Dietary salt and myeloid NFAT5 (nuclear factor of activated T cells 5) impact on the number of bone-remodelling cells and frequency of root resorption during orthodontic tooth movement.

Purpose: The aim of the study was to investigate the impact of dietary salt and the osmoprotective transcription factor nuclear factor of activated T cells 5 (NFAT5) in myeloid cells on bone remodelling cells as osteocytes, osteoblasts and osteoclasts and on force-induced dental root resorptions in a mouse model.

Methods: Control mice and mice lacking myeloid NFAT5 (nuclear factor of activated T cells 5) were either kept on low, normal or high salt diets. After one week on the specified diet an elastic band was inserted between the first and second molar to induce orthodontic tooth movement. One week later the mice were euthanised and jaws were fixed for histological analysis. Osteocyte, osteoblast and osteoclast numbers as well as extent of root resorptions were assessed histologically.

Results: Osteocyte number was diminished with high salt diet in wildtype mice. Osteoblast numbers increased with low salt diet in control mice and reduced with high salt diet in mice without NFAT5 in myeloid cells. High salt diet tended to increase osteoclast number in control mice. In mice without myeloid NFAT5, numbers of osteoclasts were reduced under high salt diet. Frequency of force-induced root resorptions tended to be dependent on dietary salt content in control mice.

Conclusion: During orthodontic tooth movement dietary salt impacts on the frequency of root resorptions and the number of osteoclasts and osteoblasts in alveolar bone of mice. This can affect bone remodelling during orthodontic treatment. Myeloid NFAT5 impacts on this salt-dependent reaction.