Wait. So Lily's new trachea is in her stomach right now?

Yes. And don't worry. It is complicated. And ground-breaking. And pretty darn awesome.

In Episode 706, "These Arms of Mine," patient Lily Price suffers from a benign growth on her windpipe that keeps recurring despite numerous surgeries to remove it. The tumor may be benign, which means non-cancerous, but the recurrence and size of the mass cause it to impinge on Lily's airway, making it extremely difficult to breathe on her own. If our surgeons at Seattle Grace-Mercy West tried to remove the whole tumor at once, they would be forced to remove Lily's entire trachea. Without a trachea, Lily would die.

What about a replacement? People get organs and tissue transplanted and replaced all the time, right? Well, not so simple. An artificial option for a trachea does not yet exist, and donor tracheas have not been proven to work. Therefore, Lily's surgical team made a decision, with Lily and her mother's consent, to try an experimental solution. They decided to grow Lily a new trachea, using her very own stem cells.

How exactly does this process work?

Surgeons would take cartilage cells and fibrous tissue from Lily's twelfth rib by harvesting a piece approximately three centimeters long. They then take the cartilage up to the lab, wash it thoroughly, and break the mixture down to a cellular level, turning it into a protein liquid. Meanwhile, the doctors constructed a piece of "scaffolding" to form her new trachea. This scaffolding? Basically looks like a clump of cotton-balls, like little tangled up fibers of mesh. They take the cell-protein-liquid and drip it onto the scaffolding, let it soak, and then wrap it into a tube (similar to the shape of a windpipe!).

And now, the "cooking" begins. The doctors place this whole thing into an incubator for, ideally, five to nine days. Once the appropriate amount of time has passed, surgeons then implant the newly-constructed trachea into the patient's body (in order to let the tissue mature), usually under a muscle bed because they keep blood vessels alive and well there. In Lily's case, the trachea went into the abdomen.

So what happens to Lily now?

Well, as Alex says, she needs to take good care of herself to protect that trachea growing away in her abdomen! After a couple of months, our surgeons hope to bring Lily back into the hospital to remove her damaged trachea from her neck and replace it with her tissue-engineered trachea, taken from her abdomen.

What is the potential of tissue-engineering?

Throughout the last two decades, many advancements in cell biology, biochemistry, and biophysics have led researchers to better understand how they might create new living tissues and organs to replace those that are missing or diseased. Scientists have experienced success with engineering tissue such as cartilage, bone, and heart valves. And currently, the tissue-engineered trachea can be used for people with cancer, emphysema, and other related illnesses. Now, the more complex the tissue, the more difficult regeneration will become. For example, whole organs such as the liver or heart, will require more time, money, and expertise to fully develop the regeneration process.

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