Custom-made human lungs are still years off. To prevent a patient’s immune system from attacking a new organ, doctors need to perform the reseeding step with cells from that patient’s own body; Niklason’s group can’t yet do that even with rats. Figuring out how to produce adult stem cells that will develop into the correct types of lung cells and not form tumors has proved difficult, although other researchers have made progress with other cell types. Niklason thinks it will take about 20 years before she can rejuvenate a human lung, but she intends to see it through. As she puts it, “I didn’t get into this to make lungs for rats.”HOW TO REMAKE A LUNG
PHASE 1: Strip It
Scientists fill a rat lung with a detergent that removes the organ’s cells, leaving behind only its inanimate collagen-based scaffolding. This is then placed in a standard nutrient-rich liquid that promotes cell growth.
PHASE 2: Build the Airways
Scientists pump epithelial cells extracted from baby rat lungs into the trachea scaffolding, which leads into other empty airways. The cells stick to the scaffolding and multiply to form the bronchi, bronchioles and alveoli, the tiny air sacs that exchange oxygen and carbon dioxide with the blood.
PHASE 3: Construct the Vessels
Making blood vessels is similar. This time, endothelial cells harvested from rat lungs are injected into the scaffolding of the lung’s pulmonary artery. The cells grow to form the lung’s veins, arteries and capillaries.