DEVELOPMENT AND IMPLEMENTATION OF INTRACYTOPLASMIC SPERM INJECTION (ICSI)

The purpose of this paper is to elucidate the experimental steps that led to the development of intracytoplasmic sperm injection (ICSI) and its application in the human. ICSI has become the most successful micr omanipulation procedure for treating male infertility. A total of 355 in vitro fertilization (IVF) cycles utilizing ICSI are described; 180 couples were previously treated in 509 IVF cycles but achieved no fert ilization and 175 couples could not be treated by IVF because of extre mely poor semen parameters. Of the 3063 metaphase II (M II) oocytes re trieved, 2970 were injected with a survival rate of 93.6%, yielding 19 17 bipronuclear zygotes (64.5%). In 148 patients, a foetal heart was e videnced by ultrasound; 11 of these patients miscarried between 7 and 13 weeks of gestation. The ongoing pregnancy rate was 38.6% (137/355) per retrieval and 40.5% (137/338) per embryo replacement. At the time of writing, there were 22 deliveries and one therapeutic abortion for a trisomy 21 chromosomal abnormality. In addition, 66 singleton, 37 tw in, 10 triplet and 1 quadruplet pregnancies were ongoing. The concentr ation of motile spermatozoa in the ejaculate only slightly influenced the fertilization rate (P < 0.001) and the pregnancy outcome (P < 0.01 ). A preliminary injection procedure utilizing intracytoplasmic inject ion of isolated sperm heads was performed in 35 M II human oocytes wit h resultant fertilization and cleavage rates of 74% and 73% respective ly. Skills in ICSI were acquired by injecting hamster and unfertilized human oocytes with human sperm. ICSI can be used to successfully trea t couples who have failed IVF or who have too few spermatozoa for conv entional in vitro insemination. Neither the semen parameters nor the o rigin of the sperm sample clearly influenced the outcome. The achievem ent of fertilization with only sperm heads suggests that the applicati on of ICSI may be able to be extended to immature sperm cells, but fur ther genetic evaluation concerning the effect of the centrosome on spi ndle formation is required.