performed metabolic engineering editing of A‐MSC‐derived exosomes (EXOs) to produce dextran sulfate EXOs (DS‐EXOs) targeting macrophages in the RA joints (Figure6A).[111] After treatment with DS‐EXOs, inducible nitric oxide synthase (iNOS) expression in macrophages decreased, while CD206 expression increased significantly (Figure 6B,C), suggesting that exosomes promote the polarization of M1 into M2. Here, NOS2 is linked to rheumatoid arthritis.