SPERM PREPARATION FOR INTRACYTOPLASMIC INJECTION - METHODS AND RELATIONSHIP TO FERTILIZATION RESULTS

Sperm preparation for intracytoplasmic sperm injection (ICSI) is descr ibed and the effect of high speed centrifugation during preparation on fertilization rate is evaluated. No significant differences were foun d in the 2-pronuclear or abnormal fertilization rates between sibling oocytes injected with sperm prepared by swim-up or mini-Percoll combin ed with high speed centrifugation. The high fertilization rate obtaine d with both methods indicates that high speed centrifugation is not ne cessary to prepare sperm for ICSI. Fertilization rates were also compa red for sperm obtained from ejaculates, fresh and frozen epididymal as pirates, and testicular biopsies. High fertilization rates were obtain ed from all groups but they were significantly higher in those oocytes injected with epididymal sperm (78% per oocyte surviving injection). The high fertilization rate with epididymal sperm may reflect sperm qu ality or may result from the method of sperm preparation for injection . Fertilization after the injection of sperm from which the tail was d islodged during immobilization was compared with that obtained using i ntact sperm. A significantly lower rate of 2-pronuclear fertilization was found in those oocytes injected with sperm heads only (55%) compar ed with intact sperm (68%), although cleavage rates between the two gr oups were similar. The use of hypo-osmotic medium to select potentiall y live sperm from an immotile sample is also described and fertilizati on was obtained after the injection of sperm with a structural defect which were selected using this technique. These results indicate that high fertilization rates can be obtained with ejaculated, epididymal a nd testicular sperm without special treatment. Fertilization can also be achieved using ICSI with immotile sperm selected by hypo-osmotic sw elling and from the injection of sperm heads. However, the injection o f sperm heads only may not be appropriate because of the risk of mosai cism from defective or absent sperm centrosomes.