Abstract: BACKGROUND: Up to now, dental implant has become an important restoration for patients with tooth loss, and bone formation around dental implants is the key to the success of dental implantation. There is often a poor bone formation around dental implants under diabetic conditions and the mechanism remains unclear. Recent studies have shown that miR-203-3p regulates bone formation in different diseases, and strongly expressed in jaw bone tissues under diabetic conditions. However, it is unclear whether miR-203-3p can influence bone formation around dental implants.
OBJECTIVE: To investigate the effect of inhibiting miR-203-3p expression on bone formation around dental implants in diabetic mice.
METHODS: Twelve mice with normal blood glucose were randomly selected as normal group from forty-eight C57BL/6J mice. The other 36 mice were selected to make diabetic models and then randomly divided into diabetic group, diabetes+antago miR-NC group, and diabetes+antago miR-203-3p group (n=12 per group). Single implant was inserted into the left maxilla of each mouse. Diabetic+antago miR-NC group was injected with antago miR-203-3p negative control, antago miR-NC (0.25 mmol/L). Diabetes+antago miR-203-3p group was injected with antago miR-203-3p (0.25 mmol/L). The other two diabetic groups were injected with the equal volume of normal saline. After 3 months, the left maxillary bone tissue of mice was collected, and the bone formation around dental implants was detected using micro-CT and hematoxylin-eosin staining. qRT-PCR was used to detect the gene expression of miR-203-3p, Smad1, alkaline phosphatase, Runx2, Osterix, and type I collagen in bone tissue around dental implants.  
RESULTS AND CONCLUSION: Micro-CT results showed that compared with the diabetic group and diabetes+antago miR-NC group, the diabetes+antago miR-203-3p group showed better alveolar bone formation around dental implants and higher bone volume fraction and bone trabecular thickness (P < 0.05). Hematoxylin-eosin staining results showed that the Lane-Sandhu score of bone formation around dental implants was higher in the diabetes+antago miR-203-3p group than the diabetic group and the diabetes+antago miR-NC group (P < 0.05). qRT-PCR results showed that the expression level of miR-203-3p gene in bone tissue around dental implants was lower (P < 0.05), while the expression levels of Smad1, alkaline phosphatase, Runx2, Osterix, and type I collagen genes were higher in the diabetes+antago miR-203-3p group than the diabetic group and the diabetes+antago miR-NC group (P < 0.05). All these findings indicate that the inhibition of miR-203-3p expression is beneficial to bone formation around dental implants in diabetic hyperglycemia, and these effects may be related to the regulation of Smad signaling pathway and the expression of osteogenesis-related factors such as alkaline phosphatase, Runx2, Osterix, and type I collagen.

Key words: diabetes mellitus, miR -203-3p, implant, bone formation, mouse, Smad1, Runx2, Osterix, alkaline phosphatase, type I collagen