Composition for increasing bone mass

It has been discovered that semaphorin 3A (Sema3A), which is expressed by osteoblastic cells, exhibits a strong bone-protecting action by simultaneously inhibiting bone resorption and promoting bone formation. It has also been found that systemic administration of Sema3A (by intravenous injection) or local administration thereof to a bone damage site makes it possible to increase bone mass of the administration target.