CD163 macrophage and erythrocyte contents in aspirated deep vein thrombus are associated with the time after onset: a pilot study

BACKGROUND Thrombolytic therapy is effective in selected patients with deep vein thrombosis (DVT). Therefore, identification of a marker that reflects the age of thrombus is of particular concern. This pilot study aimed to identify a marker that reflects the time after onset in human aspirated DVT. METHODS We histologically and immunohistochemically analyzed 16 aspirated thrombi. The times from onset to aspiration ranged from 5 to 60 days (median of 13 days). Paraffin sections were stained with hematoxylin and eosin and antibodies for fibrin, glycophorin A, integrin α2bβ3, macrophage markers (CD68, CD163, and CD206), CD34, and smooth muscle actin (SMA). RESULTS All thrombi were immunopositive for glycophorin A, fibrin, integrin α2bβ3, CD68, CD163, and CD206, and contained granulocytes. Almost all of the thrombi had small foci of CD34- or SMA-immunopositive areas. CD68- and CD163-immunopositive cell numbers were positively correlated with the time after onset, while the glycophorin A-immunopositive area was negatively correlated with the time after onset. In double immunohistochemistry, CD163-positive cells existed predominantly among the CD68-immunopositive macrophage population. CD163-positive macrophages were closely localized with glycophorin A, CD34, or SMA-positive cell-rich areas. CONCLUSIONS These findings indicate that CD163 macrophage and erythrocyte contents could be markers for evaluation of the age of thrombus in DVT. Additionally, CD163 macrophages might play a role in organization of the process of venous thrombus.