High frequency of defective sperm-zona pellucida interaction in oligozoospermic infertile men.
BACKGROUND
The ability of sperm to interact with the zona pellucida (ZP) plays a critical role during the process of human fertilization. The aim of this study is to determine frequency of defective sperm-ZP interaction in oligozoospermic infertile men.


METHODS
Sperm-ZP binding assays and the ZP-induced acrosome reaction (AR) were performed in 72 infertile men with a sperm concentration <20 x 10(6)/ml. Oocytes that had previously failed to fertilize in a clinical IVF programme were used for the tests. Motile sperm (2 x 10(6)/ml) selected by swim-up from each semen sample were incubated with four oocytes for 2 h. The number of sperm bound per ZP and the ZP-induced AR were assessed. Under these conditions, an average of < or =40 sperm bound/ZP was defined as low sperm-ZP binding and a ZP-induced AR < or =16% was defined as low ZP-induced AR.


RESULTS
In the 72 oligozoospermic men, 28% (20/72) had low sperm-ZP binding. Of those with normal sperm-ZP binding, 69% (36/52) had low ZP-induced AR. Overall, 78% (56/72) had either low ZP-binding or normal ZP binding but low ZP-induced AR. This means that only 22% (16/72) had both normal sperm-ZP binding and normal ZP-induced AR.


CONCLUSIONS
Oligozoospermic men have a very high frequency of defective sperm-ZP interaction, consistent with their low natural fertility or low fertilization rate in conventional IVF. Infertile couples with oligozoospermic semen should be treated by ICSI rather than by conventional IVF.
Liu
De Yi
DY
University of Melbourne Department of Obstetrics and Gynaecology, Reproductive Services, Royal Women's Hospital and Melbourne IVF, Victoria 3035, Australia. dyl@unimelb.edu.au
Baker
H W Gordon
HW
D020101:Acrosome Reaction; D005260:Female; D006801:Humans; D008297:Male; D009845:Oligospermia / Q000503:physiopathology* / Q000628:therapy; D013076:Sperm Count; D020554:Sperm Injections, Intracytoplasmic; D013081:Sperm Motility; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology*; D015044:Zona Pellucida