Human sperm fertilizing potential in vitro is correlated with differential expression of a head-specific mannose-ligand receptor.

Objective To determine whether different patterns of surface expression of mannose-ligand binding sites are correlated with capacitation and predictive of the ability of human sperm to recognize and fertilize eggs in vitro. Design Analysis of motile sperm populations (from fertile donors, males presenting for routine semen analysis, and men undergoing IVF) before and after incubation in capacitating media. Setting Patients from an infertility practice at a major university hospital. Interventions None. Main Outcome Measures The mannose ligand-binding capacity of sperm populations were initially assayed by solid-phase mannosylated polyacrylamide bead binding studies. Sperm surface D-mannose binding sites thus detected were localized and visualized by fluorescence microscopy after reaction with a mannosylated fluorescein isothiocyanate-labeled neoglycoprotein probe. Results were correlated with acrosomal status, reproductive histories, and IVF outcomes. Results The percent of sperm with head-directed surface expression of a mannose-specific receptor was increased in fertile donors and males exhibiting normal fertilization in IVF after incubation in albumin-supplemented Ham's F-10 medium (GIBCO Laboratories, Grand Island, NY). In normospermie males exhibiting zona binding failure in IVF, mannose-specific receptor was observed over the head surface of few incubated sperm. Conclusions The appearance of D-mannose-ligand binding sites on the surface of heads of human spermatoza is associated with zona binding ability in IVF and is a putative determinant in human gamete recognition and fertilization.