[Intracerebroventricular injection of miR-7 inhibits secondary brain injury induced by intracerebral hemorrhage via EGFR/STAT3 pathway in rats].

Objective To observe the effects of microRNA-7 (miR-7) on intracerebral hemorrhage-induced brain injury in rats and explore the underlying mechanism. Methods Seventy-five SD rats were used to establish intracerebral hemorrhage model through injection of VII collagenase into the pallidum. These rats were then divided into control, miR-7 agomir, agomir control, miR-7 antagomir and antagomir control groups, containing 15 animals in each group. On day 2 after modeling, rats were injected with 10 μL of physiological saline, miR-7 agomir, agomir control, miR-7 antagomir and antagomir control via the lateral ventricle, respectively. On day 7 after modeling, the neurological function score was evaluated, and then all rats were killed to obtain brain tissue. HE staining was conducted to observe the pathological changes of cerebral tissue. Brain water content was examined by the dried and wet mass. The expressions of miR-7, glial fibrillary acidic protein (GFAP) and epidermal growth factor receptor (EGFR) in the cerebral tissue around hemotomas were detected using real-time quantitative PCR. Western blotting was used to analyze the levels of GFAP, EGFR, signal transducers and activators of transcription 3 (STAT3) and phosphorylated STAT3 (p-STAT3) in the cerebral tissue around hemotomas. In addition, bioinformatics was used to predict the binding of miR-7 to EGFR. Both wild type luciferase reporter gene vector and corresponding mutant vector were constructed and then transfected into HEK293T cells along with miR-7 mimic for detecting the luciferase activity. Results In comparison with control group, miR-7 agomir markedly increased miR-7 level, alleviated the pathological impairment of cerebral tissues, reduced neurological function score and brain water content, and attenuated the expression levels of GFAP and EGFR and p-STAT3/STAT3 ratio in the cerebral tissue around hemotomas. An opposite effect was observed in response to miR-7 antagomir. However, their negative controls had no impact on the above indicators. There was a binding site between 3'-untranslated region within the EGFR and miR-7. Moreover, miR-7 mimic markedly decreased the luciferase activity of the reporter gene of wild type, but not its mutant. Conclusion The miR-7 can inhibit the EGFR/STAT3 signaling pathway to antagonize astrocyte activation, leading to the protection against brain injury after intracerebral hemorrhage in rats.