MMP9 and pulmonary fibrosis: In a murine chronic pulmonary granulomatous fibrosis model combined elicited by multiwall carbon nanotube (MWCNT) and mycobacterial ESAT-6 (early secreted antigenic target protein 6), the mice showed exacerbated pulmonary fibrosis and granulomatous pathology and MMP-9 was sharply elevated during this process (Malur et al., 2019).