Regulation of meiotic progression by Sertoli-cell androgen signaling

A multi-omics approach reveals that lotus root polysaccharide iron ameliorates iron deficiency-induced testicular damage by activating PPARγ to promote steroid hormone synthesis

Iron deficiency is a common nutritional issue that seriously affects male reproductive health. Lotus root polysaccharide iron (LRPF), a novel nutritional supplement, may ameliorate the damage caused by iron deficiency, however, the mechanism is unclear. In this study, we comprehensively determined the benefits of LRPF on reproduction in iron-deficient mice by integrating transcriptomics, microbiomics and serum metabolomics. Microbiomics showed that LRPF could restore changes to the intestinal microbiota caused by iron deficiency. Metabolomics results showed that LRPF stabilised steroid hormone and fatty acid metabolism in iron-deficient mice, reduced the content of ethyl chrysanthemumate (EC) and ameliorated the reproductive impairment. The transcriptomic analysis showed that LRPF regulated steroid hormone synthesis and the peroxisome proliferator-activated receptor (PPAR) signalling pathway in iron-deficient mice. In vitro experiments showed that LRPF could promote steroid hormone synthesis in Leydig cells by activating PPARγ. In conclusion, this study highlights the advantage of LRPF to improve testicular development.

Understanding testicular single cell transcriptional atlas: from developmental complications to male infertility

Spermatogenesis is a multi-step biological process where mitotically active diploid (2n) spermatogonia differentiate into haploid (n) spermatozoa via regulated meiotic programming. The alarming rise in male infertility has become a global concern during the past decade thereby demanding an extensive profiling of testicular gene expression. Advancements in Next-Generation Sequencing (NGS) technologies have revolutionized our empathy towards complex biological events including spermatogenesis. However, despite multiple attempts made in the past to reveal the testicular transcriptional signature(s) either with bulk tissues or at the single-cell, level, comprehensive reviews on testicular transcriptomics and associated disorders are limited. Notably, technologies explicating the genome-wide gene expression patterns during various stages of spermatogenic progression provide the dynamic molecular landscape of testicular transcription. Our review discusses the advantages of single-cell RNA-sequencing (Sc-RNA-seq) over bulk RNA-seq concerning testicular tissues. Additionally, we highlight the cellular heterogeneity, spatial transcriptomics, dynamic gene expression and cell-to-cell interactions with distinct cell populations within the testes including germ cells (Gc), Sertoli cells (Sc), Peritubular cells (PTc), Leydig cells (Lc), etc. Furthermore, we provide a summary of key finding of single-cell transcriptomic studies that have shed light on developmental mechanisms implicated in testicular disorders and male infertility. These insights emphasize the pivotal roles of Sc-RNA-seq in advancing our knowledge regarding testicular transcriptional landscape and may serve as a potential resource to formulate future clinical interventions for male reproductive health.

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.

Fluorochloridone induces mitochondrial dysfunction and apoptosis in primary goat Sertoli cells

Fluorochloridone (FLC), a pyrrolidone herbicide, has been recognized as a hazardous chemical. The in vitro adverse effects of FLC on the reproduction of livestock have not been assessed. This study was conducted to explore the cytotoxicity and toxicological mechanisms of FLC on cultured goat Sertoli cells. The results showed that FLC exposure significantly decreased goat Sertoli cell viability (p < 0.05) and induced oxidative stress. And FLC treatment promoted apoptosis and initiation of autophagy. Interestingly, FLC inhibited lysosomal biogenesis and blocked autophagic flux in goat Sertoli cells. The expression levels of autophagy-related proteins Atg5, LC3II, and p62 were significantly increased (p < 0.05) in FLC-treated goat Sertoli cells compared with the control. Importantly, FLC-induced ROS accumulation further causes mitochondrial dysfunction and disturbs mitophagy. FLC significantly decreased (p < 0.05) the expression levels of OPA1, MFN2, p-Drp1, FIS1, PINK1, and Parkin in goat Sertoli cells. Moreover, pretreatment with N-acetyl-l-cysteine (NAC, an antioxidant) significantly reduced (p < 0.01) FLC-induced ROS accumulation and reversed the disorder of autophagy levels. Our results indicated that FLC-induced toxicity in primary goat Sertoli cells was characterized by ROS accumulation, inducing oxidative stress, inhibiting lysosomal biogenesis, blocking autophagic flux, and promoting mitochondrial dysfunction, resulting in apoptosis via the mitochondrial pathway.

Steroid hormone signaling: multifaceted support of testicular function

Embryonic development and adult physiology are dependent on the action of steroid hormones. In particular, the reproductive system is reliant on hormonal signaling to promote gonadal function and to ensure fertility. Here we will describe hormone receptor functions and their impacts on testicular function, focusing on a specific group of essential hormones: androgens, estrogens, progesterone, cortisol, and aldosterone. In addition to focusing on hormone receptor function and localization within the testis, we will highlight the effects of altered receptor signaling, including the consequences of reduced and excess signaling activity. These hormones act through various cellular pathways and receptor types, emphasizing the need for a multifaceted research approach to understand their critical roles in testicular function. Hormones exhibit intricate interactions with each other, as evidenced, for example, by the antagonistic effects of progesterone on mineralocorticoid receptors and cortisol's impact on androgens. In light of research findings in the field demonstrating an intricate interplay between hormones, a systems biology approach is crucial for a nuanced understanding of this complex hormonal network. This review can serve as a resource for further investigation into hormonal support of male reproductive health.

Meiosis-mediated reproductive toxicity by fenitrothion in Caenorhabditis elegans from metabolomic perspective

Fenitrothion (FNT), an organophosphorus insecticide, is widely detected in the living environment. The reproductive and endocrine toxicity of FNT to biological communities has been ever reported, but potential mechanism and reproductive toxicity dose effect remain unclear. In our study, we constructed Caenorhabditis elegans model to analyze the reproductive toxicity mechanism of FNT based on metabolomics and evaluated its reproductive toxicity dose effect using benchmark dose (BMD)method. Our results showed that FNT exposure significantly reduced brood size, number of germ cells, and delayed gonadal development in nematodes. Non-targeted metabolomics revealed that FNT exposure caused significant metabolic disturbances in nematodes, leading to a significant reduction in the synthesis of cortisol and melatonin, and the latter played a mediating role in the effects of FNT on number of germ cells. We further found that the levels of these two hormones were significantly negative correlated with the expression of the androgen receptor nhr-69 and affected the meiosis of germ cells by regulating the nhr-69/ fbf-1/2 /gld-3 /fog-1/3 pathway. Meanwhile, the study found the BMDL10s for N2 and him-5 mutant were 0.411 μg/L by number of germ cells and 0.396 μg/L by number of germ cells in the meiotic zone, respectively, providing a more protective reference dose for ecological risk assessment of FNT. This study suggested that FNT can affect androgen receptor expression by inhibiting cortisol and melatonin secretion, which further mediate the meiotic pathway to affect sperm formation and exert reproductive toxicity, and provides a basis for setting reproductive toxicity limits for FNT.

Male infertility and gonadotropin treatment: What can we learn from real-world data?

Gonadotropin therapy to treat specific male infertility disorders associated with hypogonadotropic hypogonadism is evidence-based and effective in restoring spermatogenesis and fertility. In contrast, its use to improve fertility in men with idiopathic oligozoospermia or nonobstructive azoospermia remains controversial, despite being widely practiced. The existence of two major inter-related pathways for spermatogenesis, including FSH and intratesticular testosterone, provides a rationale for empiric hormone stimulation therapy in both eugonadal and hypogonadal males with idiopathic oligozoospermia or nonobstructive azoospermia. Real-world data (RWD) on gonadotropin stimulating for these patient subsets, mainly using human chorionic gonadotropin and follicle-stimulating hormone, accumulated gradually, showing a positive therapeutic effect in some patients, translated by increased sperm production, sperm quality, and sperm retrieval rates. Although more evidence is needed, current insights from RWD research indicate that selected male infertility patients might be managed more effectively using gonadotropin therapy, with potential gains for all parties involved.

Functions of Steroid Hormones in the Male Reproductive Tract as Revealed by Mouse Models

Steroid hormones are capable of diffusing through cell membranes to bind with intracellular receptors to regulate numerous physiological processes. Three classes of steroid hormones, namely androgens, estrogens and glucocorticoids, contribute to the development of the reproductive system and the maintenance of fertility. During the past 30 years, mouse models have been produced in which the expression of genes encoding steroid hormone receptors has been enhanced, partially compromised or eliminated. These mouse models have revealed many of the physiological processes regulated by androgens, estrogens and to a more limited extent glucocorticoids in the testis and male accessory organs. In this review, advances provided by mouse models that have facilitated a better understanding of the molecular regulation of testis and reproductive tract processes by steroid hormones are discussed.

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.

The potential of sertoli cells (SCs) derived exosomes and its therapeutic efficacy in male reproductive disorders

In the male reproductive system, seminiferous tubules in testis are lined by a complex stratified epithelium containing two distinct populations of cells, spermatogenic cells that develop into spermatozoa, and sertoli cells (SCs) that mainly support and nourish spermatogenic cell lineage as well as exerting powerful effect on men reproductive capacity. Different varieties of proteins, hormones, exosomes and growth factors are secreted by SCs. There are different kinds of junctions found between SCs called BTB. It was elucidated that complete absence of BTB or its dysfunction leads to infertility. To promote spermatogenesis, crosstalk of SCs with spermatogenic cells plays an important role. The ability of SCs to support germ cell productivity and development is related to its various products carrying out several functions. Exosomes (EXOs) are one of the main EVs with 30-100 nm size generating from endocytic pathway. They are produced in different parts of male reproductive system including epididymis, prostate and SCs. The most prominent characteristics of SC-based exosomes is considered mutual interaction of sertoli cells with spermatogonial stem cells and Leydig cells mainly through establishment of intercellular communication. Exosomes have gotten a lot of interest because of their role in pathobiological processes and as a cell free therapy which led to developing multiple exosome isolation methods based on different principles. Transmission of nucleic acids, proteins, and growth factors via SC-based exosomes and exosomal miRNAs are proved to have potential to be valuable biomarkers in male reproductive disease. Among testicular abnormalities, non-obstructive azoospermia and testicular cancer have been more contributed with SCs performance. The identification of key proteins and miRNAs involved in the signaling pathways related with spermatogenesis, can serve as diagnostic and regenerative targets in male infertility.

Decoding the Spermatogenesis Program: New Insights from Transcriptomic Analyses

Spermatogenesis is a complex differentiation process coordinated spatiotemporally across and along seminiferous tubules. Cellular heterogeneity has made it challenging to obtain stage-specific molecular profiles of germ and somatic cells using bulk transcriptomic analyses. This has limited our ability to understand regulation of spermatogenesis and to integrate knowledge from model organisms to humans. The recent advancement of single-cell RNA-sequencing (scRNA-seq) technologies provides insights into the cell type diversity and molecular signatures in the testis. Fine-grained cell atlases of the testis contain both known and novel cell types and define the functional states along the germ cell developmental trajectory in many species. These atlases provide a reference system for integrated interspecies comparisons to discover mechanistic parallels and to enable future studies. Despite recent advances, we currently lack high-resolution data to probe germ cell-somatic cell interactions in the tissue environment, but the use of highly multiplexed spatial analysis technologies has begun to resolve this problem. Taken together, recent single-cell studies provide an improvedunderstanding of gametogenesis to examine underlying causes of infertility and enable the development of new therapeutic interventions.

Cypermethrin inhibits proliferation of Sertoli cells through AR involving DAB2IP/PI3K/AKT signaling pathway in vitro

Cypermethrin (CP) exhibits anti-androgenic effects through antagonism on androgen receptor (AR) activation. This study was to identify whether AR-mediated disabled 2 interacting protein (DAB2IP)/phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway was involved in CP-induced mouse Sertoli cells (TM4) proliferation disorder. Real-Time Cell Analysis-iCELLigence system was to measure cell proliferation. Bioinformatic analyses were performed to identify AR-regulated genes. Quantitative Real-Time PCR and western blot were to detect the genes and proteins levels in AR-mediated DAB2IP/PI3K/AKT pathway. Results showed CP suppressed TM4 proliferation and the expression of AR. Activation of AR restored the inhibition efficacy of CP on TM4 proliferation. AR regulated DAB2IP expression and phosphorylation levels of PI3K and AKT in CP-exposed TM4 cells. In addition, knockdown of DAB2IP alleviated the inhibition efficacy of CP on cell proliferation and phosphorylation of PI3K and AKT. Taken together, AR was a modulator in CP-induced inhibition of Sertoli cells proliferation by negatively regulating DAB2IP/PI3K/AKT signaling pathway. The study may provide a new insight for the mechanisms of male reproductive toxicity induced by CP.

Flurochloridone Induced Cell Apoptosis via ER Stress and eIF2α-ATF4/ATF6-CHOP-Bim/Bax Signaling Pathways in Mouse TM4 Sertoli Cells

Flurochloridone (FLC), as a novel herbicide, has been widely used in many countries since 1980s. Current studies have shown that FLC has toxic effects on male reproduction and its target organ is testis, while the underlying mechanism is still unknown. Mouse testis Sertoli cell line TM4 cells were used as an in vitro model and treated with FLC at different doses (40, 80, 160 μM) for different times (6, 12, 24 h). Cell viability, cytotoxicity and apoptotic cells were detected by CCK-8 assay, LDH leakage assay and flow cytometry. The protein levels of GRP78, phosphorylated-eIF2α, ATF4, ATF6, CHOP, Bim and Bax were observed by Western Blot and Immunofluorescence staining. FLC inhibited cell viability and induced cytotoxicity in dose-dependent way in TM4 cells. The percentage of apoptotic cells were 6.2% ± 0.6%, 7.3% ± 0.3%, 9.8% ± 0.4%, 13.2% ± 0.2%, respectively. The expression levels of ER stress and UPR related proteins were activated over dose. Meanwhile, the pro-apoptotic proteins (Bim and Bax) were also up-regulated in dose-dependent. After pretreated with ISRIB, the inhibitor of eIF2α phosphorylation, the elevated expression of GRP78, phosphorylated-eIF2α, ATF4, ATF6, CHOP and Bim was down to normal level accordingly. In conclusion, FLC induced apoptosis in TM4 cells mediated by UPR signaling pathways.

What Does Androgen Receptor Signaling Pathway in Sertoli Cells During Normal Spermatogenesis Tell Us?

Androgen receptor signaling pathway is necessary to complete spermatogenesis in testes. Difference between androgen binding location in Sertoli cell classifies androgen receptor signaling pathway into classical signaling pathway and non-classical signaling pathway. As the only somatic cell type in seminiferous tubule, Sertoli cells are under androgen receptor signaling pathway regulation via androgen receptor located in cytoplasm and plasma membrane. Androgen receptor signaling pathway is able to regulate biological processes in Sertoli cells as well as germ cells surrounded between Sertoli cells. Our review will summarize the major discoveries of androgen receptor signaling pathway in Sertoli cells and the paracrine action on germ cells. Androgen receptor signaling pathway regulates Sertoli cell proliferation and maturation, as well as maintain the integrity of blood-testis barrier formed between Sertoli cells. Also, Spermatogonia stem cells achieve a balance between self-renewal and differentiation under androgen receptor signaling regulation. Meiotic and post-meiotic processes including Sertoli cell - Spermatid attachment and Spermatid development are guaranteed by androgen receptor signaling until the final sperm release. This review also includes one disease related to androgen receptor signaling dysfunction named as androgen insensitivity syndrome. As a step further ahead, this review may be conducive to develop therapies which can cure impaired androgen receptor signaling in Sertoli cells.

Updates in Sertoli Cell-Mediated Signaling During Spermatogenesis and Advances in Restoring Sertoli Cell Function

Since their initial description by Enrico Sertoli in 1865, Sertoli cells have continued to enchant testis biologists. Testis size and germ cell carrying capacity are intimately tied to Sertoli cell number and function. One critical Sertoli cell function is signaling from Sertoli cells to germ cells as part of regulation of the spermatogenic cycle. Sertoli cell signals can be endocrine or paracrine in nature. Here we review recent advances in understanding the interplay of Sertoli cell endocrine and paracrine signals that regulate germ cell state. Although these findings have long-term implications for treating male infertility, recent breakthroughs in Sertoli cell transplantation have more immediate implications. We summarize the surge of advances in Sertoli cell ablation and transplantation, both of which are wedded to a growing understanding of the unique Sertoli cell niche in the transitional zone of the testis.

Effect of androgens on Sertoli cell maturation in human testis from birth to puberty

Background

Androgens are well known to be necessary for spermatogenesis. The purpose of this study was to determine Sertoli cell responsiveness to androgens according to age from birth to puberty.

Results

Testicular tissue samples were studied in a population of 84 control boys classified into seven groups according to age: group 1 (1–30 days), group 2 (1–3 months), group 3 (3–6 months), group 4 (0.5–3 years), group 5 (3–6 years), group 6 (6–12 years), and group 7 (12–16 years). We compared these data with those of 2 situations of pathology linked to androgens: 1/premature secretion of testosterone: 4 cases of Leydig cell tumor (LCT) in childhood; and 2 /defect of androgen receptors (AR): 4 cases of complete form of insensitivity to androgen syndrome (CAIS). In control boys, AR immunoreactivity (ir) in Sertoli cells appeared between 4.6 and 10.8 years of age, Anti-Mullerian Hormone (AMH) ir in Sertoli cells disappeared between 9.2 and 10.2 years of age. Connexin 43 (Cx43) ir in Sertoli cells and histological features of the onset of spermatogenesis appeared between 10.8 and 13,8 years of age. Cx43 ir was significantly higher in 12–16 year-olds than in younger boys. In case of CAIS, no spermatogenesis was observed, both AR and Cx43 ir were undetectable and AMH ir was elevated in Sertoli cells even at pubertal age. In the vicinity of LCTs, spermatogenesis occurred and both AR and Cx43 ir were strongly positive and AMH ir in Sertoli cells was low for age.

Conclusions

Androgen action on Sertoli cells is required for onset of spermatogenesis and premature androgen secretion by LCT can induce spermatogenesis in the vicinity of the tumor. AR ir appeared earlier than onset of spermatogenesis, with large interindividual variability. The timing and mechanisms of Sertoli cell responsiveness to androgens are important issues for understanding the induction of spermatogenesis at puberty.

Single-Cell RNA Sequencing Defines the Regulation of Spermatogenesis by Sertoli-Cell Androgen Signaling

Androgen receptor (AR) signaling is essential for maintaining spermatogenesis and male fertility. However, the molecular mechanisms by which AR acts between male germ cells and somatic cells during spermatogenesis have not begun to be revealed until recently. With the advances obtained from the use of transgenic mice lacking AR in Sertoli cells (SCARKO) and single-cell transcriptomic sequencing (scRNA-seq), the cell specific targets of AR action as well as the genes and signaling pathways that are regulated by AR are being identified. In this study, we collected scRNA-seq data from wild-type (WT) and SCARKO mice testes at p20 and identified four somatic cell populations and two male germ cell populations. Further analysis identified that the distribution of Sertoli cells was completely different and uncovered the cellular heterogeneity and transcriptional changes between WT and SCARKO Sertoli cells. In addition, several differentially expressed genes (DEGs) in SCARKO Sertoli cells, many of which have been previously implicated in cell cycle, apoptosis and male infertility, have also been identified. Together, our research explores a novel perspective on the changes in the transcription level of various cell types between WT and SCARKO mice testes, providing new insights for the investigations of the molecular and cellular processes regulated by AR signaling in Sertoli cells.

Male fertility in mice requires classical and nonclassical androgen signaling

Molecular mechanisms by which androgens signal through the androgen receptor (AR) to maintain male fertility are poorly understood. Transgenic mice were produced expressing mutant ARs that can only (1) alter gene transcription through the classical response pathway (AR-C) or (2) activate kinase signaling cascades via the nonclassical pathway (AR-NC). AR-C is sufficient to produce sperm and fertility. Haploid germ cell production, the blood-testis barrier, and spermatid migration are supported by AR-NC. Gene expression essential for chromosome synapsis during meiosis requires AR-C. We identify targets of androgen signaling required for male fertility and provide a mechanistic explanation for meiotic germ cell arrest in the absence of androgen signaling. Prostate differentiation occurs with AR-C alone, but full development requires synergistic nonclassical signaling. Both AR signaling pathways are necessary for normal male reproductive tract development and function, validating our mouse models for studies of AR functions in other target tissues.

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.

Nonclassical androgen and estrogen signaling is essential for normal spermatogenesis

Signaling by androgens through androgen receptor (AR) is essential to complete spermatogenesis in the testis. Similarly, loss of the main estrogen receptor, estrogen receptor 1 (ESR1; also known as ERα), results in male infertility, due in part to indirect deleterious effects on the seminiferous epithelium and spermatogenesis. Effects of steroid hormones are induced primarily through genomic changes induced by hormone-mediated activation of their intracellular receptors and subsequent effects on nuclear gene transcription. However, androgens and estrogens also signal through rapid nonclassical pathways involving actions initiated at the cell membrane. Here we review the data that nonclassical androgen and estrogen signaling pathways support processes essential for male fertility in the testis and reproductive tract. The recent development of transgenic mice lacking nonclassical AR or ESR1 signaling but retaining genomic nuclear signaling has provided a powerful tool to elucidate the function of nonclassical signaling in the overall response to androgens and estrogens. Results from these mice have emphasized that nonclassical signaling is essential for full responses to these hormones, and absence of either nonclassical or classical AR or ESR1 pathways produces abnormalities in spermatogenesis and the male reproductive tract. Although additional work is required to fully understand how classical and nonclassical receptor signaling synergize to produce full steroid hormone responses, here we summarize the known physiological functions of the classical and nonclassical androgen and estrogen signaling pathways in the testis and reproductive tract.

Meiosis-specific ZFP541 repressor complex promotes developmental progression of meiotic prophase towards completion during mouse spermatogenesis

During spermatogenesis, meiosis is accompanied by a robust alteration in gene expression and chromatin status. However, it remains elusive how the meiotic transcriptional program is established to ensure completion of meiotic prophase. Here, we identify a protein complex that consists of germ-cell-specific zinc-finger protein ZFP541 and its interactor KCTD19 as the key transcriptional regulators in mouse meiotic prophase progression. Our genetic study shows that ZFP541 and KCTD19 are co-expressed from pachytene onward and play an essential role in the completion of the meiotic prophase program in the testis. Furthermore, our ChIP-seq and transcriptome analyses identify that ZFP541 binds to and suppresses a broad range of genes whose function is associated with biological processes of transcriptional regulation and covalent chromatin modification. The present study demonstrates that a germ-cell specific complex that contains ZFP541 and KCTD19 promotes the progression of meiotic prophase towards completion in male mice, and triggers the reconstruction of the transcriptional network and chromatin organization leading to post-meiotic development.

Expression Analysis of Circular RNAs in Young and Sexually Mature Boar Testes

Simple Summary

Circular RNAs are novel long non-coding RNA involved in the regulation of gene expression. Recently, the expression of circRNAs was characterized in testes of humans and bulls. However, the profiling of circRNAs and their potential biological functions in boar testicular development are yet to be known. In this study we characterized expression and biological roles of circRNAs in piglet (30 d) and adult (210 d) boar testes by high-throughput sequencing. We identified a large number of circRNAs during testicular development, of which 2326 circRNAs exhibited a significantly differential expression. Gene ontology analysis revealed that these differential expressed circRNAs might be involved in regulating spermatogenesis and hormone biosynthesis. Overall, the results indicate that circRNAs are abundantly expressed in boar testes and exhibit dynamic changes during testicular development. These findings will enable the provision of potential molecular markers for both breeding of elite boars and evaluating developmental status of boar testes.

Abstract

Testicular development is critical for male animals’ reproduction and is tightly regulated by epigenetic factors. Circular RNAs (circRNAs) were recently identified in the testes of humans and bulls. However, the expression profile of circRNAs and their potential biological functions in boar testicular development remain unclear. We identified 34,521 and 31,803 circRNAs in piglet (30 d) and adult (210 d) boar testes by high-throughput sequencing, respectively. Bioinformatics analysis revealed that these circRNAs are widely distributed on autosomes and sex chromosomes. Some of the host genes can generate multiple circRNAs. A total of 2326 differentially expressed circRNAs (DECs) derived from 1526 host genes was found in testicular development, of which 1003 circRNAs were up-regulated in adult boar testes and 1323 circRNAs were down-regulated. Furthermore, gene ontology analysis of host genes of DECs revealed that these circRNAs are mainly involved in regulating spermatogenesis, cilia motility, and hormone biosynthesis. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that the DECs are markedly enriched to stem cell pluripotency regulation, tight junctions, adhesion junctions, and cAMP signaling pathway. These results indicate that circRNAs are abundantly expressed in boar testes and exhibit dynamic changes during testicular development.

Hormonal Treatment of Men with Nonobstructive Azoospermia: What Does the Evidence Suggest?

Hormonal stimulation of spermatogenesis prior to surgery has been tested by some authors to maximize the sperm retrieval yield in patients with nonobstructive azoospermia. Although the rationale of such an approach is theoretically sound, studies have provided conflicting results, and there are unmet questions that need to be addressed. In the present narrative review, we reviewed the current knowledge about the hormonal control of spermatogenesis, the relationship between presurgical serum hormones levels and sperm retrieval rates, and the results of studies investigating the effect of hormonal treatments prior to microdissection testicular sperm extraction. We pooled the available data about sperm retrieval rate in patients with low vs. normal testosterone levels, and found that patients with normal testosterone levels had a significantly higher chance of successful sperm retrieval compared to those with subnormal T levels (OR 1.63, 95% CI 1.08–2.45, p = 0.02). These data suggest that hormonal treatment may be justified in patients with hypogonadism; on the other hand, the available evidence is insufficient to recommend hormonal therapy as standard clinical practice to improve the sperm retrieval rate in patients with nonobstructive azoospermia.

AR regulates porcine immature Sertoli cell growth via binding to RNF4 and miR-124a

Sertoli cells are the only somatic cells in the seminiferous epithelium which directly contact with germ cells. Sertoli cells exhibit polarized alignment at the basal membrane of seminiferous tubules to maintain the microenvironment for growth and development of germ cells, and therefore play a crucial role in spermatogenesis. Androgens exert their action through androgen receptor (AR) and AR signalling in the testis is essential for maintenance of spermatogonial numbers, blood-testis barrier integrity, completion of meiosis, adhesion of spermatids and spermiation. In the present study, we demonstrated that AR gene could promote the proliferation of immature porcine Sertoli cells (ST cells) and the cell cycle procession, and accelerate the transition from G1 phase into S phase in ST cells. Meanwhile, miR-124a could affect the proliferation and cell cycle procession of ST cells by targeting 3'-UTR of AR gene. Furthermore, AR bound to the RNF4 via AR DNA-binding domain (DBD) and we verified that RNF4 was necessary for AR to regulate the growth of ST cells. Above all, this study suggests that AR regulates ST cell growth via binding to RNF4 and miR-124a, which may help us to further understand the function of AR in spermatogenesis.