Enriched mesoporous bioactive glass scaffolds as bone substitutes in critical diaphyseal bone defects in rabbits.

In the field of orthopedic surgery, there is an increasing need for the development of bone replacement materials for the treatment of bone defects. One of the main focuses of biomaterials engineering are advanced bioceramics like mesoporous bioactive glasses (MBG´s). The present study compared the new bone formation after 12 weeks of implantation of MBG scaffolds with composition 82,5SiO2-10CaO-5P2O5-x 2.5SrO alone (MBGA), enriched with osteostatin, an osteoinductive peptide, (MBGO) or enriched with bone marrow aspirate (MBGB) in a long bone critical defect in radius bone of adult New Zealand rabbits. New bone formation from the MBG scaffold groups was compared to the gold standard defect filled with iliac crest autograft and to the unfilled defect. Radiographic follow-up was performed at 2, 6, and 12 weeks, and microCT and histologic examination were performed at 12 weeks. X-Ray study showed the highest bone formation scores in the group with the defect filled with autograft, followed by the MBGB group, in addition, the microCT study showed that bone within defect scores (BV/TV) were higher in the MBGO group. This difference could be explained by the higher density of newly formed bone in the osteostatin enriched MBG scaffold group. Therefore, MBG scaffold alone and enriched with osteostatin or bone marrow aspirate increase bone formation compared to defect unfilled, being higher in the osteostatin group. The present results showed the potential to treat critical bone defects by combining MBGs with osteogenic peptides such as osteostatin, with good prospects for translation into clinical practice. STATEMENT OF SIGNIFICANCE: Treatment of bone defects without the capacity for self-repair is a global problem in the field of Orthopedic Surgery, as evidenced by the fact that in the U.S alone it affects approximately 100,000 patients per year. The gold standard of treatment in these cases is the autograft, but its use has limitations both in the amount of graft to be obtained and in the morbidity produced in the donor site. In the field of materials engineering, there is a growing interest in the development of a bone substitute equivalent. Mesoporous bioactive glass (MBG´s) scaffolds with three-dimensional architecture have shown great potential for use as a bone substitutes. The osteostatin-enriched Sr-MBG used in this long bone defect in rabbit radius bone in vivo study showed an increase in bone formation close to autograft, which makes us think that it may be an option to consider as bone substitute.

Intramedullary injury combined with osteoporosis therapeutics regulates targeted local osteogenesis.

Bone marrow ablation prompts transient bone formation in nearly the entire medullary cavity before marrow regeneration occurs. Here, we establish a procedure to direct bone formation in a desired particular site within the medullary cavity for support of biomedical devices. Local intramedullary injury was performed in the tibiae of rats and parathyroid hormone (PTH), alendronate, or saline was administered. Newly generated bone in the medulla was assessed by micro-CT and histology. To evaluate the function of newly generated bone, animals received intramedullary injury in tibiae followed by daily PTH. At day-14, implants were placed in the endocortical bone and the bone response to the implants was assessed. The fate of newly generated bone was compared with and without implants. We found that neither intramedullary injury nor medication alone resulted in bone formation. However, when combined, substantial bone was generated locally inside the diaphyseal medulla. Newly formed bone disappeared without implant placement but was retained with implants. Bone was especially retained around and between the implants. This study found that local bone marrow disruption followed by PTH or alendronate generated substantial cancellous bone locally in the diaphyseal medulla. This approach offers promise as a tissue engineering tool in medicine and dentistry.

A Mouse Femoral Ostectomy Model to Assess Bone Graft Substitutes.

The shortcomings of autografts and allografts in bone defect healing have prompted researchers to develop suitable alternatives. Numerous biomaterials have been developed as bone graft substitutes each with their own advantages and disadvantages. However, in order to test if these biomaterials provide an adequate replacement of the clinical standard, a clinically representative animal model is needed to test their efficacy. In this chapter, we describe a mouse model that establishes a critical sized defect in the mid-diaphysis of the femur to evaluate the performance of bone graft substitutes. This is achieved by performing a femoral ostectomy and stabilization utilizing a femoral plate and titanium screws. The resulting defect enables the bone regenerative potential of bone graft substitutes to be investigated. Lastly, we provide instruction on assessing the torsional strength of the healed femurs to quantitatively evaluate the degree of healing as a primary outcome measure.

Effects of FK506 on the healing of diaphyseal, critical size defects in the rat femur.

There is much interest in understanding the influence of the immune system on bone healing, including a number of reports suggesting a beneficial effect of FK506 (tacrolimus) in this regard. The influence of FK506 in a rat, femoral, critical size defect was examined using locally implanted, recombinant, human (rh) BMP-2 and adenovirally-transduced, autologous, adipose-derived mesenchymal stromal cells (AD-MSCs) expressing BMP-2. FK506 was delivered systemically using an implanted osmotic pump. Empty defects and those implanted with unmodified AD-MSCs did not heal in the presence or absence of FK506. Defects treated with rhBMP-2 healed with a large callus containing thin cortices and wispy trabeculae; this, too, was unaffected by FK506. A third of defects implanted with adenovirally-transduced AD-MSCs healed, but this improved to 100 % in the presence of FK506. New bone formed in response to BMP-2 synthesised endogenously by the genetically modified cells had a slimmer callus than those healed by rhBMP-2, with improved cortication and advanced reconstitution of marrow. These results suggest that FK506 may have had little effect on the intrinsic biology of bone healing, but improved healing in response to adenovirally-transduced cells by inhibiting immune responses to the first-generation adenovirus used here. Because the genetically modified cells produced bone of higher quality at far lower doses of BMP-2, this approach should be explored in subsequent research.

Zoledronate and Raloxifene combination therapy enhances material and mechanical properties of diseased mouse bone.

Current interventions to reduce skeletal fragility are insufficient at enhancing both the quantity and quality of bone when attempting to improve overall mechanical integrity. Bisphosphonates, such as Zoledronate (ZOL), are used to treat a variety of bone disorders by increasing bone mass to decrease fracture risk, but long-term use has been shown in some settings to compromise bone quality. Alternatively, Raloxifene (RAL) has recently been demonstrated to improve tissue quality and overall mechanical properties in a cell-independent manner by binding to collagen and increasing tissue hydration. We hypothesized that a combination of RAL and ZOL would improve mechanical and material properties of bone more than either monotherapy alone by enhancing both quantity and quality. In this study, wildtype (WT) and heterozygous (OIM+/-) male mice from the Osteogenesis Imperfecta (OI) murine model were treated with either RAL, ZOL, or both from 8 weeks to 16 weeks of age. Using the OIM model allows for investigation of therapeutic effects on a quality-based bone disease. Combination treatment resulted in higher trabecular architecture, cortical mechanical properties, and cortical fracture toughness in diseased mouse bone. Two fracture toughness properties, which are direct measures of the tissue's ability to resist the initiation and propagation of a crack, were significantly improved with combination treatment in OIM+/- compared to control. There was no significant effect on fracture toughness with either monotherapy alone in either genotype. Following the mass-based effects of ZOL, trabecular bone volume fraction was significantly higher with combination treatment in both genotypes. Combination treatment resulted in higher ultimate stress in both genotypes. RAL and combination treatment in OIM+/- also increased resilience compared to the control. In conclusion, this study demonstrates the beneficial effects of using combination drug treatments to increase bone mass while simultaneously improving tissue quality, especially to enhance the mechanical integrity of diseased bone. Combination therapies could be a potential method to improve bone health and combat skeletal fragility on both the microscopic and macroscopic levels.

Sclerostin antibody reduces long bone fractures in the oim/oim model of osteogenesis imperfecta.

Osteogenesis imperfecta type III (OI) is a serious genetic condition with poor bone quality and a high fracture rate in children. In a previous study, it was shown that a monoclonal antibody neutralizing sclerostin (Scl-Ab) increases strength and vertebral bone mass while reducing the number of axial fractures in oim/oim, a mouse model of OI type III. Here, we analyze the impact of Scl-Ab on long bones in OI mice. After 9 weeks of treatment, Scl-Ab significantly reduced long bone fractures (3.6 ±â€¯0.3 versus 2.1 ±â€¯0.8 per mouse, p < 0.001). In addition, the cortical thickness of the tibial midshaft was increased (+42%, p < 0.001), as well as BMD (+28%, p < 0.001), ultimate load (+86%, p < 0.05), plastic energy (+184%; p < 0.05) and stiffness (+172%; p < 0.01) in OI Scl-Ab mice compared to OI vehicle controls. Similar effects of Scl-Ab were observed in Wild type (Wt) mice. The plastic energy, which reflects the fragility of the tissue, was lower in the OI than in the Wt and significantly improved with the Scl-Ab treatment. At the tissue level by nanoindentation, Scl-Ab slightly increased the elastic modulus in bones of both OI and Wt, while moderately increasing tissue hardness (+13% compared to the vehicle; p < 0.05) in Wt bones, but not in OI bones. Although it did not change the properties of the OI bone matrix material, Scl-Ab reduced the fracture rate of the long bones by improving its bone mass, density, geometry, and biomechanical strength. These results suggest that Scl-Ab can reduce long-bone fractures in patients with OI.

Successful treatment of pathologic femoral shaft fracture associated with large arteriovenous malformations using a 3-dimensional external fixator and teriparatide: a case report.

BACKGROUND: Arteriovenous malformations (AVMs) are rare congenital vascular lesions associated with early quiescence, late expansion, and, ultimately, infiltration and destruction of local soft tissue and bone. The extremities are a common location. Incidence of bony involvement by AVM has been reported as high as 31%. However, there are few reports on management of pathologic fracture associated with AVM. Teriparatide is a recombinant parathyroid hormone (PTH) analogue consisting of the 1-34 fragment of PTH. Recently, some reports have shown the ability of teriparatide to improve fracture healing. Here, we present a case of pathologic femoral shaft fracture associated with large AVMs that was treated successfully by external fixation and teriparatide. CASE PRESENTATION: A 68-year-old Japanese woman, previously diagnosed as having large AVMs, sustained a right femoral shaft fracture due to a fall. At the time of admission, she presented with massive swelling and venous varicosities of the right thigh. Plain radiography of the right thigh revealed femoral shaft fracture with bony erosion and calcification of soft tissue. We planned closed reduction and intramedullary nailing with a unilateral external fixator following embolization of the feeding artery. However, closed reduction using the fracture table was difficult. When we attempted open reduction, massive bleeding (1000 mL) after incision of subcutaneous tissue occurred. Finally, we carefully applied a Taylor Spatial Frame. Fracture displacement was corrected successfully and bony union was obtained with administration of teriparatide 15 months after the initial surgery. The patient is able to walk using 1 cane. CONCLUSION: We present the first report of pathologic fracture associated with large AVMs that achieved bony union using a 3-dimensional external fixator and teriparatide.

Ribose pre-treatment can protect the fatigue life of γ-irradiation sterilized bone.

Structural bone allografts are often sterilized with γ-irradiation to decrease infection risk, which unfortunately degrades the bone collagen connectivity, making the bone weak and brittle. In previous studies, we successfully protected the quasi-static mechanical properties of human cortical bone by pre-treating with ribose, prior to irradiation. This study focused on the quasi-static and fatigue tensile properties of ribose treated irradiated sterilized bone allografts. Seventy-five samples were cut from the mid-shaft diaphysis of human femurs into standardized dog-bone shape geometries for quasi-static and fatigue tensile testing. Specimens were prepared in sets of three adjacent specimens. Each set was made of a normal (N), irradiated (I) and ribose pre-treated + irradiation (R) group. The R group was incubated in a 1.2 M ribose solution before γ-irradiation. The quasi-static tensile and decalcified tests were conducted to failure under displacement control. The fatigue samples were tested under cyclic loading (10 Hz, peak stress of 45MP, minimum-to-maximum stress ratio of 0.1) until failure or reaching 10 million cycles. Ribose pre-treatment significantly improved significantly the mechanical properties of irradiation sterilized human bone in the quasi-static tensile and decalcified tests. The fatigue life of the irradiated group was impaired by 99% in comparison to the normal control. Surprisingly, the R-group has significantly superior properties over the I-group and N-group (p < 0.01, p < 0.05) (> 100%). This study shows that incubating human cortical bone in a ribose solution prior to irradiation can indeed improve the fatigue life of irradiation-sterilized cortical bone allografts.

Bisphosphonates Use and Risk of Subtrochanteric and Diaphyseal Femur Fractures in Korea: Results from the National Claim Registry.

Although Asian with bisphosphonate has been considered to have higher risk of subtrochanteric and diaphyseal femur (ST/DF) fractures, the occurrence of those fractures has been still unclear in Asia. The purpose of this study was to investigate the incidence rate of ST/DF fractures among bisphosphonate users from nationwide database in South Korea. Using national health insurance claim database, we only included the bisphosphonate users who took bisphosphonate for the first time in 2008 and evaluated the incidence rate of ST/DF fracture from 2008 to 2013. Non-user controls were matched to bisphosphonate users by propensity score matching with age and gender. Cox regression models were used to calculate hazard ratios of ST/DF fracture with and without adjustment for comorbidity. A total of 682 ST/DF fractures were observed among 348,311 bisphosphonate users. The incidence rate of ST/DF fracture among bisphosphonate users (37.75/100,000 person years, 95% CI 35.02-40.70) was higher compared with non-users (24.41/100,000 person years, 95% CI 22.31-26.71). The risk of ST/DF fracture was greater in bisphosphonate users compared with non-users (hazard ratio 1.541, 1.370-1.734; p < 0.001). The incidence rate of ST/DF fracture after bisphosphonate use could be determined in Korean patients, which can provide basal information for further studies on risk and benefit of continuing bisphosphonate.

Effects of combination treatment with alendronate and raloxifene on skeletal properties in a beagle dog model.

A growing number of studies have investigated combination treatment as an approach to treat bone disease. The goal of this study was to investigate the combination of alendronate and raloxifene with a particular focus on mechanical properties. To achieve this goal we utilized a large animal model, the beagle dog, used previously by our laboratory to study both alendronate and raloxifene monotherapies. Forty-eight skeletally mature female beagles (1-2 years old) received daily oral treatment: saline vehicle (VEH), alendronate (ALN), raloxifene (RAL) or both ALN and RAL. After 6 and 12 months of treatment, all animals underwent assessment of bone material properties using in vivo reference point indentation (RPI) and skeletal hydration using ultra-short echo magnetic resonance imaging (UTE-MRI). End point measures include imaging, histomorphometry, and mechanical properties. Bone formation rate was significantly lower in iliac crest trabecular bone of animals treated with ALN (-71%) and ALN+RAL (-81%) compared to VEH. In vivo assessment of properties by RPI yielded minimal differences between groups while UTE-MRI showed a RAL and RAL+ALN treatment regimens resulted in significantly higher bound water compared to VEH (+23 and +18%, respectively). There was no significant difference among groups for DXA- or CT-based measures lumbar vertebra, or femoral diaphysis. Ribs of RAL-treated animals were smaller and less dense compared to VEH and although mechanical properties were lower the material-level properties were equivalent to normal. In conclusion, we present a suite of data in a beagle dog model treated for one year with clinically-relevant doses of alendronate and raloxifene monotherapies or combination treatment with both agents. Despite the expected effects on bone remodeling, our study did not find the expected benefit of ALN to BMD or structural mechanical properties, and thus the viability of the combination therapy remains unclear.

Synchrotron microtomography to evaluate effects of different polychemotherapy drugs on cortical bone structure.

PURPOSE: To determine the effects of different polychemotherapy drugs on cortical bone structure, the femur diaphysis of rats were treated with two different chemotherapy drugs, AC (doxorubicin + cyclophosphamide) and TC (docetaxel + cyclophosphamide), and evaluated by 3D morphological analysis using synchrotron radiation microtomography. MATERIALS AND METHODS: Wistar rats were classified into three groups. One group received doses of docetaxel and cyclophosphamide (G1) - TC regimen; a second group received doses of doxorubicin and cyclophosphamide (G2) - AC regimen; while a control group (G0) received no further treatment. 3D tomographic images of the rats' femurs were obtained at the SYRMEP (Synchrotron Radiation for Medical Physics) beamline at the ELETTRA Synchrotron Laboratory in Trieste, Italy, using monochromatic X-rays with resolution of 9 µm. RESULTS: It could be shown that the treatment caused significant differences in morphological parameters measured from the 3D images of femur diaphysis of rats, among the studied groups, complementing a previous study using stereological methods, biochemistry and electron microscopy. CONCLUSIONS: Our results indicate that the same process of osteoporosis caused by advancing age might occur in young women treated with docetaxel + cyclophosphamide (TC) and doxorubicin + cyclophosphamide (AC). 3D microtomography was shown to be an outstanding technique for bone analysis.

Biomechanical investigation of titanium elastic nail prebending for treating diaphyseal long bone fractures.

This study numerically investigated the deformation of titanium elastic nails prebent at various degrees during implantation into the intramedullary canal of fractured bones and the mechanism by which this prebending influenced the stability of the fractured bone. Three degrees of prebending the implanted portions of the nails were used: equal to, two times, and three times the diameter of the intramedullary canal. Furthermore, a simulated diaphyseal fracture with a 5-mm gap was created in the middle shaft portion of the bone fixed with two elastic nails in a double C-type configuration. End caps were simulated using a constraint equation. To confirm that the simulation process is able to present the mechanical response of the nail inside the intramedullary, an experiment was conducted by using sawbone for validation. The results indicated that increasing the degrees of nail prebending facilitated straightening the nails against the inner aspect of canal after implantation, with increase in stability under torsion. Furthermore, reducing nail prebending caused a larger portion of the nails to move closer to the loading site and center of bone after implantation; the use of end caps prevented the nail tips from collapsing and increased axial stability. End cap use was critical for preventing the nail tips from collapsing and for increasing the stability of the nails prebent at a degree equal to the diameter of the canal with insufficient frictional force between the nail and canal. Therefore, titanium elastic nail prebending in a double C-type configuration with a degree three times the diameter of the canal represents a superior solution for treating transverse fractures without a gap, whereas that with a degree equal to the diameter of the intramedullary canal and combined with end cap use represents an advanced solution for treating comminuted fractures in a diaphyseal long bone fracture.

Bone-site-specific responses to zoledronic acid.

OBJECTIVES: Bisphosphonates are widely used to treat bone diseases such as osteoporosis. However, they may cause osteonecrosis of the jaw. Here, we investigated whether in vivo exposure to bisphosphonates has a different effect on long bone and jaw osteoclasts, and on the turnover of these different bones. MATERIALS AND METHODS: Zoledronic acid (0.5 mg kg-1 weekly) was administered intraperitoneally to 3-month-old female mice for up to 6 months. The effects on the number of osteoclasts, bone mineralization and bone formation were measured in the long bones and in the jaw. RESULTS: Long-term treatment with zoledronic acid reduced the number of jaw bone marrow cells, without affecting the number of long bone marrow cells. Zoledronic acid treatment did not affect the number of osteoclasts in vivo. Yet, the bisphosphonate increased bone volume and mineral density of both long bone and jaw. Interestingly, 6 months of treatment suppressed bone formation in the long bones without affecting the jaw. Unexpectedly, we showed that bisphosphonates can cause molar root resorption, mediated by active osteoclasts. CONCLUSIONS: Our findings provide more insight into bone-site-specific effects of bisphosphonates and into the aetiology of osteonecrosis of the jaw. We demonstrated that bisphosphonates can stimulate osteoclast activity at the molar roots.

Earlier effect of alendronate in mouse metaphyseal versus diaphyseal bone healing.

Healing of injured cancellous bone is characterized by a transient stage of rapid bone formation throughout the traumatized bone volume, often followed by similarly rapid resorption. This is different from the slower diaphyseal healing via an external callus. We, therefore, hypothesized that antiresorptive treatment might have an earlier positive effect in cancellous bone healing than in diaphyseal fractures. One hundred and twenty-three male C57bl6 mice received either an internally stabilized diaphyseal osteotomy of the femur or a screw inserted into the tibial metaphysis. The mice were randomized to daily alendronate injections (200 µg/kg/day), or control injections, and killed for mechanical testing after 14, 21, or 28 days. The hypothesis was tested by a three-way Anova (time, site, and drug). The ultimate force was increased by bisphosphonate treatment in both models. There was a significant interaction between time, site, and drug (p < 0.001) so that the full positive effect of alendronate was evident in the metaphysis at 14 days, but first after 28 days in the diaphysis. While the early effect in the metaphysis might be translated into earlier healing, the late effect in the diaphysis was due to delayed remodeling of the callus, which might have less clinical importance. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:793-799, 2017.

Localized cortical thickening of the femoral diaphysis captured on an X-ray before alendronate therapy in two cases of atypical femoral fracture.

We herein report two cases of atypical femoral fracture (AFF). X-ray examinations at the first visit of these two female patients showed a complete fracture of the femoral diaphysis diagnosed as an atypical femoral fracture (AFF). X-rays of these two cases also showed localized cortical thickening of the femoral diaphysis. Both patients had been taking alendronate for more than 3 years because of postmenopausal osteoporosis. We assumed that both of the fractures were associated with the long-term use of alendronate. However, we retrospectively identified localized cortical thickening of the femoral diaphysis on an X-ray taken before the alendronate therapy in both of these cases. Therefore, we suspected a pathogenesis of AFFs in which preexisting stress or an insufficient fracture unrelated to bisphosphonate (BP) therapy and subsequent suppression of bone turnover due to BP administration led to the occurrence of an AFF. The patient underwent surgery using intramedullary nails in both of these cases, followed by the administration of teriparatide, and they were able to walk without any support at the final follow-up examination.

Prophylactic pamidronate partially protects from glucocorticoid-induced bone loss in the mdx mouse model of Duchenne muscular dystrophy.

Glucocorticoids are extensively used to treat patients with Duchenne muscular dystrophy because of their ability to delay muscle damage, prolong ambulation and extend life. However, use of glucocorticoids significantly increases bone loss, fragility and fractures. To determine if antiresorptive bisphosphonates could prevent the effects of glucocorticoids on bone quality, we used dystrophic mdx mice treated with the glucocorticoid prednisone during 8weeks of rapid bone growth from 5 to 13weeks of age and treated some mice with the bisphosphonate pamidronate during the first two weeks of prednisone administration. Prednisone reduced long bone growth, decreased cortical bone thickness and area and decreased the strength of the femurs. Pamidronate treatment protected mice from cortical bone loss but did not increase bone strength. The combination of prednisone and pamidronate inhibited remodeling of metaphyseal trabecular bone with large numbers of trabeculae containing remnants of calcified cartilage. Prednisone improved muscle strength in the mdx mice and decreased serum creatine kinase with evidence of improved muscle histology and these effects were maintained in mice treated with pamidronate.

NF-κB decoy oligodeoxynucleotide mitigates wear particle-associated bone loss in the murine continuous infusion model.

UNLABELLED: Total joint replacement is a cost-effective surgical procedure for patients with end-stage arthritis. Wear particle-induced chronic inflammation is associated with the development of periprosthetic osteolysis. Modulation of NF-κB signaling in macrophages, osteoclasts, and mesenchymal stem cells could potentially mitigate this disease. In the current study, we examined the effects of local delivery of decoy NF-κB oligo-deoxynucleotide (ODN) on wear particle-induced bone loss in a murine continuous femoral particle infusion model. Ultra-high molecular weight polyethylene particles (UHMWPE) with or without lipopolysaccharide (LPS) were infused via osmotic pumps into hollow titanium rods placed in the distal femur of mice for 4weeks. Particle-induced bone loss was evaluated by µCT, and immunohistochemical analysis of sections from the femur. Particle infusion alone resulted in reduced bone mineral density and trabecular bone volume fraction in the distal femur. The decoy ODN reversed the particle-associated bone volume fraction loss around the implant, irrespective of the presence of LPS. Particle-infusion with LPS increased bone mineral density in the distal femur compared with particle-infusion alone. NF-κB decoy ODN reversed or further increased the bone mineral density in the femur (3-6mm from the distal end) exposed to particles alone or particles plus LPS. NF-κB decoy ODN also inhibited macrophage infiltration and osteoclast number, but had no significant effects on osteoblast numbers in femurs exposed to wear particles and LPS. Our study suggests that targeting NF-κB activity via local delivery of decoy ODN has great potential to mitigate wear particle-induced osteolysis. STATEMENT OF SIGNIFICANCE: Total joint replacement is a cost-effective surgical procedure for patients with end-stage arthritis. Chronic inflammation is crucial for the development of wear particle-associated bone loss. Modulation of NF-κB signaling in macrophages (pro-inflammatory cells), osteoclasts (bone-resorbing cells), and osteoblasts (bone-forming cells) could potentially mitigate this disease. Here we demonstrated that local delivery of decoy NF-κB oligo-deoxynucleotide (ODN) mitigated ultra-high molecular weight polyethylene (UHMWPE) wear particle induced bone loss in a clinically relevant murine model. The protective effects of decoy ODN was associated with reduced macrophage infiltration and osteoclast activation, but had no significant effects on osteoblast numbers. Our study suggests that targeting NF-κB activity via local delivery of decoy ODN has great potential to mitigate wear particle-induced bone loss.

Melatonin can Ameliorate Radiation-Induced Oxidative Stress and Inflammation-Related Deterioration of Bone Quality in Rat Femur.

The aim of the present study was to evaluate the radioprotective effects of melatonin on the biomechanical properties of bone in comparison to amifostine (WR-2721). Forty Sprague Dawley rats were divided equally into 5 groups namely; control (C), irradiation (R; single dose of 50 Gy), irradiation + WR-2721 (R + WR-2721; irradiation + 200 mg/kg WR-2721) radiation + melatonin 25 mg/kg (R + M25; irradiation + 25 mg/kg melatonin), and radiation + melatonin 50 mg/kg (R + M50; irradiation + 50 mg/kg melatonin). In order to measure extrinsic (organ-level mechanical properties of bone; the ultimate strength, deformation, stiffness, energy absorption capacity) and intrinsic (tissue-level mechanical properties of bone; ultimate stress, ultimate strain, elastic modulus, toughness) features of the bone, a three-point bending (TPB) test was performed for biomechanical evaluation. In addition, a bone mineral density (BMD) test was carried out. The BMD and extrinsic properties of the diaphyseal femur were found to be significantly higher in the R + M25 group than in group R (p < 0.05). A significant increase was observed in R + M50 (p < 0.05) in comparison to group R in the cross-sectional area of the femoral shaft and elastic modulus parameter. The protective effect of melatonin was similar to that of WR-2721. Thus, biomechanical quality of irradiated bone can be ameliorated by free radical scavenger melatonin.

Odanacatib Restores Trabecular Bone of Skeletally Mature Female Rabbits With Osteopenia but Induces Brittleness of Cortical Bone: A Comparative Study of the Investigational Drug With PTH, Estrogen, and Alendronate.

Cathepsin K (CK), a lysosomal cysteine protease, is highly expressed in mature osteoclasts and degrades type 1 collagen. Odanacatib (ODN) is a selective and reversible CK inhibitor that inhibits bone loss in preclinical and clinical studies. Although an antiresorptive, ODN does not suppress bone formation, which led us to hypothesize that ODN may display restorative effect on the osteopenic bones. In a curative study, skeletally mature New Zealand rabbits were ovarectomized (OVX) and after induction of bone loss were given a steady-state exposure of ODN (9 mM/d) for 14 weeks. Sham-operated and OVX rabbits treated with alendronate (ALD), 17b-estradiol (E2), or parathyroid hormone (PTH) served as various controls. Efficacy was evaluated by assessing bone mineral density (BMD), bone microarchitecture (using micro-computed tomography), fluorescent labeling of bone, and biomechanical strength. Skeletal Ca/P ratio was measured by scanning electron microscopy (SEM) with X-ray microanalysis, crystallinity by X-ray diffraction, and bone mineral density distribution (tissue mineralization) by backscattered SEM. Between the sham and ODN-treated osteopenic groups, lumbar and femur metaphyseal BMD, Ca/P ratio, trabecular microstructure and geometric indices, vertebral compressive strength, trabecular lining cells, cortical parameters (femoral area and thickness and periosteal deposition), and serum P1NP were largely comparable. Skeletal improvements in ALD-treated or E2-treated groups fell significantly short of the sham/ODN/PTH group. However, the ODN group displayed reduced ductility and enhanced brittleness of central femur, which might have been contributed by higher crytallinity and tissue mineralization. Rabbit bone marrow stromal cells expressed CK and when treated with ODN displayed increased formation of mineralized nodules and decreased apoptosis in serum-deficient medium compared with control. In vivo, ODN did not suppress remodeling but inhibited osteoclast activity more than ALD. Taken together, we show that ODN reverses BMD, skeletal architecture, and compressive strength in osteopenic rabbits; however, it increases crystallinity and tissue mineralization, thus leading to increased cortical bone brittleness.

Osteocyte-directed bone demineralization along canaliculi.

The mammalian skeleton stores calcium and phosphate ions in bone matrix. Osteocytes in osteocyte lacunae extend numerous dendrites into canaliculi less than a micron in diameter and which are distributed throughout bone matrix. Although osteoclasts are the primary bone-resorbing cells, osteocytes also reportedly dissolve hydroxyapatite at peri-lacunar bone matrix. However, robust three-dimensional evidence for peri-canalicular bone mineral dissolution has been lacking. Here we applied a previously reported Talbot-defocus multiscan tomography method for synchrotron X-ray microscopy and analyzed the degree of bone mineralization in mouse cortical bone around the lacuno-canalicular network, which is connected both to blood vessels and the peri- and endosteum. We detected cylindrical low mineral density regions spreading around canaliculi derived from a subset of osteocytes. Transmission electron microscopy revealed both intact and demineralized bone matrix around the canaliculus. Peri-canalicular low mineral density regions were also observed in osteopetrotic mice lacking osteoclasts, indicating that osteoclasts are dispensable for peri-canalicular demineralization. These data suggest demineralization can occur from within bone through the canalicular system, and that peri-canalicular demineralization occurs not uniformly but directed by individual osteocytes. Blockade of peri-canalicular demineralization may be a therapeutic strategy to increase bone mass and quality.