{"title":"Macrophages in the infarcted heart acquire a fibrogenic phenotype, expressing matricellular proteins, but do not undergo fibroblast conversion","authors":"","doi":"10.1016/j.yjmcc.2024.07.010","DOIUrl":null,"url":null,"abstract":"<div><div>Although some studies have suggested that macrophages may secrete structural collagens, and convert to fibroblast-like cells, macrophage to fibroblast transdifferentiation in infarcted and remodeling hearts remains controversial. Our study uses linage tracing approaches and single cell transcriptomics to examine whether macrophages undergo fibroblast conversion, and to characterize the extracellular matrix expression profile of myeloid cells in myocardial infarction. To examine whether infarct macrophages undergo fibroblast conversion, we identified macrophage-derived progeny using the inducible CX3CR1<sup>CreER</sup> mice crossed with the PDGFRα<sup>EGFP</sup> reporter line for reliable fibroblast identification. The abundant fibroblasts that infiltrated the infarcted myocardium after 7 and 28 days of coronary occlusion were not derived from CX3CR1+ macrophages. Infarct macrophages retained myeloid cell characteristics and did not undergo conversion to myofibroblasts, endothelial or vascular mural cells. Single cell RNA-seq of CSF1R+ myeloid cells harvested from control and infarcted hearts showed no significant expression of fibroblast identity genes by myeloid cell clusters. Moreover, infarct macrophages did not express significant levels of genes encoding structural collagens. However, infarct macrophage and monocyte clusters were the predominant source of the fibrogenic growth factors <em>Tgfb1</em> and <em>Pdgfb,</em> and of the matricellular proteins <em>Spp1</em>/Osteopontin, <em>Thbs1</em>/Thrombospondin-1, <em>Emilin2</em>, and <em>Fn1</em>/fibronectin, while expressing significant amounts of several other matrix genes, including <em>Vcan</em>/versican, <em>Ecm1</em> and <em>Sparc</em>. ScRNA-seq data suggested similar patterns of matrix gene expression in human myocardial infarction. In conclusion, infarct macrophages do not undergo fibroblast or myofibroblast conversion and do not exhibit upregulation of structural collagens but may contribute to fibrotic remodeling by producing several fibrogenic matricellular proteins.</div></div>","PeriodicalId":16402,"journal":{"name":"Journal of molecular and cellular cardiology","volume":null,"pages":null},"PeriodicalIF":4.9000,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of molecular and cellular cardiology","FirstCategoryId":"3","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0022282824001263","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CARDIAC & CARDIOVASCULAR SYSTEMS","Score":null,"Total":0}
引用次数: 0
Abstract
Although some studies have suggested that macrophages may secrete structural collagens, and convert to fibroblast-like cells, macrophage to fibroblast transdifferentiation in infarcted and remodeling hearts remains controversial. Our study uses linage tracing approaches and single cell transcriptomics to examine whether macrophages undergo fibroblast conversion, and to characterize the extracellular matrix expression profile of myeloid cells in myocardial infarction. To examine whether infarct macrophages undergo fibroblast conversion, we identified macrophage-derived progeny using the inducible CX3CR1CreER mice crossed with the PDGFRαEGFP reporter line for reliable fibroblast identification. The abundant fibroblasts that infiltrated the infarcted myocardium after 7 and 28 days of coronary occlusion were not derived from CX3CR1+ macrophages. Infarct macrophages retained myeloid cell characteristics and did not undergo conversion to myofibroblasts, endothelial or vascular mural cells. Single cell RNA-seq of CSF1R+ myeloid cells harvested from control and infarcted hearts showed no significant expression of fibroblast identity genes by myeloid cell clusters. Moreover, infarct macrophages did not express significant levels of genes encoding structural collagens. However, infarct macrophage and monocyte clusters were the predominant source of the fibrogenic growth factors Tgfb1 and Pdgfb, and of the matricellular proteins Spp1/Osteopontin, Thbs1/Thrombospondin-1, Emilin2, and Fn1/fibronectin, while expressing significant amounts of several other matrix genes, including Vcan/versican, Ecm1 and Sparc. ScRNA-seq data suggested similar patterns of matrix gene expression in human myocardial infarction. In conclusion, infarct macrophages do not undergo fibroblast or myofibroblast conversion and do not exhibit upregulation of structural collagens but may contribute to fibrotic remodeling by producing several fibrogenic matricellular proteins.
期刊介绍:
The Journal of Molecular and Cellular Cardiology publishes work advancing knowledge of the mechanisms responsible for both normal and diseased cardiovascular function. To this end papers are published in all relevant areas. These include (but are not limited to): structural biology; genetics; proteomics; morphology; stem cells; molecular biology; metabolism; biophysics; bioengineering; computational modeling and systems analysis; electrophysiology; pharmacology and physiology. Papers are encouraged with both basic and translational approaches. The journal is directed not only to basic scientists but also to clinical cardiologists who wish to follow the rapidly advancing frontiers of basic knowledge of the heart and circulation.