# Adipose stem cell-derived exosomes circular RNA circFryl attenuate atrial fibrosis and cardiomyocyte apoptosis in atrial fibrillation

## TL;DR

This study shows that exosomes from fat stem cells can reduce heart damage in atrial fibrillation by delivering a specific circular RNA called circFryl.

## Contribution

The study identifies a novel circFryl/miR-338-3p/TIMP4 pathway through which ADSC-derived exosomes protect against atrial fibrillation.

## Key findings

- ADSC-exosomes elevated circFryl levels and reduced atrial diameter in AF models.
- Knockdown of circFryl in exosomes abolished their protective effects on fibrosis and apoptosis.
- circFryl interacts with miR-338-3p to stabilize TIMP4 mRNA, mediating the therapeutic effects.

## Abstract

Atrial fibrillation (AF) is a prevalent arrhythmia accompanied by structural and electrical remodeling of the heart. Here, we examined the possible mechanisms behind the protective role of adipose-derived stem cell (ADSC)-derived exosomes in AF therapy.

We isolated exosomes from ADSCs. Exosome treatment was given. The left atrial diameter was measured by echocardiographic imaging. Cardiac fibrosis and damage were detected. The interaction between miR-338-3p with circFryl and tissue inhibitor of metalloproteinase mRNA (4TIMP4 mRNA) was predicted and investigated using qPCR and western blotting assay.

The overexpression of circFryl in ADSCs elevated the level of circFryl in exosomes and the myocytes, whereas knockdown of circFryl exhibited the opposite effects. Treatment with ADSC-exosomes significantly elevated circFryl level and recovered left atrial diameter, whereas knockdown of circFryl in exosomes abolished these effects. ADSC-exosomes alleviated the cardiac fibrosis and cell apoptosis in the AF model, and the knockdown of circFryl abolished these effects. ADSC-exosomes treatment suppressed viability and fibrosis and enhanced cell apoptosis in Ang-II-induced fibroblasts, which was reversed by depletion of circFryl. Online analysis of miRNA interaction targets showed potential binding between miR-338-3p with circFryl and TIMP4 mRNA. Knockdown of circFryl notably suppressed TIMP4 level, and inhibition of miR-338-3p recovered TIMP4 level. TIMP4 overexpression and miR-338-3p inhibition abolished the effects of sicircFryl in vitro and in vivo.

The ADSC-derived exosomes delivered circFryl to interact with miR-338-3p, subsequently enhancing TIMP4 mRNA stability and expression in cardiac fibroblasts and myocytes. The circFryl/miR-338-3p/TIMP4 axis mediated the protective effects of ADSC on AF.