Age-related changes in repair response are coupled to Wnt responsiveness of the pulp

Objectives: The purpose of this study was to clarify the molecular mechanisms controlling the depositing rate and differentiation features of dentin formation of dental pulp by age.
Methods: We used histology, immunohistochemistry and histomorphometric assays to examine dentin formation at young and aged mice. We employed two Wnt reporter mice to identify Wnt-responsive cells in dental pulp and lineage tracing those cells during aging. In addition, a strain of mice which has elevated Wnt signaling in DMP1 expression cells was used to uncover the role of Wnt signaling in odontoblasts and pre-odontoblasts.
Results: In this study, we found that dentin deposition rate declines with age. This decline is paralleled with a decrease of Wnt-responsive odontoblasts. We also found that enhanced Wnt signaling in odontoblasts converts the tubular dentin into osteodentin, indicating Wnt signaling regulates the rate of dentin secretion.
Conclusions: Our data suggested that the Wnt signaling regulates dentin formation and age-caused reduction of Wnt signaling is paralleled by a decline of dentin formation rate.