Osteoarthritis has a major impact on pain and athleticism of horses, and many medications are used to combat it. At the 2007 American Association of Equine Practitioners Convention, held Dec. 1-5 in Orlando, Fla., an in vitro study comparing commercial preparations of hyaluronic acid (HA, Hylartin V) and the corticosteroid triamcinolone acetate (TA, Vetalog), in terms of two measures of joint health, were presented. Elysia Schaefer, DVM, a graduate student and second-year equine surgery resident at the University of Illinois, presented the study results.

"Hyaluronic acid is an important component of cartilage that helps maintain hydrostatic pressures to resist weight-bearing forces," she explained. "Corticosteroids inhibit the production of inflammatory mediators (some of which can break down cartilage) and leukotrienes (which sustain inflammatory reactions), which are in part responsible for pain. They also block production of pro-inflammatory cytokines."

The study was carried out on normal chondrocyte (cartilage cell) pellets from six horses that were stimulated to break down the cartilage matrices by using interleukin-1 (a degadation protein). Researchers found that only the HA product significantly increased proteoglycan synthesis (proteoglycan is a necessary component of cartilage), while both products significantly increased glycosaminoglycan content of cartilage (which works to protect against the progression of arthritis).

"In this study, there was no significant interaction when combining HA and TA," noted Schaefer. "Both a high dose of HA (2 mg/mL) and of TA (0.6 mg/mL) had a protective effect on interleukin-1-stimulated chondrocytes