Stem cell therapy enriched with a bone-regenerating hormone, insulin-like growth factor-I (IGF-I), can help mend broken bones in fractures that are not healing normally, a new animal study finds. The Endocrine Society's 93rd Annual Meeting will host presentation of the results on Sunday in Boston.

A deficiency of fracture healing is a common problem affecting an estimated 600,000 people annually in North America, according to the principal investigator, Anna Spagnoli, MD, associate professor of pediatrics and biomedical engineering at the University of North Carolina at Chapel Hill.

"This problem is even more serious," Spagnoli said, "in children with osteogenesis imperfecta, or brittle bone disease, and in elderly adults with osteoporosis, because their fragile bones can easily and repeatedly break, and bone graft surgical treatment is often not successful or feasible"

Fractures that do not heal within the normal timeframe are called non-union fractures. Using an animal model of a non-union fracture, a "knockout" mouse that lacks the ability to heal broken bones, Spagnoli and her colleagues studied the effects of transplanting adult stem cells enriched with IGF-I. They took mesenchymal stem cells (adult stem cells from the bone marrow) of mice and engineered the cells to express IGF-1. Then they transplanted the treated cells into knockout mice with a fracture of the tibia, the long bone of the leg.