Indoxyl sulfate accelerates vascular smooth muscle cell calcification via microRNA-29b dependent regulation of Wnt/beta-catenin signaling

Vascular calcification (VC) is a very common phenomenon in patients with chronic kidney disease(CKD) and it increases the incidence of cardiovascular disease and leads to high mortality in CKD patients. It has been reported that some microRNAs (miRs) play roles in vascular calcification as an epigenetic regulator. Indoxyl sulfate (IS) is a protein-bound uremic toxin which has been proven as one of the major risk factors of cardiovascular disease in CKD. Here we investigated whether microRNA-29b (miR-29b) is involved in IS-induced vascular calcification. We found that vascular miR-29b was down-regulated in radial arteries of patients with end-stage renal disease. Consistently, IS also decreased miR-29b expression in human aortic smooth muscle cells (HASMCs) and potentiated their calcification. MiR-29b mimics significantly suppressed, while miR-29b anti-miR markedly enhanced, IS-induced runt-related transcription factor 2 and osteopontin expression. The expression of Wnt7b/beta-catenin in radial arteries was higher in end stage renal disease than in control group, and IS increased Wnt7b/beta-catenin expression in HASMCs as early as 3 days after stimulation. Furthermore, miR-29b mimics potently repressed Wnt7b/beta-catenin protein expression in HASMCs, whereas miR-29b anti-miR increased their expression, indicating miR-29b indeed negatively regulates Wnt7b/beta-catenin signaling. Dickkopf-1 protein, the Wnt/beta-catenin signaling inhibitor, suppressed anti-miR-29b-enhanced HASMCs calcification. Our data thus indicate that miR-29b downregulation and Wnt/beta-catenin signaling activation may be the key mechanism of IS induced vascular calcification in chronic kidney disease.