Bone morphogenetic protein-4 induced matrix turnover and osteogenic differentiation-related molecules of stem cells from apical papilla and its associated ALK/Smad signaling

Abstract

Background/purposeRevascularization procedures are used over apexification to treat teeth with necrotic pulp tissues and incomplete root formation. Clinically, inducing proliferation, migration, matrix deposition, and differentiation of stem cells from apical papilla (SCAPs) are critical for pulp regeneration. The study aimed to elucidate the impact of bone morphogenetic protein-4 (BMP-4) on plasminogen activation molecules and the osteogenic/odontogenic differentiation of SCAPs, as well as understand the related signaling mechanisms. Materials and methodsSCAPs were exposed to BMP-4 with or without signal transduction inhibitors. Cell viability was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. mRNA levels were quantified using real-time PCR. Protein expression in SCAPs was analyzed through immunofluorescent staining or western blotting. Cellular protein production was measured with enzyme-linked immunosorbent assay. ResultsBMP-4 induced suppressor of mother against decapentaplegic (Smad)1/5/8 and Smad2/3 phosphorylation and activation. It also promoted higher expression of osteogenic and odontogenic markers, including Osterix, N-cadherin, and secreted protein acidic and rich in cysteine (SPARC), in SCAPs. Additionally, BMP-4 stimulated connective tissue growth factor (CTGF), plasminogen activator inhibitor-1 (PAI-1), and urokinase plasminogen activator receptor (uPAR) expression, but inhibited uPA expression and production in SCAPs, indicating its role in matrix remodeling and cell migration. Inhibition of Smad2/3 with SB431542 and Smad1/5/8 with LDN193189 attenuated the BMP-4-induced expression Osx, N-cadherin, CTGF, SPARC, uPAR and PAI-1. ConclusionThese results indicate that BMP-4 stimulates the osteogenic and odontogenic differentiation of SCAPs by regulating matrix turnover and mineralization-related proteins. Furthermore, these processes are associated with the induction of Smad2/3 and Smad1/5/8 of SCAPs by BMP-4.