Extracellular vesicles are small structures that are secreted by cells and contain molecules called microRNAs, which can induce the recovery of damaged heart tissue. However, the therapeutic effects of extracellular vesicles are short-lived. To address this problem, researchers recently engineered a hydrogel patch capable of slowly releasing extracellular vesicles secreted from heart muscle cells. When implanted into injured rat hearts, the patch attenuated the damage, promoted recovery, and prevented heart muscle cells from dying or growing too large. According to the authors, the extended delivery of extracellular vesicles secreted from heart muscle cells may represent a promising treatment for heart injury. The study, published in Nature Biomedical Engineering, was partly funded by NHLBI.