Artificial oocyte activation: evidence for clinical readiness

Artificial oocyte activation using Ca(2+)ionophores or similar compounds is a widely applied technique in IVF laboratories. This is all the more interesting as most of the agents aiming for intracellular Ca2+ increase do not result in physiological Ca2+ oscillations but much rather cause a single Ca2+ transient. Two observations from mammals may explain why a rather non-physiological single Ca2+ peak caused by ionophores is sufficient to rescue cycles showing severe male factor infertility, deficient oocyte maturation, developmental problems in humans, or both. On the one hand, it has been shown that it is mainly the initial Ca2+ rise that drives further downstream events, in particular calcium/calmodulin-dependent protein kinase II (CaMKII) action, and on the other, it is possible that this enzyme remains active even in the absence of Ca2+. It therefore seems that mammalian oocytes can respond to a wide range of intracellular Ca2+ signals and have a surprisingly high degree of tolerance for changes in cytosolic Ca2+. As epigenetic consequences or differences in gene expression have not been studied to date, artificial oocyte activation has to be considered as experimental and should only be applied with a proper indication. (C) 2015 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.