Abstract
Stem cells from apical papilla (SCAPs) are desirable sources of dentin regeneration. Epigallocatechin-3-gallate (EGCG), a natural component of green tea, shows potential in promoting the osteogenic differentiation of bone mesenchymal stem cells. However, whether EGCG regulates the odontogenic differentiation of SCAPs and how this occurs remain unknown. SCAPs from immature human third molars (16–20 years, n = 5) were treated with a medium containing different concentrations of EGCG or bone morphogenic protein 2 (BMP2), with or without LDN193189 (an inhibitor of the canonical BMP pathway). Cell proliferation and migration were analyzed using a CCK-8 assay and wound-healing assay, respectively. Osteo-/odontogenic differentiation was evaluated via alkaline phosphatase staining, alizarin red S staining, and the expression of osteo-/odontogenic markers using qPCR and Western blotting. We found that EGCG (1 or 10 μM) promoted the proliferation of SCAPs, increased alkaline phosphatase activity and mineral deposition, and upregulated the expression of osteo-/odontogenic markers including dentin sialophosphoprotein (Dspp), dentin matrix protein-1 (Dmp-1), bone sialoprotein (Bsp), and Type I collagen (Col1), along with the elevated expression of BMP2 and phosphorylation level of Smad1/5/9 (p < 0.01). EGCG at concentrations below 10 μM had no significant influence on cell migration. Moreover, EGCG-induced osteo-/odontogenic differentiation was significantly attenuated via LDN193189 treatment (p < 0.01). Furthermore, EGCG showed the ability to promote mineralization comparable with that of recombinant BMP2. Our study demonstrated that EGCG promotes the osteo-/odontogenic differentiation of SCAPs through the BMP–Smad signaling pathway.
Highlights
Irreversible pulpitis and pulp necrosis in developing teeth usually lead to the formation of nonvital pulp tissue and the ceasing of root development
We found that EGCG at concentrations of 0.1–100 μM showed no significant effect on the proliferation of SCAPs on day 1
In order to determine whether the BMP–Smad signaling pathway was affected by EGCG treatment, SCAPs were treated with EGCG for 0.25, 0.5, 1, 2, 6, 12, or 24 h, respectively. p-Smad1/5/9, the important effector of BMP–Smad signaling, was significantly upregulated in SCAPs after EGCG treatment for at least 0.5 h (Figure 5A). These findings indicate that the BMP–Smad signaling pathway may be the downstream mechanism involved in the EGCG-induced osteo-/odontogenic differentiation of SCAPs
Summary
Irreversible pulpitis and pulp necrosis in developing teeth usually lead to the formation of nonvital pulp tissue and the ceasing of root development. The emergence of regenerative endodontics provides a promising approach to treating these diseases [1,2,3]. Stem cells from apical papilla (SCAPs) are a population of cells existing in the root apex of the immature tooth, contributing to root dentin formation and root elongation during root maturation [4,5]. SCAPs exhibit great viability and potency of multipotent differentiation, including odontogenic, osteogenic, neurogenic, and adipogenic differentiation [6,7,8]. SCAPs, along with periodontal ligament stem cells (PDLSCs), can regenerate a bio-root with periodontal ligament in vivo [6]. SCAPs are considered to be desirable cell sources in regenerative dentistry
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