Serum levels of IL-6, tumour necrosis factor alpha (TNF-α) and glycosaminoglycan. During the course of antigen-induced arthritis (AIA), (a) IL-6 levels in non-arthritic rats showed values below the detection limit of the assay. Untreated and hyaluronic acid (HA)-treated AIA rats showed significantly increased values in the short-term test and in the long-term test compared with non-arthritic rats (all P < 0.001; data not shown), but HA treatment resulted in IL-6 levels comparable with those of untreated AIA. (b) Regarding TNF-α levels, the only change was a short-term, non-significant increase in all AIA rats, whether HA-treated or untreated. (c) Serum values of glycosaminoglycan increased significantly in all AIA rats compared with non-arthritic animals (non-arthritic animals versus untreated AIA rats [short-term test], P < 0.05, non-arthritic animals versus HA-treated AIA rats, untreated AIA rats [long-term test] and HA-treated AIA rats [long-term test], P < 0.001; significance not indicated). There were no differences between short-term tests and long-term tests, or between HA-treated rats and untreated AIA rats.
Roth et al. Arthritis Research & Therapy 2005 7:R677-R686 doi:10.1186/ar1725