Abstract
The present study examined the expression of microRNA (miRNA or miR)-204 in pulp tissues, blood and saliva from pediatric patients with pulpitis and an underlying Helicobacter pylori (Hp) infection in the stomach, and the mechanism of the associated regulation by miR-204 was assessed. A total of 26 children with pulpitis who received tooth extraction at the Children's Hospital of Nanjing Medical University (Nanjing, China) between December 2014 and August 2016 were diagnosed with Hp infection in the stomach and included in the present study (HP+ group); furthermore, 19 children with pulpitis but without Hp infection in the stomach were enrolled as a control (HP- group). Pulp tissues, blood (serum) and saliva samples were collected from all subjects. Reverse-transcription quantitative polymerase chain reaction was used to determine the expression of miR-204 and matrix metalloproteinase 9 (MMP9) mRNA. Western blot analysis was performed to determine MMP9 protein expression in pulp tissues, while ELISA was performed to measure the contents of MMP9 in serum and saliva. A dual luciferase reporter assay was used to identify the direct interaction between miR-204 and its target protein. The results indicated that Hp infection in the stomach was associated with an upregulation of MMP9 mRNA and protein in pulp tissues, serum and saliva from children with pulpitis. Furthermore, the levels of miR-204 in pulp tissues, serum and saliva from children with pulpitis and Hp infection in the stomach were significantly reduced. miR-204 was confirmed to regulate the expression of MMP9 by directly binding with the 3'-untranslated region of MMP9 mRNA. The present study demonstrated that MMP9 expression in pulp tissues, blood and saliva from children with pulpitis and Hp infection in the stomach was upregulated, while miR-204 expression was downregulated. miR-204 may affect inflammatory processes and other oral diseases in children with pulpitis and Hp infection via MMP9, and may be a potential marker for the detection of Hp infection in children with pulpitis.