CTSL and rheumatoid arthritis: In addition, treatment of DEC1−/− CIA mice with LiCl, a known activator of the canonical Wnt/β-catenin signaling (55), reverses the improved RA phenotypes (Figs. 6B and S4) and the reduced expression of COX2, OB-cadherin, MMP7, CTSL, and RANKL in DEC1−/− CIA mice (Fig. 6, C and D).