Hum. Reprod. Advance Access originally published online on April 23, 2007
Human Reproduction 2007 22(7):1878-1884; doi:10.1093/humrep/dem087
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Comparison of the frequency of defective sperm–zona pellucida (ZP) binding and the ZP-induced acrosome reaction between subfertile men with normal and abnormal semen
1 Department of Obstetrics and Gynaecology, University of Melbourne, Royal Women's Hospital, 132, Grattan Street, Carlton, Victoria 3053, Australia 2 Reproductive Services, Royal Women's Hospital, 132, Grattan Street, Carlton, Victoria 3053, Australia 3 Melbourne IVF, 320 Victoria Parade, East Melbourne 3002, Australia
4 Correspondence address. Tel: +61-3-9344-2042; Fax: +61-3-9347-1761; E-mail: dyl{at}unimelb.edu.au
BACKGROUND: The aim of this study was to compare the frequency of defective sperm–zona pellucida (ZP) binding (DSZPB) and defective ZP-induced acrosome reaction (DZPIAR) in subfertile men (i.e. male partners of infertile couples) with normal and abnormal semen analyses.
METHODS: A total of 1030 subfertile men with normal semen analysis (n = 255), oligozoospermia (count < 20 x 106/ml, n = 136), severe teratozoospermia (strict normal morphology 
5%, n = 294) and mild-moderate teratozoospermia (morphology 6–14%, n = 345) were studied. Unfertilized oocytes from clinical in vitro fertilization/intracytoplasmic sperm injection were used for sperm–ZP interaction tests. After 2 h incubation of motile sperm with four oocytes, sperm tightly bound to the ZP, and the AR of ZP-bound sperm (ZPIAR) were assessed. An average of < 40 sperm bound/ZP and < 16% ZPIAR were used for diagnosis of DSZPB or DZPIAR.
RESULTS: For the groups of men with normal semen or mild-moderate teratozoospermia, severe teratozoospermia and oligozoospermia, the frequencies of DSZPB were: 13, 21, 29 and 28%, respectively, and in those normal SZPB, DZPIAR were 27, 36, 56 and 68%, respectively. Overall DSZPB and ZPIAR were 36, 49, 68 and 77% for the four groups, respectively. The highest frequencies of defective sperm–ZP interaction were in the oligozoospermia and severe teratozoospermia groups. In the normal and teratozoospermia groups, subjects with a relatively low sperm concentration (20–60 x 106/ml) had a significantly higher frequency of DZPIAR.
CONCLUSION: Defective sperm–ZP interaction is a major mechanism of male infertility. DZPIAR is more frequent than DSZPB in subfertile men with either normal or abnormal semen, suggesting that sequential sperm–ZP interaction tests are essential to detect these sperm defects.
Key words: male infertility/semen analysis/sperm–zona pellucida interaction
Submitted on December 11, 2006; resubmitted on March 4, 2007; accepted on March 6, 2007.