Upregulation of relaxin receptors in the PDL by biophysical force

Abstract

Objectives: We have previously reported that relaxin (Rln) expression from the ovary is upregulated by orthodontic tooth movement. This study was performed to test the hypothesis that Rln family peptides (Rxfps), the G-protein-coupled Rln receptor, is induced in periodontal ligament (PDL) cells to modulate the molecules involved in periodontal tissue remodeling while applying biophysical force.

Materials and methods: Rats were implanted with orthodontic appliances to investigate changes to Rxfps in vivo. An in vitro biophysical force analysis was performed to measure the level of Rxfp 1 messenger RNA (mRNA) in primary human PDL cells.

Results: The levels of Rxfp 2 transcription and translation increased in a time-dependent manner during tooth movement. Rxfp 2 was localized in the PDL by immunofluorescence. In vitro analyses revealed that the level of Rxfp 1 mRNA in PDL cells increased significantly with both compression and tension force. The levels of matrix metalloproteinase (MMP)-1, MMP-2, interleukin-6, and vascular endothelial growth factor mRNA, which are important for periodontal tissue remodeling, also changed under force application and Rln treatment.

Conclusions: PDL cells responded to Rln to modulate effector molecules for periodontal tissue remodeling by upregulating Rxfps expression under a biophysical force.

Clinical relevance: Rln and Rxfps may serve as a PDL turnover molecule complex to control orthodontic tooth movement.