Regulation of blood-testis barrier assembly in vivo by germ cells

Sendai virus-mediated RNA delivery restores fertility to congenital and chemotherapy-induced infertile female mice

Current infertility treatment strategies focus on mature gametes, leaving a significant proportion of cases with gamete progenitors that stopped complete differentiation. On the other hand, recent advancements in next-generation sequencing have identified many candidate genes that may promote maturation of germ cells. Although gene therapy has shown success in mice, concerns about the integration of DNA vectors into oocytes hinder clinical applications. Here, we present the restoration of fertility in female mice through Sendai virus (SeV)-mediated RNA delivery. Ovaries lacking Kitl expression exhibit only primordial follicles due to impaired signaling to oocytes expressing the KIT tyrosine kinase. Despite SeVs being immunogenic and larger than the blood-follicle barrier, the administration of Kitl-expressing SeVs reinitiated oogenesis in genetically infertile mice that have only primordial follicles, resulting in the birth of normal offspring through natural mating. This virus also effectively addressed iatrogenic infertility induced by busulfan, a widely used cancer chemotherapy agent. Offspring born through SeV administration and natural mating displayed normal genomic imprinting patterns and fertility. Since SeVs pose no genotoxicity risk, the successful restoration of fertility by SeVs represents a promising approach for treating congenital infertility with somatic cell defects and protecting fertility of cancer patients who may become infertile due to loss of oocytes during cancer therapy.

Inositol hexakisphosphate kinase 1 is essential for cell junction integrity in the mouse seminiferous epithelium

Inositol hexakisphosphate kinases (IP6Ks) are enzymes that catalyse the synthesis of the inositol pyrophosphate 5-IP7 which is involved in the regulation of many physiological processes in mammals. The IP6K paralog IP6K1 is expressed at high levels in the mammalian testis, and its deletion leads to sterility in male mice. Here, we show that the loss of IP6K1 in mice causes a delay in the first wave of spermatogenesis. Testes from juvenile Ip6k1 knockout mice show downregulation of transcripts that are involved in cell adhesion and formation of the testis-specific inter-Sertoli cell impermeable junction complex known as the blood-testis barrier (BTB). We demonstrate that loss of IP6K1 in the mouse testis causes BTB disruption associated with transcriptional misregulation of the tight junction protein claudin 3, and subcellular mislocalization of the gap junction protein connexin 43. In addition to BTB disruption, we also observe a loss of germ cell adhesion in the seminiferous epithelium of Ip6k1 knockout mice, ultimately resulting in premature sloughing of round spermatids into the epididymis. Mechanistically, we show that loss of IP6K1 in the testis enhances cofilin dephosphorylation in conjunction with increased AKT/ERK and integrin signalling, resulting in destabilization of the actin-based cytoskeleton in Sertoli cells and germ cell loss.

Effects of azithromycin exposure during pregnancy at different stages, doses and courses on testicular development in fetal mice

Azithromycin is a commonly used antibiotic during pregnancy, but some studies have suggested its potential developmental toxicity. Currently, the effects and mechanisms of prenatal azithromycin exposure (PAzE) on fetal testicular development are still unclear. The effects of prenatal exposure to the same drug on fetal testicular development could vary depending on different stages, doses, and courses. Hence, in this study, based on clinical medication characteristics, Kunming mice was administered intragastrically with azithromycin at different stages (mid-/late-pregnancy), doses (50, 100, 200 mg/kg·d), and courses (single-/multi-course). Fetal blood and testicular samples were collected on GD18 for relevant assessments. The results indicated that PAzE led to changes in fetal testicular morphology, reduced cell proliferation, increased apoptosis, and decreased expression of markers related to Leydig cells (Star), Sertoli cells (Wt1), and spermatogonia (Plzf). Further investigation revealed that the effects of PAzE on fetal testicular development were characterized by mid-pregnancy, high dose (clinical dose), and single course having more pronounced effects. Additionally, the TGFβ/Smad and Nrf2 signaling pathways may be involved in the changes in fetal testicular development induced by PAzE. In summary, this study confirmed that PAzE influences fetal testicular morphological development and multicellular function. It provided theoretical and experimental evidence for guiding the rational use of azithromycin during pregnancy and further exploring the mechanisms underlying its developmental toxicity on fetal testicles.

Rutin ameliorates perfluorooctanoic acid-induced testicular injury in mice by reducing oxidative stress and improving lipid metabolism

This study investigated the protective effect of rutin on reproductive and blood-testis barrier (BTB) damage induced by perfluorooctanoic acid (PFOA) exposure. In this study, male ICR mice were randomly divided into three groups, Ctrl group (ddH2O, 5 mL/kg), PFOA group (PFOA, 20 mg/kg/d, 5 mL/kg), PFOA + rutin group (PFOA, 20 mg/kg/d, 5 mL/kg; rutin, 20 mg/kg/d, 5 mL/kg). Mice were exposed to PFOA for 28 days by gavage once daily in the presence or absence of rutin. Histopathological observations demonstrated that rutin treatment during PFOA exposure can reduce structural damage to testis and epididymis such as atrophy of spermatogenic epithelium and stenosis of epididymal lumen, while increase in the number and layers of spermatogenic cells. Biochemical detection demonstrated that rutin can reduce 8-hydroxy-2'-desoxyguanosine (8-OHdG) concentration in the serum and testis tissues. Rutin can also ameliorate glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) content, and reduce malondialdehyde (MDA) and total cholesterol (TC) content in testis tissues. Biotin tracking immunofluorescence and transmission electron microscopy demonstrated that rutin can ameliorate BTB structural damage during PFOA exposure. Rutin ameliorated the stress expression of tight junction proteins occludin and claudin-11. In conclusion, our findings suggested that rutin has a degree of protection in reproductive and BTB damage, which could put forward a new perspective on the application of rutin to prevent reproductive damage.

What do we know about blood-testis barrier? current understanding of its structure and physiology

Blood-testis barrier (BTB) creates a particular compartment in the seminiferous epithelium. Contacting Sertoli cell-Sertoli cell plasma membranes possess specialized junction proteins which present a complex dynamic of formation and dismantling. Thus, these specialized structures facilitate germ cell movement across the BTB. Junctions are constantly rearranged during spermatogenesis while the BTB preserves its barrier function. Imaging methods are essential to studying the dynamic of this sophisticated structure in order to understand its functional morphology. Isolated Sertoli cell cultures cannot represent the multiple interactions of the seminiferous epithelium and in situ studies became a fundamental approach to analyze BTB dynamics. In this review, we discuss the contributions of high-resolution microscopy studies to enlarge the body of morphofunctional data to understand the biology of the BTB as a dynamic structure. The first morphological evidence of the BTB was based on a fine structure of the junctions, which was resolved with Transmission Electron Microscopy. The use of conventional Fluorescent Light Microscopy to examine labelled molecules emerged as a fundamental technique for elucidating the precise protein localization at the BTB. Then laser-scanning confocal microscopy allowed the study of three-dimensional structures and complexes at the seminiferous epithelium. Several junction proteins, like the transmembrane, scaffold and signaling proteins, were identified in the testis using traditional animal models. BTB morphology was analyzed in different physiological conditions as the spermatocyte movement during meiosis, testis development, and seasonal spermatogenesis, but also structural elements, proteins, and BTB permeability were studied. Under pathological, pharmacological, or pollutant/toxic conditions, there are significant studies that provide high-resolution images which help to understand the dynamic of the BTB. Notwithstanding the advances, further research using new technologies is required to gain information on the BTB. Super-resolution light microscopy is needed to provide new research with high-quality images of targeted molecules at a nanometer-scale resolution. Finally, we highlight research areas that warrant future studies, pinpointing new microscopy approaches and helping to improve our ability to understand this barrier complexity.

NECL2 regulates blood-testis barrier dynamics in mouse testes

The adhesion protein nectin-like molecule 2 (NECL2) is involved in spermatogenesis and participates in the connections between Sertoli cells and germ cells. Necl2 deficiency leads to infertility in male mice. We found that NECL2 is relatively highly expressed on the cell membranes of preleptotene spermatocytes. It is known that preleptotene spermatocytes pass through the blood-testis barrier (BTB) from the base of the seminiferous tubules to the lumen to complete meiosis. We hypothesized that the NECL2 protein on the surfaces of preleptotene spermatocytes has an effect on the BTB when crossing the barrier. Our results showed that Necl2 deficiency caused the levels of proteins in the BTB to be abnormal, such as those of Claudin 3, claudin 11, and Connexin43. NECL2 interacted and colocalized with adhesion proteins forming the BTB, such as Connexin43, Occludin, and N-cadherin. NECL2 regulated BTB dynamics when preleptotene spermatocytes passed through the barrier, and Necl2 deficiency caused BTB damage. Necl2 deletion significantly affected the testicular transcriptome, especially the expression of spermatogenesis-related genes. These results suggest that before meiosis and spermatid development occur, BTB dynamics regulated by NECL2 are necessary for spermatogenesis.

Characteristics of piRNAs and their comparative profiling in testes of sheep with different fertility

As a novel class of small RNAs, piRNAs are highly expressed in the animal gonads and their main known role is to inhibit transposon activity for ensuring the correctness and integrity of genome. In order to explore the characteristics of piRNAs in sheep testis and their possible regulatory roles on male reproduction, deep sequencing technology was used to sequence small RNAs and identify piRNAs in testes of sheep. The length of piRNAs in sheep testes showed a unimodal distribution between 26 and 31 nt, with a peak at 29 nt. These piRNAs exhibited obvious ping-pong signature and strand specificity. In the genome, they were mainly aligned to CDS, intron, repetitive sequence regions and unannotated regions. Furthermore, in transposon analysis, piRNAs were aligned predominantly to LINE, SINE, and LTR types of retrotransposon in sheep testes, and the piRNAs derived from each type showed obvious ping-pong signature. The piRNA clusters identified in sheep testes were mainly distributed on chromosomes 3, 7, 15, 17, 18 and 20. The results combining semen determination with pathway enrichment analysis implied that differentially expressed piRNAs between the testes of rams with different fertility might participate in spermatogenesis by regulating multiple pathways closely related to stabilization of blood-testis barrier and renewal and differentiation of spermatogonial stem cell. Taken together, the study provided new insights into the characteristics, origin and expression patterns of piRNAs in sheep testes tissue, which would help us better understand the role of piRNAs in sheep reproduction.

Whole Exome Sequencing and In Silico Analysis of Human Sertoli in Patients with Non-Obstructive Azoospermia

Non-obstructive azoospermia (NOA) is a serious cause of male infertility. The Sertoli cell responds to androgens and takes on roles supporting spermatogenesis, which may cause infertility. This work aims to enhance the genetic diagnosis of NOA via the discovery of new and hub genes implicated in human NOA and to better assess the odds of successful sperm extraction according to the individual’s genotype. Whole exome sequencing (WES) was done on three NOA patients to find key genes involved in NOA. We evaluated genome-wide transcripts (about 50,000 transcripts) by microarray between the Sertoli of non-obstructive azoospermia and normal cells. The microarray analysis of three human cases with different non-obstructive azoospermia revealed that 32 genes were upregulated, and the expressions of 113 genes were downregulated versus the normal case. For this purpose, Enrich Shiny GO, STRING, and Cytoscape online evaluations were applied to predict the functional and molecular interactions of proteins and then recognize the master pathways. The functional enrichment analysis demonstrated that the biological process (BP) terms “inositol lipid-mediated signaling”, “positive regulation of transcription by RNA polymerase II”, and “positive regulation of DNA-templated transcription” significantly changed in upregulated differentially expressed genes (DEGs). The BP investigation of downregulated DEGs highlighted “mitotic cytokinesis”, “regulation of protein-containing complex assembly”, “cytoskeleton-dependent cytokinesis”, and the “peptide metabolic process”. Overrepresented molecular function (MF) terms in upregulated DEGs included “ubiquitin-specific protease binding”, “protease binding”, “phosphatidylinositol trisphosphate phosphatase activity”, and “clathrin light chain binding”. Interestingly, the MF analysis of the downregulated DEGs revealed overexpression in “ATPase inhibitor activity”, “glutathione transferase activity”, and “ATPase regulator activity”. Our findings suggest that these genes and their interacting hub proteins could help determine the pathophysiologies of germ cell abnormalities and infertility.

Sperm-specific proteins: new implications for diagnostic development and cancer immunotherapy

Spermatozoa are comprised of many unique proteins not expressed elsewhere. Sperm-specific proteins are first expressed at puberty, after the development of immune tolerance to self-antigens, and have been assumed to remain confined inside the seminiferous tubules, protected from immune cell recognition by various mechanisms of testicular immune privilege. However, new data has shown that sperm-specific proteins are released by the tubules into the surrounding interstitial fluid; from here they can contact immune cells, potentially promote immune tolerance, and enter the circulation. These new findings have clinical implications for diagnostics and therapeutics targeted at a specific class of proteins known as cancer-testis antigens (CTA), the opportunity to identify new communication pathways in the testis, and to discover new ways to monitor testis function.

Establishment of an oligoasthenospermia mouse model based on TAp73 gene suppression

Background

Oligoasthenospermia is one of the main causes of male infertility. Researchers usually use chemical drugs to directly damage germ cells to prepare oligoasthenospermia models, which disregards the adhesion and migration between spermatogenic cells and Sertoli cells. TAp73 is a critical regulator of the adhesin of germ cell; thus, we sought to explore a novel oligoasthenospermia model based on TAp73 gene suppression.

Methods

Mice in the Pifithrin-α group were injected intraperitoneally with 2.5 mg/kg Pifithrin-α (TAp73 inhibitor) daily for 30 consecutive days. Reproductive hormone levels and epididymal sperm quality, as well as the network morphology of Sertoli cells were tested.

Results

Sperm density, motility, and the relative protein and mRNA expression of TAp73 and Nectin 2 were obviously decreased in the Pifithrin-α group compared with the normal control group. No significant distinction was observed in the relative mRNA and protein expression of ZO-1. Furthermore, the tight junctions (TJs) and apical ectoplasmic specialization (ES) were destroyed in the Pifithrin-α group.

Conclusion

The above results indicate that we successfully established a new oligoasthenospermia mouse model. This study provides a foundation for further exploration of the roles of TAp73 genes during spermatogenesis and provides new research objects for further oligospermia research and future drug discovery.

Cdc42 activity in Sertoli cells is essential for maintenance of spermatogenesis

Sertoli cells are highly polarized testicular supporting cells that simultaneously nurture multiple stages of germ cells during spermatogenesis. Proper localization of polarity protein complexes within Sertoli cells, including those responsible for blood-testis barrier formation, is vital for spermatogenesis. However, the mechanisms and developmental timing that underlie Sertoli cell polarity are poorly understood. We investigate this aspect of testicular function by conditionally deleting Cdc42, encoding a Rho GTPase involved in regulating cell polarity, specifically in Sertoli cells. Sertoli Cdc42 deletion leads to increased apoptosis and disrupted polarity of juvenile and adult testes but does not affect fetal and postnatal testicular development. The onset of the first wave of spermatogenesis occurs normally, but it fails to progress past round spermatid stages, and by young adulthood, conditional knockout males exhibit a complete loss of spermatogenic cells. These findings demonstrate that Cdc42 is essential for Sertoli cell polarity and for maintaining steady-state sperm production.

Sertoli cells of the testicular seminiferous tubule must be highly polarized to simultaneously sustain multiple stages of germ cells during spermatogenesis. Heinrich et al. use a Sertoli-specific conditional deletion mouse model to address the roles of CDC42-mediated apicobasal cell polarity in promoting testis development and spermatogenesis.

Spermiation: Insights from Studies on the Adjudin Model

Spermatogenesis is comprised of a series of cellular events that lead to the generation of haploid sperm. These events include self-renewal of spermatogonial stem cells (SSC), proliferation of spermatogonia by mitosis, differentiation of spermatogonia and spermatocytes, generation of haploid spermatids via meiosis I/II, and spermiogenesis. Spermiogenesis consists of a series of morphological events in which spermatids are being transported across the apical compartment of the seminiferous epithelium while maturing into spermatozoa, which include condensation of the genetic materials, biogenesis of acrosome, packaging of the mitocondria into the mid-piece, and elongation of the sperm tail. However, the biology of spermiation remains poorly understood. In this review, we provide in-depth analysis based on the use of bioinformatics tools and an animal model that mimics spermiation through treatment of adult rats with adjudin, a non-hormonal male contraceptive known to induce extensive germ cell exfoliation across the seminiferous epithelium, but nost notably elongating/elongated spermatids. These analyses have shed insightful information regaridng the biology of spermiation.

Sperm proteins and cancer-testis antigens are released by the seminiferous tubules in mice and men

Sperm develop from puberty in the seminiferous tubules, inside the blood-testis barrier to prevent their recognition as "non-self" by the immune system, and it is widely assumed that human sperm-specific proteins cannot access the circulatory or immune systems. Sperm-specific proteins aberrantly expressed in cancer, known as cancer-testis antigens (CTAs), are often pursued as cancer biomarkers and therapeutic targets based on the assumption they are neoantigens absent from the circulation in healthy men. Here, we identify a wide range of germ cell-derived and sperm-specific proteins, including multiple CTAs, that are selectively deposited by the Sertoli cells of the adult mouse and human seminiferous tubules into testicular interstitial fluid (TIF) that is "outside" the blood-testis barrier. From TIF, the proteins can access the circulatory- and immune systems. Disruption of spermatogenesis decreases the abundance of these proteins in mouse TIF, and a sperm-specific CTA is significantly decreased in TIF from infertile men, suggesting that exposure of certain CTAs to the immune system could depend on fertility status. The results provide a rationale for the development of blood-based tests useful in the management of male infertility and indicate CTA candidates for cancer immunotherapy and biomarker development that could show sex-specific and male-fertility-related responses.

Muscarinic acetylcholine receptor M5 is involved in spermatogenesis through the modification of cell-cell junctions

Muscarinic acetylcholine receptor (mAChR) antagonists have been reported to decrease male fertility; however, the roles of mAChRs in spermatogenesis and the underlying mechanisms are not understood yet. During spermatogenesis, extensive remodeling between Sertoli cells and/or germ cells interfaces takes place to accommodate the transport of developing germ cells across the blood-testis barrier (BTB) and adluminal compartment. The cell–cell junctions play a vital role in the spermatogenesis process. This study used ICR male mice and spermatogonial cells (C18-4) and Sertoli cells (TM-4). shRNA of control or M5 gene was injected into 5-week-old ICR mice testes. Ten days post-viral grafting, mice were deeply anesthetized with pentobarbital and the testes were collected. One testicle was fresh frozen for RNA-seq analysis or Western blotting (WB). The second testicle was fixed for immunofluorescence staining (IHF). C18-4 or TM-4 cells were treated with shRNA of control or M5 gene. Then, the cells were collected for RNA-seq analysis, WB, or IHF. Knockdown of mAChR M5 disrupted mouse spermatogenesis and damaged the actin-based cytoskeleton and many types of junction proteins in both Sertoli cells and germ cells. M5 knockdown decreased Phldb2 expression in both germ cells and Sertoli cells which suggested that Phldb2 may be involved in cytoskeleton and cell–cell junction formation to regulate spermatogenesis. Our investigation has elucidated a novel role for mAChR M5 in the regulation of spermatogenesis through the interactions of Phldb2 and cell–cell junctions. M5 may be an attractive future therapeutic target in the treatment of male reproductive disorders.

Spermatogonial Stem Cell Numbers Are Reduced by Transient Inhibition of GDNF Signaling but Restored by Self-Renewing Replication when Signaling Resumes

One cause of human male infertility is a scarcity of spermatogonial stem cells (SSCs) in testes with Sertoli cells that neither produce adequate amounts of GDNF nor form the Sertoli-Sertoli junctions that form the blood-testis barrier (BTB). These patients raise the issue of whether a pool of SSCs, depleted due to inadequate GDNF stimulation, will expand if normal signaling is restored. Here, we reduce adult mouse SSC numbers by 90% using a chemical-genetic approach that reversibly inhibits GDNF signaling. Signal resumption causes all remaining SSCs to replicate immediately, but they primarily form differentiating progenitor spermatogonia. Subsequently, self-renewing replication restores SSC numbers. Testicular GDNF levels are not increased during restoration. However, SSC replication decreases as numbers of SSCs and progenitors increase, suggesting important regulatory interactions among these cells. Finally, sequential loss of SSCs and then pachytene spermatocytes causes dissolution of the BTB, thereby recapitulating another important characteristic of some infertile men.

The role of different compounds on the integrity of blood-testis barrier: A concise review based on in vitro and in vivo studies

Sertoli cells are "nurturing cells'' in the seminiferous tubules of the testis which have essential roles in the development, proliferation and differentiation of germ cells. These cells also divide the seminiferous epithelium into a basal and an adluminal compartment and establish the blood-testis barrier (BTB). BTB shields haploid germ cells from recognition by the innate immune system. Moreover, after translocation of germ cells into the adluminal compartment their nutritional source is separated from the circulatory system being only supplied by the Sertoli cells. The integrity of BTB is influenced by several organic/ organometallic, hormonal and inflammatory substances. Moreover, several environmental contaminants such as BPA have hazardous effects on the integrity of BTB. In the current review, we summarize the results of studies that assessed the impact of these agents on the integrity of BTB. These studies have implications in understanding the molecular mechanism of male infertility and also in the male contraception.

Testis and blood-testis barrier in Covid-19 infestation: role of angiotensin-converting enzyme 2 in male infertility

Severe acute respiratory syndrome coronavirus 2 (SARS- CoV-2) that causes COVID-19 infections penetrates body cells by binding to angiotensin-converting enzyme-2 (ACE2) receptors. Evidence shows that SARS-CoV-2 can also affect the urogenital tract. Hence, it should be given serious attention when treating COVID-19-infected male patients of reproductive age group. Other viruses like HIV, mumps, papilloma and Epstein-Barr can induce viral orchitis, germ cell apoptosis, inflammation and germ cell destruction with attending infertility and tumors. The blood-testis barrier (BTB) and blood-epididymis barrier (BEB) are essential physical barricades in the male reproductive tract located between the blood vessel and seminiferous tubules in the testes. Despite the significant role of these barriers in male reproductive function, studies have shown that a wide range of viruses can still penetrate the barriers and induce testicular dysfunctions. Therefore, this mini-review highlights the role of ACE2 receptors in promoting SARS-CoV-2-induced blood-testis/epididymal barrier infiltration and testicular dysfunction.

Autologous transplantation of spermatogonial stem cells restores fertility in congenitally infertile mice

The blood-testis barrier (BTB) is thought to be indispensable for spermatogenesis because it creates a special environment for meiosis and protects haploid cells from the immune system. The BTB divides the seminiferous tubules into the adluminal and basal compartments. Spermatogonial stem cells (SSCs) have a unique ability to transmigrate from the adluminal compartment to the basal compartment through the BTB upon transplantation into the seminiferous tubule. Here, we analyzed the role of Cldn11, a major component of the BTB, in spermatogenesis using spermatogonial transplantation. Cldn11-deficient mice are infertile due to the cessation of spermatogenesis at the spermatocyte stage. Cldn11-deficient SSCs failed to colonize wild-type testes efficiently, and Cldn11-deficient SSCs that underwent double depletion of Cldn3 and Cldn5 showed minimal colonization, suggesting that claudins on SSCs are necessary for transmigration. However, Cldn11-deficient Sertoli cells increased SSC homing efficiency by >3-fold, suggesting that CLDN11 in Sertoli cells inhibits transmigration of SSCs through the BTB. In contrast to endogenous SSCs in intact Cldn11-deficient testes, those from WT or Cldn11-deficient testes regenerated sperm in Cldn11-deficient testes. The success of this autologous transplantation appears to depend on removal of endogenous germ cells for recipient preparation, which reprogrammed claudin expression patterns in Sertoli cells. Consistent with this idea, in vivo depletion of Cldn3/5 regenerated endogenous spermatogenesis in Cldn11-deficient mice. Thus, coordinated claudin expression in both SSCs and Sertoli cells expression is necessary for SSC homing and regeneration of spermatogenesis, and autologous stem cell transplantation can rescue congenital defects of a self-renewing tissue.

TBC1D20 Is Essential for Mouse Blood-Testis Barrier Integrity Through Maintaining the Epithelial Phenotype and Modulating the Maturation of Sertoli Cells

Sertoli cells are important for spermatogenesis not only by directly interacting with germ line cells in the seminiferous epithelium but also by constituting the blood-testis barrier (BTB) structure to create a favorable environment for spermatogenesis. Blind sterile (bs) male mice are infertile, with excessive germ cell apoptosis and spermatogenesis arrest. TBC1D20 (TBC1 domain family member 20) deficiency has been identified as the causative mutation in bs mice. However, whether TBC1D20 loss of function also impairs BTB integrity, which further contributes to the failed spermatogenesis of bs male mice, remains unclear. In the present study, biotin tracer assay and transmission electron microscopy showed severely disrupted BTB integrity in bs testes. Compared to the wild-type Sertoli cells, BTB components of cultured bs Sertoli cells in vitro was perturbed with downregulation of E-cadherin, ZO-1, β-catenin, and Claudin 11. The obvious rearrangement of F-actin indicated disrupted epithelial-mesenchymal balance in TBC1D20-deficient Sertoli cells. The ability of bs Sertoli cells to maintain the clone formation of spermatogonia stem cells was also obviously limited. Furthermore, the decreasing of SOX9 (sex-determining region Y box 9) and WT1 (Wilms' tumor 1) and increasing of vimentin in bs Sertoli cells indicated that TBC1D20 loss of function attenuated the differentiation progression of bs Sertoli cells. In summary, TBC1D20 loss of function impedes the maturation of adult Sertoli cells and resulted in impaired BTB integrity, which is further implicated in the infertile phenotype of bs male mice.

Restore natural fertility of Kitw/Kitwv mouse with nonobstructive azoospermia through gene editing on SSCs mediated by CRISPR-Cas9

Background

Male infertility is a serious social problem in modern society. Nonobstructive azoospermia (NOA) caused by germ cell gene defects is an important reason for male infertility, but effective clinical treatment for this disease has not been established.

Methods

We choose Kit^w/Kit^wv mouse as a research model and try to develop a new treatment strategy and “cure” its infertility. Mutant spermatogonial stem cells (SSCs) were isolated from one single unilateral testis of a 14-day-old Kit^w/Kit^wv mouse and propagated in vitro. The C to T point mutation on Kit^wv site of these SSCs was corrected through CRISPR-Cas9-mediated homology-directed repair (HDR) in vitro. Then, the repaired SSCs were screened out, proliferated, and transplanted into the remaining testis, and complete spermatogenesis was established in the recipient testis.

Results

Healthy offsprings with wild type Kit gene or Kit^w mutation were obtained through natural mating 4 months after SSC transplantation.

Conclusion

In this study, we established an effective new treatment strategy for NOA caused by germ cell gene defects through a combination of SSC isolation, CRISPR-Cas9-mediated gene editing, and SSC transplantation, which brought hope for these NOA patients to restore their natural fertility.

How does chemotherapy treatment damage the prepubertal testis?

Chemotherapy treatment is a mainstay of anticancer regimens, significantly contributing to the recent increase in childhood cancer survival rates. Conventional cancer therapy targets not only malignant but also healthy cells resulting in side effects including infertility. For prepubertal boys, there are currently no fertility preservation strategies in use, although several potential methods are under investigation. Most of the current knowledge in relation to prepubertal gonadotoxicity has been deduced from adult studies; however, the prepubertal testis is relatively quiescent in comparison to the adult. This review provides an overview of research to date in humans and animals describing chemotherapy-induced prepubertal gonadotoxicity, focusing on direct gonadal damage. Testicular damage is dependent upon the agent, dosage, administration schedule and age/pubertal status at time of treatment. The chemotherapy agents investigated so far target the germ cell population activating apoptotic pathways and may also impair Sertoli cell function. Due to use of combined chemotherapy agents for patients, the impact of individual drugs is hard to define, however, use of in vivo and in vitro animal models can overcome this problem. Furthering our understanding of how chemotherapy agents target the prepubertal testis will provide clarity to patients on the gonadotoxicity of different drugs and aid in the development of cytoprotective agents.

Melatonin attenuates detrimental effects of diabetes on the niche of mouse spermatogonial stem cells by maintaining Leydig cells

Diabetes mellitus affects a large number of men of reproductive age and it usually leads to serious reproductive disorders. However, the underlying mechanisms and specific therapies still remain largely unknown. We observed Leydig cell loss in the testes of diabetic mice. Continuous high glycemic status of testes stimulated expression of Caspase12, Grp78, and Chop, the three ERS response factors; this might induce cell cycle arrest and apoptosis of Leydig cells in response to ERS. In these diabetic mouse models, melatonin alleviated apoptosis of testicular stromal cell induced by ERS, and promoted SSCs self-renewal by recovering Leydig cells secretion of CSF1 after 8 weeks of treatment. To explore the relationship between CSF-1 and ERS in Leydig cells, we treated Leydig tumor cell line with an activator Tuniamycin and an inhibitor 4-Phenylbutyrate of ERS. Our data showed that the CSF-1 expression in mouse Leydig cell lines decreased six-fold while reversely increasing five-fold in the 4-Phenylbutyrate-treated group. Thus, melatonin likely alleviates the loss of Leydig cells in diabetic testes and provides a healthier niche for SSCs to self-renew and continually provide healthy sperm for male fertility.

Mechanistic Insights into PFOS-Mediated Sertoli Cell Injury

Studies have proven that per- and polyfluoroalkyl substances are harmful to humans, most notably perfluorooctanesulfonate (PFOS). PFOS induces rapid disorganization of actin- and microtubule (MT)-based cytoskeletons in primary cultures of rodent and human Sertoli cells, perturbing Sertoli cell gap junction communication, thereby prohibiting Sertoli cells from maintaining cellular homeostasis in the seminiferous epithelium to support spermatogenesis. PFOS perturbs several signaling proteins/pathways, such as FAK and mTORC1/rpS6/Akt1/2. The use of either an activator of Akt1/2 or overexpression of a phosphomimetic (and constitutively active) mutant of FAK or connexin 43 has demonstrated that such treatment blocks PFOS-induced Sertoli cell injury by preventing actin- and MT-based cytoskeletal disorganization. These findings thus illustrate an approach to manage PFOS-induced reproductive dysfunction.