Chronic Elevation of Parathyroid Hormone in Mice Reduces Expression of Sclerostin by Osteocytes: A Novel Mechanism for Hormonal Control of Osteoblastogenesis

Bellido, Teresita; Ali, Arshad; Gubrij, Igor; Plotkin, Lilian I.; Fu, Qiang; O’Brien, Charles A.; Manolagas, Stavros C.; Jilka, Robert L.

doi:10.1210/en.2005-0239

Cited by 573 publications

(455 citation statements)

References 23 publications

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“…At least some of the positive effects of parathyroid hormone on bone formation have been attributed to its ability to moderately down-regulate sclerostin (32)(33)(34). The inability of Scl-AbI to prevent DEXinduced inhibition of growth is therefore consistent with the findings from a study by van Buul-Offers et al (35), in which they showed that parathyroid hormone was also ineffective at reducing GC-mediated growth inhibition (36).…”

Section: Discussionsupporting

confidence: 77%

Sclerostin antibody treatment enhances bone strength but does not prevent growth retardation in young mice treated with dexamethasone

Marenzana¹,

Greenslade²,

Eddleston³

et al. 2011

Arthritis & Rheumatism

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Objective. Exposure to supraphysiologic levels of glucocorticoid drugs is known to have detrimental effects on bone formation and linear growth. Patients with sclerosteosis lack the bone regulatory protein sclerostin, have excessive bone formation, and are typically above average in height. This study was undertaken to characterize the effects of a monoclonal antibody to sclerostin (Scl-AbI) in mice exposed to dexamethasone (DEX).Methods. Young mice were concomitantly treated with DEX (or vehicle control) and Scl-AbI antibody (or isotype-matched control antibody [Ctrl-Ab]) in 2 independent studies. Linear growth, the volume and strength of the bones, and the levels of bone turnover markers were analyzed.Results. In DEX-treated mice, Scl-AbI had no significant effect on linear growth when compared to control treatment (Ctrl-Ab). However, in mice treated with DEX and Scl-ABI, a significant increase in trabecular bone at the femoral metaphysis (bone volume/total volume ؉117% versus Ctrl-Ab-treated mice) and in the width and volume of the cortical bone at the femoral diaphysis (؉24% and ؉20%, respectively, versus CtrlAb-treated mice) was noted. Scl-AbI treatment also improved mechanical strength (as assessed by 4-point bending studies) at the femoral diaphysis in DEXtreated mice (maximum load ؉60% and ultimate strength ؉47% in Scl-AbI-treated mice versus Ctrl-Abtreated mice). Elevated osteocalcin levels were not detected in DEX-treated mice that received Scl-AbI, although levels of type 5b tartrate-resistant acid phosphatase were significantly lower than those observed in mice receiving DEX and Ctrl-Ab.Conclusion. Scl-AbI treatment does not prevent the detrimental effects of DEX on linear growth, but the antibody does increase both cortical and trabecular bone and improves bone mechanical properties in DEX-treated mice.Glucocorticoid (GC)-based drugs have potent immunosuppressive and antiinflammatory properties and have assumed an important role in the treatment of many types of inflammatory and autoimmune conditions. However, drugs of this type are associated with a range of well-known side effects (1). One of the most serious problems associated with GC exposure is a deleterious effect on bone, which leads to a high proportion of patients who, after receiving long-term GC therapy, develop GC-induced osteoporosis and are susceptible to bone fractures (2). The detrimental effect of GCs on bone strength has been reported to involve many different mechanisms, including inhibition of osteoblastic bone formation, increased osteoclastic bone resorption, changes in calcium balance, and inhibition of the osteoanabolic action of sex steroids (3). More recently, it has also been proposed that GC exposure not only may cause changes to bone mass and bone architecture, but also may alter the localized material properties of bone (4).When administered to children or to growing

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Section: Discussionsupporting

confidence: 77%

Sclerostin antibody treatment enhances bone strength but does not prevent growth retardation in young mice treated with dexamethasone

Marenzana¹,

Greenslade²,

Eddleston³

et al. 2011

Arthritis & Rheumatism

View full text Add to dashboard Cite

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“…As PTH is a known inhibitor of SOST transcription, sclerostin would not be expected to be induced if PTH was the initial driver for elevated bone formation. (72)(73)(74) Indeed, subsequent decline in sclerostin later in disease progression may be attributed to the rising levels of PTH (Figs. 1D and 8B).…”

Section: Discussionmentioning

confidence: 99%

Repression of osteocyte Wnt/β-catenin signaling is an early event in the progression of renal osteodystrophy

Sabbagh

Graciolli

O’Brien

et al. 2012

Journal of Bone and Mineral Research

234

224

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Chronic kidney disease–mineral bone disorder (CKD‐MBD) is defined by abnormalities in mineral and hormone metabolism, bone histomorphometric changes, and/or the presence of soft‐tissue calcification. Emerging evidence suggests that features of CKD‐MBD may occur early in disease progression and are associated with changes in osteocyte function. To identify early changes in bone, we utilized the jck mouse, a genetic model of polycystic kidney disease that exhibits progressive renal disease. At 6 weeks of age, jck mice have normal renal function and no evidence of bone disease but exhibit continual decline in renal function and death by 20 weeks of age, when approximately 40% to 60% of them have vascular calcification. Temporal changes in serum parameters were identified in jck relative to wild‐type mice from 6 through 18 weeks of age and were subsequently shown to largely mirror serum changes commonly associated with clinical CKD‐MBD. Bone histomorphometry revealed progressive changes associated with increased osteoclast activity and elevated bone formation relative to wild‐type mice. To capture the early molecular and cellular events in the progression of CKD‐MBD we examined cell‐specific pathways associated with bone remodeling at the protein and/or gene expression level. Importantly, a steady increase in the number of cells expressing phosphor‐Ser33/37‐β‐catenin was observed both in mouse and human bones. Overall repression of Wnt/β‐catenin signaling within osteocytes occurred in conjunction with increased expression of Wnt antagonists (SOST and sFRP4) and genes associated with osteoclast activity, including receptor activator of NF‐κB ligand (RANKL). The resulting increase in the RANKL/osteoprotegerin (OPG) ratio correlated with increased osteoclast activity. In late‐stage disease, an apparent repression of genes associated with osteoblast function was observed. These data confirm that jck mice develop progressive biochemical changes in CKD‐MBD and suggest that repression of the Wnt/β‐catenin pathway is involved in the pathogenesis of renal osteodystrophy. © 2012 American Society for Bone and Mineral Research.

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“…In mice, intermittent PTH was found to decrease sclerostin expression in bone by about 50%. (66)(67)(68) In the case of continuous PTH infusion (67) or osteocyte-specific constitutively elevated PTH signaling, (69) the effect was more pronounced, with sclerostin expression being decreased by more than 80%. Experiments using in vitro approaches have shown that PTH can downregulate sclerostin expression through the MEF2 transcription complex in a downstream enhancer region for the sclerostin gene.…”

Section: Osteocytes Mechanical Loading and Interface With The Pth Pmentioning

confidence: 99%

Sclerostin: A gem from the genome leads to bone-building antibodies

Pászty

Turner

Robinson

2010

Journal of Bone and Mineral Research

113

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Discovery of SclerostinG enomics technologies and DNA sequencing have had a transformative impact on biological research, giving us unprecedented access to the genomes of numerous organisms and ushering in such new fields as systems biology (1) and, more recently, synthetic biology. (2,3) In the 1990s, the advent of highthroughput sequencing spurred application of this powerful new technology to the challenging endeavor of trying to understand the genetic basis of various inherited human diseases. One such disease was sclerosteosis, a very rare, recessively inherited highbone-mass disorder that was thought to be caused primarily by excessive osteoblast-mediated bone formation rather than by defective osteoclast-mediated bone resorption. (4,5) Within the realm of inherited high-bone-mass disorders, (6) it was the hope for a discovery in the area of osteoblast biology that made sclerosteosis particularly interesting.Indeed, the identification of new bone-building pathways that might yield novel anabolic agents had been a long-standing goal in bone biology, with hopes for therapeutic application in fracture healing, orthopedic procedures, and low-bone-mass conditions such as osteoporosis. Against this backdrop came the exciting news, independently from Mary Brunkow's group at Celltech R&D, Inc., (7,8) and from Wim Van Hul's group at the University of Antwerp, (9) that sclerosteosis was caused by mutations in a single gene (SOST) encoding a novel secreted protein. Because these were inactivating mutations, it was clear that this protein, aptly given the name sclerostin, functioned either directly or indirectly as an inhibitor of bone formation. During this same general time period, large-scale cDNA/ expressed sequence tag (EST) (10)(11)(12) and genomic DNA sequencing efforts were being made in academia and industry to rapidly identify new human genes. A novel secreted protein of unknown function, which turned out to be sclerostin, was discovered by computational mining of large DNA sequence databases using either homology-based programs (eg, BLAST) (13,14) or a special CxGxC-class cystine-knot search pattern (C Paszty, unpublished) (15) designed to identify new families of cystine-knot proteins. (16,17) Thus sclerostin emerged during an exciting era of gene discovery that was fueled, in part, by the development of important genomics technologies and the advent of high-throughput DNA sequencing.Similar to sclerostin inactivation in humans, mice with a targeted deletion of the sclerostin gene (SOST knockout mice) were found to have high bone mass, demonstrating evolutionary conservation of sclerostin's function as a negative regulator of bone formation. (18) Analysis of bones from these mice revealed that bone formation was markedly increased on each of the key skeletal surfaces where new bone is normally formed (surface of trabecular bone and internal and external surfaces of cortical bone). Consistent with the increases in bone formation and bone mass, robust increases in bone strength also were found in these anima...

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Chronic Elevation of Parathyroid Hormone in Mice Reduces Expression of Sclerostin by Osteocytes: A Novel Mechanism for Hormonal Control of Osteoblastogenesis

Cited by 573 publications

References 23 publications

Sclerostin antibody treatment enhances bone strength but does not prevent growth retardation in young mice treated with dexamethasone

Sclerostin antibody treatment enhances bone strength but does not prevent growth retardation in young mice treated with dexamethasone

Repression of osteocyte Wnt/β-catenin signaling is an early event in the progression of renal osteodystrophy

Sclerostin: A gem from the genome leads to bone-building antibodies

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