BMP6 contributes as a blood-based biomarker to clinical discrimination of patients with carotid artery stenosis: Decoding the transcriptome of plaque biology

Carotid artery stenosis (CAS) patients are classified as "symptomatic" CAS (SCAS) and "asymptomatic" CAS (ACAS) based on their symptoms. For SCAS and ACAS, complementary biomarkers are needed since the degree of stenosis is insufficient for selecting a treatment or risk assessment. Carotid plaque ulceration represents vulnerable features, and the symptomatic plaque is considered vulnerable. The current study aimed to investigate a blood-based biomarker to determine the presence of ulceration/symptoms in blood by analyzing plaque material based on surface morphology. RNA-Sequencing was performed using the Ion AmpliSeq Transcriptome Human Gene Expression Panel. Additionally, bioinformatic analysis was performed using ingenuity pathway analysis (IPA). Then, gene expression and protein levels were analyzed using Real-Time quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay. Based on IPA, immune responses, and reactive oxygen species (ROS) production, lipid transport is activated in SCAS patients. For ulcerated and smooth plaque comparison, it was determined that lipid and sterol transport, and catabolism of lipids, occurred in ulcerated plaque. Based on RT-qPCR, while tissue inhibitor of metalloproteinase 3 (<i>TIMP3</i>), Desmin (<i>DES</i>), <i>ITLN</i>, Chitinase 3-like 2 (<i>CHI3L2</i>), four and a half LIM domains 5 (<i>FHL5</i>), Clusterin (<i>CLU)</i>, and fin bud initiation factor homolog (<i>FIBIN</i>) genes were statistically significant in plaque material, C-C motif ligand 24 (<i>CCL24</i>), bone morphogenic protein 6 (<i>BMP6</i>), and interleukin 6 (<i>IL6</i>) were also significant in blood. Interestingly, these genes were downregulated in both plaque and blood. For ulcerated plaque, <i>CCL24</i> and <i>BMP6</i> were regulated in both blood and plaque, but only <i>BMP6</i> was determined to be downregulated in both. Finally, multivariate binary logistic regression shows that <i>BMP6</i> had the most remarkable ability to predict the SCAS versus ACAS discrimination (odds ratio = 0.553, p = 0.019). Although more studies are warranted, our results suggest that <i>BMP6</i> seems to be a blood-based biomarker for discriminating SCAS versus ACAS.