But in the real world, accomplishing such feats is more complex. Regenerating the jaw bone of a person undergoing radiation therapy for cancer means managing the constant bacteria bath of a human mouth as well as compensating for the damage of radiation.
"It's not just a question of whether we can make new tissue in a perfect condition. Now we're mimicking what can really happen in a person, and we don't know if the rules of regeneration might be totally different," said Paul Krebsbach, associate professor at the U-M School of Dentistry.
Krebsbach is scheduled to participate in a panel titled "Tissue Engineering for the Head and Neck," at the AAAS annual meeting Feb. 17-21 in Washington, D.C. The tissue engineering panel is slated for Feb. 20 1:45-3:15 p.m.
In the broadest sense, tissue engineering refers to growing human tissue through artificial means.
Typically it involves harvesting a small sample of cells, treating them in the lab, then reintroducing the cells into a damaged area, like a jaw bone damaged too badly to simply heal on its own. A tiny scaffold helps direct the engineered cells to the right place, then dissolves once the cells begin to generate to fill in the wound.
"In certain kinds of defects, the body cannot heal itself and the body needs a jumpstart," Krebsbach said. To heal a large wound, like that created when a cancerous tumor is removed from the jaw, that often means taking a bone graft from someplace like the hip. That approach has problems both for the wound at the donor site and for the site where it is implanted.
In addition to discussing the sometimes-messy real world applications of tissue engineering, Krebsbach plans to talk at AAAS about the potential for combining seemingly unrelated therapies to improve the benefits of tissue engineering.
For example, parathyroid hormone is given to patients with osteoporosis, a condition in which bone quality declines leaving them fragile and prone to breaking. Parathyroid hormone stimulates bone growth in these patients, and Krebsbach sees potential to use it for similar gains in tissue engineering new bone.
Bone morphogenetic proteins help cells differentiate into specific kinds of bone, and encouraging cells to make more BMPs during tissue engineering also can ramp up the effects.
"Together these therapies can overcome compromised environments," he said. "Combining therapies can help us overcome some of the complications of current therapies, too."
These approaches are not yet being tested in humans, but Krebsbach said some small clinical trials are under consideration.
If the combination therapy approach works, Krebsbach said the next step would be working with engineers to develop anatomically correct scaffolding with the same curvature and contours of natural bones. That would help a patient develop new bone almost indistinguishable from nature's original equipment.
Many researchers at University of Michigan have focused their tissue engineering efforts on the head and neck, in part because U-M Dentistry plays a leading role in the effort. Dentists have a long tradition of finding ways to fill tooth cavities that will not heal on their own, Krebsbach said, and that has led to research in biomaterials, bone and connective tissue function, and then tissue engineering.
At Michigan, tissue engineering collaboration includes dentists, M.D.s and engineers, among others. They all bring a different perspective, and it leads to scientific advances that couldn't happen in any one discipline, Krebsbach said.
"That's the beauty of tissue engineering. It has to be multi-disciplinary to work," he said.
Krebsbach will arrive at the AAAS annual meeting having just participated in a Congressional briefing Feb. 17 about stem cell research in dental research. The American Association for Dental Research, a division of the National Institutes of Health, coordinated the panel with support from the American Dental Association and the American Dental Education Association.
Krebsbach's role in the briefing was to highlight the use of adult stem cell research in craniofacial tissue regeneration.
AAAS newsroom: http://www.eurekalert.org/aaasnewsroom/2005/index.php
Krebsbach's faculty profile: http://www.dent.umich.edu/research/ccr/paulk.htm
Tissue Engineering at Michigan: http://www.dent.umich.edu/team/index.html
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