Rapid small-animal dual-energy X-ray absorptiometry using digital radiography

Effect of Memantine Treatment and Combination with Vitamin D Supplementation on Body Composition in the APP/PS1 Mouse Model of Alzheimer's Disease Following Chronic Vitamin D Deficiency

BACKGROUND

Vitamin D deficiency and altered body composition are common in Alzheimer's disease (AD). Memantine with vitamin D supplementation can protect cortical axons against amyloid-β exposure and glutamate toxicity.

OBJECTIVE

To study the effects of vitamin D deprivation and subsequent treatment with memantine and vitamin D enrichment on whole-body composition using a mouse model of AD.

METHODS

Male APPswe/PS1dE9 mice were divided into four groups at 2.5 months of age: the control group (n = 14) was fed a standard diet throughout; the remaining mice were started on a vitamin D-deficient diet at month 6. The vitamin D-deficient group (n = 14) remained on the vitamin D-deficient diet for the rest of the study. Of the remaining two groups, one had memantine (n = 14), while the other had both memantine and 10 IU/g vitamin D (n = 14), added to their diet at month 9. Serum 25(OH)D levels measured at months 6, 9, 12, and 15 confirmed vitamin D levels were lower in mice on vitamin D-deficient diets and higher in the vitamin D-supplemented mice. Micro-computed tomography was performed at month 15 to determine whole-body composition.

RESULTS

In mice deprived of vitamin D, memantine increased bone mineral content (8.7% increase, p < 0.01) and absolute skeletal tissue mass (9.3% increase, p < 0.05) and volume (9.2% increase, p < 0.05) relative to controls. This was not observed when memantine treatment was combined with vitamin D enrichment.

CONCLUSION

Combination treatment of vitamin D and memantine had no negative effects on body composition. Future studies should clarify whether vitamin D status impacts the effects of memantine treatment on bone physiology in people with AD.

Ectopic spinal calcification associated with diffuse idiopathic skeletal hyperostosis (DISH): A quantitative micro-ct analysis

Diffuse idiopathic skeletal hyperostosis (DISH) is a non-inflammatory spondyloarthropathy identified radiographically by calcification of the ligaments and/or entheses along the anterolateral aspect of the vertebral column. The etiology and pathogenesis of calcifications are unknown, and the diagnosis of DISH is currently based on radiographic criteria associated with advanced disease. To characterize the features of calcifications associated with DISH, we used micro-computed tomographic imaging to evaluate a cohort of 19 human cadaveric vertebral columns. Fifty-three percent of the cohort (n = 10; 3 females, 7 males, mean age of death = 81 years, range 67-94) met the radiographic criteria for DISH, with calcification of four or more contiguous vertebral segments. In almost all cases, the lower thoracic regions (T8-12) were affected by calcifications, consisting primarily of large, horizontal outgrowths of bony material. In contrast, calcifications localized to the upper thoracic regions demonstrated variability in their presentation and were categorized as either "continuous vertical bands" or "discontinuous-patchy" lesions. In addition to the variable morphology of the calcifications, our analysis demonstrated remarkable heterogeneity in the densities of calcifications, ranging from internal components below the density of cortical bone to regions of hyper-dense material that exceeded cortical bone. These findings establish that the current radiographic criteria for DISH capture heterogeneous presentations of ectopic spine calcification that can be differentiated based on morphology and density. These findings may indicate a naturally heterogenous disease, potential stage(s) in the natural progression of DISH, or distinct pathologies of ectopic calcifications. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Comparison of Faxitron™ versus MicroCT imaging of the skeleton of the suckling rat

Currently, in pre and postnatal development studies or in juvenile rat studies, bone growth is assessed "for cause" by simple measurements of long bone length in vivo and at termination. This manuscript compares two radiographic methods for in vivo assessment of long bones in suckling rats; 2D imaging using a Faxitron™ and 3D imaging using μCT. This paper illustrates that it is possible to image the unanaesthetised postnatal day 1 rat by Faxitron™ using a simple Micropore™ tape restraint method. With isoflurane anaesthesia, it was possible to obtain high quality μCT images of pups from day of birth. No pups were rejected by their mothers following either technique. The Faxitron™ was straightforward and fast, however the μCT 3D images were of greater overall utility. Either method could be used for longitudinal investigation of long bone observations made previously in embryofetal development studies, or for other mechanistic work.

Novel insight into stem cell trafficking in dystrophic muscles

Recently published reports have described possible cellular therapy approaches to regenerate muscle tissues using arterial route delivery. However, the kinetic of distribution of these migratory stem cells within injected animal muscular dystrophy models is unknown. Using living X-ray computed microtomography, we established that intra-arterially injected stem cells traffic to multiple muscle tissues for several hours until their migration within dystrophic muscles. Injected stem cells express multiple traffic molecules, including VLA-4, LFA-1, CD44, and the chemokine receptor CXCR4, which are likely to direct these cells into dystrophic muscles. In fact, the majority of intra-arterially injected stem cells access the muscle tissues not immediately after the injection, but after several rounds of recirculation. We set up a new, living, 3D-imaging approach, which appears to be an important way to investigate the kinetic of distribution of systemically injected stem cells within dystrophic muscle tissues, thereby providing supportive data for future clinical applications.

Experimental studies on the bone metabolism of male rats chronically exposed to cadmium intoxication using dual-energy X-ray absorptiometry

Cadmium (Cd) has been identified as the etiologic agent of itai-itai disease. The purpose of this study was to investigate whether chronic Cd exposure affects bone metabolism in a male rat model and to estimate the bone mineral density (BMD) differences in lumbar and femoral bone because of Cd exposure. Six-week-old male Hos Donryu rats were used in this experiment. Cadmium was administered at a dose of 200 ppm to rats in the diet to produce experimental chronic Cd poisoning. Bone mineral density was measured using dual-energy X-ray absorptiometry (DEXA) with a high-resolution scan collimator (0.25 mm diameter) (Hologic QDR-2000). The Cd content in renal tissue reached a critical concentration of 128.42 ± 14.38 μg/g 10 months after the administration of the element (Table 3). The average blood urea nitrogen (BUN) value was increased throughout the period of the experiment, and the serum creatinine value of the experimental group showed an increase after 2 months of Cd administration (0.46 ± 0.09 mg/dL). The concentration of urinary calcium changed in the experimental group after exposure to Cd for 12 months (15.4 ± 0.13 mg/dL). DEXA showed a greater reduction in the bone mineral density of the 5th vertebral body (L5) in rats that had ingested Cd for 4 months (0.359 ± 0.013 g/cm2) than in control rats (0.372 ± 0.012 g/cm2, P < 0.01). On the contrary, the difference in bone mineral content between rats ingesting Cd for 6–8 months and control rats was not significant. However, significant reductions in bone mineral content were again noted in rats that had ingested Cd for 12 months (0.339 ± 0.023 g/cm2) compared with the control group (0.385 ± 0.012 g/cm2, P < 0.01). The bone mineral density of the right femoral bone in control rats was 0.328 ± 0.018 g/cm2 and that in experimental rats was 0.306 ± 0.012 g/cm2, and a meaningful difference was recognized ( P < 0.05). Histological examination of the rats exposed to Cd for 12 months showed that the 5th lumbar vertebral body (L5) exhibited osteomalacia. The results of our studies show that Cd stimulated a loss of bone mineral at an early stage to a great extent in male rats. In the examination of male rats, bone injury and renal functional disorder were encountered simultaneously. This study suggested that osteomalacia was induced by a direct action of Cd on the bone through abnormal calcium homeostasis at an early stage in male rats.

Retrovirus-Mediated Gene Transfer of Receptor Activator of Nuclear Factor-κB-Fc Prevents Bone Loss in Ovariectomized Mice

Postmenopausal osteoporosis is characterized by increased bone resorption due to estrogen deficiency. Receptor activator of nuclear factor-kappaB-Fc (RANK-Fc), a fusion protein that specifically blocks receptor activator of nuclear factor ligand binding to RANK, has been known to be efficient and well tolerated in animal models of osteoporosis. Here we show that cell-based gene therapy with RANK-Fc effectively prevented bone loss in ovariectomized (OVX) mice. Thirty-one young adult female C57Bl/6 mice were used, and repeated intraperitoneal injection of mesenchymal stem cells (MSCs) transduced with retrovirus was performed as follows: 1) Sham-operated mice (n = 8); 2) OVX mice treated with phosphate-buffered saline (OVX-PBS; n = 8); 3) OVX mice injected with MSCs transduced with control retrovirus (OVX-green fluorescent protein [GFP]; n = 7); and 4) OVX mice injected with MSCs transduced with RANK-Fc (OVX-RANK-Fc; n = 8). Cellular expression of RANK-Fc was confirmed by Western blot analysis of cell lysates and conditioned medium and also by enzyme-linked immunosorbent assay for the mice serum. Measurement of bone mineral density (BMD) by dual-energy x-ray absorptiometry (PIXImus) revealed that the OVX-RANK-Fc group gained significantly higher BMD than either the OVX-PBS group or OVX-GFP group after 8 weeks. The expression of GFP, which is coexpressed with RANK-Fc, was detected by polymerase chain reaction analysis of DNA isolated from femur and intra-abdominal fat, whereas no GFP signal was identified in liver, brain, heart, lung, or bone marrow aspirates. These suggest that expression of RANK-Fc by genetically modified MSCs may be a feasible option for the prevention of bone loss induced by ovariectomy.

Measurement of bone mineral density is possible with standard radiographs: a study involving total knee replacement

BACKGROUND

Measured bone density correlates well with the mechanical properties of the bone. Our objective was to evaluate optical densitometry as a method of measuring the periprosthetic bone density of the tibial platform in total knee replacement using serial dual-energy X-ray absorptiometry (DXA) as the reference test.

METHODS

30 patients who underwent a cemented total knee replacement were followed up for over 2 years. Standard radiographs of the knee were obtained at 12 and 24 months. These were photographed with a digital camera and enhanced with image processing software. A DXA scan was performed at the same time as the reference method. 3 regions of interest were defined under the tibial plateau (medial, lateral and stem positions).

RESULTS

After 24 months of follow-up there was a significant decrease in density in the 3 regions, both with the optical and DXA methods. The concordance between methods was studied using Bland and Altman plots, Cronbach's alpha and intraclass correlation coefficients resulted in values from 0.72 to 0.87, depending on the region and the follow-up time.

INTERPRETATION

Quantification of optical density values with a standardized measurement system on conventional radiographs is a reliable and efficient method of determining the bone mineral density.

Volumetric analysis of mice lungs in a clinical magnetic resonance imaging scanner

Small animal models are widely used to study various pathologies. Magnetic resonance imaging (MRI) allows investigation of these animals in a non-invasive way. Therefore, the aim of our study was to develop and evaluate a low-cost approach to measure lung volumes in small animal MRI using a clinical scanner and a specially designed RF coil. Five mice (three of an established emphysema model and two controls) were investigated in a 1.0-T clinical scanner using a specially built small animal saddle coil and three different three-dimensional sequences; overall imaging time was approximately 16 min. Lung volumes were calculated from these images using an interactive watershed transform algorithm for semi-automatic image segmentation. The gold standard for the volume measurement was water displacement after surgical explantation. MRI measured volumes correlated significantly with ex vivo measurements on the explanted lungs (r = 0.99 to 0.89; p < 0.05). Mean lung volume in emphysema model mice was larger than in controls. High-resolution, small animal MRI using a clinical scanner is feasible for volumetric analysis and provides an alternative to a dedicated small animal scanner.

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.

Characterization of a CCD-based digital x-ray imaging system for small-animal studies: properties of spatial resolution

A digital x-ray imaging system was designed for small-animal studies. This system is a fiber-optics taper-coupled imaging system with two CCD arrays uniquely jointed. The x-ray source of the system has a small focal spot of 20 microm. This digital imaging system contains specially designed shelves to provide magnification levels, ranging from 1.5x to 5x. The system is characterized in terms of its properties of spatial resolution. An observer-based spatial resolution measurement was conducted with a line-pair target and a sector test pattern. The modulation transfer function of the system, with different magnifications, was studied by use of a 10-microm lead slit. The average resolutions at 50% and 5% modulations at 1x magnification were measured as 3.9 and 8.4 lp/mm, respectively, where lp indicates line pairs. With 5x magnification, the 50% and the 5% modulations provided 13.2- and 29.9-lp/mm, respectively, average spatial resolutions. The measurements showed consistency between the two individual CCD arrays; the difference in resolution between the two CCDs is less than 1%, even at high magnifications.