Electrical activation of the Oocytes

Intracytoplasmic sperm injection (ICSI) has become the most effective therapeutic treatment for male-factor infertility

However, total failure of fertilization still occurs in some cases, teratozoospermia , immotile spermatozoa , and even in some  unexplained cases .

The failure of fertilization after ICSI may result from either the lack or deficiency of activating factors in spermatozoa or may result from the inability of the oocyte to respond to the injected sperm.

Because the spermatozoa is injected inside the ooplasm, failure of division most probably is the result of the failure of oocyte activation.  The key event of oocyte activation is a temporal rise in the intracellular Ca²⁺ concentration.

Electro activation of the oocyte results in a rapid rise in Ca²⁺ inside the oocyte, which decreases gradually to the original level in about 300 seconds. it was demonstrated that oocyte activation enabled normal fertilization and pregnancy 

It has been reported that about 70%–80% of unfertilized oocytes after ICSI responded to electro activation.

Oocytes that fail to fertilize by 24 hours after ICSI can resume apparently normal fertilization and early embryonic development in response to electrical stimulation. Moreover, the degree of cytoplasmic activation as determined by the number of pulses applied affects fertilization efficiency and early embryonic development.

electrical stimulation resulted in a significant improvement in the fertilization rate after ICSI, in cases with previous total failure of fertilization or limited fertilization and in cases of oligoasthenoteratospermia and nonobstructive azoospermia.

What is an oocyte activation defect?

 At fertilization, oocyte activation is triggered by sperm (releasing calcium in specific patterns within the oocyte). A deficiency in this process underlies most cases of fertilization failure

How does egg activation occur?

The activation of all eggs appears to depend on an increase in the concentration of free calcium ions within the egg. Such an increase can occur in two ways: calcium ions can enter the egg from outside, or calcium ions can be released from the endoplasmic reticulum within the egg.

Dr Najeeb Layyous F.R.C.O.G

Consultant Obstetrician, Gynecologist and Infertility Specialist