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.