CDK4 and rheumatoid arthritis: Among the treatment groups in RA-FLS, the effects of P38 inhibitor on the expression of cyclin D1 and CDK4 were equivalent to the PPARγ agonist (P > 0.05), while prior to the Shentong Zhuyu Decoction (P < 0.05) (Figures 4(c)–4(e)).