Blood Testis Barrier and Somatic Cells Impairment in a Series of 35 Adult Klinefelter Syndrome Patients

The effects of fine particulate matter on the blood-testis barrier and its potential mechanisms

With the rapid expansion of industrial scale, an increasing number of fine particulate matter (PM2.5) has bringing health concerns. Although exposure to PM2.5 has been clearly associated with male reproductive toxicity, the exact mechanisms are still unclear. Recent studies demonstrated that exposure to PM2.5 can disturb spermatogenesis through destroying the blood-testis barrier (BTB), consisting of different junction types, containing tight junctions (TJs), gap junctions (GJs), ectoplasmic specialization (ES) and desmosomes. The BTB is one of the tightest blood-tissue barriers among mammals, which isolating germ cells from hazardous substances and immune cell infiltration during spermatogenesis. Therefore, once the BTB is destroyed, hazardous substances and immune cells will enter seminiferous tubule and cause adversely reproductive effects. In addition, PM2.5 also has shown to cause cells and tissues injury via inducing autophagy, inflammation, sex hormones disorder, and oxidative stress. However, the exact mechanisms of the disruption of the BTB, induced by PM2.5, are still unclear. It is suggested that more research is required to identify the potential mechanisms. In this review, we aim to understand the adverse effects on the BTB after exposure to PM2.5 and explore its potential mechanisms, which provides novel insight into accounting for PM2.5-induced BTB injury.

Raman Microspectroscopy evidence of microplastics in human semen

The presence of microplastics (MPs) in human fluids and organs is a great concern, since, as highlighted by recent studies on animal models, they could cause alterations of several physiological functions, including reproduction. In this study, semen samples collected from men living in a polluted area of the Campania Region (Southern Italy), were analyzed to assess the presence of MPs. N. 16 pigmented microplastic fragments (ranging from 2 to 6 μm in size) with spheric or irregular shapes were found in six out of ten samples. All the detected MPs were characterized in terms of morphology (size, colour, and shape) and chemical composition by Raman Microspectroscopy. Chemical composition showed the presence of polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), polyvinylchloride (PVC), polycarbonate (PC), polyoxymethylene (POM) and acrylic, suggesting ingestion and/or inhalation as a route of exposure to environmental MPs. In this work, we propose for the first time a mechanism by which MPs pass into the semen most likely through the epididymis and seminal vesicles, which are the most susceptible to inflammation.

Leydig cell metabolic disorder act as a new mechanism affecting for focal spermatogenesis in Klinefelter syndrome patients: a real world cross-sectional study base on the age

Background

Klinefelter's syndrome (KS) was once considered infertile due to congenital chromosomal abnormalities, but the presence of focal spermatozoa changed this. The key to predict and promote spermatogenesis is to find targets that regulate focal spermatogenesis.

Objective

To explore the trend of fertility changes in KS patients at different ages and identify potential therapeutic targets.

Methods

Bibliometric analysis was used to collect clinical research data on KS from the Web of Science Core Collection (WoSCC) from 1992 to 2022. A cross-sectional study was conducted on 75 KS patients who underwent microscopic testicular sperm extraction (mTESE) from 2017 to 2022 in the real world. The reproductive hormones, testicular histopathology, androgen receptors, insulin-like factor 3 (INSL3) receptors and sperm recovery rate (SRR) were analyzed.

Results

Male infertility, dysplasia, Sertoli cells, Leydig cells, testosterone and spermatogenesis were the research focuses related to KS. Luteinizing hormone (LH), testosterone, and INSL3 were evaluation indicators of Leydig cell function that fluctuate with age. Testosterone and LH peaked at ages 13-19 and 30-45, while INSL3 only peaked at ages 13-19. 27 patients (27/75) recovered sperm through mTESE and experienced SRR peaks at the ages of 20, 28, 34, and 37. The SRR of fibrosis patients was 46.15%, fatty degeneration was 7.14%, and melanosis was 40.00%. The INSL3 and androgen receptors were highly expressed and roughly balanced in focal spermatogenesis.

Conclusion

Abnormal metabolism of Leydig cells led to imbalanced expression of INSL3 and androgen receptors, which might be a potential target for spermatogenesis in KS.

The Klinefelter Syndrome and Testicular Sperm Retrieval Outcomes

Klinefelter syndrome (KS), caused by the presence of an extra X chromosome, is the most prevalent chromosomal sexual anomaly, with an estimated incidence of 1:500/1000 per male live birth (karyotype 47,XXY). High stature, tiny testicles, small penis, gynecomastia, feminine body proportions and hair, visceral obesity, and testicular failure are all symptoms of KS. Endocrine (osteoporosis, obesity, diabetes), musculoskeletal, cardiovascular, autoimmune disorders, cancer, neurocognitive disabilities, and infertility are also outcomes of KS. Causal theories are discussed in addition to hormonal characteristics and testicular histology. The retrieval of spermatozoa from the testicles for subsequent use in assisted reproduction treatments is discussed in the final sections. Despite testicular atrophy, reproductive treatments allow excellent results, with rates of 40–60% of spermatozoa recovery, 60% of clinical pregnancy, and 50% of newborns. This is followed by a review on the predictive factors for successful sperm retrieval. The risks of passing on the genetic defect to children are also discussed. Although the risk is low (0.63%) when compared to the general population (0.5–1%), patients should be informed about embryo selection through pre-implantation genetic testing (avoids clinical termination of pregnancy). Finally, readers are directed to a number of reviews where they can enhance their understanding of comprehensive diagnosis, clinical care, and fertility preservation.

Examining potential mechanisms of testicular fibrosis in Klinefelter Syndrome: A review of current understanding

BACKGROUND

Men with Klinefelter Syndrome develop some degree of seminiferous tubule degeneration, hyalinization, and fibrosis by adulthood. However, the pathophysiology surrounding testicular fibrosis in Klinefelter Syndrome patients remains incompletely understood.

OBJECTIVES

To perform a systematic review of literature studying the mechanisms of fibrosis initiation or propagation in Klinefelter Syndrome testes.

MATERIALS/METHODS

PubMed was searched systematically for articles specific to Klinefelter Syndrome and the process of fibrosis. Articles that did not contain original data or specifically addressed the target material were excluded. Additional references were extracted when pertinent from the reference lists of included studies.

RESULTS

Primary search yielded 139 articles for abstract review, which was narrowed to 16 for full-text review. Following full-text review, eight contained original data and met topic criteria, with one paper added from reference review for a total of nine papers.

DISCUSSION

The date range for included papers was 1992-2022. The proposed mechanisms of fibrosis mainly were centered around the impact of altered Sertoli cells on germ cells, the hormonal impact on Leydig cells, the inflammation mediated by mast cells, or the fibrous extracellular matrix deposition by peritubular myoid cells. Additionally, discussions of the role of the altered microvasculature and the specific proteins involved in the blood-testis barrier or the seminiferous tubule architecture are reviewed. Recent papers have incorporated advanced sequencing and offer future directions for targeted gene expression analysis. Still, much of the published data consists solely of immunohistological assessment by age range, creating difficulties in extrapolating causality.

CONCLUSION

The specific initiating factors of fibrosis of the seminiferous tubules and the propagation mechanisms unique to Klinefelter Syndrome remain incompletely understood with a relative paucity of data. Nonetheless, academic interest is increasing in this field as it may further elucidate the pathophysiology behind Klinefelter syndrome.

DDX58 expression promotes inflammation and growth arrest in Sertoli cells by stabilizing p65 mRNA in patients with Sertoli cell-only syndrome

Sertoli cell -only syndrome (SCOS) is a type of testicular pathological failure that causes male infertility and no effective treatment strategy, is available for this condition. Moreover, the molecular mechanism underlying its development remains unknown. We identified DExD/H-Box helicase 58 (DDX58) as a key gene in SCOS based on four datasets of testicular tissue samples obtained from the Gene Expression Synthesis database. DDX58 was significantly upregulated in SCOS testicular Sertoli cells. Moreover, high expression of DDX58 was positively correlated with the expression of several testicular inflammatory factors, such as IL -1β, IL-18, and IL-6. Interestingly, DDX58 could be induced in the D-galactose (D-gal)-stimulated TM4 cell injury model. Whereas silencing of DDX58 inhibited D-gal -mediated p65 expression, inflammatory cytokine release, and growth arrest. Mechanistically, we found that DDX58 acts as an RNA-binding protein, which enhances p65 expression by promoting mRNA stability. Furthermore, p65 gene silencing decreased the expression of inflammatory cytokines and inhibition of cell growth in D-gal-induced cells. In conclusion, our findings demonstrate that DDX58 promotes inflammatory responses and growth arrest in SCOS Sertoli cells by stabilizing p65 mRNA. Accordingly, the DDX58/p65 regulatory axis might be a therapeutic target for SCOS.

Bibliometric and visual analysis of blood-testis barrier research

Background: Extensive research on the blood-testis barrier has been undertaken in recent years. However, no systematic bibliometric study has been conducted on this subject. Our research aimed to identify the hotspots and frontiers of blood-testis barrier research and to serve as a guide for future scientific research and decision-making in the field.

Methods: Studies on the blood-testis barrier were found in the Web of Science Core Collection. VOSviewer, CiteSpace, and Microsoft Excel were used to conduct the bibliometric and visual analyses.

Results: We found 942 blood-testis barrier studies published in English between 1992 and 2022. The number of annual publications and citations increased significantly between 2011 and 2022, notably in the United States. China and the United States, the US Population Council, Endocrinology, and Cheng C. Yan were the most productive countries, institution, journal, and author, respectively. The study keywords indicated that blood-testis barrier research involves a variety of compositional features (tight junctions, cytoskeleton, adherens junctions), cell types (Sertoli cells, germ cells, Leydig cells, stem cells), reproductive toxicity (cadmium, nanoparticles, bisphenol-a), and relevant mechanisms (spermatogenesis, apoptosis, oxidative stress, dynamics, inflammation, immune privilege).

Conclusion: The composition and molecular processes of the blood-testis barrier as well as the blood-testis barrier in male infertility patients are the primary research hotspots in this field. In addition, future research will likely focus on treatment and the development of novel medications that target signal pathways in oxidative stress and apoptosis to preserve the blood-testis barrier. Further studies must extend to clinical diagnosis and therapy.

Expression of G-Protein-Coupled Estrogen Receptor (GPER) in Whole Testicular Tissue and Laser-Capture Microdissected Testicular Compartments of Men with Normal and Aberrant Spermatogenesis

Simple Summary

Nowadays, there is no doubt that estrogens play an important role in male reproduction, affecting testicular cell differentiation, proliferation, apoptosis and metabolism. It is also widely believed that intratesticular balance of androgens and estrogens is crucial for the testicular development and function and that the increased testicular estrogen production may be associated with spermatogenic failure. There is also growing epidemiological evidence that the exposure of men to endocrine disruptors demonstrating estrogenic activity (xenoestrogens) may lead to impairment of male fertility via interference with estrogen signaling pathways. Besides the two classical nuclear estrogen receptors, the membrane-bound G protein-coupled estrogen receptor (GPER) was described in human testicular tissue. However, there are little data on its expression in testes with disturbed spermatogenesis. In this study, we investigated the GPER expression pattern in biopsies of azoospermic men with complete and aberrant spermatogenesis. Our results showed an increased expression of the GPER in testes with impaired spermatogenesis. Moreover, they indicate a possible involvement of estrogen signaling through GPER in disturbed function of Sertoli cells—the cells that support spermatogenic process.

Abstract

In this study, we retrospectively investigated GPER expression in biopsies of azoospermic men with complete (obstructive azoospermia—OA) and aberrant spermatogenesis (nonobstructive azoospermia—NOA). Each biopsy was histologically evaluated with morphometry. The testicular GPER expression was analyzed by the immunohistochemistry and RT-PCR technique in the whole testicular tissue and in seminiferous tubules and Leydig cells after laser-capture microdissection. In laser-microdissected compartments, we also analyzed transcriptional expression of selected Leydig (CYP17A1, HSD17B3, StAR) and Sertoli cell (AMH, SCF, BMP4) function markers. Immunohistochemical staining revealed expression of GPER in the cytoplasm of Leydig and Sertoli cells. Its stronger intensity was observed in Sertoli cells of NOA biopsies. The RT-PCR analysis of the GPER mRNA level unequivocally showed its increased expression in seminiferous tubules (i.e., Sertoli cells), not Leydig cells in NOA biopsies. This increased expression correlated positively with the transcriptional level of AMH—a marker of Sertoli cell immaturity, as well as FSH serum level in NOA but not in the OA group. Our results clearly demonstrate altered GPER expression in testes with primary spermatogenic impairment that might be related to Sertoli cell maturity/function.

Successful transplantation of spermatogonial stem cells into the seminiferous tubules of busulfan-treated mice

Background

Spermatogonial stem cells (SSCs) in the testis are crucial for transferring genetic information to the next generation. Successful transplantation of SSCs to infertile men is an advanced therapeutic application in reproductive biology research.

Methods

In this experimental research, both in vitro and in vivo characterization of undifferentiated and differentiated SSCs were performed by morphology—immunocytochemistry (ICC), immunohistochemistry (IMH), Fluidigm Real-Time polymerase chain reaction (RT-PCR) and flow cytometry analysis. The isolated SSCs were finally microinjected into the rete testis of busulfan-treated mice.

The compact undifferentiated and more loosely connected round differentiated SSCs were isolated during testicular cell expansion from their specific feeder layer.

Results

ICC analysis indicated high and low expression levels of Zbtb16 in undifferentiated and differentiated germ cells. Also, IMH analysis showed different expression levels of Zbtb16 in the two different germ stem cell populations of the testicular tissue. While Fluidigm RT-PCR analysis indicated overexpression of the TAF4B germ cell gene, the expression of DAZL, VASA, and Zbtb16 were down-regulated during the differentiation of SSCs (P < 0.05). Also, flow cytometry analysis confirmed the significant downregulation of Itgb1 and Itga4 during differentiation. By transplantation of SSCs into busulfan-treated NOD/SCID mice, GFP-labeled sperm cells developed.

Conclusions

In the current study, we performed a transplantation technique that could be useful for the future microinjection of SSCs during infertility treatment and for studying in vivo differentiation of SSCs into sperm.

Spermatogonia (SSCs) in the testis transmit genetic information to the next generation. Successful SSC transplantation into infertile men is an advanced therapeutic application in reproductive biology research. In this experimental research, both in vitro and in vivo characterization of undifferentiated and differentiated SSCs were performed by morphology—immunocytochemistry (ICC), immunohistochemistry (IMH), Fluidigm Real-Time polymerase chain reaction (RT-PCR) and flow cytometry analysis. The isolated SSCs were finally microinjected into the rete testis of busulfan-treated mice. ICC analysis indicated high and low expression levels of Zbtb16 in undifferentiated and differentiated germ cells. IMH analysis showed different expression levels of Zbtb16 in both populations. Fluidigm RT-PCR analysis indicated overexpression of the TAF4B germ cell gene and the down-regulated expression of DAZL, VASA, and Zbtb16 during SSCs differentiation of (P < 0.05). Flow cytometry analysis confirmed the significant downregulation of Itgb1 and Itga4 during differentiation. By transplantation of SSCs into busulfan-treated NOD/SCID mice, GFP-labeled sperm cells developed. We performed a transplantation technique that could be useful for the future microinjection of SSCs during infertility treatment and for studying in vivo differentiation of SSCs into sperm. Data analysis confirmed that zbtb16 is expressed in the undifferentiated germ cells located on the basal membrane of seminiferous tubules and SSCs in vitro. Also, spermatogenesis was resumed, and fertility improved after transplantation of undifferentiated cells into busulfan-treated mice; thus, improvements in vitro SSCs transplantation, isolation and culture would be helpful in future clinical treatments to solve the reproductive problems of families influenced by infertility.

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.

Serum Concentrations and Gonadal Expression of INSL3 in Eighteen Males With 45,X/46,XY Mosaicism

OBJECTIVE

Insulin-like factor 3 (INSL3) is produced in the testes and has been proposed as a circulating biomarker of Leydig cell capacity, but remains undescribed in 45,X/46,XY mosaicism. The aim was to examine serum concentrations and gonadal expression of INSL3 in 45,X/46,XY mosaicism.

METHODS

Retrospectively collected data from medical records, gonadal tissue samples, and prospectively analyzed serum samples from eighteen male patients with 45,X/46,XY mosaicism (one prepubertal, four testosterone-treated, 13 untreated) were included. Biochemical, clinical, and histological outcomes were evaluated according to serum INSL3 concentrations, quantified by LC-MS/MS methodology, and gonadal INSL3 immunohistochemical expression.

RESULTS

Serum INSL3 concentrations spanned from below to above the reference range. In untreated patients, the median serum INSL3 SD score was -0.80 (IQR: -1.65 to 0.55) and no significant difference was observed between INSL3 and testosterone. There was no clear association between serum INSL3 and External Genitalia Score at diagnosis, spontaneous puberty, or sperm concentration. INSL3 and CYP11A1 expression overlapped, except for less pronounced INSL3 expression in areas with severe Leydig cell hyperplasia. No other apparent links between INSL3 expression and histological outcomes were observed.

CONCLUSIONS

In this pilot study, serum INSL3 concentrations ranged and seemed independent of other reproductive hormones and clinical features in males with 45,X/46,XY mosaicism. Discordant expression of INSL3 and CYP11A1 may explain low INSL3 and normal testosterone concentrations in some patients. Further studies are needed to elucidate the divergence between serum INSL3 and testosterone and the potential clinical use of INSL3.

Infertility considerations in klinefelter syndrome: From origin to management

Klinefelter syndrome (KS) is defined as the presence of one or more extra "X" chromosome in a male patient. It affects approximately 1 in 600 newborn males and the most common chromosomal abnormality, leading to male hypogonadism and infertility. There is a lack of data supporting best practices for KS patients' care. In this paper we review controversial issues in KS research ranging from mechanisms of variation in KS phenotype to abnormalities resulting in reduced sperm production to successful sperm retrieval disparities after testicular sperm extraction (TESE). Translation to live birth and offspring health is also examined. Finally, medical therapies used to optimize the hormonal status and chances of fertility in KS patients are reviewed. We will also discuss the experimental spermatogonial stem cell (SSC) treatments, which are considered the future for TESE negative patients.

Modeling Klinefelter Syndrome Using Induced Pluripotent Stem Cells Reveals Impaired Germ Cell Differentiation

Klinefelter syndrome (KS), with an incidence between 1/600 and 1/1,000, is the main genetic cause of male infertility. Due to the lack of an accurate study model, the detailed pathogenic mechanisms by which this X chromosome aneuploidy leads to KS features remain unknown. Here, we report the generation and characterization of induced pluripotent stem cells (iPSCs) derived from a patient with KS: 47XXY-iPSCs. In order to compare the potentials of both 47XXY-iPSCs and 46XY-iPSCs to differentiate into the germ cell lineage, we developed a directed differentiation protocol by testing different combinations of factors including bone morphogenetic protein 4 (BMP4), glial-derived neurotrophic factor (GDNF), retinoic acid (RA) and stem cell factor (SCF) for 42 days. Importantly, we found a reduced ability of 47XXY-iPSCs to differentiate into germ cells when compared to 46XY-iPSCs. In particular, upon germ cell differentiation of 47XXY-iPSCs, we found a reduced proportion of cells positive for BOLL, a protein required for germ cell development and spermatogenesis, as well as a reduced proportion of cells positive for MAGEA4, a spermatogonia marker. This reduced ability to generate germ cells was not associated with a decrease of proliferation of 47XXY-iPSC-derived cells but rather with an increase of cell death upon germ cell differentiation as revealed by an increase of LDH release and of capase-3 expression in 47XXY-iPSC-derived cells. Our study supports the idea that 47XXY-iPSCs provides an excellent in vitro model to unravel the pathophysiology and to design potential treatments for KS patients.

European academy of andrology guidelines on Klinefelter Syndrome Endorsing Organization: European Society of Endocrinology

BACKGROUND

Knowledge about Klinefelter syndrome (KS) has increased substantially since its first description almost 80 years ago. A variety of treatment options concerning the spectrum of symptoms associated with KS exists, also regarding aspects beyond testicular dysfunction. Nevertheless, the diagnostic rate is still low in relation to prevalence and no international guidelines are available for KS.

OBJECTIVE

To create the first European Academy of Andrology (EAA) guidelines on KS.

METHODS

An expert group of academicians appointed by the EAA generated a consensus guideline according to the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) system.

RESULTS

Clinical features are highly variable among patients with KS, although common characteristics are severely attenuated spermatogenesis and Leydig cell impairment, resulting in azoospermia and hypergonadotropic hypogonadism. In addition, various manifestations of neurocognitive and psychosocial phenotypes have been described as well as an increased prevalence of adverse cardiovascular, metabolic and bone-related conditions which might explain the increased morbidity/mortality in KS. Moreover, compared to the general male population, a higher prevalence of dental, coagulation and autoimmune disorders is likely to exist in patients with KS. Both genetic and epigenetic effects due to the supernumerary X chromosome as well as testosterone deficiency contribute to this pathological pattern. The majority of patients with KS is diagnosed during adulthood, but symptoms can already become obvious during infancy, childhood or adolescence. The paediatric and juvenile patients with KS require specific attention regarding their development and fertility.

CONCLUSION

These guidelines provide recommendations and suggestions to care for patients with KS in various developmental stages ranging from childhood and adolescence to adulthood. This advice is based on recent research data and respective evaluations as well as validations performed by a group of experts.

Integration and reanalysis of transcriptomics and methylomics data derived from blood and testis tissue of men with 47,XXY Klinefelter syndrome indicates the primary involvement of Sertoli cells in the testicular pathogenesis

Klinefelter syndrome (KS; 47,XXY) is the most common sex chromosomal anomaly and causes a multitude of symptoms. Often the most noticeable symptom is infertility caused by azoospermia with testicular histology showing hyalinization of tubules, germ cells loss, and Leydig cell hyperplasia. The germ cell loss begins early in life leading to partial hyalinization of the testis at puberty, but the mechanistic drivers behind this remain poorly understood. In this systematic review, we summarize the current knowledge on developmental changes in the cellularity of KS gonads supplemented by a comparative analysis of the fetal and adult gonadal transcriptome, and blood transcriptome and methylome of men with KS. We identified a high fraction of upregulated genes that escape X-chromosome inactivation, thus supporting previous hypotheses that these are the main drivers of the testicular phenotype in KS. Enrichment analysis showed overrepresentation of genes from the X- and Y-chromosome and testicular transcription factors. Furthermore, by re-evaluation of recent single cell RNA-sequencing data originating from adult KS testis, we found novel evidence that the Sertoli cell is the most affected cell type. Our results are consistent with disturbed cross-talk between somatic and germ cells in the KS testis, and with X-escapee genes acting as mediators.

41,XXY * male mice: An animal model for Klinefelter syndrome

Klinefelter syndrome (KS, 47,XXY) is the most frequent male chromosomal aneuploidy resulting in a highly heterogeneous clinical phenotype associated with hormonal dysbalance, increased rate of co-morbidities, and reduced lifespan. Two hallmarks of KS-affecting testicular functions are consistently observed: Hypergonadotropic hypogonadism and germ cell (GC) loss resulting in infertility. Although KS is being studied for decades, the underlying mechanisms for the observed pathophysiology are still unclear. Due to ethical restrictions, studies in humans are limited, and consequently, suitable animal models are needed to address the consequences of a supernumerary X chromosome. Mouse strains with comparable aneuploidies have been generated and yielded highly relevant insights into KS. We briefly describe the establishment of the KS mouse models, summarize the knowledge gained by their use, compare findings from the mouse models to those obtained in clinical studies, and also reflect on limitations of the currently used models derived from the B6Ei.Lt-Y* mouse strain, in which the Y chromosome is altered and its centromere position changed into a more distal location provoking meiotic non-disjunction. Breeding such as XY* males to XX females, the target 41,XX^Y *, and 41,XXY males are generated. Here, we summarize features of both models but report in particular findings from our 41,XX^Y * mice including some novel data on Sertoli cell characteristics.

Germ cell loss in Klinefelter syndrome: When and why?

Klinefelter syndrome (KS) is a quite common disorder with an incidence of 1-2 in 1,000 new-born males. Most patients are diagnosed in the light of a clinical checkup when consulting a fertility clinic with an unfulfilled child wish. Infertility in KS patients is caused by a massive germ cell loss, leading to azoospermia in more than 90% of the adult patients. Most seminiferous tubules in the adult KS testis are degenerated or hyalinized and testicular fibrosis can be observed, starting from puberty. However, focal spermatogenesis can be found in the testis of some patients. This offers the opportunity to extract spermatozoa from the testis by testicular sperm extraction (TESE). Nevertheless, TESE is only successful in about half of the KS adults seeking to father children. The reason for the germ cell loss remains unclear. To date, it is still debated whether the testicular tissue changes and the germ cell loss seen in KS is directly caused by an altered X-linked gene expression, the altered somatic environment, or a deficiency in the germ cells. In this review, we provide an overview of the current knowledge about the germ cell loss in KS patients.

Applications of Genome Editing Technology in Research on Chromosome Aneuploidy Disorders

Chromosomal segregation errors in germ cells and early embryonic development underlie aneuploidies, which are numerical chromosomal abnormalities causing fetal absorption, developmental anomalies, and carcinogenesis. It has been considered that human aneuploidy disorders cannot be resolved by radical treatment. However, recent studies have demonstrated that aneuploidies can be rescued to a normal diploid state using genetic engineering in cultured cells. Here, we summarize a series of studies mainly applying genome editing to eliminate an extra copy of human chromosome 21, the cause of the most common constitutional aneuploidy disorder Down syndrome. We also present findings on induced pluripotent stem cell reprogramming, which has been shown to be one of the most promising technologies for converting aneuploidies into normal diploidy without the risk of genetic alterations such as genome editing-mediated off-target effects.