The current study aimed to investigate the effects of hyaluronic acid (HA), glucocorticoids and (GC) and a co-administration (HA/GC) on cytokine-treated bovine osteochondral plugs under biomechanical stress via biotribological testing.
Osteochondral plugs were harvested from three bovine knee joints. The plugs were treated with (positive control) or without (negative control) pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) for 1 week to simulate an OA environment. After seven days, the inflammatory medium was replaced by therapeutic medium (GC, HA, or GC/HA) for additional seven days. On day 14, biotribological testing was performed using PBS as a test fluid. Testing was standardized accordingly: an initial load of 180N for 10 minutes is followed by a resting phase of 10 min. This is followed by 3 cycles of repetitive sliding tests (2 mm/s at 180 N) for 10 minutes with a resting phase of 10 minutes between each cycle. The coefficient of friction (COF) was measured constantly during testing. Gene expression analysis, metabolic activity and measurements of sGAGs were carried out.
In cytokine-treated plugs, COF increased compared to the negative control. HA led to decreased COF compared to positive control. Co-administration of HA/GC maintained the decreased COF. In all inflammatory conditions anabolic genes (COL2A1 and ACAN) decreased and catabolic genes (MMP1 and MMP13) increased compared to the negative control. Metabolic activity was lower in all inflammatory conditions compared to the untested control group at day 0. sGAG were increased in the positive control group compared to the negative control. HA and HA/GC decreased sGAGs compared to the positive control group and only adding GC alone.
Treatment of osteochondral plugs with HA led to a reduced COF and a decreased sGAG amount. A co-administration of HA/GC does not impair this effect. Thus, combining HA/GC has positive biotribological effects on bovine osteochondral plugs cultivated under inflammatory conditions.