Stefan Schlatt

• University of Münster

BACKGROUND Male germline stem cells are relevant for stem cell researchers but also for andrologists as they are crucial for testis function and initiation/maintenance of spermatogenesis. They are also considered a target for fertility preservation in the male; e.g. germ cell transplantation or testicular grafting rely on spermatogonial stem cells...

Study question What are the specific changes under gender affirming hormone therapy (GAHT) in the spermatogonial cell compartment in testicular tissues of transwomen? Summary answer GAHT has a negative effect on the most undifferentiated PIWIL4+ spermatogonia potentially leading to reduced chances for fertility preservation in transwomen. What is...

Sperm production and function require the correct establishment of DNA methylation patterns in the germline. Here, we examined the genome-wide DNA methylation changes during human spermatogenesis and its alterations in disturbed spermatogenesis. We found that spermatogenesis is associated with remodeling of the methylome, comprising a global declin...

STUDY QUESTION Twenty years after the inception of the first fertility preservation programme for pre-pubertal boys, what are the current international practices with regards to cryopreservation of immature testicular tissue? SUMMARY ANSWER Worldwide, testicular tissue has been cryopreserved from over 3000 boys under the age of 18 years for a vari...

The infertility of many couples rests on an enigmatic dysfunction of the man's sperm. To gain insight into the underlying pathomechanisms, we assessed the function of the sperm-specific multisubunit CatSper-channel complex in the sperm of almost 2,300 men undergoing a fertility workup, using a simple motility-based test. We identified a group of me...

Approximately one in twenty men have sperm counts low enough to impair fertility but little progress has been made in answering fundamental questions in andrology or in developing new diagnostic tools or management strategies in infertile men. Many of these problems increase with age, leading to a growing population of men seeking help. To address...

The detection of genetic aberrations is crucial for early therapy decisions in acute myeloid leukemia (AML) and is recommended for all patients. Since genetic testing is expensive and time-consuming, a need remains for cost-effective, fast, and broadly accessible tests to predict these aberrations in this aggressive malignancy. Here, we developed a...

Sperm production and function require the correct establishment of DNA methylation patterns in the germline. Here, we examined the genome-wide DNA methylation changes during human spermatogenesis and its alterations in disturbed spermatogenesis. We found that spermatogenesis is associated with remodeling of the methylome, comprising a global-declin...

Cryopreservation of human sperm can be offered as fertility reserve to adolescents and adults in oncological and non-oncological diseases, as a preventive measure before vasectomy and securing sperm availability in ART procedures. The methods of cryopreservation differ with regard to fresh ejaculate and surgically (epididymal or testicular) retriev...

Currently, most men with infertility cannot be given an aetiology, which reflects a lack of knowledge around gamete production and how it is affected by genetics and the environment. A failure to recognize the burden of male infertility and its potential as a biomarker for systemic illness exists. The absence of such knowledge results in patients g...

In brief: Minipuberty is a transient activity period of the hypothalamic-pituitary-gonadal axis in the postnatal and infant period including surging serum concentrations of reproductive hormones. Increasing evidence points to an important role of this period for maturation of the testes and thereby for male reproductive function. Abstract: Minip...

The spermatogonial compartment maintains spermatogenesis throughout the reproductive lifespan. Single-cell RNA sequencing (scRNA-seq) has revealed the presence of several spermatogonial clusters characterized by specific molecular signatures. However, it is unknown whether the presence of such clusters can be confirmed in terms of protein expressio...

The infertility of many couples seems to rest on an enigmatic dysfunction of the men's sperm, rendering early diagnosis and evidence-based treatment by medically assisted reproduction impossible. Using a novel laboratory test, we assessed the function of the flagellar calcium channel CatSper in sperm of almost 2,300 men undergoing a fertility worku...

So far, it has not been possible to generate human sperm and egg cells from pluripotent stem cells. However, completion of in vitro gametogenesis (IVG) is expected in the near future because progenitor cells from human gamete have already been generated. Gametes produced this way could fundamentally expand both the understanding of early human deve...

So far, it has not been possible to generate human sperm and egg cells from pluripotent stem cells. However, completion of in vitro gametogenesis (IVG) is expected in the near future because progenitor cells from human gamete have already been generated. Gametes produced this way could fundamentally expand both the understanding of early human deve...

So far, it has not been possible to generate human sperm and egg cells from pluripotent stem cells. However, completion of in vitro gametogenesis (IVG) is expected in the near future because progenitor cells from human gamete have already been generated. Gametes produced this way could fundamentally expand both the understanding of early human deve...

So far, it has not been possible to generate human sperm and egg cells from pluripotent stem cells. However, completion of in vitro gametogenesis (IVG) is expected in the near future because progenitor cells from human gamete have already been generated. Gametes produced this way could fundamentally expand both the understanding of early human deve...

Objective Germ cells of transwomen are affected by gender affirming hormone therapy (GAHT). Fertility will be lost after surgical intervention, thereby fertility preservation becomes an increasingly important topic. We investigated if the absolute number of spermatogonia in transwomen is comparable at the time of gender affirming surgery (GAS) to t...

The process of spermatogenesis—when germ cells differentiate into sperm—is tightly regulated, and misregulation in gene expression is likely to be involved in the physiopathology of male infertility. The testis is one of the most transcriptionally rich tissues; nevertheless, the specific gene expression changes occurring during spermatogenesis are...

Biomedical science is rapidly developing in terms of more transparency, openness and reproducibility of scientific publications. This is even more important for all studies that are based on results from basic semen examination. Recently two concordant documents have been published: the 6th edition of the WHO Laboratory Manual for the Examination a...

Background: Recent findings demonstrate that single nucleotide variants can cause non-obstructive azoospermia (NOA). In contrast, copy number variants (CNVs) were only analysed in few studies in infertile men. Some have reported a higher prevalence of CNVs in infertile versus fertile men. Objectives: This study aimed to elucidate if CNVs are ass...

Background: No association between the length of ejaculatory abstinence (LEA) and semen characteristics has been confirmed. A short LEA has been linked to improved sperm characteristics and a higher pregnancy rate, but its negative influence on sperm chromatin maturity and longevity may adversely affect reproductive outcomes. Objectives: We soug...

Here, we report a testis-on-chip platform for the ex vivo culture of seminiferous tubules isolated from human and non-human primate testis. Tissues are cultured in a dedicated chamber with continuous perfusion via a vascular-like channel. The platform is fabricated from PDMS using a 3D printed mold, after design has been optimized, e.g., for the ba...

Introduction Cryopreservation of immature-testicular-tissue (ITT) prior to gonadotoxic treatment, while experimental, is the only recommended option for fertility preservation in prepubertal boys. The handling and manipulation of ITT prior to banking could influence the functionality, genetic and epigenetic integrity of cells. Objectives To invest...

Cell differentiation processes are highly dependent on cell stage-specific gene expression, including timely production of alternatively spliced transcripts. One of the most transcriptionally rich tissues is the testis, where the process of spermatogenesis, or generation of male gametes, takes place. To date, germ cell-specific transcriptome dynami...

Growth factors became attractive candidates for medium supplementation to further improve the quality of embryo culture and to mimic in vivo nutrition. Granulocyte macrophage colony-stimulating factor (GM-CSF) is a cytokine influencing the maternal-fetal interface and supporting placental development in mouse and human. It is expressed in epithelia...

In the sixth edition of the World Health Organization manual for the examination and processing of human semen, extended examination methods to provide key diagnostics in the investigation of the male reproductive system function are elaborated. These go beyond the basic analysis of semen and may be useful in more specifically guiding the clinical...

The DND microRNA-mediated repression inhibitor 1 (DND1) is a conserved RNA binding protein (RBP) that plays important roles in survival and fate maintenance of primordial germ cells (PGCs) and in the development of the male germline in zebrafish and mice. Dead end was shown to be expressed in human pluripotent stem cells (PSCs), PGCs and spermatogo...

Purpose: of the research: To achieve male fertility preservation and restoration, experimental strategies for in vitro germ cell differentiation are required. The effects of two different culture conditions on in vitro maintenance and differentiation of non-human primate germ cells was studied. Three testes from three 6-month-old marmosets were cu...

Background Little information is available on steroid hormone profiles in transwomen on the day of gender affirming surgery (GAS) after gender affirming hormone therapy (GAHT). Aim We compared extended serum steroid hormone profiles of 77 transwomen with 3 different treatment regimens in order to get more insight on how GAHT changes the hormone sy...

Despite the high incidence of male infertility, only 30% of infertile men receive a causative diagnosis. To explore the regulatory mechanisms governing human germ cell function in normal and impaired spermatogenesis (crypto), we performed single-cell RNA sequencing (>30,000 cells). We find major alterations in the crypto spermatogonial compartment...

Background Anti-Müllerian hormone (AMH) and inhibin B are produced by Sertoli cells. AMH secretion indicates an immature Sertoli cell state. Inhibin B serves as a marker of male fertility. Identification of markers reflecting the presence of germ cells is of particular relevance in trans*persons undergoing gender affirming hormone therapy (GAHT), i...

This new edition provides a much-needed reference book to accommodate emerging and expanding knowledge in fertility preservation, the rapidly growing field of reproductive medicine associated with advances in oncology. Written by a team of world-leading experts in the field and comprehensive in its scope, the book covers the full range of technique...

Purpose Symptoms of hypogonadism are often reported by subjects with normal serum testosterone (T) levels. We aimed to assess the association between clinical symptoms in andrological outpatients and sex steroids levels. Methods This is a retrospective cross-sectional cohort study in an Academic clinic and research unit. International Index of Ere...

Background Sperm DNA integrity has become one of the most discussed and promising biomarkers for the assessment of male fertility. However, an easy‐to‐apply method capable of estimating DNA fragmentation in the live fraction of spermatozoa has remained elusive, preventing this parameter from being fully applied in clinical settings. Objectives To...

Despite the high incidence of male infertility, about 70% of infertile men do not receive a causative diagnosis. To gain insights into the regulatory mechanisms governing human germ cell function in normal and impaired spermatogenesis (cryptozoospermic patients, crypto), we combined single cell RNA sequencing (>30.000 cells), proteome, and histomor...

Background: It is now 11 years since publication of the WHO 2010 guidelines for semen assessment values, and it is critical to determine whether they are still valid and/or whether they should be modified. Objectives: To utilise data published since 2010 and combine these with data used in the 2010 assessment to provide an updated and more compr...

Cryopreservation of immature-testicular-tissue (ITT) prior to gonadotoxic treatment, while experimental, is the only recommended option for fertility preservation in prepubertal boys. The handling and manipulation of ITT before cryopreservation could influence the functionality of cells during fertility restoration, which this study explored by eva...

Specification of germ cell-like cells from induced pluripotent stem cells (iPSCs) has become a clinically relevant tool for research. Research on initial embryonic processes is often limited by the access to fetal tissue, and in humans the molecular events resulting in primordial germ cell (PGC) specification and sex determination remain to be eluc...

Life-long sperm production leads to the assumption that male fecundity remains unchanged throughout life. However, recently it was shown that paternal age has profound consequences for male fertility and offspring health. Paternal age effects are caused by an accumulation of germ cell mutations over time, causing severe congenital diseases. Apart f...

Zusammenfassung Wir stimmen dem in der Leitlinie genannten starken Konsens für Maßnahmen der Reproduktionsmedizin als wichtige Option zur Erfüllung des Kinderwunsches bei trans Personen uneingeschränkt zu. Informationen über diese Maßnahmen müssen Bestandteil von Behandlungen von trans Personen sein. Die geschlechtsangleichende Hormontherapie bei M...

This pilot study was conducted to explore the benefits of using a centrifugation-free device based on the migration–sedimentation (MS) technique over centrifugation-based techniques in selecting competent spermatozoa, as compared with using split human semen samples. Ejaculates from 35 men undergoing semen analysis were split into four parts where...

Signalling pathways and cellular interactions defining initial processes of testis morphogenesis, i.e. cord formation, are poorly understood. In vitro cell-based systems modelling cord formation can be utilised as platforms to interrogate processes of tubulogenesis. We aimed at testing our established cord formation in vitro model using adult human...

PurposeIn males, AMH is secreted by immature Sertoli cells; following exposure to endogenous androgens, Sertoli cells undergo a process of maturation which ultimately inhibits AMH expression to undetectable levels in the serum. However, expression of AMH receptor (AMHR-2) has never been studied in human testes, and high intratubular concentrations...

Successful in vitro spermatogenesis was reported using immature mouse testicular tissues in a fragment culture approach, raising hopes that this method could also be applied for fertility preservation in humans. Although maintaining immature human testicular tissue fragments in culture is feasible for an extended period, it remains unknown whether...

The significant rise in male infertility disorders over the years has led to extensive research efforts to recapitulate the process of male gametogenesis in vitro and to identify essential mechanisms involved in spermatogenesis, notably for clinical applications. A promising technology to bridge this research gap is organ-on-chip (OoC) technology,...

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 subpo...

Male infertility can be caused by genetic defects or anti-cancer therapy. Due to lacking fertility preservation options, especially prepubertal boys with malignant diseases not capable to cryopreserve sperm have poor prospects to father their own children. To date, immature testicular tissues are preserved with the perspective to develop in vitro s...

Cisplatin (CDDP) is one of the most important chemotherapeutic drugs in modern oncology. However, its use is limited by severe toxicities, which impair life quality after cancer. Here, we investigated the role of organic cation transporters (OCT) in mediating toxicities associated with chronic (twice the week for 4 weeks) low-dose (4 mg/kg body wei...

Children of older fathers have higher risk for certain diseases. Nevertheless, how ageing specifically affects male germ cells is so far not completely understood. In a cohort of 197 healthy men (18-84 years), we found that semen and reproductive parameters remained normal over six decades. Along with an age-dependent increase in telomere length in...

It is widely held that the first two blastomeres of mammalian embryos are equally totipotent and that this totipotency belongs in the group of the regulative properties. However, this interpretation neglects an important aspect: evidence only came from successful monozygotic twins which can speak only for those pairs of half-embryos that are able t...

Background: The most common sex chromosomal aneuploidy in males is Klinefelter syndrome, which is characterized by at least one supernumerary X chromosome. While these men have long been considered infertile, focal spermatogenesis can be observed in some patients, and sperm can be surgically retrieved and used for artificial reproductive technique...

Purpose To investigate the effect of the anticoagulation factor annexin A5 on male fertility and to provide perspective on the influence of members of the coagulation cascade on fertility. Methods Patients with normozoospermia and with unexplained severe oligozoospermia were retrospectively selected and their genomic DNA sequenced for the promoter...

Background: Ageing in men is believed to be associated with fertility decline and elevated risk of congenital disorders for the offspring. The previous studies also reported reduced germ and Sertoli cell numbers in older men. However, it is not clear whether ageing in men with normal spermatogenesis affects the testis and germ cell population dyna...

Background From a biological and clinical perspective, it is imperative to establish primate spermatogonial cultures. Due to limited availability of human testicular tissues, the macaque (Macaca fascicularis) was employed as non-human primate model. The aim of this study was to characterize the expression of somatic as well as germ cell markers in...

Fertility preservation in trans women is a crucial but thus far neglected component in the gender confirming treatment in Germany. It is difficult for trans women to access reproductive health care because centers offering treatment, psychological guidance, gender confirming surgery, as well as reproductive health services are scarce in Germany. Le...

Evidence of an age-related increase of β-synuclein (SNCB) in several parts of the visual system including the retina has been reported. SNCB is thought to function as an antagonist of α-synuclein in neurodegenerative diseases, but the exact role of SNCB remains unclear. The presented work studies two different aspects of the onset and role of SNCB...

Grafting of immature monkey testis tissue enables generation of sperm and offspring

Human spermatogonia are target for exploration of adult stem cell characteristics and potential source for the development of therapeutic applications. Almost 50 years ago, Yves Clermont stated with regard to the nature of the true stem cells: 'there is the possibility that other classes of spermatogonia exist beside the three classes (Adark, Apale...

STUDY QUESTION: Can full spermatogenesis be achieved after xenotransplantation of prepubertal primate testis tissue to the mouse, in testis or subcutaneously? SUMMARY ANSWER: Intratesticular xenotransplantation supported the differentiation of immature germ cells from marmoset (Callithrix jacchus) into spermatids and spermatozoa at 4 and 9 months p...

Der Hoden ist in zwei getrennte Kompartimente, die Samenkanälchen und das Interstitium, geteilt. Die Spermienbildung (Spermatogenese) findet in den Samenkanälchen des Hodens statt, dauert ca. 65 Tage und endet mit der Spermiation, bei der vollständig differenzierte, aber noch weitgehend unbewegliche Spermatozoen das Keimepithel verlassen. Das Grund...

Unter dem Einfluss der Gonadotropine werden mit Beginn der Pubertät beim Mädchen vermehrt Östrogene und Gestagene in den Granulosa- und Theca-interna-Zellen des Ovars gebildet. Die ovariellen Hormone sind verantwortlich für die Ausprägung der weiblichen Geschlechtsmerkmale und für den weiblichen Zyklus. In der reproduktiven Phase einer Frau, d. h....

Bei der Frau werden mehrere Millionen unreifer Eizellen als Primordialfollikel im Eierstock bereits in der Embryogenese angelegt. Ihre Zahl nimmt im Laufe des Lebens kontinuierlich ab. Erst ab Beginn der Pubertät, wenn nur noch einige Hunderttausend Primordialfollikel vorhanden sind, beginnt die Follikelreifung. Der in jedem Lebensabschnitt kleiner...

Etwa sieben Tage nach Ovulation und anschließender Verschmelzung von Ei- und Samenzelle findet die Einnistung (Nidation) des nun als Blastozyste ausgebildeten Präimplantationsembryos in die Gebärmutterschleimhaut statt. In der Frühschwangerschaft produziert der Embryo humanes Choriogonadotropin (hCG), das dem Lutenisierenden Hormon (LH) ähnlich ist...

Frauen generieren Eizellen und v. a. weibliche Sexualhormone – die Östrogene und Gestagene; Männer produzieren Spermien und v. a. männliche Sexualhormone, die Androgene. Während im Eierstock der Frau die Östrogen- und Gestagenproduktion mit der Eizellreifung räumlich und funktional kombiniert ist, finden Spermien- und Hormonproduktion beim Mann in...

Heutzutage wird der Kinderwunsch sozio-ökonomisch bedingt zunehmend auf spätere Lebensphasen verschoben. Neben bekannten Einflüssen mütterlichen Alters, mehren sich die Hinweise eines negativen Einflusses auf die Kindsgesundheit durch ein höheres Alter des Vaters. Eine Rolle könnten hierbei bspw. Mutationen oder epigenetische Keimbahnveränderungen,...

Raman Microspectroscopy represents an innovative tool for the assessment of sperm biochemical features otherwise undetectable by routine semen analysis. Previously, it was shown that induced DNA damage can be detected in smeared sperm by this technique. This novel readout may be of value for clinical settings especially if it can be transferred to...

Effect of hydration conditions on the DNA spectrum of a sperm population exposed to ultraviolet light (UV). The results shown in this figure correspond to independent sperm cells that were randomly selected in each condition.(A) Average Raman spectrum (n = 50) of the DNA of non-exposed (control) and UV light exposed (UV) sperm in hydrated condition...

Comparison between the loading values of the PC1 in S5B Fig and a typical Raman spectrum of the sperm DNA. The values were generated from the comparison of the spectra of sperm populations (control/UV exposed) evaluated in aqueous medium. (TIF)

Principal component analysis (PC3 vs PC4) of the experiments carried out in individual sperm (control/UV exposed) evaluated in dried conditions. (TIF)

Principal component analysis (PC3 vs PC4) of the experiments carried out in sperm populations (control/UV exposed) evaluated in dried conditions. (TIF)

PC_Loadings_Fig 3D. Complete set of the PC loadings associated to the Principal Component Analysis concerning the comparison of the spectra of individual sperm (control/UV exposed) evaluated in dried conditions (Fig 3D). (XLSX)

PC_Loadings_S5B Fig. Complete set of the PC loadings associated to the Principal Component Analysis concerning the comparison of the spectra of sperm populations (control/UV exposed) evaluated in aqueous medium (S5B Fig). (XLSX)

PC_Loadings_S5D Fig. Complete set of the PC loadings associated to the Principal Component Analysis concerning the comparison of the spectra of sperm populations (control/UV exposed) evaluated in dried conditions (S5D Fig). (XLSX)

Sperm chromatin structure assay (SCSA) of sperm suspensions. (Black) Non UV-Treated sperm suspension (Control) showing a low DNA Fragmentation Index (DFI); (Blue) UV-Treated sperm suspension showing a high DFI. (TIF)

Principal component analysis (PC3 vs PC4) of the experiments carried out in individual sperm (control/UV exposed) evaluated in aqueous medium. (TIF)

Principal component analysis (PC3 vs PC4) of the experiments carried out in aqueous conditions to test the effect of different media/solutions in the sperm DNA spectrum. (TIF)

Comparison between the loading values of the PC1 in S5D Fig and a typical Raman spectrum of the sperm DNA. The values were generated from the comparison of the spectra of sperm populations (control/UV exposed) evaluated in dried conditions. (TIF)

Sperm immobilization and tracking for Raman analysis. (A) Composite image of 5x5 fields at 10x, where the scratch in the form of “X” which was used as a reference to follow the individual sperm is shown. (B) Zoom-in of the internal box shown in S2A composed of 12x12 images at 100x. The Labspec 6 software allows the assignation of coordinates (x,y),...

Signals of the background of the experiments carried out in aqueous conditions. (TIF)

Principal component analysis (PC3 vs PC4) of the experiments carried out in sperm population (control/UV exposed) evaluated in aqueous medium. (TIF)

Solutions/media composition. (DOCX)