Tagging a New Source of Heart Stem Cells (IMAGE) Boston Children's Hospital Caption Pu and Zhou tagged the Wt-1 expressing epicardial cells with a fluorescent red protein, then allowed the cells to differentiate. The image shows a descendent cardiomyocyte (green) that carries the same red marker, and another cell that arose from different origins. (The blue stain indicates cell nuclei). Credit Bin Zhou, MD (Children's Hospital Boston) Usage Restrictions Please credit as indicated. 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.