Intracytoplasmic injection of human sperm into frozen-thawed hamster oocytes

Superovulated hamster oocytes were frozen by 2 M DMSO. 89% (499/561) of the oocytes survived freezing and thawing. A hamster-ICSI assay was performed to evaluate the ability of frozen-thawed oocytes to develop male pronuclei. 46% (58/127) of the oocytes had male pronuclear formation following injection of single human sperm into the cytoplasm of frozen-thawed oocytes. There was no significant difference in male pronuclear formation as compared with fresh oocytes. This study shows that hamster oocytes conserved their ability to support human sperm head decondensation and male pronuclear formation following freezing-thawing.