William Schoolcraft, MD

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       ICSI (intracytoplasmic sperm injection) is arguably the biggest  advance in assisted reproductive technology since the successful birth  of Louise Brown, 21 years ago. However, with any new techniques, the  possible risks including short and longterm health consequences of the  offspring must be considered. Thus far, the outcome data regarding ICSI  offspring has been reassuring. However, many theoretical concerns  regarding ICSI have been raised, and the validity of such concerns may  take years, or even generations, to address. Any possible risks of ICSI  seem to be outweighed by the benefits in treating males with severe male  factor infertility, where the couple=s only alternative is sperm  donation. Less clear, however, is the wisdom of applying ICSI to all IVF  cycles; that is, in cases where natural fertilization is expected to  occur at normal rates.





       There is little data comparing IVF to ICSI in non-male factor  cases. Utilization of ICSI is increasing worldwide in situations where  it is not essential for successful fertilization. In some large clinics,  more than 60% of all cycles are ICSI, and in still others, ICSI is  already routine for all IVF treatment cycles. One obvious advantage of  to the application of ICSI routinely is the near avoidance of  unexplained fertilization failure. Some have suggested its use in cases  with low egg numbers or advanced reproductive age to maximize  fertilization. The assessment of oocyte maturity and dysmorphisms is  certainly better assessed by ICSI, and this data may be used to gain  insight into oocyte quality and the appropriateness or effec tiveness of  the stimulation protocol used. ICSI is also advantageous when used in  conjunction with preimplantation genetic diagnosis, particularly polar  body biopsy. 



Proposed Concerns Regarding Routine Application of ICSI

 

       While ICSI has unarguably revolutionized the treatment of male  factor infertility, critics question its potential for a negative impact  on the genetic composition of future generations. ICSI bypasses the  biological mechanisms of sperm selection put in place by evolution.  Furthermore, ICSI in the human was not preceded by adequate animal  research. The application of ICSI in humans has, in fact, represented  the experimental model. ICSI provides the ability to improve the  reproductive potential of mutant male genotypes with the resulting  possibility of altering the genetic composition of future human  populations. 



Chromosomal Abnormalities and Male Infertility



       The incidence of chromosomal abnormalities in infertile men is  5.8% compared to 0.38% in phenotypically normal male newborns. In  another review of cytogenic studies in azoospermic and oligospermic men,  chromosomal abnormalities were found in 13.7% and 4.6% of these groups,  respectively. Klinefelter’s syndrome and Klinefelter’s mosaic were  predominant abnormalities mentioned. Non-Klinefelter’s sex chromosome  abnormalities and autosomal abnormalities were observed in 1.8% and 1.1%  of azoospermic males, respectively. In oligospermic men, autosomal  abnormalities were present in 3% of the population and sex chromosome  abnormalities in 1.6%. Indeed, Palermo has recently reported two  successful pregnancies in Klinefelter’s patients using testicular sperm  extraction in combination with ICSI. 

       Y chromosome micro deletions have a frequency in azoospermic and  oligospermic males of 9% to 18%. Translocations can also be found in men  with poor semen production with a resulting increase in trisomic  offspring. Congenital bilateral absence of the vas deferens is caused by  a mutation of the cystic fibrosis transmembrane regulator gene (CFTR).  In such cases, the female partner must be screened for CF mutations to  avoid producing an affected child. CFTR mutations have also been found  with a prevalence of 13% in men with decreased semen parameters and an  intact vas deferens. 

       Sakkas has proposed that the use of blastocyst culture to allow  the selection of the most viable embryo post embryonic genome activation  might overcome any paternal genome defects which might be introduced  through ICSI. Concerns Related to the ICSI Technique Itself

       Mitochondrial DNA is inherited exclusively from the oocyte.  Therefore, mDNA from the sperm must be eliminated at early stages of  fertilization. When ICSI is used, the entire sperm, including the plasma  membrane, is injected. This could hinder recognition and subsequent  elimination of paternal mitochondrial DNA. 

       Hewitson raised other concerns regarding the ICSI technique in a  study involving primates. Oocytes are typically aligned with the polar  body at 6 or 12 o’clock during injection so as to avoid damage to the  second miotic spindle. It is assumed that the polar body is in close  approximation to the spindle. However, in Hewitson’s study of the Rhesus  monkey, the spindle may, in fact, reside as far as 68 degrees from the  polar body, and in the human the polar body on average was 56 degrees  from the spindle (range 23-95). The damage to the miotic spindle may  therefore be more common than previously thought. 

       The same group also demonstrated that sperm nuclear decondensation  is atypical after ICSI. The apical region remains condensed longer than  the basal region. Chromosomal abnormalities could therefore be related  to this delay in decondensation. Incomplete decondensation of  chromosomes in this region could lead to asymmetrical segregation at  mitosis. The X chromosome is preferentially located in the apical region  ¾ a possible explanation of the increased incidence of sex chromosome  abnormalities in ICSI offspring. 

       There are many other differences between ICSI and conventional IVF  that could contribute negatively to the ultimate outcome of ICSI. The  natural selection of normal fertilization is bypassed by biologists who  choose a single sperm. Significant physical distortion occurs during the  injection procedure, and the use of hyaluronidase to remove  cumulus-corona cells, as well as the use of PVP for the injection medium  represents potentially adverse physiologic stress to the oocyte. The  fate of an intact acrosome and the potential toxicity of its enzymes has  not been adequately evaluated. Important proteins (e.g., gamma-tubulin)  critical to the formation of the sperm aster are present at the cortex  of the oocyte. By placing the sperm in the center of the egg during  ICSI, the normal choreography of the sperm and egg nuclei may be  altered. 

       Longterm concerns regarding ICSI offspring include cancer rates in  later years of life, reproductive potential, alterations in the pattern  of genomic imprinting, and the congenital malformation rate in children  of ICSI babies. These concerns will not be addressed for years to come.



Prospective Follow-up of Pregnancies from ICSI



       2375 ICSI pregnancies resulting in 1987 children from cycles  between April 1991 and September 1997 were assessed by the Belgium  group. Major malformations were seen in 2.3% of ICSI offspring, similar  to most general population registries and ART surveys. A 1.6% incidence  of de novo chromosomal abnormalities, with one-half being sex  chromosomes and the other half being autosomal, were also described.  Statistically significant increase in the sex chromosome abnormality  rate was seen when compared to the literature. A study to assess the  mental and psychological development of children up to the age of 2  found no differences between ICSI offspring and naturally conceived  children.

       From Cornell, Palermo compared 1753 IVF newborns to 1732 ICSI  babies. Major malformations were seen in 1.8% of IVF babies compared to  1.1% of ICSI offspring. Minor malformations were present in 1.4% of IVF  cases compared to 0.8% with ICSI. 





       Some comparisons have been made regarding the outcome of oocytes  fertilized conventionally by IVF compared to ICSI. Shoukir in 1998  described the development of supernumerary embryos to the blastocyst  stage in patients who had transfers on day 2 following either IVF or  ICSI. The percentage of spare embryos progressing to the blastocyst  stage in IVF patients was 49%, while only 26% of embryos in the ICSI  group progressed to the blastocyst stage. Aboulghar performed a  randomized prospective trial comparing IVF and ICSI in tubal factor  patients with normal semen parameters. The pregnancy and implantation  rates were similar in both groups. However, the fertilization rate was  significantly higher in the IVF group. ICSI appeared to have no  advantage in the treatment of tubal factor patients. Aboulghar also  evaluated ICSI versus convention IVF for sibling oocytes in both  unexplained infertility and borderline semen parameter cycles. In the  unexplained infertility group, a similar fertilization rate, 63% with  ICSI compared to 51% with IVF, was seen. However, total fertilization  failure occurred in 5 of 22 cases with conventional IVF compared to 0  fertilization failures with ICSI. In the borderline semen group,  fertilization rate with ICSI was 59% compared to 27% with IVF, and total  fertilization failure occurred in 11 of 24 (46%) cycles compared to 0  cases in the ICSI group. Overall, 34% of patients were saved from a  canceled embryo transfer due to total fertilization failure in cases of  unexplained infertility or borderline semen parameters when ICSI was  utilized. Hamberger evaluated patients with previous conventional  fertilization failure. Fourteen of 42 (33%) patients saw no  fertilization in a second cycle of IVF compared to no cases of  fertilization failure in ICSI treated patients. Van Steirtethem  described a small randomized trial of conventional IVF versus ICSI for  sibling oocytes in tubal factor infertility. Significantly high  fertilization was achieved in the ICSI group (68% versus 57%). However,  the percentage of embryos cleaving and embryo quality was not  significantly different. Total fertilization failure occurred in 4  conventional IVF patients versus 1 treated with ICSI. At the Colorado  Center for Reproductive Medicine, we have reviewed our 1998 experience  with conventional IVF compared to ICSI. In reviewing 153 ICSI cycles and  305 conventional IVF cycles, there appear to be no significant  differences in the fertilization rate (56% versus 60%), the percentage  of good quality day 3 embryos (52% versus 54%), pregnancy rate (61%  versus 57%), the implantation rate (31% versus 32%), or the percentage  of blastocyst formation (42% versus 46%). 

       In summary, ICSI appears to be neither helpful nor harmful when  compared to conventional IVF in the treatment of non-male factor  infertility. In cases of borderline semen parameters or unexplained  infertility, there is a significant increase in the rate of  fertilization with ICSI and a decrease in the incidence of total  fertilization failure. Despite reassuring data regarding the outcome of  ICSI offspring to date, potential long-term risks of the ICSI procedure  are still to be determined. Therefore, it appears that the application  of ICSI in all cases of IVF is unwarranted. Patients with unexplained  infertility, borderline semen parameters, or severe male factor  infertility are greatly benefitted by this technology, and the outcome  data to date certainly support its continued use. 


1. Aboulghar, M.A., Mansour, R.T., Serour, G.I., et al. (1996) Prospective controlled randomized study of in vitro fertilization versus intracytoplasmic sperm injection in the treatment of tubal factor infertility with normal semen parameters. Fertil. Steril. 66, 753-756.

2. Aboulghar, M.A., Mansour, R.T., Serour, G.I., et al. (1996) Intracytoplasmic sperm injection and conventional in vitro fertilization for sibling oocytes in cases of unexplained infertility and borderline semen. J. Assist Reprod. Genet. 13, 38-42.

3. Baschat, A., KÃ²pker, W., Al Hasani, S., Diedrick, K., Schwinger, E. (1996) Result of cytogenic analysis in men with severe subfertility prior to intracytoplasmic sperm injection. Hum. Reprod. 11:330-3.

4. Bhasin, S., DeKretser, D.M., Baker, H.W.G. (1994) clinical Review 64, Pathophysiology and natural history of male infertility. J. Clin. Endocrinol. Methab. 79: 1525-9.

5. Bonduelle, M., et al. (1998) Incidence of chromosomal aberrations in children born after assisted reproduction through intracytoplasmic sperm injection (ICSI). Hum. Reprod. 13, 781-782.

6. Bonduelle, M., Joris, H., Hofmans, K., Leibars, I, & van Steirteham, A.C. (1998) Mental development 201 ICSI children at 2 years of age. Lancet, 353, 1553.

7. Bourrouillou, G., Dastugue, N., Colombies, P. (1985) Chromosome studies in 952 infertile males with a sperm count below 10 million/ml. Hum Genet., 71: 366-7. 8. Bowen, J.R., Gibson, F.L., Leslie, G.I. & Saunders, D.M. (1997) Medical and developmental outcome at 1 year for children conceive with intracytoplasmic sperm injection. Lancet 351, 1529-1534.

9. Cumins, J.M., Jequier, A.M. (1994) Treating male infertility needs more clinical andrology, not less. Hum. Reprod., 9, 1214-9.

10. De Braekeleer, M., Ferec, M. (1996) Mutations in the cystic fibrosis gene in men with congenital bilateral absence of the vas deferens. Mol. Hum. Reprod., 2:669-77.

11. Hewitson, L., et al. (1999) Births of ICSI monkeys: Unique checkpoints during the first cell cycle at fertilization. Nature Med. 5, 431-433.

12. Palermo, G., et al. (1992) Pregnancies afer intracytoplasmic sperm injection of a single spermatozoan. Lancet 340, 17-18.

13. Palermo, G., Schlegel, P., Sills, E.S., Veeck, L.L., Zaninnovik N., Menendez, S., et al. (1998) Births after intracytoplasmic injection of sperm obtained by testicular extraction from men with nonmosaic Klinefelter=s syndrome. N. Engl. J. Med., 338: 588-90.

14. Palermo, G., Colombero, L, Schattman, G, Davis, O., Rosenwaks, Z. (1996) Evolution of pregnancies and initial follow-up of newborns delivered after intracytoplasmic sperm injection. JAMA, 276:1893-7.

15. Persson, ,J., Peters, G., Saunders, D. (1996) Genetic consequences of ICSI. Hum. Reprod. 11: 921-4.

16. Pryor, J., Kent-First, M., Muallern, A., Van Bergen, A., Nolten W., Meisner, L., et al. (1997) Prospective analysis of Y chromosome microdeletions in 200 consecutive male infertility patients. N. Engl. J. Med. 336:8:543-9.

17. Reijo, R., Lee, T., Salo, P., Alagappan, R., Brown, L., Rosenberg, M., et al. (1995) Diverse spermatogenic defects in humans caused by Y chromosome deletions encompassing a novel RNA-binding protein gene. Nature. Genet., 10:383-93.

18. Sakkas, D. (1999) The use of blastocyst culture to avoid inheritance of an abnormal paternal genome after ICSI. Hum. Reprod. 14, 4-5.

19. Shoukir, Y., Chardonnens, D., Campana, A. and Sakkas, D. (1998b) Blastocyst development from supernumerary embryos after intracytoplasmic sperm injection: a paternal influence? Hum. Reprod. 13, 1632-1637.

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Articles

ICSI (intracytoplasmic sperm injection) is arguably the biggest advance in assisted reproductive technology since the successful birth of Louise Brown, 21 years ago.

Author | William Schoolcraft, MD

Articles

ICSI: Should It Be Routine in Human in Vitro Fertilization?