Neuroimmunology regulating reparative dentinogenesis

About This Grant

PROJECT SUMMARY/ABSTRACT Deep tooth injuries and inflammation affect millions of Americans, often progressing into pulp necrosis and treated by removing, i.e. devitalizing, and replacing the dental pulp tissue with artificial materials. Vital pulp therapies (VPTs) have the potential to promote cell signaling that stops the infection and restores pulp health, but their effectiveness is limited once pulpitis is established. This is largely due to the large gap in knowledge of what signaling cascades regulate the immune response to defend the pulp versus promote tertiary dentino- genesis to repair the damage. Studies have demonstrated that sensory axons sprout during infection and injury and communicate with immune and stem cell populations during tissue healing. Insights into how neurons pro- tect and enable dentin repair can therefore create therapeutic strategies that harness this axis to heal, rather than remove, the dental pulp tissue. The long-term goal of this project is to understand the cellular mecha- nisms that protect teeth via immune and mineralizing cell responses to inflammation and damage. The applica- tion objective is to determine the role of calcitonin gene-related peptide (CGRP) in activating immune and min- eralizing cells during tooth healing, i.e. reparative dentinogenesis. Our central hypothesis is that neuronal-de- rived CGRP regulates the function of neutrophils & monocytes, surviving odontoblasts and odontoblast progen- itors via its receptor, receptor activity modifying protein 1 (Ramp1), during reparative dentinogenesis. The ra- tionale for this project is that a detailed scientific framework of cellular crosstalk during reparative dentinogene- sis is likely to identify cell-specific mechanisms that sustain and enhance tooth health. The central hypothesis will be tested with the following specific aims: 1) Determine the cell-specific effects of CGRP signaling after deep dentin trauma; 2) Identify the role of CGRP signaling in regulating inflammation and subsequent tertiary dentinogenesis after direct pulp capping procedures; and 3) Evaluate the effect of increased RAMP1 expres- sion and/or exogenous CGRP on promoting pulp healing and homogeneous mineralized tissue barrier for- mation after direct pulp capping. In aim 1, direct pulp capping will be performed on mice with conditional dele- tions of the CGRP receptor, RAMP1, in immune or mineralizing cells. The dentin pulp complex will be analyzed throughout the healing period of 1-56 days for inflammatory and mineralization responses. For aim 2, a model of pulpal inflammation will be created with an initial shallow injury on molars with lipopolysaccharide applied. This will be drilled out and restored 24 hours later, followed by a similar timeline of investigations into pulpal responses. The last aim proposes to enhance RAMP1 and therefore the ability to respond to CGRP released during injury and inflammation to establish whether this can promote pulp healing and tissue barrier formation. The research proposed in this application is innovative because it provides a clinically relevant model of deep dentin damage and repair with which to study cell-specific repair mechanisms. The proposal is significant be- cause it is expected to identify cellular mechanisms that sustain tooth vitality to advance the development of next-generation VPTs.