Background <p>Uterine spiral artery remodelling (SAR) is a fundamental developmental process that facilitates optimal placental perfusion and supports fetal growth. Central to SAR is the phenotypic transformation of vascular smooth muscle cells (VSMCs) from a contractile to a synthetic state, directed by invasive trophoblast cells. To advance these findings, we sought to elucidate the epigenetic mechanisms governing trophoblast-induced reprogramming of VSMC identity, enabling plasticity required for uterine vascular adaptation.</p> Methods <p>VSMC dedifferentiation was assessed by qRT-PCR, Western blotting, and immunofluorescence. Epigenetic alterations were evaluated by Western blotting. A chromatin remodelling PCR array was performed and validated by qRT-PCR and Western blotting. Chromatin remodelling factors were downregulated using antisense oligonucleotides (ASOs), and VSMC dedifferentiation was confirmed by Western blotting.</p> <p>E13.5 and E16.5 rat metrial glands were used for in vivo validation. An IUGR rat model was generated by administering dexamethasone from E13.5 to E20.5. In IUGR tissues, trophoblast invasion, VSMC dedifferentiation, and chromatin remodelling factor expression were validated by Western blotting.</p> Results <p>Co-culture of primary E16.5 rat trophoblast cells with VSMCs revealed a trophoblast-induced shift in the expression landscape of epigenetic regulators, resulting in upregulation of chromatin-modifying “writers” (CBP, DNMT1, DNMT3A), downregulation of “erasers” (HDAC 1,2,3), and an increase in both transcription activation marks (H3K27ac, H3K9ac) and repression marks (H3K27me3, H3K9me3). Targeted real-time PCR array profiling identified coordinated downregulation of 13 chromatin remodelling genes (ARID1B, SMARCAD1, SMARCD1, SMARCD3, BMI1, EZH2, CBX2, CBX5, CBX6, BAZ1B, ZMYND8, CHD1, MBD3,) during VSMC de-differentiation. This change in the epigenetic landscape was recapitulated in vivo within the metrial gland, the entry point of uterine spiral arteries, on E16.5. Knockdown of these factors impaired the phenotypic transition of VSMCs, establishing their mechanistic role in enabling vascular adaptation. Notably, in a model of intrauterine growth restriction (IUGR), the normal expression dynamics of chromatin remodelling factors and VSMC phenotypic markers were reversed, indicating the need for the dynamic epigenetic regulatory axis, which is essential for vascular adaptation in healthy pregnancies.</p> Conclusions <p>These findings uncover a trophoblast-driven epigenetic axis that governs VSMC plasticity during SAR and highlight its dysregulation as a potential contributor to the pathogenesis of IUGR.</p>