title: High-dose risedronate treatment partially preserves cancellous bone mass and microarchitecture during long-term disuse.
abstract: Disuse induces rapid and severe bone loss in larger mammals as a result of greatly elevated osteoclastic resorption. In this study, we tested whether risedronate (RIS), a potent inhibitor of osteoclastic activity, would effectively prevent cancellous bone loss in female beagles (5-7 years old, N = 28) subjected to single forelimb immobilization (IM) for 12 months. Age-matched, non-IM dogs served as controls (Con). Half the animals from each group received RIS 1 mg/kg p.o. daily (Con + RIS, IM + RIS). Remaining dogs received sterile water (Con, IM). Histomorphometry showed that IM caused a dramatic reduction in cancellous bone mass (-71%) of distal 2nd metacarpals, characterized by marked decreases in trabecular width (-51%) and number (-41%), and 4-fold increases in the indices of bone resorption (eroded surface, osteoclast number, and surface). Bone formation indices (calcein-labeled surface, osteoid surface, and bone formation rate) were also significantly higher in IM than in controls. Activation frequency in IM increased about 4-fold beyond control level. RIS treatment reduced, but did not abolish cancellous bone loss due to immobilization. IM animals treated with RIS lost nearly 50% of cancellous bone mass, while trabecular width and number were reduced by 31% and 25%, respectively. In both RIS-treated control and IM animals, overall bone formation parameters (mineralized bone surface fraction and bone formation rate) remained roughly at intact control levels; however, mineral apposition rate relative to intact control was reduced 40% in RIS-treated control and 86% in RIS-treated IM animals. These results indicate that high-dose RIS treatment might suppress osteoblastic function, especially under long-term disuse. Interestingly, bone resorption parameters in RIS-treated IM animals reached levels even higher than in vehicle-treated IM animals; values for eroded surface, osteoclast number, and surface were 84%, 53%, and 83% above vehicle-treated IM values, respectively. Our data indicate that risedronate treatment is partially effective in preventing cancellous bone loss during long-term disuse. Moreover, our results suggest that bisphosphonates can impair the ability of mature osteoclasts to resorb bone, but cannot overcome the strong stimulus for osteoclast recruitment caused by long-term disuse.
authors: Leni and Peter W. May Department of Orthopaedics, Mount Sinai School of Medicine, Box 1188, One Gustave L. Levy Place, New York, NY 10029, USA.
authors: Chao
authors: C
authors: Yang Li
authors: Robert J
authors: RJ
authors: Majeska
authors: Damien M
authors: DM
authors: Laudier
authors: Richard
authors: R
authors: Mann
authors: Mitchell B
authors: MB
authors: Schaffler
mesh_terms: D000818:Animals; D015519:Bone Density / Q000187:drug effects* / Q000502:physiology; D001842:Bone and Bones / Q000033:anatomy & histology / Q000187:drug effects* / Q000473:pathology* / Q000503:physiopathology; D004285:Dogs; D012968:Etidronic Acid / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D007103:Immobilization / Q000502:physiology; D000068296:Risedronic Acid
chemical_list: D000068296:Risedronic Acid; D012968:Etidronic Acid