MMP3 and pulmonary fibrosis: In a single-cell analysis performed at day 21 in a mouse model of pulmonary fibrosis induced by bleomycin, Xie et al. identified two subclusters among Col1a1 + fibroblasts: Col13a1 matrix fibroblasts with profibrotic features and Col14a1 matrix fibroblasts with proinflammatory features such as up-regulation of Col5a3, Cxcl12, Mmp3 and Dcn14.