Lipid dynamics in boar sperm studied by advanced fluorescence imaging techniques

Area of Science:

• Sperm biology
• Membrane biophysics
• Lipidomics

Background:

• Sperm membrane reorganization is crucial for fertilization.
• Understanding sperm membrane physico-chemical properties requires advanced methods.
• Lipid organization within sperm membranes influences their function.

Purpose of the Study:

• To characterize fluorescent lipid analogs' behavior in boar sperm membranes.
• To investigate leaflet-specific membrane properties in acrosomal and postacrosomal regions.
• To compare different fluorescence microscopy techniques for membrane analysis.

Main Methods:

• Fluorescence Lifetime Imaging Microscopy (FLIM)
• Fluorescence Recovery After Photobleaching (FRAP)
• Fluorescence Correlation Spectroscopy (FCS)
• Utilized NBD-labeled sphingomyelin, phosphatidylserine, and cholesterol analogs.

Main Results:

• Fluorescence lifetimes indicate a liquid-disordered phase in sperm membranes.
• A more fluid microenvironment was observed in the postacrosomal region for NBD-cholesterol and NBD-phosphatidylserine.
• Evidence suggests subpopulations with varying diffusion velocities for NBD-sphingomyelin and NBD-phosphatidylserine in the postacrosomal region.

Conclusions:

• Fluorescent lipid analogs are suitable for probing sperm membrane physicochemical properties.
• The cytoplasmic leaflet of sperm membranes appears more fluid.
• Distinct membrane domains were not clearly identified, but lipid mobility differences exist between sperm regions.