Exosomes as Critical Agents of Cardiac Regeneration Triggered by Cell Therapy

TLDR

The CADUCEUS trial demonstrated that cardiosphere‑derived cells can regenerate previously scarred heart muscle, yet the indirect mechanisms mediating this benefit remain unidentified. This study aims to identify exosomes secreted by human CDCs as the critical agents driving cardiac regeneration and protection. The authors show that CDC‑derived exosomes, enriched in microRNAs such as miR‑146a, mediate these effects. Exosome injection into injured mouse hearts reproduces the regenerative and functional improvements of CDC transplantation, while blocking exosome production abrogates these benefits, and a miR‑146a mimic partially recapitulates the exosome effects, confirming exosomes as key mediators and highlighting their therapeutic potential.

Abstract

The CADUCEUS trial of cardiosphere-derived cells (CDCs) has shown that it may be possible to regenerate injured heart muscle previously thought to be permanently scarred. The mechanisms of benefit are known to be indirect, but the mediators have yet to be identified. Here we pinpoint exosomes secreted by human CDCs as critical agents of regeneration and cardioprotection. CDC exosomes inhibit apoptosis and promote proliferation of cardiomyocytes, while enhancing angiogenesis. Injection of exosomes into injured mouse hearts recapitulates the regenerative and functional effects produced by CDC transplantation, whereas inhibition of exosome production by CDCs blocks those benefits. CDC exosomes contain a distinctive complement of microRNAs, with particular enrichment of miR-146a. Selective administration of a miR-146a mimic reproduces some (but not all) of the benefits of CDC exosomes. The findings identify exosomes as key mediators of CDC-induced regeneration, while highlighting the potential utility of exosomes as cell-free therapeutic candidates.