Role of Wnt signaling and sclerostin in bone and as therapeutic targets in skeletal disorders

Wnt signaling and its bone tissue-specific inhibitor sclerostin are key regulators of bone homeostasis. The therapeutic potential of anti-sclerostin antibodies (Scl-Abs), for bone mass recovery and fragility fracture prevention in low bone mass phenotypes, has been supported by animal studies. The Scl-Ab romosozumab is currently used for osteoporosis treatment.Wnt signaling is a key regulator of skeletal development and homeostasis; germinal mutations affecting genes encoding components, inhibitors, and enhancers of the Wnt pathways were shown to be responsible for the development of rare congenital metabolic bone disorders. Sclerostin is a bone tissue-specific inhibitor of the Wnt/β-catenin pathway, secreted by osteocytes, negatively regulating osteogenic differentiation and bone formation, and promoting osteoclastogenesis and bone resorption.Here, we reviewed current knowledge on the role of sclerostin and Wnt pathways in bone metabolism and skeletal disorders, and on the state of the art of therapy with sclerostin-neutralizing antibodies in low-bone-mass diseases.Various in vivo studies on animal models of human low-bone-mass diseases showed that targeting sclerostin to recover bone mass, restore bone strength, and prevent fragility fracture was safe and effective in osteoporosis, osteogenesis imperfecta, and osteoporosis pseudoglioma. Currently, only treatment with romosozumab, a humanized monoclonal anti-sclerostin antibody, has been approved in human clinical practice for the treatment of osteoporosis, showing a valuable capability to increase BMD at various skeletal sites and reduce the occurrence of new vertebral, non-vertebral, and hip fragility fractures in treated male and female osteoporotic patients.Preclinical studies demonstrated safety and efficacy of therapy with anti-sclerostin monoclonal antibodies in the preservation/restoration of bone mass and prevention of fragility fractures in low-bone-mass clinical phenotypes, other than osteoporosis, to be validated by clinical studies for their approved translation into prevalent clinical practice.