Role and Mechanism of circ_UBR4/miR-10a-5p/KLF4 in Regulating Vascular Smooth Muscle Cell Phenotypic Transformation in Cardiac Allograft Vasculopathy

Cardiac Allograft Vasculopathy (CAV) remains a predominant challenge in post-transplant cardiac care. The phenotypic transformation of vascular smooth muscle cells (VSMCs) is central to its progression, contributing to neointimal hyperplasia and long-term graft failure. Recent studies have highlighted the involvement of non-coding RNAs as essential modulators in VSMC regulation, opening new avenues for therapeutic exploration.In this study, we aimed to explore the role of the circ_UBR4/miR-10a-5p/KLF4 regulatory axis in VSMC phenotypic switching. Human aortic smooth muscle cells (HASMCs) underwent co-transfection with constructed plasmids of both wild-type and mutated sequences for circ_UBR4 and KLF4, along with respective miR-10a-5p mimics or controls. Functional and mechanistic assays, including dual-luciferase reporter analysis, flow cytometry, Transwell migration and invasion assays, qRT-PCR, Western blotting, and immunofluorescence, were utilized to investigate interactions and downstream effects. Our results revealed that circ_UBR4 directly interacts with miR-10a-5p, and its suppression led to attenuated VSMC proliferation and migration. This inhibitory effect was reversed by concurrent miR-10a-5p downregulation, suggesting a functional antagonism. Further analyses demonstrated that miR-10a-5p directly targets KLF4, and its overexpression resulted in decreased proliferative capacity and reduced expression of synthetic and proliferative markers (e.g., OPN, MMP-2, PCNA, and ki-67). These effects were counteracted by KLF4 overexpression. In parallel, contractile marker SM-22α showed opposing trends, further confirming phenotypic transition.Together, these findings confirm that the circ_UBR4/miR-10a-5p/KLF4 axis critically regulates VSMC phenotypic plasticity. Insights from this study provide new molecular evidence underlying CAV pathogenesis and suggest potential targets for innovative therapeutic strategies in transplant cardiology.