SPI1 Promotes Intracranial Aneurysm Formation by Inhibiting Wnt5a Transcription

SPI1 is a hub gene associated with intracranial aneurysms (IA) and is highly expressed in IA tissues. However, its functional role in IA formation remains unclear. This study aimed to investigate the effect of SPI1 on IA development and its underlying mechanisms.

An in vitro IA cell model was established using Platelet-Derived Growth Factor BB (PDGF-BB)-induced vascular smooth muscle cells (VSMCs). SPI1 expression was silenced via sh-SPI1 plasmids to assess its effects on VSMC phenotypic switching and the Wnt pathway. The binding of SPI1 to the Wnt5a promoter was verified by chromatin immunoprecipitation (ChIP) assays. Furthermore, to investigate whether SPI1 influences the contractile-to-synthetic phenotypic transition of VSMCs via the Wnt pathway, the cells were treated with the Wnt5a inhibitor Box5. The in vivo effects of SPI1 knockdown were assessed using an IA mouse model.

Compared with the control group, PDGF-BB treatment increased the expression of SPI1, synthetic phenotype markers (MMP3/9), and Wnt pathway-related proteins (β-catenin and c-Myc), while reducing the expression of contractile markers (α-SMA and SM22α) and Wnt5a. Silencing of SPI1 reversed these changes. ChIP assays further confirmed that SPI1 could bind directly to the Wnt5a promoter. Moreover, treatment with the Wnt5a inhibitor Box5 reversed the SPI1 knockdown-induced changes in Wnt5a, β-catenin, and c-Myc in VSMCs. In vivo, SPI1 knockdown alleviated vascular wall thickening in the cerebral artery ring of IA mice, improved the loss of elastic fibers, and suppressed inflammatory responses. In addition, SPI1 knockdown promoted Wnt5a expression while restoring the expression of β-catenin, c-Myc, and phenotypic markers toward control levels.

This study suggests that SPI1 promotes intracranial aneurysm formation by inhibiting Wnt5a transcription, thereby promoting activation of the canonical Wnt/β-catenin pathway and driving VSMC phenotypic switching toward a synthetic phenotype. In vivo, SPI1 knockdown alleviated vascular wall injury and inflammation. These findings indicate that the SPI1/Wnt5a signaling axis may represent a potential therapeutic target for intracranial aneurysms.