Macrophage autophagy-dependent M2 polarization mediates the protective effect of ADSC-conditioned medium against acute lung injury

BACKGROUND: Adipose-derived mesenchymal stem cell conditioned medium (ADSC-CM) has emerged as a promising cell-free therapeutic strategy for acute lung injury (ALI). ADSC-CM's anti-inflammatory effect is closely related to its ability to regulate alveolar macrophage polarization. Furthermore, autophagy in macrophages is considered to be related to the regulation of polarization. However, the specific role and mechanisms by which ADSC-CM coordinates autophagy to guide macrophage polarization are not yet fully clear and urgently require further research. METHODS: We established an in vivo rat model of LPS-induced ALI to evaluate the ameliorative effects of ADSC-CM. Concurrently, an in vitro model utilizing NR8383 alveolar macrophages was employed to investigate the underlying mechanisms. A comprehensive suite of techniques, including ELISA, flow cytometry, immunohistochemistry, Western blot, and RT-qPCR, was applied for analysis. RESULT: In in vivo experiments, ADSC-CM treatment significantly alleviated LPS-induced pneumonia. In vitro experiments revealed that ADSC-CM enhanced the autophagic flux in NR8383 cells and effectively counteracted the promotion of LPS-driven M1 pro-inflammatory phenotypes, while inducing a shift toward M2 anti-inflammatory phenotypes. This beneficial polarization was proven to be dependent on autophagy, as it was significantly reduced when autophagy was inhibited. Mechanistically, autophagy mediated by ADSC-CM was shown to regulate the STAT1/STAT6 signaling pathway and influence HIF-1α expression. CONCLUSION: Our research results indicate that ADSC-CM alleviates ALI by targeting alveolar macrophages. Its protective mechanism involves enhancing autophagy activity, thereby promoting the polarization of macrophages towards the M2 phenotype through the regulation of STAT1/STAT6 and HIF-1α pathways. This study reveals the immunomodulatory role of ADSC-CM dependent on autophagy, highlighting its potential as an acellular therapeutic strategy for treating ALI.