Published 18 October 2021
A wide-ranging ESHRE Campus workshop organised by the SIGs Andrology and Reproductive Genetics looked at current and emerging approaches for the characterisation of various causes of male infertility, including tests in the genetics of idiopathic conditions, chromosomal anomalies – notably Klinefelter syndrome – and new molecular methods for investigation.
The apparent contribution of genetics to male infertility continues to grow. Indeed, the final presentation of a three half-day Campus meeting in September, from Antoni Riera-Escamilla, described the identification of five new candidate genes to add to seven others now implicated in the aetiology of non-obstructive azoospermia. Riera-Escamilla proposed that whole genome and exome sequencing were now a valid approach to identifying genetic factors in the cause of male infertility, particularly when idiopathic.
From the 15 presentations of this virtual Campus it was evident that genes are implicated in both the quantitative and qualitative features of male reproductive impairment. Genetic causes affecting sperm numbers are commonly chromosomal in origin, and include microdeletions in the AZF subregions of the Y chromosome, Klinefelter syndrome, and chromosome structural abnormalities. Genetic factors also play a role in the aetiology of hypothalamic-pituitary axis disturbances and ductal dysfunction, such as congenital hypogonadotrophic hypogonadism (eg, Kallmann’s syndrome) and congenital absence of the vas deferens.
Of these many conditions, Ellen Goossens from the Biology of the Testis research group at the VUB Brussels described Klinefelter syndrome as the most common sex chromosome anomaly in men and the most frequent genetic cause of infertility, implicated in around 15% of all azoospermia cases. Presentations on Klinefelter syndrome occupied around one-third of this Campus meeting, and all speakers acknowledged a lack of consistency in the syndrome’s clinical presentation because of the wide variation in phenotype – and only the moderate treatment potential from TESE, and even less from prepubertal testicular tissue banking.
What does seem clear is the syndrome’s classic genotype (47,XXY) and the high rate of azoospermia (~90%) in diagnosed cases. Alongside, said urologist Robert Oates from Boston Medical Center, there’s a range of typical and atypical symptoms which may be indicative of the syndrome. The classic male profile is characterised as tall and thin, azoospermic with small testes, decreased muscle mass, gynecomastia and learning disabilities – while an atypical profile might be short and obese, very virilised, possibly fertile and with regular muscular development. Moreover, infertility might not be the only health concern for patients with Klinefelter syndrome, with greater cardiovascular, metabolic and cerebrovascular risks all evident in the adult.
According to Lise Aksglæde from Rigshospitalet in Copenhagen, these risks and other developmental problems seem greater when the additional X chromosome is paternally inherited. This, she proposed, may explain the high rate of X-linked copy number variations seen in Klinefelter, as well as evidence of impairment in the function of the androgen receptor gene. These proposals too, she explained, were based on candidate genes identified by transcriptome and methylome analysis of autosomes and sex chromosomes. Nevertheless, she said, more studies are needed to shed light on the mechanisms underlying the high phenotypic variability of Klinefelter syndrome.
Experiments in the Brussels lab of Ellen Goossens suggest that germ cell loss occurs at a very early age, suggesting that testicular tissue banking may not be a viable fertility preservation option for young men even in their adolescent years. However, testicular sperm extraction for ICSI – apparently successful in around 35-50% of adult Klinefelter patients, said Goossens – was similarly successful in boys at the onset of puberty, despite the fibrosis of the seminiferous tubules and germ cell loss notable around the time of puberty’.
Of course, any treatment at these young ages comes with considerable personal and ethical challenges. Nathalie Rives from the University of Rouen reported from her data that fertility preservation is ‘not accessible’ for most Klinefelter boys and adolescents, with parental discussion (especially about potential poor treatment outcomes) an ‘absolute necessity’. Her own data indicated that after TESE failure the majority of adult cases (81%) turned to sperm donation or adoption. She reiterated the recent recommendations of the European Academy of Andrology guidelines that testicular tissue cryopreservation or spermatogonial stem cell retrieval is ‘not recommended’ in pre-pubertal and pubertal boys with Klinefelter syndrome.(1) In adults, the same guidelines recommend semen analysis and sperm cryopreservation, and in those with confirmed azoospermia TESE for ICSI.
Another classic feature of Klinefelter along with azoospermia is hypergonadotropic hypogonadism, which, as an isolated and rare congenital condition, may be helped (for the induction of spermatogenesis) by testosterone replacement therapy. Such treatment in such cases is usually lifelong, said Csilla Krausz from the University of Florence, but in around 10% of cases the condition may be reversible – and thus represents a treatable form of azoospermia. Testosterone supplementation, however, said Nathalie Rives, was not recommended for boys in the recent European Academy of Andrology guidelines for Klinefelter syndrome.
Interestingly for this Campus meeting, congenital hypergonadotropic hypogonadism was until recently considered a monogenic disease, but, said Krausz, there are now ‘35 genes with strong/definitive clinical evidence for cHH’. Screening for a genetic cause, she added, would be important for siblings and for the health of future offspring.
It was evident at this meeting that, while emerging sequencing technologies might explain cause and improve diagnosis, there was little evidence yet of their role in treatments – except perhaps in the application of testing for DNA fragmentation in sperm cells. So far, however, and from a wealth of data presented, Nicolás Garrido from the IVI Foundation in Valencia and Coordinator of ESHRE’s SIG Andrology, concluded that existing study results ‘do not support a consistent strong relationship between abnormal DNA integrity and reproductive outcomes’. He therefore was unable to recommend ‘routine use’, so echoing some of the recent (and not so recent) reviews of DNA fragmentation tests.
One of the main reasons for Garrido’s caution was an inconsistency in studies between populations, samples, outcomes and techniques. Notably, he explained, ‘you measure all sperm, but use one sperm’. Moreover, even in cases of high DNA fragmentation index, there is no downstream influence on treatment and the tests mainly serve to identify the cause and advise on lifestyle changes. ‘Are the tests diagnostic or simply risk assessment tools?’ he asked.
Garrido added that sperm DNA fragmentation analysis is one of several proposed techniques to improve sperm selection for ICSI, but all of them, he said – intracytoplasmic morphologic sperm injection (IMSI, in which sperm is viewed under very high magnification), PICSI (physiological ICSI in which selected sperm bind to droplets of hyaluronic acid), electrophoresis and birefringence –have limited clinical application due to ‘insufficient data’.
1. Zitzmann M, Aksglaede L, Corona G,et al. European academy of andrology guidelines on Klinefelter Syndrome Endorsing Organization: European Society of Endocrinology. Andrology 2021; 9: 145-167.
CAMPUS: MALE INFERTILITY
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