CORTICAL GRANULES REACTION AFTER INTRACYTOPLASMIC SPERM INJECTION

The cortical reaction (CR) in mammalian oocytes is induced following s perm-egg membrane fusion, During intracytoplasmic sperm injection (ICS I) the physiological cascade of gamete interaction events is bypassed. The aim of this study was to explore CR occurrence after the ICSI pro cedure and its correlation with the meiotic status of the oocytes. Unf ertilized and abnormally fertilized (one-or three-pronucleate) human o ocytes were investigated. The chromosomal status was analysed by Hoech st staining. The CR occurrence and its fluorescent pattern were assess ed by confocal scanning laser microscope using the lectin lens culinar is and Texas Red staining. Our results reveal a positive correlation b etween the activation of oocytes and their CR. No CR was demonstrated in unfertilized-unactivated oocytes with or without sperm in their cyt oplasm. In partially activated oocytes showing resumption of meiosis b ut no formation of pronuclei, a moderate CR was observed. In fully act ivated oocytes displaying one or three pronuclei, a strong CR was moni tored. It was concluded that in ICSI, as in physiological fertilizatio n, oocyte activation is a prerequisite for CR.