Murine SPAM1 is secreted by the estrous uterus and oviduct in a form that can bind to sperm during capacitation: acquisition enhances hyaluronic acid-binding ability and cumulus dispersal efficiency

Area of Science:

• Reproductive Biology
• Sperm Physiology
• Glycobiology

Background:

• Epididymal sperm adhesion molecule 1 (SPAM1) is a surface hyaluronidase crucial for sperm maturation and cumulus dispersal.
• SPAM1 acquisition enhances sperm's cumulus dispersal efficiency, indicating its role in fertilization.

Purpose of the Study:

• To investigate the secretion and acquisition of SPAM1 in female reproductive tract fluids.
• To determine the functional significance of SPAM1 acquisition by sperm for fertilizing competence.

Main Methods:

• Incubation of sperm (wild-type and Spam1 null) in uterine and oviductal fluids (ULF/OF).
• Immunocytochemistry and flow cytometry to detect SPAM1 binding to sperm.
• Assays measuring hyaluronic acid binding and cumulus dispersal efficiency.

Main Results:

• SPAM1 is secreted in ULF/OF and can be acquired by sperm from these fluids.
• Acquired SPAM1 localizes to the sperm acrosome and mid-piece.
• SPAM1 acquisition significantly enhances sperm's hyaluronic acid-binding ability and cumulus dispersal efficiency.

Conclusions:

• Sperm acquire functional SPAM1 from uterine and oviductal fluids.
• Acquisition of SPAM1 from the female tract increases sperm fertilizing competence during capacitation.
• This process involves surface remodeling and acquisition of hyaluronidases for enhanced fertilization.