Tissue engineers make advances

Ability to grow complex organs still a long way off.

STOCKHOLM — Andemariam Beyene sat by the hospital window, the low Arctic sun on his face, and talked about the time he thought he would die.

Two and a half years ago doctors in Iceland, where Beyene was studying to be an engineer, discovered a golf-ball-size tumor growing into his windpipe. Despite surgery and radiation, it kept growing. In the spring of 2011, when Beyene came to Sweden to see another doctor, he was practically out of options. “I was almost dead,” he said. “There was suffering. A lot of suffering.”

But the doctor, Paolo Macchiarini, at the Karolinska Institute here, had a radical idea. He wanted to make Beyene a new windpipe, out of plastic and his own cells.

Implanting such a “bioartificial” organ would be a first-of-its-kind procedure for the field of regenerative medicine, which for decades has been promising a future of ready-made replacement organs — livers, kidneys, even hearts — built in the laboratory.

For the most part that future has remained a sci- ence-fiction fantasy. Now, however, researchers like Macchiarini are building organs with a different approach, using the body’s cells and letting the body itself do most of the work.

“The human body is so beautiful, I’m convinced we must use it in the most proper way,” said Macchiarini, a surgeon who runs a laboratory that is a leader in the field, also called tissue engineering.

So far, only a few organs have been made and transplanted, and they are relatively simple, hollow ones — like bladders and Beyene’s windpipe, which was implanted in June 2011. But scientists around the world are using similar techniques with the goal of building more complex organs. At Wake Forest University in North Carolina, for example, where the bladders were developed, researchers are working on kidneys, livers and more. Labs in China and the Netherlands are among many working on blood vessels.

The work of these new body builders is far different from the efforts that produced artificial hearts decades ago. Those devices, which are still used temporarily by some patients awaiting transplants, are sophisticated machines, but in the end they are only that: machines.

Tissue engineers aim to produce something that is more human. They want to make organs with the cells, blood vessels and nerves to become a living, functioning part of the body. Some, like Macchiarini, want to go even further — to harness the body’s repair mechanisms so that it can remake a damaged organ on its own.

Researchers are making use of advances in knowledge of stem cells, basic cells that can be transformed into types that are specific to tissues like liver or lung. They are learning more about what they call scaffolds, compounds that act like mortar to hold cells in their proper place and that also play a major role in how cells are recruited for tissue repair.

Tissue engineers caution that the work they are doing is experimental and costly, and that the creation of complex organs is still a long way off. But they are increasingly optimistic about the possibilities.

“Over 27 years, I’ve become more convinced that this is doable,” said Dr. Joseph P. Vacanti, a director of the Laboratory for Tissue Engineering and Organ Fabrication at Massachusetts General Hospital and a pioneer in the field.

In Beyene’s case, an exact copy of his windpipe was made from a porous, fibrous plastic, which was then seeded with stem cells harvested from his bone marrow.