Effects of Leydig cell elimination on testicular interstitial cell populations: characterization by scRNA-seq and immunocytochemical techniques

Background

The mammalian testicular interstitial cells are not well-defined. The present study characterized the interstitial cell types and their turnover dynamics in adult rats. Additionally, the heterogeneity of the mesenchymal population and the effects of Leydig cell elimination on interstitial homeostasis were further analyzed by scRNA-seq datasets and immunocytochemical techniques.

Methods

Interstitial cells were defined at the transcriptomic level by scRNA-seq and then confirmed and quantified with protein markers. The dividing activity of the major cell types was determined by continuous EdU labeling of the animals for one week. Some of the rats were also treated with a dose of ethylenedimethylsulfonate (EDS) to examine how the loss of Leydig cells (LCs) could affect interstitial homeostasis for three weeks.

Results

Seven interstitial cell types were identified, including cell types (percentage of the whole interstitial population) as follows: Leydig (44.6%), macrophage and dendritic (19.1%), lymphoid (6.2%), vascular endothelial (7.9%), smooth muscle (10.7%), and mesenchymal (11.5%) cells. The EdU experiment indicated that most cell types were dividing at relatively low levels (<9%) except for the mesenchymal cells (MCs, 17.1%). Further analysis of the transcriptome of MCs revealed 4 subgroups with distinct functions, including 1) glutathione metabolism and xenobiotic detoxification, 2) ROS response and AP-1 signaling, 3) extracellular matrix synthesis and binding, and 4) immune response and regulation. Stem LCs (SLCs) are primarily associated with subgroup 3, expressing ARG1 and GAP43. EDS treatment not only eliminated LCs but also increased subgroup 3 and decreased subgroups 1 and 2 of the mesenchymal population. Moreover, EDS treatment increased the division of immune cells by more than tenfold in one week.

Conclusion

Seven interstitial cell types were identified and quantified for rat testis. Many may play more diversified roles than previously realized. The elimination of LCs led to significant changes in MCs and immune cells, indicating the importance of LCs in maintaining testicular interstitial homeostasis.

Study on the cytokines related to SARS-Cov-2 in testicular cells and the interaction network between cells based on scRNA-seq data

Inflammatory cytokine storms (CS) in COVID-19 patients are associated with elevated levels of 13 specific cytokines, potentially impacting male fertility by causing testicular cell damage and disrupting the immune microenvironment. Some patients present with scrotal discomfort and orchitis. However, few studies have explored cytokine expression in testicular cells and their role in cell-to-cell communication. In this study, we integrated single-cell sequencing data sets of testicular cells, annotating 20 cell clusters using marker genes and the Human Cell Landscape database. We constructed cell pseudo-chronological trajectories, hub genes, and analyzed the cytokine interaction network between sperm cells using CellChat. Our findings identified 12 types of testicular cells, with four cytokines (IL8, CCL2, CCL3, and TNF) potentially involved in immune processes. Pseudo-chronological trajectory analysis indicated IL8 and CCL3's essential roles in testicular macrophages and endothelial cell development, affecting the immune microenvironment. We determined eight key cytokines (IL1, IL2, IL4, IL6, CCL, CSF3, TNF, and IFN-II) functions in cell interaction networks. Network analysis of exogenous cytokines directly acting on testicular cells showed IL2 potentially affecting all testicular cells, suggesting a vital role in cell communication. This research offers valuable insights into CSs effects on testicular cells and their potential impact on male fertility during COVID-19 infection.

Microbiology and immune mechanisms associated with male infertility

Up to 50% of infertility is caused by the male side. Varicocele, orchitis, prostatitis, oligospermia, asthenospermia, and azoospermia are common causes of impaired male reproductive function and male infertility. In recent years, more and more studies have shown that microorganisms play an increasingly important role in the occurrence of these diseases. This review will discuss the microbiological changes associated with male infertility from the perspective of etiology, and how microorganisms affect the normal function of the male reproductive system through immune mechanisms. Linking male infertility with microbiome and immunomics can help us recognize the immune response under different disease states, providing more targeted immune target therapy for these diseases, and even the possibility of combined immunotherapy and microbial therapy for male infertility.

Hypertension and reproductive dysfunction: a possible role of inflammation and inflammation-associated lymphangiogenesis in gonads

Hypertension is one of the most prevalent diseases that leads to end organ damage especially affecting the heart, kidney, brain, and eyes. Numerous studies have evaluated the association between hypertension and impaired sexual health, in both men and women. The detrimental effects of hypertension in men includes erectile dysfunction, decrease in semen volume, sperm count and motility, and abnormal sperm morphology. Similarly, hypertensive females exhibit decreased vaginal lubrication, reduced orgasm, and several complications in pregnancy leading to fetal and maternal morbidity and mortality. The adverse effect of hypertension on male and female fertility is attributed to hormonal imbalance and changes in the gonadal vasculature. However, mechanistic studies investigating the impact of hypertension on gonads in more detail on a molecular basis remain scarce. Hence, the aim of the current review is to address and summarize the effects of hypertension on reproductive health, and highlight the importance of research on the effects of hypertension on gonadal inflammation and lymphatics.

Relevance of angiogenesis in autoimmune testis inflammation

Experimental autoimmune orchitis (EAO) is a useful model to study organ-specific autoimmunity and chronic testicular inflammation. This model reflects testicular pathological changes reported in immunological infertility in men. Progression of EAO in rodents is associated with a significantly increased percentage of testicular endothelial cells and interstitial testicular blood vessels, indicating an ongoing angiogenic process. Vascular endothelial growth factor A (VEGFA), the main regulator of physiological and pathological angiogenesis, can stimulate endothelial cell proliferation, chemotaxis and vascular permeability. The aim of this study was to explore the role of VEGFA in the pathogenesis of testicular inflammation. Our results found VEGFA expression in Leydig cells, endothelial cells and macrophages in testis of rats with autoimmune orchitis. VEGFA level was significantly higher in testicular fluid and serum of rats at the end of the immunization period, preceding testicular damage. VEGF receptor (VEGFR) 1 is expressed mainly in testicular endothelial cells, whereas VEGFR2 was detected in germ cells and vascular smooth muscle cells. Both receptors were expressed in testicular interstitial cells. VEGFR2 increased after the immunization period in the testicular interstitium and VEGFR1 was downregulated in EAO testis. In-vivo-specific VEGFA inhibition by Bevacizumab prevented the increase in blood vessel number and reduced EAO incidence and severity. Our results unveil relevance of VEGFA-VEGFR axis during orchitis development, suggesting that VEGFA might be an early marker of testicular inflammation and Bevacizumab a therapeutic tool for treatment of testicular inflammation associated with subfertility and infertility.

T Lymphocytes and Testicular Immunity: A New Insight into Immune Regulation in Testes

The immune privilege of the testes is necessary to prevent immune attacks to gamete-specific antigens and paternal major histocompatibility complex (MHC) antigens, allowing for normal spermatogenesis. However, infection and inflammation of the male genital tract can break the immune tolerance and represent a significant cause of male infertility. Different T cell subsets have been identified in mammalian testes, which may be involved in the maintenance of immune tolerance and pathogenic immune responses in testicular infection and inflammation. We reviewed the evidence in the published literature on different T subtypes (regulatory T cells, helper T cells, cytotoxic T cells, γδ T cells, and natural killer T cells) in human and animal testes that support their regulatory roles in infertility and the orchitis pathology. While many in vitro studies have indicated the regulation potential of functional T cell subsets and their possible interaction with Sertoli cells, Leydig cells, and spermatogenesis, both under physiological and pathological processes, there have been no in situ studies to date. Nevertheless, the normal distribution and function of T cell subsets are essential for the immune privilege of the testes and intact spermatogenesis, and T cell-mediated immune response drives testicular inflammation. The distinct function of different T cell subsets in testicular homeostasis and the orchitis pathology suggests a considerable potential of targeting specific T cell subsets for therapies targeting chronic orchitis and immune infertility.

Effect of ketotifen fumarate on experimental autoimmune orchitis and torsion of the spermatic cord

The aim of this work was to study effects of ketotifen fumarate (KF) on prevention of tissue damage in testes of rats with experimental autoimmune orchitis (EAO) and on the contralateral testis in a model of prolonged testicular cord torsion (TCT). Rats with EAO or TCT were injected intraperitoneally once daily with KF or saline solution (vehicle group). Incidence and severity of testicular damage were evaluated by histopathology using an EAO score or a Johnsen score. Mast cells (MC) were identified by histochemistry and quantified. In EAO model, KF significantly reduced severity of histopathological testicular damage compared to rats in the vehicle group. KF also reduced the number of testicular MC compared to vehicle group. Similarly, in TCT model, multifocal damage of the contralateral testis was observed 30 days after testicular torsion characterized by sloughing of the germinal epithelium, seminiferous tubule atrophy, and interstitial edema. Focal signs of inflammation and fibrosis of seminiferous tubular walls were also observed. In contrast, sections of contralateral testis of rats injected with KF and killed 30 days after surgery showed normal histological features. A significant decrease in the number of MC was observed in rats treated with KF compared to untreated animals. In conclusion, we demonstrated that treatment with KF reduced testicular inflammatory process and MC infiltrates in both EAO and TCT models. The results suggest a promising treatment for infertile male patients with testicular pathologies associated with inflammation and germ cell loss.

Immune Cell Subtypes and Their Function in the Testis

Immunoregulation in the testis is characterized by a balance between immuno-suppression (or immune privilege) and the ability to react to infections and inflammation. In this review, we analyze the phenotypes of the various immune cell subtypes present in the testis, and how their functions change between homeostatic and inflammatory conditions. Starting with testicular macrophages, we explore how this heterogeneous population is shaped by the testicular microenvironment to ensure immune privilege. We then describe how dendritic cells exhibit a tolerogenic status under normal conditions, but proliferate, mature and then stimulate effector T-cell expansion under inflammatory conditions. Finally, we outline the two T-cell populations in the testis: CD4⁺/CD8⁺ αβ T cells and CD4⁺/CD8⁺ Foxp3⁺ regulatory T cells and describe the distribution and function of mast cells. All these cells help modulate innate immunity and regulate the immune response. By improving our understanding of immune cell behavior in the testis under normal and inflammatory conditions, we will be better placed to evaluate testis impairment due to immune mechanisms in affected patients.

Using high-throughput sequencing to explore the anti-inflammatory effects of α-mangostin

Lipopolysaccharide (LPS) causes an inflammatory response, and α-mangostin (α-MG) is an ingredient of a Chinese herbal medicine with anti-inflammatory effects. We investigated the mechanism by which α-MG reduces LPS-stimulated IEC-6 cells inflammation. A genome-wide examination of control, LPS-stimulated, and α-MG-pretreated cells was performed with the Illumina Hiseq sequencing platform, and gene expression was verified with quantitative real-time PCR (qPCR). Among the 37,199 genes profiled, 2014 genes were regulated in the LPS group, and 475 genes were regulated in the α-MG group. GO enrichment and KEGG pathway analyses of the differentially expressed genes (DEGs) showed that they were mainly related to inflammation and oxidative stress. Based on the transcriptomic results, we constructed a rat model of inflammatory bowel disease (IBD) with LPS and investigated the effects of α-MG on NLRP3 inflammasomes. After LPS stimulation, the rat intestinal villi were significantly detached, with congestion and hemorrhage; the intestinal epithelial cell nuclei were deformed; and the mitochondria were swollen. However, after pretreatment with α-MG, the intestinal villus congestion and hemorrhage were reduced, the epithelial nuclei were rounded, and the mitochondrial morphology was intact. qPCR and western blotting were used to detect NLRP3, caspase 1, interleukin (IL)-18, and IL-1β expression at the gene and protein levels. Their expression increased at both the transcript and protein levels after LPS stimulation, whereas it decreased after pretreatment with α-MG. This study provides new methods and ideas for the treatment of inflammation. α-MG may have utility as a drug for intestinal inflammation.

Infectious, inflammatory and 'autoimmune' male factor infertility: how do rodent models inform clinical practice?

BACKGROUND

Infection and inflammation of the reproductive tract are significant causes of male factor infertility. Ascending infections caused by sexually transmitted bacteria or urinary tract pathogens represent the most frequent aetiology of epididymo-orchitis, but viral, haematogenous dissemination is also a contributory factor. Limitations in adequate diagnosis and therapy reflect an obvious need for further understanding of human epididymal and testicular immunopathologies and their contribution to infertility. A major obstacle for advancing our knowledge is the limited access to suitable tissue samples. Similarly, the key events in the inflammatory or autoimmune pathologies affecting human male fertility are poorly amenable to close examination. Moreover, the disease processes generally have occurred long before the patient attends the clinic for fertility assessment. In this regard, data obtained from experimental animal models and respective comparative analyses have shown promise to overcome these restrictions in humans.

OBJECTIVE AND RATIONALE

This narrative review will focus on male fertility disturbances caused by infection and inflammation, and the usefulness of the most frequently applied animal models to study these conditions.

SEARCH METHODS

An extensive search in Medline database was performed without restrictions until January 2018 using the following search terms: 'infection' and/or 'inflammation' and 'testis' and/or 'epididymis', 'infection' and/or 'inflammation' and 'male genital tract', 'male infertility', 'orchitis', 'epididymitis', 'experimental autoimmune' and 'orchitis' or 'epididymitis' or 'epididymo-orchitis', antisperm antibodies', 'vasectomy'. In addition to that, reference lists of primary and review articles were reviewed for additional publications independently by each author. Selected articles were verified by each two separate authors and discrepancies discussed within the team.

OUTCOMES

There is clear evidence that models mimicking testicular and/or epididymal inflammation and infection have been instructive in a better understanding of the mechanisms of disease initiation and progression. In this regard, rodent models of acute bacterial epididymitis best reflect the clinical situation in terms of mimicking the infection pathway, pathogens selected and the damage, such as fibrotic transformation, observed. Similarly, animal models of acute testicular and epididymal inflammation using lipopolysaccharides show impairment of reproduction, endocrine function and histological tissue architecture, also seen in men. Autoimmune responses can be studied in models of experimental autoimmune orchitis (EAO) and vasectomy. In particular, the early stages of EAO development showing inflammatory responses in the form of peritubular lymphocytic infiltrates, thickening of the lamina propria of affected tubules, production of autoantibodies against testicular antigens or secretion of pro-inflammatory mediators, replicate observations in testicular sperm extraction samples of patients with 'mixed atrophy' of spermatogenesis. Vasectomy, in the form of sperm antibodies and chronic inflammation, can also be studied in animal models, providing valuable insights into the human response.

WIDER IMPLICATIONS

This is the first comprehensive review of rodent models of both infectious and autoimmune disease of testis/epididymis, and their clinical implications, i.e. their importance in understanding male infertility related to infectious and non-infectious/autoimmune disease of the reproductive organs.

Cytokines in Male Fertility and Reproductive Pathologies: Immunoregulation and Beyond

Germline development in vivo is dependent on the environment formed by somatic cells and the differentiation cues they provide; hence, the impact of local factors is highly relevant to the production of sperm. Knowledge of how somatic and germline cells interact is central to achieving biomedical goals relating to restoring, preserving or restricting fertility in humans. This review discusses the growing understanding of how cytokines contribute to testicular function and maintenance of male reproductive health, and to the pathologies associated with their abnormal activity in this organ. Here we consider both cytokines that signal through JAKs and are regulated by SOCS, and those utilizing other pathways, such as the MAP kinases and SMADs. The importance of cytokines in the establishment and maintenance of the testis as an immune-privilege site are described. Current research relating to the involvement of immune cells in testis development and disease is highlighted. This includes new data relating to testicular cancer which reinforce the understanding that tumorigenic cells shape their microenvironment through cytokine actions. Clinical implications in pathologies relating to local inflammation and to immunotherapies are discussed.

Dual role of immune cells in the testis: Protective or pathogenic for germ cells?

The purpose of this review is to describe how the immune cells present in the testis interact with the germinal epithelium contributing to survival or apoptosis of germ cells (GCs). Physiologically, the immunosuppressor testicular microenvironment protects GCs from immune attack, whereas in inflammatory conditions, tolerance is disrupted and immune cells and their mediators respond to GC self antigens, inducing damage of the germinal epithelium. Considering that experimental models of autoimmune orchitis have clarified the local immune mechanisms by which protection of the testis is compromised, we described the following topics in the testis of normal and orchitic rats: (1) cell adhesion molecule expression of seminiferous tubule specialized junctions and modulation of blood-testis barrier permeability by cytokines (2) phenotypic and functional characteristics of testicular dendritic cells, macrophages, effector and regulatory T cells and mast cells and (3) effects of pro-inflammatory cytokines (TNF-α, IL-6 and FasL) and the nitric oxide-nitric oxide synthase system on GC apoptosis.