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Human sperm fertilizing potential in vitro is correlated with differential expression of a head-specific
S Benoff1, G W Cooper, I Hurley
1North Shore University Hospital-Cornell University Medical College, Manhasset, New York 11030.
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 normospermic 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 spermatozoa is associated with zona binding ability in IVF and is a putative determinant in human gamete recognition and fertilization.