RNA Splicing of the REST Gene by SRRM4 in Vascular Smooth Muscle Cells Promotes Abdominal Aortic Aneurysm Development
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Background
The progression of abdominal aortic aneurysm (AAA) is closely associated with the phenotypic switch of vascular smooth muscle cells (VSMC). While members of the Serine/Arginine-rich splicing factor (SRs) superfamily are increasingly acknowledged for their pivotal role in modulating cell phenotype, the specific contribution of these factors to AAA development has remained underexplored.
Methods
Through integrated analyses the whole transcriptome of human and murine AAA tissues derived from clinical samples and animal models, we identified serine-arginine repeat matrix 4 (SRRM4) as a candidate gene regulating AAA formation. To investigate the role of SRRM4 in AAA formation, we used global and VSMC-specific SRRM4-knockout mice to construct AAA mouse models in two different ways. The impact of SRRM4 on AAA was further investigated in in vivo and in vitro models
Results
Elevated levels of SRRM4 mRNA and protein were observed in VSMC from both human and murine AAA tissues. Targeted silencing of SRRM4 in VSMC (but not in endothelial or myeloid cells) significantly attenuated AAA formation in both AngII- and CaCl 2- induced mouse models. Our results identify the RE1 silencing transcription factor (REST) as a critical target gene of SRRM4 in AAA, a master regulator of cellular phenotypic stability. We show that SRRM4 modulates VSMC phenotype through alternative splicing of the REST gene, resulting in a non-functional REST4 isoform. Furthermore, our study shows that REST directly represses STAT1, a mechanism by which SRRM4 influences VSMC phenotypic transition. Regarding clinical significance, inhibition of both STAT1 expression and function was shown to be beneficial in preventing AAA formation and slowing disease progression in mouse models.
Conclusions
This investigation uncovers a previously unrecognized role of SRRM4-mediated splicing of the REST gene in the progression of AAA and identifies a novel REST/STAT1 axis critical in the phenotypic modulation of VSMC. The findings of this study may provide insights for the development of innovative therapeutic strategies for AAA.
What is New?
Our study demonstrates that the RNA splicing factor SRRM4 (serine/arginine repetitive matrix 4) expression is increased in human and murine abdominal aortic aneurysm (AAA) tissues and unveils a previously undescribed role of SRRM4 in regulating AAA development.
SRRM4 promotes AAA development and progression through inducing splicing of REST (RE1 silencing transcription factor) gene and upregulating STAT1 (signal transducer and activator of transcription 1) expression, which result in extracellular matrix degradation, inflammation, and VSMC phenotypic switching.
Our study provides proof-of-concept evidence indicating the therapeutic value of STAT1 inhibition in AAA prevention and treatment.
What Are the Clinical Implications?
Our study defining a novel mechanism underlying the SRRM4/REST/STAT1 axis is crucial for developing new therapeutic strategies for AAA.
Based on these findings, we have initiated a prospective study (REST4-AAA; ClinicalTrials.gov Identifier: NCT07056491 ) to evaluate REST4 expression levels in serum of AAA patients and explore its potential as a serum biomarker for AAA prediction
Our findings indicate that fludarabine, a clinically available agent reported to selectively suppress STAT1, effectively attenuates AAA progression in mice, suggesting its potential for repurposing as a therapeutic strategy for AAA.
