Adipocytes-Derived Exosomal microRNA-1224 Inhibits M2 Macrophage Polarization in Obesity-Induced Adipose Tissue Inflammation via MSI2-Mediated Wnt/beta-Catenin Axis

Scope: Phenotypic switch of macrophage polarization in adipose tissue has been associated with obesity-induced adipose tissue inflammation (OATI). Therefore, this study aims to explore the possible mechanism of adipocytes-derived exosomes (ADEs) carrying microRNA-1224 (miR-1224) in M2 macrophage polarization of OATI. Methods and results: miR-1224-knockout (miR-1224-KO) mice for this study, and isolated primary adipocytes from high-fat diet (HFD) or normal diet (SD)-fed mice are developed. ADEs are extracted and cocultured with bone marrow-derived macrophages (BMDMs). The macrophagic crown-like structures (CLS) and M1 and M2 phenotype macrophages in epididymal white adipose tissue (epiWAT) are observed by immunohistochemistry and flow cytometry. The obtained data indicate that miR-1224 is highly expressed in adipose tissues and adipocytes of obese mice. miR-1224 knockout decreases CLS number and increases M2 macrophages polarization in epiWAT. In addition, miR-1224 can be transferred to BMDMs via ADEs, which targeted musashi RNA binding protein 2 (MSI2) expression and inactivated Wnt/beta-catenin pathway, inhibiting macrophage M2 polarization and promoting inflammatory factor release. Conclusion: Exosomal miR-1224 derived by adipocytes targets MSI2 and blocks the Wnt/beta-catenin pathway, which inhibits macrophage M2 polarization and promotes inflammatory factor release, ultimately promoting OATI.