MMP9 and Venous thrombosis: Chang et al. [21] observed abundant and moderate infiltration of macrophages and lymphocytes into the vascular appearance of VATs that developed thrombosis (n = 23) accompanied by increased expression of vascular adhesion molecule-1 (VCAM-1), proinflammatory cytokines (IL-6 and TNF-α), and matrix-9 metalloproteinase (MMP-9) compared to the vascular wall of vascular access that did not develop thrombosis (n = 13).