Zonal interdependence in the temporomandibular joint cartilage

Area of Science:

• Biomedical Engineering
• Cartilage Biology
• Dental Biomechanics

Background:

• Temporomandibular joint (TMJ) cartilage exhibits zonal arrangement with distinct cell differentiation.
• Understanding zonal interdependence is crucial for TMJ cartilage homeostasis.
• Dental biomechanical stimuli can significantly impact TMJ chondrocyte behavior.

Purpose of the Study:

• To investigate the functional interdependence of super and deep zones in TMJ cartilage.
• To analyze TMJ cartilage zonal responses to specific dental biomechanical stimulations.

Main Methods:

• Utilized genetically engineered mouse models (Sox9^CreER; Rosa26^tdTomato, Col10^CreER; Rosa26^tdTomato, Sox9^CreER; Rosa26^DTA, Col10^CreER; Rosa26^DTA) for cell labeling and ablation.
• Subjected mice to unilateral anterior crossbite (UAC) and bilateral anterior elevation (BAE) models.
• Assessed cell proliferation (Ki67), differentiation (Col-X, Osteocalcin), and anoikis (DAP3) markers.

Main Results:

• Sox9⁺ cells in the super zone showed proliferation and mature differentiation; Col10⁺ cells in the deep zone exhibited terminal differentiation.
• Selective ablation of Sox9⁺ or Col10⁺ cells led to reduced cartilage integrity, bone loss, and deformation.
• Cell ablation impaired TMJ chondrocyte responses to UAC (terminal differentiation) and BAE (proliferation), altering DAP3 expression.

Conclusions:

• TMJ cartilage zones function interdependently, with super zone cells differentiating towards deep zone characteristics.
• The deep zone's matrix is structurally essential for chondrocyte viability and function.
• Zonal interactions are critical for maintaining TMJ cartilage structure and responding to biomechanical stress.