| 1. |
- Hollberg, Karin, et al.
(författare)
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Osteoclast polarization is not required for degradation of bone matrix in rachitic FGF23 transgenic mice
- 2008
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Ingår i: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 42:6, s. 1111-1121
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Tidskriftsartikel (refereegranskat)abstract
- Hypophosphatemic transgenic (tg) mice overexpressing FGF23 in osteoblasts display disorganized growth plates and reduced bone mineral density characteristic of rickets/osteomalacia. These FGF23 tg mice were used as an in vivo model to examine the relation between osteoclast polarization, secretion of proteolytic enzymes and resorptive activity. Tg mice had increased mRNA expression levels of the ostcoblast differentiation marker Runx2 and mineralization-promoting proteins alkaline phosphatase and bone sialoprotein in the long bones compared to wild type (wt) mice. In contrast, expression of alpha 1 (1) collagen, osteocalcin, dentin matrix protein 1 and osteopontin was unchanged, indicating selective activation of osteoblasts promoting mineralization. The number of osteoclasts was unchanged in tg compared to wt mice, as determined by histomorphometry, serum levels of TRAP 5b activity as well as mRNA expression levels of TRAP and cathepsin K. However, tg mice displayed elevated serum concentrations of C-terminal telopeptide of collagen I (CTX) indicative of increased bone matrix degradation. The majority of osteoclasts in FGF23 tg mice lacked ultrastructural morphological signs of proper polarization. However, they secreted both cathepsin K and MMP-9 at levels comparable to osteoclasts with ruffled borders. Mineralization of bone matrix thus appears essential for inducing osteoclast polarization but not for secretion of osteoclast proteases. Finally, release of CTX by freshly isolated osteoclasts was increased on demineralized compared to mineralized bovine bone slices, indicating that the mineral component limits collagen degradation. We conclude that ruffled borders are implicated in acidification and subsequent demineralization of the bone matrix, however not required for matrix degradation. The data collectively provide evidence that osteoclasts, despite absence of ruffled borders, effectively participate in the degradation of hypomineralized bone matrix in rachitic FGF23 tg mice.
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| 2. |
- Kanis, JA, et al.
(författare)
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Intervention thresholds for osteoporosis in the UK
- 2005
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Ingår i: Bone. - : Elsevier BV. - 1873-2763 .- 8756-3282. ; 36:1, s. 22-32
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to determine the threshold of fracture probability at which interventions became cost-effective in women based on data from the UK. We modelled the effects of an intervention costing pound350 per year given for 5 years that decreased the risk of all osteoporotic fractures by 35% followed by a waning of effect (offset time) for a further 5 years. Sensitivity analyses included a range of treatment duration (3-10 years), intervention costs (pound300-400/year) and offset times (0-15 years). Data on costs and risks were from the UK. Costs included direct costs, but excluded indirect costs due to morbidity. A threshold for cost-effectiveness of pound30,000/QALY gained was used. With the base case (pound350 per year; 35% efficacy) treatment in women was cost-effective with a 10-year hip fracture probability that ranged from 1.1% at the age of 50 years to 9.0% at the age of 85 years. Intervention thresholds were sensitive to the assumed costs and offset time. The exclusion of osteoporotic fractures other than hip fracture significantly increased the cost-effectiveness ratio because of the substantial morbidity from such other fractures, particularly at younger ages. Cost-effective scenarios were found for women at the threshold for osteoporosis from the age of 60 years. Treatment of established osteoporosis was cost-effective irrespective of age. We conclude that the inclusion of all osteoporotic fractures has a marked effect on intervention thresholds, that these vary with age and that available treatments can be targeted cost-effectively to individuals from the UK at moderately increased fracture risk.
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| 3. |
- Marsell, Richard, et al.
(författare)
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GSK-3 inhibition by an orally active small molecule increases bone mass in rats
- 2012
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Ingår i: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 50:3, s. 619-627
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Tidskriftsartikel (refereegranskat)abstract
- Glycogen synthase kinase 3β (GSK-3β) actions are central in the canonical Wnt pathway, important in many biological processes and a potential drug target for treating several diseases. It is appreciated that a balanced Wnt canonical signaling is crucial for the maintenance of normal bone mass. In this study we investigated the effects of a potent orally active GSK-3 inhibitor, AZD2858, on bone mass in rats. Treatment (1μM) of human osteoblast cells with AZD2858 in vitro increased β-catenin levels after a short period of time. In rats, oral AZD2858 treatment caused a dose-dependent increase in trabecular bone mass compared to control after a two-week treatment with a maximum effect at a dose of 20mg/kg once daily (total BMC: 172% of control; p<0.001). A small but significant effect was also seen at cortical sites (total BMC: 111% of control; p<0.001). Biomechanical testing demonstrated an increase in both vertebral compression strength at a dose of 20mg/kg once daily (Load at failure: 370% of control, p<0.001) and diaphyseal strength of femora subjected to a three point bending test (Load at failure: 115% of control; p<0.01). Furthermore, histomorphometry showed a dramatic increase in bone formation indices, and serum markers of both bone formation (Osteocalcin, 146% of control; p<0.001) and resorption (CTX, 189% of control; p<0.001) were elevated. Our conclusion is that a GSK-3 inhibitor drug may prove effective as an anabolic strategy in the treatment of diseases characterized by low bone mass, since AZD2858 has extensive bone building effects at predominantly trabecular sites.
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| 4. |
- Sisask, Gregor, et al.
(författare)
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Rats treated with AZD2858, a GSK3 inhibitor, heal fractures rapidly without endochondral bone formation
- 2013
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Ingår i: Bone. - : Elsevier BV. - 8756-3282 .- 1873-2763. ; 54:1, s. 126-132
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Tidskriftsartikel (refereegranskat)abstract
- Fracture healing is a complex interplay between endochondral and intramembranous bone formation processes. The canonical Wnt/β-catenin pathway enhances new bone formation and may play a role in fracture healing. Glycogen synthase kinase 3β (GSK3β) is a key regulator of β-catenin degradation. In this study, we investigate the effects of AZD2858, an orally bioactive GSK3 inhibitor, on fracture healing. Femoral fractures were produced in rats after the insertion of a femoral nail. The rats were treated with oral administration of AZD2858 at a dose of 30μmol/kg (20mg/kg) daily for up to 3weeks, while control animals were administered vehicle. At 4days, and at 1, 2 and 3weeks, histological analysis was performed, and at the 2 and 3week time points, we performed peripheral quantitative computed tomography (pQCT), X-rays, and four-point bending tests. Peripheral QCT showed an increase in both mineral density (of 28% at 2weeks and 38% at 3weeks) and mineral content (of 81% at 2weeks and 93% at 3weeks) in the calluses from AZD2858 treated animals as compared to vehicle treated animals. Histological analysis demonstrated that rats treated with GSK3 inhibitor healed their fractures rapidly, but without the pre-formation of cartilage tissue. Furthermore, four-point bending tests of fractured femora from animals treated for 2 and 3weeks showed an increase in strength in treated animals compared to their vehicle-treated controls. In conclusion, AZD2858, a potent GSK3 inhibitor, has a substantial impact on fracture healing. The fractures healed with a bony callus without an obvious endochondral component, suggesting that AZD2858 drives mesenchymal cells into the osteoblastic pathway. This leads to direct bone repair in an unstable fracture milieu.
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| 5. |
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| 6. |
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| 7. |
- Kanis, JA, et al.
(författare)
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The components of excess mortality after hip fracture
- 2003
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Ingår i: Bone. - 1873-2763. ; 32:5, s. 468-473
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Tidskriftsartikel (refereegranskat)abstract
- A high excess mortality is well described after hip fracture. Deaths are in part related to comorbidity and in part due directly or indirectly to the hip fracture event itself (causally related deaths). The aim of this study was to examine the quantum and pattern of mortality following hip fracture. We studied 160,000 hip fractures in men and women aged 50 years or more, in 28.8 million person-years from the patient register of Sweden, using Poisson models applied to hip fracture patients and the general population. At all ages the risk of death was markedly increased compared with population values immediately after the event. Mortality subsequently decreased over a period of 6 months, but thereafter remained higher than that of the general population. The latter function was assumed to account for deaths related to comorbidity and the residuum assumed to be due to the hip fracture. Causally related deaths comprised 17-32% of all deaths associated with hip fracture (depending on age) and accounted for more than 1.5% of all deaths in the population aged 50 years or more. Hip fracture was a more common cause for mortality than pancreatic or stomach cancer. Thus, interventions that decreased hip fracture rate by, say, 50% would avoid 0.75% or more of all deaths.
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