Exosome Biogenesis: Meta-Analysis of Intraluminal Vesicle Size Across Species

Area of Science:

• Cell Biology
• Extracellular Vesicles
• Microscopy

Background:

• Small extracellular vesicles (sEVs), including exosomes, are key in intercellular communication.
• The properties of intraluminal vesicles (ILVs), the precursors to sEVs, remain under-characterized across species and imaging techniques.
• Understanding ILV size is crucial for comprehending sEV biogenesis and function.

Purpose of the Study:

• To systematically evaluate the size of intraluminal vesicles (ILVs) across diverse eukaryotic species.
• To compare ILV sizes with the sizes of secreted small extracellular vesicles (sEVs).
• To establish the size range and upper limit of ILVs.

Main Methods:

• Conducted two complementary meta-analyses of ILV sizes using transmission electron microscopy (TEM) and cryogenic electron microscopy (cryo-EM) data.
• Performed in situ characterization of sEVs secreted by HEK293T cells using TEM, nanoparticle tracking analysis, and super-resolution microscopy.
• Analyzed data across multiple species and imaging modalities.

Main Results:

• ILV sizes were consistently found to be under approximately 200 nm across all evaluated species and imaging modalities.
• The mean diameter of ILVs was determined to be 100.5 nm.
• ILV size distribution overlaps significantly with the size range of secreted sEVs.

Conclusions:

• Intraluminal vesicles (ILVs) possess an upper size limit of approximately 200 nm.
• ILV size characteristics are conserved across diverse species and imaging techniques.
• This study fills a critical knowledge gap regarding ILV biophysical properties and their relationship to sEVs.