The galectin-3/RAGE dyad modulates vascular osteogenesis in atherosclerosis

Abstract

Aims: Vascular calcification correlates with inflammation and plaque instabilityinadual manner, dependingon the spotty/granular (micro) or sheet-like/lamellated (macro) pattern of calcification. Modified lipoproteins trigger both inflammation and calcification via receptors for advanced lipoxidation/glycation endproducts (ALEs/AGEs). This study compared the roles of galectin-3 and receptor for AGEs (RAGE), two ALEs/AGEs-receptors with diverging effects on inflammation and bone metabolism, in the process of vascular calcification. Methods and results: We evaluated galectin-3 and RAGE expression/localization in 62 human carotid plaques and its relation to calcification pattern, plaque phenotype, and markers of inflammation and vascular osteogenesis; and the effect of galectin-3 ablation and/or exposure to an ALE/AGE on vascular smooth muscle cell (VSMC) osteogenic differentiation. While RAGE co-localized with inflammatory cells in unstable regions with microcalcification, galectin-3 was expressed also by VSMCs, especially in macrocalcified areas, whereit co-localized with alkaline phosphatase. Expression ofgalectin-3 and osteogen-ic markers was higher in macrocalcified plaques, whereas the opposite occurred for RAGE and inflammatory markers. Galectin-3-deficient VSMCs exhibited defective osteogenic differentiation, as shownbyaltered expression of osteogenic transcription factors and proteins, blunted activation of pro-osteoblastogenic Wnt/β-catenin signalling and proliferation, enhanced apoptosis, and disorganized mineralization. These abnormalities wereassociated with RAGE up-regulation, but were only in part prevented by RAGE silencing, and were partially mimicked orexacerbated by treatment with an AGE/ALE. Conclusion: These data indicate a novel molecular mechanism by which galectin-3 and RAGE modulate in divergent ways, not only inflammation, but also vascular osteogenesis, by modulating Wnt/β-catenin signalling, and independently of ALEs/AGEs. © The Author 2013.