Cellular Response to Expansion and Compression Forces in Mouse Midpalatal Suture and Surrounding Structures

Abstract

Objectives – To investigate the anatomy of the mouse palate, the midpalatal suture, and the cellular characteristics in the sutures before and immediately after midpalatal suture expansion, and as well as, to study the effects of compression force on the midpalatal suture.

Materials and Methods – Wild-type C57BL ⁄ 6 male mice, aged between 6 weeks and 12 months, were chosen for all the experiments. The complete palate of the non-operated group and the midpalatal suture-expanded or -compressed group at different ages was used for histological, micro-CT, immunohistochemistry, and sutural cell analyses. Animals in the experimental group for compression were subjected to palatal suture compression force by closing loops for the periods of 1, 3, 5, 7, 14, and 28 days.

Results – This study documents precise morphological and histological characteristics of the mouse palatal sutures. In addition to the opening of the midpalatal suture caused by expansion, both transverse and interpalatine sutures were also seen to be affected. Cellular density was decreased in different types of sutures following the application of expansion force. In respect to compression study, suture width, maxillary width, and bone volume to total volume were significantly decreased compared to control at 14 and 28 days following the application of compressive force. Compression force caused an increased cell apoptosis in midpalatal suture area. Osteoclast activity and expression of MMP-9 were increased, specifically on the nasal side.

Conclusions – The detailed morphology and histology of the mouse palate and the cellular changes that occur following midpalatal suture expansion or compression, as described here, will be helpful as a basis for further investigations of palatal suture tissue responses to mechanical force.