Changes in aggrecan populations in experimental osteoarthritis

Area of Science:

• Biochemistry
• Orthopedics
• Rheumatology

Background:

• Adult articular cartilage has two aggrecan populations: larger, CS-rich and smaller, CS-poor.
• CS content decreases with aging, primarily due to reduced larger aggrecan proportion.
• Early osteoarthritis (OA) shows increased CS in cartilage.

Purpose of the Study:

• To investigate if increased CS-rich aggrecan contributes to elevated CS in OA cartilage.
• To test the hypothesis linking aggrecan changes to OA pathogenesis.

Main Methods:

• Experimental OA induced in dogs via anterior cruciate ligament transection.
• Proteoglycans extracted from articular cartilage at various time points.
• Aggrecan populations assessed using gel electrophoresis; CS quantified via hexuronate measurement.

Main Results:

• The proportion of CS-rich aggrecan increased over time post-surgery in all joint areas.
• This increase correlated with elevated tissue mass and hexuronate levels.
• The larger, CS-rich aggrecan form accumulates in OA cartilage.

Conclusions:

• Increased larger, CS-rich aggrecan contributes to elevated CS in early experimental OA.
• This finding is notable given increased protease activity observed in OA.
• Further research may elucidate mechanisms behind this paradoxical accumulation.