We found that HUMSCs-Ex elevated M1 macrophage markers (IL-6, IL-12p40, iNOS) and inhibited M2 macrophage markers (IL-4, IL-10, Arg-1 and CD206) in a mouse model of scleroderma, thus suggesting that HUMSCs-Ex might play an antifibrotic role by regulating the M1/M2 macrophage balance. Here, ARG1 is linked to scleroderma.