Abstract
- Background
Bone homeostasis is tightly maintained by a dynamic balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption. Increased osteoclast activity contributes to pathological conditions such as osteoporosis and periodontitis, while also driving physiological processes like orthodontic tooth movement ($\text{OTM}$). However, the precise molecular mechanisms by which mechanical orthodontic forces promote osteoclast differentiation and activity remain incompletely understood.
- Methods
In this study, human cord blood-derived monocytes ($\text{HMNCs}$) were subjected to static force loading across varied durations and magnitudes to evaluate osteoclastogenesis. Proteomic profiling was performed on $\text{HMNCs}$, force-subjected $\text{HMNCs}$, and mature osteoclasts using two-dimensional gel electrophoresis ($\text{2-DE}$) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry ($\text{MALDI-TOF-MS}$). Differentially expressed protein spots were identified, and the specific biological role of manganese superoxide dismutase ($\text{SOD2}$) in osteoclast differentiation and resorptive function was functionally evaluated.
- Results
Static force significantly promoted the differentiation of $\text{HMNCs}$ into functional osteoclasts in a time- and magnitude-dependent manner. Image analysis of 2-DE gels detected $549 \pm 13$, $612 \pm 19$, and $634 \pm 16$ distinct protein spots across un-stimulated $\text{HMNCs}$, force-treated $\text{HMNCs}$, and mature osteoclasts, respectively. Proteomic analysis identified five key differentially expressed proteins: plasminogen activator inhibitor 2 ($\text{PAI-2}$, Spot 1), peroxiredoxin-6 ($\text{PRD-6}$, Spot 3), manganese superoxide dismutase ($\text{SOD2}$, Spot 6), Rho GDP-dissociation inhibitor 2 ($\text{Rho-GDI2}$, Spot 11), and L-lactate dehydrogenase B chain ($\text{L-LDH}$, Spot 15). Functional assays confirmed that $\text{SOD2}$ is essential for maintaining monocyte differentiation into mature, functional osteoclasts.
- Conclusions
Static mechanical force drives osteoclast differentiation through distinct proteomic shifts. Manganese superoxide dismutase ($\text{SOD2}$) is required to sustain osteoclast differentiation and function under mechanical loading, representing a novel biological target for regulating the rate and efficiency of orthodontic tooth movement.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4306132/