Intracytoplasmic injection of human sperm into the hamster oocyte (hamster ICSI assay) as a test for fertilizing capacity of the severe male-factor sperm

Objective: Our objective was to investigate the fertilizing ability of human sperm from severe male-factor patients, by microinjection of single sperm into the hamster oocyte.Design: Semen samples of severe male factor either with a 0% penetration rate in the zona-free hamster test or with a very low number of motile sperm for which performing the standard penetration test was impossible were used. For the control study, oligozoospermic semen samples with at least 10% penetration rate in zona free hamster test were used.Setting: All materials were collected from the National University Hospital, Singapore.Methods: There were 10 patients in both the experimental and the control groups. Intracytoplasmic sperm injection (ICSI) was carried out. The main outcome measures were sperm head decondensation and pronuclear formation.Results: Twenty-one percent of the injected sperm could decondense and undergo male pronuclear formation. This rate was not significantly different from that in the control study group (28%; P=0.13). A small proportion of the oocytes was damaged during the procedure (9.2 and 8.75% in experimental and control groups, respectively).Conclusions: Hamster-ICSI assay may be of benefit in predicting the sperm's ability for further development before allowing the patient to undergo the clinical program.