Is ICSI associated with risks of genetic disease? Implications for counselling, practice and research

Fertilization and embryonic developmental capacity of epididymal and testicular sperm and immature spermatids and spermatocytes

Spermatogenesis in mammalian species begins after birth. The gonocytes, arrested at G2 of the cell cycle in the foetus, resume mitotic proliferation after birth. As identified in the mouse, the gonocytes migrate towards the periphery of the seminiferous cords at day 4 to day 6 after birth and are located in close contact with the basal lamina. From this stage the gonocytes are referred to as primitive type A spermatogonia. These cells continue mitotic proliferation and differentiate to form type B spermatogonia. By day 10 after birth, many of the type B spermatogonia have formed preleptotene primary spermatocytes which undergo a final phase of DNA synthesis (leptotene) prior to entering meiotic prophase (zygotene).

Genetic and epigenetic risks of intracytoplasmic sperm injection method

Pregnancies achieved by assisted reproduction technologies, particularly by intracytoplasmic sperm injection (ICSI) procedures, are susceptible to genetic risks inherent to the male population treated with ICSI and additional risks inherent to this innovative procedure. The documented, as well as the theoretical, risks are discussed in the present review study. These risks mainly represent that consequences of the genetic abnormalities underlying male subfertility (or infertility) and might become stimulators for the development of novel approaches and applications in the treatment of infertility. In addition, risks with a polygenic background appearing at birth as congenital anomalies and other theoretical or stochastic risks are discussed. Recent data suggest that assisted reproductive technology might also affect epigenetic characteristics of the male gamete, the female gamete, or might have an impact on early embryogenesis. It might be also associated with an increased risk for genomic imprinting abnormalities.

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.

Somatic chromosomal abnormalities in infertile men and women

Infertility--the inability to achieve conception or sustain a pregnancy through to live birth--is very common and affects about 15% of couples. While chromosomal or genetic abnormalities associated with azoospermia, severe oligozoospermia or primary ovarian failure were of no importance for reproduction prior to the era of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), advances in assisted reproductive techniques (ART) now enable many infertile couples to have children. These developments have raised the question of the genetic consequences of ICSI: concerns of the potential harm of the invasive procedure and concerns about the genetic risk. The infertile male and female definitely have an increased risk to carry a chromosomal abnormality. Detection of such an abnormality is of fundamental importance for the diagnosis of infertility, the following treatment, the evaluation of the risk for the future child and the appropriate management of the pregnancy to be obtained. Therefore, cytogenetic screening of both partners is mandatory prior to any type of ART. The present review is based on several surveys on male and female infertility and analyzes the types and frequencies of the different reported chromosome abnormalities according to the type of impairment of spermatogenesis and the type of treatment planned or performed. With regard to assisted reproductive techniques (especially ICSI) the main types of chromosomal abnormalities are discussed and their potential risks for ICSI. If available, reported cases of performed ICSI and its outcome are presented. The detection of an abnormal karyotype should lead to comprehensive genetic counselling, which should include all well-known information about the individual type of anomaly, its clinical relevance, its possible inheritance, the genetic risk of unbalanced offspring, and the possibilities of prenatal diagnosis. Only this proceeding allows at-risk couples to make an informed decision regarding whether or not to proceed with ART. These decisions can be made only when both partners have clearly understood the genetic risks and possible consequences when ART is used.

Effect of paternal age on the frequency of cytogenetic abnormalities in human spermatozoa

Many surveys have been performed to find etiological relationships between pregnancy outcome and specific risk factors, such as exposure to chemicals and radiation or parental age. Advanced maternal age is a strong risk factor for trisomic pregnancies, albeit there are considerable variations among the different chromosomes. The definite incidence of the various structural and numerical chromosome aberrations in spontaneous abortions and liveborns is well known, as well as the rate of maternally and paternally derived rearrangements. Nevertheless studies have failed to assert an age-dependent risk for men fathering chromosomally abnormal children. New techniques using fluorescence in situ hybridization render it possible to analyze spermatozoa directly for numerical and, to some extent, for structural aberrations. This article compiles the findings of studies on human spermatozoa over the last few years.

Mouse ICSI with frozen-thawed sperm: the impact of sperm freezing procedure and sperm donor strain

Normal mouse offspring can be obtained from oocytes injected with frozen-thawed spermatozoa without cryoprotection, however, embryo development can be affected by sperm freezing procedure and sperm donor strain. In this study we observed that direct contact of mouse spermatozoa with liquid nitrogen did not affect their ability to activate injected oocytes but severely restricted subsequent in vitro embryo development to blastocyst stage. Tris-EDTA buffer and M2 were also shown to be better sperm freezing extenders than DPBS, allowing higher developmental potential. In addition, differences in embryo development obtained by intracytoplasmic sperm injection (ICSI) with frozen-thawed spermatozoa were observed between hybrid sperm donor strains. Frozen-thawed B6D2F1 spermatozoa provided higher embryo development than sperm cells from C57CBAF1.

Chromosome analysis of spontaneous abortions after in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI)

OBJECTIVE

To verify the hypothesis that the incidence of chromosomal abnormalities significantly increases in the products of conception of males with sub-fertility, treated with assisted reproduction techniques (ART).

STUDY DESIGN

All removed products of conception tissues were analyzed with standard cytogenetic techniques. A karyotype of the abortions was possible in 35 cases of IVF and 29 of ICSI.

RESULTS

15/35 (43%) IVF abortions and 14/29 (48%) ICSI abortions, respectively, have shown a chromosomal abnormality. The most frequent abnormality was monosomy X (45,X0).

CONCLUSION

No significant difference in the incidence of embryonic anomalies was found between IVF and ICSI group. However, both IVF and ICSI allow pre-implantation diagnosis and embryo chromosomal evaluation should be considered, before transfer. Genetic counselling and consideration of prenatal diagnosis is suggested as integral part of planning of treatment strategies for 'at risk couples'.

[Pregnancy outcome and the status of the newborn infant after ICSI at La Conception Hospital in Marseille]

OBJECTIVE

To evaluate obstetric outcome of pregnancies and pediatric follow-up of children born after ICSI procedure.

MATERIAL AND METHOD

Prospective study from october 1994 to September 1998 in medical assisted procreations center in La Conception hospital in Marseilles. Three hundred forty-two couples undergoing ICSI procedures.

INTERVENTIONS

analysis of pregnancy rates, prematurity rates, obstetric outcome and frequency of congenital malformations.

RESULTS

One hundred seventy-eight pregnancies have been obtained with 111 children. Multiple pregnancy rate arise 29.7%. The average term at birth in the singleton pregnancies (38.7 weeks) is higher than in the twins (35.7 weeks). The prematurity rate of delivery before 35 weeks of gestation is about 9.6%. Seven of 111 neonates was born with a congenital malformation, no cardiovascular one. One of boys presents a bilateral cryptorchidism with severe bilateral hypotrophy.

CONCLUSIONS

Our results are similar with those of others teams. Congenital malformation rates is near rates reported in others studies. However, no bilateral cryptorchidism with bilateral severe hypotrophy has been yet reported in literature.

Genetically determined male infertility and assisted reproduction techniques

This is a review of the common chromosome and genetic disorders associated with male infertility that need to be considered by the clinician and the couple in the context of treatment. Until recently the most relevant disorders have been those inherited from parents, however, with the advent of technologies enabling recovery of sperm from the testicle in men with severely damaged spermatogenesis there is increased interest in those genetic abnormalities that may occur in mitosis and meioses. It is likely that over the next ten years there will be increasing focus on this aspect of male fertility genetic disorders. This article needs to be read in conjunction with the specific in depth reviews in this journal edition.

Incidence of aneuploid spermatozoa from subfertile men: selected with motility versus hemizona-bound

Spermatozoa-zona pellucida binding selects for human spermatozoa with progressive motility, normal morphology and functional competency. We postulated that this gamete interaction would also act to select against spermatozoa with chromosomal numerical aberrations. Spermatozoa from 41 men participating in the intracytoplasmic sperm injection (ICSI) programme were evaluated for the incidence of aneuploidy of chromosomes 18, X and Y. The hemizona assay was utilized to determine whether zona-bound spermatozoa from these patients have a reduced incidence of aneuploidy compared with those selected by motility only in a standard swim-up procedure. Using multicolour fluorescence in-situ hybridization (FISH) with DNA probes specific for chromosomes 18, X and Y, the disomy rates for chromosomes 18, X, Y and XY were found to be 0.31, 0.27, 0.29 and 0. 14% respectively in the swim-up motile fraction, and 0.31, 0.33, 0. 32 and 0.19% respectively in the pellet fraction. Analysing the zona-bound spermatozoa, the disomy rates for chromosome 18, X, Y and XY were found to be 0.02, 0.15, 0.12 and 0.07% respectively. The zona-bound spermatozoa had a significantly lower frequency of aneuploidy than the swim-up motile fraction or the pellet fraction (P < 0.0001). The incidence of chromosome 18 aneuploidy, including both chromosome 18 disomy and nullisomy, in the swim-up motile fractions was significantly increased in patients with an abnormal or borderline hemizona index compared with those with a normal hemizona index (P < 0.05). We also found that a high incidence of sperm aneuploidy was associated to a certain extent with low fertilization rate, and with failure to achieve pregnancy through ICSI. This study suggests that the human zona pellucida has the capacity to select against aneuploid spermatozoa by an as yet undetermined mechanism.

Genetics and male infertility

This article reviews chromosomal and genetic disorders in the context of male fertility. Particular emphasis is on those disorders, which are encountered, in clinical practice including Klinefelter's syndrome, Kallman's syndrome, Androgen insensitivity, Y microdeletions, Y fertility gene deletions, and cystic fibrosis gene mutations. These disorders are discussed in relation to the aetiology of male fertility and also risks to children who are born of fathers with these disorders. A list of fathers' categories is proposed for outcome studies for children born after IVF-ICSI. Finally a question is proposed to catalyse debate about germ line therapy.

Analysis of spermatozoa from seven ICSI males with constitutional sex chromosomal abnormalities by fluorescent in situ hybridization

PURPOSE

The objective was to estimate the risk for subfertile males with a constitutional sex chromosomal abnormality of transmitting such a chromosome abnormality to their children, conceived by intracytoplasmic sperm injection (ICSI).

METHODS

Semen samples were obtained from seven severely oligospermic ICSI candidates. Six of them had a numerical sex chromosomal abnormality, including mosaic 45,X/46,XY, mosaic 46,XY/47, XXY, 47,XXY (Klinefelter's syndrome), and 47,XYY. One male had a structural abnormality, namely, an inversion of the Y chromosome. The semen was studied by three-color fluorescent in situ hybridization (FISH) with probes specific for chromosomes 18,X, and Y.

RESULTS

Chromosomal aneuploidy rates of any of the three chromosomes were significantly higher than the aneuploidy rates observed in three control samples but comparable to the rates observed in 10 ICSI candidates with oligoasthenoteratozoospermia (OAT) and a normal constitutional karyotype.

CONCLUSIONS

Our data indicate that males with (mosaic) sex chromosomal abnormalities have no higher risk of producing offspring with a sex chromosomal abnormality by ICSI than OAT males with a normal karyotype.

Paternal contributions to the mammalian zygote: fertilization after sperm-egg fusion

Mammalian fertilization has traditionally been regarded as a simple blending of two gametes, during which the haploid genome of the fertilizing spermatozoon constitutes the primary paternal contribution to the resulting embryo. In contrast to this view, new research provides evidence of important cytoplasmic contributions made by the fertilizing spermatozoon to the zygotic makeup, to the organization of preimplantation development, and even reproductive success of new forms of assisted fertilization. The central role of the sperm-contributed centriole in the reconstitution of zygotic centrosome has been established in most mammalian species and is put in contrast with strictly maternal centrosomal inheritance in rodents. The complementary reduction or multiplication of sperm and oocyte organelles during gametogenesis, exemplified by the differences in the biogenesis of centrosome in sperm and oocytes, represents an intriguing mechanism for avoiding their redundancy during early embryogenesis. New studies on perinuclear theca of sperm revealed its importance for both spermatogenesis and fertilization. Remodeling of the sperm chromatin into a male pronucleus is guided by oocyte-produced, reducing peptide glutathione and a number of molecules required for the reconstitution of the functional nuclear envelope and nuclear skeleton. Although some of the sperm structures are transformed into zygotic components, the elimination of others is vital to early stages of embryonic development. Sperm mitochondria, carrying potentially harmful paternal mtDNA, appear to be eliminated by a ubiquitin-dependent mechanism. Other accessory structures of the sperm axoneme, including fibrous sheath, microtubule doublets, outer dense fibers, and the striated columns of connecting piece, are discarded in an orderly fashion. The new methods of assisted fertilization, represented by intracytoplasmic sperm injection and round spermatid injection, bypass multiple steps of natural fertilization by introducing an intact spermatozoon or spermatogenic cell into oocyte cytoplasm. Consequently, the carryover of sperm accessory structures that would normally be eliminated before or during the entry of sperm into oocyte cytoplasm persist therein and may interfere with early embryonic development, thus decreasing the success rate of assisted fertilization and possibly causing severe embryonic anomalies. Similarly, foreign organelles, proteins, messenger RNAs, and mitochondrial DNAs, which may have a profound impact on the embryonic development, are propagated by the nuclear transfer of embryonic blastomeres and somatic cell nuclei. This aspect of assisted fertilization is yet to be explored by a focused effort.

A retrospective follow-up study on intracytoplasmic sperm injection

PURPOSE

Genetic aspects of male subfertility and the novelty of intracytoplasmic sperm injection (ICSI) as a new technique can influence the development of zygotes and children born after ICSI. Therefore, we evaluated the outcome of ICSI compared to in vitro fertilization (IVF).

METHODS

Data from medical records of 233 total pregnancies and the follow-up of 132 children born after IVF and 120 after ICSI were retrospectively analyzed.

RESULTS

No differences were found between ICSI and IVF for early embryonic development and obstetric outcome. In both groups the rate of women undergoing prenatal chromosomal diagnosis was low, 30.0%. The congenital malformation rate was 3.0% after IVF and 1.7% after ICSI, which was not significantly different. Follow-up on development of children born after IVF and ICSI also showed no significant differences.

CONCLUSIONS

Our results indicate that at this moment ICSI is a safe procedure. However, a consistent prospective follow-up is still mandatory to exclude possible risks.

Genetics and human reproduction

Most people want children, and most people want healthy children. For those couples with an infertility problem who have recourse to assisted reproduction, usually in vitro fertilization (IVF) or donor insemination (DI), the practitioners have a special responsibility to ensure as far as possible that the babies in whose conception they assist are in good health. How can they best tackle the challenge of inherited diseases, of which about 4000 are known today, and chromosomal malfunction?

Genetic risks of intracytoplasmic sperm injection in the treatment of male infertility: recommendations for genetic counseling and screening

OBJECTIVE

To review the most clinically significant genetic disorders associated with severe oligospermia and azoospermia in males, and to present recommendations for the genetic counseling and screening of infertile males and their partners before undertaking intracytoplasmic sperm injection (ICSI)-assisted reproduction.

DESIGN

The literature on genetic disorders associated with severe oligospermia and azoospermia was reviewed, and the most recent outcome data from surveys of ICSI-derived offspring are presented. Studies related to this topic were identified through MEDLINE.

RESULT(S)

Genetic disorders are not infrequent causes of severe oligospermia and azoospermia in males undergoing ICSI-assisted reproduction. The application of ICSI in the treatment of oligospermic or azoospermic males may result in the transmission or de novo introduction of genetic mutations or chromosomal abnormalities in their offspring. Genetic counseling and appropriate screening of couples with male infertility should be performed before their undertaking ICSI-assisted reproduction.

CONCLUSIONS

An understanding of the genetic risks and possible consequences that are inherent when ICSI is used to assist fertilization in couples with male infertility is necessary for clinicians and their patients.

Chromosome abnormalities in embryos obtained after conventional in vitro fertilization and intracytoplasmic sperm injection

OBJECTIVE

To compare the rate of numerical chromosome abnormalities in embryos derived from bipronucleated zygotes produced by intracytoplasmic sperm injection (ICSI) and conventional IVF.

DESIGN

Embryos were classified by maternal age and morphological and developmental characteristics to avoid bias when comparing chromosome abnormalities in ICSI and IVF embryos.

SETTING

The Institute for Reproductive Medicine and Science of Saint Barnabas Medical Center, West Orange, New Jersey.

PATIENT(S)

Seventy-nine couples undergoing IVF and 53 couples undergoing ICSI.

INTERVENTION(S)

Embryos donated for research were fully biopsied, and their cells were analyzed by fluorescence in situ hybridization with specific probes for chromosomes X, Y, 13, 18, and 21 and some with also a probe for chromosome 16.

MAIN OUTCOME MEASURE(S)

Embryo chromosome abnormalities.

RESULT(S)

A total of 245 embryos obtained through conventional IVF and 136 embryos obtained through ICSI were analyzed. There were no statistical differences between the rates of numerical chromosomal abnormalities detected in the IVF (61%) and ICSI (52%) embryos analyzed. Regarding gonosomal aneuploidy, the same rate was found in both ICSI (1%) and IVF groups (2%).

CONCLUSION(S)

If the parents are chromosomally normal, the results indicate that, at the embryo level and before any embryo selection has occurred in utero, ICSI does not produce more numerical chromosomal abnormalities than conventional IVF.

In vitro fertilization for male infertility: when and how?

The first observation that in vitro fertilization (IVF) was useful for treating oligozoospermia and oligoasthenozoospermia was reported by Fishel and Edwards in 1982. This was followed by a series of cases indicating the value of IVF in such cases. Conventional IVF has been modified and refined to achieve increased rates of conception in cases of male factor infertility. Methods such as high insemination concentration IVF for the treatment of teratozoospermia and microscopic IVF for the treatment of oligozoospermia have had some impact on fertilization and pregnancy rates; however, reports of success are varied. The recent advent of micromanipulation and, in particular, intracytoplasmic sperm injection (ICSI) has overshadowed the use of these modified IVF procedures. Because of the high fertilization and pregnancy rates achieved with ICSI, other micromanipulation techniques (subzonal insemination and partial zona dissection) have been abandoned; there have also been suggestions that other more conventional techniques, i.e. IVF, should also be abandoned and that ICSI become the sole technique for the treatment of infertility. The rapid increase in the number of centres using ICSI has led to extreme pressure for individual units to achieve high fertilization and pregnancy rates and there is a temptation to assign all patients to ICSI treatment. It is important that, in this highly competitive environment, new techniques are not applied haphazardly and reduced to the mere injection of gametes and achievement of pregnancy regardless of the cause of infertility. In his 1986 IVF--Historical Perspective, Fishel quoted Auguste Comte: 'to understand science it is necessary to know its history'. IVF has much recent history in animal and also human work. Although ICSI is the most significant therapeutic advance in male infertility treatment, its application to human IVF is only 4 years old, with a paucity of animal studies on which to rely. For this reason IVF still plays a very important role in the treatment of male factor infertility and should only be ruled out when it has failed previously or the number of available sperm is limited.

Intracytoplasmic sperm injection for treatment of non-obstructive azoospermia

Four cases from a tertiary care teaching medical center were studied to assess the potential of sperm extraction, fertilization and the establishment of pregnancy in couples with non-obstructive azoospermia. Four couples with non-obstructive azoospermia underwent intracytoplasmic sperm injection after testicular sperm extraction. Multiple small biopsies were obtained from each testis under general anesthesia in search for sperm, and to establish a histologic diagnosis. The histopathology includes incomplete maturation arrest, hypospermatogenesis, germ cell hypoplasia and incomplete tubular sclerosis. Testicular sperm extraction resulted in the retrieval of immotile sperm from three patients, and a few motile sperm from one patient. Of 60 oocytes which were injected with testicular sperm, 32 (53.3%) fertilized and 27 of these (84.4%) cleaved. Twelve embryos were transferred to three patients and the remaining 15 embryos were cryopreserved. In one patient, no embryos resulted. One clinical pregnancy was established and a normal female infant, weighing 7 lbs 11 oz, was delivered vaginally in August 1996. This study shows that sperm can be extracted from patients with non-obstructive azoospermia when multiple biopsies are obtained. Fertilization, cleavage, clinical pregnancy and delivery of normal babies can be achieved using intracytoplasmic injection of extracted sperm.

Establishing an intracytoplasmic sperm injection (ICSI) programme for the treatment of male factor infertility in Ireland

This paper chronicles the introduction and initial experiences of Intra Cytoplasmic Sperm Injection (ICSI) as a treatment for severe male factor infertility in Ireland. Following initial development of the technique using a bovine model, therapy was offered clinically from September 1995. Up to March 1996 a total of 60 couples underwent the procedure. Fertilisation and embryo transfers were achieved in 50 of these (83.3 percent). Fourteen (23 percent) became clinically pregnant per cycle commenced, 28 percent per embryo transfer. Despite a drop in the total number of oocytes available, fertilisation rates rose over the 6 months of the study from 22 percent to 54 percent. There were 2 miscarriages (14.2 percent) and the multiple pregnancy rate was 28.5 percent. Eight singletons, 2 twins and 2 triplet sets have been successfully delivered. Provided there is proper patient selection, ICSI should prove a valuable addition to treatment options available to infertile couples in Ireland.

Presence of mature sperm in testicular parenchyma of men with nonobstructive azoospermia: prevalence and predictive factors

OBJECTIVES

Hitherto, patients with testicular dysfunction and azoospermia had to resort to adoption, donor sperm insemination, or child-free living. The realization that a proportion of such men harbor spermatozoa in their testicular parenchyma, combined with the ability of intracytoplasmic sperm injection (ICSI) to effect pregnancy with single sperm, has prompted male infertility clinicians to explore testicular sperm extraction (TESE) in this patient population. We sought to investigate the likelihood of finding spermatozoa during TESE from men presenting with nonobstructive azoospermia and to define if any factors existed that were predictive of eventual sperm presence or absence.

METHODS

Thirty patients with nonobstructive azoospermia underwent TESE and simultaneous formal testis biopsy, cytologic analysis, and wet preparation analysis. Tissue obtained from TESE was analyzed according to a rigorous protocol, followed by exhaustive searching by trained embryologists.

RESULTS

Twenty-one patients (70%) had spermatozoa found on testicular tissue analysis. Neither patient age nor follicle-stimulating hormone (FSH) level was predictive of the ability to find sperm. With regard to histologic pattern, 50% of men with Sertoli cell-only, 75% of patients with maturation arrest, and 100% of patients with spermatids seen on histologic analysis had sperm retrieved from their testicular tissue during TESE. Absence of sperm on cytologic smear and wet preparation analysis failed to predict the presence of sperm on formal testicular tissue analysis in 40% of patients.

CONCLUSIONS

Men with nonobstructive azoospermia may have mature spermatozoa present within their testicular parenchyma. Relying on these data, patients should not be excluded from TESE based on serum FSH level, age, prior histopathologic pattern, or cytology/wet preparation results. These figures will allow clinicians to counsel patients with nonobstructive azoospermia informatively regarding TESE and their chances of having testicular sperm retrieved.