Project description:Macrophage heterogeneity within atherosclerotic plaques was explored with intravital imaging, flow cytometry, and RNA sequencing. 4 populations of cells were found with varying expression profiles and functions relevant to atherosclerosis and inflammation.
Project description:Atherosclerosis is a leading cause of death due to the rupture of arterial lesions characterized by a necrotic core and inflammatory activity. Although lesion vulnerability follows a diurnal pattern with a higher incidence of rupture in the morning, the role of circadian rhythms in atherosclerotic lesions is unclear. Here we show that apoptosis in lesions follows a diurnal pattern that is controlled through the circadian regulation of the pro-apoptotic XIAP associated factor 1 (Xaf1) by the Mir21 strands. The increased apoptosis during the transition from the inactive to the active phase is not matched with the efferocytic removal of dead cells resulting in increased necrotic core formation. Lack of Mir21 expression in macrophages decreases atherosclerosis and necrotic core formation in mice, suggesting that Mir21-mediated diurnal apoptosis promotes lesion growth. In human atherosclerotic lesions, apoptosis also follows a diurnal pattern with a peak in the morning and oscillates in-phase with XAF1 expression and anti-phase with miR-21 expression. Thus, diurnal apoptosis regulated by a Mir21-controlled macrophage death clock may contribute to circadian regulation of lesion vulnerability.
Project description:Paired samples from human femoral artery lesions were obtained during intravascular surgery exploiting Silverhawk device Microarrays were used to identify genes differentially regulated in human femoral artery atherosclerotic and corresponding restenotic plaques
Project description:Macrophages represent a major immune cell population in atherosclerotic plaques and play central role in the progression of this lipid-driven chronic inflammatory disease. Targeting immunometabolism is proposed as a strategy to revert aberrant macrophage activation to improve disease outcome. Here, we show ATP citrate lyase (Acly) to be activated in inflammatory macrophages and human atherosclerotic plaques. We demonstrate that myeloid Acly deficiency induces a stable plaque phenotype characterized by increased collagen deposition and fibrous cap thickness, along with a smaller necrotic core. In-depth functional, lipidomic, and transcriptional characterization indicate deregulated fatty acid and cholesterol biosynthesis and reduced liver X receptor activation within the macrophages in vitro. This results in macrophages that are more prone to undergo apoptosis, whilst maintaining their capacity to phagocytose apoptotic cells. Together, our results indicate that targeting macrophage metabolism improves atherosclerosis outcome and we reveal Acly as a promising therapeutic target to stabilize atherosclerotic plaques.
Project description:Phenotypic and functional diversity between macrophage subpopulations reflects their plasticity to respond to microenvironmental signals. Apart from detecting differences in expression profiles, the comparison of the transcriptomes of different macrophage populations may also allow the definition of molecular similarities between these subsets. Transcriptome analysis of human Kuppfer cells, alveolar, splenic and atherosclerotic plaque residing macrophages using microarrays, identified 42 genes that are specifically expressed in atherosclerotic plaque macrophages. We also focus on the similarities in the transcriptome of human Kupffer cells, alveolar, splenic and atherosclerotic plaque residing macrophages. We hypothesized that these macrophages share a common expression signature. We performed microarray analysis on mRNA from these macrophage subsets (n = 4 patients) and developed a novel statistical method to identify genes with significantly similar expression levels. This method calculates the maximum difference in expression level of a gene, based on the estimated confidence interval on that genes expression variance. We listed the genes by equivalence ranking relative to their expression level. False Discovery Rate (FDR) estimation was used to determine significance. We identified 500 genes that had significantly equivalent expression levels in the macrophage subsets at an 5.5% FDR using a 90% confidence interval. Equivalently expressed genes, identified by this newly developed method, may not only help to dissect common molecular mechanisms, but also to identify cell or condition specific sets of marker genes that can be used for drug targeting and molecular imaging.
Project description:Muscle injury was elicited by cardiotoxin injection into the tibialis anterior muscle. Macrophages were isolated 2 days post-injury from the regenerating muscle. We used microarray to obtain global gene expression data of muscle-derived tissue macrophage subsets. Tissue macrophages were collected from regenerating muscle samples of three animals, Ly6C+ F4/80low and Ly6C- F4/80high macrophage subsets were sorted. The global gene expression patterns of distinct macrophage subsets were analyzed on Affymetrix microarrays.
Project description:Macrophages represent a major immune cell population in atherosclerotic plaques and play central role in the progression of this lipid-driven chronic inflammatory disease. Targeting immunometabolism is proposed as a strategy to revert aberrant macrophage activation to improve disease outcome. Here, we show ATP citrate lyase (Acly) to be activated in inflammatory macrophages and human atherosclerotic plaques. We demonstrate that myeloid Acly deficiency induces a stable plaque phenotype characterized by increased collagen deposition and fibrous cap thickness, along with a smaller necrotic core. In-depth functional, lipidomic, and transcriptional characterization indicate deregulated fatty acid and cholesterol biosynthesis and reduced liver X receptor (LXR) activation within the macrophages in vitro. This results in macrophages that are more prone to undergo apoptosis, whilst presenting increased phagocytosis of apoptotic cells. Together, our results indicate that targeting macrophage metabolism improves atherosclerosis outcome and we reveal Acly as a promising therapeutic target to stabilize atherosclerotic plaques.