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The lung is a very complex organ, and that complexity is one reason why the tissue engineering of lungs is lagging behind that of other, less complex organs. It will be a while yet before any organ can be reliably grown from the starting point of a patient's own cells - though groups like the New Organ initiative hope to speed the arrival of that goal.

There is a technology to bridge the gap between the donor transplants of today and the organs grown to order of tomorrow, however: it is decellularization. A donor organ can be stripped of its cells, leaving only the structure of the extracellular matrix. When new cells are introduced, such as those derived from a recipient's stem cells, they are guided by the scaffold and chemical cues of the extracellular matrix to reassemble the correct tissues. The end result is an organ that will match the patient with little to no threat of immune of rejection. It will even possible to use organs from pigs or other similarly sized animals to create a source of decellularized tissues for transplantation.

A few years ago researchers demonstrated the ability to create and transplant decellularized rat lungs. Here this popular science article notes that decellularization in human lungs has reached the proof of concept stage. It is interesting to see that researchers are far more ready to put timelines for development on the table than they were in past years:

For the first time, scientists have created human lungs in a lab -- an exciting step forward in regenerative medicine, but an advance that likely won't help patients for many years. "It's so darn cool," said Joan Nichols, a researcher at the University of Texas Medical Branch. "It's been science fiction and we're moving into science fact."

The researchers started with lungs from two children who'd died from trauma, most likely a car accident. Their lungs were too damaged to be used for transplantation, but they did have some healthy tissue. They took one of the lungs and stripped away nearly everything, leaving a scaffolding of collagen and elastin.

The scientists then took cells from the other lung and put them on the scaffolding. They immersed the structure in a large chamber filled with a liquid "resembling Kool-Aid" which provided nutrients for the cells to grow. After about four weeks, an engineered human lung emerged. Repeating the process, they created another lung from two other children who'd died.

The lab-made lungs look very much like the real thing, just pinker, softer and less dense. Nichols said she thinks it will be another 12 years or so until they'll be ready to try using these lungs for transplants. "My students will be doing the work when I'm old and retired and can't hold a pipette anymore." Before researchers experiment on humans, they'll try out lab-made lungs on pigs.

Link: http://www.wsbt.com/news/health/Human-lung-made-in-lab-for-first-time/24491024