Adipose tissue remodeling and dysfunction, characterized by elevated inflammation and insulin resistance, play a central role in obesity -related development of type 2 diabetes (T2D) and cardiovascular diseases. Long intergenic non -coding RNAs (lincRNAs) are important regulators of cellular functions. Here, we describe the functions of linc-ADAIN (adipose anti-inflammatory), an adipose lincRNA that is downregulated in white adipose tissue of obese humans. We demonstrate that linc-ADAIN knockdown (KD) increases KLF5 and interleukin-8 (IL -8) mRNA stability and translation by interacting with IGF2BP2. Upregulation of KLF5 and IL -8, via linc-ADAIN KD, leads to an enhanced adipogenic program and adipose tissue inflammation, mirroring the obese state, in vitro and in vivo . KD of linc-ADAIN in human adipose stromal cell (ASC) hTERT adipocytes implanted into mice increases adipocyte size and macrophage infiltration compared to implanted control adipocytes, mimicking hallmark features of obesity -induced adipose tissue remodeling. linc-ADAIN is an anti-inflammatory lincRNA that limits adipose tissue expansion and lipid storage.

BACKGROUND:Atherosclerosis, a leading cause of cardiovascular disease, involves the pathological activation of various cell types, including immunocytes (eg, macrophages and T cells), smooth muscle cells (SMCs), and endothelial cells. Accumulating evidence suggests that transition of SMCs to other cell types, known as phenotypic switching, plays a central role in atherosclerosis development and complications. However, the characteristics of SMC-derived cells and the underlying mechanisms of SMC transition in disease pathogenesis remain poorly understood. Our objective is to characterize tumor cell-like behaviors of SMC-derived cells in atherosclerosis, with the ultimate goal of developing interventions targeting SMC transition for the prevention and treatment of atherosclerosis.METHODS:We used SMC lineage tracing mice and human tissues and applied a range of methods, including molecular, cellular, histological, computational, human genetics, and pharmacological approaches, to investigate the features of SMC-derived cells in atherosclerosis.RESULTS:SMC-derived cells in mouse and human atherosclerosis exhibit multiple tumor cell-like characteristics, including genomic instability, evasion of senescence, hyperproliferation, resistance to cell death, invasiveness, and activation of comprehensive cancer-associated gene regulatory networks. Specific expression of the oncogenic mutant KrasG12D in SMCs accelerates phenotypic switching and exacerbates atherosclerosis. Furthermore, we provide proof of concept that niraparib, an anticancer drug targeting DNA damage repair, attenuates atherosclerosis progression and induces regression of lesions in advanced disease in mouse models.CONCLUSIONS:Our findings demonstrate that atherosclerosis is an SMC-driven tumor-like disease, advancing our understanding of its pathogenesis and opening prospects for innovative precision molecular strategies aimed at preventing and treating atherosclerotic cardiovascular disease.

BACKGROUND:Atherosclerotic plaques are complex tissues composed of a heterogeneous mixture of cells. However, our understanding of the comprehensive transcriptional and phenotypic landscape of the cells within these lesions is limited. METHODS:To characterize the landscape of human carotid atherosclerosis in greater detail, we combined cellular indexing of transcriptomes and epitopes by sequencing and single-cell RNA sequencing to classify all cell types within lesions (n=21; 13 symptomatic) to achieve a comprehensive multimodal understanding of the cellular identities of atherosclerosis and their association with clinical pathophysiology. RESULTS:We identified 25 cell populations, each with a unique multiomic signature, including macrophages, T cells, NK (natural killer) cells, mast cells, B cells, plasma cells, neutrophils, dendritic cells, endothelial cells, fibroblasts, and smooth muscle cells (SMCs). Among the macrophages, we identified 2 proinflammatory subsets enriched in IL-1B (interleukin-1B) or C1Q expression, 2 TREM2-positive foam cells (1 expressing inflammatory genes), and subpopulations with a proliferative gene signature and SMC-specific gene signature with fibrotic pathways upregulated. Further characterization revealed various subsets of SMCs and fibroblasts, including SMC-derived foam cells. These foamy SMCs were localized in the deep intima of coronary atherosclerotic lesions. Utilizing cellular indexing of transcriptomes and epitopes by sequencing data, we developed a flow cytometry panel, using cell surface proteins CD29, CD142, and CD90, to isolate SMC-derived cells from lesions. Lastly, we observed reduced proportions of efferocytotic macrophages, classically activated endothelial cells, and contractile and modulated SMC-derived cells, while inflammatory SMCs were enriched in plaques of clinically symptomatic versus asymptomatic patients. CONCLUSIONS:Our multimodal atlas of cell populations within atherosclerosis provides novel insights into the diversity, phenotype, location, isolation, and clinical relevance of the unique cellular composition of human carotid atherosclerosis. These findings facilitate both the mapping of cardiovascular disease susceptibility loci to specific cell types and the identification of novel molecular and cellular therapeutic targets for the treatment of the disease.

Background: Smooth muscle cells (SMCs) substantially contribute to atherosclerosis through “phenotypic switching.” Our previous work identified an intermediate SMC-derived cell type, termed “SEM” cells, which was multipotent and activated in inflammatory response. Activation of retinoic acid (RA) signaling by all-trans retinoic acid (ATRA) attenuated atherosclerosis in mice coincident with dramatic suppression of SEM cell formation from SMCs. However, the regulatory mechanisms by which RA signaling modulates SMC transition to SEM cells are largely unknown. Methods: We employed molecular and cell biology techniques, SMC-linage tracing and atheroprone mouse models, and next-generation sequencing (e.g., RNA-seq, ChIP-seq) to reveal how RA signaling modulates SMC transition to SEM cells. Results: Activation of RA signaling with ATRA significantly reduced SEM cells in established atherosclerosis, as well as downregulated the expression of SEM cell marker genes (e.g., Ly6a , Ly6c1 ) and repressed inflammatory response in ex vivo SEM cells, whereas inhibition of the signaling with antagonist, BMS49334, showed opposite results. RARα occupied the promoter regions of SEM cell marker genes, and ATRA treatment significantly increased the enrichment of NCOR1 at promoters of these genes. These findings suggest that RA signaling suppresses SMC transition to SEM cells via directly repressing the expression of SEM cell marker genes. Furthermore, we found EZH2, one of the subunits of PRC2, physically interacted with RARα in SMCs and occupied the promoters of SEM cell marker genes, and its methyltransferase activity at the promoter regions was responsible for the repression of SEM cell maker genes. Moreover, activation of RA signaling inhibited SEM cell inflammatory response through LXR-mediated suppression of a series of inflammatory genes. Finally, multiple epigenetic signatures (e.g., H3K27me3, H3K27ac, H3K4me3, etc.) at TSS of SEM cell marker genes and inflammatory genes were extensively altered in response to the activation of RA signaling. Conclusions: Our findings indicate that RA signaling modulates maintenance of SEM cell identity and inflammatory function in atherosclerosis by epigenetic regulation of gene expression.