Modeling Hypoxia Induced Factors to Treat Pulpal Inflammation and Drive Regeneration

Introduction: The ability to resolve pulpal inflammation to achieve predictable regeneration of the dentin-pulp complex has remained elusive and presents a challenge for clinicians and researchers. Although the dentin-pulp complex can react naturally to injury by forming a bridge of reparative dentin that protects the pulp from further damage, this process is significantly impaired if inflammation persists. Because the secretion of inflammatory cytokines by injured pulpal cells causes significant pain and discomfort to patients, it is critical to resolve pulpal inflammation in a timely manner so as to create a microenvironment conducive for pulpal healing and reparative dentin formation. The emergent field of regenerative endodontics has encouraged the development and application of biologically driven therapies that take advantage of the intrinsic healing capacities of host cells within dental pulp and the periapical complex.

Methods: These studies were designed to test the hypothesis that exposure to hypoxic conditions can modulate the production of inflammatory cytokines/factors by mesenchymal cells in vitro. A multi-domain peptide hydrogel system that is highly conducive for the growth and differentiation of tooth-derived stem cells was used for these studies. Stem cells from human exfoliated deciduous teeth (SHEDs) were first cultured within 3-dimensional hydrogel constructs and then challenged with hypoxic stresses via addition of H₂O₂.

Results: MDP constructs were successfully generated, challenged with H₂O₂, decellularized and lyophilized, forming a potential biomaterial containing hypoxia induced repair molecules. The ability of cell-derived factors to convert the phenotype of lipopolysaccharide-primed macrophages from a proinflammatory to a pro-resolving state was examined in the presence of the lyophilized SHED cell constructs.

Conclusions: Our data suggest that hypoxia induced SHED cell products can be captured within the hydrogel system and may be useful in the resolution of pulpal inflammation to create a favorable microenvironment for regeneration of the dentin-pulp complex.

Keywords: Cytokines; growth factors; in vitro culture model; peptide hydrogels; pulpal inflammation.