Natural history of seminiferous tubule degeneration in Klinefelter syndrome

Klinefelter Syndrome: A Review

BACKGROUND

Klinefelter syndrome (KS) is an uncommonly recognised condition typified by gynaecomastia, small testes and aspermatogenesis. It is caused by a supernumerary X chromosome, resulting in a 47 XXY karyotype. Since its first description, the phenotype of KS has evolved and there is a much greater appreciation of the subtle features of the condition.

METHOD

In this review, we explore the phenotype of the KS with particular consideration to patients with pre-natal and early infancy diagnosis, given that this is becoming increasingly common. The current understanding of the genetic mechanisms of KS, caused by supernumerary X chromosome are explored and the genotype-phenotype correlation are discussed.

RESULTS

The implications of the condition both in childhood and later development are explored in detail, with particular focus on social and educational implications. Potential treatments, with emphasis on preservation of fertility are discussed. We highlight the optimal therapeutic conditions in which fertility preservation is most likely to be achieved, compared to those which can be more challenging. Finally, we discuss the other health challenges which can be associated with KS. These include poor bone health, diabetes, cardiovascular complications, and malignancy. The challenges in managing these co-morbid conditions and most up-to-date management recommendations are also explored.

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.

Assessment of testicular function in boys and adolescents

OBJECTIVE

The hypothalamic-pituitary-testicular axis is characterised by the existence of major functional changes from its establishment in fetal life until the end of puberty. The assessment of serum testosterone and gonadotrophins and semen analysis, typically used in the adult male, is not applicable during most of infancy and childhood. On the other hand, the disorders of gonadal axis have different clinical consequences depending on the developmental stage at which the dysfunction is established. This review addresses the approaches to evaluate the hypothalamic-pituitary-testicular axis in the newborn, during childhood and at pubertal age.

DESIGN

We focused on the hormonal laboratory and genetic studies as well as on the clinical signs and imaging studies that guide the aetiological diagnosis and the functional status of the gonads.

RESULTS

Serum gonadotrophin and testosterone determination is useful in the first 3-6 months after birth and at pubertal age, whereas AMH and inhibin B are useful biomarkers of testis function from birth until the end of puberty. Clinical and imaging signs are helpful to appraise testicular hormone actions during fetal and postnatal life.

CONCLUSIONS

The interpretation of results derived from the assessment of hypothalamic-pituitary-testicular in paediatric patients requires a comprehensive knowledge of the developmental physiology of the axis to understand its pathophysiology and reach an accurate diagnosis of its disorders.

Klinefelter syndrome: etiology and clinical considerations in male infertility†

Klinefelter syndrome (KS) is the most prevalent chromosomal disorder occurring in males. It is defined by an additional X chromosome, 47,XXY, resulting from errors in chromosomal segregation during parental gametogenesis. A major phenotype is impaired reproductive function, in the form of low testosterone and infertility. This review comprehensively examines the genetic and physiological factors contributing to infertility in KS, in addition to emergent assisted reproductive technologies, and the unique ethical challenges KS patients face when seeking infertility treatment. The pathology underlying KS is increased susceptibility for meiotic errors during spermatogenesis, resulting in aneuploid or even polyploid gametes. Specific genetic elements potentiating this susceptibility include polymorphisms in checkpoint genes regulating chromosomal synapsis and segregation. Physiologically, the additional sex chromosome also alters testicular endocrinology and metabolism by dysregulating interstitial and Sertoli cell function, collectively impairing normal sperm development. Additionally, epigenetic modifications like aberrant DNA methylation are being increasingly implicated in these disruptions. We also discuss assisted reproductive approaches leveraged in infertility management for KS patients. Application of assisted reproductive approaches, along with deep comprehension of the meiotic and endocrine disturbances precipitated by supernumerary X chromosomes, shows promise in enabling biological parenthood for KS individuals. This will require continued multidisciplinary collaboration between experts with background of genetics, physiology, ethics, and clinical reproductive medicine.

In Vitro Generation of Haploid Germ Cells from Human XY and XXY Immature Testes in a 3D Organoid System

Increasing survival rates of children following cancer treatment have resulted in a significant population of adult survivors with the common side effect of infertility. Additionally, the availability of genetic testing has identified Klinefelter syndrome (classic 47,XXY) as the cause of future male infertility for a significant number of prepubertal patients. This study explores new spermatogonia stem cell (SSC)-based fertility therapies to meet the needs of these patients. Testicular cells were isolated from cryopreserved human testes tissue stored from XY and XXY prepubertal patients and propagated in a two-dimensional culture. Cells were then incorporated into a 3D human testicular organoid (HTO) system. During a 3-week culture period, HTOs maintained their structure, viability, and metabolic activity. Cell-specific PCR and flow cytometry markers identified undifferentiated spermatogonia, Sertoli, Leydig, and peritubular cells within the HTOs. Testosterone was produced by the HTOs both with and without hCG stimulation. Upregulation of postmeiotic germ cell markers was detected after 23 days in culture. Fluorescence in situ hybridization (FISH) of chromosomes X, Y, and 18 identified haploid cells in the in vitro differentiated HTOs. Thus, 3D HTOs were successfully generated from isolated immature human testicular cells from both euploid (XY) and Klinefelter (XXY) patients, supporting androgen production and germ cell differentiation in vitro.

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.

Executive Dysfunction in Klinefelter Syndrome: Associations With Brain Activation and Testicular Failure

CONTEXT

Executive dysfunction is a well-recognized component of the cognitive phenotype of Klinefelter syndrome (KS), yet the neural basis of KS-associated cognitive weaknesses, and their association with testicular failure is unknown.

OBJECTIVE

We investigated executive function, brain activation, and pubertal development in adolescents with and without KS.

METHODS

Forty-three adolescents with KS (mean age 12.3 ± 2.3 years) and 41 typically developing boys (mean age 11.9 ± 1.8 years) underwent pubertal evaluation, behavioral assessment, and completed functional magnetic resonance imaging (fMRI) as they performed an executive function task, the go/no-go task. Group differences in activation were examined. Associations among activation, executive function, and pubertal development measures were tested in secondary analyses.

RESULTS

Boys with KS exhibited reduced executive function, as well as lower activation in brain regions subserving executive function, including the inferior frontal gyrus, anterior insula, dorsal anterior cingulate cortex, and caudate nucleus. Secondary analyses indicated that the magnitude of activation differences in boys with KS was associated with severity of pubertal developmental delay, as indexed by lower testosterone (t(36) = 2.285; P = .028) and lower testes volume (t(36) = 2.238; P = .031). Greater parent-reported attention difficulties were additionally associated with lower testicular volume (t(36) = -2.028; P = .050).

CONCLUSION

These findings indicate a neural basis for executive dysfunction in KS and suggest alterations in pubertal development may contribute to increased severity of this cognitive weakness. Future studies that examine whether these patterns change with testosterone replacement therapy are warranted.

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.

A rare case of mosaic Klinefelter syndrome in a 45-year-old man leading to successful live birth through ejaculated spermatozoa: a case report and literature review

Background: Men diagnosed with Klinefelter syndrome (KS) commonly exhibit non-obstructive azoospermia or rarely having sperm in their ejaculate, rendering them traditionally considered sterile prior to the introduction of intracytoplasmic sperm injection (ICSI). The presence of mosaic KS may mask the classical phenotype, resulting in underdiagnosis throughout their lifetime. Surgical sperm retrieval through Microdissection Testicular Sperm Extraction (Micro-TESE) combined with ICSI has become the gold standard approach, maximizing reproductive outcomes in these individuals. However, it is noteworthy that approximately 7% of men with KS may exhibit sperm in their ejaculate, providing an opportunity for them to achieve biological parenthood through ICSI. Case Presentation: In this report, we present an exceptional case of a 45-year-old man with Mosaic KS and severe oligozoospermia who successfully achieved pregnancy utilizing ICSI with freshly ejaculated sperm. Remarkably, this case represents the oldest recorded instance of a man with Klinefelter syndrome fathering his own biological child using sperm derived from fresh ejaculate. Conclusion: Although this case is exceedingly rare, it underscores the critical importance of exhausting all possibilities to facilitate biological parenthood in men with KS before considering alternative options such as sperm donation or adoption. By recognizing the potential for successful conception using ejaculated sperm in this population, we can provide individuals with mosaic KS the opportunity to fulfill their desire for biological offspring.

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.

Klinefelter Syndrome: What should we tell prospective parents?

Klinefelter syndrome (KS) or 47,XXY is the most common sex chromosome aneuploidy (SCA), occurring at a prevalence of 1 in 600 male pregnancies. Historically, only 25% of individuals with KS came to medical attention, for a range of issues across the life course including under-virilisation at birth, developmental and social concerns in childhood, absence, delay or arrest of puberty in adolescence or infertility in adulthood. Our understanding of the phenotypic spectrum of KS has been largely influenced by this ascertainment bias. With increasing uptake of antenatal noninvasive prenatal testing (NIPT), a corresponding increase in identification of KS has been documented. Population-based longitudinal data from infancy to adulthood on these individuals is lacking, which impedes balanced antenatal genetic counselling and raises issues for prospective parents and clinicians alike.

Testicular microlithiasis in paediatric patients with Klinefelter syndrome from infancy till adolescence: early start of degenerative process in the testes-preliminary results

To present the results of testicular ultrasonography supported by clinical and hormonal aspects in paediatric patients with Klinefelter syndrome (KS). Prospective analysis of medical files of 20 patients diagnosed with KS between 2016 and 2022. Assessed data included analysis of causes of referral, ultrasound, and clinical characterisation with hormonal evaluation of serum FSH, LH, testosterone, inhibin B, and anti-Müllerian hormone. Non-mosaic Klinefelter syndrome (47, XXY) was diagnosed in 65% of cases (13/20) by the geneticist (including 7 cases prenatally), in 25% (5/20) by the endocrinologist and in 10% (2/20) by the hematologist. Ultrasound assessment revealed bilateral testicular microlithiasis (TM) in all patients. The youngest KS patient with TM was 3 months old. TM patterns have not changed during follow-ups of up to 6 years in any of the patients. In all KS patients markedly reduced echogenicity and in pubertal KS patients, also irregular echostructure of the testes was observed. The hormonal patterns observed in the study group were typical for those already described in KS. Sertoli and Leydig cell function was intact in prepubertal patients and deteriorated after the start of puberty.

CONCLUSION

Although the degenerative process in the testicular tissue starts very early in the testes in KS and is reflected in morphological changes seen in ultrasonography, Sertoli and Leydig cell hormonal function is normal in prepubertal KS patients.

WHAT IS KNOWN

• So far, normal Leydig and Sertoli cell function was observed in infants and prepubertal KS patients.

WHAT IS NEW

• The morphological changes in the testes in KS may already be seen in early infancy.

Transcriptomic differences between fibrotic and non-fibrotic testicular tissue reveal possible key players in Klinefelter syndrome-related testicular fibrosis

Klinefelter syndrome (KS; 47,XXY) affects 1-2 in 1000 males. Most men with KS suffer from an early germ cell loss and testicular fibrosis from puberty onwards. Mechanisms responsible for these processes remain unknown. Previous genomics studies on testis tissue from men with KS focused on germ cell loss, while a transcriptomic analysis focused on testicular fibrosis has not yet been performed. This study aimed to identify factors involved in the fibrotic remodelling of KS testes by analysing the transcriptome of fibrotic and non-fibrotic testicular tissue. RNA sequencing was performed to compare the genes expressed in testicular samples with (KS and testis atrophy) and without (Sertoli cell-only syndrome and fertile controls) fibrosis (n = 5, each). Additionally, differentially expressed genes (DEGs) between KS and testis atrophy samples were studied to reveal KS-specific fibrotic genes. DEGs were considered significant when p < 0.01 and log2FC > 2. Next, downstream analyses (GO and KEGG) were performed. Lastly, RNA in situ hybridization was performed to validate the results. The first analysis (fibrotic vs non-fibrotic) resulted in 734 significant DEGs (167 up- and 567 down-regulated). Genes involved in the extracellular structure organization (e.g. VCAM1) were found up-regulated. KEGG analysis showed an up-regulation of genes involved in the TGF-β pathway. The KS vs testis atrophy analysis resulted in 539 significant DEGs (59 up- and 480 down-regulated). Chronic inflammatory response genes were found up-regulated. The overlap of X-linked DEGs from the two analyses revealed three genes: matrix-remodelling associated 5 (MXRA5), doublecortin (DCX) and variable charge X-Linked 3B (VCX3B). RNA in situ hybridization showed an overexpression of VCAM1, MXRA5 and DCX within the fibrotic group compared with the non-fibrotic group. To summarize, this study revealed DEGs between fibrotic and non-fibrotic testis tissue, including VCAM1. In addition, X-linked fibrotic genes were revealed, e.g. MXRA5, DCX and VCX3B. Their potential role in KS-related testicular fibrosis needs further study.

Delaying testicular sperm extraction in 47,XXY Klinefelter patients does not impair the sperm retrieval rate, and AMH levels are higher when TESE is positive

STUDY QUESTION

Should testicular sperm extraction (TESE) in non-mosaic 47,XXY Klinefelter syndrome (KS) patients be performed soon after puberty or could it be delayed until adulthood?

SUMMARY ANSWER

The difference in sperm retrieval rate (SRR) in TESE was not significant between the 'Young' (15-22 years old) cohort and the 'Adult' (23-43 years old) cohort of non-mosaic KS patients recruited prospectively in parallel.

WHAT IS KNOWN ALREADY

Several studies have tried to define predictive factors for TESE outcome in non-mosaic KS patients, with very heterogeneous results. Some authors have found that age was a pejorative factor and recommended performing TESE soon after puberty. To date, no predictive factors have been unanimously recognized to guide clinicians in deciding to perform TESE in azoospermic KS patients.

STUDY DESIGN, SIZE, DURATION

Two cohorts (Young: 15-22 years old; Adult: 23-43 years old) were included prospectively in parallel. A total of 157 non-mosaic 47,XXY KS patients were included between 2010 and 2020 in the reproductive medicine department of the University Hospital of Lyon, France. However 31 patients gave up before TESE, four had cryptozoospermia and three did not have a valid hormone assessment; these were excluded from this study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data for 119 patients (61 Young and 58 Adult) were analyzed. All of these patients had clinical, hormonal and seminal evaluation before conventional TESE (c-TESE).

MAIN RESULTS AND THE ROLE OF CHANCE

The global SRR was 45.4%. SRRs were not significantly different between the two age groups: Young SRR=49.2%, Adult SRR = 41.4%; P = 0.393. Anti-Müllerian hormone (AMH) and inhibin B were significantly higher in the Young group (AMH: P = 0.001, Inhibin B: P < 0.001), and also higher in patients with a positive TESE than in those with a negative TESE (AMH: P = 0.001, Inhibin B: P = 0.036). The other factors did not differ between age groups or according to TESE outcome. AMH had a better predictive value than inhibin B. SRRs were significantly higher in the upper quartile of AMH plasma levels than in the lower quartile (or in cases with AMH plasma level below the quantification limit): 67.7% versus 28.9% in the whole population (P = 0.001), 60% versus 20% in the Young group (P = 0.025) and 71.4% versus 33.3% in the Adult group (P = 0.018).

LIMITATIONS, REASONS FOR CAUTION

c-TESE was performed in the whole study; we cannot rule out the possibility of different results if microsurgical TESE had been performed. Because of the limited sensitivity of inhibin B and AMH assays, a large number of patients had values lower than the quantification limits, preventing the definition a threshold below which negative TESE can be predicted.

WIDER IMPLICATIONS OF THE FINDINGS

In contrast to some studies, age did not appear as a pejorative factor when comparing patients 15-22 and 23-44 years of age. Improved accuracy of inhibin B and AMH assays in the future might still allow discrimination of patients with persistent foci of spermatogenesis and guide clinician decision-making and patient information.

STUDY FUNDING/COMPETING INTEREST(S)

The study was supported by a grant from the French Ministry of Health D50621 (Programme Hospitalier de Recherche Clinical Régional 2008). The authors have no conflicts of interest to disclose.

TRIAL REGISTRATION NUMBER

NCT01918280.

An Adolescent Boy with Klinefelter Syndrome and 47,XXY/46,XX Mosaicism: Case Report and Review of Literature

Klinefelter syndrome is the most commonly reported sex chromosome abnormality. It is heavily underdiagnosed due to the substantial variability of clinical presentations but is generally characterized by small, firm testes, hypergonadotropic hypogonadism, and the absence of spermatogenesis. Most patients with Klinefelter syndrome have a 47,XXY genotype. If they present with mosaicism, two different cell lines are usually identified, an aneuploid 47,XXY cell line and a normal male 46,XY cell line. There are very few cases of 47,XXY mosaicism with the additional female cell line 46,XX described in the literature. We report a case of an adolescent with the male phenotype and a rare variant mosaic 47,XXY/46,XX karyotype who presented with painless bilateral gynaecomastia. 47,XXY and 46,XX mosaic cell lines were identified with GTG-banding and further characterized using fluorescent in situ hybridization. We summarized the available clinical presentations of reported male patients with 47,XXY/46,XX mosaicism. To improve the clinical management and quality of life in individuals with rare and cryptic genomic imbalances, the genetic diagnosis would need to be extended to atypical cases.

Onset and progression of puberty in Klinefelter syndrome

OBJECTIVE

Klinefelter syndrome (KS) (47,XXY and variants, KS) is the most common sex chromosome disorder in humans. However, little is known about the onset and progression of puberty in patients with KS. In this study, we describe the onset and progression of puberty in a large series of boys with KS in a single tertiary centre.

DESIGN AND PATIENTS

Retrospective data (Tanner stages, testicular length, testosterone supplementation, levels of luteinizing hormone [LH] and testosterone) before possible testosterone treatment on 72 KS patients with 47,XXY karyotype were reviewed, and G (n = 59 patients) and P (n = 56 patients) stages were plotted on puberty nomograms.

MEASUREMENTS AND RESULTS

One boy had a delayed onset of puberty, as he was at the G1 stage at the age of 13.8 years (-2.2 SDs). No observations of delay were made of boys at Stage G2. The progression of G stages was within normal limits in the majority of patients; only few boys were late at G3 (4.1%; 1 out of 24) and G4 (7.4%; 2 out of 27). Testosterone supplementation was started at the average age of 15.5 years to 35 boys (47%), 2 of whom were over 18 years old. LH level was on average 18.2 IU/L (SD: 6.3 IU/L) and testosterone 9.1 nmol/L (SD: 3.1 nmol/L) when testosterone supplementation was started.

CONCLUSIONS

Our results suggest that puberty starts within the normal age limits in boys with KS, and testosterone supplementation is not needed for the initial pubertal progression in the majority of patients.

Pubertal development in 46,XY patients with NR5A1 mutations

PURPOSE

Mutations in the NR5A1 gene, encoding the transcription factor Steroidogenic Factor-1, are associated with a highly variable genital phenotype in patients with 46,XY differences of sex development (DSD). Our objective was to analyse the pubertal development in 46,XY patients with NR5A1 mutations by the evaluation of longitudinal clinical and hormonal data at pubertal age.

METHODS

We retrospectively studied a cohort of 10 46,XY patients with a verified NR5A1 mutation and describe clinical features including the external and internal genitalia, testicular volumes, Tanner stages and serum concentrations of LH, FSH, testosterone, AMH, and inhibin B during pubertal transition.

RESULTS

Patients who first presented in early infancy due to ambiguous genitalia showed spontaneous virilization at pubertal age accompanied by a significant testosterone production despite the decreased gonadal volume. Patients with apparently female external genitalia at birth presented later in life at pubertal age either with signs of virilization and/or absence of female puberty. Testosterone levels were highly variable in this group. In all patients, gonadotropins were constantly in the upper reference range or elevated. Neither the extent of virilization at birth nor the presence of Müllerian structures reliably correlated with the degree of virilization during puberty.

CONCLUSION

Patients with NR5A1 mutations regardless of phenotype at birth may demonstrate considerable virilization at puberty. Therefore, it is important to consider sex assignment carefully and avoid irreversible procedures during infancy.

In vitro propagation of XXY human Klinefelter spermatogonial stem cells: A step towards new fertility opportunities

Klinefelter Syndrome (KS) is characterized by a masculine phenotype, supernumerary sex chromosomes (47, XXY), and impaired fertility due to loss of spermatogonial stem cells (SSCs). Early testicular cryopreservation could be an option for future fertility treatments in these patients, including SSCs transplantation or in vitro spermatogenesis. It is critically essential to adapt current in vitro SSCs propagation systems as a fertility option for KS patients. KS human testicular samples (13,15- and 17-year-old non-mosaic KS boys) were donated by patients enrolled in an experimental testicular tissue banking program. Testicular cells were isolated from cryopreserved tissue and propagated in long-term culture for 110 days. Cell-specific gene expression confirmed the presence of all four main cell types found in testes: Spermatogonia, Sertoli, Leydig, and Peritubular cells. A population of ZBTB16⁺ undifferentiated spermatogonia was identified throughout the culture using digital PCR. Flow cytometric analysis also detected an HLA^-/CD9⁺/CD49f⁺ population, indicating maintenance of a stem cell subpopulation among the spermatogonial cells. FISH staining for chromosomes X and Y showed most cells containing an XXY karyotype with a smaller number containing either XY or XX. Both XY and XX populations were able to be enriched by magnetic sorting for CD9 as a spermatogonia marker. Molecular karyotyping demonstrated genomic stability of the cultured cells, over time. Finally, single-cell RNAseq analysis confirmed transcription of ID4, TCN2, and NANOS 3 within a population of putative SSCs population. This is the first study showing successful isolation and long-term in vitro propagation of human KS testicular cells. These findings could inform the development of therapeutic fertility options for KS patients, either through in vitro spermatogenesis or transplantation of SSC, in vivo.

Testicular Tissue Banking for Fertility Preservation in Young Boys: Which Patients Should Be Included?

Due to the growing number of young patients at risk of germ cell loss, there is a need to preserve spermatogonial stem cells for patients who are not able to bank spermatozoa. Worldwide, more and more clinics are implementing testicular tissue (TT) banking programs, making it a novel, yet indispensable, discipline in the field of fertility preservation. Previously, TT cryopreservation was predominantly offered to young cancer patients before starting gonadotoxic chemo- or radiotherapy. Nowadays, most centers also bank TT from patients with non-malignant conditions who need gonadotoxic conditioning therapy prior to hematopoietic stem cell (HSCT) or bone marrow transplantation (BMT). Additionally, some centers include patients who suffer from genetic or developmental disorders associated with prepubertal germ cell loss or patients who already had a previous round of chemo- or radiotherapy. It is important to note that the surgical removal of TT is an invasive procedure. Moreover, TT cryopreservation is still considered experimental as restoration methods are not yet clinically available. For this reason, TT banking should preferably only be offered to patients who are at significant risk of becoming infertile. In our view, TT cryopreservation is recommended for young cancer patients in need of high-risk chemo- and/or radiotherapy, regardless of previous low-risk treatment. Likewise, TT banking is advised for patients with non-malignant disorders such as sickle cell disease, beta-thalassemia, and bone marrow failure, who need high-risk conditioning therapy before HSCT/BMT. TT retrieval during orchidopexy is also proposed for patients with bilateral cryptorchidism. Since patients with a medium- to low-risk treatment generally maintain their fertility, TT banking is not advised for this group. Also for Klinefelter patients, TT banking is not recommended as it does not give better outcomes than a testicular sperm extraction later in life.

In Vitro Propagation of XXY Undifferentiated Mouse Spermatogonia: Model for Fertility Preservation in Klinefelter Syndrome Patients

Klinefelter syndrome (KS) is characterized by a masculine phenotype, supernumerary sex chromosomes (usually XXY), and spermatogonial stem cell (SSC) loss in their early life. Affecting 1 out of every 650 males born, KS is the most common genetic cause of male infertility, and new fertility preservation strategies are critically important for these patients. In this study, testes from 41, XXY prepubertal (3-day-old) mice were frozen-thawed. Isolated testicular cells were cultured and characterized by qPCR, digital PCR, and flow cytometry analyses. We demonstrated that SSCs survived and were able to be propagated with testicular somatic cells in culture for up to 120 days. DNA fluorescent in situ hybridization (FISH) showed the presence of XXY spermatogonia at the beginning of the culture and a variety of propagated XY, XX, and XXY spermatogonia at the end of the culture. These data provide the first evidence that an extra sex chromosome was lost during innate SSC culture, a crucial finding in treating KS patients for preserving and propagating SSCs for future sperm production, either in vitro or in vivo. This in vitro propagation system can be translated to clinical fertility preservation for KS patients.

Comparative single-cell analysis of biopsies clarifies pathogenic mechanisms in Klinefelter syndrome

Klinefelter syndrome (KS), also known as 47, XXY, is characterized by a distinct set of physiological abnormalities, commonly including infertility. The molecular basis for Klinefelter-related infertility is still unclear, largely because of the cellular complexity of the testis and the intricate endocrine and paracrine signaling that regulates spermatogenesis. Here, we demonstrate an analysis framework for dissecting human testis pathology that uses comparative analysis of single-cell RNA-sequencing data from the biopsies of 12 human donors. By comparing donors from a range of ages and forms of infertility, we generate gene expression signatures that characterize normal testicular function and distinguish clinically distinct forms of male infertility. Unexpectedly, we identified a subpopulation of Sertoli cells within multiple individuals with KS that lack transcription from the XIST locus, and the consequence of this is increased X-linked gene expression compared to all other KS cell populations. By systematic assessment of known cell signaling pathways, we identify 72 pathways potentially active in testis, dozens of which appear upregulated in KS. Altogether our data support a model of pathogenic changes in interstitial cells cascading from loss of X inactivation in pubertal Sertoli cells and nominate dosage-sensitive factors secreted by Sertoli cells that may contribute to the process. Our findings demonstrate the value of comparative patient analysis in mapping genetic mechanisms of disease and identify an epigenetic phenomenon in KS Sertoli cells that may prove important for understanding causes of infertility and sex chromosome evolution.

A magnetic resonance imaging study in etiology of nonobstructive azoospermia

BACKGROUND

Testicular magnetic resonance imaging parameters, including apparent diffusion coefficient, fractional anisotropy, magnetization transfer ratio, and normalized metabolite concentrations represent useful noninvasive fingerprints of nonobstructive azoospermia. Nonobstructive azoospermia etiology might correlate with the spermatogenesis status.

OBJECTIVES

To assess the possible association between apparent diffusion coefficient, fractional anisotropy, magnetization transfer ratio, and normalised metabolite concentrations with nonobstructive azoospermia etiology.

MATERIALS AND METHODS

This retrospective study included 48 consecutive men with nonobstructive azoospermia and 18 age-matched controls. All participants underwent scrotal magnetic resonance imaging. The testicular apparent diffusion coefficient, fractional anisotropy, magnetization transfer ratio, and normalized metabolite concentrations were calculated. nonobstructive azoospermia men were classified into three groups, based on etiology: group 1, idiopathic; group 2, genetic causes; and group 3, non-genetic causes. Parametric and nonparametric statistical tests were used to evaluate differences in magnetic resonance imaging parameters between nonobstructive azoospermia groups and normal testes (group 4). Regression analysis was performed to assess the most predictive magnetic resonance imaging factor of nonobstructive azoospermia etiology.

RESULTS

Differences in mean apparent diffusion coefficient (p < .001), fractional anisotropy (p < .001), magnetization transfer ratio (p < .001), and normalized concentrations of total choline (p = .005), glucose (p = .012), myo-inositol (p = .024), and lipids (p = .010) were observed among groups. Regression analysis failed to identify the most discriminating magnetic resonance imaging feature for nonobstructive azoospermia etiology.

DISCUSSION AND CONCLUSION

Apparent diffusion coefficient, fractional anisotropy, magnetization transfer ratio, and normalized concentrations of total choline, glucose, myo-inositol, and lipids are helpful in discriminating nonobstructive azoospermia etiology. Magnetic resonance imaging may provide useful, noninvasive information on the microstructural and biochemical milieu of nonobstructive azoospermia testes.

Stereological properties of seminiferous tubules in infertile men with chromosomal and genetic abnormalities

BACKGROUND

Male infertility is caused by genetic anomalies in 15%-30% of cases. This study aimed to determine stereological properties of seminiferous tubules in infertile men with genetic anomalies, including Klinefelter syndrome (KS), Y chromosome microdeletions (MYC) and CFTR gene mutations (CFTR), and to compare them to seminiferous tubules of men with obstructive azoospermia of non-genetic origin (control group).

METHODS

The study was conducted on 28 human testis biopsy specimens obtained from 14 patients with MYC, 18 samples from 9 patients with KS, and 6 samples from 3 patients with CFTR. Whenever possible, a bilateral biopsy was included in the study. The control group had 33 samples from 18 patients (3 of them with a solitary testis). Qualitative and quantitative (stereological) analysis of seminiferous tubules (including the status of spermatogenesis, volume, surface area, length and number of tubules) were performed in all groups.

RESULTS

Qualitative histological analysis revealed significant impairment of spermatogenesis in KS and MYC, whereas testicular parenchyma was fully maintained in CFTR and control groups. Spermatogenesis was most seriously impaired in KS. All stereological parameters were significantly lower in KS and MYC, compared to the CFTR and control groups. The total volume, surface and length of seminiferous tubules were significantly lower in KS compared with MYC.

CONCLUSIONS

Stereological analysis is valuable in evaluating male infertility, whereas qualitative histological analysis can be helpful in assessing sperm presence in testicular tissue of patients with KS or MYK undergoing TESE.

Androgen Treatment in Adolescent Males With Hypogonadism

During adolescence, androgens are responsible for the development of secondary sexual characteristics, pubertal growth, and the anabolic effects on bone and muscle mass. Testosterone is the most abundant testicular androgen, but some effects are mediated by its conversion to the more potent androgen dihydrotestosterone (DHT) or to estradiol. Androgen deficiency, requiring replacement therapy, may occur due to a primary testicular failure or secondary to a hypothalamic–pituitary disorder. A very frequent condition characterized by a late activation of the gonadal axis that may also need androgen treatment is constitutional delay of puberty. Of the several testosterone or DHT formulations commercially available, very few are employed, and none is marketed for its use in adolescents. The most frequently used androgen therapy is based on the intramuscular administration of testosterone enanthate or cypionate every 3 to 4 weeks, with initially low doses. These are progressively increased during several months or years, in order to mimic the physiology of puberty, until adult doses are attained. Scarce experience exists with oral or transdermal formulations. Preparations containing DHT, which are not widely available, are preferred in specific conditions. Oxandrolone, a non-aromatizable drug with higher anabolic than androgenic effects, has been used in adolescents with preserved testosterone production, like Klinefelter syndrome, with positive effects on cardiometabolic health and visual, motor, and psychosocial functions. The usual protocols applied for androgen therapy in boys and adolescents are discussed.

Z-scores for comparative analyses of spermatogonial numbers throughout human development

OBJECTIVE

To normalize age-dependent effects on standardized measures of spermatogonial quantity such as the number of spermatogonia per tubular cross-section (S/T) or fertility index.

DESIGN

Published quantitative histologic data on human spermatogonial numbers were used to create Z-scores for reference means and tested on archived testicular tissue samples.

SETTING

Retrospective cohort study.

PATIENT(S)

The sample cohort comprised testicular samples from 24 boys with cancer diagnosis and 10 with Klinefelter syndrome, as part of the fertility preservation programs NORDFERTIL and Androprotect, as well as archived histologic samples from 35 prepubertal boys with acute lymphoblastic leukemia and 20 testicular biobank samples.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Z-score values for S/T and fertility index on the basis of morphology and germ cell-specific markers (MAGEA4 and/or DDX4) were calculated, and the impact of cancer therapy exposure and genetic disorders on Z-score values was evaluated.

RESULT(S)

The Z-scores for S/T values in the nontreated samples (-2.08 ± 2.20, n = 28) and samples treated with nonalkylating agents (-1.90 ± 2.60, n = 25) were comparable within ±3 standard deviations of the reference mean value but differed significantly from samples exposed to alkylating agents (-12.14 ± 9.20, n = 22) and from patients with Klinefelter syndrome (-11.56 ± 4.89, n = 8). The Z-scores for S/T were correlated with increasing cumulative exposure to alkylating agents (r = -0.7020).

CONCLUSION(S)

The Z-score values for S/T allow for the quantification of genetic and cancer treatment-related effects on testicular tissue stored for fertility preservation, facilitating their use for patient counseling.

Reproductive Chances of Men with Azoospermia Due to Spermatogenic Dysfunction

Non-obstructive azoospermia (NOA), or lack of sperm in the ejaculate due to spermatogenic dysfunction, is the most severe form of infertility. Men with this form of infertility should be evaluated prior to treatment, as there are various underlying etiologies for NOA. While a significant proportion of NOA men have idiopathic spermatogenic dysfunction, known etiologies including genetic disorders, hormonal anomalies, structural abnormalities, chemotherapy or radiation treatment, infection and inflammation may substantively affect the prognosis for successful treatment. Despite the underlying etiology for NOA, most of these infertile men are candidates for surgical sperm retrieval and subsequent use in intracytoplasmic sperm injection (ICSI). In this review, we describe common etiologies of NOA and clinical outcomes following surgical sperm retrieval and ICSI.

How Successful Is Surgical Sperm Retrieval in Klinefelter Syndrome?

Klinefelter Syndrome (KS) is characterized by the presence of an extra X chromosome. It was first diagnosed in 1942 in a group of azoospermic men. KS is the most common chromosomal abnormality encountered in infertile men and accounts for more than 10% of the causes of azoospermia. Men who are azoospermic may still father children via testicular sperm extraction followed by intracytoplasmic sperm injection (ICSI). This review article summarizes the success rates of the available techniques for surgical sperm retrieval (SSR) in KS including conventional testicular sperm extraction (cTESE) and micro testicular sperm extraction (mTESE), as well as the risks of these procedures for future fertility. The evidence indicates that the SSR rate is as successful in non-mosaic men with KS as those with normal karyotypes, with retrieval rates of up to 55% reported. The influence of different factors that affect the chances of a successful outcome are discussed. In particular, the impact of aneuploidy rate, physical characteristics, co-morbidities, reproductive endocrine balance and the use of different hormone management therapies are highlighted. Evidence is presented to suggest that the single most significant determinant for successful SSR is the age of the patient. The success of SSR is also influenced by surgical technique and operative time, as well as the skills of the surgeon and embryology team. Rescue mTESE may be used successfully following failed TESE in KS patients in combination with hormone stimulation.

Male infertility due to testicular disorders

CONTEXT

Male infertility is defined as the inability to conceive following 1 year of regular unprotected intercourse. It is the causative factor in 50% of couples and a leading indication for assisted reproductive techniques (ART). Testicular failure is the most common cause of male infertility, yet the least studied to date.

EVIDENCE ACQUISITION

The review is an evidence-based summary of male infertility due to testicular failure with a focus on etiology, clinical assessment, and current management approaches. PubMed-searched articles and relevant clinical guidelines were reviewed in detail.

EVIDENCE SYNTHESIS/RESULTS

Spermatogenesis is under multiple levels of regulation and novel molecular diagnostic tests of sperm function (reactive oxidative species and DNA fragmentation) have since been developed, and albeit currently remain as research tools. Several genetic, environmental, and lifestyle factors provoking testicular failure have been elucidated during the last decade; nevertheless, 40% of cases are idiopathic, with novel monogenic genes linked in the etiopathogenesis. Microsurgical testicular sperm extraction (micro-TESE) and hormonal stimulation with gonadotropins, selective estrogen receptor modulators, and aromatase inhibitors are recently developed therapeutic approaches for men with the most severe form of testicular failure, nonobstructive azoospermia. However, high-quality clinical trials data is currently lacking.

CONCLUSIONS

Male infertility due to testicular failure has traditionally been viewed as unmodifiable. In the absence of effective pharmacological therapies, delivery of lifestyle advice is a potentially important treatment option. Future research efforts are needed to determine unidentified factors causative in "idiopathic" male infertility and long-term follow-up studies of babies conceived through ART.

SOX13 gene downregulation in peripheral blood mononuclear cells of patients with Klinefelter syndrome

Klinefelter syndrome (KS) is the most common sex chromosome disorder in men. It is characterized by germ cell loss and other variable clinical features, including autoimmunity. The sex-determining region of Y (SRY)-box 13 (Sox13) gene is expressed in mouse spermatogonia. In addition, it has been identified as islet cell autoantigen 12 (ICA12), which is involved in the pathogenesis of autoimmune diseases, including type 1 diabetes mellitus (DM) and primary biliary cirrhosis. Sox13 expression has never been investigated in patients with KS. In this age-matched, case-control study performed on ten patients with KS and ten controls, we found that SOX13 is significantly downregulated in peripheral blood mononuclear cells of patients with KS compared to controls. This finding might be consistent with the germ cell loss typical of patients with KS. However, the role of Sox13 in the pathogenesis of germ cell loss and humoral autoimmunity in patients with KS deserves to be further explored.

Canary in the Coal Mine? Male Infertility as a Marker of Overall Health

Male factor infertility is a common problem. Evidence is emerging regarding the spectrum of systemic disease and illness harbored by infertile men who otherwise appear healthy. In this review, we present evidence that infertile men have poor overall health and increased morbidity and mortality, increased rates of both genitourinary and non-genitourinary malignancy, and greater risks of systemic disease. The review also highlights numerous genetic conditions associated with male infertility as well as emerging translational evidence of genitourinary birth defects and their impact on male infertility. Finally, parallels to the overall health of infertile women are presented. This review highlights the importance of a comprehensive health evaluation of men who present for an infertility assessment.

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.

Testicular blood supply is altered in the 41,XXY* Klinefelter syndrome mouse model

Hypergonadotropic hypogonadism is a major feature of Klinefelter syndrome (KS), assumed to be caused by testicular hormone resistance. It was previously shown that intratesticular testosterone levels in vivo and Leydig cell function in vitro seem to be normal indicating other functional constraints. We hypothesized that impaired testicular vascularization/blood flow could be a co-factor to the observed hypergonadotropic hypogonadism. We evaluated the testicular vascular system by measuring blood vessel sizes during postnatal development and testis blood flow in adult 41,XX^Y* mice. Proportional distribution and size of blood vessels were analyzed during testicular development (1, 3, 5, 7, 10, 21 dpp, 15 wpp). While ratios of the vessel/testis area were different at 15 wpp only, a lower number of smaller and mid-sized blood vessels were detected in adult KS mice. For testicular blood flow determination we applied contrast enhanced ultrasound. Floating and reperfusion time for testicular blood flow was increased in 41,XX^Y* mice (floating: XY* 28.8 ± 1.69 s vs XX^Y* 44.6 ± 5.6 s, p = 0.0192; reperfusion XY* 19.7 ± 2.8 s vs XX^Y*: 29.9 ± 6.2 s, p = 0.0134), indicating a diminished blood supply. Our data strengthen the concept that an impaired vascularization either in conjunction or as a result of altered KS testicular architecture contributes to hormone resistance.

Role of treatment with human chorionic gonadotropin and clinical parameters on testicular sperm recovery with microdissection testicular sperm extraction and intracytoplasmic sperm injection outcomes in 184 Klinefelter syndrome patients

OBJECTIVE

To investigate whether preoperative human chorionic gonadotropin (hCG) treatment can help predict the outcomes of microdissection testicular sperm extraction (micro-TESE) and affect fertility outcomes in non-mosaic Klinefelter syndrome (KS) patients.

DESIGN

Retrospective cohort study.

SETTING

University-affiliated fertility center.

PATIENT(S)

A total of 184 non-mosaic KS patients who underwent micro-TESE with or without preoperative hCG treatment from January 2016 to July 2019.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Sperm retrieval rate (SRR) with and without hCG treatment, logistic models analysis.

RESULT(S)

Eighty KS patients (43.5%) had successful sperm retrievals after micro-TESE. There was no statistically significant difference in the SRR between the group who received hCG treatment and the group that did not (44.0% vs. 43.3%). Logistic regression analyses demonstrated that the hCG treatment had no statistically significant effect on successful sperm retrieval. However, higher preoperative testosterone (T) levels seemed to be associated with a higher probability of successful sperm retrieval (multivariate adjusted odds ratio 1.09; 95% confidence interval [CI], 1.04-1.16). The prediction model for SRR on KS patients had an area under the curve of 67.3% (95% CI, 59.3-75.3%). In the hCG treatment group, the data indicated that the three parameters of testicular volume, pretreatment T level, and alterations of T were associated with the probability of successful sperm retrieval. Moreover, hCG therapy did not affect intracytoplasmic sperm injection (ICSI) outcomes. No differences in the pregnancy rate or live-birth rate were observed between the two groups.

CONCLUSION(S)

Therapy with hCG does not affect SRR or ICSI outcomes of non-mosaic KS patients. However, preoperative T levels, whether treated with hCG or not, can predict the chance of sperm retrieval with micro-TESE.

Expression profile of microRNAs in the testes of patients with Klinefelter syndrome

Klinefelter syndrome (KS) is the most common sex chromosome aneuploidy. A distinctive characteristic of KS is oligozoospermia. Despite multiple studies that have described the natural history of the degenerative process of germ cells in patients with KS, the molecular mechanisms that initiate this process are not well characterized. MicroRNA (miRNA)-mediated post-transcriptional control mechanisms have been increasingly recognized as important regulators of spermatogenesis; however, only a few studies have evaluated the role of miRNAs in the gonadal failure of these patients. Here, we describe a differential expression profile for the miRNAs in testicular tissue samples taken from KS patients. We analysed testicular tissue samples from 4 KS patients and 5 control patients (obstructive azoospermia) through next-generation sequencing, which can provide information about the mechanisms involved in the degeneration of germ cells. A distinctive differential expression profile was identified for 166 miRNAs in the KS patients: 66 were upregulated, and 100 were downregulated. An interactome analysis was performed for 7 of the upregulated and the 20 downregulated miRNAs. The results showed that the target genes are involved in the development, proliferation, and differentiation processes of spermatogenesis, which may explain their role in the development of infertility. This is the first report of a miRNA expression profile generated from testicular tissue samples of KS patients.

Rates of hypogonadism forms in Klinefelter patients undergoing testicular sperm extraction: A multicenter cross-sectional study

INTRODUCTION AND OBJECTIVES

Adult patients with Klinefelter syndrome (KS) may present with testicular volume loss and a decrease in circulating testosterone (T) levels. However, the actual rate of hypogonadism in adult KS men is unknown. We aimed to (a) assess the prevalence of different forms of hypogonadism in a cohort of KS patients with non-obstructive azoospermia (NOA); and (b) investigate potential preoperative predictor of positive sperm retrieval (SR) at surgery in the same cohort of men.

METHODS

Complete data from 103 KS men with NOA who underwent testicular sperm extraction (TESE) between 2008 and 2019 at five centers were analyzed. Comorbidities were scored with the Charlson Comorbidity Index (CCI). Patients were categorized into four groups of hypogonadism as follows: eugonadism [normal total T (tT) (≥3.03 ng/mL) and normal luteinizing hormone (LH) (≤9.4 mUI/mL)], secondary hypogonadism [low tT (≤3.03 ng/mL) and low/normal LH (≤9.4 mUI/mL)], primary hypogonadism [low tT (≤3.03 ng/mL) and elevated LH (≥9.4 mUI/mL)], and compensated hypogonadism [normal tT (≥3.03 ng/mL) and elevated LH (≥9.4 mUI/mL)]. Descriptive statistics tested the association between clinical characteristics and laboratory values among the four groups.

RESULTS

Median (IQR) patients age was 32 (24, 37) years. Baseline follicle-stimulating hormone and tT levels were 29.5 (19.9, 40.9) mUI/mL and 3.8 (2.5, 11.0) ng/mL, respectively. Eugonadism, primary hypogonadism, and compensated hypogonadism were found in 16 (15.6%), 34 (33.0%), and 53 (51.4%) men, respectively. No patients had secondary hypogonadism. Positive SR rate at TESE was 21.4% (22 patients); of 22, 15 (68.2%) patients underwent assisted reproductive technology and five (22.7%) ended in live birth children. Patients' age, BMI, CCI, FSH levels, and positive SR rates were comparable among hypogonadism groups. No preoperative parameters were associated with positive SR at logistic regressions analysis.

CONCLUSIONS

Findings from this cross-sectional study showed that 15.6% of adult KS men have normal tT values at presentation in the real-life setting. Most KS patients presented with either compensated or primary hypogonadism. Sperm retrieval rates were not associated with different forms of hypogonadism.

Epigenetics and genomics in Klinefelter syndrome

Since the first description of Klinefelter syndrome (KS) was published in 1942 in The Journal of Clinical Endocrinology, large inter-individual variability in the phenotypic presentation has been demonstrated. However, our understanding of the global impact of the additional X chromosome on the genome remains an enigma. Evidence from the existing literature of KS indicates that not just one single genetic mechanism can explain the phenotype and the variable expressivity, but several mechanisms may be at play concurrently. In this review, we describe different genetic mechanisms and recent advances in the understanding of the genome, epigenome, and transcriptome of KS and the link to the phenotype and clinical heterogeneity. Future studies are needed to unite clinical data, genomic data, and basic research attempting to understand the genetics behind KS. Unraveling the genetics of KS will be of clinical relevance as it may enable the use of polygenic risk scores to predict future disease susceptibility and enable clinical risk stratification of KS patients in the future.

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.

Gonadal dysfunction and beyond: Clinical challenges in children, adolescents, and adults with 47,XXY Klinefelter syndrome

Klinefelter syndrome (KS) is the most frequent sex chromosomal aneuploidy. The karyotype 47,XXY originates from either paternal or maternal meiotic nondisjunction during gametogenesis. KS males are very likely to exhibit marked gonadal dysfunctions, presenting both in severely attenuated spermatogenesis as well as hypergonadotropic hypogonadism. In addition, neurocognitive and psychosocial impairments, as well as cardiovascular, metabolic and bone disorders are often found in KS and might explain for an increased morbidity/mortality. All conditions in KS are likely to be induced by both gene overdosage effects resulting from supernumerary X-chromosomal genes as well as testosterone deficiency. Notwithstanding, the clinical features are highly variable between KS men. Symptoms can become obvious at infancy, childhood, or adolescence. However, the majority of KS subjects is diagnosed during adulthood. KS adolescents require specific attention regarding pubertal development, in order to exploit their remaining fertility potential and allow for timely and tailored testosterone replacement. The chances for sperm retrieval might decline with age and could be hampered by testosterone replacement; therefore, cryostorage of spermatozoa is an option during adolescence, before the decompensation of endocrine and exocrine testicular functions becomes more overt. Sperm from semen or surgically retrieved, in combination with intracytoplasmic sperm injection enables KS males to become biological fathers of healthy children. The aim of this article is to present the current knowledge on KS, to guide clinical care and to highlight research needs.

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.

Fertility in Adolescents With Klinefelter Syndrome: A Survey of Current Clinical Practice

CONTEXT

Progress has been made in determining the fertility timeline and potential in adolescents with Klinefelter syndrome; however, medical professionals are currently without protocols to guide treatment.

OBJECTIVE

To evaluate the current practices regarding fertility and andrology care in adolescent males with Klinefelter syndrome.

DESIGN

A 24-question survey was developed to elicit practitioner background/expertise and management practices. This was distributed to members of the Society for the Study of Male Reproduction, the Pediatric Endocrine Society, and the Endocrine Society.

SETTING

N/A.

PATIENTS

Adolescent males with Klinefelter syndrome.

INTERVENTION

None.

MAIN OUTCOME MEASURED

Current practices regarding fertility and andrology care.

RESULTS

232 responses were received from 133 (57%) adult endocrinologists, 60 (26%) pediatric endocrinologists, and 39 (17%) urologists. Among these, 69% of respondents were in academics, 62% practiced for > 10 years, and 65% received formal training in Klinefelter syndrome. All specialties encouraged sperm banking in late puberty, however most disagreed with the practice in early puberty. Seventy-eight percent agreed that testicular biopsy should be offered if no sperm was found in the ejaculate. The perceived optimal age for testicular biopsy varied among specialists. Clinical symptoms of hypogonadism (28%), rising gonadotropin levels (15%), and testosterone levels (15%) were the most commonly cited reasons for initiation of testosterone replacement therapy.

CONCLUSION

Fertility preservation practices in adolescents with Klinefelter syndrome vary greatly within and among the specialties caring for these patients. These findings should guide future research and highlight the importance of establishing clinical practice guidelines.

Human sex chromosome aneuploidies: The hypothalamic-pituitary-gonadal axis

Sex chromosome aneuploidies (SCA) are relatively common as a group, perhaps 1 per 500 births, but much more common at conception. Many syndromes have been noted in those with these conditions, but not so many data are available concerning the hypothalamic-pituitary-gonadal (HPG) axis. The physiology of the HPG axis is first reviewed at four epochs in time: fetal, birth and mini-puberty, childhood, and adolescence (puberty). Those sections are followed by detailed analysis of the functioning of the HPG axis in individuals with specific SCA with chromosomal numbers ranging from 45 to 49. Robust data are available for the chromosomal complements 47,XXY and 47,XXX with fewer data available for many of the others.

Do partial AZFc deletions affect the sperm retrieval rate in non-mosaic Klinefelter patients undergoing microdissection testicular sperm extraction?

BACKGROUND

The purpose of this study is to evaluate the prognostic factors for sperm retrieval and determine if Y chromosome deletion is associated with deleterious effects on spermatogenesis in non-mosaic Klinefelter patients. Whether Y chromosome deletion determines the sperm retrieval rate in non-mosaic Klinefelter patients has not yet been addressed.

METHODS

We retrospectively collected medical records of azoospermic patients from Sep 2009 to Dec 2018, and enrolled 66 non-mosaic 47, XXY patients who were receiving mTESE. The predictive values of patients age, serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone, prolactin, estradiol and Y chromosome deletion were assessed for successful sperm recovery.

RESULTS

Testicular sperm recovery was successful in 24 (36.4%) of 66 men. The mean age (36.0 vs. 36.6 years), and levels of FSH (30.0 vs 36.9 IU/L), LH (17.7 vs 21.9 IU/L), testosterone (2.4 vs. 2.1 ng/ml), prolactin (9.1 vs. 8.8 ng/ml), and estradiol (19.4 vs. 22.3 pg/ml) did not show any significant difference when comparing patients with and without successful sperm retrieval. Partial deletion of azoospermic factor c (AZFc) was noted in 5 (20.8%) of 24 patients with successful sperm retrieval, including three b2/b3 and two gr/gr deletion cases, whereas 4 (9.5%) of 42 patients with unsuccessful sperm retrieval were noted to have AZFc partial deletion (one b2/b3, one sY1206 and two gr/gr deletion), though the difference was not statistically significant (p = 0.27).

CONCLUSION

According to present results, age and AZFc partial deletion status should not be a deterrent for azoospermic males with non-mosaic Klinefelter syndrome to undergo mTESE.

Development and Disease-Dependent Dynamics of Spermatogonial Subpopulations in Human Testicular Tissues

Cancer therapy and conditioning treatments of non-malignant diseases affect spermatogonial function and may lead to male infertility. Data on the molecular properties of spermatogonia and the influence of disease and/or treatment on spermatogonial subpopulations remain limited. Here, we assessed if the density and percentage of spermatogonial subpopulation changes during development (n = 13) and due to disease and/or treatment (n = 18) in tissues stored in fertility preservation programs, using markers for spermatogonia (MAGEA4), undifferentiated spermatogonia (UTF1), proliferation (PCNA), and global DNA methylation (5mC). Throughout normal prepubertal testicular development, only the density of 5mC-positive spermatogonia significantly increased with age. In comparison, patients affected by disease and/or treatment showed a reduced density of UTF1-, PCNA- and 5mC-positive spermatogonia, whereas the percentage of spermatogonial subpopulations remained unchanged. As an exception, sickle cell disease patients treated with hydroxyurea displayed a reduction in both density and percentage of 5mC- positive spermatogonia. Our results demonstrate that, in general, a reduction in spermatogonial density does not alter the percentages of undifferentiated and proliferating spermatogonia, nor the establishment of global methylation. However, in sickle cell disease patients’, establishment of spermatogonial DNA methylation is impaired, which may be of importance for the potential use of this tissues in fertility preservation programs.

Ontogeny of Hypothalamus-Pituitary Gonadal Axis and Minipuberty: An Ongoing Debate?

The fetal hypothalamus-pituitary gonadal (HPG) axis begins to function during mid-gestation but its activity decreases during late pregnancy due to the suppressive effects of placental estrogens. Placental hormones drop immediately after birth, FSH and LH surge at around 1 week and peak between 1 and 3 months of life. The HPG axis is activated in both sexes, but a sexual dimorphism is evident with higher LH values in boys, while FSH prevails in girls. Both gonadotrophins decline in boys by around 6 months of age. In girls, LH declines at the same time as in boys, while FSH persists elevated up to 3 or 4 years of age. As a result of gonadotropin activation, testicular testosterone increases in males and ovarian estradiol rises in females. These events clinically translate into testicular and penile growth in boys, enlargement of uterus and breasts in girls. The functional impact of HPG axis activity in infancy on later reproductive function is uncertain. According to the perinatal programming theory, this period may represent an essential programming process. In boys, long-term testicular hormonal function and spermatogenesis seem to be, at least in part, regulated by minipuberty. On the contrary, the role of minipuberty in girls is still uncertain. Recently, androgen exposure during minipuberty has been correlated with later sex-typed behavior. Premature and/or SGA infants show significant differences in postnatal HPG axis activity in comparison to full-term infants and the consequences of these differences on later health and disease require further research. The sex-dimorphic HPG activation during mid-gestation is probably responsible for the body composition differences observed ad birth between boys and girls, with boys showing greater total body mass and lean mass, and a lower proportion of fat mass. Testosterone exposure during minipuberty further contributes to these differences and seems to be responsible for the significantly higher growth velocity observed in male infants. Lastly, minipuberty is a valuable "window of opportunity" for differential diagnosis of disorders of sex development and it represents the only time window before puberty when congenital hypogonadism can be diagnosed by the simple analysis of basal gonadotropin and gonadal hormone levels.

Setting Up a Cryopreservation Programme for Immature Testicular Tissue: Lessons Learned After More Than 15 Years of Experience

Young boys undergoing gonadotoxic treatments are at high risk of spermatogonial stem cell (SSC) loss and fertility problems later in life. Stem cell loss can also occur in specific genetic conditions, eg, Klinefelter syndrome (KS). Before puberty, these boys do not yet produce sperm. Hence, they cannot benefit from sperm banking. An emerging alternative is the freezing of testicular tissue aiming to preserve the SSCs for eventual autologous transplantation or in vitro maturation at adult age. Many fertility preservation programmes include cryopreservation of immature testicular tissue, although the restoration procedures are still under development. Until the end of 2018, the Universitair Ziekenhuis Brussel has frozen testicular tissues of 112 patients between 8 months and 18 years of age. Testicular tissue was removed in view of gonadotoxic cancer treatment (35%), gonadotoxic conditioning therapy for bone marrow transplantation (35%) or in boys diagnosed with KS (30%). So far, none of these boys had their testicular tissue transplanted back. This article summarizes our experience with cryopreservation of immature testicular tissue over the past 16 years (2002-2018) and describes the key issues for setting up a cryopreservation programme for immature testicular tissue as a means to safeguard the future fertility of boys at high risk of SSC loss.