Biomechanical evaluation in osteoporosis: ovariectomized rat model

Bone proliferation in osteoporotic experimental animals using alginate-pullulan-bioactive glass‑gold nanoparticles composite

In the present study, scaffold composites based on alginate-pullulan-bioactive glass‑gold nanoparticles were orthotopically implanted in an experimental model of delayed bone union, in rats, given by a metabolic pathology, namely osteoporosis. Differences between treated and untreated groups were observed and the efficacy of our biomaterial was evaluated by applying micro-CT imaging, together with histological evaluation of the osteoporotic animals with sub-critical bone defects, at 30 and 60 days. Osteoporosis was successfully induced by ovariectomy in 9-month-old rats, confirmed by micro-CT and histopathological analysis. A secondary complication from a cortical bone defect was further induced to study bone proliferation in such a delayed environment. The studied composite presents osteointegration and angiogenesis properties at 60 days post-implantation in the osteoporotic animals. These results are given by the micro-CT analysis in which higher bone mineral density and bone volume fraction were observed, alongside histopathology, stating a lack of tissue necrosis and inflammatory reaction and the presence of new woven islands within and around the implanted biomaterial. This is the first endeavor to treat cortical bone defects in osteoporotic animals using scaffold biopolymers containing bioactive glass‑gold nanoparticles instead of cement.

Effect of estrogen depression on alveolar bone microarchitecture and periodontal ligament cells during orthodontic movement

This study aimed to evaluate the effects of the estrogen depression during orthodontic tooth movement on alveolar bone microarchitecture and periodontal ligament. Female Wistar rats were divided into two groups, one consisting of non-ovariectomized animals subjected to orthodontic tooth movement, and one comprising ovariectomized animals subjected to orthodontic tooth movement. Micro-CT assessment of bone volume to total volume (BV/TV), total porosity, trabecular thickness (Tb.Th), trabecular number (Tb.N), and trabecular separation (Tb.Sp) in the alveolar bone of the orthodontically moved tooth was performed. Histomorphometric analyses were made in the periodontal ligament, and immunoexpression of RANK, RANKL, OPG, and TUNEL were quantified. Orthodontic tooth movement in the group of ovariectomized rats was faster than in non-ovariectomized animals. The alveolar bone area showed lower values of BV/TV and trabecular thickness, and higher bone porosity and trabeculae numbers in the ovariectomized rats. Histological analyses in the ovariectomized group revealed an increase in collagen fibers in the periodontal ligament. The apoptotic cell counts in the periodontal ligament were higher in the group of ovariectomized rats than in the sham-operated rats. Ovariectomy resulted in an increase in tooth movement and alteration of the alveolar bone microstructure in the first 7 day of orthodontic tooth movement, and in the presence of apoptotic cells in the periodontal ligament.

The effect of Rutin hydrate on Glucocorticoids induced osteoporosis in mandibular alveolar bone in Albino rats (Radiological, histological and histochemical study)

Background

Glucocorticoids are used in different conditions such as autoimmune disorders and organ transplantation and their administration is the most common cause of secondary osteoporosis. Rutin is a flavonoid found in many plants. Flavonoids are natural products with various therapeutic and biological effects.

Objective

Is to investigate the effect of Rutin Hydrate as a form of Rutin on glucocorticoid induced osteoporosis in mandibular alveolar bone radiologically, histologically and histochemically.

Methods

Twenty-one adult male Albino rats were randomly divided into three groups. Group I (control), group II (osteoporotic) and group III (Rutin Hydrate treated). In both group II and III rats received 21 mg/kg of methylprednisolone daily for four weeks. Then group III received 50 mg/kg of rutin hydrate in distilled water daily for another four weeks. At the end of the experiment, mandibles were dissected for radiographic assessment, then processed for histological and histochemical examination and statistical analysis.

Results

Radiologically, administration of Rutin Hydrate was able to enhance bone density than osteoporotic group. Histological examination revealed preserved cortical bone thickness that had been statistically proved. Apparently normal sized marrow cavities, some plump osteoblasts and normal osteocytes were seen in group III. Histochemical examination showed statistical increase in the area percentage of newly formed collagen in group III than group II.

Conclusions

Rutin Hydrate was able to modify the radiological and histological picture of osteoporotic alveolar bone. This was achieved by the ability of Rutin Hydrate to increase bone density, preserve cortical plates thickness and enhance new collagen formation that was proved histochemically.

Poor bone matrix quality: What can be done about it?

PURPOSE OF THE REVIEW

Bone's ability to withstand load resisting fracture and adapting to it highly depends on the quality of its matrix and its regulators. This review focuses on the contribution of bone quality to fracture resistance and possible therapeutic targets for skeletal fragility in aging and disease.

RECENT FINDINGS

The highly organized, hierarchical composite structure of bone extracellular matrix together with its (re)modeling mechanisms and microdamage dynamics determines its stiffness, strength, and toughness. Aging and disease affect the biological processes regulating bone quality, thus resulting in defective extracellular matrix and bone fragility. Targeted therapies are being developed to restore bone's mechanical integrity. However, their current limitations include low tissue selectivity and adverse side effects. Biological and mechanical insights into the mechanisms controlling bone quality, together with advances in drug delivery and studies in animal models, will accelerate the development and translation to clinical application of effective targeted-therapeutics for bone fragility.

Bovine Colostrum Supplementation Improves Bone Metabolism in an Osteoporosis-Induced Animal Model

Osteoporosis is characterized by bone loss. The present study aims to investigate the effects of bovine colostrum (BC) on bone metabolism using ovariectomized (OVX) and orchidectomized (ORX) rat models. Twenty-seven-week-old Wistar Han rats were randomly assigned as: (1) placebo control, (2) BC supplementation dose 1 (BC1: 0.5 g/day/OVX, 1 g/day/ORX), (3) BC supplementation dose 2 (BC2: 1 g/day/OVX, 1.5 g/day/ORX) and (4) BC supplementation dose 3 (BC3: 1.5 g/day/OVX, 2 g/day/ORX). Bone microarchitecture, strength, gene expression of VEGFA, FGF2, RANKL, RANK and OPG, and bone resorption/formation markers were assessed after four months of BC supplementation. Compared to the placebo, OVX rats in the BC1 group exhibited significantly higher cortical bone mineral content and trabecular bone mineral content (p < 0.01), while OVX rats in the BC3 group showed significantly higher trabecular bone mineral content (p < 0.05). ORX rats receiving BC dose 2 demonstrated significantly higher levels of trabecular bone mineral content (p < 0.05). Serum osteocalcin in the ORX was pointedly higher in all BC supplementation groups than the placebo (BC1: p < 0.05; BC2, BC3: p < 0.001). Higher doses of BC induced significantly higher relative mRNA expression of OPG, VEGFA, FGF2 and RANKL (p < 0.05). BC supplementation improves bone metabolism of OVX and ORX rats, which might be associated with the activation of the VEGFA, FGF2 and RANKL/RANK/OPG pathways.

Multiscale characterization of ovariectomized rat femur

Estrogen deficiency activates bone resorbing cells (osteoclasts) and to a lesser extent bone forming cells (osteoblasts), resulting in a gap between resorption and formation that leads to a net loss of bone. These cell activities alter bone architecture and tissue composition. Thus, the objective of this study is to examine whether multiscale (10^-2 to 10^-7 m) characterization can provide more integrated information to understand the effects of estrogen deficiency on the fracture risk of bone. This is the first study to examine the effects of estrogen deficiency on multiscale characteristics of the same bone specimen. Sprague-Dawley female rats (6 months old) were obtained for a bilateral ovariectomy (OVX) or a sham operation (sham). Micro-computed tomography of rat femurs provided bone volumetric, mineral density, and morphological parameters. Dynamic mechanical analysis, static elastic and fracture mechanical testing, and nanoindentation were also performed using the same femur. As expected, the current findings indicate that OVX reduces bone quantity (mass and bone mineral density) and quality (morphology, and fracture displacement). Additionally, they demonstrated reductions in amount and heterogeneity of tissue mineral density (TMD) and viscoelastic properties. The current results validate that multiscale characterization for the same bone specimen can provide more comprehensive insights to understand how the bone components contributed to mechanical behavior at different scales.

Ginsenoside Rg3 attenuates ovariectomy-induced osteoporosis via AMPK/mTOR signaling pathway

Ginsenoside Rg3, a ginsenoside isolated from Panax ginseng, can regulate autophagy via AMP-activated protein kinase/mammalian target of rapamycin (AMPK/mTOR) signaling pathway. AMPK/mTOR signaling and autophagy have been reported to be involved in osteogenesis. Here, the effect of Rg3 on ovariectomy (OVX)-induced osteoporosis is explored. In vivo, rats were treated with 20 mg/kg Rg3 after OVX and the body weight (BW) was monitored. Bone mineral density (BMD), hematoxylin-eosin staining of femur tissues, osteogenesis, autophagy, and AMPK/mTOR signaling were analyzed. In vitro, MC3T3-E1 cells were treated with 0, 1, 5, 10, 20, and 100 μmol/L Rg3. 10 and 20 μmol/L Rg3, which had no significant effect on cell viability and significantly affected AMPK/mTOR signaling, were chosen for further analysis. Then osteogenic differentiation was induced with Rg3 or/and AMPK inhibitor (Compound C). AMPK/mTOR signaling, autophagy, osteogenic differentiation, and mineralization by Alizarin Red staining were analyzed. The expression or activity of AMPK/mTOR signaling-related proteins, autophagy markers, and osteogenesis markers was measured by western blotting or commercial kits, and cell viability by cell counting kit-8 assay kits. Rg3 significantly alleviated OVX-induced BW increases, BMD declines and histological changes of femur tissues, promoted osteogenesis, autophagy, and AMPK signaling, but inhibited mTOR signaling in vivo. Moreover, Rg3 significantly enhanced AMPK signaling, autophagy, osteogenic differentiation, and mineralization, but suppressed mTOR signaling in vitro. However, Compound C significantly reversed Rg3-induced alterations in vitro, indicating that Rg3 regulated autophagy, osteogenic differentiation, and mineralization via AMPK/mTOR signaling. Hence, it was speculated that Rg3 might attenuate OVX-induced osteoporosis via AMPK/mTOR signaling pathway.

Resveratrol promotes osteoblastic differentiation in a rat model of postmenopausal osteoporosis by regulating autophagy

OBJECTIVE

Resveratrol is a natural polyphenolic compound that ameliorates postmenopausal osteoporosis by activating the estrogen receptor. Research has shown that resveratrol exhibits some type of estrogen receptor agonist activity, reducing the risk of breast cancer. However, its mechanism of action remains largely unknown. This study aims to investigate the effect of resveratrol on osteoblastic and osteoclastic differentiation and its potential role in the regulation of autophagy.

METHODS

Sprague Dawley (SD) rats underwent ovariectomies (OVX) and were administered resveratrol (at 10, 20 or 40 mg/kg/d) for 8 weeks. The calcium content and the bone mineral density (BMD) were measured in the lumbar vertebrae (L3) and the right distal femur-tibia bone region. The osteoblasts and osteoclasts were isolated from rat lumbar vertebrae by enzyme digestion and bone marrow induction, respectively. The cells were then cultured with resveratrol in combination with bafilomycin or leupeptin to inhibit or activate autophagy, respectively. Western blotting was used to assess the differentiation markers and autophagy-related genes in the osteoblasts and osteoclasts.

RESULTS

Compared to the sham group, the bone calcium content and BMD were significantly decreased in the OVX group (p < 0.05), while resveratrol attenuated these in a dose-dependent manner. In the osteoblasts, vascular endothelial growth factor (VEGF), and alpha-1 type I collagen (COL1A1) were markedly decreased, and in osteoclasts, the receptor activator of nuclear factor-κB ligand (RANKL) was increased in the OVX group, while resveratrol reversed this pattern in a dose-dependent manner. The inhibition of autophagy in osteoblasts and its activation in osteoclasts was observed in the OVX group. However, with resveratrol, this was reversed in a dose-dependent manner.

CONCLUSION

Overall, resveratrol promotes osteoblastic differentiation and suppresses osteoclastic differentiation in a rat model with postmenopausal osteoporosis by regulating autophagy.

Single-dose local administration of parathyroid hormone (1-34, PTH) with β-tricalcium phosphate/collagen (β-TCP/COL) enhances bone defect healing in ovariectomized rats

Parathyroid hormone (1-34, PTH) combined β-tricalcium phosphate (β-TCP) achieves stable bone regeneration without cell transplantation in previous studies. Recently, with the development of tissue engineering slow release technology, PTH used locally to promote bone defect healing become possible. This study by virtue of collagen with a combination of drugs and has a slow release properties, and investigated bone regeneration by β-TCP/collagen (β-TCP/COL) with the single local administration of PTH. After the creation of a rodent critical-sized femoral metaphyseal bone defect, β-TCP/COL was prepared by mixing sieved granules of β-TCP and atelocollagen for medical use, then β-TCP/COL with dripped PTH solution (1.0 µg) was implanted into the defect of OVX rats until death at 4 and 8 weeks. The defected area in distal femurs of rats was harvested for evaluation by histology, micro-CT, and biomechanics. The results of our study show that single-dose local administration of PTH combined local usage of β-TCP/COL can increase the healing of defects in OVX rats. Furthermore, treatments with single-dose local administration of PTH and β-TCP/COL showed a stronger effect on accelerating the local bone formation than β-TCP/COL used alone. The results from our study demonstrate that combination of single-dose local administration of PTH and β-TCP/COL had an additive effect on local bone formation in osteoporosis rats.

In vitro assessments of bone microcomputed tomography in an aged male rat model supplemented with Panax ginseng

Recent research has confirmed that Panax ginseng (P. ginseng) has effect on cultured osteoblast of the mouse. In this study we aim to validate the usefulness of tibia quantification by correlating micro-computed tomographic (microCT) images with histology analysis in the aged male rats. A total of thirty - old male WISTAR rats were used and divided into ten 8 weeks rats and ten 112 weeks aged rats with vehicle and ten 112 weeks aged rats with P. ginseng (300 mg/kg/day). Daily oral administration of P. ginseng lasted for 8 weeks. Bone histomorphometric parameters and the trabecular bone microarchitectural properties of tibia were determined by microCT scan. MicroCT analysis showed significantly lower bone mineral density (BMD) and trabecular bone number in the aged group. Ginseng prevented total BMD decrease in the tibia induced by natural aging, which was accompanied by a significant decrease in skeletal remodeling. Furthermore, the aged group with ginseng was found to have a significantly higher osteoblast. In the blood biochemistry results, serum phosphorus, calcium, osteocalcin, T3, and T4 remained unchanged. The present study indicated that P. ginseng might be a potential alternative medicine for the prevention and treatment of natural aging-induced osteoporosis in human.

Effect of Alendronate on Bone Microarchitecture in Irradiated Rats With Osteoporosis: Micro-CT and Histomorphometric Analysis

PURPOSE

The aim of the present study was to evaluate the effect of alendronate (ALN) on the bone microarchitecture of irradiated rats with estrogen deficiency, using microcomputed tomography (micro-CT) and histomorphometric analysis.

MATERIALS AND METHODS

Forty adult Wistar rats were subjected to ovariectomy and randomly divided into the following groups: control (CON), ALN, irradiated (IRR), and ALN/irradiated (ALN/IRR). Approximately 50 days after ovariectomy, the hind limbs of the rats in the IRR and ALN/IRR groups were irradiated with 15 Gy of x-radiation. The rats were euthanized 7 and 30 days after irradiation. The bone microarchitecture was analyzed using micro-CT and histomorphometry. The bone microarchitecture was evaluated using the Mann-Whitney U test, analysis of variance, and the post hoc Tukey test, with statistical significance set at 5%.

RESULTS

Irradiation had increased the thickness of the cortical bone at 7 days (P < .05) and also decreased the number of trabeculae per unit length and increased the average distance between the trabeculae (P < .05) at 30 days. ALN inhibited the deleterious effect of x-radiation, preventing the distance between the trabeculae from increasing and the number of trabeculae per unit length from decreasing (P < .05).

CONCLUSIONS

The present results have demonstrated that the initial effect of ALN could be positive, because it checked the deleterious action in the bone tissue submitted to x-radiation.

Combined treatment with alendronate and Drynaria rhizome extracts : Effect on fracture healing in osteoporotic rats

The effects of both alendronate (ALN) and Drynaria rhizome extracts (DRE) alone could promote bone healing in osteoporotic fractures but there are no reports about the combined use of ALN and DRE for promotion of bone healing of fractures in osteoporotic settings. This study investigated the effects of ALN plus DRE on fractures in osteopenic rats. Osteopenic rats underwent unilateral transverse osteotomy on the femur fixed by a sterilized Kirschner wire 2 weeks after intragastric administration of retinoic acid (80 mg/kg body weight/day). Subsequently, the animals were randomly divided into four groups: control, ALN, DRE and ALN + DRE. All rats from groups ALN, DRE and ALN + DRE received ALN (40 mg/kg, weekly), DRE (90 mg/kg/day), or both for 2, 4 and 6 weeks. The results of our study indicated that all treatment promoted fracture healing and callus formation compared to controls but ALN + DRE treatment showed significantly stronger effects than ALN or DRE alone in histological, X‑ray and biomechanical tests. These results seem to indicate that combined treatment with ALN and DRE has an additive effect on fracture healing and callus formation in osteoporotic rats.

The Effects of Nigella Sativa Seed Extract on Bone Healing in an Experimental Model

The purpose of this study was to histologically evaluate the effects on bone healing of nigella sativa seed extract applied on calvarial defects in an ovariectomized rat model. The study included 32 female rats weighing 280 to 310 g with an average age of 3 months. A defect was created with a trephine burr on each rat calvarium. The rats were divided into 2 groups (control and study) of 8 animals each. All the defects were grafted with a gelatin sponge mixed with normal saline. In the study group, nigella sativa seed extract was applied systemically using an oro-gastric tube. Half of the animals in each group were sacrificed after 2 weeks, and the others after 4 weeks. In the control groups, the defects were not completely filled with regenerated bone. Osteoblast cells were observed more in the study groups. A higher rate of osteoclasts was determined in the control groups. In addition, the nigella sativa group had a statistically greater amount of bone formation than the others group at both 2 weeks and 4 weeks (P <0.05). The systemic application of nigella sativa seed extract demonstrated incredibly positive effects on enhanced bone healing in this experimental osteoporotic model.

Effects of Ankaferd BloodStopper on bone healing in an ovariectomized osteoporotic rat model

Bone defects resulting from oncological surgical resections, congenital facial anomalies, trauma or infection represent a significant and common clinical problem. The present study aimed to evaluate the effects of a commercially-available medicinal plant extract product, Ankaferd BloodStopper (ABS), on bone healing. The present study was performed on 24 female ovariectomized (OVX) rats. A defect on each rat calvarium was created using a trephine burr prior to the rats being divided into two groups. Defects were grafted with a gelatin sponge soaked with normal saline (control group) or plant extract (experimental group). Half of the animals were sacrificed after 2 weeks and the others after 4 weeks. In the control group, the defects were not filled with regenerated bone. By contrast, in the experimental group, all defect areas had an increased amount of regenerated bone and connective tissue. Osteoblastic activity appeared to be greater in the experimental group however, osteoclastic activity was observed to be higher in the control group. At 2 and 4 weeks, there was a significant difference in the amount of newly regenerated bone observed in the experimental group compared with the control group (P<0.05). Therefore, the results of the present study indicated that local ABS application had a positive effect on bone healing in the OVX rat model.

Effect exerted by Teriparatide upon Repair Function of β-tricalcium phosphate to ovariectomised rat's femoral metaphysis defect caused by osteoporosis

In this study, we tested the effect of Teriparatide (PTH) in combination with β-tricalcium phosphate (β-TCP) as a bone void filler in an ovariectomised rat distal femoral metaphysis model.β-TCP is a completely resorbable synthetic calcium phosphate and the Teriparatide is a drug that can promote bone formation in the condition of osteoporosis. A critical size defect of 3mm in diameter, a through-hole bone defect, was drilled into each distal femur of the ovariectomised rats. The hole was filled with β-TCP and the rat was injected PTH Teriparatide (30μg/kg) in peritoneum 5 times per week. After 4and 8 weeks the animals were killed and the degree of bone healing analysed. In total, 60 animals were investigated. When the β-TCP and PTH were used, histological, biochemistry and histomor-phometric evaluations revealed significantly better bone healing in terms of quantity and quality of the newly formed bone. The Ovariectomised rats which suffer from femur metaphysis defect are cured by embedding β-tricalcuim phosphate and intermittently cured by parathyroid hormone (PTH).

Treatment study of distal femur for parathyroid hormone (1-34) and β-tricalcium phosphate on bone formation in critical-sized defects in osteopenic rats

The objective of this study was to evaluate the effect of following combined treatment with parathyroid hormone (1-34) (PTH) and β-tricalcium phosphate (β-TCP) on local bone formation in a rat 3-mm critical-sized defect at the distal femur. Fourteen weeks were allowed to pass before defect surgery for the establishment of osteopenic animal models chronically fed a low-protein diet. All animals were randomly divided into four groups: group PTH; group β-TCP, group PTH + β-TCP, and a control group. All rats then underwent a surgical procedure to create bone defects in the bilateral distal femurs, and β-TCP was implanted into critical-sized defects for the groups designated as β-TCP and group PTH + β-TCP. After the defect operation, all animals from group PTH and group PTH + β-TCP received following subcutaneous injections with PTH (60 μg/kg, three times per week) until euthanasia at 4 and 8 weeks. The distal femurs and blood were collected for evaluation. The results of study showed the strongest effect on accelerating the local bone formation with treatment β-TCP and PTH at 4 weeks and 8 weeks. The results from our study demonstrate that a combination of PTH and β-TCP had an additive effect on local bone formation in osteopenic rats chronically fed a low-protein diet.

Effect of teriparatide on repair of femoral metaphyseal defect in ovariectomized rats

OBJECTIVE

This study aimed to investigate the effect exerted by teriparatide on the repair of femoral metaphyseal defect in ovariectomized rats.

METHOD

Female Sprague-Dawley rats were ovariectomized and after 3 months a critically sized defect of 3 mm in diameter-a through-hole bone defect-was drilled into each distal femur of the ovariectomized rats. The rats were injected with teriparatide (30 μg/kg) parathyroid hormone (PTH) in the peritoneum three times per week. After 4 and 8 weeks the animals were killed and the blood and bilateral femora were harvested for biochemical analysis, histopathological observation, and micro-computed tomography (CT) examination.

RESULTS

The PTH group and control group were compared 4  and 8 weeks after surgery. PTH increased bone formation in the defect area. Moreover, PTH showed the strongest effects on bone volume per total volume, trabecular number, trabecular thickness, trabecular separation, and total fluorescence-marked new bone area. Additionally, the PTH treatment group showed inhibited serum concentrations of C-terminal telopeptide of type I collagen and enhanced expression of calcium, phosphorus, and bone alkaline phosphatase.

CONCLUSION

Our findings suggest a positive effect of PTH on defect healing in ovariectomized rats.

Modifications in bone matrix of estrogen-deficient rats treated with intermittent PTH

Bone matrix dictates strength, elasticity, and stiffness to the bone. Intermittent parathyroid hormone (iPTH), a bone-forming treatment, is widely used as a therapy for osteoporosis. We investigate whether low doses of intermittent PTH (1-34) change the profile of organic components in the bone matrix after 30 days of treatment. Forty 6-month-old female Wistar rats underwent ovariectomy and after 3 months received low doses of iPTH administered for 30 days: daily at 0.3 µg/kg/day (PTH03) or 5 µg/kg/day (PTH5); or 3 times per week at 0.25 µg/kg/day (PTH025). After euthanasia, distal femora were processed for bone histomorphometry, histochemistry for collagen and glycosaminoglycans, biochemical quantification of sulfated glycosaminoglycans, and hyaluronan by ELISA and TUNEL staining. Whole tibiae were used to estimate the bone mineral density (BMD). Histomorphometric analysis showed that PTH5 increased cancellous bone volume by 6% over vehicle-treated rats. In addition, PTH5 and PTH03 increased cortical thickness by 21% and 20%, respectively. Tibial BMD increased in PTH5-treated rats and this group exhibited lower levels of chondroitin sulfate; on the other hand, hyaluronan expression was increased. Hormonal administration in the PTH5 group led to decreased collagen maturity. Further, TUNEL-positive osteocytes were decreased in the cortical compartment of PTH5 whereas administration of PTH025 increased the osteocyte death. Our findings suggest that daily injections of PTH at low doses alter the pattern of organic components from the bone matrix, favoring the increase of bone mass.

Biomechanical properties: effects of low-level laser therapy and Biosilicate® on tibial bone defects in osteopenic rats

PURPOSE

The aim of this study was to investigate the effects of laser therapy and Biosilicate® on the biomechanical properties of bone callus in osteopenic rats.

METHODS

Fifty female Wistar rats were equally divided into 5 groups (n=10/group): osteopenic rats with intact tibiae (SC); osteopenic rats with unfilled and untreated tibial bone defects (OC); osteopenic rats whose bone defects were treated with Biosilicate® (B); osteopenic rats whose bone defects were treated with 830-nm laser, at 120 J/cm2 (L120) and osteopenic rats whose bone defects were treated with Biosilicate® and 830-nm laser, at 120 J/cm2 (BL120). Ovariectomy (OVX) was used to induce osteopenia. A non-critical bone defect was created on the tibia of the osteopenic animals 8 weeks after OVX. In Biosilicate® groups, bone defects were completely filled with the biomaterial. For the laser therapy, an 830-nm laser, 120 J/cm2 was used. On day 14 postsurgery, rats were euthanized, and tibiae were removed for biomechanical analysis.

RESULTS

Maximal load and energy absorption were higher in groups B and BL120, according to the indentation test. Animals submitted to low-level laser therapy (LLLT) did not show any significant biomechanical improvement, but the association between Biosilicate® and LLLT was shown to be efficient to enhance callus biomechanical properties. Conversely, no differences were found between study groups in the bending test.

CONCLUSIONS

Biosilicate® alone or in association with low level laser therapy improves biomechanical properties of tibial bone callus in osteopenic rats.

Evaluation of the bone healing process in an experimental tibial bone defect model in ovariectomized rats

The aim of this study was to evaluate the influence of postmenopausal bone loss (induced by ovariectomy) in the process of bone healing in a tibial bone defect model in rats by means of histological evaluation of bone defects and the analysis of the expression of genes and proteins involved in bone consolidation. Twenty female Wistar rats (12 weeks old, weighing ±250 g) were randomly divided into two groups: control group (CG) and ovariectomized group (OG). Rats of OG were submitted to ovariectomy and after 8 weeks post-surgery, all animals were submitted to the tibial bone defect model. The main histological finding analysis revealed that ovariectomized animals showed a higher amount of granulation tissue and immature newly formed bone compared to CG. Furthermore, quantitative histological analysis showed that OG presented a significant decrease in the amount of newly formed bone (p = 0.0351). RT-PCR analysis showed no difference in Runx2, ALP, RANK, RANKL and Osterix gene expression 14-day post-surgery. Interestingly, immunohistochemical evaluation showed that Runx2 was down expressed (p = 0.0001) and RANKL was up expressed (p = 0.0022) in the OG. In conclusion, these data highlight that bone loss induced by ovariectomy causes an impairment in the capacity of bone to heal mainly probably because of alterations in the imbalance of osteoblasts and osteoclasts activities.

A novel device for resistance-free biomechanical testing of the metaphysis of long bones

BACKGROUND

Biomechanical testing is an essential component of bone research. In order to test the metaphyseal region of long bones, a typical location for the nowadays increasing field of osteoporotic bone changes, three-point bending and breaking test devices are suitable and widely used. The aim of our study was to increase the effectiveness of this method by using a newly developed ball-mounted platform design. This new design eliminates the negative effects of friction, present in previous studies, caused by the lengthening of the distal tibia along its diaphyseal axis while sliding over the surface of a fixed aluminum block.

METHODS

70 tibiae of 35 twelve week old, female Sprague Dawley rats were separated into two groups for a metaphyseal bending/breaking test. Group 1 was made up of the rat's right tibiae, Group 2 of the left tibiae. Group 1 was tested on a solid metal block according to previously established testing devices whereas Group 2 was tested on the newly designed device: the resistance-free gliding, ball-mounted platform. Stiffness (N/mm), yield Load (N), and failure Load (N) were registered. In the evaluation of both testing procedures, the results of the right and left tibiae were compared according to the rat they originated from.

RESULTS

Stiffness (S) showed highly significant differences (p = 0.002) with 202.25 ± 27.010 N/mm SD (Group 1) and 184.66 ± 35.875 N/mm SD (Group 2). Yield Load (yL) showed highly significant differences (p < 0.001) with 55.31 ± 13.074 N SD (Group1) and 37.17 ± 12.464 N SD (Group2). The mean failure Load (fL) did not differ significantly (p < 0.231) between Group 1: 81.34 ± 11.972 N SD and Group 2: 79.63 ± 10.345 N SD.

CONCLUSIONS

We therefore conclude that, used in the three-point bending/breaking test, the mobile, ball-mounted platform device is able to efficiently eliminate the influence of friction in terms of stiffness and yield load. Failure Load was not affected. We suggest that the new ball-mounted platform device, when compared to other existing techniques, generates more accurate test results when used in the three-point bending/breaking test of the metaphysis of long bones.

Simultaneous subchronic exposure to selenium and diazinon as possible risk factor for osteoporosis in adult male rats

BACKGROUND

Osteoporosis and its main health outcome, fragility fractures, are large and escalating health problems. Skeletal damage may be the critical result of low-level prolonged exposure to several xenobiotics in the general population, but the mechanisms of their adverse effects are not clearly understood. The current study was aimed to investigate the possible ability of simultaneous subchronic peroral administration of selenium (Se) and diazinon (DZN) to induce changes in bone of adult male rats.In our study, twenty 1-month-old male Wistar rats were randomly divided into two experimental groups. In the first group, young males were exposed to 5 mg Na2SeO3/L and 40 mg of DZN/L in drinking water, for 90 days. Ten 1-month-old males without Se and DZN intoxication served as a control group. At the end of the experiment, macroscopic and microscopic structures of the femurs were analysed using analytical scales, sliding instrument, and polarized light microscopy.

RESULTS

The body weight, femoral length and cortical bone thickness were significantly decreased in rats simultaneously exposed to Se and DZN (P < 0.05). These rats also displayed different microstructure in the middle part of the compact bone where vascular canals expanded into central area of substantia compacta. The canals occurred only near endosteal surfaces in rats from the control group. Additionally, a smaller number of primary and secondary osteons, as well as a few resorption lacunae were observed near endosteal surfaces in rats simultaneously administered to Se and DZN. The resorption lacunae as typical structures of bone resorption manifestation are connected with an early stage of osteoporosis. Histomorphometric analysis revealed that area, perimeter, maximum and minimum diameters of primary osteons' vascular canals were significantly increased (P < 0.05) in the Se-DZN-exposed rats. On the other hand, all measured variables of Haversian canals and secondary osteons were considerable reduced (P < 0.05) in these rats.

CONCLUSIONS

Simultaneous subchronic peroral exposure to Se and DZN induces changes in macroscopic and microscopic structures of the femurs in adult male rats, and also it can be considered as possible risk factor for osteoporosis. The current study contributes to the knowledge on damaging impact of several xenobiotics on the bone.

Poor histological healing of a femoral fracture following 12 months of oestrogen deficiency in rats

SUMMARY

Fractures in post-menopausal osteoporosis cause significant morbidity; however, animal models for post-menopausal fracture healing lack the effect of ageing. Therefore, we developed a model using aged animals with chronic oestrogen deficiency, which demonstrates inferior fracture repair (decreased healing histologically, bone mineral density and content and strength). This novel model may help develop molecular strategies for osteoporotic fracture repair.

INTRODUCTION

The femur is susceptible to damage by both systemic conditions such as osteoporosis and locally by traumatic injury. The capacity for fracture repair decreases with age, while the risk of fracture increases. As studies of osteoporotic fracture healing in rats traditionally use a period of 3 months or less of oestrogen deficiency prior to fracturing, we aimed to establish a osteoporosis model in rats with chronic oestrogen deficiency by 12 months to better mimic human female osteoporosis.

METHODS

Seventy female Sprague-Dawley rats (10 weeks old) were ovariectomised or sham operated and housed for 12 months. The right femur was fractured by way of an open osteotomy and fixed with an intramedullary Kirschner wire. Animals were sacrificed at 1, 3 and 6 weeks for radiography, dual-energy X-ray absorptiometry, tensile testing and histology.

RESULTS

Bone mineral density and bone mineral content were lower by 60 and 63 %, respectively, (p < 0.05) in the bilaterally ovariectomized (OVX) groups than those in the sham groups at 6 weeks in the right fractured femurs. Maximum breaking force of the OVX group was lower than that of the sham group, with the greatest difference seen at 6 weeks following osteotomy. Histologically, the OVX groups demonstrated a delay in cellular differentiation within the fracture callus and the presence of bone resorption. The sham animals had a superior histological healing pattern with an Allen score of 4 at 6 weeks compared to a score of 1 for the OVX groups (p < 0.01).

CONCLUSIONS

Long-term ovariectomy has a deleterious effect on fracture healing in a rodent model.

Periodontal microstructure change and tooth movement pattern under different force magnitudes in ovariectomized rats: an in-vivo microcomputed tomography study

INTRODUCTION

The purpose of this study was to evaluate the dynamic changes in the periodontal microstructure and the molar displacement pattern during orthodontic tooth movement in ovariectomized rats.

METHODS

Twenty ovariectomized rats received either 100 or 30 g of orthodontic force to induce mesial movement of the maxillary left first molars over 14 days. Ten healthy rats underwent sham operations as controls. Periodontal ligament thickness, alveolar bone microstructural properties, and displacement of the molar were measured with 6 in-vivo microcomputed tomography scans for each sample.

RESULTS

The ovariectomized rats that received 100 g of orthodontic force had obvious changes in periodontal ligament thickness at day 1 and poor periodontal ligament thickness recovery from days 5 through 14. The bone volume fraction increased and the trabecular separation decreased significantly in this group at day 3, and obvious bone loss was observed at day 14. Molar linear and angular movements were also higher in this group than in the other 2 groups.

CONCLUSIONS

Relatively heavier force applications in ovariectomized rats resulted in poor periodontal ligament thickness recovery and local alveolar bone overcompression, and consequently induced undermining resorption and obvious alveolar bone loss; these led to high rates of tooth movement and molar inclination.

Structural changes in femoral bone tissue of rats after subchronic peroral exposure to selenium

Background

The role of selenium (Se) on bone microarchitecture is still poorly understood. The present study aims to investigate the macroscopic and microscopic structures of femoral bone tissue in adult male rats after subchronic peroral administration of Se.

Methods

Twenty one-month-old male Wistar rats were randomly divided into two experimental groups. In the first group (Se group) young males were exposed to 5 mg Na₂SeO₃/L in drinking water, for 90 days. Ten one-month-old males without Se administration served as a control group. At the end of the experiment, macroscopic and microscopic structures of the femurs were analysed using analytical scales, sliding instrument, and polarized light microscopy.

Results

The body weight, femoral length and cortical bone thickness were significantly decreased in Se group rats. These rats also displayed different microstructure in the middle part of the femur, both in medial and lateral views, where vascular canals expanded into the central area of the bone while, in control rats, these canals occurred only near the endosteal surfaces. Additionally, a smaller number of primary and secondary osteons was identified in Se group rats. Histomorphometric analyses revealed significant increases for area, perimeter, maximum and minimum diameters of primary osteons’ vascular canals but significant reductions for all measured variables of Haversian canals and secondary osteons.

Conclusions

Se negatively affected the macroscopic and microscopic structures of femoral bone tissue in adult male rats. The results contribute to the knowledge on damaging impact of Se on bone.

Effects of different doses of ferutinin on bone formation/resorption in ovariectomized rats

This study analyzes the effects of different doses of ferutinin on bone loss caused by estrogen deficiency in ovariectomized rats, in comparison with estradiol benzoate. Thirty female Sprague-Dawley rats were ovariectomized and treated for 30 days from the day after ovariectomy. Static/dynamic histomorphometric analyses were performed on trabecular and cortical bone of lumbar vertebrae and femurs. Very low weight increments were recorded only in all F-OVX groups, with respect to the others. Although the great differences in weight, that could imply a decrease of bone mass in F-OVX groups compared to the control ovariectomized group (C-OVX), trabecular bone in lumbar vertebrae did not show significant differences, suggesting that ferutinin, opposing estrogen deficiency, inhibits bone resorption. Newly formed cortical bone was always low in all F-OVX groups and high in C-OVX, suggesting that it is mainly devoted in answering mechanical demands. In contrast, in distal femoral metaphyses, trabecular bone was reduced and the number of osteoclasts was increased in C-OVX with respect to all other groups, suggesting that it is mainly devoted in answering metabolic demands; moreover, ferutinin dose of 2 mg/kg seemed to be more effective than the lower doses used and estrogens, particularly in those skeletal regions with higher metabolic activity. Our results suggest that the role of ferutinin in preventing osteoporosis caused by estrogen deficiency is expressed in decreasing bone erosion; moreover, in all F-OVX groups bone turnover is very low and seems correlated to the trivial body weight increase, which, in turn, depends on ferutinin treatment.

Orthodontic tooth movement and root resorption in ovariectomized rats treated by systemic administration of zoledronic acid

INTRODUCTION

The effect of zoledronic acid, a potent and novel bisphosphonate, on tooth movement and orthodontically induced root resorption in osteoporotic animals systemically treated with zoledronic acid as similarly used in postmenopausal patients has not been elucidated. Therefore, this study was undertaken.

METHODS

Fifteen 10-week-old female Wistar rats were divided into 3 groups: ovariectomy, ovariectomy + zoledronic acid, and control. Only the ovariectomy and ovariectomy + zoledronic acid groups underwent ovariectomies. Two weeks after the ovariectomy, zoledronic acid was administered only to the ovariectomy + zoledronic acid group. Four weeks after the ovariectomy, 25-g nickel-titanium closed-coil springs were applied to observe tooth movement and orthodontically induced root resorption.

RESULTS

There were significant differences in the amounts of tooth movement and orthodontically induced root resorption between the ovariectomy and the control groups, and also between the ovariectomy and the ovariectomy + zoledronic acid groups. There was no statistically significant difference in tooth movement and orthodontically induced root resorption between the ovariectomy + zoledronic acid and the control groups. Zoledronic acid inhibited significantly more tooth movement and significantly reduced the severity of orthodontically induced root resorption in the ovariectomized rats. The ovariectomy + zoledronic acid group showed almost the same results as did the control group in both tooth movement and orthodontically induced root resorption.

CONCLUSIONS

Zoledronic acid inhibits excessive orthodontic tooth movement and also reduces the risk of severe orthodontically induced root resorption in ovariectomized rats.

Lycopene effects on serum mineral elements and bone strength in rats

This study investigated the beneficial effect of lycopene on bone biomarkers in ovariectomized (OVX) rats. Female Wistar rats were either sham operated or surgically ovariectomized and then fed with lycopene for 8 weeks. Serum Ca, P, alkaline phosphatase (ALP), interleukin 6 (IL-6) and bone gla protein (BGP) concentration was significantly higher in the untreated OVX group compared with that of the sham group, whereas serum estrogen levels were lower. Bone mineral density (BMD), BMD/wt, bone mineral content (BMC), BMC/wt values, maximum load, stiffness, energy and maximum stress were significantly lower in the untreated OVX group compared with that of the sham group. Administration of lycopene (20, 30 and 40 mg/kg b.w.) for 8 weeks significantly decreased serum Ca, P, ALP, and IL-6 concentration, and enhanced serum estrogen level, BMD, BMD/wt, BMC, BMC/wt values, maximum load, stiffness, energy and maximum stress in lycopene-treated OVX groups. In conclusion, the consumption of lycopene may have the most protective effect on bone in OVX rats.

Influence of estrogen deficiency and tibolone therapy on trabecular and cortical bone evaluated by computed radiography system in rats

PURPOSE: To verify the effects of tibolone administration on trabecular and cortical bone of ovariectomized female rats by computed radiography system (CRS). METHODS: The experiment was performed on two groups of rats previously ovariectomized, one received tibolone (OVX+T) while the other did not (OVX), those groups were compared to a control group (C) not ovariectomized. Tibolone administration (1mg/day) began thirty days after the ovariectomy and the treatment remained for five months. At last, the animals were euthanized and femurs and tibias collected. Computed radiographies of the bones were obtained and the digital images were used to determine the bone optical density and cortical thickness on every group. All results were statistically evaluated with significance set at P<0.05%. RESULTS: Tibolone administration was shown to be beneficial only in the densitometric analysis of the femoral head, performing higher optical density compared to OVX. No difference was found in cortical bone thickness. CONCLUSION: Ovariectomy caused bone loss in the analyzed regions and tibolone administered in high doses over a long period showed not to be fully beneficial, but preserved bone mass in the femoral head.

Antiosteoporotic activity of Davallia formosana

ETHNOPHARMACOLOGICAL RELEVANCE

[corrected] In Taiwanese folk medicine, Davallia formosana is used to treat bone diseases, including osteoporosis.

AIM

This study evaluated the anti-osteoporotic effect of ethanolic extract derived from Davallia formosana (DFE).

MATERIALS AND METHODS

In this in vitro study, we investigated the inhibitory action of DFE on RANKL-stimulated osteoclastogenesis. The in vivo effects of DFE on bone metabolism were evaluated using ovariectomized (OVX) rats orally administered DFE (200, 500 mg/kg), alendronate (2.5 mg/kg, three times a week) or its vehicle for 12 weeks.

RESULTS

This in vitro study demonstrated that DFE inhibited osteoclast differentiation, and also isolated the active component, (-)-epicatechin 3-O-β-D-allopyranoside (ECAP). DFE did not affect the body or vaginal weight in OVX rats. The bone mineral density and bone calcium content in OVX rats were lower in the control group showing that DFE was able to prevent significant bone loss. In addition, the three point bending test and the microcomputer tomography scanning showed that DFE treatment enhanced bone strength and inhibited the deterioration of trabecular microarchitecture. In the biochemical assay, DFE decreased urinary deoxypyridinoline and calcium concentrations, but did not inhibit serum alkaline phosphatase activities, indicating that it ameliorated bone loss via inhibition of bone reabsorption.

CONCLUSIONS

These results suggest that DFE may represent a useful remedy for the treatment of bone reabsorption diseases such as osteoporosis. In addition, ECAP could be used as a marker compound to control the quality of DFE.

Effect of angiotensin II type 1 receptor blocker on osteoporotic rat femurs

BACKGROUND

Osteoblasts and osteoclasts are known to express Ang II type I (AT1) receptor in cell cultures, suggesting the existence of local renin-angiotensin system (RAS) in bone. This study was designed to investigate the effects of losartan as AT1 receptor blocker on ovariectomized rats' femur.

METHODS

Losartan (5 mg/kg/day) was administered via oral gavage for 8 weeks. Bone mineral density (BMD) was measured using dual energy X-ray absorptiometry, while tensile and three-point bending tests were performed for evaluation of biomechanical properties of bone. The trabecular porosity was analyzed by scanning electron microscopy.

RESULTS

There was a significant decrease in BMD values of ovariectomized rats' femurs which were reversed by losartan treatment. According to tensile test results, ultimate tensile strength and strain values of losartan treated ovariectomized rats' femurs increased and decreased, respectively, when compared to that of ovariectomized animals. Losartan treatment also caused a significant recovery in flexural strength and modulus parameters regarding respective control values, which mean losartan treated ovariectomized rats' femur had more force tolerance until break than ovariectomized rats' femur. Quantitative microscopic analysis showed larger trabecular porosity in ovariectomized rats than control rat femurs and it was significantly decreased after losartan treatment.

CONCLUSION

Blockage of AT1 receptor increased strength, mass and trabecular connections of ovariectomized rat femurs. Therefore, it is tempting to speculate that drugs, including AT1 receptor blockers, may be used for the treatment of osteoporosis or reduction of its detrimental effects in the future.

Radioprotective effect of sodium selenite on bone repair in the tibia of ovariectomized rats

This studyevaluated protection by selenium (Se) in the bone repair process in ovariectomized rats after irradiation. For such purpose, 80 ovariectomized female Wistar rats were randomly divided into 4 experimental groups: ovariectomized (Ov), Ov/Se, Ov/irradiated (Irr) and Ov/ Se/Irr. A bone defect was created on the tibia of all animals 40 days after ovariectomy. Two days after surgery, only the Ov/Se and Ov/Se/Irr rats received 0.8 mg Se/kg. Three days after surgery, only the Ov/Irr and Ov/Se/Irr rats received 10 Gy of x-rays on the lower limb region. The animals were euthanized at 7, 14, 21 and 28 days after surgery to assess the repair process, which was evaluated by analysis of trabecular bone number (Masson Trichrome) and birefringence analysis (Picrosirius). It was possible to observe a delay in the bone repair process in the ovariectomized/irradiated group and similarity between the ovariectomized, Ov/Se and Ov/Se/Irr groups. In conclusion, sodium selenite exerted a radioprotective effect in the bone repair of tibia of ovariectomized rats without toxicity.

Low-level laser therapy, at 60 J/cm2 associated with a Biosilicate(®) increase in bone deposition and indentation biomechanical properties of callus in osteopenic rats

We investigate the effects of a novel bioactive material (Biosilicate(®)) and low-level laser therapy (LLLT), at 60 J/cm(2), on bone-fracture consolidation in osteoporotic rats. Forty female Wistar rats are submitted to the ovariectomy, to induce osteopenia. Eight weeks after the ovariectomy, the animals are randomly divided into four groups, with 10 animals each: bone defect control group; bone defect filled with Biosilicate group; bone defect irradiated with laser at 60 J/cm(2) group; bone defect filled with Biosilicate and irradiated with LLLT, at 60 J/cm(2) group. Laser irradiation is initiated immediately after surgery and performed every 48 h for 14 days. Histopathological analysis points out that bone defects are predominantly filled with the biomaterial in specimens treated with Biosilicate. In the 60-J/cm(2) laser plus Biosilicate group, the biomaterial fills all bone defects, which also contained woven bone and granulation tissue. Also, the biomechanical properties are increased in the animals treated with Biosilicate associated to lasertherapy. Our results indicate that laser therapy improves bone repair process in contact with Biosilicate as a result of increasing bone formation as well as indentation biomechanical properties.

Expression of TGF-β1 in the blood during fracture repair in an estrogen-deficient rat model

OBJECTIVES

Previous studies have reported that osteoporosis due to estrogen deficiency influences fracture healing. Transforming growth factor (TGF-b) has been found to be involved in fracture healing via the regulation of the differentiation and activation of osteoblasts and osteoclasts. The current study aimed to determine the effects of estrogen on the expression of TGF-β1 during fracture healing in ovariectomized rats.

METHODS

Thirty female Sprague-Dawley rats weighing 200-250 g were assigned to: (i) a sham-operated group that was given a normal saline; (ii) an ovariectomized control group that was given a normal saline; or (iii) an ovariectomized + estrogen (100 mg/kg/day) group that was treated with conjugated equine estrogen. The right femur of all rats was fractured, and a Kirschner wire was inserted six weeks post-ovariectomy. Treatment with estrogen was given for another six weeks post-fracture. At the end of the study, blood samples were taken, and the right femur was harvested and subjected to biomechanical strength testing.

RESULTS

The percentage change in the plasma TGF-β1 level before treatment was significantly lower in the ovariectomized control and estrogen groups when compared with the sham group (p<0.001). After six weeks of treatment, the percentage change in the plasma TGF-β1 level in the estrogen group was significantly higher compared with the level in the ovariectomized control group (p = 0.001). The mean ultimate force was significantly increased in the ovariectomized rats treated with estrogen when compared with the ovariectomized control group (p = 0.02).

CONCLUSION

These data suggest that treatment with conjugated equine estrogen enhanced the strength of the healed bone in estrogen-deficient rats by most likely inducing the expression of TGF-β1.

Reactive oxygen species on bone mineral density and mechanics in Cu,Zn superoxide dismutase (Sod1) knockout mice

Reactive oxygen species (ROS) play a role in a number of degenerative conditions including osteoporosis. Mice deficient in Cu,Zn-superoxide dismutase (Sod1) (Sod1(-/-) mice) have elevated oxidative stress and decreased muscle mass and strength compared to wild-type mice (WT) and appear to have an accelerated muscular aging phenotype. Thus, Sod1(-/-) mice may be a good model for evaluating the effects of free radical generation on diseases associated with aging. In this experiment, we tested the hypothesis that the structural integrity of bone as measured by bending stiffness (EI; N/mm(2)) and strength (MPa) is diminished in Sod1(-/-) compared to WT mice. Femurs were obtained from male and female WT and Sod1(-/-) mice at 8months of age and three-point bending tests were used to determine bending stiffness and strength. Bones were also analyzed for bone mineral density (BMD; mg/cc) using micro-computed tomography. Femurs were approximately equal in length across all groups, and there were no significant differences in BMD or EI with respect to gender in either genotype. Although male and female mice demonstrated similar properties within each genotype, Sod1(-/-) mice exhibited lower BMD and EI of femurs from both males and females compared with gender matched WT mice. Strength of femurs was also lower in Sod1(-/-) mice compared to WT as well as between genders. These data indicate that increased oxidative stress, due to the deficiency of Sod1 is associated with decreased bone stiffness and strength and Sod1(-/-) mice may represent an appropriate model for studying disease processes in aging bone.

A novel flavonoid, 6-C-beta-d-glucopyranosyl-(2S,3S)-(+)-3',4',5,7-tetrahydroxyflavanone, isolated from Ulmus wallichiana Planchon mitigates ovariectomy-induced osteoporosis in rats

OBJECTIVE

The aim of this study was to determine the skeletal effect of 6-C-beta-d-glucopyranosyl-(2S,3S)-(+)-3',4',5,7-tetrahydroxyflavanone (GTDF)/Ulmoside A, a new compound isolated from the extract of Ulmus wallichiana in a rat model of postmenopausal bone loss.

METHODS

GTDF (1.0 and 5.0 mg kg d) was given orally to ovariectomized (OVx) rats (180-200 g) for 12 weeks. Sham operated + vehicle, ovariectomy + 17beta-estradiol (2.5 microg kg d), and ovariectomy + vehicle groups served as various controls. Bone mineral density (BMD), trabecular microarchitecture, bone biomechanical strength, levels of bone turnover/resorption markers, uterotropic effect, and plasma pharmacokinetics were studied. One-way analysis of variance was used to test significance of effects.

RESULTS

OVx rats treated with both doses of GTDF exhibited significantly higher BMD in the trabecular (distal femur, proximal tibia, and vertebrae) and cortical (femur shaft) regions compared with the ovariectomy + vehicle group. Micro-CT demonstrated that OVx rats treated with 5.0 mg kg day of GTDF had better bone microarchitectural parameters compared with the ovariectomy + vehicle group. Serum osteocalcin and urinary C-terminal teleopeptide of Type I collagen levels in OVx rats treated with GTDF (at both doses) were significantly lower than those in the ovariectomy + vehicle group. At neither of the two doses did GTDF exhibit uterine estrogenicity. A pharmacokinetic study revealed that GTDF achieved maximum plasma concentration (40.67 ng mL) at approximately 1 hour, indicating its slow absorption. Its absolute bioavailability was found to be 1.04% with a plasma elimination half-life of approximately 5 hours.

CONCLUSIONS

GTDF, a novel compound isolated from U wallichiana extract, improves bone biomechanical quality through positive modifications of BMD and trabecular microarchitecture without a hyperplastic effect on the uterus.

Influence of ferutinin on bone metabolism in ovariectomized rats. II: role in recovering osteoporosis

The aim of the present investigation, which represents an extension of a previous study, was to investigate the effect of ferutinin in recovering severe osteoporosis due to estrogen deficiency after rat ovariectomy and to compare phytoestrogen effects with those of estrogens commonly used in hormone replacement therapy (HRT) by women with postmenopausal osteoporosis. The animal model used was the Sprague-Dawley ovariectomized rat. Ferutinin was orally administered (2 mg kg(-1) per day) for 30 or 60 days starting from 2 months after ovariectomy (i.e. when osteoporosis was clearly evident) and its effects were compared with those of estradiol benzoate (1.5 microg per rat twice a week, subcutaneously injected) vs. vehicle-treated ovariectomized (OVX) and sham-operated (SHAM) rats. Histomorphometric analyses were performed on trabecular bone of lumbar vertebrae (4th and 5th) and distal femoral epiphysis, as well as on cortical bone of femoral diaphysis. Bone histomorphometric analyses showed that ferutinin seems to display the same effects on bone mass recorded with estradiol benzoate, thus suggesting that it could enhance the recovery of bone loss due to severe estrogen deficiency in OVX rats. On this basis, the authors propose listing ferutinin among the substances representing a potential alternative for the treatment of postmenopausal osteoporosis, which occurs as a result of estrogen deficiency.

Nanomechanical characterization of tissue engineered bone grown on titanium alloy in vitro

Intensive work has been performed on the characterization of the mechanical properties of mineralised tissues formed in vivo. However, the mechanical properties of bone-like tissue formed in vitro have rarely been characterised. Most research has either focused on compact cortical bone or cancellous bone, whilst leaving woven bone unaddressed. In this study, bone-like mineralised matrix was produced by osteoblasts cultured in vitro on the surface of titanium alloys. The volume of this tissue-engineered bone is so small that the conventional tensile tests or bending tests are implausible. Therefore, nanoindentation techniques which allow the characterization of the test material from the nanoscale to the microscale were adopted. These reveal the apparent elastic modulus and hardness of the calcospherulite crystals (a representative element for woven bone) are 2.35 +/- 0.73 and 0.41 +/- 0.15 GPa, respectively. The nanoscale viscoelasticity of such woven bone was further assessed by dynamic indentation analysis.

Osteoprotegerin and ligand of receptor activator of nuclear factor kappaB expression in ovariectomized rats during tooth movement

OBJECTIVE

To test the null hypothesis that increased tooth displacement in ovariectomized rats is not related to differential expressions of OPG and RANKL in the periodontium.

MATERIALS AND METHODS

Eighty-four 12-week female rats were used; half were ovariectomized and half were not. Three months later, the maxillary first molar was moved mesially. Groups of rats were sacrificed at days 0, 1, 3, 5, 7, 10, and 14 after activation. Tooth movement was measured at each time point. OPG and RANKL expressions were examined through immunohistochemistry.

RESULTS

Ovariectomized and nonovariectomized rats showed three-phase tooth movement. In both groups, OPG expression increased at the tension area and RANKL increased at the pressure area. The OPG/RANKL ratio coincided with tooth movement, especially in the linear phase from 7 to 14 days.

CONCLUSIONS

The null hypothesis is rejected. The increased rate of tooth movement in ovariectomized rats was related to differential expressions of OPG and RANKL.

The effects of nail rigidity on fracture healing in rats with osteoporosis

BACKGROUND AND PURPOSE

Stress shielding from rigid internal fixation may lead to refracture after removal of the osteosynthesis material. We investigated the effect of a low-rigidity (Ti-24Nb-4Zr-7.9Sn) intramedullary nail regarding stress shielding and bone healing of osteoporotic fractures in the rat.

METHODS

40 female Sprague-Dawley rats, aged 3 months, were divided into the following groups: sham-operation (SHAM) (n = 10), ovariectomized (OVX) (n = 10) and OVX-fracture (n = 20). 10 SHAM rats and 10 OVX rats were killed after 12 weeks to provide biomechanical data. Ovariectomy was performed 12 weeks before fracturing both femurs in 20 rats. The left fracture was stabilized with a high-rigidity titanium alloy pin (Ti-6Al-4V; elastic modulus 110 GPa) and the right with a low-rigidity (Ti-24Nb-4Zr-7.9Sn; elastic modulus 33 GPa). The bony calluses were examined by micro-CT at 6 and 12 weeks after fracture, bone volume (BV) and total volume (TV) were determined at the callus region (ROI1) and the total femur (ROI2). Subsequently, the bones were tested mechanically by a three-point bending test.

RESULTS

In the low-rigidity group, TV (ROI1) increased at 6 weeks, but BV (ROI1), BV (ROI2) were similar but maximum load increased. At 12 weeks, the maximum load and also BV (ROI1, ROI2) were increased in the low-rigidity group.

INTERPRETATION

The low-rigidity nail manufactured from Ti-24Nb-4Zr-7.9Sn showed better external callus formation, seemed to reduce effects of stress shielding, and reduced bone resorption better than the stiffer nail. The low-rigidity nail was strong enough to maintain alignment of the fracture in the osteoporotic rat model without delayed union.

Influence of ferutinin on bone metabolism in ovariectomized rats. I: role in preventing osteoporosis

Phytoestrogens play a role in maintaining bone mass in the post-menopausal period for their putative function as osteoprotective agents. The aim of the present study was to investigate the influence of Ferutinin, a phytoestrogen found in the plants of Ferula genus, on bone loss in ovariectomized rats. Such an animal model can simulate the various clinical syndromes deriving from osteoporosis. The effect of the daily oral administration of ferutinin to ovariectomized rats (dosed at 2 mg/kg per day for 30 and 60 days) was compared to that of estradiol benzoate (subcutaneously administered at the dose of 1.5 microg/rat twice a week). After the sacrifice, histomorphometrical analyses were performed on trabecular bone of L4-L5 vertebrae and distal femoral metaphysis, as well as on cortical bone of femoral diaphysis; biochemical parameters (bone mineral components and markers) were also evaluated from the rat serum. The histomorphometrical analyses of trabecular and cortical bone from lumbar vertebrae and femur showed that ferutinin has the same antiosteoporotic effect of estradiol benzoate on bone mass, and in some cases is even stronger. This fact suggests that it could prevent osteoporosis caused by severe estrogen deficiency in ovariectomized rats. The possibility of using ferutinin as an alternative to the commonly employed hormonal replacing therapy in post-menopausal women is discussed.

Quantitative trait loci that determine mouse tibial nanoindentation properties in an F2 population derived from C57BL/6J x C3H/HeJ

Use of nanoindentation technology to identify quantitative trait loci (QTL) that regulate bone properties represents a novel approach to improving our understanding of molecular mechanisms that control bone matrix properties. Tibiae for QTL mapping were from an F2 population derived from C57BL/6J and C3H/HeJ. A nanoindenter (Triboindenter; Hysitron, Minneapolis, MN) was used to conduct indentation tests on transverse sections. Genotyping was performed in The Jackson Laboratory. QTL mapping was conducted using software. We found that (1) tibiae from mice at 16 weeks of age were mature and suitable for measurement by a nanoindentor; (2) both stiffness modulus and hardness modulus in the F2 population appeared to have normal distributions, which suggested that multiple genetic factors control the bone properties; and (3) QTL for hardness were identified from five chromosomes (Chr 8, 12, 13, 17, and 19) and for stiffness, from four chromosomes (Chr 3, 8, 12, and 13). Among all detected QTL, one at the same location on Chr 12 was detected for both hardness and stiffness data. It explained the highest percentage of phenotypic variation in bone properties. Using nanoindentation technology to identify QTL that regulate bone properties yielded as many as six different chromosomal regions. Although the actual genes remain to be identified, nanoindentation will contribute to our understanding of molecular mechanisms and normal development processes that control the matrix properties of bone.