Integrated single-cell transcriptomic analysis suggests ANGPT2 as a candidate mediator of fibroblast–vascular smooth muscle cell crosstalk in Marfan syndrome

Marfan syndrome (MFS) is an inherited connective tissue disorder caused by pathogenic variants in the FBN1 gene, with the development of progressive thoracic aortic aneurysms representing one of its most life-threatening manifestations. Although fibroblasts are the primary FBN1 -expressing cells within the aortic cellular landscape, their heterogeneous remodeling in MFS and their contribution to disease pathogenesis remain inadequately understood. We integrated single-cell transcriptomic data from Marfan mouse aortas with bulk transcriptomes from both Marfan mice and human MFS patients to investigate fibroblast heterogeneity in MFS. Next, we delineated the interaction mechanisms between fibroblasts and vascular smooth muscle cells (VSMCs) through cell-cell communication analysis and in vitro stimulation assays. Ultimately, pseudotime trajectory and transcriptional regulatory analyses jointly indicated that RUNX1 might serve as a candidate upstream regulator in this process. To further assess its potential role, we conducted preliminary functional predictions through in silico cell modeling. Our findings suggest that the expansion of a specific myofibroblast subpopulation in MFS is closely associated with disease phenotypes. Integrative analyses and in vitro experiments preliminarily support myofibroblast-derived ANGPT2 as a candidate ligand that acts upon VSMCs and may function through the ITGA5/ITGB1 receptor complex. This interaction involves the PI3K-AKT signaling cascade and may contribute to the phenotypic modulation of VSMCs. In addition, RUNX1 is a possible upstream regulator associated with myofibroblast differentiation and Angpt2 expression in the context of MFS. Collectively, these findings suggest that RUNX1, ANGPT2, and PI3K may be involved in aberrant fibroblast remodeling and VSMC dysfunction in MFS aortic aneurysm. Accordingly, we propose a signaling cascade hypothesis: RUNX1 is a candidate upstream regulator of Angpt2 , and ANGPT2 may act on VSMCs and activate PI3K-AKT signaling, potentially contributing to VSMC phenotypic modulation; however, this cascade remains to be experimentally validated.