Cellular Communication Network Factor 2 Regulates Smooth Muscle Cell Transdifferentiation and Lipid Accumulation in Atherosclerosis

Medicine Cardiovascular System
Cellular Communication Network Factor 2 Atherosclerosis Smooth Muscle Cells Endoplasmic Reticulum Stress Lipid Accumulation

Background Introduction

Atherosclerosis is a complex vascular disease characterized by the progressive accumulation of lipid plaques within the arterial walls, ultimately leading to cardiovascular events such as myocardial infarction, stroke, and peripheral vascular disease. Although the current standard treatment regimen includes statins and antiplatelet agents, these therapies lack target specificity, particularly in advanced stages of the disease, often failing to completely halt or reverse the progression of atherosclerosis. Therefore, identifying new therapeutic targets has become a key focus of current research.

Vascular smooth muscle cells (VSMCs) are the main cellular component of the vascular wall and play a critical role in atherosclerosis. Under normal conditions, VSMCs exhibit a quiescent or contractile phenotype, but in response to injury or certain stimuli, they can undergo phenotypic switching to a synthetic phenotype, characterized by increased proliferation and migration. In recent years, the development of single-cell RNA sequencing (scRNA-seq) technology has enabled researchers to more deeply track the fate changes of VSMCs during atherosclerosis, revealing the mechanisms of their phenotypic switching. However, the molecular regulatory mechanisms underlying VSMC phenotypic transformation remain incompletely understood.

Cellular communication network factor 2 (CCN2) is a matricellular protein known to play important roles in various cellular processes, including proliferation, differentiation, and apoptosis. However, the role of CCN2 in vascular pathology, particularly in atherosclerosis, remains unclear. This study aims to elucidate the function and mechanisms of CCN2 in VSMC phenotypic switching and the progression of atherosclerosis.

Source of the Paper

This paper was co-authored by Qian Xu, Jisheng Sun, Claire M. Holden, and others, with the research team coming from institutions such as Emory University School of Medicine, Central South University, and the University of Saskatchewan. The paper was published online on October 4, 2024, in the journal Cardiovascular Research, with the title “Cellular communication network factor 2 regulates smooth muscle cell transdifferentiation and lipid accumulation in atherosclerosis.”

Research Process and Results

1. Analysis of CCN2 Expression in Human Atherosclerotic Tissues

The research team first analyzed single-cell RNA sequencing data from human atherosclerotic coronary arteries and found that CCN2 expression was upregulated in dedifferentiated VSMCs. Through immunohistochemical staining, the researchers further confirmed that CCN2 protein levels significantly increased in advanced lesions, particularly in VSMCs, across different stages of human coronary atherosclerosis. Additionally, plasma CCN2 protein levels were also significantly elevated in patients with coronary artery disease.

2. Impact of CCN2 Deficiency on Atherosclerosis in Mouse Models

To validate the role of CCN2 in atherosclerosis, the research team constructed an inducible VSMC-specific CCN2 knockout mouse model. The results showed that CCN2 knockout mice were highly susceptible to the development of atherosclerosis, as evidenced by a significant increase in lipid plaques within the aorta. Through ultrasound analysis and histological staining, the researchers found that CCN2 knockout mice exhibited pronounced aortic dilation, increased lipid deposition, and impaired aortic valve function.

3. Single-Cell RNA Sequencing Reveals the Impact of CCN2 Deficiency on VSMC Phenotypic Switching

By performing single-cell RNA sequencing on the aortas of CCN2 knockout mice, the researchers found that CCN2 deficiency led to significant changes in VSMC phenotype, characterized by reduced expression of contractile markers and increased expression of macrophage markers. Furthermore, CCN2 deficiency promoted the transformation of VSMCs into macrophage-like cells and increased lipid accumulation and foam cell formation.

4. Effects of CCN2 Deficiency on Endoplasmic Reticulum Stress and Lipid Metabolism

The research team further explored the impact of CCN2 deficiency on endoplasmic reticulum stress (ER stress) and lipid metabolism in VSMCs. Electron microscopy revealed that the endoplasmic reticulum lumen in VSMCs of CCN2 knockout mice was significantly dilated, with distorted membrane structures, indicating increased ER stress. Additionally, CCN2 deficiency led to upregulated expression of genes related to cholesterol synthesis, further promoting lipid accumulation and foam cell formation.

5. Inhibitory Effect of Recombinant CCN2 on VSMC Phenotypic Switching

To validate the function of CCN2, the researchers used recombinant human CCN2 (rbCCN2) in in vitro experiments. The results showed that rbCCN2 significantly inhibited cholesterol-induced lipid accumulation and foam cell transformation in VSMCs, while reversing the inhibitory effect of cholesterol on VSMC contractile markers.

Conclusion and Significance

This study found that CCN2 plays a critical protective role in VSMC phenotypic switching and the progression of atherosclerosis. CCN2 deficiency leads to VSMC phenotypic transformation, acquiring macrophage-like characteristics, and promotes lipid accumulation and foam cell formation, thereby exacerbating the development of atherosclerosis. The findings highlight the important role of CCN2 in maintaining vascular homeostasis and provide a new potential therapeutic target for atherosclerosis.

Research Highlights

  1. First to Reveal the Key Role of CCN2 in VSMC Phenotypic Switching: This study is the first to demonstrate that CCN2 deficiency leads to the transformation of VSMCs into macrophage-like cells and promotes lipid accumulation and foam cell formation.
  2. Application of Single-Cell RNA Sequencing Technology: Through single-cell RNA sequencing, the researchers deeply analyzed the impact of CCN2 deficiency on VSMC phenotype, revealing its molecular mechanisms in atherosclerosis.
  3. Discovery of Endoplasmic Reticulum Stress: The study is the first to find that CCN2 deficiency significantly increases ER stress levels in VSMCs, revealing its important role in lipid metabolism and foam cell formation.
  4. Potential Therapeutic Value of Recombinant CCN2: The results suggest that recombinant CCN2 can reverse cholesterol-induced VSMC phenotypic switching, providing new insights for the treatment of atherosclerosis.

Other Valuable Information

The findings of this study not only provide new perspectives for understanding the pathogenesis of atherosclerosis but also lay the foundation for developing targeted therapeutic strategies against CCN2. Future research could further explore the role of CCN2 in vascular inflammation, vascular remodeling, and other cardiovascular diseases, as well as its potential in clinical applications.