Abstract: Objective: To investigate the expression of Jak2/Stat3 pathway in induced rat inflammatory periapical lesions. Methods: Pulps of right mandibular first molars of twenty-five 8-week-old SD rats were exposed with PBS cotton ball. Then the molars were filled with glass ionomer and occulsal relationship was adjusted. The rats were then randomly sacrificed after 0, 7, 14, 21 and 28 days. The lower jaws were isolated and prepared for histologic, immunohistochemical, and enzyme histochemical analysis. Results: The model of apical periodontitis by PBS was successfully induced. The number of Jak2, Stat3, P-Jak2 and P-Stat3 positive cells was higher in periapical lesions compared with normal root apices (P＜0.05), and peaked at 14 days and decreased at 21 days (P＜0.05). On 28 days, the expressions of Stat3, P-Jak2 and P-Stat3 in the experimental group were almost the same as those of the control group (P＞0.05). However, the expression of Jak2 was still higher than that in the control group (P＜0.05). The formation of osteoclasts in the experimental group increased after 7 days, reached the maximum after 14 days and decreased after 21 and 28 days in contrast to that of the control group (P<0.05). The expression of Jak2/Stat3 was found synchronous with osteoclast formation. Conclusion: These findings suggest that Jak2/Stat3 pathway may play an important role in the periapical periodontitis and contribute to the initiation of periapical bone destruction.

Key words: Periapical, periodontitis, Stat3, Jak2