such communication is mediated by somatic RNAs that travel inside extracellular vesicles to the gametes where they reprogram the offspring epigenome and phenotype. How gametes learn about bodily changes has implications not only for the clinic, but also for evolutionary theory by bringing together intra- and intergenerational mechanisms of phenotypic plasticity and adaptation.

Testicular dysfunction and "its recovery effect" after cadmium exposure

In recent years, with the acceleration of industrialization, the decline of male fertility caused by heavy metal pollution has attracted much attention. However, whether the inhibition of testicular function after cadmium exposure is reversible remains to be studied. In this study, we constructed rat models of cadmium exposure and dis-exposure, and collected relative samples to observe the changes of related indicators. The results showed that cadmium exposure could reduce the fertility, inhibit the hypothalamic-pituitary-testis axis and activate hypothalamic-pituitary-adrenal axis function, the testicular GR/PI3K-AKT/AMPK signal was abnormal, cell proliferation was inhibited and apoptosis was enhanced. Four weeks after the exposure was stopped, the fertility was still decreased, testicular testosterone synthesis and spermatogenesis were inhibited, cell proliferation was inhibited and apoptosis was enhanced, but all of them were reversed. After eight weeks of cadmium exposure, the above indicators were observed to return to normal. At the same time, by giving different concentrations of corticosterone to spermatogonium, we confirmed that corticosterone may regulate the proliferation and apoptosis of spermatogonium through GR/PI3K-AKT/AMPK signal. In this study, the reproductive toxicity of cadmium, a metal environmental pollutant, was analyzed in depth to provide a new theoretical and experimental basis for ensuring male reproductive health.

Acute murine-betacoronavirus infection impairs testicular steroidogenesis and the quality of sperm production

Although several testicular alterations promoted by coronavirus infection have been demonstrated, the extent, causes, and players of testicular pathogenesis are not totally understood. The present study aimed to investigate the short-term effects on male fertility of intranasally administered murine hepatitis virus strain 3 (MHV-3), a member of the genus Betacoronavirus, which causes a severe systemic acute infection. This mouse model might be used as a in vivo prototype for investigating the impact of betacoronavirus on the endocrine and exocrine testicular functions with the advantage to be performed in a biosafety level 2 condition. Herein, we performed virological, histopathological, and molecular studies regarding the testicular spermatogenesis and the spermatic quality analyses in an MHV-3-infected C57BL/6 mice. The main outcomes showed that MHV-3 infects mouse testis and induces a testicular inflammatory state, impairing the steroidogenic pathway. The infection led to several alterations in the testicular parenchyma, such as: seminiferous epithelium sloughing, retention of residual bodies, germ cell apoptosis, alterations in intercellular junction proteins, and worse spermatogenic parameters. Moreover, the levels of plasmatic testosterone as well as the quality of sperm production reduced. Therefore, the present data suggest that the viral/inflammatory impairment of the steroidogenic pathway and the consequent imbalance of androgen levels is critical in testicular pathology, disturbing the SC barrier function and the germ cell differentiation. Our study is important for comprehending the effects of beta coronavirus infections on testis function in order to develop treatments that could prevent virus-mediated male infertility.

Histopathological evaluation of infertility: Lessons from laboratory rodents

Infertility is a growing challenge globally with emerging risk factors. There are effective laboratory tests to evaluate infertility in humans, nevertheless, some measures, especially histopathological evaluations, are invasive due to the pain inflicted when accessing the reproductive organs and obtaining samples; hence, their relevance may be limited in humans. However, these histopathological evaluations provide essential information on the etiopathogenesis of infertility and the likely mechanisms of action of potential therapeutic candidates. Also, non-invasive methods are available, such as the assay of testosterone in the blood and semen analysis, both of which are predictors of testicular functions. This review provides detailed information on the available histopathological investigations of infertility, such as qualitative and quantitative histopathological assessments of gonadal tissues, specific cell counts, and sperm morphology characterization, with a focus on the procedures, interpretation, and pathophysiological basis. Data from the literature revealed that histopathological examinations of the reproductive organs, as well as spermatozoa, are useful in understanding the pathogenesis of incident infertility. Histopathological evaluation may range from basic hematoxylin and eosin stains to some special stains. Also, histopathological findings (such as spermatogenic cells and planimetric variables, like seminiferous tubule diameter and theca cell and corpus luteum thickness) may be quantified and analyzed for comparison. Some skill is required for these investigations, which may be a limiting factor; however, they are important tools in translational medicine.

Prenatal dexamethasone exposure impairs rat blood-testis barrier function and sperm quality in adult offspring via GR/KDM1B/FSTL3/TGFβ signaling

Both epidemiological and animal studies suggest that adverse environment during pregnancy can change the offspring development programming, but it is difficult to achieve prenatal early warning. In this study we investigated the impact of prenatal dexamethasone exposure (PDE) on sperm quality and function of blood-testis barrier (BTB) in adult offspring and the underlying mechanisms. Pregnant rats were injected with dexamethasone (0.1, 0.2 and 0.4 mg·kg-1·d-1, s.c.) from GD9 to GD20. After weaning (PW4), the pups were fed with lab chow. At PW12 and PW28, the male offspring were euthanized to collect blood and testes samples. We showed that PDE significantly decreased sperm quality (including quantity and motility) in male offspring, which was associated with impaired BTB and decreased CX43/E-cadherin expression in the testis. We demonstrated that PDE induced morphological abnormalities of fetal testicle and Sertoli cell development originated from intrauterine. By tracing to fetal testicular Sertoli cells, we found that PDE dose-dependently increased expression of histone lysine demethylases (KDM1B), decreasing histone 3 lysine 9 dimethylation (H3K9me2) levels of follistatin-like-3 (FSTL3) promoter region and increased FSTL3 expression, and inhibited TGFβ signaling and CX43/E-cadherin expression in offspring before and after birth. These results were validated in TM4 Sertoli cells following dexamethasone treatment. Meanwhile, the H3K9me2 levels of FSTL3 promoter in maternal peripheral blood mononuclear cell (PBMC) and placenta were decreased and its expression increased, which was positively correlated with the changes in offspring testis. Based on analysis of human samples, we found that the H3K9me2 levels of FSTL3 promoter in maternal blood PBMC and placenta were positively correlated with fetal blood testosterone levels after prenatal dexamethasone exposure. We conclude that PDE can reduce sperm quality in adult offspring rats, which is related to the damage of testis BTB via epigenetic modification and change of FSTL3 expression in Sertoli cells. The H3K9me2 levels of the FSTL3 promoter and its expression in the maternal blood PBMC can be used as a prenatal warning marker for fetal testicular dysplasia.

Hormone Regulation in Testicular Development and Function

The testes serve as the primary source of androgens and the site of spermatogenesis, with their development and function governed by hormonal actions via endocrine and paracrine pathways. Male fertility hinges on the availability of testosterone, a cornerstone of spermatogenesis, while follicle-stimulating hormone (FSH) signaling is indispensable for the proliferation, differentiation, and proper functioning of Sertoli and germ cells. This review covers the research on how androgens, FSH, and other hormones support processes crucial for male fertility in the testis and reproductive tract. These hormones are regulated by the hypothalamic-pituitary-gonad (HPG) axis, which is either quiescent or activated at different stages of the life course, and the regulation of the axis is crucial for the development and normal function of the male reproductive system. Hormonal imbalances, whether due to genetic predispositions or environmental influences, leading to hypogonadism or hypergonadism, can precipitate reproductive disorders. Investigating the regulatory network and molecular mechanisms involved in testicular development and spermatogenesis is instrumental in developing new therapeutic methods, drugs, and male hormonal contraceptives.

Co-exposure of microcystin and nitrite enhanced spermatogenic disorders: The role of mtROS-mediated pyroptosis and apoptosis

Microcystins (MCs) and nitrites are coexisted in the environment and have reproductive toxicity. The combined toxic effect and mechanism of MCs and nitrite on spermatogenesis remain largely unclear. In the present study, co-exposure to microcystin-leucine arginine (MC-LR) and sodium nitrite (NaNO2) aggravated testicular damage of Balb/c mice and mitochondrial impairment of spermatogonia, Sertoli cells, and sperm. Furthermore, MC-LR and NaNO2 reduced sperm density with a synergistic effect. In addition, MC-LR and NaNO2 synergistically induced oxidative stress in the reproductive system by decreasing superoxide dismutase (SOD) activity and glutathione (GSH) levels and increasing levels of mitochondrial reactive oxygen species (mtROS) and reactive oxygen species (ROS). More importantly, mitoquidone mesylate (MitoQ), an inhibitor of mtROS, blocked MC-LR and NaNO2-induced spermatogonia and Sertoli cell apoptosis by inhibiting high expression of Bax, Fadd, Caspase-8, and cleaved-Caspase-3. On the other hand, MitoQ suppressed pyroptosis of Sertoli cells by inhibiting the expression of NLRP3, N-GSDMD, and cleaved-Caspase-1. Additionally, MitoQ alleviated co-exposure-induced sperm density reduction and organ index disorders in F1 generation mice. Together, co-exposure of MC-LR and NaNO2 can enhance spermatogenic disorders by mitochondrial oxidative impairment-mediated germ cell death. This study emphasizes the potential risks of MC-LR and NaNO2 on reproduction in realistic environments and highlights new insights into the cause and treatment of spermatogenic disorders.

Maternal exposure to DON during lactation induces testicular toxicity in pubertal and adult offspring mice

Deoxynivalenol (DON), a type B trichothecene mycotoxin, commonly occurs in cereal grains, and poses significant health risks to humans and animals. Numerous studies reveal its obvious toxic effects on male reproductive performance as well as its ability to transfer from the lactating mother to the suckling offspring through colostrum and milk. The objective of this study was to evaluate the toxic effect of lactational DON exposure on testicular morphology, hormonal levels, inflammation, apoptosis and proliferation of germ cells, tight junction, and sperm quality in male offspring. Sixty-six male offspring mice from lactating dams exposed to DON were euthanized at PND 21 and PND 70 to investigate the reproductive toxicity. Our results indicated that maternal DON exposure had a significant impact on the weight and volume of the testes, caused testicular histopathology, and reduced testosterone levels by downregulating expressions of StAR, CYP11A1, and CYP17A1 in male offspring. We also found that maternal DON exposure led to testicular inflammation in male offspring, which was attributed to increased levels of inflammatory markers, including IL-1β, IL-6, TNF-α, and IFN-γ. Maternal DON exposure resulted in impaired tight junctions of Sertoli cells in male offspring, as evidenced by decreased expressions of ZO-1, Occludin, and Claudin-3. In addition, maternal DON exposure caused a reduction in the number of Sertoli cells and germ cells, ultimately leading to decreased sperm count and quality in adult male offspring. Collectively, these findings provide compelling evidence that maternal exposure to DON during lactation causes testicular toxicity in both pubertal and adult male offspring.

Effect of Metformin on Sertoli Cell Fatty Acid Metabolism and Blood-Testis Barrier Formation

Sertoli cells (SCs) are essential to maintaining germ cell development. Metformin, the main pharmacologic treatment for pediatric type 2 diabetes, is administered to children during SC maturation. The present study aimed to analyze whether metformin affects SC energy metabolism and blood-testis barrier (BTB) integrity. Primary SC cultures were used for the in vitro studies. In vivo effects were studied in Sprague-Dawley rats treated with 200 mg/kg metformin from Pnd14 to Pnd30. Metformin decreased fatty acid oxidation and increased 3-hydroxybutyrate production in vitro. Moreover, it decreased the transepithelial electrical resistance across the monolayer and induced ZO-1 redistribution, suggesting an alteration of cell junctions. In vivo, a mild but significant increase in BTB permeability and ZO-1 expression was observed in the metformin group, without changes in testicular histology and meiosis progression. Additionally, adult rats that received metformin treatment during the juvenile period showed no alteration in BTB permeability or daily sperm production. In conclusion, metformin exposure may affect BTB permeability in juvenile rats, but this seems not to influence spermatogenesis progression. Considering the results obtained in adult animals, it is possible to speculate that metformin treatment during the juvenile period does not affect testicular function in adulthood.

The Male Reproductive Toxicity Caused by 2-Naphthylamine Was Related to Testicular Immunity Disorders

2-naphthylamine (NAP) was classified as a group I carcinogen associated with bladder cancer. The daily exposure is mostly from cigarette and E-cigarette smoke. NAP can lead to testicular atrophy and interstitial tissue hyperplasia; however, the outcomes of NAP treatment on spermatogenesis and the associated mechanisms have not been reported. The study aimed to investigate the effect of NAP on spermatogenesis and sperm physiologic functions after being persistently exposed to NAP at 5, 20, and 40 mg/kg for 35 days. We found that sperm motility, progressive motility, sperm average path velocity, and straight-line velocity declined remarkably in the NAP (40 mg/kg) treated group, and the sperm deformation rate rose upon NAP administration. The testis immunity- and lipid metabolism-associated processes were enriched from RNA-sequence profiling. Plvap, Ccr7, Foxn1, Trim29, Sirpb1c, Cfd, and Lpar4 involved in testis immunity and Pnliprp1 that inhibit triglyceride and cholesterol absorption were confirmed to rise dramatically in the NAP-exposed group. The increased total cholesterol and CD68 levels were observed in the testis from the NAP-exposed group. Gpx5, serving as an antioxidant in sperm plasma, and Semg1, which contributes to sperm progressive motility, were both down-regulated. We concluded that the short-term exposure to NAP caused reproductive toxicity, primarily due to the inflammatory abnormality in the testis.

Neonatal vitamin A supplementation improves sheep fertility potential

This study aimed to explore the effects of neonatal vitamin A (VA) supplementation on testis development and spermatogenesis. A total of 32 newborn lambs were intramuscularly injected with corn oil (control group) or corn oil + 2500 IU/kg BW VA (VA group). They were slaughtered and sampled at 3 weeks and 8 months of age to analyze spermatogenesis, cell proliferation, hormone secretion, antioxidant status of the testis, and adult sheep sperm parameters. Compared with the control group, the expression of spermatogonial differentiation-related genes in VA group was up-regulated (P < 0.05). Testis weight, seminiferous tubule diameter, number of spermatogonium and spermatocyte, and sperm density increased significantly in VA group at 8 months of age (P < 0.05). Neonatal VA injection upregulated the expression of the cell proliferation marker PCNA and cell cycle-related genes in the testis (P < 0.05). VA increased the concentrations of testosterone (T), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in the serum and upregulated steroidogenesis-related genes in the testis (P < 0.05). The antioxidant levels in the VA group were maintained at high levels. The total antioxidant capacity (T-AOC), antioxidant enzyme content and antioxidant-related genes were increased in the testis (P < 0.05). Furthermore, neonatal VA injection activated retinoic acid (RA) signaling to maintain the blood-testosterone barrier (BTB) in the testis of 3-week-old sheep. AMP-activated protein kinase (AMPK) and protein kinase B (AKT) signaling were also modulated in the sheep testis (P < 0.05). Taken together, VA supplementation in newborn rams promotes testis development and spermatogenesis to improve fertility.

Melatonin counteracts cadmium-induced rat testicular toxicity via the mechanistic target rapamycin (mTOR) pathway

The protective action of melatonin (MLT) against the harmful effects of cadmium (Cd) on testicular activity in rats has been documented previously; however, the involved molecular mechanisms have yet to be elucidated. Herein, we investigate the involvement of the mammalian target of rapamycin (mTOR) on the ability of MLT to counteract the damage induced by Cd on the rat testicular activity. Our study confirmed that Cd has harmful effects on the testes of rats and the protective action exerted by MLT. We reported, for the first time, that the addition of rapamycin (Rapa), a specific mTOR inhibitor, to animals co-treated with Cd and MLT completely abolished the beneficial effects exerted by MLT, indicating that the mTOR pathway partially modulates its helpful effects on Cd testicular toxicity. Interestingly, Rapa-alone treatment, provoking mTOR inhibition, produced altered morphological parameters, increased autophagy of germ and somatic cells, and reduced serum testosterone concentration. In addition, mTOR inhibition also reduced protein levels of markers of steroidogenesis (3β-Hydroxysteroid dehydrogenase) and blood-testis barrier integrity (occludin and connexin 43). Finally, Rapa altered sperm parameters as well as the ability of mature spermatozoa to perform a proper acrosome reaction. Although further investigation is needed to better clarify the molecular pathway involved in MLT action, we confirm that MLT alleviating Cd effects can be used as a supplement to enhance testicular function and improve male gamete quality.

Reproductive toxicity of cadmium stress in male animals

Cadmium (Cd) is a common heavy metal pollutant in the environment, and the widespread use of products containing Cd compounds in industry has led to excessive levels in the environment, which enter the animal body through the food chain, thus seriously affecting the reproductive development of animals. Related studies have reported that Cd severely affects spermatogonia development and spermatogenesis in animals. In contrast, the reproductive toxicity of Cd in males and its mechanism of action have not been clarified. Therefore, this paper reviewed the toxic effects of Cd on germ cells, spermatogonia somatic cells and hypothalamic-pituitary-gonadal axis (HPG axis) of male animals and its toxic action mechanisms of oxidative stress, apoptosis and autophagy from the perspectives of cytology, genetics and neuroendocrinology. The effects of Cd stress on epigenetic modification of reproductive development in male animals were also analyzed. We hope to provide a reference for the in-depth study of the toxicity of Cd on male animal reproduction.

Blood-testis barrier: a review on regulators in maintaining cell junction integrity between Sertoli cells

The blood-testis barrier (BTB) is formed adjacent to the seminiferous basement membrane. It is a distinct ultrastructure, partitioning testicular seminiferous epithelium into apical (adluminal) and basal compartments. It plays a vital role in developing and maturing spermatocytes into spermatozoa via reorganizing its structure. This enables the transportation of preleptotene spermatocytes across the BTB, from basal to adluminal compartments in the seminiferous tubules. Several bioactive peptides and biomolecules secreted by testicular cells regulate the BTB function and support spermatogenesis. These peptides activate various downstream signaling proteins and can also be the target themself, which could improve the diffusion of drugs across the BTB. The gap junction (GJ) and its coexisting junctions at the BTB maintain the immunological barrier integrity and can be the "gateway" during spermatocyte transition. These junctions are the possible route for toxicant entry, causing male reproductive dysfunction. Herein, we summarize the detailed mechanism of all the regulators playing an essential role in the maintenance of the BTB, which will help researchers to understand and find targets for drug delivery inside the testis.

Intratesticular Testosterone and Its Precursors among Azoospermic Men: A Pilot Study

PURPOSE

The study aimed to comprehensively analyze testosterone and precursor concentrations in the testicular interstitial fluid (TIF) of men with azoospermia, exploring their significance in the testicular microenvironment and their correlation with testicular sperm retrieval outcomes.

MATERIALS AND METHODS

We analyzed 37 TIF samples, including 5 from men with obstructive azoospermia (OA) and 32 from men with non-obstructive azoospermia (NOA). Liquid chromatography with tandem mass spectrometry quantified testosterone and precursor levels. Comparative assessments of the outcomes of testicular sperm retrieval were performed between the OA and NOA groups as well as among men with NOA.

RESULTS

Men with NOA who had not undergone hormone treatment exhibited significantly higher intratesticular concentrations of testosterone (median 1,528.1 vs. 207.5 ng/mL), androstenedione (median 10.6 vs. 1.9 ng/mL), and 17-OH progesterone (median 13.0 vs. 1.8 ng/mL) than men diagnosed with OA. Notably, in the subgroup of patients with NOA subjected to medical treatment, men with successful sperm retrieval had significantly reduced levels of androstenedione (median androstenedione 5.7 vs. 18.5 ng/mL, p=0.004). Upon a more detailed analysis of these men who underwent hormone manipulation treatment, the testosterone/androstenedione ratio (indicative of HSD17B3 enzyme activity) was markedly increased in men with successful sperm retrieval (median: 365.8 vs. 165.0, p=0.008) compared with individuals with NOA who had unsuccessful sperm recovery. Furthermore, within the subset of men with NOA who did not undergo medical treatment before microdissection testicular sperm extraction but achieved successful sperm retrieval, the ratio of 17-OH progesterone/progesterone (indicative of CYP17A1 activity) was substantially higher.

CONCLUSIONS

The study suggests distinct testosterone biosynthesis pathways in men with compromised spermatogenesis and those with normal spermatogenesis. Among NOA men with successful retrieval after hormone optimization therapy, there was decreased androstenedione and increased HSD17B3 enzyme activity. These findings have diagnostic and therapeutic implications for the future.

Mechanisms of imbalanced testicular homeostasis in infancy due to aberrant histone acetylation in undifferentiated spermatogonia under different concentrations of Di(2-ethylhexyl) phthalate (DEHP) exposure

Di (2-ethylhexyl) phthalate (DEHP), identified as an endocrine-disrupting chemical, is associated with reproductive toxicity. This association is particularly noteworthy in newborns with incompletely developed metabolic functions, as exposure to DEHP can induce enduring damage to the reproductive system, potentially influencing adult reproductive health. In this study, we continuously administered 40 μg/kg and 80 μg/kg DEHP to postnatal day 5 (PD5) mice for ten days to simulate low and high doses of DEHP exposure during infancy. Utilizing single-cell RNA sequencing (scRNA-seq), our analysis revealed that varying concentrations of DEHP exposure during infancy induced distinct DNA damage response characteristics in testicular Undifferentiated spermatogonia (Undiff SPG). Specifically, DNA damage triggered mitochondrial dysfunction, leading to acetyl-CoA content alterations. Subsequently, this disruption caused aberrations in histone acetylation patterns, ultimately resulting in apoptosis of Undiff SPG in the 40 μg/kg DEHP group and autophagy in the 80 μg/kg DEHP group. Furthermore, we found that DEHP exposure impacts the development and functionality of Sertoli and Leydig cells through the focal adhesion and PPAR signaling pathways, respectively. We also revealed that Leydig cells regulate the metabolic environment of Undiff SPG via Ptn-Sdc4 and Mdk-Sdc4 after DEHP exposure. Finally, our study provided pioneering evidence that disruptions in testicular homeostasis induced by DEHP exposure during infancy endure into adulthood. In summary, this study elucidates the molecular mechanisms through which DEHP exposure during infancy influences the development of testicular cell populations.

Hyperbaric oxygen preconditioning normalizes scrotal temperature, sperm quality, testicular structure, and erectile function in adult male rats subjected to exertional heat injury

Testicular hyperthermia has been noted in men who work in high ambient temperatures. Scrotal temperatures above the normal range caused germ cell loss in the testes and resulted in male subfertility. In adult male rats, exercising at a higher environmental temperature (36 °C with relative humidity of 50%, 52 min) caused exertional heat stroke (EHS) characterized by scrotal hyperthermia, impaired sperm quality, dysmorphology in testes, prostates and bladders, and erectile dysfunction. Here, we aim to ascertain whether hyperbaric oxygen preconditioning (HBOP: 100% O2 at 2.0 atm absolute [ATA] for 2 h daily for 14 days consequently before the onset of EHS) is able to prevent the problem of EHS-induced sterility, testes, prostates, and bladders dysmorphology and erectile dysfunction. At the end of exertional heat stress compared to normobaric air (NBA or non-HBOP) rats, the HBOP rats exhibited lower body core temperature (40 °C vs. 43 °C), lower scrotal temperature (34 °C vs. 36 °C), lower neurological severity scores (2.8 vs. 5.8), higher erectile ability, (5984 mmHg-sec vs. 3788 mmHg-sec), higher plasma testosterone (6.8 ng/mL vs. 3.5 ng/mL), lower plasma follicle stimulating hormone (196.3 mIU/mL vs. 513.8 mIU/mL), lower plasma luteinizing hormone (131 IU/L vs. 189 IU/L), lower plasma adrenocorticotropic hormone (5136 pg/mL vs. 6129 pg/mL), lower plasma corticosterone (0.56 ng/mL vs. 1.18 ng/mL), lower sperm loss and lower values of histopathological scores for epididymis, testis, seminal vesicle, prostate, and bladder. Our data suggest that HBOP reduces body core and scrotal hyperthermia and improves sperm loss, testis/prostate/bladder dysmorphology, and erectile dysfunction after EHS in rats.