Human sperm-oocyte recognition and infertility

The incidence of infertility related to both male and female factors continues to rise despite many advances in reproductive technologies. Some abnormalities in human gamete interaction have been shown to be due to defects in the sperm, and others have been attributed to defects in the zona pellucida (ZP). Our lack of understanding of molecular mechanisms involved in the interaction of human sperm with the ZP in fertile as compared with infertile females and males has been limited because of the unavailability of human oocytes and ethical restraints on experimental studies. It is becoming increasingly apparent that improved clinical assays are necessary for evaluating sperm-ZP interaction in order to assess the optimal procedures for successful fertilization and pregnancy. With advances in molecular biology, the genes encoding the three major human ZP proteins have been identified and complementary DNAs are available to begin to better evaluate the molecular basis of sperm-ZP interaction.