Oocyte Activation Failure: Physiological and Clinical Aspects

Despite successful treatment of infertility with assisted reproductive technology (ART), total fertilization failure (TFF) after in vitro fertilization (IVF) and even after intracytoplasmic sperm injection (ICSI) still occurs. In the current chapter, the incidence and etiology of TFF after ICSI are described. The literature on physiology of oocyte activation, electrical properties of gametes’ membranes, and ion currents is reviewed. Calcium oscillations play an essential role in fertilization, and calcium ions act as secondary messengers in different metabolic pathways and cellular processes during oocyte activation. The contribution of oocyteand spermrelated causes of fertilization failure is discussed. Many studies on the physiology of fertilization in mammals have shown that oocyte activation is triggered by the sperm factor. Methods for artificial oocyte activation (AOA) try to bypass fertilization failure by influencing physiological processes that are crucial for successful fertilization. Activation can be induced with the use of electrical, mechanical, or chemical stimuli that elevate intracellular concentrations of calcium ions. Different AOA methods and their success and safety are presented.