Aloe-emodin inhibits osteogenic differentiation and calcification of mouse vascular smooth muscle cells

Vascular calcification increases the risk of morbidity and mortality in patients with cardiovascular diseases, chronic kidney diseases, and diabetes. However, viable therapeutic methods to target vascular calcification are limited. Aloe-emodin (AE), an anthraquinone is a natural compound found in the leaves of Aloe-vera. In this study, we investigated the underlying mechanism of AE in the calcification of vascular smooth muscle cells (VSMCs) and murine thoracic aorta. We demonstrate that AE repressed not only the phenotypes of Ca²⁺ induced calcification but also level of calcium in VSMCs. AE has no effect on cell viability in VSMC cells. Alizarin red, von Kossa stainings and calcium quantification showed that Ca²⁺ induced vascular calcification is significantly decreased by AE in a concentration-dependent manner. In contrast, AE attenuated Ca²⁺ induced calcification through inhibiting osteoblast differentiation genes such as SMAD4, collagen 1α, osteopontin (OPN), Runt-related transcription factor (RUNX-2) and Osterix. AE also suppressed Ca²⁺ induced osteoblast-related protein expression including collagen 1α, bone morphogenic protein 2 (BMP-2), RUNX-2 and smooth muscle actin (SMA). Furthermore, Alizarin red, von Kossa stainings and calcium quantification showed that AE significantly inhibited the calcification of ex vivo ring formation in murine thoracic aorta, and markedly inhibited vitamin D₃ induced medial aorta calcification in vivo. Taken together, our findings suggest that AE may have therapeutic potential for the prevention of vascular calcification program.