Gene expression of cell types present in the vascular wall during the initiation and progression of atherosclerosis
A key element of atherosclerosis, the primary cause of coronary artery disease (CAD), is chronic inflammation of the vessel wall. Identifying the gene expression of the cells present in the vessel wall during atherogenesis can clarify these events and provide new research possibilities. The work presented here characterizes a putative transcription factor that contributes to atherosclerosis, identifies candidate genes involved in the activation of endothelial cells, and defines the expression patterns of CAD GWAS candidate genes in mouse vascular cells.
Zhx2, a putative transcription factor, was identified as a gene controlling plasma lipid levels using congenic mice and fine-mapping. Liver-specific Zhx2 transgenic mice on a Zhx-null background exhibited a corrected plasma lipid profile, confirming Zhx2 as the gene controlling the plasma lipid phenotype. Male Zhx2-null mice had atherosclerotic lesions nine times smaller than mice with a wild-type Zhx2 allele, a large effect that could not be fully explained by their plasma lipid profiles. Treatment of macrophages with the pro-inflammatory factor LPS elicited a strong increase in Zhx2 transcript, suggesting involvement in the inflammatory response. A bone marrow transplant of Zhx2-null hematopoietic stem cells into Zhx2 wild-type mice resulted in a more than 4-fold reduction in atherosclerotic lesion size, supporting a role for Zhx2 in the chronic immune response accompanying atherosclerosis.
Endothelial cells are a central component in the initiation and progression of atherosclerosis, and the study of their expression profile could provide valuable data. Since the cell culture of mouse aortic endothelial cells (MAECs) has been challenging, we identified an alternate method for the isolation of RNA from these cells. Microarray analysis of these transcripts identified 14 differentially expressed genes in pre-lesioned MAECs, eight of which have not been previously described in atherosclerosis. This method has also made it feasible to collect RNA samples from distinct cell types present in the vessel wall during atherosclerosis. Recent genome wide association studies on CAD have identified loci representing 56 candidate genes. We used quantitative PCR to identify the expression levels of these genes in each atherosclerotic cell type and report the results.