Sertoli Cell Number Defines and Predicts Germ and Leydig Cell Population Sizes in the Adult Mouse Testis

Exploring the interplay between inflammation and male fertility

Male fertility results from a complex interplay of physiological, environmental, and genetic factors. It is conditioned by the properly developed anatomy of the reproductive system, hormonal regulation balance, and the interplay between different cell populations that sustain an appropriate and functional environment in the testes. Unfortunately, the mechanisms sustaining male fertility are not flawless and their perturbation can lead to infertility. Inflammation is one of the factors that contribute to male infertility. In the testes, it can be brought on by varicocele, obesity, gonadal infections, leukocytospermia, physical obstructions or traumas, and consumption of toxic substances. As a result of prolonged or untreated inflammation, the testicular resident cells that sustain spermatogenesis can suffer DNA damage, lipid and protein oxidation, and mitochondrial dysfunction consequently leading to loss of function in affected Sertoli cells (SCs) and Leydig cells (LCs), and the formation of morphologically abnormal dysfunctional sperm cells that lay in the basis of male infertility and subfertility. This is due mainly to the production and secretion of pro-inflammatory mediators, including cytokines, chemokines, and reactive oxygen species (ROS) by local immune cells (macrophages, lymphocytes T, mast cells) and tissue-specific cells [SCs, LCs, peritubular myoid cells (PMCs) and germ cells (GCs)]. Depending on the location, duration, and intensity of inflammation, these mediators can exert their toxic effect on different elements of the testes. In this review, we discuss the most prevalent inflammatory factors that negatively affect male fertility and describe the different ways inflammation can impair male reproductive function.

Effects of periodontal disease on the reproductive performance and offspring of Wistar rats

BACKGROUND

Periodontitis can induce systemic inflammation, and it may affect the testicles and male reproductive performance. This study investigated the effects of periodontitis on the testicles, reproductive performance, and offspring development in male rats.

METHODS

Male Wistar rats were induced with periodontitis by ligating their first molars. After 14 days of inducing periodontal lesions, the animals were observed for an additional 54 days, corresponding to a complete cycle of spermatogenesis. Rats from the periodontitis group (GP, n = 12) and the control group (GC, n = 12) were paired with healthy females (n = 48) for 10 days, equivalent to 2 estrous cycles. Post-mating, the males underwent microtomographic, histological, and reproductive parameter assessments.

RESULTS

Microtomographic analysis revealed higher porosity around the first molar in GP (26 ± 6%) and greater distance between the amelocemental junction and the alveolar bone (1.37 [1.12-1.90] mm), indicative of bone resorption. GP also exhibited significant decreases in final body weight, reduced Sertoli and Leydig cell counts, and lowered testosterone levels compared to GC. Significant morphological alterations in sperm tails were observed in GP compared to GC.

CONCLUSIONS

Periodontitis adversely affected reproductive performance, evoking, and offspring development in male rats. These findings highlight the systemic impacts of periodontal disease on male reproductive health in an animal model.

PLAIN LANGUAGE SUMMARY

Our study investigated how periodontitis can affect male reproductive health in rats and offspring development. We induced periodontitis in male rats and, after a full cycle of sperm production, these rats were mated with healthy females. We observed that the rats with periodontitis had worse reproductive performance compared to the control group without periodontitis. Additionally, the offspring of the rats with periodontitis showed signs of compromised intrauterine development and a higher incidence of congenital malformations. These results highlight that the inflammation caused by periodontitis can have adverse effects beyond the mouth, significantly impacting male reproductive health and offspring development. These findings suggest the need for further research into the clinical implications of periodontitis on reproductive health.

BP-3 exposure at environmentally relevant concentrations induced male developmental reproductive toxicity via ER/CCL27/ROS pathway in mice

BP-3 is the most widely used ultraviolet absorber, but its toxic effects and mechanisms far from being elucidated. This study evaluated the male developmental reproductive toxicities and mechanism of low-doses of BP-3. The results indicated that BP-3 (2.28 and 228 μg/L) led to a decrease in sperm quantity, quality and testosterone level, impaired blood-testis barrier (BTB) integrity and cytoskeleton, accompanied by aggravated oxidative stress in testes of mice on postnatal day 56 (PND 56). Notably, chemokine CCL27, a driver of oxidative stress, was significantly upregulated induced by BP-3. Similar disrupted effects were detected in testes of mice on PND14, which could be antagonized by ICI 182780 (estrogen receptor antagonist). Mechanistically, BP-3 directly interacted with ER, which boosted CCL27 expression, reactive oxygen species (ROS) accumulation, and BTB and cytoskeleton impairment. In vitro, si-CCL27 and/or ROS scavenger treatment significantly antagonized BP-3-induced oxidative stress and the decrease of BTB and cytoskeleton related genes in TM4 cells. These findings demonstrate that prolonged exposure to low-doses of BP-3 resulted in detrimental effects on testicular development through activation of the ER/CCL27/ROS axis. This study provides a novel perspective understanding the male reproductive toxicity risk caused by BPs exposure at low-doses.

The role of Sertoli cell-derived miR-143-3p in male fertility declines with age

As delayed parenthood becomes more prevalent, understanding age-related testosterone decline and its impact on male fertility has gained importance. However, molecular mechanisms concerning testicular aging remain largely undiscovered. Our study highlights that miR-143-3p, present in aging Sertoli cells (SCs), is loaded into extracellular vesicles (EVs), affecting Leydig cells (LCs) and germ cells, thus disrupting testicular tissue homeostasis and spermatogenesis. Intriguingly, in SCs, transforming growth factor-β signaling promotes miR-143 precursors transcription, increasing mature miR-143-3p levels. This inhibits Smurf2, activating Smad2, and further enhancing miR-143-3p accumulation. EVs transporting miR-143-3p, originating from SCs, contribute to the age-related decline of testosterone and male fertility by targeting the luteinizing hormone receptor and retinoic acid receptor. Diminishing endogenous miR-143-3p in SCs postpones testis aging, preserving and prolonging male fertility. Thus, our study identified miR-143-3p as a key regulator of testicular function and fertility, revealing miR-143-3p as a potential therapeutic target for male abnormal sexual and reproductive function.

Age-related testosterone decline: mechanisms and intervention strategies

Contemporary societies exhibit delayed reproductive age and increased life expectancy. While the male reproductive system demonstrates relatively delayed aging compared to that of females, increasing age substantially impacts its function. A characteristic manifestation is age-induced testosterone decline. Testosterone, a crucial male sex hormone, plays pivotal roles in spermatogenesis and sexual function, and contributes significantly to metabolism, psychology, and cardiovascular health. Aging exerts profound effects on the hypothalamic-pituitary-gonadal axis and Leydig cells, precipitating testosterone reduction, which adversely affects male health. Exogenous testosterone supplementation can partially ameliorate age-related testosterone deficiency; however, its long-term safety remains contentious. Preserving endogenous testosterone production capacity during the aging process warrants further investigation as a potential intervention strategy.

HSP47 expression in the hamster Sertoli cell: An immunohistochemical study

HSP47, a chaperone whose main function is the maturation of collagen molecules, is considered a marker of fibrotic diseases. Increased collagen synthesis in the testis has been associated with various pathologies leading to seminiferous tubule regression. Our aim was to study whether HSP47 is expressed in hamster Sertoli cells both in the adult and in two physiological situations of seminiferous tubule atrophy: irreversible testicular ageing and testicular regression due to short photoperiod (reversible). Eighteen animals were divided as follows: a group of 6 young animals aged 6 months, a group of 6 animals aged 24 months, which were exposed to a long photoperiod, and a final group of 6 young animals subjected to a short photoperiod. Testicular samples were fixed in methacarn and an immunohistochemical technique was used to detect HSP47. A semiquantitative study of of this protein expresion was performed between tubular sections of aged animals with complete spermatogenesis and arrested spermatogenesis and tubular sections with arrest spermatogenesis of photoinhibited testes. Sertoli cells were positive for HSP47, the intensity being greater in tubular sections with arrested spermatogenesis in both aged and photoinhibited animals. Semiquantitative analysis corroborated this observation in the sense that the expression of this protein differed according to the functional state of the seminiferous tubules. Thus, the radio of immunoreactivity was significantly higher in tubular sections with arrested spermatogenesis in aged animals compared with regressed animals, and in the latter compared with those whose tubular sections showed complete spermatogenesis. In conclusion, HSP47 expression in Sertoli cells was found for the first time in mammals. Moreover, increased expression seemed to be related to the degree of atrophy of the seminiferous epithelium and to the reversible or non-reversible physiological state of the seminiferous epithelium.

Heat stress upregulates arachidonic acid to trigger autophagy in sertoli cells via dysfunctional mitochondrial respiratory chain function

As a key factor in determining testis size and sperm number, sertoli cells (SCs) play a crucial role in male infertility. Heat stress (HS) reduces SCs counts, negatively impacting nutrient transport and supply to germ cells, and leading to spermatogenesis failure in humans and animals. However, how HS affects the number of SCs remains unclear. We hypothesized that changes in SC metabolism contribute to the adverse effects of HS. In this study, we first observed an upregulation of arachidonic acid (AA), an unsaturated fatty acid after HS exposure by LC-MS/MS metabolome detection. By increasing ROS levels, expression of KEAP1 and NRF2 proteins as well as LC3 and LAMP2, 100 µM AA induced autophagy in SCs by activating oxidative stress (OS). We observed adverse effects of AA on mitochondria under HS with a decrease of mitochondrial number and an increase of mitochondrial membrane potential (MMP). We also found that AA alternated the oxygen transport and absorption function of mitochondria by increasing glycolysis flux and decreasing oxygen consumption rate as well as the expression of mitochondrial electron transport chain (ETC) proteins Complex I, II, V. However, pretreatment with 5 mM NAC (ROS inhibitor) and 2 µM Rotenone (mitochondrial ETC inhibitor) reversed the autophagy induced by AA. In summary, AA modulates autophagy in SCs during HS by disrupting mitochondrial ETC function, inferring that the release of AA is a switch-like response, and providing insight into the underlying mechanism of high temperatures causing male infertility.

Joint Analysis of Genome-wide DNA Methylation and Transcription Sequencing Identifies the Role of BAX Gene in Heat Stress-Induced-Sertoli Cells Apoptosis

The problem of male infertility is a global health crisis and poses a serious threat to the well-being of families. Under heat stress (HS), the reduction of Sertoli cells (SCs) inhibits energy transport and nutrient supply to germ cells, leading to spermatogenesis failure. DNA methylation of genes is a central epigenetic regulatory mechanism in mammalian reproduction. However, it remains unclear how DNA methylation regulates gene expression in heat-stressed SCs. In this study, we investigated whether the decrease in SC levels during HS could be related to epigenetic DNA modifications. The cells exposed to HS showed changes in differential methylation cytosines and regions (DMCs/DMRs) and differential expression genes (DEGs), but not in global DNA methylations. One of the most important biological processes affected by HS is cell apoptosis induced by the intrinsic apoptotic signaling pathway (GO: 2,001,244, P < 0.05) by enrichment in the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). The joint analysis showed that several gene expressions in RNA-seq and WGBS overlapped and the shortlisted genes BAX, HSPH1, HSF1B, and BAG were strongly correlated with stress response and apoptosis. Methylation-specific PCR (MSP) and flow cytometry (FCM) analyzes showed that reduced promoter methylation and enhanced gene expression of BAX with a consequence of apoptosis. The activity of BAX, as well as an increase in its expression, is likely to result in a reduction of SCs population which could further impair ATP supply and adversely affect membrane integrity. These findings provide novel insights into the molecular mechanisms through which stressors cause male reproductive dysfunction and a new molecular etiology of male infertility.

Development of peptides for targeting cell ablation agents concurrently to the Sertoli and Leydig cell populations of the testes: An approach to non-surgical sterilization

The surgical sterilization of cats and dogs has been used to prevent their unwanted breeding for decades. However, this is an expensive and invasive procedure, and often impractical in wider contexts, for example the control of feral populations. A sterilization agent that could be administered in a single injection, would not only eliminate the risks imposed by surgery but also be a much more cost-effective solution to this worldwide problem. In this study, we sought to develop a targeting peptide that would selectively bind to Leydig cells of the testes. Subsequently, after covalently attaching a cell ablation agent, Auristatin, to this peptide we aimed to apply this conjugated product (LH2Auristatin) to adult male mice in vivo, both alone and together with a previously developed Sertoli cell targeting peptide (FSH2Menadione). The application of LH2Auristatin alone resulted in an increase in sperm DNA damage, reduced mean testes weights and mean seminiferous tubule size, along with extensive germ cell apoptosis and a reduction in litter sizes. Together with FSH2Menadione there was also an increase in embryo resorptions. These promising results were observed in around a third of all treated animals. Given this variability, we discuss how these reagents might be modified in order to increase target cell ablation and improve their efficacy as sterilization agents.

Redox mechanisms of environmental toxicants on male reproductive function

Humans and wildlife, including domesticated animals, are exposed to a myriad of environmental contaminants that are derived from various human activities, including agricultural, household, cosmetic, pharmaceutical, and industrial products. Excessive exposure to pesticides, heavy metals, and phthalates consequently causes the overproduction of reactive oxygen species. The equilibrium between reactive oxygen species and the antioxidant system is preserved to maintain cellular redox homeostasis. Mitochondria play a key role in cellular function and cell survival. Mitochondria are vulnerable to damage that can be provoked by environmental exposures. Once the mitochondrial metabolism is damaged, it interferes with energy metabolism and eventually causes the overproduction of free radicals. Furthermore, it also perceives inflammation signals to generate an inflammatory response, which is involved in pathophysiological mechanisms. A depleted antioxidant system provokes oxidative stress that triggers inflammation and regulates epigenetic function and apoptotic events. Apart from that, these chemicals influence steroidogenesis, deteriorate sperm quality, and damage male reproductive organs. It is strongly believed that redox signaling molecules are the key regulators that mediate reproductive toxicity. This review article aims to spotlight the redox toxicology of environmental chemicals on male reproduction function and its fertility prognosis. Furthermore, we shed light on the influence of redox signaling and metabolism in modulating the response of environmental toxins to reproductive function. Additionally, we emphasize the supporting evidence from diverse cellular and animal studies.

Reproductive endocrinology, morphological traits, and sexual selection in a population of wild South African giraffes

Sex steroids are pervasive in mammals and evolutionarily conserved, but differences in the nuances of endocrine profiles characterize distinct species. Two sex steroids, testosterone and progesterone, feature prominently in the life history of mammalian taxa, but neither one has been analyzed from wild giraffes. Our study was designed to address this gap in knowledge by examining how these sex steroids are related to biological features and giraffe life history. We conducted the research at Rooipoort Nature Reserve a 44,000 ha private nature reserve in South Africa on a population of South African giraffes (Giraffa camelopardalis giraffa). Eleven adult giraffe cows and seven adult bulls were immobilized and various biological samples and morphological measurements were obtained. We analyzed both testosterone and progesterone using Ultra High Performance Liquid Chromotography - Tandem Mass Spectrometry (UHPLC-MS/MS). We found that non-pregnant females had lower progesterone concentrations than pregnant females and that those in the last trimester of pregnancy showed a slight drop in progesterone, as well as an increase in testosterone. Among males, chronological age was correlated with testicle size, testosterone concentrations, and ossicone volume. We propose that the progesterone decline functions partly to accelerate resumption of ovulation because giraffes become pregnant while lactating, and that the testosterone elevation provides an endocrine mileu for female defense of neonatal calves, given that lion predation is a major threat to calf survival. We suggest that male reproductive strategies are mediated by the age-related impacts of testosterone on growth in both body mass and ossicone volume as a consequence of sexual selection. We conclude by noting that the robust and solid ossicones of male giraffes function in mate competition as wedges that are used to topple opponents by raising their legs and placing them in an off-balanced position that can seriously injure them when falling to the ground.

The male reproductive toxicity after nanoplastics and microplastics exposure: Sperm quality and changes of different cells in testis

Nanoplastics (NPs) and Microplastics (MPs) pollution has become a severe threat to the planet and is a growing concern. However, their effects on male reproductive toxicity remain poorly understood. In this study, a series of morphological analyses were completed to explore the influence of NPs and MPs exposure on the testis in mice. After 12-weeks exposure, although both NPs and MPs exposure can lead to reproductive toxicity, compared with NPs exposure, exposure to MPs leads to a more significant increase in reproductive toxicity dependent on some particle size. Moreover, increased reproductive toxicities, including increased spermatogenesis disorders, and sperm physiological abnormality, oxidative stress, testis inflammation was more associated with MPs group than NPs group. Ultra-pathological structure observed by transmission electron microscopy indicated that both NPs and MPs have different effects on spermatogonia, spermatocytes and Sertoli cells. Exposure to MPs resulted in decreased Sertoli cell numbers and reduced Leydig cell area, and showed no effects on differentiation of Leydig cells by the expression level of the Insulin-Like factor 3 (INSL3) in Leydig cells. Transcriptomic sequencing analysis provided valuable insights into the differential effects of NPs and MPs on cellular processes. Specifically, our findings demonstrated that NPs were predominantly involved in the regulation of steroid biosynthesis, whereas MPs primarily influenced amino acid metabolism. This study demonstrates the effect of adult-stage reproductive toxicity in mice after exposure to NPs and MPs, which will deep the understanding of the NPs and MPs induced toxicity.

Single-cell transcriptome analysis of the germ cells and somatic cells during mitotic quiescence stage in goats

The mitotic quiescence of prospermatogonia is the event known to occur during genesis of the male germline and is tied to the development of the spermatogenic lineage. The regulatory mechanisms and the functional importance of this process have been demonstrated in mice; however, regulation of this process in human and domestic animal is still largely unknown. In this study, we employed single-cell RNA sequencing to identify transcriptional signatures of prospermatogonia and major somatic cell types in testes of goats at E85, E105, and E125. We identified both common and specific Gene Ontology categories, transcription factor regulatory networks, and cell-cell interactions in cell types from goat testis. We also analyzed the transcriptional dynamic changes in prospermatogonia, Sertoli cells, Leydig cells, and interstitial cells. Our datasets provide a useful resource for the study of domestic animal germline development.

Sertoli cell-enriched proteins in mouse and human testicular interstitial fluid

Sertoli cells support the development of sperm and the function of various somatic cells in the interstitium between the tubules. Sertoli cells regulate the function of the testicular vasculature and the development and function of the Leydig cells that produce testosterone for fertility and virility. However, the Sertoli cell-derived factors that regulate these cells are largely unknown. To define potential mechanisms by which Sertoli cells could support testicular somatic cell function, we aimed to identify Sertoli cell-enriched proteins in the testicular interstitial fluid (TIF) between the tubules. We previously resolved the proteome of TIF in mice and humans and have shown it to be a rich source of seminiferous tubule-derived proteins. In the current study, we designed bioinformatic strategies to interrogate relevant proteomic and genomic datasets to identify Sertoli cell-enriched proteins in mouse and human TIF. We analysed proteins in mouse TIF that were significantly reduced after one week of acute Sertoli cell ablation in vivo and validated which of these are likely to arise primarily from Sertoli cells based on relevant mouse testis RNASeq datasets. We used a different, but complementary, approach to identify Sertoli cell-enriched proteins in human TIF, taking advantage of high-quality human testis genomic, proteomic and immunohistochemical datasets. We identified a total of 47 and 40 Sertoli cell-enriched proteins in mouse and human TIF, respectively, including 15 proteins that are conserved in both species. Proteins with potential roles in angiogenesis, the regulation of Leydig cells or steroidogenesis, and immune cell regulation were identified. The data suggests that some of these proteins are secreted, but that Sertoli cells also deposit specific proteins into TIF via the release of extracellular vesicles. In conclusion, we have identified novel Sertoli cell-enriched proteins in TIF that are candidates for regulating somatic cell-cell communication and testis function.

Development of a model for studying the developmental consequences of oxidative sperm DNA damage by targeting redox-cycling naphthoquinones to the Sertoli cell population

Oxidative stress can be induced in the testes by a wide range of factors, including scrotal hyperthermia, varicocele, environmental toxicants, obesity and infection. The clinical consequences of such stress include the induction of genetic damage in the male germ line which may, in turn, have serious implications for the health and wellbeing of the progeny. In order to confirm the transgenerational impact of oxidative stress in the testes, we sought to develop an animal model in which this process could be analysed. Our primary approach to this problem was to induce Sertoli cells (robust, terminally differentiated, tissue-specific testicular cells whose radioresistance indicates significant resistance to oxidative stress) to generate high levels of reactive oxygen species (ROS) within the testes. To achieve this aim, six follicle-stimulating hormone (FSH) peptides were developed and compared for selective targeting to Sertoli cells both in vitro and in vivo. Menadione, a redox-cycling agent, was then conjugated to the most promising FSH candidate using a linker that had been optimised to enable maximum production of ROS in the targeted cells. A TM4 Sertoli cell line co-incubated with the FSH-menadione conjugate in vitro exhibited significantly higher levels of mitochondrial ROS generation (10-fold), lipid peroxidation (2-fold) and oxidative DNA damage (2-fold) than the vehicle control. Additionally, in a proof-of-concept study, ten weeks after a single injection of the FSH-menadione conjugate in vivo, injected male mice were found to exhibit a 1.6 fold increase in DNA double strand breaks and 13-fold increase in oxidative DNA damage to their spermatozoa while still retaining their ability to initiate a pregnancy. We suggest this model could now be used to study the influence of chronic oxidative stress on testicular function with emphasis on the impact of DNA damage in the male germ line on the mutational profile and health of future generations.

Protective role of autophagy in triptolide-induced apoptosis of TM3 Leydig cells

Background and Objectives

Triptolide (TP) is known to impair testicular development and spermatogenesis in mammals, but the mechanism of the side effects still needs to be investigated. The aim of the research is to confirm whether TP can cause autophagy in TM3 Leydig cells and the potential molecular pathway in vitro.

Methods

TM3 Leydig cells are used to investigate the molecular pathway through Western blot, detection of apoptosis, transmission electron microscopy for autophagosomes and so on.

Results

The data show that TP treatment resulted in the decreasing of the viability of TM3 cells due to the increased apoptosis. Treated with TP, the formation of autophagosomes, the decrease in P62, and the increase in the conversion of LC3-I to LC3-II suggested the induction of autophagy. The induction of autophagy has accompanied the activation of the mTOR/P70S6K signal pathway. The viability of the TM3 cells was further inhibited when they were co-treated with autophagy inhibitor, chloroquine (CQ).

Conclusion

All these data suggest that autophagy plays a very important role in antagonizing TM3 cell apoptosis during the TP exposure.

Zinc and selenium attenuate quaternary heavy metal mixture-induced testicular damage via amplification of the antioxidant system, reduction in metal accumulation, inflammatory and apoptotic biomarkers

Heavy metals (HMs) such as cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg) are highly toxic elements. They are often found together in nature as a heavy metal mixture (HMM) and are known to contribute to subfertility/infertility as environmental pollutants. This study aims to evaluate the potential benefits of treating HMM-induced testicular pathophysiology with zinc (Zn) and/or selenium (Se). Six-week-old male Sprague Dawley rats were grouped into 5 (n = 7). The control group received deionized water, while the other groups were treated with PbCl2 (20 mg kg-1), CdCl2 (1.61 mg kg-1), HgCl2 (0.40 mg kg-1), and Na2AsO3 (10 mg kg-1) in deionized water for 60 days. Additionally, groups III to V received Zn, Se, and Zn/Se, respectively, for 60 days. The study evaluated testis weight, metal accumulation, sperm analysis, FSH, LH, testosterone, prolactin, oxidative stress, antioxidants, pro-inflammatory and apoptotic markers, and presented structural changes in the testis as micrographs. HMM caused a significant increase in testis weight, metal accumulation, prolactin, oxidative stress, and pro-inflammatory and apoptotic markers, while significantly decreasing semen analysis, FSH, LH, and testosterone. Histology showed decreased spermatogenesis and spermiogenesis, as evidenced by the structure of the germ cells and spermatids. However, Zn, Se, or both ameliorated and reversed some of the observed damages. This study provides further evidence for the mitigative potential of Zn, Se, or both in reversing the damage inflicted by HMM in the testis, and as a countermeasure towards improving HM-induced decrease in public health fecundity.

Graphical abstract

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

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

The single-cell chromatin accessibility landscape in mouse perinatal testis development

Spermatogenesis depends on an orchestrated series of developing events in germ cells and full maturation of the somatic microenvironment. To date, the majority of efforts to study cellular heterogeneity in testis has been focused on single-cell gene expression rather than the chromatin landscape shaping gene expression. To advance our understanding of the regulatory programs underlying testicular cell types, we analyzed single-cell chromatin accessibility profiles in more than 25,000 cells from mouse developing testis. We showed that single-cell sequencing assay for transposase-accessible chromatin (scATAC-Seq) allowed us to deconvolve distinct cell populations and identify cis-regulatory elements (CREs) underlying cell-type specification. We identified sets of transcription factors associated with cell type-specific accessibility, revealing novel regulators of cell fate specification and maintenance. Pseudotime reconstruction revealed detailed regulatory dynamics coordinating the sequential developmental progressions of germ cells and somatic cells. This high-resolution dataset also unveiled previously unreported subpopulations within both the Sertoli and Leydig cell groups. Further, we defined candidate target cell types and genes of several genome-wide association study (GWAS) signals, including those associated with testosterone levels and coronary artery disease. Collectively, our data provide a blueprint of the 'regulon' of the mouse male germline and supporting somatic cells.

Gonadotropin administration to mimic mini-puberty in hypogonadotropic males: pump or injections?

OBJECTIVE

Newborns with congenital hypogonadotropic hypogonadism (CHH) have an impaired postnatal activation of the gonadotropic axis. Substitutive therapy with recombinant gonadotropins can be proposed to mimic physiological male mini-puberty during the first months of life. The aim of this study was to compare the clinical and biological efficacy of two treatment modalities of gonadotropins administration during mini-puberty in CHH neonates.

DESIGN

Multicenter retrospective analytical epidemiological study comparing two treatments, pump vs injection, between 2004 and 2019.

METHODS

Clinical (penile size, testis size, testicular descent) and biological parameters (serum concentrations of testosterone, anti-Müllerian hormone (AMH) and Inhibin B) were compared between the two groups by multivariate analyses.

RESULTS

Thirty-five patients were included. A significantly higher increase in penile length and testosterone level was observed in the injection group compared to the pump group (+0.16 ± 0.02 mm vs +0.10 ± 0.02 mm per day, P = 0.002; and +0.04 ± 0.007 ng/mL vs +0.01 ± 0.008 ng/mL per day, P = 0.001). In both groups, significant increases in penile length and width, testosterone, AMH, and Inhibin B levels were observed, as well as improved testicular descent (odds ratio of not being in a scrotal position at the end of treatment = 0.97 (0.96; 0.99)).

CONCLUSIONS

Early postnatal administration of recombinant gonadotropins in CHH boys is effective in stimulating penile growth, Sertoli cell proliferation, and testicular descent, with both treatment modalities.

Testicular macrophages are recruited during a narrow fetal time window and promote organ-specific developmental functions

A growing body of evidence demonstrates that fetal-derived tissue-resident macrophages have developmental functions. It has been proposed that macrophages promote testicular functions, but which macrophage populations are involved is unclear. Previous studies showed that macrophages play critical roles in fetal testis morphogenesis and described two adult testicular macrophage populations, interstitial and peritubular. There has been debate regarding the hematopoietic origins of testicular macrophages and whether distinct macrophage populations promote specific testicular functions. Here our hematopoietic lineage-tracing studies in mice show that yolk-sac-derived macrophages comprise the earliest testicular macrophages, while fetal hematopoietic stem cells (HSCs) generate monocytes that colonize the gonad during a narrow time window in a Sertoli-cell-dependent manner and differentiate into adult testicular macrophages. Finally, we show that yolk-sac-derived versus HSC-derived macrophages have distinct functions during testis morphogenesis, while interstitial macrophages specifically promote adult Leydig cell steroidogenesis. Our findings provide insight into testicular macrophage origins and their tissue-specific roles.

MicroRNA profiling reveals the role of miR-133b-3p in promoting apoptosis and inhibiting cell proliferation and testosterone synthesis in mouse TM3 cells

Late-onset hypogonadism (LOH) is an age-related clinical and biological syndrome in which serum testosterone deficiency is an important characteristic and diagnostic indicator. In this study, we firstly analyzed the difference in the expression level of three miR-133 s (including miR-133a-3p, miR-133a-5p, and miR-133b-3p) in rat testis samples, blood samples from mice before and 1 wk after testis removal, and mouse TM3 cells. Secondly, the mimics and inhibitors corresponding to the three miR-133 s of mouse were transfected into TM3 cells separately to determine the correlation between the three miRNAs. Finally, using mouse TM3 cells to analyze the effect of miR-133b overexpression or inhibition on the proliferation and apoptosis of mouse testicular Leydig cells, the effect on genes related to testosterone synthesis, and the effect on the level of testosterone in the culture medium. We found that, compared with the testis tissue of newborn rats, miR-133a-5p was increased in adult rats, and miR-133a-3p and miR-133b-3p were decreased. In addition, 1 wk after the testis was removed, the expression levels of these three miRNAs in the blood of adult mice decreased. The correlation of the three miRNAs was summarized, and it was found that miR-133b-3p played an important role in it. In TM3 cells, overexpression of miR-133b-3p suppressed the proliferation and promotes apoptosis of cells, suppressed the expression level of most genes related to cell proliferation and testosterone synthesis, and the concentration of testosterone in the culture medium decreased while these phenomena can be reversed by the inhibition of miR-133b-3p expression. It was found that miR-133b-3p can regulate testosterone production in TM3 cells at least by targeting FSCN1. The above results suggest that miR-133b-3p plays an important role in regulating testosterone synthesis. These findings also provide new candidate diagnostic indicators for late-onset hypogonadism in men and provide new clues for the further study of pathogenesis.

Ldha-Dependent Metabolic Programs in Sertoli Cells Regulate Spermiogenesis in Mouse Testis

Sertoli cells play indispensable roles in spermatogenesis by providing the advanced germ cells with structural, nutritional, and regulatory support. Lactate is regarded as an essential Sertoli-cell-derived energy metabolite that nurses various types of spermatogenic cells; however, this assumption has not been tested using genetic approaches. Here, we have reported that the depletion of lactate production in Sertoli cells by conditionally deleting lactate dehydrogenase A (Ldha) greatly affected spermatogenesis. Ldha deletion in Sertoli cells significantly reduced the lactate production and resulted in severe defects in spermatogenesis. Spermatogonia and spermatocytes did not show even mild impairments, but the spermiogenesis of Ldha conditional knockout males was severely disrupted. Further analysis revealed that 2456 metabolites were altered in the sperm of the knockout animals, and specifically, lipid metabolism was dysregulated, including choline, oleic acid, and myristic acid. Surprisingly, choline supplementation completely rescued the spermiogenesis disorder that was caused by the loss of Ldha activities. Collectively, these data have demonstrated that the interruption of Sertoli-cell-derived lactate impacted sperm development through a choline-mediated mechanism. The outcomes of these findings have revealed a novel function of lactate in spermatogenesis and have therapeutic applications in treating human infertility.

Animal models of male reproductive ageing to study testosterone production and spermatogenesis

Ageing is the time-dependent gradual decline of the functional characteristics in an organism. It has been shown that it results in the loss of reproductive health and fertility. The age-dependent decline of fertility is a potential issue as the parenthood age is increasing in Western countries, mostly due to socioeconomic factors. In comparison to women, for whom the consequences of ageing are well documented and general awareness of the population is extensively raised, the effects of ageing for male fertility and the consequences of advanced paternal age for the offspring have not been widely studied. Studies with humans are welcome but it is hard to implement relevant experimental approaches to unveil the molecular mechanisms by which ageing affects male reproductive potential. Animal models have thus been extensively used. These models are advantageous due to their reduced costs, general easy maintenance in laboratory facilities, rigorous manipulation tools, short lifespan, known genetic backgrounds, and reduced ethical constraints. Herein, we discuss animal models for the study of male reproductive ageing. The most well-known and studied reproductive ageing models are rodents and non-human primates. The data collected from these models, particularly studies on testicular ageing, steroidogenesis, and genetic and epigenetic changes in spermatogenesis are detailed. Notably, some species challenge the currently accepted ageing theories and the concept of senescence itself, which renders them interesting animal models for the study of male reproductive ageing.

Ciprofloxacin and enrofloxacin can cause reproductive toxicity via endocrine signaling pathways

Ciprofloxacin (CIP) and enrofloxacin (ENR) are veterinary antibiotics commonly utilized to treat and prevent animal diseases. Environmental and dietary antibiotic residues can directly and indirectly affect the reproductive development of animals and humans. This article investigated the reproductive toxicity of CIP in male zebrafish, showing that it could decrease the spermatogonial weight and damage the spermatogonial tissue. The sex hormone assays showed that CIP decreased fshb and lhb gene expression and plasma testosterone (T). In addition, transcriptome analysis indicated that the effect of CIP on zebrafish might be related to the endocrine signaling pathways. ENR, which was selected for further study, inhibited mouse Leydig (TM3) and Sertoli (TM4) cell proliferation and caused cell cycle arrest. The sperm concentration, serum luteotropic hormone (LH) and follicle-stimulating hormone (FSH), and T levels decreased in adolescent mice after ENR treatment for 30d in vivo. Hematoxylin and eosin (H&E) staining showed that ENR exposure potentially induced testicular injury, while the real-time quantitative PCR (qPCR) results indicated that ENR inhibited the mRNA expression of key genes in the Leydig cells (cyp11a1, 3β-HSD, and 17β-HSD), Sertoli cells (Inhbβ and Gdnf) and spermatogenic cells (Plzf, Stra8 and Dmc1). In conclusion, these findings indicated that ENR exposure might influence the development of the testes of pubescent mice.

Diet-induced obesity impairs spermatogenesis: the critical role of NLRP3 in Sertoli cells

Background

Accumulating evidence indicates a key role of Sertoli cell (SC) malfunction in spermatogenesis impairment induced by obesity. Nucleotide-binding oligomerization domain-like receptor with a pyrin domain 3 (NLRP3) is expressed in SCs, but the role of NLRP3 in the pathological process of obesity-induced male infertility remains unclear.

Methods

NLRP3-deficient mice were fed a high-fat diet for 24 weeks to establish obesity-related spermatogenesis impairment. In another set of experiments, a lentiviral vector containing a microRNA (miR)-451 inhibitor was injected into AMP-activated protein kinase α (AMPKα)-deficient mouse seminiferous tubules. Human testis samples were obtained by testicular puncture from men with obstructive azoospermia whose samples exhibited histologically normal spermatogenesis. Isolated human SCs were treated with palmitic acid (PA) to mimic obesity model in vitro.

Results

Increased NLRP3 expression was observed in the testes of obese rodents. NLRP3 was also upregulated in PA-treated human SCs. NLRP3 deficiency attenuated obesity-related male infertility. SC-derived NLRP3 promoted interleukin-1β (IL-1β) secretion to impair testosterone synthesis and sperm performance and increased matrix metalloproteinase-8 (MMP-8) expression to degrade occludin via activation of nuclear factor-kappa B (NF-κB). Increased miR-451 caused by obesity, decreased AMPKα expression and sequentially increased NADPH oxidase activity were responsible for the activation of NLRP3. miR-451 inhibition protected against obesity-related male infertility, and these protective effects were abolished by AMPKα deficiency in mice.

Conclusions

NLRP3 promoted obesity-related spermatogenesis impairment. Increased miR-451 expression, impaired AMPKα pathway and the subsequent ROS production were responsible for NLRP3 activation. Our study provides new insight into the mechanisms underlying obesity-associated male infertility.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41232-022-00203-z.

Mesenchymal stem cells promote spermatogonial stem/progenitor cell pool and spermatogenesis in neonatal mice in vitro

Prepubertal cancer treatment leads to irreversible infertility in half of the male patients. Current in vitro spermatogenesis protocols and cryopreservation techniques are inadequate to expand spermatogonial stem/progenitor cells (SSPC) from testicles. Bone marrow derived mesenchymal stem cells (BM-MSC) bearing a close resemblance to Sertoli cells, improved spermatogenesis in animal models. We asked if a co-culture setup supported by syngeneic BM-MSC that contributes to the air–liquid interphase (ALI) could lead to survival, expansion and differentiation of SSPCs in vitro. We generated an ALI platform able to provide a real-time cellular paracrine contribution consisting of syngeneic BM-MSCs to neonatal C57BL/6 mice testes. We aimed to evaluate the efficacy of this culture system on SSPC pool expansion and spermatogenesis throughout a complete spermatogenic cycle by measuring the number of total germ cells (GC), the undifferentiated and differentiating spermatogonia, the spermatocytes and the spermatids. Furthermore, we evaluated the testicular cell cycle phases, the tubular and luminal areas using histochemical, immunohistochemical and flow cytometric techniques. Cultures in present of BM-MSCs displayed survival of ID4(+) spermatogonial stem cells (SSC), expansion of SALL4(+) and OCT4(+) SSPCs, VASA(+) total GCs and Ki67(+) proliferative cells at 42 days and an increased number of SCP3(+) spermatocytes and Acrosin(+) spermatids at 28 days. BM-MSCs increased the percentage of mitotic cells within the G2-M phase of the total testicular cell cycle increased for 7 days, preserved the cell viability for 42 days and induced testicular maturation by enlargement of the tubular and luminal area for 42 days in comparison to the control. The percentage of PLZF(+) SSPCs increased within the first 28 days of culture, after which the pool started to get smaller while the number of spermatocytes and spermatids increased simultaneously. Our findings established the efficacy of syngeneic BM-MSCs on the survival and expansion of the SSPC pool and differentiation of spermatogonia to round spermatids during in vitro culture of prepubertal mice testes for 42 days. This method may be helpful in providing alternative cures for male fertility by supporting in vitro differentiated spermatids that can be used for round spermatid injection (ROSI) to female oocyte in animal models. These findings can be further exploited for personalized cellular therapy strategies to cure male infertility of prepubertal cancer survivors in clinics.

Sertoli cell PUMILIO proteins modulate mouse testis size through translational control of cell cycle regulators

Testis size determination is an important question of reproductive biology. Sertoli cells are known to be a key determinant of mammalian testis size but the underlying molecular mechanisms remain incompletely understood. Previously we showed that highly conserved germ cell RNA binding proteins, PUMILIO1(PUM1) and PUMILIO2 (PUM2), control mouse organ and body size through translational regulation, but how different cell types of the organs contribute to their organ size regulation has not been established. Here we report a somatic role of PUM in gonad size determination. PUM1 is highly expressed in the Sertoli cells of the developing testis from embryonic and postnatal mice as well as in germ cells. Removal of Sertoli cell, but not germ cell, Pum1 gene, led to reduced testis size without significantly affecting sperm number or fertility. Knockout of PUM1 target, Cdkn1b, rescued the phenotype of reduced testis size, supporting a key role of Sertoli cell PUM1 mediated Cdkn1b repression in the testis size control. Furthermore, removal of Pum2 or both Pum1 and Pum2 in the Sertoli cells also only affected the testis size, not sperm development, with the biggest size reduction in Pum1/2 double knockout mice. We propose that PUM1 and PUM2 modulate the testis size through their synergistic translational regulation of cell cycle regulators in the Sertoli cell. Further investigation of the ovary or other organs could reveal if PUM-mediated translational control of cell proliferation of the supporting cell represents a general mechanism for organ size modulation.

Perfluorooctane sulfonate induces suppression of testosterone biosynthesis via Sertoli cell-derived exosomal/miR-9-3p downregulating StAR expression in Leydig cells

Perfluorooctane sulfonate (PFOS) is associated with male reproductive disorder, but the related mechanisms are still unclear. In this study, we used in vivo and in vitro models to explore the role of Sertoli cell-derived exosomes (SC-Exo)/miR-9-3p/StAR signaling pathway on PFOS-induced suppression of testosterone biosynthesis. Forty male ICR mice were orally administrated PFOS (0.5-10 mg/kg/bw) for 4 weeks. Bodyweight, organ index, sperm count, reproductive hormones were evaluated. Primary Sertoli cells and Leydig cells were used to delineate the molecular mechanisms that mediate the effects of PFOS on testosterone biosynthesis. Our results demonstrated that PFOS dose-dependently induced a decrease in sperm count, low levels of testosterone, and damage in testicular interstitium morphology. In vitro models, PFOS significantly increased miR-9-3p levels in Sertoli cells and SC-Exo, accompanied by a decrease in testosterone secretion and StAR expression in Leydig cells when Leydig cells were exposed to SC-Exo. Meanwhile, inhibition of SC-Exo or miR-9-3p by their inhibitors significantly rescued PFOS-induced decreases in testosterone secretion and the mRNA and protein expression of the StAR gene in Leydig cells. In summary, the present study highlights the role of the SC-Exo/miR-9-3p/StAR signaling pathway in PFOS-induced suppression of testosterone biosynthesis, advancing our understanding of molecular mechanisms for PFOS-induced male reproductive disorders.

Deep SED-Net with interactive learning for multiple testicular cell types segmentation and cell composition analysis in mouse seminiferous tubules

The development of mouse spermatozoa is a continuous process from spermatogonia, spermatocytes, spermatids to mature sperm. Those developing germ cells (spermatogonia, spermatocyte, spermatids) together with supporting Sertoli cells are all enclosed inside seminiferous tubules of the testis, their identification is key to testis histology and pathology analysis. Automated segmentation of all these cells is a challenging task because of their dynamical changes in different stages. The accurate segmentation of testicular cells is critical in developing computerized spermatogenesis staging. In this paper, we present a novel segmentation model, SED-Net, which incorporates a Squeeze-and-Excitation (SE) module and a Dense unit. The SE module optimizes and obtains features from different channels, whereas the Dense unit uses fewer parameters to enhance the use of features. A human-in-the-loop strategy, named deep interactive learning, is developed to achieve better segmentation performance while reducing the workload of manual annotation and time consumption. Across a cohort of 274 seminiferous tubules from Stages VI to VIII, the SED-Net achieved a pixel accuracy of 0.930, a mean pixel accuracy of 0.866, a mean intersection over union of 0.710, and a frequency weighted intersection over union of 0.878, respectively, in terms of four types of testicular cell segmentation. There is no significant difference between manual annotated tubules and segmentation results by SED-Net in cell composition analysis for tubules from Stages VI to VIII. In addition, we performed cell composition analysis on 2346 segmented seminiferous tubule images from 12 segmented testicular section results. The results provided quantitation of cells of various testicular cell types across 12 stages. The rule reflects the cell variation tendency across 12 stages during development of mouse spermatozoa. The method could enable us to not only analyze cell morphology and staging during the development of mouse spermatozoa but also potientially could be applied to the study of reproductive diseases such as infertility.

Effects of postnatal exposure to tetrabromobisphenol A on testis development in mice and early key events

Whether or not tetrabromobisphenol A (TBBPA) has reproductive developmental toxicity remains controversial. Here, we evaluated the effects of postnatal TBBPA exposure of dams (before weaning) and pups through drinking water (15, 150, 1500 ng/mL) on testis development in mice. On postnatal day (PND) 56, we found that TBBPA exerted little effects on testis weight, anogenital distance, sperm parameters, and the serum testosterone level, but resulted in dose-dependent reductions in the seminiferous tubule area coupled with decreased Sertoli cells and spermatogonia and the number of stage VII-VIII seminiferous tubules, and cytoskeleton damage in Sertoli cells, along with down-regulated expression of marker genes for Sertoli cells, spermatogonia and spermatocyte. Further study revealed that the reduced tubule area coupled decreased Sertoli cell and germ cell numbers and marker gene expression also occurred in TBBPA-treated testes on PND 7, along with reduced cell proliferation and disordered arrangement of Sertoli cell nuclei. On PND 15, most of these testicular alterations were still observed in TBBPA-treated males, and cytoskeleton damage in Sertoli cells became observable. All observations convincingly demonstrate that postnatal exposure to TBBPA disturbed testis development in early life and ultimately caused adverse outcomes in adult testes, and that cell proliferation inhibition, the reduction in the seminiferous tubule area coupled decreased Sertoli cell and germ cell numbers and marker gene expression, and cytoskeleton damage in Sertoli cells, are early events contributing to adverse outcomes in adult testes. Our study improves the understanding of reproductive developmental toxicity of TBBPA, highlighting its risk for human health.

Follicle-stimulating hormone-mediated decline in miR-92a-3p expression in pubertal mice Sertoli cells is crucial for germ cell differentiation and fertility

Sertoli cells (Sc) are the sole target of follicle-stimulating hormone (FSH) in the testis and attain functional maturation post-birth to significantly augment germ cell (Gc) division and differentiation at puberty. Despite having an operational microRNA (miRNA) machinery, limited information is available on miRNA-mediated regulation of Sc maturation and male fertility. We have shown before that miR-92a-3p levels decline in pubertal rat Sc. In response to FSH treatment, the expressions of FSH Receptor, Claudin11 and Klf4 were found to be elevated in pubertal rat Sc coinciding with our finding of FSH-induced decline in miR-92a-3p levels. To investigate the association of miR-92a-3p and spermatogenesis, we generated transgenic mice where such pubertal decline of miR-92a-3p was prevented by its overexpression in pubertal Sc under proximal Rhox5 promoter, which is known to be activated specifically at puberty, in Sc. Our in vivo observations provided substantial evidence that FSH-induced decline in miR-92a-3p expression during Sc maturation acts as an essential prerequisite for the pubertal onset of spermatogenesis. Elevated expression of miR-92a-3p in post-pubertal testes results into functionally compromised Sc, leading to impairment of the blood-testis barrier formation and apoptosis of pre-meiotic Gc, ultimately culminating into infertility. Collectively, our data suggest that regulation of miR-92a-3p expression is crucial for Sc-mediated induction of active spermatogenesis at puberty and regulation of male fertility.

Hmga2 deficiency is associated with allometric growth retardation, infertility, and behavioral abnormalities in mice

The high mobility group AT-hook 2 (HMGA2) protein works as an architectural regulator by binding AT-rich DNA sequences to induce conformational changes affecting transcription. Genomic deletions disrupting HMGA2 coding sequences and flanking noncoding sequences cause dwarfism in mice and rabbits. Here, CRISPR/Cas9 was used in mice to generate an Hmga2 null allele that specifically disrupts only the coding sequence. The loss of one or both alleles of Hmga2 resulted in reduced body size of 20% and 60%, respectively, compared to wild-type littermates as well as an allometric reduction in skull length in Hmga2-/- mice. Both male and female Hmga2-/- mice are infertile, whereas Hmga2+/- mice are fertile. Examination of reproductive tissues of Hmga2-/- males revealed a significantly reduced size of testis, epididymis, and seminal vesicle compared to controls, and 70% of knock-out males showed externalized penis, but no cryptorchidism was observed. Sperm analyses revealed severe oligospermia in mutant males and slightly decreased sperm viability, increased DNA damage but normal sperm chromatin compaction. Testis histology surprisingly revealed a normal seminiferous epithelium, despite the significant reduction in testis size. In addition, Hmga2-/- mice showed a significantly reduced exploratory behavior. In summary, the phenotypic effects in mouse using targeted mutagenesis confirmed that Hmga2 is affecting prenatal and postnatal growth regulation, male reproductive tissue development, and presents the first indication that Hmga2 function is required for normal mouse behavior. No specific effect, despite an allometric reduction, on craniofacial development was noted in contrast to previous reports of an altered craniofacial development in mice and rabbits carrying deletions of both coding and noncoding sequences at the 5' part of Hmga2.

Assessment of Zearalenone-Induced Cell Survival and of Global Gene Regulation in Mouse TM4 Sertoli Cells

Zearalenone (ZEA) is a non-steroidal xenoestrogen mycotoxin produced by many Fusarium fungal species, which are common contaminants of cereal crops destined for worldwide human and animal consumption. ZEA has been reported in various male reproduction dysfonctions, including decreased fertility potential. In this report, the direct effect of ZEA on the immature Sertoli TM4 cell line was evaluated. The results show that high concentrations of ZEA increase reactive oxygen species via the activation of MAPK signaling. Transcriptome analysis was performed on the TM4 cell line treated with ZEA, and genes involved in sex differentiation (Fgfr2, Igf1, Notch1, Sox9) and extracellular matrix (ECM) formation (Ctgf, Fam20a, Fbn1, Mmp9, Postn, Sparcl1, Spp1) were identified at the center of the functional protein association network, suggesting that ZEA could be detrimental to the early steps of Sertoli cell differentiation.

Restoring Impaired Fertility Through Diet: Observations of Switching From High-Fat Diet During Puberty to Normal Diet in Adulthood Among Obese Male Mice

BACKGROUND

Obesity is associated with a decrease in testicular function, yet the effects and mechanisms relative to different stages of sexual development remain unclear. The aim of this study is to determine whether high-fat diet-induced obesity impairs male fertility during puberty and in adulthood, and to ascertain its underlying mechanisms. This study aims to further reveal whether restoring to a normal diet can improve impaired fertility.

METHODS

Male mice were divided into 6 groups: the group N and H exposed to a normal diet or high-fat diet during puberty. The group NN or NH were further maintained a normal diet or exposed to high-fat diet in adulthood, the group HH or HN were further maintained high-fat diet or switched to normal diet in adulthood. Metabolic parameters, fertility parameters, testicular function parameters, TUNEL staining and testicular function-related proteins were evaluated, respectively.

RESULTS

The fertility of the mice in the high-fat diet group was impaired, which validated by declines in pregnancy rates and litter weight loss. Further analysis demonstrated the increased level of oxidative stress, the increased number of spermatogenic cell apoptosis and decreased number of sperm and decreased acrosome integrity. The expression of steroidogenic acute regulatory (StAR) and spermatogenesis related proteins (WT-1) decreased. Fertility among the HN group recovered, accompanied by the recovery of metabolism, fertility and testicular function parameters, StAR and WT-1 expression.

CONCLUSIONS

The findings suggest that high-fat diet-induced obesity impairs male fertility during puberty and in adulthood. The loss of acrosome integrity, the increase of oxidative stress, the increase of cells apoptosis and the down-regulation of StAR and WT-1 may be the underlying mechanisms. Switching from high-fat diets during puberty to normal diets in adulthood can improve male fertility.

Benzophenone-3 breaches mouse Sertoli cell barrier and alters F-actin organization without evoking apoptosis

Benzophenone-3 (BP-3), one of the most commonly utilized ultraviolet filters in personal care products, has aroused public concern in recent years for its high chances of human exposure. Previous studies have found that BP-3 can impair testes development and spermatogenesis, but the targets of BP-3 are still unknown. In this study, primary Sertoli cells from 20-day-old mice were treated in vitro with 0-100 μM BP-3 for 24 h to identify its toxicity on Sertoli cells and Sertoli cell barrier. Results demonstrated that BP-3 could induce a notable change in cell morphology and impair Sertoli cell viability. The analysis of transepithelial electrical resistance showed that the integrity of the Sertoli cell barrier was destroyed by BP-3 (100 μM). Some structural proteins of the barrier including ZO-1, Occludin, and Connexin43 were lower expressed and the localization of basal ectoplasmic specializations protein β-catenin was altered because of BP-3 treatment. Further exploration suggested that BP-3 led to Sertoli cell F-actin disorganization by affecting the expression of Rictor, a key component of the mTORC2 complex. Moreover, although increased DNA damage marker γH2A.X was observed in the treatment group, the cell apoptosis rate was changeless which was further confirmed by increased BAX and stable Bcl-2 (two primary apoptosis regulating proteins). In conclusion, this study revealed that BP-3 had the potential to perturb the Sertoli cell barrier through altered junction proteins and disorganized F-actin, but it could hardly evoke Sertoli cell apoptosis.

Retinoblastoma-E2F Transcription Factor Interplay Is Essential for Testicular Development and Male Fertility

The retinoblastoma (RB) protein family members (pRB, p107 and p130) are key regulators of cell cycle progression, but also play crucial roles in apoptosis, and stem cell self-renewal and differentiation. RB proteins exert their effects through binding to E2F transcription factors, which are essential developmental and physiological regulators of tissue and organ homeostasis. According to the canonical view, phosphorylation of RB results in release of E2Fs and induction of genes needed for progress of the cell cycle. However, there are eight members in the E2F transcription factor family with both activator (E2F1-3a) and repressor (E2F3b-E2F8) roles, highlighting the functional diversity of RB-E2F pathway. In this review article we summarize the data showing that RB-E2F interaction is a key cell-autonomous mechanism responsible for establishment and maintenance of lifelong male fertility. We also review the expression pattern of RB proteins and E2F transcription factors in the testis and male germ cells. The available evidence supports that RB and E2F family members are widely and dynamically expressed in the testis, and they are known to have versatile roles during spermatogenesis. Knowledge of the function and significance of RB-E2F interplay for testicular development and spermatogenesis comes primarily from gene knock-out (KO) studies. Several studies conducted in Sertoli cell-specific pRB-KO mice have demonstrated that pRB-mediated inhibition of E2F3 is essential for Sertoli cell functional maturation and cell cycle exit, highlighting that RB-E2F interaction in Sertoli cells is paramount to male fertility. Similarly, ablation of either pRB or E2F1 in the germline results in progressive testicular atrophy due to germline stem cell (GSC) depletion, emphasizing the importance of proper RB-E2F interplay for germline maintenance and lifelong sperm production. In summary, while balanced RB-E2F interplay is essential for cell-autonomous maintenance of GSCs and, the pRB-E2F3 system in Sertoli cells is critical for providing GSC niche thus laying the basis for spermatogenesis.

circBTBD7 Promotes Immature Porcine Sertoli Cell Growth through Modulating miR-24-3p/MAPK7 Axis to Inactivate p38 MAPK Signaling Pathway

Sertoli cells are the crucial coordinators to guarantee normal spermatogenesis and male fertility. Although circular RNAs (circRNAs) exhibit developmental-stage-specific expression in porcine testicular tissues and have been thought of as potential regulatory molecules in spermatogenesis, their functions and mechanisms of action remain largely unknown, especially in domestic animals. A novel circBTBD7 was identified from immature porcine Sertoli cells using reverse transcription PCR, Sanger sequencing, and fluorescence in situ hybridization assays. Functional assays illustrated that circBTBD7 overexpression promoted cell cycle progression and cell proliferation, as well as inhibited cell apoptosis in immature porcine Sertoli cells. Mechanistically, circBTBD7 acted as a sponge for the miR-24-3p and further facilitated its target mitogen-activated protein kinase 7 (MAPK7) gene. Overexpression of miR-24-3p impeded cell proliferation and induced cell apoptosis, which further attenuated the effects of circBTBD7 overexpression. siRNA-induced MAPK7 deficiency resulted in a similar effect to miR-24-3p overexpression, and further offset the effects of miR-24-3p inhibition. Both miR-24-3p overexpression and MAPK7 knockdown upregulated the p38 phosphorylation activity. The SB202190 induced the inhibition of p38 MAPK pathway and caused an opposite effect to that of miR-24-3p overexpression and MAPK7 knockdown. Collectively, circBTBD7 promotes immature porcine Sertoli cell growth through modulating the miR-24-3p/MAPK7 axis to inactivate the p38 MAPK signaling pathway. This study expanded our knowledge of noncoding RNAs in porcine normal spermatogenesis through deciding the fate of Sertoli cells.

Folpet induces mitochondrial dysfunction and ROS-mediated apoptosis in mouse Sertoli cells

Folpet is a phthalimide type of fungicide and has been used to control several crop diseases. Although it has adverse effects on the gastrointestinal tract, its mechanism and toxic effects on testis have not been demonstrated. In the present study, we elucidated the cytotoxic effect of folpet on the mouse Sertoli cell line, TM4. Our results revealed that folpet suppressed viability and proliferative capacity of TM4 cells and further inhibited 3D spheroid formation. Moreover, folpet impeded appropriate cell cycle progression and induced apoptotic cell death in TM4 cells. It disrupted the electrochemical gradient of mitochondria and calcium homeostasis in TM4 cells. Furthermore, endoplasmic reticulum stress-related proteins were activated in folpet-treated TM4 cells, and relative reactive oxygen species (ROS) production was also increased. N-acetylcysteine (NAC) treatment reinstated the folpet-induced ROS generation in TM4 cells. Additionally, NAC restored the proliferative capacity and reduced the apoptotic cells in folpet-treated TM4 cells. Collectively, we demonstrated that folpet causes ROS-mediated apoptotic cell death with mitochondrial dysfunction and calcium dysregulation in TM4 cells.

miR-126 Controls the Apoptosis and Proliferation of Immature Porcine Sertoli Cells by Targeting the PIK3R2 Gene through the PI3K/AKT Signaling Pathway

Simple Summary

MicroRNAs (miRNAs) have been reported with potential regulatory roles in spermatogenesis. In the present study, we demonstrated that miR-126 can stimulate cell proliferation and restrain the apoptosis of immature porcine Sertoli cells by targeting the PIK3R2 gene. Through this process, miR-126 further activates the PI3K/AKT signaling pathway. These results indicated that miR-126, PIK3R2, and the PI3K/AKT signaling pathway might play pivotal regulatory roles in porcine spermatogenesis by deciding the destiny of immature Sertoli cells.

Abstract

The quantity of Sertoli cells in the adult testis decides the daily gamete formation, and accumulating evidence indicates that epigenetic factors regulate the proliferation of Sertoli cells. Research on the function and regulatory mechanism of microRNAs (miRNAs) in Sertoli cells has not been comprehensive yet, especially on domestic animals. In this article, we report that miR-126 controls the proliferation and apoptosis of immature porcine Sertoli cells based on previous studies. Our results confirmed that miR-126 elevation promotes cell cycle progression, cell proliferation and represses cell apoptosis; on the contrary, the inhibitory effects of miR-126 result in the opposite. The phosphoinositide-3-kinase regulatory subunit 2 (PIK3R2) gene, a member of the PI3K family, was verified as a direct target of miR-126 using the dual-luciferase reporter analysis. miR-126 negatively regulated the mRNA and protein expression level of PIK3R2 in immature porcine Sertoli cells. siRNA-induced PIK3R2 inhibition caused similar effects as miR-126 overexpression and eliminated the influences of miR-126 knockdown in immature porcine Sertoli cells. In addition, both miR-126 overexpression and PIK3R2 inhibition elevated the phosphorylation of PI3K and AKT, whereas the miR-126 knockdown demonstrated the contrary result. In short, miR-126 controls the proliferation and apoptosis of immature porcine Sertoli cells by targeting the PIK3R2 gene through the PI3K/AKT signaling pathway. The research supplies a theoretical and practical foundation for exploring the functional parts of miR-126 in swine sperm by defining the destiny of immature Sertoli cells.

Maternal Nutrition and Developmental Programming of Male Progeny

Simple Summary

The objective of the following review is to describe available literature on the interaction between maternal nutrition and developmental programming in male offspring. The majority of current research focuses on female offspring or fails to take offspring sex into account, though sexual dimorphisms in response to maternal diet are well-recognized. This leaves a large gap in the understanding of male developmental programming. This review will specifically discuss the impacts of maternal dietary energy and protein on bull and ram growth, development, and reproductive capacity in later life.

Abstract

Poor maternal nutrition can cause several maladaptive phenotypes in exposed offspring. While non-sex-specific and female-specific adaptations are well-documented, male-specific outcomes are still poorly understood. Of particular interest are the outcomes in bulls and rams, as developmental programming directly impacts long-term productivity of the animal as well as human food security. The following review discusses the impact of poor maternal dietary energy and protein on bull and ram developmental programming as it relates to growth, development, and reproductive capacity. The review also highlights the importance of the timing of maternal dietary insult, as early-, mid-, and late-gestational insults can all have varying effects on offspring.

MicroRNA-125a-5p modulates the proliferation and apoptosis of TM4 Sertoli cells by targeting RAB3D and regulating the PI3K/AKT signaling pathway

Sertoli cells are cells that provide protection and nutrition for developing sperm. Each stage of sperm development occurs on the surface of Sertoli cells. MicroRNA (MiR)-125a-5p is involved in male reproduction. The current research aimed to probe the role of miR-125a-5p in Sertoli cell function. Functionally, miR-125a-5p knockdown facilitated Sertoli cell proliferation, while miR-125a-5p overexpression suppressed Sertoli cell proliferation, as evidenced by 5-ethynyl-20-deoxyuridine incorporation assay. Additionally, miR-125a-5p knockdown inhibited Sertoli cell apoptosis, while miR-125a-5p upregulation facilitated Sertoli cell apoptosis, as evidenced by flow cytometry analysis. Computationally, we identified four predicted mRNA targets of miR-125a-5p. Based on the results of luciferase reporter assay, miR-125a-5p was confirmed to bind to the predicted sequence in the Ras-related protein Rab-3D (RAB3D) 3'UTR. Rescue experiments showed that miR-125a-5p suppressed the proliferative ability of TM4 Sertoli cells and facilitated their apoptosis by targeting RAB3D. Finally, our data confirmed that miR-125a-5p and RAB3D modulated activation of the PI3K/AKT pathway. In conclusion, our data showed that miR-125a-5p regulated Sertoli cell proliferation and apoptosis by targeting RAB3D and regulating the PI3K/AKT pathway.

Persistence of undifferentiated spermatogonia in aged Japanese Black cattle

Aging is a major risk factor for spermatogenesis deterioration. However, the influence of age on spermatogenic stem cells and their progenitors in bulls is largely unknown. Here, we report age‐related changes in undifferentiated and differentiating spermatogonia in Japanese Black cattle with nearly constant sperm output, by using spermatogonial markers. The numbers of differentiating spermatogonia and more differentiated spermatogenic cells were significantly decreased in aged bovine testes compared with those in young testes. In contrast, the number of undifferentiated spermatogonia was maintained, and their proliferative activity did not differ significantly between young and aged bovine testes. Although severe calcification was only observed to a small extent in aged testes, fewer Sertoli cells and interstitial fibrosis were observed in noncalcified testicular regions. These results suggest that, even in old bulls with nearly constant sperm output, testicular spermatogenic activity declined whereas undifferentiated spermatogonia numbers were maintained. Thus, we propose that undifferentiated spermatogonia may be resistant to age‐related changes in bovine testes. Because undifferentiated spermatogonia may contain stem cell activity, our findings highlight the potential utility of undifferentiated spermatogonia as an agricultural resource to produce spermatozoa beyond the natural bovine lifetime through transplantation and in vitro spermatogenesis in future animal production.

Sertoli cells as key drivers of testis function

Sertoli cells are the orchestrators of spermatogenesis; they support fetal germ cell commitment to the male pathway and are essential for germ cell development, from maintenance of the spermatogonial stem cell niche and spermatogonial populations, through meiosis and spermiogeneis and to the final release of mature spermatids during spermiation. However, Sertoli cells are also emerging as key regulators of other testis somatic cells, including supporting peritubular myoid cell development in the pre-pubertal testis and supporting the function of the testicular vasculature and in contributing to testicular immune privilege. Sertoli cells also have a major role in regulating androgen production within the testis, by specifying interstitial cells to a steroidogenic fate, contributing to androgen production in the fetal testis, and supporting fetal and adult Leydig cell development and function. Here, we provide an overview of the specific roles for Sertoli cells in the testis and highlight how these cells are key drivers of testicular sperm output, and of adult testis size and optimal function of other testicular somatic cells, including the steroidogenic Leydig cells.

Effect of Wuzi Yanzong Pills on Sertoli cells and blood-testis barrier in heat-stressed rats based on Akt signalling pathway

The blood-testis barrier (BTB) of Sertoli cells (SCs) is an important biological barrier that maintains spermatogenesis and provides a favourable microenvironment for spermatogenesis. However, heat stress can directly damage the BTB structural proteins of testicular SCs, leading to dyszoospermia. Wuzi Yanzong Pills (WYP) is a traditional Chinese medicine formula used to treat male reproductive diseases. However, whether WYP could ameliorate heat stress injury in primary SCs extracted from rat testes and BTB proteins remains unknown. Here, treatment with WYP (low, medium and high dose) increased the SC viability and the proliferation of cell antigen Ki67 significantly. Additionally, it promoted SC maturation, which presented in the form of increased androgen receptors (ARs) and decreased cytokeratin 18 (CK-18) in three WYP dose groups. WYP upregulated BTB proteins such as zonula occludens 1 (ZO-1) and occludin across all WYP groups and decreased phosphorylated Akt (p-Akt) in the middle and high-dose groups; however, ZO-1 and occludin recovery were reduced with the presence of Akt inhibitor in WYP groups. WYP improved SC viability and proliferation, and ameliorated dedifferentiation and BTB-proteins damaged by heat stress via Akt signalling. The findings present theoretical support for the effects of WYP in the management of dyszoospermia and male infertility.

Review of Sertoli cell dysfunction caused by COVID-19 that could affect male fertility

Spermatogenesis is a complex and elaborate differentiation process and is vital for male fertility. Sertoli cells play a major role in fertility and induce spermatogenesis by protecting, nourishing, and supporting germ cells. It has been speculated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could directly affect the male reproductive system, and therefore heredity and fertility. The similarity of SARS-CoV-2 to SARS-CoV could confirm this hypothesis because both viruses use angiotensin-converting enzyme (ACE2) as the receptor to enter human cells. ACE2 is expressed by Sertoli cells and other testicular cells, therefore COVID-19 has the potential to impair fertility by destroying Sertoli cells. This hypothesis should be evaluated and confirmed by monitoring fertility in patients with COVID-19.

Effective isolation of Sertoli cells from New Zealand rabbit testis

Objective:

Sertoli cells (SCs) are important sustentacular cells in the seminiferous tubules of the testis. Isolation and identification of SCs are the premise for studying their functions. Since New Zealand rabbit is a stable strain which is widely used for biomedical research and animal farming, this study aimed to develop a simple and effective protocol for SC isolation in New Zealand rabbits.

Materials and Methods:

The SCs of three 30-day-old New Zealand rabbits were isolated by incubation with enzymatic digestion I (Dulbecco’s modified Eagle medium supplemented with 1 mg/ml collagenase IV and 50 μg/ml DNase I) and digestion II (digestion I + 1 mg/ml hyaluronidase + 1 mg/ml trypsin), as well as differential plating. The cells were enriched and identified by using immunocytochemical staining and reverse transcription polymerase chain reaction analysis.

Results:

Homogeneous cells were obtained. They presented the typical large cell body and an irregular pyramidal shape after differential plating and passaging. These cells expressed mRNA of the SC marker sex-determining region Y-box 9 (SOX9) instead of the Leydig cell marker StAR. Immunocytochemically, they are positive of SOX9, GATA binding protein 4, and androgen-binding protein.

Conclusion:

The SCs were enriched from the testicular tissues of prepubertal New Zealand rabbits by a simple and effective protocol, which provides a basis for further theoretical researches and practical applications.

Sertoli cell-derived exosome-mediated transfer of miR-145-5p inhibits Leydig cell steroidogenesis by targeting steroidogenic factor 1

In the mammalian testis, two distinct populations of Sertoli cells (SCs), the immature SCs (ISCs) and adult SCs (ASCs), play significant roles in regulating the development and function of Leydig cells. However, the effect of different SC types on the function of Leydig cells is poorly understood. Here, our study showed that miR-145-5p expression was significantly different in SCs at different stages, with the highest expression observed in ISCs. Exosomes mediate the transfer of miR-145-5p from ISCs to Leydig cells. Overexpression of miR-145-5p in Leydig cells significantly downregulated steroidogenic gene expression and inhibited testosterone synthesis. Additionally, miR-145-5p functioned by directly targeted steroidogenic factor-1 (Sf-1) and downregulated the expression of SF-1, which further downregulated the expression of steroidogenic genes, induced accumulation of lipid droplets, and eventually suppressed testosterone production. These findings demonstrate that SC-derived miR-145-5p plays a significant role in regulating the functions of Leydig cells and may therefore serve as a diagnostic biomarker for male hypogonadism developmental abnormalities during puberty.