Abstract: Objective: To investigate the roles of autophagy in dental pulp injury and repair process by observing the changes of its expression after injury. Methods: Sixty 8-week-old male SD rats were exposed and directly capped on the first maxillary molars. Rats were sacrificed on days 1, 3, 7, and 14, dental pulp repair was detected with HE and Masson's trichrome staining. Inflammation markers TNF-α, CD68, and autophagy proteins LC3B and Beclin1 were detected by immunofluorescence staining. Damaged pulp tissue and dental pulp cells (DPCs) treated with LPS in vitro were extracted to detect the expression of inflammation, mineralization, and autophagy genes by real-time quantitate PCR. Results: Inflammation was increased gradually from 1st to 3rd day after operation, but no obvious inflammation was observed at 14th day. New collagen fibers were formed (P<0.05). Autophagy related proteins were mainly expressed on the cytoplasm and membrane of DPCs, odontoblasts, and vascular endothelial cells. The mRNA level of tissue showed that inflammatory markers IL-1β, CD68, and TNF-α were peaked at 3th day and then gradually decreased; the mineralization markers COL1, DSPP, and DMP1 were increased gradually after injury. LC3B and Atg5 reached the peak after 12 hours, decreased to the bottom after 24 hours, and then gradually increased; Atg12 and Beclin1 showed a trend of decreasing first and then increasing. The trend of mRNA in DPCs was consistent with pulp tissue (P<0.05). Conclusion: During the process of dental pulp injury and repair, autophagy participates in the development of pulp inflammation and promotes the repair of pulp tissue.

Key words: Autophagy, Pulp inflammation, Pulp repair