Human Vascular Progenitor Cells (IMAGE) Johns Hopkins Medicine Caption Human vascular progenitor cells (green), made from Zambidis' lab-grown naive stem cells, engraft into blood vessels (red) in a mouse retina. Credit Elias Zambidis, 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.