Hyaluronidase activity in human semen: correlation with fertilization in vitro.

OBJECTIVES

To characterize the relationship between hyaluronidase activity and the currently used methods of assessing sperm function and to determine whether the measurement of hyaluronidase activity can provide a reliable index of sperm fertilizing capacity in man.

DESIGN

Nonrandomized prospective study.

SETTING

Tertiary referral IVF and andrology clinics affiliated with the University of Toronto.

SUBJECTS

Four hundred eight samples were collected, 248 from men undergoing investigation in andrology and fertility clinics and 160 from men participating in an IVF program.

INTERVENTIONS

Semen samples were treated with NP-40 in buffer to extract hyaluronidase and applied to a circular well cut into a petri dish containing a mixture of hyaluronic acid and agar. Enzyme activity was assessed by measuring the area of substrate hydrolysis.

RESULTS

Significant positive correlations were found between hyaluronidase activity and sperm concentration, motility, and the percentage of sperm with normal morphology in the studied samples. In the IVF samples, hyaluronidase activity was found to be related significantly to the fertilization rate. Moreover, we were able to establish values of hyaluronidase below which no fertilization occurred and above which fertilization of at least one oocyte was achieved.

CONCLUSION

These results suggest that measurement of hyaluronidase activity may provide a useful method for assessing the integrity of the acrosomal enzyme system, providing a simple and reliable predictor of the fertilizing potential of human sperm.