Incorporation of the acrosome into the oocyte during intracytoplasmic sperm injection could be potentially hazardous to embryo development

Abstract

In mice and humans, a normal offspring can be obtained by injecting a single spermatozoon into an oocyte, the process called intracytoplasmic sperm injection (ICSI). When three or more mouse spermatozoa with intact acrosomes were injected into individual mouse oocytes, an increasing proportion of oocytes became deformed and lysed. Oocytes did not deform and lyse when acrosome-less spermatozoa were injected, regardless of the number of spermatozoa injected. Injection of more than four human spermatozoa into a mouse oocyte produced vacuole-like structures in each oocyte. This vacuolation did not happen when spermatozoa were freed from acrosomes before injection. Hamsters, cattle, and pigs have much larger acrosomes than the mouse or human. Injection of a single acrosome-intact hamster, bovine, and porcine spermatozoon deformed and lysed many or all mouse oocytes. This deformation did not happen when these spermatozoa were freed from acrosomes before ICSI, regardless of the number of spermatozoa injected. Because trypsin and hyaluronidase mimicked the action of acrosome-intact spermatozoa, it is likely that the acrosomal enzymes deform and lyse the oocytes. Injection of small amounts of trypsin and hyaluronidase into normally fertilized mouse eggs disturbed their pre-and postimplantation development. In view of potentially harmful effects of acrosomal enzymes on embryo development, the removal of acrosomes before ICSI is recommended for animals with large sperm acrosomes. The removal of acrosomes may increase the efficiency of ICSI in these animals. Although human and mouse spermatozoa do not need to be freed from acrosomes, the removal of acrosomes before ICSI is theoretically preferable. assisted fertilization ͉ bovine ͉ human ͉ mouse ͉ porcine

Chromosome analysis of mouse zygotes produced by intracytoplasmic injection of spermatozoa exposed to acrosome reaction inducing agents methyl-β-cyclodextrin and calcium ionophore A23187

“…These spermatozoal structures have been suggested to affect sperm chromatin remodeling in mice [2], pigs [3] and rhesus monkeys [4][5][6]. While injection of uncapacitated spermatozoa with intact acrosomes affects development of mouse ICSI embryos [7], simultaneous removal of the plasma membrane and acrosome before ICSI improves embryonic development [8]. Supportive evidence has been presented for the rat [9].…”

Pronuclear formation of freeze-dried canine spermatozoa microinjected into mouse oocytes

“…Mouse oocytes are hypersensitive to the acrosome enzyme in spermatozoa: mouse oocytes injected with acrosome-intact bull and boar spermatozoa or acrosomal enzyme(s) undergo deformation and never reach the 2-cell stage [37]. In our preliminary experiments, paternal nuclei in all of the deformed oocytes at 19-21 h after ICSI entered arrest at the time of decondensation or pronuclear formation.…”

Kinetics of human male pronuclear development in a heterologous ICSI model

“…Regardless, live offspring have been born using ICSI in a variety of species, including humans and mice [23]. However, existing reports on higher incidence of chromosome aberrations [24] and lower developmental potentials [25,26] in embryos produced by ICSI indicate that further evaluations on the effects of the incorporation of the acrosome into the oocyte are needed.…”