Sperm acquire epididymis-derived proteins through epididymosomes.

Area of Science:

• Reproductive biology
• Spermatozoa maturation
• Extracellular vesicles

Background:

• Spermatozoa undergo significant proteomic changes during epididymal transit for maturation.
• Sperm cells, being transcriptionally and translationally inert, acquire necessary components from extracellular vesicles (EVs).
• Epididymal epithelial cells release EVs known as epididymosomes, which are implicated in sperm maturation.

Purpose of the Study:

• To investigate the role of epididymosomes in transferring proteins from the epididymis to spermatozoa.
• To characterize the contribution of epididymal secretions to the sperm proteome.
• To validate the epididymal origin of specific proteins found in spermatozoa.

Main Methods:

• Integrative analysis of human and mouse data to identify epididymis-specific sperm proteins.
• High-resolution confocal microscopy to validate protein localization in epididymal tissues and sperm.
• In vitro co-incubation of mouse epididymal sperm with CFSE-labeled epididymosomes.

Main Results:

• Identified 25 conserved sperm proteins of putative epididymal origin.
• Validated four proteins (SLC27A2, EDDM3B, KRT19, WFDC8) present in epididymal epithelial cells but not testicular tubules.
• Demonstrated in vitro interaction between epididymosomes and sperm, with 12-36% of epididymosomes containing targeted proteins.

Conclusions:

• Epididymosomes are key mediators of protein transfer to spermatozoa, influencing sperm proteome and maturation.
• Epididymal clear cells (CCs) play a significant role in epididymosome production.
• Understanding these mechanisms is crucial for male reproductive health and infertility treatments.