Nutlin‐3 treatment spares cisplatin‐induced inhibition of bone healing while maintaining osteosarcoma toxicity

The majority of Osteosarcoma (OS) patients are treated with a combination of chemotherapy, resection, and limb salvage protocols. These protocols include distraction osteogenesis (DO), which is characterized by direct new bone formation. Cisplatin (CDP) is extensively used for OS chemotherapy and recent studies, using a mouse DO model, have demonstrated that CDP has profound negative effects on bone repair. Recent oncological therapeutic strategies are based on the use of standard cytotoxic drugs plus an assortment of biologic agents. Here we demonstrate that the previously reported CDP‐associated inhibition of bone repair can be modulated by the administration of a small molecule p53 inducer (nutlin‐3). The effects of nutlin‐3 on CDP osteotoxicity were studied using both pre‐ and post‐operative treatment models. In both cases the addition of nutlin‐3, bracketing CDP exposure, demonstrated robust and significant bone sparing activity (p < 0.01–0.001). In addition the combination of nutlin‐3 and CDP induced equivalent OS tumor killing in a xenograft model. Collectively, these results demonstrate that the induction of p53 peri‐operatively protects bone healing from the toxic effects of CDP, while maintaining OS toxicity. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1716–1724, 2016.     

Lipopolysaccharide-induced bone resorption is increased in TNF type 2 receptor-deficient mice in vivo

The release of tumor necrosis factor (TNF)-alpha from macrophages upon stimulation of lipopolysaccharide (LPS) is a major etiological factor of inflammatory bone disease and elicits the effects through TNF receptors type 1 and 2. Given the importance of TNF-alpha action on osteoclastic bone resorption, the role of TNF type 2 receptor (TNFR2) on bone resorption has not been elucidated well so far. The purpose of this study is to investigate the role of TNFR2 on LPS-induced inflammatory bone resorption in vivo. LPS at 10 mg/kg (Re 595) was injected subcutaneously on calvariae of wild-type (WT), TNF type 1 receptor (TNFR1)-deficient (KO), and TNFR2 KO mice, killed on day 5 after the LPS injection. The calvarial bone mineral density (BMD) was significantly decreased by LPS compared to the vehicle-injected control in WT mice, but not in TNFR1 KO mice. Interestingly, the decrease of calvarial BMD and the increase of the osteoclast number by LPS in TNFR2 KO mice seemed to be more than those in WT mice. Furthermore, the significant decrease by LPS on the BMD of tibiae, femurs, and lumber vertebrae were observed only in TNFR2 KO mice. Histomorphometric analysis of tibiae showed the significant increases of osteoclast number and surface in the LPS-injected TNFR2 KO mice, and the levels of urinary deoxypyridinoline reflected these increases of bone resorption parameters. The present data indicate that TNFR1 is critical for bone resorption at the site of LPS injection and that TNFR2 might have a protective role on the LPS-induced inflammatory bone resorption process.     

Disruption of LRP6 in osteoblasts blunts the bone anabolic activity of PTH

Mutations in low‐density lipoprotein receptor‐related protein 6 (LRP6) are associated with human skeletal disorders. LRP6 is required for parathyroid hormone (PTH)‐stimulated signaling pathways in osteoblasts. We investigated whether LRP6 in osteoblasts directly regulates bone remodeling and mediates the bone anabolic effects of PTH by specifically deleting LRP6 in mature osteoblasts in mice (LRP6 KO). Three‐month‐old LRP6 KO mice had a significant reduction in bone mass in the femora secondary spongiosa relative to their wild‐type littermates, whereas marginal changes were found in femoral tissue of 1‐month‐old LRP6 KO mice. The remodeling area of the 3‐month‐old LRP6 KO mice showed a decreased bone formation rate as detected by Goldner's Trichrome staining and calcein double labeling. Bone histomorphometric and immumohistochemical analysis revealed a reduction in osteoblasts but little change in the numbers of osteoclasts and osteoprogenitors/osteoblast precursors in LRP6 KO mice compared with wild‐type littermates. In addition, the percentage of the apoptotic osteoblasts on the bone surface was higher in LRP6 KO mice compared with wild‐type littermates. Intermittent injection of PTH had no effect on bone mass or osteoblastic bone formation in either trabecular and cortical bone in LRP6 KO mice, whereas all were enhanced in wild‐type littermates. Additionally, the anti‐apoptotic effect of PTH on osteoblasts in LRP6 KO mice was less significant compared with wild‐type mice. Therefore, our findings demonstrate that LRP6 in osteoblasts is essential for osteoblastic differentiation during bone remodeling and the anabolic effects of PTH. © 2013 American Society for Bone and Mineral Research.     

Macrophage migration inhibitory factor inhibits osteoclastogenesis

MIF is an important regulator of innate and adaptive immunity, which is produced by a variety of cell types including activated T cells and macrophages. We examined the effects of MIF on osteoclastogenesis in bone marrow (BM) cultures from WT and MIF-deficient (KO) mice as well as the bone mass of MIF KO mice.Exogenous MIF inhibited osteoclast formation in BM cultures by decreasing fusion in cells that were treated with M-CSF and RANKL. However, inhibition of OCL formation by MIF treatment was not mediated by fusion-related molecules in heterogeneous bone marrow cultures. BM cultures from MIF KO mice that were treated with M-CSF and RANKL, PTH or vitamin D had significantly increased OCL number compared to cells from WT mice. MIF also significantly inhibited OCL formation in cultures of RAW 264.7 cells that were treated with RANKL. In addition, the number of CFU-GM and Mac-1⁺ cells in the BM of MIF KO mice was greater than in WT controls. Trabecular bone volume (TBV) in the femurs and vertebrae of MIF KO mice was decreased compared to WT mice. In addition, serum bone resorption and formation markers were decreased in MIF KO mice compared to WT mice.These results demonstrate that MIF has inhibitory effects on OCL formation in vitro. We also found that BM cell cultures from MIF KO mice had an increased capacity to form osteoclasts. Furthermore, MIF KO animals had significantly decreased TBV with low turnover. We conclude that MIF is an inhibitor of osteoclastogenesis in vitro, which may regulate bone turnover via indirect mechanism in vivo.     

Dose variation and regimen modification of adjuvant chemotherapy in daily practice affect survival of stage I-II and operable stage III Taiwanese breast cancer patients

To assess the effect of a non-standard dose and regimen of adjuvant chemotherapy on the clinical outcome in stage I–II and operable stage III Taiwanese breast cancer patients. Variables studied included treatment variation (regimen and dose of adjuvant therapy), lymph node status, tumor size, histologic grade, and hormone receptor status. Cox's multivariate regression analyses were used to select prognostic factors significant for disease-free survival (DFS) and overall survival (OS). In the multivariate analysis, lymph node-positive, a tumor size greater than 5 cm, grade III, hormone receptor-negative status, and non-standard adjuvant chemotherapy were independent prognostic factors for DFS and/or OS. Node-positive patients treated with standard adjuvant chemotherapy had a significantly better DFS (HR = 0.6; P = 0.032) and OS (HR = 0.54; P = 0.025) than those treated with non-standard adjuvant chemotherapy. Breast cancer patients receiving standard adjuvant chemotherapy have a better DFS and OS than those receiving non-standard adjuvant chemotherapy.     

An individual patient data meta‐analysis on the effect of chemotherapy on survival in patients with craniofacial osteosarcoma

Chemotherapy improves the survival of patients with long bone osteosarcomas. However, the benefits of chemotherapy in the treatment of craniofacial osteosarcoma (CFOS) are still controversial. We searched PubMed and EMBASE from February 1997 to December 2016 to identify studies on CFOS. The individual patient data of these studies were pooled into a meta‐analysis. Univariate and multivariate survival analyses were performed. Thirteen studies with a total of 184 patients met our inclusion criteria. Positive resection margin was a poor prognostic factor for CFOS in the univariate and multivariate survival analyses. Chemotherapy improved overall survival (OS) and disease‐specific survival (DSS) in patients with CFOS who had tumors in the maxilla, positive resection margins, or high‐grade tumors. Patients with local tumor recurrence had better OS and DSS when treated with chemotherapy. Chemotherapy improves survival in patients with CFOS with adverse factors, such as tumors with positive margins, high‐grade tumors, and recurrent tumors.     

Impact of Pregnancy‐Associated Plasma Protein‐A Deletion on the Adult Murine Skeleton

Introduction : The metalloproteinase, pregnancy‐associated plasma protein‐A (PAPP‐A) functions to enhance local insulin‐like growth factor (IGF)‐I bioavailability through cleavage of inhibitory IGF binding proteins. Because IGF‐I is an important regulator of skeletal growth and remodeling and PAPP‐A is highly expressed by osteoblastic cells, we hypothesized that, in the absence of PAPP‐A, bone physiology would be compromised because of a blunting of local IGF‐I action even in the presence of normal circulating IGF‐I levels. Materials and Methods : pQCT, μCT, histomorphometry, and mechanical strength testing were performed on bones from PAPP‐A knockout (KO) mice and wildtype (WT) littermates at 2–12 mo of age. IGF‐I levels and bone formation and resorption markers were determined in sera from these animals. Results : Volumetric BMD in PAPP‐A KO mice measured by pQCT at the femoral midshaft, which is primarily cortical bone, was 10% less than WT at 2 mo. This difference was maintained at 4, 6, and 12 mo. Cortical thickness at this site was similarly decreased. On the other hand, trabecular bone at the distal femur (pQCT) and in the tibia (μCT) showed age‐progressive decreases in bone volume fraction in PAPP‐A KO compared with WT mice. Tibial μCT indicated a 46% relative decrease in trabecular bone volume/total volume (BV/TV) and a 28% relative decrease in trabecular thickness in PAPP‐A KO compared with WT mice at 6 mo. These trabecular deficiencies in PAPP‐A KO mice corresponded to a weakening of the bone. Serum markers and bone histomorphometry indicated that the primary impact of PAPP‐A is on skeletal remodeling resulting in a state of low‐turnover osteopenia in adult PAPP‐A KO mice. Circulating IGF‐I levels were not altered in PAPP‐A KO mice. Conclusions : PAPP‐A is a bone growth regulatory factor in vivo and, in its absence, mice show skeletal insufficiency in mass, density, architecture, and strength. The data suggest a primary role for PAPP‐A in modulating local IGF bioavailability for trabecular bone remodeling.     

Tumor Necrosis Factor Receptor -1 and -2 Double Deficiency Reduces Graft Arterial Disease in Murine Cardiac Allografts

Graft arterial disease (GAD) remains the leading cause of long-term solid organ allograft failure. Tumor necrosis factor (TNF) promotes multiple aspects of allograft rejection via binding to type 1 (p55) and type 2 (p75) receptors. We used TNF type 1 receptor deficient (TNFR1KO), type 2 receptor deficient (TNFR2KO) and receptor double-deficient (TNFRDKO) mice to assess the relative roles of TNFR in acute rejection and GAD. Heterotopic cardiac transplantation was performed between C57BL/6 (B/6) and Balb/c (B/c) mice (total allomismatches) to assess the effects on graft survival; B/6 and Bm12 mice (class II mismatches) were used to assess the effects on GAD 8 weeks after transplantation. We found that graft survival in the total allomismatch combinations was the same regardless of TNFR status. In class II mismatches, wild-type (WT) combinations showed severe GAD, and GAD was not diminished when WT hearts were transplanted into TNFRDKO hosts. TNFR1KO donors or TNFR2KO donors had GAD comparable to WT donors, however, GAD was significantly diminished in B/6 TNFRDKO donor hearts. We conclude that both p55 and p75 signals on donor vascular wall cells are involved in the development of GAD, and either TNFR is capable of mediating a response that will culminate in GAD.     

Androgen receptor disruption increases the osteogenic response to mechanical loading in male mice

In female mice, estrogen receptor‐alpha (ERα) mediates the anabolic response of bone to mechanical loading. Whether ERα plays a similar role in the male skeleton and to what extent androgens and androgen receptor (AR) affect this response in males remain unaddressed. Therefore, we studied the adaptive response of in vivo ulna loading in AR‐ERα knockout (KO) mice and corresponding male and female single KO and wild‐type (WT) littermates using dynamic histomorphometry and immunohistochemistry. Additionally, cultured bone cells from WT and AR KO mice were subjected to mechanical loading by pulsating fluid flow in the presence or absence of testosterone. In contrast with female mice, ERα inactivation in male mice had no effect on the response to loading. Interestingly, loading induced significantly more periosteal bone formation in AR KO (+320%) and AR‐ERα KO mice (+256%) compared with male WT mice (+114%) and had a stronger inhibitory effect on SOST/sclerostin expression in AR KO versus WT mice. In accordance, the fluid flow‐induced nitric oxide production was higher in the absence of testosterone in bone cells from WT but not AR KO mice. In conclusion, AR but not ERα activation limits the osteogenic response to loading in male mice possibly via an effect on WNT signaling. © 2010 American Society for Bone and Mineral Research     

Deletion of CD74, a putative MIF receptor,in mice enhances osteoclastogenesis and decreases bone mass

CD74 is a type II transmembrane protein that can act as a receptor for macrophage migration inhibitory factor (MIF) and plays a role in MIF‐regulated responses. We reported that MIF inhibited osteoclast formation and MIF knockout (KO) mice had decreased bone mass. We therefore examined if CD74 was involved in the ability of MIF to alter osteoclastogenesis in cultured bone marrow (BM) from wild‐type (WT) and CD74‐deficient (KO) male mice. We also measured the bone phenotype of CD74 KO male mice. Bone mass in the femur of 8‐week‐old mice was measured by micro–computed tomography and histomorphometry. Bone marrow cells from CD74 KO mice formed 15% more osteoclast‐like cells (OCLs) with macrophage colony‐stimulating factor (M‐CSF) and receptor activator of NF‐κB ligand (RANKL) (both at 30 ng/mL) compared to WT. Addition of MIF to WT cultures inhibited OCL formation by 16% but had no effect on CD74KO cultures. The number of colony forming unit granulocyte‐macrophage (CFU‐GM) in the bone marrow of CD74 KO mice was 26% greater than in WT controls. Trabecular bone volume (TBV) in the femurs of CD74 KO male mice was decreased by 26% compared to WT. In addition, cortical area and thickness were decreased by 14% and 11%, respectively. Histomorphometric analysis demonstrated that tartrate‐resistant acid phosphatase (TRAP)(+) osteoclast number and area were significantly increased in CD74 KO by 35% and 43%, respectively compared to WT. Finally, we examined the effect of MIF on RANKL‐induced‐signaling pathways in bone marrow macrophage (BMM) cultures. MIF treatment decreased RANKL‐induced nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) and c‐Fos protein in BMM cultures by 70% and 41%, respectively. Our data demonstrate that CD74 is required for MIF to affect in vitro osteoclastogenesis. Further, the bone phenotype of CD74 KO mice is similar to that of MIF KO mice. MIF treatment of WT cultures suppressed RANKL‐induced activator protein 1 (AP‐1) expression, which resulted in decreased osteoclast differentiation in vitro. We propose that CD74 plays a critical role in the MIF inhibition of osteoclastogenesis. © 2013 American Society for Bone and Mineral Research.     

ADAM8 enhances osteoclast precursor fusion and osteoclast formation in vitro and in vivo

ADAM8 expression is increased in the interface tissue around a loosened hip prosthesis and in the pannus and synovium of patients with rheumatoid arthritis, but its potential role in these processes is unclear. ADAM8 stimulates osteoclast (OCL) formation, but the effects of overexpression or loss of expression of ADAM8 in vivo and the mechanisms responsible for the effects of ADAM8 on osteoclastogenesis are unknown. Therefore, to determine the effects of modulating ADAM expression, we generated tartrate‐resistant acid phosphatase (TRAP)–ADAM8 transgenic mice that overexpress ADAM8 in the OCL lineage and ADAM8 knockout (ADAM8 KO) mice. TRAP‐ADAM8 mice developed osteopenia and had increased numbers of OCL precursors that formed hypermultinucleated OCLs with an increased bone‐resorbing capacity per OCL. They also had an enhanced differentiation capacity, increased TRAF6 expression, and increased NF‐κB, Erk, and Akt signaling compared with wild‐type (WT) littermates. This increased bone‐resorbing capacity per OCL was associated with increased levels of p‐Pyk2 and p‐Src activation. In contrast, ADAM8 KO mice did not display a bone phenotype in vivo, but unlike WT littermates, they did not increase RANKL production, OCL formation, or calvarial fibrosis in response to tumor necrosis factor α (TNF‐α) in vivo. Since loss of ADAM8 does not inhibit basal bone remodeling but only blocks the enhanced OCL formation in response to TNF‐α, these results suggest that ADAM8 may be an attractive therapeutic target for preventing bone destruction associated with inflammatory disease. © 2011 American Society for Bone and Mineral Research.     

Osteosarcoma in One of Identical Twins: Three Cases Report and a Literature Review

BackgroundOsteosarcoma (OS) is the most common primary malignant bone tumor occurring mainly in children and young adults. OS is usually seen in sporadic cases, and it is an extremely rare phenomenon in blood relatives, particularly among identical twins.Case PresentationThe present study reports three cases of OS occurring in only one of identical twins. The first case is a high‐grade OS in the left proximal tibia of a 16‐year‐old girl, treated with neo‐adjuvant chemotherapy, en bloc resection, and reconstruction with a modular knee tumor prosthesis. The second one is a high‐grade OS of the left proximal tibia of a 6‐year‐old girl. The patient was treated with neo‐adjuvant chemotherapy, en bloc resection, and reconstruction with inactived autograft. The third one is a conventional OS of the right proximal tibia of a 20‐year‐old woman. She was treated with neo‐adjuvant chemotherapy, en bloc resection, and reconstruction with a custom‐made prosthesis.ConclusionsThe occurrence of OS in one of identical twins is a relatively rare event but may present the best opportunity to understand the genetic mechanisms underlying the tumorigenesis and progression of this disease in humans. A longer follow‐up period and regular imaging evaluation are needed to confirm whether the identical twin of these patients will suffer OS in the future.     

TGFβ Inducible Early Gene‐1 Plays an Important Role in Mediating Estrogen Signaling in the Skeleton

TGFβ Inducible Early Gene‐1 (TIEG1) knockout (KO) mice display a sex‐specific osteopenic phenotype characterized by low bone mineral density, bone mineral content, and overall loss of bone strength in female mice. We, therefore, speculated that loss of TIEG1 expression would impair the actions of estrogen on bone in female mice. To test this hypothesis, we employed an ovariectomy (OVX) and estrogen replacement model system to comprehensively analyze the role of TIEG1 in mediating estrogen signaling in bone at the tissue, cell, and biochemical level. Dual‐energy X‐ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), and micro‐CT analyses revealed that loss of TIEG1 expression diminished the effects of estrogen throughout the skeleton and within multiple bone compartments. Estrogen exposure also led to reductions in bone formation rates and mineralizing perimeter in wild‐type mice with little to no effects on these parameters in TIEG1 KO mice. Osteoclast perimeter per bone perimeter and resorptive activity as determined by serum levels of CTX‐1 were differentially regulated after estrogen treatment in TIEG1 KO mice compared with wild‐type littermates. No significant differences were detected in serum levels of P1NP between wild‐type and TIEG1 KO mice. Taken together, these data implicate an important role for TIEG1 in mediating estrogen signaling throughout the mouse skeleton and suggest that defects in this pathway are likely to contribute to the sex‐specific osteopenic phenotype observed in female TIEG1 KO mice. © 2014 American Society for Bone and Mineral Research.     

Regulation of postnatal trabecular bone formation by the osteoblast endothelin A receptor

Endothelin‐1 (ET‐1) is a potent vasoconstrictor that also stimulates cells in the osteoblast lineage by binding to the endothelin A receptor (ETAR). ET‐1 ligand is widely secreted, particularly by the vasculature. However, the contributions of ETAR signaling to adult bone homeostasis have not been defined. ETAR was inactivated in osteoblasts by crossing ETAR‐floxed and osteocalcin‐Cre mice. Histomorphometric analyses were performed on 4‐, 8‐, and 12‐week‐old osteoblast‐targeted ETAR knockout (KO) and wild‐type (WT) male and female mice. Tibial trabecular bone volume was significantly lower from 12 weeks in KO versus WT mice in both males and females. Bone‐formation rate, osteoblast density, and in vitro osteoblast differentiation were reduced by targeted inactivation of ETAR. A separate longitudinal analysis was performed between 8 and 64 weeks to examine the effect of aging and castration on bone metabolism in ETAR KO mice. Hypogonadism did not change the rate of bone accrual in WT or KO females. However, eugonadal KO males had a significantly larger increase in tibial and femoral bone acquisition than WT mice. Male mice castrated at 8 weeks of age showed the reverse: KO mice had reduced rates of tibial and femoral BMD acquisition compared with WT mice. In vitro, ET‐1 increased osteoblast proliferation, survival, and differentiation. Dihydrotestosterone also increased osteoblast differentiation using a mechanism distinct from the actions of ET‐1. These results demonstrate that endothelin signaling in osteoblasts is an important regulator of postnatal trabecular bone remodeling and a modulator of androgen effects on bone. © 2011 American Society for Bone and Mineral Research     

PTH stimulates bone formation in mice deficient in Lrp5.

Lrp5 deficiency decreases bone formation and results in low bone mass. This study evaluated the bone anabolic response to intermittent PTH treatment in Lrp5-deficient mice. Our results indicate that Lrp5 is not essential for the stimulatory effect of PTH on cancellous and cortical bone formation. INTRODUCTION: Low-density lipoprotein receptor-related protein 5 (Lrp5), a co-receptor in canonical Wnt signaling, increases osteoblast proliferation, differentiation, and function. The purpose of this study was to use Lrp5-deficient mice to evaluate the potential role of this gene in mediating the bone anabolic effects of PTH. MATERIALS AND METHODS: Adult wildtype (WT, 23 male and 25 female) and Lrp5 knockout (KO, 27 male and 26 female) mice were treated subcutaneously with either vehicle or 80 microg/kg human PTH(1-34) on alternate days for 6 weeks. Femoral BMC and BMD were determined using DXA. Lumbar vertebrae were processed for quantitative bone histomorphometry. Bone architecture was evaluated by microCT. Data were analyzed using a multiway ANOVA. RESULTS: Cancellous and cortical bone mass were decreased with Lrp5 deficiency. Compared with WT mice, cancellous bone volume in the distal femur and the lumbar vertebra in Lrp5 KO mice was 54% and 38% lower, respectively (p<0.0001), whereas femoral cortical thickness was 11% lower in the KO mice (p<0.0001). The decrease in cancellous bone volume in the lumbar vertebrae was associated with a 45% decrease in osteoblast surface (p<0.0001) and a comparable decrease in bone formation rate (p<0.0001). Osteoclast surface, an index of bone resorption, was 24% lower in Lrp5 KO compared with WT mice (p<0.007). Treatment of mice with PTH for 6 weeks resulted in a 59% increase in osteoblast surface (p<0.0001) and a 19% increase in osteoclast surface (p=0.053) in both genotypes, but did not augment cancellous bone volume in either genotype. Femur cortical thickness was 11% higher in PTH-treated mice in comparison with vehicle-treated mice (p<0.0001), regardless of genotype. CONCLUSIONS: Whereas disruption of Lrp5 results in decreased bone mass because of decreased bone formation, Lrp5 does not seem to be essential for the stimulatory effects of PTH on cancellous and cortical bone formation.     

Targeted Deletion of the Sclerostin Gene in Mice Results in Increased Bone Formation and Bone Strength

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.     

Elevated serum IGF‐1 levels synergize PTH action on the skeleton only when the tissue IGF‐1 axis is intact

There is growing evidence that insulin‐like growth factor 1 (IGF‐1) and parathyroid hormone (PTH) have synergistic actions on bone and that part of the anabolic effects of PTH is mediated by local production of IGF‐1. In this study we analyzed the skeletal response to PTH in mouse models with manipulated endocrine or autocrine/paracrine IGF‐1. We used mice carrying a hepatic IGF‐1 transgene (HIT), which results in a threefold increase in serum IGF‐1 levels and normal tissue IGF‐1 expression, and Igf1 null mice with blunted IGF‐1 expression in tissues but threefold increases in serum IGF‐1 levels (KO‐HIT). Evaluation of skeletal growth showed that elevations in serum IGF‐1 in mice with Igf1 gene ablation in all tissues except the liver (KO‐HIT) resulted in a restoration of skeletal morphology and mechanical properties by adulthood. Intermittent PTH treatment of adult HIT mice resulted in increases in serum osteocalcin levels, femoral total cross‐sectional area, cortical bone area and cortical bone thickness, as well as bone mechanical properties. We found that the skeletal response of HIT mice to PTH was significantly higher than that of control mice, suggesting synergy between IGF‐1 and PTH on bone. In sharp contrast, although PTH‐treated KO‐HIT mice demonstrated an anabolic response in cortical and trabecular bone compartments compared with vehicle‐treated KO‐HIT mice, their response was identical to that of PTH‐treated control mice. We conclude that (1) in the presence of elevated serum IGF‐1 levels, PTH can exert an anabolic response in bone even in the total absence of tissue IGF‐1, and (2) elevations in serum IGF‐1 levels synergize PTH action on bone only if the tissue IGF‐1 axis is intact. Thus enhancement of PTH anabolic actions depends on tissue IGF‐1. © 2010 American Society for Bone and Mineral Research.     

Osteosarcoma in identical twins: A case report

Osteosarcoma (OS) is the most frequent primary malignant bone tumor, if we exclude myeloma, a hematologic systemic disease. OS is relatively uncommon, with an estimated incidence of 600 cases per year in the United States. Among siblings is an even rarer phenomenon, with scattered reports throughout the English literature¹.We report the incidence of OS in identical twins. The first case is a low-grade OS arisen in the proximal tibia of a 25-year-old man, treated with en-bloc resection and reconstruction with allograft. The second one is a high-grade OS of the distal tibia of the 33-year-old twin, developed in a previous non-ossifying fibroma (NOF) followed over the time. The patient was treated with neo-adjuvant chemotherapy, en-bloc resection and reconstruction with allograft. Our literature review did not find any case of OS in identical twins, while 26 reports of OS in siblings are described.     

滑膜肉瘤预后相关因素分析

目的 分析影响滑膜肉瘤患者预后的相关因素.方法 回顾性分析1997年9月至2008年9月就诊的66例滑膜肉瘤患者中52例获得随访的患者的临床资料.其中男性28例,女性24例;发病年龄11～71岁,均以无痛性肿块入院.通过随访了解肿瘤学预后,明确3、5年总体生存率及局部复发率.通过回顾病例,分析年龄、性别、肿瘤部位、肿瘤直径、外科边界、病理亚型、局部治疗方式、是否侵及骨与神经血管以及是否化疗9项因素对总体生存率的影响.利用Kaplan-Meier生存分析确定对生存有影响的单个因素,并通过Cox回归分析明确影响预后的独立危险因素.结果 52例患者获得随访,随访率78.8％;随访时间6 ～ 88个月,中位随访时间32个月.患者5年总体生存率为30.3％,局部复发率为32.7％,中位复发时间16个月.单因素分析结果提示:肿瘤直径＜5 cm、取得广泛外科边界、肿瘤位于四肢以及采取广泛切除联合局部放疗的患者预后较好(P＜0.05).多因素分析显示肿瘤直径,部位以及是否取得广泛外科边界是影响预后的独立危险因素.结论 肿瘤直径、部位以及是否取得广泛外科边界是影响预后的独立危险因素.     

Effects of Deletion of ERα in Osteoblast‐Lineage Cells on Bone Mass and Adaptation to Mechanical Loading Differ in Female and Male Mice

Estrogen receptor alpha (ERα) has been implicated in bone's response to mechanical loading in both males and females. ERα in osteoblast lineage cells is important for determining bone mass, but results depend on animal sex and the cellular stage at which ERα is deleted. We demonstrated previously that when ERα is deleted from mature osteoblasts and osteocytes in mixed‐background female mice, bone mass and strength are decreased. However, few studies exist examining the skeletal response to loading in bone cell–specific ERαKO mice. Therefore, we crossed ERα floxed (ERα^fl/fl) and osteocalcin‐Cre (OC‐Cre) mice to generate animals lacking ERα in mature osteoblasts and osteocytes (pOC‐ERαKO) and littermate controls (LC). At 10 weeks of age, the left tibia was loaded in vivo for 2 weeks. We analyzed bone mass through micro‐CT, bone formation rate by dynamic histomorphometry, bone strength from mechanical testing, and osteoblast and osteoclast activity by serum chemistry and immunohistochemistry. ERα in mature osteoblasts differentially regulated bone mass in males and females. Compared with LC, female pOC‐ERαKO mice had decreased cortical and cancellous bone mass, whereas male pOC‐ERαKO mice had equal or greater bone mass than LC. Bone mass results correlated with decreased compressive strength in pOC‐ERαKO female L₅ vertebrae and with increased maximum moment in pOC‐ERαKO male femora. Female pOC‐ERαKO mice responded more to mechanical loading, whereas the response of pOC‐ERαKO male animals was similar to their littermate controls. © 2015 American Society for Bone and Mineral Research. © 2015 American Society for Bone and Mineral Research.