In vitro fertilization by intracytoplasmic sperm injection

Abstract

Intracytoplasmic sperm injection (ICSI) is the latest, and by far the most efficient, variant of micromanipulation-assisted fertilization, whereby a single spermatozoon is selected, aspirated into a microinjection needle and injected to the oocyte cytoplasm. The development of this technique is mainly linked to application in human assisted reproduction for which it enables fertilization with defective spermatozoa that would not otherwise be able to penetrate an oocyte by their proper means. Because ICSI by-passes many steps of the natural fertilization process, it offers an extremely interesting model for the study of basic mechanisms underlying fertilization. This is particularly true for oocyte activation, whose mechanism needs to be revisited in light of the current ICSI research. The massive application of ICSI in human infertility treatment also represents a huge laboratory in which the impact of different genetic and epigenetic anomalies of the male gamete on fertilization and embryonic development can be studied.

Increased disruption of sperm plasma membrane at sperm immobilization promotes dissociation of perinuclear theca from sperm chromatin after intracytoplasmic sperm injection in pigs

“…It has been proposed that sperm damage caused by sperm immobilization before injection promotes breakdown of intact sperm plasma membrane, which is required for the release of the sperm factors involved in oocyte activation (Swann et al 1994) and for the disassembly of the sperm nuclear envelope that allows access of cytoplasmic factors associated with decondensation of sperm chromatin during the ICSI procedure in humans (Dozortsev et al 1994, 1995, Tesarik & Mendoza 1999. Our results show that sperm heads of boars treated with piezo pulses were stained with membrane damage marker, eosin Y, faster than sperm heads treated by rubbing, suggesting that piezo pulses cause more severe damage to the sperm plasma membrane.…”

Cytogenetic analysis of human embryos and embryonic stem cells derived from monopronuclear zygotes

“…The frequencies of the occurrence of 1PN zygotes ranged from 1.6% to 7.7% [1]. The mechanism of 1PN zygotes has been extensively studied as: a) asynchrony of the pronuclear appearance [2][3][4] or b) the male and female pronuclear fusion together [5,6], which will result in chromosomally normal embryos; while c) androgenetic or gynogenetic parthenogenesis, which will lead to haploid embryos [7,8]. The embryos from normal fertilized 1PN zygotes and those chromosomally abnormal ones look so similar in morphological appearance that it is hard to distinguish between them [9], which blocks their clinical application.…”

Ectopic expression of a Chlamydomonas mt+-specific homeodomain protein in mt− gametes initiates zygote development without gamete fusion

“…The specific signals that initiate plant embryogenesis after gamete fusion, though, have not been identified (Harada 1999). In animals, gene transcription and zygote development can be initiated by introduction of sperm into intact eggs or somatic nuclei into enucleated eggs (Latham 1999;Tesarik and Mendoza 1999), but animal cloning is extremely inefficient (Wakayama and Yanagimachi 2001) and is associated with widespread gene dysregulation (Jaenisch and Wilmut 2001). Moreover, a full understanding of the molecular mechanisms essential for activation of animal zygote genes has remained elusive.…”