artificial heart valve for young patients that is capable of growing. Currently, there is no tissue-engineered valve that will grow with a patient who needs a heart valve replacement. The team developed the device by growing skin cells from a donor lamb in a tube-shaped gel. They then created flaps that open and close like heart valves (see video) and implanted them into the lamb. The findings, published in Science Translational Medicine, revealed the valves lasted for up to a year as the animals matured into adult sheep.