Sirt1 Promotes Cardiomyocyte Differentiation Through the XR_951230.1/miR-3663-3p/SMYD1 Axis

Background: Sirtuin 1 (Sirt1) is known to regulate stem cell differentiation and cardiomyocyte function, yet its specific role and mechanism in human embryonic stem cell (hESC) differentiation into cardiomyocytes remain unclear. This study aimed to elucidate the functional contribution and molecular pathway of Sirt1 in cardiomyogenesis. Methods: A Sirt1 knockout (Sirt1^-/^-) hESC line was generated using CRISPR-Cas9 technology. The expression of key differentiation markers was analyzed by RT-qPCR at days 6, 8, and 9. The underlying mechanism was investigated through integrated RNA-sequencing (RNA-seq) analysis and dual-luciferase reporter assays. Results: Sirt1 deletion significantly downregulated the expression of mesodermal (TBX6, KDR), cardiac precursor (NKX2.5, TBX5), and mature cardiomyocyte (cTNT, Hand2) markers. Mechanistically, a competing endogenous RNA (ceRNA) axis, LncRNA XR_951230.1/miR-3663-3p/SMYD1, was identified. Sirt1 knockout reduced XR_951230.1 expression, which consequently elevated miR-3663-3p activity and suppressed its target gene SMYD1. Conclusions: These findings indicate that Sirt1 is essential for promoting hESC differentiation into cardiomyocytes, potentially via the XR_951230.1/miR-3663-3p/SMYD1 pathway. This study provides new insights into the regulatory network of stem cell-based cardiomyogenesis and suggests potential targets for stem cell-based cardiac disease therapy.