# Small extracellular vesicles enhance the survival of Sca-1+ cardiac stem cells against ROS-induced ischemic-reoxygenation injury in vitro

## TL;DR

This study shows that small extracellular vesicles from bone marrow stem cells protect heart stem cells from injury caused by oxygen deprivation and reoxygenation.

## Contribution

The study demonstrates that sEVs rich in miRNA-21-5p can precondition Sca-1+ cardiac stem cells to enhance their survival and regeneration under ischemic-reoxygenation stress.

## Key findings

- sEVs reduced apoptosis and increased proliferation in Sca-1+/CSCs under IR conditions.
- miRNA-21-5p-rich sEVs promoted cell cycle progression and stabilized HIF-1α expression.
- sEVs helped reduce oxidative stress and restore redox balance in treated cells.

## Abstract

Ischemic reperfusion (IR) generates reactive oxygen species (ROS) that inevitably result in myocardial cell death and heart failure. The regenerative power of cardiac progenitor/stem pools (CSCs), especially the Sca1+ population, in response to IR injury remains unclear.

Our work sought to investigate whether small extracellular vesicles (sEVs) isolated from bone marrow-mesenchymal stem cells (BMMSCs) could rescue CSCs, specifically Sca-1+/CSCs, from IR by increasing their proliferative capacity and limiting their apoptosis in vitro. The Sca-1+/CSCs-IR model was induced by the oxygen-glucose deprivation/reoxygenation method (OGD/R). The effects of treatment with BMMSCs-derived sEVs on oxidative stress, cell proliferation, apoptosis, and cell cycle were assessed. To further test the mechanistic action, we assessed the PTEN/pAkt/HIF-1α pathway.

Compared to hypoxic untreated CSCs, BMMSCs-derived sEVs-treated cells had shifted from their quiescent to proliferative phase (p > 0.05) and showed decreased apoptosis (p < 0.001). sEVs-treated CSCs were predominately in the S phase (11.8 ± 0.9%) (p < 0.01). We identified an abundance of miRNA-21-5P in BMMSCs. HIF-1α expression was highest in CSCs treated with sEVs (p < 0.05). Moreover, miRNA-21-5p-rich sEVs shifted the redox state, reducing oxidative stress and promoting balance (p > 0.05).

Conditioning Sca-1+/CSCs, an essential population in the postnatal heart, with sEVs rich in miRNA-21 robustly enhanced the proliferation, and synthesis phase of the cell cycle, and stabilized HIF-1α while alleviating oxidative stress and apoptosis. Such sEVs rich in miRNA-21-5p can be further used as a preconditioning tool to enhance endogenous Sca-1+/CSCs regeneration in response to IR injury.

The online version contains supplementary material available at 10.1186/s40659-025-00593-7.