Electrical activation of the oocytes after intracytoplasmic sperm injection (ICSI) may aid in enhancing the rate of fertilization in patients with severe oligoasthenoteratospermia and nonobstructive azoospermia, according to a new research article published in the recent online issue of the journal Fertility and Sterility.
Dr Ragaa Mansour, Scientific Director of the Egyptian IVF-ET Center, Cairo, Egypt, and coworkers, conducted the study to assess the impact of electrical activation of oocytes in 246 patients with severe oligoasthenospermia or nonobstructive azoospermia. Patients with a history of failed or limited fertilization following the ICSI procedure were also included. During the study, the researchers randomized sibling oocytes after ICSI into two groups: the group subjected to the electroactivation (n=1,640) and a control group (n=1,435) not exposed to electroactivation. Electrostimulation was carried out with a double-square, direct-current pulse, following which the best available embryos were transferred.
The study results showed a significantly higher fertilization rate in the electrostimulated group when compared to the control group (68% vs 60%). The oocyte degeneration rate was almost similar in the two groups. Also, the study reported the occurrence of total fertilization failure in five cycles in the control group, and none in the electroactivated group.
Intracytoplasmic sperm injection, a micromanipulation technique that aids in circumventing severe male infertility, was first introduced into clinical practice in 1992 as a treatment strategy for certain types of infertility. In a previous study, Yanagida and colleagues (Human Reproduction, 1999) evaluated the oocyte activating ability of spermatozoa obtained from patients with a history of failed conventional ICSI procedure. The researchers conducted the study by electrically stimulating the occytes for around 30 minutes after ICSI. The combination of ICSI and electrical stimulation resulted in successful pregnancy with the delivery of healthy twins by a woman whose partner’s spermatozoa failed to fertilize the oocyte after conventional ICSI procedure. Based on the study results the researchers suggested the lack or deficiency in the spermatozoa’s capacity of activating oocyte, or oocytes’ inability to respond to the penetrated spermatozoa, as the possible reasons for the failure of fertilization in similar cases.
Oocyte activation, a series of events triggered by the penetrated spermatozoa, is crucial for the initiation of the embryonic development in natural fertilization. Several previous studies have identified an increase in the concentration of intracellular-free calcium as one of the initial events involved in the activation of occyte followed by the binding of the sperm to the oocyte plasma membrane. However, various procedures have been developed to artificially activate the oocytes as well as to induce the development of blastocyst. Studies have proposed that electrical stimulation activates the oocytes by inducing Ca2+ influx by forming pores in the plasma membrane.
Oocyte activation through electrical stimulation after ICSI, if proven through further larger clinical trials, may aid in resolving the fertility problems in patients with severe oligoasthenoteratospermia and nonobstructive azoospermia, and also in patients in whom conventional ICSI has failed.
1. Mansour R, Fahmy I, Tawab NA, et al. Electrical activation of oocytes after intracytoplasmic sperm injection: a controlled randomized study. Fertil Steril. 2008 Sep 29. [Epub ahead of print].
2. Yanagida K, Katayose H, Yazawa H, et al. Successful fertilization and pregnancy following ICSI and electrical oocyte activation. Hum Reprod. 1999 May;14(5):1307-11.