Chromosomal abnormalities in 1354 Japanese patients with azoospermia due to spermatogenic dysfunction

The impact of mosaic loss of the Y chromosome (mLOY) in men of advanced age

The Y chromosome has long been considered to be a "genetic wasteland" harboring only few genes essentially involved in male sex development and spermatogenesis. However, the discovery of mosaic loss of the Y chromosome (mLOY) in older men has led to revisiting of the potential impact of the Y chromosome on health and the pathophysiological processes of multiple diseases such as cancer, Alzheimer's disease and cardiovascular disease. Hence, developing more sensitive techniques for the detection of mLOY has become an emergent concern. In this article, we present a comprehensive review of the literature regarding mLOY. Additionally, we discuss the emerging discoveries concerning mLOY as well as the underlying mechanisms promoting disease in men of advanced age.

Mosaic loss of the Y chromosome and men's health

Background

Although Y chromosomal genes are involved in male sex development, spermatogenesis, and height growth, these genes play no role in the survival or mitosis of somatic cells. Therefore, somatic cells lacking the Y chromosome can stay and proliferate in the body.

Methods

Several molecular technologies, including next-generation sequencing and multiplex PCR-based assays, are used to detect mosaic loss of the Y chromosome (mLOY) in the blood of men.

Main findings

Accumulating evidence suggests that mLOY represents the most common acquired chromosomal alteration in humans, affecting >40% of men over 70 years of age. Advanced age, tobacco smoking, and some SNPs in cell cycle genes are known to increase the frequency of mLOY. The developmental process of mLOY in elderly men remains to be clarified, but it possibly reflects recurrent mitotic elimination of Y chromosomes or clonal expansion of 45,X cell lineages. In rare cases, mLOY also occurs in young men and fetuses. MLOY has been associated with early death, cancers, and other disorders in elderly men, infertility in reproductive-aged men, and developmental defects in children.

Conclusion

Y chromosomes in men can be lost at every life stage and Y chromosomal loss is associated with various health problems.

Copy-number analysis of Y-linked loci in young men with non-obstructive azoospermia: Implications for the rarity of early onset mosaic loss of chromosome Y

PURPOSE

Mosaic loss of chromosome Y (mLOY) is a common feature in elderly men. If mLOY can also occur in young men, it may lead to spermatogenic failure due to loss of spermatogenic genes. Indeed, previous studies detected the 45,X/46,XY karyotype in a few young men with spermatogenic failure. The present study aimed to clarify the frequency of cryptic mLOY in reproductive-aged men with spermatogenic failure.

METHODS

We studied 198 men at ages 24-55 years who presented with etiology-unknown non-obstructive azoospermia. Prior this study, these patients underwent G-banding analysis for 20 leukocytes and were found to have 46,XY karyotype. We analyzed copy numbers of chromosome Y in blood cells by using semi-quantitative multiplex PCR for AMELY/AMELX, array-based comparative genomic hybridization (CGH) for the AMELY locus, and droplet digital PCR for SRY, USP9Y, and UTY.

RESULTS

Multiplex PCR showed borderline low AMELY/AMELX ratios in three patients. However, for the three patients, CGH excluded deletion of the AMELY locus, and droplet digital PCR suggested preserved copy numbers of all tested loci.

CONCLUSION

This study highlights the rarity of leukocyte mLOY in reproductive-aged men with spermatogenic failure. In addition, our data imply that standard karyotyping is sufficient to screen early onset mLOY.

Losing maleness: Somatic Y chromosome loss at every stage of a man's life

Mosaic loss of Y chromosome (LOY) is assumed to be among the most common acquired genetic variations in elderly people. Recent studies have linked aging-related mosaic LOY to the risk of Alzheimer's disease, cancer, and early death. Here, we propose that mosaic LOY can present in men at any age. Mosaic LOY appears to be associated with disorders of sex development and Turner syndrome at birth, short stature from childhood, and spermatogenic failure at reproductive age, in addition to shortened survival after 60 years of age.

Chromosomal abnormalities in 1663 infertile men with azoospermia: the clinical consequences

STUDY QUESTION

What is the prevalence of chromosomal abnormalities in azoospermic men and what are the clinical consequences in terms of increased risk for absent spermatogenesis, miscarriages and offspring with congenital malformations?

SUMMARY ANSWER

The prevalence of chromosomal abnormalities in azoospermia was 14.4%, and the number of azoospermic men needed to be screened (NNS) to identify one man with a chromosomal abnormality with increased risk for absence of spermatogenesis was 72, to prevent one miscarriage 370-739 and to prevent one child with congenital malformations 4751-23 757.

WHAT IS KNOWN ALREADY

Infertility guidelines worldwide advise screening of non-iatrogenic azoospermic men for chromosomal abnormalities, but only few data are available on the clinical consequences of this screening strategy.

STUDY DESIGN, SIZE, DURATION

This retrospective multicentre cross-sectional study of non-iatrogenic azoospermic men was performed at the University Hospital Brussels, Belgium, and the University Medical Centre Groningen, The Netherlands, between January 2000 and July 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Analysis of clinical registries retrospectively identified 1663 non-iatrogenic azoospermic men with available results of karyotyping and FSH serum levels. Iatrogenic azoospermia was an exclusion criterion, defined as azoospermia after spermatotoxic medical treatment, exogenous androgen suppletion or vasectomy and/or vasovasostomy. Also, men with a clinical diagnosis of anejaculation or hypogonadotropic hypo-androgenism and/or FSH values <1.0 U/l were excluded. Chromosomal abnormalities were categorized according to their (theoretical) impact on clinical consequences for the patient (i.e. an increased risk for absence of spermatogenesis) and adverse pregnancy outcomes (i.e. miscarriage or offspring with congenital malformations), in both normogonadotropic (FSH < 10 U/l) and hypergonadotropic (FSH ≥ 10 U/l) azoospermia. We estimated the NNS for chromosomal abnormalities to identify one man with absence of spermatogenesis and to prevent one miscarriage or one child with congenital malformations, and calculated the surgical sperm retrieval rates per chromosomal abnormality.

MAIN RESULTS AND THE ROLE OF CHANCE

The overall prevalence of chromosomal abnormalities in azoospermia was 14.4% (95% CI 12.7-16.1%), its prevalence being higher in hypergonadotropic azoospermia (20.2%, 95% CI 17.8-22.7%) compared to normogonadotropic azoospermia (4.9%, 95% CI 3.2-6.6%, P < 0.001). Klinefelter syndrome accounted for 83% (95% CI 77-87%) of abnormalities in hypergonadotropic azoospermia. The NNS to identify one man with increased risk for absence of spermatogenesis was 72, to prevent one miscarriage 370-739, and to prevent one child with congenital malformations 4751-23 757. There was no clinically significant difference in NNS between men with normogonadotropic and hypergonadotropic azoospermia. The surgical sperm retrieval rate was significantly higher in azoospermic men with a normal karyotype (60%, 95% CI 57.7-63.1%) compared to men with a chromosomal abnormality (32%, 95% CI 25.9-39.0%, P < 0.001). The sperm retrieval rate in Klinefelter syndrome was 28% (95% CI 20.7-35.0%).

LIMITATIONS, REASONS FOR CAUTION

The absolute number of chromosomal abnormalities associated with clinical consequences and adverse pregnancy outcomes in our study was limited, thereby increasing the role of chance. Further, as there are currently no large series on outcomes of pregnancies in men with chromosomal abnormalities, our conclusions are partly based on assumptions derived from the literature.

WIDER IMPLICATIONS OF THE FINDINGS

The NNS found can be used in future cost-effectiveness studies and the evaluation of current guidelines on karyotyping in non-iatrogenic azoospermia.

STUDY FUNDING/COMPETING INTEREST(S)

None to declare.

Testicular sperm extraction for patients with spinal cord injury-related anejaculation: A single-center experience

OBJECTIVES

To present a single-center experience with testicular sperm extraction and intracytoplasmic sperm injection for fathering biological children in patients with ejaculatory dysfunction as a result of spinal cord injury.

METHODS

Testicular sperm extraction was carried out in 52 male patients with ejaculatory dysfunction as a result of spinal cord injury. We investigated sperm retrieval rates and pregnancy rates from medical records. Data on age, testicular volume, hormonal status (luteinizing hormone, follicle stimulating hormone and testosterone), and time since spinal cord injury were obtained and analyzed to detect potential associations with the presence of spermatogenesis.

RESULTS

Testicular sperm retrieval was achieved in 42 of 52 patients (80.7%). Intracytoplasmic sperm injection was carried out for 37 patients, and pregnancy was achieved in 32 (86.5%). The take-home baby rate was 70.2%. In the group with successful sperm extraction, testicular volume was significantly greater, time from spinal cord injury to extraction was significantly shorter, and serum luteinizing hormone and follicle-stimulating hormone levels were significantly lower. Serum follicle-stimulating hormone levels had the strongest association with feasibility of sperm retrieval by testicular sperm extraction. Furthermore, the sperm retrieval rates of patients injured within the preceding 12 years were significantly better than those injured longer before treatment (P = 0.045).

CONCLUSIONS

Testicular sperm extraction and intracytoplasmic sperm injection seem to provide favorable results for patients with ejaculatory dysfunction as a result of spinal cord injury. However, early testicular sperm extraction is recommended, because sperm retrieval becomes more difficult with time from spinal cord injury.

Microdissection testicular sperm extraction in Japanese patients with persistent azoospermia after chemotherapy

BACKGROUND

Combinations of surgery, radiation therapy, and chemotherapy can achieve high remission rates in patients with cancer, but these treatments can have damaging effects on spermatogenesis. In particular, cytotoxic chemotherapy may lead to irreversible spermatogenic dysfunction. Microdissection testicular sperm extraction (micro-TESE) is the only method that can address infertility in cancer survivors with persistent postchemotherapy azoospermia.

METHODS

We included 66 Japanese patients with postchemotherapy azoospermia who underwent micro-TESE for sperm retrieval in this analysis. Age, oncology data, hormone profiles, and outcomes of micro-TESE and subsequent intracytoplasmic sperm injections (ICSIs) were reviewed.

RESULTS

The common disease in our patients was testicular cancer (21 patients), followed by acute lymphoblastic leukemia and Hodgkin's lymphoma (nine patients). In this cohort of 66 patients, sperm was successfully retrieved in 31 patients (47 %), and clinical pregnancy occurred in 23 cases (35 %). The live birth rate was 27 %. No significant differences in sperm retrieval, clinical pregnancy, and live birth rates were seen between testicular cancer, Hodgkin's lymphoma, non-Hodgkin's lymphoma, acute lymphoblastic leukemia, acute myeloid leukemia, or sarcoma cases. Multiple logistic regression analysis showed that the chance of retrieving sperm during micro-TESE could not be predicted by any variable.

CONCLUSIONS

Cryopreservation of sperm should be offered before any gonadotoxic chemotherapy takes place. However, micro-TESE and subsequent ICSI could be effective treatment options for patients with persistent postchemotherapy azoospermia whose sperm were not frozen before therapy. Our results suggest that micro-TESE-ICSI could benefit 27 % of such Japanese patients.