The SNHG12/microRNA-15b-5p/MYLK axis regulates vascular smooth muscle cell phenotype to affect intracranial aneurysm formation

Objective

This research was dedicated to investigating the impact of the SNHG12/microRNA (miR)-15b-5p/MYLK axis on the modulation of vascular smooth muscle cell (VSMC) phenotype and the formation of intracranial aneurysm (IA).

Methods

SNHG12, miR-15b-5p and MYLK expression in IA tissue samples from IA patients were tested by RT-qPCR and western blot. Human aortic vascular smooth muscle cells (VSMCs) were cultivated with H₂O₂ to mimic IA-like conditions in vitro, and the cell proliferation and apoptosis were measured by MTT assay and Annexin V/PI staining. IA mouse models were established by induction with systemic hypertension combined with elastase injection. The blood pressure in the tail artery of mice in each group was assessed and the pathological changes in arterial tissues were observed by HE staining and TUNEL staining. The expression of TNF-α and IL-1β, MCP-1, iNOS, caspase-3, and caspase-9 in the arterial tissues were tested by RT-qPCR and ELISA. The relationship among SNHG12, miR-15b-5p and MYLK was verified by bioinformatics, RIP, RNA pull-down, and luciferase reporter assays.

Results

The expression levels of MYLK and SNHG12 were down-regulated and that of miR-15b-5p was up-regulated in IA tissues and H₂O₂-treated human aortic VSMCs. Overexpressed MYLK or SNHG12 mitigated the decrease in proliferation and increase in apoptosis of VSMCs caused by H₂O₂ induction, and overexpression of miR-15b-5p exacerbated the decrease in proliferation and increase in apoptosis of VSMCs caused by H₂O₂ induction. Overexpression of miR-15b-5p reversed the H₂O₂-treated VSMC phenotypic changes caused by SNHG12 up-regulation, and overexpression of MYLK reversed the H₂O₂-treated VSMC phenotypic changes caused by up-regulation of miR-15b-5p. Overexpression of SNHG12 reduced blood pressure and ameliorated arterial histopathological damage and VSMC apoptosis in IA mice. The mechanical analysis uncovered that SNHG12 acted as an endogenous RNA that competed with miR-15b-5p, thus modulating the suppression of its endogenous target, MYLK.

Conclusion

Decreased expression of SNHG12 in IA may contribute to the increasing VSMC apoptosis via increasing miR-15b-5p expression and subsequently decreasing MYLK expression. These findings provide potential new strategies for the clinical treatment of IA.