March 14, 2014

By Medical Discovery News

Imagine that a patient needs an organ, like an airway to their lungs called a trachea. A scientist harvests some of the patient’s cells and attaches them to a scaffold the proper shape and size for the tube. The cells and scaffolds are placed into a tissue reactor and – ta da! – in a week or two there is an organ ready for the surgeon to transplant into the patient. While it sounds like a chapter from “Brave New World,” this science fiction scenario is a growing reality.

Bladders and ears have been grown in the laboratory, and hearts, eyes, and kidneys and other organs are in progress. These organs are close to the natural ones they’re copying – some even have their own immune system. In April 2013, surgeons at the Children’s Hospital of Illinois implanted a bioengineered trachea into a two-year-old child. This was the first surgery of its kind in the United States and one of only six worldwide.

The patient receiving the transplant was a girl named Hannah Warren who was born without a trachea, commonly called a windpipe. Since birth, she’s had a plastic pipe inserted in her mouth that went down into her lungs, allowing her to breathe. She could not eat normally or even speak. With few options available, this type of congenital defect has always meant an early death; only a few children live past the age of six.  

Bioengineered organs could change that. The key is stem cells – cells that are at an early stage of development and through the influence of their environment can produce the many specialized cells of organs and tissues. In this case, doctors harvested the girl’s immature stem cells from the marrow inside her bones. The stem cells were taken to the lab and allowed to adhere to a plastic fiber model precisely the size (about one-half inch in diameter) and structure of the trachea she needed. Once placed in an incubator called a tissue bioreactor, the stem cells colonized the plastic and started growing. While they were growing, cells communicated with neighboring cells and worked together to produce all the cells needed for a functioning trachea. 

At the end of this process, Dr. Paolo Macchiarini implanted the trachea with promising results. Since the cells in the bioengineered trachea were based on ones from her body, her immune system didn’t recognize it as foreign and reject it, a big worry for transplant recipients. Without a plastic pipe in her mouth, Hannah was able to smile for the first time.

Unfortunately, while her trachea functioned well after the surgery, her esophagus never recovered. She underwent a second surgery to fix her esophagus and died from complications. Macchiarini said that her death was not due to the implanted trachea but her own “very fragile” tissue. He called Hannah a “pioneer” in the field of regenerative medicine and plans to conduct similar operations.

The next step for bioengineered organs is clinical trials leading to Food and Drug Administration approval. This would give more scientists and physicians the opportunity to improve organ “farming” and extend this field into a therapy that could benefit many.

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