Matrix Vesicles Versus Exosomes: A Comparative Study on Their Ability to Promote Growth Plate Mineralization and...

Pathological calcification of soft tissues is a hallmark of several diseases, including cardiovascular disorders and osteoarthritis. Macrocalcifications formed under pathological conditions share key features with physiological endochondral ossification. The initiation and progression of pathological calcification involve the transdifferentiation of resident soft-tissue cells into chondrocyte-like cells, which subsequently undergo hypertrophy. These hypertrophic cells release extracellular vesicles, including small-sized vesicles (exosomes, EXOs) and a specialized class of matrix-bound extracellular vesicles known as matrix vesicles (MVs). Previous studies have demonstrated that EXOs and MVs derived from the same mineralizing cells differ in lipid and protein composition, as well as in biological function.

In this study, we investigated the biochemical and physicochemical properties of EXOs and MVs, with particular emphasis on the role of the protein corona in modulating MVs mineralization capacity and collagen-binding ability. EXOs were directly purified from the extracellular medium, while MVs were isolated from a murine vascular smooth muscle cell line using enzymatic treatment. These vesicles were compared with those obtained from chondrocytes. To assess the contribution of the protein corona, MVs were treated with a high-ionic-strength buffer to remove surface-associated proteins, generating shaved matrix vesicles (SMVs).

EXOs, MVs, and SMVs displayed distinct electrophoretic protein profiles. Modulation of tissue-nonspecific alkaline phosphatase activity and turbidimetry assays indicated that SMVs retain mineralization capacity but exhibit delayed kinetics and reduced efficiency compared with native MVs.

These findings demonstrate that the protein corona plays a critical role in regulating MVs functionality, particularly by modulating mineralization efficiency and matrix interactions. This study establishes a versatile two-cell model platform for investigating pathological calcification and provides mechanistic insights into the regulation of hypertrophic chondrocyte-like cells, supporting the development of targeted therapeutic strategies.