SPP1 and myocardial infarction: Moreover, ligand-receptor interaction analysis found that SPP1+ macrophages may act on fibroblasts through PDGF-C, PDGF-D, and thrombospondin-1 (THBS1) signaling to affect the progression of fibrosis.26 Another study using ST identified monocyte-derived basic helix-loop-helix family member e41 (Bhlhe41+) macrophages in the developing infarct zone of MI.