The present status of artificial oocyte activation in assisted reproductive technology

Intracytoplasmic sperm injection (ICSI) is the most effective treatment for achieving fertilization in assisted reproductive technology (ART). However, fertilization failure occurs. The incidence of fertilization failure after ICSI is 1-5%. Approximately 50% of fertilization failure cases could be attributed to the abnormality of sperm factor. As the fertilization fails after ICSI using mature sperm, round spermatids and globozoospermia, artificial oocyte activation may provide a means of improving fertilization rates in such cases. The oocyte activation treatments used in clinical research include calcium (Ca) ionophore treatment, electrostimulation and strontium treatment. In terms of the efficiency of oocyte activation, electrostimulation and Ca ionophore gave better outcomes than strontium treatment. Strontium treatment causes Ca²⁺ oscillations in mice, so it has been viewed favorably. However, in human oocytes calcium oscillation has not been observed. The fertilization rate after ICSI was low in the case of globozoospermia and wiht round spermatids. Some cases of pregnancy were achieved by ICSI alone and oocyte activation methods were not essential in these cases. Among the various oocyte activation methods currently used, it should be noted that issues of genetic safety have not been addressed for the combined use of these oocyte activation methods. (Reprod Med Biol 2008; 7: 133-142).