The expression of stromal cell-derived factor 1 (SDF-1) in inflamed human dental pulp

Although dental pulp progenitor/stem cells (DPSCs) are indispensable for repair after pulpal injury, the mechanisms regulating their recruitment and activation remain unknown. To address this issue, we evaluated whether DPSCs in inflamed dental pulp had an upregulation of the chemokine system, a system of proteins known to regulate cellular responses to inflammation. Stromal cell-derived factor 1 (SDF-1), a member of the CXC chemokine subfamily and its receptor CXC chemokine receptor 4 (CXCR4), were evaluated in inflamed dental pulps obtained from extracted human teeth that showed spontaneous pain and/or lingering pain in response to cold and/or heat stimulus and compared with control levels found in normal dental pulps obtained from healthy noncarious third molars. Using immunohistochemistry and real-time reverse-transcription polymerase chain reaction, the results indicated that in inflamed pulps the SDF-1/CXCR4 axis was mostly distributed in inflammatory cells and microvascular endothelial cells rather than in normal pulps. SDF-1 messenger RNA expression levels in clinically inflamed dental pulp were higher than those in healthy dental pulp. These findings suggest that SDF-1 plays an important role in the process of pulpal inflammation via the recruitment of CXCR4-expressing inflammatory cells, and the SDF-1/CXCR4 axis may be involved in the recruitment of dental pulp stem cells at the injury site.