Targeting the AMPK pathway to enhance dentin repair with novel metformin-releasing dental cements

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PROJECT SUMMARY The normal structure and function of the dentin-pulp complex in adult permanent teeth can be affected by the exposure of a vital pulp following deep caries removal, traumatic injuries, or accidental restorative procedures. To stimulate dentin repair, preserve pulp vitality and avoid more invasive and costly procedures, vital pulp therapy relies on direct pulp-capping agents. These are mainly composed of inorganic hydraulic calcium-silicate cements, where mineral trioxide aggregate (MTA) is often considered the gold standard. Despite its well-accepted therapeutic value, it remains unclear which specific underlying signaling mechanisms orchestrate reparative dentinogenesis through the differentiation of dental pulp stem cells (DPSCs) into odontoblast-like cells. Also, common drawbacks associated with MTA include long setting times and high cost. Thus, enhancing dentin repair through novel, substantially more affordable bioactive formulations with improved physico-mechanical properties that molecularly target the pulp cells responsible for its synthesis could translate into truly beneficial and highly cost-effective therapeutic outcomes. We provide the first evidence supporting the development of a novel biomaterial formulated with calcium phosphate cement/chitosan (CPCC) and metformin (Met), that triggered a significant upregulation in the expression of odontoblastic differentiation markers and mineral synthesis in DPSCs. Met is a widely used, safe and low-cost oral anti-diabetic biguanide drug, and potent activator of the AMP-activated protein kinase (AMPK) signaling pathway, a master sensing mechanism of cellular bioenergetics. These promising preliminary data imply that Met could be safely repurposed within locally delivered formulations to enhance reparative dentin by molecularly targeting AMPK. In the proposed studies, we seek to maximize dentin repair by developing a new Met-CPCC pulp-capping agent with similar mechanical and flowability properties like MTA but with a substantial, several folds of reduction in setting time and cost. This innovative formulation relies on Met to induce AMPK activation and odontoblastic differentiation in DPSCs, and CPCC to provide the alkaline, ionic building blocks for hydroxyapatite formation. To that end, we will test the central hypothesis that dentin repair following vital pulp exposure is significantly potentiated by a Met-releasing CPCC bioactive pulp-capping agent through AMPK activation and delivery of mineralized tissue-building ions. In vitro and in vivo studies will expand our initial findings through two specific aims. Aim 1 will test the hypothesis that in DPSCs, a novel Met-CPCC pulp-capping agent induces odontogenic responses in an AMPK-dependent manner. In Aim 2, we will test the hypothesis that Met-CPCC pulp-capping agent significantly enhances dentin repair and increases the hardness and elastic modulus of new dentin in a rat dentin injury model with pulp exposure in vivo. The long-term goal of this proposal is to potentiate reparative dentinogenesis with novel biologically active Met-containing dental materials targeting AMPK activation, yielding new mechanisms and improved treatments that are widely applicable to restorative and regenerative dentistry.