Prevention of glucocorticoid‐induced bone loss in mice by inhibition of RANKL

Abstract

Objective. RANKL has been implicated in the pathogenesis of glucocorticoid-induced osteoporosis. This study was undertaken to evaluate the efficacy of denosumab, a neutralizing monoclonal antibody against human RANKL (hRANKL), in a murine model of glucocorticoid-induced osteoporosis.Methods. Eight-month-old male homozygous hRANKL-knockin mice expressing a chimeric RANKL protein with a humanized exon 5 received 2.1 mg/kg of prednisolone or placebo daily over 4 weeks via subcutaneous slow-release pellets and were additionally treated with phosphate buffered saline or denosumab (10 mg/kg subcutaneously twice weekly). Two groups of wild-type mice were also treated with either prednisolone or vehicle.Results. The 4-week prednisolone treatment induced loss of vertebral and femoral volumetric bone mineral density in the hRANKL-knockin mice. Glucocorticoid-induced bone loss was associated with suppressed vertebral bone formation and increased bone resorption, as evidenced by increases in the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts, TRAP-5b protein in bone extracts, serum levels of TRAP-5b, and urinary excretion of deoxypyridinoline. Denosumab prevented prednisoloneinduced bone loss by a pronounced antiresorptive effect. Biomechanical compression tests of lumbar vertebrae revealed a detrimental effect of prednisolone on bone strength that was prevented by denosumab.Conclusion. Our findings indicate that RANKL inhibition by denosumab prevents glucocorticoidinduced loss of bone mass and strength in hRANKLknockin mice.

Regulation of bone mass and osteoclast function depend on the F-actin modulator SWAP-70

“…Processing of bone specimens and cancellous bone histomorphometry in the distal femoral metaphysis and the L 1 vertebral bodies was performed as described. (26,27) L 3 vertebral body cylinders were loaded to failure by compression with a Zwick Z020/TN2A materials-testing machine (Zwick, Ulm, Germany) with a 1-kN force detector and a force resolution of 0.01 N as described. (27) Total deoxypyridinoline concentrations (Dpd) in urine were determined after acid hydrolysis by ELISA (Total DPD; Quidel Corporation, San Diego, CA, USA) and normalized to creatinine levels.…”

Protection From Glucocorticoid-Induced Osteoporosis by Anti-Catabolic Signaling in the Absence of Sost/Sclerostin

“…(10)(11)(12)(13)(14)(16)(17)(18)(19)(20) There is a rapid, early bone loss ascribed to both prolongation of lifespan of preexisting osteoclast and increased generation of new osteoclasts. (16,21,22) This initial phase is followed by a less pronounced chronic bone loss associated with reduction of osteoblasts and osteoclasts and low bone remodeling, due to reduced synthetic activity of osteoblasts through downregulation of critical genes, including osteocalcin (OCN), increased osteoblast apoptosis, and reduced generation of osteoclasts resulting from the loss of supporting cells. (1,10,12) The Wnt/b-catenin pathway has a critical role in the control of bone acquisition and maintenance.…”

Animal models to explore the effects of glucocorticoids on skeletal growth and structure

“…GCs also directly block the induction of cytoskeletal changes in the osteoclast required for the resorptive capabilities of the cell (Kim et al 2007). There is also evidence that GCs suppress the proliferation of osteoclast precursors (Kim et al 2006) However, GC also cause an increase in receptor activator of nuclear factor kappa beta ligand (RANKL) (Hofbauer et al 2009), which is produced by both osteoblasts and osteocytes (Nakashima et al 2011, Xiong et al 2011 and downregulation of osteoprotegrin (OPG), which is a decoy receptor for RANKL. This skews the ratio of RANKL: OPG towards osteoclastogenesis.…”