[Changes of α-SMA, type I and type III collagen in gingival tissue and expression of MMP-2 and TIMP-2 in gingival crevicular fluid under orthodontic force].

PURPOSE To investigate the changes of α-smooth muscle actin (α-SMA), type Ⅰ and type Ⅲ collagen in gingival tissue and expression of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-2 (TIMP-2) in gingival crevicular fluid under orthodontic force. METHODS Seventy-four patients undergoing orthodontic treatment in Affiliated Stomatological Hospital of Nanchang University from April 2018 to April 2019 were enrolled, and randomly divided into three groups. Group A(n=24) received the treatment under 0 g of orthodontic force, group B (n=25) under 75 g of orthodontic force, and group C(n=25) under 150 g of orthodontic force. At the baseline and 4th week of treatment, the expression levels of α-SMA, type I collagen and type Ⅲ collagen in gingival tissues were detected by immunohistochemical staining. At the baseline, the 2nd, and 4th week of treatment, the expression levels of MMP-2 and TIMP-2 in gingival crevicular fluid were detected by enzyme-linked immunosorbent assay. Then the correlation between different orthodontic force and levels of α-SMA, type Ⅰ collagen, type Ⅲ collagen, MMP-2 and TIMP-2 was analyzed using Spearman correlation analysis. Statistical analysis was completed by SPSS 19.0 software package. RESULTS At the 2nd and 4th week of treatment, the expression levels of MMP-2 and TIMP-2 in gingival crevicular fluid among three groups were the lowest in group A, followed by group B and group C(P<0.05). At the 4th week of treatment, the levels of α-SMA, type Ⅰ and type Ⅲ collagen in gingival tissues among three groups were the lowest in group A, followed by group B and group C(P<0.05). The orthodontic force was positively correlated with expression levels of α-SMA, type Ⅰ collagen, type Ⅲ collagen, MMP-2 and TIMP-2(P<0.05). CONCLUSIONS The expression levels of MMP-2 and TIMP-2 in gingival crevicular fluid and myofibroblast are related to the changes of orthodontic force, which may play an important role in the reconstruction of periodontal tissue during orthodontic treatment.