PLG and peripheral nerve injury: For example, Shubayev et al. demonstrated that TNF-α-mediated MMP9 (also known as gelatinase B) production enhances macrophage recruitment in a model of peripheral nerve injury.32 Gong et al. demonstrated that mice deficient for the ECM-bound protease plasminogen (Plg) had decreased trans-ECM macrophage migration and decreased MMP9 activation.33 In addition, the authors demonstrated that MMP9 administration to Plg deficient mice resulted in increased macrophage accumulation in the ECM,33 suggesting that Plg activates MMP9 to increase ECM resident macrophages.