KLF4-dependent phenotypic modulation of smooth muscle cells has a key role in atherosclerotic plaque pathogenesis

• Published in: Nature medicine Vol. 21; no. 6; pp. 628 - 637
• Main Authors: Shankman, Laura S, Gomez, Delphine, Cherepanova, Olga A, Salmon, Morgan, Alencar, Gabriel F, Haskins, Ryan M, Swiatlowska, Pamela, Newman, Alexandra A C, Greene, Elizabeth S, Straub, Adam C, Isakson, Brant, Randolph, Gwendalyn J, Owens, Gary K
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01-06-2015; Nature Publishing Group
• Subjects: 13/106; 13/31; 13/51; 14/1; 14/28; 14/34; 38/32; 631/443/1338/2100; 631/532/2435; 631/80; Analysis; Animals; Apolipoproteins E - antagonists & inhibitors; Atherosclerosis; Atherosclerosis - genetics; Atherosclerosis - pathology; Biomedicine; Cancer Research; Cell Differentiation - genetics; Cell Lineage; Cell Tracking; Cellular biology; Cholesterol; Development and progression; Genetic aspects; Genotype & phenotype; Humans; Infectious Diseases; Kruppel-Like Transcription Factors - genetics; Lesions; Macrophages; Macrophages - pathology; Mesenchymal Stromal Cells - metabolism; Mesenchymal Stromal Cells - pathology; Metabolic Diseases; Mice; Molecular Medicine; Myocytes, Smooth Muscle - pathology; Neurosciences; Physiological aspects; Plaque, Atherosclerotic - genetics; Plaque, Atherosclerotic - pathology; Promoter Regions, Genetic; Smooth muscle; Stem cells; Studies; United States
• ISSN: 1078-8956; 1546-170X
• DOI: 10.1038/nm.3866

A high percentage of smooth muscle cells in atherosclerotic lesions lose expression of smooth muscle marker proteins and acquire the phenotype of other cell types, a process of functional importance in lesion pathogenesis that is controlled by the transcription factor KLF4.
Previous studies investigating the role of smooth muscle cells (SMCs) and macrophages in the pathogenesis of atherosclerosis have provided controversial results owing to the use of unreliable methods for clearly identifying each of these cell types. Here, using
Myh11
-CreER
T2
ROSA floxed STOP eYFP
Apoe
−/−
mice to perform SMC lineage tracing, we find that traditional methods for detecting SMCs based on immunostaining for SMC markers fail to detect >80% of SMC-derived cells within advanced atherosclerotic lesions. These unidentified SMC-derived cells exhibit phenotypes of other cell lineages, including macrophages and mesenchymal stem cells (MSCs). SMC-specific conditional knockout of Krüppel-like factor 4 (
Klf4
) resulted in reduced numbers of SMC-derived MSC- and macrophage-like cells, a marked reduction in lesion size, and increases in multiple indices of plaque stability, including an increase in fibrous cap thickness as compared to wild-type controls. On the basis of
in vivo
KLF4 chromatin immunoprecipitation–sequencing (ChIP-seq) analyses and studies of cholesterol-treated cultured SMCs, we identified >800 KLF4 target genes, including many that regulate pro-inflammatory responses of SMCs. Our findings indicate that the contribution of SMCs to atherosclerotic plaques has been greatly underestimated, and that KLF4-dependent transitions in SMC phenotype are critical in lesion pathogenesis.