Localization of pulp stem cells in chronic pulpitis

Abstract Background: Our study aimed to observe the distribution of stem cells in chronic pulpitis and to investigate the expression of specific molecules. Methods: Extracted third molar teeth were collected and divided into two groups. Experiment group was from patients with previous history of spontaneous pain and diagnosed as having chronic pulpitis. Noncarious third molars were used as control group. Dental pulp tissues were collected from these two groups. Real-time RT-PCR test was used to detect the expression of several embryonic and dentinogenic genes in dental pulp. The expression of the mesenchymal cell markers (STRO-1, CD146) and stromal cell-derived factor 1α (SDF-1α)/CXC chemokine receptor 4 (CXCR4) proteins were examined by immunohistochemical and triple immunofluorescence analysis. Results: ThemRNA levels of most embryonic and dentinogenic genes were not statistically different (p > 0.05) between the two groups. Immunohistochemical analysis revealed that in inflamed pulp, STRO-1- and CD146-positive cells mainly reside in two specific niches, both adjacent to inflammatory sites: one in the pulp core, and another in odontoblast layer. In contrast, fewer STRO-1- and CD146- positive cells appeared in the vicinity of the root apex. SDF-1α- and CXCR4-positive cells increased in zone I and II, and decreased in zone III, showing a significant correlation with STRO-1. Triple immunofluorescence analysis indicated that most STRO-1-positive cells overlapped with SDF-1α- and CXCR4-positive cells around the perivascular areas near the inflammatory site. Conclusions: This study gave a direct observation of stem cells distribution in chronic pulpitis for the first time and implies the important role of SDF-1α/CXCR4signaling in stem cells-based therapies for reparative dentinogenesis.