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.