Heparan sulphate: a putative decondensing agent for human spermatozoa in vivo

BACKGROUND: Human sperm decondense in vitro upon exposure to heparin and glutathione. The aim of this study was to evaluate whether this decondensing ability of heparin in vitro is related to structural characteristics of the molecule and to test the in‐vitro decondensing ability of other glycosaminoglycans. METHODS: Capacitated sperm obtained from normospermic semen samples were decondensed in the presence of heparin (or its equivalent) and glutathione. After fixation with glutaraldehyde, the percentage of decondensed sperm was determined under phase contrast. RESULTS: The decondensing ability of heparin was related to sulphation characteristics of the molecule: heparin, O‐desulphated heparin and N‐desulphated‐N‐acetylated heparin had similar decondensing abilities; N‐desulphated was less active and O/N‐desulphated‐N‐acetylated heparin was completely inactive. On the other hand, the decondensing ability of heparin was not affected by molecular weight, within the range 3000–18 000 kDa. When the decondensing ability of different glycosaminoglycans was tested, heparin and heparin sulphate were equally active, while chondroitin sulphate and hyaluronic acid were completely inactive and dermatan sulphate was slightly active. CONCLUSIONS: Our results indicate that heparin’s decondensing ability in vitro is related to sulphation characteristics of the molecule and suggest that heparan sulphate, a structural analogue of heparin, could be a sperm‐decondensing agent in vivo.