Structural characteristics are crucial to the benefits of guar gum in experimental osteoarthritis

• The molar mass and viscosity of GG and sulfated GG are similar.
• Oxidized gum has similar molar mass but lower viscosity than GG.
• GG solution, but not sulfated or oxidized GG, provides analgesia.
• A GG solution protects from joint damage in experimental osteoarthritis.
• Viscosupplements act by pharmacological rather than rheological mechanisms.

Protein-free guar gum (DGG) was oxidized (DGGOX) or sulfated (DGGSU) by insertion of new groups in C-6 (manose) and C-6 (galactose), for DGGOX and DGGSU, respectively. Rats were subjected to anterior cruciate ligament transection (ACLT) of the knee, joint pain recorded using the articular incapacitation test, and the analgesic effect of intraarticular 100 μg DGG, DGGOX or DGGSU solutions at days 4–7 was evaluated. Other groups received DGG or saline weekly, from days 7 to 70 and joint damage assessed using histology and biochemistry as the chondroitin sulfate (CS) content of cartilage. The molar mass of CS samples was obtained by comparing their relative electrophoretic mobility to standard CS. DGG but not DGGOX or DGGSU significantly inhibited joint pain. DGG significantly reversed the increase in CS, its reduced electrophoretic mobility, and histological changes following ACLT, as compared to vehicle. Structural integrity accounts for DGG benefits in experimental osteoarthritis.

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