[Effect of quercetin on bone formation in the mid-palatal suture of rats during rapid maxillary expansion].

Purpose: This study was aimed to investigate the effect of quercetin on rats' palatal suture during rapid maxillary expansion(RME).

Methods: Eighteen male 6-week-old（specific pathogen free，SPF） rats were randomly divided into 3 groups. Group A was control group, group B underwent expansion alone, and group C underwent expansion plus quercetin administration. Each group had 6 rats. Neither expansion nor quercetin was given to group A. Each rat in group B and C was set an orthodontic appliance with an initial expansive force (0.98 N). The rats in group C were administered with quercetin (100 mg/kg) at the same time every day after RME, while equal normal saline was given to rats in group A and B. Then the rats were sacrificed on day 14. Sections were cut perpendicular to the midpalatal suture and stained with hematoxylin and eosin (H-E) for observation of celluar response， and immunostained for evaluation of bone formation．The changes of collagen were observed through Masson's staining. Image-pro plus adhesive was used to analyze the slice absorbance, and SPSS19.0 software package was used to analyze the data.

Results: The results showed that small amount of fibrous tissue was found in the palate of group A, and there were chondrocytes, mesenchymal cells and osteoblasts. There were more fibrous tissues in the palate of group C, fibroblasts and cartilage cells increased, and osteoblasts were seen near the bone region of the palate. The number of osteoblasts in group C was significantly higher than that in group B, and there were new bone calcification deposits. The expression of BMP-2 in the midpalatal suture was significantly greater in group B than in group A at day 14 (P<0.01); the expression of BMP-2 in the midpalatal suture in group C was significantly greater than in group B (P<0.05).

Conclusions: Rapid maxillary expansion can enlarge the middle palatal suture of rats during growth and development, quercetin can promote the expression of BMP-2 in the middle palatal suture of rats during rapid maxillary expansion, make bone deposition and calcification, and accelerate new bone formation.