Calcium Ionophore Oocyte Activation in couples with Teratospermic partners undergoing Intracytoplasmic sperm Injection

Abstract

Intracytoplasmic sperm injection (ICSI) was introduced in 1992 to improve fertilization in couples with sever male factor infertility undergoing in vitro fertilization (IVF) or in couples with fertilization failure in a prior IVF cycle without detectable abnormalities of semen parameters, while the diagnostic criteria used to identify male factor infertility fail to predict with perfect accuracy poor or absent fertilization in assisted reproductive technology (ART). Studies to date support the safety and efficacy of ICSI to treat various male factor conditions. Fertilization failure still occurs in 2-3% of ICSI cycles. It was found that fertilization failure after ICSI may be explained by defects in oocyte, sperm, or ICSI procedure. Both sperm and oocyte factors are believed to be involved in failed oocyte activation after ICSI. Oocyte activation is an early event in fertilization. It caused by material in the sperm that is thought to induce calcium release from the endoplasmic reticulum and also from other structures of the oocyte. Cytologic analysis of failed fertilization of human oocytes after ICSI showed that more than half of the failed fertilized oocytes are due to oocyte activation failure. Therefore, in failed fertilized oocytes sperm may have a different status including intact, condensed head, partially to completely decondensed, and premature chromosomal condensation to metaphase arrest. Sperm nuclear chromatin decondensation failure has been related to sperm quality, a high rate of DNA fragmentation, and perhaps because of inadequate calcium activation, studies observed a correlation between the rate of DNA fragmentation and loss of oscilin activity. In addition, failed fertilization has also been attributed to acrosomal defects. Indeed, round-head spermatozoa (globozoospermia) lacking the acrosomal membrane and acrosin contents not only fails to penetrate oocytes but also if injected into an oocyte fails to initiate oocyte activation because of deficiency of sperm associated oocyte-activating factor related with acrosome and perinuclear theca. Based on initial obser¬vations showing that fertilization failure after ICSI can be overcome by subsequent treatment with a calcium mobilizing drug ,