Stem Cells (IMAGE) Penn State Caption Schematic illustrating the reduced leakage expression, tight drug induced regulation, and retained functionality of new plasmid system in stem cells and differentiated cell types. Top indicates current system being used to induce stem cells to differentiate, green indicates where plasmids are located. Bottom shows stem cells with plasmids incorporated and on right top, the cells remain as they are if no doxycycline is applied and on the bottom, they glow green showing that doxycycline activates the plasmid DNA. To the right, activated stem cells become heart cells and without doxycycline show no leakage expression, but express when activated by doxycycline. Credit Laura Randolph, Penn State Usage Restrictions Non commercial use only. 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.