In the fibroblastic foci of IPF, subepithelial myofibroblasts close to the areas of BM disruption express MMP-2 as well as MMP-9 (ref. 25), suggesting that MMPs may mediate proteinase-dependent IPF myofibroblast invasion into the BM and the disruption of BM integrity. The gene discussed is MMP9; the disease is idiopathic pulmonary fibrosis.