An accurate, precise method for general labeling of extracellular vesicles

Area of Science:

• Cell Biology
• Biotechnology
• Immunology

Background:

• Extracellular vesicles (EVs), including microvesicles and exosomes, are crucial for intercellular communication.
• Current flow cytometry methods for EV detection using membrane stains or antibodies can misidentify cell debris and require knowledge of the cells EVs originate from.

Purpose of the Study:

• To evaluate calcein AM as a reliable fluorescent marker for detecting intact extracellular vesicles (EVs) using flow cytometry.
• To differentiate between intact EVs and cell debris, overcoming limitations of existing detection methods.

Main Methods:

• Utilized calcein AM, a fluorescent dye activated within intact EVs, for flow cytometry analysis.
• Compared calcein AM labeling with antibody and lipophilic membrane stain methods on intact and permeabilized/lysed EVs.

Main Results:

• Calcein AM becomes fluorescent and EV-impermeant only after entering intact EVs, enabling specific labeling.
• Intact EVs showed no labeling with antibodies or lipophilic stains when permeabilized/lysed, unlike calcein AM.
• Calcein AM successfully differentiated intact EVs from debris, a limitation of other methods.
• Demonstrated the utility of calcein AM for detecting intact EVs from diverse cell types.

Conclusions:

• Calcein AM is a suitable and reliable tool for the flow cytometric detection of intact extracellular vesicles.
• This method offers improved specificity by distinguishing EVs from cell debris, enhancing the accuracy of EV research.