Lab-grown body parts no longer sci-fi

[okarol]

Published Monday, May 19, 2008

Lab-grown body parts no longer sci-fi

By Alan Bavley
McClatchy-Tribune News Service

COLUMBIA, Mo. | Your heart is failing critically. A transplant would save your life, but the waiting list is long and the odds are stacked against you.

So instead, doctors extract some of your bone marrow, heart and muscle cells, go back to their laboratory and return in four to six weeks with ... a freshly grown heart.

Engineering body parts — tissues and whole organs that are genetically compatible and available on demand — sounds like science fiction. But researchers at medical centers around the world are working to make it a reality.

Already, a handful of children with spina bifida have received new bladders. Replacement blood vessels are being tested on dialysis patients. And researchers have re-created a beating rat heart.

Replacement parts grown in the lab may provide the best hope for fulfilling the unmet demand for organ transplants.

More than 95,000 people in the United States are on waiting lists for transplants. On average, one person dies every 90 minutes while waiting for an organ.

Other alternatives to organ transplants are elusive.

Transplants from animals, for example, face serious risks of rejection or viral infections. And mechanical organs, such as heart pumps, have been only a temporary solution.

“If we want to live forever, we need to do better,” said Gabor Forgacs of the University of Missouri in Columbia.

Forgacs, a Hungarian-born biophysicist, directs the university’s bioprinting program. In his basement lab, he is using a gleaming metal machine, a distant cousin of a computer printer, to build living blood vessels.

He has succeeded in making vessels that branch the way real veins and arteries do. He hopes to make replacement blood vessels that can be used in surgery, then fabricate human tissues with fully functioning blood systems that can be used to test new drugs. Ultimately, he wants to build replacement organs in his lab.

“That’s everybody’s dream,” Forgacs said.

Tissue engineering, as Forgacs’ field is called, is still very much in its infancy, the National Science Foundation says.

Even so, it has attracted more than $3.5 billion in investments for research, almost all from the private sector.

Because it relies on patients’ cells, tissue engineering avoids the ethical controversies surrounding embryonic stem cells and therapeutic cloning.

Recent advances in growing human cells in the lab and in creating artificial materials that are compatible with living tissue have opened new possibilities for building organs.

But just like any infant, tissue engineering took some early tumbles.

Investors began pumping money into research and development in the 1990s. But the science had not advanced far enough. Some pioneering tissue engineering companies sought bankruptcy protection.

That first wave of tissue engineering did yield some useful products, such as artificial skin grafts that are used to treat diabetic skin ulcers. But many of the awe-inspiring breakthroughs that scientists are talking about are still many years away, Nerem cautioned.

“The real potential for tissue engineering is the vital organs, but we’re a ways away from that, even though there’s some exciting things being done,” he said.

Replacement parts for orthopedic surgery, such as bones, tendons and ligaments, may be 10 years from the operating room, Nerem said. Organs will take significantly longer.

One engineered organ that is available, though, is the urinary bladder.

Anthony Atala of Wake Forest University has successfully implanted new bladders in children, and they are being tested on adults. It’s a project Atala started 18 years ago.

“The research does go slow,” he said. “You can only push the technology so fast.”

But Atala, a pediatric urological surgeon, had strong motivations for proceeding with his research. Among his young patients were children with spina bifida whose bladders had malfunctioned, leaving them at risk of kidney failure.

Atala would perform surgery to replace their organs with new ones built from pieces of their intestines. But substituting the bladder with intestinal tissue can lead to long-term complications, from metabolic problems to infections and an increased risk of cancer.

“Here we were putting these things into babies with a life expectancy of 70 years,” Atala said.

The first hurdle Atala faced was getting bladder cells to grow in the lab.

“They were thought to be types that couldn’t grow well outside the body. We had to go through several years, and finally we were successful after much trial and error.”

The next step was creating a “scaffold” that would hold the cells as they grew into the shape of a bladder. Atala devised a biodegradable scaffold made of collagen, the protein that gives structure to skin.

To make a new bladder, Atala plants the patient’s cells onto the bladder-shaped scaffold. After about seven weeks, the cells have grown to cover the structure, and the new bladder is implanted. The patient’s body adopts the new organ, branching out blood vessels to nourish it.

In 2006, Atala published results on the first seven children to receive the engineered bladders. Tests have shown that their new organs functioned as well as bladders fashioned from intestines, but without the complications.

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