# Identification of Connexin 26 on Extracellular Vesicles from Human Cardiomyocytes and Plasma: Novel Insights into miRNA Loading and Oxidative Injury

## TL;DR

This study shows that Connexin 26 is present on heart cell-derived extracellular vesicles and may play a role in heart disease by influencing microRNA transport and signaling.

## Contribution

First identification of Connexin 26 on extracellular vesicles from human cardiomyocytes and plasma, revealing a new non-gap junction role in cardiac signaling.

## Key findings

- Cx26 is present on EVs from human cardiomyocytes and plasma.
- Oxidative injury reduces Cx26 levels in EVs and alters EV concentration.
- Cx26 modulates the loading of miR-1 and miR-30a into EVs, suggesting a novel signaling role.

## Abstract

Connexin 26 (Cx26), a gap junction protein, is poorly understood in the context of cardiac milieu, including extracellular vesicles (EVs). Here, we report for the first time the presence of Cx26 on EVs obtained from human induced pluripotent stem cell-derived cardiomyocytes and human plasma. Using an in vitro model of oxidative stress and apoptosis in dH9c2 cardiomyocytes, we observed a significant decrease in Cx26 levels in EVs released by injured cells, accompanied by changes in EV concentration, particularly in exosomes. Our findings revealed that Cx26 modulates the selective loading of specific microRNAs, namely miR-1 and miR-30a, into EVs, suggesting a novel non-canonical, gap junction-independent role of Cx26 in EV-mediated cardiac signaling. Analysis of plasma EVs from healthy donors confirmed the presence of Cx26-positive EVs of cardiomyocyte origin, indicated by co-staining with cardiac troponin T. These findings suggest that further studies on the measurement of Cx26 on circulating EVs from patients with ischemic heart disease and heart failure are warranted to clarify its potential as a biomarker for cardiomyocyte injury in cardiomyopathies with oxidative stress and apoptosis.