Mesenchymal stromal cells-extracellular vesicles: protein corona as a camouflage mechanism?

Mesenchymal stromal cells (MSCs) showed promising potential for regenerative and therapeutic applications for several pathologies and conditions. Their potential is mainly ascribed to the factors and extracellular vesicles (EVs) they release, which are now envisioned as cell-free therapeutics in cutting-edge clinical studies. A main cornerstone is the preferential uptake by target cells and tissues, in contrast to clearance by phagocytic cells or removal from circulation before reaching the final destination. Recent literature has suggested how the surface properties of EVs might influence their half-life, bio-distribution, and specific uptake. In particular, the concept of a protein corona surrounding EVs emerged. Especially for culture-purified EVs, the process of tailoring a treatment or tissue-specific corona was explored. Liam-Or et al. examined the impact of protein corona on MSC-EVs when specific proteins, preferentially albumin, were adsorbed from media on the EV surface before isolation. This resulted in improved uptake by liver parenchymal cells and reduced incorporation by macrophages, together with an increased half-life in the circulation system. Thus, producing MSC-EVs with an albumin-enriched protein corona might be a camouflage strategy to enhance non-phagocytic uptake in the liver. This research might be a milestone for future studies on other EVs-camouflage approaches tailored to specific tissues and therapeutic applications.