Tissue factor exposing microparticles in inflammatory bowel disease

Background Circulating procoagulant microparticles (MPs) are thought to be involved in the pathogenesis of venous thromboembolism in patients with inflammatory bowel disease (IBD). However, the exposure of tissue factor, the primary initiator of coagulation activation, on microparticles (TF+MPs) and its association with hemostasis activation has not yet been studied in IBD patients. Methods In this case–control study 49 IBD patients (28 Crohn's disease, 21 ulcerative colitis) and 49 sex- and age-matched, healthy controls were included. Clinical disease activity (Crohn's Disease Activity Index and Clinical Activity Index, respectively) was assessed and IBD-related data were determined by chart review. Numbers, cellular origin and procoagulant activity of TF+MPs in plasma were determined using flow cytometry and a chromogenic activity assay. D-dimer and high-sensitive C-reactive protein (CRP) served as markers for coagulation activation and inflammation, respectively. The primary endpoint was the number of TF+MPs in IBD patients compared to controls. Results Median number (interquartile range) of TF+MPs was higher in IBD patients than in controls (14.0 (11.9–22.8)×103/mL vs. 11.9 (11.9–19.1)×103/mL plasma, P=0.029). This finding was due to generally higher plasma levels of MPs from platelets and leukocytes in IBD patients. However, the number of TF+MPs was neither correlated with their procoagulant activity and D-dimer nor with disease activity and CRP. Conclusions Increased numbers of circulating TF+MPs represent a new facet of hemostatic abnormalities in IBD. However, the lack of association with activation of the coagulation system and disease activity questions their pathogenetic role for venous thromboembolism in this patient group.