The PEI/pGV-mascRNA complex was prepared by mixing in vivo-jetPEI with pGV-mascRNA at N/P ratio of 4 at which free pGV-mascRNA was no longer detectable (Fig. 4A). To assess the efficacy of mascRNA against RA, mice with collagen-induced arthritis (CIA) were intravenously injected with PEI/pGV-mascRNA complexes either alone or combined with peritoneally administered 5Z-7 10 days after a collagen boost (i.e. 31 days after arthritis induction on day 0). The CIA mice were randomly divided into four groups (n = 5 per group): no treatment group, plasmid control (pGV-NC) group, mascRNA-overexpressing plasmid (pGV-mascRNA) group, and pGV-mascRNA+5Z-7 group. The plasmid pGV-NC or pGV-mascRNA (20 μg per mouse) was formulated with in vivo-jetPEI at N/P ratio of 4 and intravenously injected into the mice on days 31, 38, and 45, respectively. 5Z-7-oxozeaenol (5Z-7) (1 mg/kg) was injected intraperitoneally on days 31, 35, 38, 42, 45 49 and 52. For stable transfection, RAW264.7 cells were transfected with pGV-mascRNA or empty vector (pGV-NC) by means of jetPEI-Macrophage (Polyplus, Cat# 103-05 N) according to the manufacturer’ instruction.