Hypoxic ASCs-derived Exosomes Attenuate Colitis by Regulating Macrophage Polarization via miR-216a-5p/HMGB1 Axis

Exosomes derived from mesenchymal stem cells have shown therapeutic effects for colitis. As a more clinically accessible resource, the therapeutic potential of exosomes from adipose-derived stem cells (ASCs) has not been fully elucidated, and whether hypoxia precondition could improve the therapeutic effect of ASC-derived exosomes in colitis remains elusive.

In this study, exosomes were derived from ASCs under normoxia (NExos) and hypoxia (HExos) and were identified by detecting their morphology, size distribution, and exosome surface markers. The concentration of inflammation-related cytokines was detected by ELISA, and macrophage phenotype-related genes were determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), western blot, and immunofluorescence. A miRNA microarray sequencing analysis was conducted to confirm the differentially expressed miRNAs. Dextran sulfate sodium-induced colitis was employed as an in vivo assay.

Administration of NExos alleviated inflammation by modulating the balance of macrophages both in cellular assays and in vivo experiments, and HExos showed higher therapeutic efficiency than NExos. The miR-216a-5p in HExos was significantly enriched and promoted macrophage M2 polarization through transfer to macrophages by exosomes. The miR-216a-5p was confirmed to target the 3'-UTR of HMGB1. Mechanistically, hypoxia-induced ASCs release miR-216a-5p in an exosomal way that induced macrophage M2 polarization by regulating the HMGB1/TLR4/NF-κB signaling pathway.

Exosomal miR-216a-5p released from hypoxia-prime ASCs showed higher therapeutic efficiency than NExos in experimental colitis by promoting the M2 macrophage phenotype, which indicated that hypoxia prime may represent a promising approach to optimizing the function of ASC-derived exosomes.