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W. Scott Simonet

Bio: W. Scott Simonet is an academic researcher from Amgen. The author has contributed to research in topics: Osteoporosis & Sclerostin. The author has an hindex of 14, co-authored 16 publications receiving 9039 citations.

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Journal ArticleDOI
15 May 2003-Nature
TL;DR: Discovery of the RANK signalling pathway in the osteoclast has provided insight into the mechanisms of osteoporosis and activation of bone resorption, and how hormonal signals impact bone structure and mass.
Abstract: Osteoclasts are specialized cells derived from the monocyte/macrophage haematopoietic lineage that develop and adhere to bone matrix, then secrete acid and lytic enzymes that degrade it in a specialized, extracellular compartment. Discovery of the RANK signalling pathway in the osteoclast has provided insight into the mechanisms of osteoclastogenesis and activation of bone resorption, and how hormonal signals impact bone structure and mass. Further study of this pathway is providing the molecular basis for developing therapeutics to treat osteoporosis and other diseases of bone loss.

5,760 citations

Journal ArticleDOI
TL;DR: Sclerosteosis is a rare high bone mass genetic disorder in humans caused by inactivating mutations in SOST, the gene encoding sclerostin, which has emerged as a key negative regulator of bone mass.
Abstract: Introduction: Sclerosteosis is a rare high bone mass genetic disorder in humans caused by inactivating mutations in SOST, the gene encoding sclerostin. Based on these data, sclerostin has emerged as a key negative regulator of bone mass. We generated SOST knockout (KO) mice to gain a more detailed understanding of the effects of sclerostin deficiency on bone. Materials and Methods: Gene targeting was used to inactivate SOST and generate a line of SOST KO mice. Radiography, densitometry, μCT, histomorphometry, and mechanical testing were used to characterize the impact of sclerostin deficiency on bone in male and female mice. Comparisons were made between same sex KO and wildtype (WT) mice. Results: The results for male and female SOST KO mice were similar, with differences only in the magnitude of some effects. SOST KO mice had increased radiodensity throughout the skeleton, with general skeletal morphology being normal in appearance. DXA analysis of lumbar vertebrae and whole leg showed that there was a significant increase in BMD (>50%) at both sites. μCT analysis of femur showed that bone volume was significantly increased in both the trabecular and cortical compartments. Histomorphometry of trabecular bone revealed a significant increase in osteoblast surface and no significant change in osteoclast surface in SOST KO mice. The bone formation rate in SOST KO mice was significantly increased for trabecular bone (>9-fold) at the distal femur, as well as for the endocortical and periosteal surfaces of the femur midshaft. Mechanical testing of lumbar vertebrae and femur showed that bone strength was significantly increased at both sites in SOST KO mice. Conclusions:SOST KO mice have a high bone mass phenotype characterized by marked increases in BMD, bone volume, bone formation, and bone strength. These results show that sclerostin is a key negative regulator of a powerful, evolutionarily conserved bone formation pathway that acts on both trabecular and cortical bone.

874 citations

Journal ArticleDOI
TL;DR: Preclinical results establish sclerostin's role as a pivotal negative regulator of bone formation in the aging skeleton and suggest that antibody‐mediated inhibition of sclerOSTin represents a promising new therapeutic approach for the anabolic treatment of bone‐related disorders, such as postmenopausal osteoporosis.
Abstract: The development of bone-rebuilding anabolic agents for potential use in the treatment of bone loss conditions, such as osteoporosis, has been a long-standing goal. Genetic studies in humans and mice have shown that the secreted protein sclerostin is a key negative regulator of bone formation, although the magnitude and extent of sclerostin's role in the control of bone formation in the aging skeleton is still unclear. To study this unexplored area of sclerostin biology and to assess the pharmacologic effects of sclerostin inhibition, we used a cell culture model of bone formation to identify a sclerostin neutralizing monoclonal antibody (Scl-AbII) for testing in an aged ovariectomized rat model of postmenopausal osteoporosis. Six-month-old female rats were ovariectomized and left untreated for 1 yr to allow for significant estrogen deficiency-induced bone loss, at which point Scl-AbII was administered for 5 wk. Scl-AbII treatment in these animals had robust anabolic effects, with marked increases in bone formation on trabecular, periosteal, endocortical, and intracortical surfaces. This not only resulted in complete reversal, at several skeletal sites, of the 1 yr of estrogen deficiency-induced bone loss, but also further increased bone mass and bone strength to levels greater than those found in non-ovariectomized control rats. Taken together, these preclinical results establish sclerostin's role as a pivotal negative regulator of bone formation in the aging skeleton and, furthermore, suggest that antibody-mediated inhibition of sclerostin represents a promising new therapeutic approach for the anabolic treatment of bone-related disorders, such as postmenopausal osteoporosis.

750 citations

Journal ArticleDOI
TL;DR: Findings indicate that the OPG/OPGL/RANK signaling pathway may play an important role in both pathological and physiological calcification processes and may also explain the observed high clinical incidence of vascular calcification in the osteoporotic patient population.
Abstract: High systemic levels of osteoprotegerin (OPG) in OPG transgenic mice cause osteopetrosis with normal tooth eruption and bone elongation and inhibit the development and activity of endosteal, but not periosteal, osteoclasts. We demonstrate that both intravenous injection of recombinant OPG protein and transgenic overexpression of OPG in OPG−/2 mice effectively rescue the osteoporotic bone phenotype observed in OPG-deficient mice. However, intravenous injection of recombinant OPG over a 4-wk period could not reverse the arterial calcification observed in OPG−/− mice. In contrast, transgenic OPG delivered from mid-gestation through adulthood does prevent the formation of arterial calcification in OPG−/− mice. Although OPG is normally expressed in arteries, OPG ligand (OPGL) and receptor activator of NF-κB (RANK) are not detected in the arterial walls of wild-type adult mice. Interestingly, OPGL and RANK transcripts are detected in the calcified arteries of OPG−/− mice. Furthermore, RANK transcript expression coincides with the presence of multinuclear osteoclast-like cells. These findings indicate that the OPG/OPGL/RANK signaling pathway may play an important role in both pathological and physiological calcification processes. Such findings may also explain the observed high clinical incidence of vascular calcification in the osteoporotic patient population.

547 citations

Journal ArticleDOI
TL;DR: This Review chronicles the events that led to an increased understanding of bone resorption, the elucidation of the signalling pathway mediated by osteoprotegerin, receptor activator of NF-κB and RANK ligand (RANKL) and its role in osteoclast biology, as well as the evolution of recombinant RankL antagonists, which culminated in the development of the therapeutic RANKL-targeted antibody denosumab.
Abstract: Bone is a complex tissue that provides mechanical support for muscles and joints, protection for vital organs, a mineral reservoir that is essential for calcium homeostasis, and the environment and niches required for haematopoiesis. The regulation of bone mass in mammals is governed by a complex interplay between bone-forming cells termed osteoblasts and bone-resorbing cells termed osteoclasts, and is guided physiologically by a diverse set of hormones, cytokines and growth factors. The balance between these processes changes over time, causing an elevated risk of fractures with age. Osteoclasts may also be activated in the cancer setting, leading to bone pain, fracture, spinal cord compression and other significant morbidities. This Review chronicles the events that led to an increased understanding of bone resorption, the elucidation of the signalling pathway mediated by osteoprotegerin, receptor activator of NF-κB (RANK) and RANK ligand (RANKL) and its role in osteoclast biology, as well as the evolution of recombinant RANKL antagonists, which culminated in the development of the therapeutic RANKL-targeted antibody denosumab.

509 citations


Cited by
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Journal ArticleDOI
TL;DR: This review summarizes the current state of knowledge of the functions of NOX enzymes in physiology and pathology.
Abstract: For a long time, superoxide generation by an NADPH oxidase was considered as an oddity only found in professional phagocytes. Over the last years, six homologs of the cytochrome subunit of the phag...

5,873 citations

Journal ArticleDOI
18 Apr 1997-Cell
TL;DR: Data show that OPG can act as a soluble factor in the regulation of bone mass and imply a utility for OPG in the treatment of osteoporosis associated with increased osteoclast activity.

5,050 citations

Journal ArticleDOI
17 Nov 2006-Cell
TL;DR: Understanding of the origins and nature of cancer metastasis and the selection of traits that are advantageous to cancer cells is promoted.

3,863 citations

Journal ArticleDOI
TL;DR: Denosumab given subcutaneously twice yearly for 36 months was associated with a reduction in the risk of vertebral, nonvertebral, and hip fractures in women with osteoporosis.
Abstract: Methods We enrolled 7868 women between the ages of 60 and 90 years who had a bone mineral density T score of less than −2.5 but not less than −4.0 at the lumbar spine or total hip. Subjects were randomly assigned to receive either 60 mg of denosumab or placebo subcutaneously every 6 months for 36 months. The primary end point was new vertebral fracture. Secondary end points included nonvertebral and hip fractures. Results As compared with placebo, denosumab reduced the risk of new radiographic vertebral fracture, with a cumulative incidence of 2.3% in the denosumab group, versus 7.2% in the placebo group (risk ratio, 0.32; 95% confidence interval [CI], 0.26 to 0.41; P<0.001) — a relative decrease of 68%. Denosumab reduced the risk of hip fracture, with a cumulative incidence of 0.7% in the denosumab group, versus 1.2% in the placebo group (hazard ratio, 0.60; 95% CI, 0.37 to 0.97; P = 0.04) — a relative decrease of 40%. Denosumab also reduced the risk of nonvertebral fracture, with a cumulative incidence of 6.5% in the denosumab group, versus 8.0% in the placebo group (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P = 0.01) — a relative decrease of 20%. There was no increase in the risk of cancer, infection, cardiovascular disease, delayed fracture healing, or hypocalcemia, and there were no cases of osteonecrosis of the jaw and no adverse reactions to the injection of denosumab. Conclusions Denosumab given subcutaneously twice yearly for 36 months was associated with a reduction in the risk of vertebral, nonvertebral, and hip fractures in women with osteoporosis. (ClinicalTrials.gov number, NCT00089791.)

2,687 citations

Journal ArticleDOI
TL;DR: Bone metastasis causes severe bone pain and can result in fractures without any injury, as well as other life-threatening conditions, and patients with prostate cancer who usually have bone metastasis that shows increased new bone formation also have increased bone destruction in the same lesions.
Abstract: Extract: Cancer frequently spreads to bone, a process termed bone metastasis. Up to 70% of patients with breast cancer or prostate cancer, and 15 to 30% of patients with lung, colon, bladder or kidney cancer develop bone metastasis. Once tumors go to bone, such as in patients with breast cancer or prostate cancer, they are incurable, and only 20% of patients with breast cancer are still alive five years after they are found to have bone metastasis. It is estimated that about 350,000 people die with bone metastasis each year in the United States. Bone metastasis causes severe bone pain and can result in fractures without any injury, as well as other life-threatening conditions. There are two major types of bone metastasis, one in which bone destruction is the predominant feature and the other one in which new bone formation is predominant. Bone metastasis where bone destruction is the predominant feature is known as osteolytic, and that in which new bone formation is the primary feature is called osteoblastic. This classification for metastasis is really two extremes of a continuum because many patients can have both osteolytic and osteoblastic or mixtures of both in their bone metastasis. In fact, patients with prostate cancer who usually have bone metastasis that shows increased new bone formation also have increased bone destruction in the same lesions.

2,287 citations