Researchers around the world are making groundbreaking progress in engineering replacement organs. Since the first successes with bioengineered skin–which can be used for grafts to treat people with burns, for example–tissue engineers have created lab-grown cartilage, bone and, most recently, whole organs such as bladders.
“Scientists genuinely believe that in years to come, labs will be filled with rows of hearts and livers that can be taken off the shelf and tailored to you,” says Lindsey Dew, who has just started a PhD in tissue engineering at the University of Sheffield. “Tissue engineering is the future of medicine.”
How Organs are Grown Today
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.
Engineering an organ usually means starting with a scaffold to supply the basic structure. This is often donated. The team behind the world’s first bioengineered windpipe transplant, for example, started this way, stripping the donor’s cells from the structure before seeding it with stem cells from the recipient’s bone marrow.
Stem cells can be encouraged to develop almost any type of cell, given the right environment, and once the recipient’s cells had populated the scaffold, it could be transplanted. Unlike donated organs, those custom-made in this way are not rejected by the body. That means recipients are spared a lifetime of taking immune-suppressing drugs.
First Successes with Custom-made Organs
One of the first successes came two years ago, when a team at Karolinska University Hospital in Stockholm, Sweden, transplanted a synthetic windpipe for the first time. Beyene was the lucky recipient.
The trachea was developed by Alexander Seifalian and his colleagues at University College London. With a background in nuclear physics, Seifalian also studied nuclear medicine and biochemistry before settling on tissue engineering. “It’s the next generation of medical treatment,” he says. “When you’re developing organs, you’re saving lives and improving people’s lives. That got me excited.”
His team built the organ in just 10 days. Seifalian first crafted a glass mold of Beyene’s windpipe based on a CT scan, then the team used the mold to create a replica made from porous polymers. They coated this scaffold with growth factors – chemical cues to goad stem cells into becoming specific cell types – then soaked the structure in a solution of stem cells extracted from Beyene’s bone marrow. During this time, the cells take hold in the scaffold’s millions of tiny holes. Today, Beyene remains in good health. “It was the highlight of my life,” says Seifalian.
Since then, Seifalian’s team has built tear ducts and bypass grafts from similar materials. Lab-grown urethras, coronary arteries, heart valves and stents are next. Other groups are creating new organs by printing them. Ben Shepherd and colleagues at Organovo, a bioengineering company based in San Diego, California, used a 3D printer loaded with human cells to build a functional “mini-liver”. Although only a few millimeters wide and a mere half a millimeter thick, it produced detoxification enzymes just like a full-sized liver.
Body Shop of the Future
Seifalian’s long-term ambition is to scale up production. “It would be virtually like having a shop,” he says. “People could order an organ and I would make it and send it to them.” Organs such as windpipes, ears or noses would ideally still be made to order, but blood vessels or heart valves could be manufactured in various standard sizes.
Work is proceeding at other institutions. 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. Researchers in regenerative medicine at the Texas Heart Institute in Houston are experimenting with how to create hearts for people in need of transplants.
The Heart Makers - Nature
Tissue engineers aim to make organs with the cells, blood vessels and nerves to become a living, functioning part of the body. Some, like Dr. Macchiarini, a surgeon who runs a laboratory that is a leader in the field, want to go even further—to harness the body’s repair mechanisms so that it can remake a damaged organ on its own. He envisions developing even better scaffolds and implanting them without cells, relying on drugs to stimulate the body to send cells to the site. His ultimate dream is to eliminate even the synthetic scaffold. Instead, drugs would enable the body to rebuild its own scaffold.
“Don’t touch the patient,” Dr. Macchiarini said. “Just use his body to recreate his own organ. It would be fantastic.”