Profiling expression and immune cell abundance of atherosclerotic plaques: role of hyperglycemia

To identify molecular clues explaining the burden of cardiovascular events in diabetic patients we aimed to characterize gene expression profiles and immune infiltration in atheromatous plaque. Plaques RNA profiles were obtained from 117 patients underwent carotid endarterectomy, by means of high coverage (30 million pairs of 100 bp reads/sample) paired-end RNA-sequencing on Illumina NexSeq500, following Illumina-based strand specific protocol. Differential expression genes (DEGs) were assessed in patients with impaired (IGM; defined as IGT, IFG or T2D according to American Diabetes Association; n=93) versus normal glucose metabolism (NGM; n=24), by using edgeR package. CIBERSORT was used to estimate the relative abundance of 22 different immune cell types (LM22) within plaque samples. Differences between IGM and NGM plaques were tested and correlation matrix settled-up to explore the overall heterogeneity of immune infiltration. We found 43 DEGs in IGM vs NGM plaques (adj.p<0.05), among which 10 encoding immunoglobulin variable chains genes, and 13 encoding protein, all variably involved in immune cell signaling, adhesion, extracellular matrix interaction. Up on 22 immune cell types tested, in both IGM and NGM plaques, 12 were detected, with a higher amount of B cells naïve, T cells CD4 memory resting, M0- and M2-macrophages, and mast cells activated. As compared to NGM counterparts, IGM plaques showed significantly lower abundance in CD8 T cells (p=0,04). As showed by correlation analyses the overall immune infiltration was changed between two groups. Indeed, though not significantly, in both NGM and IGM plaques, B cells naïve, CD8 T cells and resting memory CD4 T cells abundance positively associates. In contrast, while in NGM plaques, M1- M2-macrophages, activated mast cells and neutrophils positively associates, in IGM counterparts, such mutually correlations mostly fail, and activated mast cells and M2-macrophage abundance show significantly negative association. Similarly, in IGM samples compared to NGM, M0-macrophages show a stronger negative correlation (p<0.05) with monocytes and activated NK cells the abundance. Although preliminary, such data could help improve the basic understanding of atherosclerosis in T2D.