Abstract 11990: Insulin-Like Growth Factor Binding Protein 2 is a Novel Marker of Early Smooth Muscle Cell Phenotype Modulation in Thoracic Aortic Aneurysm

Abstract

Introduction: Single cell RNA sequencing (scRNAseq) enables high resolution analysis of vascular smooth muscle cell (SMC) phenotype modulation in thoracic aortic aneurysm. Insulin-like growth factor binding protein-2 ( Igfbp2 ) expression by SMCs is activated early in a murine Marfan syndrome (MFS) aortic aneurysm model. IGFBP2 modulates IGF1 bioavailability and interacts directly with SMCs via integrins. We hypothesize that IGFBP2 is a marker of early SMC modulation in human aortopathy. Methods: Surgically resected aortic aneurysm tissue was collected from patients spanning the clinical spectrum of monogenic aortopathies ( ACTA2, FBN1, TGFBR1 (n=2), TGFB2, or SMAD3 variants). Tissues were digested and processed for scRNAseq. SMC clusters from all patients were jointly analyzed with pseudotemporal trajectory analysis to reconstruct the SMC phenotypic continuum. Primary MFS human (n=5) aortic root SMCs underwent IGFBP2 silencing via siRNA followed by bulk RNAseq. Results: scRNAseq identified two main SMC clusters, comprising 39% of all cells in the dataset, including a quiescent contractile SMCs and a modulated, synthetic subset. Pseudotemporal ordering generated a continuous ‘pseudotime’ scale inversely correlated with contractile gene (e.g., CNN1, MYH11) expression, modeling gradual de-differentiation in vivo . We identified similar markers of late SMC modulation (e.g., TNFRSF11B , MMP2, CYTL1, COL1A1 ) in patients of all genotypes. IGFBP2 expression showed comparatively earlier activation and peak with reduced expression late in pseudotime. Silencing IGFBP2 in human MFS SMCs in vitro significantly depressed contractile gene expression. Conclusions: SMC modulation occurs in consistent pattern across hereditary aortopathy subtypes. IGFBP2 activation occurs early in this trajectory, marking cells in phenotypic transition. IGFBP2 may promote contractile phenotype maintenance, presenting a novel pathway for potential therapies.