Regenerative medicine is making great progress in the specific area of tissue engineering, with tissue scaffolds for stem cells marking first milestones in clinical use.
For the first time in the United States, the developer of a bioengineered windpipe has implanted a trachea into a patient who was born without one, and who would have eventually died without it. The patient, a two and one-half year old child, is the youngest in the world to receive a bioengineered organ.
Regenerative medicine is making great progress in the specific area of tissue engineering, with tissue scaffolds for stem cells marking first milestones in clinical use. Paolo Macchiarini, the regenerative medicine specialist and the surgeon who conducted the transplant, is among those driving these medical advances.
The trachea itself is an advance over other scaffold-based organs, such as bladders and livers, because it incorporates a patient’s own stem cells isolated from his or her bone marrow, rather than differentiated cells, such as bladder cells, that are specific to the organ being transplanted.
Macchiarini, a surgeon at the Karolinska Institute in Stockholm, first used the approach with stem cells in 2008 and has implanted five tracheas in adults to date. Working with children, however, “completely changed my thinking about regenerative medicine,” he says. The stem cell approach to building organs may work best with children, he thinks, because of their natural ability to grow and heal.
In the past 5 to 10 years, improved understanding of the extracellular matrix–a meshwork of fibers, proteins, and chemical signals supporting cell-to-cell communication and placement–together with advances in isolating and growing stem cells, has made this type of artificial organ possible.
To create the trachea, a team at Children’s Hospital of Illinois, led by visitor Macchiarini, followed the same procedure as in the other five transplants. They scanned and imaged the windpipe area, made a synthetic trachea appropriate in size from porous and fibrous plastic polymers, and then seeded the scaffold with stem cells taken from the child’s bone marrow. Next, they incubated the scaffold in a bioreactor with nutrient-rich liquid to promote cell growth. After a day and a half, they reseeded the trachea with more stem cells, injected it with drugs to stimulate stem cell health and growth, and finally implanted it during a nine hour operation.
There was no need to give post-operative immunosuppressant drugs to prevent implant rejection since the scaffold is artificial and the cells are the patient’s own.
The one-of-a-kind operation is allowed under U.S. Food and Drug Administration rules covering compassionate use to save the life of a patient, but some experts say that even small clinical trials would move the field of regenerative medicine forward faster, by providing more data and a better understanding of how this type of implant functions. Macchiarini is ready to begin a clinical trial in the United States and Children’s Hospital will work with him if the FDA will approve it. “We are far away from understanding this process,” he says, “Far, far away.”
May 10, 2013