Toll-like receptor 9 gene expression in the post-thrombotic syndrome, residual thrombosis and recurrent deep venous thrombosis: A case-control study

- In the chronic phase of thrombosis the inflammation process is extinguished.
- TLR9 expression seems lower in patients with DVT and residual thrombosis.
- TLR9 expression was significantly higher in patients with recurrent DVT.
- The pathophysiology behind TLR9 expression and recurrent DVT is unclear.
- Future research will show whether TLR9 is useful in the prediction of recurrence.

ObjectiveAnimal models suggest that toll-like receptor 9 (TLR9) promotes thrombus resolution after acute deep venous thrombosis (DVT). We hypothesized that TLR9 expression is lower in patients with post-thrombotic syndrome (PTS) and investigated the role of TLR9 in residual thrombosis (RT) and recurrence.MethodsPatients with a history of DVT with PTS (cases, n = 30) and without PTS after minimal 24 months follow-up (controls, n = 30) were selected. Healthy individuals (HI, n = 29) without DVT were included as reference. TLR9 mRNA expression in leukocytes was determined by qPCR and normalized to the housekeeping succinate dehydrogenase subunit A gene using the ΔCt method. Sub analyses were performed to explore the TLR9 expression in patients with and without RT and multiple DVT episodes.ResultsThe median TLR9 expression was 0.45 (interquartile range 0.31 to 0.93), 0.39 (0.25 to 0.69) and 0.62 (0.32 to 0.75) in cases, controls and HI respectively (p = 0.61). The median TLR9 expression was 0.39 (0.26 to 0.51) in patients with RT compared to 0.55 (0.30 to 0.86, p = 0.13) in those without. The median TLR9 expression was significantly lower in patients who had one DVT compared to patients with recurrent DVT, 0.37 (0.23 to 0.63) versus 0.55 (0.43 to 0.96) respectively (p < 0.01).ConclusionNo significant difference in TLR9 expression was found between cases, controls and HI. However TLR9 expression seems lower in individuals with DVT and RT, albeit not significant. Interestingly, TLR9 might play a role in recurrent DVT, as the TLR9 expression was significantly higher in patients with recurrent DVT.