Kristian Almstrup

Rigshospitalet | rigshospitalet · Department of Growth and Reproduction

Testicular germ cell tumours (TGCTs) are the most frequent cancer type in young men and originate from the common precursor germ cell neoplasia in situ (GCNIS). For decades, clinical management of patients with TGCT has relied on classic serum tumour markers: α-fetoprotein, human chorionic gonadotropin subunit-β and lactate dehydrogenase. In the pa...

Background: P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) are short (21 to 35 nucleotides in length) and noncoding and are found almost exclusively in germ cells, where they regulate aberrant expression of transposable elements and postmeiotic gene expression. Critical to the processing of piRNAs is the protein poly(A)-specific R...

A severe decline in child births has occurred over the past half century, which will lead to considerable population declines, particularly in industrialized regions. A crucial question is whether this decline can be explained by economic and behavioural factors alone, as suggested by demographic reports, or to what degree biological factors are al...

The testis produces gametes through spermatogenesis and evolves rapidly at both the morphological and molecular level in mammals 1–6 , probably owing to the evolutionary pressure on males to be reproductively successful ⁷ . However, the molecular evolution of individual spermatogenic cell types across mammals remains largely uncharacterized. Here w...

Puberty marks numerous physiological processes which are initiated by central activation of the hypothalamic–pituitary–gonadal axis, followed by development of secondary sexual characteristics. To a large extent, pubertal timing is heritable, but current knowledge of genetic polymorphisms only explains few months in the large inter-individual varia...

A major part of the human Y chromosome consists of palindromes with multiple copies of genes primarily expressed in testis, many of which have been claimed to affect male fertility. Here we examine copy number variation in these palindromes based on whole genome sequence data from 11,527 Icelandic men. Using a subset of 7947 men grouped into 1449 p...

Study question Is there an association between genetic polymorphisms in LIN28B with LIN28B expression and semen quality in spermatozoa from oligozoospermic men? Summary answer LIN28B is downregulated in spermatozoa of oligozoospermic men and explains 39% of sperm count variability. One SNP (rs314280) was associated with low LIN28B mRNA expression....

Fast phase-contrast imaging offered by modern synchrotron facilities opens the possibility of imaging dynamic processes of biological material such as cells. Cells are mainly composed of carbon and hydrogen, which have low X-ray attenuation, making cell studies with X-ray tomography challenging. At specific low energies, cells provide contrast, but...

Background Puberty marks the transition from childhood to adulthood and is initiated by activation of a pulsatile GnRH secretion from the hypothalamus. MKRN3 functions as a pre-pubertal break on the GnRH pulse generator and hypothalamic expression and circulating levels of MKRN3 decrease peri-pubertally. In rodents, microRNA miR-30b seems to direct...

The most prominent RNA modification – N6-methyladenosine (m6A) – affects gene regulation and cancer progression. The extent and effect of m6A on long non-coding RNAs (lncRNAs) is, however, still not clear. The most established method for m6A detection is methylated RNA immunoprecipitation and sequencing (MeRIP-seq). However, Oxford Nanopore Technol...

Non-obstructive azoospermia (NOA) is the most severe form of male infertility and typically incurable. Defining the genetic basis of NOA has proven challenging, and the most advanced classification of NOA subforms is not based on genetics, but simple description of testis histology. In this study, we exome-sequenced over 1000 clinically diagnosed N...

Background: It has been estimated that microorganisms are involved in the pathogenesis of approximately 20% of all cancers. Testicular germ cell tumours (TGCTs) are the most common type of malignancy in young men and arise from the precursor cell, germ cell neoplasia in situ (GCNIS). The microbiome of seminal plasma and testicular tissue has not b...

Infertility affects around 7% of the male population and can be due to severe spermatogenic failure (SPGF), resulting in no or very few sperm in the ejaculate. We initially identified a homozygous frameshift variant in FKBP6 in a man with extreme oligozoospermia. Subsequently, we screened a total of 2,699 men with SPGF and detected rare bi-allelic...

Objective Self-reported psychological stress has been associated with decreased semen quality. Cortisol levels in scalp hair (hair cortisol concentration, HCC) has emerged as a potential objective marker of psychological stress. Thus, we investigated if HCC was associated with markers of testicular function. Furthermore, we examined whether three c...

Non-obstructive azoospermia (NOA) is the most severe form of male infertility and typically incurable with current medicine. Due to the biological complexity of sperm production, defining the genetic basis of NOA has proven challenging, and to date, the most advanced classification of NOA subforms is based on simple description of testis histology....

Small noncoding RNAs (sncRNAs) are pieces of RNA with a length below 200 bp and represent a diverse group of RNAs having many different biological functions. The best described subtype is the microRNAs which primarily function in posttranscriptional gene regulation and appear essential for most physiological processes. Of particular interest for th...

Background: Testicular germ cell tumors (TGCTs), histologically classified as seminomas and non-seminomas, are believed to arise from primordial gonocytes, with the maturation process blocked when are subjected to DNA methylation reprogramming. Single-nucleotide polymorphisms (SNPs) in DNA methylation machinery and folate-dependent one-carbon meta...

Background: Couples increasingly experience infertility and seek help from assisted reproductive techniques to become pregnant. However, 5%-15% of the couples that are selected for in vitro fertilisation (IVF) experience a total fertilisation failure (TFF), where no zygotes develop despite oocytes and semen parameters appear to be normal. We hypot...

STUDY QUESTION What is the load, distribution and added clinical value of secondary findings (SFs) identified in exome sequencing (ES) of patients with non-obstructive azoospermia (NOA)? SUMMARY ANSWER One in 28 NOA cases carried an identifiable, medically actionable SF. WHAT IS KNOWN ALREADY In addition to molecular diagnostics, ES allows assess...

Objective: To evaluate if optimised and standardised diagnostic procedures would improve detection of germ cell neoplasia in situ (GCNIS) in the contralateral testis of patients with testicular germ cell tumour (TGCT), and decrease the rate of metachronous tumours, which in the nationwide Danish study was estimated as 1.9%. Patients and methods:...

De novo mutations are known to play a prominent role in sporadic disorders with reduced fitness. We hypothesize that de novo mutations play an important role in severe male infertility and explain a portion of the genetic causes of this understudied disorder. To test this hypothesis, we utilize trio-based exome sequencing in a cohort of 185 inferti...

The testis is a key male reproductive organ that produces gametes through the process of spermatogenesis. Testis morphologies and spermatogenesis evolve rapidly in mammals, presumably due to the evolutionary pressure on males to be reproductively successful. The rapid evolution of the testis was shown to be reflected at the molecular level based on...

STUDY QUESTION Do selective serotonin reuptake inhibitor (SSRI) antidepressants affect the function of human sperm? SUMMARY ANSWER The SSRI antidepressant Sertraline (e.g. Zoloft) inhibits the sperm-specific Ca2+ channel CatSper and affects human sperm function in vitro. WHAT IS KNOWN ALREADY In human sperm, CatSper translates changes of the chem...

Context: Insulin-like growth factor-I (IGF-I) is important for postnatal growth and may be of diagnostic value in infants suspected of pituitary disease. However, little is known about the impact of IGF-I and its determinants on infant growth. Importantly, detailed reference ranges for IGF-I and IGF binding protein-3 (IGFBP-3) concentrations durin...

Purpose Principal component analysis (PCA) is a mathematical model which simplifies data into new, combined variables. Optimal treatment of pediatric congenital adrenal hyperplasia (CAH) remains a challenge and requires evaluation of all biochemical and clinical markers. The aim of this study was to introduce PCA methodology as a tool to optimize m...

Study question Do Selective Serotonin Reuptake Inhibitor (SSRI) antidepressants affect the function of human sperm? Summary answer The SSRI-antidepressant Sertraline (e.g. Zoloft) inhibits the sperm-specific Ca2+ channel CatSper and affects human sperm function in vitro. What is known already In human sperm, CatSper translates changes of the chem...

Testicular germ cell tumors (TGCT) are the most common tumor in young white men and have a high heritability. In this study, the international Testicular Cancer Consortium assemble 10,156 and 179,683 men with and without TGCT, respectively, for a genome-wide association study. This meta-analysis identifies 22 TGCT susceptibility loci, bringing the...

Zebrafish (Danio rerio) spermatogenesis is well studied, and although some differences exist, it is an important model for the study of human spermatogenesis. TRPC6 gene is involved in protein binding and neurodevelopment, and recent exome sequencing of an infertile cohort by our group revealed a likely damaging homozygous variant in a man with idi...

Background Infertility affects 15–25% of all couples during their reproductive life span. It is a significant societal and public health problem with potential psychological, social, and economic consequences. Furthermore, infertility has been linked to adverse long-term health outcomes. Despite the advanced diagnostic and therapeutic techniques av...

Circulating miRNAs secreted by testicular germ cell tumors (TGCT) show great potential as novel non-invasive biomarkers for diagnosis of TGCT. Seminal plasma (SP) represents a biofluid closer to the primary site. Here, we investigate whether small RNAs in SP can be used to diagnose men with TGCTs or the precursor lesions, germ cell neoplasia in sit...

Background: Studies evaluating the association between peripheral blood leukocyte telomere length and testicular germ cell tumor (TGCT) risk have produced conflicting results. Methods: Using available genotype data from the Testicular Cancer Consortium (TECAC), polygenic risk score (PRS) and mendelian randomization (MR) analyses of genetic varia...

Azoospermia is a condition defined as the absence of spermatozoa in the ejaculate, but the testicular phenotype of men with azoospermia may be very variable, ranging from full spermatogenesis, through arrested maturation of germ cells at different stages, to completely degenerated tissue with ghost tubules. Hence, information regarding the cell-typ...

Background Spermatogenesis depends on stimulation by follicle‐stimulating hormone (FSH) which binds to FSH receptors (FSHR) on testicular Sertoli cells. Three FSH‐related single‐nucleotide polymorphisms (SNPs), FSHB ‐211G>T (rs10835638), FSHR ‐29G>A (rs1394205) and FSHR 2039A>G (rs6166) affect FSH action, and have been suggested to affect testicula...

Background: Pubertal timing is closely linked to growth regulated by the growth hormone/insulin-like factor (GH/IGF) axis that includes IGF-regulating factors such as pregnancy-associated plasma protein-A/A2 (PAPP-A/PAPP-A2) and stanniocalcin 2 (STC2). We investigated the association between height, IGF-I concentration, and PAPPA, PAPPA2, and STC2...

Puberty marks a transition period, which leads to the attainment of adult sexual maturity. Timing of puberty is a strongly heritable trait. However, large genetic association studies can only explain a fraction of the observed variability and striking secular trends suggest that lifestyle and/or environmental factors are important. Using liquid-chr...

The acrosome of the spermatozoa is required for fertilization and in the raw ejaculate the percentage of viable acrosome-intact spermatozoa, the acrosomal status, is higher among men with good semen quality. Here we investigated if the acrosomal status of the processed semen preparations used at a fertility clinic can also be informative and whethe...

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 h...

Context Transient thelarche (TT), i.e., the appearance, regression and subsequent reappearance of breast buds, is a frequent phenomenon, but little is known about pubertal transition in these girls. Objective To describe pubertal progression, growth, genotypes, reproductive hormones, and growth factors in girls with TT compared to those who do not...

Activin A promotes fetal mouse testis development, including by driving Sertoli cell proliferation and cord morphogenesis, but its mechanisms of action are undefined. We performed RNA-seq on testicular somatic cells from fetal activin A-deficient mice (Inhba KO) and wildtype littermates at embryonic ages E13.5 and E15.5. Analysis of whole gonads pr...

New microRNA-based serum biomarkers (miRNA-367-3p, -371a-3p, -372-3p, and -373-3p) have shown great potential for the detection of testicular germ cell tumors (TGCTs), but few studies have investigated the clinical utility and performance of these tests in treatment monitoring. In this study, circulating miRNA levels were measured, together with se...

Context Voice break (VB), as a landmark of advanced male puberty in genome-wide association studies (GWAS), has revealed that pubertal timing is a highly polygenic trait. Although, VB is easily recorded in large cohorts, it holds quite low precision as a marker of puberty. In contrast, gonadarche and pubarche are early and clinically well-defined m...

Male subfertility is often associated with sub-optimal health status and traditional semen and hormone analysis reveals only limited information about the reduced fertility potential. Circulating small non-coding RNAs (sncRNAs) are paracrine and endocrine messengers, with prognostic potential. Here, we utilised small RNA-Seq to identify novel cell-...

Ca2+-signaling is essential to normal sperm cell function and male fertility. Similarly, the acrosome reaction is vital for the ability of a human sperm cell to penetrate the zona pellucida and fertilize the egg. It is therefore of great interest to test compounds (e.g., environmental chemicals or drug candidates) for their effect on Ca2+-signaling...

We question whether the expression of GalNAc-T3, the only known O-GalNAc-transferase present in germ cells, is correlated with qualitative and functional parameters of spermatozoa. We investigated the expression of GalNAc-T3 in ejaculated spermatozoa with immunocytochemistry in swim-up purified and acrosome-reacted spermatozoa from quality-control...

Study question: Are infertile men with reduced semen quality at risk of a further decrease in testicular function? Summary answer: Infertile men with severely reduced semen quality risk further deterioration of semen quality 15 years after treatment for infertility, and a lower baseline sperm concentration was associated with a more pronounced i...

The most common human sex chromosomal disorder is Klinefelter syndrome (KS; 47,XXY). Adult patients with KS display a diverse phenotype but are nearly always infertile, due to testicular degeneration at puberty. To identify mechanisms causing the selective destruction of the seminiferous epithelium, we performed RNA-sequencing of 24 fixed paraffin-...

SOX8 is an HMG-box transcription factor closely related to SRY and SOX9. Deletion of the gene encoding Sox8 in mice causes reproductive dysfunction but the role of SOX8 in humans is unknown. Here, we show that SOX8 is expressed in the somatic cells of the early developing gonad in the human and influences human sex determination. We identified two...

SOX8 is an HMG-box transcription factor closely related to SRY and SOX9. Deletion of the gene encoding Sox8 in mice causes reproductive dysfunction but the role of SOX8 in humans is unknown. Here, we show that SOX8 is expressed in the somatic cells of the early developing gonad in the human and influences human sex-determination. We identified two...

Objective: Fetal Anti-Müllerian hormone (AMH) is responsible for normal male sexual differentiation and circulating AMH is used as a marker of testicular tissue in newborns with Disorders of Sex Development. Little is known about the mechanism of action in postnatal life. A recent genome wide association study (GWAS) reported genetic variation of...

Study question: Is it possible, in an unbiased and clinical relevant way, to determine the number of viable acrosome-intact human spermatozoa in ejaculates and to use this as a measure of fertility chances? Summary answer: Image cytometry enables easy and unbiased quantification of viable acrosome-intact spermatozoa and it correlates with semen...

JMJD1C, a member of the Jumonji-domain containing histone demethylases protein family, has been associated with levels of sex-hormone binding globulin (SHBG) and testosterone in men, and knock-out rodent models show age-dependent infertility. The objective of this study was to investigate whether single nucleotide polymorphisms (SNPs) nearby JMJD1C...

Testicular germ cell cancer (TGCC) is derived from germ cell neoplasia in situ (GCNIS), which arises due to niche disturbances affecting the Sertoli cells. It is believed that exogenous endocrine factors have a crucial role in governing neoplastic transformation but on a strong hereditary background. Follicle-stimulating hormone (FSH) is the major...