Effects of lactoferrin on bone resorption of midpalatal suture during rapid expansion in rats

•Lactoferrin does not inhibit osteoclastogenesis in the midpalatal suture during RPE. •Lactoferrin does not inhibit osteoclast-induced bone resorption during RPE. •Lactoferrin could prevent relative bone mineral density from declining during RPE. •Lactoferrin may improve the stability of maxillary expansion by promoting osteogenesis. Introduction The aim of this study was to investigate the effect of lactoferrin (LF) on bone resorption of rats' midpalatal sutures during rapid palatal expansion. Methods Sixty male 5-week-old Wistar rats were randomly divided into 3 groups: expansion only (EO), expansion plus LF (E + LF), and sham device (control). Results Microcomputed tomography showed that the bone volume/tissue volume ratio and the relative bone mineral density of the suture bone were significantly increased in the E + LF group compared with the EO group. Histochemical staining suggested that the activity of osteoblast-like cells and the amount of new bone formation were stimulated in the E + LF group whereas the activity of osteoclasts showed no obvious difference between groups. On the other hand, the immunohistochemical and the real-time polymerase chain reaction results showed that the expressions of receptor activator of nuclear factor kappa B ligand and osteoprotegerin had no significant difference between the EO and E + LF groups. Conclusions These findings demonstrated that LF could stimulate bone volume and bone density in midpalatal sutures during the suture remodeling process under tensile force. However, this enhancement effect was not caused by the reduction of bone resorption.