The intra-articular injection of glucocorticoids (GC) is an effective method to shortly reduce pain and inflammation in patients suffering from knee osteoarthritis. Also, hyaluronic acid (HA) is used to restore lubrication within the joint, acting as a chondroprotective agent. The combination of HA and GC showed benefits in clinical studies, but data on the cellular level and tissue are lacking. Therefore, the study aimed to investigate the chondroprotective and anti-inflammatory effect of GC and HA alone and in combination on cytokine-treated osteochondral (OC) plugs.
OC plugs (diameter 8 and 10 mm) were harvested from bovine knee joints and treated with pro-inflammatory cytokines (IL-1β, IL-17) for three days before 10% of the test substances (GC, HA, GC/HA) were added to the culture medium. Then, incubation was performed for additional 11 days. Finally, after 14 days, cells within the tissue were analyzed concerning their metabolic activity and expression of anabolic and catabolic genes. One OC plug of each condition was used for histological analysis, while the supernatant was used to determine sulfated glycosaminoglycans (sGAG) and pro-inflammatory cytokines. Also, coefficient of friction (COF) was measured using a cartilage-on-cartilage tribological test system.
The expression of anabolic genes was increased by treating OC plugs with GC or the GC/HA combination. Also, the two substances led to a substantial reduction of catabolic gene expression. The metabolic activity of chondrocytes was on the same level in each condition. Treatment with cytokines resulted in a loss of proteoglycan content of the cartilage tissue, which was improved by adding GC or GC/HA to the culture medium. The addition of HA to the culture medium resulted in a lower COF than using GC or GC/HA.
Supplementing cytokine-treated OC plugs with a combination of GC and HA showed higher anti-inflammatory and chondroprotective properties in an explant culture model than single supplementation.