Hydrogen Stem Cells (IMAGE) Johns Hopkins Medicine Caption Hydrogel applied to beating rat hearts improves stem cell uptake by the heart muscle and speeds up tissue healing after heart attack. Credit Johns Hopkins Medicine Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.