Differential Pattern of Circulating MicroRNA Expression in Patients with Intracranial Atherosclerosis

Background: Intracranial atherosclerosis (ICAS) is a major cause of ischemic stroke, yet fundamental studies regarding epigenetic regulation of ICAS are lacking. We hypothesized that, due to anatomical and/or functional differences, extracranial atherosclerosis is distinct from ICAS, which may explain the clinical variability as well. Methods: We chose a number of miRNAs involved in various steps of atherogenesis (namely, miR-712/205-5p/-3p, miR-106b-3p/-5p, miR-146a-3p/-5p, miR-100-3p/miR-5p, miR-200c-3p/-5p, miR-532-3p/-5p, and miR-126-3p/-5p) and examined their plasma levels in a cohort of patients with carotid stenosis > 50% (n = 35, mean age: 65 years, 54% male; 12 patients had ICAS). Results: A differential pattern of circulating miR expression was found in ICAS patients: there was an overexpression of miR-712/205-5p, miR-106b-5p, miR-146a-5p, miR-200c-5p, miR-532-3p, and miR-126-3p. The following miRs were underexpressed in intracranial atherosclerosis-miR-712/205-3p and miR-100-3p. These changes represent a plethora of atherogenic mechanisms: smooth muscle cell migration (miR-712/205, miR-532), foam cell formation (miR-106b, miR-146a), endothelial dysfunction (miR-200c), low-density lipoprotein-induced vascular damage (miR-100), and leukocyte recruitment (miR-126). In symptomatic ICAS patients, we observed a statistically significant upregulation of miR-712/205-3p and miR-146a-5p. Conclusions: Overall, the findings of our pilot study revealed several new and interesting associations: (1) intracranial atherosclerosis seems to have a different epigenetic profile (regarding circulating microRNA expression) than isolated extracranial vessel involvement; (2) ischemic stroke in ICAS may be potentiated by other pathophysiologic mechanisms than in extracranial-only atherosclerosis (ECAS). Certain miRs (e.g., miR-712/205) seem to have a larger impact on ICAS than on extracranial atherosclerosis; this may be potentially linked to difference between extra- and intracranial artery morphology and physiology, and/or may lead to the said differences. This underscores the importance of making a distinction in future epigenetic studies between ECAS and ICAS, as the mechanisms of atherogenesis are likely to vary.