Stem cells may help bone healing

The Daily Tar Heel ^ | 06.26.08 | M.K. Ayers

[Coleus]

A recent medical breakthrough at UNC may help thousands every year whose broken bones do not heal.  Researchers who transplanted adult mouse stem cells into mice with fractured bones showed that the cells could help heal the fractures. Anna Spagnoli, associate professor of pediatrics and biomedical engineering at UNC and senior author of the study, said it was meant to determine whether adult stem cells could be used to improve the healing tissue at a fractured site and whether the cells went directly to the injury once transplanted.  She said that as a pediatrician, she has worked with children with brittle bone disease and became interested in researching treatments for fracture healing.

Spagnoli said fracture healing is a major medical problem in the United States. The condition is often found in women with osteoporosis. It can cause intense pain and immobilization, and can require constant medical supervision and assistance. "Most of the time we really don't know why they don't heal," Spagnoli said. "We think the most important reason why these patients don't heal is because they lack stem cells." Current treatments for fracture healing include using bone grafts or prosthetic materials to aid in healing a fracture. But bone grafts are painful and difficult, especially in children whose bones are not yet fully grown, and prosthetic materials do not integrate with bones and can wear out over time or become toxic.

After finding that stem cells helped the mice's bones heal, Spagnoli said the researchers wanted to determine whether they were attracted directly to the injury, and what made them turn into bone and cartilage once they arrived. "We need to man the cells," Spagnoli said. "Steer the cells to go to the fractured site and improve the healing." In order to track the stem cells, researchers used luciferase - the same substance that causes fireflies to glow - to follow the cells in the mice's bodies. By tracking them, the scientists discovered that the molecule CXCR4 directed the stem cells toward the fracture.

After studying the stem cells more closely, they found that IGF-1, an insulin-like growth factor, caused the cells to turn into bone and cartilage at the break.  Spagnoli said she hopes the study, which started about three years ago, will lead to clinical trials to prove that the procedure also can work in humans. Spagnoli plans to continue to study IGF-1 and its functions. "It makes more bone and cartilage but how does it do that? We don't know," she said. But for now, she and the first author of the study, Dr. Froilan Granero-Molto, plan to enjoy a bottle of Spanish wine they have been saving for the end of the study.