Deciphering Platelets: Are They Cells or an Evolved Form of Extracellular Vesicles?

Abstract

Platelets are abundant in blood, where they maintain the integrity of the vasculature. Megakaryocytes, the cells responsible for platelet genesis, produce membrane protrusions from which as many as 5000 anucleate platelets can be released into the bloodstream. Platelets lack genomic DNA but contain different molecules, such as RNA, as well as organelles transmitted from the parent megakaryocyte. There is no consensus in the scientific community on whether platelets are cells or not: for example, they are sometimes called cells, small cells, anucleated cells, cell fragments, or megakaryocyte fragments. Extracellular vesicles are particles delimited by a lipid bilayer that are released from cells but cannot replicate on their own. Like platelets, extracellular vesicles lack a nucleus and carry components from their donor cell. Herein, we will explore various viewpoints suggesting that platelets may be cells, albeit not conventional cells, or may be a previously unrecognized type of extracellular vesicle. Beyond a mere debate over terminology, this perspective seeks to help properly define and classify platelets, aiming for better integration into the concept of either cells or extracellular vesicles. This will foster a clearer understanding and drive advances in platelet research.

Keywords: blood platelets; extracellular vesicles; megakaryocytes; organelles.