J Leukoc Biol. 2025 Aug 7:qiaf114. doi: 10.1093/jleuko/qiaf114. Online ahead of print.
ABSTRACT
Macrophages have a dual role in tissue healing after injury as they perform tissue repair functions but can also precipitate tissue damage or promote fibrosis. Platelets, beyond their role in thrombosis and hemostasis, are crucial mediators of inflammation and interact with macrophages. Platelet-macrophage interactions have been proposed to modulate macrophage phenotype, including their profibrotic functions, but the full extent of the platelet impact on the macrophage transcriptome is unknown. Here, we aimed to investigate how platelets affect macrophage activation in vitro. Using experimental myocardial infarction (MI) in mice as a model of sterile tissue injury, we readily visualized the direct interaction of platelets with macrophages in the ischemic heart using fluorescence microscopy. Bulk RNA-sequencing of mouse bone marrow-derived macrophages co-cultured in vitro with thrombin-activated platelets showed a widespread pro-inflammatory activation, with up-regulation of genes associated with inflammation (Il1b, Trem1, Tlr2, Cd14), angiogenesis (Vegfa) and response to hypoxia (Hif1a). Resting platelets also led to activation of inflammatory gene expression by macrophages, albeit to a much lesser extent. Activated or resting platelets, or the platelet-derived chemokine CXCL4, had a limited impact on macrophage expression of pro-fibrotic genes (Spp1, Fn1). Using a transwell assay, we further demonstrate that the pro-inflammatory effects of platelets on the macrophage transcriptome was largely contact dependent. Altogether, our work shows that platelets interact with macrophages in the ischemic heart and polarize macrophages towards a pro-inflammatory phenotype in vitro, with potential implications for cardiac macrophage inflammatory activation after acute experimental MI.
PMID:40795250 | DOI:10.1093/jleuko/qiaf114