[Assessment of human sperm function and clinical management of male infertility].

In this article, we provide an update review on the implication of the assessment of human sperm function and the management of male infertility in clinical assisted reproductive technology (ART) known as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). In most ART clinics, the assessment of male fertility is still mainly based on routine semen analysis but it is inaccurate in predicting sperm fertilizing ability. Thus it is often difficult to determine if IVF or ICSI will be an optimal treatment for patients in the initial cycle. Before introduction of ICSI, frequency of low ( <30%) fertilization rate in IVF was very high (20-35% of patients). Evidence suggests that sperm defects are the major contributors to complete failure of fertilization in IVF. Most common sperm defects are oligozoospermia, asthenozoospermia and teratozoospermia though many of the patients are shown to be normal in routine semen analysis. In the literature, many new sperm function tests have been developed, including sperm DNA normalities assessed by Acridine Orange (AO), sperm-zona pellucida (ZP) binding, the ZP-induced acrosome reaction (AR) , sperm-ZP penetration and recently hyaluronan binding assay (HBA). For routine semen analysis, sperm morphology is one of the most useful values for the prediction of sperm function but is also the most difficult test to perform accurately and consistently. Oocytes that failed to fertilize in clinical IVF/ICSI are valuable biological materials for testing sperm function. The human ZP selectively binds sperm with normal morphology and an intact acrosome. The ZP-induced AR is highly correlated with sperm-ZP penetration and disordered ZP-induced AR causes infertility in about 25% men with unexplained infertility with normal semen analysis. Both oligozoospermic (sperm count < 20 x 10(6) /ml) and severe teratozoospermia (strict normal sperm morphology < or =5%) men have a very high ( >70%) frequency of defective sperm-ZP interaction. Thus patients with defects of sperm-ZP interaction should be identified and treated with ICSI since they have high risk of low or zero fertilization rate in IVF. HBA test highly correlates with sperm motility and normal morphology but provides no additional information about sperm fertility. Clinical value of sperm DNA normalities detected by AO for the prediction of ART outcomes is currently still inconclusive and requires further investigation. In conclusion, addition of some of these new sperm tests to routine semen analysis could significantly improve the management of male infertility in clinical ART.