The aim of this study is to determine the expression levels and clinical significance of circulating microRNAs (miRNAs), let-7e and miR-338 at different stages following ischemic stroke (IS). Seventy-two patients with IS at the acute stage were enrolled and monitored at different stages, and 51 healthy volunteers were served as the normal controls. Expression of let-7e and miR-338 in serum and cerebral spinal fluid (CSF) samples was analyzed by real-time quantitative PCR. The relationship between expression levels of let-7e and miR-338, National Institutes of Health Stroke Scale (NIHSS) scores, and the levels of serum CRP was analyzed, respectively. Compared to healthy controls, serum let-7e expression levels were significantly increased, while serum miR-338 expression levels were slightly increased in IS patients. Expression levels of Let-7e in serum varied at different stages in IS patients with the lowest expression in the recover stage and highest expression in the acute stage. However, serum miR-338 expression in IS patients was not significantly different in any stage. Compared to healthy controls and nonacute stages of IS groups, let-7e expression in CSF was markedly upregulated in IS patients at the acute stage. Different from that of let-7e, miR-338 expression in CSF was upregulated in IS patients only at the subacute stage but not in the acute stage. Meanwhile, let-7e, which was not significantly correlated with NIHSS scores (r = 0.29, P > 0.05), was positively correlated with the serum CRP levels (r = 0.67, P = 0.033). There is no significant correlation between the miR-338 expression levels and NIHSS scores or serum CRP levels. Moreover, let-7e, but not miR-338, had a high consistency in expression when tested both in CSF and serum samples. Finally, serum let-7e showed a specificity up to 73.4 % and a sensitivity of 82.8 % in IS patients at the acute stage, whereas serum miR-338 in IS patients showed a specificity up to 53.2 % and a sensitivity of 71.9 % in the acute stage. Expression levels of let-7e in serum may serve as a useful noninvasive circulating biomarker for the acute stage of ischemic stroke.
Keywords: Acute stage; Circulating biomarker; Ischemic stroke; Let-7e; MicroRNA-338.