Imbalance of Interleukin-17+ T-cell and Foxp3+ Regulatory T-cell Dynamics in Rat Periapical Lesions

Abstract Introduction Interleukin (IL)-17+ T-helper (Th17) cells and Foxp3+ regulatory T (Treg) cells are CD4+ T-helper cells with reciprocal functions in immunology and bone metabolism. The present study aimed to investigate the expression dynamics of Th17 and Treg cells in rat periapical lesions as well as their correlation with bone resorption. Methods Experimental pulp exposures were made in the lower first molars of 28 Wistar rats to induce periapical lesions. Rats were killed on days 0, 7, 21, and 35. Mandibles were prepared for micro–computed tomography scanning, histologic observation, immunohistochemistry, enzyme histochemistry, and double immunofluorescence analysis. Results Through 3-dimensional and 2-dimensional measurements, the volume and area of periapical lesions visibly increased from day 7 to day 21 and then expanded slowly between days 21 and 35. IL-17–positive cells markedly increased from day 7 to day 35. However, Foxp3-positive cells remained at low levels until day 21 and then dramatically increased by day 35. The IL-17+ /Foxp3+ ratio and number of osteoclasts simultaneously increased from day 7 to day 21 and then decreased on day 35. Finally, the distinct distribution of CD4+ /IL-17+ Th17 and CD4+ /Foxp3+ Treg cells was observed on days 7 and 35. Conclusions Our findings imply the imbalance of IL-17+ T cell and Foxp3+ Treg cell dynamics in induced periapical lesions, which may play an important role in periapical lesion progression.