Histochemical localization of putative stem cells in irreversible pulpitis.

OBJECTIVES: Our study aimed to observe the distribution of putative stem cells in irreversible pulpitis and to investigate the expression of specific molecules. SUBJECTS AND METHODS: Extracted third molar teeth were collected and divided into two groups: the normal pulp group and inflamed pulp group. Real-time PCR was applied to detect the expression of several embryonic and dentinogenic genes. The expression of mesenchymal cell markers (STRO-1, CD90, and CD146) and stromal cell-derived factor 1alpha (SDF-1alpha)/CXC chemokine receptor 4 (CXCR4) proteins was examined by immunohistochemical analysis. RESULTS: The expression levels of most embryonic and dentinogenic genes were not statistically different between the two groups. Immunohistochemical analysis revealed that in inflamed pulp, cells with positive expression for STRO-1, CD90, and CD146 mainly resided in two specific niches, both adjacent to inflammatory sites: one in the pulp core and another in the odontoblast layer. SDF-1alpha- and CXCR4-positive cells were significantly correlated with STRO-1-positive cells. Double immunofluorescence analysis indicated that STRO-1-positive cells overlapped with SDF-1alpha- and CXCR4-positive cells near the inflammatory site. CONCLUSIONS: This study gave a direct observation of putative stem cells distributed in irreversible pulpitis and implied a role of SDF-1alpha/CXCR4 signaling in stem cell-based therapies for reparative dentinogenesis.