RAGE, Receptor of Advanced Glycation Endoproducts, Negatively Regulates Chondrocytes Differentiation

RAGE, receptor for advanced glycation endoproducts (AGE), has been characterized as an activator of osteoclastgenesis. However, whether RAGE directly regulates chondrocyte proliferation and differentiation is unclear. Here, we show that RAGE has an inhibitory role in chondrocyte differentiation. RAGE expression was observed in chondrocytes from the prehypertrophic to hypertrophic regions. In cultured cells, overexpression of RAGE or dominant-negative-RAGE (DN-RAGE) demonstrated that RAGE inhibited cartilaginous matrix production, while DN-RAGE promoted production. Additionally, RAGE regulated Ihh and Col10a1 negatively but upregulated PTHrP receptor. Ihh promoter analysis and real-time PCR analysis suggested that downregulation of Cdxs was the key for RAGE-induced inhibition of chondrocyte differentiation. Overexpression of the NF-κB inhibitor I-κB-SR inhibited RAGE-induced NF-κB activation, but did not influence inhibition of cartilaginous matrix production by RAGE. The inhibitory action of RAGE was restored by the Rho family GTPases inhibitor Toxin B. Furthermore, inhibitory action on Ihh, Col10a1 and Cdxs was reproduced by constitutively active forms, L63RhoA, L61Rac, and L61Cdc42, but not by I-κB-SR. Cdx1 induced Ihh and Col10a1 expressions and directly interacted with Ihh promoter. Retinoic acid (RA) partially rescued the inhibitory action of RAGE. These data combined suggests that RAGE negatively regulates chondrocyte differentiation at the prehypertrophic stage by modulating NF-κB-independent and Rho family GTPases-dependent mechanisms.