To determine whether mandibular condylar cartilage degradation induced by experimentally abnormal occlusion could be ameliorated via systemic administration of strontium or NBD peptide.
Six-week-old female C57BL/6J mice were used. From the seventh day after mock operation or unilateral anterior crossbite (UAC) treatment, the control and UAC mice were further respectively pharmacologically treated for 2 weeks or 4 weeks of saline (CON + Saline and UAC + Saline groups), SrCl2 (CON + SrCl2 and UAC + SrCl2 groups) or NBD peptide (CON + NBD peptide and UAC + NBD peptide groups). Changes in condylar cartilage and subchondral bone were assessed 21 and 35 days after mock operation or UAC procedure by histology and micro-CT. Real-time PCR and/or immunohistochemistry (IHC) were performed to evaluate changes in expression levels of col2a1, aggrecan, ADAMTS-5, tnf-α, il-1β, nfkbia, nuclear factor-kappaB phospho-p65 in condylar cartilage, and rankl/rank/opg in both condylar cartilage and subchondral bone.
Cartilage degradation with decreased col2a1 and aggrecan expression, and increased ADAMTS-5, tnf-α/il1-β, nfkbia and NF-κB phospho-p65 was observed in UAC + Saline groups. Subchondral bone loss with increased osteoclast numbers and decreased opg/rankl ratio was found in UAC + Saline groups compared to age-match CON + Saline groups. Cartilage degradation and subchondral bone loss were reversed by treatment of SrCl2 or NBD peptide while the same dosage in control mice induced few changes in condylar cartilage and subchondral bone.
The results demonstrate reverse effect of systemic administration of strontium or NBD peptide on UAC-induced condylar cartilage degradation and subchondral bone loss.