Objective: To evaluate the ability of hyaluronic acid (HA), with and without transforming growth factor beta (1GF-beta), to stabilize the catabolic processes associated with atrophy of articular cartilage.
Animals: 20 adult, skeletally normal, hound-type dogs.
Procedure: Dogs (20 to 30 kg) were randomly assigned to 1 of 5 groups. One group served as untreated controls. Bivalve casts were placed on the left hind limbs of the remaining 16 dogs to limit weightbearing and motion of the limb for 92 days. One group served as the cast control. Beginning on day 56, 3 groups received aseptic intra-articular injections in the left stifles of either 5 mg of HA or 5 mg of HA containing either 20 or 50 micrograms of TGF-beta. Intraarticular injections were repeated at 4-day intervals until the end of the study. Or day 92, stifles were harvested at necroscropy. Medial femoral condyle were histologically processed, and the articular cartilage was stained for the presence of proteoglycans, stromelysin, tumor necrosis facto (TNF) alpha, and TNF receptors (p55 and p75).
Results: Decreased metachromasia was evident in the cartilage matrix of all cast groups, with the smallest decrease in the HA-treated group. Stromelysin was immunolocalized in articular cartilage of the cast (left) limbs of cast control and both HA/TGF-beta-treated groups. TNF-alpha was localized in articular cartilage of all cast (left) and right limbs, except those of the HA-treated group. Receptors for TNF were observed in both limbs of untreated control and cast control groups and cast limbs of HA/TGF-3-treated groups. The receptors were not localized in the right limbs of the HA with or without TGF-beta-treated groups. TGF-beta did not decrease stromelysin or TNF-alpha or receptors at the doses used.
Conclusions: HA may mediate a chondrostabilizing influence on articular cartilage by down-regulating TNF-alpha importantly. HA appeared to exert its inhibitory influence on TNF-alpha, as well as stromelysin and TNF receptors, on a systemic basis.
Clinical relevance: Results provide insight into the mode of action of HA as a therapeutic agent for arthritis and its stabilizing influence on cartilage metabolism.