Studies of Local Bone Remodeling: The Calvarial Injection Assay

There are several assays available to study the effects of cytokines, drugs, and hormones on bone cells in vitro. However, as the complex interactions between cells are disrupted, these in vitro assays do not always reflect what happens in vivo. The calvarial injection method, originally described by Boyce et al. (1 ), is valuable for studying the effects of substances on bone metabolism in vivo. In this assay, the substance to be tested is injected subcutaneously over the calvarium of a mouse. At the end of the assay the animal is euthanized, and the calvarium dissected and analyzed by microscopy. Although the assay was originally used to study effects of cytokines on osteoclast formation and activity (1 ,2 ), it has also been used to study the effects of drugs on bone formation (3 ).