Tissue Engineer Finding Ways to Build Bones

Nov. 21, 2006 -- Most people begin life with good bones. But time and trauma take their toll. Age makes bones brittle, while diseases like osteoporosis can make them soft or change their shape. According to the World Health Authority, joint diseases account for half of all chronic conditions in people over age 65, back pain is the second leading cause of sick leave and osteoporotic fractures have doubled in the last decade.

Tissue engineers, among them the University of Virginia’s Edward Botchwey, are devising new ways not simply to repair bone, but to restore it to health. They begin with a three-dimensional, biodegradable matrix, seeded with bone cells, placed in a bioreactor and infused with the nutrients and molecules that bone cells need to stay alive and to organize themselves into functioning bone tissue. These scaffolds are then implanted in a patient’s body, where they degrade as the bone cells mature.

The success of these bone grafts depends on their developing their own blood supply — or at least possessing an enhanced ability to grow new blood vessels. Botchwey, a biomedical engineer, is exploring a number of approaches to help that process along. For instance, he is experimenting with a class of small molecules that mimic the activity of vascular endothelial growth factor (VEGF), a naturally occurring substance that stimulates the formation of blood vessels. Unlike VEGF, these small molecules can withstand the rigors of being incorporated into biomechanical scaffolding material.

With cell biologist Roy Ogle, also at U.Va., Botchwey is exploring adding a line of unique stem cells to the matrix. The materials typically used to promote the growth of bone cells are detrimental to the growth of blood vessels. Ogle’s stem cells promote the growth of blood and bone tissue. Finally, Botchwey is working to increase the utility of bioreactors, the special incubators that provide a controlled environment for initial bone tissue growth. With U.Va. mechanical engineer Joseph Humphrey, he is developing a tool to categorize the fluid dynamics of different kinds of bioreactors, enabling researchers to extrapolate conclusions from one system to another.

“These three approaches have much in common,” Botchwey says. “Each sheds light on what we need to do to have successful integration of bone tissue with the host. They also illustrate the depth of resources available at U.Va. and the spirit of collaboration that flourishes here.”

For more information about Botchwey’s research, visit http://bme.virginia.edu/people/faculty/botchwey/