Bone morphogenetic protein-9 activates Smad and ERK pathways and supports human osteoclast function and survival in vitro

► Human osteoclasts express BMP receptors (BMPR-IA, BMPR-IB, ALK1, and BMPR-II). ► BMP-9 increases bone resorption, and reduces osteoclast apoptosis. ► BMP-9 induces phosphorylation of Smad-1/5/8 and ERK 1/2 proteins in osteoclasts.