News in Tissue Engineering: Tracheas

The trachea is a vital human body part. It is a tube that connects the larynx to the lungs, allowing humans to breath. Tracheal collapse happens as a result of some heart conditions, Cushing’s syndrome, and some respiratory conditions, including lung cancer that has spread. Without a trachea it is impossible to breath. There are extreme options, such as having a tracheotomy in order to avoid having to breathe through the mouth, but these are very invasive and uncomfortable procedures. Tissue engineering has been applied to the trachea over the past few years in an astonishing way, and will continue to do so, setting new levels of treatment.

Science Daily, 2008: First Tissue-Engineered Trachea Successfully Transplanted

In this article we see that the scientists utilized two of the three components I talked about in my August 8th post, i.e. cells and scaffold. The scaffold, in this case, is a 7cm section of decellularized trachea from a donor. The donor was deceased – it is not possible to donate a trachea section while still alive. 7cm is a really large area to consider in terms of modern tissue engineering, as much research is done on a much smaller scale. The term decellularized means that the tissue was stripped of all cells to make it less immunogenic to the recipient. However, the physical structure of the organ is retained and, importantly, its biological activity, as the proteins that make up the structure are kept and still active. This scaffold was then seeded with cells that had been collected from the recipient, i.e. autologous cells, so that there would be no graft/host response. Seeding the cells is important because it provides the organ with a dynamic, living presence instead of just implanting an empty construct.

New York Times 2011: Synthetic Windpipe is Used to Replace Cancerous One

In this article we see that a similar approach of seeding autologous cells on a tracheal scaffold was taken. However, in this instance the scaffold material is different, instead of being a donated natural scaffold, it is a synthetic polymer material. This has several associated pros and cons. The pros of using this approach are that it doesn’t require a donor and associated organ processing logistics, but, more importantly, the scaffold can be shaped to fit the recipient exactly using modeling and advanced fabrication techniques, whereas donor tracheas are often not a good fit. The major con of the system is that the scaffold is inert and not biologically active and covered in normal tracheal proteins the way that the previous scientific group described. In order to overcome this issue, the group at the Karolinska Institute also grew the cells on the scaffold in a bioreactor, but added in several growth factors that they hoped would induce the cells to differentiate as desired, and start the biological pathways that would continue to affect how the cells behave even after transplanted.

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