Posted on behalf of Penny Sarchet.
Today, headlines abound proclaiming the world’s first transplantation of a biosynthetic organ.
On 9 June, surgeon Paolo Macchiarini, from the University of Barcelona, successfully replaced the windpipe of a cancer patient with a trachea grown in the lab. One month later, the patient – Andemariam Teklesenbet Beyene – is cancer-free and expected to be discharged from hospital today.
This feat of medical bioengineering in fact only differs from a number of other similar transplants in subtle ways. These small differences, however, strongly hint at future directions for growing organs in the lab.
What did they do?
The synthesis and transplantation of Beyene’s new trachea was a collaboration led by Macchiarini and Alex Seifalian at University College London.
To grow a new trachea in the lab, you need both cells and a scaffold. Using CT scans of the patient, the scientists built a scaffold that was a perfect fit for Beyene using a glass mould and a special nanocomposite material.
This nanocomposite contains millions of tiny holes. When the scaffold was incubated in a bioreactor, these holes provided a large surface area for adult stem cells, taken from Beyene’s bone marrow, allowing the entire scaffold to become “seeded” with tissue.
Because the new trachea was made using the patient’s own stem cells, the need to take immuno-suppressant drugs to prevent organ rejection is eliminated.
What had been done before?
This transplant was the latest in a series of advances by Macchiarini. The experiments began in pigs, with Macchiarini using de-cellularised donated tracheae as the scaffolds for cells to form new tissue on.
The next challenge was to do this in humans. In 2008, Claudia Castillo, a tuberculosis sufferer, became the recipient of the world’s first tissue-engineered organ transplant. The windpipe she needed was made by growing her cells over a scaffold made from the trachea of a donor who had recently died.
This high-profile transplant was quickly followed in 2010 by another – Macchiarini this time replacing a larger region in a child suffering from Long Segment Congenital Tracheal Stenosis.
What’s really new about the most recent transplant is not that the new organ was grown in the lab or that it was made from the patient’s own cells, but that the scaffold was generated de novo from a nanomaterial. This advance does away with the need for a donor, allowing the new organ to be made to order with no wait.
What other synthetic transplants are there?
Tracheas are not the only organs being synthetically generated. In 2006, a team successfully crafted bladder sacs from fragments of bladder tissue and transplanted them into 7 children and, in 2007, ten patients were given biosynthetic corneas.
What’s exciting about Macchiarini’s work is that it makes use of stem cells. This could prove important for replacing cancerous organs whose cells would be unsuitable for generating a transplant.
“The next big challenge is organs that are not tubes”, explains Anthony Hollander, from the University of Bristol. Whilst hollow organs like tracheae and urethras can be grown around a mold, organs with complicated structures will be harder to engineer. Researchers in Detroit have made some progress with bioartifical hearts, but Hollander can’t see this making use of synthetic scaffolds because of the complexity of the organ.
Seifalian expands “I believe purely biological organs just made from cells will be slow to progress to human applications, but hybrid organs (synthetic scaffolds with tissue engineering) would be ideal for regenerative medicine and organ generation”. He lists coronary artery grafts, heart valves, biolayer skins and breast filler as among his current projects, whilst Macchiarini’s next move will be creating a new windpipe for a South Korean baby born without a trachea, due to take place later this year.
Image: photo by jetheriot via Flickr under Creative Commons.