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Quantitative Analysis of Cellular Composition in Advanced Atherosclerotic Lesions of Smooth Muscle Cell Lineage-Tracing Mice
Published on: February 20, 2019
Gene profiling of cathepsin K deficiency in atherogenesis: profibrotic but lipogenic
S P M Lutgens1, N Kisters, E Lutgens
1Departments of Pathology, Cardiovascular Research Institute Maastricht (CARIM), University of Maastricht, P. Debyelaan 25, Maastricht, The Netherlands.
Abstract:
Recently, we showed that cathepsin K deficiency reduces atherosclerotic plaque progression, induces plaque fibrosis, but aggravates macrophage foam cell formation in the ApoE -/- mouse. To obtain more insight into the molecular mechanisms by which cathepsin K disruption evokes the observed phenotypic changes, we used microarray analysis for gene expression profiling of aortic arches of CatK -/-/ApoE -/- and ApoE -/- mice on a mouse oligo microarray. Out of 20 280 reporters, 444 were significantly differentially expressed (p-value of < 0.05, fold change of > or = 1.4 or < or = - 1.4, and intensity value of > 2.5 times background in at least one channel). Ingenuity Pathway Analysis and GenMAPP revealed upregulation of genes involved in lipid uptake, trafficking, and intracellular storage, including caveolin - 1, - 2, - 3 and CD36, and profibrotic genes involved in transforming growth factor beta (TGFbeta) signalling, including TGFbeta2, latent TGFbeta binding protein-1 (LTBP1), and secreted protein, acidic and rich in cysteine (SPARC), in CatK -/-/ApoE -/- mice. Differential gene expression was confirmed at the mRNA and protein levels. In vitro modified low density lipoprotein (LDL) uptake assays, using bone marrow derived macrophages preincubated with caveolae and scavenger receptor inhibitors, confirmed the importance of caveolins and CD36 in increasing modified LDL uptake in the absence of cathepsin K. In conclusion, we suggest that cathepsin K deficiency alters plaque phenotype not only by decreasing proteolytic activity, but also by stimulating TGFbeta signalling. Besides this profibrotic effect, cathepsin K deficiency has a lipogenic effect owing to increased lipid uptake mediated by CD36 and caveolins.
Insights
Cathepsin K deficiency impacts atherosclerosis by increasing lipid uptake via CD36 and caveolins, and stimulating transforming growth factor beta (TGF-β) signaling, leading to altered plaque development.
Area of Science:
- Cardiovascular Biology
- Molecular Mechanisms of Atherosclerosis
- Gene Expression Profiling
Background:
- Cathepsin K deficiency previously shown to reduce atherosclerotic plaque progression and induce fibrosis.
- However, it also aggravates macrophage foam cell formation in ApoE-/- mice.
- Molecular mechanisms underlying these phenotypic changes require further investigation.
Purpose of the Study:
- To elucidate the molecular mechanisms by which cathepsin K disruption influences atherosclerotic plaque phenotype.
- To identify key genes and signaling pathways affected by cathepsin K deficiency in atherosclerosis.
Main Methods:
- Gene expression profiling using microarray analysis of aortic arches from CatK-/-/ApoE-/- and ApoE-/- mice.
- Ingenuity Pathway Analysis and GenMAPP for pathway identification.
- In vitro modified low-density lipoprotein (LDL) uptake assays with bone marrow-derived macrophages.
Main Results:
- Microarray analysis identified 444 differentially expressed genes between the two mouse groups.
- Upregulation of genes involved in lipid uptake (caveolin-1, -2, -3, CD36) and TGF-β signaling (TGF-β2, LTBP1, SPARC) was observed in CatK-/-/ApoE-/- mice.
- In vitro assays confirmed CD36 and caveolins mediate increased modified LDL uptake in the absence of cathepsin K.
Conclusions:
- Cathepsin K deficiency alters atherosclerotic plaque phenotype through decreased proteolytic activity and stimulated TGF-β signaling.
- Cathepsin K deficiency promotes a lipogenic effect by enhancing lipid uptake mediated by CD36 and caveolins.
