The role of endothelin B receptor in bone modelling during orthodontic tooth movement: a study on ET(B) knockout rats

The endothelin system has an important role in bone modelling during orthodontic tooth movement (OTM); however, little is known about the involvement of endothelin B receptors (ET(B)) in this process. The aim of this study was to evaluate the role of ET(B) in bone modelling during OTM using ET(B) knockout rats (ET(B)-KO). Thirty-two male rats were divided into 4 groups (n = 8 per group): the ET(B)-KO appliance group, ET(B)-KO control group, wild type (ET(B)-WT) appliance group, and ET(B)-WT control group. The appliance consisted of a super-elastic closed-coil spring placed between the first and second left maxillary molar and the incisors. Tooth movement was measured on days 0 and 35, and maxillary alveolar bone volume, osteoblast, and osteoclast volume were determined histomorphometrically on day 35 of OTM. Next, we determined the serum endothelin 1 (ET-1) level and gene expression levels of the osteoclast activity marker cathepsin K and osteoblast activity markers osteocalcin and dentin matrix acidic phosphoprotein 1 (DMP1) on day 35. The ET(B)-KO appliance group showed significantly lower osteoblast activity, diminished alveolar bone volume and less OTM than the ET(B)-WT appliance group. Our results showed that ET(B) is involved in bone modelling in the late stage of OTM.