Sperm uptake of epididymal sperm adhesion molecule 1 (SPAM1)in vitrohas recently been shown to be a marker of sperm maturation, since acquisition of this surface hyaluronidase increases cumulus dispersal efficiency. Here, we demonstrate that this glycosyl phosphatidylinositol-linked sperm antigen, previously shown to be expressed during estrous in the female reproductive tract, is secreted in the uterine and oviductal fluids (ULF and OF respectively) in a 67 kDa form, which can bind to sperm. We show that it can be acquired by caudal sperm fromSpam1null,Spam1-deficient mutant, and wild-type (WT) micein vitroduring incubation in ULF or OF at 37 °C, as detected by immunocytochemistry and flow cytometry. SPAM1 binding after ULF incubation was localized predominantly to the acrosome and the mid-piece of the flagella ofSpam1null sperm in a pattern identical to that of WT sperm. After ULF incubation, WT sperm demonstrated a significantly (P<0.001) enhanced hyaluronic acid-binding ability, and the involvement of SPAM1 in this activity was shown by a significant (P<0.001) decrease in binding when sperm were exposed to SPAM1 antiserum-inhibited ULF. Importantly, whenSpam1null sperm were exposed to ULF with SPAM1 accessible (in the presence of pre-immune serum) or inaccessible (in the presence of SPAM1 antiserum) for uptake, there was a significant difference in cumulus dispersal efficiency. Taken together, these results suggest that in the sperm surface remodeling that occurs prior to and during capacitation, the fertilizing competence of sperm is increased via acquisition of SPAM1, and likely other hyaluronidases, from the female tract.
Is sperm hyaluronic acid binding ability predictive for clinical success of intracytoplasmic sperm injection: PICSI vs. ICSI?
