SPP1 and idiopathic pulmonary fibrosis: Based on the previously established association of pro-fibrotic SPP1+ macrophages with cirrhotic liver and lungs from idiopathic pulmonary fibrosis (IPF) patients (Morse et al., 2019; Ramachandran et al., 2019), we hypothesised that this macrophage population can be detected in other human tissues and can associate with broader fibrotic disease state.