Objective: To study the change of microRNA during the early stage of high phosphorus induced vascular smooth muscle cell (VSMC) calcification and its related mechanism.
Methods: The in vitro calcification model was created through stimulating VSMC cell line A7r5 with high Pi (2.6 mmol/L) for 7 d. The calcification was validated through ocresolphthalein complexone colorimetry to detect the cellular calcium content, real-time PCR to measure the calcification-related gene expression and alizarin red staining to observe the formation of calcium nodules. Based on the cell calcification model, microRNA microarray array was applied to screen the profiles of microRNA expression in VSMC following high Pi stimulation for different periods (0, 3 and 12 h). The array data were analyzed by TAM tool to explore the activated signaling pathway.
Results: The calcium content of A7r5 cells induced by high Pi was increased 9.6 times high as cells without Pi treatment (P<0.05). VSMC contractile phenotype genes (SM-α actin, SM22) were down-regulated (P<0.05), while calcification-related genes (BMP2, MSX2, Runx2) were up-regulated (P<0.05) in VSMC stimulated by high Pi. The calcium nodules were obviously formed in cells after 7 d high Pi treatment. In microarray experiment, 680 individual microRNAs were detected in high Pi-treated VSMCs at different time points (0, 3 and 12 h). Among these genes, miR-183, miR-664 and miR-9* were increased whereas miR-542-5P, let-7f and miR-29a were decreased in time-dependent manners. Twenty-six kinds of signaling pathways, including cell apoptosis, differentiation and proliferation, were significantly activated. All these activated pathways were associated with calcification.
Conclusion: This study implies that microRNA changed in high Pi-induced VSMCs may involve in the process of calcification.