Wnt signaling during fracture repair.

Bone is one of the few tissues in the body with the capacity to regenerate and repair itself. Fractures usually are completely repaired in a relatively short time, but in a small percentage of cases, healing never occurs and nonunion is the result. Fracture repair and bone regeneration require the localized reactivation of signaling cascades that are crucial for skeletal development. The Wnt/beta-catenin signaling pathway is one such developmental pathway whose role in bone formation and regeneration recently has been appreciated. During the past decade, much has been learned about how Wnt pathways regulate bone mass. Small molecules and biologics aimed at this pathway are now being tested as potential new anabolic agents. This article reviews recent data demonstrating that Wnt pathways are active during fracture repair and that increasing the activities of Wnt pathway components accelerates bone regeneration.