Reprogramming tumor-associated macrophages using exosomes from M1 macrophages.

Macrophages, abundant in tumors, are classified as M1 or M2 types with M2 dominating the tumor microenvironment. Shifting macrophages from M2 to M1 using exosomes is a promising intervention. The properties of exosomes depend on their source cells. M1-exosomes are expected to polarize macrophages towards M1 phenotype. We compared M1-exosomes and M0-exosomes' effects on M2 macrophage polarization. The RAW264.7 cells were cultured and one group of them was exposed to LPS. The serum-free medium was collected and exosomes were extracted. Exosomes were analyzed by scanning and transmission electron microscopy, dynamic light scattering and Western blot. Subsequently, M1 or M0 exosomes were applied to M2 macrophages induced by IL4. The macrophages polarization, including M1 and M2 genes and surface markers expression, cytokines secretion, and phagocytosis ability were evaluated. It was demonstrated that M1-exosomes induced macrophage polarization toward the M1 phenotype, characterized by an upregulation of M1-specific markers and a downregulation of M2 markers. Furthermore, the secretion of TNF-α was increased, while the secretion of IL-10 was decreased. The phagocytosis ability of M1-exosome-treated macrophages was also augmented. This research suggested that M1-exosomes might be promising candidates for modulating immune response in situations marked by an overabundance of M2 polarization, like in cancer.