Macrophage-derived Apoptotic Vesicles Regulate Fate Commitment of Mesenchymal Stem Cells Via MiR155

Background: In tissue engineering, mesenchymal stem cells (MSCs) are common seed cells because of abundant sources, strong proliferation ability and immunomodulatory function. Numerous researches have demonstrated that MSC-macrophage crosstalk played a key role in the tissue engineering. Macrophages could regulate the differentiation of MSCs via different molecular mechanisms, including extracellular vesicles. Apoptotic macrophages could generate large amounts of apoptotic vesicles (apoVs). ApoVs are rich in proteins, RNA (microRNAs, mRNAs, ncRNAs, etc.) and lipids, and are a key intercellular communication mediator that can exert different regulatory effects on recipient cells. MiRNAs account for about half of the total RNAs of extracellular vesicles, and play important roles in biological processes such as cell proliferation and differentiation, whereas the functions of macrophage-derived apoVs remain largely unknown. There was no research to clarify the role of macrophage-derived apoVs in MSC fate choices. In this study, we aimed to characterize macrophage-derived apoVs, and investigate the roles of macrophage-derived apoVs in the fate commitment of MSCs.

Methods: We characterized macrophage-derived apoVs, and investigated their role in MSC osteogenesis and adipogenesis in vitro and in vivo. Furthermore, we performed microRNA loss- and gain-of-function experiments and western blot to determine the molecular mechanism.

Results: Macrophages could produce a large number of apoVs after apoptosis. MSCs could uptake apoVs. Then, we found that macrophage-derived apoVs inhibited osteogenesis and promoted adipogenesis of MSCs in vitro and in vivo. In mechanism, apoVs were enriched for microRNA155 (miR155), and apoVs regulated osteogenesis and adipogenesis of MSCs by delivering miR155. Besides, miR155 regulated osteogenesis and adipogenesis of MSCs cultured with macrophage-derived apoVs via the SMAD2 signaling pathway.

Conclusions: Macrophage-derived apoVs could regulate the osteogenesis and adipogenesis of MSCs through delivering miR155, which provided novel insights for MSC-mediated tissue engineering.