Artificial Oocyte Activation (AOA) Following Intracytoplasmic Sperm Injection (ICSI)

- Introduction

Intracytoplasmic sperm injection (ICSI) is a widely employed fertility treatment technique utilised in clinics worldwide. The process entails the meticulous selection of a solitary sperm cell and its direct injection into an egg cell, also known as an oocyte. For the past thirty years, a small number of highly trained and skilled embryologists specialising in assisted reproductive technologies have manually performed the complex ICSI procedure [1].

ICSI has shown to be highly effective, with fertilisation rates reaching up to 70%. However, a small percentage of cycles (1-5%) may encounter either complete failure of fertilisation or low fertilisation rates (<30%). This phenomenon emphasises the intricate nature of fertilisation and the influence of multiple factors on the outcomes of intracytoplasmic sperm injection (ICSI), which justifies the need for additional research to enhance protocols [2].

Oocyte activation deficiencies (OADs) have been identified as the main cause of total fertilisation failure (TFF) after ICSI. The deficiencies in question are multifactorial, meaning they can arise from various causes, such as inherent abnormalities in either the spermatozoon or the oocyte [2, 3].

Oocyte activation is a complex series of molecular events that occur when sperm enters the oocyte. This process leads to periodic releases of calcium from the endoplasmic reticulum [4-6]. Artificial oocyte activation (AOA) is a treatment that aims to trigger calcium release after ICSI artificially. This is done using different methods such as chemicals, mechanical means, or electrical stimulation [7]. Calcium ionophores, such as ionomycin and calcimycin, are frequently used chemical agents for AOA. They work by causing the release of calcium from the endoplasmic reticulum and promoting the entry of calcium from outside the cell [2, 3, 8]. AOA is primarily utilised in patients who experience fertilisation failure or a reduced fertilisation rate following ICSI.

Multiple studies have shown that AOA effectively enhances the fertilisation rate in such patients [9-12]. In addition, it has been discovered that augmented calcium signalling plays a vital role in causing changes in fertilised oocyte nuclei and cytoplasm. This process triggers oocyte activation and the initial stages of embryogenesis [7, 8]. Furthermore, evidence indicates that AOA may improve the growth and development of embryos [10, 13, 14]. This guideline aims to aid embryologists in making informed decisions regarding the performance of AOA procedures.