[The expression and significance of RORγT in periapical granulomas and radicular cysts]

To identify retinoic acid-related orphan nuclear receptor-γT (RORγT), the specific markers of T helper 17 (Th17) cells by immunohistochemical analysis to confirm the presence of Th17 cells in periapical lesions.

Eighteen radicular cysts (RCs) and 22 periapical granulomas (PGs) were collected in the Department of Oral Pathology after periapical surgery as the experimental samples. Five alveolar bone samples were obtained from a group of impacted third molars recommended for extraction as the control samples. The protein expression of RORγT was measured by immunohistochemical analysis for all samples. In addition, the protein expression of IL-17 was measured at the same time. Statistical analysis was performed using SPSS 17.0 software package to evaluate the differences of expression of RORγT and IL-17 according to type of lesion (PG vs. RC vs. control group) and intensity of the inflammatory infiltration (mild vs. moderate vs. severe vs. control group).

RORγT+ cells were detected in all periapical lesions tissues, and the expression of RORγT was significantly higher in periapical lesions than in normal tissues which had no expression of RORγT (P<0.05). Significant differences in the expression of RORγT were observed among healthy tissues, lesions with mild inflammation, moderate inflammation and severe inflammation (P<0.05), respectively. Positive correlations between RORγT and IL-17 protein levels were observed in PGs (r=0.935,P<0.05) and RCs (r=0.803,P<0.05), respectively.

The results demonstrates a significant increase in the expression of RORγT in patients suffering from periapical lesions in comparison with normal control subjects, indicating that Th17 cells are more likely to exist in periapical lesions.