Mammary Gland Stem Cells in Mice (IMAGE) Princeton University Caption Researchers from Princeton University's Department of Molecular Biology have identified a small RNA molecule that helps maintain the activity of stem cells in both healthy and cancerous breast tissue. Above, the microscopic image shows different cell types in the normal mammary ducts of a mouse. The luminal cells (red) are milk-producing cells and the basal cells (green) have contractile functions, but also are responsible for regenerating the mammary gland, as they contain the majority of mammary gland stem cells. These stem cells, located in the outer layer of the gland, are exposed to microenvironmental factors and interact with various immune cells, including macrophages, in the mammary gland. Credit Image courtesy of Toni Celià-Terrassa and Yibin Kang, Department of Molecular Biology Usage Restrictions Image courtesy of Toni Celià-Terrassa and Yibin Kang, Department of Molecular Biology 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.