#5. Building a Human Heart Valve
The World Heath Organization estimates that some 600,000 people around the world will need replacement heart valves within the next three years. British scientists delivered those patients some hopeful news: A team of researchers led by Dr. Magdi Yacoub of the Imperial College of London saw 10 years of work come to fruition this spring, when they grew bone marrow stem cells into functioning human heart-valve tissue. Yacoub hopes that the tissue can be grown into the shape of a heart valve using a special collagen scaffolding. Yacoub's advancements build on the ongoing efforts of scientists around the world to grow new heart valves and other body parts. If Yacoub's tissue holds up in animal trials, he estimates it could be used in human heart-valve transplant patients within 3 to 5 years.