Does intracytoplasmic sperm injection lead to a rise in the frequency of microdeletions in the AZFc region of the Y chromosome in future generations?

The Y chromosome in the era of intracytoplasmic sperm injection: a personal review

The Y chromosome contains 60 multicopy genes composed of nine different gene families concentrated in regions of multiple repeat sequences called amplicons arranged in mirror images called palindromes. This pattern is susceptible to deletions caused by homologous recombination with itself, and can explain the presence of small numbers of sperm in otherwise azoospermic men.

ICSI: Hype or hazard?

Ever since its introduction in clinical practice more than 10 years ago, intracytoplasmic sperm injection (ICSI) has been the subject of ongoing debate regarding its indications and safety. ICSI is hyped because of its potential to give couples with severe male factor infertility a chance to conceive, and because of its apparently low fertilization failure rate compared with 'classic' in vitro fertilization (IVF). Concerns about ICSI are related to technical, biological and genetic hazards. ICSI has been branded 'the ultimate rape of the oocyte', as the oocyte membrane is mechanically pierced, appearing to bypass all biological and genetic selection. ICSI has been linked in a number of reports to an increased incidence of chromosomal anomalies, congenital abnormalities and perinatal hazards in offspring conceived with this technique. The etiology of the increased risk of chromosomal anomalies in ICSI offspring, especially sex-chromosome anomalies, is thought to be partly multifactorial, partly andrological, related to paternal karyotypic abnormalities and/or abnormal sperm. The majority of studies on ICSI and IVF offspring have, setting aside inconsistencies in methodology and classification, not shown significant differences between the two techniques in terms of congenital abnormalities, however, compared to naturally conceived offspring there does show an increased risk. This risk is attributed mainly to parental factors such as maternal age, poor sperm quality and infertility as an independent risk factor. Perinatal hazards may include low birth weight and perinatal mortality. Behavioural and psychological development is carefully monitored in ICSI and IVF children with no significant differences to the development of naturally conceived children, but many factors are involved including demographics. Follow-up studies are essential to the technique of ICSI. It is our duty to inform patients of the concerns and benefits to this treatment, based on the latest data available.

Screening for chromosomal abnormalities in 2650 infertile couples undergoing ICSI

Chromosomal abnormalities are the major contributor to the genetic risks of infertility treatment associated with intracytoplasmic sperm injection (ICSI). The study objective was to assess prospectively the frequency of chromosomal aberrations in couples undergoing ICSI. A total of 2650 infertile couples (5300 patients) underwent chromosome analysis before undergoing ICSI in the Egyptian IVF-ET Centre. Heparinized blood samples were cultured, harvested and banded according to standard methods. Overall, 96.94% of the patients studied (5138/5300) had a normal karyotype, while the remaining 162 patients (3.06%) had an abnormal karyotype. Male patients constituted the majority of abnormalities; 138 males (85.19%) and 24 females (14.81%). These chromosomal aberrations included 117 cases (2.2%) of sex chromosome abnormalities; 113 males and four females. Forty-five patients (0.85%) had autosomal aberrations; 25 of them were males and 20 were females. The current data show that chromosomal abnormalities affect 3.06% of infertile patients, and occur in both sexes, but more predominantly in males undergoing ICSI for male factor infertility. It is recommended that chromosomal analysis be performed before undergoing ICSI, to identify patients who can be offered preimplantation genetic diagnosis.

ICSI: a technique too far?

Even now 10 years after its introduction, there is still debate on the possible adverse effects of intracytoplasmic sperm injection (ICSI). ICSI has raised a lot of concerns because of the mechanical perforation of the oocyte, the possible transmission of foreign genetic material, the use of immature or senescent germ cells and the association between genetic disorders and some forms of male infertility. To date, the data available indicate that ICSI is a safe procedure provided this treatment is performed in clinics with the highest standards of expertise and with a continuous follow-up programme for the offspring. It is becoming increasingly apparent that it is not ICSI itself, but the background risks of the ICSI patients that represent the major risk factor with regard to congenital malformations. More sex-chromosome abnormalities have been reported in ICSI offspring. Again, the risk of aneuploidy in ICSI progeny reflects the higher aneuploidy rate in the sperm of ICSI fathers. Whether ICSI will eventually perpetuate male infertility is far from clear, because at present the inheritance pattern of idiopathic male infertility is unknown. All ICSI candidates should nevertheless be thoroughly screened and counselled. As long as follow-up studies have a limited power to detect small increases in malformations and as long as no information is available on long-term and next-generation cohorts, ICSI must be used with caution and only when no alternative evidence-based therapy is available. All ICSI candidates should be rigorously screened and thoroughly informed of the limitations of current screening methods and our limited knowledge of the genetic background to male infertility. They should be told that there might be a slight increase in congenital malformation rate after ICSI, but that this increase is probably the result of their own 'background risk'. Well-informed patients are in the best position to judge whether the concerns outweigh the benefits of ICSI.

Clinical characterization of 42 oligospermic or azoospermic men with microdeletion of the AZFc region of the Y chromosome, and of 18 children conceived via ICSI

BACKGROUND

Severe spermatogenic compromise may be the result of a Y-chromosomal deletion of the AZFc region. Prior studies are limited to relatively small numbers of AZFc-deleted men. In this study, we have fully characterized 42 infertile men with a Y chromosome microdeletion strictly confined to the AZFc region, and we report on 18 children conceived through the use of ICSI.

METHODS

A total of 42 oligospermic or azoospermic men had AZFc deletions. History, physical examination, karyotype, FSH, LH, testosterone, testis histology and results of ICSI using ejaculated or testis sperm were retrospectively accumulated in two academic clinical practices.

RESULTS

All men were somatically healthy. Karyotypes were 46,XY in all but two men. FSH, LH, testosterone and testis histology could not differentiate those with oligospermia or azoospermia, nor could they predict whether sperm could be found in harvested testis tissue. Paternal age was not increased. Sperm production appeared stable over time. The results of ICSI were not affected by the AZFc deletion. All but one of the offspring were healthy. The sons inherited the AZFc deletion with no increase in length.

CONCLUSIONS

AZFc-deleted men are somatically healthy, will most likely have useable sperm, will have stable sperm production over time and will have a good chance to experience biological paternity, but their sons will also be AZFc-deleted.

Type and frequency of chromosome aberrations in 781 couples undergoing intracytoplasmic sperm injection

Cytogenetic investigations were performed in 781 couples prior to intracytoplasmic sperm injection (ICSI) because of severe male infertility or fertilization failures in previous in-vitro fertilization attempts. Out of these 1562 patients, 1012 had a normal karyotype without any aberrations (64.8%), 204 patients had an abnormal karyotypes (13.1%). These chromosome aberrations included constitutional aberrations (4.4%), fragile sites of autosomes (3.0%), low level mosaicism of sex chromosomes (4.0%) and secondary structural chromosome aberrations (4.2%). Combinations of different types of abnormalities were stated. Another 346 patients (22.1%) showed single cell aberrations; the significance of these is unclear at the moment. Constitutional chromosome aberrations were detected in 69 patients. The following chromosome aberrations were observed: 35 sex chromosomal aberrations (comprising hyperploidies of X or Y chromosomes, mosaicisms and derivative X and Y chromosomes), 34 autosomal aberrations including 14 reciprocal translocations, five Robertsonian translocations, six inversions, one marker chromosome, one trisomy 18 mosaicism and seven other structural aberrations. Three autosomal regions showed fragile sites: 6q13 in 2.9% of the patients, 17p12 and 10q24 in 0.05% each. In conclusion, our data show that a high number of infertile couples in an ICSI programme are affected by chromosome aberrations which occur in both sexes. It is suggested that a chromosomal analysis should be performed on both partners before ICSI treatment is initiated.

Men with infertility caused by AZFc deletion can produce sons by intracytoplasmic sperm injection, but are likely to transmit the deletion and infertility

Deletion of the AZFc region of the Y chromosome is the most frequent molecularly defined cause of spermatogenic failure. We report three unrelated men in whom azoospermia or severe oligozoospermia was caused by de-novo AZFc deletions, and who produced sons by intracytoplasmic sperm injection (ICSI). We employed polymerase chain reaction (PCR) assays to examine the Y chromosomes of their four infant sons. All four sons were found to have inherited the Y chromosome deletions. Such sons are likely to be infertile as adults. This likelihood should be taken into account when counselling couples considering ICSI to circumvent infertility due to severe oligozoospermia or non-obstructive azoospermia.