Myofibroblast-Derived Exosomes Contribute to Development of a Susceptible Substrate for Atrial Fibrillation

Abstract

Objective: Atrial fibrosis plays a critical role in atrial fibrillation (AF). A key event in the pathogenesis of fibrosis is the activation of fibroblasts (FBs) into myofibroblasts (MFBs). Paracrine factors released from MFBs lead to ion channel expression changes in cardiomyocytes (CMs). Downregulation of L-type calcium channel Ca v 1.2 expression is a hallmark of AF-associated ionic remodeling. However, whether exosome (Exo)-mediated crosstalk between MFBs and CMs regulates Ca v 1.2 expression remains unknown. Methods: Atrial FBs and CMs were isolated and cultured from neonatal rats by enzymatic digestion. The activation of FBs into MFBs was induced by angiotensin II. Co-culture assay and in vitro Exo treatment were used to determine the effect of MFB-derived Exos on Ca v 1.2 expression. Confocal Ca 2+ imaging was performed to examine the adrenergic stimulation-elicited Ca 2+ influx signals. The levels of potential Ca v 1.2-inhibitory mi-croRNAs (miRNAs) were measured by qRT-PCR. Results: Untreated FBs expressed limited amounts of alpha smooth muscle actin (α-SMA), while angiotensin II induced a signifi-cant upregulation of α-SMA-expressing MFBs. Co-cultures of MFBs and CMs resulted in downregulation of Ca v 1.2 expression in CMs, which was largely abolished by pretreatment of MFBs with exosomal inhibitor GW4869. More importantly, treatment with MFB-derived Exos caused repression of Ca v 1.2 expression in CMs. Additionally, the adrenergic receptor agonist-elicited Ca 2+ influx signals in CMs were remarkably attenuated by pretreatment with MFB-derived Exos, corresponding to the paralleled change in Ca v 1.2 expression. Finally, miR-21-3p, a potential Ca v 1.2-inhibitory miRNA, was enriched in MFB-derived Exos and upregulated in CMs in response to MFB-derived Exos. Conclusion: We uncover an Exo-mediated crosstalk between MFBs and CMs, contributing to increased vulnerability to AF by reducing the expression of Ca v 1.2 in CMs.

Blockade of Exosome Release Suppresses Atrial Fibrillation by Alleviating Atrial Fibrosis in Canines With Prolonged Atrial Pacing

“…The changes in AERPs could be related to some ion channel-related miRNAs contained in exosomes. A previous study also showed that Ang II-treated cardiac fibroblast-derived exosomes contained miR-21-3p, which could regulate the expression of Cav1.2 and contribute to the development of a susceptible substrate for atrial fibrillation (13). However, we did not further explore the mechanism by which inhibition of exosome release directly changed AERPs.…”

“…Moreover, it has been demonstrated that, compared with the control group, the epicardial adipose tissue of patients with AF secretes more exosomes, and the expression of pro-inflammatory and pro-fibrotic factors is higher in exosomes (12). In addition, a recent study reported that myofibroblast-derived exosomes reduced the expression of voltage-gated L-type calcium channel subunit α1c (Ca v 1.2) and increased the vulnerability to AF (13). Based on these studies, we hypothesized that the increased secretion of exosomes was likely to promote AF.…”

The Role of Exosomes and Their Cargos in the Mechanism, Diagnosis, and Treatment of Atrial Fibrillation

“…They found that exosomes secreted by MFBs can act on cardiomyocytes (CMs) and cause the latter to down-regulate the expression of the L-type calcium channel Cav1.2, which is a typical AF-associated ionic remodeling marker. Further studies have shown the miR-21-3p in exosomes may be the inhibitory molecule responsible for this down-regulation ( 60 ). In addition, it has been observed that the lncRNA NRON (ncRNA repressor of the nuclear factor of activated T cells) can promote polarization of M2 macrophages to reduce atrial fibrosis, and a study by Li et al showed that exosomes are involved in this process.…”

“…The miR-21-3p in exosomes has been shown to be related to the mechanism of AF ( 60 ). And many other miRNAs have been reported to be associated with AF.…”

Mesenchymal Stem Cells-derived Exosomal miR-148a-3p Alleviates Atrial Fibrosis and Vulnerability to Atrial Fibrillation Through Targeting ALK5/Smad2 Axis

“…For the sake of verifying the effects of MSCs-Exo on proliferation, phenotypic switching and secretion functions of broblasts, Ang-II was used to stimulate atrial broblasts (FBs) to trans-differentiate into myo broblasts (MFBs) [14]. The differentiation was con rmed using immuno uorescence staining for α-SMA, a speci c marker for MFBs.…”