miRNA‐21 deficiency impairs alveolar socket healing in mice

BACKGROUND: MicroRNAs (miRNAs) are small noncoding RNAs demonstrated as critical post‐transcriptional modulators in dental tissues and bone regeneration, particularly miR‐21‐5p. However, the role of miR‐21‐5p in the healing of alveolar sockets following tooth extraction remains unknown. In this study we evaluated the influence of miR‐21‐5p in the healing of alveolar socket after tooth extraction. METHODS: Eight miR‐21‐5p knockout mice and eight littermate controls underwent tooth extraction of the upper right incisor. After a healing period of 14 days microCT and histological analyses were performed. RESULTS: MicroCT analysis showed that the percentage of bone in the extraction socket was significantly higher in the control group than in the miR‐21 knockout mice; either in the coronal (39.0%, CI 31.8 to 48.0 versus 23.0%, CI 17.8 to 35.2, P = 0.03) or in the middle part of the alveolar socket (56.0%, CI 50.9 to 62.5 versus 43.5% CI 28.6 to 54.6, P = 0.03). These differences were not noted in the apical part of the extraction socket. Histological analysis supported the microCT findings. Newly bone volume per tissue volume (BV/TV) was significantly higher in the control group when compared to miR‐21 knockout mice, 27.4% (CI 20.6 to 32.9) versus 19.0% (CI 14.7 to 21.5, P < 0.05), respectively. Surprisingly, no evident signs of buccal bone resorption were observed in both groups. CONCLUSION: Despite the limitation of one observation period, these findings suggest that miR‐21‐5p delays the early healing of alveolar socket following tooth extraction. Whether miR‐21‐5p is essential for healing of alveolar sockets remains to be elucidated.