Fibroblasts (image) University of North Carolina Health Care Share Print E-Mail Caption Fibroblasts (red) express endothelial markers (green), making the heart cells in mice appear yellow. The green blood vessels running horizontally are partly composed of red/yellow cells, suggesting that fibroblasts are incorporated into blood vessels. Credit Eric Ubil, PhD Usage Restrictions None Share Print E-Mail 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.