Gene ontology analysis of the TNF signaling pathway in early orthodontic tooth movement of rats with periodontitis

To investigate the expression and function of the TNF signaling pathway in the early stage of orthodontic tooth movement with periodontitis and to provide evidence to study the early inflammatory response in patients with periodontitis orthodontic treatment.

Sixteen SD rats were randomly divided into four groups: group A--12 h of orthodontic tooth movement of the bilateral maxillary first molars in rats with periodontitis; group B--periodontitis model of the bilateral maxillary first molars without orthodontic tooth movement; group C--12 h of orthodontic tooth movement of the same teeth in rats with healthy periodontium; group D--control group without operations. The bilateral maxillary first molars and surrounding periodontal tissue of each group were collected for gene chip detection. Pathway enrichment analysis, qRT-PCR and GO (gene ontology) analysis were performed to identify differential genes involved in the TNF signaling pathway.

Gene chip results showed that the TNF signaling pathway was significantly upregulated in group A, group B and group C (P < 0.01). Among the differential genes involved in the pathway, 28 were upregulated and 5 were downregulated in group A, 12 were upregulated and 4 were downregulated in group B, and 12 were upregulated and 1 was downregulated in group C (P < 0.05). The most significant GO items included "response to lipopolysaccharide", "inflammatory response", "positive regulation of NF-κB transcription factor activity", "positive regulation of NF-κB import into nucleus" and "response to hypoxia"(P < 0.001). qRT-PCR results showed no significant difference in TNF-α mRNA expression in group C compared with that in group D, TNF-α was upregulated in both groups A and B (P < 0.01), and mRNA expression decreased in the following order: group A > group B > group C (P < 0.05). Compared with group D, the expression levels of prostaglandin-endoperoxide synthase 2 (PTGS2) and interleukin-6 (IL-6) in groups A, B and C were significantly upregulated (P < 0.05), but the expression levels of PTGS2 and IL-6 in group A were lower than those in group B (P < 0.05).

The TNF signaling pathway is activated in the early stage of orthodontic tooth movement in rats with periodontitis. The pathway products participate in many biological processes and play an important role in the inflammatory response and bone absorption.