Dental Pulp Cell Conditioning through Polyinosinic-Polycytidylic Acid Activation of Toll-like Receptor 3 for Amplification of Trophic Factors.

INTRODUCTION

Regeneration of the pulp-dentin complex hinges on functionally diverse growth factors, cytokines, chemokines, signaling molecules, and other secreted factors collectively referred to as trophic factors. The delivery of exogenous factors and the induced release of endogenous dentin-bound factors by conditioning agents have been explored toward these goals. The aim of this study was to investigate a promising regeneration strategy based on the conditioning of dental pulp cells (DPCs) with polyinosinic-polycytidylic acid (poly[I:C]) for the amplification of endogenous trophic factors.

METHODS

DPCs were isolated from human dental pulps, propagated in culture, and treated with an optimized dose of poly(I:C). The 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide assay and metabolite analysis were conducted to monitor the cytotoxicity of poly(I:C). Enzyme-linked immunosorbent assays and quantitative polymerase chain reaction assays were performed to quantify the induction of trophic factors in response to DPC conditioning. Statistical significance was P < .05.

RESULTS

The analysis of 32 trophic factors involved in Wnt signaling, cell migration and chemotaxis, cell proliferation and differentiation, extracellular matrix remodeling and angiogenesis, and immunoregulation revealed that DPCs abundantly express many trophic factors including AMF, BDNF, BMP2, FGF1, FGF2, FGF5, HGF, MCP1, NGF, SDF1, TGFβ1, TIMP1, TIMP2, TIMP3, and VEGFA, many of which were further induced by DPC conditioning; induction was significant for BDNF, EGF, HGF, LIF, MCP1, SDF1, IL6, IL11, MMP9, and TIMP1. Both DPC proliferation and lactate production (P < .05) were inhibited by 8 μg/mL poly(I:C) relative to the control.

CONCLUSIONS

In vitro DPC conditioning through poly(I:C) activation of toll-like receptor 3 led to the amplification of trophic factors involved in tissue repair. The strategy offers promise for endodontic regeneration and tooth repair and warrants further investigation.