Joint-dependent response to impact and implications for post-traumatic osteoarthritis

Area of Science:

• Biomedical Engineering
• Orthopedics
• Cell Biology

Background:

• Osteoarthritis (OA) prevalence varies significantly across different joints.
• Most research on OA focuses on a single joint, typically the knee, with findings extrapolated to other joints.
• Limited studies compare mechanical properties and gene expression between different joint cartilages.

Purpose of the Study:

• To evaluate cartilage from eight equine joints to understand varying susceptibilities to post-traumatic OA (PTOA).
• To investigate differences in cell death and anabolic gene expression profiles in cartilage after injury.
• To provide evidence for developing joint-specific clinical treatments for OA.

Main Methods:

• Harvested adult equine cartilage explants from eight joints: shoulder, elbow, carpal, metacarpophalangeal, patellofemoral, tarsal, metatarsophalangeal, and proximal interphalangeal.
• Injured cartilage explants using a loading model (30 MPa within 1 second).
• Quantified fractional dissipated energy, cell density, cell death, and gene expression using multiphoton microscopy.

Main Results:

• Proximal interphalangeal joints exhibited the highest fractional dissipated energy (94%).
• Cell density was highest in the superficial zone, with metacarpophalangeal and metatarsophalangeal joints showing peak density.
• While overall cell death increased significantly after injury, it did not differ significantly between joints. Gene expression varied significantly between joints, with CD-RAP expression showing distinct patterns before and after injury, particularly in the patellofemoral joint.

Conclusions:

• Joint cartilage possesses distinct baseline characteristics (cell density, gene expression) and injury responses (energy dissipation, gene expression changes).
• These inherent differences contribute to variable OA prevalence and susceptibility to PTOA among joints.
• Understanding joint-specific responses to injury is crucial for developing targeted OA prevention and treatment strategies.