Single-cell analysis of developing and azoospermia human testicles reveals central role of Sertoli cells

Germline-specific deletion of testis-highly expressed Lrwd1 reveals nonessential roles in male fertility

Genetic etiologies constitute a major contributor to male factor infertility, a global health concern impacting over 7% of the reproductive-aged male population. Comprehensive transcriptomic profiling has identified more than 2300 mouse testicular-predominant genes, with knockout models functionally validating the critical role of numerous loci in preserving fertility. However, the biological significance of large portions of the male germ cell genes remains unclear. The present study aimed to investigate the function of leucine-rich repeats and WD40 repeat domain-containing protein 1 (Lrwd1) in male reproduction. Here we generated germ cell-specific Lrwd1 knockout mice with Stra8-Cre (Lrwd1-sKO) using CRISPR/Cas9 technology and assessed their fertility. Our results demonstrated that the absence of Lrwd1 did not affect the fertility of male mice, and no significant differences in sperm morphology were observed between Lrwd1-sKO and control mice. Histological analysis of testicular and epididymal tissues revealed that seminiferous tubules contained all stages of germ cell development, including mature spermatozoa, without noticeable alterations. Additionally, the progression of spermatocytes through prophase I was not impaired in ablation of Lrwd1 in germ cell. These findings suggest that Lrwd1 is not essential for spermatogenesis or male fertility in mice, indicating that it does not play a critical role in reproductive function under normal physiological conditions.

scRNA-seq and scATAC-seq reveal that Sertoli cell mediates spermatogenesis disorders through stage-specific communications in non-obstructive azoospermia

Non-obstructive azoospermia (NOA) belongs to male infertility due to spermatogenesis failure. However, evidence for cell type-specific abnormalities of spermatogenesis disorders in NOA remains lacking. We performed single-cell RNA sequencing (scRNA-seq) and single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq) on testicular tissues from patients with obstructive azoospermia (OA) and NOA. HE staining confirmed the structural abnormalities of the seminiferous tubules in NOA patients. We identified 12 germ cell subtypes (spermatogonial stem cell-0 [SSC0], SSC1, SSC2, diffing-spermatogonia [Diffing-SPG], diffed-spermatogonia [Diffed-SPG], pre-leptotene [Pre-Lep], leptotene-zygotene [L-Z], pachytene [Pa], diplotene [Di], spermatids-1 [SPT1], SPT2, and SPT3) and 8 Sertoli cell subtypes (SC1-SC8). Among them, three novel Sertoli cell subtype phenotypes were identified, namely SC4/immature, SC7/mature, and SC8/further mature Sertoli cells. For each germ or Sertoli cell subtype, we identified unique new markers, among which immunofluorescence confirmed co-localization of ST3GAL4, A2M, ASB9, and TEX19 and DDX4 (classical marker of germ cell). PRAP1, BST2, and CCDC62 were co-expressed with SOX9 (classical marker of Sertoli cell) in testes tissues also confirmed by immunofluorescence. The interaction between germ cell subtypes and Sertoli cell subtypes exhibits stage-specific-matching pattern, as evidenced by SC1/2/5/7 involving in SSC0-2 development, SC3 participating in the whole process of spermiogenesis, SC4/6 participating in Diffing and Diffed-SPG development, and SC8 involving in the final stage of SPT3. This pattern of specific interactions between subtypes of germ cell and Sertoli cell was confirmed by immunofluorescence of novel markers in testes tissues. The interaction was mainly regulated by the Notch1/2/3 signaling. Our study profiled the single-cell transcriptome of human spermatogenesis and provided many potential molecular markers for developing testicular puncture-specific marker kits for NOA patients.

Anatomical considerations, testicular, and scrotal anatomy of nonobstructive azoospermia patients

ABSTRACT

Infertility, defined as the inability to conceive after 1 year of regular unprotected intercourse, impacts 10%-20% of couples globally. Both male and female factors contribute equally to this condition. Azoospermia, particularly nonobstructive azoospermia (NOA), which affects 10%-15% of infertile men, represents a significant challenge in male infertility. The advent of assisted reproductive technology (ART), specifically microdissection testicular sperm extraction (micro-TESE) followed by intracytoplasmic sperm injection (ICSI), offers a possibility for men with NOA to father biological children. Recent studies have focused on the predictors of sperm retrieval in NOA patients, such as age, testicular volume, and follicle-stimulating hormone (FSH) level. This review aims to explore the limited data on the anatomical characteristics of NOA patients and provide surgical considerations for micro-TESE, thereby enhancing understanding and improving outcomes for this challenging condition.

RGS14 binds to GNAI3 and regulates the proliferation and apoptosis of human spermatogonial stem cells by affecting PLPP2 expression and MAPK signaling

Background

Non-obstructive azoospermia (NOA) represents a severe form of male infertility, characterized by the absence of sperm in the ejaculate due to impaired spermatogenesis. Spermatogonial stem cells (SSCs), which ensure continuous sperm production, are critical for maintaining male fertility. Despite their importance, the molecular mechanisms governing SSC fate determination and their role in NOA pathogenesis remain incompletely understood. This study investigates the regulatory networks underlying SSC dysfunction in NOA patients.

Results

Using single-cell RNA sequencing, we identified significant downregulation of RGS14 in SSCs of NOA patients compared to normal testes. Immunofluorescence validation confirmed RGS14 localization primarily in SSCs. Functional assays demonstrated that RGS14 knockdown in SSC lines markedly suppressed cell proliferation and induced apoptosis. RNA-sequencing analyses revealed that RGS14 deficiency inhibited PLPP2 expression and MAPK signaling activation. Notably, PLPP2 overexpression rescued the phenotypic defects caused by RGS14 depletion. Protein-protein interaction assays and co-immunoprecipitation experiments further established that RGS14 physically interacts with GNAI3 to coordinately regulate cell proliferation and PLPP2 expression. Expression validation in NOA testes demonstrated concurrent downregulation of GNAI3 and PLPP2 in NOA patients, implicating their dysregulation in spermatogenic failure.

Conclusion

Our findings uncover a novel RGS14-GNAI3-PLPP2 regulatory axis critical for SSC homeostasis. The dysregulation of these molecules contributes to SSC dysfunction and NOA pathogenesis. These data not only elucidate RGS14's role in SSC fate determination but also identify RGS14 and its interactome as promising therapeutic targets for restoring spermatogenesis in male infertility.

Environmental toxicant 2,3,7,8-tetrachlorodibenzo-p-dioxin induces non-obstructive azoospermia: New insights from network toxicology, integrated machine learning, and biomolecular modeling

OBJECTIVE

As industrial pollution intensifies, global male semen quality has been declining at a rate of 2.64 % per year in the 21st century. Among the various types of infertility, non-obstructive azoospermia (NOA) is the most severe and is closely associated with exposure to environmental toxins. The molecular mechanisms by which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a typical persistent organic pollutant, induces NOA have yet to be systematically elucidated.

METHODS

This study employed the single-sample Gene Set Enrichment Analysis (ssGSEA) method to identify key toxicological pathways and constructed a diagnostic model based on 113 machine learning algorithms. By integrating Weighted Gene Co-expression Network Analysis (WGCNA) and single-cell analysis, we identified hub genes associated with the Sertoli Cell-Only Syndrome (SCOS) subtype. Finally, biomolecular modeling was conducted to validate the binding efficacy of the hub genes with TCDD.

RESULTS

Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis based on the ssGSEA method indicated that TCDD may disrupt spermatogenesis by activating the Tumor Necrosis Factor (TNF) and Mitogen-Activated Protein Kinase (MAPK) signaling pathways while inhibiting the Vascular Endothelial Growth Factor (VEGF) signaling pathway, ultimately leading to NOA. Through the integration of machine learning techniques, 5 hub genes (AUC > 0.7) induced by TCDD and associated with NOA were identified: Androgen receptor (AR), Chromodomain Helicase DNA-Binding Protein 1 (CHD1), Discoidin Domain Receptor Tyrosine Kinase 2 (DDR2), Retinoic Acid Receptor-Related Orphan Receptor Alpha (RORA), and Glutamate Ionotropic Receptor AMPA Type Subunit 1 (GRIA1). WGCNA and single-cell analysis revealed that AR and DDR2 were specifically expressed in the testicular tissues of NOA patients and were closely associated with SCOS (p < 0.05). Immune infiltration analysis suggested that TCDD induces abnormal infiltration of various immune cells, indicating its close relationship with immune inflammatory responses (p < 0.05). Biomolecular modeling further demonstrated a strong binding affinity between AR and TCDD (∆G = -8.3 kcal·mol⁻¹, Etotal = -37.79 kcal·mol⁻¹), highlighting the critical role of AR in TCDD-induced NOA.

CONCLUSIONS

This study reveals the potential molecular mechanisms by which TCDD induces NOA, providing new targets for the development of diagnostic and therapeutic strategies.

Single-cell transcriptomic atlas of the human testis across the reproductive lifespan

Testicular aging is associated with declining reproductive health, but the molecular mechanisms are unclear. Here we generate a dataset of 214,369 single-cell transcriptomes from testicular cells of 35 individuals aged 21-69, offering a resource for studying testicular aging and physiology. Machine learning analysis reveals a stronger aging response in somatic cells compared to germ cells. Two waves of aging-related changes are identified: the first in peritubular cells of donors in their 30s, marked by increased basement membrane thickness, indicating a priming state for aging. In their 50s, testicular cells exhibit functional changes, including altered steroid metabolism in Leydig cells and immune responses in macrophages. Further analyses reveal the impact of body mass index on spermatogenic capacity as age progresses, particularly after age 45. Altogether, our findings illuminate molecular alterations during testis aging and their relationship with body mass index, providing a foundation for future research and offering potential diagnostic markers and therapeutic targets.

3D Bioprinted Coaxial Testis Model Using Human Induced Pluripotent Stem Cells:A Step Toward Bicompartmental Cytoarchitecture and Functionalization

Fertility preservation following pediatric cancer therapy programs has become a major avenue of infertility research. In vitro spermatogenesis (IVS) aims to generate sperm from banked prepubertal testicular tissues in a lab setting using specialized culture conditions. While successful using rodent tissues, progress with human tissues is limited by the scarcity of human prepubertal testicular tissues for research. This study posits that human induced pluripotent stem cells (hiPSCs) can model human prepubertal testicular tissue to facilitate the development of human IVS conditions. Testicular cells derived from hiPSCs are characterized for phenotype markers and profiled transcriptionally. HiPSC-derived testicular cells are bioprinted into core-shell constructs representative of testis cytoarchitecture and found to capture functional aspects of prepubertal testicular tissues within 7 days under xeno-free conditions. Moreover, hiPSC-derived Sertoli cells illustrate the capacity to mature under pubertal-like conditions. The utility of the model is tested by comparing 2 methods of supplementing retinoic acid (RA), the vitamin responsible for inducing spermatogenesis. The model reveals a significant gain in activity under microsphere-released RA compared to RA medium supplementation, indicating that the fragility of free RA in vitro may be a contributing factor to the molecular dysfunction observed in human IVS studies to date.

Single-cell sequencing in non-obstructive azoospermia: insights from primary and re-analysis studies

Non-obstructive azoospermia (NOA) constitutes one of the most severe forms of male infertility. Recent advancements in single-cell sequencing have significantly contributed to understanding the molecular landscape of NOA in human testicular tissues, elucidating the factors that underpin spermatogenic dysfunction. This technology has improved our understanding of the condition at a cellular level. Concurrently, bioinformatics developments have facilitated the re-analysis of publicly available single-cell datasets, offering novel insights into the disorder. Nevertheless, a comprehensive review integrating primary and re-analysis studies of single-cell sequencing in NOA is lacking. This review systematically evaluates 10 primary studies reporting original single-cell sequencing data of human NOA testicular samples and 22 secondary studies that re-analyzed these published data. We explore single-cell sequencing applications in germ cells, Sertoli cells, and Leydig cells, offering a comprehensive overview of molecular insights into spermatogenic dysfunction. Our review highlights novel findings in secondary studies, including the roles of transcriptional regulators, RNA transcription, endocrine disruptors, and microtubular cytoskeleton, thereby bridging primary studies and re-analysis studies. Additionally, we discussed future research directions and the challenges of translating single-cell research findings into clinical applications. In summary, single-cell sequencing offers a high-resolution, single-cell perspective of NOA testicular tissue, paving the way for innovative therapeutic strategies in male infertility.

Preparation, characterization, and stability of selenium nanoparticles decorated with Mori Fructus polysaccharide and its protective effects in bisphenol A-induced Sertoli cells

Bisphenol A (BPA) is an endocrine disruptor universally present in food packaging, which may cause oxidative stress and reproductive toxicity through migration to food and ingestion then. Both Mori Fructus and selenium have excellent antioxidant ability and good therapeutic effects on reproductive improvement. Hence, in this work, Mori Fructus polysaccharide (MFP) was selected as a stabilizer to synthesize MFP‑selenium nanoparticles (MFP-SeNPs) by chemical reduction method. The structural properties, stability and antioxidant activity of MFP-SeNPs were subsequently characterized and studied. The results suggested that spherical MFP-SeNPs (average size 80.73 nm, zeta potential -31.8 mV) with zero-valent and well dispersion was successfully synthesized with 1 mg/mL MFP as a stabilizer, which could be stabilized at 4 °C for 35 d. Compared with MFP and SeNPs, MFP-SeNPs had stronger radical scavenging ability, it could also decrease the levels of MDA and ROS and enhance the GSH-px and SOD activity through PI3K/Akt pathways in BPA-induced TM4 cells. Taken together, MFP-SeNPs could become a potential antioxidant to improve male reproductive functions in the future food field.

From biological marker to clinical application: the role of anti-Müllerian hormone for delayed puberty and idiopathic non-obstructive azoospermia in males

Graphical abstract

Role of anti-Müllerian hormone (AMH) in male development and fertility prediction. (A) AMH levels in normal development, constitutional delay of growth and puberty (CDGP) and central hypogonadotropic hypogonadism (CHH) models. In normal males, AMH declines with puberty; in CDGP and CHH, AMH is normal or slightly elevated or abnormally low, indicating delayed or impaired pubertal progression. (B) AMH as a predictor of successful sperm retrieval (SSR) in idiopathic non-obstructive azoospermia. Lower AMH levels (<2.6 ng/mL) correlate with higher SSR in microdissection testicular sperm extraction.

Abstract

Anti-Müllerian hormone (AMH), a biomarker secreted by Sertoli cells in the testes, has emerged as a critical indicator of male reproductive function with significant clinical application potential. AMH reflects Sertoli cell activity and plays a pivotal role across different stages of male gonadal function. First, in prepubertal males, AMH levels are crucial for assessing testicular development and the progression of puberty, with delayed or insufficient AMH secretion often being associated with disorders such as delayed puberty. Second, in reproductive-age males, AMH serves as an important biomarker for evaluating spermatogenic capacity, particularly in cases of idiopathic non-obstructive azoospermia. In these patients, AMH levels can help predict the success of testicular sperm extraction, thereby influencing fertility treatment strategies. This review explores the physiological mechanisms of AMH and its diagnostic and prognostic significance in both delayed puberty and fertility disorders in reproductive-age males. While AMH shows great promise in the management of hypogonadism, further research is needed to validate its clinical utility and refine treatment protocols for optimizing patient outcomes.

Unveiling Leydig cell heterogeneity and its role in male infertility: A single-cell transcriptomic study of human testicular tissue

Male infertility and impaired spermatogenesis are significant concerns in reproductive health, often linked to disruptions in the cellular and molecular processes within the testis. The cellular composition and transcriptional dynamics of human testicular tissue are crucial for understanding these issues. Previous studies have largely relied on bulk tissue analysis, which obscures the distinct roles and interactions of specific cell types. Here, through a comprehensive single-cell transcriptomic analysis of human testes across various developmental stages and pathological conditions, we reveal the intricate cellular heterogeneity and the molecular mechanisms underlying testicular function. Our study identifies significant disruptions in the differentiation trajectories of Germ cells in conditions such as Klinefelter syndrome (KS), AZFa deletion, and Sertoli-cell-only syndrome (SCOS). We further uncover key transcription factors and regulatory networks governing Leydig cell function, particularly those related to steroidogenesis and hormonal regulation. These findings highlight the organized yet complex cellular and molecular landscape of the testis and uncover critical pathways altered in male infertility. Collectively, our data suggest that targeted therapeutic strategies could be developed to address specific disruptions in testicular cell populations and their associated regulatory networks.

Pluripotency factor Tex10 finetunes Wnt signaling for spermatogenesis and primordial germ cell development

Testis-specific transcript 10 (Tex10) is highly expressed in the testis, embryonic stem cells (ESCs), and primordial germ cells (PGCs). We previously generated a Tex10 knockout mouse model demonstrating its critical roles in ESC pluripotency and preimplantation development. Here, using conditional knockout mice and dTAG-degron ESCs, we show Tex10 is required for spermatogenesis and ESC-to-PGCLC differentiation. Specifically, Tex10-null spermatocytes arrest at metaphase I, compromising round spermatid formation. Tex10 depletion and overexpression compromise and enhance ESC-to-PGCLC differentiation, respectively. Mechanistically, bulk and single-cell RNA sequencing reveals that Tex10 depletion downregulates genes involved in pluripotency, PGC development, and spermatogenesis while upregulating genes promoting somatic programs. Chromatin occupancy study reveals that Tex10 binds to H3K4me3-marked promoters of Psmd3 and Psmd7, negative regulators of Wnt signaling, and activates their expression, thereby restraining Wnt signaling. Our study identifies Tex10 as a previously unappreciated factor in spermatogenesis and PGC development, offering potential therapeutic insights for treating male infertility.

An integrated transcriptomic analysis unveils the regulatory roles of RNA binding proteins during human spermatogenesis

Background

RNA-binding proteins (RBPs) have emerged as key regulators in testis development and spermatogenesis, yet a comprehensive understanding of their expression dynamics has been lacking.

Methods

This study leverages published single-cell RNA sequencing (scRNA-seq) data to elucidate the complex expression patterns of RBP genes during postnatal testis development and spermatogenesis. Additionally, it uses bulk RNA-seq data to explore the regulatory impact of RBPs on alternative splicing (AS) in non-obstructive azoospermia (NOA).

Results

We have identified cell-specific RNA-binding protein (RBP) genes in various cell types throughout testis development. Notably, distinct RBP gene clusters exhibit significant differential expression, particularly in Sertoli cells as they mature from neonatal to adult stages. Our analysis has revealed temporally-regulated RBP clusters that correlate with the developmental progression of Sertoli cells and the advancement of spermatogenesis. Moreover, we have established links between specific RBPs and the pathogenesis of non-obstructive azoospermia (NOA) through the regulation of alternative splicing (AS) events. Additionally, RPL10, RPL39, and SETX have been identified as potential diagnostic biomarkers for NOA.

Conclusion

This research provided an in-depth look at RBP expression patterns during human testis development and spermatogenesis. It not only deepens our basic comprehension of male fertility and infertility but also indicates promising directions for the creation of innovative diagnostic and treatment methods for NOA.

Chronic asymptomatic orchitis in dogs alters Sertoli cell number and maturation status

Infertility due to non-obstructive azoospermia is a common diagnosis in infertile male dogs. Chronic asymptomatic orchitis (CAO) has been postulated as a significant cause of non-obstructive azoospermia in acquired male canine infertility. Despite severe microenvironmental changes, some resilient spermatogonial stem cells persist in CAO-affected testes. As Sertoli cells play an essential role in spermatogenesis and the testicular micromilieu, they represent a new target for CAO potential treatment and consequently deserve further investigation. To investigate Sertoli cell number and maturational status, different markers [Vimentin, anti-Müllerian hormone (AMH), and cytokeratin-18 (CK18)] were evaluated in healthy and CAO-affected testes at mRNA and protein levels. Sertoli cell number was reduced in CAO-affected dogs. Sertoli cells also partly returned to an immature status, as indicated by the expression of AMH and CK18 at mRNA and protein levels. The degree of spermatogenesis disruption matched with the degree of Sertoli cell alterations. The investigation of CAO in this study is limited by the number of samples and the lack of testicular volume measurements, but this does not diminish its importance in new findings. In conclusion, this study identifies alterations in Sertoli cell number and maturation status as a cause or consequence of CAO. The results indicate the need to restore Sertoli cell function as a potential therapeutic target for a successful restart of spermatogenesis.

Analysis of toxicity and mechanisms of busulfan in non-obstructive azoospermia: A genomic and toxicological approach integrating molecular docking, single-cell sequencing, and experimentation in vivo

Environmental pollutants, including chemical contaminants, heavy metals, and pesticides, have been linked to adverse effects on male reproductive health, particularly sperm quality. Non-obstructive azoospermia (NOA) is a severe form of male infertility caused by intrinsic testicular dysfunction, leading to a complete absence of sperm in the ejaculate. Busulfan, an alkylating chemotherapeutic agent widely used to treat chronic myelogenous leukemia, is known to induce NOA through its toxic effects on spermatogonial stem cells (SSCs). This study aimed to identify key molecular targets and pathways disrupted by busulfan in the testicular environment. By integrating molecular docking, single-cell RNA sequencing, and in vivo experimentation, the study identified POLE and LRAT as critical proteins. These proteins were shown to interact strongly with busulfan, leading to genomic instability and increased germ cell apoptosis during spermatogenesis. Additionally, the immune landscape of NOA-affected testes revealed significant changes in immune cell infiltration, potentially worsening the condition. These findings offer new insights into the mechanisms of busulfan-induced NOA and suggest potential therapeutic targets for preserving male fertility in chemotherapy patients. This research advances the understanding of chemotherapy-induced reproductive toxicity and emphasizes the need for strategies to reduce its negative effects on fertility.

Dynamic transcriptomic and regulatory networks underpinning the transition from fetal primordial germ cells to spermatogonia in mice

The transition from fetal primordial germ cells (PGCs) to spermatogonia (SPG) is critical for male germ cell development; however, the detailed transcriptomic dynamics and regulation underlying this transition remain poorly understood. Here by interrogating the comprehensive transcriptome atlas dataset of mouse male germ cells and gonadal cells development, we elucidated the regulatory networks underlying this transition. Our single-cell transcriptome analysis revealed that the transition from PGCs to SPG was characterized by global hypertranscription. A total of 315 highly active regulators were identified to be potentially involved in this transition, among which a non-transcription factor (TF) regulator TAGLN2 was validated to be essential for spermatogonial stem cells (SSCs) maintenance and differentiation. Metabolism profiling analysis also revealed dynamic changes in metabolism-related gene expression during PGC to SPG transition. Furthermore, we uncovered that intricate cell-cell communication exerted potential functions in the regulation of hypertranscription in germ cells by collaborating with stage-specific active regulators. Collectively, our work extends the understanding of molecular mechanisms underlying male germ cell development, offering insights into the recapitulation of germ cell generation in vitro.

Altered Sertoli Cell Function Contributes to Spermatogenic Arrest in Dogs with Chronic Asymptomatic Orchitis

Acquired infertility due to chronic asymptomatic orchitis (CAO) is a common finding in male dogs. It is characterized by spermatogenic arrest, a significant reduction in spermatogonia, immune cell infiltration and a disruption of the blood-testis barrier. Sertoli cells are a key factor for spermatogenesis and the testicular micromilieu. We hypothesize altered Sertoli cell function to be involved in the pathogenesis of canine CAO. Consequently, the aim was to gain further insights into the spermatogonial stem cell niche and Sertoli cell function in CAO-affected dogs. Therefore, the testicular expression of the Sertoli cell-derived factors bFGF, GDNF, WNT5A, BMP4, CXCL12 and LDHC were evaluated in 15 CAO testis tissues and 10 normospermic controls by relative quantitative real-time PCR (qPCR). Additionally, the protein expression patterns of bFGF, GDNF and WNT5A were visualized immunohistochemically (IHC). This study revealed an overexpression of bFGF (IHC, p < 0.0001), GDNF (qPCR, p = 0.0036), WNT5A (IHC, p = 0.0066) and CXCL12 (qPCR, p = 0.0003) and a reduction in BMP4 (qPCR, p = 0.0041) and LDHC (qPCR, p = 0.0003) in CAO-affected testis in dogs, clearly confirming impaired Sertoli cell function in canine CAO. Sertoli cell function is essential for spermatogenesis and must be considered for potential therapeutic approaches.

Insights from the single-cell level: lineage trajectory and somatic-germline interactions during spermatogenesis in dwarf surfclam Mulinia lateralis

BACKGROUND

Spermatogenesis is a complex process of cellular differentiation that commences with the division of spermatogonia stem cells, ultimately resulting in the production of functional spermatozoa. However, a substantial gap remains in our understanding of the molecular mechanisms and key driver genes that underpin this process, particularly in invertebrates. The dwarf surfclam (Mulinia lateralis) is considered an optimal bivalve model due to its relatively short generation time and ease of breeding in laboratory settings.

RESULTS

In this study, over 4,600 testicular cells from various samples were employed to identify single-cell heterogeneity on a more comprehensive scale. The four germ cell populations (spermatogonia, primary spermatocytes, secondary spermatocytes, and round spermatids/spermatozoa) and three somatic populations (follicle cell, hemocyte, and nerve cell) were characterized. The four types of germ cells exhibited disparate cell cycle statuses and an uninterrupted developmental trajectory, progressing from spermatogonia to spermatids/spermatozoa. Pseudotime analysis indicates that gene expression, translation, ATP metabolic process, and microtubule-based process are involved in the transition of germ cell types. Weighted gene coexpression network analysis (WGCNA) identified four modules corresponding to the four types of germ cells, as well as key transcription factors (e.g., MYC, SREBF1, SOXH) that may play a critical role in these cell types. Furthermore, our findings revealed that there is extensive bidirectional communication between the somatic cells and the germline cells, including the FGF and TGF-β signaling pathways, as well as other ligand-receptor pairs, such as NTN1-NEO1 and PLG-PLGRKT.

CONCLUSIONS

This study provides a comprehensive single-cell transcriptome landscape of the gonad, which will contribute to the understanding of germ cell fate transition during spermatogenesis, and the development of germ cell manipulation technologies in mollusks.

Multi-omics analysis and experimental verification reveal testicular fatty acid metabolism disorder in non-obstructive azoospermia

Increasing evidence implicates disruptions in testicular fatty acid metabolism as a contributing factor in non-obstructive azoospermia (NOA), a severe form of male infertility. However, the precise mechanisms linking fatty acid metabolism to NOA pathogenesis have not yet been fully elucidated. Multi-omics analyses, including microarray analysis, single-cell RNA sequencing (scRNA-seq), and metabolomics, were utilized to investigate disruptions in fatty acid metabolism associated with NOA using data from public databases. Results identified ACSL6, ACSBG2, and OLAH as key genes linked to fatty acid metabolism dysregulation, suggesting their potential causative roles in NOA. A marked reduction in omega-3 polyunsaturated fatty acids, especially docosahexaenoic acid (DHA), was observed, potentially contributing to the pathological process of NOA. Sertoli cells in NOA patients exhibited apparent fatty acid metabolic dysfunction, with PPARG identified as a key transcription factor (TF) regulating this process. Functional analyses demonstrated that PPARG is crucial for maintaining blood-testis barrier (BTB) integrity and promoting spermatogenesis via regulation of fatty acid metabolism. These findings reveal the pivotal role of fatty acid metabolism in NOA and identify PPARG as a potential therapeutic target.

scRNA-Seq-Based Transcriptome Profiling and Relevant Bioinformatics Approaches to Uncover Novel Insights in Studying Human Spermatogenesis

This study employs single-cell RNA sequencing (scRNA-seq) to investigate human spermatogenesis across developmental stages and under pathological conditions, including non-obstructive azoospermia (NOA). The analysis highlights the critical role of Sertoli cells in supporting germ cell development by providing structural support, paracrine factors, and essential nutrients. Pathological conditions, such as NOA and Klinefelter syndrome, reveal significant disruptions in Sertoli cell function, including impaired cell signaling, mitochondrial activity, and transcriptional regulation. These changes are closely linked to defects in germ cell progression and spermatogenic failure. Comparative profiling also identifies stage-specific transcriptional changes in both Sertoli and Leydig cells, uncovering their dynamic interactions with germ cells. This work provides new insights into the cellular and molecular mechanisms of spermatogenesis and identifies potential biomarkers and therapeutic targets, particularly emphasizing the pivotal contributions of Sertoli cells in maintaining testicular homeostasis and fertility.

Multiomics identification of programmed cell death-related characteristics for nonobstructive azoospermia based on a 675-combination machine learning computational framework

BACKGROUND

Abnormal programmed cell death (PCD) plays a central role in spermatogenic dysfunction. However, the molecular mechanisms and biomarkers of PCD in patients with nonobstructive azoospermia (NOA) remain unclear.

METHODS

The genetic conditions of NOA patients were analysed using bulk transcriptomic, single-cell transcriptomic, single nucleotide polymorphism (SNP), and clinical data from multiple centres. A total of 675 machine learning methods were applied to construct models from 12 different PCDs and to screen for distinctive genes. A new PCDscore system was created to measure the degree of PCD in patients. Using the NOA mouse model, TUNEL, qRT-PCR, Western blotting, and immunohistochemistry (IHC) were utilized to validate the PCD status in NOA testes and the expression levels of hub PCD-related genes (PCDRGs). Mouse testicular samples were used for sequencing of the whole transcriptome. The sequencing results were used to evaluate the correlation between PCD scores and expression of hub genes.

RESULTS

A PCDscore system was built using 12 characteristic PCDRGs chosen by machine learning. PCD scores correlated with gene interaction and immune activity changes. Leydig, Sertoli, and T cells were prominent in cell interactions with PCDscore changes. PCDscore in the NOA mouse testis was increased. Among the 12 PCDRGs, BCL2L14, GGA1, GPX4, PHKG2, and SLC39A8 were strongly linked to spermatogenesis. BCL2L14, GGA1, GPX4, and PHKG2 strongly correlated with PCD statuses. The changes in the expression of these genes may be due to the effects of SNPs, which may lead to the male reproductive system disorders.

CONCLUSIONS

Our study provides new insights into PCD-related mechanisms in NOA patients via multiomics and proposes reliable models for the diagnosis of NOA via the use of PCD biomarkers. A deeper understanding of these mechanisms may aid in the clinical diagnosis and treatment of NOA.

microRNA as an Important Mediator in the Regulation of Male Gallus gallus domesticus Reproduction: Current State of the Problem

During all periods of male ontogenesis, physiological processes responsible for the correct functioning of reproductive organs and spermatogenesis are under the influence of various factors (neuro-humoral, genetic, and paratypical). Recently, the attention of researchers has increasingly turned to the study of epigenetic factors. In scientific publications, one can increasingly find references to the direct role of microRNAs, small non-coding RNAs involved in post-transcriptional regulation of gene expression, in the processes of development and functioning of reproductive organs. Although the role of microRNAs in the reproduction of mammals, including humans, has been intensively studied, this area of knowledge in birds remains under-researched and limited to single experiments. This is likely due to the unique features of embryogenesis and the structure of the avian reproductive system. This review summarizes the current state of knowledge on the role of microRNAs in avian reproduction. Insight into the molecular basis of spermatogenesis in Gallus gallus domesticus is provided. Data on the functions and mechanisms by which microRNAs influence the processes of growth, development, and formation of rooster germ cells that determine the necessary morphofunctional qualitative characteristics of mature spermatozoa are summarized. Particular attention is paid to miRNA biogenesis as an important step affecting the success of spermatogenesis, as well as the role of miRNAs in avian sex differentiation during early embryogenesis. The modern literature sources systematized in this review, revealing the questions about the role of miRNAs in the reproductive function of birds, create a theoretical basis and define new perspectives and directions for further research in this field.

Immunocompetent mouse models revealed that S100A4+ monocytes/macrophages facilitate long-term Zika virus infection in the testes

During its global epidemic, Zika virus (ZIKV) attracted widespread attention due to its link with various severe neurological symptoms and potential harm to male fertility. However, the understanding of how ZIKV invades and persists in the male reproductive system is limited due to the lack of immunocompetent small animal models. In this study, immunocompetent murine models were generated by using anti-IFNAR antibody blocked C57BL/6 male mice and human STAT2 (hSTAT2) knock in (KI) male mice. After infection, viral RNA could persist in the testes even after the disappearance of viremia. We also found a population of ZIKV-susceptible S100A4+ monocytes/macrophages that were recruited into testes from peripheral blood and played a crucial role for ZIKV infection in the testis. By using single-cell RNA sequencing, we also proved that S100A4+ monocytes/macrophages had a great impact on the microenvironment of ZIKV-infected testes, thus promoting ZIKV-induced testicular lesions. In conclusion, this study proposed a novel mechanism of long-term ZIKV infection in the male reproductive system.

Genes and Pathways Underpinning Klinefelter Syndrome at Bulk and Single-Cell Levels

Klinefelter syndrome (KS) is the most frequent genetic anomaly in infertile men. Given its unclear mechanism, we aim to investigate critical genes and pathways in the pathogenesis of KS based on three bulk and one single-cell transcriptome data sets from Gene Expression Omnibus. We merged two data sets (GSE42331 and GSE47584) with human KS whole blood samples. When comparing the control and KS samples, five hub genes, including defensin alpha 4 (DEFA4), bactericidal permeability increasing protein (BPI), myeloperoxidase (MPO), intelectin 1 (ITLN1), and Xg Glycoprotein (XG), were identified. Besides, infiltrated degree of certain immune cells such as CD56bright NK cell were positively associated with the expression of ITLN1 and XG. Kyoto Encyclopedia of Genes and Genomes analysis identified upregulated phosphatidylinositol 3-kinase (PI3K)/AKT pathway in KS. Gene set enrichment analysis followed by gene set variation analysis confirmed the upregulation of G2M checkpoint and heme metabolism in KS. Thereafter, the GSE200680 data set was used for external validation of the expression variation of hub genes from healthy to KS testicular samples, and each hub gene yielded excellent discriminatory capability for KS without exception. At the single-cell level, the GSE136353 data set was utilized to evaluate intercellular communication between different cell types in KS patient, and strong correlations were detected between macrophages/ dendritic cells/ NK cells and the other cell types. Collectively, we provided hub genes, pathways, immune cell infiltration degree, and cell-cell communication in KS, warranting novel insights into the pathogenesis of this disease.

Spatial Transcriptomics Reveals the Temporal Architecture of the Seminiferous Epithelial Cycle and Precise Sertoli-Germ Synchronization

Spermatogenesis is characterized by the seminiferous epithelial cycle, a periodic pattern of germ cell differentiation with a wave-like progression along the length of seminiferous tubules. While key signaling and metabolic components of the cycle are known, the transcriptional changes across the cycle and the correlations between germ cell and somatic lineages remain undefined. Here, we use spatial transcriptomics via RNA SeqFISH+ to profile 2,638 genes in 216,090 cells in mouse testis and identify a periodic transcriptional pattern across tubules that precisely recapitulates the seminiferous epithelial cycle, enabling us to map cells to specific timepoints along the developmental cycle. Analyzing gene expression in somatic cells reveals that Sertoli cells exhibit a cyclic transcriptional profile closely synchronized with germ cell development while other somatic cells do not demonstrate such synchronization. Remarkably, in mouse testis with drug-induced ablation of germ cells, Sertoli cells independently maintain their cyclic transcriptional dynamics. By analyzing expression data, we identify an innate retinoic acid cycle, a network of transcription factors with cyclic activation, and signaling from germ cells that could interact with this network. Together, this work leverages spatial geometries for mapping the temporal dynamics and reveals a regulatory mechanism in spermatogenesis where Sertoli cells oscillate and coordinate with the cyclical progression of germ cell development.

Long-term culture of human Sertoli cells from adult Klinefelter patients as a first step to develop new tools for unravelling the testicular physiopathology

STUDY QUESTION

Are Sertoli cells (SCs) from adult Klinefelter men (47,XXY) capable of proliferating in vitro and maintaining their main phenotypical and functional characteristics as do SCs from adult 46,XY patients?

SUMMARY ANSWER

Isolated SCs from patients with Klinefelter syndrome (KS) can be expanded in vitro while maintaining their characteristics and a stable karyotype, similar to SCs from 46,XY patients.

WHAT IS KNOWN ALREADY

The mechanism leading to testicular tissue degeneration in KS is still unknown. A few recent studies highlight the main role played by SCs in the physiopathology of the disease, but new study models based on co-culture or testicular organoids are needed to further understand the SC's involvement in the mechanism of testicular degeneration and fibrosis, and to find therapeutical targets. KS SC expansion could be the first step towards developing such in vitro study models. SCs have been isolated from 46,XY men and expanded in vitro while maintaining the expression of phenotypical and functional markers, but propagation of SCs from KS men has not been achieved yet.

STUDY DESIGN, SIZE, DURATION

Testicular tissue was obtained during a testicular sperm extraction procedure for infertility treatment between 2019 and 2021 from three azoospermic adult KS (47,XXY) men (33±3.6 years old) and from three control patients (46,XY) (36±2 years old) presenting with obstructive azoospermia. SCs isolated from frozen-thawed tissue of KS and 46,XY patients were cultured for 60 days and compared. All patients signed an informed consent according to the ethical board approval of the study protocol.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Testicular biopsies obtained from KS (n = 3) and 46,XY (n = 3) adult patients were slow-frozen. After tissue thawing SCs were isolated using a double-step enzymatic digestion and differential plating, and cultured for 60 days in DMEM medium containing FBS. Analyses were performed at different culture times (passages 5 (P5) and 10 (P10)). Quantification of cells using immunofluorescence (IF) for cell type-specific markers (Sox9, GATA4, ACTA2, INSL3, MAGEA4), SCs characterization using both IF and quantitative real-time PCR for GDNF, BMP4, AR and CLDN11 and cells karyotyping were performed.

MAIN RESULTS AND THE ROLE OF CHANCE

We demonstrate for the first time that a small population of human SCs isolated from frozen-thawed testis of adult KS patients can be expanded in vitro while retaining expression of characteristic markers of SCs and the 47,XXY karyotype, and exhibiting cell-specific functional proteins and gene expression (GDNF, BMP4, AR, and CLDN11) after 60 days in culture. At P10, 83.39 ± 4.2% of cultured cells from KS men and 85.34 ± 4.1% from 46,XY men expressed Sox9, and 88.8 ± 3.9% of KS cells versus 82.9 ± 3.2% of the control cells were positive for GATA4 without any differences between two groups; both Sox9 and GATA4 are typical SC markers. No differences were found between KS and 46,XY SCs in vitro in terms of cells expansion (exponential growth between P1 and P10 with an average cell count of 2.8±1.5×107 versus 3.8±1.2×107 respectively for the KS and control groups at P10). There was no significant statistical difference for functional proteins and genes expressions (GDNF, BMP4, AR, and CLDN11) neither between KS SCs and control SCs nor between P5 and P10.

LIMITATIONS, REASONS FOR CAUTION

The small number of donor samples is a limitation but it is due to limited availability of tissue for research in KS populations. Although no differences were observed in SCs function in the culture of isolated SCs after 60 days, the possibility of a SCs dysfunction needs to be investigated in more complex 3-dimensional models allowing the establishment of a proper cell organization and further analyses of cell functions and interactions during longer culture periods.

WIDER IMPLICATIONS OF THE FINDINGS

The demonstration of the possibility to propagate KS SCs in vitro could be useful to build new in vitro models for deciphering testicular cell interactions, determining deficient signalling pathways involved in impaired spermatogenesis, and identifying targets for infertility treatment in KS. As the cell numbers achieved in this study are higher than cell numbers used to develop testicular organoids, we may expect to be able to understand the behaviour and physiopathology of SCs in the disease during the long-term culture of these organoids. Such models could be further applied to understand other causes of deficiencies in seminiferous tubules.

STUDY FUNDING/COMPETING INTEREST(S)

M.G.G is funded by a grant from the Cliniques Universitaires Saint-Luc (FRC) for the research project on Klinefelter Syndrome Physiopathology. The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

NCT05997706.

How the extra X chromosome impairs the development of male fetal germ cells

The dosage of X-linked genes is accurately regulated with the development of fetal germ cells (FGCs)1,2. How aberrant dosage of X-linked genes impairs FGC development in humans remains poorly understood. FGCs of patients with Klinefelter syndrome (KS), who have an extra X chromosome, provide natural models for addressing this issue3. Here we demonstrate that most human FGCs in KS are arrested at an early stage, characterized by the upregulation of genes related to pluripotency, the WNT pathway and the TGF-β pathway, along with the downregulation of genes involved in FGC differentiation. The limited KS FGCs that are capable of reaching the late stage remain relatively naive. X chromosomes are not inactivated and the dosage of X-linked genes is excessive in KS FGCs. X-linked genes dominate the differentially expressed genes and are enriched in critical biological processes associated with the developmental delay of KS FGCs. Moreover, aberrant interactions between Sertoli cells and FGCs disrupt the migration of late FGCs to the basement membrane in KS. Notably, inhibition of the TGF-β pathway improves the differentiation of KS FGCs. Our findings elucidate how the extra X chromosome impairs the development of male FGCs and reveal the initial molecular events preceding germ cell loss in KS.

Integrating Microarray Data and Single-Cell RNA-Seq Reveals Key Gene Involved in Spermatogonia Stem Cell Aging

The in vitro generation of spermatogonial stem cells (SSCs) from embryonic stem cells (ESCs) offers a viable approach for addressing male infertility. A multitude of molecules participate in this intricate process, which requires additional elucidation. Despite the decline in SSCs in aged testes, SSCs are deemed immortal since they can multiply for three years with repeated transplantation. Nonetheless, the examination of aging is challenging due to the limited quantity and absence of precise indicators. Using a microarray, we assessed genome-wide transcripts (about 55,000 transcripts) of fibroblasts and SSCs. The WGCNA approach was then used to look for SSC-specific transcription factors (TFs) and hub SSC-specific genes based on ATAC-seq, DNase-seq, RNA-seq, and microarray data from the GEO databases as well as gene expression data (RNA-seq and microarray data). The microarray analysis of three human cases with different SSCs revealed that 6 genes were upregulated, and the expression of 23 genes was downregulated compared to the normal case in relation to aging genes. To reach these results, online assessments of Enrich Shiny GO, STRING, and Cytoscape were used to forecast the molecular and functional connections of proteins before identifying the master routes. The biological process and molecular function keywords of cell-matrix adhesion, telomerase activity, and telomere cap complex were shown to be significantly altered in upregulated differentially expressed genes (DEGs) by the functional enrichment analysis. According to our preliminary research, cell-specific TFs and TF-mediated GRNs are involved in the creation of SSCs. In order to maximize the induction efficiency of ESC differentiation into SSCs in vitro, hub SSC-specific genes and important SSC-specific TFs were identified, and sophisticated network regulation was proposed. According to our research, these genes and the hub proteins that they interact with may be able to shine a light on the pathophysiologies of infertility and aberrant germ cells.

Alteration of the metabolite interconversion enzyme in sperm and Sertoli cell of non-obstructive azoospermia: a microarray data and in-silico analysis

Numerous variables that regulate the metabolism of Sertoli cells and sperm have been identified, one of which is sex steroid hormones. These hormones play a vital role in maintaining energy homeostasis, influencing the overall metabolic balance of the human body. The proper functioning of the reproductive system is closely linked to energy status, as the reproductive axis responds to metabolic signals. The aim of this study was to investigate the gene expression patterns of metabolite interconversion enzymes in testicular cells (Sertoli cells and spermatogonia) of non-obstructive azoospermia (NOA) patients, as compared to normal controls, to understand the molecular mechanisms contributing to NOA. We used microarray and bioinformatics techniques to analyze 2912 genes encoding metabolite interconversion enzymes, including methyltransferase, monooxygenase, transmembrane reductase, and phosphohydrolase, in both testicular cells and normal samples. In sperm, the upregulation of MOXD1, ACAD10, PCYT1A, ARG1, METTL6, GPLD1, MAOA, and CYP46A1 was observed, while ENTPD2, CPT1C, ADC, and CYB5B were downregulated. Similarly, in the Sertoli cells of three NOA patients, RPIA, PIK3C3, LYPLA2, CA11, MBOAT7, and HDHD2 were upregulated, while NAA25, MAN2A1, CYB561, PNPLA5, RRM2, and other genes were downregulated. Using STRING and Cytoscape, we predicted the functional and molecular interactions of these proteins and identified key hub genes. Pathway enrichment analysis highlighted significant roles for G1/S-specific transcription, pyruvate metabolism, and citric acid metabolism in sperm, and the p53 signaling pathway and folate metabolism in Sertoli cells. Additionally, Weighted Gene Co-expression Network Analysis (WGCNA) and single-cell RNA sequencing (scRNA-seq) were performed to validate these findings, revealing significant alterations in gene expression and cellular distribution in NOA patients. Together, these results provide new insights into the molecular mechanisms underlying NOA and identify potential therapeutic targets.

RNA-binding protein IGF2BP1 is required for spermatogenesis in an age-dependent manner

Post-transcriptional regulation mediated by RNA binding proteins is crucial for male germline development. Insulin-like growth factor 2 mRNA-binding protein 1 (IGF2BP1), an RNA binding protein, is specifically expressed in human and mouse male gonads and is involved in manifold biological processes and tumorigenesis. However, the function of IGF2BP1 in mammalian spermatogenesis remains poorly understood. Herein, we generated an Igf2bp1 conditional knockout mouse model using Nanos3-Cre. Germ cell deficiency of Igf2bp1 in mice caused spermatogenic defects in an age-dependent manner, resulting in decreased numbers of undifferentiated spermatogonia and increased germ cell apoptosis. Immunoprecipitation-mass spectrometry analysis revealed that ELAV-like RNA binding protein 1, a well-recognized mRNA stabilizer, interacted with IGF2BP1. Single cell RNA-sequencing showed distinct mRNA profiles in spermatogonia from conditional knockout versus wide type mice. Further research showed that IGF2BP1 plays a vital role in the modulation of spermatogenesis by regulating Lin28a mRNA, which is essential for clonal expansion of undifferentiated spermatogonia. Thus, our results highlight the crucial effects of IGF2BP1 on spermatogonia for the long-term maintenance of spermatogenesis.

Possible involvement of a MEG3-miR-21-SPRY1-NF-κB feedback loop in spermatogenic cells proliferation, autophagy, and apoptosis

Non-obstructive azoospermia (NOA) is the most incurable form of male infertility with a complex etiology. Long non-cording RNAs (lncRNAs) were associated with regulating spermatogenesis. Herein, differentially expressed lncRNAs between NOA and control male were screened by RNA-seq analysis. MEG3 was upregulated in NOA tissues and inhibited cell proliferation and promoted cell autophagy and apoptosis in vitro. Through RNA immunoprecipitation (RIP), biotin pull-down assays, and dual-luciferase reporter assays, MEG3 was proved to act as a competing endogenous RNA of microRNA (miR)-21 and thus influenced the SPRY1/ERK/mTOR signaling pathway. Additionally, bioinformatic prediction and chip assay revealed that MEG3 was possibly regulated by nuclear factor κB (NF-κB) and SPRY1/NF-κB/MEG3 formed a feedback loop. Seminiferous tubule microinjection further investigated the effects of MEG3 on testes in vivo. These findings demonstrated that MEG3-miR-21-SPRY1-NF-κB probably acted as a feedback loop leading to azoospermia. Our study might provide a target and theoretical basis for diagnosing and treating NOA.

Loss-of-function in testis-specific serine/threonine protein kinase triggers male infertility in an invasive moth

Genetic biocontrol technologies present promising and eco-friendly strategies for the management of pest and insect-transmitted diseases. Although considerable advancements achieve in gene drive applications targeting mosquitoes, endeavors to combat agricultural pests have been somewhat restricted. Here, we identify that the testis-specific serine/threonine kinases (TSSKs) family is uniquely expressed in the testes of Cydia pomonella, a prominent global invasive species. We further generated male moths with disrupted the expression of TSSKs and those with TSSKs disrupted using RNA interference and CRISPR/Cas9 genetic editing techniques, resulting in significant disruptions in spermiogenesis, decreased sperm motility, and hindered development of eggs. Further explorations into the underlying post-transcriptional regulatory mechanisms reveales the involvement of lnc117962 as a competing endogenous RNA (ceRNA) for miR-3960, thereby regulating TSSKs. Notably, orchard trials demonstrates that the release of male strains can effectively suppress population growth. Our findings indicate that targeting TSSKs could serve as a feasible avenue for managing C. pomonella populations, offering significant insights and potential strategies for controlling invasive pests through genetic sterile insect technique (gSIT) technology.

Single-cell RNA sequencing reveals transcriptomic landscape and potential targets for human testicular ageing

STUDY QUESTION

What is the molecular landscape underlying the functional decline of human testicular ageing?

SUMMARY ANSWER

The present study provides a comprehensive single-cell transcriptomic atlas of testes from young and old humans and offers insights into the molecular mechanisms and potential targets for human testicular ageing.

WHAT IS KNOWN ALREADY

Testicular ageing is known to cause male age-related fertility decline and hypogonadism. Dysfunction of testicular cells has been considered as a key factor for testicular ageing.

STUDY DESIGN, SIZE, DURATION

Human testicular biopsies were collected from three young individuals and three old individuals to perform single-cell RNA sequencing (scRNA-seq). The key results were validated in a larger cohort containing human testicular samples from 10 young donors and 10 old donors.

PARTICIPANTS/MATERIALS, SETTING, METHODS

scRNA-seq was used to identify gene expression signatures for human testicular cells during ageing. Ageing-associated changes of gene expression in spermatogonial stem cells (SSCs) and Leydig cells (LCs) were analysed by gene set enrichment analysis and validated by immunofluorescent and functional assays. Cell-cell communication analysis was performed using CellChat.

MAIN RESULTS AND THE ROLE OF CHANCE

The single-cell transcriptomic landscape of testes from young and old men was surveyed, revealing age-related changes in germline and somatic niche cells. In-depth evaluation of the gene expression dynamics in germ cells revealed that the disruption of the base-excision repair pathway is a prominent characteristic of old SSCs, suggesting that defective DNA repair in SSCs may serve as a potential driver for increased de novo germline mutations with age. Further analysis of ageing-associated transcriptional changes demonstrated that stress-related changes and cytokine pathways accumulate in old somatic cells. Age-related impairment of redox homeostasis in old LCs was identified and pharmacological treatment with antioxidants alleviated this cellular dysfunction of LCs and promoted testosterone production. Lastly, our results revealed that decreased pleiotrophin signalling was a contributing factor for impaired spermatogenesis in testicular ageing.

LARGE SCALE DATA

The scRNA-seq sequencing and processed data reported in this paper were deposited at the Genome Sequence Archive (https://ngdc.cncb.ac.cn/), under the accession number HRA002349.

LIMITATIONS, REASONS FOR CAUTION

Owing to the difficulty in collecting human testis tissue, the sample size was limited. Further in-depth functional and mechanistic studies are warranted in future.

WIDER IMPLICATIONS OF THE FINDINGS

These findings provide a comprehensive understanding of the cell type-specific mechanisms underlying human testicular ageing at a single-cell resolution, and suggest potential therapeutic targets that may be leveraged to address age-related male fertility decline and hypogonadism.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Key Research and Development Program of China (2022YFA1104100), the National Natural Science Foundation of China (32130046, 82171564, 82101669, 82371611, 82371609, 82301796), the Natural Science Foundation of Guangdong Province, China (2022A1515010371), the Major Project of Medical Science and Technology Development Research Center of National Health Planning Commission, China (HDSL202001000), the Open Project of NHC Key Laboratory of Male Reproduction and Genetics (KF202001), the Guangdong Province Regional Joint Fund-Youth Fund Project (2021A1515110921, 2022A1515111201), and the China Postdoctoral Science Foundation (2021M703736). The authors declare no conflict of interest.

Biallelic RXFP2 variants lead to congenital bilateral cryptorchidism and male infertility, supporting a role of RXFP2 in spermatogenesis

STUDY QUESTION

Does RXFP2 disruption impair male fertility?

SUMMARY ANSWER

We identified biallelic variants in RXFP2 in patients with male infertility due to spermatogenic arrest at the spermatid stage, supporting a role of RXFP2 in human spermatogenesis, specifically in germ cell maturation.

WHAT IS KNOWN ALREADY

Since RXFP2, the receptor for INSL3, plays a crucial role in testicular descent during prenatal development, biallelic variants lead to bilateral cryptorchidism, as described in four families to date. While animal models have also suggested a function in spermatogenesis, the postnatal functions of RXFP2 and its ligand INSL3, produced in large amounts by the testes from puberty throughout adulthood, are largely unknown.

STUDY DESIGN, SIZE, DURATION

A family with two male members affected by impaired fertility due to spermatogenic maturation arrest and a history of bilateral cryptorchidism underwent clinical, endocrinological, histological, genomic, in vitro cellular, and in silico investigations.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The endocrinological and histological findings were correlated with publicly available single-cell RNA sequencing (scRNA-seq) data. The genomic defects have been characterized using long-read sequencing and validated with in silico modeling and an in vitro cyclic AMP reporter gene assay.

MAIN RESULTS AND THE ROLE OF CHANCE

An intragenic deletion of exon 1-5 of RXFP2 (NM_130806.5) was detected in trans with a hemizygous missense variant c.229G>A, p.(Glu77Lys). The p.(Glu77Lys) variant caused no clear change in cell surface expression or ability to bind INSL3, but displayed absence of a cAMP signal in response to INSL3, indicating a loss-of-function. Testicular biopsy in the proband showed a maturation arrest at the spermatid stage, corresponding to the highest level of RXFP2 expression in scRNA-seq data, thereby providing a potential explanation for the impaired fertility.

LIMITATIONS, REASONS FOR CAUTION

Although this is so far the only study of human cases that supports the role of RXFP2 in spermatogenic maturation, this is corroborated by several animal studies that have already demonstrated a postnatal function of INSL3 and RXFP2 in spermatogenesis.

WIDER IMPLICATIONS OF THE FINDINGS

This study corroborates RXFP2 as gene implicated in autosomal recessive congenital bilateral cryptorchidism due to biallelic variants, rather than autosomal-dominant cryptorchidism due to monoallelic RXFP2 variants. Our findings also support that RXFP2 is essential in human spermatogenesis, specifically in germ cell maturation, and that biallelic disruption can cause male infertility through spermatogenic arrest at the spermatid stage.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was provided by the Bellux Society for Pediatric Endocrinology and Diabetology (BELSPEED) and supported by a Research Foundation Flanders (FWO) senior clinical investigator grant (E.D.B., 1802220N) and a Ghent University Hospital Special Research Fund grant (M.C., FIKO-IV institutional fund). The authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Molecular and spatial signatures of human and rat corpus cavernosum physiopathological processes at single-cell resolution

The composition and cellular heterogeneity of the corpus cavernosum (CC) microenvironment have been characterized, but the spatial heterogeneity at the molecular level remains unexplored. In this study, we integrate single-cell RNA sequencing (scRNA-seq) and spatial transcriptome sequencing to comprehensively chart the spatial cellular landscape of the human and rat CC under normal and disease conditions. We observe differences in the proportions of cell subtypes and marker genes between humans and rats. Based on the analysis of the fibroblast (FB) niche, we also find that the enrichment scores of mechanical force signaling vary across different regions and correlate with the spatial distribution of FB subtypes. In vitro, the soft and hard extracellular matrix (ECM) induces the differentiation of FBs into apolipoprotein (APO)+ FBs and cartilage oligomeric matrix protein (COMP)+ FBs, respectively. In summary, our study provides a cross-species and physiopathological transcriptomic atlas of the CC, contributing to a further understanding of the molecular anatomy and regulation of penile erection.

Decoding the pathogenesis of spermatogenic failure in cryptorchidism through single-cell transcriptomic profiling

Cryptorchidism, commonly known as undescended testis, affects 1%-9% of male newborns, posing infertility and testis tumor risks. Despite its prevalence, the detailed pathophysiology underlying male infertility within cryptorchidism remains unclear. Here, we profile and analyze 46,644 single-cell transcriptomes from individual testicular cells obtained from adult males diagnosed with cryptorchidism and healthy controls. Spermatogenesis compromise in cryptorchidism links primarily to spermatogonium self-renewal and differentiation dysfunctions. We illuminate the involvement of testicular somatic cells, including immune cells, thereby unveiling the activation and degranulation of mast cells in cryptorchidism. Mast cells are identified as contributors to interstitial fibrosis via transforming growth factor β1 (TGF-β1) and cathepsin G secretion. Furthermore, significantly increased levels of secretory proteins indicate mast cell activation and testicular fibrosis in the seminal plasma of individuals with cryptorchidism compared to controls. These insights serve as valuable translational references, enriching our comprehension of testicular pathogenesis and informing more precise diagnosis and targeted therapeutic strategies for cryptorchidism.

PTN from Leydig cells activates SDC2 and modulates human spermatogonial stem cell proliferation and survival via GFRA1

BACKGROUND

Spermatogonial stem cells (SSCs) are essential for the maintenance and initiation of male spermatogenesis. Despite the advances in understanding SSC biology in mouse models, the mechanisms underlying human SSC development remain elusive.

RESULTS

Here, we analyzed the signaling pathways involved in SSC regulation by testicular somatic cells using single-cell sequencing data (GEO datasets: GSE149512 and GSE112013) and identified that Leydig cells communicate with SSCs through pleiotrophin (PTN) and its receptor syndecan-2 (SDC2). Immunofluorescence, STRING prediction, and protein immunoprecipitation assays confirmed the interaction between PTN and SDC2 in spermatogonia, but their co-localization was observed only in approximately 50% of the cells. The knockdown of SDC2 in human SSC lines impaired cell proliferation, DNA synthesis, and the expression of PLZF, a key marker for SSC self-renewal. Transcriptome analysis revealed that SDC2 knockdown downregulated the expression of GFRA1, a crucial factor for SSC proliferation and self-renewal, and inhibited the HIF-1 signaling pathway. Exogenous PTN rescued the proliferation and GFRA1 expression in SDC2 knockdown SSC lines. In addition, we found downregulation of PTN and SDC2 as well as altered localization in non-obstructive azoospermia (NOA) patients, suggesting that downregulation of PTN and SDC2 may be associated with impaired spermatogenesis.

CONCLUSIONS

Our results uncover a novel mechanism of human SSC regulation by the testicular microenvironment and suggest a potential therapeutic target for male infertility.

EEF1B2 regulates the proliferation and apoptosis of human spermatogonial stem cell lines through TAF4B

Background

Spermatogonial stem cells (SSCs) are essential for male fertility, maintaining sperm production throughout life. While mouse SSCs have been studied extensively, the mechanisms regulating human SSCs are less understood.

Objectives

To investigate the role of EEF1B2 in regulating human SSC proliferation and apoptosis.

Material and methods

Single cell RNA sequencing (scRNA-seq) analysis was utilized to investigate the differentially expressed genes of SSC. The distribution of EEF1B2 in the human testis was examined using immunofluorescence and immunohistochemistry techniques. Cell proliferation, DNA replication, and self-renewal were analyzed using CCK8, EdU, Western blot, and flow cytometry. RNA sequencing was employed to analyze the downstream target molecules and signaling pathways of EEF1B2.

Results

In this study, we analyzed single-cell sequencing data from human testicular samples and identified EEF1B2 as a protein highly expressed in SSCs, with expression decreasing during development. Immunohistochemistry and immunofluorescence confirmed this pattern and showed co-localization with the proliferation marker KI67. Knockdown of EEF1B2 in human SSC lines impaired proliferation and viability, reducing self-renewal proteins like PLZF and CCNE1. RNA sequencing revealed decreased TAF4B following EEF1B2 knockdown, which could be rescued by replenishing TAF4B. Testicular SSCs from non-obstructive azoospermia (NOA) patients also showed reduced EEF1B2.

Discussion and conclusion

Our findings reveal a novel regulatory mechanism involving EEF1B2 and TAF4B in human SSCs, suggesting EEF1B2 deficiency may contribute to male infertility.

SMARTdb: An Integrated Database for Exploring Single-cell Multi-omics Data of Reproductive Medicine

Single-cell multi-omics sequencing has greatly accelerated reproductive research in recent years, and the data are continually growing. However, utilizing these data resources is challenging for wet-lab researchers. A comprehensive platform for exploring single-cell multi-omics data related to reproduction is urgently needed. Here, we introduce the single-cell multi-omics atlas of reproduction (SMARTdb), an integrative and user-friendly platform for exploring molecular dynamics of reproductive development, aging, and disease, which covers multi-omics, multi-species, and multi-stage data. We curated and analyzed single-cell transcriptomic and epigenomic data of over 2.0 million cells from 6 species across the entire lifespan. A series of powerful functionalities are provided, such as "Query gene expression", "DIY expression plot", "DNA methylation plot", and "Epigenome browser". With SMARTdb, we found that the male germ cell-specific expression pattern of RPL39L and RPL10L is conserved between human and other model animals. Moreover, DNA hypomethylation and open chromatin may collectively regulate the specific expression pattern of RPL39L in both male and female germ cells. In summary, SMARTdb is a powerful platform for convenient data mining and gaining novel insights into reproductive development, aging, and disease. SMARTdb is publicly available at https://smart-db.cn.

Effects of Heat Stress-Induced Sex Hormone Dysregulation on Reproduction and Growth in Male Adolescents and Beneficial Foods

Heat stress due to climate warming can significantly affect the synthesis of sex hormones in male adolescents, which can impair the ability of the hypothalamus to secrete gonadotropin-releasing hormone on the hypothalamic-pituitary-gonadal axis, which leads to a decrease in luteinizing hormone and follicle-stimulating hormone, which ultimately negatively affects spermatogenesis and testosterone synthesis. For optimal spermatogenesis, the testicular temperature should be 2-6 °C lower than body temperature. Heat stress directly affects the testes, damaging them and reducing testosterone synthesis. Additionally, chronic heat stress abnormally increases the level of aromatase in Leydig cells, which increases estradiol synthesis while decreasing testosterone, leading to an imbalance of sex hormones and spermatogenesis failure. Low levels of testosterone in male adolescents lead to delayed puberty and incomplete sexual maturation, negatively affect height growth and bone mineral density, and can lead to a decrease in lean body mass and an increase in fat mass. In order for male adolescents to acquire healthy reproductive capacity, it is recommended to provide sufficient nutrition and energy, avoid exposure to heat stress, and provide foods and supplements to prevent or repair testosterone reduction, germ cell damage, and sperm count reduction caused by heat stress so that they can enter a healthy adulthood.

Single-cell RNA sequencing technology in human spermatogenesis: Progresses and perspectives

Spermatogenesis, a key part of the spermiation process, is regulated by a combination of key cells, such as primordial germ cells, spermatogonial stem cells, and somatic cells, such as Sertoli cells. Abnormal spermatogenesis can lead to azoospermia, testicular tumors, and other diseases related to male infertility. The application of single-cell RNA sequencing (scRNA-seq) technology in male reproduction is gradually increasing with its unique insight into deep mining and analysis. The data cover different periods of neonatal, prepubertal, pubertal, and adult stages. Different types of male infertility diseases including obstructive and non-obstructive azoospermia (NOA), Klinefelter Syndrome (KS), Sertoli Cell Only Syndrome (SCOS), and testicular tumors are also covered. We briefly review the principles and application of scRNA-seq and summarize the research results and application directions in spermatogenesis in different periods and pathological states. Moreover, we discuss the challenges of applying this technology in male reproduction and the prospects of combining it with other technologies.

Primate-Specific DAZ Regulates Translation of Cell Proliferation-Related mRNAs and is Essential for Maintenance of Spermatogonia

Primate-specific DAZ (deleted in azoospermia) has evolved in the azoospermia factor c (AZFc) locus on the Y chromosome. Loss of DAZ is associated with azoospermia in patients with deletion of the AZFc region (AZFc_del). However, the molecular mechanisms of DAZ in spermatogenesis remain uncertain. In this study, the molecular mechanism of DAZ is identified, which is unknown since it is identified 40 years ago because of the lack of a suitable model. Using clinical samples and cell models, it is shown that DAZ plays an important role in spermatogenesis and that loss of DAZ is associated with defective proliferation of c-KIT-positive spermatogonia in patients with AZFc_del. Mechanistically, it is shown that knockdown of DAZ significantly downregulated global translation and subsequently decreased cell proliferation. Furthermore, DAZ interacted with PABPC1 via the DAZ repeat domain to regulate global translation. DAZ targeted mRNAs that are involved in cell proliferation and cell cycle phase transition. These findings indicate that DAZ is a master translational regulator and essential for the maintenance of spermatogonia. Loss of DAZ may result in defective proliferation of c-KIT-positive spermatogonia and spermatogenic failure.

Integrative bioinformatics analysis to identify ferroptosis-related genes in non-obstructive azoospermia

PURPOSE

The objective of this study was to discern ferroptosis-related genes (FRGs) linked to non-obstructive azoospermia and investigate the associated molecular mechanisms.

METHOD

A dataset related to azoospermia was retrieved from the Gene Expression Omnibus database, and FRGs were sourced from GeneCards. Ferroptosis-related differentially expressed genes (FRDEGs) were discerned. Subsequently, these genes underwent analyses encompassing Gene Ontology and Kyoto Encyclopedia of Genes and Genomes, as well as protein-protein interaction (PPI) networks and assessments of functional similarity. Following the identification of hub genes, an exploration of immune infiltration, single-cell expression, diagnostic utility, and interactions involving hub genes, RNA-binding proteins (RBPs), transcription factors (TFs), microRNAs (miRNAs), and drugs was conducted.

RESULTS

A total of 35 differentially expressed FRGs were discerned. These genes demonstrated enrichment in functions and pathways associated with ferroptosis. From the PPI network, eight hub genes were selected. Functional similarity analysis highlighted the potential pivotal roles of HMOX1 and GPX4 in azoospermia. Analysis of immune cell infiltration indicated a significant decrease in activated dendritic cells in the azoospermia group, with notable correlations between hub genes, particularly SAT1 and HMGCR, and immune cell infiltration. Unique expression patterns of hub genes across various cell types in the human testis were observed, with GPX4 prominently enriched in spermatid/sperm. Eight hub genes exhibited robust diagnostic value (AUC > 0.75). Lastly, a comprehensive hub gene-miRNA-TF-RBP-drug network was constructed.

CONCLUSION

In summary, our investigation unveiled eight FRDEGs associated with azoospermia, which hold potential as biomarkers for the diagnosis and treatment of azoospermia.

Elucidating the Transcriptional States of Spermatogenesis-Joint Analysis of Germline and Supporting Cell, Mice and Human, Normal and Perturbed, Bulk and Single-Cell RNA-Seq

In studying the molecular underpinning of spermatogenesis, we expect to understand the fundamental biological processes better and potentially identify genes that may lead to novel diagnostic and therapeutic strategies toward precision medicine in male infertility. In this review, we emphasized our perspective that the path forward necessitates integrative studies that rely on complementary approaches and types of data. To comprehensively analyze spermatogenesis, this review proposes four axes of integration. First, spanning the analysis of spermatogenesis in the healthy state alongside pathologies. Second, the experimental analysis of model systems (in which we can deploy treatments and perturbations) alongside human data. Third, the phenotype is measured alongside its underlying molecular profiles using known markers augmented with unbiased profiles. Finally, the testicular cells are studied as ecosystems, analyzing the germ cells alongside the states observed in the supporting somatic cells. Recently, the study of spermatogenesis has been advancing using single-cell RNA sequencing, where scientists have uncovered the unique stages of germ cell development in mice, revealing new regulators of spermatogenesis and previously unknown cell subtypes in the testis. An in-depth analysis of meiotic and postmeiotic stages led to the discovery of marker genes for spermatogonia, Sertoli and Leydig cells and further elucidated all the other germline and somatic cells in the testis microenvironment in normal and pathogenic conditions. The outcome of an integrative analysis of spermatogenesis using advanced molecular profiling technologies such as scRNA-seq has already propelled our biological understanding, with additional studies expected to have clinical implications for the study of male fertility. By uncovering new genes and pathways involved in abnormal spermatogenesis, we may gain insights into subfertility or sterility.

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.

DDX20 is required for cell-cycle reentry of prospermatogonia and establishment of spermatogonial stem cell pool during testicular development in mice

RNA-binding proteins (RBPs), as key regulators of mRNA fate, are abundantly expressed in the testis. However, RBPs associated with human male infertility remain largely unknown. Through bioinformatic analyses, we identified 62 such RBPs, including an evolutionarily conserved RBP, DEAD-box helicase 20 (DDX20). Male germ-cell-specific inactivation of Ddx20 at E15.5 caused T1-propsermatogonia (T1-ProSG) to fail to reenter cell cycle during the first week of testicular development in mice. Consequently, neither the foundational spermatogonial stem cell (SSC) pool nor progenitor spermatogonia were ever formed in the knockout testes. Mechanistically, DDX20 functions to control the translation of its target mRNAs, many of which encode cell-cycle-related regulators, by interacting with key components of the translational machinery in prospermatogonia. Our data demonstrate a previously unreported function of DDX20 as a translational regulator of critical cell-cycle-related genes, which is essential for cell-cycle reentry of T1-ProSG and formation of the SSC pool.

Linc00513 sponges miR-7 to modulate TGF-β signaling in azoospermia

Azoospermia, or the complete absence of sperm in the ejaculate, affects about 1% of men worldwide and is a significant fertility challenge. This study investigates Linc00513, a long non-coding RNA, and its potential role in regulating the TGF-β signaling pathway, a key player in spermatogenesis, in the context of azoospermia. We show that Linc00513 expression is significantly lower in testicular tissues from azoospermic patients than in HS1 controls. Linc00513 interacts directly with microRNA-7 (miR-7) via complementary base pairing, acting as a competing endogenous RNA (ceRNA). This interaction effectively inhibits miR-7's inhibitory action on the TGF-β receptor 1 (TGFBR1), a critical component of the TGF-β signaling cascade. Downregulating Linc00513 reduces TGFBR1 repression and increases TGF-β signaling in azoospermic testes. Functional assays with spermatogonial cell lines support these findings. Silencing Linc00513 leads to increased cell proliferation and decreased apoptosis, similar to TGF-β inhibition. Overexpression of miR-7 inhibits the effects of Linc00513 on TGF-β signaling. Our study sheds new light on how Linc00513, miR-7, and the TGF-β signaling pathway interact in azoospermia. Linc00513 regulates TGFBR1 expression and thus influences spermatogonial cell fate by acting as a miR-7 ceRNA. These findings identify a potential therapeutic target for azoospermia treatment, paving the way for future research into restoring fertility in affected individuals.

Mapping the Development of Human Spermatogenesis Using Transcriptomics-Based Data: A Scoping Review

In vitro maturation (IVM) is a promising fertility restoration strategy for patients with nonobstructive azoospermia or for prepubertal boys to obtain fertilizing-competent spermatozoa. However, in vitro spermatogenesis is still not achieved with human immature testicular tissue. Knowledge of various human testicular transcriptional profiles from different developmental periods helps us to better understand the testis development. This scoping review aims to describe the testis development and maturation from the fetal period towards adulthood and to find information to optimize IVM. Research papers related to native and in vitro cultured human testicular cells and single-cell RNA-sequencing (scRNA-seq) were identified and critically reviewed. Special focus was given to gene ontology terms to facilitate the interpretation of the biological function of related genes. The different consecutive maturation states of both the germ and somatic cell lineages were described. ScRNA-seq regularly showed major modifications around 11 years of age to eventually reach the adult state. Different spermatogonial stem cell (SSC) substates were described and scRNA-seq analyses are in favor of a paradigm shift, as the Adark and Apale spermatogonia populations could not distinctly be identified among the different SSC states. Data on the somatic cell lineage are limited, especially for Sertoli cells due technical issues related to cell size. During cell culture, scRNA-seq data showed that undifferentiated SSCs were favored in the presence of an AKT-signaling pathway inhibitor. The involvement of the oxidative phosphorylation pathway depended on the maturational state of the cells. Commonly identified cell signaling pathways during the testis development and maturation highlight factors that can be essential during specific maturation stages in IVM.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

X‑chromosome loss rescues Sertoli cell maturation and spermatogenesis in Klinefelter syndrome

Klinefelter syndrome (47,XXY) causes infertility with a testicular histology comprising two types of Sertoli cell-only tubules, representing mature and immature-like Sertoli cells, and occasionally focal spermatogenesis. Here, we show that the immature-like Sertoli cells highly expressed XIST and had two X-chromosomes, while the mature Sertoli cells lacked XIST expression and had only one X-chromosome. Sertoli cells supporting focal spermatogenesis also lacked XIST expression and the additional X-chromosome, while the spermatogonia expressed XIST despite having only one X-chromosome. XIST was expressed in Sertoli cells until puberty, where a gradual loss was observed. Our results suggest that a micro-mosaic loss of the additional X-chromosome is needed for Sertoli cells to mature and to allow focal spermatogenesis.