Protective Abilities of Interleukin-10 in Blood-Induced Joint Damage.

PURPOSE: Joint bleeds occur frequently in patients suffering from haemophilia or can occur as a consequence of joint trauma. Even a limited number of bleeds has been demonstrated to lead to severe joint damage in time (1,2). With respect to the mechanisms of blood induced joint damage, we have demonstrated that monocytes/macrophages within the mononuclear cell population together with the red blood cells as present in blood are responsible for the irreversible inhibition of cartilage matrix synthesis. Small amounts of IL-1 that are produced by activated monocytes/macrophages increase the production of hydrogen peroxide (H₂O₂) by chondrocytes. The hydrogen peroxide reacts with haemoglobin-derived iron from damaged and phagocytosed red blood cells, which results in the formation of hydroxyl radicals in the vicinity of chondrocytes. This leads to chondrocyte apoptosis and with that the irreversible inhibition of cartilage matrix synthesis (2). In search of possible interventions to prevent or limit the cartilage damaging effects of joint bleeds, we tested interleukin-10 (IL-10) as an inflammation controlling cytokine on blood-induced cartilage damage.

METHODS: Healthy human articular cartilage tissue explants were cultured in the presence or absence of 50% v/v blood for 4 days, followed by a recovery period of 12 days. IL-10 was added in 0.1, 1 or 10 ng/ml. Also cartilage and synovium in case of haemophilic arthropathy, obtained at joint replacement surgery, was cultured in the presence of IL-10 (10 ng/ml). The effect on cartilage matrix proteoglycan synthesis, -release, and -content were determined as well as the IL-1β and TNFα production by the synovium.

RESULTS: IL-10 was able to prevent the decrease in proteoglycan synthesis and the increase in proteoglycan release of cartilage exposed to blood dose dependently (p<0.05). As a consequence, the decrease in proteoglycan content after blood exposure could be prevented dose dependently (p<0.05). With 10 ng/ml IL-10, which is still a low dose for local therapeutic treatment, at least 50% reduction in adverse effects was observed (p<0.05). The matrix turnover of haemophilic cartilage improved upon addition of IL-10 and also the production of IL-1β and TNFα by haemophilic synovium decreased in the presence of IL-10 (all p<0.05).

CONCLUSIONS: The present results show that interleukin-10 prevents the direct harmful effects of blood on articular cartilage and has a beneficial effect on the matrix turnover of haemophilic cartilage and pro-inflammatory cytokine production by haemophilic synovium. Therefore, although treatment studies in addition to prevention studies have to be performed; IL-10 might be worthwhile to test in clinical practice for local treatment of joint haemorrhages, to prevent joint damage in time.