Human gamete micromanipulation and intracytoplasmic sperm injection (ICI) : its impact on severe male infertility

[摘要] ENGLISH ABSTRACT:Intracytoplasmic sperm injection (ICSI) introduced a revolutionary way of treatment for malefactor infertility. With the exception of some cases of non-obstructive azoospermia, all othermale factor infertility cases have the potential to be successfully treated with ICS!. The onlyprerequisite seems to be the presence of a motile or viable immotile sperm cell for each oocyte.In this study we report on our own experience with the development and implementation of theICSI method in the Reproductive Biology Unit at Tygerberg Hospita!. An analysis of 5 years ofICSI experience showed that semen parameters, sperm morphology, motility and concentrationdid not influence fertilization and pregnancy rates adversely. In most cases, patients who couldnot be treated with in vitro fertilization (IVF) and gamete intrafallopian transfer (GIFT), due to poorsemen parameters or fertilization failure, were treated successfully with ICS!. Even a case ofglobozoospermia was treated successfully with ICS!.Testicular spermatozoa, fresh or frozen-thawed, also resulted in excellent fertilization andpregnancy rates. Cryopreservation of testicular samples facilitated the management of theinfertile couple, aiding the coordination of the recovery of vital gametes from both partners andalso limiting the repetition of testicular biopsies. Incubation (maturation) of testicular spermatozoaalso induced an enhancement in pregnancy rates.It can be concluded that ICSI proved to be a treatment method with success similar to that of invitro fertilization (IVF) and gamete intrafallopian transfer (GIFT), in spite of a severe male factor.The study also indicated transfer route and embryo quality (viability) to be very important factorsin the success of ICS!. The tubal transfer route was shown to be a significant contributor to thepregnancy success (compared to uterine transfer) as was the transfer of embryos that showedearly division to the 2-cell stage, 26 hours post injection. The transfer of early dividing embryosinto the fallopian tube resulted in a pregnancy rate of almost 40%, a result similar to that of GIFTwith a mild male factor.The role of the oocyte in fertilization and pregnancy success was also revealed indirectly by theintroduction of ICS!. Visual observation of denuded oocytes was possible and manymorphological features, normal and abnormal, can be observed. Immature oocytes can also beidentified and it was shown that they could be successfully matured in vitro before injection.In this study transmission electron microscopy (TEM) was used to study abnormalities in oocytemorphology. The standard method was adapted and modified for single cell TEM. Theabnormalities observed included lysosomal and non-lysosomal degeneration (yellowish or darklycoloured oocytes), degeneration and vacuole formation (vacuolated oocytes), large secondarylysosomes filled with multiple small lipid droplets - lipofuscin body (refractile body) and afragmented oocyte. It was also possible to study at ultrastructural level, possible reasons forfertilization failure in ICS!. Different stages of oocyte activation failure, cytoplasmic immaturity,sperm cell extrusion, abnormal sperm cell decondensation, female spindle abnormalities andtechnique related factors were observed. TEM was also successfully implemented to elucidate the reason for infertility in a patient with alongstanding, unexplained history of infertility. TEM evaluation of two of the patient's unfertilizedoocytes revealed a spindle abnormality with contributing cytoskeletal anomalies at ultrastructurallevel. The modified TEM technique offers a valuable tool to study this small, but important groupof patients with unexplained infertility. ThisTEM study opened up a new, valuable and interestingavenue of research with both diagnostic and prognostic value for patients with unexplainedinfertility.ICSI is therefore a valuable method in the treatment of especially male factor infertility. It is themost advanced fertilization technique developed in the last decade in this field. Not only canalmost all male factor patients be treated, but unexplained female infertility can also be exposed,studied and hopefully in future also be treated with micromanipulation methods.

[发布机构] Stellenbosch University