Comparison insight dual X-ray absorptiometry (DXA), histomorphometry, ash weight, and morphometric indices for bone evaluation in an animal model (the orchidectomized rat) of male osteoporosis

Assessment of the effect of pulsed electromagnetic field application on the healing of bone defects in rats with heparin-induced osteoporosis

Osteoporosis is a systemic skeletal disease characterized by an increase in bone fragility and fracture risk due to low bone mass and deterioration of bone tissue. Application of pulsed electromagnetic fields (PEMF), a non-invasive method with a low complication risk, is known to stimulate bone formation. The present study examines the histomorphometric and biochemical effects of PEMF application on the healing of bone defects in rats with heparin-induced secondary osteoporosis. Briefly, 12-month-old male Sprague-Dawley rats were examined in a prospective, randomized, single-blind study. Osteoporosis was induced by administering a daily dose of 2 IU/g heparin for 33 days. Bone defects were created on the right femur on Day 35. PEMF of an average intensity of 0.8 ± 0.2 mT and a frequency of 7.3 Hz, was applied for 1 h/day, for 28 days following surgery. Bone healing was evaluated by histomorphometric and biochemical analyses. The heparin + PEMF group displayed the largest amount of new bone area (P = .002) and the lowest mean CTx on Day 63 (P = .05). This study demonstrates that heparin administration leads to bone loss and osteoporosis, whereas the application of PEMF decreases this effect.

The Effects of Chemical Castration with Degarelix on Bone Turnover: Densitometric and Biomechanics Bone Properties of Male Rats

BACKGROUND

Gonadotropin releasing hormone (GnRH) antagonists may cause chemical castration in males by suppressing the pituitary-gonadal axis, hence reducing testosterone level. There are limited data on the effects of degarelix, a newer series of potent and long acting GnRH antagonist on bone.

OBJECTIVES

The current study aimed at determining the effects of degarelix on bone turnover, bone densitometry, and bone mechanical strength in male rats.

METHODS

Eighteen male Sprague-Dawley rats were randomly divided into sham (SHAM), orchidectomized (ORX), and degarelix-induced (DGX) groups. Chemical castration was performed by subcutaneous degarelix injection (2 mg/kg) at the scapular region. The rats were scanned for baseline bone mineral area (BMA), bone mineral content (BMC), and bone mineral density (BMD) using dual-energy x-ray absorptiometry (DXA). Following six weeks of experimental period, BMA, BMC, and BMD were measured again with DXA and blood was collected for testosterone and bone biomarkers (osteocalcin and C-terminal of type I collagen crosslink (CTX-1)) measurements. The rats were euthanized and femora were dissected for bone biomechanical strength analysis.

RESULTS

Bilateral orchidectomy and degarelix administration significantly lowered serum testosterone level, decreased whole body BMC, femoral BMA, femoral BMC, and femoral BMD (P < 0.05) compared with the SHAM group. However, no significant changes were observed in bone biochemical markers and bone mechanical strength in all experimental groups.

CONCLUSIONS

In conclusion, degarelix administration had comparable effects on bone as bilateral orchidectomy. Administration of degarelix provides an alternative method of inducing testosterone deficient-osteopenia in male rats without need for removing the testes.

Dual-energy X-ray absorptiometry, peripheral quantitative computed tomography, and micro-computed tomography techniques are discordant for bone density and geometry measurements in the guinea pig

This study aims to examine agreement among bone mineral content (BMC) and density (BMD) estimates obtained using dual-energy X-ray absorptiometry (DXA), peripheral quantitative computed tomography (pQCT), and micro-computed tomography (μCT) against high-resolution μCT and bone ash of the guinea pig femur. Middle-aged (n = 40, 86 weeks) male guinea pigs underwent in vivo followed by ex vivo DXA (Hologic QDR 4500A) scanning for intact and excised femur BMC and areal density. To assess bone architecture and strength, excised femurs were scanned on pQCT (Stratec XCT 2000L) as well as on two μCT scanners (LaTheta LCT-200; Skyscan 1174), followed by three-point bending test. Reproducibility was determined using triplicate scans; and agreement assessed using Bland-Altman plots with reference methods being high-resolution μCT (Skyscan) for BMD and bone ashing for BMC. All techniques showed satisfactory ex vivo precision (CV 0.05-4.3 %). However, bias compared to the reference method was highest (207.5 %) in trabecular bone volume fraction (BV/TV) measured by LaTheta, and unacceptable in most total femur and cortical bone measurements. Volumetric BMD (vBMD) and BV/TV derived by LaTheta and pQCT at the distal metaphysis were biased from the Skyscan by an average of 49.3 and 207.5 %, respectively. Variability of vBMD, BV/TV and cross-sectional area at the diaphysis ranged from -5.5 to 30.8 %. LaTheta best quantified total femur BMC with an upper bias of 3.3 %. The observed differences among imaging techniques can be attributable to inherent dissimilarity in construction design, calibration, segmentation and scanning resolution used. These bone imaging tools are precise but are not comparable, at least when assessing guinea pig bones.

Osteoarthritic versus osteoporotic bone and intra-skeletal variations in normal bone: evaluation with µCT and bone histomorphometry

Several studies have shown that in contrast to osteoporosis (OP), osteoarthritis (OA) is characterized by high bone mineral density (BMD). Bone strength not only depends on mineral content as determined by dual X-ray absorptiometry (DXA), but also on bone microarchitecture. We studied intertrochanteric bone from normal controls and OA and OP patients by bone histomorphometry (BHM) and microcomputed tomography (µCT) as well as DXA in order to first, test the differences between OA and OP comparing both groups to healthy controls, second, to assess variations between three different skeletal sites in controls and third, to determine the level of agreement between µCT, BHM, and DXA. Analysis was performed on 115 samples from OA and OP patients, and controls. We found significant differences between OA and OP samples in structural parameters and in the osteoid fraction (p < 0.05). The majority of the intra-skeletal differences were shown between lumbar spine and femoral head samples (p < 0.05). Significant agreements were found between µCT and BHM and DXA (r = 0.32-0.45, p < 0.05). Our findings suggest differences in intertrochanteric bone between OA and OP, the age-related intra-skeletal variations and a correlation between microscopic and macroscopic bone evaluation methods.

Trabecular microarchitecture in established osteoporosis: relationship between vertebrae, distal radius and calcaneus by X-ray imaging texture analysis

INTRODUCTION

Osteoporosis is an alteration of bone mass and microarchitecture leading to an increased risk of fractures. A radiograph is a 2D projection of the 3D bone network exposing a texture, that can be assessed by texture analysis. We compared the trabecular microarchitecture of the spine, radius and calcaneus in a series of osteoporotic cadavers.

MATERIALS AND METHODS

Thirty-four cadavers (11 men, 23 women), mean age 85.2±2.1years, were radiographed from T4 to L5 to identify those with vertebral fractures (FV). Non-fractured vertebrae (NFV), radius and calcaneus were taken and analyzed by densitometry, radiography and texture analysis under run-length, skeletonization of the trabeculae, and fractal geometry.

RESULTS

Six subjects (five women, one man) were selected, mean age 82.5±5.5years. Twelve calcanei and 10 radii were taken. Two radii were excluded. The texture of NFV was significantly correlated (P<0.01) with that of the radius for horizontal run-lengths. No relationship between the texture of NFV and calcaneus was found.

DISCUSSION

In the horizontal direction (perpendicular to the stress lines), the microarchitecture of NFV and radius showed a disappearance of the transverse rods anchoring the plates. Due to its particular microarchitecture, the calcaneus is not representative of the vertebral status.

CONCLUSION

Bone densitometry provides no information about microarchitecture. Texture analysis of X-ray images of the radius would be a minimally invasive tool, providing an early detection of microarchitectural alterations.

LEVEL OF EVIDENCE

IV retrospective study.

Effects of aluminum exposure on bone mineral density, mineral, and trace elements in rats

The purpose of the study was to investigate the effects of aluminum (Al) exposure on bone mineral elements, trace elements, and bone mineral density (BMD) in rats. One hundred Wistar rats were divided randomly into two groups. Experimental rats were given drinking water containing aluminum chloride (AlCl(3), 430 mg Al(3+)/L), whereas control rats were given distilled water for up to 150 days. Ten rats were sacrificed in each group every 30 days. The levels of Al, calcium (Ca), phosphorus (P), magnesium (Mg), zinc (Zn), iron (Fe), copper (Cu), manganese (Mn), selenium (Se), boron (B), and strontium (Sr) in bone and the BMD of femur were measured. Al-treated rats showed lower deposition of Ca, P, and Mg compared with control rats. Levels of trace elements (Zn, Fe, Cu, Mn, Se, B, and Sr) were significantly lower in the Al-treated group than in the control group from day 60, and the BMD of the femur metaphysis in the Al-treated group was significantly lower than in the control group on days 120 and 150. These findings indicate that long-term Al exposure reduces the levels of mineral and trace elements in bone. As a result, bone loss was induced (particularly in cancellous bone).

Pharmacologic inhibitors of IkappaB kinase suppress growth and migration of mammary carcinosarcoma cells in vitro and prevent osteolytic bone metastasis in vivo

The NF-kappaB signaling pathway is known to play an important role in the regulation of osteoclastic bone resorption and cancer cell growth. Previous studies have shown that genetic inactivation of IkappaB kinase (IKK), a key component of NF-kappaB signaling, inhibits osteoclastogenesis, but the effects of pharmacologic IKK inhibitors on osteolytic bone metastasis are unknown. Here, we studied the effects of the IKK inhibitors celastrol, BMS-345541, parthenolide, and wedelolactone on the proliferation and migration of W256 cells in vitro and osteolytic bone destruction in vivo. All compounds tested inhibited the growth and induced apoptosis of W256 cells as evidenced by caspase-3 activation and nuclear morphology. Celastrol, BMS-345541, and parthenolide abolished IL1beta and tumor necrosis factor alpha-induced IkappaB phosphorylation and prevented nuclear translocation of NF-kappaB and DNA binding. Celastrol and parthenolide but not BMS-345541 prevented the activation of both IKKalpha and IKKbeta, and celastrol inhibited IKKalpha/beta activation by preventing the phosphorylation of TAK1, a key receptor-associated factor upstream of IKK. Celastrol and parthenolide markedly reduced the mRNA expression of matrix metalloproteinase 9 and urinary plasminogen activator, and inhibited W256 migration. Administration of celastrol or parthenolide at a dose of 1 mg/kg/day suppressed trabecular bone loss and reduced the number and size of osteolytic bone lesions following W256 injection in rats. Histomorphometric analysis showed that both compounds decreased osteoclast number and inhibited bone resorption. In conclusion, pharmacologic inhibitors of IKK are effective in preventing osteolytic bone metastasis in this model and might represent a promising class of agents to the prevention and treatment of metastatic bone disease associated with breast cancer.

The effect of ovariectomy combined with hindlimb unloading and reloading on the long bones of mature Sprague-Dawley rats

OBJECTIVE

To determine the effect of loss of ovarian function and mechanical loading (ie, inactivity) alone or in combination on bone mass and strength.

DESIGN

Mature (aged 6 mo) rats were ovariectomized to induce loss of ovarian function and bone. Hindlimb unloading (HLU) was used to determine the effect of mechanical unloading and reloading on bone mass and strength. Bone mass of the femur and tibia was determined using dual-energy x-ray absorptiometry. Femoral and tibial bone strength was determined by a three-point bending test and by a torsion test.

RESULTS

Ovariectomy (OVX) alone decreased total bone mineral density (BMD) in the femur (-5.5%, P=0.03) and tibia (-7.3%, P=0.01) compared with that for sham-operated animals. HLU alone for 4 weeks had no significant effect on bone. Together OVX/HLU accentuated BMD loss in the femur (-10.5%, P<0.01) compared with that for sham-operated animals. The femur was more sensitive than the tibia to the combination of OVX/HLU, indicated by the reduction (-5.3%, P<0.05) of total BMD below that achieved by OVX alone. Torsion tests showed that OVX/HLU but not OVX or HLU alone reduced bone strength. There was a correlation between lower femoral total BMD (r2=0.65, P<0.001) and reduced torque strength. Bone loss did not continue during the 2 weeks of reloading.

CONCLUSIONS

OVX accompanied by mechanical unloading results in more rapid and severe bone loss than either OVX or unloading alone and therefore is associated with a greater likelihood of osteoporosis.

Orchidectomy models of osteoporosis

Long considered a disease of post-menopausal women, osteoporosis is increasingly being recognized among the growing population of elderly men. Androgen deficiency may be associated with an increase of bone resorption in elderly men and so, with remodeling imbalance and fracture risk. It is firmly established that androgen withdrawal induced by orchidectomy (ORX) results in decreased bone mass in animal models especially in rodents. The mature rat is the model of choice. Skeletal effects of ORX in rats have been studied at the tissular and cellular level. It induces a decrease of BMD and BV/TV with microarchitecture alterations due to an increased bone remodeling. The present chapter focuses on the ORX surgery in rats and mice.

Multiphasic Biomaterials: A Concept for Bone Substitutes Developed in the "Pays de la Loire"

This paper reports on the research into multiphase bone substitutes carried out by laboratories from the ‘Pays de la Loire’ region in France. This collaborative research was funded by both the French Government and the Regional Council in the period 2000-2007. Calcium phosphate bioceramics, polymers and combinations have been developed as bone substitutes for various maxillofacial and orthopaedic applications. These bone substitutes should support and regenerate bone tissue and resorb after implantation. In the bone tissue engineering area, they have been combined with autologous bone marrow cells or bioactive factors. The bone substitutes were tested in various animal models mimicking clinical situations or under pathological conditions (osteoporosis). In order to complete our research, the multiphase materials were also evaluated in clinical trials.

Mandibular bone loss in an animal model of male osteoporosis (orchidectomized rat): a radiographic and densitometric study

In humans, hypogonadism is associated with osteoporosis and can be studied by densitometry (DXA) on the vertebrae or long bones. There is some controversy about the relationships between bone loss in these sites and in the mandible. Osteoporosis has been suggested as a risk factor for dental problems. In the rat, orchidectomy (ORX) is associated with an increased bone resorption resulting in bone loss. We have studied the time effects of ORX on the alveolar bone in the rat. Forty-eight male Wistar rats were divided into four groups and studied over 2, 4, 8 and 16 weeks. In each group, six rats were ORX and six sham-operated (SHAM) animals were used as control. The mandible of each rat was dissected. Numeric radiographs, centered on the molar region, were obtained. Bone loss was observed qualitatively at 16 weeks in ORX animals. Quantitative modifications were confirmed by texture analysis of numeric radiographs using the run-length technique. The bone mineral content (BMC) and density (BMD) of the hemimandible and in a region centered on the molars were measured by DXA. The coefficient of variation (CV) for BMC was poor on the whole bone and no differences could be observed even at 16 weeks. For BMC of the molar region, the CV was improved and significant bone loss occurred in the ORX group at 16 weeks ( P<0.016). This study confirms that in the male rat, the reduction of sex hormones induced by ORX is associated with a decrease in bone mass in the mandible.

Dual-energy X-ray absorptiometry of birds: an examination of excised skeletal specimens

The ability of dual-energy X-ray absorptiometry (DXA) to measure bone mineral content and density of bird bones has received little attention. This paper represents the first comprehensive study of the methods, precision, and reproducibility of DXA (GE-Lunar DPX-L) for the uniquely shaped, thin and pneumatic bones of birds. Skeletal elements and portions represented by 26 regions of interest (ROIs) are presented and evaluated for the gallinaceous bird species, wild turkey (Meleagris gallopavo), ruffed grouse (Bonasa umbellus) and bobwhite quail (Colinus virginianus). Using Lunar small animal software and the methods described in this paper, photodensitometry of bird bones is possible and opens new opportunities for using birds in clinical models in veterinarian science, osteoporosis studies, space biology, and even archaeological and paleontological research.

Comparison of pencil-, fan-, and cone-beam dual X-ray absorptiometers for evaluation of bone mineral content in excised rat bone

The aim of the present study was to assess the reproducibility and accuracy of measurements done on excised rat bone with three different generations of densitometers: Hologic QDR2000 pencil beam, Hologic QDR4500 fan beam, and Lunar PIXImus cone beam. The coefficients of variation for repeated measurements of bone mineral content (BMC) were 0.62 and 0.85% for pencil beam, 1.73 and 3.59% for fan beam, and 0.70 and 1.52% for cone beam for femur and tibia, respectively. BMC and ash weight were linearly correlated: 0.998 for pencil, 0.984 for fan, and 0.995 for cone beam. However, the three densitometers overestimated BMC by 10.9, 12.6, and 3.1%, respectively, and the overestimation was found to be dependent on the net BMC. The highest coefficient of correlation was found between BMC measurements from pencil and cone beam (r = 0.995). Data from cone-beam DXA were, respectively, 8.8 and 9.2% lower than those from penciland fan-beam DXA. We conclude that the three DXA instruments precisely and accurately measure BMC in excised rat bone; however, DXA overestimates BMC with a dependence on the bone ash weight. This dependence was less pronounced with the cone-beam technology.