Improvement of Femoral Bone Quality After Low-Magnitude,High-Frequency Mechanical Stimulation in the Ovariectomized Rat as an Osteopenia Model

The treatment and prevention of osteoporosis involve great challenges. Nonpharmacological and supportive therapy procedures, sport, and physical exercises seem to prevent bone loss and improve bone mass. In the present study, we examined the effect of whole-body vertical vibration (WBVV) on femoral intertrochanteric bone quality in the rat osteoporosis model. Sixty female Sprague–Dawley rats, 3-month old, were ovariectomized (OVX) or sham-operated. After 3 months, each group was divided into two subgroups. In one of the subgroups, rats were treated with WBVV at 90 Hz (3.9 g) for 35 days; the second subgroup remained untreated. After killing the animals, biomechanical strength and trabecular bone architecture of the proximal region of femurs were analyzed. New cortical bone appositions and mineral density of femurs were additionally measured. Treatment with WBVV resulted in improved biomechanical properties. Maximal load and stiffness of the intertrochanteric region of femurs after WBVV were significantly enhanced. Maximal load and stiffness in treated OVX animals reached the levels observed in untreated sham rats. WBVV significantly improved all measured histomorphometric parameters in the trabecular area. Treated rats showed significantly improved mineral content in ashed femurs compared to untreated animals. A comparison of widths of fluorescence bands in cortical bone of subtrochanteric cross sections did not show any significant differences between the groups after WBVV. Low-magnitude, high-frequency mechanical stimulation improves bone strength in the proximal femur and may be a possible nonpharmacologic treatment option for postmenopausal osteoporosis.     

Long-term minodronic acid (ONO-5920/YM529) treatment suppresses increased bone turnover, plus prevents reduction in bone mass and bone strength in ovariectomized rats with established osteopenia

The present study examined the effect of the highly potent nitrogen-containing bisphosphonate, minodronic acid (ONO-5920/YM529), on bone mineral density (BMD), bone turnover, bone histomorphometry and bone strength in ovariectomized (OVX) rats. Female F344/DuCrj rats, aged 14 weeks, were OVX or sham operated. After 3 months, the OVX rats showed an increase in bone turnover, and a decrease in bone mass and bone strength. Minodronic acid was administered orally once a day for 12 months at doses of 0, 0.006, 0.03 and 0.15 mg/kg from 3 months after OVX. Minodronic acid dose-dependently inhibited the decrease in BMD of lumbar vertebrae and femur. In the femur, treatment with 0.15 mg/kg minodronic acid increased the BMD of distal and mid sites to sham levels. Minodronic acid dose-dependently suppressed OVX-induced increase in urinary deoxypyridinoline, a bone resorption marker, after a month of treatment and these effects were maintained for 12 months of treatment. Minodronic acid also decreased serum osteocalcin, a bone formation marker. In bone histomorphometric analysis after 12 months of treatment, OVX rats showed an increase in bone resorption (Oc.S/BS and N.Oc/BS) and bone formation (MS/BS and BFR/BV) at lumbar vertebral bodies. Minodronic acid suppressed the OVX-induced increase in bone turnover at tissue level. Trabecular bone volume, trabecular thickness and trabecular number of lumbar vertebral bodies were decreased after OVX. Minodronic acid increased these structural indices, indicating that it prevented the deterioration in trabecular architecture. In a mechanical test at 12 months of treatment, ultimate load of lumbar vertebral bodies and mid femur in the OVX-control group was decreased compared to the sham group. Minodronic acid prevented the reduction in bone strength at both sites. In particular, in the mid femur, treatment with 0.03 and 0.15 mg/kg minodronic acid increased bone strength to sham levels or greater. In conclusion, minodronic acid suppressed increased bone turnover, plus prevented the decrease in BMD, deterioration of bone microarchitecture and reduction in bone strength in OVX rats with established osteopenia. These results suggest that minodronic acid may be clinically useful for treatment of osteoporosis.     

Sclerostin antibody prevented progressive bone loss in combined ovariectomized and concurrent functional disuse

Osteoporosis is characterized by low bone mass and compromised trabecular architecture, and is commonly occurred in post-menopausal women with estrogen deficiency. In addition, prolonged mechanical unloading, i.e., long term bed rest, can exaggerate the bone loss. Sclerostin is a Wnt signaling antagonist and acts as a negative regulator for bone formation. A sclerostin-neutralizing antibody (Scl-Ab) increased bone mineral density in women with postmenopausal osteoporosis and healthy men. The objective of this study was to characterize the condition of bone loss in ovariectomized (OVX) rats with concurrent mechanical unloading and evaluate the effect of sclerostin antibody treatment in mitigating the prospective severe bone loss conditions in this model. Four-month-old OVX- or sham-operated female SD rats were used in this study. They were subjected to functional disuse induced by hind-limb suspension (HLS) or free ambulance after 2 days of arrival. Subcutaneous injections with either vehicle or Scl-Ab at 25 mg/kg were made twice per week for 5 weeks from the time of HLS. μCT analyses demonstrated a significant decrease in distal metaphyseal trabecular architecture integrity with HLS, OVX and HLS + OVX (bone volume fraction decreased by 29%, 71% and 87% respectively). The significant improvements of various trabecular bone parameters (bone volume fraction increased by 111%, 229% and 297% respectively as compared with placebo group) with the administration of Scl-Ab are associated with stronger mechanical property and increased bone formation by histomorphometry. These results together indicate that Scl-Ab prevented the loss of trabecular bone mass and cortical bone strength in OVX rat model with concurrent mechanical unloading. The data suggested that monoclonal sclerostin-neutralizing antibody represents a promising therapeutic approach for severe osteoporosis induced by estrogen deficiency with concurrent mechanical unloading.     

A nonprostanoid EP4 receptor selective prostaglandin E2 agonist restores bone mass and strength in aged, ovariectomized rats.

CP432 is a newly discovered, nonprostanoid EP4 receptor selective prostaglandin E2 agonist. CP432 stimulates trabecular and cortical bone formation and restores bone mass and bone strength in aged ovariectomized rats with established osteopenia. INTRODUCTION: The purpose of this study was to determine whether a newly discovered, nonprostanoid EP4 receptor selective prostaglandin E2 (PGE2) agonist, CP432, could produce bone anabolic effects in aged, ovariectomized (OVX) rats with established osteopenia. MATERIALS AND METHODS: CP432 at 0.3, 1, or 3 mg/kg/day was given for 6 weeks by subcutaneous injection to 12-month-old rats that had been OVX for 8.5 months. The effects on bone mass, bone formation, bone resorption, and bone strength were determined. RESULTS: Total femoral BMD increased significantly in OVX rats treated with CP432 at all doses. CP432 completely restored trabecular bone volume of the third lumbar vertebral body accompanied with a dose-dependent decrease in osteoclast number and osteoclast surface and a dose-dependent increase in mineralizing surface, mineral apposition rate, and bone formation rate-tissue reference in OVX rats. CP432 at 1 and 3 mg/kg/day significantly increased total tissue area, cortical bone area, and periosteal and endocortical bone formation in the tibial shafts compared with both sham and OVX controls. CP432 at all doses significantly and dose-dependently increased ultimate strength in the fifth lumber vertebral body compared with both sham and OVX controls. At 1 and 3 mg/kg/day, CP432 significantly increased maximal load in a three-point bending test of femoral shaft compared with both sham and OVX controls. CONCLUSIONS: CP432 completely restored trabecular and cortical bone mass and strength in established osteopenic, aged OVX rats by stimulating bone formation and inhibiting bone resorption on trabecular and cortical surfaces.     

Effects of h-PTH on cancellous bone mass, connectivity, and bone strength in ovariectomized rats with and without sciatic-neurectomy.

The purpose of this study was to determine whether h-PTH (1-34) treatment would recover cancellous bone connectivity and bone strength in ovariectomized (OVX) or ovariectomized and sciatic-neurectomized (OVX+NX) rats. Seven-month-old female Wistar rats were treated with h-PTH or vehicle (6.0 microg/kg, six times a week, subcutaneously) for four weeks beginning 4, 8, or 12 weeks after OVX or OVX+NX. These were compared to age-matched baseline and sham-operated groups. Right tibiae were used for bone histomorphometry and node-strut analysis, and left tibiae were used for mechanical testing. The bone formation rates in the OVX and OVX+NX rats treated with h-PTH were significantly higher than those in their baseline controls. h-PTH treatment increased the node numbers and failure energies in the OVX rats, compared to their baseline controls, at all time points. However, in the OVX+NX rats, the effects of h-PTH treatment on the node number and failure energy were observed only at four weeks after surgery, but not at eight weeks or 12 weeks after surgery. These results suggest that the lowest limit, at which trabecular connectivity and bone strength are able to be restored by h-PTH, occurred between four and eight weeks in OVX+NX rats, but not in OVX rats. h-PTH cannot recover trabecular connectivity and bone strength in advanced osteopenia.     

Risedronate preserves trabecular architecture and increases bone strength in vertebra of ovariectomized minipigs as measured by three-dimensional microcomputed tomography.

Risedronate reduces the risk of new vertebral fractures up to 70% within 1 year of treatment in patients with osteoporosis. Both increases in bone mass and preservation of bone architecture are thought to contribute to antifracture effects. Our objectives were to determine the effects of risedronate on trabecular bone mass and architecture and to determine the relative contributions of mass and architecture to strength in the vertebra of ovariectomized (OVX) minipigs. The minipigs were OVX at 18 months of age and were treated daily for 18 months with either vehicle or risedronate at doses of 0.5 mg/kg per day or 2.5 mg/kg per day. The three-dimensional (3D) bone architecture of the L4 vertebral cores of Sinclair S1 minipigs was evaluated by 3D microcomputed tomography (muCT). Compared with the OVX control, the vertebral bone volume (bone volume/tissue volume [BV/TV]) was higher in both treated groups (p < 0.05). The architectural changes were more significant at the 2.5-mg/kg dose and were more prevalent at the cranial-caudal ends compared with the midsection. At the higher dose, the trabecular thickness (Tb.Th), trabecular number (Tb.N), and connectivity were higher, and marrow star volume (Ma.St.V) and trabecular separation (Tb.Sp) were lower (p < 0.05). The trabecular separation variation index (TSVI), a new measure to approximate structural variations, was smaller in the 2.5-mg/kg-treated group (p < 0.05). In this group, a significant preservation of trabeculae orthogonal to the cranial-caudal axis was confirmed by a decrease in the degree of anisotropy (DA) and an increase in the percent Cross-strut (% Cross-strut; p < 0.05). Both normalized maximum load (strength) and normalized stiffness of the same vertebral cores were higher in the 2.5-mg/kg risedronate group compared with the OVX group (p < 0.05). BV/TV alone could explain 76% of the variability of the bone strength. The combination of bone volume and architectural variables explained >90% of the strength. The study showed that risedronate preserved trabecular architecture in the vertebra of OVX minipigs, and that bone strength is tightly coupled to bone mass and architecture.     

Recovery of proximal tibia bone mineral density and strength, but not cancellous bone architecture, after long-term bisphosphonate or selective estrogen receptor modulator therapy in aged rats.

Various bisphosphonates and the selective estrogen receptor modulator (SERM) raloxifene are approved treatments of postmenopausal osteoporosis. They increase bone mineral density (BMD), decrease bone turnover, and reduce vertebral fracture incidence through different cellular mechanisms. We investigated the bone cellular activities, architecture, mineral content/density, and strength of ovariectomized (ovx) rats on a long-term bisphosphonate or SERM treatment, at doses of either agent correcting bone strength. Eleven weeks postovariectomy, 6-month-old rats were treated with the SERM MDL 103,323 or with the bisphosphonate pamidronate for 5 months. Doses of pamidronate and MDL 103,323 were selected from previous studies showing correction of the ovx-induced decrease of ultimate strength of proximal tibia. Ultimate and yield strengths, BMD, and histomorphometric parameters were all quantified at the same site, i.e., the proximal tibia metaphysis. Long-term pamidronate decreases bone turnover and bone formation activity, leading to trabecular thinning. MDL 103,323 decreases bone turnover to a lesser extent, and slightly protects trabecular architecture by uncoupling bone resorption and formation activities. The yield strength is corrected by pamidronate, but not by MDL 103,323 treatment. However, neither compound restores the ovariectomy-induced cancellous bone loss. Total tissue area and cortical thickness are unchanged with pamidronate or MDL 103,323 treatment, indicating that cortical bone mass, thickness, and cross-sectional area are not modified. The discrepancy between proximal tibia BMD and mechanical resistance to fracture modifications, on the one hand, and cancellous bone volume, on the other hand, could be due to changes in the degree of mineralization of bone matrix and/or of the intrinsic properties of the bone matrix.     

Both hPTH(1-34) and bFGF increase trabecular bone mass in osteopenic rats but they have different effects on trabecular bone architecture.

Osteoporosis is a syndrome of excessive skeletal fragility that results from both the loss of trabecular bone mass and trabecular bone connectivity. Recently, bFGF has been found to increase trabecular bone mass in osteoporotic rats. The purpose of this study was to compare how trabecular bone architecture, bone cell activity, and strength are altered by two different bone anabolic agents, bFGF and hPTH(1-34), in an osteopenic rat model. MATERIALS AND METHODS: Six-month-old female Sprague-Dawley rats (n = 74) were ovariectomized (OVX) or sham-operated (sham) and maintained untreated for 2 months. Then OVX rats were subcutaneously injected with basic fibroblast factor (bFGF; 1 mg/kg, 5 days/week), human parathyroid hormone [hPTH(1-34); 40 microg/kg, 5 days/week], or vehicle for 60 days (days 60-120). Sham-operated and one group of OVX animals were injected with vehicle. Biochemical markers of bone turnover (urinary deoxypyridinoline cross-links; Quidel Corp., San Diego, CA, USA) and serum osteocalcin (Biomedical Technologies, Stroughton, MA, USA) were obtained at study days 0, 60, 90, and 120 and analyzed by ELISA. At death, the right proximal tibial metaphysis was removed, and microcomputed tomography was performed for trabecular bone structure and processed for histomorphometry to assess bone cell activity. The left proximal tibia was used for nanoindentation/mechanical testing of individual trabeculae. The data were analyzed with Kruskal Wallis and post hoc testing as needed. RESULTS: Ovariectomy at day 60 resulted in about a 50% loss of trabecular bone volume compared with sham-treated animals. By day 120 post-OVX, OVX + vehicle treated animals had decreased trabecular bone volume, connectivity, number, and high bone turnover compared with sham-operated animals [p < 0.05 from sham-, hPTH(1-34)-, and bFGF-treated groups]. Treatment of OVX animals with bFGF and hPTH(1-34) both increased trabecular bone mass, but hPTH(1-34) increased trabecular thickness and bFGF increased trabecular number and connectivity. Histomorphometry revealed increased mineralizing surface and bone formation rate in both bFGF and hPTH(1-34) animals. However, osteoid volume was greater in bFGF-treated animals compared with both the hPTH(1-34) and OVX + vehicle animals (p < 0.05). Nanoindentation by atomic force microscope was performed on approximately 20 individual trabeculae per animal (three animals per group) and demonstrated that elastic modulus and hardness of the trabeculae in bFGF-treated animals were similar to that of the hPTH-treated and sham + vehicle-treated animals. CONCLUSION: Both hPTH(1-34) and bFGF are anabolic agents in the osteopenic female rat. However, hPTH(1-34) increases trabecular bone volume primarily by thickening existing trabeculae, whereas bFGF adds trabecular bone mass through increasing trabecular number and trabecular connectivity. These results suggest the possibility of sequential treatment paradigms for severe osteoporosis.     

Effect of Estrogen Deficiency on Cancellous and Cortical Bone Structure and Strength of the Femoral Neck in Rats

Eighty mature Sprague-Dawley rats were weight matched before ovariectomy (Ovx) or Sham surgery (Sham). Sham rats had free access to food and water throughout the experiment, whereas Ovx rats were kept on the pair-fed diet. Rats were euthanized at 4, 8, and 12 weeks after surgery, and had received fluorochrome bone markers at 9 and 2 days prior to euthanasia. In addition 10 rats were euthanized at the time of surgery serving as baseline controls. All rats were also scanned for body composition and bone mineral parameters by DEXA before surgery and euthanasia. Left proximal femurs (femoral necks) were used for bone histomorphometry, whereas right femurs were used for in vitro DEXA measurements and mechanical testing. Despite pair-feeding, ovariectomized rats had increased body weights and fat body mass, whereas the percent lean body mass steadily declined throughout the experiment. Mineral density of the whole femur and femoral neck was significantly higher in the Sham rats relative to Ovx animals. Ovariectomy reduced trabecular number and thickness, and increased trabecular separation and bone marrow space at the femoral midneck location. The structure of the remaining trabeculae was dramatically changed toward simpler struts as revealed by nodal analyses. Cortical thickness in Ovx rats was reduced because of the high endocortical resorption, which, in addition to cancellous bone resorption, resulted in fewer endocortico-trabecular connections. Femoral necks obtained from ovariectomized rats had reduced strength and were less stiff relative to controls. Because of the enormous clinical significance of the proximal femur for osteoporosis in humans, and the opportunity for studying bone BMD, mass, structure, and strength at the same skeletal location, the femoral neck appears superior to other skeletal sites routinely used for bone histomorphometry or mechanical testing in the Ovx rat model. Received: 25 September 1996 / Accepted: 24 March 1997     

硬化蛋白抗体和跑台运动对老龄去势大鼠骨重建的影响

目的探讨硬化蛋白抗体和跑台运动对老龄去势大鼠骨重建的影响。方法 8月龄雌性Wistar大鼠,按体质量随机分层分为5组:Sham组(假手术组)、OVX组(去卵巢组)、OVX+E组(去卵巢+运动组)、OVX+S组(去卵巢+硬化蛋白抗体组)、OVX+E+S组(去卵巢+运动+硬化蛋白抗体组)。在14w后取材进行相关指标测试。结果 1单纯性的运动锻炼能降低脂肪量,增加骨小梁数目,减少骨吸收标记物NTx水平,防止老龄去势大鼠全身、股骨骨密度发生下降。2单纯性的硬化蛋白抗体治疗能增加骨形成标志物OC,提高去势大鼠的皮质孔隙率、皮质骨体积和皮质骨厚度,提高骨密度。3运动与硬化蛋白抗体交互作用时,可以降低脂肪量,提高骨密度和皮质骨参数,增加骨量和骨强度,提高OC水平、降低NTx水平。结论适度的跑台运动可以防止老龄去势大鼠骨量丢失,改善去势大鼠骨健康。硬化蛋白抗体疗法可以增加皮质骨骨量和骨强度,预防去势大鼠绝经后对骨代谢的不良影响。硬化蛋白和运动表现出良好的协同作用,对老龄去势大鼠骨重建具有积极的作用。     

Effects of Treatment with Parathyroid Hormone 1–84 on Quantity and Biomechanical Properties of Thoracic Vertebral Trabecular Bone in Ovariectomized Rhesus Monkeys

Osteoporosis is characterized by impaired bone quality leading to increased susceptibility to fracture, particularly of the thoracic spine. However, the lumbar spine is studied most commonly. We investigated the effects of 16 months of treatment with full-length parathyroid hormone (PTH) 1–84 (5, 10, or 25 μg/kg) on bone mineral density (BMD) and on architecture and biomechanical properties of trabecular bone at the thoracic spine of ovariectomized (OVX) adult rhesus monkeys and compared the results with those from the lumbar spine. At baseline, 9 months after surgery, dual-energy X-ray absorptiometric BMD at T9–T12 was 7% lower in OVX than in sham animals. All PTH(1–84) doses increased BMD to sham levels within 7 months. Micro-computed tomography of T10 vertebrae showed that trabecular bone volume and connectivity were higher in PTH(1–84)-treated animals than in sham controls, primarily through a significantly greater trabecular number. Peripheral quantitative computed tomography of trabecular bone cores from T11 and T12 confirmed that PTH(1–84) increased BMD. Compression testing of the cores showed that PTH(1–84) treatment increased stiffness, modulus, yield load, and yield stress to levels significantly greater than in sham animals, with the largest effect in the 10 μg/kg group (35–54% greater than in OVX controls). Thus, PTH(1–84) treatment increased BMD and the biomechanical properties of trabecular bone at the thoracic spine of OVX rhesus monkeys. The 10 μg/kg dose produced the greatest effect on trabecular strength, possibly because the highest dose stimulated bone remodeling excessively. Importantly, the changes observed were similar to those in lumbar vertebrae, thereby validating extrapolation of results from the lumbar to the thoracic spine.     

Glucocorticoid-treated mice have localized changes in trabecular bone material properties and osteocyte lacunar size that are not observed in placebo-treated or estrogen-deficient mice.

This study compares changes in bone microstructure in 6-month-old male GC-treated and female ovariectomized mice to their respective controls. In addition to a reduction in trabecular bone volume, GC treatment reduced bone mineral and elastic modulus of bone adjacent to osteocytes that was not observed in control mice nor estrogen-deficient mice. These microstructural changes in combination with the macrostructural changes could amplify the bone fragility in this metabolic bone disease. INTRODUCTION: Patients with glucocorticoid (GC)-induced secondary osteoporosis tend to fracture at higher bone mineral densities than patients with postmenopausal osteoporosis. This suggests that GCs may alter bone material properties in addition to BMD and bone macrostructure. MATERIALS AND METHODS: Changes in trabecular bone structure, elastic modulus, and mineral to matrix ratio of the fifth lumbar vertebrae was assessed in prednisolone-treated mice and placebo-treated controls for comparison with estrogen-deficient mice and sham-operated controls. Compression testing of the third lumbar vertebrae was performed to assess whole bone strength. RESULTS: Significant reductions in trabecular bone volume and whole bone strength occurred in both prednisolone-treated and estrogen-deficient mice compared with controls after 21 days (p < 0.05). The average elastic modulus over the entire surface of each trabecula was similar in all the experimental groups. However, localized changes within the trabeculae in areas surrounding the osteocyte lacunae were observed only in the prednisolone-treated mice. The size of the osteocyte lacunae was increased, reduced elastic modulus around the lacunae was observed, and a "halo" of hypomineralized bone surrounding the lacunae was observed. This was associated with reduced (nearly 40%) mineral to matrix ratio determined by Raman microspectroscopy. These localized changes in elastic modulus and bone mineral to matrix ratio were not observed in the other three experimental groups. CONCLUSIONS: Based on these results, it seems that GCs may have direct effects on osteocytes, resulting in a modification of their microenvironment. These changes, including an enlargement of their lacunar space and the generation of a surrounding sphere of hypomineralized bone, seem to produce highly localized changes in bone material properties that may influence fracture risk.     

Effects of a prostaglandin EP4 agonist, ONO-4819, and risedronate on trabecular microstructure and bone strength in mature ovariectomized rats

The effects of a prostaglandin EP4 agonist, ONO-4819, and risedronate, a representative anti-resorptive drug, on trabecular microarchitecture and biomechanical properties were investigated in mature estrogen-deficient rats; and effects which affected microstructural components that contributed to the improvement of bone strength were also determined. Thirty-three-week-old OVX rats were treated with various doses of ONO-4819, risedronate, or their combination for 11 weeks. Bone mineral density (BMD), trabecular microstructure, and biomechanical strength were determined at the proximal tibia by peripheral quantitative CT, micro CT, and finite element analysis, respectively. Bone histomorphometry was performed at the same site. The results of trabecular structure analysis indicated that whereas risedronate functioned mainly in maintaining trabecular connectivity, ONO-4819 converted the fragile rod-like trabeculae caused by estrogen deficiency to a plate-like structure. In addition, ONO-4819 is one of the few drugs that are capable of increasing trabecular thickness. When the 2 drugs were combined, the beneficial effects of each drug on the trabecular microarchitecture were maintained, resulting in their additive effects on bone strength. The results of bone histomorphometry suggest that ONO-4819 caused an increase in the rate of bone formation by stimulating the differentiation/recruitment of osteoblasts as well as their mineralizing function. ONO-4819 did not stimulate bone resorption, but rather exerted an anti-resorptive function within a certain dose range. ONO-4819 and risedronate increased BMD and improved trabecular structure and biomechanical strength in an additive and independent manner. Thus, EP4 agonist ONO-4819 in combination with risedronate may be an effective treatment for osteoporosis.     

双侧卵巢切除山羊不同时间段骨形态计量学与骨密度的变化

采用骨病理形态学、骨计量学与骨密度测定法,动态观察了山羊假手术组（Ｓｈａｍ）和双侧卵巢切除组（ＯＶＸ）术前、术后３月、６月、１２月和１８月各不同时间段髂骨骨病理形态学、骨小梁体积百分比（Ｖｖ％）,骨小梁宽度和腰椎（Ｌ２－Ｌ４）骨密度的变化。结果显示：Ｓｈａｍ组术后各时间段髂骨骨病理形态学、骨小梁体积百分比和骨小当宽度无明显变化（Ｐ〉０．０５）。Ｌ２￣Ｌ４骨密度呈缓慢上升趋势,至术后１８月比术前增高     

A physical, chemical, and mechanical study of lumbar vertebrae from normal, ovariectomized, and nandrolone decanoate-treated cynomolgus monkeys (Macaca fascicularis)

Ovariectomized cynomolgus monkeys have previously been investigated as a nonhuman primate model of postmenopausal osteoporosis (Jerome et al., Bone Miner 9:527-540; 1994). In the present study, Fourier transform infrared microspectroscopy (FTIRM) was used to verify that differences in bone mineral quality and quantity in the vertebrae of mature intact (INT) and ovariectomized (ovx) monkeys were analogous to those seen in osteoporotic and nondiseased human bones. FTIRM spectra were acquired from 15 trabeculae per vertebra from three ovx and three INT adult monkeys (mean age 8 years). These spectra were compared with those of both trabecular and previously reported osteonal bone obtained from 3 "normal" and 11 postmenopausal osteoporotic human subjects. While variations in the mineral:matrix ratio (mineral content), carbonate:phosphate ratio, and crystallinity are typical for trabecular bone from iliac crests of normal human subjects, the values of these parameters were relatively static for trabecular bone from postmenopausal osteoporotic human subjects. In general, trabecular bone from postmenopausal osteoporotic human subjects exhibited decreased mineral content (1.0 +/- 0.5 vs. 2.9 +/- 0.6), increased crystallinity, and increased carbonate:phosphate relative to controls. Similarly, trabecular bone from ovariectomized monkeys exhibited lower mineral content (5.8 +/- 0.2) compared with the INT group (6.2 +/- 0.2; p 相似文献   

Osteoprotective effect of propranolol in ovariectomized rats: a comparison with zoledronic acid and alfacalcidol

Background

Currently β-adrenergic receptor blockers are considered to be potential drugs under investigation for preventive or therapeutic effect in osteoporosis. However, there is no published data showing the comparative study of β-blockers with well accepted agents for the treatment of osteoporosis. To address this question, we compared the effects of propranolol with well accepted treatments like zoledronic acid and alfacalcidol in an animal model of postmenopausal osteoporosis.

Methods

Five days after ovariectomy, 36 ovariectomized (OVX) rats were divided into 6 equal groups, randomized to treatments zoledronic acid (100 μg/kg, intravenous single dose); alfacalcidol (0.5 μg/kg, oral gauge daily); propranolol (0.1 mg/kg, subcutaneously 5 days per week) for 12 weeks. Untreated OVX and sham OVX were used as controls. At the end of treatment serum calcium and alkaline phosphatase were assayed. Femurs were removed and tested for bone density, bone porosity, bone mechanical properties and trabecular micro-architecture.

Results

Propranolol showed a significant decrease in alkaline phosphatase levels and bone porosity in comparison to OVX control. Moreover, propranolol significantly improved bone density, bone mechanical properties and inhibited the deterioration of trabecular microarchitecture when compared with OVX control. The osteoprotective effect of propranolol was comparable with zoledronic acid and alfacalcidol.

Conclusions

Based on this comparative study, the results strongly suggest that propranolol can be a candidate therapeutic drug for the management of postmenopausal osteoporosis.     

骨质疏松大鼠股骨内单次注射辛伐他汀强化骨骼的实验研究

 目的 研究骨质疏松骨骼局部注射辛伐他汀刺激成骨的效果, 探索疏松骨骼局部给药预 防脆性骨折的治疗方法。 方法36 只3 月龄雌性SD 大鼠双侧卵巢切除后加低钙饮食3个月, 制备大鼠 骨质疏松模型。实验大鼠随机分为3 组, 每组12 只, 分别在实验大鼠的左侧股骨髓腔内单次注射辛伐 他汀溶液5 mg、10 mg, 对照组单纯注射空白载体。分别在术后1 个月及术后5 个月每组随机处死半数 大鼠(n=6)并取材。双能X 线骨密度仪测定骨密度、Micro-CT扫描并定量分析骨组织形态改变、骨生物 力学测试研究骨骼力学性能的变化。 结果 辛伐他汀局部注射后1 个月和5 个月, 辛伐他汀注射组的 骨密度、骨微结构参数如骨皮质厚度、骨小梁密度及连接率明显优于对照组, 股骨髁及股骨颈的力学性 能明显高于对照组。单次注射辛伐他汀的局部骨强化效果至少持续5 个月, 对照组骨量则持续丢失, 力 学性能持续降低。 结论 疏松骨骼单次注射小剂量辛伐他汀可强效而持久地促进皮质骨形成及骨小梁 改建, 改善骨骼微结构, 增加骨密度及骨强度, 可作为强化局部、防治骨质疏松骨折的新选择。     

A comparison of alfacalcidol and menatetrenone for the treatment of bone loss in an ovariectomized rat model of osteoporosis

We conducted this study to evaluate the characteristic effects of alfacalcidol (ALF) and menatetrenone (VK) in preventing bone loss using an ovariectomized rat model of osteoporosis. Bilateral ovariectomy (OVX) or sham operation was performed on 10-month-old female Wistar rats. OVX caused a significant decrease in the bone mass and the mechanical strength of the lumbar vertebra as well as the femur 6 months after surgery. VK treatment (30 mg/kg, food intake) required a 6-month period to prevent the bone loss induced by estrogen deficiency, whereas ALF (0.1 or 0.2 mg/kg, p.o.) increased the bone mass and the mechanical strength of the lumbar vertebra as well as the femur in a 3-month treatment period, far above the level in the sham-operated rats. Neither ALF or VK caused hypercalcemia, despite administration for as long as 6 months. By doing a micro-CT analysis of the vertebral trabecular microstructure, it was revealed that ALF treatment increased the interconnections and the plate-like structures and that VK significantly increased the trabecular number. It was also indicated that the increase in spinal strength by ALF treatment was closely associated with improvement of the microstructure, but not VK. The results of histomorphometric analysis showed that ALF caused a significant suppression of bone resorption yet maintained formation in the endocortical perimeter, and also stimulated bone formation in the periosteal perimeter, thereby causing an increase in cortical area. No marked effect of VK on histomorphometric parameters was observed, whereas VK as well as ALF maintained the material strength at femoral midshaft of the normal level, suggesting that VK affected bone quality and thereby prevented the decrease in mechanical strength of femur caused by OVX. In conclusion, it was demonstrated that the two drugs, ALF and VK, differed markedly in their potency and mechanisms for improving bone strength. These results have important implications in understanding the characteristic actions of vitamin K and active vitamin D on bone metabolism.     

Additional Weight Bearing during Exercise and Estrogen in the Rat: The Effect on Bone Mass, Turnover, and Structure

Mechanical loading and estrogen play important roles in bone homeostasis. The aim of this study was to evaluate the effects of mechanical loading on trabecular bone in the proximal femur of ovariectomized rats. We hypothesized that mechanical loading suppresses bone resorption and increases bone formation, which differs from the suppressive effects of estrogen on both resorption and formation. Furthermore, we expected to find changes in trabecular architecture elicited by the effects of mechanical loading and estrogen deficiency. Sixty female Wistar rats, 12 weeks old, were assigned to either the sedentary groups sham surgery (SED), ovariectomy (SED+OVX), and ovariectomy with estrogen replacement (SED+OVX+E2) or to the exercise groups EX, EX+OVX, EX+OVX+E2. Following ovariectomy, 5 microg 17beta-estradiol was given once weekly to the estrogen replacement groups. Exercise consisted of running with a backpack (load +/-20% of body weight) for 15 minutes/day, 5 days/week, for 19 weeks. Dual-energy X-ray absorptiometry (DXA) scans were performed before (T0), during (T6), and after (T19) the exercise period to obtain bone mineral content (BMC) and bone mineral density (BMD) data. After the exercise program, all rats were killed and right and left femora were dissected and prepared for micro-CT scanning and histomorphometric analysis of the proximal femoral metaphysis. After 19 weeks, increases in BMC (P = 0.010) and BMD (P = 0.031) were significant. At T19, mechanical loading had a significant effect on BMC (P = 0.025) and BMD (P = 0.010), and an interaction between mechanical loading and estrogen (P = 0.023) was observed. Bone volume and trabecular number decreased significantly after ovariectomy, while trabecular separation, mineralizing surface, bone formation rate, osteoclast surface, degree of anisotropy, and structure model index increased significantly after ovariectomy (P < 0.05). Trabecular bone turnover and structural parameters in the proximal femur were not affected by exercise. Estrogen deficiency resulted in a less dense and more oriented trabecular bone structure with increased marrow cavity and a decreased number of trabeculae. In conclusion, mechanical loading has beneficial effects on BMC and BMD of the ovariectomized rat. This indicates that the load in the backpack was high enough to elicit an osteogenic response sufficient to compensate for the ovariectomy-induced bone loss. The results confirm that estrogen suppresses both bone resorption and bone formation in the proximal metaphysis in the femoral head of our rat-with-backpack model. The effects of mechanical loading on the trabecular bone of the femoral head were not significant. This study suggests that the effect of mechanical loading in the rat-with-backpack model mainly occurs at cortical bone sites.     

Changes in proximal femur bone properties following ovariectomy and their association with resistance to fracture

Bone strength depends on several material and structural properties, but findings concerning the best predictors of bone mechanical performance are conflicting. The aim of this study was to investigate how a broad set of bone properties in the proximal femur are influenced by age and hormonal status, and how these properties together determine bone strength. Twenty-five Wistar rats were ovariectomized (OVX, n = 13) or sham operated (SHAM, n = 12) at 5 months of age, and killed after 9 months. Another group of rats was killed at 5 months as baseline control (BSL, n = 7). At sacrifice, serum 17β-estradiol and bone turnover marker concentrations were determined in the serum. Both femurs were collected for assessment of trabecular microarchitecture, femoral neck geometry, radiographic absorptiometry, calcium and phosphate content, and biomechanical properties. While stiffness was mostly associated with proximal femur trabecular microarchitecture and mineralization degree, bone strength was mostly linked to bone size and femoral neck geometry, which predicted almost 50% of its variance. Despite the decrease in cortical and trabecular bone as well as in mineralization degree following estrogen loss, bone strength was not reduced in OVX animals compared to BSL or sham-operated rats. This was due to a change in femoral neck geometry as well as to an increase in femur size in OVX, which apparently compensated their lower bone volume and mineral content, thereby preserving bone strength. Estrogen loss leads to a deterioration of bone tissue quality, but bone strength was preserved at the expense of geometric adaptations.