Marine Isaias Hernandez has been able to grow back most of the missing muscle from his leg, including skeletal muscle, thanks to an experimental treatment involving an injection of a a growth promoting substance extracted from pig bladders. Hernandez lost 70% of his right thigh muscles from a mortar exploded attack in Afghanistan. Normally this type of injury would lead to an amputation. From the article: "In preparation for the operation, corporal Hernandez was made to build up the remaining 30 per cent of muscle left on the damaged thigh. Surgeons then sliced into the thigh, placing a thin slice of a substance called extracellular matrix. The surgery is the result of a $70 million investment by the US military into regenerative medicine research."