Fertilizing capacity of epididymal and testicular sperm using intracytoplasmic sperm injection (ICSI)

Abstract

For men with uncorrectable obstructive azoospermia, their only hope of fathering a child is microsurgical epididymal sperm aspiration (MESA) combined with in vitro fertilization (IVF). In 1988, proximal epididymal sperm were demonstrated to have better motility than senescent sperm in the distal epididymis, and it was thought that retrieval of motile sperm from the proximal epididymis would yield reliable fertilization and pregnancy rates after conventional IVF. However, the results to date have been poor, and although a minority of patients achieved good fertilization rates with IVF, the vast majority (81%) had consistently poor or no fertilization and the pregnancy rate averaged only 9%. Recently, intracytoplasmic sperm injection (ICSI) has been successfully used to achieve fertilization and pregnancies for patients with extreme oligoasthenozoospermia. ICSI has therefore been applied to cases of obstructive azoospermia and, in this report, 67 MESA-IVF cases are compared with 72 MESA-ICSI cases. The principle that motile sperm from the proximal segments of the epididymis should be used for ICSI was followed, although in the most severe cases in which there was an absence of the epididymis (or absence of sperm in the epididymis), testicular sperm were obtained from macerated testicular biopsies. These sperm only exhibited a weak, twitching motion. In 72 consecutive MESA cases, ICSI resulted in fertilization and normal embryos for transfer in 90% of the cases, with an overall fertilization rate of 46%, a cleavage rate of 68%, and ongoing or delivered pregnancy rates of 46% per transfer and 42% per cycle. The pregnancy and take-home baby rates increased from 9% and 4.5% with IVF to 53% and 42% with ICSI. There were no differences between the results for fresh epididymal, frozen epididymal or testicular sperm, and the number of eggs collected did not affect the outcome. The results were also unaffected by the aetiology of the obstruction such as congenital absence of the vas deferens or failed vasoepididymostomy. The only significant factor which affected the pregnancy rate was female age. It is concluded that although complex mechanisms involving epididymal transport may be beneficial for conventional fertilization of human oocytes (in vivo or in vitro), none of these mechanisms are required for fertilization after ICSI. Given the excellent results with epididymal and testicular sperm, ICSI is obligatory for all future MESA patients. Finally, the use of ICSI with testicular sperm from men with non-obstructive azoospermia is also discussed.