RHO and osteoporosis: Osteoclasts are the main target of bisphosphonates in the treatment of osteoporosis, and the prenylation of small GTPases (such as Ras, Rho and Rac) in osteoclasts contributes to the regulation of various cellular processes such as maintenance of cell morphology, integrin signaling, membrane ruffling, endosome transport and apoptosis27–30.