Neutrophil Extracellular Traps promote joint damage in hemophilia.

Abstract

Abstract Hemophilic arthropathy (HA) is the pathophysiology resulting from recurrent joint bleeding in hemophilia. HA leads to joint damage, chronic pain and poor quality of life. Despite advances in the treatment to prevent joint bleeding, HA continues to be a major morbidity affecting hemophilia patients and the mechanism contributing to HA remains elusive. Recent evidence suggests that joint-bleeding may promote the release of erythrocyte and tissue-derived damage-associated-molecular-pattern molecules (DAMPs) that can trigger the sterile inflammation in the joints, however, the innate immune pathways remain unclear. We used a model of knee joint injury-induced HA in FVIII-total knockout (F8TKO) mice and samples from hemophilia patients diagnosed with HA. In vivo multiphoton-excitation fluorescence imaging of injured synovial cavity in live F8TKO or control mice was used to assess NETs formation within joint capsule. Imaging-flow-cytometry and ELISA assays were used to evaluate circulating NETs in HA patients and mice with knee-injury. Bleeding severity scoring, histology, IHC and confocal imaging of joints were conducted to assess the joint injury in mice. F8TKO but not control mice manifested knee-joint injury and severity of bleeding 5-days post knee-injury. Knee-joint injury was associated with increased neutrophil accumulation and NETs shedding within the synovium of F8TKO mice. Circulating NETs were abundant in the plasma of patients diagnosed with HA and F8TKO following injury but not plasma of controls. These findings are the first to suggest that NETs contribute to pathogenesis of HA. Currently, study is underway to identify the innate immune pathways that promote NETs shedding, leading to joint-damage in hemophilia.