Does ICSI require acrosomal disruption? An ultrastructural study.
BACKGROUND
Aggressive immobilization of sperm prior to ICSI significantly improves fertilization rates, but the mechanism of this effect is not yet clear. This study was performed in order to assess the characteristics of mechanically immobilized human sperm by transmission electron microscope (TEM).


METHODS
Sperm obtained from ejaculated semen samples from three different donors were immobilized in a standard manner for ICSI. They were then injected into the perivitelline space of mouse oocytes in order to be able to locate them by TEM. Intact motile sperm injected subzonally served as controls (n=160). Finally, the 'carrier' oocytes were fixed and processed for TEM.


RESULTS
A total of 300 sperm were mechanically immobilized and inserted into the perivitelline space of mouse oocytes. Ultrathin sections revealed consistent alterations in the acrosomal region including disruption of the plasma membrane, and disruption, vesiculation or even loss of the acrosome. Thus, all of the sperm assessed had undergone some disorganization of the head, in contrast to a majority of control sperm.


CONCLUSIONS
Immobilization of sperm for ICSI by compressing and rolling the sperm tails induces a variable disruption and sometimes loss of the acrosome. This could well be a reason for the higher success rates when ICSI is performed using immobilized sperm.
Takeuchi
Takumi
T
The Center for Reproductive Medicine and Infertility, Weill Medical College of Cornell University, 505 East 70th Street, HT-336, New York, NY 10021, USA.
Colombero
Liliana T
LT
Neri
Queenie V
QV
Rosenwaks
Zev
Z
Palermo
Gianpiero D
GD
D000177:Acrosome / Q000648:ultrastructure*; D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D005260:Female; D006801:Humans; D007103:Immobilization; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008854:Microscopy, Electron; D009865:Oocytes / Q000648:ultrastructure; D013077:Sperm Head / Q000648:ultrastructure; D020554:Sperm Injections, Intracytoplasmic; D013081:Sperm Motility