Role of transforming growth factor-β and extracellular regulated protein kinases in lipopolysaccharide-induced osteoblastic differentiation of porcine aortic valve interstitial cells

Abstract

Objective To investigate the role of transforming growth factor-β (TGF-β1) and extracellular regulated protein kinases (ERK) in lipopolysaccharide (LPS)-induced osteoblastic differentiation of porcine aortic valve interstitial cells (PVICs). Methods In vitro cultured PVICs were treated with LPS (4 μg/mL) to induce their osteogenic differentiation, and early and late osteogenic differentiation abilities of the cells were assessed using alkaline phosphatase (ALP) staining and Alizarin red S staining. The expression levels of Runx2, OPN and OCN mRNAs in the cells were detected using RT-qPCR, and those of TGF-β1, TGF-βR, Bax, Smad2/3 and ERK1/2 proteins were determined using Western blotting. Results In cultured PVICs, LPS treatment significantly increased alkaline phosphatase activity, deposition of calcium salts, and the expression levels of Runx2, OPN and OCN mRNA (P < 0.01). In addition to the increase of the expression of osteoblastic differentiation markers, the protein expression of TGF-β1, TGF-βR, Smad2/3 and ERK1/2 were also significantly increased in LPS-treated PVICs (P < 0.05); treatment with PD98059, a specific ERK1/2 inhibitor, significantly abolished LPS-induced increase in the protein expression of ERK1/2, Bax, and Runx2 (P < 0.05). Conclusion LPS induces osteoblastic differentiation of PVICs probably by activating TGF-β1/Smads and ERK signaling pathways.

Keywords

• calcific aortic valve disease
• valve interstitial cells
• osteogenic differentiation
• transforming growth factor-β1
• extracellular regulated protein kinases