Artificial oocyte activation with calcium ionophore A23187 in ICSI cycles with sperm from different origins

Abstract

OBJECTIVE: Missing oocyte activation is the most frequent cause of fertilization failure after ICSI. Oocyte activation is characterized by intracellular calcium oscillations, caused by a recently described phospholipase, PLC-zeta, present in the sperm. Different methods have been proposed to overcome oocyte activation failure in ICSI cycles, including chemical artificial oocyte activation (AOA). There are few studies focused on AOA when sperm from different origins are used. We evaluated the effect of AOA, induced with the calcium ionophore A23187, on ICSI cycles using ejaculated, epididymal, or testicular sperm. DESIGN: Case-control study. MATERIALS AND METHODS: The study included 314 couples undergoing ICSI cycles. The cycles were divided into three experimental groups according to sperm origin: EJACULATED (n=92), EPIDIDYMAL (n=82), and the TESTICULAR (n=140). For each experimental group, cycles in which AOA was applied (subgroup AOA) were matched with cycles in which AOA was not applied (subgroup control-CT). The ICSI outcomes Fertilization; high quality embryos; implantation, rate and miscarriage rates were compared between the AOA and CT subgroups. In order to exclude ovarian factor infertility, the cycles of woman less than 36 years of age were evaluated separately. RESULTS: No significant difference was observed between subgroups for the three sperm origin groups in all evaluated parameters. In cycles in which the female's age was less than 36 years old, no difference was observed in the fertilization, pregnancy or miscarriage rate between subgroups from any spermatozoa origin group. However, AOA was able to increase the high-quality embryos (74.5% vs. 53.0% P = 0.011) and implantation rates (19,3% vs. 10,5% P = 0,0025) when using ejaculated spermatozoa, and AOA also increased the high quality embryos rate (64.4% vs. 50.3%, P = 0,006) when using epididymal spermatozoa. CONCLUSIONS: This is the first large study comparing the effect of AOA on ICSI cycles using sperm from different origin. The reason why, the oocytes injected with ejaculated and epididymal sperm were able to positively respond to AOA while those injected with testicular sperm could not, may be explained by a relation between sperm maturity and the function of oocyte activation. One such hypothesis would be that PLC-zeta is at a different concentration or is inactivated in immature sperm. In addition, AOA improved ICSI outcomes, only in oocytes derived from younger women, which suggests that the oocyte also plays a role in oocyte activation.