Cytokines in the pathogenesis of hemophilic arthropathy

Hemophilic arthropathy (HA) is one of the most common and typical manifestation in the course of recurrent bleeding episodes in patients with hemophilia. Clinical and subclinical joint bleeding episodes gradually lead to irreversible changes manifesting themselves as pain, progressing ankylosis, marked limitation of the range of motion, muscle atrophy and osteoporosis commonly concomitant with joint deformity resulting from chronic proliferative synovitis and both cartilage and bone degeneration leading to the final functional impairment of the joint. In spite of numerous studies, the pathophysiology of HA has not been fully elucidated, especially as regards immunopathological mechanisms which are associated with the subclinical and early stage of the disease and to be more precise, with chronic joint inflammation. It needs to be emphasized that the pathophysiological processes occurring in a joint with HA are most probably highly mediated by interactions within the cytokine network and other inflammatory mediators present in the tissues of affected joint. Among numerous compounds participating in the induction of an inflammatory process in the pathogenesis of HA, cytokines seem to play a leading role. The most important group controlling the disease seems to be well known inflammatory cytokines, including IL-1β, TNFα and IL-6. The second group with antagonistic effect is formed by anti-inflammatory cytokines such as IL-4 and IL-10. The role of inflammatory and anti-inflammatory cytokines in the pathogenesis of HA with respect to cellular and intracellular signaling pathways is still under investigation. This review, summarizes and discusses the current knowledge about cytokine network in the pathogenesis of HA, indicating possible molecular and cellular mechanisms that may provide potential new therapeutic directions.