FDA Guidelines and animal models for osteoporosis

Chronic Cadmium Treatment Induces Tubular Nephropathy and Osteomalacic Osteopenia in Ovariectomized Cynomolgus Monkeys

In an attempt to establish a primate model of chronic cadmium toxicosis, we ovariectomized cynomolgus monkeys and treated them with CdCl2 by repeated intravenous injections for 13 to 15 months. The animals showed normocytic-normochromic anemia. The cadmium treatment resulted in increases of urinary enzyme activity indicative of renal tubular degeneration. Histopathology of the kidney revealed renal proximal tubular atrophy accompanied by interstitial fibrosis. Decreased bone mineral density was evident in the trabecular and cortical zones of the lumbar vertebra and femur, with osteoid accumulation around the trabeculae and Haversian canals. Iron deposition at the mineralization front and osteoclasts hyperplasia were indicative of impairment of bone mineralization and an increase of resorption. Blood inorganic phosphorus and 1α,25(OH)2 vitamin D3 levels decreased and urinary deoxypyridinoline level increased in cadmium-treated animals. The renal and bone lesions closely resemble those of itai-itai disease patients, the most severe case of cadmium toxicosis in terms of clinical chemistry and histopathology. Thus, ovariectomized monkeys chronically exposed to cadmium can serve as a primate itai-itai disease model, which is beneficial for developing novel therapeutic methods, investigating the mechanisms of the renal and bone lesions, and establishing more clearly defined criteria for diagnosing the disease.

Effects of multi-deficiencies-diet on bone parameters of peripheral bone in ovariectomized mature rat

Many postmenopausal women have vitamin D and calcium deficiency. Therefore, vitamin D and calcium supplementation is recommended for all patients with osteopenia and osteoporosis. We used an experimental rat model to test the hypothesis that induction of osteoporosis is more efficiently achieved in peripheral bone through combining ovariectomy with a unique multi-deficiencies diet (vitamin D depletion and deficient calcium, vitamin K and phosphorus). 14-week-old Sprague-Dawley rats served as controls to examine the initial bone status. 11 rats were bilaterally ovariectomized (OVX) and fed with multi-deficiencies diet. Three months later the treated group and the Sham group (n = 8) were euthanized. Bone biomechanical competence of the diaphyseal bone was examined on both, tibia and femur. Image analysis was performed on tibia via µCT, and on femur via histological analysis. Lower torsional stiffness indicated inferior mechanical competence of the tibia in 3 month OVX+Diet. Proximal metaphyseal region of the tibia showed a diminished bone tissue portion to total tissue in the µCT despite the increased total area as evaluated in both µCT and histology. Cortical bone showed higher porosity and smaller cross sectional thickness of the tibial diaphysis in the OVX+Diet rats. A lower ALP positive area and elevated serum level of RANKL exhibited the unbalanced cellular interaction in bone remodeling in the OVX+Diet rat after 3 month of treatment. Interestingly, more adipose tissue area in bone marrow indicated an effect of bone loss similar to that observed in osteoporotic patients. Nonetheless, the presence of osteoid and elevated serum level of PTH, BGP and Opn suggest the development of osteomalacia rather than an osteoporosis. As the treatment and fracture management of both osteoporotic and osteomalacia patients are clinically overlapping, this study provides a preclinical animal model to be utilized in local supplementation of minerals, drugs and growth factors in future fracture healing studies.

Bisphosphonate-induced reductions in rat femoral bone energy absorption and toughness are testing rate-dependent

Bisphosphonates have been used for years to suppress bone turnover and reduce fracture risk. Bisphosphonates have recently been associated with atypical femoral fractures, which are catastrophic, low trauma, brittle fractures that appear to occur more frequently than in untreated individuals. Previous work using a dog model has demonstrated bisphosphonate-induced reductions in bone toughness (the inverse of brittleness), yet data are lacking to show this occurs in rodents. The goal of this study was to determine if bisphosphonate-induced alterations in toughness could be quantified in rats. At 26 weeks of age, skeletally mature rats (n = 32 total) were given an injection of either zoledronate (100 μg/kg body weight) or vehicle (0.5 ml saline). Five weeks post-injection, both femora were collected and analyzed for geometry and mechanical properties. To assess the effect of testing rate on the biomechanical outcomes, the left femora were broken at 2 mm/min, while the right femora were broken at 20 mm/min. The results showed a significantly lower energy to failure in zoledronate-treated animals compared to vehicle at the slow testing rate (-15%, p < 0.05) with no difference at the faster rate. While there was not a significant interaction between drug and testing rate for toughness to fracture (p = 0.07), toughness between ultimate stress and fracture was significantly lower with zoledronate only at the slow rate (-40%, p < 0.05). These data document that bisphosphonate-induced reductions in energy absorption and toughness can be quantified in rats yet they are highly dependent on testing rate.

Effect of mechanical stretch on the proliferation and differentiation of BMSCs from ovariectomized rats

Osteoporosis is characterized by a broken balance between bone formation and bone resorption. Mechanical stress has been considered to be an important factor in bone modeling and remodeling. However, biological responses of stromal cells in osteoporosis to mechanical stimuli remain unknown. To explore the correlation between mechanical stress and osteoblastic differentiation of bone mesenchymal stem cells (BMSCs) in osteoporosis, we built an osteoporosis model in ovariectomized (OVX) rats, and then investigated proliferation, alkaline phosphatase (ALP) activity, and the expression of osteoblastic genes in BMSCs under mechanical stress of 5 and 10% elongation, using the Flexercell Strain system. The proliferation of BMSCs was detected using alamarBlue. The expression of osteoblastic genes was analyzed by real-time quantitative polymerase chain reaction. Protein expression was examined by Western blotting. BMSCs (OVX) and BMSCs (Sham-operated, Sham in short) proliferations were inhibited at 5 and 10% elongation at day 3, compared with the un-stretched group, while BMSCs (OVX) proliferation was slower than BMSCs (Sham). ALP activity increased significantly at 10% elongation in both cells, but it was less active in BMSCs (OVX) than BMSCs (Sham). At days 3 and 7, the mRNA expression of osteoblastic genes was unregulated by mechanical stretch (5 and 10 % elongation); however, osteoblastic gene expression in BMSCs (OVX) was less than that in BMSCs (Sham). The mRNA and protein expression of Runx2 showed similar trends in BMSCs (OVX) under mechanical stretch. These results indicate that the mechanical stretch stimulates osteoblastic differentiation of BMSCs (OVX); however, this differentiation was weaker than that of BMSCs (Sham).

Sheep model for osteoporosis: sustainability and biomechanical relevance of low turnover osteoporosis induced by hypothalamic-pituitary disconnection

Hypothalamo-pituitary disconnection (HPD) leads to low bone turnover and osteoporosis in sheep. To determine the sustainability of bone loss and its biomechanical relevance, we studied HPD-sheep 24 months after surgery (HPD + OVX-24) in comparison to untreated control (Control), ovariectomized sheep (OVX), and sheep 12 months after HPD (HPD + OVX-12). We performed histomorphometric, HR-pQCT, and qBEI analyses, as well as biomechanical testing of all ewes studied. Twenty-four months after HPD, histomorphometric analyses of the iliac crest showed a significant reduction of BV/TV by 60% in comparison to Control. Cortical thickness of the femora measured by HR-pQCT did not change between 12 and 24 months after HPD but remained decreased by 30%. These structural changes were caused by a persisting depression of osteoblast and osteoclast cellular activity. Biomechanical testing of the femora showed a significant reduction of bending strength, whereas calcium content and distribution was found to be unchanged. In conclusion, HPD surgery leads to a persisting low turnover status with negative turnover balance in sheep followed by dramatic cortical and trabecular bone loss with consequent biomechanical impairment.

Lasofoxifene (CP-336,156), a novel selective estrogen receptor modulator, in preclinical studies

Estrogen replacement therapy is reported to reduce the incidence of vertebral fractures in postmenopausal women, however, its compliance is limited because of side effects and safety concerns. Estrogen's side effects on breast and uterine tissues leading to the potential increased risk of uterine and breast cancer limit widespread estrogen usage. Thus, there is a significant medical need for a therapy that protects against postmenopausal bone loss but is free of estrogen's negative effects on reproductive tissues. Selective estrogen receptor modulators (SERMs) have been investigated as an alternative to hormone replacement therapy. One such compound, raloxifene, has been approved for the prevention and treatment of osteoporosis. Lasofoxifene (LAS), a new, nonsteroidal, and potent SERM, is an estrogen antagonist or agonist depending on the target tissue. LAS selectively binds with high affinity to human estrogen receptors. In ovariectomized (OVX) rat studies, LAS prevented the decrease in femoral bone mineral density, tibial and lumbar vertebral trabecular bone mass at an ED100 of about 60 μg/kg/day. LAS inhibited the activation of trabecular and endocortical bone resorption and bone turnover in tibial metaphyses and diaphyses, and lumbar vertebral body in OVX rats. In addition, LAS decreased total serum cholesterol, inhibited body weight gain and increased soleus muscle weight in OVX rats. Similarly, LAS prevented bone loss induced by orchidectomy or aging in male rats by decreasing bone resorption and bone turnover while it had no effect in the prostate. Further, LAS decreased total serum cholesterol in intact aged male rats or in orchidectomized male rats. Synergestic skeletal effects were found with LAS in combination with bone anabolic agents such as prostaglandin E2 (PGE2), parathyroid hormone (PTH) or a growth hormone secretagoue (GHS) in OVX rats. In combination with estrogen, LAS inhibited the uterine stimulating effects of estrogen but did not block the bone protective effects of estrogen. In immature and aged female rats, LAS did not affect the uterine weight and uterine histology. In OVX adult female rats, LAS slightly but significantly increased uterine weight. These results demonstrated that LAS produced effects on the skeleton indistinguishable from estrogen in female and male rats. However, unlike estrogen, LAS had little effect on uterine weight and cellular proliferation of uterus in female rats. In preclinical anti-tumor studies, LAS inhibited human breast cancer growth in mice bearing MCF7 tumors, prevented NMU-induced mammary carcinomas and possessed chemotherapeutic effects in NMU-induced carcinomas in rats. Therefore, we conclude that LAS possesses the antiestrogenic effects in breast tissue and estrogenic effects in bone and serum cholesterol, but lacks estrogen's side effects on uterine tissue. These data support the therapeutic potential of LAS for the prevention and treatment of postmenopausal bone loss and mammary carcinomas in humans.

Implications of combined ovariectomy/multi-deficiency diet on rat bone with age-related variation in bone parameters and bone loss at multiple skeletal sites by DEXA

BACKGROUND

Osteoporosis is a multi-factorial, chronic, skeletal disease highly prevalent in post-menopausal women and is influenced by hormonal and dietary factors. Because animal models are imperative for disease diagnostics, the present study establishes and evaluates enhanced osteoporosis obtained through combined ovariectomy and deficient diet by DEXA (dual-energy X-ray absorptiometry) for a prolonged time period.

MATERIAL/METHODS

Sprague-Dawley rats were randomly divided into sham (laparotomized) and OVX-diet (ovariectomized and fed with deficient diet) groups. Different skeletal sites were scanned by DEXA at the following time points: M0 (baseline), M12 (12 months post-surgery), and M14 (14 months post-surgery). Parameters analyzed included BMD (bone mineral density), BMC (bone mineral content), bone area, and fat (%). Regression analysis was performed to determine the interrelationships between BMC, BMD, and bone area from M0 to M14.

RESULTS

BMD and BMC were significantly lower in OVX-diet rats at M12 and M14 compared to sham rats. The Z-scores were below -5 in OVX-diet rats at M12, but still decreased at M14 in OVX-diet rats. Bone area and percent fat were significantly lower in OVX-diet rats at M14 compared to sham rats. The regression coefficients for BMD vs. bone area, BMC vs. bone area, and BMC vs. BMD of OVX-diet rats increased with time. This is explained by differential percent change in BMD, BMC, and bone area with respect to time and disease progression.

CONCLUSIONS

Combined ovariectomy and deficient diet in rats caused significant reduction of BMD, BMC, and bone area, with nearly 40% bone loss after 14 months, indicating the development of severe osteoporosis. An increasing regression coefficient of BMD vs. bone area with disease progression emphasizes bone area as an important parameter, along with BMD and BMC, for prediction of fracture risk.

NELL-1 injection maintains long-bone quantity and quality in an ovariectomy-induced osteoporotic senile rat model

Over 10 million Americans have osteoporosis, and is the predominant cause of fractures in the elderly. Treatment of fractures in the setting of osteoporosis is complicated by a suboptimal bone regenerative response due to a decline in the number of osteoblasts, their function, and survival. Consequently, an osteogenic therapeutic to prevent and treat fractures in patients with osteoporosis is needed. Nel-like molecule-1 (NELL-1), a novel osteoinductive growth factor, has been shown to promote bone regeneration. In this study, we aim to demonstrate the capacity of recombinant NELL-1 to prevent ovariectomy (OVX)-induced osteoporosis in a senile rat model. Ten-month-old female Sprague-Dawley rats underwent either sham surgery or OVX. Subsequently, 50 μL of 600 μg/mL NELL-1 lyophilized onto a 0-50-μm tricalcium phosphate (TCP) carrier was injected into the femoral bone marrow cavity while phosphate-buffered saline (PBS) control was injected into the contralateral femur. Our microcomputed tomography results showed that OVX+PBS/TCP control femurs showed a continuous decrease in the bone volume (BV) and bone mineral density (BMD) from 2 to 8 weeks post-OVX. In contrast, OVX+NELL-1/TCP femurs showed resistance to OVX-induced bone resorption showing BV and BMD levels similar to that of SHAM femurs at 8 weeks post-OVX. Histology showed increased endosteal-woven bone, as well as decreased adipocytes in the bone marrow of NELL-1-treated femurs compared to control. NELL-1-treated femurs also showed increased immunostaining for bone differentiation markers osteopontin and osteocalcin. These findings were validated in vitro, in which addition of NELL-1 in OVX bone marrow stem cells resulted in increased osteogenic differentiation. Thus, NELL-1 effectively enhances in situ osteogenesis in the bone marrow, making it potentially useful in the prevention and treatment of osteoporotic fractures.

Comparison of Tamoxifen and Testosterone Propionate in Male Rats: Differential Prevention of Orchidectomy Effects on Sex Organs, Bone Mass, Growth, and the Growth Hormone-IGF-I Axis

Testis dysfunction can weaken bone and reduce muscle mass as well as impair sexual function. Testosterone (T) therapy has useful effects on sex organs, bone, and muscle in T-deficient males, but prostate concerns can preclude T use in some men. Although estrogens or other drugs can protect bone in men, gynecomastia makes estrogens unappealing, and other drugs may also be undesirable in some cases. Selective estrogen receptor modulators (SERMs) inhibit estrogen-evoked sex organ growth but mimic estrogen effects on bone and cholesterol and are advantageous for some women. SERMs may also be useful in men who must avoid androgens. As a preclinical test of this idea, tamoxifen (a SERM) and testosterone propionate (TP, a classic androgen) were compared for their efficacy in preventing varied effects of orchidectomy (ORX) in adult male rats. ORX led to ventral prostate and seminal vesicle atrophy and decreases in somatic growth, proximal tibia bone mineral density (BMD), and serum growth hormone (GH) and insulin-like growth factor I (IGF-I). ORX also increased anterior pituitary glandular kallikrein, serum cholesterol, and body temperature. Pituitary prolactin (PRL) content was unaltered. ORX effects on sex organs, somatic growth, IGF-I, cholesterol, body temperature, and pituitary kallikrein were prevented by TP at 1 mg/kg (3 doses per week), but BMD and GH were unresponsive. ORX effects on BMD and GH were prevented by TP at 10 mg/kg, but this dose evoked supraphysiologic increases in sex organs and PRL, failed to restore somatic growth, and further reduced IGF-I. Tamoxifen (1 mg/kg daily) prevented ORX effects on BMD, GH, and cholesterol without altering basal or TP-induced sex organ growth and further reduced IGF-I and somatic growth. Tamoxifen did not alter basal PRL but blocked increases caused by TP at 10 mg/kg. In summary, tamoxifen prevented ORX effects on bone and cholesterol in male rats without affecting sex organs or PRL and might be useful for men who must avoid androgens. Unexpectedly, a TP dose that replicated testis effects on sex organs and other targets had no effect on BMD or GH, and a larger TP dose that restored BMD and GH was worse at replicating normal male physiology. In addition, correlation/regression results suggested that the GH-IGF-I axis contributes to changes in BMD.

Stimulated angiogenesis for fracture healing augmented by low-magnitude, high-frequency vibration in a rat model-evaluation of pulsed-wave doppler, 3-D power Doppler ultrasonography and micro-CT microangiography

This study aimed to investigate the mechanism of low-magnitude high-frequency vibration (LMHFV) treatment on angiogenesis and blood flow for enhancement of fracture healing. Nine-month-old ovariectomized (OVX) and sham-operated (Sham) rats received closed fractures creation at the femora and were randomized into LMHFV treatment (Sham-V, OVX-V) or control (Sham-C, OVX-C) groups. Pulsed-wave Doppler indicated an increase in blood flow velocity of the femoral artery at weeks 2 (OVX pair: p = 0.030) and 4 (OVX pair: p = 0.012; Sham pair: p = 0.020) post-treatment. Significantly enhanced vascular volume (VV) at the fracture site in the vibration groups was demonstrated by 3-D high-frequency power Doppler at week 2 (Sham pair: p = 0.021) and micro-computed tomography (microCT) microangiography at weeks 2 (OVX pair: p = 0.009) and 4 (OVX pair: p = 0.034), which echoed the osteogenesis findings by radiographic and microCT analysis. VV in the OVX groups was inferior to the Sham groups. However, OVX-V showed higher percentages of angiogenic enhancement than Sham-V. Despite impaired neo-angiogenesis in osteoporotic fractures, LMHFV could increase blood flow and angiogenesis in both normal and osteoporotic fractures, thus enhancing fracture healing.

Estrogen regulates iron homeostasis through governing hepatic hepcidin expression via an estrogen response element

Iron is essential for the human being, involving in oxygen transport, energy metabolism and DNA synthesis. Iron homeostasis is tightly governed by the hepcidin-ferroportin axis, of which hepcidin is the master regulator. Excess iron is associated with various diseases including osteopenia and osteoporosis, which are closely related to the alternation of the endogenous estrogen level. To verify the biological effect of estrogen on iron metabolism, we established a mouse model of estrogen deficiency by ovariectomy. We demonstrated that the hemoglobin content and serum iron level decreased, whereas the tissue iron level in liver and spleen increased in the ovariectomized mice. Moreover, the transcription of hepatic hepcidin was elevated in ovariectomized mice compared to the control mice. We further demonstrated that there was an estrogen response element (ERE) in the promoter region of the hepcidin gene. The assay using the luciferase reporter system confirmed the existence of a functional ERE in the hepcidin promoter, as the estradiol treatment reduced hepcidin expression in cells transfected with ERE-intact construct, with no response to estradiol in cells transfected with ERE-devoid construct. In conclusion, estrogen greatly contributes to iron homeostasis by regulating hepatic hepcidin expression directly through a functional ERE in the promoter region of hepcidin gene. These findings might help build a better understanding towards the etiology of postmenopausal osteoporosis accompanied by excess tissue iron (such as iron retention of osteoclasts in bone) under estrogen deficiency.

Effects of alendronate on lumbar posterolateral fusion using hydroxyapatite in rabbits

There are controversies regarding the effect of alendronate on spine fusion. In order to study the effects of alendronate on fusion with porous hydroxyapatite, a total of 47 rabbits underwent posterolateral lumbar fusion. The rabbits received saline (control group), alendronate 0.5 mg/kg/week (low-dose group), or alendronate 1 mg/kg/week (high-dose group) per oral beginning 2 weeks before surgery. All animals were euthanized 12 weeks after surgery, and the extent of fusion was assessed by radiographs, manual palpation, computed tomography (CT) scan, mechanical testing, and histologic examination. The fusion rates by manual palpation, radiography, and CT scan were similar in all groups. There was no significant difference in pixel optic density from the CT scan. Biomechanical testing showed the tensile strength of the control group was higher than that of the treatment group including the low- and high-dose group. In histologic examination, the fusion masses of control animals were characterized by a higher predominance of well-incorporated, trabeculated bone with a prominent marrow element. The treatment group showed a higher proportion of woven bone structures and thicker bony trabeculae. There was no significant difference in the fusion rate, but the tensile strength of treatment group was significantly lower. Histologic examination showed that alendronate inhibited bone resorption and remodeling.

Histomorphometric analysis of the spine and femur in ovariectomized rats using micro-computed tomographic scan

OBJECTIVE

The purpose of this study was to evaluate the different patterns of bone loss between the lumbar spine and the femur after ovariectomy in rats.

METHODS

Twenty-four female Sprague-Dawley rats underwent a sham operation (the sham group) or bilateral ovariectomy (the ovariectomized group). Four and eight weeks after operation, six rats from each of the two groups were euthanized. Serum biochemical markers of bone turnover including osteocalcin and alkaline phosphatase (ALP), which are sensitive biochemical markers of bone formation, and the telopeptide fragment of type I collagen C-terminus (CTX), which is a sensitive biochemical marker of bone resorption, were analyzed. Bone histomorphometric parameters of the 4th lumbar vertebrae and femur were determined by micro-computed tomography.

RESULTS

Ovariectomized rats were found to have higher osteocalcin, ALP and CTX levels than sham controls. Additionally, 8 weeks after ovariectomy in the OVX group, serum levels of osteocalcin, ALP and CTX were significantly higher than those of 4 weeks after ovariectomy. Bone loss after ovariectomy was more extensive in the 4th lumbar spine compared to the femur. Bone loss in the 4th lumbar spine was mainly caused by trabecular thinning, but in the femur, it was mainly caused by trabecular elimination.

CONCLUSION

The present study demonstrates different patterns of bone loss between the 4th lumbar spine and the femur in ovariectomized rats. Therefore, when considering animal models of osteoporosis, it is important that bone sites should be taken into account.

The Change of Bone Metabolism in Ovariectomized Rats : Analyses of MicroCT Scan and Biochemical Markers of Bone Turnover

Objective

The purpose of this study was to verify the appropriateness of ovariectomized rats as the osteoporosis animal model.

Methods

Twelve female Sprague-Dawley rats underwent a sham operation (the sham group) or bilateral ovariectomy [the ovariectomy (OVX) group]. Eight weeks after operations, serum biochemical markers of bone turnover were analyzed; osteocalcin and alkaline phosphatase, which are sensitive biochemical markers of bone formation, and C-terminal telopeptide fragment of type I collagen C-terminus (CTX), which is a sensitive biochemical marker of bone resorption. Bone histomorphometric parameters and microarchitectural properties of 4th lumbar vertebrae were determined by micro-computed tomographic (CT) scan.

Results

The OVX group showed on average 75.4% higher osteocalcin and 72.5% higher CTX levels than the sham group, indicating increased bone turnover. Micro-CT analysis showed significantly lower bone mineral density (BMD) (p=0.005) and cortical BMD (p=0.021) in the OVX group. Furthermore, the OVX group was found to have a significantly lower trabecular bone volume fraction (p=0.002).

Conclusion

Our results showed that bone turnover was significantly increased and bone mass was significantly decreased 8 weeks after ovariectomy in rats. Thus, we propose that the ovariectomized rat model be considered a reproducible and reliable model of osteoporosis.

Bone regeneration related to calcium phosphate-coated implants in osteoporotic animal models: a meta-analysis

BACKGROUND

Osteoporosis is a frequent human metabolic bone disorder. Prospectively, global ageing of populations will lead to a major increase of subjects being diagnosed with osteoporosis and in need for dental rehabilitation. However, as local osteoporosis of the jaws affects bone quantity and quality of edentulous regions, osseointegration of dental implants might be hampered. Consequently, calcium phosphate ceramic-coated implants have been suggested to compensate for low bone quantity/density and for impaired bone healing in osteoporosis. Nonetheless, up to now no meta-analytical assessment of the relevant preclinical literature to quantify such a possible positive effect has been undertaken.

MATERIALS AND METHODS

PubMed search, limited to animal models, to identify a possible positive effect of calcium phosphate-coated implants on bone regeneration, was carried out. Further, the reference lists of related review articles and publications selected for inclusion in this review were systematically screened. The primary outcome variables were bone-to-implant contact percentage as assessed histomorphometrically and mechanical stability testing.

RESULTS

The electronic search in the database of the National Library of Medicine resulted in the identification of 2704 titles. These titles were initially screened by the two independent reviewers for possible inclusion, resulting in further consideration of 51 publications. Screening the abstracts led to 22 full-text articles. From these articles, 16 reports were excluded. Finally, six of these original research reports could be selected for evaluation. Additionally, eight publications were identified by manual search. Thus, a total of 14 articles were included for analysis.

CONCLUSIONS

It was concluded that (1) in osteoporotic animal models calcium phosphate ceramic-coated implants are associated with improved bone-to-implant healing as compared to noncoated implants. Moreover, (2) essentially due to quality characteristics of the analyzed original research articles a negative impact of osteoporosis on bone-to-implant healing could not be confirmed. Besides, (3) the established positive bone-to-implant healing effect of calcium phosphate ceramic coatings does not differ between osteoporotic and nonosteoporotic, healthy animal models.

Characteristics of bone metabolism markers during the healing of osteoporotic versus nonosteoporotic metaphyseal long bone fractures: a matched pair analysis

PURPOSE

The activity and metabolism of fracture healing can be monitored quantitatively by measuring bone turnover markers (BTMs) in serum or urine. However, in osteoporotic bone, the exact metabolism processes during the healing of metaphyseal fractures remain unknown. There is no diagnostic approach which currently allows dynamic insight into the fracture healing processes in order to monitor the progression of healing and to assist in therapeutic decision making.

METHODS

Between March 2007 and February 2009, 30 patients over 50 years of age who suffered a metaphyseal fracture were included in our study. The levels of the osteoanabolic marker BAP (bone-specific alkaline phosphatase) and osteocatabolic marker β-CTX [crosslinked C-(CTX)-telopeptide-of-type-I-collagen] were monitored during the fracture healing of osteoporotic and nonosteoporotic fractures for a duration of 8 weeks.

RESULTS

After an initial decrease of BAP in the first week, the BAP level steadily increased through the fourth week in both groups. The levels of BAP in the osteoporotic group surpassed the healthy group. β-CTX steadily increased in healthy bone up to the fourth week; in osteoporotic bone, β-CTX first increased and, thereafter, decreased from the first week onwards.

CONCLUSIONS

In this work, the first molecular biological aspects of osteoporotic fracture healing have been uncovered, helping to explain the mechanisms of delayed fracture healing in osteoporotic bone. The early decrease of reduced β-CTX as well as elevated BAP during the healing process may be the first aspects within the delayed healing of osteoporotic bone. Further studies are necessary in order to achieve more detailed insight to fracture healing and to ascertain the progression of fracture healing as being essential (criteria) for therapeutic decision making.

[Effect of Sophoricoside on histomorphology of bone in ovariectomized rats]

OBJECTIVE

To evaluate the potential preventive effect of Sophoricoside on bone loss in ovariectomized rats.

METHODS

Female SD rats (n=50, 6 months old) were either sham-operated (SHAM group, n=10) or ovariectomized (n=40). Three days after operation, ovariectomized rats were randomly assigned to groups as follows: 10 received Sophoricoside 4 mg.kg(-1).d(-1) (SL group), 10 received Sophoricoside 8 mg.kg(-1).d(-1) (SM group), 10 received Sophoricoside 16 mg.kg(-1).d(-1) (SH group) and 10 were untreated (OVX group). After Sophoricoside were given orally for one month, the histomorphometric parameters in the secondary spongiosa of proximal tibia and lumbar vertebrae were examined.

RESULTS

Compared with OVX group, SM and SH two kinds of treatment caused 15.28% and 22.81% increment in percent trabecular area (BV/TV, %) in the secondary spongiosa of proximal tibia, 14.23% and 21.2% increment in lumbar vertebrae. Accordingly in these two groups, there was a significant decrease in trabecular separation (FLAW, microm), but increment in trabecular width (Tb. Th, microm) and conjunction points (JOINT). But in SL group, the preventive effect was not observed.

CONCLUSION

Sophoricoside can be efficient in preventing ovariectomy-induced bone loss in rats.

Densitometry, radiography, and histological assessment of collagen as methods to evaluate femoral bones in an experimental model of osteoporosis

SUMMARY

All methods to detect experimental loss of bone present technique limitations. The sensitivities of image and histological analyses to detect the effects of teriparatide in rats with bone loss after ovariectomy were evaluated. All methods were qualitatively valid.

INTRODUCTION

The standardization of methods to assess bone loss after ovariectomy is crucial to establish the degree of experimental osteoporosis. In general, methods per image or histological techniques are used. To validate these two ways to determine the degree of bone loss in ovariectomized rats, we evaluated the sensitivities of bone densitometry, conventional radiography, and histological analysis of the area occupied by collagen, detecting the effects of teriparatide treatment in the femur of ovariectomized rats with bone loss.

METHODS

Wistar rats were divided into three groups: a control group, in which the animals were only subjected to laparotomy; an ovariectomized group, in which bilateral removal of the ovaries was performed; and an ovariectomized + teriparatide group, in which bilateral removal of the ovaries was performed, and the animals were treated with 3 μg/100 g/day of teriparatide. Three months following the ovariectomy, bone densitometry, radiographic densitometry, and histological analysis of the area occupied by collagen fibers were carried out in the femur diaphysis.

RESULTS

The bone densitometry revealed 11.2% reduction in femur density; in the conventional radiography, the loss of bone mass was 14.5%, and with the histological analysis, a 40.9% reduction in the area occupied by collagen was detected in the femur diaphysis.

CONCLUSIONS

In conclusion, histological analysis could not be quantitatively compared with the methods of bone densitometry and conventional radiography; however, all of these methods were qualitatively valid for assessing the loss of bone stemming from ovariectomy and the therapeutic effect of teriparatide in the prevention of osteoporosis.

Low intensity pulsed ultrasound enhances fracture healing in both ovariectomy-induced osteoporotic and age-matched normal bones

Low intensity pulsed ultrasound (LIPUS) was proven to enhance fracture healing effectively. Similar effect of LIPUS on accelerating the osteoporotic fracture healing was therefore hypothesized. The normal and osteoporotic fracture healings under this non-invasive biophysical intervention of LIPUS were compared and investigated. Closed femoral fracture procedures were performed on 120 Sprague-Dawley rats, in which 60 of them were ovariectomized (OVX). The rats were randomly assigned into four groups: sham OVX with treatment (Sham-T), sham OVX control (Sham-C), OVX with treatment (OVX-T) and OXV control (OVX-C). LIPUS treatment was 20 min a day, 5 days a week for durations of 2, 4, or 8 weeks. Results from weekly radiography, histomorphometry, micro-computed tomography and mechanical test showed both the treatment groups were with better healing responses than their control groups. Moreover, between the normal and the osteoporotic treatment groups, a significantly higher (p = 0.015) callus width (week 4), higher ratio of increment in bone volume to tissue volume ratio value (7.4% more), faster response of endochondral ossification and a higher stiffness measurement were observed in the osteoporotic treatment group. These comparable results on healing responses imply that LIPUS can be applied clinically to enhance both normal and osteoporotic fracture healing.

Femoral metaphysis bending test of rat: introduction and validation of a novel biomechanical testing protocol for osteoporosis

BACKGROUND

The diaphysis bending test is generally accepted to assess the biomechanical properties of bone in osteoporotic animals. However, bone strength loss was more pronounced at the metaphysis than diaphysis. Therefore, the biomechanical test should be focused on the metaphysis. This study aimed to validate a novel biomechanical test for femoral metaphysis in ovariectomized rats.

METHODS

Twenty 5-month-old female Sprague-Dawley rats were randomly divided into the ovariectomized (OVX) and sham-operated (Sham) groups. Examination of femur bone mineral density (BMD) and histomorphometry of the distal femur were performed. Femur biomechanical parameters (maximal load, yield load, and stiffness) were determined by the diaphysis bending test and a novel designed metaphysis bending test. Pearson's correlations were used to analyze the relationships between the biomechanical parameters and BMD or bone histomorphometry indexes (%Tb.Ar, Tb.N, Tb.Th), respectively.

RESULTS

The femur BMD, bone histomorphometry indexes, and biomechanical parameters of OVX were inferior to those of the Sham group (P < 0.05). In the diaphysis bending test, the mean difference of the maximum load and yield load between the OVX and Sham groups were 13.83 ± 5.27 and 15.69 ± 4.15 N, which were significantly lower than in the metaphysis bending test (43.34 ± 4.27, 48.90 ± 4.35 N; all P < 0.05). Positive correlations between biomechanical parameters and femur BMD or bone histomorphometry indexes were observed in both the diaphysis bending and metaphysis bending test. The biomechanical parameters in the metaphysis bending test showed stronger correlations with BMD and bone histomorphometry indexes.

CONCLUSIONS

The femoral metaphysis bending test was validated to assess osteoporosis in our study, and it was more sensitive than the diaphysis bending test in evaluating the change of biomechanical properties of the femur in osteoporotic rats.

Pinealectomy affects bone mineral density and structure--an experimental study in sheep

Background

Osteoporosis and associated fractures are a major public health burden and there is great need for a large animal model. Melatonin, the hormone of the pineal gland, has been shown to influence bone metabolism. This study aims to evaluate whether absence of melatonin due to pinealectomy affects the bone mass, structure and remodeling in an ovine animal model.

Methods

Female sheep were arranged into four groups: Control, surgically ovariectomized (Ovx), surgically pinealectomized (Px) and Ovx+Px. Before and 6 months after surgery, iliac crest biopsies were harvested and structural parameters were measured using μCT. Markers of bone formation and resorption were determined. To evaluate long term changes after pinealectomy, bone mineral density (BMD) was analyzed at the distal radius at 0, 3, 9, 18 and 30 months.

Results

Cancellous bone volume (BV/TV) declined after 6 months by -13.3% Px and -21.5% OvxPx. The bone loss was due to increased trabecular separation as well as decreased thickness. The histomorphometric quantification and determination of collagen degradation products showed increased bone resorption following pinealectomy. Ovariectomy alone results in a transient bone loss at the distal radius followed by continuous increase to baseline levels. The bone resorption activity after pinealectomy causes a bone loss which was not transient, since a continuous decrease in BMD was observed until 30 months.

Conclusions

The changes after pinealectomy in sheep are indicative of bone loss. Overall, these findings suggest that the pineal gland may influence bone metabolism and that pinealectomy can be used to induce bone loss in sheep.

Effects of α-tocopherol on the early phase of osteoporotic fracture healing

Fracture healing is a complex process, which is more complicated if the bone is osteoporotic. One of the vitamin E isomers, α-tocopherol, has been found to prevent osteoporosis and improve bone fracture healing but its role in the healing of osteoporotic fractures is still unclear. We carried out a study on the effects of α-tocopherol supplementation on osteoporotic fracture healing using an ovariectomized rat model, whereby we focused on the early phase of fracture healing, that is, the phase with excessive production of free radicals. Twenty-four female Sprague-Dawley rats were divided into three groups: sham-operated (SO), ovariectomized-control (OVC), and ovariectomized + α-tocopherol supplementation (ATF) groups. The right femora of all the rats were fractured at mid-diaphysis and K-wires were inserted for internal fixation. After 2 weeks of treatment, the rats were euthanized and the femora were dissected out for measurement of callous volume by CT-scan and radiological staging of callous formation and fracture healing. The oxidative parameters of the fractured femora were also measured. The results showed that the callous volume and callous staging were not different between the groups. However, the fracture healing stage of the OVC group was lower than the SO group, while α-tocopherol supplementation in the ATF group had improved the healing until it was comparable to the SO group. The activities of the anti-oxidatant enzymes, superoxide dismutase, and glutathione peroxidase in the ATF group were found to be significantly higher than in the OVC group. In conclusion, α-tocopherol improved fracture healing but had no effect on the callous volume and staging. The improvement in fracture healing may be due to the increased activities of the anti-oxidatant enzymes in the bone during the early phase of fracture healing of osteoporotic bone.

Anti-osteoporosis activity of Cibotium barometz extract on ovariectomy-induced bone loss in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Recent research has confirmed that Cibotium barometz could inhibits osteoclast formation with no affect on BMM cell viability. However, the influence of Cibotium barometz on osteoporosis in animals is relatively unknown. The purpose of this study is to systemically investigate the effects of Cibotium barometz extract (CBE) on ovariectomy-induced osteoporosis in rats.

MATERIALS AND METHODS

A total of Seventy-two 3-month-old female Sprague-Dawley rats were used and randomly divided into sham-operated group and five ovariectomized (OVX) groups: OVX with vehicle; OVX with 17β-estradiol (E2, 25 μg/kg/day); OVX with CBE of graded doses (100, 300, or 500 mg/kg/day). Daily oral administration of E2 or CBE began 4 weeks after the surgery and lasted for 16 weeks. Bone mass, bone turnover and strength were analyzed by DEXA, biochemical markers and three-point bending test. The trabecular bone microarchitecture was evaluated by MicroCT.

RESULTS

CBE prevented total BMD decrease in the femur induced by OVX, which was accompanied by a significant decrease in skeletal remodeling, as was evidenced by the decreased levels of the bone turnover markers, such as osteocalcin (OC), alkaline phosphatese (ALP), deoxypyridinoline (DPD), and urinary Ca and P excretions. The treatment could also enhance the bone strength and prevent the deterioration of trabecular microarchitecture.

CONCLUSIONS

The present study indicated that Cibotium barometz extract might be a potential alternative medicine for the prevention and treatment of postmenopausal osteoporosis.

Effects of resistance training on matrix metalloproteinase-2 activity and biomechanical and physical properties of bone in ovariectomized and intact rats

The purpose of this study was to investigate the influence of resistance training on the activity of matrix metalloproteinase (MMP)-2 and bone biomechanical properties in ovariectomized and intact rats. Forty-eight female rats were divided into two distinct groups, ovariectomized (OVX) and intact (Int), which were subdivided into three similar subgroups: sedentary, acute exercise and chronic exercise. Rats performed a resistance training for 12 weeks in which animals climbed a vertical ladder of 1.1 m with weights attached to their tails. Sessions were performed with an interval of 3, 4-9 and 8-12 days scaled dynamic movements of climbing. Biomechanical and physical analyses were performed using a universal testing machine, and MMP-2 activity analysis by zymography. Bone density (BD), mineral density (MD), maximum load and fracture load was reduced in sedentary and acute exercise OVX groups compared with the sedentary intact group (P<0.05); in contrast, chronically trained groups (OVX and Int) showed a significant increase in BD, MD and fracture load compared with all the other groups. MMP-2 activity in chronically trained groups also showed a significant increase, while the sedentary OVX group showed a decrease in MMP-2 activity compared with the intact sedentary group (P<0.05). Our results suggest that the resistance training proposed in our work was efficient in reverting the deleterious effects of ovariectomy on bone tissue, and also produced modeling effects in intact rats. On the other hand, ovariectomy reduced the activity of MMP-2 and produced deleterious effects on bone tissue, mimicking menopause intrinsically.

Absence of positive effect of black cohosh (Cimicifuga racemosa) on fracture healing in osteopenic rodent model

The healing of predominantly metaphyseal fractures in postmenopausal osteoporosis is delayed and comparatively poor. Due to the potential side effects of HRT, natural alternatives are appealing. The aim of this study was to determine whether Cimicifuga racemosa extract BNO 1055 improves metaphyseal fracture healing in severe osteopenic bone in rats. Thirty-three 12-week-old female rats developed severe osteopenia during 10 weeks after ovariectomy. After metaphyseal tibial-osteotomy and standardized T-plate-osteosynthesis, the healing periods in ovariectomized rats (C), 17-α-estradiol (E) and Cimicifuga racemosa (CR) supplemented diets were assessed for 35 days. Changes in callus morphology were evaluated qualitatively by biomechanical testing and quantitatively in microradiographies and fluorochrome-labeled histological sections. The CR-supplementation slightly improved callus quality and trabecular bone formation. It significantly enhanced the endosteal callus density compared to C group (Cl.Dn.e C: 59.08 ± 21.89, E: 45.95 ± 18.39, CR: 60.85 ± 18.66*), though most of the other morphological parameters examined showed no improvement. The time course of fracture healing did not change due to CR. Estrogen-supplementation enhanced the biomechanical properties of the fracture site. Trabecular bone was improved indicating the physiological endosteal healing process. The CR-supplementation did not exhibit positive effects in severe (senile) osteopenic fracture healing as seen in early (postmenopausal) osteoporosis in rats. Callus formation was slightly improved under CR. Estrogen improved fracture healing in severe osteopenic bone, while the extent of callus formation played a minor role.

Relationship between age, skeletal site, and time post-ovariectomy on bone mineral and trabecular microarchitecture in rats

The ovariectomized (OVX) rat is widely used in osteoporosis research, but no standard model exists. The individual effects of rat age, skeletal site, and time post-ovariectomy (post-OVX) on bone have been examined. However, the relationship between them is not yet fully explored. This study examined how various combinations of rat age, skeletal site, and time post-OVX affect bone mineral and microarchitecture. The rats used were 12 (n = 28), 24 (n = 28), and 44 (n = 31) weeks old. In each age group, approximately half underwent OVX and other half underwent Sham surgeries. Bone mineral (content and density) and trabecular morphology was assessed at 2, 5, 10, 15, 20, 25, and 30 weeks post-surgery. Sites examined included the proximal tibia, spine, distal femur, and proximal femur. Overall, the proximal tibia showed the earliest and greatest differences between OVX and Sham groups. The 24-week-old group showed the best osteoporotic response. The 12-week-old group showed growth effects, whilst the 44-week-old group showed aging effects. The response of certain sites to OVX was also found to depend on the rat age used. These findings may aid in explaining discrepancies reported in the literature as well as synergistic combinations that may signify advanced conditions. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:189-196, 2011.

Sclerostin monoclonal antibody therapy with AMG 785: a potential treatment for osteoporosis

IMPORTANCE OF THE FIELD

Osteoporosis is a common skeletal disease characterized by loss of bone strength that leads to increased risk of fractures. Fractures of the hip and spine are associated with disability, increased risk of death and high healthcare costs. Recent improvement in the understanding of the molecular regulators of bone metabolism has led to the investigation and development of new therapeutic agents with novel mechanisms of action that may offer advantages over currently available treatments for osteoporosis.

AREAS COVERED IN THIS REVIEW

Sclerostin is a small protein secreted by osteocytes that downregulates osteoblast-mediated bone formation. This is a review of the rationale, mechanism of action, preclinical and clinical development of AMG 785 (CDP7851), an investigational humanized mAb that inhibits the activity of sclerostin, resulting in increased bone formation.

WHAT THE READER WILL GAIN

The reader will gain an insight into the potential use of sclerostin mAb therapy for the treatment of osteoporosis.

TAKE HOME MESSAGE

Preclinical studies and an early report of a clinical study suggest that inhibition of sclerostin with AMG 785 may provide skeletal benefit for patients with osteoporosis.

Bone mineral density changes after ovariectomy in rats as an osteopenic model : stepwise description of double dorso-lateral approach

OBJECTIVE

This study describes a method for inducing osteopenia using bilateral ovariectomy (OVX), which causes significant changes in bone mineral density (BMD) in rats.

METHODS

Twenty-five 10-week-old female Sprague Dawley rats were used. Five rats were euthanized after two weeks, and BMD was measured in their femora. The other 20 rats were assigned to one of two groups : a sham group (n = 10), which underwent a sham operation, and an OVX group (n = 10), which underwent bilateral OVX at 12 weeks of age. After six weeks, five rats from each group were euthanized, and BMD was measured in their femora. The same procedures were performed in the remaining rats form each group eight weeks later.

RESULTS

The femur BMD was significantly lower in the six-week OVX group than in the six-week sham group, and in the eight-week OVX group than in the eight-week sham group.

CONCLUSION

Bilateral OVX is a safe method for creating an osteopenic rat model. The significant decrease in BMD appears six weeks after bilateral OVX.

Gene expression and distribution of key bone turnover markers in the callus of estrogen-deficient, vitamin D-depleted rats

An experimental rat model was used to test the hypothesis that in osteoporosis (OP) the molecular composition of the extracellular matrix in the fracture callus is disturbed. OP was induced at 10 weeks of age by ovariectomy and a vitamin D(3)-deficient diet, and sham-operated animals fed normal diet served as controls. Three months later a closed tibial fracture was made and stabilized with an intramedullary nail. After 3 and 6 weeks of healing, the animals were killed and the fracture calluses examined with global gene expression, in situ mRNA expression, and ultrastructural protein distribution of four bone turnover markers: osteopontin, bone sialoprotein, tartrate-resistant acid phosphatase, and cathepsin K. Global gene expression showed a relatively small number of differently regulated genes, mostly upregulated and at 3 weeks. The four chosen markers were not differently regulated, and only minor differences in the in situ mRNA expression and ultrastructural protein distribution were detected. Gene expression and composition of fracture calluses are not generally disturbed in experimental OP.

Characterization of a rabbit osteoporosis model induced by ovariectomy and glucocorticoid

BACKGROUND AND PURPOSE

Experimental models of osteoporosis in rabbits are useful to investigate anabolic agents because rabbits have an active Haversian remodeling and achieve skeletal maturity quickly. In this study, an experimental model of osteoporosis in rabbits induced by a combination of ovariectomy and glucocorticoid was characterized to provide a useful model for prevention and therapy of osteoporosis.

METHODS

32 skeletally mature female rabbits were divided randomly into 4 groups: sham control, bilateral ovariectomy (OVX), 1mg/kg/day methylprednisolone (MP) for 8 weeks, and OVX in combination with MP. All rabbits were killed 10 weeks after surgery. Bone mineral density (BMD) of lumbar spine was measured by dual-energy X-ray absorptiometry at baseline, and at 6 and 10 weeks postoperatively. Bone microarchitecture and mechanical properties of lumbar vertebrae were investigated by high-resolution micro-computed tomography and compression test, respectively, after killing.

RESULTS

Mean BMD of the OVX+MP group at 10 weeks was reduced by about 36% from baseline (p < 0.001). Bone microarchitecture of lumbar vertebrae in the OVX+MP group indicated osteoporosis-associated deterioration. There was a statistically significant reduction in maximum load, stiffness, and energy absorption capacity of lumbar vertebrae in the OVX+MP group, but not in the OVX group, compared to the sham control. In the MP group, BMD and some microarchitecture parameters such as trabecular thickness and bone volume fraction were reduced. The mechanical properties were not statistically significantly different from those in the sham control group, however, although a negative trend was observed.

INTERPRETATION

Osteopenia can be induced experimentally in rabbits through a combination of OVX and MP, and can be evaluated by BMD, bone microstructure, and mechanical parameters.

Ultra-short echo-time MRI detects changes in bone mineralization and water content in OVX rat bone in response to alendronate treatment

In this work we hypothesize that bisphosphonate treatment following ovariectomy manifests in increased phosphorus and decreased water concentration, both quantifiable nondestructively with ultra-short echo-time (UTE) (31)P and (1)H-MRI techniques. We evaluated this hypothesis in ovariectomized (OVX) rats undergoing treatment with two regimens of alendronate. Sixty female four-month-old rats were divided into four groups of 15 animals each: ovariectomized (OVX), OVX treatment groups ALN1 and ALN2, receiving 5 microg/kg/day and 25 microg/kg/day of alendronate, and a sham-operated group (NO) serving as control. Treatment, starting 1 week post-surgery, lasted for 50 days at which time animals were sacrificed. Whole bones from the left and right femora were extracted from all the animals. (31)P and (1)H water concentration were measured by UTE MRI at 162 and 400 MHz in the femoral shaft and the results compared with other measures of mineral and matrix properties obtained by (31)P solution NMR, CT density, ash weight, and water measured by dehydration. Mechanical parameters (elastic modulus, EM, and ultimate strength, US) were obtained by three-point bending. The following quantities were lower in OVX relative to NO: phosphorus concentration measured by (31)P-MRI (-8%; 11.4+/-0.9 vs. 12.4+/-0.8%, p<0.005), (31)P-NMR (-4%; 12.8+/-0.4 vs. 13.3+/-0.8 %, p<0.05) and micro-CT density (-2.5%; 1316+/-34 vs. 1349+/-32 mg/cm(3), p=0.005). In contrast, water concentration by (1)H-MRI was elevated in OVX relative to NO (+6%; 15.5+/-1.7 vs. 14.6+/-1.4 %, p<0.05). Alendronate treatment increased phosphorus concentration and decreased water concentration in a dose-dependent manner, the higher dose yielding significant changes relative to values found in OVX animals: (31)P-MRI (+14%; p<0.0001), (31)P-NMR (+9%; p<0.0001), ash content (+1.5%; p<0.005), micro-CT mineralization density (+2.8%; p<0.05), and (1)H-MRI, (-19%, p<0.0001). The higher dose raised phosphorus concentration above and water concentration below NO levels: (31)P-MRI (+6%; p<0.05), (31)P-NMR (+5%; p=0.01), ash content (+1.5%; p=0.005), (1)H-MRI (-14%; p<0.0001), and drying water (-10%; p<0.0005). Finally, the group means of phosphorus concentration were positively correlated with EM and US (R(2)> or =0.98, p<0.001 to p<0.05) even though the pooled data from individual animals were not. The results highlight the implications of estrogen depletion and bisphosphonate treatment on mineral composition and mechanical properties and the potential of solid-state MR imaging to detect these changes in situ in an animal model of rat ovariectomy.

Effect of a prostaglandin EP4 receptor agonist on early fixation of hydroxyapatite/titanium composite- and titanium-coated rough-surfaced implants in ovariectomized rats

The agonist of the prostaglandin EP4 receptor can increase bone density in osteoporosis. Using ovariectomized (OVX) and sham-operated (SO) rats, the effects of the EP4 receptor agonist, ONO-4819, and hydroxyapatite (HA) on implant-bone fixation in implants with a rough surface were investigated. Female Wistar rats (12 weeks old) were divided into either SO or bilateral OVX groups. Twenty four weeks later, either hydroxyapatite/titanium (HA/Ti) composite-coated or Ti-coated implants were implanted into the femora, and the animals were treated with either ONO-4819 or saline for 4 weeks. The fixation strength of the HA/Ti-coated implants was higher than that of the Ti-coated implants in the saline-treated OVX rats. In the OVX rats, ONO-4819 enhanced fixation of the rough Ti-coated implants to levels similar to that of HA/Ti-coated implants. These data suggest that a combination of treatment with an EP4 receptor agonist and a rough-surfaced implant might be useful in increasing the early fixation of cement-less arthroplasty, particularly in elderly patients with osteoporosis.

Bone ingrowth into porous silicon nitride

Achieving solid skeletal attachment is a requirement for the clinical success of orthopedic implants. Porous or roughened surfaces and coatings have been developed and used with mixed success to achieve attachment due to bone ingrowth. Silicon nitride is a high performance ceramic whose strength, imaging properties, and biocompatibility make it a candidate material for orthopedic implants. A porous form of silicon nitride, cancellous-structured ceramic (CSC), has been developed. CSC is a nonresorbable, partially radiolucent porous structure that can be bonded to orthopedic implants made of silicon nitride to facilitate skeletal attachment. The purpose of this study was to quantify the extent and rate of bone ingrowth into CSC in a large animal model. Cylindrical implants were placed bilaterally using staged surgeries in the medial femoral condyle of six sheep. Condyles were retrieved after 3 and 6 months in situ and prepared for examination of bone growth under SEM. Bone grew into CSC to extents and at rates similar to those reported for other titanium porous surfaces in studies involving large animals and postmortem retrievals in humans. Bone ingrowth was observed at depths of penetration greater than 3 mm in some implants after only 12 weeks in situ. Bone ingrowth into CSC is a viable method for achieving skeletal attachment.

Contribution of the intra-specimen variations in tissue mineralization to PTH- and raloxifene-induced changes in stiffness of rat vertebrae

The intra-specimen spatial variation in mineralization of bone tissue can be changed by drug treatments that alter bone remodeling. However, the contribution of such changes to the overall biomechanical effect of a treatment on bone strength is not known. To provide insight into this issue, we used a rat model to determine the effects of ovariectomy, parathyroid hormone, and raloxifene (vs. sham) on the contribution of spatial variations in mineralization to treatment-induced changes in vertebral stiffness. Mineral density was measured from 6-microm voxel-sized quantitative micro-CT scans. Whole-vertebral and trabecular stiffness values were estimated using finite element analysis of these micro-CT scans, first including all intra-specimen variations in mineral density in the model and then excluding such variations by using a specimen-specific average density throughout each specimen. As expected, we found appreciable effects of treatment on overall bone stiffness, the effect being greater for the trabecular compartment (up to 52% reduction vs. sham, p<0.0001) than the whole vertebra (p=0.055). Intra-specimen mean mineralization was not changed with treatment but the intra-specimen variation in mineralization was, although the effect was small (4%). Intra-specimen spatial variations in mineralization accounted for 10-12% and 5-6% of overall stiffness of the trabecular compartment and whole vertebral body, respectively. However, after accounting for all treatment effects on bone geometry and trabecular microstructure, any treatment effects due to changes in mineralization were negligible (<2%), although statistically detectable (p<0.02). We conclude that, despite a role in the general biomechanical behavior of bone, the spatial variations in tissue mineralization, as measured by quantitative micro-CT, did not appreciably contribute to ovariectomy-, PTH-, or raloxifene-induced changes in stiffness of the whole bone or the trabecular compartment in these rat vertebrae.

Beyond oncology--application of HPMA copolymers in non-cancerous diseases

Macromolecular drug conjugates have been developed to improve the efficacy and safety profile of various therapeutic agents for many years. Among them, N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer-drug conjugates are the most extensively studied delivery platforms for the effective treatment of cancer. In recent years, the applications of HPMA copolymers for the treatment of a broader range of non-cancerous diseases have also been explored. This review highlights the recent developments in the rational design, synthesis, and evaluation of novel HPMA copolymer-drug conjugates for non-cancerous diseases, such as musculoskeletal diseases, infectious diseases and spinal cord injury. The translation potential of these applications is also briefly discussed.

Improvement of trochanteric bone quality in an osteoporosis model after short-term treatment with parathyroid hormone: a new mechanical test for trochanteric region of rat femur

We have examined the changes induced in the trochanteric region of femur of ovariectomized rat after administration of estradiol and parathyroid hormone. We have developed a reproducible biomechanical test and produced trochanteric fractures to evaluate stiffness and strength of this region in addition to histomorphometry.

INTRODUCTION

We investigated the short-term effects of parathyroid hormone (PTH) and estrogen (E) on the strength of the rat trochanteric region in a new mechanical test.

METHODS

Forty-four 3-month-old female Sprague-Dawley rats were ovariectomized and 8 weeks later treated with soy-free diet (C), daily applications of orally supplied E (0.5 mg/kg food) or subcutaneously injected PTH (0.014 mg/kg), for 5 weeks, and an additional untreated group was added as sham-operated. The femurs were examined for biomechanical and histomorphometric changes.

RESULTS

Our new mechanical test was validated in a right-left comparison. The PTH treatment induced significantly superior biomechanical results (F (max) = 225.3 N, stiffness = 314.9 N/mm) compared to E (F (max) = 182.9 N, stiffness = 237.2 N/mm), C (F (max) = 166.03 N, stiffness = 235.56 N/mm), and sham (F (max) = 192.1 N, stiffness = 267.2 N/mm). Animals of the PTH group demonstrated a significantly improved trabecular bone structure and area (75.67%) in comparison to the E (61.04%) and C (57.18%) groups.

CONCLUSION

Our new biomechanical test is valid and produces trochanteric fracture. Our results show that the short-term antiosteoporotic effects of PTH are in the trochanteric region of ovariectomized rat superior to E.

Do estrogen and alendronate improve metaphyseal fracture healing when applied as osteoporosis prophylaxis?

Osteoporosis is accompanied by predominantly metaphyseal fractures with a delayed and qualitatively reduced healing process. This study addressed the question of whether fracture healing in the context of osteoporosis prophylaxis is improved with estrogen (E) or alendronate (ALN). Thirty-six ovariectomized and 12 sham-operated 12-week-old rats received soy-free (osteoporotic C, sham), E-, or ALN- supplemented diets. After 10 weeks, a metaphyseal tibia osteotomy and standardized T-plate fixation were performed. After a 5-week healing process, the fracture callus was evaluated qualitatively by biomechanical bending test and quantitatively in microradiographic sections. The time course of callus formation was examined using fluorochrome-labeled histological sections. Administration of E improved the biomechanical properties of callus (stiffness [N/mm]: sham: 110.2 + or - 76.07, C: 41.28 + or - 33.70, E: 85.72 + or - 47.24, ALN: 72.07 + or - 34.68). The resistance to microfracturing seen in E-treated animals was significantly enhanced and even superior to sham (yield load [N] sham: 27.44 + or - 9.72, C: 21.04 + or - 12.47, E: 42.85 + or - 13.74(Delta), ALN: 25.28 + or - 6.4(.)) (* P < 0.05 vs. sham group, (Delta) P < 0.05 vs. C group, (*) P < 0.05 vs. E group). Trabecular bone in particular was improved, indicating the presence of physiological endosteal bridging (Tr.Dn [%] sham: 10.53 + or - 18.9, C: 1.01 + or - 0.14, E: 24.13 + or - 34.09(Delta), ALN: 3.99 + or - 8.3(.)). ALN did not help bone healing, as shown by mechanical tests. Compared to the C group, statistically, ALN did not show worse properties. The induction of callus formation under ALN treatment was slightly delayed (Tt.Cl [mm(2)] sham: 3.68 + or - 0.66, C: 3.44 + or - 0.42, E: 3.69 + or - 0.58, ALN: 3.06 + or - 0.56). Osteoporotic metaphyseal fracture healing was qualitatively and quantitatively improved by E prophylaxis. The process of fracture healing occurred nearly physiologically (shamlike). Notably, ALN hardly improved metaphyseal callus properties when assessed as osteoporosis prophylaxis, but to a lesser extent than E.

Effects of low-magnitude, high-frequency mechanical stimulation in the rat osteopenia model

SUMMARY

In this study, short-term, whole-body vertical vibration at 90 Hz improved trabecular bone quality. There was an improvement of bone quality and density in both osteoporotic and control rats. This treatment may therefore be an attractive option for the treatment of osteoporosis.

INTRODUCTION

Aside from pharmacological treatment options, physical exercise is known to augment bone mass. In this study, the effects of whole-body vertical vibration (WBVV) on bone quality and density were evaluated using an osteoporotic rat model.

METHODS

Sixty female Sprague Dawley rats were ovariectomized (C) or sham (SHAM) operated at the age of 3 months. After 3 months, both groups were divided into two subgroups that received either WBVV at 90 Hz for 35 days or no treatment. After sacrificing the rats, we evaluated vertebral bone strength, histomorphometric parameters, and bone mineral density (BMD).

RESULTS

Treatment with WBVV resulted in improved biomechanical properties. The yield load after WBVV was significantly enhanced. According to yield load and Young's modulus, the treated OVX rats reached the level of the untreated SHAM animals. In all measured histomorphometric parameters, WBVV significantly improved bone density. Treatment with WBVV demonstrated greater effects on the trabecular bone compared to the cortical bone. The ash-BMD index showed significant differences between treated and untreated rats.

CONCLUSION

Using WBVV as a non-pharmacological supportive treatment option for osteoporosis demonstrated an enhancement of bone strength and bone mass. This procedure may be an attractive option for the treatment of osteoporosis.

Du-Zhong (Eucommia ulmoides Oliv.) cortex extract prevent OVX-induced osteoporosis in rats

Du-Zhong, rich in polyphenolic compounds such as lignans, phenolic acid, and flavonoids, is a kidney-tonifying herbal medicine with a long history of safe use for treatment of bone fractures and joint diseases in China. In the present study, we examined whether Du-Zhong cortex extract (DZCE) with graded doses exerted its preventive effects on estrogen deficiency-induced osteoporosis. Eighty 3-month-old female Sprague-Dawley rats were used and randomly assigned into sham-operated group (Sham) and five ovariectomy (OVX) subgroups, i.e. OVX with vehicle (OVX); OVX with 17alpha-ethinylestradiol (E(2), 25 microg/kg/day); OVX with DZCE of graded doses (100, 300, or 500 mg/kg/day). Daily oral administration of DZCE or E(2) started on week 4 after OVX for 16 weeks. Treatment with DZCE at higher doses (300 or 500 mg/kg/day) was found to be able to significantly prevent OVX-induced decrease in biomechanical quality of femur such as maximum stress and Young's modulus. The mechanical changes were associated with the prevention of a further bone mineral density (BMD) decrease or even with some improvements in microarchitecture. DZCE dose-dependently inhibited total BMD decrease in the femur caused by OVX, which was accompanied by a significant decrease in skeletal remodeling, as was evidenced by the decreased levels of the bone turnover markers osteocalcin (OC), alkaline phosphatese (ALP), deoxypyridinoline (DPD), and urinary Ca and P excretions. muCT analysis of the femoral metaphysis showed that DZCE at the highest doses (500 mg/kg/day) significantly prevents decrease in bone volume/tissue volume (BV/TV), connect density (Conn.D), trabecula number (Tb.N) and trabecula thickness (Tb.Th), and increase in trabecula separation (Tb.Sp) and structure model index (SMI) in OVX rats. We conclude that 16 weeks of DZCE treatment improves bone biomechanical quality through modifications of BMD, and trabecular microarchitecture without hyperplastic effect on uterus, and it might be a potential alternative medicine for treatment of postmenopausal osteoporosis.

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.

Vitex agnus castus as prophylaxis for osteopenia after orchidectomy in rats compared with estradiol and testosterone supplementation

Osteoporosis research undertaken in males is rare and there are only a few therapeutic options. Phytoestrogens might be a safe alternative for prophylaxis. Sixty 3-month-old male rats were orchidectomized and divided into five groups. The groups either received soy-free food (C), estradiol (E), testosterone (T) or Vitex agnus castus in different concentrations (AC high/AC low) for 12 weeks. The tibia metaphysis was tested biomechanically and histomorphometrically. The AC high group reached 87% of the biomechanical values of the estradiol group and was significantly superior to the control group. Testosterone supplementation resulted in poor biomechanical properties. The cortical bone parameters of the AC group were similar to the control group, while supplementation with estradiol and testosterone demonstrated a reduction of cortical bone. The AC high group reached 88.4% of trabecular bone area, 80.7% of trabecular number and 66.9% of the number of trabecular nodes compared with estradiol supplementation. Vitex agnus castus demonstrated osteoprotective effects in males. It preserves the cortical as well as the trabecular bone and might be a safe alternative for HRT. Testosterone supplementation has positive effects on trabecular bone, which are concurrently counteracted by the loss of cortical bone.

Effect of testosterone, raloxifene and estrogen replacement on the microstructure and biomechanics of metaphyseal osteoporotic bones in orchiectomized male rats

Introduction

Currently, osteoporosis research is rarely undertaken in males but an increase in male life expectancy in the company of hypogonadism suggests the necessity for potential therapeutic options.

Materials and methods

In this study, the changes in bone structure under standardized testosterone- (T), raloxifene- (R) and estrogen (E)-supplemented diets were analyzed in osteoporotic castrated male rats.

Results

Unexpected biomechanical results could be only explained by the histomorphometry, but not by BMD measurements obtained from the qCT. All tested substances showed a significant improvement in the trabecular network (trabecular bone area for C: 2.55 mm², T: 4.25 mm², R: 4.22 mm² and E: 4.28 mm²), and suggests that the bone structure was preserved. For the metaphyseal cortical bone, a significant loss was detected in T (CBP: 18.7%) compared to R (CBP: 30.0%), E (CBP: 26.8%) and even to the osteoporotic control (CBP: 28.6%). This explains the observed early mechanical final failure after T supplementation. However, due to the preserved trabecular bone in T, the occurrence of the first microfractures (yL: 49 ± 21.4 N) was significantly later than in the osteoporotic control (yL: 39.5 ± 15.5 N). Raloxifene performed well in hindering the bone loss associated with osteoporosis. However, its effect (yL: 83.3 ± 16.5 N) did not approach the protective effect of E (yL: 99.2 ± 21.1 N).

Conclusion

Testosterone only preserved the deterioration of the trabecular bone but not of the cortical bone. Raloxifene prevented the bone loss associated with osteoporosis at all bony structures. This effect did not approach the protective effect of estrogen on trabecular bone, but it is more suitable for male individuals because it has no feminizing effects on the subject.

Validation of the sheep as a large animal model for the study of vertebral osteoporosis

Rats have long been the animal of choice for research in the field of osteoporosis. In the search for a complementary large animal model the sheep appears useful but hitherto the extent of bone loss from the spine has failed to reach a level that is generally accepted as osteoporotic in humans. Osteoporosis was induced in ten sheep using ovariectomy, low calcium diet and steroid injection for 6 months. Bone samples of iliac crest (IC), lumbar spine (LS), and proximal femur (PF) from the osteoporotic sheep were compared with those from four normal sheep using densitometry, histomorphometry, biochemistry and basic mechanical testing. The differences were examined using an analysis of variance with Tukey-Kramer test. Overall, the bone mineral density at LS and PF decreased more than 25% after treatment. Trabecular bone volume decreased by 29.2, 33.4 and 42.6% in IC, LS and PF, respectively. The failure load of the LS in axial compression was reduced to 2,003 from 6,140 N. The extent of bone loss was sufficient to categorise these sheep as osteoporotic although the pattern of bone loss varied between sites. Reduced mechanical competence in LS confirmed the suitability of this model for evaluation of potential treatments for osteoporosis.