IDO1 and rheumatoid arthritis: In contrast, E-SF-MSCs in an RA joint-mimetic milieu with hypoxia and pro-inflammatory cytokines (h+/i+ E-SF-MSCs) exhibited senescence-related cellular effects, including increased apoptosis, telomere shortening, elevated β-galactosidase activity, attenuation of IDO activity, and inhibited PBMC proliferation, which were similar to observations made in non-treated L-SF-MSCs (h-/i- L-SF-MSC).