To investigate the effects of all-trans retinoic acid (ATRA) on arthritis and the expressions of inflammatory cytokines and cartilage damage related proteases of the collagen-induced arthritis model (CIA) rats 
The CIA model of rheumatoid arthritis was induced with C2 and incomplete Freund's adjuvant. The rats were randomly divided into control group, CIA model group and two ATRA dose groups (ATRA 0.50 mg/kg group and ATRA 1.00 mg/kg group). ATRA were given three times per week for six weeks in ATRA groups. Morphological changes, arthritis index (AI) scores, the semi-quantitative scores of pathology damage, the protein expressions of cartilage damage related proteases and the serum levels of TNF-α, IL-17A, IFN-γ, IL-4, IL-10 were observed.
The AI scores of ATRA groups were similar to CIA model group ( 
ATRA, which was able to inhibit pro-inflammatory cytokines secretion, could correct the imbalance of Th1/Th2 and Th17/Treg. ATRA also can reduce the expressions of cartilage damage related proteases, which proved that ATRA may have a beneficial effect on rheumatoid arthritis.