Small extracellular vesicles derived from auricular chondrocytes promote secretion of interleukin 10 in bone marrow M1-like macrophages.

INTRODUCTION: Elucidation of the paracrine interaction between chondrocytes and macrophages is useful for understanding the mechanisms of cartilage regeneration. Extracellular vesicles are granular substances with a diameter of approximately 150 nm, surrounded by a phospholipid bilayer membrane. In recent years, research has been conducted on clinical applications of extracellular vesicles. It has been shown that macrophages promote cartilage maturation, and macrophages acquire anti-inflammatory properties through cartilage, but the detailed mechanism of paracrine action involving extracellular vesicles remains unclear. Therefore, we focused on the effect of chondrocyte-derived extracellular vesicles on changes in macrophage characteristics. METHODS: Macrophages induced with granulocyte-macrophage colony stimulating factor (M1-like macrophages) and auricular chondrocytes were co-cultured using cell culture inserts and exosome inhibitors, and the expression of macrophage markers were analyzed. Next, extracellular vesicles separated from auricular chondrocytes were added to in vitro macrophage culture medium, and time-lapse observations of macrophage uptake of auricular chondrocyte-derived extracellular vesicles were performed. In addition, the effects of extracellular vesicles on the expression of macrophage markers were also analyzed. RESULTS: The expression of CD206, an M2 macrophage marker, was increased in macrophages due to the paracrine effect of chondrocytes, and CD206 expression was further increased by pharmacological inhibition of chondrocyte-derived exosomes. It was shown that chondrocyte-derived extracellular vesicles were taken up by macrophages and promoted the production of interleukin-10, an anti-inflammatory cytokine while reducing CD206 expression. CONCLUSIONS: Auricular chondrocyte-derived extracellular vesicles promoted the production of interleukin-10 in bone marrow M1-like macrophages but reduced CD206 expression.