Relationship between localization of proteoglycans and induction of neurotrophic factors in mouse dental pulp

Abstract

ObjectivesDental pulp is composed of an odontoblastic layer, a subodontoblastic layer, and a central part. Although extracellular matrices affect the cells residing in these regions, the precise role of proteoglycans in dental pulp is incompletely understood. Hence, we investigated the immunolocalization of glucosaminoglycans, such as heparan sulfate and chondroitin sulfate, as well as core proteins of proteoglycans, such as perlecan and versican, in adult mouse dental pulp. MethodsLocalization of glucosaminoglycans and proteoglycans in dental pulp was evaluated immunohistochemically. Dental pulp cells cultured with or without fibroblast growth factor 2 (FGF2) and heparin were stained with Alizarin red S to visualize calcified nodules. Real-time PCR was used to assess the levels of gene expression of neurotrophic factors in cultured cells. ResultsHeparan sulfate and perlecan were mainly localized in the subodontoblastic layer, whereas chondroitin sulfate and versican were restricted to the center of dental pulp. Similar to perlecan, Erk1/2, a signaling transducer of FGF, was localized in the subodontoblastic layer. Moreover, we show that simultaneous treatment of cultured dental pulp cells with recombinant human FGF2 and heparin induced the expression of glial cell-derived neurotrophic factor (GDNF). ConclusionsThese data suggest that heparan sulfate proteoglycans, such as perlecan, enhance the expression of GDNF by facilitating FGF-induced Erk1/2 signaling in the subodontoblastic layer.