Assisted oocyte activation

Assisted oocyte activation (AOA) is the technique that simulates the effect of sperm penetration into an oocyte inducing oocyte activation. This technique is used in combination with intracytoplasmic sperm injection (ICSI) to improve the outcome of the fertilization process. It is mostly beneficial and recommended in those cases, when classic ICSI fails. This accounts approximately up to 5 % of ICSI cycles. In most cases, the fail of ICSI is related to oocyte activation deficiency (the oocyte incapacity to continue development after fertilization). This may be due to morphologically altered sperm cells (teratozoospermia) which usually does not contain chemical substances necessary for induction of oocyte activation. This implies the use of other assisted reproduction techniques (ART) such as IMSI (morphologically selected sperm injection) prior to AOA itself. The AOA uses various methods to simulate the natural process of oocyte activation. Some assisted activation treatments such as Ca2+ (calcium)-ionophore, strontium chloride (vzorec) and ionomycin, promote an increase in intracellular free calcium concentrations by the release of calcium from cytoplasmic stores. Others such as electrical stimulus promote influx of calcium from the extracellular medium and some treatments such as ethanol promote both effects.