Activation of unfertilized human oocytes after intracytoplasmic sperm injection

Abstract

OBJECTIVE: To determine the effect of two different methods on artificial activation of unfertilized human oocytes following intracytoplasmic sperm injection (ICSI). DESIGN: Laboratory study with unfertilized oocytes. MATERIALS AND METHODS: Seventy-five oocytes that did not show any signs of normal fertilization (no 2 pronuclear formation and no second polar body extrusion) by 24h after ICSI were randomly allocated into 2 treatment groups: Group 1 (32 oocytes), the oocytes were exposed to 7% (v/v) ethanol for 6 minutes; and in Group 2 (43 oocytes), the oocytes were exposed to 5 μmol/L ionomycin (Sigma) for 5 minutes. The oocyte activation is defined in the present study: 1) Extrusion of the second polar body; and 2) Formation of 2 pronuclei. The activated oocytes were cultured in vitro for 3-5 days. The activation rate, normal pronuclear formation, cleavage, and the embryonic development were compared between groups. RESULTS: In Group 1, 10 (31.3%) out of 32 unfertilized oocytes were activated, and 7 of them cleaved. Among them, 7 cleaved embryos, 4 of them developed to 2-4 cell stage, 2 to of them further developed to 5-8 cell stage, and 1 morula stage produced eventually. In Group 2, 24 (55.8%) out of 43 unfertilized oocytes were activated, and 17 of them cleaved. Among them, 9 cleaved embryos developed to 2-4 cell stage, 5 of them developed to 5-8 cell stage, 3 of them developed to morula stage, and 2 of them further developed to blastocyst stage. CONCLUSIONS: These results show that the unfertilized human oocytes 24 after ICSI can be activated by ethanol or ionomycin stimulation. The activated oocytes can be developed to blastocyst stage. The results also show that ionomycin is more efficient compared with ethanol. The resulted embryos may be used for embryonic stem cell study.