MMP9 and acute respiratory distress syndrome: We hypothesized that proteins previously shown to be elevated in patients with pulmonary fibrosis (Amphiregulin [32, 33], MMP-9 [34, 35], MMP-7 [35], P-selectin [36], S100A12 [35], and CXCL12 [37]) would be elevated in patients who develop fibroproliferative ARDS.