STUDYING THE LANDSCAPE OF SMAD7 TARGETING MIRNAS REGULATED BY CALCIUM SILICATE PARTICLES

Abstract

Aim:- To identify the miRNAs which target Smad7 protein, and identify the mechanism of regulation of Smad7 targeting miRNAs by calcium silicate particles. Introduction:- Smad proteins are negative regulators of the bone morphogenic protein (BMP) and the transforming growth factor-β (TGF-β) signaling pathways. They are regulated by miRNAs which either promote or suppress their expression. Calcium silicate (CS) is an amorphous crystal used as a drug carrier and promoter in osteogeneration. Materials & Methods:- The list of miRNAs targeting Smad7 is predicted using an online miRNA database called miRDB. The potential positions or seed regions where the miRNA binds to Smad7 is identified using an online database TargetScan. Human osteoblast cells are treated with a conditioned medium which contains calcium silicate. The expression of Smad7 and hsa-miR-4524a-5p are studied in the osteoblast cells by real time polymerase chain reaction (real time PCR). Results:- The main miRNAs that target Smad7 — hsa-miR-4524a-5p and hsa-miR-4524b-5p — are upregulated by calcium silicate, which in turn leads to the downregulation of Smad7. This inhibits the expression of the TGF-beta-BMP pathway which plays a vital role in osteoclastic activity and bone remodeling. Discussion:- Smad7 stimulates the binding of Smad2 and Smad3 to Smad4 for their expression by the TGF-β-BMP pathway. The main miRNAs that target Smad7 are hsa-miR-4524a-5p and hsa-miR-4524b-5p. These miRNA are upregulated by calcium silicate, which in turn leads to the downregulation of Smad7. This inhibits the expression of the TGF-β-BMP pathway which plays a vital role in osteoclastic activity and bone remodeling. Thus bone formation and bone remodeling is enhanced. Conclusion:- By understanding the molecular mechanism of miRNA regulation, we have evaluated the osteogenic potential of calcium silicate. The significant elevation in hsa-miR-4524a-5p expression leading to the downregulation of Smad7 expression is responsible for the increased osteogenesis.