MMP19 and idiopathic pulmonary fibrosis: Clustering of alveolar fibroblasts from the HLCA core and all IPF datasets21,24,58,62,64 shows that cells from patients with IPF predominantly cluster together in a single cluster (Fig. 6f,g and Extended Data Fig. 10b) characterized by high expression of genes previously associated with IPF64,73,74 (CCL2, COL1A1, CTHRC1 and MMP19), as well as further fibrosis-associated markers (SERPINE1, an inhibitor of extracellular matrix breakdown75, and HIF1A, a chronic hypoxia response gene76; Fig. 6h and Supplementary Table 14).