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. 2015 Jun 16;65(23):2526-37.
doi: 10.1016/j.jacc.2015.03.570.

An Endocrine Genetic Signal Between Blood Cells and Vascular Smooth Muscle Cells: Role of MicroRNA-223 in Smooth Muscle Function and Atherogenesis

Zhen Shan  1 , Shanshan Qin  1 , Wen Li  2 , Weibin Wu  2 , Jian Yang  1 , Maoping Chu  3 , Xiaokun Li  3 , Yuqing Huo  4 , Gary L Schaer  1 , Shenming Wang  5 , Chunxiang Zhang  6
Affiliations

An Endocrine Genetic Signal Between Blood Cells and Vascular Smooth Muscle Cells: Role of MicroRNA-223 in Smooth Muscle Function and Atherogenesis

Zhen Shan et al. J Am Coll Cardiol. .

Abstract

Background: MicroRNA-223 (miR-223) is a hematopoietic lineage cell-specific microRNA. However, a significant amount of miR-223 has been identified in vascular smooth muscle cells (VSMCs) and vascular walls that should not have endogenous miR-223.

Objectives: This study sought to determine the sources of miR-223 in normal and atherosclerotic arteries and the role of miR-223 in atherogenesis.

Methods: The levels and sources of miR-223 in blood cells (leukocytes and platelets), serum, blood microparticles, VSMCs, and vascular walls were determined. Both in vivo and in vitro studies were conducted to evaluate miR-223 secretion by blood cells and the ability of miR-223 to enter VSMCs and vascular walls. Subsequent changes in and the effects of miR-223 levels on serum and arteries in atherosclerotic animals and patients were investigated.

Results: Blood cells were able to secrete miR-223 into serum. MicroRNA-223 from blood cells was the most abundant cell-free miRNA in blood. Blood cell-secreted miR-223 could enter VSMCs and vascular walls, which produced strong biological effects via its target genes. In both atherosclerotic apolipoprotein-E knockout mice and patients with atherosclerosis, miR-223 levels were significantly increased in serum and atherosclerotic vascular walls. The atherosclerotic lesions in apolipoprotein-E knockout mice were exacerbated by miR-223 knockdown. The effect of miR-223 on atherogenesis was verified using miR-223 knockout mice.

Conclusions: Blood cell-secreted miR-223 enters vascular cells and walls, and appears to play important roles in VSMC function and atherogenesis. As a novel endocrine genetic signal between blood cells and vascular cells, miR-223 may provide a novel mechanism and new therapeutic target for atherosclerosis.

Keywords: atherosclerosis; bone marrow; insulin-like growth factor 1 receptor; microRNAs.

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Figures

FIGURE 1
FIGURE 1. miR-223 in Circulating Serum, VSMCs, and Vessels
(A) Microparticles arise from different sources in serum (n = 6). (B) The extracellular distribution of micro-ribonucleic acid (miR)-223 in 2 parts of serum. (C) MicroRNA-223 exhibits varying stability in microparticles and supernatant parts within 24 h. (D) The cycle threshold (Ct) levels of miR-223 and U6 in water (H2O) (negative control) and in passaged vascular smooth muscle cells (VSMCs) cultured in serum-free medium. (E) Platelet-derived growth factor (PDGF) (20 ng/ml) stimulation does not induce any miR-223 expression in passaged VSMCs. (F) A significant amount of miR-223 can be found in freshly isolated VSMCs. (G) A significant amount of miR-223 can be found in normal vascular walls. Absolute quantification of miR-223, miR-222, and miR-34a in (H) passaged VSMCs, (I) freshly isolated VSMCs, and (J) normal vascular walls. *p < 0.05 compared with control subjects. EC = endothelial cell.
FIGURE 2
FIGURE 2. Blood Cell-Secreted miR-223 in Extracellular Space, VSMCs, and Vascular Walls
(A) MiR-223 levels rose in culture medium of THP-1 macrophages with increasing cell numbers. (B) Culture medium of THP-1 macrophages were added into culture medium of VSMCs; miR-223 levels were increased in VSMCs with miR-223–containing medium. (C) THP-1 macrophage-secreted, Cy3-marked miR-223 (red color) in the upper chamber of a co-culture system could enter VSMCs in the lower chamber through the extracellular medium. (D) MicroRNA-223 levels were higher in the group in which fresh serum isolated from rats was added into a culture medium (at 10%) of VSMCs for 24 h. (E) Neutrophils in blood were depleted by vinblastine (2.5 mg/kg intraperitoneally). (F) Platelets in blood were depleted by antimouse thrombocyte serum (50 μl intraperitoneally). (G) The levels of miR-223 in serum and aortas were decreased in mice that had depletion of neutrophils. (H) MicroRNA-223 levels in serum and aortas decreased in mice with depletion of platelets. *p < 0.05 compared with control groups. Abbreviations as in Figure 1.
FIGURE 3
FIGURE 3. miR-223 Levels from Subjects With Atherosclerosis and in Injured Arteries
(A) Serum levels of miR-223 from atherosclerotic apolipoprotein E knockout mice and from patients with higher atherosclerosis levels compared with normal control subjects. (B) MiR-223 levels rose in balloon-injured rat carotid arteries, (C) ligation-injured mouse carotid arteries, (D) atherosclerotic aortas from apolipoprotein E knockout mice, and (E) atherosclerotic human arteries compared with normal controls. (F) The successful rat carotid artery balloon injury, (G) mouse carotid artery ligation injury in mice, (H) mouse atherosclerotic aorta, and (I) human atherosclerotic artery were confirmed by histology. *p < 0.05 compared with control groups. Abbreviations as in Figure 1.
FIGURE 4
FIGURE 4. Cellular Functions of miR-223 in VSMCs
The effect of miR-223 on PDGF-induced VSMC proliferation as determined by (A) MTT assay and by (B) 5-ethynyl-2′-deoxyuridine (EdU) method. (C) The EdU-positive VSMCs from different groups. The effect of miR-223 on (D) VSMC migration determined by the Boyden chamber assay seen in (E) representative images from different groups. (F) The effect of miR-223 on VSMC apoptosis determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis, seen in (G) representative images from different groups. *p < 0.05 compared with control groups. DAPI = 4′,6-diamidino-2-phenylindole; other abbreviations as in Figure 1.
FIGURE 5
FIGURE 5. IGF-1R/PI3K-Akt: Downstream Signaling Pathway of miR-223 in VSMCs
(A) Computational analysis suggests that human insulin-like growth factor 1 receptor (IGF-1R) has an miR-223 binding site in its 3′-UTR. (B) Representative Western blots show IGF-1R protein levels from different groups. Overexpression of miR-223 decreased the expression of IGF-1R at (C) the protein level and the (D) messenger RNA (mRNA) level in VSMCs. (E) Luciferase assay in HEK 293 cells co-transfected with a fragment of the 3′-UTR of IGF-1R mRNA containing the conserved miR-223 binding sequence, and either vehicle, an empty plasmid (pDNR-CMV), or a plasmid expressing miR-223 (pmiR-223). An IGF-1R 3′-UTR mutated fragment was used as a mutated control group. (F) Representative Western blots show IGF-1R protein levels in aortas from miR-223 knockout mice and wild-type control mice. (G) IGF-1R expression in aortas from miR-223 knockout mice was higher than that from wild-type control mice. (H) Representative Western blots show p-AKT and total AKT (t-AKT) from different groups. (I) Overexpression of miR-223 decreased expression of p-AKT in VSMCs. *p < 0.05 compared with control groups. GADPH = glyceraldehyde-3-phosphate dehydrogenase; hsa = human; other abbreviations as in Figure 1.
FIGURE 6
FIGURE 6. Effects of miR-223 on Atherogenesis
(A) Serum levels and (B) vascular levels of miR-223 in mice were knocked down by locked nucleic acid miRNA inhibitor for miR-223 (LN-anti-miR-223; 30 mg/kg intraperitoneally biweekly). (C) Atherosclerotic lesion areas (red color by oil red O staining) in aortas from apolipoprotein-E knockout mice treated with LN-anti-miR-223 or scramble control. (D) MicroRNA-223 inhibition by LN-anti-miR-223 significantly increased atherosclerotic lesion areas in apolipoprotein-E knockout mice with a Western diet. (E) Vascular neointimal lesion growth in miR-223 knockout mice was significantly increased compared with wild-type control mice in a model of carotid artery ligation injury. (F) Vascular neointimal formation in carotid arteries from wild-type C57BL/6 mice and miR-223 knockout mice. *p < 0.05 compared with control groups. Abbreviations as in Figures 1 and 3.
CENTRAL ILLUSTRATION
CENTRAL ILLUSTRATION. Blood Cell-Secreted miR-223 in Atherosclerotic Vascular Disease
Inflammatory blood cells, such as leukocytes and platelets, which are originally from hematopoietic cells in bone marrow, can secrete the hematopoietic lineage, cell-specific micro-ribonucleic acid (miR)-223 into circulating serum. This miR-223 can then enter vascular cells (e.g., vascular smooth muscle cells [VSMCs] and vascular walls) and work as a novel endocrine genetic signal (like a hormone) in VSMCs to regulate their biological functions, such as proliferation, migration, and apoptosis via target genes such as insulin-like growth factor 1 receptor (IGF-1R) and the P13K-Akt pathway. Under pathological conditions, such as atherosclerosis and vascular injury, blood cells release more miR-223, which results in increased levels of miR-223 in VSMCs and vascular walls. The increased miR-223 helps protect against atherosclerotic vascular disease (vascular neointimal formation and atherosclerosis). P = phosphate.
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