New Insights Into Sperm Ultrastructure Through Enhanced Scanning Electron Microscopy.

Area of Science:

• Reproductive Biology
• Cellular Ultrastructure Analysis
• Microscopy Techniques

Background:

• Sperm morphology analysis is crucial for understanding male fertility and infertility.
• Scanning electron microscopy (SEM) is traditionally used for surface topology but is now vital for 3D ultrastructure analysis.
• High-quality sample preservation is essential for obtaining meaningful nanometer-scale SEM data.

Purpose of the Study:

• To develop robust protocols for sperm imaging using scanning electron microscopy (SEM).
• To leverage sperm's adherence to gold-coated surfaces for improved sample preparation.
• To enable detailed analysis of both external and internal sperm morphology, including 3D ultrastructure.

Main Methods:

• Demonstrated rapid and robust adherence of sperm to gold-coated surfaces.
• Developed three distinct protocols: chemically fixed monolayers for external morphology (SEM).
• Developed two high-pressure freezing-based protocols for internal morphology (fast SEM) and 3D ultrastructure (focused ion-beam SEM tomography).

Main Results:

• Successfully prepared sperm samples for various SEM imaging needs.
• Achieved detailed insights into mouse sperm ultrastructure.
• Identified novel structures within the fibrous sheath and domain-specific interactions between the plasma membrane and exosome-like structures.

Conclusions:

• The developed SEM protocols provide valuable tools for sperm analysis.
• These methods offer unprecedented insights into sperm ultrastructure, advancing our understanding of male gametes.
• The findings contribute to the study of male fertility and the etiological factors of infertility.