Adult stem cells improve healing of broken bones

Adult stem cells improve healing of broken bones and could eventually serve as a new treatment for the 10 to 20 percent of fractures that fail to heal, according to a new study. The results were presented Monday, June 16, at The Endocrine Society's 90th Annual Meeting in San Francisco, by Froilan Granero-Molto, PhD, research associate of the University of North Carolina.

"Lack of fracture repair often leads to several surgeries, long periods of immobilization, pain, bone deformities, and sometimes death," said the study's senior investigator, Anna Spagnoli, MD, of the University of North Carolina. "The precise reason why a patient's fracture does not heal remains unknown in most cases."

Researchers believe a key reason for bone union failure may be a deficiency in adult stem cells, which normally become reparative cells in response to damage. Stem cells in human bone marrow, called mesenchymal stem cells, can become bone, cartilage, fat, muscle, and blood vessel cells, according to Spagnoli. Directing these stem cells into the repair mode is one of the objectives of a new branch of medicine called regenerative medicine.

These adult stem cells, which can be obtained from a patient's bone marrow in a minimally invasive procedure, have been reported to improve fracture healing in a few patients, Spagnoli said. However, animal studies are needed before clinical trials can begin.

Therefore, Spagnoli and her coworkers performed a study in mice with leg fractures. They took adult stem cells from the bone marrow of mice and engineered the cells to express a potent bone regenerator, insulin-like growth factor 1 (IGF-1). Then they transplanted the treated cells into mice with a fracture of the tibia, the long bone of the leg. Using computed tomography (CT or CAT) scanning, they showed that the treated mice had better fracture healing than did untreated controls. They found that the stem cells migrated to the fracture site and increased the bone and cartilage that bridged the bone gap.

"Our study provided critical data needed to implement a novel therapeutic approach in patients with impaired fracture healing," Spagnoli said.

If scientists can duplicate the results of this animal study in humans, it may lead to a way to help the 600,000 people in the United States every year who suffer fractures that do not heal properly, she added.

Use of adult stem cells would have several advantages over embryonic stem cells. According to Spagnoli, they do not have the ethical controversy that surrounds embryonic stem cells, and they may avoid the immune rejection response, since the patient's own cells can be used.