Abstract
This study examined the effects and mechanisms of strontium ranelate (SrRn)-a drug used to treat osteoporosis-on the proliferation and differentiation/mineralization of cloned dental pulp-like cells (mouse dental papillae cells; MDPs). It also determined whether topical application of SrRn to exposed dental pulp tissue promotes the formation of mineralized tissue in vivo. The MDPs were cultured with or without SrRn, and cell proliferation, odonto-/osteoblastic gene expression, mineralized nodule formation, and Akt phosphorylation were evaluated. The formation of mineralized tissue in SrRn-treated pulp tissue in rat upper first molars was evaluated histologically. The SrRn up-regulated cell proliferation and expression of Alp (alkaline phosphatase), Bsp (bone sialoprotein), Dmp (dentin matrix acidic phosphoprotein)-1, Dspp (dentin sialophosphoprotein), and Oc (osteocalcin) in a dose-dependent manner. Mineralized nodule formation was also enhanced by SrRn. NPS-2143, a calcium-sensing receptor (CaSR) antagonist, and siRNA against the CaSR gene blocked SrRn-induced proliferation, odonto-/osteoblastic gene expression, and mineralized nodule formation. SrRn induced Akt phosphorylation, and this was blocked by NPS-2143. Topical application of SrRn to exposed rat molar pulps induced the formation of osteodentin-like mineralized tissue. Our study revealed for the first time that SrRn promotes proliferation and odonto-/osteogenic differentiation/mineralization of MDPs via PI3K/Akt signaling activated by CaSR in vitro; mineralized tissue forms from the dental pulp in vivo.