Iowa State University

Inside Iowa State
August 8, 1997

Body work

Researcher searches for secret to body repairing itself

by Skip Derra

Many people yearn for their youth, but Carole Heath is trying to do something about it. Heath, an associate professor of chemical engineering, wants to turn back the body's biological clock to its growth years with the eventual goal of helping the body repair itself.

Heath's work could lead to new treatments, even cures, for such wide- ranging maladies as osteoarthritis, nerve damage and diabetes. In three projects -- one focusing on cartilage, another on nerve regeneration and a third on insulin generating cells called islets -- Heath and her students are looking for the secrets of what triggers cell development and tissue growth.

"Many of our body's cells stop growing when we stop growing," Heath said. "We want to find the environmental conditions that essentially turn these cells back into their development stage."

There are similarities among the three projects. All rely on the use of polymer materials to help the cells along in their regeneration; draw from Heath's expertise in two very different fields, chemical engineering and biology; and are in their relative infancy.

The most advanced of the three is a project on cartilage regeneration. This project eventually could help people with osteoarthritis, a degenerative condition of the joints caused when cartilage wears out. Heath and her students already have taken cartilage cells from horses and used them to grow cartilage "pads" in a process that eventually could be modified for human tissue. Her group now is focusing on putting the newly grown cartilage under pressure to see how that affects its growth.

"You can grow cartilage outside the body and it has the same chemical composition as native tissue," Heath said. "But the structure of the regenerative tissue is not the same as the structure of the native tissue. Tissue structure is crucial to the ability of the tissue to withstand and distribute forces over joints."

In the lab, Heath applies intermittent pressure to cartilage samples her group has "grown." The applied pressure seems to make the tissue more durable.

"The tissue is tougher and that's what we want," she said. "The ultimate goal is to grow cartilage and store it frozen, so it can be used in surgery as an implant to treat osteoarthritis."

Polyglycolic acid, a non-woven mesh, provides structural support for the developing cartilage. Heath uses another polymer in work on nerve regeneration. In both instances, the polymer eventually is absorbed into the body, leaving the newly regenerated tissue on its own.

For the nerve work, the polymer acts as a bridge between the two severed ends of a nerve. Nerves in human extremities have limited regenerative ability. In cases of severe nerve damage, a surgeon will take a nerve from another part of the body and graft it over the damaged nerve to create fusion between the ends.

"We're producing a bio-artificial nerve graft, which will bridge the two ends of a nerve that has been severed," Heath said.

Polymers have been used by other groups to foster nerve growth, but Heath's work differs because it's designed as a "living conduit."

"We're putting living cells, called Schwann cells, in our polymer," she said. "Schwann cells are a key player in the nerve regeneration process. They provide nerve growth factor and supply it at cut nerves. They also have receptors at the surface where nerves contact them. This enhances nerve regeneration even further."

Heath's third project focuses on the body's ability to generate insulin. Her team is working on producing islets for the human pancreas. Islets are pancreatic cells that produce insulin. Because a diabetic loses these islets (and the ability to produce insulin) the idea is either to regenerate the islets or take them from animals and use them in humans. Both would require very delicate procedures.

The work is still in very early stages, Heath said, with the team working on ways to separate islets from the rest of the cells in a pancreas. Islets make up only about 2 percent of the cells in a pancreas.

The team has been successful in using magnetic beads with antibodies attached to sort out the islets. They've demonstrated the technique on rat islets and plan to begin pig studies this fall.

Once the islets are separated, they'll need to be coated, Heath said. Once again, a polymer likely will play a key role.

The polymer material coats the islet so the body doesn't reject it. The coating also has to allow nutrients into the tiny islet cells and let the cells secrete insulin. The coating step is still a number of years away for the team.

In the meantime, students in Heath's group are separating the islets, carefully feeding them and watching for the cells to secrete insulin.

"We eventually would like to grow islets," she said. "That way we don't have to transplant them from animals and worry about viruses or ethical considerations."

All three of Heath's projects are many years from completion. But she added, "Look how long it takes a person to grow and you'll understand the time scale we're working on."

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