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

## TL;DR

This study shows that Sirt1 helps human embryonic stem cells turn into heart muscle cells through a specific molecular pathway.

## Contribution

The study identifies a novel ceRNA axis (XR_951230.1/miR-3663-3p/SMYD1) regulated by Sirt1 during cardiomyocyte differentiation.

## Key findings

- Sirt1 deletion reduced mesodermal and cardiac precursor marker expression in hESCs.
- Sirt1 regulates the XR_951230.1/miR-3663-3p/SMYD1 pathway during cardiomyogenesis.
- The study reveals a new regulatory network for stem cell-based heart cell development.

## Abstract

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.