A patient will be discharged from a hospital in Sweden today after his cancerous windpipe was removed and replaced by the world's first artificial trachea, made of his own stem cells grown on a man-made plastic matrix.
"This is the first permanent artificial organ ever," says Paolo Macchiarini, professor of regenerative surgery at the Karolinksa Institute in Stockholm, who led the international research team.
Just as remarkable as the man-made windpipe, he says, is how quickly it was produced. Collaborators in Sweden, London and the U.S. created the trachea from scratch in just two days for a 36-year-old man whose cancer was so far advanced that only emergency surgery offered him any chance of survival.
Rejection is unlikely because the new trachea was made of a special plastic polymer and the patient's own cells, Macchiarini says.
"Frankly speaking, I was very much scared," said the patient, Andemariam Teklesenbet of Eritrea, a student at the University of Iceland in Reykjavik. "I was about to refuse the surgery, but Dr. Macchiarini explained everything to me. I prayed. I accepted it. I believed in it."
The procedure represents yet another step in the evolution of tissue engineering that began with skin in the 1980s and later with bladders and blood vessels, says George Daley, director of stem cell transplantation at Children's Hospital Boston.
Daley says the scientific advance is less significant than the fact that the researchers have developed a new clinical application for this technology.
"The scientific advance is pretty minimal," he says. "Tissue engineers have been marrying cells to matrices to regrow parts for many years."
Macchiarini performed a similar procedure in 2008 in Barcelona. A patient named Claudia Castillo received a windpipe that had been removed from an organ donor and, over a period of weeks, cleared of all of its original cells, leaving just a matrix that could be coated with the patient's own stem cells.
Macchiarini has performed about 10 implantations using donor windpipes since then, he says.
In this case, Macchiarini says, researchers didn't have time to wait for a donor trachea and risk rejection of the organ.
He says he began by removing the patient's bone marrow and filtering out certain cells, called mononucleocytes. These cells, when treated with growth factors and other substances, morph into the cells that form the rings on the trachea. Then a team led by Alexander Seifalian at the University College of London worked round-the-clock to produce a Y-shaped matrix that would replace the cancerous portion of the patient's windpipe and connect with his lungs.
David Green's team at Harvard Biosciences in Holliston, Mass., traveled to Stockholm and placed the matrix and the solution of cells into a custom-made device called a bioreactor. The bioreactor keeps the body temperature constant and rotates the matrix once per minute as a rotisserie turns a chicken.
With every revolution, the lower part of the matrix dips into the cell broth, coating it and at the same time exposing the living cells to oxygen.
Within 48 hours, the man-made windpipe was ready for implantation. Doctors not only replaced Teklesenbet's windpipe, they gave it a blood supply by sliding a section of tissue from his stomach up through his diaphragm, a standard technique, Macchiarini says.
Green says similar bioreactors are being used to engineer heart and lung tissues, which so far have been tested only in rodents. Macchiarini says, "My dream as a surgeon is, rather than doing transplants of the heart, liver and lungs, is to use regenerative medicine to restore the function of cells damaged by aging and disease."
Teklesenbet says the dream has come true for him. "It is a wonderful thing for me," he said in a telephone interview, still hoarse from surgery. "I know about transplantation, but I never thought transplantation of the airway could happen."
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