[Exosomes from folic acid-treated subpatellar fat pad-derived mesenchymal stem cells promote M2 polarization of macrophages in vitro].

OBJECTIVES: To evaluate the effect of exosomes derived from folic acid (FA)-treated infrapatellar fat pad mesenchymal stem cells (IPFP-MSCs) on M1 and M2 polarization of macrophages in vitro. METHODS: Infrapatellar fat pad tissues were obtained from surgical patients without knee osteoarthritis to isolate IPFP-MSCs. The exosomes were extracted from the cell cultures with or without FA treatment and identified by transmission electron microscopy, TEM, NTA and Western blotting. RAW264.7 cells were induced with lipopolysaccharide (LPS) and incubated with exosomes from FA-treated or untreated IPFP-MSCs for 12 h, and Exos uptake was observed using confocal microscopy. The changes in expression levels of IL-1β, IL-6, TNF-α, iNOS, ARG1, MRC1, and CD206 in the macrophages were detected using qRT-PCR, ELISA, flow cytometry and immunofluorescence staining. RESULTS: The exosomes derived from IPFP-MSCs showed a typical cup shape, were positive for CD9 and CD81, and could be uptaken by macrophages. In LPS-induced macrophages, incubation with exosomes from FA-treated IPFP-MSCs significantly decreased the expressions of IL-1β, IL-6, TNF‑α, and NOS2, and increased the expressions of ARG1 and MRC1. Treatment of the macrophages with exosomes from FA-treated IPFP-MSCs significantly lowered CD86-positive cell percentage, increased CD206-positive cells and the CD206/CD86 ratio, lowered cellular expression of iNOS, and enhanced the expression of CD206. CONCLUSIONS: Exosomes from FA-treated IPFP-MSCs promotes M2 polarization of macrophages more effectively than exosomes from unmodified IPFP-MSCs, suggesting a new exosome modification strategy for targeted treatment of knee osteoarthritis.