Elevated cross-talk between subchondral bone and cartilage in osteoarthritic joints

Area of Science:

• Orthopedics
• Rheumatology
• Biomedical Engineering

Background:

• Osteoarthritis (OA) is a leading cause of disability.
• Subchondral bone's role in OA pathogenesis is suspected but lacks direct evidence.
• Potential cross-talk between subchondral bone and articular cartilage is suggested by solute transport in normal joints.

Purpose of the Study:

• To test the hypothesis that increased cross-talk between subchondral bone and articular cartilage occurs in OA.
• To investigate changes in calcified cartilage and osteochondral interface permeability in OA models.
• To identify structural changes in subchondral bone and calcified cartilage associated with OA.

Main Methods:

• Utilized two OA models: ageing and destabilization of the medial meniscus (DMM).
• Quantified sodium fluorescein diffusivity in calcified joint matrix using fluorescence loss induced by photobleaching (FLIP).
• Assessed vascular invasion into calcified cartilage and measured subchondral bone and calcified cartilage layer thickness.

Main Results:

• No significant changes in tissue matrix permeability were detected in OA joints.
• Increased vascularization of calcified cartilage observed in both aged (+100%) and DMM (+50%) OA models.
• A 60% thinning of subchondral bone and calcified cartilage layers noted in aged OA joints.

Conclusions:

• Results suggest an elevated capacity for cross-talk between subchondral bone and articular cartilage in OA.
• Increased vascularization and bone thinning may contribute to OA development.
• Further research is needed to elucidate the directionality and molecular mediators of this cross-talk and its therapeutic potential.