Resolvin E1 Actions on Axin2+ Dental Pulp Stem Cells in Experimental Pulpitis

Abstract

Background: Root canal therapy (RCT) is the primary treatment for irreversible pulpitis. While long-term success is common, RCT leads to tooth desiccation and increased root fracture necessitating tooth removal. The ideal therapeutic goal is dental pulp regeneration. Resolvins are specialized pro-resolving mediators (SPMs) derived from omega-3 fatty acids. Resolvin E1 (RvE1) has been shown to promote dental pulp repair, and Resolvin D2 (RvD2) ameliorated apical periodontitis in rat models. To further explore the potential of SPM therapy in pulp regeneration and treatment of pulpitis, we investigated the actions of RvE1 on experimentally exposed pulps with or without infection in a genetically defined mouse model.

Materials and methods: In lineage tracing experiments, 6 to 8-week-old Axin2Cre-Dox;Ai14 mice with exposed pulps were treated with topical RvE1 or ethanol in PBS (vehicle) immediately after pulp exposure (direct pulp capping) or after 24-hour exposure to the oral cavity and sealed with glass ionomer cement; the Cre recombinase was induced by doxycycline on the same day. The mice were sacrificed on days 7, 14, and 28 to track the fate of Axin2-tdTomato+ cells in the dental pulp. Mouse dental pulp stem cells (mDPSCs) were isolated and characterized using mesenchymal stem cell positive and negative markers, including CD90, CD146, CD34 and CD45, by flow cytometry analysis. The impact of RvE1 on cell proliferation and odontoblastic differentiation in inflammatory conditions was evaluated by Ki67-stain flow cytometry analysis, alizarin red staining and quantitative PCR. Wild-type mice were used for further investigation of RvE1 in infected pulps. Hematoxylin-eosin and gram staining were used to assess inflammation and severity of bacterial invasion in canals. Micro-CT and tartrate-resistant acid phosphatase were used to determine the development of apical periodontitis and osteoclastogenesis in periapical tissues, respectively.

Results: RvE1 promoted Axin2-tdTomato+ cell expansion and odontoblastic differentiation in a mouse direct pulp capping model. In vitro, RvE1 facilitated mDPSC proliferation, odontoblastic differentiation and rescued LPS-induced impairment effects. In 24-hour exposed infected pulps, RvE1 suppressed inflammatory infiltration and bacterial invasion in root canals. Furthermore, RvE1 prevented the development of apical periodontitis and reduced osteoclastogenesis in periapical tissues.

Conclusions: Topical treatment with RvE1 facilitates dental pulp regenerative properties, inflammation resolution, and reduces infection severity, further preventing apical periodontitis. The comprehensive benefits of RvE1 support further investigation into using RvE1 as a novel nonsurgical therapeutic option for treating endodontic diseases.