Artificial oocyte activation with calcium ionophore A23187 in intracytoplasmic sperm injection cycles using surgically retrieved spermatozoa

Abstract

OBJECTIVE: Recent reports have suggested that fertilization failure after intracytoplasmic sperm injection (ICSI) may be due to the inability of the spermatozoa to trigger oocyte activation which, is characterized by a rise in intracellular calcium concentration. Treatment with calcium ionophore may increase the free intracellular calcium, thereby mimicking physiological cell-signaling mechanisms resulting in oocyte activation. However, to date, there have been few studies using AOA in ICSI cycles with testicular or epididymal sperm, retrieved from patients with either obstructive (OA) or non-obstructive azoospermia (NOA). We evaluated the effect of AOA with the calcium ionophore A23187 on ICSI cycles using sperm surgically retrieved. DESIGN: Case-control study. MATERIALS AND METHODS: The study was performed on 204 couples undergoing surgical sperm retrieval for ICSI. The cycles were divided into three groups according to the origin of the sperm and the type of azoospermia: (i) testicle sperm of NOA patients, TEST-NOA (n=58) (ii) testicle sperm of OA patients, TEST-OA group (n=48), and (iii) epididymis sperm of obstructive OA, EPID-OA (n=98). For each experimental group, cycles in which AOA was applied (subgroup activation) were compared with cycles in which AOA was not applied (subgroup control). RESULTS: The subgroups were not statistically different for fertilization, high-quality embryos, implantation, or pregnancy rates when testicular sperm were retrieved from both types of azoospermia (TEST-NOA and TEST-OA groups). When epidydimal sperm were injected, we observed a significant increase in high-quality embryo rate when AOA was performed (64.8% vs 48.0%, p=0.045). However, no significant difference was observed in the other evaluated parameters. CONCLUSIONS: We have demonstrated for the first time that, when epidydimal sperm are injected, AOA is able to increase the high-quality embryo rate. The reason why AOA did not improve the outcomes of ICSI cycles using testicular sperm may be explained by the sperm maturity status. We suggest that although the increase of intracellular calcium can be induced by extra-physiologic stimulus, testicular spermatozoon is unable to maintain the calcium oscillations, which is the key event leading to fertilization and further embryonic development. In summary, our results demonstrated that AOA might be useful in improving ICSI outcomes in azoospermic patients when epididymal, but not testicular, sperm are injected, independently on the type of azoospermia.